6 @documentencoding UTF-8
7 @settitle GNU Guix Reference Manual
13 Copyright @copyright{} 2012, 2013, 2014, 2015 Ludovic Courtès@*
14 Copyright @copyright{} 2013, 2014 Andreas Enge@*
15 Copyright @copyright{} 2013 Nikita Karetnikov@*
16 Copyright @copyright{} 2015 Mathieu Lirzin@*
17 Copyright @copyright{} 2014 Pierre-Antoine Rault@*
18 Copyright @copyright{} 2015 Taylan Ulrich Bayırlı/Kammer
20 Permission is granted to copy, distribute and/or modify this document
21 under the terms of the GNU Free Documentation License, Version 1.3 or
22 any later version published by the Free Software Foundation; with no
23 Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
24 copy of the license is included in the section entitled ``GNU Free
25 Documentation License''.
28 @dircategory Package management
30 * guix: (guix). Guix, the functional package manager.
31 * guix package: (guix)Invoking guix package
32 Managing packages with Guix.
33 * guix build: (guix)Invoking guix build
34 Building packages with Guix.
35 * guix system: (guix)Invoking guix system
36 Managing the operating system configuration.
39 @dircategory Software development
41 * guix environment: (guix)Invoking guix environment
42 Building development environments with Guix.
46 @title GNU Guix Reference Manual
47 @subtitle Using the GNU Guix Functional Package Manager
48 @author The GNU Guix Developers
51 @vskip 0pt plus 1filll
52 Edition @value{EDITION} @*
60 @c *********************************************************************
64 This document describes GNU Guix version @value{VERSION}, a functional
65 package management tool written for the GNU system.
68 * Introduction:: What is Guix about?
69 * Installation:: Installing Guix.
70 * Package Management:: Package installation, upgrade, etc.
71 * Emacs Interface:: Using Guix from Emacs.
72 * Programming Interface:: Using Guix in Scheme.
73 * Utilities:: Package management commands.
74 * GNU Distribution:: Software for your friendly GNU system.
75 * Contributing:: Your help needed!
77 * Acknowledgments:: Thanks!
78 * GNU Free Documentation License:: The license of this manual.
79 * Concept Index:: Concepts.
80 * Programming Index:: Data types, functions, and variables.
83 --- The Detailed Node Listing ---
87 * Binary Installation:: Getting Guix running in no time!
88 * Requirements:: Software needed to build and run Guix.
89 * Running the Test Suite:: Testing Guix.
90 * Setting Up the Daemon:: Preparing the build daemon's environment.
91 * Invoking guix-daemon:: Running the build daemon.
92 * Application Setup:: Application-specific setup.
96 * Build Environment Setup:: Preparing the isolated build environment.
97 * Daemon Offload Setup:: Offloading builds to remote machines.
101 * Features:: How Guix will make your life brighter.
102 * Invoking guix package:: Package installation, removal, etc.
103 * Substitutes:: Downloading pre-built binaries.
104 * Packages with Multiple Outputs:: Single source package, multiple outputs.
105 * Invoking guix gc:: Running the garbage collector.
106 * Invoking guix pull:: Fetching the latest Guix and distribution.
107 * Invoking guix archive:: Exporting and importing store files.
111 * Initial Setup: Emacs Initial Setup. Preparing @file{~/.emacs}.
112 * Package Management: Emacs Package Management. Managing packages and generations.
113 * Popup Interface: Emacs Popup Interface. Magit-like interface for guix commands.
114 * Prettify Mode: Emacs Prettify. Abbreviating @file{/gnu/store/@dots{}} file names.
115 * Build Log Mode: Emacs Build Log. Highlighting Guix build logs.
116 * Completions: Emacs Completions. Completing @command{guix} shell command.
117 * Development: Emacs Development. Tools for Guix developers.
119 Programming Interface
121 * Defining Packages:: Defining new packages.
122 * Build Systems:: Specifying how packages are built.
123 * The Store:: Manipulating the package store.
124 * Derivations:: Low-level interface to package derivations.
125 * The Store Monad:: Purely functional interface to the store.
126 * G-Expressions:: Manipulating build expressions.
130 * package Reference:: The package data type.
131 * origin Reference:: The origin data type.
135 * Invoking guix build:: Building packages from the command line.
136 * Invoking guix edit:: Editing package definitions.
137 * Invoking guix download:: Downloading a file and printing its hash.
138 * Invoking guix hash:: Computing the cryptographic hash of a file.
139 * Invoking guix import:: Importing package definitions.
140 * Invoking guix refresh:: Updating package definitions.
141 * Invoking guix lint:: Finding errors in package definitions.
142 * Invoking guix size:: Profiling disk usage.
143 * Invoking guix graph:: Visualizing the graph of packages.
144 * Invoking guix environment:: Setting up development environments.
145 * Invoking guix publish:: Sharing substitutes.
146 * Invoking guix challenge:: Challenging substitute servers.
147 * Invoking guix container:: Process isolation.
151 * System Installation:: Installing the whole operating system.
152 * System Configuration:: Configuring the operating system.
153 * Installing Debugging Files:: Feeding the debugger.
154 * Security Updates:: Deploying security fixes quickly.
155 * Package Modules:: Packages from the programmer's viewpoint.
156 * Packaging Guidelines:: Growing the distribution.
157 * Bootstrapping:: GNU/Linux built from scratch.
158 * Porting:: Targeting another platform or kernel.
162 * Using the Configuration System:: Customizing your GNU system.
163 * operating-system Reference:: Detail of operating-system declarations.
164 * File Systems:: Configuring file system mounts.
165 * Mapped Devices:: Block device extra processing.
166 * User Accounts:: Specifying user accounts.
167 * Locales:: Language and cultural convention settings.
168 * Services:: Specifying system services.
169 * Setuid Programs:: Programs running with root privileges.
170 * X.509 Certificates:: Authenticating HTTPS servers.
171 * Name Service Switch:: Configuring libc's name service switch.
172 * Initial RAM Disk:: Linux-Libre bootstrapping.
173 * GRUB Configuration:: Configuring the boot loader.
174 * Invoking guix system:: Instantiating a system configuration.
175 * Defining Services:: Adding new service definitions.
179 * Base Services:: Essential system services.
180 * Networking Services:: Network setup, SSH daemon, etc.
181 * X Window:: Graphical display.
182 * Desktop Services:: D-Bus and desktop services.
183 * Database Services:: SQL databases.
184 * Web Services:: Web servers.
185 * Various Services:: Other services.
189 * Service Composition:: The model for composing services.
190 * Service Types and Services:: Types and services.
191 * Service Reference:: API reference.
192 * dmd Services:: A particular type of service.
196 * Software Freedom:: What may go into the distribution.
197 * Package Naming:: What's in a name?
198 * Version Numbers:: When the name is not enough.
199 * Synopses and Descriptions:: Helping users find the right package.
200 * Python Modules:: Taming the snake.
201 * Perl Modules:: Little pearls.
202 * Fonts:: Fond of fonts.
206 * Building from Git:: The latest and greatest.
207 * Running Guix Before It Is Installed:: Hacker tricks.
208 * The Perfect Setup:: The right tools.
209 * Coding Style:: Hygiene of the contributor.
210 * Submitting Patches:: Share your work.
214 * Programming Paradigm:: How to compose your elements.
215 * Modules:: Where to store your code?
216 * Data Types and Pattern Matching:: Implementing data structures.
217 * Formatting Code:: Writing conventions.
222 @c *********************************************************************
224 @chapter Introduction
226 GNU Guix@footnote{``Guix'' is pronounced like ``geeks'', or ``ɡiːks''
227 using the international phonetic alphabet (IPA).} is a functional
228 package management tool for the GNU system. Package management consists
229 of all activities that relate to building packages from sources,
230 honoring their build-time and run-time dependencies,
231 installing packages in user environments, upgrading installed packages
232 to new versions or rolling back to a previous set, removing unused
233 software packages, etc.
235 @cindex functional package management
236 The term @dfn{functional} refers to a specific package management
237 discipline pioneered by Nix (@pxref{Acknowledgments}).
238 In Guix, the package build and installation process is seen
239 as a function, in the mathematical sense. That function takes inputs,
240 such as build scripts, a compiler, and libraries, and
241 returns an installed package. As a pure function, its result depends
242 solely on its inputs---for instance, it cannot refer to software or
243 scripts that were not explicitly passed as inputs. A build function
244 always produces the same result when passed a given set of inputs. It
245 cannot alter the system's environment in
246 any way; for instance, it cannot create, modify, or delete files outside
247 of its build and installation directories. This is achieved by running
248 build processes in isolated environments (or @dfn{containers}), where only their
249 explicit inputs are visible.
252 The result of package build functions is @dfn{cached} in the file
253 system, in a special directory called @dfn{the store} (@pxref{The
254 Store}). Each package is installed in a directory of its own, in the
255 store---by default under @file{/gnu/store}. The directory name contains
256 a hash of all the inputs used to build that package; thus, changing an
257 input yields a different directory name.
259 This approach is the foundation of Guix's salient features: support for
260 transactional package upgrade and rollback, per-user installation, and
261 garbage collection of packages (@pxref{Features}).
263 Guix has a command-line interface, which allows users to build, install,
264 upgrade, and remove packages, as well as a Scheme programming interface.
266 @cindex Guix System Distribution
268 Last but not least, Guix is used to build a distribution of the GNU
269 system, with many GNU and non-GNU free software packages. The Guix
270 System Distribution, or GNU@tie{}GuixSD, takes advantage of the core
271 properties of Guix at the system level. With GuixSD, users
272 @emph{declare} all aspects of the operating system configuration, and
273 Guix takes care of instantiating that configuration in a reproducible,
274 stateless fashion. @xref{GNU Distribution}.
276 @c *********************************************************************
278 @chapter Installation
280 GNU Guix is available for download from its website at
281 @url{http://www.gnu.org/software/guix/}. This section describes the
282 software requirements of Guix, as well as how to install it and get
285 Note that this section is concerned with the installation of the package
286 manager, which can be done on top of a running GNU/Linux system. If,
287 instead, you want to install the complete GNU operating system,
288 @pxref{System Installation}.
291 * Binary Installation:: Getting Guix running in no time!
292 * Requirements:: Software needed to build and run Guix.
293 * Running the Test Suite:: Testing Guix.
294 * Setting Up the Daemon:: Preparing the build daemon's environment.
295 * Invoking guix-daemon:: Running the build daemon.
296 * Application Setup:: Application-specific setup.
299 @node Binary Installation
300 @section Binary Installation
302 This section describes how to install Guix on an arbitrary system from a
303 self-contained tarball providing binaries for Guix and for all its
304 dependencies. This is often quicker than installing from source, which
305 is described in the next sections. The only requirement is to have
308 Installing goes along these lines:
312 Download the binary tarball from
313 @indicateurl{ftp://alpha.gnu.org/gnu/guix/guix-binary-@value{VERSION}.@var{system}.tar.xz}@footnote{As
314 usual, make sure to download the associated @file{.sig} file and to
315 verify the authenticity of the tarball against it!}, where @var{system}
316 is @code{x86_64-linux} for an @code{x86_64} machine already running the
317 kernel Linux, and so on.
324 # tar --warning=no-timestamp -xf \
325 guix-binary-@value{VERSION}.@var{system}.tar.xz
326 # mv var/guix /var/ && mv gnu /
329 This creates @file{/gnu/store} (@pxref{The Store}) and @file{/var/guix}.
330 The latter contains a ready-to-use profile for @code{root} (see next
333 Do @emph{not} unpack the tarball on a working Guix system since that
334 would overwrite its own essential files.
336 The @code{--warning=no-timestamp} option makes sure GNU@tie{}tar does
337 not emit warnings about ``implausibly old time stamps'' (such
338 warnings were triggered by GNU@tie{}tar 1.26 and older; recent
340 They stem from the fact that all the
341 files in the archive have their modification time set to zero (which
342 means January 1st, 1970.) This is done on purpose to make sure the
343 archive content is independent of its creation time, thus making it
347 Make @code{root}'s profile available under @file{~/.guix-profile}:
350 # ln -sf /var/guix/profiles/per-user/root/guix-profile \
355 Create the group and user accounts for build users as explained below
356 (@pxref{Build Environment Setup}).
362 # ~root/.guix-profile/bin/guix-daemon --build-users-group=guixbuild
365 On hosts using the systemd init system, drop
366 @file{~root/.guix-profile/lib/systemd/system/guix-daemon.service} in
367 @file{/etc/systemd/system}.
370 Make the @command{guix} command available to other users on the machine,
374 # mkdir -p /usr/local/bin
376 # ln -s /var/guix/profiles/per-user/root/guix-profile/bin/guix
380 To use substitutes from @code{hydra.gnu.org} (@pxref{Substitutes}),
384 # guix archive --authorize < ~root/.guix-profile/share/guix/hydra.gnu.org.pub
388 And that's it! For additional tips and tricks, @pxref{Application
391 The @code{guix} package must remain available in @code{root}'s
392 profile, or it would become subject to garbage collection---in which
393 case you would find yourself badly handicapped by the lack of the
394 @command{guix} command.
396 The tarball in question can be (re)produced and verified simply by
397 running the following command in the Guix source tree:
400 make guix-binary.@var{system}.tar.xz
405 @section Requirements
407 This section lists requirements when building Guix from source. The
408 build procedure for Guix is the same as for other GNU software, and is
409 not covered here. Please see the files @file{README} and @file{INSTALL}
410 in the Guix source tree for additional details.
412 GNU Guix depends on the following packages:
415 @item @url{http://gnu.org/software/guile/, GNU Guile}, version 2.0.7 or later;
416 @item @url{http://gnupg.org/, GNU libgcrypt};
417 @item @url{http://www.gnu.org/software/make/, GNU Make}.
420 The following dependencies are optional:
425 @url{http://savannah.nongnu.org/projects/guile-json/, Guile-JSON} will
426 allow you to use the @command{guix import pypi} command (@pxref{Invoking
427 guix import}). It is of
428 interest primarily for developers and not for casual users.
430 Installing @uref{http://gnutls.org/, GnuTLS-Guile} will
431 allow you to access @code{https} URLs with the @command{guix download}
432 command (@pxref{Invoking guix download}), the @command{guix import pypi}
433 command, and the @command{guix import cpan} command. This is primarily
434 of interest to developers. @xref{Guile Preparations, how to install the
435 GnuTLS bindings for Guile,, gnutls-guile, GnuTLS-Guile}.
438 Unless @code{--disable-daemon} was passed to @command{configure}, the
439 following packages are also needed:
442 @item @url{http://sqlite.org, SQLite 3};
443 @item @url{http://www.bzip.org, libbz2};
444 @item @url{http://gcc.gnu.org, GCC's g++}, with support for the
448 When a working installation of @url{http://nixos.org/nix/, the Nix package
449 manager} is available, you
450 can instead configure Guix with @code{--disable-daemon}. In that case,
451 Nix replaces the three dependencies above.
453 Guix is compatible with Nix, so it is possible to share the same store
454 between both. To do so, you must pass @command{configure} not only the
455 same @code{--with-store-dir} value, but also the same
456 @code{--localstatedir} value. The latter is essential because it
457 specifies where the database that stores metadata about the store is
458 located, among other things. The default values for Nix are
459 @code{--with-store-dir=/nix/store} and @code{--localstatedir=/nix/var}.
460 Note that @code{--disable-daemon} is not required if
461 your goal is to share the store with Nix.
463 @node Running the Test Suite
464 @section Running the Test Suite
466 After a successful @command{configure} and @code{make} run, it is a good
467 idea to run the test suite. It can help catch issues with the setup or
468 environment, or bugs in Guix itself---and really, reporting test
469 failures is a good way to help improve the software. To run the test
476 Test cases can run in parallel: you can use the @code{-j} option of
477 GNU@tie{}make to speed things up. The first run may take a few minutes
478 on a recent machine; subsequent runs will be faster because the store
479 that is created for test purposes will already have various things in
482 Upon failure, please email @email{bug-guix@@gnu.org} and attach the
483 @file{test-suite.log} file. When @file{tests/@var{something}.scm}
484 fails, please also attach the @file{@var{something}.log} file available
485 in the top-level build directory. Please specify the Guix version being
486 used as well as version numbers of the dependencies
487 (@pxref{Requirements}) in your message.
489 @node Setting Up the Daemon
490 @section Setting Up the Daemon
493 Operations such as building a package or running the garbage collector
494 are all performed by a specialized process, the @dfn{build daemon}, on
495 behalf of clients. Only the daemon may access the store and its
496 associated database. Thus, any operation that manipulates the store
497 goes through the daemon. For instance, command-line tools such as
498 @command{guix package} and @command{guix build} communicate with the
499 daemon (@i{via} remote procedure calls) to instruct it what to do.
501 The following sections explain how to prepare the build daemon's
502 environment. Also @ref{Substitutes}, for information on how to allow
503 the daemon to download pre-built binaries.
506 * Build Environment Setup:: Preparing the isolated build environment.
507 * Daemon Offload Setup:: Offloading builds to remote machines.
510 @node Build Environment Setup
511 @subsection Build Environment Setup
513 In a standard multi-user setup, Guix and its daemon---the
514 @command{guix-daemon} program---are installed by the system
515 administrator; @file{/gnu/store} is owned by @code{root} and
516 @command{guix-daemon} runs as @code{root}. Unprivileged users may use
517 Guix tools to build packages or otherwise access the store, and the
518 daemon will do it on their behalf, ensuring that the store is kept in a
519 consistent state, and allowing built packages to be shared among users.
522 When @command{guix-daemon} runs as @code{root}, you may not want package
523 build processes themselves to run as @code{root} too, for obvious
524 security reasons. To avoid that, a special pool of @dfn{build users}
525 should be created for use by build processes started by the daemon.
526 These build users need not have a shell and a home directory: they will
527 just be used when the daemon drops @code{root} privileges in build
528 processes. Having several such users allows the daemon to launch
529 distinct build processes under separate UIDs, which guarantees that they
530 do not interfere with each other---an essential feature since builds are
531 regarded as pure functions (@pxref{Introduction}).
533 On a GNU/Linux system, a build user pool may be created like this (using
534 Bash syntax and the @code{shadow} commands):
536 @c See http://lists.gnu.org/archive/html/bug-guix/2013-01/msg00239.html
537 @c for why `-G' is needed.
539 # groupadd --system guixbuild
540 # for i in `seq -w 1 10`;
542 useradd -g guixbuild -G guixbuild \
543 -d /var/empty -s `which nologin` \
544 -c "Guix build user $i" --system \
550 The number of build users determines how many build jobs may run in
551 parallel, as specified by the @option{--max-jobs} option
552 (@pxref{Invoking guix-daemon, @option{--max-jobs}}). The
553 @code{guix-daemon} program may then be run as @code{root} with the
554 following command@footnote{If your machine uses the systemd init system,
555 dropping the @file{@var{prefix}/lib/systemd/system/guix-daemon.service}
556 file in @file{/etc/systemd/system} will ensure that
557 @command{guix-daemon} is automatically started.}:
560 # guix-daemon --build-users-group=guixbuild
565 This way, the daemon starts build processes in a chroot, under one of
566 the @code{guixbuilder} users. On GNU/Linux, by default, the chroot
567 environment contains nothing but:
569 @c Keep this list in sync with libstore/build.cc! -----------------------
572 a minimal @code{/dev} directory, created mostly independently from the
573 host @code{/dev}@footnote{``Mostly'', because while the set of files
574 that appear in the chroot's @code{/dev} is fixed, most of these files
575 can only be created if the host has them.};
578 the @code{/proc} directory; it only shows the container's processes
579 since a separate PID name space is used;
582 @file{/etc/passwd} with an entry for the current user and an entry for
586 @file{/etc/group} with an entry for the user's group;
589 @file{/etc/hosts} with an entry that maps @code{localhost} to
593 a writable @file{/tmp} directory.
596 If you are installing Guix as an unprivileged user, it is still possible
597 to run @command{guix-daemon} provided you pass @code{--disable-chroot}.
598 However, build processes will not be isolated from one another, and not
599 from the rest of the system. Thus, build processes may interfere with
600 each other, and may access programs, libraries, and other files
601 available on the system---making it much harder to view them as
602 @emph{pure} functions.
605 @node Daemon Offload Setup
606 @subsection Using the Offload Facility
610 When desired, the build daemon can @dfn{offload}
611 derivation builds to other machines
612 running Guix, using the @code{offload} @dfn{build hook}. When that
613 feature is enabled, a list of user-specified build machines is read from
614 @file{/etc/guix/machines.scm}; anytime a build is requested, for
615 instance via @code{guix build}, the daemon attempts to offload it to one
616 of the machines that satisfies the derivation's constraints, in
617 particular its system type---e.g., @file{x86_64-linux}. Missing
618 prerequisites for the build are copied over SSH to the target machine,
619 which then proceeds with the build; upon success the output(s) of the
620 build are copied back to the initial machine.
622 The @file{/etc/guix/machines.scm} file typically looks like this:
626 (name "eightysix.example.org")
627 (system "x86_64-linux")
629 (speed 2.)) ; incredibly fast!
632 (name "meeps.example.org")
633 (system "mips64el-linux")
636 (string-append (getenv "HOME")
637 "/.lsh/identity-for-guix"))))
641 In the example above we specify a list of two build machines, one for
642 the @code{x86_64} architecture and one for the @code{mips64el}
645 In fact, this file is---not surprisingly!---a Scheme file that is
646 evaluated when the @code{offload} hook is started. Its return value
647 must be a list of @code{build-machine} objects. While this example
648 shows a fixed list of build machines, one could imagine, say, using
649 DNS-SD to return a list of potential build machines discovered in the
650 local network (@pxref{Introduction, Guile-Avahi,, guile-avahi, Using
651 Avahi in Guile Scheme Programs}). The @code{build-machine} data type is
654 @deftp {Data Type} build-machine
655 This data type represents build machines the daemon may offload builds
656 to. The important fields are:
661 The remote machine's host name.
664 The remote machine's system type---e.g., @code{"x86_64-linux"}.
667 The user account to use when connecting to the remote machine over SSH.
668 Note that the SSH key pair must @emph{not} be passphrase-protected, to
669 allow non-interactive logins.
673 A number of optional fields may be specified:
678 Port number of the machine's SSH server (default: 22).
681 The SSH private key file to use when connecting to the machine.
683 Currently offloading uses GNU@tie{}lsh as its SSH client
684 (@pxref{Invoking lsh,,, GNU lsh Manual}). Thus, the key file here must
685 be an lsh key file. This may change in the future, though.
687 @item parallel-builds
688 The number of builds that may run in parallel on the machine (1 by
692 A ``relative speed factor''. The offload scheduler will tend to prefer
693 machines with a higher speed factor.
696 A list of strings denoting specific features supported by the machine.
697 An example is @code{"kvm"} for machines that have the KVM Linux modules
698 and corresponding hardware support. Derivations can request features by
699 name, and they will be scheduled on matching build machines.
704 The @code{guix} command must be in the search path on the build
705 machines, since offloading works by invoking the @code{guix archive} and
706 @code{guix build} commands. In addition, the Guix modules must be in
707 @code{$GUILE_LOAD_PATH} on the build machine---you can check whether
708 this is the case by running:
711 lsh build-machine guile -c '(use-modules (guix config))'
714 There's one last thing to do once @file{machines.scm} is in place. As
715 explained above, when offloading, files are transferred back and forth
716 between the machine stores. For this to work, you first need to
717 generate a key pair on each machine to allow the daemon to export signed
718 archives of files from the store (@pxref{Invoking guix archive}):
721 # guix archive --generate-key
725 Each build machine must authorize the key of the master machine so that
726 it accepts store items it receives from the master:
729 # guix archive --authorize < master-public-key.txt
733 Likewise, the master machine must authorize the key of each build machine.
735 All the fuss with keys is here to express pairwise mutual trust
736 relations between the master and the build machines. Concretely, when
737 the master receives files from a build machine (and @i{vice versa}), its
738 build daemon can make sure they are genuine, have not been tampered
739 with, and that they are signed by an authorized key.
742 @node Invoking guix-daemon
743 @section Invoking @command{guix-daemon}
745 The @command{guix-daemon} program implements all the functionality to
746 access the store. This includes launching build processes, running the
747 garbage collector, querying the availability of a build result, etc. It
748 is normally run as @code{root} like this:
751 # guix-daemon --build-users-group=guixbuild
755 For details on how to set it up, @pxref{Setting Up the Daemon}.
758 @cindex container, build environment
759 @cindex build environment
760 @cindex reproducible builds
761 By default, @command{guix-daemon} launches build processes under
762 different UIDs, taken from the build group specified with
763 @code{--build-users-group}. In addition, each build process is run in a
764 chroot environment that only contains the subset of the store that the
765 build process depends on, as specified by its derivation
766 (@pxref{Programming Interface, derivation}), plus a set of specific
767 system directories. By default, the latter contains @file{/dev} and
768 @file{/dev/pts}. Furthermore, on GNU/Linux, the build environment is a
769 @dfn{container}: in addition to having its own file system tree, it has
770 a separate mount name space, its own PID name space, network name space,
771 etc. This helps achieve reproducible builds (@pxref{Features}).
773 When the daemon performs a build on behalf of the user, it creates a
774 build directory under @file{/tmp} or under the directory specified by
775 its @code{TMPDIR} environment variable; this directory is shared with
776 the container for the duration of the build. Be aware that using a
777 directory other than @file{/tmp} can affect build results---for example,
778 with a longer directory name, a build process that uses Unix-domain
779 sockets might hit the name length limitation for @code{sun_path}, which
780 it would otherwise not hit.
782 The build directory is automatically deleted upon completion, unless the
783 build failed and the client specified @option{--keep-failed}
784 (@pxref{Invoking guix build, @option{--keep-failed}}).
786 The following command-line options are supported:
789 @item --build-users-group=@var{group}
790 Take users from @var{group} to run build processes (@pxref{Setting Up
791 the Daemon, build users}).
793 @item --no-substitutes
795 Do not use substitutes for build products. That is, always build things
796 locally instead of allowing downloads of pre-built binaries
797 (@pxref{Substitutes}).
799 By default substitutes are used, unless the client---such as the
800 @command{guix package} command---is explicitly invoked with
801 @code{--no-substitutes}.
803 When the daemon runs with @code{--no-substitutes}, clients can still
804 explicitly enable substitution @i{via} the @code{set-build-options}
805 remote procedure call (@pxref{The Store}).
807 @item --substitute-urls=@var{urls}
808 @anchor{daemon-substitute-urls}
809 Consider @var{urls} the default whitespace-separated list of substitute
810 source URLs. When this option is omitted, @indicateurl{http://hydra.gnu.org}
813 This means that substitutes may be downloaded from @var{urls}, as long
814 as they are signed by a trusted signature (@pxref{Substitutes}).
817 @item --no-build-hook
818 Do not use the @dfn{build hook}.
820 The build hook is a helper program that the daemon can start and to
821 which it submits build requests. This mechanism is used to offload
822 builds to other machines (@pxref{Daemon Offload Setup}).
824 @item --cache-failures
825 Cache build failures. By default, only successful builds are cached.
827 When this option is used, @command{guix gc --list-failures} can be used
828 to query the set of store items marked as failed; @command{guix gc
829 --clear-failures} removes store items from the set of cached failures.
830 @xref{Invoking guix gc}.
832 @item --cores=@var{n}
834 Use @var{n} CPU cores to build each derivation; @code{0} means as many
837 The default value is @code{0}, but it may be overridden by clients, such
838 as the @code{--cores} option of @command{guix build} (@pxref{Invoking
841 The effect is to define the @code{NIX_BUILD_CORES} environment variable
842 in the build process, which can then use it to exploit internal
843 parallelism---for instance, by running @code{make -j$NIX_BUILD_CORES}.
845 @item --max-jobs=@var{n}
847 Allow at most @var{n} build jobs in parallel. The default value is
848 @code{1}. Setting it to @code{0} means that no builds will be performed
849 locally; instead, the daemon will offload builds (@pxref{Daemon Offload
850 Setup}), or simply fail.
853 Produce debugging output.
855 This is useful to debug daemon start-up issues, but then it may be
856 overridden by clients, for example the @code{--verbosity} option of
857 @command{guix build} (@pxref{Invoking guix build}).
859 @item --chroot-directory=@var{dir}
860 Add @var{dir} to the build chroot.
862 Doing this may change the result of build processes---for instance if
863 they use optional dependencies found in @var{dir} when it is available,
864 and not otherwise. For that reason, it is not recommended to do so.
865 Instead, make sure that each derivation declares all the inputs that it
868 @item --disable-chroot
869 Disable chroot builds.
871 Using this option is not recommended since, again, it would allow build
872 processes to gain access to undeclared dependencies. It is necessary,
873 though, when @command{guix-daemon} is running under an unprivileged user
876 @item --disable-log-compression
877 Disable compression of the build logs.
879 Unless @code{--lose-logs} is used, all the build logs are kept in the
880 @var{localstatedir}. To save space, the daemon automatically compresses
881 them with bzip2 by default. This option disables that.
883 @item --disable-deduplication
884 @cindex deduplication
885 Disable automatic file ``deduplication'' in the store.
887 By default, files added to the store are automatically ``deduplicated'':
888 if a newly added file is identical to another one found in the store,
889 the daemon makes the new file a hard link to the other file. This can
890 noticeably reduce disk usage, at the expense of slightly increased
891 input/output load at the end of a build process. This option disables
894 @item --gc-keep-outputs[=yes|no]
895 Tell whether the garbage collector (GC) must keep outputs of live
898 When set to ``yes'', the GC will keep the outputs of any live derivation
899 available in the store---the @code{.drv} files. The default is ``no'',
900 meaning that derivation outputs are kept only if they are GC roots.
902 @item --gc-keep-derivations[=yes|no]
903 Tell whether the garbage collector (GC) must keep derivations
904 corresponding to live outputs.
906 When set to ``yes'', as is the case by default, the GC keeps
907 derivations---i.e., @code{.drv} files---as long as at least one of their
908 outputs is live. This allows users to keep track of the origins of
909 items in their store. Setting it to ``no'' saves a bit of disk space.
911 Note that when both @code{--gc-keep-derivations} and
912 @code{--gc-keep-outputs} are used, the effect is to keep all the build
913 prerequisites (the sources, compiler, libraries, and other build-time
914 tools) of live objects in the store, regardless of whether these
915 prerequisites are live. This is convenient for developers since it
916 saves rebuilds or downloads.
918 @item --impersonate-linux-2.6
919 On Linux-based systems, impersonate Linux 2.6. This means that the
920 kernel's @code{uname} system call will report 2.6 as the release number.
922 This might be helpful to build programs that (usually wrongfully) depend
923 on the kernel version number.
926 Do not keep build logs. By default they are kept under
927 @code{@var{localstatedir}/guix/log}.
929 @item --system=@var{system}
930 Assume @var{system} as the current system type. By default it is the
931 architecture/kernel pair found at configure time, such as
934 @item --listen=@var{socket}
935 Listen for connections on @var{socket}, the file name of a Unix-domain
936 socket. The default socket is
937 @file{@var{localstatedir}/daemon-socket/socket}. This option is only
938 useful in exceptional circumstances, such as if you need to run several
939 daemons on the same machine.
943 @node Application Setup
944 @section Application Setup
946 When using Guix on top of GNU/Linux distribution other than GuixSD---a
947 so-called @dfn{foreign distro}---a few additional steps are needed to
948 get everything in place. Here are some of them.
952 @anchor{locales-and-locpath}
953 @cindex locales, when not on GuixSD
956 Packages installed @i{via} Guix will not use the host system's locale
957 data. Instead, you must first install one of the locale packages
958 available with Guix and then define the @code{GUIX_LOCPATH} environment
962 $ guix package -i glibc-locales
963 $ export GUIX_LOCPATH=$HOME/.guix-profile/lib/locale
966 Note that the @code{glibc-locales} package contains data for all the
967 locales supported by the GNU@tie{}libc and weighs in at around
968 110@tie{}MiB. Alternately, the @code{glibc-utf8-locales} is smaller but
969 limited to a few UTF-8 locales.
971 The @code{GUIX_LOCPATH} variable plays a role similar to @code{LOCPATH}
972 (@pxref{Locale Names, @code{LOCPATH},, libc, The GNU C Library Reference
973 Manual}). There are two important differences though:
977 @code{GUIX_LOCPATH} is honored only by Guix's libc, and not by the libc
978 provided by foreign distros. Thus, using @code{GUIX_LOCPATH} allows you
979 to make sure the the foreign distro's programs will not end up loading
980 incompatible locale data.
983 libc suffixes each entry of @code{GUIX_LOCPATH} with @code{/X.Y}, where
984 @code{X.Y} is the libc version---e.g., @code{2.22}. This means that,
985 should your Guix profile contain a mixture of programs linked against
986 different libc version, each libc version will only try to load locale
987 data in the right format.
990 This is important because the locale data format used by different libc
991 versions may be incompatible.
993 @subsection X11 Fonts
995 The majority of graphical applications use Fontconfig to locate and
996 load fonts and perform X11-client-side rendering. Guix's
997 @code{fontconfig} package looks for fonts in @file{$HOME/.guix-profile}
998 by default. Thus, to allow graphical applications installed with Guix
999 to display fonts, you will have to install fonts with Guix as well.
1000 Essential font packages include @code{gs-fonts}, @code{font-dejavu}, and
1001 @code{font-gnu-freefont-ttf}.
1003 To display text written in Chinese languages, Japanese, or Korean in
1004 graphical applications, consider installing
1005 @code{font-adobe-source-han-sans} or @code{font-wqy-zenhei}. The former
1006 has multiple outputs, one per language family (@pxref{Packages with
1007 Multiple Outputs}). For instance, the following command installs fonts
1008 for Chinese languages:
1011 guix package -i font-adobe-source-han-sans:cn
1016 @c *********************************************************************
1017 @node Package Management
1018 @chapter Package Management
1020 The purpose of GNU Guix is to allow users to easily install, upgrade, and
1021 remove software packages, without having to know about their build
1022 procedure or dependencies. Guix also goes beyond this obvious set of
1025 This chapter describes the main features of Guix, as well as the package
1026 management tools it provides. Two user interfaces are provided for
1027 routine package management tasks: A command-line interface described below
1028 (@pxref{Invoking guix package, @code{guix package}}), as well as a visual user
1029 interface in Emacs described in a subsequent chapter (@pxref{Emacs Interface}).
1032 * Features:: How Guix will make your life brighter.
1033 * Invoking guix package:: Package installation, removal, etc.
1034 * Substitutes:: Downloading pre-built binaries.
1035 * Packages with Multiple Outputs:: Single source package, multiple outputs.
1036 * Invoking guix gc:: Running the garbage collector.
1037 * Invoking guix pull:: Fetching the latest Guix and distribution.
1038 * Invoking guix archive:: Exporting and importing store files.
1044 When using Guix, each package ends up in the @dfn{package store}, in its
1045 own directory---something that resembles
1046 @file{/gnu/store/xxx-package-1.2}, where @code{xxx} is a base32 string
1047 (note that Guix comes with an Emacs extension to shorten those file
1048 names, @pxref{Emacs Prettify}.)
1050 Instead of referring to these directories, users have their own
1051 @dfn{profile}, which points to the packages that they actually want to
1052 use. These profiles are stored within each user's home directory, at
1053 @code{$HOME/.guix-profile}.
1055 For example, @code{alice} installs GCC 4.7.2. As a result,
1056 @file{/home/alice/.guix-profile/bin/gcc} points to
1057 @file{/gnu/store/@dots{}-gcc-4.7.2/bin/gcc}. Now, on the same machine,
1058 @code{bob} had already installed GCC 4.8.0. The profile of @code{bob}
1059 simply continues to point to
1060 @file{/gnu/store/@dots{}-gcc-4.8.0/bin/gcc}---i.e., both versions of GCC
1061 coexist on the same system without any interference.
1063 The @command{guix package} command is the central tool to manage
1064 packages (@pxref{Invoking guix package}). It operates on those per-user
1065 profiles, and can be used @emph{with normal user privileges}.
1067 The command provides the obvious install, remove, and upgrade
1068 operations. Each invocation is actually a @emph{transaction}: either
1069 the specified operation succeeds, or nothing happens. Thus, if the
1070 @command{guix package} process is terminated during the transaction,
1071 or if a power outage occurs during the transaction, then the user's
1072 profile remains in its previous state, and remains usable.
1074 In addition, any package transaction may be @emph{rolled back}. So, if,
1075 for example, an upgrade installs a new version of a package that turns
1076 out to have a serious bug, users may roll back to the previous instance
1077 of their profile, which was known to work well. Similarly, the global
1078 system configuration is subject to transactional upgrades and roll-back
1079 (@pxref{Using the Configuration System}).
1081 All those packages in the package store may be @emph{garbage-collected}.
1082 Guix can determine which packages are still referenced by the user
1083 profiles, and remove those that are provably no longer referenced
1084 (@pxref{Invoking guix gc}). Users may also explicitly remove old
1085 generations of their profile so that the packages they refer to can be
1088 @cindex reproducibility
1089 @cindex reproducible builds
1090 Finally, Guix takes a @dfn{purely functional} approach to package
1091 management, as described in the introduction (@pxref{Introduction}).
1092 Each @file{/gnu/store} package directory name contains a hash of all the
1093 inputs that were used to build that package---compiler, libraries, build
1094 scripts, etc. This direct correspondence allows users to make sure a
1095 given package installation matches the current state of their
1096 distribution. It also helps maximize @dfn{build reproducibility}:
1097 thanks to the isolated build environments that are used, a given build
1098 is likely to yield bit-identical files when performed on different
1099 machines (@pxref{Invoking guix-daemon, container}).
1102 This foundation allows Guix to support @dfn{transparent binary/source
1103 deployment}. When a pre-built binary for a @file{/gnu/store} item is
1104 available from an external source---a @dfn{substitute}, Guix just
1105 downloads it and unpacks it;
1106 otherwise, it builds the package from source, locally
1107 (@pxref{Substitutes}).
1109 Control over the build environment is a feature that is also useful for
1110 developers. The @command{guix environment} command allows developers of
1111 a package to quickly set up the right development environment for their
1112 package, without having to manually install the package's dependencies
1113 in their profile (@pxref{Invoking guix environment}).
1115 @node Invoking guix package
1116 @section Invoking @command{guix package}
1118 The @command{guix package} command is the tool that allows users to
1119 install, upgrade, and remove packages, as well as rolling back to
1120 previous configurations. It operates only on the user's own profile,
1121 and works with normal user privileges (@pxref{Features}). Its syntax
1125 guix package @var{options}
1128 Primarily, @var{options} specifies the operations to be performed during
1129 the transaction. Upon completion, a new profile is created, but
1130 previous @dfn{generations} of the profile remain available, should the user
1133 For example, to remove @code{lua} and install @code{guile} and
1134 @code{guile-cairo} in a single transaction:
1137 guix package -r lua -i guile guile-cairo
1140 @command{guix package} also supports a @dfn{declarative approach}
1141 whereby the user specifies the exact set of packages to be available and
1142 passes it @i{via} the @option{--manifest} option
1143 (@pxref{profile-manifest, @option{--manifest}}).
1145 For each user, a symlink to the user's default profile is automatically
1146 created in @file{$HOME/.guix-profile}. This symlink always points to the
1147 current generation of the user's default profile. Thus, users can add
1148 @file{$HOME/.guix-profile/bin} to their @code{PATH} environment
1149 variable, and so on.
1150 @cindex search paths
1151 If you are not using the Guix System Distribution, consider adding the
1152 following lines to your @file{~/.bash_profile} (@pxref{Bash Startup
1153 Files,,, bash, The GNU Bash Reference Manual}) so that newly-spawned
1154 shells get all the right environment variable definitions:
1157 GUIX_PROFILE="$HOME/.guix-profile" \
1158 source "$HOME/.guix-profile/etc/profile"
1161 In a multi-user setup, user profiles are stored in a place registered as
1162 a @dfn{garbage-collector root}, which @file{$HOME/.guix-profile} points
1163 to (@pxref{Invoking guix gc}). That directory is normally
1164 @code{@var{localstatedir}/profiles/per-user/@var{user}}, where
1165 @var{localstatedir} is the value passed to @code{configure} as
1166 @code{--localstatedir}, and @var{user} is the user name. The
1167 @file{per-user} directory is created when @command{guix-daemon} is
1168 started, and the @var{user} sub-directory is created by @command{guix
1171 The @var{options} can be among the following:
1175 @item --install=@var{package} @dots{}
1176 @itemx -i @var{package} @dots{}
1177 Install the specified @var{package}s.
1179 Each @var{package} may specify either a simple package name, such as
1180 @code{guile}, or a package name followed by a hyphen and version number,
1181 such as @code{guile-1.8.8} or simply @code{guile-1.8} (in the latter
1182 case, the newest version prefixed by @code{1.8} is selected.)
1184 If no version number is specified, the
1185 newest available version will be selected. In addition, @var{package}
1186 may contain a colon, followed by the name of one of the outputs of the
1187 package, as in @code{gcc:doc} or @code{binutils-2.22:lib}
1188 (@pxref{Packages with Multiple Outputs}). Packages with a corresponding
1189 name (and optionally version) are searched for among the GNU
1190 distribution modules (@pxref{Package Modules}).
1192 @cindex propagated inputs
1193 Sometimes packages have @dfn{propagated inputs}: these are dependencies
1194 that automatically get installed along with the required package
1195 (@pxref{package-propagated-inputs, @code{propagated-inputs} in
1196 @code{package} objects}, for information about propagated inputs in
1197 package definitions).
1199 @anchor{package-cmd-propagated-inputs}
1200 An example is the GNU MPC library: its C header files refer to those of
1201 the GNU MPFR library, which in turn refer to those of the GMP library.
1202 Thus, when installing MPC, the MPFR and GMP libraries also get installed
1203 in the profile; removing MPC also removes MPFR and GMP---unless they had
1204 also been explicitly installed independently.
1206 Besides, packages sometimes rely on the definition of environment
1207 variables for their search paths (see explanation of
1208 @code{--search-paths} below). Any missing or possibly incorrect
1209 environment variable definitions are reported here.
1211 @c XXX: keep me up-to-date
1212 Finally, when installing a GNU package, the tool reports the
1213 availability of a newer upstream version. In the future, it may provide
1214 the option of installing directly from the upstream version, even if
1215 that version is not yet in the distribution.
1217 @item --install-from-expression=@var{exp}
1219 Install the package @var{exp} evaluates to.
1221 @var{exp} must be a Scheme expression that evaluates to a
1222 @code{<package>} object. This option is notably useful to disambiguate
1223 between same-named variants of a package, with expressions such as
1224 @code{(@@ (gnu packages base) guile-final)}.
1226 Note that this option installs the first output of the specified
1227 package, which may be insufficient when needing a specific output of a
1228 multiple-output package.
1230 @item --install-from-file=@var{file}
1231 @itemx -f @var{file}
1232 Install the package that the code within @var{file} evaluates to.
1234 As an example, @var{file} might contain a definition like this
1235 (@pxref{Defining Packages}):
1238 @verbatiminclude package-hello.scm
1241 Developers may find it useful to include such a @file{package.scm} file
1242 in the root of their project's source tree that can be used to test
1243 development snapshots and create reproducible development environments
1244 (@pxref{Invoking guix environment}).
1246 @item --remove=@var{package} @dots{}
1247 @itemx -r @var{package} @dots{}
1248 Remove the specified @var{package}s.
1250 As for @code{--install}, each @var{package} may specify a version number
1251 and/or output name in addition to the package name. For instance,
1252 @code{-r glibc:debug} would remove the @code{debug} output of
1255 @item --upgrade[=@var{regexp} @dots{}]
1256 @itemx -u [@var{regexp} @dots{}]
1257 Upgrade all the installed packages. If one or more @var{regexp}s are
1258 specified, upgrade only installed packages whose name matches a
1259 @var{regexp}. Also see the @code{--do-not-upgrade} option below.
1261 Note that this upgrades package to the latest version of packages found
1262 in the distribution currently installed. To update your distribution,
1263 you should regularly run @command{guix pull} (@pxref{Invoking guix
1266 @item --do-not-upgrade[=@var{regexp} @dots{}]
1267 When used together with the @code{--upgrade} option, do @emph{not}
1268 upgrade any packages whose name matches a @var{regexp}. For example, to
1269 upgrade all packages in the current profile except those containing the
1270 substring ``emacs'':
1273 $ guix package --upgrade . --do-not-upgrade emacs
1276 @item @anchor{profile-manifest}--manifest=@var{file}
1277 @itemx -m @var{file}
1278 @cindex profile declaration
1279 @cindex profile manifest
1280 Create a new generation of the profile from the manifest object
1281 returned by the Scheme code in @var{file}.
1283 This allows you to @emph{declare} the profile's contents rather than
1284 constructing it through a sequence of @code{--install} and similar
1285 commands. The advantage is that @var{file} can be put under version
1286 control, copied to different machines to reproduce the same profile, and
1289 @c FIXME: Add reference to (guix profile) documentation when available.
1290 @var{file} must return a @dfn{manifest} object, which is roughly a list
1293 @findex packages->manifest
1295 (use-package-modules guile emacs)
1300 ;; Use a specific package output.
1301 (list guile-2.0 "debug")))
1305 Roll back to the previous @dfn{generation} of the profile---i.e., undo
1306 the last transaction.
1308 When combined with options such as @code{--install}, roll back occurs
1309 before any other actions.
1311 When rolling back from the first generation that actually contains
1312 installed packages, the profile is made to point to the @dfn{zeroth
1313 generation}, which contains no files apart from its own meta-data.
1315 Installing, removing, or upgrading packages from a generation that has
1316 been rolled back to overwrites previous future generations. Thus, the
1317 history of a profile's generations is always linear.
1319 @item --switch-generation=@var{pattern}
1320 @itemx -S @var{pattern}
1321 Switch to a particular generation defined by @var{pattern}.
1323 @var{pattern} may be either a generation number or a number prefixed
1324 with ``+'' or ``-''. The latter means: move forward/backward by a
1325 specified number of generations. For example, if you want to return to
1326 the latest generation after @code{--roll-back}, use
1327 @code{--switch-generation=+1}.
1329 The difference between @code{--roll-back} and
1330 @code{--switch-generation=-1} is that @code{--switch-generation} will
1331 not make a zeroth generation, so if a specified generation does not
1332 exist, the current generation will not be changed.
1334 @item --search-paths[=@var{kind}]
1335 @cindex search paths
1336 Report environment variable definitions, in Bash syntax, that may be
1337 needed in order to use the set of installed packages. These environment
1338 variables are used to specify @dfn{search paths} for files used by some
1339 of the installed packages.
1341 For example, GCC needs the @code{CPATH} and @code{LIBRARY_PATH}
1342 environment variables to be defined so it can look for headers and
1343 libraries in the user's profile (@pxref{Environment Variables,,, gcc,
1344 Using the GNU Compiler Collection (GCC)}). If GCC and, say, the C
1345 library are installed in the profile, then @code{--search-paths} will
1346 suggest setting these variables to @code{@var{profile}/include} and
1347 @code{@var{profile}/lib}, respectively.
1349 The typical use case is to define these environment variables in the
1353 $ eval `guix package --search-paths`
1356 @var{kind} may be one of @code{exact}, @code{prefix}, or @code{suffix},
1357 meaning that the returned environment variable definitions will either
1358 be exact settings, or prefixes or suffixes of the current value of these
1359 variables. When omitted, @var{kind} defaults to @code{exact}.
1361 This option can also be used to compute the @emph{combined} search paths
1362 of several profiles. Consider this example:
1365 $ guix package -p foo -i guile
1366 $ guix package -p bar -i guile-json
1367 $ guix package -p foo -p bar --search-paths
1370 The last command above reports about the @code{GUILE_LOAD_PATH}
1371 variable, even though, taken individually, neither @file{foo} nor
1372 @file{bar} would lead to that recommendation.
1375 @item --profile=@var{profile}
1376 @itemx -p @var{profile}
1377 Use @var{profile} instead of the user's default profile.
1380 Produce verbose output. In particular, emit the environment's build log
1381 on the standard error port.
1384 Use the bootstrap Guile to build the profile. This option is only
1385 useful to distribution developers.
1389 In addition to these actions @command{guix package} supports the
1390 following options to query the current state of a profile, or the
1391 availability of packages:
1395 @item --search=@var{regexp}
1396 @itemx -s @var{regexp}
1397 List the available packages whose name, synopsis, or description matches
1398 @var{regexp}. Print all the meta-data of matching packages in
1399 @code{recutils} format (@pxref{Top, GNU recutils databases,, recutils,
1400 GNU recutils manual}).
1402 This allows specific fields to be extracted using the @command{recsel}
1403 command, for instance:
1406 $ guix package -s malloc | recsel -p name,version
1414 Similarly, to show the name of all the packages available under the
1415 terms of the GNU@tie{}LGPL version 3:
1418 $ guix package -s "" | recsel -p name -e 'license ~ "LGPL 3"'
1425 @item --show=@var{package}
1426 Show details about @var{package}, taken from the list of available packages, in
1427 @code{recutils} format (@pxref{Top, GNU recutils databases,, recutils, GNU
1431 $ guix package --show=python | recsel -p name,version
1439 You may also specify the full name of a package to only get details about a
1440 specific version of it:
1442 $ guix package --show=python-3.3.5 | recsel -p name,version
1449 @item --list-installed[=@var{regexp}]
1450 @itemx -I [@var{regexp}]
1451 List the currently installed packages in the specified profile, with the
1452 most recently installed packages shown last. When @var{regexp} is
1453 specified, list only installed packages whose name matches @var{regexp}.
1455 For each installed package, print the following items, separated by
1456 tabs: the package name, its version string, the part of the package that
1457 is installed (for instance, @code{out} for the default output,
1458 @code{include} for its headers, etc.), and the path of this package in
1461 @item --list-available[=@var{regexp}]
1462 @itemx -A [@var{regexp}]
1463 List packages currently available in the distribution for this system
1464 (@pxref{GNU Distribution}). When @var{regexp} is specified, list only
1465 installed packages whose name matches @var{regexp}.
1467 For each package, print the following items separated by tabs: its name,
1468 its version string, the parts of the package (@pxref{Packages with
1469 Multiple Outputs}), and the source location of its definition.
1471 @item --list-generations[=@var{pattern}]
1472 @itemx -l [@var{pattern}]
1473 Return a list of generations along with their creation dates; for each
1474 generation, show the installed packages, with the most recently
1475 installed packages shown last. Note that the zeroth generation is never
1478 For each installed package, print the following items, separated by
1479 tabs: the name of a package, its version string, the part of the package
1480 that is installed (@pxref{Packages with Multiple Outputs}), and the
1481 location of this package in the store.
1483 When @var{pattern} is used, the command returns only matching
1484 generations. Valid patterns include:
1487 @item @emph{Integers and comma-separated integers}. Both patterns denote
1488 generation numbers. For instance, @code{--list-generations=1} returns
1491 And @code{--list-generations=1,8,2} outputs three generations in the
1492 specified order. Neither spaces nor trailing commas are allowed.
1494 @item @emph{Ranges}. @code{--list-generations=2..9} prints the
1495 specified generations and everything in between. Note that the start of
1496 a range must be lesser than its end.
1498 It is also possible to omit the endpoint. For example,
1499 @code{--list-generations=2..}, returns all generations starting from the
1502 @item @emph{Durations}. You can also get the last @emph{N}@tie{}days, weeks,
1503 or months by passing an integer along with the first letter of the
1504 duration. For example, @code{--list-generations=20d} lists generations
1505 that are up to 20 days old.
1508 @item --delete-generations[=@var{pattern}]
1509 @itemx -d [@var{pattern}]
1510 When @var{pattern} is omitted, delete all generations except the current
1513 This command accepts the same patterns as @option{--list-generations}.
1514 When @var{pattern} is specified, delete the matching generations. When
1515 @var{pattern} specifies a duration, generations @emph{older} than the
1516 specified duration match. For instance, @code{--delete-generations=1m}
1517 deletes generations that are more than one month old.
1519 If the current generation matches, it is @emph{not} deleted. Also, the
1520 zeroth generation is never deleted.
1522 Note that deleting generations prevents roll-back to them.
1523 Consequently, this command must be used with care.
1527 Finally, since @command{guix package} may actually start build
1528 processes, it supports all the common build options that @command{guix
1529 build} supports (@pxref{Invoking guix build, common build options}).
1532 @section Substitutes
1535 @cindex pre-built binaries
1536 Guix supports transparent source/binary deployment, which means that it
1537 can either build things locally, or download pre-built items from a
1538 server. We call these pre-built items @dfn{substitutes}---they are
1539 substitutes for local build results. In many cases, downloading a
1540 substitute is much faster than building things locally.
1542 Substitutes can be anything resulting from a derivation build
1543 (@pxref{Derivations}). Of course, in the common case, they are
1544 pre-built package binaries, but source tarballs, for instance, which
1545 also result from derivation builds, can be available as substitutes.
1547 The @code{hydra.gnu.org} server is a front-end to a build farm that
1548 builds packages from the GNU distribution continuously for some
1549 architectures, and makes them available as substitutes. This is the
1550 default source of substitutes; it can be overridden by passing the
1551 @option{--substitute-urls} option either to @command{guix-daemon}
1552 (@pxref{daemon-substitute-urls,, @code{guix-daemon --substitute-urls}})
1553 or to client tools such as @command{guix package}
1554 (@pxref{client-substitute-urls,, client @option{--substitute-urls}
1558 @cindex digital signatures
1559 To allow Guix to download substitutes from @code{hydra.gnu.org}, you
1560 must add its public key to the access control list (ACL) of archive
1561 imports, using the @command{guix archive} command (@pxref{Invoking guix
1562 archive}). Doing so implies that you trust @code{hydra.gnu.org} to not
1563 be compromised and to serve genuine substitutes.
1565 This public key is installed along with Guix, in
1566 @code{@var{prefix}/share/guix/hydra.gnu.org.pub}, where @var{prefix} is
1567 the installation prefix of Guix. If you installed Guix from source,
1568 make sure you checked the GPG signature of
1569 @file{guix-@value{VERSION}.tar.gz}, which contains this public key file.
1570 Then, you can run something like this:
1573 # guix archive --authorize < hydra.gnu.org.pub
1576 Once this is in place, the output of a command like @code{guix build}
1577 should change from something like:
1580 $ guix build emacs --dry-run
1581 The following derivations would be built:
1582 /gnu/store/yr7bnx8xwcayd6j95r2clmkdl1qh688w-emacs-24.3.drv
1583 /gnu/store/x8qsh1hlhgjx6cwsjyvybnfv2i37z23w-dbus-1.6.4.tar.gz.drv
1584 /gnu/store/1ixwp12fl950d15h2cj11c73733jay0z-alsa-lib-1.0.27.1.tar.bz2.drv
1585 /gnu/store/nlma1pw0p603fpfiqy7kn4zm105r5dmw-util-linux-2.21.drv
1593 $ guix build emacs --dry-run
1594 The following files would be downloaded:
1595 /gnu/store/pk3n22lbq6ydamyymqkkz7i69wiwjiwi-emacs-24.3
1596 /gnu/store/2ygn4ncnhrpr61rssa6z0d9x22si0va3-libjpeg-8d
1597 /gnu/store/71yz6lgx4dazma9dwn2mcjxaah9w77jq-cairo-1.12.16
1598 /gnu/store/7zdhgp0n1518lvfn8mb96sxqfmvqrl7v-libxrender-0.9.7
1603 This indicates that substitutes from @code{hydra.gnu.org} are usable and
1604 will be downloaded, when possible, for future builds.
1606 Guix ignores substitutes that are not signed, or that are not signed by
1607 one of the keys listed in the ACL. It also detects and raises an error
1608 when attempting to use a substitute that has been tampered with.
1610 The substitute mechanism can be disabled globally by running
1611 @code{guix-daemon} with @code{--no-substitutes} (@pxref{Invoking
1612 guix-daemon}). It can also be disabled temporarily by passing the
1613 @code{--no-substitutes} option to @command{guix package}, @command{guix
1614 build}, and other command-line tools.
1617 Today, each individual's control over their own computing is at the
1618 mercy of institutions, corporations, and groups with enough power and
1619 determination to subvert the computing infrastructure and exploit its
1620 weaknesses. While using @code{hydra.gnu.org} substitutes can be
1621 convenient, we encourage users to also build on their own, or even run
1622 their own build farm, such that @code{hydra.gnu.org} is less of an
1623 interesting target. One way to help is by publishing the software you
1624 build using @command{guix publish} so that others have one more choice
1625 of server to download substitutes from (@pxref{Invoking guix publish}).
1627 Guix has the foundations to maximize build reproducibility
1628 (@pxref{Features}). In most cases, independent builds of a given
1629 package or derivation should yield bit-identical results. Thus, through
1630 a diverse set of independent package builds, we can strengthen the
1631 integrity of our systems. The @command{guix challenge} command aims to
1632 help users assess substitute servers, and to assist developers in
1633 finding out about non-deterministic package builds (@pxref{Invoking guix
1636 In the future, we want Guix to have support to publish and retrieve
1637 binaries to/from other users, in a peer-to-peer fashion. If you would
1638 like to discuss this project, join us on @email{guix-devel@@gnu.org}.
1641 @node Packages with Multiple Outputs
1642 @section Packages with Multiple Outputs
1644 @cindex multiple-output packages
1645 @cindex package outputs
1647 Often, packages defined in Guix have a single @dfn{output}---i.e., the
1648 source package leads exactly one directory in the store. When running
1649 @command{guix package -i glibc}, one installs the default output of the
1650 GNU libc package; the default output is called @code{out}, but its name
1651 can be omitted as shown in this command. In this particular case, the
1652 default output of @code{glibc} contains all the C header files, shared
1653 libraries, static libraries, Info documentation, and other supporting
1656 Sometimes it is more appropriate to separate the various types of files
1657 produced from a single source package into separate outputs. For
1658 instance, the GLib C library (used by GTK+ and related packages)
1659 installs more than 20 MiB of reference documentation as HTML pages.
1660 To save space for users who do not need it, the documentation goes to a
1661 separate output, called @code{doc}. To install the main GLib output,
1662 which contains everything but the documentation, one would run:
1665 guix package -i glib
1668 The command to install its documentation is:
1671 guix package -i glib:doc
1674 Some packages install programs with different ``dependency footprints''.
1675 For instance, the WordNet package install both command-line tools and
1676 graphical user interfaces (GUIs). The former depend solely on the C
1677 library, whereas the latter depend on Tcl/Tk and the underlying X
1678 libraries. In this case, we leave the command-line tools in the default
1679 output, whereas the GUIs are in a separate output. This allows users
1680 who do not need the GUIs to save space. The @command{guix size} command
1681 can help find out about such situations (@pxref{Invoking guix size}).
1682 @command{guix graph} can also be helpful (@pxref{Invoking guix graph}).
1684 There are several such multiple-output packages in the GNU distribution.
1685 Other conventional output names include @code{lib} for libraries and
1686 possibly header files, @code{bin} for stand-alone programs, and
1687 @code{debug} for debugging information (@pxref{Installing Debugging
1688 Files}). The outputs of a packages are listed in the third column of
1689 the output of @command{guix package --list-available} (@pxref{Invoking
1693 @node Invoking guix gc
1694 @section Invoking @command{guix gc}
1696 @cindex garbage collector
1697 Packages that are installed but not used may be @dfn{garbage-collected}.
1698 The @command{guix gc} command allows users to explicitly run the garbage
1699 collector to reclaim space from the @file{/gnu/store} directory. It is
1700 the @emph{only} way to remove files from @file{/gnu/store}---removing
1701 files or directories manually may break it beyond repair!
1703 The garbage collector has a set of known @dfn{roots}: any file under
1704 @file{/gnu/store} reachable from a root is considered @dfn{live} and
1705 cannot be deleted; any other file is considered @dfn{dead} and may be
1706 deleted. The set of garbage collector roots includes default user
1707 profiles, and may be augmented with @command{guix build --root}, for
1708 example (@pxref{Invoking guix build}).
1710 Prior to running @code{guix gc --collect-garbage} to make space, it is
1711 often useful to remove old generations from user profiles; that way, old
1712 package builds referenced by those generations can be reclaimed. This
1713 is achieved by running @code{guix package --delete-generations}
1714 (@pxref{Invoking guix package}).
1716 The @command{guix gc} command has three modes of operation: it can be
1717 used to garbage-collect any dead files (the default), to delete specific
1718 files (the @code{--delete} option), to print garbage-collector
1719 information, or for more advanced queries. The garbage collection
1720 options are as follows:
1723 @item --collect-garbage[=@var{min}]
1724 @itemx -C [@var{min}]
1725 Collect garbage---i.e., unreachable @file{/gnu/store} files and
1726 sub-directories. This is the default operation when no option is
1729 When @var{min} is given, stop once @var{min} bytes have been collected.
1730 @var{min} may be a number of bytes, or it may include a unit as a
1731 suffix, such as @code{MiB} for mebibytes and @code{GB} for gigabytes
1732 (@pxref{Block size, size specifications,, coreutils, GNU Coreutils}).
1734 When @var{min} is omitted, collect all the garbage.
1738 Attempt to delete all the store files and directories specified as
1739 arguments. This fails if some of the files are not in the store, or if
1740 they are still live.
1742 @item --list-failures
1743 List store items corresponding to cached build failures.
1745 This prints nothing unless the daemon was started with
1746 @option{--cache-failures} (@pxref{Invoking guix-daemon,
1747 @option{--cache-failures}}).
1749 @item --clear-failures
1750 Remove the specified store items from the failed-build cache.
1752 Again, this option only makes sense when the daemon is started with
1753 @option{--cache-failures}. Otherwise, it does nothing.
1756 Show the list of dead files and directories still present in the
1757 store---i.e., files and directories no longer reachable from any root.
1760 Show the list of live store files and directories.
1764 In addition, the references among existing store files can be queried:
1770 List the references (respectively, the referrers) of store files given
1776 List the requisites of the store files passed as arguments. Requisites
1777 include the store files themselves, their references, and the references
1778 of these, recursively. In other words, the returned list is the
1779 @dfn{transitive closure} of the store files.
1781 @xref{Invoking guix size}, for a tool to profile the size of an
1782 element's closure. @xref{Invoking guix graph}, for a tool to visualize
1783 the graph of references.
1787 Lastly, the following options allow you to check the integrity of the
1788 store and to control disk usage.
1792 @item --verify[=@var{options}]
1793 @cindex integrity, of the store
1794 @cindex integrity checking
1795 Verify the integrity of the store.
1797 By default, make sure that all the store items marked as valid in the
1798 daemon's database actually exist in @file{/gnu/store}.
1800 When provided, @var{options} must a comma-separated list containing one
1801 or more of @code{contents} and @code{repair}.
1803 When passing @option{--verify=contents}, the daemon will compute the
1804 content hash of each store item and compare it against its hash in the
1805 database. Hash mismatches are reported as data corruptions. Because it
1806 traverses @emph{all the files in the store}, this command can take a
1807 long time, especially on systems with a slow disk drive.
1809 @cindex repairing the store
1810 Using @option{--verify=repair} or @option{--verify=contents,repair}
1811 causes the daemon to try to repair corrupt store items by fetching
1812 substitutes for them (@pxref{Substitutes}). Because repairing is not
1813 atomic, and thus potentially dangerous, it is available only to the
1814 system administrator.
1817 @cindex deduplication
1818 Optimize the store by hard-linking identical files---this is
1819 @dfn{deduplication}.
1821 The daemon performs deduplication after each successful build or archive
1822 import, unless it was started with @code{--disable-deduplication}
1823 (@pxref{Invoking guix-daemon, @code{--disable-deduplication}}). Thus,
1824 this option is primarily useful when the daemon was running with
1825 @code{--disable-deduplication}.
1829 @node Invoking guix pull
1830 @section Invoking @command{guix pull}
1832 Packages are installed or upgraded to the latest version available in
1833 the distribution currently available on your local machine. To update
1834 that distribution, along with the Guix tools, you must run @command{guix
1835 pull}: the command downloads the latest Guix source code and package
1836 descriptions, and deploys it.
1838 On completion, @command{guix package} will use packages and package
1839 versions from this just-retrieved copy of Guix. Not only that, but all
1840 the Guix commands and Scheme modules will also be taken from that latest
1841 version. New @command{guix} sub-commands added by the update also
1842 become available@footnote{Under the hood, @command{guix pull} updates
1843 the @file{~/.config/guix/latest} symbolic link to point to the latest
1844 Guix, and the @command{guix} command loads code from there.}.
1846 The @command{guix pull} command is usually invoked with no arguments,
1847 but it supports the following options:
1851 Produce verbose output, writing build logs to the standard error output.
1853 @item --url=@var{url}
1854 Download the source tarball of Guix from @var{url}.
1856 By default, the tarball is taken from its canonical address at
1857 @code{gnu.org}, for the stable branch of Guix.
1860 Use the bootstrap Guile to build the latest Guix. This option is only
1861 useful to Guix developers.
1865 @node Invoking guix archive
1866 @section Invoking @command{guix archive}
1868 The @command{guix archive} command allows users to @dfn{export} files
1869 from the store into a single archive, and to later @dfn{import} them.
1870 In particular, it allows store files to be transferred from one machine
1871 to another machine's store. For example, to transfer the @code{emacs}
1872 package to a machine connected over SSH, one would run:
1875 guix archive --export -r emacs | ssh the-machine guix archive --import
1879 Similarly, a complete user profile may be transferred from one machine
1880 to another like this:
1883 guix archive --export -r $(readlink -f ~/.guix-profile) | \
1884 ssh the-machine guix-archive --import
1888 However, note that, in both examples, all of @code{emacs} and the
1889 profile as well as all of their dependencies are transferred (due to
1890 @code{-r}), regardless of what is already available in the target
1891 machine's store. The @code{--missing} option can help figure out which
1892 items are missing from the target's store.
1894 Archives are stored in the ``Nix archive'' or ``Nar'' format, which is
1895 comparable in spirit to `tar', but with a few noteworthy differences
1896 that make it more appropriate for our purposes. First, rather than
1897 recording all Unix meta-data for each file, the Nar format only mentions
1898 the file type (regular, directory, or symbolic link); Unix permissions
1899 and owner/group are dismissed. Second, the order in which directory
1900 entries are stored always follows the order of file names according to
1901 the C locale collation order. This makes archive production fully
1904 When exporting, the daemon digitally signs the contents of the archive,
1905 and that digital signature is appended. When importing, the daemon
1906 verifies the signature and rejects the import in case of an invalid
1907 signature or if the signing key is not authorized.
1908 @c FIXME: Add xref to daemon doc about signatures.
1910 The main options are:
1914 Export the specified store files or packages (see below.) Write the
1915 resulting archive to the standard output.
1917 Dependencies are @emph{not} included in the output, unless
1918 @code{--recursive} is passed.
1922 When combined with @code{--export}, this instructs @command{guix
1923 archive} to include dependencies of the given items in the archive.
1924 Thus, the resulting archive is self-contained: it contains the closure
1925 of the exported store items.
1928 Read an archive from the standard input, and import the files listed
1929 therein into the store. Abort if the archive has an invalid digital
1930 signature, or if it is signed by a public key not among the authorized
1931 keys (see @code{--authorize} below.)
1934 Read a list of store file names from the standard input, one per line,
1935 and write on the standard output the subset of these files missing from
1938 @item --generate-key[=@var{parameters}]
1939 @cindex signing, archives
1940 Generate a new key pair for the daemons. This is a prerequisite before
1941 archives can be exported with @code{--export}. Note that this operation
1942 usually takes time, because it needs to gather enough entropy to
1943 generate the key pair.
1945 The generated key pair is typically stored under @file{/etc/guix}, in
1946 @file{signing-key.pub} (public key) and @file{signing-key.sec} (private
1947 key, which must be kept secret.) When @var{parameters} is omitted,
1948 an ECDSA key using the Ed25519 curve is generated, or, for Libgcrypt
1949 versions before 1.6.0, it is a 4096-bit RSA key.
1950 Alternately, @var{parameters} can specify
1951 @code{genkey} parameters suitable for Libgcrypt (@pxref{General
1952 public-key related Functions, @code{gcry_pk_genkey},, gcrypt, The
1953 Libgcrypt Reference Manual}).
1956 @cindex authorizing, archives
1957 Authorize imports signed by the public key passed on standard input.
1958 The public key must be in ``s-expression advanced format''---i.e., the
1959 same format as the @file{signing-key.pub} file.
1961 The list of authorized keys is kept in the human-editable file
1962 @file{/etc/guix/acl}. The file contains
1963 @url{http://people.csail.mit.edu/rivest/Sexp.txt, ``advanced-format
1964 s-expressions''} and is structured as an access-control list in the
1965 @url{http://theworld.com/~cme/spki.txt, Simple Public-Key Infrastructure
1968 @item --extract=@var{directory}
1969 @itemx -x @var{directory}
1970 Read a single-item archive as served by substitute servers
1971 (@pxref{Substitutes}) and extract it to @var{directory}. This is a
1972 low-level operation needed in only very narrow use cases; see below.
1974 For example, the following command extracts the substitute for Emacs
1975 served by @code{hydra.gnu.org} to @file{/tmp/emacs}:
1979 http://hydra.gnu.org/nar/@dots{}-emacs-24.5 \
1980 | bunzip2 | guix archive -x /tmp/emacs
1983 Single-item archives are different from multiple-item archives produced
1984 by @command{guix archive --export}; they contain a single store item,
1985 and they do @emph{not} embed a signature. Thus this operation does
1986 @emph{no} signature verification and its output should be considered
1989 The primary purpose of this operation is to facilitate inspection of
1990 archive contents coming from possibly untrusted substitute servers.
1994 To export store files as an archive to the standard output, run:
1997 guix archive --export @var{options} @var{specifications}...
2000 @var{specifications} may be either store file names or package
2001 specifications, as for @command{guix package} (@pxref{Invoking guix
2002 package}). For instance, the following command creates an archive
2003 containing the @code{gui} output of the @code{git} package and the main
2004 output of @code{emacs}:
2007 guix archive --export git:gui /gnu/store/...-emacs-24.3 > great.nar
2010 If the specified packages are not built yet, @command{guix archive}
2011 automatically builds them. The build process may be controlled with the
2012 same options that can be passed to the @command{guix build} command
2013 (@pxref{Invoking guix build, common build options}).
2015 @c *********************************************************************
2018 @c *********************************************************************
2019 @node Programming Interface
2020 @chapter Programming Interface
2022 GNU Guix provides several Scheme programming interfaces (APIs) to
2023 define, build, and query packages. The first interface allows users to
2024 write high-level package definitions. These definitions refer to
2025 familiar packaging concepts, such as the name and version of a package,
2026 its build system, and its dependencies. These definitions can then be
2027 turned into concrete build actions.
2029 Build actions are performed by the Guix daemon, on behalf of users. In a
2030 standard setup, the daemon has write access to the store---the
2031 @file{/gnu/store} directory---whereas users do not. The recommended
2032 setup also has the daemon perform builds in chroots, under a specific
2033 build users, to minimize interference with the rest of the system.
2036 Lower-level APIs are available to interact with the daemon and the
2037 store. To instruct the daemon to perform a build action, users actually
2038 provide it with a @dfn{derivation}. A derivation is a low-level
2039 representation of the build actions to be taken, and the environment in
2040 which they should occur---derivations are to package definitions what
2041 assembly is to C programs. The term ``derivation'' comes from the fact
2042 that build results @emph{derive} from them.
2044 This chapter describes all these APIs in turn, starting from high-level
2045 package definitions.
2048 * Defining Packages:: Defining new packages.
2049 * Build Systems:: Specifying how packages are built.
2050 * The Store:: Manipulating the package store.
2051 * Derivations:: Low-level interface to package derivations.
2052 * The Store Monad:: Purely functional interface to the store.
2053 * G-Expressions:: Manipulating build expressions.
2056 @node Defining Packages
2057 @section Defining Packages
2059 The high-level interface to package definitions is implemented in the
2060 @code{(guix packages)} and @code{(guix build-system)} modules. As an
2061 example, the package definition, or @dfn{recipe}, for the GNU Hello
2062 package looks like this:
2065 (define-module (gnu packages hello)
2066 #:use-module (guix packages)
2067 #:use-module (guix download)
2068 #:use-module (guix build-system gnu)
2069 #:use-module (guix licenses)
2070 #:use-module (gnu packages gawk))
2072 (define-public hello
2078 (uri (string-append "mirror://gnu/hello/hello-" version
2082 "0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i"))))
2083 (build-system gnu-build-system)
2084 (arguments `(#:configure-flags '("--enable-silent-rules")))
2085 (inputs `(("gawk" ,gawk)))
2086 (synopsis "Hello, GNU world: An example GNU package")
2087 (description "Guess what GNU Hello prints!")
2088 (home-page "http://www.gnu.org/software/hello/")
2093 Without being a Scheme expert, the reader may have guessed the meaning
2094 of the various fields here. This expression binds variable @code{hello}
2095 to a @code{<package>} object, which is essentially a record
2096 (@pxref{SRFI-9, Scheme records,, guile, GNU Guile Reference Manual}).
2097 This package object can be inspected using procedures found in the
2098 @code{(guix packages)} module; for instance, @code{(package-name hello)}
2099 returns---surprise!---@code{"hello"}.
2101 With luck, you may be able to import part or all of the definition of
2102 the package you are interested in from another repository, using the
2103 @code{guix import} command (@pxref{Invoking guix import}).
2105 In the example above, @var{hello} is defined into a module of its own,
2106 @code{(gnu packages hello)}. Technically, this is not strictly
2107 necessary, but it is convenient to do so: all the packages defined in
2108 modules under @code{(gnu packages @dots{})} are automatically known to
2109 the command-line tools (@pxref{Package Modules}).
2111 There are a few points worth noting in the above package definition:
2115 The @code{source} field of the package is an @code{<origin>} object
2116 (@pxref{origin Reference}, for the complete reference).
2117 Here, the @code{url-fetch} method from @code{(guix download)} is used,
2118 meaning that the source is a file to be downloaded over FTP or HTTP.
2120 The @code{mirror://gnu} prefix instructs @code{url-fetch} to use one of
2121 the GNU mirrors defined in @code{(guix download)}.
2123 The @code{sha256} field specifies the expected SHA256 hash of the file
2124 being downloaded. It is mandatory, and allows Guix to check the
2125 integrity of the file. The @code{(base32 @dots{})} form introduces the
2126 base32 representation of the hash. You can obtain this information with
2127 @code{guix download} (@pxref{Invoking guix download}) and @code{guix
2128 hash} (@pxref{Invoking guix hash}).
2131 When needed, the @code{origin} form can also have a @code{patches} field
2132 listing patches to be applied, and a @code{snippet} field giving a
2133 Scheme expression to modify the source code.
2136 @cindex GNU Build System
2137 The @code{build-system} field specifies the procedure to build the
2138 package (@pxref{Build Systems}). Here, @var{gnu-build-system}
2139 represents the familiar GNU Build System, where packages may be
2140 configured, built, and installed with the usual @code{./configure &&
2141 make && make check && make install} command sequence.
2144 The @code{arguments} field specifies options for the build system
2145 (@pxref{Build Systems}). Here it is interpreted by
2146 @var{gnu-build-system} as a request run @file{configure} with the
2147 @code{--enable-silent-rules} flag.
2150 The @code{inputs} field specifies inputs to the build process---i.e.,
2151 build-time or run-time dependencies of the package. Here, we define an
2152 input called @code{"gawk"} whose value is that of the @var{gawk}
2153 variable; @var{gawk} is itself bound to a @code{<package>} object.
2155 Note that GCC, Coreutils, Bash, and other essential tools do not need to
2156 be specified as inputs here. Instead, @var{gnu-build-system} takes care
2157 of ensuring that they are present (@pxref{Build Systems}).
2159 However, any other dependencies need to be specified in the
2160 @code{inputs} field. Any dependency not specified here will simply be
2161 unavailable to the build process, possibly leading to a build failure.
2164 @xref{package Reference}, for a full description of possible fields.
2166 Once a package definition is in place, the
2167 package may actually be built using the @code{guix build} command-line
2168 tool (@pxref{Invoking guix build}). You can easily jump back to the
2169 package definition using the @command{guix edit} command
2170 (@pxref{Invoking guix edit}).
2171 @xref{Packaging Guidelines}, for
2172 more information on how to test package definitions, and
2173 @ref{Invoking guix lint}, for information on how to check a definition
2174 for style conformance.
2176 Eventually, updating the package definition to a new upstream version
2177 can be partly automated by the @command{guix refresh} command
2178 (@pxref{Invoking guix refresh}).
2180 Behind the scenes, a derivation corresponding to the @code{<package>}
2181 object is first computed by the @code{package-derivation} procedure.
2182 That derivation is stored in a @code{.drv} file under @file{/gnu/store}.
2183 The build actions it prescribes may then be realized by using the
2184 @code{build-derivations} procedure (@pxref{The Store}).
2186 @deffn {Scheme Procedure} package-derivation @var{store} @var{package} [@var{system}]
2187 Return the @code{<derivation>} object of @var{package} for @var{system}
2188 (@pxref{Derivations}).
2190 @var{package} must be a valid @code{<package>} object, and @var{system}
2191 must be a string denoting the target system type---e.g.,
2192 @code{"x86_64-linux"} for an x86_64 Linux-based GNU system. @var{store}
2193 must be a connection to the daemon, which operates on the store
2194 (@pxref{The Store}).
2198 @cindex cross-compilation
2199 Similarly, it is possible to compute a derivation that cross-builds a
2200 package for some other system:
2202 @deffn {Scheme Procedure} package-cross-derivation @var{store} @
2203 @var{package} @var{target} [@var{system}]
2204 Return the @code{<derivation>} object of @var{package} cross-built from
2205 @var{system} to @var{target}.
2207 @var{target} must be a valid GNU triplet denoting the target hardware
2208 and operating system, such as @code{"mips64el-linux-gnu"}
2209 (@pxref{Configuration Names, GNU configuration triplets,, configure, GNU
2210 Configure and Build System}).
2214 * package Reference :: The package data type.
2215 * origin Reference:: The origin data type.
2219 @node package Reference
2220 @subsection @code{package} Reference
2222 This section summarizes all the options available in @code{package}
2223 declarations (@pxref{Defining Packages}).
2225 @deftp {Data Type} package
2226 This is the data type representing a package recipe.
2230 The name of the package, as a string.
2232 @item @code{version}
2233 The version of the package, as a string.
2236 An origin object telling how the source code for the package should be
2237 acquired (@pxref{origin Reference}).
2239 @item @code{build-system}
2240 The build system that should be used to build the package (@pxref{Build
2243 @item @code{arguments} (default: @code{'()})
2244 The arguments that should be passed to the build system. This is a
2245 list, typically containing sequential keyword-value pairs.
2247 @item @code{inputs} (default: @code{'()})
2248 Package or derivation inputs to the build. This is a list of lists,
2249 where each list has the name of the input (a string) as its first
2250 element, a package or derivation object as its second element, and
2251 optionally the name of the output of the package or derivation that
2252 should be used, which defaults to @code{"out"}.
2254 @item @anchor{package-propagated-inputs}@code{propagated-inputs} (default: @code{'()})
2255 @cindex propagated inputs
2256 This field is like @code{inputs}, but the specified packages will be
2257 force-installed alongside the package they belong to
2258 (@pxref{package-cmd-propagated-inputs, @command{guix package}}, for
2259 information on how @command{guix package} deals with propagated inputs.)
2261 For example this is necessary when a library needs headers of another
2262 library to compile, or needs another shared library to be linked
2263 alongside itself when a program wants to link to it.
2265 @item @code{native-inputs} (default: @code{'()})
2266 This field is like @code{inputs}, but in case of a cross-compilation it
2267 will be ensured that packages for the architecture of the build machine
2268 are present, such that executables from them can be used during the
2271 This is typically where you would list tools needed at build time but
2272 not at run time, such as Autoconf, Automake, pkg-config, Gettext, or
2273 Bison. @command{guix lint} can report likely mistakes in this area
2274 (@pxref{Invoking guix lint}).
2276 @item @code{self-native-input?} (default: @code{#f})
2277 This is a Boolean field telling whether the package should use itself as
2278 a native input when cross-compiling.
2280 @item @code{outputs} (default: @code{'("out")})
2281 The list of output names of the package. @xref{Packages with Multiple
2282 Outputs}, for typical uses of additional outputs.
2284 @item @code{native-search-paths} (default: @code{'()})
2285 @itemx @code{search-paths} (default: @code{'()})
2286 A list of @code{search-path-specification} objects describing
2287 search-path environment variables honored by the package.
2289 @item @code{replacement} (default: @code{#f})
2290 This must either @code{#f} or a package object that will be used as a
2291 @dfn{replacement} for this package. @xref{Security Updates, grafts},
2294 @item @code{synopsis}
2295 A one-line description of the package.
2297 @item @code{description}
2298 A more elaborate description of the package.
2300 @item @code{license}
2301 The license of the package; a value from @code{(guix licenses)}.
2303 @item @code{home-page}
2304 The URL to the home-page of the package, as a string.
2306 @item @code{supported-systems} (default: @var{%supported-systems})
2307 The list of systems supported by the package, as strings of the form
2308 @code{architecture-kernel}, for example @code{"x86_64-linux"}.
2310 @item @code{maintainers} (default: @code{'()})
2311 The list of maintainers of the package, as @code{maintainer} objects.
2313 @item @code{location} (default: source location of the @code{package} form)
2314 The source location of the package. It's useful to override this when
2315 inheriting from another package, in which case this field is not
2316 automatically corrected.
2321 @node origin Reference
2322 @subsection @code{origin} Reference
2324 This section summarizes all the options available in @code{origin}
2325 declarations (@pxref{Defining Packages}).
2327 @deftp {Data Type} origin
2328 This is the data type representing a source code origin.
2332 An object containing the URI of the source. The object type depends on
2333 the @code{method} (see below). For example, when using the
2334 @var{url-fetch} method of @code{(guix download)}, the valid @code{uri}
2335 values are: a URL represented as a string, or a list thereof.
2338 A procedure that will handle the URI.
2343 @item @var{url-fetch} from @code{(guix download)}
2344 download a file the HTTP, HTTPS, or FTP URL specified in the
2347 @item @var{git-fetch} from @code{(guix git-download)}
2348 clone the Git version control repository, and check out the revision
2349 specified in the @code{uri} field as a @code{git-reference} object; a
2350 @code{git-reference} looks like this:
2354 (url "git://git.debian.org/git/pkg-shadow/shadow")
2355 (commit "v4.1.5.1"))
2360 A bytevector containing the SHA-256 hash of the source. Typically the
2361 @code{base32} form is used here to generate the bytevector from a
2364 @item @code{file-name} (default: @code{#f})
2365 The file name under which the source code should be saved. When this is
2366 @code{#f}, a sensible default value will be used in most cases. In case
2367 the source is fetched from a URL, the file name from the URL will be
2368 used. For version control checkouts, it's recommended to provide the
2369 file name explicitly because the default is not very descriptive.
2371 @item @code{patches} (default: @code{'()})
2372 A list of file names containing patches to be applied to the source.
2374 @item @code{snippet} (default: @code{#f})
2375 A quoted piece of code that will be run in the source directory to make
2376 any modifications, which is sometimes more convenient than a patch.
2378 @item @code{patch-flags} (default: @code{'("-p1")})
2379 A list of command-line flags that should be passed to the @code{patch}
2382 @item @code{patch-inputs} (default: @code{#f})
2383 Input packages or derivations to the patching process. When this is
2384 @code{#f}, the usual set of inputs necessary for patching are provided,
2385 such as GNU@tie{}Patch.
2387 @item @code{modules} (default: @code{'()})
2388 A list of Guile modules that should be loaded during the patching
2389 process and while running the code in the @code{snippet} field.
2391 @item @code{imported-modules} (default: @code{'()})
2392 The list of Guile modules to import in the patch derivation, for use by
2395 @item @code{patch-guile} (default: @code{#f})
2396 The Guile package that should be used in the patching process. When
2397 this is @code{#f}, a sensible default is used.
2403 @section Build Systems
2405 @cindex build system
2406 Each package definition specifies a @dfn{build system} and arguments for
2407 that build system (@pxref{Defining Packages}). This @code{build-system}
2408 field represents the build procedure of the package, as well implicit
2409 dependencies of that build procedure.
2411 Build systems are @code{<build-system>} objects. The interface to
2412 create and manipulate them is provided by the @code{(guix build-system)}
2413 module, and actual build systems are exported by specific modules.
2415 @cindex bag (low-level package representation)
2416 Under the hood, build systems first compile package objects to
2417 @dfn{bags}. A @dfn{bag} is like a package, but with less
2418 ornamentation---in other words, a bag is a lower-level representation of
2419 a package, which includes all the inputs of that package, including some
2420 that were implicitly added by the build system. This intermediate
2421 representation is then compiled to a derivation (@pxref{Derivations}).
2423 Build systems accept an optional list of @dfn{arguments}. In package
2424 definitions, these are passed @i{via} the @code{arguments} field
2425 (@pxref{Defining Packages}). They are typically keyword arguments
2426 (@pxref{Optional Arguments, keyword arguments in Guile,, guile, GNU
2427 Guile Reference Manual}). The value of these arguments is usually
2428 evaluated in the @dfn{build stratum}---i.e., by a Guile process launched
2429 by the daemon (@pxref{Derivations}).
2431 The main build system is @var{gnu-build-system}, which implements the
2432 standard build procedure for GNU packages and many other packages. It
2433 is provided by the @code{(guix build-system gnu)} module.
2435 @defvr {Scheme Variable} gnu-build-system
2436 @var{gnu-build-system} represents the GNU Build System, and variants
2437 thereof (@pxref{Configuration, configuration and makefile conventions,,
2438 standards, GNU Coding Standards}).
2440 @cindex build phases
2441 In a nutshell, packages using it configured, built, and installed with
2442 the usual @code{./configure && make && make check && make install}
2443 command sequence. In practice, a few additional steps are often needed.
2444 All these steps are split up in separate @dfn{phases},
2445 notably@footnote{Please see the @code{(guix build gnu-build-system)}
2446 modules for more details about the build phases.}:
2450 Unpack the source tarball, and change the current directory to the
2451 extracted source tree. If the source is actually a directory, copy it
2452 to the build tree, and enter that directory.
2454 @item patch-source-shebangs
2455 Patch shebangs encountered in source files so they refer to the right
2456 store file names. For instance, this changes @code{#!/bin/sh} to
2457 @code{#!/gnu/store/@dots{}-bash-4.3/bin/sh}.
2460 Run the @file{configure} script with a number of default options, such
2461 as @code{--prefix=/gnu/store/@dots{}}, as well as the options specified
2462 by the @code{#:configure-flags} argument.
2465 Run @code{make} with the list of flags specified with
2466 @code{#:make-flags}. If the @code{#:parallel-builds?} argument is true
2467 (the default), build with @code{make -j}.
2470 Run @code{make check}, or some other target specified with
2471 @code{#:test-target}, unless @code{#:tests? #f} is passed. If the
2472 @code{#:parallel-tests?} argument is true (the default), run @code{make
2476 Run @code{make install} with the flags listed in @code{#:make-flags}.
2478 @item patch-shebangs
2479 Patch shebangs on the installed executable files.
2482 Strip debugging symbols from ELF files (unless @code{#:strip-binaries?}
2483 is false), copying them to the @code{debug} output when available
2484 (@pxref{Installing Debugging Files}).
2487 @vindex %standard-phases
2488 The build-side module @code{(guix build gnu-build-system)} defines
2489 @var{%standard-phases} as the default list of build phases.
2490 @var{%standard-phases} is a list of symbol/procedure pairs, where the
2491 procedure implements the actual phase.
2493 The list of phases used for a particular package can be changed with the
2494 @code{#:phases} parameter. For instance, passing:
2497 #:phases (alist-delete 'configure %standard-phases)
2500 means that all the phases described above will be used, except the
2501 @code{configure} phase.
2503 In addition, this build system ensures that the ``standard'' environment
2504 for GNU packages is available. This includes tools such as GCC, libc,
2505 Coreutils, Bash, Make, Diffutils, grep, and sed (see the @code{(guix
2506 build-system gnu)} module for a complete list.) We call these the
2507 @dfn{implicit inputs} of a package, because package definitions don't
2508 have to mention them.
2511 Other @code{<build-system>} objects are defined to support other
2512 conventions and tools used by free software packages. They inherit most
2513 of @var{gnu-build-system}, and differ mainly in the set of inputs
2514 implicitly added to the build process, and in the list of phases
2515 executed. Some of these build systems are listed below.
2517 @defvr {Scheme Variable} cmake-build-system
2518 This variable is exported by @code{(guix build-system cmake)}. It
2519 implements the build procedure for packages using the
2520 @url{http://www.cmake.org, CMake build tool}.
2522 It automatically adds the @code{cmake} package to the set of inputs.
2523 Which package is used can be specified with the @code{#:cmake}
2526 The @code{#:configure-flags} parameter is taken as a list of flags
2527 passed to the @command{cmake} command. The @code{#:build-type}
2528 parameter specifies in abstract terms the flags passed to the compiler;
2529 it defaults to @code{"RelWithDebInfo"} (short for ``release mode with
2530 debugging information''), which roughly means that code is compiled with
2531 @code{-O2 -g}, as is the case for Autoconf-based packages by default.
2534 @defvr {Scheme Variable} glib-or-gtk-build-system
2535 This variable is exported by @code{(guix build-system glib-or-gtk)}. It
2536 is intended for use with packages making use of GLib or GTK+.
2538 This build system adds the following two phases to the ones defined by
2539 @var{gnu-build-system}:
2542 @item glib-or-gtk-wrap
2543 The phase @code{glib-or-gtk-wrap} ensures that programs found under
2544 @file{bin/} are able to find GLib's ``schemas'' and
2545 @uref{https://developer.gnome.org/gtk3/stable/gtk-running.html, GTK+
2546 modules}. This is achieved by wrapping the programs in launch scripts
2547 that appropriately set the @code{XDG_DATA_DIRS} and @code{GTK_PATH}
2548 environment variables.
2550 It is possible to exclude specific package outputs from that wrapping
2551 process by listing their names in the
2552 @code{#:glib-or-gtk-wrap-excluded-outputs} parameter. This is useful
2553 when an output is known not to contain any GLib or GTK+ binaries, and
2554 where wrapping would gratuitously add a dependency of that output on
2557 @item glib-or-gtk-compile-schemas
2558 The phase @code{glib-or-gtk-compile-schemas} makes sure that all GLib's
2559 @uref{https://developer.gnome.org/gio/stable/glib-compile-schemas.html,
2560 GSettings schemas} are compiled. Compilation is performed by the
2561 @command{glib-compile-schemas} program. It is provided by the package
2562 @code{glib:bin} which is automatically imported by the build system.
2563 The @code{glib} package providing @command{glib-compile-schemas} can be
2564 specified with the @code{#:glib} parameter.
2567 Both phases are executed after the @code{install} phase.
2570 @defvr {Scheme Variable} python-build-system
2571 This variable is exported by @code{(guix build-system python)}. It
2572 implements the more or less standard build procedure used by Python
2573 packages, which consists in running @code{python setup.py build} and
2574 then @code{python setup.py install --prefix=/gnu/store/@dots{}}.
2576 For packages that install stand-alone Python programs under @code{bin/},
2577 it takes care of wrapping these programs so their @code{PYTHONPATH}
2578 environment variable points to all the Python libraries they depend on.
2580 Which Python package is used can be specified with the @code{#:python}
2584 @defvr {Scheme Variable} perl-build-system
2585 This variable is exported by @code{(guix build-system perl)}. It
2586 implements the standard build procedure for Perl packages, which either
2587 consists in running @code{perl Build.PL --prefix=/gnu/store/@dots{}},
2588 followed by @code{Build} and @code{Build install}; or in running
2589 @code{perl Makefile.PL PREFIX=/gnu/store/@dots{}}, followed by
2590 @code{make} and @code{make install}; depending on which of
2591 @code{Build.PL} or @code{Makefile.PL} is present in the package
2592 distribution. Preference is given to the former if both @code{Build.PL}
2593 and @code{Makefile.PL} exist in the package distribution. This
2594 preference can be reversed by specifying @code{#t} for the
2595 @code{#:make-maker?} parameter.
2597 The initial @code{perl Makefile.PL} or @code{perl Build.PL} invocation
2598 passes flags specified by the @code{#:make-maker-flags} or
2599 @code{#:module-build-flags} parameter, respectively.
2601 Which Perl package is used can be specified with @code{#:perl}.
2604 @defvr {Scheme Variable} r-build-system
2605 This variable is exported by @code{(guix build-system r)}. It
2606 implements the build procedure used by @uref{http://r-project.org, R}
2607 packages, which essentially is little more than running @code{R CMD
2608 INSTALL --library=/gnu/store/@dots{}} in an environment where
2609 @code{R_LIBS_SITE} contains the paths to all R package inputs. Tests
2610 are run after installation using the R function
2611 @code{tools::testInstalledPackage}.
2614 @defvr {Scheme Variable} ruby-build-system
2615 This variable is exported by @code{(guix build-system ruby)}. It
2616 implements the RubyGems build procedure used by Ruby packages, which
2617 involves running @code{gem build} followed by @code{gem install}.
2619 The @code{source} field of a package that uses this build system
2620 typically references a gem archive, since this is the format that Ruby
2621 developers use when releasing their software. The build system unpacks
2622 the gem archive, potentially patches the source, runs the test suite,
2623 repackages the gem, and installs it. Additionally, directories and
2624 tarballs may be referenced to allow building unreleased gems from Git or
2625 a traditional source release tarball.
2627 Which Ruby package is used can be specified with the @code{#:ruby}
2628 parameter. A list of additional flags to be passed to the @command{gem}
2629 command can be specified with the @code{#:gem-flags} parameter.
2632 @defvr {Scheme Variable} waf-build-system
2633 This variable is exported by @code{(guix build-system waf)}. It
2634 implements a build procedure around the @code{waf} script. The common
2635 phases---@code{configure}, @code{build}, and @code{install}---are
2636 implemented by passing their names as arguments to the @code{waf}
2639 The @code{waf} script is executed by the Python interpreter. Which
2640 Python package is used to run the script can be specified with the
2641 @code{#:python} parameter.
2644 @defvr {Scheme Variable} haskell-build-system
2645 This variable is exported by @code{(guix build-system haskell)}. It
2646 implements the Cabal build procedure used by Haskell packages, which
2647 involves running @code{runhaskell Setup.hs configure
2648 --prefix=/gnu/store/@dots{}} and @code{runhaskell Setup.hs build}.
2649 Instead of installing the package by running @code{runhaskell Setup.hs
2650 install}, to avoid trying to register libraries in the read-only
2651 compiler store directory, the build system uses @code{runhaskell
2652 Setup.hs copy}, followed by @code{runhaskell Setup.hs register}. In
2653 addition, the build system generates the package documentation by
2654 running @code{runhaskell Setup.hs haddock}, unless @code{#:haddock? #f}
2655 is passed. Optional Haddock parameters can be passed with the help of
2656 the @code{#:haddock-flags} parameter. If the file @code{Setup.hs} is
2657 not found, the build system looks for @code{Setup.lhs} instead.
2659 Which Haskell compiler is used can be specified with the @code{#:haskell}
2660 parameter which defaults to @code{ghc}.
2663 @defvr {Scheme Variable} emacs-build-system
2664 This variable is exported by @code{(guix build-system emacs)}. It
2665 implements an installation procedure similar to the one of Emacs' own
2666 packaging system (@pxref{Packages,,, emacs, The GNU Emacs Manual}).
2668 It first creates the @code{@var{package}-autoloads.el} file, then it
2669 byte compiles all Emacs Lisp files. Differently from the Emacs
2670 packaging system, the Info documentation files are moved to the standard
2671 documentation directory and the @file{dir} file is deleted. Each
2672 package is installed in its own directory under
2673 @file{share/emacs/site-lisp/guix.d}.
2676 Lastly, for packages that do not need anything as sophisticated, a
2677 ``trivial'' build system is provided. It is trivial in the sense that
2678 it provides basically no support: it does not pull any implicit inputs,
2679 and does not have a notion of build phases.
2681 @defvr {Scheme Variable} trivial-build-system
2682 This variable is exported by @code{(guix build-system trivial)}.
2684 This build system requires a @code{#:builder} argument. This argument
2685 must be a Scheme expression that builds the package's output(s)---as
2686 with @code{build-expression->derivation} (@pxref{Derivations,
2687 @code{build-expression->derivation}}).
2696 Conceptually, the @dfn{store} is where derivations that have been
2697 successfully built are stored---by default, under @file{/gnu/store}.
2698 Sub-directories in the store are referred to as @dfn{store paths}. The
2699 store has an associated database that contains information such as the
2700 store paths referred to by each store path, and the list of @emph{valid}
2701 store paths---paths that result from a successful build.
2703 The store is always accessed by the daemon on behalf of its clients
2704 (@pxref{Invoking guix-daemon}). To manipulate the store, clients
2705 connect to the daemon over a Unix-domain socket, send it requests, and
2706 read the result---these are remote procedure calls, or RPCs.
2708 The @code{(guix store)} module provides procedures to connect to the
2709 daemon, and to perform RPCs. These are described below.
2711 @deffn {Scheme Procedure} open-connection [@var{file}] [#:reserve-space? #t]
2712 Connect to the daemon over the Unix-domain socket at @var{file}. When
2713 @var{reserve-space?} is true, instruct it to reserve a little bit of
2714 extra space on the file system so that the garbage collector can still
2715 operate, should the disk become full. Return a server object.
2717 @var{file} defaults to @var{%default-socket-path}, which is the normal
2718 location given the options that were passed to @command{configure}.
2721 @deffn {Scheme Procedure} close-connection @var{server}
2722 Close the connection to @var{server}.
2725 @defvr {Scheme Variable} current-build-output-port
2726 This variable is bound to a SRFI-39 parameter, which refers to the port
2727 where build and error logs sent by the daemon should be written.
2730 Procedures that make RPCs all take a server object as their first
2733 @deffn {Scheme Procedure} valid-path? @var{server} @var{path}
2734 Return @code{#t} when @var{path} is a valid store path.
2737 @deffn {Scheme Procedure} add-text-to-store @var{server} @var{name} @var{text} [@var{references}]
2738 Add @var{text} under file @var{name} in the store, and return its store
2739 path. @var{references} is the list of store paths referred to by the
2740 resulting store path.
2743 @deffn {Scheme Procedure} build-derivations @var{server} @var{derivations}
2744 Build @var{derivations} (a list of @code{<derivation>} objects or
2745 derivation paths), and return when the worker is done building them.
2746 Return @code{#t} on success.
2749 Note that the @code{(guix monads)} module provides a monad as well as
2750 monadic versions of the above procedures, with the goal of making it
2751 more convenient to work with code that accesses the store (@pxref{The
2755 @i{This section is currently incomplete.}
2758 @section Derivations
2761 Low-level build actions and the environment in which they are performed
2762 are represented by @dfn{derivations}. A derivation contain the
2763 following pieces of information:
2767 The outputs of the derivation---derivations produce at least one file or
2768 directory in the store, but may produce more.
2771 The inputs of the derivations, which may be other derivations or plain
2772 files in the store (patches, build scripts, etc.)
2775 The system type targeted by the derivation---e.g., @code{x86_64-linux}.
2778 The file name of a build script in the store, along with the arguments
2782 A list of environment variables to be defined.
2786 @cindex derivation path
2787 Derivations allow clients of the daemon to communicate build actions to
2788 the store. They exist in two forms: as an in-memory representation,
2789 both on the client- and daemon-side, and as files in the store whose
2790 name end in @code{.drv}---these files are referred to as @dfn{derivation
2791 paths}. Derivations paths can be passed to the @code{build-derivations}
2792 procedure to perform the build actions they prescribe (@pxref{The
2795 The @code{(guix derivations)} module provides a representation of
2796 derivations as Scheme objects, along with procedures to create and
2797 otherwise manipulate derivations. The lowest-level primitive to create
2798 a derivation is the @code{derivation} procedure:
2800 @deffn {Scheme Procedure} derivation @var{store} @var{name} @var{builder} @
2801 @var{args} [#:outputs '("out")] [#:hash #f] [#:hash-algo #f] @
2802 [#:recursive? #f] [#:inputs '()] [#:env-vars '()] @
2803 [#:system (%current-system)] [#:references-graphs #f] @
2804 [#:allowed-references #f] [#:leaked-env-vars #f] [#:local-build? #f] @
2805 [#:substitutable? #t]
2806 Build a derivation with the given arguments, and return the resulting
2807 @code{<derivation>} object.
2809 When @var{hash} and @var{hash-algo} are given, a
2810 @dfn{fixed-output derivation} is created---i.e., one whose result is
2811 known in advance, such as a file download. If, in addition,
2812 @var{recursive?} is true, then that fixed output may be an executable
2813 file or a directory and @var{hash} must be the hash of an archive
2814 containing this output.
2816 When @var{references-graphs} is true, it must be a list of file
2817 name/store path pairs. In that case, the reference graph of each store
2818 path is exported in the build environment in the corresponding file, in
2819 a simple text format.
2821 When @var{allowed-references} is true, it must be a list of store items
2822 or outputs that the derivation's output may refer to.
2824 When @var{leaked-env-vars} is true, it must be a list of strings
2825 denoting environment variables that are allowed to ``leak'' from the
2826 daemon's environment to the build environment. This is only applicable
2827 to fixed-output derivations---i.e., when @var{hash} is true. The main
2828 use is to allow variables such as @code{http_proxy} to be passed to
2829 derivations that download files.
2831 When @var{local-build?} is true, declare that the derivation is not a
2832 good candidate for offloading and should rather be built locally
2833 (@pxref{Daemon Offload Setup}). This is the case for small derivations
2834 where the costs of data transfers would outweigh the benefits.
2836 When @var{substitutable?} is false, declare that substitutes of the
2837 derivation's output should not be used (@pxref{Substitutes}). This is
2838 useful, for instance, when building packages that capture details of the
2839 host CPU instruction set.
2843 Here's an example with a shell script as its builder, assuming
2844 @var{store} is an open connection to the daemon, and @var{bash} points
2845 to a Bash executable in the store:
2848 (use-modules (guix utils)
2852 (let ((builder ; add the Bash script to the store
2853 (add-text-to-store store "my-builder.sh"
2854 "echo hello world > $out\n" '())))
2855 (derivation store "foo"
2856 bash `("-e" ,builder)
2857 #:inputs `((,bash) (,builder))
2858 #:env-vars '(("HOME" . "/homeless"))))
2859 @result{} #<derivation /gnu/store/@dots{}-foo.drv => /gnu/store/@dots{}-foo>
2862 As can be guessed, this primitive is cumbersome to use directly. A
2863 better approach is to write build scripts in Scheme, of course! The
2864 best course of action for that is to write the build code as a
2865 ``G-expression'', and to pass it to @code{gexp->derivation}. For more
2866 information, @pxref{G-Expressions}.
2868 Once upon a time, @code{gexp->derivation} did not exist and constructing
2869 derivations with build code written in Scheme was achieved with
2870 @code{build-expression->derivation}, documented below. This procedure
2871 is now deprecated in favor of the much nicer @code{gexp->derivation}.
2873 @deffn {Scheme Procedure} build-expression->derivation @var{store} @
2874 @var{name} @var{exp} @
2875 [#:system (%current-system)] [#:inputs '()] @
2876 [#:outputs '("out")] [#:hash #f] [#:hash-algo #f] @
2877 [#:recursive? #f] [#:env-vars '()] [#:modules '()] @
2878 [#:references-graphs #f] [#:allowed-references #f] @
2879 [#:local-build? #f] [#:substitutable? #t] [#:guile-for-build #f]
2880 Return a derivation that executes Scheme expression @var{exp} as a
2881 builder for derivation @var{name}. @var{inputs} must be a list of
2882 @code{(name drv-path sub-drv)} tuples; when @var{sub-drv} is omitted,
2883 @code{"out"} is assumed. @var{modules} is a list of names of Guile
2884 modules from the current search path to be copied in the store,
2885 compiled, and made available in the load path during the execution of
2886 @var{exp}---e.g., @code{((guix build utils) (guix build
2887 gnu-build-system))}.
2889 @var{exp} is evaluated in an environment where @code{%outputs} is bound
2890 to a list of output/path pairs, and where @code{%build-inputs} is bound
2891 to a list of string/output-path pairs made from @var{inputs}.
2892 Optionally, @var{env-vars} is a list of string pairs specifying the name
2893 and value of environment variables visible to the builder. The builder
2894 terminates by passing the result of @var{exp} to @code{exit}; thus, when
2895 @var{exp} returns @code{#f}, the build is considered to have failed.
2897 @var{exp} is built using @var{guile-for-build} (a derivation). When
2898 @var{guile-for-build} is omitted or is @code{#f}, the value of the
2899 @code{%guile-for-build} fluid is used instead.
2901 See the @code{derivation} procedure for the meaning of
2902 @var{references-graphs}, @var{allowed-references}, @var{local-build?},
2903 and @var{substitutable?}.
2907 Here's an example of a single-output derivation that creates a directory
2908 containing one file:
2911 (let ((builder '(let ((out (assoc-ref %outputs "out")))
2912 (mkdir out) ; create /gnu/store/@dots{}-goo
2913 (call-with-output-file (string-append out "/test")
2915 (display '(hello guix) p))))))
2916 (build-expression->derivation store "goo" builder))
2918 @result{} #<derivation /gnu/store/@dots{}-goo.drv => @dots{}>
2922 @node The Store Monad
2923 @section The Store Monad
2927 The procedures that operate on the store described in the previous
2928 sections all take an open connection to the build daemon as their first
2929 argument. Although the underlying model is functional, they either have
2930 side effects or depend on the current state of the store.
2932 The former is inconvenient: the connection to the build daemon has to be
2933 carried around in all those functions, making it impossible to compose
2934 functions that do not take that parameter with functions that do. The
2935 latter can be problematic: since store operations have side effects
2936 and/or depend on external state, they have to be properly sequenced.
2938 @cindex monadic values
2939 @cindex monadic functions
2940 This is where the @code{(guix monads)} module comes in. This module
2941 provides a framework for working with @dfn{monads}, and a particularly
2942 useful monad for our uses, the @dfn{store monad}. Monads are a
2943 construct that allows two things: associating ``context'' with values
2944 (in our case, the context is the store), and building sequences of
2945 computations (here computations include accesses to the store.) Values
2946 in a monad---values that carry this additional context---are called
2947 @dfn{monadic values}; procedures that return such values are called
2948 @dfn{monadic procedures}.
2950 Consider this ``normal'' procedure:
2953 (define (sh-symlink store)
2954 ;; Return a derivation that symlinks the 'bash' executable.
2955 (let* ((drv (package-derivation store bash))
2956 (out (derivation->output-path drv))
2957 (sh (string-append out "/bin/bash")))
2958 (build-expression->derivation store "sh"
2959 `(symlink ,sh %output))))
2962 Using @code{(guix monads)} and @code{(guix gexp)}, it may be rewritten
2963 as a monadic function:
2966 (define (sh-symlink)
2967 ;; Same, but return a monadic value.
2968 (mlet %store-monad ((drv (package->derivation bash)))
2969 (gexp->derivation "sh"
2970 #~(symlink (string-append #$drv "/bin/bash")
2974 There several things to note in the second version: the @code{store}
2975 parameter is now implicit and is ``threaded'' in the calls to the
2976 @code{package->derivation} and @code{gexp->derivation} monadic
2977 procedures, and the monadic value returned by @code{package->derivation}
2978 is @dfn{bound} using @code{mlet} instead of plain @code{let}.
2980 As it turns out, the call to @code{package->derivation} can even be
2981 omitted since it will take place implicitly, as we will see later
2982 (@pxref{G-Expressions}):
2985 (define (sh-symlink)
2986 (gexp->derivation "sh"
2987 #~(symlink (string-append #$bash "/bin/bash")
2992 @c <https://syntaxexclamation.wordpress.com/2014/06/26/escaping-continuations/>
2993 @c for the funny quote.
2994 Calling the monadic @code{sh-symlink} has no effect. As someone once
2995 said, ``you exit a monad like you exit a building on fire: by running''.
2996 So, to exit the monad and get the desired effect, one must use
2997 @code{run-with-store}:
3000 (run-with-store (open-connection) (sh-symlink))
3001 @result{} /gnu/store/...-sh-symlink
3004 Note that the @code{(guix monad-repl)} module extends Guile's REPL with
3005 new ``meta-commands'' to make it easier to deal with monadic procedures:
3006 @code{run-in-store}, and @code{enter-store-monad}. The former, is used
3007 to ``run'' a single monadic value through the store:
3010 scheme@@(guile-user)> ,run-in-store (package->derivation hello)
3011 $1 = #<derivation /gnu/store/@dots{}-hello-2.9.drv => @dots{}>
3014 The latter enters a recursive REPL, where all the return values are
3015 automatically run through the store:
3018 scheme@@(guile-user)> ,enter-store-monad
3019 store-monad@@(guile-user) [1]> (package->derivation hello)
3020 $2 = #<derivation /gnu/store/@dots{}-hello-2.9.drv => @dots{}>
3021 store-monad@@(guile-user) [1]> (text-file "foo" "Hello!")
3022 $3 = "/gnu/store/@dots{}-foo"
3023 store-monad@@(guile-user) [1]> ,q
3024 scheme@@(guile-user)>
3028 Note that non-monadic values cannot be returned in the
3029 @code{store-monad} REPL.
3031 The main syntactic forms to deal with monads in general are provided by
3032 the @code{(guix monads)} module and are described below.
3034 @deffn {Scheme Syntax} with-monad @var{monad} @var{body} ...
3035 Evaluate any @code{>>=} or @code{return} forms in @var{body} as being
3039 @deffn {Scheme Syntax} return @var{val}
3040 Return a monadic value that encapsulates @var{val}.
3043 @deffn {Scheme Syntax} >>= @var{mval} @var{mproc} ...
3044 @dfn{Bind} monadic value @var{mval}, passing its ``contents'' to monadic
3045 procedures @var{mproc}@dots{}@footnote{This operation is commonly
3046 referred to as ``bind'', but that name denotes an unrelated procedure in
3047 Guile. Thus we use this somewhat cryptic symbol inherited from the
3048 Haskell language.}. There can be one @var{mproc} or several of them, as
3053 (with-monad %state-monad
3055 (lambda (x) (return (+ 1 x)))
3056 (lambda (x) (return (* 2 x)))))
3060 @result{} some-state
3064 @deffn {Scheme Syntax} mlet @var{monad} ((@var{var} @var{mval}) ...) @
3066 @deffnx {Scheme Syntax} mlet* @var{monad} ((@var{var} @var{mval}) ...) @
3068 Bind the variables @var{var} to the monadic values @var{mval} in
3069 @var{body}. The form (@var{var} -> @var{val}) binds @var{var} to the
3070 ``normal'' value @var{val}, as per @code{let}.
3072 @code{mlet*} is to @code{mlet} what @code{let*} is to @code{let}
3073 (@pxref{Local Bindings,,, guile, GNU Guile Reference Manual}).
3076 @deffn {Scheme System} mbegin @var{monad} @var{mexp} ...
3077 Bind @var{mexp} and the following monadic expressions in sequence,
3078 returning the result of the last expression.
3080 This is akin to @code{mlet}, except that the return values of the
3081 monadic expressions are ignored. In that sense, it is analogous to
3082 @code{begin}, but applied to monadic expressions.
3086 The @code{(guix monads)} module provides the @dfn{state monad}, which
3087 allows an additional value---the state---to be @emph{threaded} through
3088 monadic procedure calls.
3090 @defvr {Scheme Variable} %state-monad
3091 The state monad. Procedures in the state monad can access and change
3092 the state that is threaded.
3094 Consider the example below. The @code{square} procedure returns a value
3095 in the state monad. It returns the square of its argument, but also
3096 increments the current state value:
3100 (mlet %state-monad ((count (current-state)))
3101 (mbegin %state-monad
3102 (set-current-state (+ 1 count))
3105 (run-with-state (sequence %state-monad (map square (iota 3))) 0)
3110 When ``run'' through @var{%state-monad}, we obtain that additional state
3111 value, which is the number of @code{square} calls.
3114 @deffn {Monadic Procedure} current-state
3115 Return the current state as a monadic value.
3118 @deffn {Monadic Procedure} set-current-state @var{value}
3119 Set the current state to @var{value} and return the previous state as a
3123 @deffn {Monadic Procedure} state-push @var{value}
3124 Push @var{value} to the current state, which is assumed to be a list,
3125 and return the previous state as a monadic value.
3128 @deffn {Monadic Procedure} state-pop
3129 Pop a value from the current state and return it as a monadic value.
3130 The state is assumed to be a list.
3133 @deffn {Scheme Procedure} run-with-state @var{mval} [@var{state}]
3134 Run monadic value @var{mval} starting with @var{state} as the initial
3135 state. Return two values: the resulting value, and the resulting state.
3138 The main interface to the store monad, provided by the @code{(guix
3139 store)} module, is as follows.
3141 @defvr {Scheme Variable} %store-monad
3142 The store monad---an alias for @var{%state-monad}.
3144 Values in the store monad encapsulate accesses to the store. When its
3145 effect is needed, a value of the store monad must be ``evaluated'' by
3146 passing it to the @code{run-with-store} procedure (see below.)
3149 @deffn {Scheme Procedure} run-with-store @var{store} @var{mval} [#:guile-for-build] [#:system (%current-system)]
3150 Run @var{mval}, a monadic value in the store monad, in @var{store}, an
3151 open store connection.
3154 @deffn {Monadic Procedure} text-file @var{name} @var{text} [@var{references}]
3155 Return as a monadic value the absolute file name in the store of the file
3156 containing @var{text}, a string. @var{references} is a list of store items that the
3157 resulting text file refers to; it defaults to the empty list.
3160 @deffn {Monadic Procedure} interned-file @var{file} [@var{name}] @
3162 Return the name of @var{file} once interned in the store. Use
3163 @var{name} as its store name, or the basename of @var{file} if
3164 @var{name} is omitted.
3166 When @var{recursive?} is true, the contents of @var{file} are added
3167 recursively; if @var{file} designates a flat file and @var{recursive?}
3168 is true, its contents are added, and its permission bits are kept.
3170 The example below adds a file to the store, under two different names:
3173 (run-with-store (open-connection)
3174 (mlet %store-monad ((a (interned-file "README"))
3175 (b (interned-file "README" "LEGU-MIN")))
3176 (return (list a b))))
3178 @result{} ("/gnu/store/rwm@dots{}-README" "/gnu/store/44i@dots{}-LEGU-MIN")
3183 The @code{(guix packages)} module exports the following package-related
3186 @deffn {Monadic Procedure} package-file @var{package} [@var{file}] @
3187 [#:system (%current-system)] [#:target #f] @
3188 [#:output "out"] Return as a monadic
3189 value in the absolute file name of @var{file} within the @var{output}
3190 directory of @var{package}. When @var{file} is omitted, return the name
3191 of the @var{output} directory of @var{package}. When @var{target} is
3192 true, use it as a cross-compilation target triplet.
3195 @deffn {Monadic Procedure} package->derivation @var{package} [@var{system}]
3196 @deffnx {Monadic Procedure} package->cross-derivation @var{package} @
3197 @var{target} [@var{system}]
3198 Monadic version of @code{package-derivation} and
3199 @code{package-cross-derivation} (@pxref{Defining Packages}).
3204 @section G-Expressions
3206 @cindex G-expression
3207 @cindex build code quoting
3208 So we have ``derivations'', which represent a sequence of build actions
3209 to be performed to produce an item in the store (@pxref{Derivations}).
3210 Those build actions are performed when asking the daemon to actually
3211 build the derivations; they are run by the daemon in a container
3212 (@pxref{Invoking guix-daemon}).
3214 @cindex strata of code
3215 It should come as no surprise that we like to write those build actions
3216 in Scheme. When we do that, we end up with two @dfn{strata} of Scheme
3217 code@footnote{The term @dfn{stratum} in this context was coined by
3218 Manuel Serrano et al.@: in the context of their work on Hop. Oleg
3219 Kiselyov, who has written insightful
3220 @url{http://okmij.org/ftp/meta-programming/#meta-scheme, essays and code
3221 on this topic}, refers to this kind of code generation as
3222 @dfn{staging}.}: the ``host code''---code that defines packages, talks
3223 to the daemon, etc.---and the ``build code''---code that actually
3224 performs build actions, such as making directories, invoking
3225 @command{make}, etc.
3227 To describe a derivation and its build actions, one typically needs to
3228 embed build code inside host code. It boils down to manipulating build
3229 code as data, and Scheme's homoiconicity---code has a direct
3230 representation as data---comes in handy for that. But we need more than
3231 Scheme's normal @code{quasiquote} mechanism to construct build
3234 The @code{(guix gexp)} module implements @dfn{G-expressions}, a form of
3235 S-expressions adapted to build expressions. G-expressions, or
3236 @dfn{gexps}, consist essentially in three syntactic forms: @code{gexp},
3237 @code{ungexp}, and @code{ungexp-splicing} (or simply: @code{#~},
3238 @code{#$}, and @code{#$@@}), which are comparable respectively to
3239 @code{quasiquote}, @code{unquote}, and @code{unquote-splicing}
3240 (@pxref{Expression Syntax, @code{quasiquote},, guile, GNU Guile
3241 Reference Manual}). However, there are major differences:
3245 Gexps are meant to be written to a file and run or manipulated by other
3249 When a high-level object such as a package or derivation is unquoted
3250 inside a gexp, the result is as if its output file name had been
3254 Gexps carry information about the packages or derivations they refer to,
3255 and these dependencies are automatically added as inputs to the build
3256 processes that use them.
3259 @cindex lowering, of high-level objects in gexps
3260 This mechanism is not limited to package and derivation
3261 objects: @dfn{compilers} able to ``lower'' other high-level objects to
3262 derivations or files in the store can be defined,
3263 such that these objects can also be inserted
3264 into gexps. For example, a useful type of high-level object that can be
3265 inserted in a gexp is ``file-like objects'', which make it easy to
3266 add files to the store and refer to them in
3267 derivations and such (see @code{local-file} and @code{plain-file}
3270 To illustrate the idea, here is an example of a gexp:
3277 (symlink (string-append #$coreutils "/bin/ls")
3281 This gexp can be passed to @code{gexp->derivation}; we obtain a
3282 derivation that builds a directory containing exactly one symlink to
3283 @file{/gnu/store/@dots{}-coreutils-8.22/bin/ls}:
3286 (gexp->derivation "the-thing" build-exp)
3289 As one would expect, the @code{"/gnu/store/@dots{}-coreutils-8.22"} string is
3290 substituted to the reference to the @var{coreutils} package in the
3291 actual build code, and @var{coreutils} is automatically made an input to
3292 the derivation. Likewise, @code{#$output} (equivalent to @code{(ungexp
3293 output)}) is replaced by a string containing the derivation's output
3296 @cindex cross compilation
3297 In a cross-compilation context, it is useful to distinguish between
3298 references to the @emph{native} build of a package---that can run on the
3299 host---versus references to cross builds of a package. To that end, the
3300 @code{#+} plays the same role as @code{#$}, but is a reference to a
3301 native package build:
3304 (gexp->derivation "vi"
3307 (system* (string-append #+coreutils "/bin/ln")
3309 (string-append #$emacs "/bin/emacs")
3310 (string-append #$output "/bin/vi")))
3311 #:target "mips64el-linux")
3315 In the example above, the native build of @var{coreutils} is used, so
3316 that @command{ln} can actually run on the host; but then the
3317 cross-compiled build of @var{emacs} is referenced.
3319 The syntactic form to construct gexps is summarized below.
3321 @deffn {Scheme Syntax} #~@var{exp}
3322 @deffnx {Scheme Syntax} (gexp @var{exp})
3323 Return a G-expression containing @var{exp}. @var{exp} may contain one
3324 or more of the following forms:
3328 @itemx (ungexp @var{obj})
3329 Introduce a reference to @var{obj}. @var{obj} may have one of the
3330 supported types, for example a package or a
3331 derivation, in which case the @code{ungexp} form is replaced by its
3332 output file name---e.g., @code{"/gnu/store/@dots{}-coreutils-8.22}.
3334 If @var{obj} is a list, it is traversed and references to supported
3335 objects are substituted similarly.
3337 If @var{obj} is another gexp, its contents are inserted and its
3338 dependencies are added to those of the containing gexp.
3340 If @var{obj} is another kind of object, it is inserted as is.
3342 @item #$@var{obj}:@var{output}
3343 @itemx (ungexp @var{obj} @var{output})
3344 This is like the form above, but referring explicitly to the
3345 @var{output} of @var{obj}---this is useful when @var{obj} produces
3346 multiple outputs (@pxref{Packages with Multiple Outputs}).
3349 @itemx #+@var{obj}:output
3350 @itemx (ungexp-native @var{obj})
3351 @itemx (ungexp-native @var{obj} @var{output})
3352 Same as @code{ungexp}, but produces a reference to the @emph{native}
3353 build of @var{obj} when used in a cross compilation context.
3355 @item #$output[:@var{output}]
3356 @itemx (ungexp output [@var{output}])
3357 Insert a reference to derivation output @var{output}, or to the main
3358 output when @var{output} is omitted.
3360 This only makes sense for gexps passed to @code{gexp->derivation}.
3363 @itemx (ungexp-splicing @var{lst})
3364 Like the above, but splices the contents of @var{lst} inside the
3368 @itemx (ungexp-native-splicing @var{lst})
3369 Like the above, but refers to native builds of the objects listed in
3374 G-expressions created by @code{gexp} or @code{#~} are run-time objects
3375 of the @code{gexp?} type (see below.)
3378 @deffn {Scheme Procedure} gexp? @var{obj}
3379 Return @code{#t} if @var{obj} is a G-expression.
3382 G-expressions are meant to be written to disk, either as code building
3383 some derivation, or as plain files in the store. The monadic procedures
3384 below allow you to do that (@pxref{The Store Monad}, for more
3385 information about monads.)
3387 @deffn {Monadic Procedure} gexp->derivation @var{name} @var{exp} @
3388 [#:system (%current-system)] [#:target #f] [#:graft? #t] @
3389 [#:hash #f] [#:hash-algo #f] @
3390 [#:recursive? #f] [#:env-vars '()] [#:modules '()] @
3391 [#:module-path @var{%load-path}] @
3392 [#:references-graphs #f] [#:allowed-references #f] @
3393 [#:leaked-env-vars #f] @
3394 [#:script-name (string-append @var{name} "-builder")] @
3395 [#:local-build? #f] [#:substitutable? #t] [#:guile-for-build #f]
3396 Return a derivation @var{name} that runs @var{exp} (a gexp) with
3397 @var{guile-for-build} (a derivation) on @var{system}; @var{exp} is
3398 stored in a file called @var{script-name}. When @var{target} is true,
3399 it is used as the cross-compilation target triplet for packages referred
3402 Make @var{modules} available in the evaluation context of @var{exp};
3403 @var{modules} is a list of names of Guile modules searched in
3404 @var{module-path} to be copied in the store, compiled, and made available in
3405 the load path during the execution of @var{exp}---e.g., @code{((guix
3406 build utils) (guix build gnu-build-system))}.
3408 @var{graft?} determines whether packages referred to by @var{exp} should be grafted when
3411 When @var{references-graphs} is true, it must be a list of tuples of one of the
3415 (@var{file-name} @var{package})
3416 (@var{file-name} @var{package} @var{output})
3417 (@var{file-name} @var{derivation})
3418 (@var{file-name} @var{derivation} @var{output})
3419 (@var{file-name} @var{store-item})
3422 The right-hand-side of each element of @var{references-graphs} is automatically made
3423 an input of the build process of @var{exp}. In the build environment, each
3424 @var{file-name} contains the reference graph of the corresponding item, in a simple
3427 @var{allowed-references} must be either @code{#f} or a list of output names and packages.
3428 In the latter case, the list denotes store items that the result is allowed to
3429 refer to. Any reference to another store item will lead to a build error.
3431 The other arguments are as for @code{derivation} (@pxref{Derivations}).
3434 @cindex file-like objects
3435 The @code{local-file}, @code{plain-file}, @code{computed-file},
3436 @code{program-file}, and @code{scheme-file} procedures below return
3437 @dfn{file-like objects}. That is, when unquoted in a G-expression,
3438 these objects lead to a file in the store. Consider this G-expression:
3441 #~(system* (string-append #$glibc "/sbin/nscd") "-f"
3442 #$(local-file "/tmp/my-nscd.conf"))
3445 The effect here is to ``intern'' @file{/tmp/my-nscd.conf} by copying it
3446 to the store. Once expanded, for instance @i{via}
3447 @code{gexp->derivation}, the G-expression refers to that copy under
3448 @file{/gnu/store}; thus, modifying or removing the file in @file{/tmp}
3449 does not have any effect on what the G-expression does.
3450 @code{plain-file} can be used similarly; it differs in that the file
3451 content is directly passed as a string.
3453 @deffn {Scheme Procedure} local-file @var{file} [@var{name}] @
3455 Return an object representing local file @var{file} to add to the store; this
3456 object can be used in a gexp. @var{file} will be added to the store under @var{name}--by
3457 default the base name of @var{file}.
3459 When @var{recursive?} is true, the contents of @var{file} are added recursively; if @var{file}
3460 designates a flat file and @var{recursive?} is true, its contents are added, and its
3461 permission bits are kept.
3463 This is the declarative counterpart of the @code{interned-file} monadic
3464 procedure (@pxref{The Store Monad, @code{interned-file}}).
3467 @deffn {Scheme Procedure} plain-file @var{name} @var{content}
3468 Return an object representing a text file called @var{name} with the given
3469 @var{content} (a string) to be added to the store.
3471 This is the declarative counterpart of @code{text-file}.
3474 @deffn {Scheme Procedure} computed-file @var{name} @var{gexp} @
3475 [#:modules '()] [#:options '(#:local-build? #t)]
3476 Return an object representing the store item @var{name}, a file or
3477 directory computed by @var{gexp}. @var{modules} specifies the set of
3478 modules visible in the execution context of @var{gexp}. @var{options}
3479 is a list of additional arguments to pass to @code{gexp->derivation}.
3481 This is the declarative counterpart of @code{gexp->derivation}.
3484 @deffn {Monadic Procedure} gexp->script @var{name} @var{exp}
3485 Return an executable script @var{name} that runs @var{exp} using
3486 @var{guile} with @var{modules} in its search path.
3488 The example below builds a script that simply invokes the @command{ls}
3492 (use-modules (guix gexp) (gnu packages base))
3494 (gexp->script "list-files"
3495 #~(execl (string-append #$coreutils "/bin/ls")
3499 When ``running'' it through the store (@pxref{The Store Monad,
3500 @code{run-with-store}}), we obtain a derivation that produces an
3501 executable file @file{/gnu/store/@dots{}-list-files} along these lines:
3504 #!/gnu/store/@dots{}-guile-2.0.11/bin/guile -ds
3506 (execl (string-append "/gnu/store/@dots{}-coreutils-8.22"/bin/ls")
3511 @deffn {Scheme Procedure} program-file @var{name} @var{exp} @
3512 [#:modules '()] [#:guile #f]
3513 Return an object representing the executable store item @var{name} that
3514 runs @var{gexp}. @var{guile} is the Guile package used to execute that
3515 script, and @var{modules} is the list of modules visible to that script.
3517 This is the declarative counterpart of @code{gexp->script}.
3520 @deffn {Monadic Procedure} gexp->file @var{name} @var{exp}
3521 Return a derivation that builds a file @var{name} containing @var{exp}.
3523 The resulting file holds references to all the dependencies of @var{exp}
3524 or a subset thereof.
3527 @deffn {Scheme Procedure} scheme-file @var{name} @var{exp}
3528 Return an object representing the Scheme file @var{name} that contains
3531 This is the declarative counterpart of @code{gexp->file}.
3534 @deffn {Monadic Procedure} text-file* @var{name} @var{text} @dots{}
3535 Return as a monadic value a derivation that builds a text file
3536 containing all of @var{text}. @var{text} may list, in addition to
3537 strings, objects of any type that can be used in a gexp: packages,
3538 derivations, local file objects, etc. The resulting store file holds
3539 references to all these.
3541 This variant should be preferred over @code{text-file} anytime the file
3542 to create will reference items from the store. This is typically the
3543 case when building a configuration file that embeds store file names,
3547 (define (profile.sh)
3548 ;; Return the name of a shell script in the store that
3549 ;; initializes the 'PATH' environment variable.
3550 (text-file* "profile.sh"
3551 "export PATH=" coreutils "/bin:"
3552 grep "/bin:" sed "/bin\n"))
3555 In this example, the resulting @file{/gnu/store/@dots{}-profile.sh} file
3556 will references @var{coreutils}, @var{grep}, and @var{sed}, thereby
3557 preventing them from being garbage-collected during its lifetime.
3560 @deffn {Scheme Procedure} mixed-text-file @var{name} @var{text} @dots{}
3561 Return an object representing store file @var{name} containing
3562 @var{text}. @var{text} is a sequence of strings and file-like objects,
3566 (mixed-text-file "profile"
3567 "export PATH=" coreutils "/bin:" grep "/bin")
3570 This is the declarative counterpart of @code{text-file*}.
3573 Of course, in addition to gexps embedded in ``host'' code, there are
3574 also modules containing build tools. To make it clear that they are
3575 meant to be used in the build stratum, these modules are kept in the
3576 @code{(guix build @dots{})} name space.
3578 @cindex lowering, of high-level objects in gexps
3579 Internally, high-level objects are @dfn{lowered}, using their compiler,
3580 to either derivations or store items. For instance, lowering a package
3581 yields a derivation, and lowering a @code{plain-file} yields a store
3582 item. This is achieved using the @code{lower-object} monadic procedure.
3584 @deffn {Monadic Procedure} lower-object @var{obj} [@var{system}] @
3586 Return as a value in @var{%store-monad} the derivation or store item
3587 corresponding to @var{obj} for @var{system}, cross-compiling for
3588 @var{target} if @var{target} is true. @var{obj} must be an object that
3589 has an associated gexp compiler, such as a @code{<package>}.
3593 @c *********************************************************************
3597 This section describes tools primarily targeted at developers and users
3598 who write new package definitions. They complement the Scheme
3599 programming interface of Guix in a convenient way.
3602 * Invoking guix build:: Building packages from the command line.
3603 * Invoking guix edit:: Editing package definitions.
3604 * Invoking guix download:: Downloading a file and printing its hash.
3605 * Invoking guix hash:: Computing the cryptographic hash of a file.
3606 * Invoking guix import:: Importing package definitions.
3607 * Invoking guix refresh:: Updating package definitions.
3608 * Invoking guix lint:: Finding errors in package definitions.
3609 * Invoking guix size:: Profiling disk usage.
3610 * Invoking guix graph:: Visualizing the graph of packages.
3611 * Invoking guix environment:: Setting up development environments.
3612 * Invoking guix publish:: Sharing substitutes.
3613 * Invoking guix challenge:: Challenging substitute servers.
3614 * Invoking guix container:: Process isolation.
3617 @node Invoking guix build
3618 @section Invoking @command{guix build}
3620 The @command{guix build} command builds packages or derivations and
3621 their dependencies, and prints the resulting store paths. Note that it
3622 does not modify the user's profile---this is the job of the
3623 @command{guix package} command (@pxref{Invoking guix package}). Thus,
3624 it is mainly useful for distribution developers.
3626 The general syntax is:
3629 guix build @var{options} @var{package-or-derivation}@dots{}
3632 @var{package-or-derivation} may be either the name of a package found in
3633 the software distribution such as @code{coreutils} or
3634 @code{coreutils-8.20}, or a derivation such as
3635 @file{/gnu/store/@dots{}-coreutils-8.19.drv}. In the former case, a
3636 package with the corresponding name (and optionally version) is searched
3637 for among the GNU distribution modules (@pxref{Package Modules}).
3639 Alternatively, the @code{--expression} option may be used to specify a
3640 Scheme expression that evaluates to a package; this is useful when
3641 disambiguation among several same-named packages or package variants is
3644 The @var{options} may be zero or more of the following:
3648 @item --file=@var{file}
3649 @itemx -f @var{file}
3651 Build the package or derivation that the code within @var{file}
3654 As an example, @var{file} might contain a package definition like this
3655 (@pxref{Defining Packages}):
3658 @verbatiminclude package-hello.scm
3661 @item --expression=@var{expr}
3662 @itemx -e @var{expr}
3663 Build the package or derivation @var{expr} evaluates to.
3665 For example, @var{expr} may be @code{(@@ (gnu packages guile)
3666 guile-1.8)}, which unambiguously designates this specific variant of
3667 version 1.8 of Guile.
3669 Alternately, @var{expr} may be a G-expression, in which case it is used
3670 as a build program passed to @code{gexp->derivation}
3671 (@pxref{G-Expressions}).
3673 Lastly, @var{expr} may refer to a zero-argument monadic procedure
3674 (@pxref{The Store Monad}). The procedure must return a derivation as a
3675 monadic value, which is then passed through @code{run-with-store}.
3679 Build the packages' source derivations, rather than the packages
3682 For instance, @code{guix build -S gcc} returns something like
3683 @file{/gnu/store/@dots{}-gcc-4.7.2.tar.bz2}, which is GCC's source tarball.
3685 The returned source tarball is the result of applying any patches and
3686 code snippets specified in the package's @code{origin} (@pxref{Defining
3690 Fetch and return the source of @var{package-or-derivation} and all their
3691 dependencies, recursively. This is a handy way to obtain a local copy
3692 of all the source code needed to build @var{packages}, allowing you to
3693 eventually build them even without network access. It is an extension
3694 of the @code{--source} option and can accept one of the following
3695 optional argument values:
3699 This value causes the @code{--sources} option to behave in the same way
3700 as the @code{--source} option.
3703 Build all packages' source derivations, including any source that might
3704 be listed as @code{inputs}. This is the default value.
3707 $ guix build --sources tzdata
3708 The following derivations will be built:
3709 /gnu/store/@dots{}-tzdata2015b.tar.gz.drv
3710 /gnu/store/@dots{}-tzcode2015b.tar.gz.drv
3714 Build all packages' source derivations, as well as all source
3715 derivations for packages' transitive inputs. This can be used e.g. to
3716 prefetch package source for later offline building.
3719 $ guix build --sources=transitive tzdata
3720 The following derivations will be built:
3721 /gnu/store/@dots{}-tzcode2015b.tar.gz.drv
3722 /gnu/store/@dots{}-findutils-4.4.2.tar.xz.drv
3723 /gnu/store/@dots{}-grep-2.21.tar.xz.drv
3724 /gnu/store/@dots{}-coreutils-8.23.tar.xz.drv
3725 /gnu/store/@dots{}-make-4.1.tar.xz.drv
3726 /gnu/store/@dots{}-bash-4.3.tar.xz.drv
3732 @item --system=@var{system}
3733 @itemx -s @var{system}
3734 Attempt to build for @var{system}---e.g., @code{i686-linux}---instead of
3735 the host's system type.
3737 An example use of this is on Linux-based systems, which can emulate
3738 different personalities. For instance, passing
3739 @code{--system=i686-linux} on an @code{x86_64-linux} system allows users
3740 to build packages in a complete 32-bit environment.
3742 @item --target=@var{triplet}
3743 @cindex cross-compilation
3744 Cross-build for @var{triplet}, which must be a valid GNU triplet, such
3745 as @code{"mips64el-linux-gnu"} (@pxref{Configuration Names, GNU
3746 configuration triplets,, configure, GNU Configure and Build System}).
3748 @item --with-source=@var{source}
3749 Use @var{source} as the source of the corresponding package.
3750 @var{source} must be a file name or a URL, as for @command{guix
3751 download} (@pxref{Invoking guix download}).
3753 The ``corresponding package'' is taken to be one specified on the
3754 command line whose name matches the base of @var{source}---e.g., if
3755 @var{source} is @code{/src/guile-2.0.10.tar.gz}, the corresponding
3756 package is @code{guile}. Likewise, the version string is inferred from
3757 @var{source}; in the previous example, it's @code{2.0.10}.
3759 This option allows users to try out versions of packages other than the
3760 one provided by the distribution. The example below downloads
3761 @file{ed-1.7.tar.gz} from a GNU mirror and uses that as the source for
3762 the @code{ed} package:
3765 guix build ed --with-source=mirror://gnu/ed/ed-1.7.tar.gz
3768 As a developer, @code{--with-source} makes it easy to test release
3772 guix build guile --with-source=../guile-2.0.9.219-e1bb7.tar.xz
3775 @dots{} or to build from a checkout in a pristine environment:
3778 $ git clone git://git.sv.gnu.org/guix.git
3779 $ guix build guix --with-source=./guix
3783 Do not ``graft'' packages. In practice, this means that package updates
3784 available as grafts are not applied. @xref{Security Updates}, for more
3785 information on grafts.
3789 Return the derivation paths, not the output paths, of the given
3792 @item --root=@var{file}
3793 @itemx -r @var{file}
3794 Make @var{file} a symlink to the result, and register it as a garbage
3798 Return the build log file names or URLs for the given
3799 @var{package-or-derivation}s, or raise an error if build logs are
3802 This works regardless of how packages or derivations are specified. For
3803 instance, the following invocations are equivalent:
3806 guix build --log-file `guix build -d guile`
3807 guix build --log-file `guix build guile`
3808 guix build --log-file guile
3809 guix build --log-file -e '(@@ (gnu packages guile) guile-2.0)'
3812 If a log is unavailable locally, and unless @code{--no-substitutes} is
3813 passed, the command looks for a corresponding log on one of the
3814 substitute servers (as specified with @code{--substitute-urls}.)
3816 So for instance, let's say you want to see the build log of GDB on MIPS
3817 but you're actually on an @code{x86_64} machine:
3820 $ guix build --log-file gdb -s mips64el-linux
3821 http://hydra.gnu.org/log/@dots{}-gdb-7.10
3824 You can freely access a huge library of build logs!
3827 @cindex common build options
3828 In addition, a number of options that control the build process are
3829 common to @command{guix build} and other commands that can spawn builds,
3830 such as @command{guix package} or @command{guix archive}. These are the
3835 @item --load-path=@var{directory}
3836 @itemx -L @var{directory}
3837 Add @var{directory} to the front of the package module search path
3838 (@pxref{Package Modules}).
3840 This allows users to define their own packages and make them visible to
3841 the command-line tools.
3845 Keep the build tree of failed builds. Thus, if a build fail, its build
3846 tree is kept under @file{/tmp}, in a directory whose name is shown at
3847 the end of the build log. This is useful when debugging build issues.
3851 Do not build the derivations.
3854 When substituting a pre-built binary fails, fall back to building
3857 @item --substitute-urls=@var{urls}
3858 @anchor{client-substitute-urls}
3859 Consider @var{urls} the whitespace-separated list of substitute source
3860 URLs, overriding the default list of URLs of @command{guix-daemon}
3861 (@pxref{daemon-substitute-urls,, @command{guix-daemon} URLs}).
3863 This means that substitutes may be downloaded from @var{urls}, provided
3864 they are signed by a key authorized by the system administrator
3865 (@pxref{Substitutes}).
3867 @item --no-substitutes
3868 Do not use substitutes for build products. That is, always build things
3869 locally instead of allowing downloads of pre-built binaries
3870 (@pxref{Substitutes}).
3872 @item --no-build-hook
3873 Do not attempt to offload builds @i{via} the daemon's ``build hook''
3874 (@pxref{Daemon Offload Setup}). That is, always build things locally
3875 instead of offloading builds to remote machines.
3877 @item --max-silent-time=@var{seconds}
3878 When the build or substitution process remains silent for more than
3879 @var{seconds}, terminate it and report a build failure.
3881 @item --timeout=@var{seconds}
3882 Likewise, when the build or substitution process lasts for more than
3883 @var{seconds}, terminate it and report a build failure.
3885 By default there is no timeout. This behavior can be restored with
3888 @item --verbosity=@var{level}
3889 Use the given verbosity level. @var{level} must be an integer between 0
3890 and 5; higher means more verbose output. Setting a level of 4 or more
3891 may be helpful when debugging setup issues with the build daemon.
3893 @item --cores=@var{n}
3895 Allow the use of up to @var{n} CPU cores for the build. The special
3896 value @code{0} means to use as many CPU cores as available.
3898 @item --max-jobs=@var{n}
3900 Allow at most @var{n} build jobs in parallel. @xref{Invoking
3901 guix-daemon, @code{--max-jobs}}, for details about this option and the
3902 equivalent @command{guix-daemon} option.
3906 Behind the scenes, @command{guix build} is essentially an interface to
3907 the @code{package-derivation} procedure of the @code{(guix packages)}
3908 module, and to the @code{build-derivations} procedure of the @code{(guix
3909 derivations)} module.
3911 In addition to options explicitly passed on the command line,
3912 @command{guix build} and other @command{guix} commands that support
3913 building honor the @code{GUIX_BUILD_OPTIONS} environment variable.
3915 @defvr {Environment Variable} GUIX_BUILD_OPTIONS
3916 Users can define this variable to a list of command line options that
3917 will automatically be used by @command{guix build} and other
3918 @command{guix} commands that can perform builds, as in the example
3922 $ export GUIX_BUILD_OPTIONS="--no-substitutes -c 2 -L /foo/bar"
3925 These options are parsed independently, and the result is appended to
3926 the parsed command-line options.
3930 @node Invoking guix edit
3931 @section Invoking @command{guix edit}
3933 @cindex package definition, editing
3934 So many packages, so many source files! The @command{guix edit} command
3935 facilitates the life of packagers by pointing their editor at the source
3936 file containing the definition of the specified packages. For instance:
3939 guix edit gcc-4.8 vim
3943 launches the program specified in the @code{VISUAL} or in the
3944 @code{EDITOR} environment variable to edit the recipe of GCC@tie{}4.8.4
3947 If you are using Emacs, note that the Emacs user interface provides
3948 similar functionality in the ``package info'' and ``package list''
3949 buffers created by @kbd{M-x guix-search-by-name} and similar commands
3950 (@pxref{Emacs Commands}).
3953 @node Invoking guix download
3954 @section Invoking @command{guix download}
3956 When writing a package definition, developers typically need to download
3957 the package's source tarball, compute its SHA256 hash, and write that
3958 hash in the package definition (@pxref{Defining Packages}). The
3959 @command{guix download} tool helps with this task: it downloads a file
3960 from the given URI, adds it to the store, and prints both its file name
3961 in the store and its SHA256 hash.
3963 The fact that the downloaded file is added to the store saves bandwidth:
3964 when the developer eventually tries to build the newly defined package
3965 with @command{guix build}, the source tarball will not have to be
3966 downloaded again because it is already in the store. It is also a
3967 convenient way to temporarily stash files, which may be deleted
3968 eventually (@pxref{Invoking guix gc}).
3970 The @command{guix download} command supports the same URIs as used in
3971 package definitions. In particular, it supports @code{mirror://} URIs.
3972 @code{https} URIs (HTTP over TLS) are supported @emph{provided} the
3973 Guile bindings for GnuTLS are available in the user's environment; when
3974 they are not available, an error is raised. @xref{Guile Preparations,
3975 how to install the GnuTLS bindings for Guile,, gnutls-guile,
3976 GnuTLS-Guile}, for more information.
3978 The following option is available:
3981 @item --format=@var{fmt}
3983 Write the hash in the format specified by @var{fmt}. For more
3984 information on the valid values for @var{fmt}, @pxref{Invoking guix hash}.
3987 @node Invoking guix hash
3988 @section Invoking @command{guix hash}
3990 The @command{guix hash} command computes the SHA256 hash of a file.
3991 It is primarily a convenience tool for anyone contributing to the
3992 distribution: it computes the cryptographic hash of a file, which can be
3993 used in the definition of a package (@pxref{Defining Packages}).
3995 The general syntax is:
3998 guix hash @var{option} @var{file}
4001 @command{guix hash} has the following option:
4005 @item --format=@var{fmt}
4007 Write the hash in the format specified by @var{fmt}.
4009 Supported formats: @code{nix-base32}, @code{base32}, @code{base16}
4010 (@code{hex} and @code{hexadecimal} can be used as well).
4012 If the @option{--format} option is not specified, @command{guix hash}
4013 will output the hash in @code{nix-base32}. This representation is used
4014 in the definitions of packages.
4018 Compute the hash on @var{file} recursively.
4020 In this case, the hash is computed on an archive containing @var{file},
4021 including its children if it is a directory. Some of @var{file}'s
4022 meta-data is part of the archive; for instance, when @var{file} is a
4023 regular file, the hash is different depending on whether @var{file} is
4024 executable or not. Meta-data such as time stamps has no impact on the
4025 hash (@pxref{Invoking guix archive}).
4026 @c FIXME: Replace xref above with xref to an ``Archive'' section when
4031 @node Invoking guix import
4032 @section Invoking @command{guix import}
4034 @cindex importing packages
4035 @cindex package import
4036 @cindex package conversion
4037 The @command{guix import} command is useful for people willing to add a
4038 package to the distribution but who'd rather do as little work as
4039 possible to get there---a legitimate demand. The command knows of a few
4040 repositories from which it can ``import'' package meta-data. The result
4041 is a package definition, or a template thereof, in the format we know
4042 (@pxref{Defining Packages}).
4044 The general syntax is:
4047 guix import @var{importer} @var{options}@dots{}
4050 @var{importer} specifies the source from which to import package
4051 meta-data, and @var{options} specifies a package identifier and other
4052 options specific to @var{importer}. Currently, the available
4057 Import meta-data for the given GNU package. This provides a template
4058 for the latest version of that GNU package, including the hash of its
4059 source tarball, and its canonical synopsis and description.
4061 Additional information such as the package's dependencies and its
4062 license needs to be figured out manually.
4064 For example, the following command returns a package definition for
4068 guix import gnu hello
4071 Specific command-line options are:
4074 @item --key-download=@var{policy}
4075 As for @code{guix refresh}, specify the policy to handle missing OpenPGP
4076 keys when verifying the package's signature. @xref{Invoking guix
4077 refresh, @code{--key-download}}.
4082 Import meta-data from the @uref{https://pypi.python.org/, Python Package
4083 Index}@footnote{This functionality requires Guile-JSON to be installed.
4084 @xref{Requirements}.}. Information is taken from the JSON-formatted
4085 description available at @code{pypi.python.org} and usually includes all
4086 the relevant information, including package dependencies.
4088 The command below imports meta-data for the @code{itsdangerous} Python
4092 guix import pypi itsdangerous
4097 Import meta-data from @uref{https://rubygems.org/,
4098 RubyGems}@footnote{This functionality requires Guile-JSON to be
4099 installed. @xref{Requirements}.}. Information is taken from the
4100 JSON-formatted description available at @code{rubygems.org} and includes
4101 most relevant information, including runtime dependencies. There are
4102 some caveats, however. The meta-data doesn't distinguish between
4103 synopses and descriptions, so the same string is used for both fields.
4104 Additionally, the details of non-Ruby dependencies required to build
4105 native extensions is unavailable and left as an exercise to the
4108 The command below imports meta-data for the @code{rails} Ruby package:
4111 guix import gem rails
4116 Import meta-data from @uref{https://www.metacpan.org/, MetaCPAN}.
4117 Information is taken from the JSON-formatted meta-data provided through
4118 @uref{https://api.metacpan.org/, MetaCPAN's API} and includes most
4119 relevant information, such as module dependencies. License information
4120 should be checked closely. If Perl is available in the store, then the
4121 @code{corelist} utility will be used to filter core modules out of the
4122 list of dependencies.
4124 The command command below imports meta-data for the @code{Acme::Boolean}
4128 guix import cpan Acme::Boolean
4133 Import meta-data from @uref{http://cran.r-project.org/, CRAN}, the
4134 central repository for the @uref{http://r-project.org, GNU@tie{}R
4135 statistical and graphical environment}.
4137 Information is extracted from the HTML package description.
4139 The command command below imports meta-data for the @code{Cairo}
4143 guix import cran Cairo
4147 Import meta-data from a local copy of the source of the
4148 @uref{http://nixos.org/nixpkgs/, Nixpkgs distribution}@footnote{This
4149 relies on the @command{nix-instantiate} command of
4150 @uref{http://nixos.org/nix/, Nix}.}. Package definitions in Nixpkgs are
4151 typically written in a mixture of Nix-language and Bash code. This
4152 command only imports the high-level package structure that is written in
4153 the Nix language. It normally includes all the basic fields of a
4156 When importing a GNU package, the synopsis and descriptions are replaced
4157 by their canonical upstream variant.
4159 Usually, you will first need to do:
4162 export NIX_REMOTE=daemon
4166 so that @command{nix-instantiate} does not try to open the Nix database.
4168 As an example, the command below imports the package definition of
4169 LibreOffice (more precisely, it imports the definition of the package
4170 bound to the @code{libreoffice} top-level attribute):
4173 guix import nix ~/path/to/nixpkgs libreoffice
4178 Import meta-data from Haskell community's central package archive
4179 @uref{https://hackage.haskell.org/, Hackage}. Information is taken from
4180 Cabal files and includes all the relevant information, including package
4183 Specific command-line options are:
4188 Read a Cabal file from the standard input.
4189 @item --no-test-dependencies
4191 Do not include dependencies required by the test suites only.
4192 @item --cabal-environment=@var{alist}
4193 @itemx -e @var{alist}
4194 @var{alist} is a Scheme alist defining the environment in which the
4195 Cabal conditionals are evaluated. The accepted keys are: @code{os},
4196 @code{arch}, @code{impl} and a string representing the name of a flag.
4197 The value associated with a flag has to be either the symbol
4198 @code{true} or @code{false}. The value associated with other keys
4199 has to conform to the Cabal file format definition. The default value
4200 associated with the keys @code{os}, @code{arch} and @code{impl} is
4201 @samp{linux}, @samp{x86_64} and @samp{ghc} respectively.
4204 The command below imports meta-data for the latest version of the
4205 @code{HTTP} Haskell package without including test dependencies and
4206 specifying the value of the flag @samp{network-uri} as @code{false}:
4209 guix import hackage -t -e "'((\"network-uri\" . false))" HTTP
4212 A specific package version may optionally be specified by following the
4213 package name by a hyphen and a version number as in the following example:
4216 guix import hackage mtl-2.1.3.1
4221 Import meta-data from an Emacs Lisp Package Archive (ELPA) package
4222 repository (@pxref{Packages,,, emacs, The GNU Emacs Manual}).
4224 Specific command-line options are:
4227 @item --archive=@var{repo}
4228 @itemx -a @var{repo}
4229 @var{repo} identifies the archive repository from which to retrieve the
4230 information. Currently the supported repositories and their identifiers
4234 @uref{http://elpa.gnu.org/packages, GNU}, selected by the @code{gnu}
4235 identifier. This is the default.
4238 @uref{http://stable.melpa.org/packages, MELPA-Stable}, selected by the
4239 @code{melpa-stable} identifier.
4242 @uref{http://melpa.org/packages, MELPA}, selected by the @code{melpa}
4248 The structure of the @command{guix import} code is modular. It would be
4249 useful to have more importers for other package formats, and your help
4250 is welcome here (@pxref{Contributing}).
4252 @node Invoking guix refresh
4253 @section Invoking @command{guix refresh}
4255 The primary audience of the @command{guix refresh} command is developers
4256 of the GNU software distribution. By default, it reports any packages
4257 provided by the distribution that are outdated compared to the latest
4258 upstream version, like this:
4262 gnu/packages/gettext.scm:29:13: gettext would be upgraded from 0.18.1.1 to 0.18.2.1
4263 gnu/packages/glib.scm:77:12: glib would be upgraded from 2.34.3 to 2.37.0
4266 It does so by browsing each package's FTP directory and determining the
4267 highest version number of the source tarballs therein. The command
4268 knows how to update specific types of packages: GNU packages, ELPA
4269 packages, etc.---see the documentation for @option{--type} below. The
4270 are many packages, though, for which it lacks a method to determine
4271 whether a new upstream release is available. However, the mechanism is
4272 extensible, so feel free to get in touch with us to add a new method!
4274 When passed @code{--update}, it modifies distribution source files to
4275 update the version numbers and source tarball hashes of those packages'
4276 recipes (@pxref{Defining Packages}). This is achieved by downloading
4277 each package's latest source tarball and its associated OpenPGP
4278 signature, authenticating the downloaded tarball against its signature
4279 using @command{gpg}, and finally computing its hash. When the public
4280 key used to sign the tarball is missing from the user's keyring, an
4281 attempt is made to automatically retrieve it from a public key server;
4282 when it's successful, the key is added to the user's keyring; otherwise,
4283 @command{guix refresh} reports an error.
4285 The following options are supported:
4289 @item --expression=@var{expr}
4290 @itemx -e @var{expr}
4291 Consider the package @var{expr} evaluates to.
4293 This is useful to precisely refer to a package, as in this example:
4296 guix refresh -l -e '(@@@@ (gnu packages commencement) glibc-final)'
4299 This command lists the dependents of the ``final'' libc (essentially all
4304 Update distribution source files (package recipes) in place. This is
4305 usually run from a checkout of the Guix source tree (@pxref{Running
4306 Guix Before It Is Installed}):
4309 $ ./pre-inst-env guix refresh -s non-core
4312 @xref{Defining Packages}, for more information on package definitions.
4314 @item --select=[@var{subset}]
4315 @itemx -s @var{subset}
4316 Select all the packages in @var{subset}, one of @code{core} or
4319 The @code{core} subset refers to all the packages at the core of the
4320 distribution---i.e., packages that are used to build ``everything
4321 else''. This includes GCC, libc, Binutils, Bash, etc. Usually,
4322 changing one of these packages in the distribution entails a rebuild of
4323 all the others. Thus, such updates are an inconvenience to users in
4324 terms of build time or bandwidth used to achieve the upgrade.
4326 The @code{non-core} subset refers to the remaining packages. It is
4327 typically useful in cases where an update of the core packages would be
4330 @item --type=@var{updater}
4331 @itemx -t @var{updater}
4332 Select only packages handled by @var{updater} (may be a comma-separated
4333 list of updaters). Currently, @var{updater} may be one of:
4337 the updater for GNU packages;
4339 the updater for @uref{http://elpa.gnu.org/, ELPA} packages;
4341 the updater for @uref{http://cran.r-project.org/, CRAN} packages;
4343 the updater for @uref{https://pypi.python.org, PyPI} packages.
4346 For instance, the following commands only checks for updates of Emacs
4347 packages hosted at @code{elpa.gnu.org} and updates of CRAN packages:
4350 $ guix refresh --type=elpa,cran
4351 gnu/packages/statistics.scm:819:13: r-testthat would be upgraded from 0.10.0 to 0.11.0
4352 gnu/packages/emacs.scm:856:13: emacs-auctex would be upgraded from 11.88.6 to 11.88.9
4357 In addition, @command{guix refresh} can be passed one or more package
4358 names, as in this example:
4361 $ ./pre-inst-env guix refresh -u emacs idutils gcc-4.8.4
4365 The command above specifically updates the @code{emacs} and
4366 @code{idutils} packages. The @code{--select} option would have no
4367 effect in this case.
4369 When considering whether to upgrade a package, it is sometimes
4370 convenient to know which packages would be affected by the upgrade and
4371 should be checked for compatibility. For this the following option may
4372 be used when passing @command{guix refresh} one or more package names:
4376 @item --list-updaters
4378 List available updaters and exit (see @option{--type} above.)
4380 @item --list-dependent
4382 List top-level dependent packages that would need to be rebuilt as a
4383 result of upgrading one or more packages.
4387 Be aware that the @code{--list-dependent} option only
4388 @emph{approximates} the rebuilds that would be required as a result of
4389 an upgrade. More rebuilds might be required under some circumstances.
4392 $ guix refresh --list-dependent flex
4393 Building the following 120 packages would ensure 213 dependent packages are rebuilt:
4394 hop-2.4.0 geiser-0.4 notmuch-0.18 mu-0.9.9.5 cflow-1.4 idutils-4.6 @dots{}
4397 The command above lists a set of packages that could be built to check
4398 for compatibility with an upgraded @code{flex} package.
4400 The following options can be used to customize GnuPG operation:
4404 @item --gpg=@var{command}
4405 Use @var{command} as the GnuPG 2.x command. @var{command} is searched
4406 for in @code{$PATH}.
4408 @item --key-download=@var{policy}
4409 Handle missing OpenPGP keys according to @var{policy}, which may be one
4414 Always download missing OpenPGP keys from the key server, and add them
4415 to the user's GnuPG keyring.
4418 Never try to download missing OpenPGP keys. Instead just bail out.
4421 When a package signed with an unknown OpenPGP key is encountered, ask
4422 the user whether to download it or not. This is the default behavior.
4425 @item --key-server=@var{host}
4426 Use @var{host} as the OpenPGP key server when importing a public key.
4430 @node Invoking guix lint
4431 @section Invoking @command{guix lint}
4432 The @command{guix lint} is meant to help package developers avoid common
4433 errors and use a consistent style. It runs a number of checks on a
4434 given set of packages in order to find common mistakes in their
4435 definitions. Available @dfn{checkers} include (see
4436 @code{--list-checkers} for a complete list):
4441 Validate certain typographical and stylistic rules about package
4442 descriptions and synopses.
4444 @item inputs-should-be-native
4445 Identify inputs that should most likely be native inputs.
4449 @itemx source-file-name
4450 Probe @code{home-page} and @code{source} URLs and report those that are
4451 invalid. Check that the source file name is meaningful, e.g. is not
4452 just a version number or ``git-checkout'', and should not have a
4453 @code{file-name} declared (@pxref{origin Reference}).
4456 Report known vulnerabilities found in the Common Vulnerabilities and
4457 Exposures (CVE) database
4458 @uref{https://nvd.nist.gov/download.cfm#CVE_FEED, published by the US
4462 Warn about obvious source code formatting issues: trailing white space,
4463 use of tabulations, etc.
4466 The general syntax is:
4469 guix lint @var{options} @var{package}@dots{}
4472 If no package is given on the command line, then all packages are checked.
4473 The @var{options} may be zero or more of the following:
4479 Only enable the checkers specified in a comma-separated list using the
4480 names returned by @code{--list-checkers}.
4482 @item --list-checkers
4484 List and describe all the available checkers that will be run on packages
4489 @node Invoking guix size
4490 @section Invoking @command{guix size}
4492 The @command{guix size} command helps package developers profile the
4493 disk usage of packages. It is easy to overlook the impact of an
4494 additional dependency added to a package, or the impact of using a
4495 single output for a package that could easily be split (@pxref{Packages
4496 with Multiple Outputs}). These are the typical issues that
4497 @command{guix size} can highlight.
4499 The command can be passed a package specification such as @code{gcc-4.8}
4500 or @code{guile:debug}, or a file name in the store. Consider this
4504 $ guix size coreutils
4505 store item total self
4506 /gnu/store/@dots{}-coreutils-8.23 70.0 13.9 19.8%
4507 /gnu/store/@dots{}-gmp-6.0.0a 55.3 2.5 3.6%
4508 /gnu/store/@dots{}-acl-2.2.52 53.7 0.5 0.7%
4509 /gnu/store/@dots{}-attr-2.4.46 53.2 0.3 0.5%
4510 /gnu/store/@dots{}-gcc-4.8.4-lib 52.9 15.7 22.4%
4511 /gnu/store/@dots{}-glibc-2.21 37.2 37.2 53.1%
4515 The store items listed here constitute the @dfn{transitive closure} of
4516 Coreutils---i.e., Coreutils and all its dependencies, recursively---as
4517 would be returned by:
4520 $ guix gc -R /gnu/store/@dots{}-coreutils-8.23
4523 Here the output shows 3 columns next to store items. The first column,
4524 labeled ``total'', shows the size in mebibytes (MiB) of the closure of
4525 the store item---that is, its own size plus the size of all its
4526 dependencies. The next column, labeled ``self'', shows the size of the
4527 item itself. The last column shows the ratio of the item's size to the
4528 space occupied by all the items listed here.
4530 In this example, we see that the closure of Coreutils weighs in at
4531 70@tie{}MiB, half of which is taken by libc. (That libc represents a
4532 large fraction of the closure is not a problem @i{per se} because it is
4533 always available on the system anyway.)
4535 When the package passed to @command{guix size} is available in the
4536 store, @command{guix size} queries the daemon to determine its
4537 dependencies, and measures its size in the store, similar to @command{du
4538 -ms --apparent-size} (@pxref{du invocation,,, coreutils, GNU
4541 When the given package is @emph{not} in the store, @command{guix size}
4542 reports information based on information about the available substitutes
4543 (@pxref{Substitutes}). This allows it to profile disk usage of store
4544 items that are not even on disk, only available remotely.
4546 The available options are:
4550 @item --substitute-urls=@var{urls}
4551 Use substitute information from @var{urls}.
4552 @xref{client-substitute-urls, the same option for @code{guix build}}.
4554 @item --map-file=@var{file}
4555 Write to @var{file} a graphical map of disk usage as a PNG file.
4557 For the example above, the map looks like this:
4559 @image{images/coreutils-size-map,5in,, map of Coreutils disk usage
4560 produced by @command{guix size}}
4562 This option requires that
4563 @uref{http://wingolog.org/software/guile-charting/, Guile-Charting} be
4564 installed and visible in Guile's module search path. When that is not
4565 the case, @command{guix size} fails as it tries to load it.
4567 @item --system=@var{system}
4568 @itemx -s @var{system}
4569 Consider packages for @var{system}---e.g., @code{x86_64-linux}.
4573 @node Invoking guix graph
4574 @section Invoking @command{guix graph}
4577 Packages and their dependencies form a @dfn{graph}, specifically a
4578 directed acyclic graph (DAG). It can quickly become difficult to have a
4579 mental model of the package DAG, so the @command{guix graph} command is
4580 here to provide a visual representation of the DAG. @command{guix
4581 graph} emits a DAG representation in the input format of
4582 @uref{http://www.graphviz.org/, Graphviz}, so its output can be passed
4583 directly to Graphviz's @command{dot} command, for instance. The general
4587 guix graph @var{options} @var{package}@dots{}
4590 For example, the following command generates a PDF file representing the
4591 package DAG for the GNU@tie{}Core Utilities, showing its build-time
4595 guix graph coreutils | dot -Tpdf > dag.pdf
4598 The output looks like this:
4600 @image{images/coreutils-graph,2in,,Dependency graph of the GNU Coreutils}
4602 Nice little graph, no?
4604 But there's more than one graph! The one above is concise: it's the
4605 graph of package objects, omitting implicit inputs such as GCC, libc,
4606 grep, etc. It's often useful to have such a concise graph, but
4607 sometimes you want to see more details. @command{guix graph} supports
4608 several types of graphs, allowing you to choose the level of details:
4612 This is the default type, the one we used above. It shows the DAG of
4613 package objects, excluding implicit dependencies. It is concise, but
4614 filters out many details.
4617 This is the package DAG, @emph{including} implicit inputs.
4619 For instance, the following command:
4622 guix graph --type=bag-emerged coreutils | dot -Tpdf > dag.pdf
4625 ... yields this bigger graph:
4627 @image{images/coreutils-bag-graph,,5in,Detailed dependency graph of the GNU Coreutils}
4629 At the bottom of the graph, we see all the implicit inputs of
4630 @var{gnu-build-system} (@pxref{Build Systems, @code{gnu-build-system}}).
4632 Now, note that the dependencies of those implicit inputs---that is, the
4633 @dfn{bootstrap dependencies} (@pxref{Bootstrapping})---are not shown
4634 here, for conciseness.
4637 Similar to @code{bag-emerged}, but this time including all the bootstrap
4640 @item bag-with-origins
4641 Similar to @code{bag}, but also showing origins and their dependencies.
4644 This is the most detailed representation: It shows the DAG of
4645 derivations (@pxref{Derivations}) and plain store items. Compared to
4646 the above representation, many additional nodes are visible, including
4647 builds scripts, patches, Guile modules, etc.
4651 All the above types correspond to @emph{build-time dependencies}. The
4652 following graph type represents the @emph{run-time dependencies}:
4656 This is the graph of @dfn{references} of a package output, as returned
4657 by @command{guix gc --references} (@pxref{Invoking guix gc}).
4659 If the given package output is not available in the store, @command{guix
4660 graph} attempts to obtain dependency information from substitutes.
4663 The available options are the following:
4666 @item --type=@var{type}
4667 @itemx -t @var{type}
4668 Produce a graph output of @var{type}, where @var{type} must be one of
4669 the values listed above.
4672 List the supported graph types.
4674 @item --expression=@var{expr}
4675 @itemx -e @var{expr}
4676 Consider the package @var{expr} evaluates to.
4678 This is useful to precisely refer to a package, as in this example:
4681 guix graph -e '(@@@@ (gnu packages commencement) gnu-make-final)'
4686 @node Invoking guix environment
4687 @section Invoking @command{guix environment}
4689 @cindex reproducible build environments
4690 @cindex development environments
4691 The purpose of @command{guix environment} is to assist hackers in
4692 creating reproducible development environments without polluting their
4693 package profile. The @command{guix environment} tool takes one or more
4694 packages, builds all of the necessary inputs, and creates a shell
4695 environment to use them.
4697 The general syntax is:
4700 guix environment @var{options} @var{package}@dots{}
4703 The following example spawns a new shell set up for the development of
4707 guix environment guile
4710 If the specified packages are not built yet, @command{guix environment}
4711 automatically builds them. The new shell's environment is an augmented
4712 version of the environment that @command{guix environment} was run in.
4713 It contains the necessary search paths for building the given package
4714 added to the existing environment variables. To create a ``pure''
4715 environment in which the original environment variables have been unset,
4716 use the @code{--pure} option@footnote{Users sometimes wrongfully augment
4717 environment variables such as @code{PATH} in their @file{~/.bashrc}
4718 file. As a consequence, when @code{guix environment} launches it, Bash
4719 may read @file{~/.bashrc}, thereby introducing ``impurities'' in these
4720 environment variables. It is an error to define such environment
4721 variables in @file{.bashrc}; instead, they should be defined in
4722 @file{.bash_profile}, which is sourced only by log-in shells.
4723 @xref{Bash Startup Files,,, bash, The GNU Bash Reference Manual}, for
4724 details on Bash start-up files.}.
4726 @vindex GUIX_ENVIRONMENT
4727 @command{guix environment} defines the @code{GUIX_ENVIRONMENT}
4728 variable in the shell it spaws. This allows users to, say, define a
4729 specific prompt for development environments in their @file{.bashrc}
4730 (@pxref{Bash Startup Files,,, bash, The GNU Bash Reference Manual}):
4733 if [ -n "$GUIX_ENVIRONMENT" ]
4735 export PS1="\u@@\h \w [dev]\$ "
4739 Additionally, more than one package may be specified, in which case the
4740 union of the inputs for the given packages are used. For example, the
4741 command below spawns a shell where all of the dependencies of both Guile
4742 and Emacs are available:
4745 guix environment guile emacs
4748 Sometimes an interactive shell session is not desired. An arbitrary
4749 command may be invoked by placing the @code{--} token to separate the
4750 command from the rest of the arguments:
4753 guix environment guile -- make -j4
4756 In other situations, it is more convenient to specify the list of
4757 packages needed in the environment. For example, the following command
4758 runs @command{python} from an environment containing Python@tie{}2.7 and
4762 guix environment --ad-hoc python2-numpy python-2.7 -- python
4765 Furthermore, one might want the dependencies of a package and also some
4766 additional packages that are not build-time or runtime dependencies, but
4767 are useful when developing nonetheless. Because of this, the
4768 @code{--ad-hoc} flag is positional. Packages appearing before
4769 @code{--ad-hoc} are interpreted as packages whose dependencies will be
4770 added to the environment. Packages appearing after are interpreted as
4771 packages that will be added to the environment directly. For example,
4772 the following command creates a Guix development environment that
4773 additionally includes Git and strace:
4776 guix environment guix --ad-hoc git strace
4779 Sometimes it is desirable to isolate the environment as much as
4780 possible, for maximal purity and reproducibility. In particular, when
4781 using Guix on a host distro that is not GuixSD, it is desirable to
4782 prevent access to @file{/usr/bin} and other system-wide resources from
4783 the development environment. For example, the following command spawns
4784 a Guile REPL in a ``container'' where only the store and the current
4785 working directory are mounted:
4788 guix environment --ad-hoc --container guile -- guile
4792 The @code{--container} option requires Linux-libre 3.19 or newer.
4795 The available options are summarized below.
4798 @item --expression=@var{expr}
4799 @itemx -e @var{expr}
4800 Create an environment for the package or list of packages that
4801 @var{expr} evaluates to.
4803 For example, running:
4806 guix environment -e '(@@ (gnu packages maths) petsc-openmpi)'
4809 starts a shell with the environment for this specific variant of the
4815 guix environment --ad-hoc -e '(@@ (gnu) %base-packages)'
4818 starts a shell with all the GuixSD base packages available.
4820 @item --load=@var{file}
4821 @itemx -l @var{file}
4822 Create an environment for the package or list of packages that the code
4823 within @var{file} evaluates to.
4825 As an example, @var{file} might contain a definition like this
4826 (@pxref{Defining Packages}):
4829 @verbatiminclude environment-gdb.scm
4833 Include all specified packages in the resulting environment, as if an
4834 @i{ad hoc} package were defined with them as inputs. This option is
4835 useful for quickly creating an environment without having to write a
4836 package expression to contain the desired inputs.
4838 For instance, the command:
4841 guix environment --ad-hoc guile guile-sdl -- guile
4844 runs @command{guile} in an environment where Guile and Guile-SDL are
4847 Note that this example implicitly asks for the default output of
4848 @code{guile} and @code{guile-sdl} but it is possible to ask for a
4849 specific output---e.g., @code{glib:bin} asks for the @code{bin} output
4850 of @code{glib} (@pxref{Packages with Multiple Outputs}).
4852 This option may be composed with the default behavior of @command{guix
4853 environment}. Packages appearing before @code{--ad-hoc} are interpreted
4854 as packages whose dependencies will be added to the environment, the
4855 default behavior. Packages appearing after are interpreted as packages
4856 that will be added to the environment directly.
4859 Unset existing environment variables when building the new environment.
4860 This has the effect of creating an environment in which search paths
4861 only contain package inputs.
4863 @item --search-paths
4864 Display the environment variable definitions that make up the
4867 @item --system=@var{system}
4868 @itemx -s @var{system}
4869 Attempt to build for @var{system}---e.g., @code{i686-linux}.
4874 Run @var{command} within an isolated container. The current working
4875 directory outside the container is mapped to @file{/env} inside the
4876 container. Additionally, the spawned process runs as the current user
4877 outside the container, but has root privileges in the context of the
4882 For containers, share the network namespace with the host system.
4883 Containers created without this flag only have access to the loopback
4886 @item --expose=@var{source}[=@var{target}]
4887 For containers, expose the file system @var{source} from the host system
4888 as the read-only file system @var{target} within the container. If
4889 @var{target} is not specified, @var{source} is used as the target mount
4890 point in the container.
4892 The example below spawns a Guile REPL in a container in which the user's
4893 home directory is accessible read-only via the @file{/exchange}
4897 guix environment --container --expose=$HOME=/exchange guile -- guile
4900 @item --share=@var{source}[=@var{target}]
4901 For containers, share the file system @var{source} from the host system
4902 as the writable file system @var{target} within the container. If
4903 @var{target} is not specified, @var{source} is used as the target mount
4904 point in the container.
4906 The example below spawns a Guile REPL in a container in which the user's
4907 home directory is accessible for both reading and writing via the
4908 @file{/exchange} directory:
4911 guix environment --container --share=$HOME=/exchange guile -- guile
4915 It also supports all of the common build options that @command{guix
4916 build} supports (@pxref{Invoking guix build, common build options}).
4918 @node Invoking guix publish
4919 @section Invoking @command{guix publish}
4921 The purpose of @command{guix publish} is to enable users to easily share
4922 their store with others, which can then use it as a substitute server
4923 (@pxref{Substitutes}).
4925 When @command{guix publish} runs, it spawns an HTTP server which allows
4926 anyone with network access to obtain substitutes from it. This means
4927 that any machine running Guix can also act as if it were a build farm,
4928 since the HTTP interface is compatible with Hydra, the software behind
4929 the @code{hydra.gnu.org} build farm.
4931 For security, each substitute is signed, allowing recipients to check
4932 their authenticity and integrity (@pxref{Substitutes}). Because
4933 @command{guix publish} uses the system's signing key, which is only
4934 readable by the system administrator, it must be started as root; the
4935 @code{--user} option makes it drop root privileges early on.
4937 The signing key pair must be generated before @command{guix publish} is
4938 launched, using @command{guix archive --generate-key} (@pxref{Invoking
4941 The general syntax is:
4944 guix publish @var{options}@dots{}
4947 Running @command{guix publish} without any additional arguments will
4948 spawn an HTTP server on port 8080:
4954 Once a publishing server has been authorized (@pxref{Invoking guix
4955 archive}), the daemon may download substitutes from it:
4958 guix-daemon --substitute-urls=http://example.org:8080
4961 The following options are available:
4964 @item --port=@var{port}
4965 @itemx -p @var{port}
4966 Listen for HTTP requests on @var{port}.
4968 @item --listen=@var{host}
4969 Listen on the network interface for @var{host}. The default is to
4970 accept connections from any interface.
4972 @item --user=@var{user}
4973 @itemx -u @var{user}
4974 Change privileges to @var{user} as soon as possible---i.e., once the
4975 server socket is open and the signing key has been read.
4977 @item --repl[=@var{port}]
4978 @itemx -r [@var{port}]
4979 Spawn a Guile REPL server (@pxref{REPL Servers,,, guile, GNU Guile
4980 Reference Manual}) on @var{port} (37146 by default). This is used
4981 primarily for debugging a running @command{guix publish} server.
4984 Enabling @command{guix publish} on a GuixSD system is a one-liner: just
4985 add a call to @code{guix-publish-service} in the @code{services} field
4986 of the @code{operating-system} declaration (@pxref{guix-publish-service,
4987 @code{guix-publish-service}}).
4990 @node Invoking guix challenge
4991 @section Invoking @command{guix challenge}
4993 @cindex reproducible builds
4994 @cindex verifiable builds
4996 Do the binaries provided by this server really correspond to the source
4997 code it claims to build? Is this package's build process deterministic?
4998 These are the questions the @command{guix challenge} command attempts to
5001 The former is obviously an important question: Before using a substitute
5002 server (@pxref{Substitutes}), you'd rather @emph{verify} that it
5003 provides the right binaries, and thus @emph{challenge} it. The latter
5004 is what enables the former: If package builds are deterministic, then
5005 independent builds of the package should yield the exact same result,
5006 bit for bit; if a server provides a binary different from the one
5007 obtained locally, it may be either corrupt or malicious.
5009 We know that the hash that shows up in @file{/gnu/store} file names is
5010 the hash of all the inputs of the process that built the file or
5011 directory---compilers, libraries, build scripts,
5012 etc. (@pxref{Introduction}). Assuming deterministic build processes,
5013 one store file name should map to exactly one build output.
5014 @command{guix challenge} checks whether there is, indeed, a single
5015 mapping by comparing the build outputs of several independent builds of
5016 any given store item.
5018 The command's output looks like this:
5021 $ guix challenge --substitute-urls="http://hydra.gnu.org http://guix.example.org"
5022 updating list of substitutes from 'http://hydra.gnu.org'... 100.0%
5023 updating list of substitutes from 'http://guix.example.org'... 100.0%
5024 /gnu/store/@dots{}-openssl-1.0.2d contents differ:
5025 local hash: 0725l22r5jnzazaacncwsvp9kgf42266ayyp814v7djxs7nk963q
5026 http://hydra.gnu.org/nar/@dots{}-openssl-1.0.2d: 0725l22r5jnzazaacncwsvp9kgf42266ayyp814v7djxs7nk963q
5027 http://guix.example.org/nar/@dots{}-openssl-1.0.2d: 1zy4fmaaqcnjrzzajkdn3f5gmjk754b43qkq47llbyak9z0qjyim
5028 /gnu/store/@dots{}-git-2.5.0 contents differ:
5029 local hash: 00p3bmryhjxrhpn2gxs2fy0a15lnip05l97205pgbk5ra395hyha
5030 http://hydra.gnu.org/nar/@dots{}-git-2.5.0: 069nb85bv4d4a6slrwjdy8v1cn4cwspm3kdbmyb81d6zckj3nq9f
5031 http://guix.example.org/nar/@dots{}-git-2.5.0: 0mdqa9w1p6cmli6976v4wi0sw9r4p5prkj7lzfd1877wk11c9c73
5032 /gnu/store/@dots{}-pius-2.1.1 contents differ:
5033 local hash: 0k4v3m9z1zp8xzzizb7d8kjj72f9172xv078sq4wl73vnq9ig3ax
5034 http://hydra.gnu.org/nar/@dots{}-pius-2.1.1: 0k4v3m9z1zp8xzzizb7d8kjj72f9172xv078sq4wl73vnq9ig3ax
5035 http://guix.example.org/nar/@dots{}-pius-2.1.1: 1cy25x1a4fzq5rk0pmvc8xhwyffnqz95h2bpvqsz2mpvlbccy0gs
5039 In this example, @command{guix challenge} first scans the store to
5040 determine the set of locally-built derivations---as opposed to store
5041 items that were downloaded from a substitute server---and then queries
5042 all the substitute servers. It then reports those store items for which
5043 the servers obtained a result different from the local build.
5045 @cindex non-determinism, in package builds
5046 As an example, @code{guix.example.org} always gets a different answer.
5047 Conversely, @code{hydra.gnu.org} agrees with local builds, except in the
5048 case of Git. This might indicate that the build process of Git is
5049 non-deterministic, meaning that its output varies as a function of
5050 various things that Guix does not fully control, in spite of building
5051 packages in isolated environments (@pxref{Features}). Most common
5052 sources of non-determinism include the addition of timestamps in build
5053 results, the inclusion of random numbers, and directory listings sorted
5054 by inode number. See @uref{http://reproducible.debian.net/howto/}, for
5057 To find out what's wrong with this Git binary, we can do something along
5058 these lines (@pxref{Invoking guix archive}):
5061 $ wget -q -O - http://hydra.gnu.org/nar/@dots{}-git-2.5.0 \
5062 | guix archive -x /tmp/git
5063 $ diff -ur --no-dereference /gnu/store/@dots{}-git.2.5.0 /tmp/git
5066 This command shows the difference between the files resulting from the
5067 local build, and the files resulting from the build on
5068 @code{hydra.gnu.org} (@pxref{Overview, Comparing and Merging Files,,
5069 diffutils, Comparing and Merging Files}). The @command{diff} command
5070 works great for text files. When binary files differ, a better option
5071 is @uref{http://diffoscope.org/, Diffoscope}, a tool that helps
5072 visualize differences for all kinds of files.
5074 Once you've done that work, you can tell whether the differences are due
5075 to a non-deterministic build process or to a malicious server. We try
5076 hard to remove sources of non-determinism in packages to make it easier
5077 to verify substitutes, but of course, this is a process, one that
5078 involves not just Guix but a large part of the free software community.
5079 In the meantime, @command{guix challenge} is one tool to help address
5082 If you are writing packages for Guix, you are encouraged to check
5083 whether @code{hydra.gnu.org} and other substitute servers obtain the
5084 same build result as you did with:
5087 $ guix challenge @var{package}
5091 ... where @var{package} is a package specification such as
5092 @code{guile-2.0} or @code{glibc:debug}.
5094 The general syntax is:
5097 guix challenge @var{options} [@var{packages}@dots{}]
5100 The one option that matters is:
5104 @item --substitute-urls=@var{urls}
5105 Consider @var{urls} the whitespace-separated list of substitute source
5111 @node Invoking guix container
5112 @section Invoking @command{guix container}
5116 As of version @value{VERSION}, this tool is experimental. The interface
5117 is subject to radical change in the future.
5120 The purpose of @command{guix container} is to manipulate processes
5121 running within an isolated environment, commonly known as a
5122 ``container'', typically created by the @command{guix environment}
5123 (@pxref{Invoking guix environment}) and @command{guix system container}
5124 (@pxref{Invoking guix system}) commands.
5126 The general syntax is:
5129 guix container @var{action} @var{options}@dots{}
5132 @var{action} specifies the operation to perform with a container, and
5133 @var{options} specifies the context-specific arguments for the action.
5135 The following actions are available:
5139 Execute a command within the context of a running container.
5144 guix container exec @var{pid} @var{program} @var{arguments}@dots{}
5147 @var{pid} specifies the process ID of the running container.
5148 @var{program} specifies an executable file name within the container's
5149 root file system. @var{arguments} are the additional options that will
5150 be passed to @var{program}.
5152 The following command launches an interactive login shell inside a
5153 GuixSD container, started by @command{guix system container}, and whose
5157 guix container exec 9001 /run/current-system/profile/bin/bash --login
5160 Note that the @var{pid} cannot be the parent process of a container. It
5161 must be the container's PID 1 or one of its child processes.
5165 @c *********************************************************************
5166 @node GNU Distribution
5167 @chapter GNU Distribution
5169 @cindex Guix System Distribution
5171 Guix comes with a distribution of the GNU system consisting entirely of
5172 free software@footnote{The term ``free'' here refers to the
5173 @url{http://www.gnu.org/philosophy/free-sw.html,freedom provided to
5174 users of that software}.}. The
5175 distribution can be installed on its own (@pxref{System Installation}),
5176 but it is also possible to install Guix as a package manager on top of
5177 an installed GNU/Linux system (@pxref{Installation}). To distinguish
5178 between the two, we refer to the standalone distribution as the Guix
5179 System Distribution, or GuixSD.
5181 The distribution provides core GNU packages such as GNU libc, GCC, and
5182 Binutils, as well as many GNU and non-GNU applications. The complete
5183 list of available packages can be browsed
5184 @url{http://www.gnu.org/software/guix/packages,on-line} or by
5185 running @command{guix package} (@pxref{Invoking guix package}):
5188 guix package --list-available
5191 Our goal has been to provide a practical 100% free software distribution of
5192 Linux-based and other variants of GNU, with a focus on the promotion and
5193 tight integration of GNU components, and an emphasis on programs and
5194 tools that help users exert that freedom.
5196 Packages are currently available on the following platforms:
5201 Intel/AMD @code{x86_64} architecture, Linux-Libre kernel;
5204 Intel 32-bit architecture (IA32), Linux-Libre kernel;
5207 ARMv7-A architecture with hard float, Thumb-2 and NEON,
5208 using the EABI hard-float ABI, and Linux-Libre kernel.
5210 @item mips64el-linux
5211 little-endian 64-bit MIPS processors, specifically the Loongson series,
5212 n32 application binary interface (ABI), and Linux-Libre kernel.
5216 GuixSD itself is currently only available on @code{i686} and @code{x86_64}.
5219 For information on porting to other architectures or kernels,
5223 * System Installation:: Installing the whole operating system.
5224 * System Configuration:: Configuring the operating system.
5225 * Installing Debugging Files:: Feeding the debugger.
5226 * Security Updates:: Deploying security fixes quickly.
5227 * Package Modules:: Packages from the programmer's viewpoint.
5228 * Packaging Guidelines:: Growing the distribution.
5229 * Bootstrapping:: GNU/Linux built from scratch.
5230 * Porting:: Targeting another platform or kernel.
5233 Building this distribution is a cooperative effort, and you are invited
5234 to join! @xref{Contributing}, for information about how you can help.
5236 @node System Installation
5237 @section System Installation
5239 @cindex Guix System Distribution
5240 This section explains how to install the Guix System Distribution
5241 on a machine. The Guix package manager can
5242 also be installed on top of a running GNU/Linux system,
5243 @pxref{Installation}.
5246 @c This paragraph is for people reading this from tty2 of the
5247 @c installation image.
5248 You're reading this documentation with an Info reader. For details on
5249 how to use it, hit the @key{RET} key (``return'' or ``enter'') on the
5250 link that follows: @pxref{Help,,, info, Info: An Introduction}. Hit
5251 @kbd{l} afterwards to come back here.
5254 @subsection Limitations
5256 As of version @value{VERSION}, the Guix System Distribution (GuixSD) is
5257 not production-ready. It may contain bugs and lack important
5258 features. Thus, if you are looking for a stable production system that
5259 respects your freedom as a computer user, a good solution at this point
5260 is to consider @url{http://www.gnu.org/distros/free-distros.html, one of
5261 more established GNU/Linux distributions}. We hope you can soon switch
5262 to the GuixSD without fear, of course. In the meantime, you can
5263 also keep using your distribution and try out the package manager on top
5264 of it (@pxref{Installation}).
5266 Before you proceed with the installation, be aware of the following
5267 noteworthy limitations applicable to version @value{VERSION}:
5271 The installation process does not include a graphical user interface and
5272 requires familiarity with GNU/Linux (see the following subsections to
5273 get a feel of what that means.)
5276 The system does not yet provide full GNOME and KDE desktops. Xfce and
5277 Enlightenment are available though, if graphical desktop environments
5278 are your thing, as well as a number of X11 window managers.
5281 Support for the Logical Volume Manager (LVM) is missing.
5284 Few system services are currently supported out-of-the-box
5288 More than 2,000 packages are available, but you may
5289 occasionally find that a useful package is missing.
5292 You've been warned. But more than a disclaimer, this is an invitation
5293 to report issues (and success stories!), and join us in improving it.
5294 @xref{Contributing}, for more info.
5296 @subsection USB Stick Installation
5298 An installation image for USB sticks can be downloaded from
5299 @indicateurl{ftp://alpha.gnu.org/gnu/guix/guixsd-usb-install-@value{VERSION}.@var{system}.xz},
5300 where @var{system} is one of:
5304 for a GNU/Linux system on Intel/AMD-compatible 64-bit CPUs;
5307 for a 32-bit GNU/Linux system on Intel-compatible CPUs.
5310 This image contains a single partition with the tools necessary for an
5311 installation. It is meant to be copied @emph{as is} to a large-enough
5314 To copy the image to a USB stick, follow these steps:
5318 Decompress the image using the @command{xz} command:
5321 xz -d guixsd-usb-install-@value{VERSION}.@var{system}.xz
5325 Insert a USB stick of 1@tie{}GiB or more in your machine, and determine
5326 its device name. Assuming that USB stick is known as @file{/dev/sdX},
5327 copy the image with:
5330 dd if=guixsd-usb-install-@value{VERSION}.x86_64 of=/dev/sdX
5333 Access to @file{/dev/sdX} usually requires root privileges.
5336 Once this is done, you should be able to reboot the system and boot from
5337 the USB stick. The latter usually requires you to get in the BIOS' boot
5338 menu, where you can choose to boot from the USB stick.
5340 @subsection Preparing for Installation
5342 Once you have successfully booted the image on the USB stick, you should
5343 end up with a root prompt. Several console TTYs are configured and can
5344 be used to run commands as root. TTY2 shows this documentation,
5345 browsable using the Info reader commands (@pxref{Help,,, info, Info: An
5346 Introduction}). The installation system runs the GPM mouse daemon,
5347 which allows you to select text with the left mouse button and to paste
5348 it with the middle button.
5350 To install the system, you would:
5355 Configure the network, by running:
5358 ifconfig eno1 up && dhclient eno1
5361 to get an automatically assigned IP address from the wired
5362 network interface controller@footnote{
5363 @c http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-net_id.c#n20
5364 The name @code{eno1} is for the first on-board Ethernet controller. The
5365 interface name for an Ethernet controller that is in the first slot of
5366 the first PCI bus, for instance, would be @code{enp1s0}. Use
5367 @command{ifconfig -a} to list all the available network interfaces.},
5368 or using the @command{ifconfig} command.
5370 The system automatically loads drivers for your network interface
5373 Setting up network access is almost always a requirement because the
5374 image does not contain all the software and tools that may be needed.
5377 Unless this has already been done, you must partition, and then format
5378 the target partition.
5380 Preferably, assign partitions a label so that you can easily and
5381 reliably refer to them in @code{file-system} declarations (@pxref{File
5382 Systems}). This is typically done using the @code{-L} option of
5383 @command{mkfs.ext4} and related commands.
5385 @c FIXME: Uncomment this once GRUB fully supports encrypted roots.
5386 @c A typical command sequence may be:
5390 @c @dots{} Create partitions etc.@dots{}
5391 @c # cryptsetup luksFormat /dev/sdX1
5392 @c # cryptsetup open --type luks /dev/sdX1 my-partition
5393 @c # mkfs.ext4 -L my-root /dev/mapper/my-partition
5396 The installation image includes Parted (@pxref{Overview,,, parted, GNU
5397 Parted User Manual}), @command{fdisk}, Cryptsetup/LUKS for disk
5398 encryption, and e2fsprogs, the suite of tools to manipulate
5399 ext2/ext3/ext4 file systems.
5402 Once that is done, mount the target root partition under @file{/mnt}.
5405 Lastly, run @code{deco start cow-store /mnt}.
5407 This will make @file{/gnu/store} copy-on-write, such that packages added
5408 to it during the installation phase will be written to the target disk
5409 rather than kept in memory.
5414 @subsection Proceeding with the Installation
5416 With the target partitions ready, you now have to edit a file and
5417 provide the declaration of the operating system to be installed. To
5418 that end, the installation system comes with two text editors: GNU nano
5419 (@pxref{Top,,, nano, GNU nano Manual}), and GNU Zile, an Emacs clone.
5420 It is better to store that file on the target root file system, say, as
5421 @file{/mnt/etc/config.scm}.
5423 @xref{Using the Configuration System}, for examples of operating system
5424 configurations. These examples are available under
5425 @file{/etc/configuration} in the installation image, so you can copy
5426 them and use them as a starting point for your own configuration.
5428 Once you are done preparing the configuration file, the new system must
5429 be initialized (remember that the target root file system is mounted
5433 guix system init /mnt/etc/config.scm /mnt
5437 This will copy all the necessary files, and install GRUB on
5438 @file{/dev/sdX}, unless you pass the @option{--no-grub} option. For
5439 more information, @pxref{Invoking guix system}. This command may trigger
5440 downloads or builds of missing packages, which can take some time.
5442 Once that command has completed---and hopefully succeeded!---you can run
5443 @command{reboot} and boot into the new system. The @code{root} password
5444 in the new system is initially empty; other users' passwords need to be
5445 initialized by running the @command{passwd} command as @code{root},
5446 unless your configuration specifies otherwise
5447 (@pxref{user-account-password, user account passwords}).
5449 Join us on @code{#guix} on the Freenode IRC network or on
5450 @file{guix-devel@@gnu.org} to share your experience---good or not so
5453 @subsection Building the Installation Image
5455 The installation image described above was built using the @command{guix
5456 system} command, specifically:
5459 guix system disk-image --image-size=850MiB gnu/system/install.scm
5462 @xref{Invoking guix system}, for more information. See
5463 @file{gnu/system/install.scm} in the source tree for more information
5464 about the installation image.
5466 @node System Configuration
5467 @section System Configuration
5469 @cindex system configuration
5470 The Guix System Distribution supports a consistent whole-system configuration
5471 mechanism. By that we mean that all aspects of the global system
5472 configuration---such as the available system services, timezone and
5473 locale settings, user accounts---are declared in a single place. Such
5474 a @dfn{system configuration} can be @dfn{instantiated}---i.e., effected.
5476 One of the advantages of putting all the system configuration under the
5477 control of Guix is that it supports transactional system upgrades, and
5478 makes it possible to roll-back to a previous system instantiation,
5479 should something go wrong with the new one (@pxref{Features}). Another
5480 one is that it makes it easy to replicate the exact same configuration
5481 across different machines, or at different points in time, without
5482 having to resort to additional administration tools layered on top of
5483 the system's own tools.
5484 @c Yes, we're talking of Puppet, Chef, & co. here. ↑
5486 This section describes this mechanism. First we focus on the system
5487 administrator's viewpoint---explaining how the system is configured and
5488 instantiated. Then we show how this mechanism can be extended, for
5489 instance to support new system services.
5492 * Using the Configuration System:: Customizing your GNU system.
5493 * operating-system Reference:: Detail of operating-system declarations.
5494 * File Systems:: Configuring file system mounts.
5495 * Mapped Devices:: Block device extra processing.
5496 * User Accounts:: Specifying user accounts.
5497 * Locales:: Language and cultural convention settings.
5498 * Services:: Specifying system services.
5499 * Setuid Programs:: Programs running with root privileges.
5500 * X.509 Certificates:: Authenticating HTTPS servers.
5501 * Name Service Switch:: Configuring libc's name service switch.
5502 * Initial RAM Disk:: Linux-Libre bootstrapping.
5503 * GRUB Configuration:: Configuring the boot loader.
5504 * Invoking guix system:: Instantiating a system configuration.
5505 * Defining Services:: Adding new service definitions.
5508 @node Using the Configuration System
5509 @subsection Using the Configuration System
5511 The operating system is configured by providing an
5512 @code{operating-system} declaration in a file that can then be passed to
5513 the @command{guix system} command (@pxref{Invoking guix system}). A
5514 simple setup, with the default system services, the default Linux-Libre
5515 kernel, initial RAM disk, and boot loader looks like this:
5517 @findex operating-system
5519 @include os-config-bare-bones.texi
5522 This example should be self-describing. Some of the fields defined
5523 above, such as @code{host-name} and @code{bootloader}, are mandatory.
5524 Others, such as @code{packages} and @code{services}, can be omitted, in
5525 which case they get a default value.
5527 @vindex %base-packages
5528 The @code{packages} field lists
5529 packages that will be globally visible on the system, for all user
5530 accounts---i.e., in every user's @code{PATH} environment variable---in
5531 addition to the per-user profiles (@pxref{Invoking guix package}). The
5532 @var{%base-packages} variable provides all the tools one would expect
5533 for basic user and administrator tasks---including the GNU Core
5534 Utilities, the GNU Networking Utilities, the GNU Zile lightweight text
5535 editor, @command{find}, @command{grep}, etc. The example above adds
5536 tcpdump to those, taken from the @code{(gnu packages admin)} module
5537 (@pxref{Package Modules}).
5539 @vindex %base-services
5540 The @code{services} field lists @dfn{system services} to be made
5541 available when the system starts (@pxref{Services}).
5542 The @code{operating-system} declaration above specifies that, in
5543 addition to the basic services, we want the @command{lshd} secure shell
5544 daemon listening on port 2222 (@pxref{Networking Services,
5545 @code{lsh-service}}). Under the hood,
5546 @code{lsh-service} arranges so that @code{lshd} is started with the
5547 right command-line options, possibly with supporting configuration files
5548 generated as needed (@pxref{Defining Services}).
5550 @cindex customization, of services
5551 @findex modify-services
5552 Occasionally, instead of using the base services as is, you will want to
5553 customize them. For instance, to change the configuration of
5554 @code{guix-daemon} and Mingetty (the console log-in), you may write the
5555 following instead of @var{%base-services}:
5558 (modify-services %base-services
5559 (guix-service-type config =>
5562 (use-substitutes? #f)
5563 (extra-options '("--gc-keep-outputs"))))
5564 (mingetty-service-type config =>
5565 (mingetty-configuration
5567 (motd (plain-file "motd" "Hi there!")))))
5571 The effect here is to change the options passed to @command{guix-daemon}
5572 when it is started, as well as the ``message of the day'' that appears
5573 when logging in at the console. @xref{Service Reference,
5574 @code{modify-services}}, for more on that.
5576 The configuration for a typical ``desktop'' usage, with the X11 display
5577 server, a desktop environment, network management, power management, and
5578 more, would look like this:
5581 @include os-config-desktop.texi
5584 @xref{Desktop Services}, for the exact list of services provided by
5585 @var{%desktop-services}. @xref{X.509 Certificates}, for background
5586 information about the @code{nss-certs} package that is used here.
5587 @xref{operating-system Reference}, for details about all the available
5588 @code{operating-system} fields.
5590 Assuming the above snippet is stored in the @file{my-system-config.scm}
5591 file, the @command{guix system reconfigure my-system-config.scm} command
5592 instantiates that configuration, and makes it the default GRUB boot
5593 entry (@pxref{Invoking guix system}).
5595 The normal way to change the system's configuration is by updating this
5596 file and re-running @command{guix system reconfigure}. One should never
5597 have to touch files in @command{/etc} or to run commands that modify the
5598 system state such as @command{useradd} or @command{grub-install}. In
5599 fact, you must avoid that since that would not only void your warranty
5600 but also prevent you from rolling back to previous versions of your
5601 system, should you ever need to.
5603 @cindex roll-back, of the operating system
5604 Speaking of roll-back, each time you run @command{guix system
5605 reconfigure}, a new @dfn{generation} of the system is created---without
5606 modifying or deleting previous generations. Old system generations get
5607 an entry in the GRUB boot menu, allowing you to boot them in case
5608 something went wrong with the latest generation. Reassuring, no? The
5609 @command{guix system list-generations} command lists the system
5610 generations available on disk.
5612 At the Scheme level, the bulk of an @code{operating-system} declaration
5613 is instantiated with the following monadic procedure (@pxref{The Store
5616 @deffn {Monadic Procedure} operating-system-derivation os
5617 Return a derivation that builds @var{os}, an @code{operating-system}
5618 object (@pxref{Derivations}).
5620 The output of the derivation is a single directory that refers to all
5621 the packages, configuration files, and other supporting files needed to
5622 instantiate @var{os}.
5625 @node operating-system Reference
5626 @subsection @code{operating-system} Reference
5628 This section summarizes all the options available in
5629 @code{operating-system} declarations (@pxref{Using the Configuration
5632 @deftp {Data Type} operating-system
5633 This is the data type representing an operating system configuration.
5634 By that, we mean all the global system configuration, not per-user
5635 configuration (@pxref{Using the Configuration System}).
5638 @item @code{kernel} (default: @var{linux-libre})
5639 The package object of the operating system kernel to use@footnote{Currently
5640 only the Linux-libre kernel is supported. In the future, it will be
5641 possible to use the GNU@tie{}Hurd.}.
5643 @item @code{kernel-arguments} (default: @code{'()})
5644 List of strings or gexps representing additional arguments to pass on
5645 the kernel's command-line---e.g., @code{("console=ttyS0")}.
5647 @item @code{bootloader}
5648 The system bootloader configuration object. @xref{GRUB Configuration}.
5650 @item @code{initrd} (default: @code{base-initrd})
5651 A two-argument monadic procedure that returns an initial RAM disk for
5652 the Linux kernel. @xref{Initial RAM Disk}.
5654 @item @code{firmware} (default: @var{%base-firmware})
5656 List of firmware packages loadable by the operating system kernel.
5658 The default includes firmware needed for Atheros-based WiFi devices
5659 (Linux-libre module @code{ath9k}.)
5661 @item @code{host-name}
5664 @item @code{hosts-file}
5666 A file-like object (@pxref{G-Expressions, file-like objects}) for use as
5667 @file{/etc/hosts} (@pxref{Host Names,,, libc, The GNU C Library
5668 Reference Manual}). The default is a file with entries for
5669 @code{localhost} and @var{host-name}.
5671 @item @code{mapped-devices} (default: @code{'()})
5672 A list of mapped devices. @xref{Mapped Devices}.
5674 @item @code{file-systems}
5675 A list of file systems. @xref{File Systems}.
5677 @item @code{swap-devices} (default: @code{'()})
5678 @cindex swap devices
5679 A list of strings identifying devices to be used for ``swap space''
5680 (@pxref{Memory Concepts,,, libc, The GNU C Library Reference Manual}).
5681 For example, @code{'("/dev/sda3")}.
5683 @item @code{users} (default: @code{%base-user-accounts})
5684 @itemx @code{groups} (default: @var{%base-groups})
5685 List of user accounts and groups. @xref{User Accounts}.
5687 @item @code{skeletons} (default: @code{(default-skeletons)})
5688 A monadic list of pairs of target file name and files. These are the
5689 files that will be used as skeletons as new accounts are created.
5691 For instance, a valid value may look like this:
5694 (mlet %store-monad ((bashrc (text-file "bashrc" "\
5695 export PATH=$HOME/.guix-profile/bin")))
5696 (return `((".bashrc" ,bashrc))))
5699 @item @code{issue} (default: @var{%default-issue})
5700 A string denoting the contents of the @file{/etc/issue} file, which is
5701 what displayed when users log in on a text console.
5703 @item @code{packages} (default: @var{%base-packages})
5704 The set of packages installed in the global profile, which is accessible
5705 at @file{/run/current-system/profile}.
5707 The default set includes core utilities, but it is good practice to
5708 install non-core utilities in user profiles (@pxref{Invoking guix
5711 @item @code{timezone}
5712 A timezone identifying string---e.g., @code{"Europe/Paris"}.
5714 @item @code{locale} (default: @code{"en_US.utf8"})
5715 The name of the default locale (@pxref{Locale Names,,, libc, The GNU C
5716 Library Reference Manual}). @xref{Locales}, for more information.
5718 @item @code{locale-definitions} (default: @var{%default-locale-definitions})
5719 The list of locale definitions to be compiled and that may be used at
5720 run time. @xref{Locales}.
5722 @item @code{locale-libcs} (default: @code{(list @var{glibc})})
5723 The list of GNU@tie{}libc packages whose locale data and tools are used
5724 to build the locale definitions. @xref{Locales}, for compatibility
5725 considerations that justify this option.
5727 @item @code{name-service-switch} (default: @var{%default-nss})
5728 Configuration of libc's name service switch (NSS)---a
5729 @code{<name-service-switch>} object. @xref{Name Service Switch}, for
5732 @item @code{services} (default: @var{%base-services})
5733 A list of service objects denoting system services. @xref{Services}.
5735 @item @code{pam-services} (default: @code{(base-pam-services)})
5737 @cindex pluggable authentication modules
5738 Linux @dfn{pluggable authentication module} (PAM) services.
5739 @c FIXME: Add xref to PAM services section.
5741 @item @code{setuid-programs} (default: @var{%setuid-programs})
5742 List of string-valued G-expressions denoting setuid programs.
5743 @xref{Setuid Programs}.
5745 @item @code{sudoers-file} (default: @var{%sudoers-specification})
5746 @cindex sudoers file
5747 The contents of the @file{/etc/sudoers} file as a file-like object
5748 (@pxref{G-Expressions, @code{local-file} and @code{plain-file}}).
5750 This file specifies which users can use the @command{sudo} command, what
5751 they are allowed to do, and what privileges they may gain. The default
5752 is that only @code{root} and members of the @code{wheel} group may use
5759 @subsection File Systems
5761 The list of file systems to be mounted is specified in the
5762 @code{file-systems} field of the operating system's declaration
5763 (@pxref{Using the Configuration System}). Each file system is declared
5764 using the @code{file-system} form, like this:
5768 (mount-point "/home")
5769 (device "/dev/sda3")
5773 As usual, some of the fields are mandatory---those shown in the example
5774 above---while others can be omitted. These are described below.
5776 @deftp {Data Type} file-system
5777 Objects of this type represent file systems to be mounted. They
5778 contain the following members:
5782 This is a string specifying the type of the file system---e.g.,
5785 @item @code{mount-point}
5786 This designates the place where the file system is to be mounted.
5789 This names the ``source'' of the file system. By default it is the name
5790 of a node under @file{/dev}, but its meaning depends on the @code{title}
5791 field described below.
5793 @item @code{title} (default: @code{'device})
5794 This is a symbol that specifies how the @code{device} field is to be
5797 When it is the symbol @code{device}, then the @code{device} field is
5798 interpreted as a file name; when it is @code{label}, then @code{device}
5799 is interpreted as a partition label name; when it is @code{uuid},
5800 @code{device} is interpreted as a partition unique identifier (UUID).
5802 UUIDs may be converted from their string representation (as shown by the
5803 @command{tune2fs -l} command) using the @code{uuid} form, like this:
5807 (mount-point "/home")
5810 (device (uuid "4dab5feb-d176-45de-b287-9b0a6e4c01cb")))
5813 The @code{label} and @code{uuid} options offer a way to refer to disk
5814 partitions without having to hard-code their actual device
5815 name@footnote{Note that, while it is tempting to use
5816 @file{/dev/disk/by-uuid} and similar device names to achieve the same
5817 result, this is not recommended: These special device nodes are created
5818 by the udev daemon and may be unavailable at the time the device is
5821 However, when a file system's source is a mapped device (@pxref{Mapped
5822 Devices}), its @code{device} field @emph{must} refer to the mapped
5823 device name---e.g., @file{/dev/mapper/root-partition}---and consequently
5824 @code{title} must be set to @code{'device}. This is required so that
5825 the system knows that mounting the file system depends on having the
5826 corresponding device mapping established.
5828 @item @code{flags} (default: @code{'()})
5829 This is a list of symbols denoting mount flags. Recognized flags
5830 include @code{read-only}, @code{bind-mount}, @code{no-dev} (disallow
5831 access to special files), @code{no-suid} (ignore setuid and setgid
5832 bits), and @code{no-exec} (disallow program execution.)
5834 @item @code{options} (default: @code{#f})
5835 This is either @code{#f}, or a string denoting mount options.
5837 @item @code{needed-for-boot?} (default: @code{#f})
5838 This Boolean value indicates whether the file system is needed when
5839 booting. If that is true, then the file system is mounted when the
5840 initial RAM disk (initrd) is loaded. This is always the case, for
5841 instance, for the root file system.
5843 @item @code{check?} (default: @code{#t})
5844 This Boolean indicates whether the file system needs to be checked for
5845 errors before being mounted.
5847 @item @code{create-mount-point?} (default: @code{#f})
5848 When true, the mount point is created if it does not exist yet.
5850 @item @code{dependencies} (default: @code{'()})
5851 This is a list of @code{<file-system>} objects representing file systems
5852 that must be mounted before (and unmounted after) this one.
5854 As an example, consider a hierarchy of mounts: @file{/sys/fs/cgroup} is
5855 a dependency of @file{/sys/fs/cgroup/cpu} and
5856 @file{/sys/fs/cgroup/memory}.
5861 The @code{(gnu system file-systems)} exports the following useful
5864 @defvr {Scheme Variable} %base-file-systems
5865 These are essential file systems that are required on normal systems,
5866 such as @var{%pseudo-terminal-file-system} and @var{%immutable-store} (see
5867 below.) Operating system declarations should always contain at least
5871 @defvr {Scheme Variable} %pseudo-terminal-file-system
5872 This is the file system to be mounted as @file{/dev/pts}. It supports
5873 @dfn{pseudo-terminals} created @i{via} @code{openpty} and similar
5874 functions (@pxref{Pseudo-Terminals,,, libc, The GNU C Library Reference
5875 Manual}). Pseudo-terminals are used by terminal emulators such as
5879 @defvr {Scheme Variable} %shared-memory-file-system
5880 This file system is mounted as @file{/dev/shm} and is used to support
5881 memory sharing across processes (@pxref{Memory-mapped I/O,
5882 @code{shm_open},, libc, The GNU C Library Reference Manual}).
5885 @defvr {Scheme Variable} %immutable-store
5886 This file system performs a read-only ``bind mount'' of
5887 @file{/gnu/store}, making it read-only for all the users including
5888 @code{root}. This prevents against accidental modification by software
5889 running as @code{root} or by system administrators.
5891 The daemon itself is still able to write to the store: it remounts it
5892 read-write in its own ``name space.''
5895 @defvr {Scheme Variable} %binary-format-file-system
5896 The @code{binfmt_misc} file system, which allows handling of arbitrary
5897 executable file types to be delegated to user space. This requires the
5898 @code{binfmt.ko} kernel module to be loaded.
5901 @defvr {Scheme Variable} %fuse-control-file-system
5902 The @code{fusectl} file system, which allows unprivileged users to mount
5903 and unmount user-space FUSE file systems. This requires the
5904 @code{fuse.ko} kernel module to be loaded.
5907 @node Mapped Devices
5908 @subsection Mapped Devices
5910 @cindex device mapping
5911 @cindex mapped devices
5912 The Linux kernel has a notion of @dfn{device mapping}: a block device,
5913 such as a hard disk partition, can be @dfn{mapped} into another device,
5914 with additional processing over the data that flows through
5915 it@footnote{Note that the GNU@tie{}Hurd makes no difference between the
5916 concept of a ``mapped device'' and that of a file system: both boil down
5917 to @emph{translating} input/output operations made on a file to
5918 operations on its backing store. Thus, the Hurd implements mapped
5919 devices, like file systems, using the generic @dfn{translator} mechanism
5920 (@pxref{Translators,,, hurd, The GNU Hurd Reference Manual}).}. A
5921 typical example is encryption device mapping: all writes to the mapped
5922 device are encrypted, and all reads are deciphered, transparently.
5924 Mapped devices are declared using the @code{mapped-device} form:
5928 (source "/dev/sda3")
5930 (type luks-device-mapping))
5934 @cindex disk encryption
5936 This example specifies a mapping from @file{/dev/sda3} to
5937 @file{/dev/mapper/home} using LUKS---the
5938 @url{http://code.google.com/p/cryptsetup,Linux Unified Key Setup}, a
5939 standard mechanism for disk encryption. The @file{/dev/mapper/home}
5940 device can then be used as the @code{device} of a @code{file-system}
5941 declaration (@pxref{File Systems}). The @code{mapped-device} form is
5944 @deftp {Data Type} mapped-device
5945 Objects of this type represent device mappings that will be made when
5946 the system boots up.
5950 This string specifies the name of the block device to be mapped, such as
5954 This string specifies the name of the mapping to be established. For
5955 example, specifying @code{"my-partition"} will lead to the creation of
5956 the @code{"/dev/mapper/my-partition"} device.
5959 This must be a @code{mapped-device-kind} object, which specifies how
5960 @var{source} is mapped to @var{target}.
5964 @defvr {Scheme Variable} luks-device-mapping
5965 This defines LUKS block device encryption using the @command{cryptsetup}
5966 command, from the same-named package. This relies on the
5967 @code{dm-crypt} Linux kernel module.
5971 @subsection User Accounts
5973 User accounts and groups are entirely managed through the
5974 @code{operating-system} declaration. They are specified with the
5975 @code{user-account} and @code{user-group} forms:
5981 (supplementary-groups '("wheel" ;allow use of sudo, etc.
5983 "video" ;video devices such as webcams
5984 "cdrom")) ;the good ol' CD-ROM
5985 (comment "Bob's sister")
5986 (home-directory "/home/alice"))
5989 When booting or upon completion of @command{guix system reconfigure},
5990 the system ensures that only the user accounts and groups specified in
5991 the @code{operating-system} declaration exist, and with the specified
5992 properties. Thus, account or group creations or modifications made by
5993 directly invoking commands such as @command{useradd} are lost upon
5994 reconfiguration or reboot. This ensures that the system remains exactly
5997 @deftp {Data Type} user-account
5998 Objects of this type represent user accounts. The following members may
6003 The name of the user account.
6006 This is the name (a string) or identifier (a number) of the user group
6007 this account belongs to.
6009 @item @code{supplementary-groups} (default: @code{'()})
6010 Optionally, this can be defined as a list of group names that this
6013 @item @code{uid} (default: @code{#f})
6014 This is the user ID for this account (a number), or @code{#f}. In the
6015 latter case, a number is automatically chosen by the system when the
6018 @item @code{comment} (default: @code{""})
6019 A comment about the account, such as the account's owner full name.
6021 @item @code{home-directory}
6022 This is the name of the home directory for the account.
6024 @item @code{shell} (default: Bash)
6025 This is a G-expression denoting the file name of a program to be used as
6026 the shell (@pxref{G-Expressions}).
6028 @item @code{system?} (default: @code{#f})
6029 This Boolean value indicates whether the account is a ``system''
6030 account. System accounts are sometimes treated specially; for instance,
6031 graphical login managers do not list them.
6033 @anchor{user-account-password}
6034 @item @code{password} (default: @code{#f})
6035 You would normally leave this field to @code{#f}, initialize user
6036 passwords as @code{root} with the @command{passwd} command, and then let
6037 users change it with @command{passwd}. Passwords set with
6038 @command{passwd} are of course preserved across reboot and
6041 If you @emph{do} want to have a preset password for an account, then
6042 this field must contain the encrypted password, as a string.
6043 @xref{crypt,,, libc, The GNU C Library Reference Manual}, for more information
6044 on password encryption, and @ref{Encryption,,, guile, GNU Guile Reference
6045 Manual}, for information on Guile's @code{crypt} procedure.
6050 User group declarations are even simpler:
6053 (user-group (name "students"))
6056 @deftp {Data Type} user-group
6057 This type is for, well, user groups. There are just a few fields:
6063 @item @code{id} (default: @code{#f})
6064 The group identifier (a number). If @code{#f}, a new number is
6065 automatically allocated when the group is created.
6067 @item @code{system?} (default: @code{#f})
6068 This Boolean value indicates whether the group is a ``system'' group.
6069 System groups have low numerical IDs.
6071 @item @code{password} (default: @code{#f})
6072 What, user groups can have a password? Well, apparently yes. Unless
6073 @code{#f}, this field specifies the group's password.
6078 For convenience, a variable lists all the basic user groups one may
6081 @defvr {Scheme Variable} %base-groups
6082 This is the list of basic user groups that users and/or packages expect
6083 to be present on the system. This includes groups such as ``root'',
6084 ``wheel'', and ``users'', as well as groups used to control access to
6085 specific devices such as ``audio'', ``disk'', and ``cdrom''.
6088 @defvr {Scheme Variable} %base-user-accounts
6089 This is the list of basic system accounts that programs may expect to
6090 find on a GNU/Linux system, such as the ``nobody'' account.
6092 Note that the ``root'' account is not included here. It is a
6093 special-case and is automatically added whether or not it is specified.
6100 A @dfn{locale} defines cultural conventions for a particular language
6101 and region of the world (@pxref{Locales,,, libc, The GNU C Library
6102 Reference Manual}). Each locale has a name that typically has the form
6103 @code{@var{language}_@var{territory}.@var{codeset}}---e.g.,
6104 @code{fr_LU.utf8} designates the locale for the French language, with
6105 cultural conventions from Luxembourg, and using the UTF-8 encoding.
6107 @cindex locale definition
6108 Usually, you will want to specify the default locale for the machine
6109 using the @code{locale} field of the @code{operating-system} declaration
6110 (@pxref{operating-system Reference, @code{locale}}).
6112 That locale must be among the @dfn{locale definitions} that are known to
6113 the system---and these are specified in the @code{locale-definitions}
6114 slot of @code{operating-system}. The default value includes locale
6115 definition for some widely used locales, but not for all the available
6116 locales, in order to save space.
6118 If the locale specified in the @code{locale} field is not among the
6119 definitions listed in @code{locale-definitions}, @command{guix system}
6120 raises an error. In that case, you should add the locale definition to
6121 the @code{locale-definitions} field. For instance, to add the North
6122 Frisian locale for Germany, the value of that field may be:
6125 (cons (locale-definition
6126 (name "fy_DE.utf8") (source "fy_DE"))
6127 %default-locale-definitions)
6130 Likewise, to save space, one might want @code{locale-definitions} to
6131 list only the locales that are actually used, as in:
6134 (list (locale-definition
6135 (name "ja_JP.eucjp") (source "ja_JP")
6136 (charset "EUC-JP")))
6140 The compiled locale definitions are available at
6141 @file{/run/current-system/locale/X.Y}, where @code{X.Y} is the libc
6142 version, which is the default location where the GNU@tie{}libc provided
6143 by Guix looks for locale data. This can be overridden using the
6144 @code{LOCPATH} environment variable (@pxref{locales-and-locpath,
6145 @code{LOCPATH} and locale packages}).
6147 The @code{locale-definition} form is provided by the @code{(gnu system
6148 locale)} module. Details are given below.
6150 @deftp {Data Type} locale-definition
6151 This is the data type of a locale definition.
6156 The name of the locale. @xref{Locale Names,,, libc, The GNU C Library
6157 Reference Manual}, for more information on locale names.
6160 The name of the source for that locale. This is typically the
6161 @code{@var{language}_@var{territory}} part of the locale name.
6163 @item @code{charset} (default: @code{"UTF-8"})
6164 The ``character set'' or ``code set'' for that locale,
6165 @uref{http://www.iana.org/assignments/character-sets, as defined by
6171 @defvr {Scheme Variable} %default-locale-definitions
6172 An arbitrary list of commonly used UTF-8 locales, used as the default
6173 value of the @code{locale-definitions} field of @code{operating-system}
6177 @cindex normalized codeset in locale names
6178 These locale definitions use the @dfn{normalized codeset} for the part
6179 that follows the dot in the name (@pxref{Using gettextized software,
6180 normalized codeset,, libc, The GNU C Library Reference Manual}). So for
6181 instance it has @code{uk_UA.utf8} but @emph{not}, say,
6185 @subsubsection Locale Data Compatibility Considerations
6187 @cindex incompatibility, of locale data
6188 @code{operating-system} declarations provide a @code{locale-libcs} field
6189 to specify the GNU@tie{}libc packages that are used to compile locale
6190 declarations (@pxref{operating-system Reference}). ``Why would I
6191 care?'', you may ask. Well, it turns out that the binary format of
6192 locale data is occasionally incompatible from one libc version to
6195 @c See <https://sourceware.org/ml/libc-alpha/2015-09/msg00575.html>
6196 @c and <https://lists.gnu.org/archive/html/guix-devel/2015-08/msg00737.html>.
6197 For instance, a program linked against libc version 2.21 is unable to
6198 read locale data produced with libc 2.22; worse, that program
6199 @emph{aborts} instead of simply ignoring the incompatible locale
6200 data@footnote{Versions 2.23 and later of GNU@tie{}libc will simply skip
6201 the incompatible locale data, which is already an improvement.}.
6202 Similarly, a program linked against libc 2.22 can read most, but not
6203 all, the locale data from libc 2.21 (specifically, @code{LC_COLLATE}
6204 data is incompatible); thus calls to @code{setlocale} may fail, but
6205 programs will not abort.
6207 The ``problem'' in GuixSD is that users have a lot of freedom: They can
6208 choose whether and when to upgrade software in their profiles, and might
6209 be using a libc version different from the one the system administrator
6210 used to build the system-wide locale data.
6212 Fortunately, unprivileged users can also install their own locale data
6213 and define @var{GUIX_LOCPATH} accordingly (@pxref{locales-and-locpath,
6214 @code{GUIX_LOCPATH} and locale packages}).
6216 Still, it is best if the system-wide locale data at
6217 @file{/run/current-system/locale} is built for all the libc versions
6218 actually in use on the system, so that all the programs can access
6219 it---this is especially crucial on a multi-user system. To do that, the
6220 administrator can specify several libc packages in the
6221 @code{locale-libcs} field of @code{operating-system}:
6224 (use-package-modules base)
6228 (locale-libcs (list glibc-2.21 (canonical-package glibc))))
6231 This example would lead to a system containing locale definitions for
6232 both libc 2.21 and the current version of libc in
6233 @file{/run/current-system/locale}.
6237 @subsection Services
6239 @cindex system services
6240 An important part of preparing an @code{operating-system} declaration is
6241 listing @dfn{system services} and their configuration (@pxref{Using the
6242 Configuration System}). System services are typically daemons launched
6243 when the system boots, or other actions needed at that time---e.g.,
6244 configuring network access.
6246 Services are managed by GNU@tie{}dmd (@pxref{Introduction,,, dmd, GNU
6247 dmd Manual}). On a running system, the @command{deco} command allows
6248 you to list the available services, show their status, start and stop
6249 them, or do other specific operations (@pxref{Jump Start,,, dmd, GNU dmd
6250 Manual}). For example:
6256 The above command, run as @code{root}, lists the currently defined
6257 services. The @command{deco doc} command shows a synopsis of the given
6262 Run libc's name service cache daemon (nscd).
6265 The @command{start}, @command{stop}, and @command{restart} sub-commands
6266 have the effect you would expect. For instance, the commands below stop
6267 the nscd service and restart the Xorg display server:
6271 Service nscd has been stopped.
6272 # deco restart xorg-server
6273 Service xorg-server has been stopped.
6274 Service xorg-server has been started.
6277 The following sections document the available services, starting with
6278 the core services, that may be used in an @code{operating-system}
6282 * Base Services:: Essential system services.
6283 * Networking Services:: Network setup, SSH daemon, etc.
6284 * X Window:: Graphical display.
6285 * Desktop Services:: D-Bus and desktop services.
6286 * Database Services:: SQL databases.
6287 * Web Services:: Web servers.
6288 * Various Services:: Other services.
6292 @subsubsection Base Services
6294 The @code{(gnu services base)} module provides definitions for the basic
6295 services that one expects from the system. The services exported by
6296 this module are listed below.
6298 @defvr {Scheme Variable} %base-services
6299 This variable contains a list of basic services (@pxref{Service Types
6300 and Services}, for more information on service objects) one would
6301 expect from the system: a login service (mingetty) on each tty, syslogd,
6302 libc's name service cache daemon (nscd), the udev device manager, and
6305 This is the default value of the @code{services} field of
6306 @code{operating-system} declarations. Usually, when customizing a
6307 system, you will want to append services to @var{%base-services}, like
6311 (cons* (avahi-service) (lsh-service) %base-services)
6315 @deffn {Scheme Procedure} host-name-service @var{name}
6316 Return a service that sets the host name to @var{name}.
6319 @deffn {Scheme Procedure} mingetty-service @var{config}
6320 Return a service to run mingetty according to @var{config}, a
6321 @code{<mingetty-configuration>} object, which specifies the tty to run, among
6325 @deftp {Data Type} mingetty-configuration
6326 This is the data type representing the configuration of Mingetty, which
6327 implements console log-in.
6332 The name of the console this Mingetty runs on---e.g., @code{"tty1"}.
6335 A file-like object containing the ``message of the day''.
6337 @item @code{auto-login} (default: @code{#f})
6338 When true, this field must be a string denoting the user name under
6339 which the the system automatically logs in. When it is @code{#f}, a
6340 user name and password must be entered to log in.
6342 @item @code{login-program} (default: @code{#f})
6343 This must be either @code{#f}, in which case the default log-in program
6344 is used (@command{login} from the Shadow tool suite), or a gexp denoting
6345 the name of the log-in program.
6347 @item @code{login-pause?} (default: @code{#f})
6348 When set to @code{#t} in conjunction with @var{auto-login}, the user
6349 will have to press a key before the log-in shell is launched.
6351 @item @code{mingetty} (default: @var{mingetty})
6352 The Mingetty package to use.
6357 @cindex name service cache daemon
6359 @deffn {Scheme Procedure} nscd-service [@var{config}] [#:glibc glibc] @
6360 [#:name-services '()]
6361 Return a service that runs libc's name service cache daemon (nscd) with the
6362 given @var{config}---an @code{<nscd-configuration>} object. @xref{Name
6363 Service Switch}, for an example.
6366 @defvr {Scheme Variable} %nscd-default-configuration
6367 This is the default @code{<nscd-configuration>} value (see below) used
6368 by @code{nscd-service}. This uses the caches defined by
6369 @var{%nscd-default-caches}; see below.
6372 @deftp {Data Type} nscd-configuration
6373 This is the type representing the name service cache daemon (nscd)
6378 @item @code{name-services} (default: @code{'()})
6379 List of packages denoting @dfn{name services} that must be visible to
6380 the nscd---e.g., @code{(list @var{nss-mdns})}.
6382 @item @code{glibc} (default: @var{glibc})
6383 Package object denoting the GNU C Library providing the @command{nscd}
6386 @item @code{log-file} (default: @code{"/var/log/nscd.log"})
6387 Name of nscd's log file. This is where debugging output goes when
6388 @code{debug-level} is strictly positive.
6390 @item @code{debug-level} (default: @code{0})
6391 Integer denoting the debugging levels. Higher numbers mean more
6392 debugging output is logged.
6394 @item @code{caches} (default: @var{%nscd-default-caches})
6395 List of @code{<nscd-cache>} objects denoting things to be cached; see
6401 @deftp {Data Type} nscd-cache
6402 Data type representing a cache database of nscd and its parameters.
6406 @item @code{database}
6407 This is a symbol representing the name of the database to be cached.
6408 Valid values are @code{passwd}, @code{group}, @code{hosts}, and
6409 @code{services}, which designate the corresponding NSS database
6410 (@pxref{NSS Basics,,, libc, The GNU C Library Reference Manual}).
6412 @item @code{positive-time-to-live}
6413 @itemx @code{negative-time-to-live} (default: @code{20})
6414 A number representing the number of seconds during which a positive or
6415 negative lookup result remains in cache.
6417 @item @code{check-files?} (default: @code{#t})
6418 Whether to check for updates of the files corresponding to
6421 For instance, when @var{database} is @code{hosts}, setting this flag
6422 instructs nscd to check for updates in @file{/etc/hosts} and to take
6425 @item @code{persistent?} (default: @code{#t})
6426 Whether the cache should be stored persistently on disk.
6428 @item @code{shared?} (default: @code{#t})
6429 Whether the cache should be shared among users.
6431 @item @code{max-database-size} (default: 32@tie{}MiB)
6432 Maximum size in bytes of the database cache.
6434 @c XXX: 'suggested-size' and 'auto-propagate?' seem to be expert
6435 @c settings, so leave them out.
6440 @defvr {Scheme Variable} %nscd-default-caches
6441 List of @code{<nscd-cache>} objects used by default by
6442 @code{nscd-configuration} (see above.)
6444 It enables persistent and aggressive caching of service and host name
6445 lookups. The latter provides better host name lookup performance,
6446 resilience in the face of unreliable name servers, and also better
6447 privacy---often the result of host name lookups is in local cache, so
6448 external name servers do not even need to be queried.
6452 @deffn {Scheme Procedure} syslog-service [#:config-file #f]
6453 Return a service that runs @code{syslogd}. If configuration file name
6454 @var{config-file} is not specified, use some reasonable default
6458 @anchor{guix-configuration-type}
6459 @deftp {Data Type} guix-configuration
6460 This data type represents the configuration of the Guix build daemon.
6461 @xref{Invoking guix-daemon}, for more information.
6464 @item @code{guix} (default: @var{guix})
6465 The Guix package to use.
6467 @item @code{build-group} (default: @code{"guixbuild"})
6468 Name of the group for build user accounts.
6470 @item @code{build-accounts} (default: @code{10})
6471 Number of build user accounts to create.
6473 @item @code{authorize-key?} (default: @code{#t})
6474 Whether to authorize the substitute key for @code{hydra.gnu.org}
6475 (@pxref{Substitutes}).
6477 @item @code{use-substitutes?} (default: @code{#t})
6478 Whether to use substitutes.
6480 @item @code{substitute-urls} (default: @var{%default-substitute-urls})
6481 The list of URLs where to look for substitutes by default.
6483 @item @code{extra-options} (default: @code{'()})
6484 List of extra command-line options for @command{guix-daemon}.
6486 @item @code{lsof} (default: @var{lsof})
6487 @itemx @code{lsh} (default: @var{lsh})
6488 The lsof and lsh packages to use.
6493 @deffn {Scheme Procedure} guix-service @var{config}
6494 Return a service that runs the Guix build daemon according to
6498 @deffn {Scheme Procedure} udev-service [#:udev udev]
6499 Run @var{udev}, which populates the @file{/dev} directory dynamically.
6502 @deffn {Scheme Procedure} console-keymap-service @var{file}
6503 Return a service to load console keymap from @var{file} using
6504 @command{loadkeys} command.
6507 @deffn {Scheme Procedure} gpm-service-type [#:gpm @var{gpm}] @
6509 Run @var{gpm}, the general-purpose mouse daemon, with the given
6510 command-line @var{options}. GPM allows users to use the mouse in the console,
6511 notably to select, copy, and paste text. The default value of @var{options}
6512 uses the @code{ps2} protocol, which works for both USB and PS/2 mice.
6514 This service is not part of @var{%base-services}.
6517 @anchor{guix-publish-service}
6518 @deffn {Scheme Procedure} guix-publish-service [#:guix @var{guix}] @
6519 [#:port 80] [#:host "localhost"]
6520 Return a service that runs @command{guix publish} listening on @var{host}
6521 and @var{port} (@pxref{Invoking guix publish}).
6523 This assumes that @file{/etc/guix} already contains a signing key pair as
6524 created by @command{guix archive --generate-key} (@pxref{Invoking guix
6525 archive}). If that is not the case, the service will fail to start.
6529 @node Networking Services
6530 @subsubsection Networking Services
6532 The @code{(gnu services networking)} module provides services to configure
6533 the network interface.
6535 @cindex DHCP, networking service
6536 @deffn {Scheme Procedure} dhcp-client-service [#:dhcp @var{isc-dhcp}]
6537 Return a service that runs @var{dhcp}, a Dynamic Host Configuration
6538 Protocol (DHCP) client, on all the non-loopback network interfaces.
6541 @deffn {Scheme Procedure} static-networking-service @var{interface} @var{ip} @
6542 [#:gateway #f] [#:name-services @code{'()}]
6543 Return a service that starts @var{interface} with address @var{ip}. If
6544 @var{gateway} is true, it must be a string specifying the default network
6549 @cindex network management
6550 @deffn {Scheme Procedure} wicd-service [#:wicd @var{wicd}]
6551 Return a service that runs @url{https://launchpad.net/wicd,Wicd}, a network
6552 management daemon that aims to simplify wired and wireless networking.
6554 This service adds the @var{wicd} package to the global profile, providing
6555 several commands to interact with the daemon and configure networking:
6556 @command{wicd-client}, a graphical user interface, and the @command{wicd-cli}
6557 and @command{wicd-curses} user interfaces.
6560 @deffn {Scheme Procedure} ntp-service [#:ntp @var{ntp}] @
6561 [#:name-service @var{%ntp-servers}]
6562 Return a service that runs the daemon from @var{ntp}, the
6563 @uref{http://www.ntp.org, Network Time Protocol package}. The daemon will
6564 keep the system clock synchronized with that of @var{servers}.
6567 @defvr {Scheme Variable} %ntp-servers
6568 List of host names used as the default NTP servers.
6571 @deffn {Scheme Procedure} tor-service [@var{config-file}] [#:tor @var{tor}]
6572 Return a service to run the @uref{https://torproject.org, Tor} anonymous
6575 The daemon runs as the @code{tor} unprivileged user. It is passed
6576 @var{config-file}, a file-like object, with an additional @code{User tor}
6577 line. Run @command{man tor} for information about the configuration file.
6580 @deffn {Scheme Procedure} bitlbee-service [#:bitlbee bitlbee] @
6581 [#:interface "127.0.0.1"] [#:port 6667] @
6582 [#:extra-settings ""]
6583 Return a service that runs @url{http://bitlbee.org,BitlBee}, a daemon that
6584 acts as a gateway between IRC and chat networks.
6586 The daemon will listen to the interface corresponding to the IP address
6587 specified in @var{interface}, on @var{port}. @code{127.0.0.1} means that only
6588 local clients can connect, whereas @code{0.0.0.0} means that connections can
6589 come from any networking interface.
6591 In addition, @var{extra-settings} specifies a string to append to the
6595 Furthermore, @code{(gnu services ssh)} provides the following service.
6597 @deffn {Scheme Procedure} lsh-service [#:host-key "/etc/lsh/host-key"] @
6598 [#:daemonic? #t] [#:interfaces '()] [#:port-number 22] @
6599 [#:allow-empty-passwords? #f] [#:root-login? #f] @
6600 [#:syslog-output? #t] [#:x11-forwarding? #t] @
6601 [#:tcp/ip-forwarding? #t] [#:password-authentication? #t] @
6602 [#:public-key-authentication? #t] [#:initialize? #t]
6603 Run the @command{lshd} program from @var{lsh} to listen on port @var{port-number}.
6604 @var{host-key} must designate a file containing the host key, and readable
6607 When @var{daemonic?} is true, @command{lshd} will detach from the
6608 controlling terminal and log its output to syslogd, unless one sets
6609 @var{syslog-output?} to false. Obviously, it also makes lsh-service
6610 depend on existence of syslogd service. When @var{pid-file?} is true,
6611 @command{lshd} writes its PID to the file called @var{pid-file}.
6613 When @var{initialize?} is true, automatically create the seed and host key
6614 upon service activation if they do not exist yet. This may take long and
6615 require interaction.
6617 When @var{initialize?} is false, it is up to the user to initialize the
6618 randomness generator (@pxref{lsh-make-seed,,, lsh, LSH Manual}), and to create
6619 a key pair with the private key stored in file @var{host-key} (@pxref{lshd
6620 basics,,, lsh, LSH Manual}).
6622 When @var{interfaces} is empty, lshd listens for connections on all the
6623 network interfaces; otherwise, @var{interfaces} must be a list of host names
6626 @var{allow-empty-passwords?} specifies whether to accept log-ins with empty
6627 passwords, and @var{root-login?} specifies whether to accept log-ins as
6630 The other options should be self-descriptive.
6633 @defvr {Scheme Variable} %facebook-host-aliases
6634 This variable contains a string for use in @file{/etc/hosts}
6635 (@pxref{Host Names,,, libc, The GNU C Library Reference Manual}). Each
6636 line contains a entry that maps a known server name of the Facebook
6637 on-line service---e.g., @code{www.facebook.com}---to the local
6638 host---@code{127.0.0.1} or its IPv6 equivalent, @code{::1}.
6640 This variable is typically used in the @code{hosts-file} field of an
6641 @code{operating-system} declaration (@pxref{operating-system Reference,
6642 @file{/etc/hosts}}):
6645 (use-modules (gnu) (guix))
6648 (host-name "mymachine")
6651 ;; Create a /etc/hosts file with aliases for "localhost"
6652 ;; and "mymachine", as well as for Facebook servers.
6654 (string-append (local-host-aliases host-name)
6655 %facebook-host-aliases))))
6658 This mechanism can prevent programs running locally, such as Web
6659 browsers, from accessing Facebook.
6662 The @code{(gnu services avahi)} provides the following definition.
6664 @deffn {Scheme Procedure} avahi-service [#:avahi @var{avahi}] @
6665 [#:host-name #f] [#:publish? #t] [#:ipv4? #t] @
6666 [#:ipv6? #t] [#:wide-area? #f] @
6667 [#:domains-to-browse '()]
6668 Return a service that runs @command{avahi-daemon}, a system-wide
6669 mDNS/DNS-SD responder that allows for service discovery and
6670 "zero-configuration" host name lookups (see @uref{http://avahi.org/}), and
6671 extends the name service cache daemon (nscd) so that it can resolve
6672 @code{.local} host names using
6673 @uref{http://0pointer.de/lennart/projects/nss-mdns/, nss-mdns}. Additionally,
6674 add the @var{avahi} package to the system profile so that commands such as
6675 @command{avahi-browse} are directly usable.
6677 If @var{host-name} is different from @code{#f}, use that as the host name to
6678 publish for this machine; otherwise, use the machine's actual host name.
6680 When @var{publish?} is true, publishing of host names and services is allowed;
6681 in particular, avahi-daemon will publish the machine's host name and IP
6682 address via mDNS on the local network.
6684 When @var{wide-area?} is true, DNS-SD over unicast DNS is enabled.
6686 Boolean values @var{ipv4?} and @var{ipv6?} determine whether to use IPv4/IPv6
6692 @subsubsection X Window
6694 Support for the X Window graphical display system---specifically
6695 Xorg---is provided by the @code{(gnu services xorg)} module. Note that
6696 there is no @code{xorg-service} procedure. Instead, the X server is
6697 started by the @dfn{login manager}, currently SLiM.
6699 @deffn {Scheme Procedure} slim-service [#:allow-empty-passwords? #f] @
6700 [#:auto-login? #f] [#:default-user ""] [#:startx] @
6701 [#:theme @var{%default-slim-theme}] @
6702 [#:theme-name @var{%default-slim-theme-name}]
6703 Return a service that spawns the SLiM graphical login manager, which in
6704 turn starts the X display server with @var{startx}, a command as returned by
6705 @code{xorg-start-command}.
6709 SLiM automatically looks for session types described by the @file{.desktop}
6710 files in @file{/run/current-system/profile/share/xsessions} and allows users
6711 to choose a session from the log-in screen using @kbd{F1}. Packages such as
6712 @var{xfce}, @var{sawfish}, and @var{ratpoison} provide @file{.desktop} files;
6713 adding them to the system-wide set of packages automatically makes them
6714 available at the log-in screen.
6716 In addition, @file{~/.xsession} files are honored. When available,
6717 @file{~/.xsession} must be an executable that starts a window manager
6718 and/or other X clients.
6720 When @var{allow-empty-passwords?} is true, allow logins with an empty
6721 password. When @var{auto-login?} is true, log in automatically as
6724 If @var{theme} is @code{#f}, the use the default log-in theme; otherwise
6725 @var{theme} must be a gexp denoting the name of a directory containing the
6726 theme to use. In that case, @var{theme-name} specifies the name of the
6730 @defvr {Scheme Variable} %default-theme
6731 @defvrx {Scheme Variable} %default-theme-name
6732 The G-Expression denoting the default SLiM theme and its name.
6735 @deffn {Scheme Procedure} xorg-start-command [#:guile] @
6736 [#:configuration-file #f] [#:xorg-server @var{xorg-server}]
6737 Return a derivation that builds a @var{guile} script to start the X server
6738 from @var{xorg-server}. @var{configuration-file} is the server configuration
6739 file or a derivation that builds it; when omitted, the result of
6740 @code{xorg-configuration-file} is used.
6742 Usually the X server is started by a login manager.
6745 @deffn {Scheme Procedure} xorg-configuration-file @
6746 [#:drivers '()] [#:resolutions '()] [#:extra-config '()]
6747 Return a configuration file for the Xorg server containing search paths for
6748 all the common drivers.
6750 @var{drivers} must be either the empty list, in which case Xorg chooses a
6751 graphics driver automatically, or a list of driver names that will be tried in
6752 this order---e.g., @code{(\"modesetting\" \"vesa\")}.
6754 Likewise, when @var{resolutions} is the empty list, Xorg chooses an
6755 appropriate screen resolution; otherwise, it must be a list of
6756 resolutions---e.g., @code{((1024 768) (640 480))}.
6758 Last, @var{extra-config} is a list of strings or objects appended to the
6759 @code{text-file*} argument list. It is used to pass extra text to be added
6760 verbatim to the configuration file.
6763 @deffn {Scheme Procedure} screen-locker-service @var{package} [@var{name}]
6764 Add @var{package}, a package for a screen-locker or screen-saver whose
6765 command is @var{program}, to the set of setuid programs and add a PAM entry
6766 for it. For example:
6769 (screen-locker-service xlockmore "xlock")
6772 makes the good ol' XlockMore usable.
6776 @node Desktop Services
6777 @subsubsection Desktop Services
6779 The @code{(gnu services desktop)} module provides services that are
6780 usually useful in the context of a ``desktop'' setup---that is, on a
6781 machine running a graphical display server, possibly with graphical user
6784 To simplify things, the module defines a variable containing the set of
6785 services that users typically expect on a machine with a graphical
6786 environment and networking:
6788 @defvr {Scheme Variable} %desktop-services
6789 This is a list of services that builds upon @var{%base-services} and
6790 adds or adjust services for a typical ``desktop'' setup.
6792 In particular, it adds a graphical login manager (@pxref{X Window,
6793 @code{slim-service}}), screen lockers,
6794 a network management tool (@pxref{Networking
6795 Services, @code{wicd-service}}), energy and color management services,
6796 the @code{elogind} login and seat manager, the Polkit privilege service,
6797 the GeoClue location service, an NTP client (@pxref{Networking
6798 Services}), the Avahi daemon, and has the name service switch service
6799 configured to be able to use @code{nss-mdns} (@pxref{Name Service
6803 The @var{%desktop-services} variable can be used as the @code{services}
6804 field of an @code{operating-system} declaration (@pxref{operating-system
6805 Reference, @code{services}}).
6807 The actual service definitions provided by @code{(gnu services dbus)}
6808 and @code{(gnu services desktop)} are described below.
6810 @deffn {Scheme Procedure} dbus-service [#:dbus @var{dbus}] [#:services '()]
6811 Return a service that runs the ``system bus'', using @var{dbus}, with
6812 support for @var{services}.
6814 @uref{http://dbus.freedesktop.org/, D-Bus} is an inter-process communication
6815 facility. Its system bus is used to allow system services to communicate
6816 and be notified of system-wide events.
6818 @var{services} must be a list of packages that provide an
6819 @file{etc/dbus-1/system.d} directory containing additional D-Bus configuration
6820 and policy files. For example, to allow avahi-daemon to use the system bus,
6821 @var{services} must be equal to @code{(list avahi)}.
6824 @deffn {Scheme Procedure} elogind-service [#:config @var{config}]
6825 Return a service that runs the @code{elogind} login and
6826 seat management daemon. @uref{https://github.com/andywingo/elogind,
6827 Elogind} exposes a D-Bus interface that can be used to know which users
6828 are logged in, know what kind of sessions they have open, suspend the
6829 system, inhibit system suspend, reboot the system, and other tasks.
6831 Elogind handles most system-level power events for a computer, for
6832 example suspending the system when a lid is closed, or shutting it down
6833 when the power button is pressed.
6835 The @var{config} keyword argument specifies the configuration for
6836 elogind, and should be the result of a @code{(elogind-configuration
6837 (@var{parameter} @var{value})...)} invocation. Available parameters and
6838 their default values are:
6841 @item kill-user-processes?
6843 @item kill-only-users
6845 @item kill-exclude-users
6847 @item inhibit-delay-max-seconds
6849 @item handle-power-key
6851 @item handle-suspend-key
6853 @item handle-hibernate-key
6855 @item handle-lid-switch
6857 @item handle-lid-switch-docked
6859 @item power-key-ignore-inhibited?
6861 @item suspend-key-ignore-inhibited?
6863 @item hibernate-key-ignore-inhibited?
6865 @item lid-switch-ignore-inhibited?
6867 @item holdoff-timeout-seconds
6871 @item idle-action-seconds
6873 @item runtime-directory-size-percent
6875 @item runtime-directory-size
6880 @code{("mem" "standby" "freeze")}
6883 @item hibernate-state
6885 @item hibernate-mode
6886 @code{("platform" "shutdown")}
6887 @item hybrid-sleep-state
6889 @item hybrid-sleep-mode
6890 @code{("suspend" "platform" "shutdown")}
6894 @deffn {Scheme Procedure} polkit-service @
6895 [#:polkit @var{polkit}]
6896 Return a service that runs the
6897 @uref{http://www.freedesktop.org/wiki/Software/polkit/, Polkit privilege
6898 management service}, which allows system administrators to grant access to
6899 privileged operations in a structured way. By querying the Polkit service, a
6900 privileged system component can know when it should grant additional
6901 capabilities to ordinary users. For example, an ordinary user can be granted
6902 the capability to suspend the system if the user is logged in locally.
6905 @deffn {Scheme Procedure} upower-service [#:upower @var{upower}] @
6906 [#:watts-up-pro? #f] @
6907 [#:poll-batteries? #t] @
6908 [#:ignore-lid? #f] @
6909 [#:use-percentage-for-policy? #f] @
6910 [#:percentage-low 10] @
6911 [#:percentage-critical 3] @
6912 [#:percentage-action 2] @
6914 [#:time-critical 300] @
6915 [#:time-action 120] @
6916 [#:critical-power-action 'hybrid-sleep]
6917 Return a service that runs @uref{http://upower.freedesktop.org/,
6918 @command{upowerd}}, a system-wide monitor for power consumption and battery
6919 levels, with the given configuration settings. It implements the
6920 @code{org.freedesktop.UPower} D-Bus interface, and is notably used by
6924 @deffn {Scheme Procedure} udisks-service [#:udisks @var{udisks}]
6925 Return a service for @uref{http://udisks.freedesktop.org/docs/latest/,
6926 UDisks}, a @dfn{disk management} daemon that provides user interfaces with
6927 notifications and ways to mount/unmount disks. Programs that talk to UDisks
6928 include the @command{udisksctl} command, part of UDisks, and GNOME Disks.
6931 @deffn {Scheme Procedure} colord-service [#:colord @var{colord}]
6932 Return a service that runs @command{colord}, a system service with a D-Bus
6933 interface to manage the color profiles of input and output devices such as
6934 screens and scanners. It is notably used by the GNOME Color Manager graphical
6935 tool. See @uref{http://www.freedesktop.org/software/colord/, the colord web
6936 site} for more information.
6939 @deffn {Scheme Procedure} geoclue-application name [#:allowed? #t] [#:system? #f] [#:users '()]
6940 Return an configuration allowing an application to access GeoClue
6941 location data. @var{name} is the Desktop ID of the application, without
6942 the @code{.desktop} part. If @var{allowed?} is true, the application
6943 will have access to location information by default. The boolean
6944 @var{system?} value indicates that an application is a system component
6945 or not. Finally @var{users} is a list of UIDs of all users for which
6946 this application is allowed location info access. An empty users list
6947 means that all users are allowed.
6950 @defvr {Scheme Variable} %standard-geoclue-applications
6951 The standard list of well-known GeoClue application configurations,
6952 granting authority to GNOME's date-and-time utility to ask for the
6953 current location in order to set the time zone, and allowing the Firefox
6954 (IceCat) and Epiphany web browsers to request location information.
6955 Firefox and Epiphany both query the user before allowing a web page to
6956 know the user's location.
6959 @deffn {Scheme Procedure} geoclue-service [#:colord @var{colord}] @
6961 [#:wifi-geolocation-url "https://location.services.mozilla.com/v1/geolocate?key=geoclue"] @
6963 [#:wifi-submission-url "https://location.services.mozilla.com/v1/submit?key=geoclue"] @
6964 [#:submission-nick "geoclue"] @
6965 [#:applications %standard-geoclue-applications]
6966 Return a service that runs the GeoClue location service. This service
6967 provides a D-Bus interface to allow applications to request access to a
6968 user's physical location, and optionally to add information to online
6969 location databases. See
6970 @uref{https://wiki.freedesktop.org/www/Software/GeoClue/, the GeoClue
6971 web site} for more information.
6974 @node Database Services
6975 @subsubsection Database Services
6977 The @code{(gnu services databases)} module provides the following service.
6979 @deffn {Scheme Procedure} postgresql-service [#:postgresql postgresql] @
6980 [#:config-file] [#:data-directory ``/var/lib/postgresql/data'']
6981 Return a service that runs @var{postgresql}, the PostgreSQL database
6984 The PostgreSQL daemon loads its runtime configuration from
6985 @var{config-file} and stores the database cluster in
6986 @var{data-directory}.
6990 @subsubsection Web Services
6992 The @code{(gnu services web)} module provides the following service:
6994 @deffn {Scheme Procedure} nginx-service [#:nginx nginx] @
6995 [#:log-directory ``/var/log/nginx''] @
6996 [#:run-directory ``/var/run/nginx''] @
6999 Return a service that runs @var{nginx}, the nginx web server.
7001 The nginx daemon loads its runtime configuration from @var{config-file}.
7002 Log files are written to @var{log-directory} and temporary runtime data
7003 files are written to @var{run-directory}. For proper operation, these
7004 arguments should match what is in @var{config-file} to ensure that the
7005 directories are created when the service is activated.
7009 @node Various Services
7010 @subsubsection Various Services
7012 The @code{(gnu services lirc)} module provides the following service.
7014 @deffn {Scheme Procedure} lirc-service [#:lirc lirc] @
7015 [#:device #f] [#:driver #f] [#:config-file #f] @
7016 [#:extra-options '()]
7017 Return a service that runs @url{http://www.lirc.org,LIRC}, a daemon that
7018 decodes infrared signals from remote controls.
7020 Optionally, @var{device}, @var{driver} and @var{config-file}
7021 (configuration file name) may be specified. See @command{lircd} manual
7024 Finally, @var{extra-options} is a list of additional command-line options
7025 passed to @command{lircd}.
7029 @node Setuid Programs
7030 @subsection Setuid Programs
7032 @cindex setuid programs
7033 Some programs need to run with ``root'' privileges, even when they are
7034 launched by unprivileged users. A notorious example is the
7035 @command{passwd} program, which users can run to change their
7036 password, and which needs to access the @file{/etc/passwd} and
7037 @file{/etc/shadow} files---something normally restricted to root, for
7038 obvious security reasons. To address that, these executables are
7039 @dfn{setuid-root}, meaning that they always run with root privileges
7040 (@pxref{How Change Persona,,, libc, The GNU C Library Reference Manual},
7041 for more info about the setuid mechanisms.)
7043 The store itself @emph{cannot} contain setuid programs: that would be a
7044 security issue since any user on the system can write derivations that
7045 populate the store (@pxref{The Store}). Thus, a different mechanism is
7046 used: instead of changing the setuid bit directly on files that are in
7047 the store, we let the system administrator @emph{declare} which programs
7048 should be setuid root.
7050 The @code{setuid-programs} field of an @code{operating-system}
7051 declaration contains a list of G-expressions denoting the names of
7052 programs to be setuid-root (@pxref{Using the Configuration System}).
7053 For instance, the @command{passwd} program, which is part of the Shadow
7054 package, can be designated by this G-expression (@pxref{G-Expressions}):
7057 #~(string-append #$shadow "/bin/passwd")
7060 A default set of setuid programs is defined by the
7061 @code{%setuid-programs} variable of the @code{(gnu system)} module.
7063 @defvr {Scheme Variable} %setuid-programs
7064 A list of G-expressions denoting common programs that are setuid-root.
7066 The list includes commands such as @command{passwd}, @command{ping},
7067 @command{su}, and @command{sudo}.
7070 Under the hood, the actual setuid programs are created in the
7071 @file{/run/setuid-programs} directory at system activation time. The
7072 files in this directory refer to the ``real'' binaries, which are in the
7075 @node X.509 Certificates
7076 @subsection X.509 Certificates
7078 @cindex HTTPS, certificates
7079 @cindex X.509 certificates
7081 Web servers available over HTTPS (that is, HTTP over the transport-layer
7082 security mechanism, TLS) send client programs an @dfn{X.509 certificate}
7083 that the client can then use to @emph{authenticate} the server. To do
7084 that, clients verify that the server's certificate is signed by a
7085 so-called @dfn{certificate authority} (CA). But to verify the CA's
7086 signature, clients must have first acquired the CA's certificate.
7088 Web browsers such as GNU@tie{}IceCat include their own set of CA
7089 certificates, such that they are able to verify CA signatures
7092 However, most other programs that can talk HTTPS---@command{wget},
7093 @command{git}, @command{w3m}, etc.---need to be told where CA
7094 certificates can be found.
7096 @cindex @code{nss-certs}
7097 In GuixSD, this is done by adding a package that provides certificates
7098 to the @code{packages} field of the @code{operating-system} declaration
7099 (@pxref{operating-system Reference}). GuixSD includes one such package,
7100 @code{nss-certs}, which is a set of CA certificates provided as part of
7101 Mozilla's Network Security Services.
7103 Note that it is @emph{not} part of @var{%base-packages}, so you need to
7104 explicitly add it. The @file{/etc/ssl/certs} directory, which is where
7105 most applications and libraries look for certificates by default, points
7106 to the certificates installed globally.
7108 Unprivileged users can also install their own certificate package in
7109 their profile. A number of environment variables need to be defined so
7110 that applications and libraries know where to find them. Namely, the
7111 OpenSSL library honors the @code{SSL_CERT_DIR} and @code{SSL_CERT_FILE}
7112 variables. Some applications add their own environment variables; for
7113 instance, the Git version control system honors the certificate bundle
7114 pointed to by the @code{GIT_SSL_CAINFO} environment variable.
7117 @node Name Service Switch
7118 @subsection Name Service Switch
7120 @cindex name service switch
7122 The @code{(gnu system nss)} module provides bindings to the
7123 configuration file of libc's @dfn{name service switch} or @dfn{NSS}
7124 (@pxref{NSS Configuration File,,, libc, The GNU C Library Reference
7125 Manual}). In a nutshell, the NSS is a mechanism that allows libc to be
7126 extended with new ``name'' lookup methods for system databases, which
7127 includes host names, service names, user accounts, and more (@pxref{Name
7128 Service Switch, System Databases and Name Service Switch,, libc, The GNU
7129 C Library Reference Manual}).
7131 The NSS configuration specifies, for each system database, which lookup
7132 method is to be used, and how the various methods are chained
7133 together---for instance, under which circumstances NSS should try the
7134 next method in the list. The NSS configuration is given in the
7135 @code{name-service-switch} field of @code{operating-system} declarations
7136 (@pxref{operating-system Reference, @code{name-service-switch}}).
7139 @cindex .local, host name lookup
7140 As an example, the declaration below configures the NSS to use the
7141 @uref{http://0pointer.de/lennart/projects/nss-mdns/, @code{nss-mdns}
7142 back-end}, which supports host name lookups over multicast DNS (mDNS)
7143 for host names ending in @code{.local}:
7146 (name-service-switch
7147 (hosts (list %files ;first, check /etc/hosts
7149 ;; If the above did not succeed, try
7150 ;; with 'mdns_minimal'.
7152 (name "mdns_minimal")
7154 ;; 'mdns_minimal' is authoritative for
7155 ;; '.local'. When it returns "not found",
7156 ;; no need to try the next methods.
7157 (reaction (lookup-specification
7158 (not-found => return))))
7160 ;; Then fall back to DNS.
7164 ;; Finally, try with the "full" 'mdns'.
7169 Don't worry: the @code{%mdns-host-lookup-nss} variable (see below)
7170 contains this configuration, so you won't have to type it if all you
7171 want is to have @code{.local} host lookup working.
7173 Note that, in this case, in addition to setting the
7174 @code{name-service-switch} of the @code{operating-system} declaration,
7175 you also need to use @code{avahi-service} (@pxref{Networking Services,
7176 @code{avahi-service}}), or @var{%desktop-services}, which includes it
7177 (@pxref{Desktop Services}). Doing this makes @code{nss-mdns} accessible
7178 to the name service cache daemon (@pxref{Base Services,
7179 @code{nscd-service}}).
7181 For convenience, the following variables provide typical NSS
7184 @defvr {Scheme Variable} %default-nss
7185 This is the default name service switch configuration, a
7186 @code{name-service-switch} object.
7189 @defvr {Scheme Variable} %mdns-host-lookup-nss
7190 This is the name service switch configuration with support for host name
7191 lookup over multicast DNS (mDNS) for host names ending in @code{.local}.
7194 The reference for name service switch configuration is given below. It
7195 is a direct mapping of the C library's configuration file format, so
7196 please refer to the C library manual for more information (@pxref{NSS
7197 Configuration File,,, libc, The GNU C Library Reference Manual}).
7198 Compared to libc's NSS configuration file format, it has the advantage
7199 not only of adding this warm parenthetic feel that we like, but also
7200 static checks: you'll know about syntax errors and typos as soon as you
7201 run @command{guix system}.
7203 @deftp {Data Type} name-service-switch
7205 This is the data type representation the configuration of libc's name
7206 service switch (NSS). Each field below represents one of the supported
7223 The system databases handled by the NSS. Each of these fields must be a
7224 list of @code{<name-service>} objects (see below.)
7228 @deftp {Data Type} name-service
7230 This is the data type representing an actual name service and the
7231 associated lookup action.
7235 A string denoting the name service (@pxref{Services in the NSS
7236 configuration,,, libc, The GNU C Library Reference Manual}).
7238 Note that name services listed here must be visible to nscd. This is
7239 achieved by passing the @code{#:name-services} argument to
7240 @code{nscd-service} the list of packages providing the needed name
7241 services (@pxref{Base Services, @code{nscd-service}}).
7244 An action specified using the @code{lookup-specification} macro
7245 (@pxref{Actions in the NSS configuration,,, libc, The GNU C Library
7246 Reference Manual}). For example:
7249 (lookup-specification (unavailable => continue)
7250 (success => return))
7255 @node Initial RAM Disk
7256 @subsection Initial RAM Disk
7258 @cindex initial RAM disk (initrd)
7259 @cindex initrd (initial RAM disk)
7260 For bootstrapping purposes, the Linux-Libre kernel is passed an
7261 @dfn{initial RAM disk}, or @dfn{initrd}. An initrd contains a temporary
7262 root file system, as well as an initialization script. The latter is
7263 responsible for mounting the real root file system, and for loading any
7264 kernel modules that may be needed to achieve that.
7266 The @code{initrd} field of an @code{operating-system} declaration allows
7267 you to specify which initrd you would like to use. The @code{(gnu
7268 system linux-initrd)} module provides two ways to build an initrd: the
7269 high-level @code{base-initrd} procedure, and the low-level
7270 @code{expression->initrd} procedure.
7272 The @code{base-initrd} procedure is intended to cover most common uses.
7273 For example, if you want to add a bunch of kernel modules to be loaded
7274 at boot time, you can define the @code{initrd} field of the operating
7275 system declaration like this:
7278 (initrd (lambda (file-systems . rest)
7279 ;; Create a standard initrd that has modules "foo.ko"
7280 ;; and "bar.ko", as well as their dependencies, in
7281 ;; addition to the modules available by default.
7282 (apply base-initrd file-systems
7283 #:extra-modules '("foo" "bar")
7287 The @code{base-initrd} procedure also handles common use cases that
7288 involves using the system as a QEMU guest, or as a ``live'' system whose
7289 root file system is volatile.
7291 @deffn {Monadic Procedure} base-initrd @var{file-systems} @
7292 [#:qemu-networking? #f] [#:virtio? #f] [#:volatile-root? #f] @
7293 [#:extra-modules '()] [#:mapped-devices '()]
7294 Return a monadic derivation that builds a generic initrd. @var{file-systems} is
7295 a list of file-systems to be mounted by the initrd, possibly in addition to
7296 the root file system specified on the kernel command line via @code{--root}.
7297 @var{mapped-devices} is a list of device mappings to realize before
7298 @var{file-systems} are mounted (@pxref{Mapped Devices}).
7300 When @var{qemu-networking?} is true, set up networking with the standard QEMU
7301 parameters. When @var{virtio?} is true, load additional modules so the initrd can
7302 be used as a QEMU guest with para-virtualized I/O drivers.
7304 When @var{volatile-root?} is true, the root file system is writable but any changes
7307 The initrd is automatically populated with all the kernel modules necessary
7308 for @var{file-systems} and for the given options. However, additional kernel
7309 modules can be listed in @var{extra-modules}. They will be added to the initrd, and
7310 loaded at boot time in the order in which they appear.
7313 Needless to say, the initrds we produce and use embed a
7314 statically-linked Guile, and the initialization program is a Guile
7315 program. That gives a lot of flexibility. The
7316 @code{expression->initrd} procedure builds such an initrd, given the
7317 program to run in that initrd.
7319 @deffn {Monadic Procedure} expression->initrd @var{exp} @
7320 [#:guile %guile-static-stripped] [#:name "guile-initrd"] @
7322 Return a derivation that builds a Linux initrd (a gzipped cpio archive)
7323 containing @var{guile} and that evaluates @var{exp}, a G-expression,
7324 upon booting. All the derivations referenced by @var{exp} are
7325 automatically copied to the initrd.
7327 @var{modules} is a list of Guile module names to be embedded in the
7331 @node GRUB Configuration
7332 @subsection GRUB Configuration
7337 The operating system uses GNU@tie{}GRUB as its boot loader
7338 (@pxref{Overview, overview of GRUB,, grub, GNU GRUB Manual}). It is
7339 configured using @code{grub-configuration} declarations. This data type
7340 is exported by the @code{(gnu system grub)} module, and described below.
7342 @deftp {Data Type} grub-configuration
7343 The type of a GRUB configuration declaration.
7348 This is a string denoting the boot device. It must be a device name
7349 understood by the @command{grub-install} command, such as
7350 @code{/dev/sda} or @code{(hd0)} (@pxref{Invoking grub-install,,, grub,
7353 @item @code{menu-entries} (default: @code{()})
7354 A possibly empty list of @code{menu-entry} objects (see below), denoting
7355 entries to appear in the GRUB boot menu, in addition to the current
7356 system entry and the entry pointing to previous system generations.
7358 @item @code{default-entry} (default: @code{0})
7359 The index of the default boot menu entry. Index 0 is for the current
7362 @item @code{timeout} (default: @code{5})
7363 The number of seconds to wait for keyboard input before booting. Set to
7364 0 to boot immediately, and to -1 to wait indefinitely.
7366 @item @code{theme} (default: @var{%default-theme})
7367 The @code{grub-theme} object describing the theme to use.
7372 Should you want to list additional boot menu entries @i{via} the
7373 @code{menu-entries} field above, you will need to create them with the
7374 @code{menu-entry} form:
7376 @deftp {Data Type} menu-entry
7377 The type of an entry in the GRUB boot menu.
7382 The label to show in the menu---e.g., @code{"GNU"}.
7385 The Linux kernel to boot.
7387 @item @code{linux-arguments} (default: @code{()})
7388 The list of extra Linux kernel command-line arguments---e.g.,
7389 @code{("console=ttyS0")}.
7392 A G-Expression or string denoting the file name of the initial RAM disk
7393 to use (@pxref{G-Expressions}).
7398 @c FIXME: Write documentation once it's stable.
7399 Themes are created using the @code{grub-theme} form, which is not
7402 @defvr {Scheme Variable} %default-theme
7403 This is the default GRUB theme used by the operating system, with a
7404 fancy background image displaying the GNU and Guix logos.
7408 @node Invoking guix system
7409 @subsection Invoking @code{guix system}
7411 Once you have written an operating system declaration, as seen in the
7412 previous section, it can be @dfn{instantiated} using the @command{guix
7413 system} command. The synopsis is:
7416 guix system @var{options}@dots{} @var{action} @var{file}
7419 @var{file} must be the name of a file containing an
7420 @code{operating-system} declaration. @var{action} specifies how the
7421 operating system is instantiate. Currently the following values are
7426 Build the operating system described in @var{file}, activate it, and
7427 switch to it@footnote{This action is usable only on systems already
7430 This effects all the configuration specified in @var{file}: user
7431 accounts, system services, global package list, setuid programs, etc.
7433 It also adds a GRUB menu entry for the new OS configuration, and moves
7434 entries for older configurations to a submenu---unless
7435 @option{--no-grub} is passed.
7437 @c The paragraph below refers to the problem discussed at
7438 @c <http://lists.gnu.org/archive/html/guix-devel/2014-08/msg00057.html>.
7439 It is highly recommended to run @command{guix pull} once before you run
7440 @command{guix system reconfigure} for the first time (@pxref{Invoking
7441 guix pull}). Failing to do that you would see an older version of Guix
7442 once @command{reconfigure} has completed.
7445 Build the operating system's derivation, which includes all the
7446 configuration files and programs needed to boot and run the system.
7447 This action does not actually install anything.
7450 Populate the given directory with all the files necessary to run the
7451 operating system specified in @var{file}. This is useful for first-time
7452 installations of GuixSD. For instance:
7455 guix system init my-os-config.scm /mnt
7458 copies to @file{/mnt} all the store items required by the configuration
7459 specified in @file{my-os-config.scm}. This includes configuration
7460 files, packages, and so on. It also creates other essential files
7461 needed for the system to operate correctly---e.g., the @file{/etc},
7462 @file{/var}, and @file{/run} directories, and the @file{/bin/sh} file.
7464 This command also installs GRUB on the device specified in
7465 @file{my-os-config}, unless the @option{--no-grub} option was passed.
7468 @cindex virtual machine
7470 @anchor{guix system vm}
7471 Build a virtual machine that contain the operating system declared in
7472 @var{file}, and return a script to run that virtual machine (VM).
7473 Arguments given to the script are passed as is to QEMU.
7475 The VM shares its store with the host system.
7477 Additional file systems can be shared between the host and the VM using
7478 the @code{--share} and @code{--expose} command-line options: the former
7479 specifies a directory to be shared with write access, while the latter
7480 provides read-only access to the shared directory.
7482 The example below creates a VM in which the user's home directory is
7483 accessible read-only, and where the @file{/exchange} directory is a
7484 read-write mapping of the host's @file{$HOME/tmp}:
7487 guix system vm my-config.scm \
7488 --expose=$HOME --share=$HOME/tmp=/exchange
7491 On GNU/Linux, the default is to boot directly to the kernel; this has
7492 the advantage of requiring only a very tiny root disk image since the
7493 host's store can then be mounted.
7495 The @code{--full-boot} option forces a complete boot sequence, starting
7496 with the bootloader. This requires more disk space since a root image
7497 containing at least the kernel, initrd, and bootloader data files must
7498 be created. The @code{--image-size} option can be used to specify the
7503 Return a virtual machine or disk image of the operating system declared
7504 in @var{file} that stands alone. Use the @option{--image-size} option
7505 to specify the size of the image.
7507 When using @code{vm-image}, the returned image is in qcow2 format, which
7508 the QEMU emulator can efficiently use.
7510 When using @code{disk-image}, a raw disk image is produced; it can be
7511 copied as is to a USB stick, for instance. Assuming @code{/dev/sdc} is
7512 the device corresponding to a USB stick, one can copy the image on it
7513 using the following command:
7516 # dd if=$(guix system disk-image my-os.scm) of=/dev/sdc
7520 Return a script to run the operating system declared in @var{file}
7521 within a container. Containers are a set of lightweight isolation
7522 mechanisms provided by the kernel Linux-libre. Containers are
7523 substantially less resource-demanding than full virtual machines since
7524 the kernel, shared objects, and other resources can be shared with the
7525 host system; this also means they provide thinner isolation.
7527 Currently, the script must be run as root in order to support more than
7528 a single user and group. The container shares its store with the host
7531 As with the @code{vm} action (@pxref{guix system vm}), additional file
7532 systems to be shared between the host and container can be specified
7533 using the @option{--share} and @option{--expose} options:
7536 guix system container my-config.scm \
7537 --expose=$HOME --share=$HOME/tmp=/exchange
7541 This option requires Linux-libre 3.19 or newer.
7546 @var{options} can contain any of the common build options provided by
7547 @command{guix build} (@pxref{Invoking guix build}). In addition,
7548 @var{options} can contain one of the following:
7551 @item --system=@var{system}
7552 @itemx -s @var{system}
7553 Attempt to build for @var{system} instead of the host's system type.
7554 This works as per @command{guix build} (@pxref{Invoking guix build}).
7558 Return the derivation file name of the given operating system without
7561 @item --image-size=@var{size}
7562 For the @code{vm-image} and @code{disk-image} actions, create an image
7563 of the given @var{size}. @var{size} may be a number of bytes, or it may
7564 include a unit as a suffix (@pxref{Block size, size specifications,,
7565 coreutils, GNU Coreutils}).
7567 @item --on-error=@var{strategy}
7568 Apply @var{strategy} when an error occurs when reading @var{file}.
7569 @var{strategy} may be one of the following:
7572 @item nothing-special
7573 Report the error concisely and exit. This is the default strategy.
7576 Likewise, but also display a backtrace.
7579 Report the error and enter Guile's debugger. From there, you can run
7580 commands such as @code{,bt} to get a backtrace, @code{,locals} to
7581 display local variable values, and more generally inspect the program's
7582 state. @xref{Debug Commands,,, guile, GNU Guile Reference Manual}, for
7583 a list of available debugging commands.
7587 Note that all the actions above, except @code{build} and @code{init},
7588 rely on KVM support in the Linux-Libre kernel. Specifically, the
7589 machine should have hardware virtualization support, the corresponding
7590 KVM kernel module should be loaded, and the @file{/dev/kvm} device node
7591 must exist and be readable and writable by the user and by the daemon's
7594 Once you have built, configured, re-configured, and re-re-configured
7595 your GuixSD installation, you may find it useful to list the operating
7596 system generations available on disk---and that you can choose from the
7601 @item list-generations
7602 List a summary of each generation of the operating system available on
7603 disk, in a human-readable way. This is similar to the
7604 @option{--list-generations} option of @command{guix package}
7605 (@pxref{Invoking guix package}).
7607 Optionally, one can specify a pattern, with the same syntax that is used
7608 in @command{guix package --list-generations}, to restrict the list of
7609 generations displayed. For instance, the following command displays
7610 generations up to 10-day old:
7613 $ guix system list-generations 10d
7618 The @command{guix system} command has even more to offer! The following
7619 sub-commands allow you to visualize how your system services relate to
7622 @anchor{system-extension-graph}
7625 @item extension-graph
7626 Emit in Dot/Graphviz format to standard output the @dfn{service
7627 extension graph} of the operating system defined in @var{file}
7628 (@pxref{Service Composition}, for more information on service
7634 $ guix system extension-graph @var{file} | dot -Tpdf > services.pdf
7637 produces a PDF file showing the extension relations among services.
7639 @anchor{system-dmd-graph}
7641 Emit in Dot/Graphviz format to standard output the @dfn{dependency
7642 graph} of dmd services of the operating system defined in @var{file}.
7643 @xref{dmd Services}, for more information and for an example graph.
7648 @node Defining Services
7649 @subsection Defining Services
7651 The previous sections show the available services and how one can combine
7652 them in an @code{operating-system} declaration. But how do we define
7653 them in the first place? And what is a service anyway?
7656 * Service Composition:: The model for composing services.
7657 * Service Types and Services:: Types and services.
7658 * Service Reference:: API reference.
7659 * dmd Services:: A particular type of service.
7662 @node Service Composition
7663 @subsubsection Service Composition
7667 Here we define a @dfn{service} as, broadly, something that extends the
7668 operating system's functionality. Often a service is a process---a
7669 @dfn{daemon}---started when the system boots: a secure shell server, a
7670 Web server, the Guix build daemon, etc. Sometimes a service is a daemon
7671 whose execution can be triggered by another daemon---e.g., an FTP server
7672 started by @command{inetd} or a D-Bus service activated by
7673 @command{dbus-daemon}. Occasionally, a service does not map to a
7674 daemon. For instance, the ``account'' service collects user accounts
7675 and makes sure they exist when the system runs; the ``udev'' service
7676 collects device management rules and makes them available to the eudev
7677 daemon; the @file{/etc} service populates the system's @file{/etc}
7680 @cindex service extensions
7681 GuixSD services are connected by @dfn{extensions}. For instance, the
7682 secure shell service @emph{extends} dmd---GuixSD's initialization system,
7683 running as PID@tie{}1---by giving it the command lines to start and stop
7684 the secure shell daemon (@pxref{Networking Services,
7685 @code{lsh-service}}); the UPower service extends the D-Bus service by
7686 passing it its @file{.service} specification, and extends the udev
7687 service by passing it device management rules (@pxref{Desktop Services,
7688 @code{upower-service}}); the Guix daemon service extends dmd by passing
7689 it the command lines to start and stop the daemon, and extends the
7690 account service by passing it a list of required build user accounts
7691 (@pxref{Base Services}).
7693 All in all, services and their ``extends'' relations form a directed
7694 acyclic graph (DAG). If we represent services as boxes and extensions
7695 as arrows, a typical system might provide something like this:
7697 @image{images/service-graph,,5in,Typical service extension graph.}
7699 @cindex system service
7700 At the bottom, we see the @dfn{system service}, which produces the
7701 directory containing everything to run and boot the system, as returned
7702 by the @command{guix system build} command. @xref{Service Reference},
7703 to learn about the other service types shown here.
7704 @xref{system-extension-graph, the @command{guix system extension-graph}
7705 command}, for information on how to generate this representation for a
7706 particular operating system definition.
7708 @cindex service types
7709 Technically, developers can define @dfn{service types} to express these
7710 relations. There can be any number of services of a given type on the
7711 system---for instance, a system running two instances of the GNU secure
7712 shell server (lsh) has two instances of @var{lsh-service-type}, with
7713 different parameters.
7715 The following section describes the programming interface for service
7718 @node Service Types and Services
7719 @subsubsection Service Types and Services
7721 A @dfn{service type} is a node in the DAG described above. Let us start
7722 with a simple example, the service type for the Guix build daemon
7723 (@pxref{Invoking guix-daemon}):
7726 (define guix-service-type
7730 (list (service-extension dmd-root-service-type guix-dmd-service)
7731 (service-extension account-service-type guix-accounts)
7732 (service-extension activation-service-type guix-activation)))))
7736 It defines a two things:
7740 A name, whose sole purpose is to make inspection and debugging easier.
7743 A list of @dfn{service extensions}, where each extension designates the
7744 target service type and a procedure that, given the service's
7745 parameters, returns a list of object to extend the service of that type.
7747 Every service type has at least one service extension. The only
7748 exception is the @dfn{boot service type}, which is the ultimate service.
7751 In this example, @var{guix-service-type} extends three services:
7754 @item dmd-root-service-type
7755 The @var{guix-dmd-service} procedure defines how the dmd service is
7756 extended. Namely, it returns a @code{<dmd-service>} object that defines
7757 how @command{guix-daemon} is started and stopped (@pxref{dmd Services}).
7759 @item account-service-type
7760 This extension for this service is computed by @var{guix-accounts},
7761 which returns a list of @code{user-group} and @code{user-account}
7762 objects representing the build user accounts (@pxref{Invoking
7765 @item activation-service-type
7766 Here @var{guix-activation} is a procedure that returns a gexp, which is
7767 a code snippet to run at ``activation time''---e.g., when the service is
7771 A service of this type is instantiated like this:
7774 (service guix-service-type
7777 (use-substitutes? #f)))
7780 The second argument to the @code{service} form is a value representing
7781 the parameters of this specific service instance.
7782 @xref{guix-configuration-type, @code{guix-configuration}}, for
7783 information about the @code{guix-configuration} data type.
7785 @var{guix-service-type} is quite simple because it extends other
7786 services but is not extensible itself.
7788 @c @subsubsubsection Extensible Service Types
7790 The service type for an @emph{extensible} service looks like this:
7793 (define udev-service-type
7794 (service-type (name 'udev)
7796 (list (service-extension dmd-root-service-type
7799 (compose concatenate) ;concatenate the list of rules
7800 (extend (lambda (config rules)
7802 (($ <udev-configuration> udev initial-rules)
7804 (udev udev) ;the udev package to use
7805 (rules (append initial-rules rules)))))))))
7808 This is the service type for the
7809 @uref{https://wiki.gentoo.org/wiki/Project:Eudev, eudev device
7810 management daemon}. Compared to the previous example, in addition to an
7811 extension of @var{dmd-root-service-type}, we see two new fields:
7815 This is the procedure to @dfn{compose} the list of extensions to
7816 services of this type.
7818 Services can extend the udev service by passing it lists of rules; we
7819 compose those extensions simply by concatenating them.
7822 This procedure defines how the service's value is @dfn{extended} with
7823 the composition of the extensions.
7825 Udev extensions are composed into a list of rules, but the udev service
7826 value is itself a @code{<udev-configuration>} record. So here, we
7827 extend that record by appending the list of rules is contains to the
7828 list of contributed rules.
7831 There can be only one instance of an extensible service type such as
7832 @var{udev-service-type}. If there were more, the
7833 @code{service-extension} specifications would be ambiguous.
7835 Still here? The next section provides a reference of the programming
7836 interface for services.
7838 @node Service Reference
7839 @subsubsection Service Reference
7841 We have seen an overview of service types (@pxref{Service Types and
7842 Services}). This section provides a reference on how to manipulate
7843 services and service types. This interface is provided by the
7844 @code{(gnu services)} module.
7846 @deffn {Scheme Procedure} service @var{type} @var{value}
7847 Return a new service of @var{type}, a @code{<service-type>} object (see
7848 below.) @var{value} can be any object; it represents the parameters of
7849 this particular service instance.
7852 @deffn {Scheme Procedure} service? @var{obj}
7853 Return true if @var{obj} is a service.
7856 @deffn {Scheme Procedure} service-kind @var{service}
7857 Return the type of @var{service}---i.e., a @code{<service-type>} object.
7860 @deffn {Scheme Procedure} service-parameters @var{service}
7861 Return the value associated with @var{service}. It represents its
7865 Here is an example of how a service is created and manipulated:
7869 (service nginx-service-type
7870 (nginx-configuration
7872 (log-directory log-directory)
7873 (run-directory run-directory)
7874 (file config-file))))
7879 (eq? (service-kind s) nginx-service-type)
7883 The @code{modify-services} form provides a handy way to change the
7884 parameters of some of the services of a list such as
7885 @var{%base-services} (@pxref{Base Services, @code{%base-services}}). Of
7886 course, you could always use standard list combinators such as
7887 @code{map} and @code{fold} to do that (@pxref{SRFI-1, List Library,,
7888 guile, GNU Guile Reference Manual}); @code{modify-services} simply
7889 provides a more concise form for this common pattern.
7891 @deffn {Scheme Syntax} modify-services @var{services} @
7892 (@var{type} @var{variable} => @var{body}) @dots{}
7894 Modify the services listed in @var{services} according to the given
7895 clauses. Each clause has the form:
7898 (@var{type} @var{variable} => @var{body})
7901 where @var{type} is a service type, such as @var{guix-service-type}, and
7902 @var{variable} is an identifier that is bound within @var{body} to the
7903 value of the service of that @var{type}. @xref{Using the Configuration
7904 System}, for an example.
7906 This is a shorthand for:
7909 (map (lambda (service) @dots{}) @var{services})
7913 Next comes the programming interface for service types. This is
7914 something you want to know when writing new service definitions, but not
7915 necessarily when simply looking for ways to customize your
7916 @code{operating-system} declaration.
7918 @deftp {Data Type} service-type
7919 @cindex service type
7920 This is the representation of a @dfn{service type} (@pxref{Service Types
7925 This is a symbol, used only to simplify inspection and debugging.
7927 @item @code{extensions}
7928 A non-empty list of @code{<service-extension>} objects (see below.)
7930 @item @code{compose} (default: @code{#f})
7931 If this is @code{#f}, then the service type denotes services that cannot
7932 be extended---i.e., services that do not receive ``values'' from other
7935 Otherwise, it must be a one-argument procedure. The procedure is called
7936 by @code{fold-services} and is passed a list of values collected from
7937 extensions. It must return a value that is a valid parameter value for
7938 the service instance.
7940 @item @code{extend} (default: @code{#f})
7941 If this is @code{#f}, services of this type cannot be extended.
7943 Otherwise, it must be a two-argument procedure: @code{fold-services}
7944 calls it, passing it the service's initial value as the first argument
7945 and the result of applying @code{compose} to the extension values as the
7949 @xref{Service Types and Services}, for examples.
7952 @deffn {Scheme Procedure} service-extension @var{target-type} @
7954 Return a new extension for services of type @var{target-type}.
7955 @var{compute} must be a one-argument procedure: @code{fold-services}
7956 calls it, passing it the value associated with the service that provides
7957 the extension; it must return a valid value for the target service.
7960 @deffn {Scheme Procedure} service-extension? @var{obj}
7961 Return true if @var{obj} is a service extension.
7964 At the core of the service abstraction lies the @code{fold-services}
7965 procedure, which is responsible for ``compiling'' a list of services
7966 down to a single directory that contains everything needed to boot and
7967 run the system---the directory shown by the @command{guix system build}
7968 command (@pxref{Invoking guix system}). In essence, it propagates
7969 service extensions down the service graph, updating each node parameters
7970 on the way, until it reaches the root node.
7972 @deffn {Scheme Procedure} fold-services @var{services} @
7973 [#:target-type @var{system-service-type}]
7974 Fold @var{services} by propagating their extensions down to the root of
7975 type @var{target-type}; return the root service adjusted accordingly.
7978 Lastly, the @code{(gnu services)} module also defines several essential
7979 service types, some of which are listed below.
7981 @defvr {Scheme Variable} system-service-type
7982 This is the root of the service graph. It produces the system directory
7983 as returned by the @command{guix system build} command.
7986 @defvr {Scheme Variable} boot-service-type
7987 The type of the ``boot service'', which produces the @dfn{boot script}.
7988 The boot script is what the initial RAM disk runs when booting.
7991 @defvr {Scheme Variable} etc-service-type
7992 The type of the @file{/etc} service. This service can be extended by
7993 passing it name/file tuples such as:
7996 (list `("issue" ,(plain-file "issue" "Welcome!\n")))
7999 In this example, the effect would be to add an @file{/etc/issue} file
8000 pointing to the given file.
8003 @defvr {Scheme Variable} setuid-program-service-type
8004 Type for the ``setuid-program service''. This service collects lists of
8005 executable file names, passed as gexps, and adds them to the set of
8006 setuid-root programs on the system (@pxref{Setuid Programs}).
8009 @defvr {Scheme Variable} profile-service-type
8010 Type of the service that populates the @dfn{system profile}---i.e., the
8011 programs under @file{/run/current-system/profile}. Other services can
8012 extend it by passing it lists of packages to add to the system profile.
8017 @subsubsection dmd Services
8021 The @code{(gnu services dmd)} provides a way to define services managed
8022 by GNU@tie{}dmd, which is GuixSD initialization system---the first
8023 process that is started when the system boots, aka. PID@tie{}1
8024 (@pxref{Introduction,,, dmd, GNU dmd Manual}).
8026 Services in dmd can depend on each other. For instance, the SSH daemon
8027 may need to be started after the syslog daemon has been started, which
8028 in turn can only happen once all the file systems have been mounted.
8029 The simple operating system defined earlier (@pxref{Using the
8030 Configuration System}) results in a service graph like this:
8032 @image{images/dmd-graph,,5in,Typical dmd service graph.}
8034 You can actually generate such a graph for any operating system
8035 definition using the @command{guix system dmd-graph} command
8036 (@pxref{system-dmd-graph, @command{guix system dmd-graph}}).
8038 The @var{%dmd-root-service} is a service object representing PID@tie{}1,
8039 of type @var{dmd-root-service-type}; it can be extended by passing it
8040 lists of @code{<dmd-service>} objects.
8042 @deftp {Data Type} dmd-service
8043 The data type representing a service managed by dmd.
8046 @item @code{provision}
8047 This is a list of symbols denoting what the service provides.
8049 These are the names that may be passed to @command{deco start},
8050 @command{deco status}, and similar commands (@pxref{Invoking deco,,,
8051 dmd, GNU dmd Manual}). @xref{Slots of services, the @code{provides}
8052 slot,, dmd, GNU dmd Manual}, for details.
8054 @item @code{requirements} (default: @code{'()})
8055 List of symbols denoting the dmd services this one depends on.
8057 @item @code{respawn?} (default: @code{#t})
8058 Whether to restart the service when it stops, for instance when the
8059 underlying process dies.
8062 @itemx @code{stop} (default: @code{#~(const #f)})
8063 The @code{start} and @code{stop} fields refer to dmd's facilities to
8064 start and stop processes (@pxref{Service De- and Constructors,,, dmd,
8065 GNU dmd Manual}). They are given as G-expressions that get expanded in
8066 the dmd configuration file (@pxref{G-Expressions}).
8068 @item @code{documentation}
8069 A documentation string, as shown when running:
8072 deco doc @var{service-name}
8075 where @var{service-name} is one of the symbols in @var{provision}
8076 (@pxref{Invoking deco,,, dmd, GNU dmd Manual}).
8078 @item @code{modules} (default: @var{%default-modules})
8079 This is the list of modules that must be in scope when @code{start} and
8080 @code{stop} are evaluated.
8082 @item @code{imported-modules} (default: @var{%default-imported-modules})
8083 This is the list of modules to import in the execution environment of
8089 @defvr {Scheme Variable} dmd-root-service-type
8090 The service type for the dmd ``root service''---i.e., PID@tie{}1.
8092 This is the service type that extensions target when they want to create
8093 dmd services (@pxref{Service Types and Services}, for an example). Each
8094 extension must pass a list of @code{<dmd-service>}.
8097 @defvr {Scheme Variable} %dmd-root-service
8098 This service represents PID@tie{}1.
8102 @node Installing Debugging Files
8103 @section Installing Debugging Files
8105 @cindex debugging files
8106 Program binaries, as produced by the GCC compilers for instance, are
8107 typically written in the ELF format, with a section containing
8108 @dfn{debugging information}. Debugging information is what allows the
8109 debugger, GDB, to map binary code to source code; it is required to
8110 debug a compiled program in good conditions.
8112 The problem with debugging information is that is takes up a fair amount
8113 of disk space. For example, debugging information for the GNU C Library
8114 weighs in at more than 60 MiB. Thus, as a user, keeping all the
8115 debugging info of all the installed programs is usually not an option.
8116 Yet, space savings should not come at the cost of an impediment to
8117 debugging---especially in the GNU system, which should make it easier
8118 for users to exert their computing freedom (@pxref{GNU Distribution}).
8120 Thankfully, the GNU Binary Utilities (Binutils) and GDB provide a
8121 mechanism that allows users to get the best of both worlds: debugging
8122 information can be stripped from the binaries and stored in separate
8123 files. GDB is then able to load debugging information from those files,
8124 when they are available (@pxref{Separate Debug Files,,, gdb, Debugging
8127 The GNU distribution takes advantage of this by storing debugging
8128 information in the @code{lib/debug} sub-directory of a separate package
8129 output unimaginatively called @code{debug} (@pxref{Packages with
8130 Multiple Outputs}). Users can choose to install the @code{debug} output
8131 of a package when they need it. For instance, the following command
8132 installs the debugging information for the GNU C Library and for GNU
8136 guix package -i glibc:debug guile:debug
8139 GDB must then be told to look for debug files in the user's profile, by
8140 setting the @code{debug-file-directory} variable (consider setting it
8141 from the @file{~/.gdbinit} file, @pxref{Startup,,, gdb, Debugging with
8145 (gdb) set debug-file-directory ~/.guix-profile/lib/debug
8148 From there on, GDB will pick up debugging information from the
8149 @code{.debug} files under @file{~/.guix-profile/lib/debug}.
8151 In addition, you will most likely want GDB to be able to show the source
8152 code being debugged. To do that, you will have to unpack the source
8153 code of the package of interest (obtained with @code{guix build
8154 --source}, @pxref{Invoking guix build}), and to point GDB to that source
8155 directory using the @code{directory} command (@pxref{Source Path,
8156 @code{directory},, gdb, Debugging with GDB}).
8158 @c XXX: keep me up-to-date
8159 The @code{debug} output mechanism in Guix is implemented by the
8160 @code{gnu-build-system} (@pxref{Build Systems}). Currently, it is
8161 opt-in---debugging information is available only for those packages
8162 whose definition explicitly declares a @code{debug} output. This may be
8163 changed to opt-out in the future, if our build farm servers can handle
8164 the load. To check whether a package has a @code{debug} output, use
8165 @command{guix package --list-available} (@pxref{Invoking guix package}).
8168 @node Security Updates
8169 @section Security Updates
8172 As of version @value{VERSION}, the feature described in this section is
8176 @cindex security updates
8177 Occasionally, important security vulnerabilities are discovered in core
8178 software packages and must be patched. Guix follows a functional
8179 package management discipline (@pxref{Introduction}), which implies
8180 that, when a package is changed, @emph{every package that depends on it}
8181 must be rebuilt. This can significantly slow down the deployment of
8182 fixes in core packages such as libc or Bash, since basically the whole
8183 distribution would need to be rebuilt. Using pre-built binaries helps
8184 (@pxref{Substitutes}), but deployment may still take more time than
8188 To address that, Guix implements @dfn{grafts}, a mechanism that allows
8189 for fast deployment of critical updates without the costs associated
8190 with a whole-distribution rebuild. The idea is to rebuild only the
8191 package that needs to be patched, and then to ``graft'' it onto packages
8192 explicitly installed by the user and that were previously referring to
8193 the original package. The cost of grafting is typically very low, and
8194 order of magnitudes lower than a full rebuild of the dependency chain.
8196 @cindex replacements of packages, for grafts
8197 For instance, suppose a security update needs to be applied to Bash.
8198 Guix developers will provide a package definition for the ``fixed''
8199 Bash, say @var{bash-fixed}, in the usual way (@pxref{Defining
8200 Packages}). Then, the original package definition is augmented with a
8201 @code{replacement} field pointing to the package containing the bug fix:
8208 (replacement bash-fixed)))
8211 From there on, any package depending directly or indirectly on Bash that
8212 is installed will automatically be ``rewritten'' to refer to
8213 @var{bash-fixed} instead of @var{bash}. This grafting process takes
8214 time proportional to the size of the package, but expect less than a
8215 minute for an ``average'' package on a recent machine.
8217 Currently, the graft and the package it replaces (@var{bash-fixed} and
8218 @var{bash} in the example above) must have the exact same @code{name}
8219 and @code{version} fields. This restriction mostly comes from the fact
8220 that grafting works by patching files, including binary files, directly.
8221 Other restrictions may apply: for instance, when adding a graft to a
8222 package providing a shared library, the original shared library and its
8223 replacement must have the same @code{SONAME} and be binary-compatible.
8226 @node Package Modules
8227 @section Package Modules
8229 From a programming viewpoint, the package definitions of the
8230 GNU distribution are provided by Guile modules in the @code{(gnu packages
8231 @dots{})} name space@footnote{Note that packages under the @code{(gnu
8232 packages @dots{})} module name space are not necessarily ``GNU
8233 packages''. This module naming scheme follows the usual Guile module
8234 naming convention: @code{gnu} means that these modules are distributed
8235 as part of the GNU system, and @code{packages} identifies modules that
8236 define packages.} (@pxref{Modules, Guile modules,, guile, GNU Guile
8237 Reference Manual}). For instance, the @code{(gnu packages emacs)}
8238 module exports a variable named @code{emacs}, which is bound to a
8239 @code{<package>} object (@pxref{Defining Packages}).
8241 The @code{(gnu packages @dots{})} module name space is
8242 automatically scanned for packages by the command-line tools. For
8243 instance, when running @code{guix package -i emacs}, all the @code{(gnu
8244 packages @dots{})} modules are scanned until one that exports a package
8245 object whose name is @code{emacs} is found. This package search
8246 facility is implemented in the @code{(gnu packages)} module.
8248 @cindex customization, of packages
8249 @cindex package module search path
8250 Users can store package definitions in modules with different
8251 names---e.g., @code{(my-packages emacs)}@footnote{Note that the file
8252 name and module name must match. For instance, the @code{(my-packages
8253 emacs)} module must be stored in a @file{my-packages/emacs.scm} file
8254 relative to the load path specified with @option{--load-path} or
8255 @code{GUIX_PACKAGE_PATH}. @xref{Modules and the File System,,,
8256 guile, GNU Guile Reference Manual}, for details.}. These package definitions
8257 will not be visible by default. Thus, users can invoke commands such as
8258 @command{guix package} and @command{guix build} have to be used with the
8259 @code{-e} option so that they know where to find the package. Better
8260 yet, they can use the
8261 @code{-L} option of these commands to make those modules visible
8262 (@pxref{Invoking guix build, @code{--load-path}}), or define the
8263 @code{GUIX_PACKAGE_PATH} environment variable. This environment
8264 variable makes it easy to extend or customize the distribution and is
8265 honored by all the user interfaces.
8267 @defvr {Environment Variable} GUIX_PACKAGE_PATH
8268 This is a colon-separated list of directories to search for package
8269 modules. Directories listed in this variable take precedence over the
8270 distribution's own modules.
8273 The distribution is fully @dfn{bootstrapped} and @dfn{self-contained}:
8274 each package is built based solely on other packages in the
8275 distribution. The root of this dependency graph is a small set of
8276 @dfn{bootstrap binaries}, provided by the @code{(gnu packages
8277 bootstrap)} module. For more information on bootstrapping,
8278 @pxref{Bootstrapping}.
8280 @node Packaging Guidelines
8281 @section Packaging Guidelines
8283 The GNU distribution is nascent and may well lack some of your favorite
8284 packages. This section describes how you can help make the distribution
8285 grow. @xref{Contributing}, for additional information on how you can
8288 Free software packages are usually distributed in the form of
8289 @dfn{source code tarballs}---typically @file{tar.gz} files that contain
8290 all the source files. Adding a package to the distribution means
8291 essentially two things: adding a @dfn{recipe} that describes how to
8292 build the package, including a list of other packages required to build
8293 it, and adding @dfn{package meta-data} along with that recipe, such as a
8294 description and licensing information.
8296 In Guix all this information is embodied in @dfn{package definitions}.
8297 Package definitions provide a high-level view of the package. They are
8298 written using the syntax of the Scheme programming language; in fact,
8299 for each package we define a variable bound to the package definition,
8300 and export that variable from a module (@pxref{Package Modules}).
8301 However, in-depth Scheme knowledge is @emph{not} a prerequisite for
8302 creating packages. For more information on package definitions,
8303 @pxref{Defining Packages}.
8305 Once a package definition is in place, stored in a file in the Guix
8306 source tree, it can be tested using the @command{guix build} command
8307 (@pxref{Invoking guix build}). For example, assuming the new package is
8308 called @code{gnew}, you may run this command from the Guix build tree
8309 (@pxref{Running Guix Before It Is Installed}):
8312 ./pre-inst-env guix build gnew --keep-failed
8315 Using @code{--keep-failed} makes it easier to debug build failures since
8316 it provides access to the failed build tree. Another useful
8317 command-line option when debugging is @code{--log-file}, to access the
8320 If the package is unknown to the @command{guix} command, it may be that
8321 the source file contains a syntax error, or lacks a @code{define-public}
8322 clause to export the package variable. To figure it out, you may load
8323 the module from Guile to get more information about the actual error:
8326 ./pre-inst-env guile -c '(use-modules (gnu packages gnew))'
8329 Once your package builds correctly, please send us a patch
8330 (@pxref{Contributing}). Well, if you need help, we will be happy to
8331 help you too. Once the patch is committed in the Guix repository, the
8332 new package automatically gets built on the supported platforms by
8333 @url{http://hydra.gnu.org/jobset/gnu/master, our continuous integration
8337 Users can obtain the new package definition simply by running
8338 @command{guix pull} (@pxref{Invoking guix pull}). When
8339 @code{hydra.gnu.org} is done building the package, installing the
8340 package automatically downloads binaries from there
8341 (@pxref{Substitutes}). The only place where human intervention is
8342 needed is to review and apply the patch.
8346 * Software Freedom:: What may go into the distribution.
8347 * Package Naming:: What's in a name?
8348 * Version Numbers:: When the name is not enough.
8349 * Synopses and Descriptions:: Helping users find the right package.
8350 * Python Modules:: Taming the snake.
8351 * Perl Modules:: Little pearls.
8352 * Fonts:: Fond of fonts.
8355 @node Software Freedom
8356 @subsection Software Freedom
8358 @c Adapted from http://www.gnu.org/philosophy/philosophy.html.
8360 The GNU operating system has been developed so that users can have
8361 freedom in their computing. GNU is @dfn{free software}, meaning that
8362 users have the @url{http://www.gnu.org/philosophy/free-sw.html,four
8363 essential freedoms}: to run the program, to study and change the program
8364 in source code form, to redistribute exact copies, and to distribute
8365 modified versions. Packages found in the GNU distribution provide only
8366 software that conveys these four freedoms.
8368 In addition, the GNU distribution follow the
8369 @url{http://www.gnu.org/distros/free-system-distribution-guidelines.html,free
8370 software distribution guidelines}. Among other things, these guidelines
8371 reject non-free firmware, recommendations of non-free software, and
8372 discuss ways to deal with trademarks and patents.
8374 Some packages contain a small and optional subset that violates the
8375 above guidelines, for instance because this subset is itself non-free
8376 code. When that happens, the offending items are removed with
8377 appropriate patches or code snippets in the package definition's
8378 @code{origin} form (@pxref{Defining Packages}). That way, @code{guix
8379 build --source} returns the ``freed'' source rather than the unmodified
8383 @node Package Naming
8384 @subsection Package Naming
8386 A package has actually two names associated with it:
8387 First, there is the name of the @emph{Scheme variable}, the one following
8388 @code{define-public}. By this name, the package can be made known in the
8389 Scheme code, for instance as input to another package. Second, there is
8390 the string in the @code{name} field of a package definition. This name
8391 is used by package management commands such as
8392 @command{guix package} and @command{guix build}.
8394 Both are usually the same and correspond to the lowercase conversion of
8395 the project name chosen upstream, with underscores replaced with
8396 hyphens. For instance, GNUnet is available as @code{gnunet}, and
8397 SDL_net as @code{sdl-net}.
8399 We do not add @code{lib} prefixes for library packages, unless these are
8400 already part of the official project name. But @pxref{Python
8401 Modules} and @ref{Perl Modules} for special rules concerning modules for
8402 the Python and Perl languages.
8404 Font package names are handled differently, @pxref{Fonts}.
8407 @node Version Numbers
8408 @subsection Version Numbers
8410 We usually package only the latest version of a given free software
8411 project. But sometimes, for instance for incompatible library versions,
8412 two (or more) versions of the same package are needed. These require
8413 different Scheme variable names. We use the name as defined
8414 in @ref{Package Naming}
8415 for the most recent version; previous versions use the same name, suffixed
8416 by @code{-} and the smallest prefix of the version number that may
8417 distinguish the two versions.
8419 The name inside the package definition is the same for all versions of a
8420 package and does not contain any version number.
8422 For instance, the versions 2.24.20 and 3.9.12 of GTK+ may be packaged as follows:
8430 (define-public gtk+-2
8436 If we also wanted GTK+ 3.8.2, this would be packaged as
8438 (define-public gtk+-3.8
8445 @node Synopses and Descriptions
8446 @subsection Synopses and Descriptions
8448 As we have seen before, each package in GNU@tie{}Guix includes a
8449 synopsis and a description (@pxref{Defining Packages}). Synopses and
8450 descriptions are important: They are what @command{guix package
8451 --search} searches, and a crucial piece of information to help users
8452 determine whether a given package suits their needs. Consequently,
8453 packagers should pay attention to what goes into them.
8455 Synopses must start with a capital letter and must not end with a
8456 period. They must not start with ``a'' or ``the'', which usually does
8457 not bring anything; for instance, prefer ``File-frobbing tool'' over ``A
8458 tool that frobs files''. The synopsis should say what the package
8459 is---e.g., ``Core GNU utilities (file, text, shell)''---or what it is
8460 used for---e.g., the synopsis for GNU@tie{}grep is ``Print lines
8461 matching a pattern''.
8463 Keep in mind that the synopsis must be meaningful for a very wide
8464 audience. For example, ``Manipulate alignments in the SAM format''
8465 might make sense for a seasoned bioinformatics researcher, but might be
8466 fairly unhelpful or even misleading to a non-specialized audience. It
8467 is a good idea to come up with a synopsis that gives an idea of the
8468 application domain of the package. In this example, this might give
8469 something like ``Manipulate nucleotide sequence alignments'', which
8470 hopefully gives the user a better idea of whether this is what they are
8473 @cindex Texinfo markup, in package descriptions
8474 Descriptions should take between five and ten lines. Use full
8475 sentences, and avoid using acronyms without first introducing them.
8476 Descriptions can include Texinfo markup, which is useful to introduce
8477 ornaments such as @code{@@code} or @code{@@dfn}, bullet lists, or
8478 hyperlinks (@pxref{Overview,,, texinfo, GNU Texinfo}). However you
8479 should be careful when using some characters for example @samp{@@} and
8480 curly braces which are the basic special characters in Texinfo
8481 (@pxref{Special Characters,,, texinfo, GNU Texinfo}). User interfaces
8482 such as @command{guix package --show} take care of rendering it
8485 Synopses and descriptions are translated by volunteers
8486 @uref{http://translationproject.org/domain/guix-packages.html, at the
8487 Translation Project} so that as many users as possible can read them in
8488 their native language. User interfaces search them and display them in
8489 the language specified by the current locale.
8491 Translation is a lot of work so, as a packager, please pay even more
8492 attention to your synopses and descriptions as every change may entail
8493 additional work for translators. In order to help them, it is possible
8494 to make recommendations or instructions visible to them by inserting
8495 special comments like this (@pxref{xgettext Invocation,,, gettext, GNU
8499 ;; TRANSLATORS: "X11 resize-and-rotate" should not be translated.
8500 (description "ARandR is designed to provide a simple visual front end
8501 for the X11 resize-and-rotate (RandR) extension. @dots{}")
8505 @node Python Modules
8506 @subsection Python Modules
8508 We currently package Python 2 and Python 3, under the Scheme variable names
8509 @code{python-2} and @code{python} as explained in @ref{Version Numbers}.
8510 To avoid confusion and naming clashes with other programming languages, it
8511 seems desirable that the name of a package for a Python module contains
8512 the word @code{python}.
8514 Some modules are compatible with only one version of Python, others with both.
8515 If the package Foo compiles only with Python 3, we name it
8516 @code{python-foo}; if it compiles only with Python 2, we name it
8517 @code{python2-foo}. If it is compatible with both versions, we create two
8518 packages with the corresponding names.
8520 If a project already contains the word @code{python}, we drop this;
8521 for instance, the module python-dateutil is packaged under the names
8522 @code{python-dateutil} and @code{python2-dateutil}.
8526 @subsection Perl Modules
8528 Perl programs standing for themselves are named as any other package,
8529 using the lowercase upstream name.
8530 For Perl packages containing a single class, we use the lowercase class name,
8531 replace all occurrences of @code{::} by dashes and prepend the prefix
8533 So the class @code{XML::Parser} becomes @code{perl-xml-parser}.
8534 Modules containing several classes keep their lowercase upstream name and
8535 are also prepended by @code{perl-}. Such modules tend to have the word
8536 @code{perl} somewhere in their name, which gets dropped in favor of the
8537 prefix. For instance, @code{libwww-perl} becomes @code{perl-libwww}.
8543 For fonts that are in general not installed by a user for typesetting
8544 purposes, or that are distributed as part of a larger software package,
8545 we rely on the general packaging rules for software; for instance, this
8546 applies to the fonts delivered as part of the X.Org system or fonts that
8547 are part of TeX Live.
8549 To make it easier for a user to search for fonts, names for other packages
8550 containing only fonts are constructed as follows, independently of the
8551 upstream package name.
8553 The name of a package containing only one font family starts with
8554 @code{font-}; it is followed by the foundry name and a dash @code{-}
8555 if the foundry is known, and the font family name, in which spaces are
8556 replaced by dashes (and as usual, all upper case letters are transformed
8558 For example, the Gentium font family by SIL is packaged under the name
8559 @code{font-sil-gentium}.
8561 For a package containing several font families, the name of the collection
8562 is used in the place of the font family name.
8563 For instance, the Liberation fonts consist of three families,
8564 Liberation Sans, Liberation Serif and Liberation Mono.
8565 These could be packaged separately under the names
8566 @code{font-liberation-sans} and so on; but as they are distributed together
8567 under a common name, we prefer to package them together as
8568 @code{font-liberation}.
8570 In the case where several formats of the same font family or font collection
8571 are packaged separately, a short form of the format, prepended by a dash,
8572 is added to the package name. We use @code{-ttf} for TrueType fonts,
8573 @code{-otf} for OpenType fonts and @code{-type1} for PostScript Type 1
8579 @section Bootstrapping
8581 @c Adapted from the ELS 2013 paper.
8583 @cindex bootstrapping
8585 Bootstrapping in our context refers to how the distribution gets built
8586 ``from nothing''. Remember that the build environment of a derivation
8587 contains nothing but its declared inputs (@pxref{Introduction}). So
8588 there's an obvious chicken-and-egg problem: how does the first package
8589 get built? How does the first compiler get compiled? Note that this is
8590 a question of interest only to the curious hacker, not to the regular
8591 user, so you can shamelessly skip this section if you consider yourself
8594 @cindex bootstrap binaries
8595 The GNU system is primarily made of C code, with libc at its core. The
8596 GNU build system itself assumes the availability of a Bourne shell and
8597 command-line tools provided by GNU Coreutils, Awk, Findutils, `sed', and
8598 `grep'. Furthermore, build programs---programs that run
8599 @code{./configure}, @code{make}, etc.---are written in Guile Scheme
8600 (@pxref{Derivations}). Consequently, to be able to build anything at
8601 all, from scratch, Guix relies on pre-built binaries of Guile, GCC,
8602 Binutils, libc, and the other packages mentioned above---the
8603 @dfn{bootstrap binaries}.
8605 These bootstrap binaries are ``taken for granted'', though we can also
8606 re-create them if needed (more on that later).
8608 @unnumberedsubsec Preparing to Use the Bootstrap Binaries
8610 @c As of Emacs 24.3, Info-mode displays the image, but since it's a
8611 @c large image, it's hard to scroll. Oh well.
8612 @image{images/bootstrap-graph,6in,,Dependency graph of the early bootstrap derivations}
8614 The figure above shows the very beginning of the dependency graph of the
8615 distribution, corresponding to the package definitions of the @code{(gnu
8616 packages bootstrap)} module. At this level of detail, things are
8617 slightly complex. First, Guile itself consists of an ELF executable,
8618 along with many source and compiled Scheme files that are dynamically
8619 loaded when it runs. This gets stored in the @file{guile-2.0.7.tar.xz}
8620 tarball shown in this graph. This tarball is part of Guix's ``source''
8621 distribution, and gets inserted into the store with @code{add-to-store}
8622 (@pxref{The Store}).
8624 But how do we write a derivation that unpacks this tarball and adds it
8625 to the store? To solve this problem, the @code{guile-bootstrap-2.0.drv}
8626 derivation---the first one that gets built---uses @code{bash} as its
8627 builder, which runs @code{build-bootstrap-guile.sh}, which in turn calls
8628 @code{tar} to unpack the tarball. Thus, @file{bash}, @file{tar},
8629 @file{xz}, and @file{mkdir} are statically-linked binaries, also part of
8630 the Guix source distribution, whose sole purpose is to allow the Guile
8631 tarball to be unpacked.
8633 Once @code{guile-bootstrap-2.0.drv} is built, we have a functioning
8634 Guile that can be used to run subsequent build programs. Its first task
8635 is to download tarballs containing the other pre-built binaries---this
8636 is what the @code{.tar.xz.drv} derivations do. Guix modules such as
8637 @code{ftp-client.scm} are used for this purpose. The
8638 @code{module-import.drv} derivations import those modules in a directory
8639 in the store, using the original layout. The
8640 @code{module-import-compiled.drv} derivations compile those modules, and
8641 write them in an output directory with the right layout. This
8642 corresponds to the @code{#:modules} argument of
8643 @code{build-expression->derivation} (@pxref{Derivations}).
8645 Finally, the various tarballs are unpacked by the
8646 derivations @code{gcc-bootstrap-0.drv}, @code{glibc-bootstrap-0.drv},
8647 etc., at which point we have a working C tool chain.
8650 @unnumberedsubsec Building the Build Tools
8652 @c TODO: Add a package-level dependency graph generated from (gnu
8655 Bootstrapping is complete when we have a full tool chain that does not
8656 depend on the pre-built bootstrap tools discussed above. This
8657 no-dependency requirement is verified by checking whether the files of
8658 the final tool chain contain references to the @file{/gnu/store}
8659 directories of the bootstrap inputs. The process that leads to this
8660 ``final'' tool chain is described by the package definitions found in
8661 the @code{(gnu packages commencement)} module.
8663 @c See <http://lists.gnu.org/archive/html/gnu-system-discuss/2012-10/msg00000.html>.
8664 The first tool that gets built with the bootstrap binaries is
8665 GNU Make, which is a prerequisite for all the following packages.
8666 From there Findutils and Diffutils get built.
8668 Then come the first-stage Binutils and GCC, built as pseudo cross
8669 tools---i.e., with @code{--target} equal to @code{--host}. They are
8670 used to build libc. Thanks to this cross-build trick, this libc is
8671 guaranteed not to hold any reference to the initial tool chain.
8673 From there the final Binutils and GCC are built. GCC uses @code{ld}
8674 from the final Binutils, and links programs against the just-built libc.
8675 This tool chain is used to build the other packages used by Guix and by
8676 the GNU Build System: Guile, Bash, Coreutils, etc.
8678 And voilà! At this point we have the complete set of build tools that
8679 the GNU Build System expects. These are in the @code{%final-inputs}
8680 variable of the @code{(gnu packages commencement)} module, and are
8681 implicitly used by any package that uses @code{gnu-build-system}
8682 (@pxref{Build Systems, @code{gnu-build-system}}).
8685 @unnumberedsubsec Building the Bootstrap Binaries
8687 Because the final tool chain does not depend on the bootstrap binaries,
8688 those rarely need to be updated. Nevertheless, it is useful to have an
8689 automated way to produce them, should an update occur, and this is what
8690 the @code{(gnu packages make-bootstrap)} module provides.
8692 The following command builds the tarballs containing the bootstrap
8693 binaries (Guile, Binutils, GCC, libc, and a tarball containing a mixture
8694 of Coreutils and other basic command-line tools):
8697 guix build bootstrap-tarballs
8700 The generated tarballs are those that should be referred to in the
8701 @code{(gnu packages bootstrap)} module mentioned at the beginning of
8704 Still here? Then perhaps by now you've started to wonder: when do we
8705 reach a fixed point? That is an interesting question! The answer is
8706 unknown, but if you would like to investigate further (and have
8707 significant computational and storage resources to do so), then let us
8711 @section Porting to a New Platform
8713 As discussed above, the GNU distribution is self-contained, and
8714 self-containment is achieved by relying on pre-built ``bootstrap
8715 binaries'' (@pxref{Bootstrapping}). These binaries are specific to an
8716 operating system kernel, CPU architecture, and application binary
8717 interface (ABI). Thus, to port the distribution to a platform that is
8718 not yet supported, one must build those bootstrap binaries, and update
8719 the @code{(gnu packages bootstrap)} module to use them on that platform.
8721 Fortunately, Guix can @emph{cross compile} those bootstrap binaries.
8722 When everything goes well, and assuming the GNU tool chain supports the
8723 target platform, this can be as simple as running a command like this
8727 guix build --target=armv5tel-linux-gnueabi bootstrap-tarballs
8730 For this to work, the @code{glibc-dynamic-linker} procedure in
8731 @code{(gnu packages bootstrap)} must be augmented to return the right
8732 file name for libc's dynamic linker on that platform; likewise,
8733 @code{system->linux-architecture} in @code{(gnu packages linux)} must be
8734 taught about the new platform.
8736 Once these are built, the @code{(gnu packages bootstrap)} module needs
8737 to be updated to refer to these binaries on the target platform. That
8738 is, the hashes and URLs of the bootstrap tarballs for the new platform
8739 must be added alongside those of the currently supported platforms. The
8740 bootstrap Guile tarball is treated specially: it is expected to be
8741 available locally, and @file{gnu-system.am} has rules do download it for
8742 the supported architectures; a rule for the new platform must be added
8745 In practice, there may be some complications. First, it may be that the
8746 extended GNU triplet that specifies an ABI (like the @code{eabi} suffix
8747 above) is not recognized by all the GNU tools. Typically, glibc
8748 recognizes some of these, whereas GCC uses an extra @code{--with-abi}
8749 configure flag (see @code{gcc.scm} for examples of how to handle this).
8750 Second, some of the required packages could fail to build for that
8751 platform. Lastly, the generated binaries could be broken for some
8754 @c *********************************************************************
8755 @include contributing.texi
8757 @c *********************************************************************
8758 @node Acknowledgments
8759 @chapter Acknowledgments
8761 Guix is based on the @uref{http://nixos.org/nix/, Nix package manager},
8762 which was designed and
8763 implemented by Eelco Dolstra, with contributions from other people (see
8764 the @file{nix/AUTHORS} file in Guix.) Nix pioneered functional package
8765 management, and promoted unprecedented features, such as transactional
8766 package upgrades and rollbacks, per-user profiles, and referentially
8767 transparent build processes. Without this work, Guix would not exist.
8769 The Nix-based software distributions, Nixpkgs and NixOS, have also been
8770 an inspiration for Guix.
8772 GNU@tie{}Guix itself is a collective work with contributions from a
8773 number of people. See the @file{AUTHORS} file in Guix for more
8774 information on these fine people. The @file{THANKS} file lists people
8775 who have helped by reporting bugs, taking care of the infrastructure,
8776 providing artwork and themes, making suggestions, and more---thank you!
8779 @c *********************************************************************
8780 @node GNU Free Documentation License
8781 @appendix GNU Free Documentation License
8783 @include fdl-1.3.texi
8785 @c *********************************************************************
8787 @unnumbered Concept Index
8790 @node Programming Index
8791 @unnumbered Programming Index
8799 @c ispell-local-dictionary: "american";