gnu/system/linux-container.scm

   1 ;;; GNU Guix --- Functional package management for GNU
   2 ;;; Copyright © 2015 David Thompson <davet@gnu.org>
   3 ;;; Copyright © 2016, 2017, 2019 Ludovic Courtès <ludo@gnu.org>
   4 ;;;
   5 ;;; This file is part of GNU Guix.
   6 ;;;
   7 ;;; GNU Guix is free software; you can redistribute it and/or modify it
   8 ;;; under the terms of the GNU General Public License as published by
   9 ;;; the Free Software Foundation; either version 3 of the License, or (at
  10 ;;; your option) any later version.
  11 ;;;
  12 ;;; GNU Guix is distributed in the hope that it will be useful, but
  13 ;;; WITHOUT ANY WARRANTY; without even the implied warranty of
  14 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 ;;; GNU General Public License for more details.
  16 ;;;
  17 ;;; You should have received a copy of the GNU General Public License
  18 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
  19
  20 (define-module (gnu system linux-container)
  21   #:use-module (ice-9 match)
  22   #:use-module (srfi srfi-1)
  23   #:use-module (guix config)
  24   #:use-module (guix store)
  25   #:use-module (guix gexp)
  26   #:use-module (guix derivations)
  27   #:use-module (guix monads)
  28   #:use-module (guix modules)
  29   #:use-module (gnu build linux-container)
  30   #:use-module (gnu services)
  31   #:use-module (gnu services base)
  32   #:use-module (gnu system)
  33   #:use-module (gnu system file-systems)
  34   #:export (system-container
  35             containerized-operating-system
  36             container-script))
  37
  38 (define (container-essential-services os)
  39   "Return a list of essential services corresponding to OS, a
  40 non-containerized OS.  This procedure essentially strips essential services
  41 from OS that are needed on the bare metal and not in a container."
  42   (define base
  43     (remove (lambda (service)
  44               (memq (service-kind service)
  45                     (list (service-kind %linux-bare-metal-service)
  46                           firmware-service-type
  47                           system-service-type)))
  48             (operating-system-essential-services os)))
  49
  50   (cons (service system-service-type
  51                  (let ((locale (operating-system-locale-directory os)))
  52                    (with-monad %store-monad
  53                      (return `(("locale" ,locale))))))
  54         base))
  55
  56 (define (containerized-operating-system os mappings)
  57   "Return an operating system based on OS for use in a Linux container
  58 environment.  MAPPINGS is a list of <file-system-mapping> to realize in the
  59 containerized OS."
  60   (define user-file-systems
  61     (remove (lambda (fs)
  62               (let ((target (file-system-mount-point fs))
  63                     (source (file-system-device fs)))
  64                 (or (string=? target (%store-prefix))
  65                     (string=? target "/")
  66                     (and (string? source)
  67                          (string-prefix? "/dev/" source))
  68                     (string-prefix? "/dev" target)
  69                     (string-prefix? "/sys" target))))
  70             (operating-system-file-systems os)))
  71
  72   (define (mapping->fs fs)
  73     (file-system (inherit (file-system-mapping->bind-mount fs))
  74       (needed-for-boot? #t)))
  75
  76   (define useless-services
  77     ;; Services that make no sense in a container.  Those that attempt to
  78     ;; access /dev/tty[0-9] in particular cannot work in a container.
  79     (list console-font-service-type
  80           mingetty-service-type
  81           agetty-service-type))
  82
  83   (operating-system
  84     (inherit os)
  85     (swap-devices '()) ; disable swap
  86     (essential-services (container-essential-services os))
  87     (services (remove (lambda (service)
  88                         (memq (service-kind service)
  89                               useless-services))
  90                       (operating-system-user-services os)))
  91     (file-systems (append (map mapping->fs (cons %store-mapping mappings))
  92                           %container-file-systems
  93                           user-file-systems))))
  94
  95 (define* (container-script os #:key (mappings '()))
  96   "Return a derivation of a script that runs OS as a Linux container.
  97 MAPPINGS is a list of <file-system> objects that specify the files/directories
  98 that will be shared with the host system."
  99   (let* ((os           (containerized-operating-system os mappings))
 100          (file-systems (filter file-system-needed-for-boot?
 101                                (operating-system-file-systems os)))
 102          (specs        (map file-system->spec file-systems)))
 103
 104     (define script
 105       (with-imported-modules (source-module-closure
 106                               '((guix build utils)
 107                                 (gnu build linux-container)))
 108         #~(begin
 109             (use-modules (gnu build linux-container)
 110                          (gnu system file-systems) ;spec->file-system
 111                          (guix build utils))
 112
 113             (call-with-container (map spec->file-system '#$specs)
 114               (lambda ()
 115                 (setenv "HOME" "/root")
 116                 (setenv "TMPDIR" "/tmp")
 117                 (setenv "GUIX_NEW_SYSTEM" #$os)
 118                 (for-each mkdir-p '("/run" "/bin" "/etc" "/home" "/var"))
 119                 (primitive-load (string-append #$os "/boot")))
 120               ;; A range of 65536 uid/gids is used to cover 16 bits worth of
 121               ;; users and groups, which is sufficient for most cases.
 122               ;;
 123               ;; See: http://www.freedesktop.org/software/systemd/man/systemd-nspawn.html#--private-users=
 124               #:host-uids 65536))))
 125
 126     (gexp->script "run-container" script)))