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63302a4e | 1 | ;;; GNU Guix --- Functional package management for GNU |
b6b95685 | 2 | ;;; Copyright © 2017, 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org> |
63302a4e LC |
3 | ;;; |
4 | ;;; This file is part of GNU Guix. | |
5 | ;;; | |
6 | ;;; GNU Guix is free software; you can redistribute it and/or modify it | |
7 | ;;; under the terms of the GNU General Public License as published by | |
8 | ;;; the Free Software Foundation; either version 3 of the License, or (at | |
9 | ;;; your option) any later version. | |
10 | ;;; | |
11 | ;;; GNU Guix is distributed in the hope that it will be useful, but | |
12 | ;;; WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | ;;; GNU General Public License for more details. | |
15 | ;;; | |
16 | ;;; You should have received a copy of the GNU General Public License | |
17 | ;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>. | |
18 | ||
19 | (define-module (gnu build shepherd) | |
20 | #:use-module (gnu system file-systems) | |
21 | #:use-module (gnu build linux-container) | |
22 | #:use-module (guix build utils) | |
8ce6f4dc | 23 | #:use-module (guix utils) |
63302a4e | 24 | #:use-module (srfi srfi-1) |
b6b95685 | 25 | #:use-module (srfi srfi-26) |
63302a4e | 26 | #:use-module (ice-9 match) |
8ce6f4dc MO |
27 | #:export (make-forkexec-constructor/container |
28 | fork+exec-command/container)) | |
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29 | |
30 | ;;; Commentary: | |
31 | ;;; | |
32 | ;;; This module provides extensions to the GNU Shepherd. In particular, it | |
33 | ;;; provides a helper to start services in a container. | |
34 | ;;; | |
35 | ;;; Code: | |
36 | ||
37 | (define (clean-up file) | |
38 | (when file | |
39 | (catch 'system-error | |
40 | (lambda () | |
41 | (delete-file file)) | |
42 | (lambda args | |
43 | (unless (= ENOENT (system-error-errno args)) | |
44 | (apply throw args)))))) | |
45 | ||
46 | (define-syntax-rule (catch-system-error exp) | |
47 | (catch 'system-error | |
48 | (lambda () | |
49 | exp) | |
50 | (const #f))) | |
51 | ||
52 | (define (default-namespaces args) | |
53 | ;; Most daemons are here to talk to the network, and most of them expect to | |
54 | ;; run under a non-zero UID. | |
55 | (fold delq %namespaces '(net user))) | |
56 | ||
57 | (define* (default-mounts #:key (namespaces (default-namespaces '()))) | |
58 | (define (tmpfs directory) | |
59 | (file-system | |
60 | (device "none") | |
63302a4e LC |
61 | (mount-point directory) |
62 | (type "tmpfs") | |
63 | (check? #f))) | |
64 | ||
0cb9c9d1 | 65 | (define accounts |
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66 | ;; This is for processes in the default user namespace but living in a |
67 | ;; different mount namespace, so that they can lookup users. | |
0cb9c9d1 LC |
68 | (list (file-system-mapping |
69 | (source "/etc/passwd") (target source)) | |
70 | (file-system-mapping | |
71 | (source "/etc/group") (target source)))) | |
63302a4e | 72 | |
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73 | (append (cons (tmpfs "/tmp") %container-file-systems) |
74 | (let ((mappings `(,@(if (memq 'net namespaces) | |
75 | '() | |
5ccec771 | 76 | %network-file-mappings) |
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77 | ,@(if (and (memq 'mnt namespaces) |
78 | (not (memq 'user namespaces))) | |
0cb9c9d1 | 79 | accounts |
63302a4e | 80 | '()) |
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81 | |
82 | ;; Tell the process what timezone we're in. This | |
83 | ;; makes sure that, for instance, its syslog | |
84 | ;; messages have the correct timestamp. | |
85 | ,(file-system-mapping | |
86 | (source "/etc/localtime") | |
87 | (target source)) | |
88 | ||
63302a4e LC |
89 | ,%store-mapping))) ;XXX: coarse-grain |
90 | (map file-system-mapping->bind-mount | |
91 | (filter (lambda (mapping) | |
92 | (file-exists? (file-system-mapping-source mapping))) | |
93 | mappings))))) | |
94 | ||
95 | ;; XXX: Lazy-bind the Shepherd to avoid a compile-time dependency. | |
96 | (module-autoload! (current-module) | |
b6b95685 | 97 | '(shepherd service) |
8ce6f4dc MO |
98 | '(fork+exec-command read-pid-file exec-command |
99 | %precious-signals)) | |
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100 | (module-autoload! (current-module) |
101 | '(shepherd system) '(unblock-signals)) | |
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102 | |
103 | (define* (read-pid-file/container pid pid-file #:key (max-delay 5)) | |
104 | "Read PID-FILE in the container namespaces of PID, which exists in a | |
105 | separate mount and PID name space. Return the \"outer\" PID. " | |
106 | (match (container-excursion* pid | |
107 | (lambda () | |
108 | (read-pid-file pid-file | |
109 | #:max-delay max-delay))) | |
110 | (#f | |
8a02e45d LC |
111 | ;; Send SIGTERM to the whole process group. |
112 | (catch-system-error (kill (- pid) SIGTERM)) | |
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113 | #f) |
114 | ((? integer? container-pid) | |
115 | ;; XXX: When COMMAND is started in a separate PID namespace, its | |
116 | ;; PID is always 1, but that's not what Shepherd needs to know. | |
117 | pid))) | |
118 | ||
119 | (define* (make-forkexec-constructor/container command | |
120 | #:key | |
121 | (namespaces | |
122 | (default-namespaces args)) | |
123 | (mappings '()) | |
124 | (user #f) | |
125 | (group #f) | |
126 | (log-file #f) | |
127 | pid-file | |
128 | (pid-file-timeout 5) | |
129 | (directory "/") | |
130 | (environment-variables | |
131 | (environ)) | |
132 | #:rest args) | |
133 | "This is a variant of 'make-forkexec-constructor' that starts COMMAND in | |
134 | NAMESPACES, a list of Linux namespaces such as '(mnt ipc). MAPPINGS is the | |
135 | list of <file-system-mapping> to make in the case of a separate mount | |
136 | namespace, in addition to essential bind-mounts such /proc." | |
137 | (define container-directory | |
138 | (match command | |
139 | ((program _ ...) | |
140 | (string-append "/var/run/containers/" (basename program))))) | |
141 | ||
142 | (define auto-mappings | |
143 | `(,@(if log-file | |
144 | (list (file-system-mapping | |
145 | (source log-file) | |
146 | (target source) | |
147 | (writable? #t))) | |
148 | '()))) | |
149 | ||
150 | (define mounts | |
151 | (append (map file-system-mapping->bind-mount | |
152 | (append auto-mappings mappings)) | |
153 | (default-mounts #:namespaces namespaces))) | |
154 | ||
155 | (lambda args | |
156 | (mkdir-p container-directory) | |
157 | ||
158 | (when log-file | |
159 | ;; Create LOG-FILE so we can map it in the container. | |
160 | (unless (file-exists? log-file) | |
464caf72 LC |
161 | (call-with-output-file log-file (const #t)) |
162 | (when user | |
163 | (let ((pw (getpwnam user))) | |
164 | (chown log-file (passwd:uid pw) (passwd:gid pw)))))) | |
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165 | |
166 | (let ((pid (run-container container-directory | |
167 | mounts namespaces 1 | |
168 | (lambda () | |
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169 | ;; First restore the default handlers. |
170 | (for-each (cut sigaction <> SIG_DFL) | |
171 | %precious-signals) | |
172 | ||
173 | ;; Unblock any signals that have been blocked | |
174 | ;; by the parent process. | |
175 | (unblock-signals %precious-signals) | |
176 | ||
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177 | (mkdir-p "/var/run") |
178 | (clean-up pid-file) | |
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179 | |
180 | (exec-command command | |
181 | #:user user | |
182 | #:group group | |
183 | #:log-file log-file | |
184 | #:directory directory | |
185 | #:environment-variables | |
186 | environment-variables))))) | |
187 | (if pid-file | |
188 | (if (or (memq 'mnt namespaces) (memq 'pid namespaces)) | |
189 | (read-pid-file/container pid pid-file | |
190 | #:max-delay pid-file-timeout) | |
191 | (read-pid-file pid-file #:max-delay pid-file-timeout)) | |
192 | pid)))) | |
193 | ||
8ce6f4dc MO |
194 | (define* (fork+exec-command/container command |
195 | #:key pid | |
196 | #:allow-other-keys | |
197 | #:rest args) | |
198 | "This is a variant of 'fork+exec-command' procedure, that joins the | |
199 | namespaces of process PID beforehand." | |
200 | (container-excursion* pid | |
201 | (lambda () | |
202 | (apply fork+exec-command command | |
203 | (strip-keyword-arguments '(#:pid) args))))) | |
204 | ||
63302a4e LC |
205 | ;; Local Variables: |
206 | ;; eval: (put 'container-excursion* 'scheme-indent-function 1) | |
207 | ;; End: | |
208 | ||
209 | ;;; shepherd.scm ends here |