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Diffstat (limited to 'gnu/build/shepherd.scm')
| -rw-r--r-- | gnu/build/shepherd.scm | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/gnu/build/shepherd.scm b/gnu/build/shepherd.scm new file mode 100644 index 0000000000..8fc74bc482 --- /dev/null +++ b/gnu/build/shepherd.scm @@ -0,0 +1,177 @@ +;;; GNU Guix --- Functional package management for GNU +;;; Copyright © 2017 Ludovic Courtès <ludo@gnu.org> +;;; +;;; This file is part of GNU Guix. +;;; +;;; GNU Guix is free software; you can redistribute it and/or modify it +;;; under the terms of the GNU General Public License as published by +;;; the Free Software Foundation; either version 3 of the License, or (at +;;; your option) any later version. +;;; +;;; GNU Guix is distributed in the hope that it will be useful, but +;;; WITHOUT ANY WARRANTY; without even the implied warranty of +;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +;;; GNU General Public License for more details. +;;; +;;; You should have received a copy of the GNU General Public License +;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>. + +(define-module (gnu build shepherd) + #:use-module (gnu system file-systems) + #:use-module (gnu build linux-container) + #:use-module (guix build utils) + #:use-module (srfi srfi-1) + #:use-module (ice-9 match) + #:export (make-forkexec-constructor/container)) + +;;; Commentary: +;;; +;;; This module provides extensions to the GNU Shepherd. In particular, it +;;; provides a helper to start services in a container. +;;; +;;; Code: + +(define (clean-up file) + (when file + (catch 'system-error + (lambda () + (delete-file file)) + (lambda args + (unless (= ENOENT (system-error-errno args)) + (apply throw args)))))) + +(define-syntax-rule (catch-system-error exp) + (catch 'system-error + (lambda () + exp) + (const #f))) + +(define (default-namespaces args) + ;; Most daemons are here to talk to the network, and most of them expect to + ;; run under a non-zero UID. + (fold delq %namespaces '(net user))) + +(define* (default-mounts #:key (namespaces (default-namespaces '()))) + (define (tmpfs directory) + (file-system + (device "none") + (title 'device) + (mount-point directory) + (type "tmpfs") + (check? #f))) + + (define passwd + ;; This is for processes in the default user namespace but living in a + ;; different mount namespace, so that they can lookup users. + (file-system-mapping + (source "/etc/passwd") (target source))) + + (define nscd-socket + (file-system-mapping + (source "/var/run/nscd") (target source) + (writable? #t))) + + (append (cons (tmpfs "/tmp") %container-file-systems) + (let ((mappings `(,@(if (memq 'net namespaces) + '() + (cons nscd-socket + %network-file-mappings)) + ,@(if (and (memq 'mnt namespaces) + (not (memq 'user namespaces))) + (list passwd) + '()) + ,%store-mapping))) ;XXX: coarse-grain + (map file-system-mapping->bind-mount + (filter (lambda (mapping) + (file-exists? (file-system-mapping-source mapping))) + mappings))))) + +;; XXX: Lazy-bind the Shepherd to avoid a compile-time dependency. +(module-autoload! (current-module) + '(shepherd service) '(read-pid-file exec-command)) + +(define* (read-pid-file/container pid pid-file #:key (max-delay 5)) + "Read PID-FILE in the container namespaces of PID, which exists in a +separate mount and PID name space. Return the \"outer\" PID. " + (match (container-excursion* pid + (lambda () + (read-pid-file pid-file + #:max-delay max-delay))) + (#f + (catch-system-error (kill pid SIGTERM)) + #f) + ((? integer? container-pid) + ;; XXX: When COMMAND is started in a separate PID namespace, its + ;; PID is always 1, but that's not what Shepherd needs to know. + pid))) + +(define* (make-forkexec-constructor/container command + #:key + (namespaces + (default-namespaces args)) + (mappings '()) + (user #f) + (group #f) + (log-file #f) + pid-file + (pid-file-timeout 5) + (directory "/") + (environment-variables + (environ)) + #:rest args) + "This is a variant of 'make-forkexec-constructor' that starts COMMAND in +NAMESPACES, a list of Linux namespaces such as '(mnt ipc). MAPPINGS is the +list of <file-system-mapping> to make in the case of a separate mount +namespace, in addition to essential bind-mounts such /proc." + (define container-directory + (match command + ((program _ ...) + (string-append "/var/run/containers/" (basename program))))) + + (define auto-mappings + `(,@(if log-file + (list (file-system-mapping + (source log-file) + (target source) + (writable? #t))) + '()))) + + (define mounts + (append (map file-system-mapping->bind-mount + (append auto-mappings mappings)) + (default-mounts #:namespaces namespaces))) + + (lambda args + (mkdir-p container-directory) + + (when log-file + ;; Create LOG-FILE so we can map it in the container. + (unless (file-exists? log-file) + (call-with-output-file log-file (const #t)))) + + (let ((pid (run-container container-directory + mounts namespaces 1 + (lambda () + (mkdir-p "/var/run") + (clean-up pid-file) + (clean-up log-file) + + (exec-command command + #:user user + #:group group + #:log-file log-file + #:directory directory + #:environment-variables + environment-variables))))) + (if pid-file + (if (or (memq 'mnt namespaces) (memq 'pid namespaces)) + (read-pid-file/container pid pid-file + #:max-delay pid-file-timeout) + (read-pid-file pid-file #:max-delay pid-file-timeout)) + pid)))) + +;; Local Variables: +;; eval: (put 'container-excursion* 'scheme-indent-function 1) +;; End: + +;;; shepherd.scm ends here |