;;; 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 accounts ;; This is for processes in the default user namespace but living in a ;; different mount namespace, so that they can lookup users. (list (file-system-mapping (source "/etc/passwd") (target source)) (file-system-mapping (source "/etc/group") (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))) accounts '()) ,%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