1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
|
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2017, 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2020 Mathieu Othacehe <othacehe@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 (guix utils)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-26)
#:use-module (ice-9 match)
#:export (make-forkexec-constructor/container
fork+exec-command/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")
(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))))
(append (cons (tmpfs "/tmp") %container-file-systems)
(let ((mappings `(,@(if (memq 'net namespaces)
'()
%network-file-mappings)
,@(if (and (memq 'mnt namespaces)
(not (memq 'user namespaces)))
accounts
'())
;; Tell the process what timezone we're in. This
;; makes sure that, for instance, its syslog
;; messages have the correct timestamp.
,(file-system-mapping
(source "/etc/localtime")
(target source))
,%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)
'(fork+exec-command read-pid-file exec-command
%precious-signals))
(module-autoload! (current-module)
'(shepherd system) '(unblock-signals))
(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
;; Send SIGTERM to the whole process group.
(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))
(when user
(let ((pw (getpwnam user)))
(chown log-file (passwd:uid pw) (passwd:gid pw))))))
(let ((pid (run-container container-directory
mounts namespaces 1
(lambda ()
;; First restore the default handlers.
(for-each (cut sigaction <> SIG_DFL)
%precious-signals)
;; Unblock any signals that have been blocked
;; by the parent process.
(unblock-signals %precious-signals)
(mkdir-p "/var/run")
(clean-up pid-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))))
(define* (fork+exec-command/container command
#:key pid
#:allow-other-keys
#:rest args)
"This is a variant of 'fork+exec-command' procedure, that joins the
namespaces of process PID beforehand. If there is no support for containers,
on Hurd systems for instance, fallback to direct forking."
(let ((container-support?
(file-exists? "/proc/self/ns"))
(fork-proc (lambda ()
(apply fork+exec-command command
(strip-keyword-arguments '(#:pid) args)))))
(if container-support?
(container-excursion* pid fork-proc)
(fork-proc))))
;; Local Variables:
;; eval: (put 'container-excursion* 'scheme-indent-function 1)
;; End:
;;; shepherd.scm ends here
|