aboutsummaryrefslogtreecommitdiff
path: root/gnu/services/shepherd.scm
blob: 7277273686e1bd2e109af3b925e7a780271e3b09 (plain)
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
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013, 2014, 2015, 2016, 2018, 2019, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2017 Clément Lassieur <clement@lassieur.org>
;;; Copyright © 2018 Carlo Zancanaro <carlo@zancanaro.id.au>
;;; Copyright © 2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be>
;;;
;;; 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 services shepherd)
  #:use-module (guix ui)
  #:use-module (guix sets)
  #:use-module (guix gexp)
  #:use-module (guix store)
  #:use-module (guix records)
  #:use-module (guix derivations)                 ;imported-modules, etc.
  #:use-module (guix utils)
  #:use-module (gnu services)
  #:use-module (gnu services herd)
  #:use-module (gnu packages admin)
  #:use-module (ice-9 match)
  #:use-module (ice-9 vlist)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-34)
  #:use-module (srfi srfi-35)
  #:export (shepherd-configuration
            shepherd-configuration?
            shepherd-configuration-shepherd
            shepherd-configuration-services

            shepherd-root-service-type
            %shepherd-root-service
            shepherd-service-type

            shepherd-service
            shepherd-service?
            shepherd-service-documentation
            shepherd-service-provision
            shepherd-service-canonical-name
            shepherd-service-requirement
            shepherd-service-one-shot?
            shepherd-service-respawn?
            shepherd-service-start
            shepherd-service-stop
            shepherd-service-auto-start?
            shepherd-service-modules

            shepherd-action
            shepherd-action?
            shepherd-action-name
            shepherd-action-documentation
            shepherd-action-procedure

            %default-modules

            shepherd-service-file

            shepherd-service-lookup-procedure
            shepherd-service-back-edges
            shepherd-service-upgrade

            user-processes-service-type

            assert-valid-graph))

;;; Commentary:
;;;
;;; Instantiating system services as a shepherd configuration file.
;;;
;;; Code:


(define-record-type* <shepherd-configuration>
  shepherd-configuration make-shepherd-configuration
  shepherd-configuration?
  (shepherd shepherd-configuration-shepherd
            (default shepherd)) ; package
  (services shepherd-configuration-services
            (default '()))) ; list of <shepherd-service>

(define (shepherd-boot-gexp config)
  "Return a gexp starting the shepherd service."
  (let ((shepherd (shepherd-configuration-shepherd config))
        (services (shepherd-configuration-services config)))
  #~(begin
      ;; Keep track of the booted system.
      (false-if-exception (delete-file "/run/booted-system"))

      ;; Make /run/booted-system, an indirect GC root, point to the store item
      ;; /run/current-system points to.  Use 'canonicalize-path' rather than
      ;; 'readlink' to make sure we get the store item.
      (symlink (canonicalize-path "/run/current-system")
               "/run/booted-system")

      ;; Close any remaining open file descriptors to be on the safe
      ;; side.  This must be the very last thing we do, because
      ;; Guile has internal FDs such as 'sleep_pipe' that need to be
      ;; alive.
      (let loop ((fd 3))
        (when (< fd 1024)
          (false-if-exception (close-fdes fd))
          (loop (+ 1 fd))))

      ;; Start shepherd.
      (execl #$(file-append shepherd "/bin/shepherd")
             "shepherd" "--config"
             #$(shepherd-configuration-file services shepherd)))))

(define shepherd-packages
  (compose list shepherd-configuration-shepherd))

(define shepherd-root-service-type
  (service-type
   (name 'shepherd-root)
   ;; Extending the root shepherd service (aka. PID 1) happens by
   ;; concatenating the list of services provided by the extensions.
   (compose concatenate)
   (extend (lambda (config extra-services)
             (shepherd-configuration
               (inherit config)
               (services (append (shepherd-configuration-services config)
                                 extra-services)))))
   (extensions (list (service-extension boot-service-type
                                        shepherd-boot-gexp)
                     (service-extension profile-service-type
                                        shepherd-packages)))
   (default-value (shepherd-configuration))
   (description
    "Run the GNU Shepherd as PID 1---i.e., the operating system's first
process.  The Shepherd takes care of managing services such as daemons by
ensuring they are started and stopped in the right order.")))

(define %shepherd-root-service
  ;; The root shepherd service, aka. PID 1.  Its parameter is a
  ;; <shepherd-configuration>.
  (service shepherd-root-service-type))

(define-syntax shepherd-service-type
  (syntax-rules (description)
    "Return a <service-type> denoting a simple shepherd service--i.e., the type
for a service that extends SHEPHERD-ROOT-SERVICE-TYPE and nothing else.  When
DEFAULT is given, use it as the service's default value."
    ((_ service-name proc default (description text))
     (service-type
      (name service-name)
      (extensions
       (list (service-extension shepherd-root-service-type
                                (compose list proc))))
      (default-value default)
      (description text)))
    ((_ service-name proc (description text))
     (service-type
      (name service-name)
      (extensions
       (list (service-extension shepherd-root-service-type
                                (compose list proc))))
      (description text)))))

(define %default-imported-modules
  ;; Default set of modules imported for a service's consumption.
  '((guix build utils)
    (guix build syscalls)))

(define %default-modules
  ;; Default set of modules visible in a service's file.
  `((shepherd service)
    (oop goops)
    ((guix build utils) #:hide (delete))
    (guix build syscalls)))

(define-record-type* <shepherd-service>
  shepherd-service make-shepherd-service
  shepherd-service?
  (documentation shepherd-service-documentation        ;string
                 (default "[No documentation.]"))
  (provision     shepherd-service-provision)           ;list of symbols
  (requirement   shepherd-service-requirement          ;list of symbols
                 (default '()))
  (one-shot?     shepherd-service-one-shot?            ;Boolean
                 (default #f))
  (respawn?      shepherd-service-respawn?             ;Boolean
                 (default #t))
  (start         shepherd-service-start)               ;g-expression (procedure)
  (stop          shepherd-service-stop                 ;g-expression (procedure)
                 (default #~(const #f)))
  (actions       shepherd-service-actions              ;list of <shepherd-action>
                 (default '()))
  (auto-start?   shepherd-service-auto-start?          ;Boolean
                 (default #t))
  (modules       shepherd-service-modules              ;list of module names
                 (default %default-modules)))

(define-record-type* <shepherd-action>
  shepherd-action make-shepherd-action
  shepherd-action?
  (name          shepherd-action-name)            ;symbol
  (procedure     shepherd-action-procedure)       ;gexp
  (documentation shepherd-action-documentation))  ;string

(define (shepherd-service-canonical-name service)
  "Return the 'canonical name' of SERVICE."
  (first (shepherd-service-provision service)))

(define (assert-valid-graph services)
  "Raise an error if SERVICES does not define a valid shepherd service graph,
for instance if a service requires a nonexistent service, or if more than one
service uses a given name.

These are constraints that shepherd's 'register-service' verifies but we'd
better verify them here statically than wait until PID 1 halts with an
assertion failure."
  (define provisions
    ;; The set of provisions (symbols).  Bail out if a symbol is given more
    ;; than once.
    (fold (lambda (service set)
            (define (assert-unique symbol)
              (when (set-contains? set symbol)
                (raise (condition
                        (&message
                         (message
                          (format #f (G_ "service '~a' provided more than once")
                                  symbol)))))))

            (for-each assert-unique (shepherd-service-provision service))
            (fold set-insert set (shepherd-service-provision service)))
          (setq 'shepherd)
          services))

  (define (assert-satisfied-requirements service)
    ;; Bail out if the requirements of SERVICE aren't satisfied.
    (for-each (lambda (requirement)
                (unless (set-contains? provisions requirement)
                  (raise (condition
                          (&message
                           (message
                            (format #f (G_ "service '~a' requires '~a', \
which is not provided by any service")
                                    (match (shepherd-service-provision service)
                                      ((head . _) head)
                                      (_          service))
                                    requirement)))))))
              (shepherd-service-requirement service)))

  (for-each assert-satisfied-requirements services))

(define %store-characters
  ;; Valid store characters; see 'checkStoreName' in the daemon.
  (string->char-set
   "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+-._?="))

(define (shepherd-service-file-name service)
  "Return the file name where the initialization code for SERVICE is to be
stored."
  (let ((provisions (string-join (map symbol->string
                                      (shepherd-service-provision service)))))
    (string-append "shepherd-"
                   (string-map (lambda (chr)
                                 (if (char-set-contains? %store-characters chr)
                                     chr
                                     #\-))
                               provisions)
                   ".scm")))

(define (shepherd-service-file service)
  "Return a file defining SERVICE."
  (scheme-file (shepherd-service-file-name service)
               (with-imported-modules %default-imported-modules
                 #~(begin
                     (use-modules #$@(shepherd-service-modules service))

                     (make <service>
                       #:docstring '#$(shepherd-service-documentation service)
                       #:provides '#$(shepherd-service-provision service)
                       #:requires '#$(shepherd-service-requirement service)

                       ;; The 'one-shot?' slot is new in Shepherd 0.6.0.
                       ;; Older versions ignore it.
                       #:one-shot? '#$(shepherd-service-one-shot? service)

                       #:respawn? '#$(shepherd-service-respawn? service)
                       #:start #$(shepherd-service-start service)
                       #:stop #$(shepherd-service-stop service)
                       #:actions
                       (make-actions
                        #$@(map (match-lambda
                                  (($ <shepherd-action> name proc doc)
                                   #~(#$name #$doc #$proc)))
                                (shepherd-service-actions service))))))))

(define (scm->go file shepherd)
  "Compile FILE, which contains code to be loaded by shepherd's config file,
and return the resulting '.go' file. SHEPHERD is used as shepherd package."
  (let-system (system target)
    (with-extensions (list shepherd)
      (computed-file (string-append (basename (scheme-file-name file) ".scm")
                                    ".go")
                     #~(begin
                         (use-modules (system base compile)
                                      (system base target))

                         ;; Do the same as the Shepherd's 'load-in-user-module'.
                         (let ((env (make-fresh-user-module)))
                           (module-use! env (resolve-interface '(oop goops)))
                           (module-use! env (resolve-interface '(shepherd service)))
                           (with-target #$(or target #~%host-type)
                             (lambda _
                               (compile-file #$file #:output-file #$output
                                             #:env env)))))

                     ;; It's faster to build locally than to download.
                     #:options '(#:local-build? #t
                                 #:substitutable? #f)))))

(define (shepherd-configuration-file services shepherd)
  "Return the shepherd configuration file for SERVICES.  SHEPHERD is used
as shepherd package."
  (assert-valid-graph services)

  (let ((files (map shepherd-service-file services))
        (scm->go (cute scm->go <> shepherd)))
    (define config
      #~(begin
          (use-modules (srfi srfi-34)
                       (system repl error-handling))

          ;; Specify the default environment visible to all the services.
          ;; Without this statement, all the environment variables of PID 1
          ;; are inherited by child services.
          (default-environment-variables
            '("PATH=/run/current-system/profile/bin"))

          ;; Booting off a DVD, especially on a slow machine, can make
          ;; everything slow.  Thus, increase the timeout compared to the
          ;; default 5s in the Shepherd 0.7.0.  See
          ;; <https://bugs.gnu.org/40572>.
          (default-pid-file-timeout 30)

          ;; Arrange to spawn a REPL if something goes wrong.  This is better
          ;; than a kernel panic.
          (call-with-error-handling
            (lambda ()
              (apply register-services
                     (parameterize ((current-warning-port
                                     (%make-void-port "w")))
                       (map load-compiled '#$(map scm->go files))))))

          (format #t "starting services...~%")
          (for-each (lambda (service)
                      ;; In the Shepherd 0.3 the 'start' method can raise
                      ;; '&action-runtime-error' if it fails, so protect
                      ;; against it.  (XXX: 'action-runtime-error?' is not
                      ;; exported is 0.3, hence 'service-error?'.)
                      (guard (c ((service-error? c)
                                 (format (current-error-port)
                                         "failed to start service '~a'~%"
                                         service)))
                        (start service)))
                    '#$(append-map shepherd-service-provision
                                   (filter shepherd-service-auto-start?
                                           services)))

          ;; Hang up stdin.  At this point, we assume that 'start' methods
          ;; that required user interaction on the console (e.g.,
          ;; 'cryptsetup open' invocations, post-fsck emergency REPL) have
          ;; completed.  User interaction becomes impossible after this
          ;; call; this avoids situations where services wrongfully lead
          ;; PID 1 to read from stdin (the console), which users may not
          ;; have access to (see <https://bugs.gnu.org/23697>).
          (redirect-port (open-input-file "/dev/null")
                         (current-input-port))))

    (scheme-file "shepherd.conf" config)))

(define* (shepherd-service-lookup-procedure services
                                            #:optional
                                            (provision
                                             shepherd-service-provision))
  "Return a procedure that, when passed a symbol, return the item among
SERVICES that provides this symbol.  PROVISION must be a one-argument
procedure that takes a service and returns the list of symbols it provides."
  (let ((services (fold (lambda (service result)
                          (fold (cut vhash-consq <> service <>)
                                result
                                (provision service)))
                        vlist-null
                        services)))
    (lambda (name)
      (match (vhash-assq name services)
        ((_ . service) service)
        (#f            #f)))))

(define* (shepherd-service-back-edges services
                                      #:key
                                      (provision shepherd-service-provision)
                                      (requirement shepherd-service-requirement))
  "Return a procedure that, when given a <shepherd-service> from SERVICES,
returns the list of <shepherd-service> that depend on it.

Use PROVISION and REQUIREMENT as one-argument procedures that return the
symbols provided/required by a service."
  (define provision->service
    (shepherd-service-lookup-procedure services provision))

  (define edges
    (fold (lambda (service edges)
            (fold (lambda (requirement edges)
                    (vhash-consq (provision->service requirement) service
                                 edges))
                  edges
                  (requirement service)))
          vlist-null
          services))

  (lambda (service)
    (vhash-foldq* cons '() service edges)))

(define (shepherd-service-upgrade live target)
  "Return two values: the subset of LIVE (a list of <live-service>) that needs
to be unloaded, and the subset of TARGET (a list of <shepherd-service>) that
need to be restarted to complete their upgrade."
  (define (essential? service)
    (memq (first (live-service-provision service))
          '(root shepherd)))

  (define lookup-target
    (shepherd-service-lookup-procedure target
                                       shepherd-service-provision))

  (define lookup-live
    (shepherd-service-lookup-procedure live
                                       live-service-provision))

  (define (running? service)
    (and=> (lookup-live (shepherd-service-canonical-name service))
           live-service-running))

  (define live-service-dependents
    (shepherd-service-back-edges live
                                 #:provision live-service-provision
                                 #:requirement live-service-requirement))

  (define (obsolete? service)
    (match (lookup-target (first (live-service-provision service)))
      (#f (every obsolete? (live-service-dependents service)))
      (_  #f)))

  (define to-restart
    ;; Restart services that are currently running.
    (filter running? target))

  (define to-unload
    ;; Unload services that are no longer required.
    (remove essential? (filter obsolete? live)))

  (values to-unload to-restart))


;;;
;;; User processes.
;;;

(define %do-not-kill-file
  ;; Name of the file listing PIDs of processes that must survive when halting
  ;; the system.  Typical example is user-space file systems.
  "/etc/shepherd/do-not-kill")

(define (user-processes-shepherd-service requirements)
  "Return the 'user-processes' Shepherd service with dependencies on
REQUIREMENTS (a list of service names).

This is a synchronization point used to make sure user processes and daemons
get started only after crucial initial services have been started---file
system mounts, etc.  This is similar to the 'sysvinit' target in systemd."
  (define grace-delay
    ;; Delay after sending SIGTERM and before sending SIGKILL.
    4)

  (list (shepherd-service
         (documentation "When stopped, terminate all user processes.")
         (provision '(user-processes))
         (requirement requirements)
         (start #~(const #t))
         (stop #~(lambda _
                   (define (kill-except omit signal)
                     ;; Kill all the processes with SIGNAL except those listed
                     ;; in OMIT and the current process.
                     (let ((omit (cons (getpid) omit)))
                       (for-each (lambda (pid)
                                   (unless (memv pid omit)
                                     (false-if-exception
                                      (kill pid signal))))
                                 (processes))))

                   (define omitted-pids
                     ;; List of PIDs that must not be killed.
                     (if (file-exists? #$%do-not-kill-file)
                         (map string->number
                              (call-with-input-file #$%do-not-kill-file
                                (compose string-tokenize
                                         (@ (ice-9 rdelim) read-string))))
                         '()))

                   (define (now)
                     (car (gettimeofday)))

                   (define (sleep* n)
                     ;; Really sleep N seconds.
                     ;; Work around <http://bugs.gnu.org/19581>.
                     (define start (now))
                     (let loop ((elapsed 0))
                       (when (> n elapsed)
                         (sleep (- n elapsed))
                         (loop (- (now) start)))))

                   (define lset= (@ (srfi srfi-1) lset=))

                   (display "sending all processes the TERM signal\n")

                   (if (null? omitted-pids)
                       (begin
                         ;; Easy: terminate all of them.
                         (kill -1 SIGTERM)
                         (sleep* #$grace-delay)
                         (kill -1 SIGKILL))
                       (begin
                         ;; Kill them all except OMITTED-PIDS.  XXX: We would
                         ;; like to (kill -1 SIGSTOP) to get a fixed list of
                         ;; processes, like 'killall5' does, but that seems
                         ;; unreliable.
                         (kill-except omitted-pids SIGTERM)
                         (sleep* #$grace-delay)
                         (kill-except omitted-pids SIGKILL)
                         (delete-file #$%do-not-kill-file)))

                   (let wait ()
                     ;; Reap children, if any, so that we don't end up with
                     ;; zombies and enter an infinite loop.
                     (let reap-children ()
                       (define result
                         (false-if-exception
                          (waitpid WAIT_ANY (if (null? omitted-pids)
                                                0
                                                WNOHANG))))

                       (when (and (pair? result)
                                  (not (zero? (car result))))
                         (reap-children)))

                     (let ((pids (processes)))
                       (unless (lset= = pids (cons 1 omitted-pids))
                         (format #t "waiting for process termination\
 (processes left: ~s)~%"
                                 pids)
                         (sleep* 2)
                         (wait))))

                   (display "all processes have been terminated\n")
                   #f))
         (respawn? #f))))

(define user-processes-service-type
  (service-type
   (name 'user-processes)
   (extensions (list (service-extension shepherd-root-service-type
                                        user-processes-shepherd-service)))
   (compose concatenate)
   (extend append)

   ;; The value is the list of Shepherd services 'user-processes' depends on.
   ;; Extensions can add new services to this list.
   (default-value '())

   (description "The @code{user-processes} service is responsible for
terminating all the processes so that the root file system can be re-mounted
read-only, just before rebooting/halting.  Processes still running after a few
seconds after @code{SIGTERM} has been sent are terminated with
@code{SIGKILL}.")))

;;; shepherd.scm ends here