;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013-2016, 2018-2024 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 packages)
#:use-module (guix utils)
#:use-module ((guix diagnostics)
#:select (define-with-syntax-properties formatted-message))
#: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-limit
shepherd-service-respawn-delay
shepherd-service-respawn?
shepherd-service-start
shepherd-service-stop
shepherd-service-free-form
shepherd-service-auto-start?
shepherd-service-modules
shepherd-action
shepherd-action?
shepherd-action-name
shepherd-action-documentation
shepherd-action-procedure
shepherd-configuration-action
%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-0.10)) ; file-like
(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")
;; Ensure open file descriptors are close-on-exec so shepherd doesn't
;; inherit them.
(let loop ((fd 3))
(when (< fd 1024)
(false-if-exception
(let ((flags (fcntl fd F_GETFD)))
(when (zero? (logand flags FD_CLOEXEC))
(fcntl fd F_SETFD (logior FD_CLOEXEC flags)))))
(loop (+ fd 1))))
;; 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)
((guix build utils) #:hide (delete))
(guix build syscalls)))
(define-with-syntax-properties (validate-provision (provision properties))
(match provision
(((? symbol?) ..1) provision)
(_
(raise
(make-compound-condition
(condition
(&error-location
(location (source-properties->location properties))))
(formatted-message
(G_ "'provision' must be a non-empty list of symbols")))))))
(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
(sanitize validate-provision))
(requirement shepherd-service-requirement ;list of symbols
(default '()))
(one-shot? shepherd-service-one-shot? ;Boolean
(default #f))
(respawn? shepherd-service-respawn? ;Boolean
(default #t))
(respawn-limit shepherd-service-respawn-limit
(default #f))
(respawn-delay shepherd-service-respawn-delay
(default #f))
(free-form shepherd-service-free-form ;#f | g-expression (service)
(default #f))
(start shepherd-service-start ;g-expression (procedure)
(default #~(const #t)))
(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/regular service)
"Return a file defining SERVICE, a service whose 'free-form' field is #f."
(scheme-file (shepherd-service-file-name service)
(with-imported-modules %default-imported-modules
#~(begin
(use-modules #$@(shepherd-service-modules service))
(service
'#$(shepherd-service-provision service)
#:documentation '#$(shepherd-service-documentation service)
#:requirement '#$(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)
#$@(if (shepherd-service-respawn-limit service)
`(#:respawn-limit
,(shepherd-service-respawn-limit service))
'())
#$@(if (shepherd-service-respawn-delay service)
`(#:respawn-delay
,(shepherd-service-respawn-delay service))
'())
#:start #$(shepherd-service-start service)
#:stop #$(shepherd-service-stop service)
#:actions
(actions
#$@(map (match-lambda
(($ <shepherd-action> name proc doc)
#~(#$name #$doc #$proc)))
(shepherd-service-actions service))))))))
(define (shepherd-service-file/free-form service)
"Return a file defining SERVICE, a service whose 'free-form' field is set."
(scheme-file (shepherd-service-file-name service)
(with-imported-modules %default-imported-modules
#~(begin
(use-modules #$@(shepherd-service-modules service))
#$(shepherd-service-free-form service)))))
(define (shepherd-service-file service)
"Return a file defining SERVICE."
(if (shepherd-service-free-form service)
(shepherd-service-file/free-form service)
(shepherd-service-file/regular service)))
(define (scm->go file shepherd)
"Compile FILE, which contains code to be loaded by shepherd's config file,
and return the resulting '.go' file. SHEPHERD is used as shepherd package."
(define shepherd&co
(cons shepherd
(match (lookup-package-input shepherd "guile-fibers")
(#f '())
(fibers (list fibers)))))
(let-system (system target)
(with-extensions shepherd&co
(computed-file (string-append (basename (scheme-file-name file) ".scm")
".go")
#~(begin
(use-modules (system base compile)
(system base target))
;; Do the same as the Shepherd's 'load-in-user-module'.
(let ((env (make-fresh-user-module)))
(module-use! env (resolve-interface '(shepherd service)))
(with-target #$(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-action file)
"Return a 'configuration' action to display FILE, which should be the name
of the service's configuration file."
(shepherd-action
(name 'configuration)
(documentation "Display the name of this service's configuration file.")
(procedure #~(lambda (_)
(format #t "~a~%" #$file)
#$file))))
(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-1))
(define (make-user-module)
;; Copied from (shepherd support), where it's private.
(let ((m (make-fresh-user-module)))
(module-use! m (resolve-interface '(shepherd service)))
m))
;; There's code run from shepherd that uses 'call-with-input-file' &
;; co.--e.g., the 'urandom-seed' service. Starting from Shepherd
;; 0.9.2, users need to make sure not to leak non-close-on-exec file
;; descriptors to child processes. To address that, replace the
;; standard bindings with O_CLOEXEC variants.
(set! call-with-input-file
(lambda (file proc)
(call-with-port (open file (logior O_RDONLY O_CLOEXEC))
proc)))
(set! call-with-output-file
(lambda (file proc)
(call-with-port (open file (logior O_WRONLY O_CREAT O_CLOEXEC))
proc)))
;; 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)
;; Load service files one by one; filter out those that could not be
;; loaded--e.g., due to an unbound variable--such that an error in
;; one service definition does not prevent the system from booting.
(register-services
(parameterize ((current-warning-port (%make-void-port "w")))
(filter-map (lambda (file)
(with-exception-handler
(lambda (exception)
(format #t "Exception caught \
while loading '~a': ~s~%"
file exception)
#f)
(lambda ()
(save-module-excursion
(lambda ()
(set-current-module (make-user-module))
(load-compiled file))))
#:unwind? #t))
'#$(map scm->go files))))
(format #t "starting services...~%")
(let ((services-to-start
'#$(append-map shepherd-service-provision
(filter shepherd-service-auto-start?
services))))
(start-in-the-background services-to-start)
;; 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 "/dev/null" (logior O_RDONLY O_CLOEXEC))
(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. Essential services must
;; be kept and transient services such as inetd child services should be
;; kept as well--they'll vanish eventually.
(remove (lambda (live)
(or (essential? live)
(live-service-transient? live)))
(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
