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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013, 2014, 2015, 2016, 2018, 2019, 2020 Ludovic Courtès <>
;;; Copyright © 2017 Clément Lassieur <>
;;; Copyright © 2018 Carlo Zancanaro <>
;;; Copyright © 2020 Jan (janneke) Nieuwenhuizen <>
;;; 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
;;; 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 <>.
(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-root-service-type
;;; Commentary:
;;; Instantiating system services as a shepherd configuration file.
;;; Code:
(define (shepherd-boot-gexp services)
;; Keep track of the booted system.
(false-if-exception (delete-file "/run/booted-system"))
(symlink (readlink "/run/current-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))))
(define shepherd-root-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 append)
(extensions (list (service-extension boot-service-type
(service-extension profile-service-type
(const (list shepherd)))))
"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 list of
;; <shepherd-service> objects.
(service shepherd-root-service-type '()))
(define-syntax shepherd-service-type
(syntax-rules ()
"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)
(name service-name)
(list (service-extension shepherd-root-service-type
(compose list proc))))
(default-value default)))
((_ service-name proc)
(name service-name)
(list (service-extension shepherd-root-service-type
(compose list proc))))))))
(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
(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
(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
(format #f (G_ "service '~a' provided more than once")
(for-each assert-unique (shepherd-service-provision service))
(fold set-insert set (shepherd-service-provision service)))
(setq 'shepherd)
(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
(format #f (G_ "service '~a' requires '~a', \
which is not provided by any service")
(match (shepherd-service-provision service)
((head . _) head)
(_ service))
(shepherd-service-requirement service)))
(for-each assert-satisfied-requirements services))
(define (shepherd-service-file-name service)
"Return the file name where the initialization code for SERVICE is to be
(let ((provisions (string-join (map symbol->string
(shepherd-service-provision service)))))
(string-append "shepherd-"
(string-map (match-lambda
(#\/ #\-)
(#\ #\-)
(chr chr))
(define (shepherd-service-file service)
"Return a file defining SERVICE."
(scheme-file (shepherd-service-file-name service)
(with-imported-modules %default-imported-modules
(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)
#$@(map (match-lambda
(($ <shepherd-action> name proc doc)
#~(#$name #$doc #$proc)))
(shepherd-service-actions service))))))))
(define (scm->go file)
"Compile FILE, which contains code to be loaded by shepherd's config file,
and return the resulting '.go' file."
(let-system (system target)
(with-extensions (list shepherd)
(computed-file (string-append (basename (scheme-file-name file) ".scm")
(use-modules (system base compile)
(system base target))
;; Do the same as the Shepherd's 'load-in-user-module'.
(let ((env (make-fresh-user-module)))
(module-use! env (resolve-interface '(oop goops)))
(module-use! env (resolve-interface '(shepherd service)))
(with-target #$(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)
"Return the shepherd configuration file for SERVICES."
(assert-valid-graph services)
(let ((files (map shepherd-service-file services)))
(define config
(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.
;; 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
;; <>.
(default-pid-file-timeout 30)
;; Arrange to spawn a REPL if something goes wrong. This is better
;; than a kernel panic.
(lambda ()
(apply register-services
(parameterize ((current-warning-port
(%make-void-port "w")))
(map load-compiled '#$(map scm->go files))))))
(format #t "starting services...~%")
(for-each (lambda (service)
;; In the Shepherd 0.3 the 'start' method can raise
;; '&action-runtime-error' if it fails, so protect
;; against it. (XXX: 'action-runtime-error?' is not
;; exported is 0.3, hence 'service-error?'.)
(guard (c ((service-error? c)
(format (current-error-port)
"failed to start service '~a'~%"
(start service)))
'#$(append-map shepherd-service-provision
(filter shepherd-service-auto-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 <>).
(redirect-port (open-input-file "/dev/null")
(scheme-file "shepherd.conf" config)))
(define* (shepherd-service-lookup-procedure services
"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 <>)
(provision service)))
(lambda (name)
(match (vhash-assq name services)
((_ . service) service)
(#f #f)))))
(define* (shepherd-service-back-edges services
(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
(requirement service)))
(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
(define lookup-live
(shepherd-service-lookup-procedure live
(define (running? service)
(and=> (lookup-live (shepherd-service-canonical-name service))
(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.
(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.
(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)
(kill pid signal))))
(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 <>.
(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)
;; Easy: terminate all of them.
(kill -1 SIGTERM)
(sleep* #$grace-delay)
(kill -1 SIGKILL))
;; Kill them all except OMITTED-PIDS. XXX: We would
;; like to (kill -1 SIGSTOP) to get a fixed list of
;; processes, like 'killall5' does, but that seems
;; unreliable.
(kill-except omitted-pids SIGTERM)
(sleep* #$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
(waitpid WAIT_ANY (if (null? omitted-pids)
(when (and (pair? result)
(not (zero? (car result))))
(let ((pids (processes)))
(unless (lset= = pids (cons 1 omitted-pids))
(format #t "waiting for process termination\
(processes left: ~s)~%"
(sleep* 2)
(display "all processes have been terminated\n")
(respawn? #f))))
(define user-processes-service-type
(name 'user-processes)
(extensions (list (service-extension shepherd-root-service-type
(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
;;; shepherd.scm ends here