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guix/gnu/services.scm
Ricardo Wurmus a247f5c753
services: Support DELETE in MODIFY-SERVICES macro. 
* gnu/services.scm (%modify-service): Add clause for DELETE syntax.
(modify-services): Use FILTER-MAP; adjust docstring.
* doc/guix.texi (System Services): Mention alternative syntax.
(X Window): Use MODIFY-SERVICES syntax.
2021-04-12 17:49:07 +02:00

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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2015, 2016, 2017, 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2016 Chris Marusich <cmmarusich@gmail.com>
;;; Copyright © 2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
;;; Copyright © 2020, 2021 Ricardo Wurmus <rekado@elephly.net>
;;;
;;; 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)
#:use-module (guix gexp)
#:use-module (guix monads)
#:use-module (guix store)
#:use-module (guix records)
#:use-module (guix profiles)
#:use-module (guix discovery)
#:use-module (guix combinators)
#:use-module (guix channels)
#:use-module (guix describe)
#:use-module (guix sets)
#:use-module (guix ui)
#:use-module (guix diagnostics)
#:autoload (guix openpgp) (openpgp-format-fingerprint)
#:use-module (guix modules)
#:use-module (gnu packages base)
#:use-module (gnu packages bash)
#:use-module (gnu packages hurd)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-9)
#:use-module (srfi srfi-9 gnu)
#:use-module (srfi srfi-26)
#:use-module (srfi srfi-34)
#:use-module (srfi srfi-35)
#:use-module (ice-9 vlist)
#:use-module (ice-9 match)
#:autoload (ice-9 pretty-print) (pretty-print)
#:export (service-extension
service-extension?
service-extension-target
service-extension-compute
service-type
service-type?
service-type-name
service-type-extensions
service-type-compose
service-type-extend
service-type-default-value
service-type-description
service-type-location
%service-type-path
fold-service-types
lookup-service-types
service
service?
service-kind
service-value
service-parameters ;deprecated
simple-service
modify-services
service-back-edges
instantiate-missing-services
fold-services
service-error?
missing-value-service-error?
missing-value-service-error-type
missing-value-service-error-location
missing-target-service-error?
missing-target-service-error-service
missing-target-service-error-target-type
ambiguous-target-service-error?
ambiguous-target-service-error-service
ambiguous-target-service-error-target-type
system-service-type
provenance-service-type
sexp->system-provenance
system-provenance
boot-service-type
cleanup-service-type
activation-service-type
activation-service->script
%linux-bare-metal-service
%hurd-rc-script
%hurd-startup-service
special-files-service-type
extra-special-file
etc-service-type
etc-directory
setuid-program-service-type
profile-service-type
firmware-service-type
gc-root-service-type
%boot-service
%activation-service
etc-service)
#:re-export (;; Note: Re-export 'delete' to allow for proper syntax matching
;; in 'modify-services' forms. See
;; <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26805#16>.
delete))
;;; Comment:
;;;
;;; This module defines a broad notion of "service types" and "services."
;;;
;;; A service type describe how its instances extend instances of other
;;; service types. For instance, some services extend the instance of
;;; ACCOUNT-SERVICE-TYPE by providing it with accounts and groups to create;
;;; others extend SHEPHERD-ROOT-SERVICE-TYPE by passing it instances of
;;; <shepherd-service>.
;;;
;;; When applicable, the service type defines how it can itself be extended,
;;; by providing one procedure to compose extensions, and one procedure to
;;; extend itself.
;;;
;;; A notable service type is SYSTEM-SERVICE-TYPE, which has a single
;;; instance, which is the root of the service DAG. Its value is the
;;; derivation that produces the 'system' directory as returned by
;;; 'operating-system-derivation'.
;;;
;;; The 'fold-services' procedure can be passed a list of procedures, which it
;;; "folds" by propagating extensions down the graph; it returns the root
;;; service after the applying all its extensions.
;;;
;;; Code:
(define-record-type <service-extension>
(service-extension target compute)
service-extension?
(target service-extension-target) ;<service-type>
(compute service-extension-compute)) ;params -> params
(define &no-default-value
;; Value used to denote service types that have no associated default value.
'(no default value))
(define-record-type* <service-type> service-type make-service-type
service-type?
(name service-type-name) ;symbol (for debugging)
;; Things extended by services of this type.
(extensions service-type-extensions) ;list of <service-extensions>
;; Given a list of extensions, "compose" them.
(compose service-type-compose ;list of Any -> Any
(default #f))
;; Extend the services' own parameters with the extension composition.
(extend service-type-extend ;list of Any -> parameters
(default #f))
;; Optional default value for instances of this type.
(default-value service-type-default-value ;Any
(default &no-default-value))
;; Meta-data.
(description service-type-description ;string
(default #f))
(location service-type-location ;<location>
(default (and=> (current-source-location)
source-properties->location))
(innate)))
(define (write-service-type type port)
(format port "#<service-type ~a ~a>"
(service-type-name type)
(number->string (object-address type) 16)))
(set-record-type-printer! <service-type> write-service-type)
(define %distro-root-directory
;; Absolute file name of the module hierarchy.
(dirname (search-path %load-path "guix.scm")))
(define %service-type-path
;; Search path for service types.
(make-parameter `((,%distro-root-directory . "gnu/services")
(,%distro-root-directory . "gnu/system"))))
(define (all-service-modules)
"Return the default set of service modules."
(cons (resolve-interface '(gnu services))
(all-modules (%service-type-path)
#:warn warn-about-load-error)))
(define* (fold-service-types proc seed
#:optional
(modules (all-service-modules)))
"For each service type exported by one of MODULES, call (PROC RESULT). SEED
is used as the initial value of RESULT."
(fold-module-public-variables (lambda (object result)
(if (service-type? object)
(proc object result)
result))
seed
modules))
(define lookup-service-types
(let ((table
(delay (fold-service-types (lambda (type result)
(vhash-consq (service-type-name type)
type result))
vlist-null))))
(lambda (name)
"Return the list of services with the given NAME (a symbol)."
(vhash-foldq* cons '() name (force table)))))
;; Services of a given type.
(define-record-type <service>
(make-service type value)
service?
(type service-kind)
(value service-value))
(define-syntax service
(syntax-rules ()
"Return a service instance of TYPE. The service value is VALUE or, if
omitted, TYPE's default value."
((_ type value)
(make-service type value))
((_ type)
(%service-with-default-value (current-source-location)
type))))
(define (%service-with-default-value location type)
"Return a instance of service type TYPE with its default value, if any. If
TYPE does not have a default value, an error is raised."
;; TODO: Currently this is a run-time error but with a little bit macrology
;; we could turn it into an expansion-time error.
(let ((default (service-type-default-value type)))
(if (eq? default &no-default-value)
(let ((location (source-properties->location location)))
(raise
(make-compound-condition
(condition
(&missing-value-service-error (type type) (location location)))
(formatted-message (G_ "~a: no value specified \
for service of type '~a'")
(location->string location)
(service-type-name type)))))
(service type default))))
(define-condition-type &service-error &error
service-error?)
(define-condition-type &missing-value-service-error &service-error
missing-value-service-error?
(type missing-value-service-error-type)
(location missing-value-service-error-location))
;;;
;;; Helpers.
;;;
(define service-parameters
;; Deprecated alias.
service-value)
(define (simple-service name target value)
"Return a service that extends TARGET with VALUE. This works by creating a
singleton service type NAME, of which the returned service is an instance."
(let* ((extension (service-extension target identity))
(type (service-type (name name)
(extensions (list extension)))))
(service type value)))
(define-syntax %modify-service
(syntax-rules (=> delete)
((_ svc (delete kind) clauses ...)
(if (eq? (service-kind svc) kind)
#f
(%modify-service svc clauses ...)))
((_ service)
service)
((_ svc (kind param => exp ...) clauses ...)
(if (eq? (service-kind svc) kind)
(let ((param (service-value svc)))
(service (service-kind svc)
(begin exp ...)))
(%modify-service svc clauses ...)))))
(define-syntax modify-services
(syntax-rules ()
"Modify the services listed in SERVICES according to CLAUSES and return
the resulting list of services. Each clause must have the form:
(TYPE VARIABLE => BODY)
where TYPE is a service type, such as 'guix-service-type', and VARIABLE is an
identifier that is bound within BODY to the value of the service of that
TYPE. Consider this example:
(modify-services %base-services
(guix-service-type config =>
(guix-configuration
(inherit config)
(use-substitutes? #f)
(extra-options '(\"--gc-keep-derivations\"))))
(mingetty-service-type config =>
(mingetty-configuration
(inherit config)
(motd (plain-file \"motd\" \"Hi there!\"))))
(delete udev-service-type))
It changes the configuration of the GUIX-SERVICE-TYPE instance, and that of
all the MINGETTY-SERVICE-TYPE instances, and it deletes instances of the
UDEV-SERVICE-TYPE.
This is a shorthand for (filter-map (lambda (svc) ...) %base-services)."
((_ services clauses ...)
(filter-map (lambda (service)
(%modify-service service clauses ...))
services))))
;;;
;;; Core services.
;;;
(define (system-derivation entries mextensions)
"Return as a monadic value the derivation of the 'system' directory
containing the given entries."
(mlet %store-monad ((extensions (mapm/accumulate-builds identity
mextensions)))
(lower-object
(file-union "system"
(append entries (concatenate extensions))))))
(define system-service-type
;; This is the ultimate service type, the root of the service DAG. The
;; service of this type is extended by monadic name/item pairs. These items
;; end up in the "system directory" as returned by
;; 'operating-system-derivation'.
(service-type (name 'system)
(extensions '())
(compose identity)
(extend system-derivation)
(description
"Build the operating system top-level directory, which in
turn refers to everything the operating system needs: its kernel, initrd,
system profile, boot script, and so on.")))
(define (compute-boot-script _ gexps)
;; Reverse GEXPS so that extensions appear in the boot script in the right
;; order. That is, user extensions would come first, and extensions added
;; by 'essential-services' (e.g., running shepherd) are guaranteed to come
;; last.
(gexp->file "boot"
;; Clean up and activate the system, then spawn shepherd.
#~(begin #$@(reverse gexps))))
(define (boot-script-entry mboot)
"Return, as a monadic value, an entry for the boot script in the system
directory."
(mlet %store-monad ((boot mboot))
(return `(("boot" ,boot)))))
(define boot-service-type
;; The service of this type is extended by being passed gexps. It
;; aggregates them in a single script, as a monadic value, which becomes its
;; value.
(service-type (name 'boot)
(extensions
(list (service-extension system-service-type
boot-script-entry)))
(compose identity)
(extend compute-boot-script)
(description
"Produce the operating system's boot script, which is spawned
by the initrd once the root file system is mounted.")))
(define %boot-service
;; The service that produces the boot script.
(service boot-service-type #t))
;;;
;;; Provenance tracking.
;;;
(define (object->pretty-string obj)
"Like 'object->string', but using 'pretty-print'."
(call-with-output-string
(lambda (port)
(pretty-print obj port))))
(define (channel->code channel)
"Return code to build CHANNEL, ready to be dropped in a 'channels.scm'
file."
;; Since the 'introduction' field is backward-incompatible, and since it's
;; optional when using the "official" 'guix channel, include it if and only
;; if we're referring to a different channel.
(let ((intro (and (not (equal? (list channel) %default-channels))
(channel-introduction channel))))
`(channel (name ',(channel-name channel))
(url ,(channel-url channel))
(branch ,(channel-branch channel))
(commit ,(channel-commit channel))
,@(if intro
`((introduction
(make-channel-introduction
,(channel-introduction-first-signed-commit intro)
(openpgp-fingerprint
,(openpgp-format-fingerprint
(channel-introduction-first-commit-signer
intro))))))
'()))))
(define (channel->sexp channel)
"Return an sexp describing CHANNEL. The sexp is _not_ code and is meant to
be parsed by tools; it's potentially more future-proof than code."
;; TODO: Add CHANNEL's introduction. Currently we can't do that because
;; older 'guix system describe' expect exactly name/url/branch/commit
;; without any additional fields.
`(channel (name ,(channel-name channel))
(url ,(channel-url channel))
(branch ,(channel-branch channel))
(commit ,(channel-commit channel))))
(define (sexp->channel sexp)
"Return the channel corresponding to SEXP, an sexp as found in the
\"provenance\" file produced by 'provenance-service-type'."
(match sexp
(('channel ('name name)
('url url)
('branch branch)
('commit commit)
rest ...)
;; XXX: In the future REST may include a channel introduction.
(channel (name name) (url url)
(branch branch) (commit commit)))))
(define (provenance-file channels config-file)
"Return a 'provenance' file describing CHANNELS, a list of channels, and
CONFIG-FILE, which can be either #f or a <local-file> containing the OS
configuration being used."
(scheme-file "provenance"
#~(provenance
(version 0)
(channels #+@(if channels
(map channel->sexp channels)
'()))
(configuration-file #+config-file))))
(define (provenance-entry config-file)
"Return system entries describing the operating system provenance: the
channels in use and CONFIG-FILE, if it is true."
(define profile
(current-profile))
(define channels
(and=> profile profile-channels))
(mbegin %store-monad
(let ((config-file (cond ((string? config-file)
;; CONFIG-FILE has been passed typically via
;; 'guix system reconfigure CONFIG-FILE' so we
;; can assume it's valid: tell 'local-file' to
;; not emit a warning.
(local-file (assume-valid-file-name config-file)
"configuration.scm"))
((not config-file)
#f)
(else
config-file))))
(return `(("provenance" ,(provenance-file channels config-file))
,@(if channels
`(("channels.scm"
,(plain-file "channels.scm"
(object->pretty-string
`(list
,@(map channel->code channels))))))
'())
,@(if config-file
`(("configuration.scm" ,config-file))
'()))))))
(define provenance-service-type
(service-type (name 'provenance)
(extensions
(list (service-extension system-service-type
provenance-entry)))
(default-value #f) ;the OS config file
(description
"Store provenance information about the system in the system
itself: the channels used when building the system, and its configuration
file, when available.")))
(define (sexp->system-provenance sexp)
"Parse SEXP, an s-expression read from /run/current-system/provenance or
similar, and return two values: the list of channels listed therein, and the
OS configuration file or #f."
(match sexp
(('provenance ('version 0)
('channels channels ...)
('configuration-file config-file))
(values (map sexp->channel channels)
config-file))
(_
(values '() #f))))
(define (system-provenance system)
"Given SYSTEM, the file name of a system generation, return two values: the
list of channels SYSTEM is built from, and its configuration file. If that
information is missing, return the empty list (for channels) and possibly
#false (for the configuration file)."
(catch 'system-error
(lambda ()
(sexp->system-provenance
(call-with-input-file (string-append system "/provenance")
read)))
(lambda _
(values '() #f))))
;;;
;;; Cleanup.
;;;
(define (cleanup-gexp _)
"Return a gexp to clean up /tmp and similar places upon boot."
(with-imported-modules '((guix build utils))
#~(begin
(use-modules (guix build utils))
;; Clean out /tmp and /var/run.
;;
;; XXX This needs to happen before service activations, so it
;; has to be here, but this also implicitly assumes that /tmp
;; and /var/run are on the root partition.
(letrec-syntax ((fail-safe (syntax-rules ()
((_ exp rest ...)
(begin
(catch 'system-error
(lambda () exp)
(const #f))
(fail-safe rest ...)))
((_)
#t))))
;; Ignore I/O errors so the system can boot.
(fail-safe
;; Remove stale Shadow lock files as they would lead to
;; failures of 'useradd' & co.
(delete-file "/etc/group.lock")
(delete-file "/etc/passwd.lock")
(delete-file "/etc/.pwd.lock") ;from 'lckpwdf'
;; Force file names to be decoded as UTF-8. See
;; <https://bugs.gnu.org/26353>.
(setenv "GUIX_LOCPATH"
#+(file-append glibc-utf8-locales "/lib/locale"))
(setlocale LC_CTYPE "en_US.utf8")
(delete-file-recursively "/tmp")
(delete-file-recursively "/var/run")
(mkdir "/tmp")
(chmod "/tmp" #o1777)
(mkdir "/var/run")
(chmod "/var/run" #o755)
(delete-file-recursively "/run/udev/watch.old"))))))
(define cleanup-service-type
;; Service that cleans things up in /tmp and similar.
(service-type (name 'cleanup)
(extensions
(list (service-extension boot-service-type
cleanup-gexp)))
(description
"Delete files from @file{/tmp}, @file{/var/run}, and other
temporary locations at boot time.")))
(define* (activation-service->script service)
"Return as a monadic value the activation script for SERVICE, a service of
ACTIVATION-SCRIPT-TYPE."
(activation-script (service-value service)))
(define (activation-script gexps)
"Return the system's activation script, which evaluates GEXPS."
(define actions
(map (cut program-file "activate-service.scm" <>) gexps))
(program-file "activate.scm"
(with-imported-modules (source-module-closure
'((gnu build activation)
(guix build utils)))
#~(begin
(use-modules (gnu build activation)
(guix build utils))
;; Make sure the user accounting database exists. If it
;; does not exist, 'setutxent' does not create it and
;; thus there is no accounting at all.
(close-port (open-file "/var/run/utmpx" "a0"))
;; Same for 'wtmp', which is populated by mingetty et
;; al.
(mkdir-p "/var/log")
(close-port (open-file "/var/log/wtmp" "a0"))
;; Set up /run/current-system. Among other things this
;; sets up locales, which the activation snippets
;; executed below may expect.
(activate-current-system)
;; Run the services' activation snippets.
;; TODO: Use 'load-compiled'.
(for-each primitive-load '#$actions)))))
(define (gexps->activation-gexp gexps)
"Return a gexp that runs the activation script containing GEXPS."
#~(primitive-load #$(activation-script gexps)))
(define (activation-profile-entry gexps)
"Return, as a monadic value, an entry for the activation script in the
system directory."
(mlet %store-monad ((activate (lower-object (activation-script gexps))))
(return `(("activate" ,activate)))))
(define (second-argument a b) b)
(define activation-service-type
(service-type (name 'activate)
(extensions
(list (service-extension boot-service-type
gexps->activation-gexp)
(service-extension system-service-type
activation-profile-entry)))
(compose identity)
(extend second-argument)
(description
"Run @dfn{activation} code at boot time and upon
@command{guix system reconfigure} completion.")))
(define %activation-service
;; The activation service produces the activation script from the gexps it
;; receives.
(service activation-service-type #t))
(define %modprobe-wrapper
;; Wrapper for the 'modprobe' command that knows where modules live.
;;
;; This wrapper is typically invoked by the Linux kernel ('call_modprobe',
;; in kernel/kmod.c), a situation where the 'LINUX_MODULE_DIRECTORY'
;; environment variable is not set---hence the need for this wrapper.
(let ((modprobe "/run/current-system/profile/bin/modprobe"))
(program-file "modprobe"
#~(begin
(setenv "LINUX_MODULE_DIRECTORY"
"/run/booted-system/kernel/lib/modules")
;; FIXME: Remove this crutch when the patch #40422,
;; updating to kmod 27 is merged.
(setenv "MODPROBE_OPTIONS"
"-C /etc/modprobe.d")
(apply execl #$modprobe
(cons #$modprobe (cdr (command-line))))))))
(define %linux-kernel-activation
;; Activation of the Linux kernel running on the bare metal (as opposed to
;; running in a container.)
#~(begin
;; Tell the kernel to use our 'modprobe' command.
(activate-modprobe #$%modprobe-wrapper)
;; Let users debug their own processes!
(activate-ptrace-attach)))
(define %linux-bare-metal-service
;; The service that does things that are needed on the "bare metal", but not
;; necessary or impossible in a container.
(simple-service 'linux-bare-metal
activation-service-type
%linux-kernel-activation))
(define %hurd-rc-script
;; The RC script to be started upon boot.
(program-file "rc"
(with-imported-modules (source-module-closure
'((guix build utils)
(gnu build hurd-boot)
(guix build syscalls)))
#~(begin
(use-modules (guix build utils)
(gnu build hurd-boot)
(guix build syscalls)
(ice-9 match)
(system repl repl)
(srfi srfi-1)
(srfi srfi-26))
(boot-hurd-system)))))
(define (hurd-rc-entry rc)
"Return, as a monadic value, an entry for the RC script in the system
directory."
(mlet %store-monad ((rc (lower-object rc)))
(return `(("rc" ,rc)))))
(define hurd-startup-service-type
;; The service that creates the initial SYSTEM/rc startup file.
(service-type (name 'startup)
(extensions
(list (service-extension system-service-type hurd-rc-entry)))
(default-value %hurd-rc-script)))
(define %hurd-startup-service
;; The service that produces the RC script.
(service hurd-startup-service-type %hurd-rc-script))
(define special-files-service-type
;; Service to install "special files" such as /bin/sh and /usr/bin/env.
(service-type
(name 'special-files)
(extensions
(list (service-extension activation-service-type
(lambda (files)
#~(activate-special-files '#$files)))))
(compose concatenate)
(extend append)
(description
"Add special files to the root file system---e.g.,
@file{/usr/bin/env}.")))
(define (extra-special-file file target)
"Use TARGET as the \"special file\" FILE. For example, TARGET might be
(file-append coreutils \"/bin/env\")
and FILE could be \"/usr/bin/env\"."
(simple-service (string->symbol (string-append "special-file-" file))
special-files-service-type
`((,file ,target))))
(define (etc-directory service)
"Return the directory for SERVICE, a service of type ETC-SERVICE-TYPE."
(files->etc-directory (service-value service)))
(define (files->etc-directory files)
(define (assert-no-duplicates files)
(let loop ((files files)
(seen (set)))
(match files
(() #t)
(((file _) rest ...)
(when (set-contains? seen file)
(raise (formatted-message (G_ "duplicate '~a' entry for /etc")
file)))
(loop rest (set-insert file seen))))))
;; Detect duplicates early instead of letting them through, eventually
;; leading to a build failure of "etc.drv".
(assert-no-duplicates files)
(file-union "etc" files))
(define (etc-entry files)
"Return an entry for the /etc directory consisting of FILES in the system
directory."
(with-monad %store-monad
(return `(("etc" ,(files->etc-directory files))))))
(define etc-service-type
(service-type (name 'etc)
(extensions
(list
(service-extension activation-service-type
(lambda (files)
(let ((etc
(files->etc-directory files)))
#~(activate-etc #$etc))))
(service-extension system-service-type etc-entry)))
(compose concatenate)
(extend append)
(description "Populate the @file{/etc} directory.")))
(define (etc-service files)
"Return a new service of ETC-SERVICE-TYPE that populates /etc with FILES.
FILES must be a list of name/file-like object pairs."
(service etc-service-type files))
(define setuid-program-service-type
(service-type (name 'setuid-program)
(extensions
(list (service-extension activation-service-type
(lambda (programs)
#~(activate-setuid-programs
(list #$@programs))))))
(compose concatenate)
(extend append)
(description
"Populate @file{/run/setuid-programs} with the specified
executables, making them setuid-root.")))
(define (packages->profile-entry packages)
"Return a system entry for the profile containing PACKAGES."
;; XXX: 'mlet' is needed here for one reason: to get the proper
;; '%current-target' and '%current-target-system' bindings when
;; 'packages->manifest' is called, and thus when the 'package-inputs'
;; etc. procedures are called on PACKAGES. That way, conditionals in those
;; inputs see the "correct" value of these two parameters. See
;; <https://issues.guix.gnu.org/44952>.
(mlet %store-monad ((_ (current-target-system)))
(return `(("profile" ,(profile
(content (packages->manifest
(delete-duplicates packages eq?)))))))))
(define profile-service-type
;; The service that populates the system's profile---i.e.,
;; /run/current-system/profile. It is extended by package lists.
(service-type (name 'profile)
(extensions
(list (service-extension system-service-type
packages->profile-entry)))
(compose concatenate)
(extend append)
(description
"This is the @dfn{system profile}, available as
@file{/run/current-system/profile}. It contains packages that the sysadmin
wants to be globally available to all the system users.")))
(define (firmware->activation-gexp firmware)
"Return a gexp to make the packages listed in FIRMWARE loadable by the
kernel."
(let ((directory (directory-union "firmware" firmware)))
;; Tell the kernel where firmware is.
#~(activate-firmware (string-append #$directory "/lib/firmware"))))
(define firmware-service-type
;; The service that collects firmware.
(service-type (name 'firmware)
(extensions
(list (service-extension activation-service-type
firmware->activation-gexp)))
(compose concatenate)
(extend append)
(description
"Make ``firmware'' files loadable by the operating system
kernel. Firmware may then be uploaded to some of the machine's devices, such
as Wifi cards.")))
(define (gc-roots->system-entry roots)
"Return an entry in the system's output containing symlinks to ROOTS."
(mlet %store-monad ((entry (gexp->derivation
"gc-roots"
#~(let ((roots '#$roots))
(mkdir #$output)
(chdir #$output)
(for-each symlink
roots
(map number->string
(iota (length roots))))))))
(return (if (null? roots)
'()
`(("gc-roots" ,entry))))))
(define gc-root-service-type
;; A service to associate extra garbage-collector roots to the system. This
;; is a simple hack that guarantees that the system retains references to
;; the given list of roots. Roots must be "lowerable" objects like
;; packages, or derivations.
(service-type (name 'gc-roots)
(extensions
(list (service-extension system-service-type
gc-roots->system-entry)))
(compose concatenate)
(extend append)
(description
"Register garbage-collector roots---i.e., store items that
will not be reclaimed by the garbage collector.")
(default-value '())))
;;;
;;; Service folding.
;;;
(define-condition-type &missing-target-service-error &service-error
missing-target-service-error?
(service missing-target-service-error-service)
(target-type missing-target-service-error-target-type))
(define-condition-type &ambiguous-target-service-error &service-error
ambiguous-target-service-error?
(service ambiguous-target-service-error-service)
(target-type ambiguous-target-service-error-target-type))
(define (missing-target-error service target-type)
(raise
(condition (&missing-target-service-error
(service service)
(target-type target-type))
(&message
(message
(format #f (G_ "no target of type '~a' for service '~a'")
(service-type-name target-type)
(service-type-name
(service-kind service))))))))
(define (service-back-edges services)
"Return a procedure that, when passed a <service>, returns the list of
<service> objects that depend on it."
(define (add-edges service edges)
(define (add-edge extension edges)
(let ((target-type (service-extension-target extension)))
(match (filter (lambda (service)
(eq? (service-kind service) target-type))
services)
((target)
(vhash-consq target service edges))
(()
(missing-target-error service target-type))
(x
(raise
(condition (&ambiguous-target-service-error
(service service)
(target-type target-type))
(&message
(message
(format #f
(G_ "more than one target service of type '~a'")
(service-type-name target-type))))))))))
(fold add-edge edges (service-type-extensions (service-kind service))))
(let ((edges (fold add-edges vlist-null services)))
(lambda (node)
(reverse (vhash-foldq* cons '() node edges)))))
(define (instantiate-missing-services services)
"Return SERVICES, a list, augmented with any services targeted by extensions
and missing from SERVICES. Only service types with a default value can be
instantiated; other missing services lead to a
'&missing-target-service-error'."
(define (adjust-service-list svc result instances)
(fold2 (lambda (extension result instances)
(define target-type
(service-extension-target extension))
(match (vhash-assq target-type instances)
(#f
(let ((default (service-type-default-value target-type)))
(if (eq? &no-default-value default)
(missing-target-error svc target-type)
(let ((new (service target-type)))
(values (cons new result)
(vhash-consq target-type new instances))))))
(_
(values result instances))))
result
instances
(service-type-extensions (service-kind svc))))
(let loop ((services services))
(define instances
(fold (lambda (service result)
(vhash-consq (service-kind service) service
result))
vlist-null services))
(define adjusted
(fold2 adjust-service-list
services instances
services))
;; If we instantiated services, they might in turn depend on missing
;; services. Loop until we've reached fixed point.
(if (= (length adjusted) (vlist-length instances))
adjusted
(loop adjusted))))
(define* (fold-services services
#:key (target-type system-service-type))
"Fold SERVICES by propagating their extensions down to the root of type
TARGET-TYPE; return the root service adjusted accordingly."
(define dependents
(service-back-edges services))
(define (matching-extension target)
(let ((target (service-kind target)))
(match-lambda
(($ <service-extension> type)
(eq? type target)))))
(define (apply-extension target)
(lambda (service)
(match (find (matching-extension target)
(service-type-extensions (service-kind service)))
(($ <service-extension> _ compute)
(compute (service-value service))))))
(match (filter (lambda (service)
(eq? (service-kind service) target-type))
services)
((sink)
;; Use the state monad to keep track of already-visited services in the
;; graph and to memoize their value once folded.
(run-with-state
(let loop ((sink sink))
(mlet %state-monad ((visited (current-state)))
(match (vhash-assq sink visited)
(#f
(mlet* %state-monad
((dependents (mapm %state-monad loop (dependents sink)))
(visited (current-state))
(extensions -> (map (apply-extension sink) dependents))
(extend -> (service-type-extend (service-kind sink)))
(compose -> (service-type-compose (service-kind sink)))
(params -> (service-value sink))
(service
->
;; Distinguish COMPOSE and EXTEND because PARAMS typically
;; has a different type than the elements of EXTENSIONS.
(if extend
(service (service-kind sink)
(extend params (compose extensions)))
sink)))
(mbegin %state-monad
(set-current-state (vhash-consq sink service visited))
(return service))))
((_ . service) ;SINK was already visited
(return service)))))
vlist-null))
(()
(raise
(make-compound-condition
(condition (&missing-target-service-error
(service #f)
(target-type target-type)))
(formatted-message (G_ "service of type '~a' not found")
(service-type-name target-type)))))
(x
(raise
(condition (&ambiguous-target-service-error
(service #f)
(target-type target-type))
(&message
(message
(format #f
(G_ "more than one target service of type '~a'")
(service-type-name target-type)))))))))
;;; services.scm ends here.
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