5152d13b51
* gnu/services.scm: Export 'service-back-edges' and <service-type>
accessors.
* tests/services.scm ("service-back-edges"): New test.
450 lines
16 KiB
Scheme
450 lines
16 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2015 Ludovic Courtès <ludo@gnu.org>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation; either version 3 of the License, or (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (gnu services)
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#:use-module (guix gexp)
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#:use-module (guix monads)
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#:use-module (guix store)
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#:use-module (guix records)
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#:use-module (guix sets)
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#:use-module (guix ui)
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#:use-module (gnu packages base)
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#:use-module (gnu packages bash)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-9)
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#:use-module (srfi srfi-9 gnu)
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#:use-module (srfi srfi-26)
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#:use-module (srfi srfi-34)
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#:use-module (srfi srfi-35)
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#:use-module (ice-9 vlist)
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#:use-module (ice-9 match)
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#:export (service-extension
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service-extension?
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service-type
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service-type?
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service-type-name
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service-type-extensions
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service-type-compose
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service-type-extend
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service
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service?
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service-kind
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service-parameters
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service-back-edges
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fold-services
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service-error?
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missing-target-service-error?
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missing-target-service-error-service
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missing-target-service-error-target-type
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ambiguous-target-service-error?
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ambiguous-target-service-error-service
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ambiguous-target-service-error-target-type
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boot-service-type
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activation-service-type
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activation-service->script
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etc-service-type
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etc-directory
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setuid-program-service-type
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firmware-service-type
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%boot-service
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%activation-service
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etc-service
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file-union)) ;XXX: for lack of a better place
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;;; Comment:
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;;;
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;;; This module defines a broad notion of "service types" and "services."
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;;;
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;;; A service type describe how its instances extend instances of other
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;;; service types. For instance, some services extend the instance of
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;;; ACCOUNT-SERVICE-TYPE by providing it with accounts and groups to create;
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;;; others extend DMD-ROOT-SERVICE-TYPE by passing it instances of
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;;; <dmd-service>.
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;;;
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;;; When applicable, the service type defines how it can itself be extended,
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;;; by providing one procedure to compose extensions, and one procedure to
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;;; extend itself.
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;;;
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;;; A notable service type is BOOT-SERVICE-TYPE, which has a single instance,
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;;; %BOOT-SERVICE. %BOOT-SERVICE constitutes the root of the service DAG. It
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;;; produces the boot script that the initrd loads.
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;;;
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;;; The 'fold-services' procedure can be passed a list of procedures, which it
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;;; "folds" by propagating extensions down the graph; it returns the root
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;;; service after the applying all its extensions.
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;;;
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;;; Code:
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(define-record-type <service-extension>
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(service-extension target compute)
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service-extension?
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(target service-extension-target) ;<service-type>
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(compute service-extension-compute)) ;params -> params
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(define-record-type* <service-type> service-type make-service-type
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service-type?
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(name service-type-name) ;symbol (for debugging)
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;; Things extended by services of this type.
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(extensions service-type-extensions) ;list of <service-extensions>
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;; Given a list of extensions, "compose" them.
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(compose service-type-compose ;list of Any -> Any
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(default #f))
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;; Extend the services' own parameters with the extension composition.
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(extend service-type-extend ;list of Any -> parameters
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(default #f)))
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(define (write-service-type type port)
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(format port "#<service-type ~a ~a>"
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(service-type-name type)
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(number->string (object-address type) 16)))
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(set-record-type-printer! <service-type> write-service-type)
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;; Services of a given type.
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(define-record-type <service>
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(service type parameters)
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service?
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(type service-kind)
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(parameters service-parameters))
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;;;
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;;; Core services.
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;;;
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(define (compute-boot-script mexps)
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(mlet %store-monad ((gexps (sequence %store-monad mexps)))
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(gexp->file "boot"
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#~(begin
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(use-modules (guix build utils))
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;; Clean out /tmp and /var/run.
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;;
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;; XXX This needs to happen before service activations, so
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;; it has to be here, but this also implicitly assumes
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;; that /tmp and /var/run are on the root partition.
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(false-if-exception (delete-file-recursively "/tmp"))
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(false-if-exception (delete-file-recursively "/var/run"))
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(false-if-exception (mkdir "/tmp"))
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(false-if-exception (chmod "/tmp" #o1777))
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(false-if-exception (mkdir "/var/run"))
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(false-if-exception (chmod "/var/run" #o755))
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;; Activate the system and spawn dmd.
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#$@gexps))))
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(define (second-argument a b) b)
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(define boot-service-type
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;; The service of this type is extended by being passed gexps as monadic
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;; values. It aggregates them in a single script, as a monadic value, which
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;; becomes its 'parameters'. It is the only service that extends nothing.
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(service-type (name 'boot)
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(extensions '())
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(compose compute-boot-script)
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(extend second-argument)))
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(define %boot-service
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;; This is the ultimate service, the root of the service DAG.
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(service boot-service-type #t))
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(define* (file-union name files) ;FIXME: Factorize.
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"Return a <computed-file> that builds a directory containing all of FILES.
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Each item in FILES must be a list where the first element is the file name to
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use in the new directory, and the second element is a gexp denoting the target
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file."
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(computed-file name
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#~(begin
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(mkdir #$output)
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(chdir #$output)
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#$@(map (match-lambda
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((target source)
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#~(symlink #$source #$target)))
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files))))
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(define (directory-union name things)
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"Return a directory that is the union of THINGS."
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(match things
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((one)
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;; Only one thing; return it.
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one)
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(_
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(computed-file name
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#~(begin
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(use-modules (guix build union))
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(union-build #$output '#$things))
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#:modules '((guix build union))))))
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(define (modprobe-wrapper)
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"Return a wrapper for the 'modprobe' command that knows where modules live.
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This wrapper is typically invoked by the Linux kernel ('call_modprobe', in
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kernel/kmod.c), a situation where the 'LINUX_MODULE_DIRECTORY' environment
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variable is not set---hence the need for this wrapper."
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(let ((modprobe "/run/current-system/profile/bin/modprobe"))
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(gexp->script "modprobe"
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#~(begin
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(setenv "LINUX_MODULE_DIRECTORY"
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"/run/booted-system/kernel/lib/modules")
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(apply execl #$modprobe
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(cons #$modprobe (cdr (command-line))))))))
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(define* (activation-service->script service)
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"Return as a monadic value the activation script for SERVICE, a service of
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ACTIVATION-SCRIPT-TYPE."
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(activation-script (service-parameters service)))
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(define (activation-script gexps)
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"Return the system's activation script, which evaluates GEXPS."
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(define %modules
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'((gnu build activation)
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(gnu build linux-boot)
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(gnu build linux-modules)
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(gnu build file-systems)
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(guix build utils)
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(guix build syscalls)
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(guix elf)))
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(define (service-activations)
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;; Return the activation scripts for SERVICES.
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(mapm %store-monad
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(cut gexp->file "activate-service" <>)
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gexps))
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(mlet* %store-monad ((actions (service-activations))
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(modules (imported-modules %modules))
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(compiled (compiled-modules %modules))
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(modprobe (modprobe-wrapper)))
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(gexp->file "activate"
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#~(begin
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(eval-when (expand load eval)
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;; Make sure 'use-modules' below succeeds.
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(set! %load-path (cons #$modules %load-path))
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(set! %load-compiled-path
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(cons #$compiled %load-compiled-path)))
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(use-modules (gnu build activation))
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;; Make sure /bin/sh is valid and current.
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(activate-/bin/sh
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(string-append #$(canonical-package bash) "/bin/sh"))
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;; Tell the kernel to use our 'modprobe' command.
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(activate-modprobe #$modprobe)
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;; Let users debug their own processes!
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(activate-ptrace-attach)
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;; Run the services' activation snippets.
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;; TODO: Use 'load-compiled'.
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(for-each primitive-load '#$actions)
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;; Set up /run/current-system.
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(activate-current-system)))))
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(define (gexps->activation-gexp gexps)
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"Return a gexp that runs the activation script containing GEXPS."
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(mlet %store-monad ((script (activation-script gexps)))
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(return #~(primitive-load #$script))))
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(define activation-service-type
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(service-type (name 'activate)
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(extensions
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(list (service-extension boot-service-type
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gexps->activation-gexp)))
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(compose append)
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(extend second-argument)))
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(define %activation-service
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;; The activation service produces the activation script from the gexps it
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;; receives.
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(service activation-service-type #t))
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(define (etc-directory service)
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"Return the directory for SERVICE, a service of type ETC-SERVICE-TYPE."
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(files->etc-directory (service-parameters service)))
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(define (files->etc-directory files)
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(file-union "etc" files))
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(define etc-service-type
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(service-type (name 'etc)
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(extensions
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(list
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(service-extension activation-service-type
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(lambda (files)
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(let ((etc
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(files->etc-directory files)))
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#~(activate-etc #$etc))))))
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(compose concatenate)
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(extend append)))
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(define (etc-service files)
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"Return a new service of ETC-SERVICE-TYPE that populates /etc with FILES.
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FILES must be a list of name/file-like object pairs."
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(service etc-service-type files))
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(define setuid-program-service-type
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(service-type (name 'setuid-program)
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(extensions
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(list (service-extension activation-service-type
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(lambda (programs)
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#~(activate-setuid-programs
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(list #$@programs))))))
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(compose concatenate)
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(extend append)))
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(define (firmware->activation-gexp firmware)
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"Return a gexp to make the packages listed in FIRMWARE loadable by the
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kernel."
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(let ((directory (directory-union "firmware" firmware)))
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;; Tell the kernel where firmware is.
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#~(activate-firmware (string-append #$directory "/lib/firmware"))))
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(define firmware-service-type
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;; The service that collects firmware.
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(service-type (name 'firmware)
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(extensions
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(list (service-extension activation-service-type
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firmware->activation-gexp)))
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(compose concatenate)
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(extend append)))
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;;;
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;;; Service folding.
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;;;
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(define-condition-type &service-error &error
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service-error?)
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(define-condition-type &missing-target-service-error &service-error
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missing-target-service-error?
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(service missing-target-service-error-service)
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(target-type missing-target-service-error-target-type))
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(define-condition-type &ambiguous-target-service-error &service-error
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ambiguous-target-service-error?
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(service ambiguous-target-service-error-service)
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(target-type ambiguous-target-service-error-target-type))
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(define (service-back-edges services)
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"Return a procedure that, when passed a <service>, returns the list of
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<service> objects that depend on it."
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(define (add-edges service edges)
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(define (add-edge extension edges)
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(let ((target-type (service-extension-target extension)))
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(match (filter (lambda (service)
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(eq? (service-kind service) target-type))
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services)
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((target)
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(vhash-consq target service edges))
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(()
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(raise
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(condition (&missing-target-service-error
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(service service)
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(target-type target-type))
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(&message
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(message
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(format #f (_ "no target of type '~a' for service ~s")
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(service-type-name target-type)
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service))))))
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(x
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(raise
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(condition (&ambiguous-target-service-error
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(service service)
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(target-type target-type))
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(&message
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(message
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(format #f
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(_ "more than one target service of type '~a'")
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(service-type-name target-type))))))))))
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(fold add-edge edges (service-type-extensions (service-kind service))))
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(let ((edges (fold add-edges vlist-null services)))
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(lambda (node)
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(reverse (vhash-foldq* cons '() node edges)))))
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(define* (fold-services services #:key (target-type boot-service-type))
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"Fold SERVICES by propagating their extensions down to the root of type
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TARGET-TYPE; return the root service adjusted accordingly."
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(define dependents
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(service-back-edges services))
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(define (matching-extension target)
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(let ((target (service-kind target)))
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(match-lambda
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(($ <service-extension> type)
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(eq? type target)))))
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(define (apply-extension target)
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(lambda (service)
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(match (find (matching-extension target)
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(service-type-extensions (service-kind service)))
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(($ <service-extension> _ compute)
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(compute (service-parameters service))))))
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(match (filter (lambda (service)
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(eq? (service-kind service) target-type))
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services)
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((sink)
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(let loop ((sink sink))
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(let* ((dependents (map loop (dependents sink)))
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(extensions (map (apply-extension sink) dependents))
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(extend (service-type-extend (service-kind sink)))
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(compose (service-type-compose (service-kind sink)))
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(params (service-parameters sink)))
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;; We distinguish COMPOSE and EXTEND because PARAMS typically has a
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;; different type than the elements of EXTENSIONS.
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(if extend
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(service (service-kind sink)
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(extend params (compose extensions)))
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sink))))
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(()
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(raise
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(condition (&missing-target-service-error
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(service #f)
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(target-type target-type))
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(&message
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(message (format #f (_ "service of type '~a' not found")
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(service-type-name target-type)))))))
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(x
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(raise
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(condition (&ambiguous-target-service-error
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(service #f)
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(target-type target-type))
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(&message
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(message
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(format #f
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(_ "more than one target service of type '~a'")
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(service-type-name target-type)))))))))
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;;; services.scm ends here.
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