mirror of
git://git.savannah.gnu.org/guix.git
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2a4309de43
Previously 'fold-services' could end up traversing the same services in the graph several times, which is what this change addresses. The hit rate on the 'add-data-to-store' cache goves from 9% to 8% on "guix system build desktop.tmpl -nd", and the number of lookups in that cache goes from 4458 to 4383. * gnu/services.scm (fold-services): Turn 'loop' into a monadic procedure in %STATE-MONAD and use it to memoize values of visited services.
825 lines
32 KiB
Scheme
825 lines
32 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2015, 2016, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
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;;; Copyright © 2016 Chris Marusich <cmmarusich@gmail.com>
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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 profiles)
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#:use-module (guix discovery)
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#:use-module (guix combinators)
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#:use-module (guix sets)
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#:use-module (guix ui)
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#:use-module ((guix utils) #:select (source-properties->location))
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#:use-module (guix modules)
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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-extension-target
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service-extension-compute
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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-type-default-value
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service-type-description
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service-type-location
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%service-type-path
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fold-service-types
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lookup-service-types
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service
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service?
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service-kind
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service-value
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service-parameters ;deprecated
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simple-service
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modify-services
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service-back-edges
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instantiate-missing-services
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fold-services
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service-error?
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missing-value-service-error?
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missing-value-service-error-type
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missing-value-service-error-location
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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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system-service-type
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boot-service-type
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cleanup-service-type
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activation-service-type
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activation-service->script
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%linux-bare-metal-service
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special-files-service-type
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extra-special-file
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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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profile-service-type
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firmware-service-type
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gc-root-service-type
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%boot-service
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%activation-service
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etc-service))
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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 SHEPHERD-ROOT-SERVICE-TYPE by passing it instances of
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;;; <shepherd-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 SYSTEM-SERVICE-TYPE, which has a single
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;;; instance, which is the root of the service DAG. Its value is the
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;;; derivation that produces the 'system' directory as returned by
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;;; 'operating-system-derivation'.
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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 &no-default-value
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;; Value used to denote service types that have no associated default value.
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'(no default value))
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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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;; Optional default value for instances of this type.
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(default-value service-type-default-value ;Any
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(default &no-default-value))
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;; Meta-data.
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(description service-type-description ;string
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(default #f))
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(location service-type-location ;<location>
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(default (and=> (current-source-location)
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source-properties->location))
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(innate)))
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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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(define %distro-root-directory
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;; Absolute file name of the module hierarchy.
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(dirname (search-path %load-path "guix.scm")))
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(define %service-type-path
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;; Search path for service types.
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(make-parameter `((,%distro-root-directory . "gnu/services")
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(,%distro-root-directory . "gnu/system"))))
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(define (all-service-modules)
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"Return the default set of service modules."
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(cons (resolve-interface '(gnu services))
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(all-modules (%service-type-path)
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#:warn warn-about-load-error)))
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(define* (fold-service-types proc seed
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#:optional
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(modules (all-service-modules)))
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"For each service type exported by one of MODULES, call (PROC RESULT). SEED
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is used as the initial value of RESULT."
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(fold-module-public-variables (lambda (object result)
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(if (service-type? object)
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(proc object result)
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result))
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seed
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modules))
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(define lookup-service-types
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(let ((table
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(delay (fold-service-types (lambda (type result)
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(vhash-consq (service-type-name type)
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type result))
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vlist-null))))
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(lambda (name)
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"Return the list of services with the given NAME (a symbol)."
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(vhash-foldq* cons '() name (force table)))))
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;; Services of a given type.
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(define-record-type <service>
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(make-service type value)
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service?
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(type service-kind)
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(value service-value))
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(define-syntax service
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(syntax-rules ()
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"Return a service instance of TYPE. The service value is VALUE or, if
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omitted, TYPE's default value."
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((_ type value)
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(make-service type value))
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((_ type)
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(%service-with-default-value (current-source-location)
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type))))
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(define (%service-with-default-value location type)
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"Return a instance of service type TYPE with its default value, if any. If
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TYPE does not have a default value, an error is raised."
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;; TODO: Currently this is a run-time error but with a little bit macrology
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;; we could turn it into an expansion-time error.
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(let ((default (service-type-default-value type)))
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(if (eq? default &no-default-value)
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(let ((location (source-properties->location location)))
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(raise
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(condition
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(&missing-value-service-error (type type) (location location))
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(&message
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(message (format #f (G_ "~a: no value specified \
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for service of type '~a'")
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(location->string location)
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(service-type-name type)))))))
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(service type default))))
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(define-condition-type &service-error &error
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service-error?)
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(define-condition-type &missing-value-service-error &service-error
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missing-value-service-error?
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(type missing-value-service-error-type)
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(location missing-value-service-error-location))
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;;;
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;;; Helpers.
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;;;
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(define service-parameters
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;; Deprecated alias.
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service-value)
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(define (simple-service name target value)
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"Return a service that extends TARGET with VALUE. This works by creating a
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singleton service type NAME, of which the returned service is an instance."
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(let* ((extension (service-extension target identity))
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(type (service-type (name name)
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(extensions (list extension)))))
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(service type value)))
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(define-syntax %modify-service
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(syntax-rules (=>)
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((_ service)
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service)
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((_ svc (kind param => exp ...) clauses ...)
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(if (eq? (service-kind svc) kind)
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(let ((param (service-value svc)))
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(service (service-kind svc)
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(begin exp ...)))
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(%modify-service svc clauses ...)))))
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(define-syntax modify-services
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(syntax-rules ()
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"Modify the services listed in SERVICES according to CLAUSES and return
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the resulting list of services. Each clause must have the form:
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(TYPE VARIABLE => BODY)
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where TYPE is a service type, such as 'guix-service-type', and VARIABLE is an
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identifier that is bound within BODY to the value of the service of that
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TYPE. Consider this example:
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(modify-services %base-services
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(guix-service-type config =>
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(guix-configuration
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(inherit config)
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(use-substitutes? #f)
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(extra-options '(\"--gc-keep-derivations\"))))
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(mingetty-service-type config =>
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(mingetty-configuration
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(inherit config)
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(motd (plain-file \"motd\" \"Hi there!\")))))
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It changes the configuration of the GUIX-SERVICE-TYPE instance, and that of
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all the MINGETTY-SERVICE-TYPE instances.
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This is a shorthand for (map (lambda (svc) ...) %base-services)."
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((_ services clauses ...)
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(map (lambda (service)
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(%modify-service service clauses ...))
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services))))
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;;;
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;;; Core services.
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;;;
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(define (system-derivation mentries mextensions)
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"Return as a monadic value the derivation of the 'system' directory
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containing the given entries."
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(mlet %store-monad ((entries mentries)
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(extensions (sequence %store-monad mextensions)))
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(lower-object
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(file-union "system"
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(append entries (concatenate extensions))))))
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(define system-service-type
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;; This is the ultimate service type, the root of the service DAG. The
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;; service of this type is extended by monadic name/item pairs. These items
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;; end up in the "system directory" as returned by
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;; 'operating-system-derivation'.
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(service-type (name 'system)
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(extensions '())
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(compose identity)
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(extend system-derivation)
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(description
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"Build the operating system top-level directory, which in
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turn refers to everything the operating system needs: its kernel, initrd,
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system profile, boot script, and so on.")))
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(define (compute-boot-script _ gexps)
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;; Reverse GEXPS so that extensions appear in the boot script in the right
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;; order. That is, user extensions would come first, and extensions added
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;; by 'essential-services' (e.g., running shepherd) are guaranteed to come
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;; last.
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(gexp->file "boot"
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;; Clean up and activate the system, then spawn shepherd.
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#~(begin #$@(reverse gexps))))
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(define (boot-script-entry mboot)
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"Return, as a monadic value, an entry for the boot script in the system
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directory."
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(mlet %store-monad ((boot mboot))
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(return `(("boot" ,boot)))))
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(define boot-service-type
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;; The service of this type is extended by being passed gexps. It
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;; aggregates them in a single script, as a monadic value, which becomes its
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;; value.
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(service-type (name 'boot)
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(extensions
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(list (service-extension system-service-type
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boot-script-entry)))
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(compose identity)
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(extend compute-boot-script)
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(description
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"Produce the operating system's boot script, which is spawned
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by the initrd once the root file system is mounted.")))
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(define %boot-service
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;; The service that produces the boot script.
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(service boot-service-type #t))
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(define (cleanup-gexp _)
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"Return a gexp to clean up /tmp and similar places upon boot."
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(with-imported-modules '((guix build utils))
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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 it
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;; has to be here, but this also implicitly assumes that /tmp
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;; and /var/run are on the root partition.
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(letrec-syntax ((fail-safe (syntax-rules ()
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((_ exp rest ...)
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(begin
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(catch 'system-error
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(lambda () exp)
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(const #f))
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(fail-safe rest ...)))
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((_)
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#t))))
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;; Ignore I/O errors so the system can boot.
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(fail-safe
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;; Remove stale Shadow lock files as they would lead to
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;; failures of 'useradd' & co.
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(delete-file "/etc/group.lock")
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(delete-file "/etc/passwd.lock")
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(delete-file "/etc/.pwd.lock") ;from 'lckpwdf'
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;; Force file names to be decoded as UTF-8. See
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;; <https://bugs.gnu.org/26353>.
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(setenv "GUIX_LOCPATH"
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#+(file-append glibc-utf8-locales "/lib/locale"))
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(setlocale LC_CTYPE "en_US.utf8")
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(delete-file-recursively "/tmp")
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(delete-file-recursively "/var/run")
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(mkdir "/tmp")
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(chmod "/tmp" #o1777)
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(mkdir "/var/run")
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(chmod "/var/run" #o755)
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(delete-file-recursively "/run/udev/watch.old"))))))
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(define cleanup-service-type
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;; Service that cleans things up in /tmp and similar.
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(service-type (name 'cleanup)
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(extensions
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(list (service-extension boot-service-type
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cleanup-gexp)))
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(description
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"Delete files from @file{/tmp}, @file{/var/run}, and other
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temporary locations at boot time.")))
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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-value 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 actions
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(map (cut program-file "activate-service.scm" <>) gexps))
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(program-file "activate.scm"
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(with-imported-modules (source-module-closure
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'((gnu build activation)
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(guix build utils)))
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#~(begin
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(use-modules (gnu build activation)
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(guix build utils))
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;; Make sure the user accounting database exists. If it
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;; does not exist, 'setutxent' does not create it and
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;; thus there is no accounting at all.
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(close-port (open-file "/var/run/utmpx" "a0"))
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;; Same for 'wtmp', which is populated by mingetty et
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;; al.
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(mkdir-p "/var/log")
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(close-port (open-file "/var/log/wtmp" "a0"))
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;; Set up /run/current-system. Among other things this
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;; sets up locales, which the activation snippets
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;; executed below may expect.
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(activate-current-system)
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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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(define (gexps->activation-gexp gexps)
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"Return a gexp that runs the activation script containing GEXPS."
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#~(primitive-load #$(activation-script gexps)))
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(define (second-argument a b) b)
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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 identity)
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(extend second-argument)
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(description
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"Run @dfn{activation} code at boot time and upon
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@command{guix system reconfigure} completion.")))
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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 %modprobe-wrapper
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;; Wrapper for the 'modprobe' command that knows where modules live.
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;;
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;; This wrapper is typically invoked by the Linux kernel ('call_modprobe',
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;; in kernel/kmod.c), a situation where the 'LINUX_MODULE_DIRECTORY'
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;; environment 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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(program-file "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 #$modprobe (cdr (command-line))))))))
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(define %linux-kernel-activation
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;; Activation of the Linux kernel running on the bare metal (as opposed to
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;; running in a container.)
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#~(begin
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;; Tell the kernel to use our 'modprobe' command.
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||
(activate-modprobe #$%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 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 '#$files)))))
|
||
(compose concatenate)
|
||
(extend append)
|
||
(description
|
||
"Add special files to the root file system---e.g.,
|
||
@file{/usr/bin/env}.")))
|
||
|
||
(define (extra-special-file file target)
|
||
"Use TARGET as the \"special file\" FILE. For example, TARGET might be
|
||
(file-append coreutils \"/bin/env\")
|
||
and FILE could be \"/usr/bin/env\"."
|
||
(simple-service (string->symbol (string-append "special-file-" file))
|
||
special-files-service-type
|
||
`((,file ,target))))
|
||
|
||
(define (etc-directory service)
|
||
"Return the directory for SERVICE, a service of type ETC-SERVICE-TYPE."
|
||
(files->etc-directory (service-value service)))
|
||
|
||
(define (files->etc-directory files)
|
||
(file-union "etc" files))
|
||
|
||
(define (etc-entry files)
|
||
"Return an entry for the /etc directory consisting of FILES in the system
|
||
directory."
|
||
(with-monad %store-monad
|
||
(return `(("etc" ,(files->etc-directory files))))))
|
||
|
||
(define etc-service-type
|
||
(service-type (name 'etc)
|
||
(extensions
|
||
(list
|
||
(service-extension activation-service-type
|
||
(lambda (files)
|
||
(let ((etc
|
||
(files->etc-directory files)))
|
||
#~(activate-etc #$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 #$@programs))))))
|
||
(compose concatenate)
|
||
(extend append)
|
||
(description
|
||
"Populate @file{/run/setuid-programs} with the specified
|
||
executables, making them setuid-root.")))
|
||
|
||
(define (packages->profile-entry packages)
|
||
"Return a system entry for the profile containing PACKAGES."
|
||
(mlet %store-monad ((profile (profile-derivation
|
||
(packages->manifest
|
||
(delete-duplicates packages eq?)))))
|
||
(return `(("profile" ,profile)))))
|
||
|
||
(define profile-service-type
|
||
;; The service that populates the system's profile---i.e.,
|
||
;; /run/current-system/profile. It is extended by package lists.
|
||
(service-type (name 'profile)
|
||
(extensions
|
||
(list (service-extension system-service-type
|
||
packages->profile-entry)))
|
||
(compose concatenate)
|
||
(extend append)
|
||
(description
|
||
"This is the @dfn{system profile}, available as
|
||
@file{/run/current-system/profile}. It contains packages that the sysadmin
|
||
wants to be globally available to all the system users.")))
|
||
|
||
(define (firmware->activation-gexp firmware)
|
||
"Return a gexp to make the packages listed in FIRMWARE loadable by the
|
||
kernel."
|
||
(let ((directory (directory-union "firmware" firmware)))
|
||
;; Tell the kernel where firmware is.
|
||
#~(activate-firmware (string-append #$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
|
||
(condition (&missing-target-service-error
|
||
(service #f)
|
||
(target-type target-type))
|
||
(&message
|
||
(message (format #f (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.
|