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services: Add 'provenance-service-type'.

* gnu/services.scm (object->pretty-string)
(channel->code, channel->sexp, provenance-file)
(provenance-entry): New procedures.
(provenance-service-type): New variable.
* gnu/system.scm (operating-system-with-provenance): New procedure.
* doc/guix.texi (Service Reference): Document 'provenance-service-type'.
gn-latest-20200428
Ludovic Courtès 2 years ago
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  1. 44
      doc/guix.texi
  2. 87
      gnu/services.scm
  3. 10
      gnu/system.scm

44
doc/guix.texi

@ -27043,6 +27043,50 @@ programs under @file{/run/current-system/profile}. Other services can
extend it by passing it lists of packages to add to the system profile.
@end defvr
@cindex provenance tracking, of the operating system
@defvr {Scheme Variable} provenance-service-type
This is the type of the service that records @dfn{provenance meta-data}
in the system itself. It creates several files under
@file{/run/current-system}:
@table @file
@item channels.scm
This is a ``channel file'' that can be passed to @command{guix pull -C}
or @command{guix time-machine -C}, and which describes the channels used
to build the system, if that information was available
(@pxref{Channels}).
@item configuration.scm
This is the file that was passed as the value for this
@code{provenance-service-type} service. By default, @command{guix
system reconfigure} automatically passes the OS configuration file it
received on the command line.
@item provenance
This contains the same information as the two other files but in a
format that is more readily processable.
@end table
In general, these two pieces of information (channels and configuration
file) are enough to reproduce the operating system ``from source''.
@quotation Caveats
This information is necessary to rebuild your operating system, but it
is not always sufficient. In particular, @file{configuration.scm}
itself is insufficient if it is not self-contained---if it refers to
external Guile modules or to extra files. If you want
@file{configuration.scm} to be self-contained, we recommend that modules
or files it refers to be part of a channel.
Besides, provenance meta-data is ``silent'' in the sense that it does
not change the bits contained in your system, @emph{except for the
meta-data bits themselves}. Two different OS configurations or sets of
channels can lead to the same system, bit-for-bit; when
@code{provenance-service-type} is used, these two systems will have
different meta-data and thus different store file names, which makes
comparison less trivial.
@end quotation
@end defvr
@node Shepherd Services
@subsection Shepherd Services

87
gnu/services.scm

@ -25,6 +25,8 @@
#: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 utils) #:select (source-properties->location))
@ -39,6 +41,7 @@
#: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
@ -82,6 +85,7 @@
ambiguous-target-service-error-target-type
system-service-type
provenance-service-type
boot-service-type
cleanup-service-type
activation-service-type
@ -370,6 +374,89 @@ by the initrd once the root file system is mounted.")))
;; 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."
`(channel (name ',(channel-name channel))
(url ,(channel-url channel))
(branch ,(channel-branch channel))
(commit ,(channel-commit channel))))
(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."
`(channel (name ,(channel-name channel))
(url ,(channel-url channel))
(branch ,(channel-branch channel))
(commit ,(channel-commit channel))))
(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)
(local-file 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.")))
;;;
;;; Cleanup.
;;;
(define (cleanup-gexp _)
"Return a gexp to clean up /tmp and similar places upon boot."
(with-imported-modules '((guix build utils))

10
gnu/system.scm

@ -110,6 +110,7 @@
system-linux-image-file-name
operating-system-with-gc-roots
operating-system-with-provenance
boot-parameters
boot-parameters?
@ -540,6 +541,15 @@ bookkeeping."
gc-root-service-type roots)
(operating-system-user-services os)))))
(define* (operating-system-with-provenance os #:optional config-file)
"Return a variant of OS that stores its own provenance information,
including CONFIG-FILE, if available. This is achieved by adding an instance
of PROVENANCE-SERVICE-TYPE to its services."
(operating-system
(inherit os)
(services (cons (service provenance-service-type config-file)
(operating-system-user-services os)))))
;;;
;;; /etc.

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