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services: Add 'modify-services'.

* gnu/services.scm (%modify-service, modify-services): New macros.
* gnu/services/base.scm (mingetty-service-type, guix-service-type):
* emacs/guix-devel.el (guix-devel-keywords): Add 'modify-services'.
  Ditto in 'guix-devel-scheme-indent' call.
* doc/guix.texi (Using the Configuration System): Give an example of
  (Service Reference): Document it.
Ludovic Courtès 5 years ago
5 changed files with 114 additions and 6 deletions
  1. +1
  2. +67
  3. +2
  4. +42
  5. +2

+ 1
- 0
.dir-locals.el View File

@@ -23,6 +23,7 @@
(eval . (put 'lambda* 'scheme-indent-function 1))
(eval . (put 'substitute* 'scheme-indent-function 1))
(eval . (put 'modify-phases 'scheme-indent-function 1))
(eval . (put 'modify-services 'scheme-indent-function 1))
(eval . (put 'with-directory-excursion 'scheme-indent-function 1))
(eval . (put 'package 'scheme-indent-function 0))
(eval . (put 'origin 'scheme-indent-function 0))

+ 67
- 6
doc/guix.texi View File

@@ -5363,16 +5363,40 @@ The @code{services} field lists @dfn{system services} to be made
available when the system starts (@pxref{Services}).
The @code{operating-system} declaration above specifies that, in
addition to the basic services, we want the @command{lshd} secure shell
daemon listening on port 2222, and allowing remote @code{root} logins
(@pxref{Invoking lshd,,, lsh, GNU lsh Manual}). Under the hood,
daemon listening on port 2222 (@pxref{Networking Services,
@code{lsh-service}}). Under the hood,
@code{lsh-service} arranges so that @code{lshd} is started with the
right command-line options, possibly with supporting configuration files
generated as needed (@pxref{Defining Services}). @xref{operating-system
Reference}, for details about the available @code{operating-system}
generated as needed (@pxref{Defining Services}).

@cindex customization, of services
@findex modify-services
Occasionally, instead of using the base services as is, you will want to
customize them. For instance, to change the configuration of
@code{guix-daemon} and Mingetty (the console log-in), you may write the
following instead of @var{%base-services}:

(modify-services %base-services
(guix-service-type config =>
(inherit config)
(use-substitutes? #f)
(extra-options '("--gc-keep-outputs"))))
(mingetty-service-type config =>
(inherit config)
(motd (plain-file "motd" "Hi there!")))))
@end lisp

The effect here is to change the options passed to @command{guix-daemon}
when it is started, as well as the ``message of the day'' that appears
when logging in at the console. @xref{Service Reference,
@code{modify-services}}, for more on that.

The configuration for a typical ``desktop'' usage, with the X11 display
server, a desktop environment, network management, an SSH server, and
server, a desktop environment, network management, power management, and
more, would look like this:

@@ -5382,6 +5406,8 @@ more, would look like this:
@xref{Desktop Services}, for the exact list of services provided by
@var{%desktop-services}. @xref{X.509 Certificates}, for background
information about the @code{nss-certs} package that is used here.
@xref{operating-system Reference}, for details about all the available
@code{operating-system} fields.

Assuming the above snippet is stored in the @file{my-system-config.scm}
file, the @command{guix system reconfigure my-system-config.scm} command
@@ -7539,6 +7565,41 @@ Here is an example of how a service is created and manipulated:
@result{} #t
@end example

The @code{modify-services} form provides a handy way to change the
parameters of some of the services of a list such as
@var{%base-services} (@pxref{Base Services, @code{%base-services}}). Of
course, you could always use standard list combinators such as
@code{map} and @code{fold} to do that (@pxref{SRFI-1, List Library,,
guile, GNU Guile Reference Manual}); @code{modify-services} simply
provides a more concise form for this common pattern.

@deffn {Scheme Syntax} modify-services @var{services} @
(@var{type} @var{variable} => @var{body}) @dots{}

Modify the services listed in @var{services} according to the given
clauses. Each clause has the form:

(@var{type} @var{variable} => @var{body})
@end example

where @var{type} is a service type, such as @var{guix-service-type}, and
@var{variable} is an identifier that is bound within @var{body} to the
value of the service of that @var{type}. @xref{Using the Configuration
System}, for an example.

This is a shorthand for:

(map (lambda (service) @dots{}) @var{services})
@end example
@end deffn

Next comes the programming interface for service types. This is
something you want to know when writing new service definitions, but not
necessarily when simply looking for ways to customize your
@code{operating-system} declaration.

@deftp {Data Type} service-type
@cindex service type
This is the representation of a @dfn{service type} (@pxref{Service Types

+ 2
- 0
emacs/guix-devel.el View File

@@ -198,6 +198,7 @@ to find 'modify-phases' keywords."
@@ -288,6 +289,7 @@ Each rule should have a form (SYMBOL VALUE). See `put' for details."
(mlet 2)
(mlet* 2)
(modify-phases 1)
(modify-services 1)
(munless 1)
(mwhen 1)
(operating-system 0)

+ 42
- 0
gnu/services.scm View File

@@ -48,6 +48,7 @@


@@ -133,6 +134,47 @@
(parameters service-parameters))

(define-syntax %modify-service
(syntax-rules (=>)
((_ service)
((_ svc (kind param => exp ...) clauses ...)
(if (eq? (service-kind svc) kind)
(let ((param (service-parameters 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. Each clause
must have the form:


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 =>
(inherit config)
(use-substitutes? #f)
(extra-options '(\"--gc-keep-derivations\"))))
(mingetty-service-type config =>
(inherit config)
(motd (plain-file \"motd\" \"Hi there!\")))))

It changes the configuration of the GUIX-SERVICE-TYPE instance, and that of
all the MINGETTY-SERVICE-TYPE instances.

This is a shorthand for (map (lambda (svc) ...) %base-services)."
((_ services clauses ...)
(map (lambda (service)
(%modify-service service clauses ...))


+ 2
- 0
gnu/services/base.scm View File

@@ -57,6 +57,7 @@

@@ -74,6 +75,7 @@