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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/guix.texi | 87 |
1 files changed, 54 insertions, 33 deletions
diff --git a/doc/guix.texi b/doc/guix.texi index b3ba5ce4fb..112c32939d 100644 --- a/doc/guix.texi +++ b/doc/guix.texi @@ -16,8 +16,9 @@ Copyright @copyright{} 2013 Nikita Karetnikov@* Copyright @copyright{} 2015, 2016 Mathieu Lirzin@* Copyright @copyright{} 2014 Pierre-Antoine Rault@* Copyright @copyright{} 2015 Taylan Ulrich Bayırlı/Kammer@* -Copyright @copyright{} 2015, 2016 Leo Famulari -Copyright @copyright{} 2016 Ben Woodcroft +Copyright @copyright{} 2015, 2016 Leo Famulari@* +Copyright @copyright{} 2016 Ben Woodcroft@* +Copyright @copyright{} 2016 Chris Marusich Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or @@ -6158,28 +6159,42 @@ 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}: +customize them. To do this, use @code{modify-services} (@pxref{Service +Reference, @code{modify-services}}) to modify the list. + +For example, suppose you want to modify @code{guix-daemon} and Mingetty +(the console log-in) in the @var{%base-services} list (@pxref{Base +Services, @code{%base-services}}). To do that, you can write the +following in your operating system declaration: @lisp -(modify-services %base-services - (guix-service-type config => - (guix-configuration - (inherit config) - (use-substitutes? #f) - (extra-options '("--gc-keep-outputs")))) - (mingetty-service-type config => - (mingetty-configuration - (inherit config) - (motd (plain-file "motd" "Hi there!"))))) +(define %my-services + ;; My very own list of services. + (modify-services %base-services + (guix-service-type config => + (guix-configuration + (inherit config) + (use-substitutes? #f) + (extra-options '("--gc-keep-derivations")))) + (mingetty-service-type config => + (mingetty-configuration + (inherit config) + (motd (plain-file "motd" "Howdy!")))))) + +(operating-system + ;; @dots{} + (services %my-services)) @end lisp -@noindent -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. +This changes the configuration---i.e., the service parameters---of the +@code{guix-service-type} instance, and that of all the +@code{mingetty-service-type} instances in the @var{%base-services} list. +Observe how this is accomplished: first, we arrange for the original +configuration to be bound to the identifier @code{config} in the +@var{body}, and then we write the @var{body} so that it evaluates to the +desired configuration. In particular, notice how we use @code{inherit} +to create a new configuration which has the same values as the old +configuration, but with a few modifications. The configuration for a typical ``desktop'' usage, with the X11 display server, a desktop environment, network management, power management, and @@ -10035,11 +10050,12 @@ Here is an example of how a service is created and manipulated: 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. +@var{%base-services} (@pxref{Base Services, @code{%base-services}}). It +evalutes to a list of 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{} @@ -10051,16 +10067,21 @@ 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. +where @var{type} is a service type---e.g., +@code{guix-service-type}---and @var{variable} is an identifier that is +bound within the @var{body} to the service parameters---e.g., a +@code{guix-configuration} instance---of the original service of that +@var{type}. -This is a shorthand for: +The @var{body} should evaluate to the new service parameters, which will +be used to configure the new service. This new service will replace the +original in the resulting list. Because a service's service parameters +are created using @code{define-record-type*}, you can write a succint +@var{body} that evaluates to the new service parameters by using the +@code{inherit} feature that @code{define-record-type*} provides. + +@xref{Using the Configuration System} for example usage. -@example -(map (lambda (service) @dots{}) @var{services}) -@end example @end deffn Next comes the programming interface for service types. This is |