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authorLudovic Courtès <ludo@gnu.org>2015-04-12 22:34:47 +0200
committerLudovic Courtès <ludo@gnu.org>2015-04-12 22:34:47 +0200
commit4c9050c63d707222730fc6112415f4324e0c7c37 (patch)
tree008ae5e139c9317c983b4dda90f0064156799d61 /doc
parent99af4996ea4822b2da884bd51539b8a6e9863f99 (diff)
downloadguix-4c9050c63d707222730fc6112415f4324e0c7c37.tar
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doc: Add example showing how to customize 'nscd-service'.
* doc/guix.texi (Name Service Switch): Add link to nss-mdns. Add example show how to pass #:name-services to 'nscd-service'. (Base Services): Add link from 'nscd-service' to the above. * gnu/services/base.scm (nscd-service): Update docstring accordingly.
Diffstat (limited to 'doc')
-rw-r--r--doc/guix.texi38
1 files changed, 35 insertions, 3 deletions
diff --git a/doc/guix.texi b/doc/guix.texi
index c0af4cb722..872caa8bf0 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -4531,7 +4531,8 @@ the ``message of the day''.
Return a service that runs libc's name service cache daemon (nscd) with
the given @var{config}---an @code{<nscd-configuration>} object.
Optionally, @code{#:name-services} is a list of packages that provide
-name service switch (NSS) modules needed by nscd.
+name service switch (NSS) modules needed by nscd. @xref{Name Service
+Switch}, for an example.
@end deffn
@defvr {Scheme Variable} %nscd-default-configuration
@@ -4898,9 +4899,12 @@ next method in the list. The NSS configuration is given in the
@code{name-service-switch} field of @code{operating-system} declarations
(@pxref{operating-system Reference, @code{name-service-switch}}).
-@c See <http://0pointer.de/lennart/projects/nss-mdns/>.
+@cindex nss-mdns
+@cindex .local, host name lookup
As an example, the declaration below configures the NSS to use the
-@code{nss-mdns} back-end for host name lookups:
+@uref{http://0pointer.de/lennart/projects/nss-mdns/, @code{nss-mdns}
+back-end}, which supports host name lookups over multicast DNS (mDNS)
+for host names ending in @code{.local}:
@example
(name-service-switch
@@ -4926,6 +4930,34 @@ As an example, the declaration below configures the NSS to use the
(name "mdns")))))
@end example
+Note that, in this case, in addition to setting the
+@code{name-service-switch} of the @code{operating-system} declaration,
+@code{nscd-service} must be told where to find the @code{nss-mdns}
+shared library (@pxref{Base Services, @code{nscd-service}}). Since the
+@code{nscd} service is part of @var{%base-services}, you may want to
+customize it by adding this snippet in the operating system
+configuration file:
+
+@example
+(use-modules (guix) (gnu))
+
+(define %my-base-services
+ ;; Replace the default nscd service with one that knows
+ ;; about nss-mdns.
+ (map (lambda (mservice)
+ ;; "Bind" the MSERVICE monadic value to inspect it.
+ (mlet %store-monad ((service mservice))
+ (if (member 'nscd (service-provision service))
+ (nscd-service (nscd-configuration)
+ #:name-services (list nss-mdns))
+ mservice)))
+ %base-services))
+@end example
+
+@noindent
+@dots{} and then refer to @var{%my-base-services} instead of
+@var{%base-services} in the @code{operating-system} declaration.
+
The reference for name service switch configuration is given below. It
is a direct mapping of the C library's configuration file format, so
please refer to the C library manual for more information (@pxref{NSS