services: Add Shepherd 'configuration' action to various services.

* gnu/services/avahi.scm (avahi-shepherd-service): Add 'actions' field.
* gnu/services/base.scm (nscd-actions): Add call to
'shepherd-configuration-action'.
* gnu/services/desktop.scm (upower-shepherd-service): Add 'actions'
field.
(elogind-shepherd-service): Likewise.
* gnu/services/dict.scm (dicod-shepherd-service): Likewise.
* gnu/services/networking.scm (openntpd-shepherd-service): Likewise.
(tor-shepherd-service): Likewise.
* gnu/services/ssh.scm (openssh-shepherd-service): Likewise.
* gnu/services/web.scm (nginx-shepherd-service): Likewise.
* gnu/services/xorg.scm (gdm-shepherd-service): Likewise.
* gnu/tests/base.scm (run-basic-test)["nscd configuration action"]: New
test.
* doc/guix.texi (Services): Document it.

1 files changed, 11 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 9dddaf4f2f..eaecfd0daa 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -17654,6 +17654,17 @@ Service xorg-server has been stopped.
 Service xorg-server has been started.
 @end example
 
+@cindex configuration, action for shepherd services
+@cindex configuration file, of a shepherd service
+For some services, @command{herd configuration} returns the name of the
+service's configuration file, which can be handy to inspect its
+configuration:
+
+@example
+# herd configuration sshd
+/gnu/store/@dots{}-sshd_config
+@end example
+
 The following sections document the available services, starting with
 the core services, that may be used in an @code{operating-system}
 declaration.