services: syslog: Use syslog-configuration.

* gnu/services/base.scm (<syslog-configuration>): New variable.
  (syslog-service-type): Use <syslog-configuration>.
  (syslog-service): Use <syslog-configuration>.
* gnu/tests/base.scm (%avahi-os): Use <syslog-configuration>.
* doc/guix.texi (syslog-configuration-type): Add @deftp.
  (syslog-service): Update @deffn.

doc/guix.texi

@@ -7719,12 +7719,23 @@ privacy---often the result of host name lookups is in local cache, so
 external name servers do not even need to be queried.
 @end defvr
 
+@anchor{syslog-configuration-type}
+@deftp {Data Type} syslog-configuration
+This data type represents the configuration of the syslog daemon.
 
-@deffn {Scheme Procedure} syslog-service @
-             [#:config-file @var{%default-syslog.conf}]
-Return a service that runs @command{syslogd}.  If the configuration file
-name @var{config-file} is not specified, use some reasonable default
-settings.
+@table @asis
+@item @code{syslogd} (default: @code{#~(string-append #$inetutils "/libexec/syslogd")})
+The syslog daemon to use.
+
+@item @code{config-file} (default: @code{%default-syslog.conf})
+The syslog configuration file to use.
+
+@end table
+@end deftp
+
+@anchor{syslog-service}
+@deffn {Scheme Procedure} syslog-service @var{config}
+Return a service that runs a syslog daemon according to @var{config}.
 
 @xref{syslogd invocation,,, inetutils, GNU Inetutils}, for more
 information on the configuration file syntax.

gnu/services/base.scm

@@ -82,6 +82,9 @@ (define-module (gnu services base)
 
             nscd-service-type
             nscd-service
+
+            syslog-configuration
+            syslog-configuration?
             syslog-service
             syslog-service-type
             %default-syslog.conf
@@ -885,17 +888,27 @@ (define* (nscd-service #:optional (config %nscd-default-configuration))
 Service Switch}, for an example."
   (service nscd-service-type config))
 
+
+(define-record-type* <syslog-configuration>
+  syslog-configuration  make-syslog-configuration
+  syslog-configuration?
+  (syslogd              syslog-configuration-syslogd
+                        (default #~(string-append #$inetutils "/libexec/syslogd")))
+  (config-file          syslog-configuration-config-file
+                        (default %default-syslog.conf)))
+
 (define syslog-service-type
   (shepherd-service-type
    'syslog
-   (lambda (config-file)
+   (lambda (config)
      (shepherd-service
       (documentation "Run the syslog daemon (syslogd).")
       (provision '(syslogd))
       (requirement '(user-processes))
       (start #~(make-forkexec-constructor
-                (list (string-append #$inetutils "/libexec/syslogd")
-                      "--no-detach" "--rcfile" #$config-file)))
+                (list #$(syslog-configuration-syslogd config)
+                      "--no-detach"
+                      "--rcfile" #$(syslog-configuration-config-file config))))
       (stop #~(make-kill-destructor))))))
 
 ;; Snippet adapted from the GNU inetutils manual.
@@ -921,14 +934,14 @@ (define %default-syslog.conf
      mail.*                                  /var/log/maillog
 "))
 
-(define* (syslog-service #:key (config-file %default-syslog.conf))
-  "Return a service that runs @command{syslogd}.  If configuration file
-name @var{config-file} is not specified, use some reasonable default
-settings.
+(define* (syslog-service #:optional (config (syslog-configuration)))
+  "Return a service that runs @command{syslogd} and takes
+@var{<syslog-configuration>} as a parameter.
 
 @xref{syslogd invocation,,, inetutils, GNU Inetutils}, for more
 information on the configuration file syntax."
-  (service syslog-service-type config-file))
+  (service syslog-service-type config))
+
 
 (define pam-limits-service-type
   (let ((security-limits

gnu/tests/base.scm

@@ -384,9 +384,12 @@ (define %avahi-os
                                               (log-file "/dev/console")))
                        (syslog-service-type config
                                             =>
+                                            (syslog-configuration
+                                             (inherit config)
+                                             (config-file
                                               (plain-file
                                                "syslog.conf"
-                                             "*.* /dev/console\n")))))))
+                                               "*.* /dev/console\n")))))))))
 
 (define (run-nss-mdns-test)
   ;; Test resolution of '.local' names via libc.  Start the marionette service