services: dbus: Add a VERBOSE? configuration option.

* gnu/services/dbus.scm (<dbus-configuration>)[verbose?]: New field.
(dbus-shepherd-service): Use it.
(dbus-service)[verbose?]: Add argument and update doc.
* doc/guix.texi (Desktop Services): Document it.

2 files changed, 24 insertions, 7 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 967145a627..4c2c856c79 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -21767,9 +21767,14 @@ The actual service definitions included in @code{%desktop-services} and
 provided by @code{(gnu services dbus)} and @code{(gnu services desktop)}
 are described below.
 
-@deffn {Scheme Procedure} dbus-service [#:dbus @var{dbus}] [#:services '()]
+@deffn {Scheme Procedure} dbus-service [#:dbus @var{dbus}] [#:services '()] @
+                                       [#:verbose?]
 Return a service that runs the ``system bus'', using @var{dbus}, with
-support for @var{services}.
+support for @var{services}.  When @var{verbose?} is true, it causes the
+@samp{DBUS_VERBOSE} environment variable to be set to @samp{1}; a
+verbose-enabled D-Bus package such as @code{dbus-verbose} should be
+provided as @var{dbus} in this scenario.  The verbose output is logged
+to @file{/var/log/dbus-daemon.log}.
 
 @uref{https://dbus.freedesktop.org/, D-Bus} is an inter-process communication
 facility.  Its system bus is used to allow system services to communicate
diff --git a/gnu/services/dbus.scm b/gnu/services/dbus.scm
index ef6b82c572..52cb1e3a51 100644
--- a/gnu/services/dbus.scm
+++ b/gnu/services/dbus.scm
@@ -53,7 +53,9 @@
   (dbus      dbus-configuration-dbus              ;file-like
              (default dbus))
   (services  dbus-configuration-services          ;list of <package>
-             (default '())))
+             (default '()))
+  (verbose?  dbus-configuration-verbose?          ;boolean
+             (default #f)))
 
 (define (system-service-directory services)
   "Return the system service directory, containing @code{.service} files for
@@ -191,7 +193,7 @@ includes the @code{etc/dbus-1/system.d} directories of each package listed in
 
 (define dbus-shepherd-service
   (match-lambda
-    (($ <dbus-configuration> dbus)
+    (($ <dbus-configuration> dbus _ verbose?)
      (list (shepherd-service
             (documentation "Run the D-Bus system daemon.")
             (provision '(dbus-system))
@@ -199,6 +201,12 @@ includes the @code{etc/dbus-1/system.d} directories of each package listed in
             (start #~(make-forkexec-constructor
                       (list (string-append #$dbus "/bin/dbus-daemon")
                             "--nofork" "--system" "--syslog-only")
+                      #$@(if verbose?
+                             ;; Since the verbose output goes to the console,
+                             ;; not syslog, add a log file to capture it.
+                             '(#:environment-variables '("DBUS_VERBOSE=1")
+                               #:log-file "/var/log/dbus-daemon.log")
+                             '())
                       #:pid-file "/var/run/dbus/pid"))
             (stop #~(make-kill-destructor)))))))
 
@@ -234,9 +242,12 @@ includes the @code{etc/dbus-1/system.d} directories of each package listed in
 bus.  It allows programs and daemons to communicate and is also responsible
 for spawning (@dfn{activating}) D-Bus services on demand.")))
 
-(define* (dbus-service #:key (dbus dbus) (services '()))
+(define* (dbus-service #:key (dbus dbus) (services '()) verbose?)
   "Return a service that runs the \"system bus\", using @var{dbus}, with
-support for @var{services}.
+support for @var{services}.  When @var{verbose?} is true, it causes the
+@samp{DBUS_VERBOSE} environment variable to be set to @samp{1}; a
+verbose-enabled D-Bus package such as @code{dbus-verbose} should be provided
+as @var{dbus} in this scenario.
 
 @uref{http://dbus.freedesktop.org/, D-Bus} is an inter-process communication
 facility.  Its system bus is used to allow system services to communicate and
@@ -248,7 +259,8 @@ and policy files.  For example, to allow avahi-daemon to use the system bus,
 @var{services} must be equal to @code{(list avahi)}."
   (service dbus-root-service-type
            (dbus-configuration (dbus dbus)
-                               (services services))))
+                               (services services)
+                               (verbose? verbose?))))
 
 (define (wrapped-dbus-service service program variables)
   "Return a wrapper for @var{service}, a package containing a D-Bus service,