spec: briefly describe Name, Exec and User keys

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=66608
Reviewed-by: Chengwei Yang <chengwei.yang@intel.com>

diff --git a/doc/dbus-specification.xml b/doc/dbus-specification.xml
index e6e75fde98dd592b14705e7f96f0df4e650ad7b5..51d6cb6fb169ed98a3ab4e6d5571a520d49423ff 100644 (file)
--- a/doc/dbus-specification.xml
+++ b/doc/dbus-specification.xml
@@ -4662,6 +4662,11 @@
           <listitem><para>Comment format</para></listitem>
         </itemizedlist>
 
+        Service description files must contain a
+        <literal>D-BUS Service</literal> group with at least the keys
+        <literal>Name</literal> (the well-known name of the service)
+        and <literal>Exec</literal> (the command to be executed).
+
         <figure>
          <title>Example service description file</title>
          <programlisting>
@@ -4672,6 +4677,14 @@
           </programlisting>
        </figure>
       </para>
+
+      <para>
+        Additionally, service description files for the well-known system
+        bus on Unix must contain a <literal>User</literal> key, whose value
+        is the name of a user account (e.g. <literal>root</literal>).
+        The system service will be run as that user.
+      </para>
+
       <para>
         When an application asks to start a service by name, the bus daemon tries to
         find a service that will own that name. It then tries to spawn the