doc: update "daemon (start|stop)" documentation

Clarify various aspects related to configuration.

doc/repmgr-daemon-stop.sgml

@@ -36,6 +36,13 @@
       </para>
     </note>
 
+   <important>
+      <para>
+        The <filename>repmgr.conf</filename> parameter <varname>repmgrd_service_stop_command</varname>
+        must be set for <command>repmgr daemon stop</command> to work; see section
+        <xref linkend="repmgr-daemon-stop-configuration"> for details.
+      </para>
+    </important>
   </refsect1>
 
   <refsect1>
@@ -107,6 +114,44 @@
     </variablelist>
   </refsect1>
 
+  <refsect1 id="repmgr-daemon-stop-configuration" xreflabel="repmgr daemon stop configuration">
+    <title>Configuration file settings</title>
+    <para>
+     The following parameter in <filename>repmgr.conf</filename> is relevant
+     to <command>repmgr daemon stop</command>:
+    </para>
+
+    <variablelist>
+
+      <varlistentry>
+        <indexterm>
+          <primary>repmgrd_service_stop_command</primary>
+          <secondary>with &quot;repmgr daemon stop&quot;</secondary>
+        </indexterm>
+
+        <term><option>repmgrd_service_stop_command</option></term>
+        <listitem>
+          <para>
+            <command>repmgr daemon stop</command> will execute the command defined by the
+            <varname>repmgrd_service_stop_command</varname> parameter in <filename>repmgr.conf</filename>.
+            This must be set to a shell command which will stop <application>repmgrd</application>;
+            if &repmgr; was installed from a package, this will be the service command defined by the
+            package. For more details see <link linkend="appendix-packages">Appendix: &repmgr; package details</link>.
+          </para>
+          <important>
+            <para>
+              If &repmgr; was installed from a system package, and you do not configure
+              <varname>repmgrd_service_stop_command</varname> to an appropriate service command, this may
+              result in the system becoming confused about the state of the <application>repmgrd</application>
+              service; this is particularly the case with <literal>systemd</literal>.
+            </para>
+          </important>
+        </listitem>
+      </varlistentry>
+    </variablelist>
+
+  </refsect1>
+
   <refsect1>
     <title>Exit codes</title>
     <para>
@@ -148,7 +193,7 @@
   <refsect1>
     <title>See also</title>
     <para>
-      <xref linkend="repmgr-daemon-start">, <xref linkend="repmgr-daemon-status">
+      <xref linkend="repmgr-daemon-start">, <xref linkend="repmgr-daemon-status">, <xref linkend="repmgrd-daemon">
     </para>
   </refsect1>