debug-generator: Add unit and drop-in credentials

These allow adding extra units and drop-ins via credentials.

man/systemd-debug-generator.xml

@@ -6,7 +6,7 @@
 %entities;
 ]>
 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
-<refentry id="systemd-debug-generator">
+<refentry id="systemd-debug-generator" xmlns:xi="http://www.w3.org/2001/XInclude">
 
   <refentryinfo>
     <title>systemd-debug-generator</title>
@@ -70,6 +70,36 @@
     <citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
   </refsect1>
 
+  <refsect1>
+    <title>System Credentials</title>
+
+    <variablelist class='system-credentials'>
+      <varlistentry>
+        <term><varname>systemd.extra-unit.*</varname></term>
+
+        <listitem><para>Credentials prefixed with <literal>systemd.extra-unit.</literal> specify additional
+        units to add to the final system. Note that these additional units are added to both the initrd and
+        the final system. <varname>ConditionPathExists=!/etc/initrd-release</varname> can be used to make
+        sure the unit is conditioned out in the initrd.</para>
+
+        <xi:include href="version-info.xml" xpointer="v256"/></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>systemd.unit-dropin.*</varname></term>
+
+        <listitem><para>Credentials prefixed with <literal>systemd.unit-dropin.</literal> add drop-ins for
+        the corresponding units in the final system. Each credential must be suffixed with the full unit name
+        including the unit extension. Its contents must be a valid unit drop-in file. Only one drop-in per
+        unit can be specified. The name of the generated drop-in will be
+        <literal>50-credential.conf</literal>. Note that these additional drop-ins are added to both the
+        initrd and the final system.</para>
+
+        <xi:include href="version-info.xml" xpointer="v256"/></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
   <refsect1>
     <title>See Also</title>
     <para><simplelist type="inline">