=== modified file 'intro.xml'
--- intro.xml	2019-04-10 20:33:13 +0000
+++ intro.xml	2019-08-04 12:42:49 +0000
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
-<!ENTITY TIMESTAMP "2019-04-10">
+<!ENTITY TIMESTAMP "2019-08-04">
 <!ENTITY % common SYSTEM "common.ent">
 %common;
 ]>
@@ -384,7 +384,36 @@
       plugin requirements.
     </para>
   </refsect1>
-  
+
+  <refsect1 id="systemd">
+    <title>SYSTEMD</title>
+    <para>
+      More advanced startup systems like <citerefentry><refentrytitle
+      >systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      already have their own plugin-like mechanisms for allowing
+      multiple agents to independently retrieve a password and deliver
+      it to the subsystem requesting a password to unlock the root
+      file system.  On these systems, it would make no sense to run
+      <citerefentry><refentrytitle>plugin-runner</refentrytitle
+      ><manvolnum>8mandos</manvolnum></citerefentry>, the plugins of
+      which would largely duplicate the work of (and conflict with)
+      the existing systems prompting for passwords.
+    </para>
+    <para>
+      As for <citerefentry><refentrytitle>systemd</refentrytitle
+      ><manvolnum>1</manvolnum></citerefentry> in particular, it has
+      its own <ulink
+      url="https://www.freedesktop.org/wiki/Software/systemd/PasswordAgents/"
+      >Password Agents</ulink> system.  Mandos uses this via its
+      <citerefentry><refentrytitle>password-agent</refentrytitle
+      ><manvolnum>8mandos</manvolnum></citerefentry> program, which
+      is run instead of <citerefentry><refentrytitle
+      >plugin-runner</refentrytitle><manvolnum>8mandos</manvolnum
+      ></citerefentry> when <citerefentry><refentrytitle
+      >systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+      is used during system startup.
+    </para>
+  </refsect1>
   <refsect1 id="bugs">
     <title>BUGS</title>
     <xi:include href="bugs.xml"/>
@@ -405,6 +434,8 @@
       <manvolnum>8</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>plugin-runner</refentrytitle>
       <manvolnum>8mandos</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>password-agent</refentrytitle>
+      <manvolnum>8mandos</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>mandos-client</refentrytitle>
       <manvolnum>8mandos</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>password-prompt</refentrytitle>