man: update pam_elogind and elogind-logind man pages a bit

This builds on @utezduyar's #4640, but extends on it.

Fixes: #4550
Replaces: #4640

1 files changed, 31 insertions, 19 deletions

diff --git a/man/pam_elogind.xml b/man/pam_elogind.xml
index 80235b37c..af9877c0e 100644
--- a/man/pam_elogind.xml
+++ b/man/pam_elogind.xml
@@ -55,24 +55,27 @@
     <title>Description</title>
 
     <para><command>pam_elogind</command> registers user sessions with
-    the elogind login manager and hence the elogind control group
-    hierarchy.</para>
+    the systemd login manager
+    <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+    and hence the systemd control group hierarchy.</para>
 
-    <para>On login, this module ensures the following:</para>
+    <para>On login, this module — in conjunction with <filename>systemd-logind.service</filename> — ensures the
+    following:</para>
 
     <orderedlist>
-      <listitem><para>If it does not exist yet, the user runtime
-      directory <filename>/run/user/$USER</filename> is created and
-      its ownership changed to the user that is logging
-      in.</para></listitem>
-
-      <listitem><para>The <varname>$XDG_SESSION_ID</varname>
-      environment variable is initialized. If auditing is available
-      and <command>pam_loginuid.so</command> was run before this
-      module (which is highly recommended), the variable is
-      initialized from the auditing session id
-      (<filename>/proc/self/sessionid</filename>). Otherwise, an
+      <listitem><para>If it does not exist yet, the user runtime directory <filename>/run/user/$UID</filename> is
+      either created or mounted as new <literal>tmpfs</literal> file system with quota applied, and its ownership
+      changed to the user that is logging in.</para></listitem>
+
+      <listitem><para>The <varname>$XDG_SESSION_ID</varname> environment variable is initialized. If auditing is
+      available and <command>pam_loginuid.so</command> was run before this module (which is highly recommended), the
+      variable is initialized from the auditing session id (<filename>/proc/self/sessionid</filename>). Otherwise, an
       independent session counter is used.</para></listitem>
+
+      <listitem><para>A new systemd scope unit is created for the session. If this is the first concurrent session of
+      the user, an implicit per-user slice unit below <filename>user.slice</filename> is automatically created and the
+      scope placed into it. An instance of the system service <filename>user@.service</filename>, which runs the
+      systemd user manager instance, is started.  </para></listitem>
     </orderedlist>
 
     <para>On logout, this module ensures the following:</para>
@@ -80,14 +83,19 @@
     <orderedlist>
       <listitem><para>If enabled in
       <citerefentry><refentrytitle>logind.conf</refentrytitle>
-      <manvolnum>5</manvolnum></citerefentry>, all processes of the
-      session are terminated.</para></listitem>
+      <manvolnum>5</manvolnum></citerefentry> (<varname>KillUserProcesses=</varname>), all processes of the session are
+      terminated. If the last concurrent session of a user ends, the user's systemd instance will be terminated too,
+      and so will the user's slice unit.</para></listitem>
 
       <listitem><para>If the last concurrent session of a user ends,
       the <varname>$XDG_RUNTIME_DIR</varname> directory and all its
       contents are removed, too.</para></listitem>
     </orderedlist>
 
+    <para>If the system was not booted up with systemd as init system,
+    this module does nothing and immediately returns
+    <constant>PAM_SUCCESS</constant>.</para>
+
   </refsect1>
 
   <refsect1>
@@ -182,7 +190,7 @@
         as <constant>AF_UNIX</constant> sockets, FIFOs, PID files and
         similar. It is guaranteed that this directory is local and
         offers the greatest possible file system feature set the
-        operating system provides. For further details see the <ulink
+        operating system provides. For further details, see the <ulink
         url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
         Base Directory Specification</ulink>.</para></listitem>
       </varlistentry>
@@ -264,13 +272,17 @@ session    required     pam_elogind.so</programlisting>
   <refsect1>
     <title>See Also</title>
     <para>
-      <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry project='man-pages'><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
       <citerefentry project='man-pages'><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
       <citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
-      <citerefentry project='man-pages'><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+      <citerefentry project='man-pages'><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
     </para>
   </refsect1>