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<refentry id="pam_systemd">
<refentryinfo>
<title>pam_systemd</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>pam_systemd</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>pam_systemd</refname>
<refpurpose>Register user sessions in the systemd control group hierarchy</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>pam_systemd.so</command>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>pam_systemd</command> registers user
sessions in the systemd control group
hierarchy.</para>
<para>On login, this module ensures the following:</para>
<orderedlist>
<listitem><para>If it does not exist yet the
user runtime directory
<filename>/var/run/user/$USER</filename> is
created and its ownership changed to the user
that is logging in.</para></listitem>
<listitem><para>If
<option>create-session=1</option> is set the
<varname>$XDG_SESSION_ID</varname> environment
variable is initialized. If auditing is
available and
<command>pam_loginuid.so</command> run before
this module (which es 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>If
<option>create-session=1</option> is set a new
control group
<filename>/user/$USER/$XDG_SESSION_ID</filename>
is created and the login process moved into
it.</para></listitem>
<listitem><para>If
<option>create-session=0</option> is set a new
control group
<filename>/user/$USER/no-session</filename>
is created and the login process moved into
it.</para></listitem>
</orderedlist>
<para>On logout, this module ensures the following:</para>
<orderedlist>
<listitem><para>If
<varname>$XDG_SESSION_ID</varname> is set and
<option>kill-session=1</option> specified, all
remaining processes in the
<filename>/user/$USER/$XDG_SESSION_ID</filename>
control group are killed and the control group
removed.</para></listitem>
<listitem><para>If
<varname>$XDG_SESSION_ID</varname> is set and
<option>kill-session=0</option> specified, all
remaining processes in the
<filename>/user/$USER/$XDG_SESSION_ID</filename>
control group are migrated to
<filename>/user/$USER/no-session</filename> and
the original control group
removed.</para></listitem>
<listitem><para>If
<option>kill-user=1</option> is specified, and
no other user session control group remains
except
<filename>/user/$USER/no-session</filename>
all remaining processes in the
<filename>/user/$USER</filename> hierarchy
are killed and the control group removed.</para></listitem>
<listitem><para>If
<option>kill-user=0</option> is specified, and
no process remains in the
<filename>/user/$USER</filename> hierarchy the
control group is removed.</para></listitem>
<listitem><para>If the
<filename>/user/$USER</filename> control group
was removed the
<varname>$XDG_RUNTIME_DIR</varname> directory
and all its contents are
removed, too.</para></listitem>
</orderedlist>
<para>If the system was not booted up with systemd as
init system this module does nothing and immediately
returns PAM_SUCCESS.</para>
</refsect1>
<refsect1>
<title>Options</title>
<para>The following options are understood:</para>
<variablelist>
<varlistentry>
<term><option>create-session=</option></term>
<listitem><para>Takes a boolean
argument. If true, a new session is
created: the
<varname>$XDG_SESSION_ID</varname>
environment variable is set and the
login process moved to the
<filename>/user/$USER/$XDG_SESSION_ID</filename>
control group. It is recommended that
all services that are directly created
on the user's behalf set this
option. Only for services that shall
automatically be terminated when the
user logs out completely otherwise,
<varname>create-session=0</varname>
should be set.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>kill-session=</option></term>
<listitem><para>Takes a boolean
argument. If true, all processes
created by the user during his session
and from his session will be
terminated when he logs out from his
session.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>kill-user=</option></term>
<listitem><para>Takes a boolean
argument. If true, all processes
created by the user during his session
and from his session will be
terminated after he logged out
completely. This is a weaker version
of <option>kill-session=1</option> and is
more friendly for users logged in more
than once as their processes are
terminated only on their complete
logout.</para></listitem>
</varlistentry>
</variablelist>
<para>Note that setting <varname>kill-user=1</varname>
or even <varname>kill-session=1</varname> will break
tools like
<citerefentry><refentrytitle>screen</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
</refsect1>
<refsect1>
<title>Module Types Provided</title>
<para>Only <option>session</option> is provided.</para>
</refsect1>
<refsect1>
<title>Environment</title>
<variablelist>
<varlistentry>
<term><varname>$XDG_SESSION_ID</varname></term>
<listitem><para>A session identifier,
suitable to be used in file names. The
string itself should be considered
opaque, although often it is just the
audit session ID as reported by
<filename>/proc/self/sessionid</filename>. Each
ID will be assigned only once during
machine uptime. It may hence be used
to uniquely label files or other
resources of this
session.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>$XDG_RUNTIME_DIR</varname></term>
<listitem><para>Path to a user-private
user-writable directory that is bound
to the user login time on the
machine. It is automatically created
the first time a user logs in and
removed on his final logout. If a user
logs in twice at the same time, both
sessions will see the same
<varname>$XDG_RUNTIME_DIR</varname>
and the same contents. If a user logs
in once, then logs out again, and logs
in again, the directory contents will
have been lost in between, but
applications should not rely on this
behaviour and must be able to deal with
stale files. To store session-private
data in this directory the user should
include the value of <varname>$XDG_SESSION_ID</varname>
in the filename. This directory shall
be used for runtime file system
objects such as AF_UNIX 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.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Example</title>
<programlisting>#%PAM-1.0
auth required pam_unix.so
auth required pam_nologin.so
account required pam_unix.so
password required pam_unix.so
session required pam_unix.so
session required pam_loginuid.so
session required pam_systemd.so create-session=1 kill-user=1</programlisting>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>