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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 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>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
                        is 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 is
                        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 is 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 which 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>

                <para>If the options are omitted they default to
                <option>create-session=1</option>,
                <option>kill-session=0</option>,
                <option>kill-user=0</option>.</para>
        </refsect1>

        <refsect1>
                <title>Module Types Provided</title>

                <para>Only <option>session</option> is provided.</para>
        </refsect1>

        <refsect1>
                <title>Environment</title>

                <para>The following environment variables are set for the processes of the user's session:</para>

                <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 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>