systemd/man/pam_systemd.xml

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        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

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<refentry id="pam_systemd" conditional='HAVE_PAM'>

        <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 login manager</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <para><filename>pam_systemd.so</filename></para>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><command>pam_systemd</command> registers user
                sessions in 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>

                <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> 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
                        slice below <filename>user.slice</filename> is
                        automatically created and the scope placed in
                        it. In instance of the system service
                        <filename>user@.service</filename> which runs
                        the systemd user manager
                        instance.</para></listitem>
                </orderedlist>

                <para>On logout, this module ensures the following:</para>

                <orderedlist>
                        <listitem><para>If this is enabled, all
                        processes of the session are terminated. If
                        the last concurrent session of a user ends, his
                        user 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 PAM_SUCCESS.</para>

        </refsect1>

        <refsect1>
                <title>Options</title>

                <para>The following options are understood:</para>

                <variablelist class='pam-directives'>

                        <varlistentry>
                                <term><option>class=</option></term>

                                <listitem><para>Takes a string
                                argument which sets the session class.
                                The XDG_SESSION_CLASS environmental variable
                                takes precedence.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>debug=</option></term>

                                <listitem><para>Takes a boolean
                                argument. If yes, the module will log
                                debugging information as it
                                operates.</para></listitem>
                        </varlistentry>
                </variablelist>
        </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 class='environment-variables'>
                        <varlistentry>
                                <term><varname>$XDG_SESSION_ID</varname></term>

                                <listitem><para>A session identifier,
                                suitable to be used in filenames. 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>$XDG_RUNTIME_DIR</varname>
                                and the same contents. If a user logs
                                in once, then logs out again, and logs
                                in again, the directory contents will
                                have been lost in between, but
                                applications should not rely on this
                                behavior and must be able to deal with
                                stale files. To store session-private
                                data in this directory, the user should
                                include the value of <varname>$XDG_SESSION_ID</varname>
                                in the filename. This directory shall
                                be used for runtime file system
                                objects such as <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.</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</programlisting>
        </refsect1>

        <refsect1>
                <title>See Also</title>
                <para>
                        <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><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.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>

</refentry>