systemd/man/pam_systemd.xml

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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 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 control group
                        <filename>/user/$USER/$XDG_SESSION_ID</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>$XDG_SESSION_ID</varname> is set and
                        <option>kill-session-processes=1</option> specified, all
                        remaining processes in the
                        <filename>/user/$USER/$XDG_SESSION_ID</filename>
                        control group are killed and the control group
                        is removed.</para></listitem>

                        <listitem><para>If the last subgroup of 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 class='pam-directives'>
                        <varlistentry>
                                <term><option>kill-session-processes=</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-only-users=</option></term>

                                <listitem><para>Takes a comma
                                separated list of user names or
                                numeric user ids as argument. If this
                                option is used the effect of the
                                <option>kill-session-processes=</option> options
                                will apply only to the listed
                                users. If this option is not used the
                                option applies to all local
                                users. Note that
                                <option>kill-exclude-users=</option>
                                takes precedence over this list and is
                                hence subtracted from the list
                                specified here.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>kill-exclude-users=</option></term>

                                <listitem><para>Takes a comma
                                separated list of user names or
                                numeric user ids as argument. Users
                                listed in this argument will not be
                                subject to the effect of
                                <option>kill-session-processes=</option>.  Note
                                that this option takes precedence
                                over
                                <option>kill-only-users=</option>, and
                                hence whatever is listed for
                                <option>kill-exclude-users=</option>
                                is guaranteed to never be killed by
                                this PAM module, independent of any
                                other configuration
                                setting.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>controllers=</option></term>

                                <listitem><para>Takes a comma
                                separated list of control group
                                controllers in which hierarchies a
                                user/session control group will be
                                created by default for each user
                                logging in, in addition to the control
                                group in the named 'name=systemd'
                                hierarchy. If omitted, defaults to an
                                empty list.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>reset-controllers=</option></term>

                                <listitem><para>Takes a comma
                                separated list of control group
                                controllers in which hierarchies the
                                logged in processes will be reset to
                                the root control
                                group.</para></listitem>
                        </varlistentry>

                        <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>

                <para>Note that setting
                <varname>kill-session-processes=1</varname> will break tools
                like
                <citerefentry><refentrytitle>screen</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>

                <para>Note that
                <varname>kill-session-processes=1</varname> is a
                stricter version of
                <varname>KillUserProcesses=1</varname> which may be
                configured system-wide in
                <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
                former kills processes of a session as soon as it
                ends, the latter kills processes as soon as the last
                session of the user ends.</para>

                <para>If the options are omitted they default to
                <option>kill-session-processes=0</option>,
                <option>kill-only-users=</option>,
                <option>kill-exclude-users=</option>,
                <option>controllers=</option>,
                <option>reset-controllers=</option>,
                <option>debug=no</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 class='environment-variables'>
                        <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>$XDG_RUNTIME_DIR</varname>
                                and the same contents. If a user logs
                                in once, then logs out again, and logs
                                in again, the directory contents will
                                have been lost in between, but
                                applications should not rely on this
                                behavior and must be able to deal with
                                stale files. To store session-private
                                data in this directory the user should
                                include the value of <varname>$XDG_SESSION_ID</varname>
                                in the filename. This directory shall
                                be used for runtime file system
                                objects such as 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-session-processes=1</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>
                </para>
        </refsect1>

</refentry>