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<refentry id="pam_systemd" conditional='HAVE_PAM'>
<refpurpose>Register user sessions in the systemd login manager</refpurpose>
<para><command>pam_systemd</command> registers user sessions with
the systemd login manager
and hence the systemd control group hierarchy.</para>
<para>The module also applies various resource management and runtime parameters to the new session, as
configured in the <ulink url="">JSON User Records</ulink> of the user, when
one is defined.</para>
<para>On login, this module — in conjunction with <filename>systemd-logind.service</filename> — ensures the
<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></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>
<listitem><para>The <literal>$TZ</literal>, <literal>$EMAIL</literal> and <literal>$LANG</literal>
environment variables are configured for the user, based on the respective data from the user's JSON
record (if it is defined). Moreover, any environment variables explicitly configured in the user record
are imported, and the umask, nice level, and resource limits initialized.</para></listitem>
<para>On logout, this module ensures the following:</para>
<listitem><para>If enabled in
<manvolnum>5</manvolnum></citerefentry> (<varname>KillUserProcesses=</varname>), all processes of the session are
terminated. If the last concurrent session of a user ends, the user's systemd instance will be terminated too,
and so will the user's slice unit.</para></listitem>
<listitem><para>If the last concurrent session of a user ends,
the user runtime directory <filename>/run/user/$UID</filename> and all its
contents are removed, too.</para></listitem>
<para>If the system was not booted up with systemd as init system,
this module does nothing and immediately returns
<para>The following options are understood:</para>
<variablelist class='pam-directives'>
<listitem><para>Takes a string argument which sets the session class. The <varname>XDG_SESSION_CLASS</varname>
environment variable (see below) takes precedence. One of <literal>user</literal>, <literal>greeter</literal>,
<literal>lock-screen</literal> or <literal>background</literal>. See
<citerefentry><refentrytitle>sd_session_get_class</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
details about the session class.</para></listitem>
<listitem><para>Takes a string argument which sets the session type. The <varname>XDG_SESSION_TYPE</varname>
environment variable (see below) takes precedence. One of <literal>unspecified</literal>,
<literal>tty</literal>, <literal>x11</literal>, <literal>wayland</literal> or <literal>mir</literal>. See
<citerefentry><refentrytitle>sd_session_get_type</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
details about the session type.</para></listitem>
<listitem><para>Takes a single, short identifier string for the desktop environment. The
<varname>XDG_SESSION_DESKTOP</varname> environment variable (see below) takes precedence. This may be used to
indicate the session desktop used, where this applies and if this information is available. For example:
<literal>GNOME</literal>, or <literal>KDE</literal>. It is recommended to use the same identifiers and
capitalization as for <varname>$XDG_CURRENT_DESKTOP</varname>, as defined by the <ulink
url="">Desktop Entry
Specification</ulink>. (However, note that the option only takes a single item, and not a colon-separated list
like <varname>$XDG_CURRENT_DESKTOP</varname>.) See
<citerefentry><refentrytitle>sd_session_get_desktop</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
further details.</para></listitem>
<listitem><para>Takes an optional boolean argument. If yes or without the argument, the module will log
debugging information as it operates.</para></listitem>
<title>Module Types Provided</title>
<para>Only <option>session</option> is provided.</para>
<para>The following environment variables are initialized by the module and available to the processes of the
user's session:</para>
<variablelist class='environment-variables'>
<listitem><para>A short 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. Combine this ID with the boot
identifier, as returned by
<citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>, for a
globally unique identifier.</para></listitem>
<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 the user's 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. For further details, see the <ulink
Base Directory Specification</ulink>. <varname>$XDG_RUNTIME_DIR</varname>
is not set if the current user is not the original user of the session.</para></listitem>
<listitem><para>If a JSON user record is known for the user logging in these variables are
initialized from the respective data in the record.</para></listitem>
<para>The following environment variables are read by the module and may be used by the PAM service to pass
metadata to the module. If these variables are not set when the PAM module is invoked but can be determined
otherwise they are set by the module, so that these variables are initialized for the session and applications if
known at all.</para>
<variablelist class='environment-variables'>
<listitem><para>The session type. This may be used instead of <varname>type=</varname> on the module parameter
line, and is usually preferred.</para></listitem>
<listitem><para>The session class. This may be used instead of <varname>class=</varname> on the module parameter
line, and is usually preferred.</para></listitem>
<listitem><para>The desktop identifier. This may be used instead of <varname>desktop=</varname> on the module
parameter line, and is usually preferred.</para></listitem>
<listitem><para>The seat name the session shall be registered
for, if any.</para></listitem>
<listitem><para>The VT number the session shall be registered
for, if any. (Only applies to seats with a VT available, such
as <literal>seat0</literal>)</para></listitem>
<para>If not set, <command>pam_systemd</command> will initialize
<varname>$XDG_SEAT</varname> and <varname>$XDG_VTNR</varname>
based on the <varname>$DISPLAY</varname> variable (if the latter is set).</para>
<title>Session limits</title>
<para>PAM modules earlier in the stack, that is those that come before <command></command>,
can set session scope limits using the PAM context objects. The data for these objects is provided as <constant>NUL</constant>-terminated C strings
and maps directly to the respective unit resource control directives. Note that these limits apply to individual sessions of the user,
they do not apply to all user processes as a combined whole. In particular, the per-user <command>user@.service</command> unit instance,
which runs the <command>systemd --user</command> manager process and its children, and is tracked outside of any session, being shared
by all the user's sessions, is not covered by these limits.
<para> See
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information about the resources.
Also, see <citerefentry project='man-pages'><refentrytitle>pam_set_data</refentrytitle><manvolnum>3</manvolnum></citerefentry> for additional information about how to set
the context objects.
<variablelist class='pam-directives'>
<listitem><para>Sets unit <varname>MemoryMax=</varname>.</para></listitem>
<listitem><para>Sets unit <varname>TasksMax=</varname>.</para></listitem>
<listitem><para>Sets unit <varname>CPUWeight=</varname>.</para></listitem>
<listitem><para>Sets unit <varname>IOWeight=</varname>.</para></listitem>
<listitem><para>Sets unit <varname>RuntimeMaxSec=</varname>.</para></listitem>
<para>Example data as can be provided from an another PAM module:
pam_set_data(handle, "systemd.memory_max", (void *)"200M", cleanup);
pam_set_data(handle, "systemd.tasks_max", (void *)"50", cleanup);
pam_set_data(handle, "systemd.cpu_weight", (void *)"100", cleanup);
pam_set_data(handle, "systemd.io_weight", (void *)"340", cleanup);
pam_set_data(handle, "systemd.runtime_max_sec", (void *)"3600", cleanup);
<para>Here's an example PAM configuration fragment that allows users sessions to be managed by
auth sufficient
-auth sufficient
auth required
account required
-account sufficient
account sufficient
account required
-password sufficient
password sufficient sha512 shadow try_first_pass use_authtok
password required
-session optional revoke
-session optional
-session optional
<command>-session optional</command>
session required</programlisting>
<title>See Also</title>
<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>,