350 lines
16 KiB
XML
350 lines
16 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="pam_systemd" conditional='HAVE_PAM'>
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<refentryinfo>
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<title>pam_systemd</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>pam_systemd</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>pam_systemd</refname>
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<refpurpose>Register user sessions in the systemd login manager</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>pam_systemd.so</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>pam_systemd</command> registers user sessions with
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the systemd login manager
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<citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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and hence the systemd control group hierarchy.</para>
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<para>The module also applies various resource management and runtime parameters to the new session, as
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configured in the <ulink url="https://systemd.io/USER_RECORD">JSON User Record</ulink> of the user, when
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one is defined.</para>
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<para>On login, this module — in conjunction with <filename>systemd-logind.service</filename> — ensures the
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following:</para>
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<orderedlist>
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<listitem><para>If it does not exist yet, the user runtime directory <filename>/run/user/$UID</filename> is
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either created or mounted as new <literal>tmpfs</literal> file system with quota applied, and its ownership
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changed to the user that is logging in.</para></listitem>
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<listitem><para>The <varname>$XDG_SESSION_ID</varname> environment variable is initialized. If auditing is
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available and <command>pam_loginuid.so</command> was run before this module (which is highly recommended), the
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variable is initialized from the auditing session id (<filename>/proc/self/sessionid</filename>). Otherwise, an
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independent session counter is used.</para></listitem>
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<listitem><para>A new systemd scope unit is created for the session. If this is the first concurrent session of
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the user, an implicit per-user slice unit below <filename>user.slice</filename> is automatically created and the
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scope placed into it. An instance of the system service <filename>user@.service</filename>, which runs the
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systemd user manager instance, is started.</para></listitem>
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<listitem><para>The <literal>$TZ</literal>, <literal>$EMAIL</literal> and <literal>$LANG</literal>
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environment variables are configured for the user, based on the respective data from the user's JSON
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record (if it is defined). Moreover, any environment variables explicitly configured in the user record
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are imported, and the umask, nice level, and resource limits initialized.</para></listitem>
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</orderedlist>
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<para>On logout, this module ensures the following:</para>
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<orderedlist>
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<listitem><para>If enabled in
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<citerefentry><refentrytitle>logind.conf</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry> (<varname>KillUserProcesses=</varname>), all processes of the session are
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terminated. If the last concurrent session of a user ends, the user's systemd instance will be terminated too,
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and so will the user's slice unit.</para></listitem>
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<listitem><para>If the last concurrent session of a user ends,
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the user runtime directory <filename>/run/user/$UID</filename> and all its
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contents are removed, too.</para></listitem>
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</orderedlist>
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<para>If the system was not booted up with systemd as init system,
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this module does nothing and immediately returns
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<constant>PAM_SUCCESS</constant>.</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>The following options are understood:</para>
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<variablelist class='pam-directives'>
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<varlistentry>
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<term><varname>class=</varname></term>
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<listitem><para>Takes a string argument which sets the session class. The <varname>XDG_SESSION_CLASS</varname>
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environment variable (see below) takes precedence. One of <literal>user</literal>, <literal>greeter</literal>,
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<literal>lock-screen</literal> or <literal>background</literal>. See
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<citerefentry><refentrytitle>sd_session_get_class</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
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details about the session class.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>type=</varname></term>
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<listitem><para>Takes a string argument which sets the session type. The <varname>XDG_SESSION_TYPE</varname>
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environment variable (see below) takes precedence. One of <literal>unspecified</literal>,
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<literal>tty</literal>, <literal>x11</literal>, <literal>wayland</literal> or <literal>mir</literal>. See
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<citerefentry><refentrytitle>sd_session_get_type</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
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details about the session type.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>desktop=</varname></term>
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<listitem><para>Takes a single, short identifier string for the desktop environment. The
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<varname>XDG_SESSION_DESKTOP</varname> environment variable (see below) takes precedence. This may be used to
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indicate the session desktop used, where this applies and if this information is available. For example:
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<literal>GNOME</literal>, or <literal>KDE</literal>. It is recommended to use the same identifiers and
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capitalization as for <varname>$XDG_CURRENT_DESKTOP</varname>, as defined by the <ulink
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url="http://standards.freedesktop.org/desktop-entry-spec/latest/">Desktop Entry
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Specification</ulink>. (However, note that the option only takes a single item, and not a colon-separated list
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like <varname>$XDG_CURRENT_DESKTOP</varname>.) See
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<citerefentry><refentrytitle>sd_session_get_desktop</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
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further details.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>debug</varname><optional>=</optional></term>
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<listitem><para>Takes an optional boolean argument. If yes or without the argument, the module will log
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debugging information as it operates.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Module Types Provided</title>
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<para>Only <option>session</option> is provided.</para>
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</refsect1>
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<refsect1>
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<title>Environment</title>
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<para>The following environment variables are initialized by the module and available to the processes of the
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user's session:</para>
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<variablelist class='environment-variables'>
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<varlistentry>
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<term><varname>$XDG_SESSION_ID</varname></term>
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<listitem><para>A short session identifier, suitable to be used in filenames. The string itself should be
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considered opaque, although often it is just the audit session ID as reported by
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<filename>/proc/self/sessionid</filename>. Each ID will be assigned only once during machine uptime. It may
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hence be used to uniquely label files or other resources of this session. Combine this ID with the boot
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identifier, as returned by
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<citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>, for a
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globally unique identifier.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>$XDG_RUNTIME_DIR</varname></term>
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<listitem><para>Path to a user-private user-writable directory
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that is bound to the user login time on the machine. It is
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automatically created the first time a user logs in and
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removed on the user's final logout. If a user logs in twice at
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the same time, both sessions will see the same
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<varname>$XDG_RUNTIME_DIR</varname> and the same contents. If
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a user logs in once, then logs out again, and logs in again,
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the directory contents will have been lost in between, but
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applications should not rely on this behavior and must be able
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to deal with stale files. To store session-private data in
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this directory, the user should include the value of
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<varname>$XDG_SESSION_ID</varname> in the filename. This
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directory shall be used for runtime file system objects such
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as <constant>AF_UNIX</constant> sockets, FIFOs, PID files and
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similar. It is guaranteed that this directory is local and
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offers the greatest possible file system feature set the
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operating system provides. For further details, see the <ulink
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url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
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Base Directory Specification</ulink>. <varname>$XDG_RUNTIME_DIR</varname>
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is not set if the current user is not the original user of the session.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>$TZ</varname></term>
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<term><varname>$EMAIL</varname></term>
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<term><varname>$LANG</varname></term>
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<listitem><para>If a JSON user record is known for the user logging in these variables are
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initialized from the respective data in the record.</para></listitem>
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</varlistentry>
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</variablelist>
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<para>The following environment variables are read by the module and may be used by the PAM service to pass
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metadata to the module. If these variables are not set when the PAM module is invoked but can be determined
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otherwise they are set by the module, so that these variables are initialized for the session and applications if
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known at all.</para>
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<variablelist class='environment-variables'>
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<varlistentry>
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<term><varname>$XDG_SESSION_TYPE</varname></term>
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<listitem><para>The session type. This may be used instead of <varname>type=</varname> on the module parameter
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line, and is usually preferred.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>$XDG_SESSION_CLASS</varname></term>
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<listitem><para>The session class. This may be used instead of <varname>class=</varname> on the module parameter
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line, and is usually preferred.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>$XDG_SESSION_DESKTOP</varname></term>
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<listitem><para>The desktop identifier. This may be used instead of <varname>desktop=</varname> on the module
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parameter line, and is usually preferred.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>$XDG_SEAT</varname></term>
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<listitem><para>The seat name the session shall be registered
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for, if any.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>$XDG_VTNR</varname></term>
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<listitem><para>The VT number the session shall be registered
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for, if any. (Only applies to seats with a VT available, such
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as <literal>seat0</literal>)</para></listitem>
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</varlistentry>
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</variablelist>
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<para>If not set, <command>pam_systemd</command> will initialize
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<varname>$XDG_SEAT</varname> and <varname>$XDG_VTNR</varname>
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based on the <varname>$DISPLAY</varname> variable (if the latter is set).</para>
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</refsect1>
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<refsect1>
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<title>Session limits</title>
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<para>PAM modules earlier in the stack, that is those that come before <command>pam_systemd.so</command>,
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can set session scope limits using the PAM context objects. The data for these objects is provided as <constant>NUL</constant>-terminated C strings
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and maps directly to the respective unit resource control directives. Note that these limits apply to individual sessions of the user,
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they do not apply to all user processes as a combined whole. In particular, the per-user <command>user@.service</command> unit instance,
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which runs the <command>systemd --user</command> manager process and its children, and is tracked outside of any session, being shared
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by all the user's sessions, is not covered by these limits.
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</para>
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<para> See
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<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information about the resources.
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Also, see <citerefentry project='man-pages'><refentrytitle>pam_set_data</refentrytitle><manvolnum>3</manvolnum></citerefentry> for additional information about how to set
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the context objects.
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</para>
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<variablelist class='pam-directives'>
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<varlistentry>
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<term><varname>systemd.memory_max=</varname></term>
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<listitem><para>Sets unit <varname>MemoryMax=</varname>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>systemd.tasks_max=</varname></term>
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<listitem><para>Sets unit <varname>TasksMax=</varname>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>systemd.cpu_weight=</varname></term>
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<listitem><para>Sets unit <varname>CPUWeight=</varname>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>systemd.io_weight=</varname></term>
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<listitem><para>Sets unit <varname>IOWeight=</varname>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>systemd.runtime_max_sec=</varname></term>
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<listitem><para>Sets unit <varname>RuntimeMaxSec=</varname>.</para></listitem>
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</varlistentry>
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</variablelist>
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<para>Example data as can be provided from an another PAM module:
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<programlisting>
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pam_set_data(handle, "systemd.memory_max", (void *)"200M", cleanup);
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pam_set_data(handle, "systemd.tasks_max", (void *)"50", cleanup);
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pam_set_data(handle, "systemd.cpu_weight", (void *)"100", cleanup);
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pam_set_data(handle, "systemd.io_weight", (void *)"340", cleanup);
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pam_set_data(handle, "systemd.runtime_max_sec", (void *)"3600", cleanup);
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</programlisting>
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</para>
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</refsect1>
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<refsect1>
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<title>Example</title>
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<para>Here's an example PAM configuration fragment that allows users sessions to be managed by
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<filename>systemd-logind.service</filename>:</para>
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<programlisting>#%PAM-1.0
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auth sufficient pam_unix.so
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-auth sufficient pam_systemd_home.so
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auth required pam_deny.so
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account required pam_nologin.so
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-account sufficient pam_systemd_home.so
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account sufficient pam_unix.so
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account required pam_permit.so
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-password sufficient pam_systemd_home.so
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password sufficient pam_unix.so sha512 shadow try_first_pass try_authtok
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password required pam_deny.so
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-session optional pam_keyinit.so revoke
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-session optional pam_loginuid.so
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-session optional pam_systemd_home.so
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<command>-session optional pam_systemd.so</command>
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session required pam_unix.so</programlisting>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>pam_systemd_home</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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