systemd/man/pam_systemd.xml
Zbigniew Jędrzejewski-Szmek 2230a2908b man: add a note about $XDG_SEAT and $XDG_VTNR to pam_systemd(8)
Issue #6499 requests that a mention that those varibles can be set in the
environment is added. But the man page already says that. There isn't much
detail, but a man page does not need to and in this case should not include
all the details. Instead a note is added that those vars can be derived from
$DISPLAY.

Closes #6499.
2018-03-24 14:16:31 +01:00

296 lines
12 KiB
XML

<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"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 with
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 — in conjunction with <filename>systemd-logind.service</filename> — ensures the
following:</para>
<orderedlist>
<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>pam_loginuid.so</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>
</orderedlist>
<para>On logout, this module ensures the following:</para>
<orderedlist>
<listitem><para>If enabled in
<citerefentry><refentrytitle>logind.conf</refentrytitle>
<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/$UID</filename> and all its
contents are removed, too.</para></listitem>
</orderedlist>
<para>If the system was not booted up with systemd as init system,
this module does nothing and immediately returns
<constant>PAM_SUCCESS</constant>.</para>
</refsect1>
<refsect1>
<title>Options</title>
<para>The following options are understood:</para>
<variablelist class='pam-directives'>
<varlistentry>
<term><option>class=</option></term>
<listitem><para>Takes a string argument which sets the session
class. The XDG_SESSION_CLASS environmental variable takes
precedence. One of
<literal>user</literal>,
<literal>greeter</literal>,
<literal>lock-screen</literal> or
<literal>background</literal>. See
<citerefentry><refentrytitle>sd_session_get_class</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for details about the session class.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>type=</option></term>
<listitem><para>Takes a string argument which sets the session
type. The XDG_SESSION_TYPE environmental variable takes
precedence. One of
<literal>unspecified</literal>,
<literal>tty</literal>,
<literal>x11</literal>,
<literal>wayland</literal> or
<literal>mir</literal>. See
<citerefentry><refentrytitle>sd_session_get_type</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for details about the session type.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>debug<optional>=</optional></option></term>
<listitem><para>Takes an optional
boolean argument. If yes or without
the argument, the module will log
debugging information as it
operates.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Module Types Provided</title>
<para>Only <option>session</option> is provided.</para>
</refsect1>
<refsect1>
<title>Environment</title>
<para>The following environment variables are set for the
processes of the user's session:</para>
<variablelist class='environment-variables'>
<varlistentry>
<term><varname>$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>$XDG_RUNTIME_DIR</varname></term>
<listitem><para>Path to a user-private user-writable directory
that is bound to the user login time on the machine. It is
automatically created the first time a user logs in and
removed on the user's final logout. If a user logs in twice at
the same time, both sessions will see the same
<varname>$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>$XDG_SESSION_ID</varname> in the filename. This
directory shall be used for runtime file system objects such
as <constant>AF_UNIX</constant> sockets, FIFOs, PID files and
similar. It is guaranteed that this directory is local and
offers the greatest possible file system feature set the
operating system provides. For further details, see the <ulink
url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
Base Directory Specification</ulink>. <varname>$XDG_RUNTIME_DIR</varname>
is not set if the current user is not the original user of the session.</para></listitem>
</varlistentry>
</variablelist>
<para>The following environment variables are read by the module
and may be used by the PAM service to pass metadata to the
module:</para>
<variablelist class='environment-variables'>
<varlistentry>
<term><varname>$XDG_SESSION_TYPE</varname></term>
<listitem><para>The session type. This may be used instead of
<option>session=</option> on the module parameter line, and is
usually preferred.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>$XDG_SESSION_CLASS</varname></term>
<listitem><para>The session class. This may be used instead of
<option>class=</option> on the module parameter line, and is
usually preferred.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>$XDG_SESSION_DESKTOP</varname></term>
<listitem><para>A single, short identifier string for the
desktop environment. This may be used to indicate the session
desktop used, where this applies and if this information is
available. For example: <literal>GNOME</literal>, or
<literal>KDE</literal>. It is recommended to use the same
identifiers and capitalization as for
<varname>$XDG_CURRENT_DESKTOP</varname>, as defined by the
<ulink
url="http://standards.freedesktop.org/desktop-entry-spec/latest/">Desktop
Entry Specification</ulink>. (However, note that
<varname>$XDG_SESSION_DESKTOP</varname> only takes a single
item, and not a colon-separated list like
<varname>$XDG_CURRENT_DESKTOP</varname>.) See
<citerefentry><refentrytitle>sd_session_get_desktop</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for more details.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>$XDG_SEAT</varname></term>
<listitem><para>The seat name the session shall be registered
for, if any.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>$XDG_VTNR</varname></term>
<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>
</varlistentry>
</variablelist>
<para>If not set, <command>pam_systemd</command> will determine the
values for <varname>$XDG_SEAT</varname> and <varname>$XDG_VTNR</varname>
based on the <varname>$DISPLAY</varname> variable.</para>
</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 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>,
<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>