1 <?xml version='
1.0'
?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
6 <refentry id=
"pam_systemd" conditional='HAVE_PAM' xmlns:
xi=
"http://www.w3.org/2001/XInclude">
9 <title>pam_systemd
</title>
10 <productname>systemd
</productname>
14 <refentrytitle>pam_systemd
</refentrytitle>
15 <manvolnum>8</manvolnum>
19 <refname>pam_systemd
</refname>
20 <refpurpose>Register user sessions in the systemd login manager
</refpurpose>
24 <para><filename>pam_systemd.so
</filename></para>
28 <title>Description
</title>
30 <para><command>pam_systemd
</command> registers user sessions with
31 the systemd login manager
32 <citerefentry><refentrytitle>systemd-logind.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
33 and hence the systemd control group hierarchy.
</para>
35 <para>The module also applies various resource management and runtime parameters to the new session, as
36 configured in the
<ulink url=
"https://systemd.io/USER_RECORD">JSON User Records
</ulink> of the user, when
37 one is defined.
</para>
39 <para>On login, this module — in conjunction with
<filename>systemd-logind.service
</filename> — ensures the
43 <listitem><para>If it does not exist yet, the user runtime directory
<filename>/run/user/$UID
</filename> is
44 either created or mounted as new
<literal>tmpfs
</literal> file system with quota applied, and its ownership
45 changed to the user that is logging in.
</para></listitem>
47 <listitem><para>The
<varname>$XDG_SESSION_ID
</varname> environment variable is initialized. If auditing is
48 available and
<command>pam_loginuid.so
</command> was run before this module (which is highly recommended), the
49 variable is initialized from the auditing session id (
<filename>/proc/self/sessionid
</filename>). Otherwise, an
50 independent session counter is used.
</para></listitem>
52 <listitem><para>A new systemd scope unit is created for the session. If this is the first concurrent session of
53 the user, an implicit per-user slice unit below
<filename>user.slice
</filename> is automatically created and the
54 scope placed into it. An instance of the system service
<filename>user@.service
</filename>, which runs the
55 systemd user manager instance, is started.
</para></listitem>
57 <listitem><para>The
<literal>$TZ
</literal>,
<literal>$EMAIL
</literal> and
<literal>$LANG
</literal>
58 environment variables are configured for the user, based on the respective data from the user's JSON
59 record (if it is defined). Moreover, any environment variables explicitly configured in the user record
60 are imported, and the umask, nice level, and resource limits initialized.
</para></listitem>
63 <para>On logout, this module ensures the following:
</para>
66 <listitem><para>If enabled in
67 <citerefentry><refentrytitle>logind.conf
</refentrytitle>
68 <manvolnum>5</manvolnum></citerefentry> (
<varname>KillUserProcesses=
</varname>), all processes of the session are
69 terminated. If the last concurrent session of a user ends, the user's systemd instance will be terminated too,
70 and so will the user's slice unit.
</para></listitem>
72 <listitem><para>If the last concurrent session of a user ends,
73 the user runtime directory
<filename>/run/user/$UID
</filename> and all its
74 contents are removed, too.
</para></listitem>
77 <para>If the system was not booted up with systemd as init system,
78 this module does nothing and immediately returns
79 <constant>PAM_SUCCESS
</constant>.
</para>
84 <title>Options
</title>
86 <para>The following options are understood:
</para>
88 <variablelist class='pam-directives'
>
91 <term><varname>class=
</varname></term>
93 <listitem><para>Takes a string argument which sets the session class. The
94 <varname>XDG_SESSION_CLASS
</varname> environment variable (see below) takes precedence. See
95 <citerefentry><refentrytitle>sd_session_get_class
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
96 for a way to query the class of a session. The following session classes are defined:
</para>
99 <title>Session Classes
</title>
100 <tgroup cols='
2' align='left' colsep='
1' rowsep='
1'
>
101 <colspec colname=
"name" />
102 <colspec colname=
"explanation" />
106 <entry>Explanation
</entry>
111 <entry><constant>user
</constant></entry>
112 <entry>A regular interactive user session. This is the default class for sessions for which a TTY or X display is known at session registration time.
</entry>
115 <entry><constant>user-early
</constant></entry>
116 <entry>Similar to
<literal>user
</literal> but sessions of this class are not ordered after
<filename>systemd-user-sessions.service
</filename>, i.e. may be started before regular sessions are allowed to be established. This session class is the default for sessions of the root user that would otherwise qualify for the
<constant>user
</constant> class, see above. (Added in v256.)
</entry>
119 <entry><constant>user-incomplete
</constant></entry>
120 <entry>Similar to
<literal>user
</literal> but for sessions which are not fully set up yet, i.e. have no home directory mounted or similar. This is used by
<citerefentry><refentrytitle>systemd-homed.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry> to allow users to log in via
<command>ssh
</command> before their home directory is mounted, delaying the mount until the user provided the unlock password. Sessions of this class are upgraded to the regular
<constant>user
</constant> class once the home directory is activated.
</entry>
123 <entry><constant>greeter
</constant></entry>
124 <entry>Similar to
<literal>user
</literal> but for sessions that are spawned by a display manager ephemerally and which prompt the user for login credentials.
</entry>
127 <entry><constant>lock-screen
</constant></entry>
128 <entry>Similar to
<literal>user
</literal> but for sessions that are spawned by a display manager ephemerally and which show a lock screen that can be used to unlock locked user accounts or sessions.
</entry>
131 <entry><constant>background
</constant></entry>
132 <entry>Used for background sessions, such as those invoked by
<command>cron
</command> and similar tools. This is the default class for sessions for which no TTY or X display is known at session registration time.
</entry>
135 <entry><constant>background-light
</constant></entry>
136 <entry>Similar to
<constant>background
</constant>, but sessions of this class will not pull in the
<filename>user@.service
</filename> of the user, and thus possibly have no services of the user running. (Added in v256.)
</entry>
139 <entry><constant>manager
</constant></entry>
140 <entry>The
<filename>user@.service
</filename> service of the user is registered under this session class. (Added in v256.)
</entry>
143 <entry><constant>manager-early
</constant></entry>
144 <entry>Similar to
<constant>manager
</constant>, but for the root user. Compare with the
<constant>user
</constant> vs.
<constant>user-early
</constant> situation. (Added in v256.)
</entry>
150 <xi:include href=
"version-info.xml" xpointer=
"v197"/></listitem>
154 <term><varname>type=
</varname></term>
156 <listitem><para>Takes a string argument which sets the session type. The
<varname>XDG_SESSION_TYPE
</varname>
157 environment variable (see below) takes precedence. One of
<literal>unspecified
</literal>,
158 <literal>tty
</literal>,
<literal>x11
</literal>,
<literal>wayland
</literal> or
<literal>mir
</literal>. See
159 <citerefentry><refentrytitle>sd_session_get_type
</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
160 details about the session type.
</para>
162 <xi:include href=
"version-info.xml" xpointer=
"v209"/></listitem>
166 <term><varname>desktop=
</varname></term>
168 <listitem><para>Takes a single, short identifier string for the desktop environment. The
169 <varname>XDG_SESSION_DESKTOP
</varname> environment variable (see below) takes precedence. This may be used to
170 indicate the session desktop used, where this applies and if this information is available. For example:
171 <literal>GNOME
</literal>, or
<literal>KDE
</literal>. It is recommended to use the same identifiers and
172 capitalization as for
<varname>$XDG_CURRENT_DESKTOP
</varname>, as defined by the
<ulink
173 url=
"https://standards.freedesktop.org/desktop-entry-spec/latest/">Desktop Entry
174 Specification
</ulink>. (However, note that the option only takes a single item, and not a colon-separated list
175 like
<varname>$XDG_CURRENT_DESKTOP
</varname>.) See
176 <citerefentry><refentrytitle>sd_session_get_desktop
</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
177 further details.
</para>
179 <xi:include href=
"version-info.xml" xpointer=
"v240"/></listitem>
183 <term><varname>default-capability-bounding-set=
</varname></term>
184 <term><varname>default-capability-ambient-set=
</varname></term>
186 <listitem><para>Takes a comma-separated list of process capabilities
187 (e.g.
<constant>CAP_WAKE_ALARM
</constant>,
<constant>CAP_BLOCK_SUSPEND
</constant>, …) to set for the
188 invoked session's processes, if the user record does not encode appropriate sets of capabilities
189 directly. See
<citerefentry
190 project='man-pages'
><refentrytitle>capabilities
</refentrytitle><manvolnum>7</manvolnum></citerefentry>
191 for details on the capabilities concept. If not specified, the default bounding set is left as is
192 (i.e. usually contains the full set of capabilities). The default ambient set is set to
193 <constant>CAP_WAKE_ALARM
</constant> for regular users if the PAM session is associated with a local
194 seat or if it is invoked for the
<literal>systemd-user
</literal> service. Otherwise defaults to the
197 <xi:include href=
"version-info.xml" xpointer=
"v254"/></listitem>
201 <term><varname>debug
</varname><optional>=
</optional></term>
203 <listitem><para>Takes an optional boolean argument. If yes or without the argument, the module will log
204 debugging information as it operates.
</para></listitem>
210 <title>Module Types Provided
</title>
212 <para>Only
<option>session
</option> is provided.
</para>
216 <title>Environment
</title>
218 <para>The following environment variables are initialized by the module and available to the processes of the
219 user's session:
</para>
221 <variablelist class='environment-variables'
>
223 <term><varname>$XDG_SESSION_ID
</varname></term>
225 <listitem><para>A short session identifier, suitable to be used in filenames. The string itself should be
226 considered opaque, although often it is just the audit session ID as reported by
227 <filename>/proc/self/sessionid
</filename>. Each ID will be assigned only once during machine uptime. It may
228 hence be used to uniquely label files or other resources of this session. Combine this ID with the boot
229 identifier, as returned by
230 <citerefentry><refentrytitle>sd_id128_get_boot
</refentrytitle><manvolnum>3</manvolnum></citerefentry>, for a
231 globally unique identifier.
</para></listitem>
235 <term><varname>$XDG_RUNTIME_DIR
</varname></term>
237 <listitem><para>Path to a user-private user-writable directory
238 that is bound to the user login time on the machine. It is
239 automatically created the first time a user logs in and
240 removed on the user's final logout. If a user logs in twice at
241 the same time, both sessions will see the same
242 <varname>$XDG_RUNTIME_DIR
</varname> and the same contents. If
243 a user logs in once, then logs out again, and logs in again,
244 the directory contents will have been lost in between, but
245 applications should not rely on this behavior and must be able
246 to deal with stale files. To store session-private data in
247 this directory, the user should include the value of
248 <varname>$XDG_SESSION_ID
</varname> in the filename. This
249 directory shall be used for runtime file system objects such
250 as
<constant>AF_UNIX
</constant> sockets, FIFOs, PID files and
251 similar. It is guaranteed that this directory is local and
252 offers the greatest possible file system feature set the
253 operating system provides. For further details, see the
<ulink
254 url=
"https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
255 Base Directory Specification
</ulink>.
<varname>$XDG_RUNTIME_DIR
</varname>
256 is not set if the current user is not the original user of the session.
</para></listitem>
260 <term><varname>$TZ
</varname></term>
261 <term><varname>$EMAIL
</varname></term>
262 <term><varname>$LANG
</varname></term>
264 <listitem><para>If a JSON user record is known for the user logging in these variables are
265 initialized from the respective data in the record.
</para>
267 <xi:include href=
"version-info.xml" xpointer=
"v245"/></listitem>
272 <para>The following environment variables are read by the module and may be used by the PAM service to pass
273 metadata to the module. If these variables are not set when the PAM module is invoked but can be determined
274 otherwise they are set by the module, so that these variables are initialized for the session and applications if
277 <variablelist class='environment-variables'
>
279 <term><varname>$XDG_SESSION_TYPE
</varname></term>
281 <listitem><para>The session type. This may be used instead of
<varname>type=
</varname> on the module parameter
282 line, and is usually preferred.
</para>
284 <xi:include href=
"version-info.xml" xpointer=
"v209"/></listitem>
288 <term><varname>$XDG_SESSION_CLASS
</varname></term>
290 <listitem><para>The session class. This may be used instead of
<varname>class=
</varname> on the module parameter
291 line, and is usually preferred.
</para>
293 <xi:include href=
"version-info.xml" xpointer=
"v209"/></listitem>
297 <term><varname>$XDG_SESSION_DESKTOP
</varname></term>
299 <listitem><para>The desktop identifier. This may be used instead of
<varname>desktop=
</varname> on the module
300 parameter line, and is usually preferred.
</para>
302 <xi:include href=
"version-info.xml" xpointer=
"v209"/></listitem>
306 <term><varname>$XDG_SEAT
</varname></term>
308 <listitem><para>The seat name the session shall be registered
311 <xi:include href=
"version-info.xml" xpointer=
"v209"/></listitem>
315 <term><varname>$XDG_VTNR
</varname></term>
317 <listitem><para>The VT number the session shall be registered
318 for, if any. (Only applies to seats with a VT available, such
319 as
<literal>seat0
</literal>)
</para>
321 <xi:include href=
"version-info.xml" xpointer=
"v209"/></listitem>
325 <para>If not set,
<command>pam_systemd
</command> will initialize
326 <varname>$XDG_SEAT
</varname> and
<varname>$XDG_VTNR
</varname>
327 based on the
<varname>$DISPLAY
</varname> variable (if the latter is set).
</para>
331 <title>Session limits
</title>
333 <para>PAM modules earlier in the stack, that is those that come before
<command>pam_systemd.so
</command>,
334 can set session scope limits using the PAM context objects. The data for these objects is provided as
<constant>NUL
</constant>-terminated C strings
335 and maps directly to the respective unit resource control directives. Note that these limits apply to individual sessions of the user,
336 they do not apply to all user processes as a combined whole. In particular, the per-user
<command>user@.service
</command> unit instance,
337 which runs the
<command>systemd --user
</command> manager process and its children, and is tracked outside of any session, being shared
338 by all the user's sessions, is not covered by these limits.
342 <citerefentry><refentrytitle>systemd.resource-control
</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information about the resources.
343 Also, see
<citerefentry project='man-pages'
><refentrytitle>pam_set_data
</refentrytitle><manvolnum>3</manvolnum></citerefentry> for additional information about how to set
347 <variablelist class='pam-directives'
>
349 <term><varname>systemd.memory_max=
</varname></term>
351 <listitem><para>Sets unit
<varname>MemoryMax=
</varname>.
</para>
353 <xi:include href=
"version-info.xml" xpointer=
"v239"/></listitem>
357 <term><varname>systemd.tasks_max=
</varname></term>
359 <listitem><para>Sets unit
<varname>TasksMax=
</varname>.
</para>
361 <xi:include href=
"version-info.xml" xpointer=
"v239"/></listitem>
365 <term><varname>systemd.cpu_weight=
</varname></term>
367 <listitem><para>Sets unit
<varname>CPUWeight=
</varname>.
</para>
369 <xi:include href=
"version-info.xml" xpointer=
"v239"/></listitem>
373 <term><varname>systemd.io_weight=
</varname></term>
375 <listitem><para>Sets unit
<varname>IOWeight=
</varname>.
</para>
377 <xi:include href=
"version-info.xml" xpointer=
"v239"/></listitem>
381 <term><varname>systemd.runtime_max_sec=
</varname></term>
383 <listitem><para>Sets unit
<varname>RuntimeMaxSec=
</varname>.
</para>
385 <xi:include href=
"version-info.xml" xpointer=
"v244"/></listitem>
389 <para>Example data as can be provided from an another PAM module:
391 pam_set_data(handle,
"systemd.memory_max", (void *)
"200M", cleanup);
392 pam_set_data(handle,
"systemd.tasks_max", (void *)
"50", cleanup);
393 pam_set_data(handle,
"systemd.cpu_weight", (void *)
"100", cleanup);
394 pam_set_data(handle,
"systemd.io_weight", (void *)
"340", cleanup);
395 pam_set_data(handle,
"systemd.runtime_max_sec", (void *)
"3600", cleanup);
402 <title>Example
</title>
404 <para>Here's an example PAM configuration fragment that allows users sessions to be managed by
405 <filename>systemd-logind.service
</filename>:
</para>
407 <programlisting>#%PAM-
1.0
408 auth sufficient pam_unix.so
409 -auth sufficient pam_systemd_home.so
410 auth required pam_deny.so
412 account required pam_nologin.so
413 -account sufficient pam_systemd_home.so
414 account sufficient pam_unix.so
415 account required pam_permit.so
417 -password sufficient pam_systemd_home.so
418 password sufficient pam_unix.so sha512 shadow try_first_pass
419 password required pam_deny.so
421 -session optional pam_keyinit.so revoke
422 -session optional pam_loginuid.so
423 -session optional pam_systemd_home.so
424 <command>-session optional pam_systemd.so
</command>
425 session required pam_unix.so
</programlisting>
429 <title>See Also
</title>
430 <para><simplelist type=
"inline">
431 <member><citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
432 <member><citerefentry><refentrytitle>systemd-logind.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
433 <member><citerefentry><refentrytitle>logind.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
434 <member><citerefentry><refentrytitle>loginctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
435 <member><citerefentry><refentrytitle>pam_systemd_home
</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
436 <member><citerefentry project='man-pages'
><refentrytitle>pam.conf
</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
437 <member><citerefentry project='man-pages'
><refentrytitle>pam.d
</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
438 <member><citerefentry project='man-pages'
><refentrytitle>pam
</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
439 <member><citerefentry project='man-pages'
><refentrytitle>pam_loginuid
</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
440 <member><citerefentry><refentrytitle>systemd.scope
</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
441 <member><citerefentry><refentrytitle>systemd.slice
</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
442 <member><citerefentry><refentrytitle>systemd.service
</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>