1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
6 SPDX-License-Identifier: LGPL-2.1+
8 This file is part of elogind.
10 Copyright 2010 Lennart Poettering
12 elogind is free software; you can redistribute it and/or modify it
13 under the terms of the GNU Lesser General Public License as published by
14 the Free Software Foundation; either version 2.1 of the License, or
15 (at your option) any later version.
17 elogind is distributed in the hope that it will be useful, but
18 WITHOUT ANY WARRANTY; without even the implied warranty of
19 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 Lesser General Public License for more details.
22 You should have received a copy of the GNU Lesser General Public License
23 along with elogind; If not, see <http://www.gnu.org/licenses/>.
26 <refentry id="elogind"
27 xmlns:xi="http://www.w3.org/2001/XInclude">
30 <title>elogind</title>
31 <productname>elogind</productname>
35 <contrib>Developer</contrib>
36 <firstname>Lennart</firstname>
37 <surname>Poettering</surname>
38 <email>lennart@poettering.net</email>
44 <refentrytitle>elogind</refentrytitle>
45 <!-- 0 /// elogind is in section 8
46 <manvolnum>1</manvolnum>
48 <manvolnum>8</manvolnum>
53 <!-- 0 /// Well, elogind isn't that much...
54 <refname>systemd</refname>
55 <refname>init</refname>
56 <refpurpose>systemd system and service manager</refpurpose>
58 <refname>elogind</refname>
59 <refpurpose>Login manager</refpurpose>
64 <!-- 0 /// elogind has a different synopsis of course...
66 <command>/usr/lib/systemd/systemd</command>
67 <arg choice="opt" rep="repeat">OPTIONS</arg>
70 <command>init</command>
71 <arg choice="opt" rep="repeat">OPTIONS</arg>
72 <arg choice="req">COMMAND</arg>
76 <command>elogind</command>
77 <arg choice="opt" rep="repeat">OPTIONS</arg>
78 <arg choice="req">COMMAND</arg>
84 <title>Description</title>
86 <!-- 0 /// elogind does not need that much explanation.
87 <para>systemd is a system and service manager for Linux operating
88 systems. When run as first process on boot (as PID 1), it acts as
89 init system that brings up and maintains userspace
92 <para>For compatibility with SysV, if systemd is called as
93 <command>init</command> and a PID that is not 1, it will execute
94 <command>telinit</command> and pass all command line arguments
95 unmodified. That means <command>init</command> and
96 <command>telinit</command> are mostly equivalent when invoked from
97 normal login sessions. See
98 <citerefentry><refentrytitle>telinit</refentrytitle><manvolnum>8</manvolnum></citerefentry>
99 for more information.</para>
101 <para>When run as a system instance, systemd interprets the
102 configuration file <filename>system.conf</filename> and the files
103 in <filename>system.conf.d</filename> directories; when run as a
104 user instance, systemd interprets the configuration file
105 <filename>user.conf</filename> and the files in
106 <filename>user.conf.d</filename> directories. See
107 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
108 for more information.</para>
110 <para><command>elogind</command> is a system service that
111 manages user logins. It is responsible for:</para>
114 <listitem><para>Keeping track of users and sessions, their
115 processes and their idle state</para></listitem>
117 <listitem><para>Providing PolicyKit-based access for users to
118 operations such as system shutdown or sleep</para></listitem>
120 <listitem><para>Implementing a shutdown/sleep inhibition logic
121 for applications</para></listitem>
123 <listitem><para>Handling of power/sleep hardware
124 keys</para></listitem>
126 <listitem><para>Multi-seat management</para></listitem>
128 <listitem><para>Session switch management</para></listitem>
130 <listitem><para>Device access management for
131 users</para></listitem>
135 <para>User sessions are registered in elogind via the
136 <citerefentry><refentrytitle>pam_elogind</refentrytitle><manvolnum>8</manvolnum></citerefentry>
140 <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
141 for information about the configuration of this service.</para>
144 url="http://www.freedesktop.org/wiki/Software/systemd/multiseat">Multi-Seat
145 on Linux</ulink> for an introduction into basic concepts of logind
146 such as users, sessions and seats.</para>
149 url="http://www.freedesktop.org/wiki/Software/systemd/logind">
150 logind D-Bus API Documentation</ulink> for information about the
151 APIs <filename>logind</filename> provides.</para>
153 <para>For more information on the inhibition logic see the <ulink
154 url="http://www.freedesktop.org/wiki/Software/systemd/inhibit">Inhibitor
155 Lock Developer Documentation</ulink>.</para>
160 <title>Options</title>
162 <para>The following options are understood:</para>
165 <!-- 0 /// This list is much shorter with elogind of course.
167 <term><option>--test</option></term>
169 <listitem><para>Determine startup sequence, dump it and exit.
170 This is an option useful for debugging only.</para></listitem>
173 <term><option>--dump-configuration-items</option></term>
175 <listitem><para>Dump understood unit configuration items. This
176 outputs a terse but complete list of configuration items
177 understood in unit definition files.</para></listitem>
180 <term><option>--unit=</option></term>
182 <listitem><para>Set default unit to activate on startup. If
183 not specified, defaults to
184 <filename>default.target</filename>.</para></listitem>
187 <term><option>--system</option></term>
188 <term><option>--user</option></term>
190 <listitem><para>For <option>--system</option>, tell systemd to
191 run a system instance, even if the process ID is not 1, i.e.
192 systemd is not run as init process. <option>--user</option>
193 does the opposite, running a user instance even if the process
194 ID is 1. Normally, it should not be necessary to pass these
195 options, as systemd automatically detects the mode it is
196 started in. These options are hence of little use except for
197 debugging. Note that it is not supported booting and
198 maintaining a full system with systemd running in
199 <option>--system</option> mode, but PID not 1. In practice,
200 passing <option>--system</option> explicitly is only useful in
201 conjunction with <option>--test</option>.</para></listitem>
204 <term><option>--dump-core</option></term>
206 <listitem><para>Enable core dumping on crash. This switch has
207 no effect when running as user instance. This setting may also
208 be enabled during boot on the kernel command line via the
209 <varname>systemd.dump_core=</varname> option, see
210 below.</para></listitem>
214 <term><option>--crash-vt=</option><replaceable>VT</replaceable></term>
216 <listitem><para>Switch to a specific virtual console (VT) on
217 crash. Takes a positive integer in the range 1–63, or a
218 boolean argument. If an integer is passed, selects which VT to
219 switch to. If <constant>yes</constant>, the VT kernel messages
220 are written to is selected. If <constant>no</constant>, no VT
221 switch is attempted. This switch has no effect when running as
222 user instance. This setting may also be enabled during boot,
223 on the kernel command line via the
224 <varname>systemd.crash_vt=</varname> option, see
226 <!-- FIXME: there is no crash_vt command line option? -->
227 <!-- 0 /// elogind check_tree.pl can not mangle closed comments.
228 below.</para></listitem>
232 <term><option>--crash-shell</option></term>
234 <listitem><para>Run a shell on crash. This switch has no
235 effect when running as user instance. This setting may also be
236 enabled during boot, on the kernel command line via the
237 <varname>systemd.crash_shell=</varname> option, see
238 below.</para></listitem>
242 <term><option>--crash-reboot</option></term>
244 <listitem><para>Automatically reboot the system on crash. This
245 switch has no effect when running as user instance. This
246 setting may also be enabled during boot, on the kernel command
247 line via the <varname>systemd.crash_reboot=</varname> option,
248 see below.</para></listitem>
252 <term><option>--confirm-spawn</option></term>
254 <listitem><para>Ask for confirmation when spawning processes.
255 This switch has no effect when run as user
256 instance.</para></listitem>
259 <term><option>--show-status=</option></term>
261 <listitem><para>Takes a boolean argument or the special value <constant>auto</constant>. If on, terse unit
262 status information is shown on the console during boot-up and shutdown. If off, no such status information is
263 shown. If set to <constant>auto</constant> behavior is similar to off, except that it is automatically switched
264 to on, as soon as the first unit failure or significant boot delay is encountered. This switch has no effect
265 when invoked as user instance. If specified, overrides both the kernel command line setting
266 <varname>systemd.show_status=</varname> (see below) and the configuration file option
267 <option>ShowStatus=</option>, see
268 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
271 <term><option>--log-target=</option></term>
273 <listitem><para>Set log target. Argument must be one of
274 <option>console</option>,
275 <option>journal</option>,
276 <option>kmsg</option>,
277 <option>journal-or-kmsg</option>,
278 <option>null</option>.</para></listitem>
281 <term><option>--log-level=</option></term>
283 <listitem><para>Set log level. As
284 argument this accepts a numerical log
285 level or the well-known <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
286 symbolic names (lowercase):
287 <option>emerg</option>,
288 <option>alert</option>,
289 <option>crit</option>,
290 <option>err</option>,
291 <option>warning</option>,
292 <option>notice</option>,
293 <option>info</option>,
294 <option>debug</option>.</para></listitem>
297 <term><option>--log-color=</option></term>
299 <listitem><para>Highlight important log messages. Argument is
300 a boolean value. If the argument is omitted, it defaults to
301 <option>true</option>.</para></listitem>
304 <term><option>--log-location=</option></term>
306 <listitem><para>Include code location in log messages. This is
307 mostly relevant for debugging purposes. Argument is a boolean
308 value. If the argument is omitted it defaults to
309 <option>true</option>.</para></listitem>
312 <term><option>--default-standard-output=</option></term>
313 <term><option>--default-standard-error=</option></term>
315 <listitem><para>Sets the default output or error output for
316 all services and sockets, respectively. That is, controls the
317 default for <option>StandardOutput=</option> and
318 <option>StandardError=</option> (see
319 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
320 for details). Takes one of
321 <option>inherit</option>,
322 <option>null</option>,
323 <option>tty</option>,
324 <option>journal</option>,
325 <option>journal+console</option>,
326 <option>syslog</option>,
327 <option>syslog+console</option>,
328 <option>kmsg</option>,
329 <option>kmsg+console</option>. If the
331 <option>--default-standard-output=</option> defaults to
332 <option>journal</option> and
333 <option>--default-standard-error=</option> to
334 <option>inherit</option>.</para></listitem>
338 <term><option>--machine-id=</option></term>
340 <listitem><para>Override the machine-id set on the hard drive,
341 useful for network booting or for containers. May not be set
342 to all zeros.</para></listitem>
346 <term><option>--service-watchdogs=</option></term>
348 <listitem><para>Globally enable/disable all service watchdog timeouts and emergency
349 actions. This setting may also be specified during boot, on the kernel
350 command line via the <varname>systemd.service_watchdogs=</varname>
351 option, see below. Defaults to enabled.</para></listitem>
354 <xi:include href="standard-options.xml" xpointer="help" />
355 <xi:include href="standard-options.xml" xpointer="version" />
358 <term><option>-D</option></term>
359 <term><option>--daemon</option></term>
361 <listitem><para>Daemonize elogind by double-forking
362 into background.</para></listitem>
366 <term><option>-h</option></term>
367 <term><option>--help</option></term>
369 <listitem><para>Show the helpt text and exit.</para></listitem>
375 <!-- 0 /// The whole concpets section is unneeded in elogind
377 <title>Concepts</title>
379 <para>systemd provides a dependency system between various
380 entities called "units" of 11 different types. Units encapsulate
381 various objects that are relevant for system boot-up and
382 maintenance. The majority of units are configured in unit
383 configuration files, whose syntax and basic set of options is
385 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
386 however some are created automatically from other configuration,
387 dynamically from system state or programmatically at runtime.
388 Units may be "active" (meaning started, bound, plugged in, …,
389 depending on the unit type, see below), or "inactive" (meaning
390 stopped, unbound, unplugged, …), as well as in the process of
391 being activated or deactivated, i.e. between the two states (these
392 states are called "activating", "deactivating"). A special
393 "failed" state is available as well, which is very similar to
394 "inactive" and is entered when the service failed in some way
395 (process returned error code on exit, or crashed, an operation
396 timed out, or after too many restarts). If this state is entered,
397 the cause will be logged, for later reference. Note that the
398 various unit types may have a number of additional substates,
399 which are mapped to the five generalized unit states described
402 <para>The following unit types are available:</para>
405 <listitem><para>Service units, which start and control daemons
406 and the processes they consist of. For details, see
407 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
409 <listitem><para>Socket units, which encapsulate local IPC or
410 network sockets in the system, useful for socket-based
411 activation. For details about socket units, see
412 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
413 for details on socket-based activation and other forms of
415 <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
417 <listitem><para>Target units are useful to group units, or
418 provide well-known synchronization points during boot-up, see
419 <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
421 <listitem><para>Device units expose kernel devices in systemd
422 and may be used to implement device-based activation. For
424 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
426 <listitem><para>Mount units control mount points in the file
427 system, for details see
428 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
430 <listitem><para>Automount units provide automount capabilities,
431 for on-demand mounting of file systems as well as parallelized
433 <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
435 <listitem><para>Timer units are useful for triggering activation
436 of other units based on timers. You may find details in
437 <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
439 <listitem><para>Swap units are very similar to mount units and
440 encapsulate memory swap partitions or files of the operating
441 system. They are described in
442 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
444 <listitem><para>Path units may be used to activate other
445 services when file system objects change or are modified. See
446 <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
448 <listitem><para>Slice units may be used to group units which
449 manage system processes (such as service and scope units) in a
450 hierarchical tree for resource management purposes. See
451 <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
453 <listitem><para>Scope units are similar to service units, but
454 manage foreign processes instead of starting them as well. See
455 <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
459 <para>Units are named as their configuration files. Some units
460 have special semantics. A detailed list is available in
461 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
463 <para>systemd knows various kinds of dependencies, including
464 positive and negative requirement dependencies (i.e.
465 <varname>Requires=</varname> and <varname>Conflicts=</varname>) as
466 well as ordering dependencies (<varname>After=</varname> and
467 <varname>Before=</varname>). NB: ordering and requirement
468 dependencies are orthogonal. If only a requirement dependency
469 exists between two units (e.g. <filename>foo.service</filename>
470 requires <filename>bar.service</filename>), but no ordering
471 dependency (e.g. <filename>foo.service</filename> after
472 <filename>bar.service</filename>) and both are requested to start,
473 they will be started in parallel. It is a common pattern that both
474 requirement and ordering dependencies are placed between two
475 units. Also note that the majority of dependencies are implicitly
476 created and maintained by systemd. In most cases, it should be
477 unnecessary to declare additional dependencies manually, however
478 it is possible to do this.</para>
480 <para>Application programs and units (via dependencies) may
481 request state changes of units. In systemd, these requests are
482 encapsulated as 'jobs' and maintained in a job queue. Jobs may
483 succeed or can fail, their execution is ordered based on the
484 ordering dependencies of the units they have been scheduled
487 <para>On boot systemd activates the target unit
488 <filename>default.target</filename> whose job is to activate
489 on-boot services and other on-boot units by pulling them in via
490 dependencies. Usually, the unit name is just an alias (symlink) for
491 either <filename>graphical.target</filename> (for fully-featured
492 boots into the UI) or <filename>multi-user.target</filename> (for
493 limited console-only boots for use in embedded or server
494 environments, or similar; a subset of graphical.target). However,
495 it is at the discretion of the administrator to configure it as an
496 alias to any other target unit. See
497 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
498 for details about these target units.</para>
500 <para>Processes systemd spawns are placed in individual Linux
501 control groups named after the unit which they belong to in the
502 private systemd hierarchy. (see <ulink
503 url="https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt">cgroups.txt</ulink>
504 for more information about control groups, or short "cgroups").
505 systemd uses this to effectively keep track of processes. Control
506 group information is maintained in the kernel, and is accessible
507 via the file system hierarchy (beneath
508 <filename>/sys/fs/cgroup/systemd/</filename>), or in tools such as
509 <citerefentry project='man-pages'><refentrytitle>systemd-cgls</refentrytitle><manvolnum>1</manvolnum></citerefentry>
511 <citerefentry project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>
512 (<command>ps xawf -eo pid,user,cgroup,args</command> is
513 particularly useful to list all processes and the systemd units
514 they belong to.).</para>
516 <para>systemd is compatible with the SysV init system to a large
517 degree: SysV init scripts are supported and simply read as an
518 alternative (though limited) configuration file format. The SysV
519 <filename>/dev/initctl</filename> interface is provided, and
520 compatibility implementations of the various SysV client tools are
521 available. In addition to that, various established Unix
522 functionality such as <filename>/etc/fstab</filename> or the
523 <filename>utmp</filename> database are supported.</para>
525 <para>systemd has a minimal transaction system: if a unit is
526 requested to start up or shut down it will add it and all its
527 dependencies to a temporary transaction. Then, it will verify if
528 the transaction is consistent (i.e. whether the ordering of all
529 units is cycle-free). If it is not, systemd will try to fix it up,
530 and removes non-essential jobs from the transaction that might
531 remove the loop. Also, systemd tries to suppress non-essential
532 jobs in the transaction that would stop a running service. Finally
533 it is checked whether the jobs of the transaction contradict jobs
534 that have already been queued, and optionally the transaction is
535 aborted then. If all worked out and the transaction is consistent
536 and minimized in its impact it is merged with all already
537 outstanding jobs and added to the run queue. Effectively this
538 means that before executing a requested operation, systemd will
539 verify that it makes sense, fixing it if possible, and only
540 failing if it really cannot work.</para>
542 <para>systemd contains native implementations of various tasks
543 that need to be executed as part of the boot process. For example,
544 it sets the hostname or configures the loopback network device. It
545 also sets up and mounts various API file systems, such as
546 <filename>/sys</filename> or <filename>/proc</filename>.</para>
548 <para>For more information about the concepts and
549 ideas behind systemd, please refer to the
550 <ulink url="http://0pointer.de/blog/projects/systemd.html">Original Design Document</ulink>.</para>
552 <para>Note that some but not all interfaces provided
553 by systemd are covered by the
554 <ulink url="https://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
555 Stability Promise</ulink>.</para>
557 <para>Units may be generated dynamically at boot and system
558 manager reload time, for example based on other configuration
559 files or parameters passed on the kernel command line. For details, see
560 <citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
562 <para>Systems which invoke systemd in a container or initrd
563 environment should implement the
564 <ulink url="https://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container Interface</ulink> or
565 <ulink url="https://www.freedesktop.org/wiki/Software/systemd/InitrdInterface">initrd Interface</ulink>
566 specifications, respectively.</para>
570 <!-- 0 /// The whole directories section is unneeded in elogind
572 <title>Directories</title>
576 <term>System unit directories</term>
578 <listitem><para>The systemd system manager reads unit
579 configuration from various directories. Packages that want to
580 install unit files shall place them in the directory returned
581 by <command>pkg-config systemd
582 --variable=systemdsystemunitdir</command>. Other directories
583 checked are <filename>/usr/local/lib/systemd/system</filename>
584 and <filename>/usr/lib/systemd/system</filename>. User
585 configuration always takes precedence. <command>pkg-config
586 systemd --variable=systemdsystemconfdir</command> returns the
587 path of the system configuration directory. Packages should
588 alter the content of these directories only with the
589 <command>enable</command> and <command>disable</command>
591 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
592 tool. Full list of directories is provided in
593 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
600 <term>User unit directories</term>
602 <listitem><para>Similar rules apply for the user unit
603 directories. However, here the
604 <ulink url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
605 Base Directory specification</ulink> is followed to find
606 units. Applications should place their unit files in the
607 directory returned by <command>pkg-config systemd
608 --variable=systemduserunitdir</command>. Global configuration
609 is done in the directory reported by <command>pkg-config
610 systemd --variable=systemduserconfdir</command>. The
611 <command>enable</command> and <command>disable</command>
613 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
614 tool can handle both global (i.e. for all users) and private
615 (for one user) enabling/disabling of units. Full list of
616 directories is provided in
617 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
624 <term>SysV init scripts directory</term>
626 <listitem><para>The location of the SysV init script directory
627 varies between distributions. If systemd cannot find a native
628 unit file for a requested service, it will look for a SysV
629 init script of the same name (with the
630 <filename>.service</filename> suffix
631 removed).</para></listitem>
637 <term>SysV runlevel link farm directory</term>
639 <listitem><para>The location of the SysV runlevel link farm
640 directory varies between distributions. systemd will take the
641 link farm into account when figuring out whether a service
642 shall be enabled. Note that a service unit with a native unit
643 configuration file cannot be started by activating it in the
644 SysV runlevel link farm.</para></listitem>
650 <!-- 0 /// The whole Signals section is unneeded in elogind
652 <title>Signals</title>
656 <term><constant>SIGTERM</constant></term>
658 <listitem><para>Upon receiving this signal the systemd system
659 manager serializes its state, reexecutes itself and
660 deserializes the saved state again. This is mostly equivalent
661 to <command>systemctl daemon-reexec</command>.</para>
663 <para>systemd user managers will start the
664 <filename>exit.target</filename> unit when this signal is
665 received. This is mostly equivalent to <command>systemctl
666 --user start exit.target
667 --job-mode=replace-irreversible</command>.</para></listitem>
671 <term><constant>SIGINT</constant></term>
673 <listitem><para>Upon receiving this signal the systemd system
674 manager will start the
675 <filename>ctrl-alt-del.target</filename> unit. This is mostly
676 equivalent to <command>systemctl start ctrl-alt-del.target
677 --job-mode=replace-irreversible</command>. If this signal is
678 received more than 7 times per 2s, an immediate reboot is
679 triggered. Note that pressing Ctrl-Alt-Del on the console
680 will trigger this signal. Hence, if a reboot is hanging,
681 pressing Ctrl-Alt-Del more than 7 times in 2s is a relatively
682 safe way to trigger an immediate reboot.</para>
684 <para>systemd user managers treat this signal the same way as
685 <constant>SIGTERM</constant>.</para></listitem>
689 <term><constant>SIGWINCH</constant></term>
691 <listitem><para>When this signal is received the systemd
692 system manager will start the
693 <filename>kbrequest.target</filename> unit. This is mostly
694 equivalent to <command>systemctl start
695 kbrequest.target</command>.</para>
697 <para>This signal is ignored by systemd user
698 managers.</para></listitem>
702 <term><constant>SIGPWR</constant></term>
704 <listitem><para>When this signal is received the systemd
705 manager will start the <filename>sigpwr.target</filename>
706 unit. This is mostly equivalent to <command>systemctl start
707 sigpwr.target</command>.</para></listitem>
711 <term><constant>SIGUSR1</constant></term>
713 <listitem><para>When this signal is received the systemd
714 manager will try to reconnect to the D-Bus
715 bus.</para></listitem>
719 <term><constant>SIGUSR2</constant></term>
721 <listitem><para>When this signal is received the systemd
722 manager will log its complete state in human-readable form.
723 The data logged is the same as printed by
724 <command>systemd-analyze dump</command>.</para></listitem>
728 <term><constant>SIGHUP</constant></term>
730 <listitem><para>Reloads the complete daemon configuration.
731 This is mostly equivalent to <command>systemctl
732 daemon-reload</command>.</para></listitem>
736 <term><constant>SIGRTMIN+0</constant></term>
738 <listitem><para>Enters default mode, starts the
739 <filename>default.target</filename> unit. This is mostly
740 equivalent to <command>systemctl isolate
741 default.target</command>.</para></listitem>
745 <term><constant>SIGRTMIN+1</constant></term>
747 <listitem><para>Enters rescue mode, starts the
748 <filename>rescue.target</filename> unit. This is mostly
749 equivalent to <command>systemctl isolate
750 rescue.target</command>.</para></listitem>
754 <term><constant>SIGRTMIN+2</constant></term>
756 <listitem><para>Enters emergency mode, starts the
757 <filename>emergency.service</filename> unit. This is mostly
758 equivalent to <command>systemctl isolate
759 emergency.service</command>.</para></listitem>
763 <term><constant>SIGRTMIN+3</constant></term>
765 <listitem><para>Halts the machine, starts the
766 <filename>halt.target</filename> unit. This is mostly
767 equivalent to <command>systemctl start halt.target
768 --job-mode=replace-irreversible</command>.</para>
773 <term><constant>SIGRTMIN+4</constant></term>
775 <listitem><para>Powers off the machine, starts the
776 <filename>poweroff.target</filename> unit. This is mostly
777 equivalent to <command>systemctl start poweroff.target
778 --job-mode=replace-irreversible</command>.</para>
783 <term><constant>SIGRTMIN+5</constant></term>
785 <listitem><para>Reboots the machine, starts the
786 <filename>reboot.target</filename> unit. This is mostly
787 equivalent to <command>systemctl start reboot.target
788 --job-mode=replace-irreversible</command>.</para>
793 <term><constant>SIGRTMIN+6</constant></term>
795 <listitem><para>Reboots the machine via kexec, starts the
796 <filename>kexec.target</filename> unit. This is mostly
797 equivalent to <command>systemctl start kexec.target
798 --job-mode=replace-irreversible</command>.</para>
803 <term><constant>SIGRTMIN+13</constant></term>
805 <listitem><para>Immediately halts the machine.</para></listitem>
809 <term><constant>SIGRTMIN+14</constant></term>
811 <listitem><para>Immediately powers off the machine.</para></listitem>
815 <term><constant>SIGRTMIN+15</constant></term>
817 <listitem><para>Immediately reboots the machine.</para></listitem>
821 <term><constant>SIGRTMIN+16</constant></term>
823 <listitem><para>Immediately reboots the machine with kexec.</para></listitem>
827 <term><constant>SIGRTMIN+20</constant></term>
829 <listitem><para>Enables display of status messages on the
830 console, as controlled via
831 <varname>systemd.show_status=1</varname> on the kernel command
832 line.</para></listitem>
836 <term><constant>SIGRTMIN+21</constant></term>
838 <listitem><para>Disables display of
839 status messages on the console, as
841 <varname>systemd.show_status=0</varname>
842 on the kernel command
843 line.</para></listitem>
847 <term><constant>SIGRTMIN+22</constant></term>
848 <term><constant>SIGRTMIN+23</constant></term>
850 <listitem><para>Sets the log level to <literal>debug</literal>
851 (or <literal>info</literal> on
852 <constant>SIGRTMIN+23</constant>), as controlled via
853 <varname>systemd.log_level=debug</varname> (or
854 <varname>systemd.log_level=info</varname> on
855 <constant>SIGRTMIN+23</constant>) on the kernel command
856 line.</para></listitem>
860 <term><constant>SIGRTMIN+24</constant></term>
862 <listitem><para>Immediately exits the manager (only available
863 for --user instances).</para></listitem>
867 <term><constant>SIGRTMIN+26</constant></term>
868 <term><constant>SIGRTMIN+27</constant></term>
869 <term><constant>SIGRTMIN+28</constant></term>
871 <listitem><para>Sets the log target to
872 <literal>journal-or-kmsg</literal> (or
873 <literal>console</literal> on
874 <constant>SIGRTMIN+27</constant>, <literal>kmsg</literal> on
875 <constant>SIGRTMIN+28</constant>), as controlled via
876 <varname>systemd.log_target=journal-or-kmsg</varname> (or
877 <varname>systemd.log_target=console</varname> on
878 <constant>SIGRTMIN+27</constant> or
879 <varname>systemd.log_target=kmsg</varname> on
880 <constant>SIGRTMIN+28</constant>) on the kernel command
881 line.</para></listitem>
887 <!-- 0 /// The whole environment section is unneeded in elogind
889 <title>Environment</title>
891 <variablelist class='environment-variables'>
893 <term><varname>$SYSTEMD_LOG_LEVEL</varname></term>
894 <listitem><para>systemd reads the log level from this
895 environment variable. This can be overridden with
896 <option>--log-level=</option>.</para></listitem>
900 <term><varname>$SYSTEMD_LOG_TARGET</varname></term>
901 <listitem><para>systemd reads the log target from this
902 environment variable. This can be overridden with
903 <option>--log-target=</option>.</para></listitem>
907 <term><varname>$SYSTEMD_LOG_COLOR</varname></term>
908 <listitem><para>Controls whether systemd highlights important
909 log messages. This can be overridden with
910 <option>--log-color=</option>.</para></listitem>
914 <term><varname>$SYSTEMD_LOG_LOCATION</varname></term>
915 <listitem><para>Controls whether systemd prints the code
916 location along with log messages. This can be overridden with
917 <option>--log-location=</option>.</para></listitem>
921 <term><varname>$XDG_CONFIG_HOME</varname></term>
922 <term><varname>$XDG_CONFIG_DIRS</varname></term>
923 <term><varname>$XDG_DATA_HOME</varname></term>
924 <term><varname>$XDG_DATA_DIRS</varname></term>
926 <listitem><para>The systemd user manager uses these variables
927 in accordance to the <ulink
928 url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
929 Base Directory specification</ulink> to find its
930 configuration.</para></listitem>
934 <term><varname>$SYSTEMD_UNIT_PATH</varname></term>
936 <listitem><para>Controls where systemd looks for unit
937 files.</para></listitem>
941 <term><varname>$SYSTEMD_SYSVINIT_PATH</varname></term>
943 <listitem><para>Controls where systemd looks for SysV init
944 scripts.</para></listitem>
948 <term><varname>$SYSTEMD_SYSVRCND_PATH</varname></term>
950 <listitem><para>Controls where systemd looks for SysV init
951 script runlevel link farms.</para></listitem>
955 <term><varname>$SYSTEMD_COLORS</varname></term>
957 <listitem><para>The value must be a boolean. Controls whether colorized output should be
958 generated. This can be specified to override the decision that <command>systemd</command>
959 makes based on <varname>$TERM</varname> and what the console is connected to.</para>
964 <term><varname>$LISTEN_PID</varname></term>
965 <term><varname>$LISTEN_FDS</varname></term>
966 <term><varname>$LISTEN_FDNAMES</varname></term>
968 <listitem><para>Set by systemd for supervised processes during
969 socket-based activation. See
970 <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
971 for more information.</para></listitem>
975 <term><varname>$NOTIFY_SOCKET</varname></term>
977 <listitem><para>Set by systemd for supervised processes for
978 status and start-up completion notification. See
979 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
980 for more information.</para></listitem>
986 <!-- 0 /// The whole kernel section is unneeded in elogind
988 <title>Kernel Command Line</title>
990 <para>When run as system instance systemd parses a number of
991 kernel command line arguments<footnote><para>If run inside a Linux
992 container these arguments may be passed as command line arguments
993 to systemd itself, next to any of the command line options listed
994 in the Options section above. If run outside of Linux containers,
995 these arguments are parsed from <filename>/proc/cmdline</filename>
996 instead.</para></footnote>:</para>
998 <variablelist class='kernel-commandline-options'>
1000 <term><varname>systemd.unit=</varname></term>
1001 <term><varname>rd.systemd.unit=</varname></term>
1003 <listitem><para>Overrides the unit to activate on boot.
1004 Defaults to <filename>default.target</filename>. This may be
1005 used to temporarily boot into a different boot unit, for
1006 example <filename>rescue.target</filename> or
1007 <filename>emergency.service</filename>. See
1008 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1009 for details about these units. The option prefixed with
1010 <literal>rd.</literal> is honored only in the initial RAM disk
1011 (initrd), while the one that is not prefixed only in the main
1012 system.</para></listitem>
1016 <term><varname>systemd.dump_core</varname></term>
1018 <listitem><para>Takes a boolean argument or enables the option if specified
1019 without an argument. If enabled, the systemd manager (PID 1) dumps core when
1020 it crashes. Otherwise, no core dump is created. Defaults to enabled.</para>
1025 <term><varname>systemd.crash_chvt</varname></term>
1027 <listitem><para>Takes a positive integer, or a boolean argument. Can be also
1028 specified without an argument, with the same effect as a positive boolean. If
1029 a positive integer (in the range 1–63) is specified, the system manager (PID
1030 1) will activate the specified virtual terminal (VT) when it
1031 crashes. Defaults to disabled, meaning that no such switch is attempted. If
1032 set to enabled, the VT the kernel messages are written to is selected.
1037 <term><varname>systemd.crash_shell</varname></term>
1039 <listitem><para>Takes a boolean argument or enables the option if specified
1040 without an argument. If enabled, the system manager (PID 1) spawns a shell
1041 when it crashes, after a 10s delay. Otherwise, no shell is spawned. Defaults
1042 to disabled, for security reasons, as the shell is not protected by password
1043 authentication.</para></listitem>
1047 <term><varname>systemd.crash_reboot</varname></term>
1049 <listitem><para>Takes a boolean argument or enables the option if specified
1050 without an argument. If enabled, the system manager (PID 1) will reboot the
1051 machine automatically when it crashes, after a 10s delay. Otherwise, the
1052 system will hang indefinitely. Defaults to disabled, in order to avoid a
1053 reboot loop. If combined with <varname>systemd.crash_shell</varname>, the
1054 system is rebooted after the shell exits.</para></listitem>
1058 <term><varname>systemd.confirm_spawn</varname></term>
1060 <listitem><para>Takes a boolean argument or a path to the virtual console
1061 where the confirmation messages should be emitted. Can be also specified
1062 without an argument, with the same effect as a positive boolean. If enabled,
1063 the system manager (PID 1) asks for confirmation when spawning processes
1064 using <option>/dev/console</option>. If a path or a console name (such as
1065 <literal>ttyS0</literal>) is provided, the virtual console pointed to by this
1066 path or described by the give name will be used instead. Defaults to disabled.
1071 <term><varname>systemd.service_watchdogs=</varname></term>
1073 <listitem><para>Takes a boolean argument. If disabled, all service runtime
1074 watchdogs (<option>WatchdogSec=</option>) and emergency actions (e.g.
1075 <option>OnFailure=</option> or <option>StartLimitAction=</option>) are
1076 ignored by the system manager (PID 1); see
1077 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1078 Defaults to enabled, i.e. watchdogs and failure actions are processed
1079 normally. The hardware watchdog is not affected by this
1080 option.</para></listitem>
1084 <term><varname>systemd.show_status</varname></term>
1086 <listitem><para>Takes a boolean argument or the constant
1087 <constant>auto</constant>. Can be also specified without an argument, with
1088 the same effect as a positive boolean. If enabled, the systemd manager (PID
1089 1) shows terse service status updates on the console during bootup.
1090 <constant>auto</constant> behaves like <option>false</option> until a unit
1091 fails or there is a significant delay in boot. Defaults to enabled, unless
1092 <option>quiet</option> is passed as kernel command line option, in which case
1093 it defaults to <constant>auto</constant>. If specified overrides the system
1094 manager configuration file option <option>ShowStatus=</option>, see
1095 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1096 However, the process command line option <option>--show-status=</option>
1097 takes precedence over both this kernel command line option and the
1098 configuration file option.</para></listitem>
1102 <term><varname>systemd.log_target=</varname></term>
1103 <term><varname>systemd.log_level=</varname></term>
1104 <term><varname>systemd.log_location=</varname></term>
1105 <term><varname>systemd.log_color</varname></term>
1107 <listitem><para>Controls log output, with the same effect as the
1108 <varname>$SYSTEMD_LOG_TARGET</varname>,
1109 <varname>$SYSTEMD_LOG_LEVEL</varname>,
1110 <varname>$SYSTEMD_LOG_LOCATION</varname>,
1111 <varname>$SYSTEMD_LOG_COLOR</varname> environment variables described above.
1112 <varname>systemd.log_color</varname> can be specified without an argument,
1113 with the same effect as a positive boolean.</para></listitem>
1117 <term><varname>systemd.default_standard_output=</varname></term>
1118 <term><varname>systemd.default_standard_error=</varname></term>
1119 <listitem><para>Controls default standard output and error
1120 output for services, with the same effect as the
1121 <option>--default-standard-output=</option> and
1122 <option>--default-standard-error=</option> command line
1123 arguments described above, respectively.</para></listitem>
1127 <term><varname>systemd.setenv=</varname></term>
1129 <listitem><para>Takes a string argument in the form
1130 VARIABLE=VALUE. May be used to set default environment
1131 variables to add to forked child processes. May be used more
1132 than once to set multiple variables.</para></listitem>
1136 <term><varname>systemd.machine_id=</varname></term>
1138 <listitem><para>Takes a 32 character hex value to be
1139 used for setting the machine-id. Intended mostly for
1140 network booting where the same machine-id is desired
1141 for every boot.</para></listitem>
1145 <term><varname>systemd.unified_cgroup_hierarchy</varname></term>
1147 <listitem><para>When specified without an argument or with a true argument,
1148 enables the usage of
1149 <ulink url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">unified cgroup hierarchy</ulink>
1150 (a.k.a. cgroups-v2). When specified with a false argument, fall back to
1151 hybrid or full legacy cgroup hierarchy.</para>
1153 <para>If this option is not specified, the default behaviour is determined
1154 during compilation (the <option>--with-default-hierarchy=</option>
1155 option). If the kernel does not support unified cgroup hierarchy, the legacy
1156 hierarchy will be used even if this option is specified.</para>
1161 <term><varname>systemd.legacy_systemd_cgroup_controller</varname></term>
1163 <listitem><para>Takes effect if the full unified cgroup hierarchy is not used
1164 (see previous option). When specified without an argument or with a true
1165 argument, disables the use of "hybrid" cgroup hierarchy (i.e. a cgroups-v2
1166 tree used for systemd, and
1167 <ulink url="https://www.kernel.org/doc/Documentation/cgroup-v1/">legacy
1168 cgroup hierarchy</ulink>, a.k.a. cgroups-v1, for other controllers), and
1169 forces a full "legacy" mode. When specified with a false argument, enables
1170 the use of "hybrid" hierarchy.</para>
1172 <para>If this option is not specified, the default behaviour is determined
1173 during compilation (the <option>--with-default-hierarchy=</option>
1174 option). If the kernel does not support unified cgroup hierarchy, the legacy
1175 hierarchy will be used even if this option is specified.</para>
1180 <term><varname>quiet</varname></term>
1182 <listitem><para>Turn off status output at boot, much like
1183 <varname>systemd.show_status=false</varname> would. Note that
1184 this option is also read by the kernel itself and disables
1185 kernel log output. Passing this option hence turns off the
1186 usual output from both the system manager and the kernel.
1191 <term><varname>debug</varname></term>
1193 <listitem><para>Turn on debugging output. This is equivalent
1194 to <varname>systemd.log_level=debug</varname>. Note that this
1195 option is also read by the kernel itself and enables kernel
1196 debug output. Passing this option hence turns on the debug
1197 output from both the system manager and the
1198 kernel.</para></listitem>
1202 <term><varname>emergency</varname></term>
1203 <term><varname>rd.emergency</varname></term>
1204 <term><varname>-b</varname></term>
1206 <listitem><para>Boot into emergency mode. This is equivalent
1207 to <varname>systemd.unit=emergency.target</varname> or
1208 <varname>rd.systemd.unit=emergency.target</varname>, respectively, and
1209 provided for compatibility reasons and to be easier to type.</para></listitem>
1213 <term><varname>rescue</varname></term>
1214 <term><varname>rd.rescue</varname></term>
1215 <term><varname>single</varname></term>
1216 <term><varname>s</varname></term>
1217 <term><varname>S</varname></term>
1218 <term><varname>1</varname></term>
1220 <listitem><para>Boot into rescue mode. This is equivalent to
1221 <varname>systemd.unit=rescue.target</varname> or
1222 <varname>rd.systemd.unit=rescue.target</varname>, respectively, and
1223 provided for compatibility reasons and to be easier to type.</para></listitem>
1227 <term><varname>2</varname></term>
1228 <term><varname>3</varname></term>
1229 <term><varname>4</varname></term>
1230 <term><varname>5</varname></term>
1232 <listitem><para>Boot into the specified legacy SysV runlevel.
1233 These are equivalent to
1234 <varname>systemd.unit=runlevel2.target</varname>,
1235 <varname>systemd.unit=runlevel3.target</varname>,
1236 <varname>systemd.unit=runlevel4.target</varname>, and
1237 <varname>systemd.unit=runlevel5.target</varname>,
1238 respectively, and provided for compatibility reasons and to be
1239 easier to type.</para></listitem>
1243 <term><varname>locale.LANG=</varname></term>
1244 <term><varname>locale.LANGUAGE=</varname></term>
1245 <term><varname>locale.LC_CTYPE=</varname></term>
1246 <term><varname>locale.LC_NUMERIC=</varname></term>
1247 <term><varname>locale.LC_TIME=</varname></term>
1248 <term><varname>locale.LC_COLLATE=</varname></term>
1249 <term><varname>locale.LC_MONETARY=</varname></term>
1250 <term><varname>locale.LC_MESSAGES=</varname></term>
1251 <term><varname>locale.LC_PAPER=</varname></term>
1252 <term><varname>locale.LC_NAME=</varname></term>
1253 <term><varname>locale.LC_ADDRESS=</varname></term>
1254 <term><varname>locale.LC_TELEPHONE=</varname></term>
1255 <term><varname>locale.LC_MEASUREMENT=</varname></term>
1256 <term><varname>locale.LC_IDENTIFICATION=</varname></term>
1258 <listitem><para>Set the system locale to use. This overrides
1259 the settings in <filename>/etc/locale.conf</filename>. For
1260 more information, see
1261 <citerefentry project='man-pages'><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1263 <citerefentry project='man-pages'><refentrytitle>locale</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
1268 <para>For other kernel command line parameters understood by
1269 components of the core OS, please refer to
1270 <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
1274 <!-- 0 /// The whole sockets section is unneeded in elogind
1276 <title>Sockets and FIFOs</title>
1280 <term><filename>/run/systemd/notify</filename></term>
1282 <listitem><para>Daemon status notification socket. This is an
1283 <constant>AF_UNIX</constant> datagram socket and is used to
1284 implement the daemon notification logic as implemented by
1285 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
1290 <term><filename>/run/systemd/private</filename></term>
1292 <listitem><para>Used internally as communication channel
1294 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1295 and the systemd process. This is an
1296 <constant>AF_UNIX</constant> stream socket. This interface is
1297 private to systemd and should not be used in external
1298 projects.</para></listitem>
1302 <term><filename>/dev/initctl</filename></term>
1304 <listitem><para>Limited compatibility support for the SysV
1305 client interface, as implemented by the
1306 <filename>systemd-initctl.service</filename> unit. This is a
1307 named pipe in the file system. This interface is obsolete and
1308 should not be used in new applications.</para></listitem>
1315 <title>See Also</title>
1317 <!-- 0 /// elogind does not have that much to see also...
1318 The <ulink url="https://www.freedesktop.org/wiki/Software/systemd/">systemd Homepage</ulink>,
1319 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1320 <citerefentry project='man-pages'><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1321 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1322 <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1323 <citerefentry><refentrytitle>systemd-notify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1324 <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1325 <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
1326 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1327 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1328 <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1329 <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1330 <citerefentry project='man-pages'><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1331 <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1333 The <ulink url="https://github.com/elogind/elogind/">elogind Homepage</ulink>,
1334 <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1335 <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1336 <citerefentry><refentrytitle>pam_elogind</refentrytitle><manvolnum>8</manvolnum></citerefentry>