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>
345 <xi:include href="standard-options.xml" xpointer="help" />
346 <xi:include href="standard-options.xml" xpointer="version" />
349 <term><option>-D</option></term>
350 <term><option>--daemon</option></term>
351 <term><option>--service-watchdogs=</option></term>
353 <listitem><para>Daemonize elogind by double-forking
354 into background.</para></listitem>
355 <listitem><para>Globally enable/disable all service watchdog timeouts and emergency
356 actions. This setting may also be specified during boot, on the kernel
357 command line via the <varname>elogind.service_watchdogs=</varname>
358 option, see below. Defaults to enabled.</para></listitem>
362 <term><option>-h</option></term>
363 <term><option>--help</option></term>
365 <listitem><para>Show the helpt text and exit.</para></listitem>
371 <!-- 0 /// The whole concpets section is unneeded in elogind
373 <title>Concepts</title>
375 <para>systemd provides a dependency system between various
376 entities called "units" of 11 different types. Units encapsulate
377 various objects that are relevant for system boot-up and
378 maintenance. The majority of units are configured in unit
379 configuration files, whose syntax and basic set of options is
381 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
382 however some are created automatically from other configuration,
383 dynamically from system state or programmatically at runtime.
384 Units may be "active" (meaning started, bound, plugged in, …,
385 depending on the unit type, see below), or "inactive" (meaning
386 stopped, unbound, unplugged, …), as well as in the process of
387 being activated or deactivated, i.e. between the two states (these
388 states are called "activating", "deactivating"). A special
389 "failed" state is available as well, which is very similar to
390 "inactive" and is entered when the service failed in some way
391 (process returned error code on exit, or crashed, an operation
392 timed out, or after too many restarts). If this state is entered,
393 the cause will be logged, for later reference. Note that the
394 various unit types may have a number of additional substates,
395 which are mapped to the five generalized unit states described
398 <para>The following unit types are available:</para>
401 <listitem><para>Service units, which start and control daemons
402 and the processes they consist of. For details, see
403 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
405 <listitem><para>Socket units, which encapsulate local IPC or
406 network sockets in the system, useful for socket-based
407 activation. For details about socket units, see
408 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
409 for details on socket-based activation and other forms of
411 <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
413 <listitem><para>Target units are useful to group units, or
414 provide well-known synchronization points during boot-up, see
415 <citerefentry><refentrytitle>systemd.target</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
417 <listitem><para>Device units expose kernel devices in systemd
418 and may be used to implement device-based activation. For
420 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
422 <listitem><para>Mount units control mount points in the file
423 system, for details see
424 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
426 <listitem><para>Automount units provide automount capabilities,
427 for on-demand mounting of file systems as well as parallelized
429 <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
431 <listitem><para>Timer units are useful for triggering activation
432 of other units based on timers. You may find details in
433 <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
435 <listitem><para>Swap units are very similar to mount units and
436 encapsulate memory swap partitions or files of the operating
437 system. They are described in
438 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
440 <listitem><para>Path units may be used to activate other
441 services when file system objects change or are modified. See
442 <citerefentry><refentrytitle>systemd.path</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
444 <listitem><para>Slice units may be used to group units which
445 manage system processes (such as service and scope units) in a
446 hierarchical tree for resource management purposes. See
447 <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
449 <listitem><para>Scope units are similar to service units, but
450 manage foreign processes instead of starting them as well. See
451 <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
455 <para>Units are named as their configuration files. Some units
456 have special semantics. A detailed list is available in
457 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
459 <para>systemd knows various kinds of dependencies, including
460 positive and negative requirement dependencies (i.e.
461 <varname>Requires=</varname> and <varname>Conflicts=</varname>) as
462 well as ordering dependencies (<varname>After=</varname> and
463 <varname>Before=</varname>). NB: ordering and requirement
464 dependencies are orthogonal. If only a requirement dependency
465 exists between two units (e.g. <filename>foo.service</filename>
466 requires <filename>bar.service</filename>), but no ordering
467 dependency (e.g. <filename>foo.service</filename> after
468 <filename>bar.service</filename>) and both are requested to start,
469 they will be started in parallel. It is a common pattern that both
470 requirement and ordering dependencies are placed between two
471 units. Also note that the majority of dependencies are implicitly
472 created and maintained by systemd. In most cases, it should be
473 unnecessary to declare additional dependencies manually, however
474 it is possible to do this.</para>
476 <para>Application programs and units (via dependencies) may
477 request state changes of units. In systemd, these requests are
478 encapsulated as 'jobs' and maintained in a job queue. Jobs may
479 succeed or can fail, their execution is ordered based on the
480 ordering dependencies of the units they have been scheduled
483 <para>On boot systemd activates the target unit
484 <filename>default.target</filename> whose job is to activate
485 on-boot services and other on-boot units by pulling them in via
486 dependencies. Usually, the unit name is just an alias (symlink) for
487 either <filename>graphical.target</filename> (for fully-featured
488 boots into the UI) or <filename>multi-user.target</filename> (for
489 limited console-only boots for use in embedded or server
490 environments, or similar; a subset of graphical.target). However,
491 it is at the discretion of the administrator to configure it as an
492 alias to any other target unit. See
493 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
494 for details about these target units.</para>
496 <para>Processes systemd spawns are placed in individual Linux
497 control groups named after the unit which they belong to in the
498 private systemd hierarchy. (see <ulink
499 url="https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt">cgroups.txt</ulink>
500 for more information about control groups, or short "cgroups").
501 systemd uses this to effectively keep track of processes. Control
502 group information is maintained in the kernel, and is accessible
503 via the file system hierarchy (beneath
504 <filename>/sys/fs/cgroup/systemd/</filename>), or in tools such as
505 <citerefentry project='man-pages'><refentrytitle>systemd-cgls</refentrytitle><manvolnum>1</manvolnum></citerefentry>
507 <citerefentry project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>
508 (<command>ps xawf -eo pid,user,cgroup,args</command> is
509 particularly useful to list all processes and the systemd units
510 they belong to.).</para>
512 <para>systemd is compatible with the SysV init system to a large
513 degree: SysV init scripts are supported and simply read as an
514 alternative (though limited) configuration file format. The SysV
515 <filename>/dev/initctl</filename> interface is provided, and
516 compatibility implementations of the various SysV client tools are
517 available. In addition to that, various established Unix
518 functionality such as <filename>/etc/fstab</filename> or the
519 <filename>utmp</filename> database are supported.</para>
521 <para>systemd has a minimal transaction system: if a unit is
522 requested to start up or shut down it will add it and all its
523 dependencies to a temporary transaction. Then, it will verify if
524 the transaction is consistent (i.e. whether the ordering of all
525 units is cycle-free). If it is not, systemd will try to fix it up,
526 and removes non-essential jobs from the transaction that might
527 remove the loop. Also, systemd tries to suppress non-essential
528 jobs in the transaction that would stop a running service. Finally
529 it is checked whether the jobs of the transaction contradict jobs
530 that have already been queued, and optionally the transaction is
531 aborted then. If all worked out and the transaction is consistent
532 and minimized in its impact it is merged with all already
533 outstanding jobs and added to the run queue. Effectively this
534 means that before executing a requested operation, systemd will
535 verify that it makes sense, fixing it if possible, and only
536 failing if it really cannot work.</para>
538 <para>systemd contains native implementations of various tasks
539 that need to be executed as part of the boot process. For example,
540 it sets the hostname or configures the loopback network device. It
541 also sets up and mounts various API file systems, such as
542 <filename>/sys</filename> or <filename>/proc</filename>.</para>
544 <para>For more information about the concepts and
545 ideas behind systemd, please refer to the
546 <ulink url="http://0pointer.de/blog/projects/systemd.html">Original Design Document</ulink>.</para>
548 <para>Note that some but not all interfaces provided
549 by systemd are covered by the
550 <ulink url="https://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise">Interface
551 Stability Promise</ulink>.</para>
553 <para>Units may be generated dynamically at boot and system
554 manager reload time, for example based on other configuration
555 files or parameters passed on the kernel command line. For details, see
556 <citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
558 <para>Systems which invoke systemd in a container or initrd
559 environment should implement the
560 <ulink url="https://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container Interface</ulink> or
561 <ulink url="https://www.freedesktop.org/wiki/Software/systemd/InitrdInterface">initrd Interface</ulink>
562 specifications, respectively.</para>
566 <!-- 0 /// The whole directories section is unneeded in elogind
568 <title>Directories</title>
572 <term>System unit directories</term>
574 <listitem><para>The systemd system manager reads unit
575 configuration from various directories. Packages that want to
576 install unit files shall place them in the directory returned
577 by <command>pkg-config systemd
578 --variable=systemdsystemunitdir</command>. Other directories
579 checked are <filename>/usr/local/lib/systemd/system</filename>
580 and <filename>/usr/lib/systemd/system</filename>. User
581 configuration always takes precedence. <command>pkg-config
582 systemd --variable=systemdsystemconfdir</command> returns the
583 path of the system configuration directory. Packages should
584 alter the content of these directories only with the
585 <command>enable</command> and <command>disable</command>
587 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
588 tool. Full list of directories is provided in
589 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
596 <term>User unit directories</term>
598 <listitem><para>Similar rules apply for the user unit
599 directories. However, here the
600 <ulink url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
601 Base Directory specification</ulink> is followed to find
602 units. Applications should place their unit files in the
603 directory returned by <command>pkg-config systemd
604 --variable=systemduserunitdir</command>. Global configuration
605 is done in the directory reported by <command>pkg-config
606 systemd --variable=systemduserconfdir</command>. The
607 <command>enable</command> and <command>disable</command>
609 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
610 tool can handle both global (i.e. for all users) and private
611 (for one user) enabling/disabling of units. Full list of
612 directories is provided in
613 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
620 <term>SysV init scripts directory</term>
622 <listitem><para>The location of the SysV init script directory
623 varies between distributions. If systemd cannot find a native
624 unit file for a requested service, it will look for a SysV
625 init script of the same name (with the
626 <filename>.service</filename> suffix
627 removed).</para></listitem>
633 <term>SysV runlevel link farm directory</term>
635 <listitem><para>The location of the SysV runlevel link farm
636 directory varies between distributions. systemd will take the
637 link farm into account when figuring out whether a service
638 shall be enabled. Note that a service unit with a native unit
639 configuration file cannot be started by activating it in the
640 SysV runlevel link farm.</para></listitem>
646 <!-- 0 /// The whole Signals section is unneeded in elogind
648 <title>Signals</title>
652 <term><constant>SIGTERM</constant></term>
654 <listitem><para>Upon receiving this signal the systemd system
655 manager serializes its state, reexecutes itself and
656 deserializes the saved state again. This is mostly equivalent
657 to <command>systemctl daemon-reexec</command>.</para>
659 <para>systemd user managers will start the
660 <filename>exit.target</filename> unit when this signal is
661 received. This is mostly equivalent to <command>systemctl
662 --user start exit.target
663 --job-mode=replace-irreversible</command>.</para></listitem>
667 <term><constant>SIGINT</constant></term>
669 <listitem><para>Upon receiving this signal the systemd system
670 manager will start the
671 <filename>ctrl-alt-del.target</filename> unit. This is mostly
672 equivalent to <command>systemctl start ctrl-alt-del.target
673 --job-mode=replace-irreversible</command>. If this signal is
674 received more than 7 times per 2s, an immediate reboot is
675 triggered. Note that pressing Ctrl-Alt-Del on the console
676 will trigger this signal. Hence, if a reboot is hanging,
677 pressing Ctrl-Alt-Del more than 7 times in 2s is a relatively
678 safe way to trigger an immediate reboot.</para>
680 <para>systemd user managers treat this signal the same way as
681 <constant>SIGTERM</constant>.</para></listitem>
685 <term><constant>SIGWINCH</constant></term>
687 <listitem><para>When this signal is received the systemd
688 system manager will start the
689 <filename>kbrequest.target</filename> unit. This is mostly
690 equivalent to <command>systemctl start
691 kbrequest.target</command>.</para>
693 <para>This signal is ignored by systemd user
694 managers.</para></listitem>
698 <term><constant>SIGPWR</constant></term>
700 <listitem><para>When this signal is received the systemd
701 manager will start the <filename>sigpwr.target</filename>
702 unit. This is mostly equivalent to <command>systemctl start
703 sigpwr.target</command>.</para></listitem>
707 <term><constant>SIGUSR1</constant></term>
709 <listitem><para>When this signal is received the systemd
710 manager will try to reconnect to the D-Bus
711 bus.</para></listitem>
715 <term><constant>SIGUSR2</constant></term>
717 <listitem><para>When this signal is received the systemd
718 manager will log its complete state in human-readable form.
719 The data logged is the same as printed by
720 <command>systemd-analyze dump</command>.</para></listitem>
724 <term><constant>SIGHUP</constant></term>
726 <listitem><para>Reloads the complete daemon configuration.
727 This is mostly equivalent to <command>systemctl
728 daemon-reload</command>.</para></listitem>
732 <term><constant>SIGRTMIN+0</constant></term>
734 <listitem><para>Enters default mode, starts the
735 <filename>default.target</filename> unit. This is mostly
736 equivalent to <command>systemctl isolate
737 default.target</command>.</para></listitem>
741 <term><constant>SIGRTMIN+1</constant></term>
743 <listitem><para>Enters rescue mode, starts the
744 <filename>rescue.target</filename> unit. This is mostly
745 equivalent to <command>systemctl isolate
746 rescue.target</command>.</para></listitem>
750 <term><constant>SIGRTMIN+2</constant></term>
752 <listitem><para>Enters emergency mode, starts the
753 <filename>emergency.service</filename> unit. This is mostly
754 equivalent to <command>systemctl isolate
755 emergency.service</command>.</para></listitem>
759 <term><constant>SIGRTMIN+3</constant></term>
761 <listitem><para>Halts the machine, starts the
762 <filename>halt.target</filename> unit. This is mostly
763 equivalent to <command>systemctl start halt.target
764 --job-mode=replace-irreversible</command>.</para>
769 <term><constant>SIGRTMIN+4</constant></term>
771 <listitem><para>Powers off the machine, starts the
772 <filename>poweroff.target</filename> unit. This is mostly
773 equivalent to <command>systemctl start poweroff.target
774 --job-mode=replace-irreversible</command>.</para>
779 <term><constant>SIGRTMIN+5</constant></term>
781 <listitem><para>Reboots the machine, starts the
782 <filename>reboot.target</filename> unit. This is mostly
783 equivalent to <command>systemctl start reboot.target
784 --job-mode=replace-irreversible</command>.</para>
789 <term><constant>SIGRTMIN+6</constant></term>
791 <listitem><para>Reboots the machine via kexec, starts the
792 <filename>kexec.target</filename> unit. This is mostly
793 equivalent to <command>systemctl start kexec.target
794 --job-mode=replace-irreversible</command>.</para>
799 <term><constant>SIGRTMIN+13</constant></term>
801 <listitem><para>Immediately halts the machine.</para></listitem>
805 <term><constant>SIGRTMIN+14</constant></term>
807 <listitem><para>Immediately powers off the machine.</para></listitem>
811 <term><constant>SIGRTMIN+15</constant></term>
813 <listitem><para>Immediately reboots the machine.</para></listitem>
817 <term><constant>SIGRTMIN+16</constant></term>
819 <listitem><para>Immediately reboots the machine with kexec.</para></listitem>
823 <term><constant>SIGRTMIN+20</constant></term>
825 <listitem><para>Enables display of status messages on the
826 console, as controlled via
827 <varname>systemd.show_status=1</varname> on the kernel command
828 line.</para></listitem>
832 <term><constant>SIGRTMIN+21</constant></term>
834 <listitem><para>Disables display of
835 status messages on the console, as
837 <varname>systemd.show_status=0</varname>
838 on the kernel command
839 line.</para></listitem>
843 <term><constant>SIGRTMIN+22</constant></term>
844 <term><constant>SIGRTMIN+23</constant></term>
846 <listitem><para>Sets the log level to <literal>debug</literal>
847 (or <literal>info</literal> on
848 <constant>SIGRTMIN+23</constant>), as controlled via
849 <varname>systemd.log_level=debug</varname> (or
850 <varname>systemd.log_level=info</varname> on
851 <constant>SIGRTMIN+23</constant>) on the kernel command
852 line.</para></listitem>
856 <term><constant>SIGRTMIN+24</constant></term>
858 <listitem><para>Immediately exits the manager (only available
859 for --user instances).</para></listitem>
863 <term><constant>SIGRTMIN+26</constant></term>
864 <term><constant>SIGRTMIN+27</constant></term>
865 <term><constant>SIGRTMIN+28</constant></term>
867 <listitem><para>Sets the log target to
868 <literal>journal-or-kmsg</literal> (or
869 <literal>console</literal> on
870 <constant>SIGRTMIN+27</constant>, <literal>kmsg</literal> on
871 <constant>SIGRTMIN+28</constant>), as controlled via
872 <varname>systemd.log_target=journal-or-kmsg</varname> (or
873 <varname>systemd.log_target=console</varname> on
874 <constant>SIGRTMIN+27</constant> or
875 <varname>systemd.log_target=kmsg</varname> on
876 <constant>SIGRTMIN+28</constant>) on the kernel command
877 line.</para></listitem>
883 <!-- 0 /// The whole environment section is unneeded in elogind
885 <title>Environment</title>
887 <variablelist class='environment-variables'>
889 <term><varname>$SYSTEMD_LOG_LEVEL</varname></term>
890 <listitem><para>systemd reads the log level from this
891 environment variable. This can be overridden with
892 <option>--log-level=</option>.</para></listitem>
896 <term><varname>$SYSTEMD_LOG_TARGET</varname></term>
897 <listitem><para>systemd reads the log target from this
898 environment variable. This can be overridden with
899 <option>--log-target=</option>.</para></listitem>
903 <term><varname>$SYSTEMD_LOG_COLOR</varname></term>
904 <listitem><para>Controls whether systemd highlights important
905 log messages. This can be overridden with
906 <option>--log-color=</option>.</para></listitem>
910 <term><varname>$SYSTEMD_LOG_LOCATION</varname></term>
911 <listitem><para>Controls whether systemd prints the code
912 location along with log messages. This can be overridden with
913 <option>--log-location=</option>.</para></listitem>
917 <term><varname>$XDG_CONFIG_HOME</varname></term>
918 <term><varname>$XDG_CONFIG_DIRS</varname></term>
919 <term><varname>$XDG_DATA_HOME</varname></term>
920 <term><varname>$XDG_DATA_DIRS</varname></term>
922 <listitem><para>The systemd user manager uses these variables
923 in accordance to the <ulink
924 url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
925 Base Directory specification</ulink> to find its
926 configuration.</para></listitem>
930 <term><varname>$SYSTEMD_UNIT_PATH</varname></term>
932 <listitem><para>Controls where systemd looks for unit
933 files.</para></listitem>
937 <term><varname>$SYSTEMD_SYSVINIT_PATH</varname></term>
939 <listitem><para>Controls where systemd looks for SysV init
940 scripts.</para></listitem>
944 <term><varname>$SYSTEMD_SYSVRCND_PATH</varname></term>
946 <listitem><para>Controls where systemd looks for SysV init
947 script runlevel link farms.</para></listitem>
951 <term><varname>$SYSTEMD_COLORS</varname></term>
953 <listitem><para>The value must be a boolean. Controls whether colorized output should be
954 generated. This can be specified to override the decision that <command>systemd</command>
955 makes based on <varname>$TERM</varname> and what the console is connected to.</para>
960 <term><varname>$LISTEN_PID</varname></term>
961 <term><varname>$LISTEN_FDS</varname></term>
962 <term><varname>$LISTEN_FDNAMES</varname></term>
964 <listitem><para>Set by systemd for supervised processes during
965 socket-based activation. See
966 <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
967 for more information.</para></listitem>
971 <term><varname>$NOTIFY_SOCKET</varname></term>
973 <listitem><para>Set by systemd for supervised processes for
974 status and start-up completion notification. See
975 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
976 for more information.</para></listitem>
982 <!-- 0 /// The whole kernel section is unneeded in elogind
984 <title>Kernel Command Line</title>
986 <para>When run as system instance systemd parses a number of
987 kernel command line arguments<footnote><para>If run inside a Linux
988 container these arguments may be passed as command line arguments
989 to systemd itself, next to any of the command line options listed
990 in the Options section above. If run outside of Linux containers,
991 these arguments are parsed from <filename>/proc/cmdline</filename>
992 instead.</para></footnote>:</para>
994 <variablelist class='kernel-commandline-options'>
996 <term><varname>systemd.unit=</varname></term>
997 <term><varname>rd.systemd.unit=</varname></term>
999 <listitem><para>Overrides the unit to activate on boot.
1000 Defaults to <filename>default.target</filename>. This may be
1001 used to temporarily boot into a different boot unit, for
1002 example <filename>rescue.target</filename> or
1003 <filename>emergency.service</filename>. See
1004 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1005 for details about these units. The option prefixed with
1006 <literal>rd.</literal> is honored only in the initial RAM disk
1007 (initrd), while the one that is not prefixed only in the main
1008 system.</para></listitem>
1012 <term><varname>systemd.dump_core</varname></term>
1014 <listitem><para>Takes a boolean argument or enables the option if specified
1015 without an argument. If enabled, the systemd manager (PID 1) dumps core when
1016 it crashes. Otherwise, no core dump is created. Defaults to enabled.</para>
1021 <term><varname>systemd.crash_chvt</varname></term>
1023 <listitem><para>Takes a positive integer, or a boolean argument. Can be also
1024 specified without an argument, with the same effect as a positive boolean. If
1025 a positive integer (in the range 1–63) is specified, the system manager (PID
1026 1) will activate the specified virtual terminal (VT) when it
1027 crashes. Defaults to disabled, meaning that no such switch is attempted. If
1028 set to enabled, the VT the kernel messages are written to is selected.
1033 <term><varname>systemd.crash_shell</varname></term>
1035 <listitem><para>Takes a boolean argument or enables the option if specified
1036 without an argument. If enabled, the system manager (PID 1) spawns a shell
1037 when it crashes, after a 10s delay. Otherwise, no shell is spawned. Defaults
1038 to disabled, for security reasons, as the shell is not protected by password
1039 authentication.</para></listitem>
1043 <term><varname>systemd.crash_reboot</varname></term>
1045 <listitem><para>Takes a boolean argument or enables the option if specified
1046 without an argument. If enabled, the system manager (PID 1) will reboot the
1047 machine automatically when it crashes, after a 10s delay. Otherwise, the
1048 system will hang indefinitely. Defaults to disabled, in order to avoid a
1049 reboot loop. If combined with <varname>systemd.crash_shell</varname>, the
1050 system is rebooted after the shell exits.</para></listitem>
1054 <term><varname>systemd.confirm_spawn</varname></term>
1056 <listitem><para>Takes a boolean argument or a path to the virtual console
1057 where the confirmation messages should be emitted. Can be also specified
1058 without an argument, with the same effect as a positive boolean. If enabled,
1059 the system manager (PID 1) asks for confirmation when spawning processes
1060 using <option>/dev/console</option>. If a path or a console name (such as
1061 <literal>ttyS0</literal>) is provided, the virtual console pointed to by this
1062 path or described by the give name will be used instead. Defaults to disabled.
1067 <term><varname>systemd.service_watchdogs=</varname></term>
1069 <listitem><para>Takes a boolean argument. If disabled, all service runtime
1070 watchdogs (<option>WatchdogSec=</option>) and emergency actions (e.g.
1071 <option>OnFailure=</option> or <option>StartLimitAction=</option>) are
1072 ignored by the system manager (PID 1); see
1073 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1074 Defaults to enabled, i.e. watchdogs and failure actions are processed
1075 normally. The hardware watchdog is not affected by this
1076 option.</para></listitem>
1080 <term><varname>systemd.show_status</varname></term>
1082 <listitem><para>Takes a boolean argument or the constant
1083 <constant>auto</constant>. Can be also specified without an argument, with
1084 the same effect as a positive boolean. If enabled, the systemd manager (PID
1085 1) shows terse service status updates on the console during bootup.
1086 <constant>auto</constant> behaves like <option>false</option> until a unit
1087 fails or there is a significant delay in boot. Defaults to enabled, unless
1088 <option>quiet</option> is passed as kernel command line option, in which case
1089 it defaults to <constant>auto</constant>. If specified overrides the system
1090 manager configuration file option <option>ShowStatus=</option>, see
1091 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1092 However, the process command line option <option>--show-status=</option>
1093 takes precedence over both this kernel command line option and the
1094 configuration file option.</para></listitem>
1098 <term><varname>systemd.log_target=</varname></term>
1099 <term><varname>systemd.log_level=</varname></term>
1100 <term><varname>systemd.log_location=</varname></term>
1101 <term><varname>systemd.log_color</varname></term>
1103 <listitem><para>Controls log output, with the same effect as the
1104 <varname>$SYSTEMD_LOG_TARGET</varname>,
1105 <varname>$SYSTEMD_LOG_LEVEL</varname>,
1106 <varname>$SYSTEMD_LOG_LOCATION</varname>,
1107 <varname>$SYSTEMD_LOG_COLOR</varname> environment variables described above.
1108 <varname>systemd.log_color</varname> can be specified without an argument,
1109 with the same effect as a positive boolean.</para></listitem>
1113 <term><varname>systemd.default_standard_output=</varname></term>
1114 <term><varname>systemd.default_standard_error=</varname></term>
1115 <listitem><para>Controls default standard output and error
1116 output for services, with the same effect as the
1117 <option>--default-standard-output=</option> and
1118 <option>--default-standard-error=</option> command line
1119 arguments described above, respectively.</para></listitem>
1123 <term><varname>systemd.setenv=</varname></term>
1125 <listitem><para>Takes a string argument in the form
1126 VARIABLE=VALUE. May be used to set default environment
1127 variables to add to forked child processes. May be used more
1128 than once to set multiple variables.</para></listitem>
1132 <term><varname>systemd.machine_id=</varname></term>
1134 <listitem><para>Takes a 32 character hex value to be
1135 used for setting the machine-id. Intended mostly for
1136 network booting where the same machine-id is desired
1137 for every boot.</para></listitem>
1141 <term><varname>systemd.unified_cgroup_hierarchy</varname></term>
1143 <listitem><para>When specified without an argument or with a true argument,
1144 enables the usage of
1145 <ulink url="https://www.kernel.org/doc/Documentation/cgroup-v2.txt">unified cgroup hierarchy</ulink>
1146 (a.k.a. cgroups-v2). When specified with a false argument, fall back to
1147 hybrid or full legacy cgroup hierarchy.</para>
1149 <para>If this option is not specified, the default behaviour is determined
1150 during compilation (the <option>--with-default-hierarchy=</option>
1151 option). If the kernel does not support unified cgroup hierarchy, the legacy
1152 hierarchy will be used even if this option is specified.</para>
1157 <term><varname>systemd.legacy_systemd_cgroup_controller</varname></term>
1159 <listitem><para>Takes effect if the full unified cgroup hierarchy is not used
1160 (see previous option). When specified without an argument or with a true
1161 argument, disables the use of "hybrid" cgroup hierarchy (i.e. a cgroups-v2
1162 tree used for systemd, and
1163 <ulink url="https://www.kernel.org/doc/Documentation/cgroup-v1/">legacy
1164 cgroup hierarchy</ulink>, a.k.a. cgroups-v1, for other controllers), and
1165 forces a full "legacy" mode. When specified with a false argument, enables
1166 the use of "hybrid" hierarchy.</para>
1168 <para>If this option is not specified, the default behaviour is determined
1169 during compilation (the <option>--with-default-hierarchy=</option>
1170 option). If the kernel does not support unified cgroup hierarchy, the legacy
1171 hierarchy will be used even if this option is specified.</para>
1176 <term><varname>quiet</varname></term>
1178 <listitem><para>Turn off status output at boot, much like
1179 <varname>systemd.show_status=false</varname> would. Note that
1180 this option is also read by the kernel itself and disables
1181 kernel log output. Passing this option hence turns off the
1182 usual output from both the system manager and the kernel.
1187 <term><varname>debug</varname></term>
1189 <listitem><para>Turn on debugging output. This is equivalent
1190 to <varname>systemd.log_level=debug</varname>. Note that this
1191 option is also read by the kernel itself and enables kernel
1192 debug output. Passing this option hence turns on the debug
1193 output from both the system manager and the
1194 kernel.</para></listitem>
1198 <term><varname>emergency</varname></term>
1199 <term><varname>rd.emergency</varname></term>
1200 <term><varname>-b</varname></term>
1202 <listitem><para>Boot into emergency mode. This is equivalent
1203 to <varname>systemd.unit=emergency.target</varname> or
1204 <varname>rd.systemd.unit=emergency.target</varname>, respectively, and
1205 provided for compatibility reasons and to be easier to type.</para></listitem>
1209 <term><varname>rescue</varname></term>
1210 <term><varname>rd.rescue</varname></term>
1211 <term><varname>single</varname></term>
1212 <term><varname>s</varname></term>
1213 <term><varname>S</varname></term>
1214 <term><varname>1</varname></term>
1216 <listitem><para>Boot into rescue mode. This is equivalent to
1217 <varname>systemd.unit=rescue.target</varname> or
1218 <varname>rd.systemd.unit=rescue.target</varname>, respectively, and
1219 provided for compatibility reasons and to be easier to type.</para></listitem>
1223 <term><varname>2</varname></term>
1224 <term><varname>3</varname></term>
1225 <term><varname>4</varname></term>
1226 <term><varname>5</varname></term>
1228 <listitem><para>Boot into the specified legacy SysV runlevel.
1229 These are equivalent to
1230 <varname>systemd.unit=runlevel2.target</varname>,
1231 <varname>systemd.unit=runlevel3.target</varname>,
1232 <varname>systemd.unit=runlevel4.target</varname>, and
1233 <varname>systemd.unit=runlevel5.target</varname>,
1234 respectively, and provided for compatibility reasons and to be
1235 easier to type.</para></listitem>
1239 <term><varname>locale.LANG=</varname></term>
1240 <term><varname>locale.LANGUAGE=</varname></term>
1241 <term><varname>locale.LC_CTYPE=</varname></term>
1242 <term><varname>locale.LC_NUMERIC=</varname></term>
1243 <term><varname>locale.LC_TIME=</varname></term>
1244 <term><varname>locale.LC_COLLATE=</varname></term>
1245 <term><varname>locale.LC_MONETARY=</varname></term>
1246 <term><varname>locale.LC_MESSAGES=</varname></term>
1247 <term><varname>locale.LC_PAPER=</varname></term>
1248 <term><varname>locale.LC_NAME=</varname></term>
1249 <term><varname>locale.LC_ADDRESS=</varname></term>
1250 <term><varname>locale.LC_TELEPHONE=</varname></term>
1251 <term><varname>locale.LC_MEASUREMENT=</varname></term>
1252 <term><varname>locale.LC_IDENTIFICATION=</varname></term>
1254 <listitem><para>Set the system locale to use. This overrides
1255 the settings in <filename>/etc/locale.conf</filename>. For
1256 more information, see
1257 <citerefentry project='man-pages'><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1259 <citerefentry project='man-pages'><refentrytitle>locale</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
1264 <para>For other kernel command line parameters understood by
1265 components of the core OS, please refer to
1266 <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
1270 <!-- 0 /// The whole sockets section is unneeded in elogind
1272 <title>Sockets and FIFOs</title>
1276 <term><filename>/run/systemd/notify</filename></term>
1278 <listitem><para>Daemon status notification socket. This is an
1279 <constant>AF_UNIX</constant> datagram socket and is used to
1280 implement the daemon notification logic as implemented by
1281 <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
1286 <term><filename>/run/systemd/private</filename></term>
1288 <listitem><para>Used internally as communication channel
1290 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1291 and the systemd process. This is an
1292 <constant>AF_UNIX</constant> stream socket. This interface is
1293 private to systemd and should not be used in external
1294 projects.</para></listitem>
1298 <term><filename>/dev/initctl</filename></term>
1300 <listitem><para>Limited compatibility support for the SysV
1301 client interface, as implemented by the
1302 <filename>systemd-initctl.service</filename> unit. This is a
1303 named pipe in the file system. This interface is obsolete and
1304 should not be used in new applications.</para></listitem>
1311 <title>See Also</title>
1313 <!-- 0 /// elogind does not have that much to see also...
1314 The <ulink url="https://www.freedesktop.org/wiki/Software/systemd/">systemd Homepage</ulink>,
1315 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1316 <citerefentry project='man-pages'><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1317 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1318 <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1319 <citerefentry><refentrytitle>systemd-notify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1320 <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1321 <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
1322 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1323 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1324 <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1325 <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1326 <citerefentry project='man-pages'><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1327 <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1329 The <ulink url="https://github.com/elogind/elogind/">elogind Homepage</ulink>,
1330 <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1331 <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1332 <citerefentry><refentrytitle>pam_elogind</refentrytitle><manvolnum>8</manvolnum></citerefentry>