1SYSTEMD(1) systemd SYSTEMD(1)
2
6 systemd, init - systemd system and service manager
7
9 /usr/lib/systemd/systemd [OPTIONS...]
10 init [OPTIONS...] {COMMAND}
12
14 systemd is a system and service manager for Linux operating systems.
15 When run as first process on boot (as PID 1), it acts as init system
16 that brings up and maintains userspace services. Separate instances are
17 started for logged-in users to start their services.
18 systemd is usually not invoked directly by the user, but is installed
20 as the /sbin/init symlink and started during early boot. The user
21 manager instances are started automatically through the
22 user@.service(5) service.
23 For compatibility with SysV, if the binary is called as init and is not
25 the first process on the machine (PID is not 1), it will execute
26 telinit and pass all command line arguments unmodified. That means init
27 and telinit are mostly equivalent when invoked from normal login
28 sessions. See telinit(8) for more information.
29 When run as a system instance, systemd interprets the configuration
31 file system.conf and the files in system.conf.d directories; when run
32 as a user instance, systemd interprets the configuration file user.conf
33 and the files in user.conf.d directories. See systemd-system.conf(5)
34 for more information.
35
37 systemd provides a dependency system between various entities called
38 "units" of 11 different types. Units encapsulate various objects that
39 are relevant for system boot-up and maintenance. The majority of units
40 are configured in unit configuration files, whose syntax and basic set
41 of options is described in systemd.unit(5), however some are created
42 automatically from other configuration files, dynamically from system
43 state or programmatically at runtime. Units may be "active" (meaning
44 started, bound, plugged in, ..., depending on the unit type, see
45 below), or "inactive" (meaning stopped, unbound, unplugged, ...), as
46 well as in the process of being activated or deactivated, i.e. between
47 the two states (these states are called "activating", "deactivating").
48 A special "failed" state is available as well, which is very similar to
49 "inactive" and is entered when the service failed in some way (process
50 returned error code on exit, or crashed, an operation timed out, or
51 after too many restarts). If this state is entered, the cause will be
52 logged, for later reference. Note that the various unit types may have
53 a number of additional substates, which are mapped to the five
54 generalized unit states described here.
55 The following unit types are available:
57 1. Service units, which start and control daemons and the processes
59 they consist of. For details, see systemd.service(5).
60 2. Socket units, which encapsulate local IPC or network sockets in the
62 system, useful for socket-based activation. For details about
63 socket units, see systemd.socket(5), for details on socket-based
64 activation and other forms of activation, see daemon(7).
65 3. Target units are useful to group units, or provide well-known
67 synchronization points during boot-up, see systemd.target(5).
68 4. Device units expose kernel devices in systemd and may be used to
70 implement device-based activation. For details, see
71 systemd.device(5).
72 5. Mount units control mount points in the file system, for details
74 see systemd.mount(5).
75 6. Automount units provide automount capabilities, for on-demand
77 mounting of file systems as well as parallelized boot-up. See
78 systemd.automount(5).
79 7. Timer units are useful for triggering activation of other units
81 based on timers. You may find details in systemd.timer(5).
82 8. Swap units are very similar to mount units and encapsulate memory
84 swap partitions or files of the operating system. They are
85 described in systemd.swap(5).
86 9. Path units may be used to activate other services when file system
88 objects change or are modified. See systemd.path(5).
89 10. Slice units may be used to group units which manage system
91 processes (such as service and scope units) in a hierarchical tree
92 for resource management purposes. See systemd.slice(5).
93 11. Scope units are similar to service units, but manage foreign
95 processes instead of starting them as well. See systemd.scope(5).
96 Units are named as their configuration files. Some units have special
98 semantics. A detailed list is available in systemd.special(7).
99 systemd knows various kinds of dependencies, including positive and
101 negative requirement dependencies (i.e. Requires= and Conflicts=) as
102 well as ordering dependencies (After= and Before=). NB: ordering and
103 requirement dependencies are orthogonal. If only a requirement
104 dependency exists between two units (e.g. foo.service requires
105 bar.service), but no ordering dependency (e.g. foo.service after
106 bar.service) and both are requested to start, they will be started in
107 parallel. It is a common pattern that both requirement and ordering
108 dependencies are placed between two units. Also note that the majority
109 of dependencies are implicitly created and maintained by systemd. In
110 most cases, it should be unnecessary to declare additional dependencies
111 manually, however it is possible to do this.
112 Application programs and units (via dependencies) may request state
114 changes of units. In systemd, these requests are encapsulated as 'jobs'
115 and maintained in a job queue. Jobs may succeed or can fail, their
116 execution is ordered based on the ordering dependencies of the units
117 they have been scheduled for.
118 On boot systemd activates the target unit default.target whose job is
120 to activate on-boot services and other on-boot units by pulling them in
121 via dependencies. Usually, the unit name is just an alias (symlink) for
122 either graphical.target (for fully-featured boots into the UI) or
123 multi-user.target (for limited console-only boots for use in embedded
124 or server environments, or similar; a subset of graphical.target).
125 However, it is at the discretion of the administrator to configure it
126 as an alias to any other target unit. See systemd.special(7) for
127 details about these target units.
128 systemd only keeps a minimal set of units loaded into memory.
130 Specifically, the only units that are kept loaded into memory are those
131 for which at least one of the following conditions is true:
132 1. It is in an active, activating, deactivating or failed state (i.e.
134 in any unit state except for "inactive")
135 2. It has a job queued for it
137 3. It is a dependency of at least one other unit that is loaded into
139 memory
140 4. It has some form of resource still allocated (e.g. a service unit
142 that is inactive but for which a process is still lingering that
143 ignored the request to be terminated)
144 5. It has been pinned into memory programmatically by a D-Bus call
146 systemd will automatically and implicitly load units from disk — if
148 they are not loaded yet — as soon as operations are requested for them.
149 Thus, in many respects, the fact whether a unit is loaded or not is
150 invisible to clients. Use systemctl list-units --all to comprehensively
151 list all units currently loaded. Any unit for which none of the
152 conditions above applies is promptly unloaded. Note that when a unit is
153 unloaded from memory its accounting data is flushed out too. However,
154 this data is generally not lost, as a journal log record is generated
155 declaring the consumed resources whenever a unit shuts down.
156 Processes systemd spawns are placed in individual Linux control groups
158 named after the unit which they belong to in the private systemd
159 hierarchy. (see cgroups.txt[1] for more information about control
160 groups, or short "cgroups"). systemd uses this to effectively keep
161 track of processes. Control group information is maintained in the
162 kernel, and is accessible via the file system hierarchy (beneath
163 /sys/fs/cgroup/systemd/), or in tools such as systemd-cgls(1) or ps(1)
164 (ps xawf -eo pid,user,cgroup,args is particularly useful to list all
165 processes and the systemd units they belong to.).
166 systemd is compatible with the SysV init system to a large degree: SysV
168 init scripts are supported and simply read as an alternative (though
169 limited) configuration file format. The SysV /dev/initctl interface is
170 provided, and compatibility implementations of the various SysV client
171 tools are available. In addition to that, various established Unix
172 functionality such as /etc/fstab or the utmp database are supported.
173 systemd has a minimal transaction system: if a unit is requested to
175 start up or shut down it will add it and all its dependencies to a
176 temporary transaction. Then, it will verify if the transaction is
177 consistent (i.e. whether the ordering of all units is cycle-free). If
178 it is not, systemd will try to fix it up, and removes non-essential
179 jobs from the transaction that might remove the loop. Also, systemd
180 tries to suppress non-essential jobs in the transaction that would stop
181 a running service. Finally it is checked whether the jobs of the
182 transaction contradict jobs that have already been queued, and
183 optionally the transaction is aborted then. If all worked out and the
184 transaction is consistent and minimized in its impact it is merged with
185 all already outstanding jobs and added to the run queue. Effectively
186 this means that before executing a requested operation, systemd will
187 verify that it makes sense, fixing it if possible, and only failing if
188 it really cannot work.
189 Note that transactions are generated independently of a unit's state at
191 runtime, hence, for example, if a start job is requested on an already
192 started unit, it will still generate a transaction and wake up any
193 inactive dependencies (and cause propagation of other jobs as per the
194 defined relationships). This is because the enqueued job is at the time
195 of execution compared to the target unit's state and is marked
196 successful and complete when both satisfy. However, this job also pulls
197 in other dependencies due to the defined relationships and thus leads
198 to, in our example, start jobs for any of those inactive units getting
199 queued as well.
200 systemd contains native implementations of various tasks that need to
202 be executed as part of the boot process. For example, it sets the
203 hostname or configures the loopback network device. It also sets up and
204 mounts various API file systems, such as /sys/ or /proc/.
205 For more information about the concepts and ideas behind systemd,
207 please refer to the Original Design Document[2].
208 Note that some but not all interfaces provided by systemd are covered
210 by the Interface Portability and Stability Promise[3].
211 Units may be generated dynamically at boot and system manager reload
213 time, for example based on other configuration files or parameters
214 passed on the kernel command line. For details, see
215 systemd.generator(7).
216 The D-Bus API of systemd is described in org.freedesktop.systemd1(5)
218 and org.freedesktop.LogControl1(5).
219 Systems which invoke systemd in a container or initrd environment
221 should implement the Container Interface[4] or initrd Interface[5]
222 specifications, respectively.
223
225 System unit directories
226 The systemd system manager reads unit configuration from various
227 directories. Packages that want to install unit files shall place
228 them in the directory returned by pkg-config systemd
229 --variable=systemdsystemunitdir. Other directories checked are
230 /usr/local/lib/systemd/system and /usr/lib/systemd/system. User
231 configuration always takes precedence. pkg-config systemd
232 --variable=systemdsystemconfdir returns the path of the system
233 configuration directory. Packages should alter the content of these
234 directories only with the enable and disable commands of the
235 systemctl(1) tool. Full list of directories is provided in
236 systemd.unit(5).
237 User unit directories
239 Similar rules apply for the user unit directories. However, here
240 the XDG Base Directory specification[6] is followed to find units.
241 Applications should place their unit files in the directory
242 returned by pkg-config systemd --variable=systemduserunitdir.
243 Global configuration is done in the directory reported by
244 pkg-config systemd --variable=systemduserconfdir. The enable and
245 disable commands of the systemctl(1) tool can handle both global
246 (i.e. for all users) and private (for one user) enabling/disabling
247 of units. Full list of directories is provided in systemd.unit(5).
248 SysV init scripts directory
250 The location of the SysV init script directory varies between
251 distributions. If systemd cannot find a native unit file for a
252 requested service, it will look for a SysV init script of the same
253 name (with the .service suffix removed).
254 SysV runlevel link farm directory
256 The location of the SysV runlevel link farm directory varies
257 between distributions. systemd will take the link farm into account
258 when figuring out whether a service shall be enabled. Note that a
259 service unit with a native unit configuration file cannot be
260 started by activating it in the SysV runlevel link farm.
261
263 SIGTERM
264 Upon receiving this signal the systemd system manager serializes
265 its state, reexecutes itself and deserializes the saved state
266 again. This is mostly equivalent to systemctl daemon-reexec.
267 systemd user managers will start the exit.target unit when this
269 signal is received. This is mostly equivalent to systemctl --user
270 start exit.target --job-mode=replace-irreversibly.
271 SIGINT
273 Upon receiving this signal the systemd system manager will start
274 the ctrl-alt-del.target unit. This is mostly equivalent to
275 systemctl start ctrl-alt-del.target
276 --job-mode=replace-irreversibly. If this signal is received more
277 than 7 times per 2s, an immediate reboot is triggered. Note that
278 pressing Ctrl+Alt+Del on the console will trigger this signal.
279 Hence, if a reboot is hanging, pressing Ctrl+Alt+Del more than 7
280 times in 2 seconds is a relatively safe way to trigger an immediate
281 reboot.
282 systemd user managers treat this signal the same way as SIGTERM.
284 SIGWINCH
286 When this signal is received the systemd system manager will start
287 the kbrequest.target unit. This is mostly equivalent to systemctl
288 start kbrequest.target.
289 This signal is ignored by systemd user managers.
291 SIGPWR
293 When this signal is received the systemd manager will start the
294 sigpwr.target unit. This is mostly equivalent to systemctl start
295 sigpwr.target.
296 SIGUSR1
298 When this signal is received the systemd manager will try to
299 reconnect to the D-Bus bus.
300 SIGUSR2
302 When this signal is received the systemd manager will log its
303 complete state in human-readable form. The data logged is the same
304 as printed by systemd-analyze dump.
305 SIGHUP
307 Reloads the complete daemon configuration. This is mostly
308 equivalent to systemctl daemon-reload.
309 SIGRTMIN+0
311 Enters default mode, starts the default.target unit. This is mostly
312 equivalent to systemctl isolate default.target.
313 SIGRTMIN+1
315 Enters rescue mode, starts the rescue.target unit. This is mostly
316 equivalent to systemctl isolate rescue.target.
317 SIGRTMIN+2
319 Enters emergency mode, starts the emergency.service unit. This is
320 mostly equivalent to systemctl isolate emergency.service.
321 SIGRTMIN+3
323 Halts the machine, starts the halt.target unit. This is mostly
324 equivalent to systemctl start halt.target
325 --job-mode=replace-irreversibly.
326 SIGRTMIN+4
328 Powers off the machine, starts the poweroff.target unit. This is
329 mostly equivalent to systemctl start poweroff.target
330 --job-mode=replace-irreversibly.
331 SIGRTMIN+5
333 Reboots the machine, starts the reboot.target unit. This is mostly
334 equivalent to systemctl start reboot.target
335 --job-mode=replace-irreversibly.
336 SIGRTMIN+6
338 Reboots the machine via kexec, starts the kexec.target unit. This
339 is mostly equivalent to systemctl start kexec.target
340 --job-mode=replace-irreversibly.
341 SIGRTMIN+13
343 Immediately halts the machine.
344 SIGRTMIN+14
346 Immediately powers off the machine.
347 SIGRTMIN+15
349 Immediately reboots the machine.
350 SIGRTMIN+16
352 Immediately reboots the machine with kexec.
353 SIGRTMIN+20
355 Enables display of status messages on the console, as controlled
356 via systemd.show_status=1 on the kernel command line.
357 SIGRTMIN+21
359 Disables display of status messages on the console, as controlled
360 via systemd.show_status=0 on the kernel command line.
361 SIGRTMIN+22
363 Sets the service manager's log level to "debug", in a fashion
364 equivalent to systemd.log_level=debug on the kernel command line.
365 SIGRTMIN+23
367 Restores the log level to its configured value. The configured
368 value is derived from – in order of priority – the value specified
369 with systemd.log-level= on the kernel command line, or the value
370 specified with LogLevel= in the configuration file, or the built-in
371 default of "info".
372 SIGRTMIN+24
374 Immediately exits the manager (only available for --user
375 instances).
376 SIGRTMIN+25
378 Upon receiving this signal the systemd manager will reexecute
379 itself. This is mostly equivalent to systemctl daemon-reexec except
380 that it will be done asynchronously.
381 The systemd system manager treats this signal the same way as
383 SIGTERM.
384 SIGRTMIN+26
386 Restores the log target to its configured value. The configured
387 value is derived from – in order of priority – the value specified
388 with systemd.log-target= on the kernel command line, or the value
389 specified with LogTarget= in the configuration file, or the
390 built-in default.
391 SIGRTMIN+27, SIGRTMIN+28
393 Sets the log target to "console" on SIGRTMIN+27 (or "kmsg" on
394 SIGRTMIN+28), in a fashion equivalent to systemd.log_target=console
395 (or systemd.log_target=kmsg on SIGRTMIN+28) on the kernel command
396 line.
397
399 The environment block for the system manager is initially set by the
400 kernel. (In particular, "key=value" assignments on the kernel command
401 line are turned into environment variables for PID 1). For the user
402 manager, the system manager sets the environment as described in the
403 "Environment Variables in Spawned Processes" section of
404 systemd.exec(5). The DefaultEnvironment= setting in the system manager
405 applies to all services including user@.service. Additional entries may
406 be configured (as for any other service) through the Environment= and
407 EnvironmentFile= settings for user@.service (see systemd.exec(5)).
408 Also, additional environment variables may be set through the
409 ManagerEnvironment= setting in systemd-system.conf(5) and systemd-
410 user.conf(5).
411 Some of the variables understood by systemd:
413 $SYSTEMD_LOG_LEVEL
415 The maximum log level of emitted messages (messages with a higher
416 log level, i.e. less important ones, will be suppressed). Either
417 one of (in order of decreasing importance) emerg, alert, crit, err,
418 warning, notice, info, debug, or an integer in the range 0...7. See
419 syslog(3) for more information.
420 This can be overridden with --log-level=.
422 $SYSTEMD_LOG_COLOR
424 A boolean. If true, messages written to the tty will be colored
425 according to priority.
426 This can be overridden with --log-color=.
428 $SYSTEMD_LOG_TIME
430 A boolean. If true, console log messages will be prefixed with a
431 timestamp.
432 This can be overridden with --log-time=.
434 $SYSTEMD_LOG_LOCATION
436 A boolean. If true, messages will be prefixed with a filename and
437 line number in the source code where the message originates.
438 This can be overridden with --log-location=.
440 $SYSTEMD_LOG_TID
442 A boolean. If true, messages will be prefixed with the current
443 numerical thread ID (TID).
444 $SYSTEMD_LOG_TARGET
446 The destination for log messages. One of console (log to the
447 attached tty), console-prefixed (log to the attached tty but with
448 prefixes encoding the log level and "facility", see syslog(3), kmsg
449 (log to the kernel circular log buffer), journal (log to the
450 journal), journal-or-kmsg (log to the journal if available, and to
451 kmsg otherwise), auto (determine the appropriate log target
452 automatically, the default), null (disable log output).
453 This can be overridden with --log-target=.
455 $XDG_CONFIG_HOME, $XDG_CONFIG_DIRS, $XDG_DATA_HOME, $XDG_DATA_DIRS
457 The systemd user manager uses these variables in accordance to the
458 XDG Base Directory specification[6] to find its configuration.
459 $SYSTEMD_UNIT_PATH, $SYSTEMD_GENERATOR_PATH,
461 $SYSTEMD_ENVIRONMENT_GENERATOR_PATH
462 Controls where systemd looks for unit files and generators.
463 These variables may contain a list of paths, separated by colons
465 (":"). When set, if the list ends with an empty component ("...:"),
466 this list is prepended to the usual set of paths. Otherwise, the
467 specified list replaces the usual set of paths.
468 $SYSTEMD_PAGER
470 Pager to use when --no-pager is not given; overrides $PAGER. If
471 neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known
472 pager implementations are tried in turn, including less(1) and
473 more(1), until one is found. If no pager implementation is
474 discovered no pager is invoked. Setting this environment variable
475 to an empty string or the value "cat" is equivalent to passing
476 --no-pager.
477 Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER (as well
479 as $PAGER) will be silently ignored.
480 $SYSTEMD_LESS
482 Override the options passed to less (by default "FRSXMK").
483 Users might want to change two options in particular:
485 K
487 This option instructs the pager to exit immediately when Ctrl+C
488 is pressed. To allow less to handle Ctrl+C itself to switch
489 back to the pager command prompt, unset this option.
490 If the value of $SYSTEMD_LESS does not include "K", and the
492 pager that is invoked is less, Ctrl+C will be ignored by the
493 executable, and needs to be handled by the pager.
494 X
496 This option instructs the pager to not send termcap
497 initialization and deinitialization strings to the terminal. It
498 is set by default to allow command output to remain visible in
499 the terminal even after the pager exits. Nevertheless, this
500 prevents some pager functionality from working, in particular
501 paged output cannot be scrolled with the mouse.
502 See less(1) for more discussion.
504 $SYSTEMD_LESSCHARSET
506 Override the charset passed to less (by default "utf-8", if the
507 invoking terminal is determined to be UTF-8 compatible).
508 $SYSTEMD_PAGERSECURE
510 Takes a boolean argument. When true, the "secure" mode of the pager
511 is enabled; if false, disabled. If $SYSTEMD_PAGERSECURE is not set
512 at all, secure mode is enabled if the effective UID is not the same
513 as the owner of the login session, see geteuid(2) and
514 sd_pid_get_owner_uid(3). In secure mode, LESSSECURE=1 will be set
515 when invoking the pager, and the pager shall disable commands that
516 open or create new files or start new subprocesses. When
517 $SYSTEMD_PAGERSECURE is not set at all, pagers which are not known
518 to implement secure mode will not be used. (Currently only less(1)
519 implements secure mode.)
520 Note: when commands are invoked with elevated privileges, for
522 example under sudo(8) or pkexec(1), care must be taken to ensure
523 that unintended interactive features are not enabled. "Secure" mode
524 for the pager may be enabled automatically as describe above.
525 Setting SYSTEMD_PAGERSECURE=0 or not removing it from the inherited
526 environment allows the user to invoke arbitrary commands. Note that
527 if the $SYSTEMD_PAGER or $PAGER variables are to be honoured,
528 $SYSTEMD_PAGERSECURE must be set too. It might be reasonable to
529 completely disable the pager using --no-pager instead.
530 $SYSTEMD_COLORS
532 Takes a boolean argument. When true, systemd and related utilities
533 will use colors in their output, otherwise the output will be
534 monochrome. Additionally, the variable can take one of the
535 following special values: "16", "256" to restrict the use of colors
536 to the base 16 or 256 ANSI colors, respectively. This can be
537 specified to override the automatic decision based on $TERM and
538 what the console is connected to.
539 $SYSTEMD_URLIFY
541 The value must be a boolean. Controls whether clickable links
542 should be generated in the output for terminal emulators supporting
543 this. This can be specified to override the decision that systemd
544 makes based on $TERM and other conditions.
545 $LISTEN_PID, $LISTEN_FDS, $LISTEN_FDNAMES
547 Set by systemd for supervised processes during socket-based
548 activation. See sd_listen_fds(3) for more information.
549 $NOTIFY_SOCKET
551 Set by systemd for supervised processes for status and start-up
552 completion notification. See sd_notify(3) for more information.
553 For further environment variables understood by systemd and its various
555 components, see Known Environment Variables[7].
556
558 When run as the system instance, systemd parses a number of options
559 listed below. They can be specified as kernel command line arguments
560 which are parsed from a number of sources depending on the environment
561 in which systemd is executed. If run inside a Linux container, these
562 options are parsed from the command line arguments passed to systemd
563 itself, next to any of the command line options listed in the Options
564 section above. If run outside of Linux containers, these arguments are
565 parsed from /proc/cmdline and from the "SystemdOptions" EFI variable
566 (on EFI systems) instead. Options from /proc/cmdline have higher
567 priority. The following variables are understood:
568 systemd.unit=, rd.systemd.unit=
570 Overrides the unit to activate on boot. Defaults to default.target.
571 This may be used to temporarily boot into a different boot unit,
572 for example rescue.target or emergency.service. See
573 systemd.special(7) for details about these units. The option
574 prefixed with "rd." is honored only in the initial RAM disk
575 (initrd), while the one that is not prefixed only in the main
576 system.
577 systemd.dump_core
579 Takes a boolean argument or enables the option if specified without
580 an argument. If enabled, the systemd manager (PID 1) dumps core
581 when it crashes. Otherwise, no core dump is created. Defaults to
582 enabled.
583 systemd.crash_chvt
585 Takes a positive integer, or a boolean argument. Can be also
586 specified without an argument, with the same effect as a positive
587 boolean. If a positive integer (in the range 1–63) is specified,
588 the system manager (PID 1) will activate the specified virtual
589 terminal when it crashes. Defaults to disabled, meaning that no
590 such switch is attempted. If set to enabled, the virtual terminal
591 the kernel messages are written to is used instead.
592 systemd.crash_shell
594 Takes a boolean argument or enables the option if specified without
595 an argument. If enabled, the system manager (PID 1) spawns a shell
596 when it crashes, after a 10s delay. Otherwise, no shell is spawned.
597 Defaults to disabled, for security reasons, as the shell is not
598 protected by password authentication.
599 systemd.crash_reboot
601 Takes a boolean argument or enables the option if specified without
602 an argument. If enabled, the system manager (PID 1) will reboot the
603 machine automatically when it crashes, after a 10s delay.
604 Otherwise, the system will hang indefinitely. Defaults to disabled,
605 in order to avoid a reboot loop. If combined with
606 systemd.crash_shell, the system is rebooted after the shell exits.
607 systemd.confirm_spawn
609 Takes a boolean argument or a path to the virtual console where the
610 confirmation messages should be emitted. Can be also specified
611 without an argument, with the same effect as a positive boolean. If
612 enabled, the system manager (PID 1) asks for confirmation when
613 spawning processes using /dev/console. If a path or a console name
614 (such as "ttyS0") is provided, the virtual console pointed to by
615 this path or described by the give name will be used instead.
616 Defaults to disabled.
617 systemd.service_watchdogs=
619 Takes a boolean argument. If disabled, all service runtime
620 watchdogs (WatchdogSec=) and emergency actions (e.g. OnFailure= or
621 StartLimitAction=) are ignored by the system manager (PID 1); see
622 systemd.service(5). Defaults to enabled, i.e. watchdogs and failure
623 actions are processed normally. The hardware watchdog is not
624 affected by this option.
625 systemd.show_status
627 Takes a boolean argument or the constants error and auto. Can be
628 also specified without an argument, with the same effect as a
629 positive boolean. If enabled, the systemd manager (PID 1) shows
630 terse service status updates on the console during bootup. With
631 error, only messages about failures are shown, but boot is
632 otherwise quiet. auto behaves like false until there is a
633 significant delay in boot. Defaults to enabled, unless quiet is
634 passed as kernel command line option, in which case it defaults to
635 error. If specified overrides the system manager configuration file
636 option ShowStatus=, see systemd-system.conf(5).
637 systemd.status_unit_format=
639 Takes name, description or combined as the value. If name, the
640 system manager will use unit names in status messages. If combined,
641 the system manager will use unit names and description in status
642 messages. When specified, overrides the system manager
643 configuration file option StatusUnitFormat=, see systemd-
644 system.conf(5).
645 systemd.log_color, systemd.log_level=, systemd.log_location,
647 systemd.log_target=, systemd.log_time, systemd.log_tid
648 Controls log output, with the same effect as the
649 $SYSTEMD_LOG_COLOR, $SYSTEMD_LOG_LEVEL, $SYSTEMD_LOG_LOCATION,
650 $SYSTEMD_LOG_TARGET, $SYSTEMD_LOG_TIME, and $SYSTEMD_LOG_TID
651 environment variables described above. systemd.log_color,
652 systemd.log_location, systemd.log_time, and systemd.log_tid= can be
653 specified without an argument, with the same effect as a positive
654 boolean.
655 systemd.default_standard_output=, systemd.default_standard_error=
657 Controls default standard output and error output for services and
658 sockets. That is, controls the default for StandardOutput= and
659 StandardError= (see systemd.exec(5) for details). Takes one of
660 inherit, null, tty, journal, journal+console, kmsg, kmsg+console.
661 If the argument is omitted systemd.default-standard-output=
662 defaults to journal and systemd.default-standard-error= to inherit.
663 systemd.setenv=
665 Takes a string argument in the form VARIABLE=VALUE. May be used to
666 set default environment variables to add to forked child processes.
667 May be used more than once to set multiple variables.
668 systemd.machine_id=
670 Takes a 32 character hex value to be used for setting the
671 machine-id. Intended mostly for network booting where the same
672 machine-id is desired for every boot.
673 systemd.unified_cgroup_hierarchy
675 When specified without an argument or with a true argument, enables
676 the usage of unified cgroup hierarchy[8] (a.k.a. cgroups-v2). When
677 specified with a false argument, fall back to hybrid or full legacy
678 cgroup hierarchy.
679 If this option is not specified, the default behaviour is
681 determined during compilation (the -Ddefault-hierarchy= meson
682 option). If the kernel does not support unified cgroup hierarchy,
683 the legacy hierarchy will be used even if this option is specified.
684 systemd.legacy_systemd_cgroup_controller
686 Takes effect if the full unified cgroup hierarchy is not used (see
687 previous option). When specified without an argument or with a true
688 argument, disables the use of "hybrid" cgroup hierarchy (i.e. a
689 cgroups-v2 tree used for systemd, and legacy cgroup hierarchy[9],
690 a.k.a. cgroups-v1, for other controllers), and forces a full
691 "legacy" mode. When specified with a false argument, enables the
692 use of "hybrid" hierarchy.
693 If this option is not specified, the default behaviour is
695 determined during compilation (the -Ddefault-hierarchy= meson
696 option). If the kernel does not support unified cgroup hierarchy,
697 the legacy hierarchy will be used even if this option is specified.
698 systemd.set_credential=
700 Sets a system credential, which can then be propagated to system
701 services using the LoadCredential= setting, see systemd.exec(5) for
702 details. Takes a pair of credential name and value, separated by a
703 colon. Note that the kernel command line is typically accessible by
704 unprivileged programs in /proc/cmdline. Thus, this mechanism is not
705 suitable for transferring sensitive data. Use it only for data that
706 is not sensitive (e.g. public keys/certificates, rather than
707 private keys), or in testing/debugging environments.
708 For further information see System and Service Credentials[10]
710 documentation.
711 systemd.import_credentials=
713 Takes a boolean argument. If false disables importing credentials
714 from the kernel command line, qemu_fw_cfg subsystem or the kernel
715 command line.
716 quiet
718 Turn off status output at boot, much like systemd.show_status=no
719 would. Note that this option is also read by the kernel itself and
720 disables kernel log output. Passing this option hence turns off the
721 usual output from both the system manager and the kernel.
722 debug
724 Turn on debugging output. This is equivalent to
725 systemd.log_level=debug. Note that this option is also read by the
726 kernel itself and enables kernel debug output. Passing this option
727 hence turns on the debug output from both the system manager and
728 the kernel.
729 emergency, rd.emergency, -b
731 Boot into emergency mode. This is equivalent to
732 systemd.unit=emergency.target or rd.systemd.unit=emergency.target,
733 respectively, and provided for compatibility reasons and to be
734 easier to type.
735 rescue, rd.rescue, single, s, S, 1
737 Boot into rescue mode. This is equivalent to
738 systemd.unit=rescue.target or rd.systemd.unit=rescue.target,
739 respectively, and provided for compatibility reasons and to be
740 easier to type.
741 2, 3, 4, 5
743 Boot into the specified legacy SysV runlevel. These are equivalent
744 to systemd.unit=runlevel2.target, systemd.unit=runlevel3.target,
745 systemd.unit=runlevel4.target, and systemd.unit=runlevel5.target,
746 respectively, and provided for compatibility reasons and to be
747 easier to type.
748 locale.LANG=, locale.LANGUAGE=, locale.LC_CTYPE=, locale.LC_NUMERIC=,
750 locale.LC_TIME=, locale.LC_COLLATE=, locale.LC_MONETARY=,
751 locale.LC_MESSAGES=, locale.LC_PAPER=, locale.LC_NAME=,
752 locale.LC_ADDRESS=, locale.LC_TELEPHONE=, locale.LC_MEASUREMENT=,
753 locale.LC_IDENTIFICATION=
754 Set the system locale to use. This overrides the settings in
755 /etc/locale.conf. For more information, see locale.conf(5) and
756 locale(7).
757 For other kernel command line parameters understood by components of
759 the core OS, please refer to kernel-command-line(7).
760
762 systemd is only very rarely invoked directly, since it is started early
763 and is already running by the time users may interact with it.
764 Normally, tools like systemctl(1) are used to give commands to the
765 manager. Since systemd is usually not invoked directly, the options
766 listed below are mostly useful for debugging and special purposes.
767 Introspection and debugging options
769 Those options are used for testing and introspection, and systemd may
770 be invoked with them at any time:
771 --dump-configuration-items
773 Dump understood unit configuration items. This outputs a terse but
774 complete list of configuration items understood in unit definition
775 files.
776 --dump-bus-properties
778 Dump exposed bus properties. This outputs a terse but complete list
779 of properties exposed on D-Bus.
780 --test
782 Determine the initial start-up transaction (i.e. the list of jobs
783 enqueued at start-up), dump it and exit — without actually
784 executing any of the determined jobs. This option is useful for
785 debugging only. Note that during regular service manager start-up
786 additional units not shown by this operation may be started,
787 because hardware, socket, bus or other kinds of activation might
788 add additional jobs as the transaction is executed. Use --system to
789 request the initial transaction of the system service manager (this
790 is also the implied default), combine with --user to request the
791 initial transaction of the per-user service manager instead.
792 --system, --user
794 When used in conjunction with --test, selects whether to calculate
795 the initial transaction for the system instance or for a per-user
796 instance. These options have no effect when invoked without --test,
797 as during regular (i.e. non---test) invocations the service manager
798 will automatically detect whether it shall operate in system or
799 per-user mode, by checking whether the PID it is run as is 1 or
800 not. Note that it is not supported booting and maintaining a system
801 with the service manager running in --system mode but with a PID
802 other than 1.
803 -h, --help
805 Print a short help text and exit.
806 --version
808 Print a short version string and exit.
809 Options that duplicate kernel command line settings
811 Those options correspond directly to options listed above in "Kernel
812 Command Line". Both forms may be used equivalently for the system
813 manager, but it is recommended to use the forms listed above in this
814 context, because they are properly namespaced. When an option is
815 specified both on the kernel command line and as a normal command line
816 argument, the latter has higher precedence.
817 When systemd is used as a user manager, the kernel command line is
819 ignored and only the options described below are understood.
820 Nevertheless, systemd is usually started in this mode through the
821 user@.service(5) service, which is shared between all users. It may be
822 more convenient to use configuration files to modify settings (see
823 systemd-user.conf(5)), or environment variables. See the "Environment"
824 section above for a discussion of how the environment block is set.
825 --unit=
827 Set default unit to activate on startup. If not specified, defaults
828 to default.target. See systemd.unit= above.
829 --dump-core
831 Enable core dumping on crash. This switch has no effect when
832 running as user instance. Same as systemd.dump_core= above.
833 --crash-vt=VT
835 Switch to a specific virtual console (VT) on crash. This switch has
836 no effect when running as user instance. Same as
837 systemd.crash_chvt= above (but not the different spelling!).
838 --crash-shell
840 Run a shell on crash. This switch has no effect when running as
841 user instance. See systemd.crash_shell= above.
842 --crash-reboot
844 Automatically reboot the system on crash. This switch has no effect
845 when running as user instance. See systemd.crash_reboot above.
846 --confirm-spawn
848 Ask for confirmation when spawning processes. This switch has no
849 effect when run as user instance. See systemd.confirm_spawn above.
850 --show-status
852 Show terse unit status information on the console during boot-up
853 and shutdown. See systemd.show_status above.
854 --log-color
856 Highlight important log messages. See systemd.log_color above.
857 --log-level=
859 Set log level. See systemd.log_level above.
860 --log-location
862 Include code location in log messages. See systemd.log_location
863 above.
864 --log-target=
866 Set log target. See systemd.log_target above.
867 --log-time=
869 Prefix console messages with timestamp. See systemd.log_time above.
870 --machine-id=
872 Override the machine-id set on the hard drive. See
873 systemd.machine_id= above.
874 --service-watchdogs
876 Globally enable/disable all service watchdog timeouts and emergency
877 actions. See systemd.service_watchdogs above.
878 --default-standard-output=, --default-standard-error=
880 Sets the default output or error output for all services and
881 sockets, respectively. See systemd.default_standard_output= and
882 systemd.default_standard_error= above.
883
885 /run/systemd/notify
886 Daemon status notification socket. This is an AF_UNIX datagram
887 socket and is used to implement the daemon notification logic as
888 implemented by sd_notify(3).
889 /run/systemd/private
891 Used internally as communication channel between systemctl(1) and
892 the systemd process. This is an AF_UNIX stream socket. This
893 interface is private to systemd and should not be used in external
894 projects.
895 /dev/initctl
897 Limited compatibility support for the SysV client interface, as
898 implemented by the systemd-initctl.service unit. This is a named
899 pipe in the file system. This interface is obsolete and should not
900 be used in new applications.
901
903 The systemd Homepage[11], systemd-system.conf(5), locale.conf(5),
904 systemctl(1), journalctl(1), systemd-notify(1), daemon(7), sd-
905 daemon(3), org.freedesktop.systemd1(5), systemd.unit(5),
906 systemd.special(7), pkg-config(1), kernel-command-line(7), bootup(7),
907 systemd.directives(7)
908
910 1. cgroups.txt
911 https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
912 2. Original Design Document
914 http://0pointer.de/blog/projects/systemd.html
915 3. Interface Portability and Stability Promise
917 https://systemd.io/PORTABILITY_AND_STABILITY/
918 4. Container Interface
920 https://systemd.io/CONTAINER_INTERFACE
921 5. initrd Interface
923 https://systemd.io/INITRD_INTERFACE/
924 6. XDG Base Directory specification
926 http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
927 7. Known Environment Variables
929 https://systemd.io/ENVIRONMENT
930 8. unified cgroup hierarchy
932 https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html
933 9. legacy cgroup hierarchy
935 https://www.kernel.org/doc/Documentation/cgroup-v1/
936 10. System and Service Credentials
938 https://systemd.io/CREDENTIALS
939 11. systemd Homepage
941 https://www.freedesktop.org/wiki/Software/systemd/
942systemd 251 SYSTEMD(1)