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, dynamically from system state
43 or programmatically at runtime. Units may be "active" (meaning started,
44 bound, plugged in, ..., depending on the unit type, see below), or
45 "inactive" (meaning stopped, unbound, unplugged, ...), as well as in
46 the process of being activated or deactivated, i.e. between the two
47 states (these states are called "activating", "deactivating"). A
48 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 some sort of at least one other unit that is
139 loaded into 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 our example, start jobs for any of those inactive units
199 getting 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 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 Systems which invoke systemd in a container or initrd environment
218 should implement the Container Interface[4] or initrd Interface[5]
219 specifications, respectively.
220
222 System unit directories
223 The systemd system manager reads unit configuration from various
224 directories. Packages that want to install unit files shall place
225 them in the directory returned by pkg-config systemd
226 --variable=systemdsystemunitdir. Other directories checked are
227 /usr/local/lib/systemd/system and /usr/lib/systemd/system. User
228 configuration always takes precedence. pkg-config systemd
229 --variable=systemdsystemconfdir returns the path of the system
230 configuration directory. Packages should alter the content of these
231 directories only with the enable and disable commands of the
232 systemctl(1) tool. Full list of directories is provided in
233 systemd.unit(5).
234 User unit directories
236 Similar rules apply for the user unit directories. However, here
237 the XDG Base Directory specification[6] is followed to find units.
238 Applications should place their unit files in the directory
239 returned by pkg-config systemd --variable=systemduserunitdir.
240 Global configuration is done in the directory reported by
241 pkg-config systemd --variable=systemduserconfdir. The enable and
242 disable commands of the systemctl(1) tool can handle both global
243 (i.e. for all users) and private (for one user) enabling/disabling
244 of units. Full list of directories is provided in systemd.unit(5).
245 SysV init scripts directory
247 The location of the SysV init script directory varies between
248 distributions. If systemd cannot find a native unit file for a
249 requested service, it will look for a SysV init script of the same
250 name (with the .service suffix removed).
251 SysV runlevel link farm directory
253 The location of the SysV runlevel link farm directory varies
254 between distributions. systemd will take the link farm into account
255 when figuring out whether a service shall be enabled. Note that a
256 service unit with a native unit configuration file cannot be
257 started by activating it in the SysV runlevel link farm.
258
260 SIGTERM
261 Upon receiving this signal the systemd system manager serializes
262 its state, reexecutes itself and deserializes the saved state
263 again. This is mostly equivalent to systemctl daemon-reexec.
264 systemd user managers will start the exit.target unit when this
266 signal is received. This is mostly equivalent to systemctl --user
267 start exit.target --job-mode=replace-irreversibly.
268 SIGINT
270 Upon receiving this signal the systemd system manager will start
271 the ctrl-alt-del.target unit. This is mostly equivalent to
272 systemctl start ctrl-alt-del.target
273 --job-mode=replace-irreversibly. If this signal is received more
274 than 7 times per 2s, an immediate reboot is triggered. Note that
275 pressing Ctrl+Alt+Del on the console will trigger this signal.
276 Hence, if a reboot is hanging, pressing Ctrl+Alt+Del more than 7
277 times in 2 seconds is a relatively safe way to trigger an immediate
278 reboot.
279 systemd user managers treat this signal the same way as SIGTERM.
281 SIGWINCH
283 When this signal is received the systemd system manager will start
284 the kbrequest.target unit. This is mostly equivalent to systemctl
285 start kbrequest.target.
286 This signal is ignored by systemd user managers.
288 SIGPWR
290 When this signal is received the systemd manager will start the
291 sigpwr.target unit. This is mostly equivalent to systemctl start
292 sigpwr.target.
293 SIGUSR1
295 When this signal is received the systemd manager will try to
296 reconnect to the D-Bus bus.
297 SIGUSR2
299 When this signal is received the systemd manager will log its
300 complete state in human-readable form. The data logged is the same
301 as printed by systemd-analyze dump.
302 SIGHUP
304 Reloads the complete daemon configuration. This is mostly
305 equivalent to systemctl daemon-reload.
306 SIGRTMIN+0
308 Enters default mode, starts the default.target unit. This is mostly
309 equivalent to systemctl isolate default.target.
310 SIGRTMIN+1
312 Enters rescue mode, starts the rescue.target unit. This is mostly
313 equivalent to systemctl isolate rescue.target.
314 SIGRTMIN+2
316 Enters emergency mode, starts the emergency.service unit. This is
317 mostly equivalent to systemctl isolate emergency.service.
318 SIGRTMIN+3
320 Halts the machine, starts the halt.target unit. This is mostly
321 equivalent to systemctl start halt.target
322 --job-mode=replace-irreversibly.
323 SIGRTMIN+4
325 Powers off the machine, starts the poweroff.target unit. This is
326 mostly equivalent to systemctl start poweroff.target
327 --job-mode=replace-irreversibly.
328 SIGRTMIN+5
330 Reboots the machine, starts the reboot.target unit. This is mostly
331 equivalent to systemctl start reboot.target
332 --job-mode=replace-irreversibly.
333 SIGRTMIN+6
335 Reboots the machine via kexec, starts the kexec.target unit. This
336 is mostly equivalent to systemctl start kexec.target
337 --job-mode=replace-irreversibly.
338 SIGRTMIN+13
340 Immediately halts the machine.
341 SIGRTMIN+14
343 Immediately powers off the machine.
344 SIGRTMIN+15
346 Immediately reboots the machine.
347 SIGRTMIN+16
349 Immediately reboots the machine with kexec.
350 SIGRTMIN+20
352 Enables display of status messages on the console, as controlled
353 via systemd.show_status=1 on the kernel command line.
354 SIGRTMIN+21
356 Disables display of status messages on the console, as controlled
357 via systemd.show_status=0 on the kernel command line.
358 SIGRTMIN+22
360 Sets the service manager's log level to "debug", in a fashion
361 equivalent to systemd.log_level=debug on the kernel command line.
362 SIGRTMIN+23
364 Restores the log level to its configured value. The configured
365 value is derived from – in order of priority – the value specified
366 with systemd.log-level= on the kernel command line, or the value
367 specified with LogLevel= in the configuration file, or the built-in
368 default of "info".
369 SIGRTMIN+24
371 Immediately exits the manager (only available for --user
372 instances).
373 SIGRTMIN+26
375 Restores the log target to its configured value. The configured
376 value is derived from – in order of priority – the value specified
377 with systemd.log-target= on the kernel command line, or the value
378 specified with LogTarget= in the configuration file, or the
379 built-in default.
380 SIGRTMIN+27, SIGRTMIN+28
382 Sets the log target to "console" on SIGRTMIN+27 (or "kmsg" on
383 SIGRTMIN+28), in a fashion equivalent to systemd.log_target=console
384 (or systemd.log_target=kmsg on SIGRTMIN+28) on the kernel command
385 line.
386
388 $SYSTEMD_LOG_LEVEL
389 systemd reads the log level from this environment variable. This
390 can be overridden with --log-level=.
391 $SYSTEMD_LOG_TARGET
393 systemd reads the log target from this environment variable. This
394 can be overridden with --log-target=.
395 $SYSTEMD_LOG_COLOR
397 Controls whether systemd highlights important log messages. This
398 can be overridden with --log-color=.
399 $SYSTEMD_LOG_LOCATION
401 Controls whether systemd prints the code location along with log
402 messages. This can be overridden with --log-location=.
403 $XDG_CONFIG_HOME, $XDG_CONFIG_DIRS, $XDG_DATA_HOME, $XDG_DATA_DIRS
405 The systemd user manager uses these variables in accordance to the
406 XDG Base Directory specification[6] to find its configuration.
407 $SYSTEMD_UNIT_PATH
409 Controls where systemd looks for unit files.
410 $SYSTEMD_SYSVINIT_PATH
412 Controls where systemd looks for SysV init scripts.
413 $SYSTEMD_SYSVRCND_PATH
415 Controls where systemd looks for SysV init script runlevel link
416 farms.
417 $SYSTEMD_PAGER
419 Pager to use when --no-pager is not given; overrides $PAGER. If
420 neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known
421 pager implementations are tried in turn, including less(1) and
422 more(1), until one is found. If no pager implementation is
423 discovered no pager is invoked. Setting this environment variable
424 to an empty string or the value "cat" is equivalent to passing
425 --no-pager.
426 $SYSTEMD_LESS
428 Override the options passed to less (by default "FRSXMK").
429 Users might want to change two options in particular:
431 K
433 This option instructs the pager to exit immediately when Ctrl+C
434 is pressed. To allow less to handle Ctrl+C itself to switch
435 back to the pager command prompt, unset this option.
436 If the value of $SYSTEMD_LESS does not include "K", and the
438 pager that is invoked is less, Ctrl+C will be ignored by the
439 executable, and needs to be handled by the pager.
440 X
442 This option instructs the pager to not send termcap
443 initialization and deinitialization strings to the terminal. It
444 is set by default to allow command output to remain visible in
445 the terminal even after the pager exits. Nevertheless, this
446 prevents some pager functionality from working, in particular
447 paged output cannot be scrolled with the mouse.
448 See less(1) for more discussion.
450 $SYSTEMD_LESSCHARSET
452 Override the charset passed to less (by default "utf-8", if the
453 invoking terminal is determined to be UTF-8 compatible).
454 $SYSTEMD_COLORS
456 The value must be a boolean. Controls whether colorized output
457 should be generated. This can be specified to override the decision
458 that systemd makes based on $TERM and what the console is connected
459 to.
460 $SYSTEMD_URLIFY
462 The value must be a boolean. Controls whether clickable links
463 should be generated in the output for terminal emulators supporting
464 this. This can be specified to override the decision that systemd
465 makes based on $TERM and other conditions.
466 $LISTEN_PID, $LISTEN_FDS, $LISTEN_FDNAMES
468 Set by systemd for supervised processes during socket-based
469 activation. See sd_listen_fds(3) for more information.
470 $NOTIFY_SOCKET
472 Set by systemd for supervised processes for status and start-up
473 completion notification. See sd_notify(3) for more information.
474 For further environment variables understood by systemd and its various
476 components, see Known Environment Variables[7].
477
479 When run as the system instance systemd parses a number of options
480 listed below. They can be specified as kernel command line
481 arguments[8], or through the "SystemdOptions" EFI variable (on EFI
482 systems). The kernel command line has higher priority. Following
483 variables are understood:
484 systemd.unit=, rd.systemd.unit=
486 Overrides the unit to activate on boot. Defaults to default.target.
487 This may be used to temporarily boot into a different boot unit,
488 for example rescue.target or emergency.service. See
489 systemd.special(7) for details about these units. The option
490 prefixed with "rd." is honored only in the initial RAM disk
491 (initrd), while the one that is not prefixed only in the main
492 system.
493 systemd.dump_core
495 Takes a boolean argument or enables the option if specified without
496 an argument. If enabled, the systemd manager (PID 1) dumps core
497 when it crashes. Otherwise, no core dump is created. Defaults to
498 enabled.
499 systemd.crash_chvt
501 Takes a positive integer, or a boolean argument. Can be also
502 specified without an argument, with the same effect as a positive
503 boolean. If a positive integer (in the range 1–63) is specified,
504 the system manager (PID 1) will activate the specified virtual
505 terminal (VT) when it crashes. Defaults to disabled, meaning that
506 no such switch is attempted. If set to enabled, the VT the kernel
507 messages are written to is selected.
508 systemd.crash_shell
510 Takes a boolean argument or enables the option if specified without
511 an argument. If enabled, the system manager (PID 1) spawns a shell
512 when it crashes, after a 10s delay. Otherwise, no shell is spawned.
513 Defaults to disabled, for security reasons, as the shell is not
514 protected by password authentication.
515 systemd.crash_reboot
517 Takes a boolean argument or enables the option if specified without
518 an argument. If enabled, the system manager (PID 1) will reboot the
519 machine automatically when it crashes, after a 10s delay.
520 Otherwise, the system will hang indefinitely. Defaults to disabled,
521 in order to avoid a reboot loop. If combined with
522 systemd.crash_shell, the system is rebooted after the shell exits.
523 systemd.confirm_spawn
525 Takes a boolean argument or a path to the virtual console where the
526 confirmation messages should be emitted. Can be also specified
527 without an argument, with the same effect as a positive boolean. If
528 enabled, the system manager (PID 1) asks for confirmation when
529 spawning processes using /dev/console. If a path or a console name
530 (such as "ttyS0") is provided, the virtual console pointed to by
531 this path or described by the give name will be used instead.
532 Defaults to disabled.
533 systemd.service_watchdogs=
535 Takes a boolean argument. If disabled, all service runtime
536 watchdogs (WatchdogSec=) and emergency actions (e.g. OnFailure= or
537 StartLimitAction=) are ignored by the system manager (PID 1); see
538 systemd.service(5). Defaults to enabled, i.e. watchdogs and failure
539 actions are processed normally. The hardware watchdog is not
540 affected by this option.
541 systemd.show_status
543 Takes a boolean argument or the constants error and auto. Can be
544 also specified without an argument, with the same effect as a
545 positive boolean. If enabled, the systemd manager (PID 1) shows
546 terse service status updates on the console during bootup. With
547 error, only messages about failures are shown, but boot is
548 otherwise quiet. auto behaves like false until there is a
549 significant delay in boot. Defaults to enabled, unless quiet is
550 passed as kernel command line option, in which case it defaults to
551 error. If specified overrides the system manager configuration file
552 option ShowStatus=, see systemd-system.conf(5).
553 systemd.status_unit_format=
555 Takes either name or description as the value. If name, the system
556 manager will use unit names in status messages. If specified,
557 overrides the system manager configuration file option
558 StatusUnitFormat=, see systemd-system.conf(5).
559 systemd.log_target=, systemd.log_level=, systemd.log_location=,
561 systemd.log_color
562 Controls log output, with the same effect as the
563 $SYSTEMD_LOG_TARGET, $SYSTEMD_LOG_LEVEL, $SYSTEMD_LOG_LOCATION,
564 $SYSTEMD_LOG_COLOR environment variables described above.
565 systemd.log_color can be specified without an argument, with the
566 same effect as a positive boolean.
567 systemd.default_standard_output=, systemd.default_standard_error=
569 Controls default standard output and error output for services and
570 sockets. That is, controls the default for StandardOutput= and
571 StandardError= (see systemd.exec(5) for details). Takes one of
572 inherit, null, tty, journal, journal+console, kmsg, kmsg+console.
573 If the argument is omitted systemd.default-standard-output=
574 defaults to journal and systemd.default-standard-error= to inherit.
575 systemd.setenv=
577 Takes a string argument in the form VARIABLE=VALUE. May be used to
578 set default environment variables to add to forked child processes.
579 May be used more than once to set multiple variables.
580 systemd.machine_id=
582 Takes a 32 character hex value to be used for setting the
583 machine-id. Intended mostly for network booting where the same
584 machine-id is desired for every boot.
585 systemd.unified_cgroup_hierarchy
587 When specified without an argument or with a true argument, enables
588 the usage of unified cgroup hierarchy[9] (a.k.a. cgroups-v2). When
589 specified with a false argument, fall back to hybrid or full legacy
590 cgroup hierarchy.
591 If this option is not specified, the default behaviour is
593 determined during compilation (the -Ddefault-hierarchy= meson
594 option). If the kernel does not support unified cgroup hierarchy,
595 the legacy hierarchy will be used even if this option is specified.
596 systemd.legacy_systemd_cgroup_controller
598 Takes effect if the full unified cgroup hierarchy is not used (see
599 previous option). When specified without an argument or with a true
600 argument, disables the use of "hybrid" cgroup hierarchy (i.e. a
601 cgroups-v2 tree used for systemd, and legacy cgroup hierarchy[10],
602 a.k.a. cgroups-v1, for other controllers), and forces a full
603 "legacy" mode. When specified with a false argument, enables the
604 use of "hybrid" hierarchy.
605 If this option is not specified, the default behaviour is
607 determined during compilation (the -Ddefault-hierarchy= meson
608 option). If the kernel does not support unified cgroup hierarchy,
609 the legacy hierarchy will be used even if this option is specified.
610 quiet
612 Turn off status output at boot, much like systemd.show_status=no
613 would. Note that this option is also read by the kernel itself and
614 disables kernel log output. Passing this option hence turns off the
615 usual output from both the system manager and the kernel.
616 debug
618 Turn on debugging output. This is equivalent to
619 systemd.log_level=debug. Note that this option is also read by the
620 kernel itself and enables kernel debug output. Passing this option
621 hence turns on the debug output from both the system manager and
622 the kernel.
623 emergency, rd.emergency, -b
625 Boot into emergency mode. This is equivalent to
626 systemd.unit=emergency.target or rd.systemd.unit=emergency.target,
627 respectively, and provided for compatibility reasons and to be
628 easier to type.
629 rescue, rd.rescue, single, s, S, 1
631 Boot into rescue mode. This is equivalent to
632 systemd.unit=rescue.target or rd.systemd.unit=rescue.target,
633 respectively, and provided for compatibility reasons and to be
634 easier to type.
635 2, 3, 4, 5
637 Boot into the specified legacy SysV runlevel. These are equivalent
638 to systemd.unit=runlevel2.target, systemd.unit=runlevel3.target,
639 systemd.unit=runlevel4.target, and systemd.unit=runlevel5.target,
640 respectively, and provided for compatibility reasons and to be
641 easier to type.
642 locale.LANG=, locale.LANGUAGE=, locale.LC_CTYPE=, locale.LC_NUMERIC=,
644 locale.LC_TIME=, locale.LC_COLLATE=, locale.LC_MONETARY=,
645 locale.LC_MESSAGES=, locale.LC_PAPER=, locale.LC_NAME=,
646 locale.LC_ADDRESS=, locale.LC_TELEPHONE=, locale.LC_MEASUREMENT=,
647 locale.LC_IDENTIFICATION=
648 Set the system locale to use. This overrides the settings in
649 /etc/locale.conf. For more information, see locale.conf(5) and
650 locale(7).
651 For other kernel command line parameters understood by components of
653 the core OS, please refer to kernel-command-line(7).
654
656 systemd is only very rarely invoked directly, since it is started early
657 and is already running by the time users may interact with it.
658 Normally, tools like systemctl(1) are used to give commands to the
659 manager. Since systemd is usually not invoked directly, the options
660 listed below are mostly useful for debugging and special purposes.
661 Introspection and debugging options
663 Those options are used for testing and introspection, and systemd may
664 be invoked with them at any time:
665 --dump-configuration-items
667 Dump understood unit configuration items. This outputs a terse but
668 complete list of configuration items understood in unit definition
669 files.
670 --dump-bus-properties
672 Dump exposed bus properties. This outputs a terse but complete list
673 of properties exposed on D-Bus.
674 --test
676 Determine the initial start-up transaction (i.e. the list of jobs
677 enqueued at start-up), dump it and exit — without actually
678 executing any of the determined jobs. This option is useful for
679 debugging only. Note that during regular service manager start-up
680 additional units not shown by this operation may be started,
681 because hardware, socket, bus or other kinds of activation might
682 add additional jobs as the transaction is executed. Use --system to
683 request the initial transaction of the system service manager (this
684 is also the implied default), combine with --user to request the
685 initial transaction of the per-user service manager instead.
686 --system, --user
688 When used in conjunction with --test, selects whether to calculate
689 the initial transaction for the system instance or for a per-user
690 instance. These options have no effect when invoked without --test,
691 as during regular (i.e. non---test) invocations the service manager
692 will automatically detect whether it shall operate in system or
693 per-user mode, by checking whether the PID it is run as is 1 or
694 not. Note that it is not supported booting and maintaining a system
695 with the service manager running in --system mode but with a PID
696 other than 1.
697 -h, --help
699 Print a short help text and exit.
700 --version
702 Print a short version string and exit.
703 Options that duplicate kernel command line settings
705 Those options correspond directly to options listed above in "Kernel
706 Command Line". Both forms may be used equivalently for the system
707 manager, but it is recommended to use the forms listed above in this
708 context, because they are properly namespaced. When an option is
709 specified both on the kernel command line, and as a normal command line
710 argument, the latter has higher precedence.
711 When systemd is used a user manager, the kernel command line is ignored
713 and the options described are understood. Nevertheless, systemd is
714 usually started in this mode through the user@.service(5) service,
715 which is shared between all users, and it may be more convenient to use
716 configuration files to modify settings, see systemd-user.conf(5), or a
717 drop-in that specifies one of the environment variables listed above in
718 "Environment, see systemd.unit(5).
719 --unit=
721 Set default unit to activate on startup. If not specified, defaults
722 to default.target. See systemd.unit= above.
723 --dump-core
725 Enable core dumping on crash. This switch has no effect when
726 running as user instance. Same as systemd.dump_core= above.
727 --crash-vt=VT
729 Switch to a specific virtual console (VT) on crash. This switch has
730 no effect when running as user instance. Same as
731 systemd.crash_chvt= above (but not the different spelling!).
732 --crash-shell
734 Run a shell on crash. This switch has no effect when running as
735 user instance. See systemd.crash_shell= above.
736 --crash-reboot
738 Automatically reboot the system on crash. This switch has no effect
739 when running as user instance. See systemd.crash_reboot above.
740 --confirm-spawn
742 Ask for confirmation when spawning processes. This switch has no
743 effect when run as user instance. See systemd.confirm_spawn above.
744 --show-status
746 Show terse unit status information is shown on the console during
747 boot-up and shutdown. See systemd.show_status above.
748 --log-target=
750 Set log target. See systemd.log_target above.
751 --log-level=
753 Set log level. See systemd.log_level above.
754 --log-color
756 Highlight important log messages. See systemd.log_color above.
757 --log-location
759 Include code location in log messages. See systemd.log_location
760 above.
761 --machine-id=
763 Override the machine-id set on the hard drive. See
764 systemd.machine_id= above.
765 --service-watchdogs
767 Globally enable/disable all service watchdog timeouts and emergency
768 actions. See systemd.service_watchdogs above.
769 --default-standard-output=, --default-standard-error=
771 Sets the default output or error output for all services and
772 sockets, respectively. See systemd.default_standard_output= and
773 systemd.default_standard_error= above.
774
776 /run/systemd/notify
777 Daemon status notification socket. This is an AF_UNIX datagram
778 socket and is used to implement the daemon notification logic as
779 implemented by sd_notify(3).
780 /run/systemd/private
782 Used internally as communication channel between systemctl(1) and
783 the systemd process. This is an AF_UNIX stream socket. This
784 interface is private to systemd and should not be used in external
785 projects.
786 /dev/initctl
788 Limited compatibility support for the SysV client interface, as
789 implemented by the systemd-initctl.service unit. This is a named
790 pipe in the file system. This interface is obsolete and should not
791 be used in new applications.
792
794 The systemd Homepage[11], systemd-system.conf(5), locale.conf(5),
795 systemctl(1), journalctl(1), systemd-notify(1), daemon(7), sd-
796 daemon(3), systemd.unit(5), systemd.special(5), pkg-config(1), kernel-
797 command-line(7), bootup(7), systemd.directives(7)
798
800 1. cgroups.txt
801 https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
802 2. Original Design Document
804 http://0pointer.de/blog/projects/systemd.html
805 3. Interface Stability Promise
807 https://www.freedesktop.org/wiki/Software/systemd/InterfaceStabilityPromise
808 4. Container Interface
810 https://systemd.io/CONTAINER_INTERFACE
811 5. initrd Interface
813 https://www.freedesktop.org/wiki/Software/systemd/InitrdInterface
814 6. XDG Base Directory specification
816 http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
817 7. Known Environment Variables
819 https://systemd.io/ENVIRONMENT
820 8. If run inside a Linux container these arguments may be passed as
822 command line arguments to systemd itself, next to any of the
823 command line options listed in the Options section above. If run
824 outside of Linux containers, these arguments are parsed from
825 /proc/cmdline instead.
826 9. unified cgroup hierarchy
828 https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html
829 10. legacy cgroup hierarchy
831 https://www.kernel.org/doc/Documentation/cgroup-v1/
832 11. systemd Homepage
834 https://www.freedesktop.org/wiki/Software/systemd/
835systemd 245 SYSTEMD(1)