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 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+26
378 Restores the log target to its configured value. The configured
379 value is derived from – in order of priority – the value specified
380 with systemd.log-target= on the kernel command line, or the value
381 specified with LogTarget= in the configuration file, or the
382 built-in default.
383 SIGRTMIN+27, SIGRTMIN+28
385 Sets the log target to "console" on SIGRTMIN+27 (or "kmsg" on
386 SIGRTMIN+28), in a fashion equivalent to systemd.log_target=console
387 (or systemd.log_target=kmsg on SIGRTMIN+28) on the kernel command
388 line.
389
391 The environment block for the system manager is initially set by the
392 kernel. (In particular, "key=value" assignments on the kernel command
393 line are returned into environment variables for PID 1). For the user
394 manager, the system manager sets the environment as described in the
395 "Environment Variables in Spawned Processes" section of
396 systemd.exec(5). The DefaultEnvironment= setting in the system manager
397 applies to all services including user@.service. Additional entries may
398 be configured (as for any other service) through the Environment= and
399 EnvironmentFile= settings for user@.service (see systemd.exec(5)).
400 Also, additional environment variables may be set through the
401 ManagerEnvironment= setting in systemd-system.conf(5) and systemd-
402 user.conf(5).
403 Some of the variables understood by systemd:
405 $SYSTEMD_LOG_LEVEL
407 The maximum log level of emitted messages (messages with a higher
408 log level, i.e. less important ones, will be suppressed). Either
409 one of (in order of decreasing importance) emerg, alert, crit, err,
410 warning, notice, info, debug, or an integer in the range 0...7. See
411 syslog(3) for more information.
412 This can be overridden with --log-level=.
414 $SYSTEMD_LOG_COLOR
416 A boolean. If true, messages written to the tty will be colored
417 according to priority.
418 This can be overridden with --log-color=.
420 $SYSTEMD_LOG_TIME
422 A boolean. If true, log messages will be prefixed with a timestamp.
423 This can be overridden with --log-time=.
425 $SYSTEMD_LOG_LOCATION
427 A boolean. If true, messages will be prefixed with a filename and
428 line number in the source code where the message originates.
429 This can be overridden with --log-location=.
431 $SYSTEMD_LOG_TID
433 A boolean. If true, messages will be prefixed with the current
434 numerical thread ID (TID).
435 $SYSTEMD_LOG_TARGET
437 The destination for log messages. One of console (log to the
438 attached tty), console-prefixed (log to the attached tty but with
439 prefixes encoding the log level and "facility", see syslog(3), kmsg
440 (log to the kernel circular log buffer), journal (log to the
441 journal), journal-or-kmsg (log to the journal if available, and to
442 kmsg otherwise), auto (determine the appropriate log target
443 automatically, the default), null (disable log output).
444 This can be overridden with --log-target=.
446 $XDG_CONFIG_HOME, $XDG_CONFIG_DIRS, $XDG_DATA_HOME, $XDG_DATA_DIRS
448 The systemd user manager uses these variables in accordance to the
449 XDG Base Directory specification[6] to find its configuration.
450 $SYSTEMD_UNIT_PATH, $SYSTEMD_GENERATOR_PATH,
452 $SYSTEMD_ENVIRONMENT_GENERATOR_PATH
453 Controls where systemd looks for unit files and generators.
454 These variables may contain a list of paths, separated by colons
456 (":"). When set, if the list ends with an empty component ("...:"),
457 this list is prepended to the usual set of paths. Otherwise, the
458 specified list replaces the usual set of paths.
459 $SYSTEMD_PAGER
461 Pager to use when --no-pager is not given; overrides $PAGER. If
462 neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known
463 pager implementations are tried in turn, including less(1) and
464 more(1), until one is found. If no pager implementation is
465 discovered no pager is invoked. Setting this environment variable
466 to an empty string or the value "cat" is equivalent to passing
467 --no-pager.
468 $SYSTEMD_LESS
470 Override the options passed to less (by default "FRSXMK").
471 Users might want to change two options in particular:
473 K
475 This option instructs the pager to exit immediately when Ctrl+C
476 is pressed. To allow less to handle Ctrl+C itself to switch
477 back to the pager command prompt, unset this option.
478 If the value of $SYSTEMD_LESS does not include "K", and the
480 pager that is invoked is less, Ctrl+C will be ignored by the
481 executable, and needs to be handled by the pager.
482 X
484 This option instructs the pager to not send termcap
485 initialization and deinitialization strings to the terminal. It
486 is set by default to allow command output to remain visible in
487 the terminal even after the pager exits. Nevertheless, this
488 prevents some pager functionality from working, in particular
489 paged output cannot be scrolled with the mouse.
490 See less(1) for more discussion.
492 $SYSTEMD_LESSCHARSET
494 Override the charset passed to less (by default "utf-8", if the
495 invoking terminal is determined to be UTF-8 compatible).
496 $SYSTEMD_PAGERSECURE
498 Takes a boolean argument. When true, the "secure" mode of the pager
499 is enabled; if false, disabled. If $SYSTEMD_PAGERSECURE is not set
500 at all, secure mode is enabled if the effective UID is not the same
501 as the owner of the login session, see geteuid(2) and
502 sd_pid_get_owner_uid(3). In secure mode, LESSSECURE=1 will be set
503 when invoking the pager, and the pager shall disable commands that
504 open or create new files or start new subprocesses. When
505 $SYSTEMD_PAGERSECURE is not set at all, pagers which are not known
506 to implement secure mode will not be used. (Currently only less(1)
507 implements secure mode.)
508 Note: when commands are invoked with elevated privileges, for
510 example under sudo(8) or pkexec(1), care must be taken to ensure
511 that unintended interactive features are not enabled. "Secure" mode
512 for the pager may be enabled automatically as describe above.
513 Setting SYSTEMD_PAGERSECURE=0 or not removing it from the inherited
514 environment allows the user to invoke arbitrary commands. Note that
515 if the $SYSTEMD_PAGER or $PAGER variables are to be honoured,
516 $SYSTEMD_PAGERSECURE must be set too. It might be reasonable to
517 completely disable the pager using --no-pager instead.
518 $SYSTEMD_COLORS
520 Takes a boolean argument. When true, systemd and related utilities
521 will use colors in their output, otherwise the output will be
522 monochrome. Additionally, the variable can take one of the
523 following special values: "16", "256" to restrict the use of colors
524 to the base 16 or 256 ANSI colors, respectively. This can be
525 specified to override the automatic decision based on $TERM and
526 what the console is connected to.
527 $SYSTEMD_URLIFY
529 The value must be a boolean. Controls whether clickable links
530 should be generated in the output for terminal emulators supporting
531 this. This can be specified to override the decision that systemd
532 makes based on $TERM and other conditions.
533 $LISTEN_PID, $LISTEN_FDS, $LISTEN_FDNAMES
535 Set by systemd for supervised processes during socket-based
536 activation. See sd_listen_fds(3) for more information.
537 $NOTIFY_SOCKET
539 Set by systemd for supervised processes for status and start-up
540 completion notification. See sd_notify(3) for more information.
541 For further environment variables understood by systemd and its various
543 components, see Known Environment Variables[7].
544
546 When run as the system instance systemd parses a number of options
547 listed below. They can be specified as kernel command line
548 arguments[8], or through the "SystemdOptions" EFI variable (on EFI
549 systems). The kernel command line has higher priority. Following
550 variables are understood:
551 systemd.unit=, rd.systemd.unit=
553 Overrides the unit to activate on boot. Defaults to default.target.
554 This may be used to temporarily boot into a different boot unit,
555 for example rescue.target or emergency.service. See
556 systemd.special(7) for details about these units. The option
557 prefixed with "rd." is honored only in the initial RAM disk
558 (initrd), while the one that is not prefixed only in the main
559 system.
560 systemd.dump_core
562 Takes a boolean argument or enables the option if specified without
563 an argument. If enabled, the systemd manager (PID 1) dumps core
564 when it crashes. Otherwise, no core dump is created. Defaults to
565 enabled.
566 systemd.crash_chvt
568 Takes a positive integer, or a boolean argument. Can be also
569 specified without an argument, with the same effect as a positive
570 boolean. If a positive integer (in the range 1–63) is specified,
571 the system manager (PID 1) will activate the specified virtual
572 terminal when it crashes. Defaults to disabled, meaning that no
573 such switch is attempted. If set to enabled, the virtual terminal
574 the kernel messages are written to is used instead.
575 systemd.crash_shell
577 Takes a boolean argument or enables the option if specified without
578 an argument. If enabled, the system manager (PID 1) spawns a shell
579 when it crashes, after a 10s delay. Otherwise, no shell is spawned.
580 Defaults to disabled, for security reasons, as the shell is not
581 protected by password authentication.
582 systemd.crash_reboot
584 Takes a boolean argument or enables the option if specified without
585 an argument. If enabled, the system manager (PID 1) will reboot the
586 machine automatically when it crashes, after a 10s delay.
587 Otherwise, the system will hang indefinitely. Defaults to disabled,
588 in order to avoid a reboot loop. If combined with
589 systemd.crash_shell, the system is rebooted after the shell exits.
590 systemd.confirm_spawn
592 Takes a boolean argument or a path to the virtual console where the
593 confirmation messages should be emitted. Can be also specified
594 without an argument, with the same effect as a positive boolean. If
595 enabled, the system manager (PID 1) asks for confirmation when
596 spawning processes using /dev/console. If a path or a console name
597 (such as "ttyS0") is provided, the virtual console pointed to by
598 this path or described by the give name will be used instead.
599 Defaults to disabled.
600 systemd.service_watchdogs=
602 Takes a boolean argument. If disabled, all service runtime
603 watchdogs (WatchdogSec=) and emergency actions (e.g. OnFailure= or
604 StartLimitAction=) are ignored by the system manager (PID 1); see
605 systemd.service(5). Defaults to enabled, i.e. watchdogs and failure
606 actions are processed normally. The hardware watchdog is not
607 affected by this option.
608 systemd.show_status
610 Takes a boolean argument or the constants error and auto. Can be
611 also specified without an argument, with the same effect as a
612 positive boolean. If enabled, the systemd manager (PID 1) shows
613 terse service status updates on the console during bootup. With
614 error, only messages about failures are shown, but boot is
615 otherwise quiet. auto behaves like false until there is a
616 significant delay in boot. Defaults to enabled, unless quiet is
617 passed as kernel command line option, in which case it defaults to
618 error. If specified overrides the system manager configuration file
619 option ShowStatus=, see systemd-system.conf(5).
620 systemd.status_unit_format=
622 Takes either name or description as the value. If name, the system
623 manager will use unit names in status messages. If specified,
624 overrides the system manager configuration file option
625 StatusUnitFormat=, see systemd-system.conf(5).
626 systemd.log_color, systemd.log_level=, systemd.log_location,
628 systemd.log_target=, systemd.log_time, systemd.log_tid
629 Controls log output, with the same effect as the
630 $SYSTEMD_LOG_COLOR, $SYSTEMD_LOG_LEVEL, $SYSTEMD_LOG_LOCATION,
631 $SYSTEMD_LOG_TARGET, $SYSTEMD_LOG_TIME, and $SYSTEMD_LOG_TID
632 environment variables described above. systemd.log_color,
633 systemd.log_location, systemd.log_time, and systemd.log_tid= can be
634 specified without an argument, with the same effect as a positive
635 boolean.
636 systemd.default_standard_output=, systemd.default_standard_error=
638 Controls default standard output and error output for services and
639 sockets. That is, controls the default for StandardOutput= and
640 StandardError= (see systemd.exec(5) for details). Takes one of
641 inherit, null, tty, journal, journal+console, kmsg, kmsg+console.
642 If the argument is omitted systemd.default-standard-output=
643 defaults to journal and systemd.default-standard-error= to inherit.
644 systemd.setenv=
646 Takes a string argument in the form VARIABLE=VALUE. May be used to
647 set default environment variables to add to forked child processes.
648 May be used more than once to set multiple variables.
649 systemd.machine_id=
651 Takes a 32 character hex value to be used for setting the
652 machine-id. Intended mostly for network booting where the same
653 machine-id is desired for every boot.
654 systemd.unified_cgroup_hierarchy
656 When specified without an argument or with a true argument, enables
657 the usage of unified cgroup hierarchy[9] (a.k.a. cgroups-v2). When
658 specified with a false argument, fall back to hybrid or full legacy
659 cgroup hierarchy.
660 If this option is not specified, the default behaviour is
662 determined during compilation (the -Ddefault-hierarchy= meson
663 option). If the kernel does not support unified cgroup hierarchy,
664 the legacy hierarchy will be used even if this option is specified.
665 systemd.legacy_systemd_cgroup_controller
667 Takes effect if the full unified cgroup hierarchy is not used (see
668 previous option). When specified without an argument or with a true
669 argument, disables the use of "hybrid" cgroup hierarchy (i.e. a
670 cgroups-v2 tree used for systemd, and legacy cgroup hierarchy[10],
671 a.k.a. cgroups-v1, for other controllers), and forces a full
672 "legacy" mode. When specified with a false argument, enables the
673 use of "hybrid" hierarchy.
674 If this option is not specified, the default behaviour is
676 determined during compilation (the -Ddefault-hierarchy= meson
677 option). If the kernel does not support unified cgroup hierarchy,
678 the legacy hierarchy will be used even if this option is specified.
679 quiet
681 Turn off status output at boot, much like systemd.show_status=no
682 would. Note that this option is also read by the kernel itself and
683 disables kernel log output. Passing this option hence turns off the
684 usual output from both the system manager and the kernel.
685 debug
687 Turn on debugging output. This is equivalent to
688 systemd.log_level=debug. Note that this option is also read by the
689 kernel itself and enables kernel debug output. Passing this option
690 hence turns on the debug output from both the system manager and
691 the kernel.
692 emergency, rd.emergency, -b
694 Boot into emergency mode. This is equivalent to
695 systemd.unit=emergency.target or rd.systemd.unit=emergency.target,
696 respectively, and provided for compatibility reasons and to be
697 easier to type.
698 rescue, rd.rescue, single, s, S, 1
700 Boot into rescue mode. This is equivalent to
701 systemd.unit=rescue.target or rd.systemd.unit=rescue.target,
702 respectively, and provided for compatibility reasons and to be
703 easier to type.
704 2, 3, 4, 5
706 Boot into the specified legacy SysV runlevel. These are equivalent
707 to systemd.unit=runlevel2.target, systemd.unit=runlevel3.target,
708 systemd.unit=runlevel4.target, and systemd.unit=runlevel5.target,
709 respectively, and provided for compatibility reasons and to be
710 easier to type.
711 locale.LANG=, locale.LANGUAGE=, locale.LC_CTYPE=, locale.LC_NUMERIC=,
713 locale.LC_TIME=, locale.LC_COLLATE=, locale.LC_MONETARY=,
714 locale.LC_MESSAGES=, locale.LC_PAPER=, locale.LC_NAME=,
715 locale.LC_ADDRESS=, locale.LC_TELEPHONE=, locale.LC_MEASUREMENT=,
716 locale.LC_IDENTIFICATION=
717 Set the system locale to use. This overrides the settings in
718 /etc/locale.conf. For more information, see locale.conf(5) and
719 locale(7).
720 For other kernel command line parameters understood by components of
722 the core OS, please refer to kernel-command-line(7).
723
725 systemd is only very rarely invoked directly, since it is started early
726 and is already running by the time users may interact with it.
727 Normally, tools like systemctl(1) are used to give commands to the
728 manager. Since systemd is usually not invoked directly, the options
729 listed below are mostly useful for debugging and special purposes.
730 Introspection and debugging options
732 Those options are used for testing and introspection, and systemd may
733 be invoked with them at any time:
734 --dump-configuration-items
736 Dump understood unit configuration items. This outputs a terse but
737 complete list of configuration items understood in unit definition
738 files.
739 --dump-bus-properties
741 Dump exposed bus properties. This outputs a terse but complete list
742 of properties exposed on D-Bus.
743 --test
745 Determine the initial start-up transaction (i.e. the list of jobs
746 enqueued at start-up), dump it and exit — without actually
747 executing any of the determined jobs. This option is useful for
748 debugging only. Note that during regular service manager start-up
749 additional units not shown by this operation may be started,
750 because hardware, socket, bus or other kinds of activation might
751 add additional jobs as the transaction is executed. Use --system to
752 request the initial transaction of the system service manager (this
753 is also the implied default), combine with --user to request the
754 initial transaction of the per-user service manager instead.
755 --system, --user
757 When used in conjunction with --test, selects whether to calculate
758 the initial transaction for the system instance or for a per-user
759 instance. These options have no effect when invoked without --test,
760 as during regular (i.e. non---test) invocations the service manager
761 will automatically detect whether it shall operate in system or
762 per-user mode, by checking whether the PID it is run as is 1 or
763 not. Note that it is not supported booting and maintaining a system
764 with the service manager running in --system mode but with a PID
765 other than 1.
766 -h, --help
768 Print a short help text and exit.
769 --version
771 Print a short version string and exit.
772 Options that duplicate kernel command line settings
774 Those options correspond directly to options listed above in "Kernel
775 Command Line". Both forms may be used equivalently for the system
776 manager, but it is recommended to use the forms listed above in this
777 context, because they are properly namespaced. When an option is
778 specified both on the kernel command line and as a normal command line
779 argument, the latter has higher precedence.
780 When systemd is used as a user manager, the kernel command line is
782 ignored and only the options described below are understood.
783 Nevertheless, systemd is usually started in this mode through the
784 user@.service(5) service, which is shared between all users. It may be
785 more convenient to use configuration files to modify settings (see
786 systemd-user.conf(5)), or environment variables. See the "Environment"
787 section above for a discussion of how the environment block is set.
788 --unit=
790 Set default unit to activate on startup. If not specified, defaults
791 to default.target. See systemd.unit= above.
792 --dump-core
794 Enable core dumping on crash. This switch has no effect when
795 running as user instance. Same as systemd.dump_core= above.
796 --crash-vt=VT
798 Switch to a specific virtual console (VT) on crash. This switch has
799 no effect when running as user instance. Same as
800 systemd.crash_chvt= above (but not the different spelling!).
801 --crash-shell
803 Run a shell on crash. This switch has no effect when running as
804 user instance. See systemd.crash_shell= above.
805 --crash-reboot
807 Automatically reboot the system on crash. This switch has no effect
808 when running as user instance. See systemd.crash_reboot above.
809 --confirm-spawn
811 Ask for confirmation when spawning processes. This switch has no
812 effect when run as user instance. See systemd.confirm_spawn above.
813 --show-status
815 Show terse unit status information on the console during boot-up
816 and shutdown. See systemd.show_status above.
817 --log-color
819 Highlight important log messages. See systemd.log_color above.
820 --log-level=
822 Set log level. See systemd.log_level above.
823 --log-location
825 Include code location in log messages. See systemd.log_location
826 above.
827 --log-target=
829 Set log target. See systemd.log_target above.
830 --log-time=
832 Prefix messages with timestamp. See systemd.log_time above.
833 --machine-id=
835 Override the machine-id set on the hard drive. See
836 systemd.machine_id= above.
837 --service-watchdogs
839 Globally enable/disable all service watchdog timeouts and emergency
840 actions. See systemd.service_watchdogs above.
841 --default-standard-output=, --default-standard-error=
843 Sets the default output or error output for all services and
844 sockets, respectively. See systemd.default_standard_output= and
845 systemd.default_standard_error= above.
846
848 /run/systemd/notify
849 Daemon status notification socket. This is an AF_UNIX datagram
850 socket and is used to implement the daemon notification logic as
851 implemented by sd_notify(3).
852 /run/systemd/private
854 Used internally as communication channel between systemctl(1) and
855 the systemd process. This is an AF_UNIX stream socket. This
856 interface is private to systemd and should not be used in external
857 projects.
858 /dev/initctl
860 Limited compatibility support for the SysV client interface, as
861 implemented by the systemd-initctl.service unit. This is a named
862 pipe in the file system. This interface is obsolete and should not
863 be used in new applications.
864
866 The systemd Homepage[11], systemd-system.conf(5), locale.conf(5),
867 systemctl(1), journalctl(1), systemd-notify(1), daemon(7), sd-
868 daemon(3), org.freedesktop.systemd1(5), systemd.unit(5),
869 systemd.special(7), pkg-config(1), kernel-command-line(7), bootup(7),
870 systemd.directives(7)
871
873 1. cgroups.txt
874 https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
875 2. Original Design Document
877 http://0pointer.de/blog/projects/systemd.html
878 3. Interface Portability and Stability Promise
880 https://systemd.io/PORTABILITY_AND_STABILITY/
881 4. Container Interface
883 https://systemd.io/CONTAINER_INTERFACE
884 5. initrd Interface
886 https://systemd.io/INITRD_INTERFACE/
887 6. XDG Base Directory specification
889 http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
890 7. Known Environment Variables
892 https://systemd.io/ENVIRONMENT
893 8. If run inside a Linux container these arguments may be passed as
895 command line arguments to systemd itself, next to any of the
896 command line options listed in the Options section above. If run
897 outside of Linux containers, these arguments are parsed from
898 /proc/cmdline instead.
899 9. unified cgroup hierarchy
901 https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html
902 10. legacy cgroup hierarchy
904 https://www.kernel.org/doc/Documentation/cgroup-v1/
905 11. systemd Homepage
907 https://www.freedesktop.org/wiki/Software/systemd/
908systemd 248 SYSTEMD(1)