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+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, console log messages will be prefixed with a
423 timestamp.
424 This can be overridden with --log-time=.
426 $SYSTEMD_LOG_LOCATION
428 A boolean. If true, messages will be prefixed with a filename and
429 line number in the source code where the message originates.
430 This can be overridden with --log-location=.
432 $SYSTEMD_LOG_TID
434 A boolean. If true, messages will be prefixed with the current
435 numerical thread ID (TID).
436 $SYSTEMD_LOG_TARGET
438 The destination for log messages. One of console (log to the
439 attached tty), console-prefixed (log to the attached tty but with
440 prefixes encoding the log level and "facility", see syslog(3), kmsg
441 (log to the kernel circular log buffer), journal (log to the
442 journal), journal-or-kmsg (log to the journal if available, and to
443 kmsg otherwise), auto (determine the appropriate log target
444 automatically, the default), null (disable log output).
445 This can be overridden with --log-target=.
447 $XDG_CONFIG_HOME, $XDG_CONFIG_DIRS, $XDG_DATA_HOME, $XDG_DATA_DIRS
449 The systemd user manager uses these variables in accordance to the
450 XDG Base Directory specification[6] to find its configuration.
451 $SYSTEMD_UNIT_PATH, $SYSTEMD_GENERATOR_PATH,
453 $SYSTEMD_ENVIRONMENT_GENERATOR_PATH
454 Controls where systemd looks for unit files and generators.
455 These variables may contain a list of paths, separated by colons
457 (":"). When set, if the list ends with an empty component ("...:"),
458 this list is prepended to the usual set of paths. Otherwise, the
459 specified list replaces the usual set of paths.
460 $SYSTEMD_PAGER
462 Pager to use when --no-pager is not given; overrides $PAGER. If
463 neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known
464 pager implementations are tried in turn, including less(1) and
465 more(1), until one is found. If no pager implementation is
466 discovered no pager is invoked. Setting this environment variable
467 to an empty string or the value "cat" is equivalent to passing
468 --no-pager.
469 $SYSTEMD_LESS
471 Override the options passed to less (by default "FRSXMK").
472 Users might want to change two options in particular:
474 K
476 This option instructs the pager to exit immediately when Ctrl+C
477 is pressed. To allow less to handle Ctrl+C itself to switch
478 back to the pager command prompt, unset this option.
479 If the value of $SYSTEMD_LESS does not include "K", and the
481 pager that is invoked is less, Ctrl+C will be ignored by the
482 executable, and needs to be handled by the pager.
483 X
485 This option instructs the pager to not send termcap
486 initialization and deinitialization strings to the terminal. It
487 is set by default to allow command output to remain visible in
488 the terminal even after the pager exits. Nevertheless, this
489 prevents some pager functionality from working, in particular
490 paged output cannot be scrolled with the mouse.
491 See less(1) for more discussion.
493 $SYSTEMD_LESSCHARSET
495 Override the charset passed to less (by default "utf-8", if the
496 invoking terminal is determined to be UTF-8 compatible).
497 $SYSTEMD_PAGERSECURE
499 Takes a boolean argument. When true, the "secure" mode of the pager
500 is enabled; if false, disabled. If $SYSTEMD_PAGERSECURE is not set
501 at all, secure mode is enabled if the effective UID is not the same
502 as the owner of the login session, see geteuid(2) and
503 sd_pid_get_owner_uid(3). In secure mode, LESSSECURE=1 will be set
504 when invoking the pager, and the pager shall disable commands that
505 open or create new files or start new subprocesses. When
506 $SYSTEMD_PAGERSECURE is not set at all, pagers which are not known
507 to implement secure mode will not be used. (Currently only less(1)
508 implements secure mode.)
509 Note: when commands are invoked with elevated privileges, for
511 example under sudo(8) or pkexec(1), care must be taken to ensure
512 that unintended interactive features are not enabled. "Secure" mode
513 for the pager may be enabled automatically as describe above.
514 Setting SYSTEMD_PAGERSECURE=0 or not removing it from the inherited
515 environment allows the user to invoke arbitrary commands. Note that
516 if the $SYSTEMD_PAGER or $PAGER variables are to be honoured,
517 $SYSTEMD_PAGERSECURE must be set too. It might be reasonable to
518 completely disable the pager using --no-pager instead.
519 $SYSTEMD_COLORS
521 Takes a boolean argument. When true, systemd and related utilities
522 will use colors in their output, otherwise the output will be
523 monochrome. Additionally, the variable can take one of the
524 following special values: "16", "256" to restrict the use of colors
525 to the base 16 or 256 ANSI colors, respectively. This can be
526 specified to override the automatic decision based on $TERM and
527 what the console is connected to.
528 $SYSTEMD_URLIFY
530 The value must be a boolean. Controls whether clickable links
531 should be generated in the output for terminal emulators supporting
532 this. This can be specified to override the decision that systemd
533 makes based on $TERM and other conditions.
534 $LISTEN_PID, $LISTEN_FDS, $LISTEN_FDNAMES
536 Set by systemd for supervised processes during socket-based
537 activation. See sd_listen_fds(3) for more information.
538 $NOTIFY_SOCKET
540 Set by systemd for supervised processes for status and start-up
541 completion notification. See sd_notify(3) for more information.
542 For further environment variables understood by systemd and its various
544 components, see Known Environment Variables[7].
545
547 When run as the system instance systemd parses a number of options
548 listed below. They can be specified as kernel command line
549 arguments[8], or through the "SystemdOptions" EFI variable (on EFI
550 systems). The kernel command line has higher priority. Following
551 variables are understood:
552 systemd.unit=, rd.systemd.unit=
554 Overrides the unit to activate on boot. Defaults to default.target.
555 This may be used to temporarily boot into a different boot unit,
556 for example rescue.target or emergency.service. See
557 systemd.special(7) for details about these units. The option
558 prefixed with "rd." is honored only in the initial RAM disk
559 (initrd), while the one that is not prefixed only in the main
560 system.
561 systemd.dump_core
563 Takes a boolean argument or enables the option if specified without
564 an argument. If enabled, the systemd manager (PID 1) dumps core
565 when it crashes. Otherwise, no core dump is created. Defaults to
566 enabled.
567 systemd.crash_chvt
569 Takes a positive integer, or a boolean argument. Can be also
570 specified without an argument, with the same effect as a positive
571 boolean. If a positive integer (in the range 1–63) is specified,
572 the system manager (PID 1) will activate the specified virtual
573 terminal when it crashes. Defaults to disabled, meaning that no
574 such switch is attempted. If set to enabled, the virtual terminal
575 the kernel messages are written to is used instead.
576 systemd.crash_shell
578 Takes a boolean argument or enables the option if specified without
579 an argument. If enabled, the system manager (PID 1) spawns a shell
580 when it crashes, after a 10s delay. Otherwise, no shell is spawned.
581 Defaults to disabled, for security reasons, as the shell is not
582 protected by password authentication.
583 systemd.crash_reboot
585 Takes a boolean argument or enables the option if specified without
586 an argument. If enabled, the system manager (PID 1) will reboot the
587 machine automatically when it crashes, after a 10s delay.
588 Otherwise, the system will hang indefinitely. Defaults to disabled,
589 in order to avoid a reboot loop. If combined with
590 systemd.crash_shell, the system is rebooted after the shell exits.
591 systemd.confirm_spawn
593 Takes a boolean argument or a path to the virtual console where the
594 confirmation messages should be emitted. Can be also specified
595 without an argument, with the same effect as a positive boolean. If
596 enabled, the system manager (PID 1) asks for confirmation when
597 spawning processes using /dev/console. If a path or a console name
598 (such as "ttyS0") is provided, the virtual console pointed to by
599 this path or described by the give name will be used instead.
600 Defaults to disabled.
601 systemd.service_watchdogs=
603 Takes a boolean argument. If disabled, all service runtime
604 watchdogs (WatchdogSec=) and emergency actions (e.g. OnFailure= or
605 StartLimitAction=) are ignored by the system manager (PID 1); see
606 systemd.service(5). Defaults to enabled, i.e. watchdogs and failure
607 actions are processed normally. The hardware watchdog is not
608 affected by this option.
609 systemd.show_status
611 Takes a boolean argument or the constants error and auto. Can be
612 also specified without an argument, with the same effect as a
613 positive boolean. If enabled, the systemd manager (PID 1) shows
614 terse service status updates on the console during bootup. With
615 error, only messages about failures are shown, but boot is
616 otherwise quiet. auto behaves like false until there is a
617 significant delay in boot. Defaults to enabled, unless quiet is
618 passed as kernel command line option, in which case it defaults to
619 error. If specified overrides the system manager configuration file
620 option ShowStatus=, see systemd-system.conf(5).
621 systemd.status_unit_format=
623 Takes name, description or combined as the value. If name, the
624 system manager will use unit names in status messages. If combined,
625 the system manager will use unit names and description in status
626 messages. When specified, overrides the system manager
627 configuration file option StatusUnitFormat=, see systemd-
628 system.conf(5).
629 systemd.log_color, systemd.log_level=, systemd.log_location,
631 systemd.log_target=, systemd.log_time, systemd.log_tid
632 Controls log output, with the same effect as the
633 $SYSTEMD_LOG_COLOR, $SYSTEMD_LOG_LEVEL, $SYSTEMD_LOG_LOCATION,
634 $SYSTEMD_LOG_TARGET, $SYSTEMD_LOG_TIME, and $SYSTEMD_LOG_TID
635 environment variables described above. systemd.log_color,
636 systemd.log_location, systemd.log_time, and systemd.log_tid= can be
637 specified without an argument, with the same effect as a positive
638 boolean.
639 systemd.default_standard_output=, systemd.default_standard_error=
641 Controls default standard output and error output for services and
642 sockets. That is, controls the default for StandardOutput= and
643 StandardError= (see systemd.exec(5) for details). Takes one of
644 inherit, null, tty, journal, journal+console, kmsg, kmsg+console.
645 If the argument is omitted systemd.default-standard-output=
646 defaults to journal and systemd.default-standard-error= to inherit.
647 systemd.setenv=
649 Takes a string argument in the form VARIABLE=VALUE. May be used to
650 set default environment variables to add to forked child processes.
651 May be used more than once to set multiple variables.
652 systemd.machine_id=
654 Takes a 32 character hex value to be used for setting the
655 machine-id. Intended mostly for network booting where the same
656 machine-id is desired for every boot.
657 systemd.unified_cgroup_hierarchy
659 When specified without an argument or with a true argument, enables
660 the usage of unified cgroup hierarchy[9] (a.k.a. cgroups-v2). When
661 specified with a false argument, fall back to hybrid or full legacy
662 cgroup hierarchy.
663 If this option is not specified, the default behaviour is
665 determined during compilation (the -Ddefault-hierarchy= meson
666 option). If the kernel does not support unified cgroup hierarchy,
667 the legacy hierarchy will be used even if this option is specified.
668 systemd.legacy_systemd_cgroup_controller
670 Takes effect if the full unified cgroup hierarchy is not used (see
671 previous option). When specified without an argument or with a true
672 argument, disables the use of "hybrid" cgroup hierarchy (i.e. a
673 cgroups-v2 tree used for systemd, and legacy cgroup hierarchy[10],
674 a.k.a. cgroups-v1, for other controllers), and forces a full
675 "legacy" mode. When specified with a false argument, enables the
676 use of "hybrid" hierarchy.
677 If this option is not specified, the default behaviour is
679 determined during compilation (the -Ddefault-hierarchy= meson
680 option). If the kernel does not support unified cgroup hierarchy,
681 the legacy hierarchy will be used even if this option is specified.
682 quiet
684 Turn off status output at boot, much like systemd.show_status=no
685 would. Note that this option is also read by the kernel itself and
686 disables kernel log output. Passing this option hence turns off the
687 usual output from both the system manager and the kernel.
688 debug
690 Turn on debugging output. This is equivalent to
691 systemd.log_level=debug. Note that this option is also read by the
692 kernel itself and enables kernel debug output. Passing this option
693 hence turns on the debug output from both the system manager and
694 the kernel.
695 emergency, rd.emergency, -b
697 Boot into emergency mode. This is equivalent to
698 systemd.unit=emergency.target or rd.systemd.unit=emergency.target,
699 respectively, and provided for compatibility reasons and to be
700 easier to type.
701 rescue, rd.rescue, single, s, S, 1
703 Boot into rescue mode. This is equivalent to
704 systemd.unit=rescue.target or rd.systemd.unit=rescue.target,
705 respectively, and provided for compatibility reasons and to be
706 easier to type.
707 2, 3, 4, 5
709 Boot into the specified legacy SysV runlevel. These are equivalent
710 to systemd.unit=runlevel2.target, systemd.unit=runlevel3.target,
711 systemd.unit=runlevel4.target, and systemd.unit=runlevel5.target,
712 respectively, and provided for compatibility reasons and to be
713 easier to type.
714 locale.LANG=, locale.LANGUAGE=, locale.LC_CTYPE=, locale.LC_NUMERIC=,
716 locale.LC_TIME=, locale.LC_COLLATE=, locale.LC_MONETARY=,
717 locale.LC_MESSAGES=, locale.LC_PAPER=, locale.LC_NAME=,
718 locale.LC_ADDRESS=, locale.LC_TELEPHONE=, locale.LC_MEASUREMENT=,
719 locale.LC_IDENTIFICATION=
720 Set the system locale to use. This overrides the settings in
721 /etc/locale.conf. For more information, see locale.conf(5) and
722 locale(7).
723 For other kernel command line parameters understood by components of
725 the core OS, please refer to kernel-command-line(7).
726
728 systemd is only very rarely invoked directly, since it is started early
729 and is already running by the time users may interact with it.
730 Normally, tools like systemctl(1) are used to give commands to the
731 manager. Since systemd is usually not invoked directly, the options
732 listed below are mostly useful for debugging and special purposes.
733 Introspection and debugging options
735 Those options are used for testing and introspection, and systemd may
736 be invoked with them at any time:
737 --dump-configuration-items
739 Dump understood unit configuration items. This outputs a terse but
740 complete list of configuration items understood in unit definition
741 files.
742 --dump-bus-properties
744 Dump exposed bus properties. This outputs a terse but complete list
745 of properties exposed on D-Bus.
746 --test
748 Determine the initial start-up transaction (i.e. the list of jobs
749 enqueued at start-up), dump it and exit — without actually
750 executing any of the determined jobs. This option is useful for
751 debugging only. Note that during regular service manager start-up
752 additional units not shown by this operation may be started,
753 because hardware, socket, bus or other kinds of activation might
754 add additional jobs as the transaction is executed. Use --system to
755 request the initial transaction of the system service manager (this
756 is also the implied default), combine with --user to request the
757 initial transaction of the per-user service manager instead.
758 --system, --user
760 When used in conjunction with --test, selects whether to calculate
761 the initial transaction for the system instance or for a per-user
762 instance. These options have no effect when invoked without --test,
763 as during regular (i.e. non---test) invocations the service manager
764 will automatically detect whether it shall operate in system or
765 per-user mode, by checking whether the PID it is run as is 1 or
766 not. Note that it is not supported booting and maintaining a system
767 with the service manager running in --system mode but with a PID
768 other than 1.
769 -h, --help
771 Print a short help text and exit.
772 --version
774 Print a short version string and exit.
775 Options that duplicate kernel command line settings
777 Those options correspond directly to options listed above in "Kernel
778 Command Line". Both forms may be used equivalently for the system
779 manager, but it is recommended to use the forms listed above in this
780 context, because they are properly namespaced. When an option is
781 specified both on the kernel command line and as a normal command line
782 argument, the latter has higher precedence.
783 When systemd is used as a user manager, the kernel command line is
785 ignored and only the options described below are understood.
786 Nevertheless, systemd is usually started in this mode through the
787 user@.service(5) service, which is shared between all users. It may be
788 more convenient to use configuration files to modify settings (see
789 systemd-user.conf(5)), or environment variables. See the "Environment"
790 section above for a discussion of how the environment block is set.
791 --unit=
793 Set default unit to activate on startup. If not specified, defaults
794 to default.target. See systemd.unit= above.
795 --dump-core
797 Enable core dumping on crash. This switch has no effect when
798 running as user instance. Same as systemd.dump_core= above.
799 --crash-vt=VT
801 Switch to a specific virtual console (VT) on crash. This switch has
802 no effect when running as user instance. Same as
803 systemd.crash_chvt= above (but not the different spelling!).
804 --crash-shell
806 Run a shell on crash. This switch has no effect when running as
807 user instance. See systemd.crash_shell= above.
808 --crash-reboot
810 Automatically reboot the system on crash. This switch has no effect
811 when running as user instance. See systemd.crash_reboot above.
812 --confirm-spawn
814 Ask for confirmation when spawning processes. This switch has no
815 effect when run as user instance. See systemd.confirm_spawn above.
816 --show-status
818 Show terse unit status information on the console during boot-up
819 and shutdown. See systemd.show_status above.
820 --log-color
822 Highlight important log messages. See systemd.log_color above.
823 --log-level=
825 Set log level. See systemd.log_level above.
826 --log-location
828 Include code location in log messages. See systemd.log_location
829 above.
830 --log-target=
832 Set log target. See systemd.log_target above.
833 --log-time=
835 Prefix console messages with timestamp. See systemd.log_time above.
836 --machine-id=
838 Override the machine-id set on the hard drive. See
839 systemd.machine_id= above.
840 --service-watchdogs
842 Globally enable/disable all service watchdog timeouts and emergency
843 actions. See systemd.service_watchdogs above.
844 --default-standard-output=, --default-standard-error=
846 Sets the default output or error output for all services and
847 sockets, respectively. See systemd.default_standard_output= and
848 systemd.default_standard_error= above.
849
851 /run/systemd/notify
852 Daemon status notification socket. This is an AF_UNIX datagram
853 socket and is used to implement the daemon notification logic as
854 implemented by sd_notify(3).
855 /run/systemd/private
857 Used internally as communication channel between systemctl(1) and
858 the systemd process. This is an AF_UNIX stream socket. This
859 interface is private to systemd and should not be used in external
860 projects.
861 /dev/initctl
863 Limited compatibility support for the SysV client interface, as
864 implemented by the systemd-initctl.service unit. This is a named
865 pipe in the file system. This interface is obsolete and should not
866 be used in new applications.
867
869 The systemd Homepage[11], systemd-system.conf(5), locale.conf(5),
870 systemctl(1), journalctl(1), systemd-notify(1), daemon(7), sd-
871 daemon(3), org.freedesktop.systemd1(5), systemd.unit(5),
872 systemd.special(7), pkg-config(1), kernel-command-line(7), bootup(7),
873 systemd.directives(7)
874
876 1. cgroups.txt
877 https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
878 2. Original Design Document
880 http://0pointer.de/blog/projects/systemd.html
881 3. Interface Portability and Stability Promise
883 https://systemd.io/PORTABILITY_AND_STABILITY/
884 4. Container Interface
886 https://systemd.io/CONTAINER_INTERFACE
887 5. initrd Interface
889 https://systemd.io/INITRD_INTERFACE/
890 6. XDG Base Directory specification
892 http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
893 7. Known Environment Variables
895 https://systemd.io/ENVIRONMENT
896 8. If run inside a Linux container these arguments may be passed as
898 command line arguments to systemd itself, next to any of the
899 command line options listed in the Options section above. If run
900 outside of Linux containers, these arguments are parsed from
901 /proc/cmdline instead.
902 9. unified cgroup hierarchy
904 https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html
905 10. legacy cgroup hierarchy
907 https://www.kernel.org/doc/Documentation/cgroup-v1/
908 11. systemd Homepage
910 https://www.freedesktop.org/wiki/Software/systemd/
911systemd 249 SYSTEMD(1)