1KERNEL-COMMAND-LINE(7) kernel-command-line KERNEL-COMMAND-LINE(7)
2
6 kernel-command-line - Kernel command line parameters
7
9 /proc/cmdline
10
12 The kernel, the programs running in the initrd and in the host system
13 may be configured at boot via kernel command line arguments. In
14 addition, various systemd tools look at the EFI variable
15 "SystemdOptions" (if available). Both sources are combined, but the
16 kernel command line has higher priority. Please note that the EFI
17 variable is only used by systemd tools, and is ignored by the kernel
18 and other user space tools, so it is not a replacement for the kernel
19 command line.
20 For command line parameters understood by the kernel, please see
22 kernel-parameters.html[1] and bootparam(7).
23 For command line parameters understood by the initrd, see
25 dracut.cmdline(7), or the documentation of the specific initrd
26 implementation of your installation.
27
29 systemd.unit=, rd.systemd.unit=, systemd.dump_core, systemd.crash_chvt,
30 systemd.crash_shell, systemd.crash_reboot, systemd.confirm_spawn,
31 systemd.service_watchdogs, systemd.show_status,
32 systemd.status_unit_format=, systemd.log_target=, systemd.log_level=,
33 systemd.log_location=, systemd.log_color,
34 systemd.default_standard_output=, systemd.default_standard_error=,
35 systemd.setenv=, systemd.machine_id=, systemd.set_credential=,
36 systemd.import_credentials=, systemd.reload_limit_interval_sec=,
37 systemd.reload_limit_burst=
38 Parameters understood by the system and service manager to control
39 system behavior. For details, see systemd(1).
40 systemd.mask=, systemd.wants=, systemd.debug_shell
42 Additional parameters understood by systemd-debug-generator(8), to
43 mask or start specific units at boot, or invoke a debug shell on
44 tty9.
45 systemd.run=, systemd.run_success_action=, systemd.run_failure_action=
47 Additional parameters understood by systemd-run-generator(8), to
48 run a command line specified on the kernel command line as system
49 service after booting up.
50 systemd.early_core_pattern=
52 During early boot, the generation of core dump files is disabled
53 until a core dump handler (if any) takes over. This parameter
54 allows specifying an absolute path where core dump files should be
55 stored until a handler is installed. The path should be absolute
56 and may contain specifiers, see core(5) for details.
57 systemd.restore_state=
59 This parameter is understood by several system tools to control
60 whether or not they should restore system state from the previous
61 boot. For details, see systemd-backlight@.service(8) and systemd-
62 rfkill.service(8).
63 systemd.volatile=
65 This parameter controls whether the system shall boot up in
66 volatile mode. Takes a boolean argument, or the special value
67 "state". If false (the default), normal boot mode is selected, the
68 root directory and /var/ are mounted as specified on the kernel
69 command line or /etc/fstab, or otherwise configured. If true, full
70 state-less boot mode is selected. In this case the root directory
71 is mounted as volatile memory file system ("tmpfs"), and only /usr/
72 is mounted from the file system configured as root device, in
73 read-only mode. This enables fully state-less boots were the
74 vendor-supplied OS is used as shipped, with only default
75 configuration and no stored state in effect, as /etc/ and /var/ (as
76 well as all other resources shipped in the root file system) are
77 reset at boot and lost on shutdown. If this setting is set to
78 "state" the root file system is mounted read-only, however /var/ is
79 mounted as a volatile memory file system ("tmpfs"), so that the
80 system boots up with the normal configuration applied, but all
81 state reset at boot and lost at shutdown. If this setting is set to
82 "overlay" the root file system is set up as "overlayfs" mount
83 combining the read-only root directory with a writable "tmpfs", so
84 that no modifications are made to disk, but the file system may be
85 modified nonetheless with all changes being lost at reboot. For
86 details, see systemd-volatile-root.service(8) and systemd-fstab-
87 generator(8).
88 quiet
90 Parameter understood by both the kernel and the system and service
91 manager to control console log verbosity. For details, see
92 systemd(1).
93 debug
95 Parameter understood by both the kernel and the system and service
96 manager to control console log verbosity. For details, see
97 systemd(1).
98 -b, rd.emergency, emergency, rd.rescue, rescue, single, s, S, 1, 2, 3,
100 4, 5
101 Parameters understood by the system and service manager, as
102 compatibility and convenience options. For details, see systemd(1).
103 locale.LANG=, locale.LANGUAGE=, locale.LC_CTYPE=, locale.LC_NUMERIC=,
105 locale.LC_TIME=, locale.LC_COLLATE=, locale.LC_MONETARY=,
106 locale.LC_MESSAGES=, locale.LC_PAPER=, locale.LC_NAME=,
107 locale.LC_ADDRESS=, locale.LC_TELEPHONE=, locale.LC_MEASUREMENT=,
108 locale.LC_IDENTIFICATION=
109 Parameters understood by the system and service manager to control
110 locale and language settings. For details, see systemd(1).
111 fsck.mode=, fsck.repair=
113 Parameters understood by the file system checker services. For
114 details, see systemd-fsck@.service(8).
115 quotacheck.mode=
117 Parameter understood by the file quota checker service. For
118 details, see systemd-quotacheck.service(8).
119 systemd.journald.forward_to_syslog=, systemd.journald.forward_to_kmsg=,
121 systemd.journald.forward_to_console=, systemd.journald.forward_to_wall=
122 Parameters understood by the journal service. For details, see
123 systemd-journald.service(8).
124 vconsole.keymap=, vconsole.keymap_toggle=, vconsole.font=,
126 vconsole.font_map=, vconsole.font_unimap=
127 Parameters understood by the virtual console setup logic. For
128 details, see vconsole.conf(5).
129 udev.log_level=, rd.udev.log_level=, udev.children_max=,
131 rd.udev.children_max=, udev.exec_delay=, rd.udev.exec_delay=,
132 udev.event_timeout=, rd.udev.event_timeout=, udev.timeout_signal=,
133 rd.udev.timeout_signal=, udev.blockdev_read_only,
134 rd.udev.blockdev_read_only, net.ifnames=, net.naming-scheme=
135 Parameters understood by the device event managing daemon. For
136 details, see systemd-udevd.service(8).
137 plymouth.enable=
139 May be used to disable the Plymouth boot splash. For details, see
140 plymouth(8).
141 luks=, rd.luks=, luks.crypttab=, rd.luks.crypttab=, luks.name=,
143 rd.luks.name=, luks.uuid=, rd.luks.uuid=, luks.options=,
144 rd.luks.options=, luks.key=, rd.luks.key=
145 Configures the LUKS full-disk encryption logic at boot. For
146 details, see systemd-cryptsetup-generator(8).
147 fstab=, rd.fstab=
149 Configures the /etc/fstab logic at boot. For details, see systemd-
150 fstab-generator(8).
151 root=, rootfstype=, rootflags=, ro, rw
153 Configures the root file system and its file system type and mount
154 options, as well as whether it shall be mounted read-only or
155 read-write initially. For details, see systemd-fstab-generator(8).
156 If root= is not set (or set to "gpt-auto") the automatic root
158 partition discovery implemented by systemd-gpt-auto-generator(8)
159 will be in effect. In this case rootfstype=, rootflags=, ro, rw
160 will be interpreted by systemd-gpt-auto-generator.
161 mount.usr=, mount.usrfstype=, mount.usrflags=
163 Configures the /usr file system (if required) and its file system
164 type and mount options. For details, see systemd-fstab-
165 generator(8).
166 veritytab=, rd.veritytab=, roothash=, systemd.verity=,
168 rd.systemd.verity=, systemd.verity_root_data=,
169 systemd.verity_root_hash=, systemd.verity.root_options=, usrhash=,
170 systemd.verity_usr_data=, systemd.verity_usr_hash=,
171 systemd.verity_usr_options=
172 Configures the integrity protection root hash for the root and /usr
173 file systems, and other related parameters. For details, see
174 systemd-veritysetup-generator(8).
175 systemd.getty_auto=
177 Configures whether the serial-getty@.service will run. For details,
178 see systemd-getty-generator(8).
179 systemd.gpt_auto=, rd.systemd.gpt_auto=
181 Configures whether GPT based partition auto-discovery shall be
182 attempted. For details, see systemd-gpt-auto-generator(8).
183 systemd.default_timeout_start_sec=
185 Overrides the default start job timeout DefaultTimeoutStartSec= at
186 boot. For details, see systemd-system.conf(5).
187 systemd.watchdog_device=
189 Overrides the watchdog device path WatchdogDevice=. For details,
190 see systemd-system.conf(5).
191 systemd.watchdog_sec=
193 Overrides the watchdog timeout settings otherwise configured with
194 RuntimeWatchdog=, RebootWatchdog= and KExecWatchdogSec=. Takes a
195 time value (if no unit is specified, seconds is the implicitly
196 assumed time unit) or the special strings "off" or "default". For
197 details, see systemd-system.conf(5).
198 systemd.watchdog_pre_sec=
200 Overrides the watchdog pre-timeout settings otherwise configured
201 with RuntimeWatchdogPreSec=. Takes a time value (if no unit is
202 specified, seconds is the implicitly assumed time unit) or the
203 special strings "off" or "default". For details, see systemd-
204 system.conf(5).
205 systemd.watchdog_pretimeout_governor=
207 Overrides the watchdog pre-timeout settings otherwise configured
208 with RuntimeWatchdogPreGovernor=. Takes a string value. For
209 details, see systemd-system.conf(5).
210 systemd.cpu_affinity=
212 Overrides the CPU affinity mask for the service manager and the
213 default for all child processes it forks. This takes precedence
214 over CPUAffinity=, see systemd-system.conf(5) for details.
215 modules_load=, rd.modules_load=
217 Load a specific kernel module early at boot. For details, see
218 systemd-modules-load.service(8).
219 nameserver=, domain=
221 Configures DNS server information and search domains, see systemd-
222 resolved.service(8) for details.
223 resume=, resumeflags=
225 Enables resume from hibernation using the specified device and
226 mount options. All fstab(5)-like paths are supported. For details,
227 see systemd-hibernate-resume-generator(8).
228 systemd.firstboot=
230 Takes a boolean argument, defaults to on. If off, systemd-
231 firstboot.service(8) will not query the user for basic system
232 settings, even if the system boots up for the first time and the
233 relevant settings are not initialized yet. Not to be confused with
234 systemd.condition-first-boot= (see below), which overrides the
235 result of the ConditionFirstBoot= unit file condition, and thus
236 controls more than just systemd-firstboot.service behaviour.
237 systemd.condition-needs-update=
239 Takes a boolean argument. If specified, overrides the result of
240 ConditionNeedsUpdate= unit condition checks. See systemd.unit(5)
241 for details.
242 systemd.condition-first-boot=
244 Takes a boolean argument. If specified, overrides the result of
245 ConditionFirstBoot= unit condition checks. See systemd.unit(5) for
246 details. Not to be confused with systemd.firstboot= which only
247 controls behaviour of the systemd-firstboot.service system service
248 but has no effect on the condition check (see above).
249 systemd.clock-usec=
251 Takes a decimal, numeric timestamp in µs since January 1st 1970,
252 00:00am, to set the system clock to. The system time is set to the
253 specified timestamp early during boot. It is not propagated to the
254 hardware clock (RTC).
255 systemd.random-seed=
257 Takes a base64 encoded random seed value to credit with full
258 entropy to the kernel's random pool during early service manager
259 initialization. This option is useful in testing environments where
260 delays due to random pool initialization in entropy starved virtual
261 machines shall be avoided.
262 Note that if this option is used the seed is accessible to
264 unprivileged programs from /proc/cmdline. This option is hence a
265 security risk when used outside of test systems, since the
266 (possibly) only seed used for initialization of the kernel's
267 entropy pool might be easily acquired by unprivileged programs.
268 It is recommended to pass 512 bytes of randomized data (as that
270 matches the Linux kernel pool size), which may be generated with a
271 command like the following:
272 dd if=/dev/urandom bs=512 count=1 status=none | base64 -w 0
274 Again: do not use this option outside of testing environments, it's
276 a security risk elsewhere, as secret key material derived from the
277 entropy pool can possibly be reconstructed by unprivileged
278 programs.
279 systemd.hostname=
281 Accepts a hostname to set during early boot. If specified takes
282 precedence over what is set in /etc/hostname. Note that this does
283 not bar later runtime changes to the hostname, it simply controls
284 the initial hostname set during early boot.
285
287 systemd 252
288 Kernel command-line arguments systemd.unified_cgroup_hierarchy and
289 systemd.legacy_systemd_cgroup_controller were deprecated. Please
290 switch to the unified cgroup hierarchy.
291
293 systemd(1), systemd-system.conf(5), bootparam(7), dracut.cmdline(7),
294 systemd-debug-generator(8), systemd-fsck@.service(8), systemd-
295 quotacheck.service(8), systemd-journald.service(8), systemd-vconsole-
296 setup.service(8), systemd-udevd.service(8), plymouth(8), systemd-
297 cryptsetup-generator(8), systemd-veritysetup-generator(8), systemd-
298 fstab-generator(8), systemd-getty-generator(8), systemd-gpt-auto-
299 generator(8), systemd-volatile-root.service(8), systemd-modules-
300 load.service(8), systemd-backlight@.service(8), systemd-
301 rfkill.service(8), systemd-hibernate-resume-generator(8), systemd-
302 firstboot.service(8), bootctl(1)
303
305 1. kernel-parameters.html
306 https://docs.kernel.org/admin-guide/kernel-parameters.html
307systemd 253 KERNEL-COMMAND-LINE(7)