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c66e7bc7 1<?xml version='1.0'?> <!--*-nxml-*-->
3a54a157 2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
12b42c76 3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
db9ecf05 4<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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5
6<refentry id="kernel-command-line">
7
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8 <refentryinfo>
9 <title>kernel-command-line</title>
10 <productname>systemd</productname>
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11 </refentryinfo>
12
13 <refmeta>
14 <refentrytitle>kernel-command-line</refentrytitle>
15 <manvolnum>7</manvolnum>
16 </refmeta>
17
18 <refnamediv>
19 <refname>kernel-command-line</refname>
20 <refpurpose>Kernel command line parameters</refpurpose>
21 </refnamediv>
22
23 <refsynopsisdiv>
24 <para><filename>/proc/cmdline</filename></para>
25 </refsynopsisdiv>
26
27 <refsect1>
28 <title>Description</title>
29
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30 <para>The kernel, the programs running in the initrd and in the host system may be configured at boot via
31 kernel command line arguments. In addition, various systemd tools look at the EFI variable
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32 <literal>SystemdOptions</literal> (if available). Both sources are combined, but the kernel command line
33 has higher priority. Please note that <emphasis>the EFI variable is only used by systemd tools, and is
34 ignored by the kernel and other user space tools</emphasis>, so it is not a replacement for the kernel
35 command line.</para>
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36
37 <para>For command line parameters understood by the kernel, please
ab1f7245 38 see
0e685823 39 <ulink url="https://docs.kernel.org/admin-guide/kernel-parameters.html"><filename>kernel-parameters.html</filename></ulink>
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40 and
41 <citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
42
b66a6e1a 43 <para>For command line parameters understood by the initrd, see
af105d03 44 <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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45 or the documentation of the specific initrd implementation of your
46 installation.</para>
47 </refsect1>
48
49 <refsect1>
50 <title>Core OS Command Line Arguments</title>
51
52 <variablelist class='kernel-commandline-options'>
53 <varlistentry>
54 <term><varname>systemd.unit=</varname></term>
55 <term><varname>rd.systemd.unit=</varname></term>
770c4777 56 <term><varname>systemd.dump_core</varname></term>
c6885f5f 57 <term><varname>systemd.early_core_pattern=</varname></term>
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58 <term><varname>systemd.crash_chvt</varname></term>
59 <term><varname>systemd.crash_shell</varname></term>
60 <term><varname>systemd.crash_reboot</varname></term>
61 <term><varname>systemd.confirm_spawn</varname></term>
2a12e32e 62 <term><varname>systemd.service_watchdogs</varname></term>
770c4777 63 <term><varname>systemd.show_status</varname></term>
36cf4507 64 <term><varname>systemd.status_unit_format=</varname></term>
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65 <term><varname>systemd.log_target=</varname></term>
66 <term><varname>systemd.log_level=</varname></term>
798d3a52 67 <term><varname>systemd.log_location=</varname></term>
770c4777 68 <term><varname>systemd.log_color</varname></term>
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69 <term><varname>systemd.default_standard_output=</varname></term>
70 <term><varname>systemd.default_standard_error=</varname></term>
71 <term><varname>systemd.setenv=</varname></term>
ee48dbd5 72 <term><varname>systemd.machine_id=</varname></term>
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73 <term><varname>systemd.set_credential=</varname></term>
74 <term><varname>systemd.import_credentials=</varname></term>
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75 <term><varname>systemd.reload_limit_interval_sec=</varname></term>
76 <term><varname>systemd.reload_limit_burst=</varname></term>
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77 <listitem>
78 <para>Parameters understood by the system and service
79 manager to control system behavior. For details, see
80 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
81 </listitem>
82 </varlistentry>
83
84 <varlistentry>
85 <term><varname>systemd.mask=</varname></term>
86 <term><varname>systemd.wants=</varname></term>
1d84ad94 87 <term><varname>systemd.debug_shell</varname></term>
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88 <listitem>
89 <para>Additional parameters understood by
90 <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
91 to mask or start specific units at boot, or invoke a debug
92 shell on tty9.</para>
93 </listitem>
94 </varlistentry>
95
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96 <varlistentry>
97 <term><varname>systemd.run=</varname></term>
98 <term><varname>systemd.run_success_action=</varname></term>
99 <term><varname>systemd.run_failure_action=</varname></term>
100 <listitem>
101 <para>Additional parameters understood by
102 <citerefentry><refentrytitle>systemd-run-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, to
103 run a command line specified on the kernel command line as system service after booting up.</para>
104 </listitem>
105 </varlistentry>
106
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107 <varlistentry>
108 <term><varname>systemd.early_core_pattern=</varname></term>
109 <listitem>
110 <para>During early boot, the generation of core dump files is disabled until a core dump handler (if any)
11fcfc53 111 takes over. This parameter allows specifying an absolute path where core dump files should be stored until
c6885f5f 112 a handler is installed. The path should be absolute and may contain specifiers, see
b7a47345 113 <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details.</para>
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114 </listitem>
115 </varlistentry>
116
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117 <varlistentry>
118 <term><varname>systemd.restore_state=</varname></term>
119 <listitem>
120 <para>This parameter is understood by several system tools
121 to control whether or not they should restore system state
122 from the previous boot. For details, see
123 <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
124 and
af105d03 125 <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
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126 </para>
127 </listitem>
128 </varlistentry>
129
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130 <varlistentry>
131 <term><varname>systemd.volatile=</varname></term>
132 <listitem>
133 <para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
134 the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
3b121157 135 directory and <filename>/var/</filename> are mounted as specified on the kernel command line or
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136 <filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
137 this case the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
3b121157 138 <filename>/usr/</filename> is mounted from the file system configured as root device, in read-only mode. This
91214a37 139 enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
3b121157 140 configuration and no stored state in effect, as <filename>/etc/</filename> and <filename>/var/</filename> (as
91214a37 141 well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
13070a70 142 setting is set to <literal>state</literal> the root file system is mounted read-only, however
3b121157 143 <filename>/var/</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
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144 system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. If
145 this setting is set to <literal>overlay</literal> the root file system is set up as
146 <literal>overlayfs</literal> mount combining the read-only root directory with a writable
147 <literal>tmpfs</literal>, so that no modifications are made to disk, but the file system may be modified
148 nonetheless with all changes being lost at reboot. For details, see
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149 <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
150 and
151 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
152 </listitem>
153 </varlistentry>
154
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155 <varlistentry>
156 <term><varname>quiet</varname></term>
157 <listitem>
158 <para>Parameter understood by both the kernel and the system
159 and service manager to control console log verbosity. For
160 details, see
161 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
162 </listitem>
163 </varlistentry>
164
165 <varlistentry>
166 <term><varname>debug</varname></term>
167 <listitem>
168 <para>Parameter understood by both the kernel and the system
169 and service manager to control console log verbosity. For
170 details, see
171 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
172 </listitem>
173 </varlistentry>
174
175 <varlistentry>
176 <term><varname>-b</varname></term>
dcd61450 177 <term><varname>rd.emergency</varname></term>
798d3a52 178 <term><varname>emergency</varname></term>
dcd61450 179 <term><varname>rd.rescue</varname></term>
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180 <term><varname>rescue</varname></term>
181 <term><varname>single</varname></term>
182 <term><varname>s</varname></term>
183 <term><varname>S</varname></term>
184 <term><varname>1</varname></term>
185 <term><varname>2</varname></term>
186 <term><varname>3</varname></term>
187 <term><varname>4</varname></term>
188 <term><varname>5</varname></term>
189 <listitem>
190 <para>Parameters understood by the system and service
dcd61450 191 manager, as compatibility and convenience options. For details, see
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192 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
193 </listitem>
194 </varlistentry>
195
196 <varlistentry>
197 <term><varname>locale.LANG=</varname></term>
198 <term><varname>locale.LANGUAGE=</varname></term>
199 <term><varname>locale.LC_CTYPE=</varname></term>
200 <term><varname>locale.LC_NUMERIC=</varname></term>
201 <term><varname>locale.LC_TIME=</varname></term>
202 <term><varname>locale.LC_COLLATE=</varname></term>
203 <term><varname>locale.LC_MONETARY=</varname></term>
204 <term><varname>locale.LC_MESSAGES=</varname></term>
205 <term><varname>locale.LC_PAPER=</varname></term>
206 <term><varname>locale.LC_NAME=</varname></term>
207 <term><varname>locale.LC_ADDRESS=</varname></term>
208 <term><varname>locale.LC_TELEPHONE=</varname></term>
209 <term><varname>locale.LC_MEASUREMENT=</varname></term>
210 <term><varname>locale.LC_IDENTIFICATION=</varname></term>
211 <listitem>
212 <para>Parameters understood by the system and service
213 manager to control locale and language settings. For
214 details, see
215 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
216 </listitem>
217 </varlistentry>
218
219 <varlistentry>
220 <term><varname>fsck.mode=</varname></term>
221 <term><varname>fsck.repair=</varname></term>
222
223 <listitem>
224 <para>Parameters understood by the file system checker
225 services. For details, see
226 <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
227 </listitem>
228 </varlistentry>
229
230 <varlistentry>
231 <term><varname>quotacheck.mode=</varname></term>
232
233 <listitem>
234 <para>Parameter understood by the file quota checker
235 service. For details, see
236 <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
237 </listitem>
238 </varlistentry>
239
240 <varlistentry>
241 <term><varname>systemd.journald.forward_to_syslog=</varname></term>
242 <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
243 <term><varname>systemd.journald.forward_to_console=</varname></term>
244 <term><varname>systemd.journald.forward_to_wall=</varname></term>
245
246 <listitem>
247 <para>Parameters understood by the journal service. For
248 details, see
249 <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
250 </listitem>
251 </varlistentry>
252
253 <varlistentry>
254 <term><varname>vconsole.keymap=</varname></term>
72ccee50 255 <term><varname>vconsole.keymap_toggle=</varname></term>
798d3a52 256 <term><varname>vconsole.font=</varname></term>
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257 <term><varname>vconsole.font_map=</varname></term>
258 <term><varname>vconsole.font_unimap=</varname></term>
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259
260 <listitem>
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261 <para>Parameters understood by the virtual console setup logic. For details, see
262 <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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263 </listitem>
264 </varlistentry>
265
266 <varlistentry>
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267 <term><varname>udev.log_level=</varname></term>
268 <term><varname>rd.udev.log_level=</varname></term>
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269 <term><varname>udev.children_max=</varname></term>
270 <term><varname>rd.udev.children_max=</varname></term>
271 <term><varname>udev.exec_delay=</varname></term>
272 <term><varname>rd.udev.exec_delay=</varname></term>
273 <term><varname>udev.event_timeout=</varname></term>
274 <term><varname>rd.udev.event_timeout=</varname></term>
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275 <term><varname>udev.timeout_signal=</varname></term>
276 <term><varname>rd.udev.timeout_signal=</varname></term>
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277 <term><varname>udev.blockdev_read_only</varname></term>
278 <term><varname>rd.udev.blockdev_read_only</varname></term>
798d3a52 279 <term><varname>net.ifnames=</varname></term>
f7e81fd9 280 <term><varname>net.naming-scheme=</varname></term>
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281
282 <listitem>
283 <para>Parameters understood by the device event managing
284 daemon. For details, see
285 <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
286 </listitem>
287 </varlistentry>
288
289 <varlistentry>
290 <term><varname>plymouth.enable=</varname></term>
291
292 <listitem>
293 <para>May be used to disable the Plymouth boot splash. For
294 details, see
295 <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
296 </listitem>
297 </varlistentry>
298
299 <varlistentry>
300 <term><varname>luks=</varname></term>
301 <term><varname>rd.luks=</varname></term>
302 <term><varname>luks.crypttab=</varname></term>
303 <term><varname>rd.luks.crypttab=</varname></term>
304 <term><varname>luks.name=</varname></term>
305 <term><varname>rd.luks.name=</varname></term>
306 <term><varname>luks.uuid=</varname></term>
307 <term><varname>rd.luks.uuid=</varname></term>
308 <term><varname>luks.options=</varname></term>
309 <term><varname>rd.luks.options=</varname></term>
310 <term><varname>luks.key=</varname></term>
311 <term><varname>rd.luks.key=</varname></term>
312
313 <listitem>
314 <para>Configures the LUKS full-disk encryption logic at
315 boot. For details, see
316 <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
317 </listitem>
318 </varlistentry>
319
320 <varlistentry>
321 <term><varname>fstab=</varname></term>
322 <term><varname>rd.fstab=</varname></term>
323
324 <listitem>
325 <para>Configures the <filename>/etc/fstab</filename> logic
326 at boot. For details, see
327 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
328 </listitem>
329 </varlistentry>
330
331 <varlistentry>
332 <term><varname>root=</varname></term>
333 <term><varname>rootfstype=</varname></term>
d6a12e7c 334 <term><varname>rootflags=</varname></term>
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335 <term><varname>ro</varname></term>
336 <term><varname>rw</varname></term>
337
338 <listitem>
339 <para>Configures the root file system and its file system
340 type and mount options, as well as whether it shall be
17ec531f 341 mounted read-only or read-write initially. For details,
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342 see
343 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
344 </listitem>
345 </varlistentry>
346
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347 <varlistentry>
348 <term><varname>mount.usr=</varname></term>
349 <term><varname>mount.usrfstype=</varname></term>
350 <term><varname>mount.usrflags=</varname></term>
351
352 <listitem>
353 <para>Configures the /usr file system (if required) and
354 its file system type and mount options. For details, see
355 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
356 </listitem>
357 </varlistentry>
358
2f3dfc6f 359 <varlistentry>
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360 <term><varname>veritytab=</varname></term>
361 <term><varname>rd.veritytab=</varname></term>
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362 <term><varname>roothash=</varname></term>
363 <term><varname>systemd.verity=</varname></term>
364 <term><varname>rd.systemd.verity=</varname></term>
365 <term><varname>systemd.verity_root_data=</varname></term>
366 <term><varname>systemd.verity_root_hash=</varname></term>
0141102f 367 <term><varname>systemd.verity.root_options=</varname></term>
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368 <term><varname>usrhash=</varname></term>
369 <term><varname>systemd.verity_usr_data=</varname></term>
370 <term><varname>systemd.verity_usr_hash=</varname></term>
371 <term><varname>systemd.verity_usr_options=</varname></term>
2f3dfc6f 372 <listitem>
e5196eee 373 <para>Configures the integrity protection root hash for the root and <filename>/usr</filename> file systems, and other related
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374 parameters. For details, see
375 <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
376 </listitem>
377 </varlistentry>
378
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379 <varlistentry>
380 <term><varname>systemd.getty_auto=</varname></term>
381
382 <listitem>
383 <para>Configures whether the <filename>serial-getty@.service</filename> will run.
384 For details, see
385 <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
386 </listitem>
387 </varlistentry>
388
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389 <varlistentry>
390 <term><varname>systemd.gpt_auto=</varname></term>
391 <term><varname>rd.systemd.gpt_auto=</varname></term>
392
393 <listitem>
394 <para>Configures whether GPT based partition auto-discovery
395 shall be attempted. For details, see
396 <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
397 </listitem>
398 </varlistentry>
399
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400 <varlistentry>
401 <term><varname>systemd.default_timeout_start_sec=</varname></term>
402
403 <listitem>
ba669952 404 <para>Overrides the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at
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405 boot. For details, see
406 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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407 </listitem>
408 </varlistentry>
409
410 <varlistentry>
411 <term><varname>systemd.watchdog_device=</varname></term>
412
413 <listitem>
ba669952 414 <para>Overrides the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
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415 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
416 </listitem>
417 </varlistentry>
418
419 <varlistentry>
420 <term><varname>systemd.watchdog_sec=</varname></term>
421
422 <listitem>
ba669952 423 <para>Overrides the watchdog timeout settings otherwise configured with
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424 <varname>RuntimeWatchdog=</varname>, <varname>RebootWatchdog=</varname> and
425 <varname>KExecWatchdogSec=</varname>. Takes a time value (if no unit is specified, seconds is the
426 implicitly assumed time unit) or the special strings <literal>off</literal> or
427 <literal>default</literal>. For details, see
c75396c3 428 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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429 </listitem>
430 </varlistentry>
431
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432 <varlistentry>
433 <term><varname>systemd.watchdog_pre_sec=</varname></term>
434
435 <listitem>
436 <para>Overrides the watchdog pre-timeout settings otherwise configured with
437 <varname>RuntimeWatchdogPreSec=</varname>. Takes a time value (if no unit is specified, seconds is the
438 implicitly assumed time unit) or the special strings <literal>off</literal> or
439 <literal>default</literal>. For details, see
440 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
441 </listitem>
442 </varlistentry>
443
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444 <varlistentry>
445 <term><varname>systemd.watchdog_pretimeout_governor=</varname></term>
446
447 <listitem>
448 <para>Overrides the watchdog pre-timeout settings otherwise configured with
449 <varname>RuntimeWatchdogPreGovernor=</varname>. Takes a string value. For details, see
450 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
451 </listitem>
452 </varlistentry>
453
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454 <varlistentry>
455 <term><varname>systemd.cpu_affinity=</varname></term>
456
457 <listitem>
458 <para>Overrides the CPU affinity mask for the service manager and the default for all child
459 processes it forks. This takes precedence over <varname>CPUAffinity=</varname>, see
460 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
461 for details.</para>
462 </listitem>
463 </varlistentry>
464
798d3a52 465 <varlistentry>
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466 <term><varname>modules_load=</varname></term>
467 <term><varname>rd.modules_load=</varname></term>
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468
469 <listitem>
470 <para>Load a specific kernel module early at boot. For
471 details, see
472 <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
473 </listitem>
474 </varlistentry>
475
476 <varlistentry>
477 <term><varname>resume=</varname></term>
8b6805a2 478 <term><varname>resumeflags=</varname></term>
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479
480 <listitem>
481 <para>Enables resume from hibernation using the specified
8b6805a2 482 device and mount options. All
3ba3a79d 483 <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-like
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484 paths are supported. For details, see
485 <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
486 </listitem>
487 </varlistentry>
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488
489 <varlistentry>
490 <term><varname>systemd.firstboot=</varname></term>
491
492 <listitem><para>Takes a boolean argument, defaults to on. If off,
493 <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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494 will not query the user for basic system settings, even if the system boots up for the first time and
495 the relevant settings are not initialized yet. Not to be confused with
496 <varname>systemd.condition-first-boot=</varname> (see below), which overrides the result of the
497 <varname>ConditionFirstBoot=</varname> unit file condition, and thus controls more than just
498 <filename>systemd-firstboot.service</filename> behaviour.</para></listitem>
f582cbca 499 </varlistentry>
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500
501 <varlistentry>
502 <term><varname>systemd.condition-needs-update=</varname></term>
503
504 <listitem><para>Takes a boolean argument. If specified, overrides the result of
505 <varname>ConditionNeedsUpdate=</varname> unit condition checks. See
506 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
507 details.</para></listitem>
508 </varlistentry>
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509
510 <varlistentry>
511 <term><varname>systemd.condition-first-boot=</varname></term>
512
513 <listitem><para>Takes a boolean argument. If specified, overrides the result of
514 <varname>ConditionFirstBoot=</varname> unit condition checks. See
515 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
516 details. Not to be confused with <varname>systemd.firstboot=</varname> which only controls behaviour
517 of the <filename>systemd-firstboot.service</filename> system service but has no effect on the
518 condition check (see above).</para></listitem>
519 </varlistentry>
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520
521 <varlistentry>
522 <term><varname>systemd.clock-usec=</varname></term>
523
524 <listitem><para>Takes a decimal, numeric timestamp in µs since January 1st 1970, 00:00am, to set the
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525 system clock to. The system time is set to the specified timestamp early during boot. It is not
526 propagated to the hardware clock (RTC).</para></listitem>
527 </varlistentry>
528
529 <varlistentry>
530 <term><varname>systemd.random-seed=</varname></term>
531
532 <listitem><para>Takes a base64 encoded random seed value to credit with full entropy to the kernel's
533 random pool during early service manager initialization. This option is useful in testing
534 environments where delays due to random pool initialization in entropy starved virtual machines shall
535 be avoided.</para>
536
537 <para>Note that if this option is used the seed is accessible to unprivileged programs from
538 <filename>/proc/cmdline</filename>. This option is hence a security risk when used outside of test
539 systems, since the (possibly) only seed used for initialization of the kernel's entropy pool might be
540 easily acquired by unprivileged programs.</para>
541
542 <para>It is recommended to pass 512 bytes of randomized data (as that matches the Linux kernel pool
543 size), which may be generated with a command like the following:</para>
544
545 <programlisting>dd if=/dev/urandom bs=512 count=1 status=none | base64 -w 0</programlisting>
546
547 <para>Again: do not use this option outside of testing environments, it's a security risk elsewhere,
548 as secret key material derived from the entropy pool can possibly be reconstructed by unprivileged
549 programs.</para>
550 </listitem>
3753325b 551 </varlistentry>
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552
553 <varlistentry>
554 <term><varname>systemd.hostname=</varname></term>
555
556 <listitem><para>Accepts a hostname to set during early boot. If specified takes precedence over what
557 is set in <filename>/etc/hostname</filename>. Note that this does not bar later runtime changes to
558 the hostname, it simply controls the initial hostname set during early boot.</para></listitem>
559 </varlistentry>
798d3a52 560 </variablelist>
7a9e0bd0 561 </refsect1>
798d3a52 562
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563 <refsect1>
564 <title>History</title>
565
566 <variablelist>
567 <varlistentry>
568 <term>systemd 252</term>
569 <listitem><para>Kernel command-line arguments <varname>systemd.unified_cgroup_hierarchy</varname>
570 and <varname>systemd.legacy_systemd_cgroup_controller</varname> were deprecated. Please switch to
571 the unified cgroup hierarchy.</para></listitem>
572 </varlistentry>
573 </variablelist>
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574 </refsect1>
575
576 <refsect1>
577 <title>See Also</title>
578 <para>
579 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
d1698b82 580 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
798d3a52 581 <citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
af105d03 582 <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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583 <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
584 <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
585 <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
586 <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
587 <citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
588 <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
589 <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
590 <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
2f3dfc6f 591 <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
798d3a52 592 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
21d00e52 593 <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
798d3a52 594 <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
91214a37 595 <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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596 <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
597 <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
af105d03 598 <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
f582cbca 599 <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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600 <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
601 <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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602 </para>
603 </refsect1>
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604
605</refentry>