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