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1<?xml version='1.0'?> <!--*-nxml-*-->
2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
12b42c76 3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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4
5<!--
572eb058 6 SPDX-License-Identifier: LGPL-2.1+
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7-->
8
9<refentry id="kernel-command-line">
10
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11 <refentryinfo>
12 <title>kernel-command-line</title>
13 <productname>systemd</productname>
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14 </refentryinfo>
15
16 <refmeta>
17 <refentrytitle>kernel-command-line</refentrytitle>
18 <manvolnum>7</manvolnum>
19 </refmeta>
20
21 <refnamediv>
22 <refname>kernel-command-line</refname>
23 <refpurpose>Kernel command line parameters</refpurpose>
24 </refnamediv>
25
26 <refsynopsisdiv>
27 <para><filename>/proc/cmdline</filename></para>
28 </refsynopsisdiv>
29
30 <refsect1>
31 <title>Description</title>
32
33 <para>The kernel, the initial RAM disk (initrd) and
34 basic userspace functionality may be configured at boot via
35 kernel command line arguments.</para>
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>
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57 <term><varname>systemd.dump_core</varname></term>
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>
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64 <term><varname>systemd.log_target=</varname></term>
65 <term><varname>systemd.log_level=</varname></term>
798d3a52 66 <term><varname>systemd.log_location=</varname></term>
770c4777 67 <term><varname>systemd.log_color</varname></term>
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68 <term><varname>systemd.default_standard_output=</varname></term>
69 <term><varname>systemd.default_standard_error=</varname></term>
70 <term><varname>systemd.setenv=</varname></term>
ee48dbd5 71 <term><varname>systemd.machine_id=</varname></term>
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72 <term><varname>systemd.unified_cgroup_hierarchy</varname></term>
73 <term><varname>systemd.legacy_systemd_cgroup_controller</varname></term>
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74 <listitem>
75 <para>Parameters understood by the system and service
76 manager to control system behavior. For details, see
77 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
78 </listitem>
79 </varlistentry>
80
81 <varlistentry>
82 <term><varname>systemd.mask=</varname></term>
83 <term><varname>systemd.wants=</varname></term>
1d84ad94 84 <term><varname>systemd.debug_shell</varname></term>
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85 <listitem>
86 <para>Additional parameters understood by
87 <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
88 to mask or start specific units at boot, or invoke a debug
89 shell on tty9.</para>
90 </listitem>
91 </varlistentry>
92
93 <varlistentry>
94 <term><varname>systemd.restore_state=</varname></term>
95 <listitem>
96 <para>This parameter is understood by several system tools
97 to control whether or not they should restore system state
98 from the previous boot. For details, see
99 <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
100 and
af105d03 101 <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
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102 </para>
103 </listitem>
104 </varlistentry>
105
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106 <varlistentry>
107 <term><varname>systemd.volatile=</varname></term>
108 <listitem>
109 <para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
110 the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
111 directory and <filename>/var</filename> are mounted as specified on the kernel command line or
112 <filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
113 this case the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
114 <filename>/usr</filename> is mounted from the file system configured as root device, in read-only mode. This
115 enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
116 configuration and no stored state in effect, as <filename>/etc</filename> and <filename>/var</filename> (as
117 well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
118 setting is set to <literal>state</literal> the root file system is mounted as usual, however
119 <filename>/var</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
120 system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. For details,
121 see
122 <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
123 and
124 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
125 </listitem>
126 </varlistentry>
127
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128 <varlistentry>
129 <term><varname>quiet</varname></term>
130 <listitem>
131 <para>Parameter understood by both the kernel and the system
132 and service manager to control console log verbosity. For
133 details, see
134 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
135 </listitem>
136 </varlistentry>
137
138 <varlistentry>
139 <term><varname>debug</varname></term>
140 <listitem>
141 <para>Parameter understood by both the kernel and the system
142 and service manager to control console log verbosity. For
143 details, see
144 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
145 </listitem>
146 </varlistentry>
147
148 <varlistentry>
149 <term><varname>-b</varname></term>
dcd61450 150 <term><varname>rd.emergency</varname></term>
798d3a52 151 <term><varname>emergency</varname></term>
dcd61450 152 <term><varname>rd.rescue</varname></term>
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153 <term><varname>rescue</varname></term>
154 <term><varname>single</varname></term>
155 <term><varname>s</varname></term>
156 <term><varname>S</varname></term>
157 <term><varname>1</varname></term>
158 <term><varname>2</varname></term>
159 <term><varname>3</varname></term>
160 <term><varname>4</varname></term>
161 <term><varname>5</varname></term>
162 <listitem>
163 <para>Parameters understood by the system and service
dcd61450 164 manager, as compatibility and convenience options. For details, see
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165 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
166 </listitem>
167 </varlistentry>
168
169 <varlistentry>
170 <term><varname>locale.LANG=</varname></term>
171 <term><varname>locale.LANGUAGE=</varname></term>
172 <term><varname>locale.LC_CTYPE=</varname></term>
173 <term><varname>locale.LC_NUMERIC=</varname></term>
174 <term><varname>locale.LC_TIME=</varname></term>
175 <term><varname>locale.LC_COLLATE=</varname></term>
176 <term><varname>locale.LC_MONETARY=</varname></term>
177 <term><varname>locale.LC_MESSAGES=</varname></term>
178 <term><varname>locale.LC_PAPER=</varname></term>
179 <term><varname>locale.LC_NAME=</varname></term>
180 <term><varname>locale.LC_ADDRESS=</varname></term>
181 <term><varname>locale.LC_TELEPHONE=</varname></term>
182 <term><varname>locale.LC_MEASUREMENT=</varname></term>
183 <term><varname>locale.LC_IDENTIFICATION=</varname></term>
184 <listitem>
185 <para>Parameters understood by the system and service
186 manager to control locale and language settings. For
187 details, see
188 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
189 </listitem>
190 </varlistentry>
191
192 <varlistentry>
193 <term><varname>fsck.mode=</varname></term>
194 <term><varname>fsck.repair=</varname></term>
195
196 <listitem>
197 <para>Parameters understood by the file system checker
198 services. For details, see
199 <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
200 </listitem>
201 </varlistentry>
202
203 <varlistentry>
204 <term><varname>quotacheck.mode=</varname></term>
205
206 <listitem>
207 <para>Parameter understood by the file quota checker
208 service. For details, see
209 <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
210 </listitem>
211 </varlistentry>
212
213 <varlistentry>
214 <term><varname>systemd.journald.forward_to_syslog=</varname></term>
215 <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
216 <term><varname>systemd.journald.forward_to_console=</varname></term>
217 <term><varname>systemd.journald.forward_to_wall=</varname></term>
218
219 <listitem>
220 <para>Parameters understood by the journal service. For
221 details, see
222 <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
223 </listitem>
224 </varlistentry>
225
226 <varlistentry>
227 <term><varname>vconsole.keymap=</varname></term>
72ccee50 228 <term><varname>vconsole.keymap_toggle=</varname></term>
798d3a52 229 <term><varname>vconsole.font=</varname></term>
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230 <term><varname>vconsole.font_map=</varname></term>
231 <term><varname>vconsole.font_unimap=</varname></term>
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232
233 <listitem>
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234 <para>Parameters understood by the virtual console setup logic. For details, see
235 <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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236 </listitem>
237 </varlistentry>
238
239 <varlistentry>
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240 <term><varname>udev.log_priority=</varname></term>
241 <term><varname>rd.udev.log_priority=</varname></term>
242 <term><varname>udev.children_max=</varname></term>
243 <term><varname>rd.udev.children_max=</varname></term>
244 <term><varname>udev.exec_delay=</varname></term>
245 <term><varname>rd.udev.exec_delay=</varname></term>
246 <term><varname>udev.event_timeout=</varname></term>
247 <term><varname>rd.udev.event_timeout=</varname></term>
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248 <term><varname>net.ifnames=</varname></term>
249
250 <listitem>
251 <para>Parameters understood by the device event managing
252 daemon. For details, see
253 <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
254 </listitem>
255 </varlistentry>
256
257 <varlistentry>
258 <term><varname>plymouth.enable=</varname></term>
259
260 <listitem>
261 <para>May be used to disable the Plymouth boot splash. For
262 details, see
263 <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
264 </listitem>
265 </varlistentry>
266
267 <varlistentry>
268 <term><varname>luks=</varname></term>
269 <term><varname>rd.luks=</varname></term>
270 <term><varname>luks.crypttab=</varname></term>
271 <term><varname>rd.luks.crypttab=</varname></term>
272 <term><varname>luks.name=</varname></term>
273 <term><varname>rd.luks.name=</varname></term>
274 <term><varname>luks.uuid=</varname></term>
275 <term><varname>rd.luks.uuid=</varname></term>
276 <term><varname>luks.options=</varname></term>
277 <term><varname>rd.luks.options=</varname></term>
278 <term><varname>luks.key=</varname></term>
279 <term><varname>rd.luks.key=</varname></term>
280
281 <listitem>
282 <para>Configures the LUKS full-disk encryption logic at
283 boot. For details, see
284 <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
285 </listitem>
286 </varlistentry>
287
288 <varlistentry>
289 <term><varname>fstab=</varname></term>
290 <term><varname>rd.fstab=</varname></term>
291
292 <listitem>
293 <para>Configures the <filename>/etc/fstab</filename> logic
294 at boot. For details, see
295 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
296 </listitem>
297 </varlistentry>
298
299 <varlistentry>
300 <term><varname>root=</varname></term>
301 <term><varname>rootfstype=</varname></term>
d6a12e7c 302 <term><varname>rootflags=</varname></term>
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303 <term><varname>ro</varname></term>
304 <term><varname>rw</varname></term>
305
306 <listitem>
307 <para>Configures the root file system and its file system
308 type and mount options, as well as whether it shall be
309 mounted read-only or read-writable initially. For details,
310 see
311 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
312 </listitem>
313 </varlistentry>
314
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315 <varlistentry>
316 <term><varname>mount.usr=</varname></term>
317 <term><varname>mount.usrfstype=</varname></term>
318 <term><varname>mount.usrflags=</varname></term>
319
320 <listitem>
321 <para>Configures the /usr file system (if required) and
322 its file system type and mount options. For details, see
323 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
324 </listitem>
325 </varlistentry>
326
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327 <varlistentry>
328 <term><varname>roothash=</varname></term>
329 <term><varname>systemd.verity=</varname></term>
330 <term><varname>rd.systemd.verity=</varname></term>
331 <term><varname>systemd.verity_root_data=</varname></term>
332 <term><varname>systemd.verity_root_hash=</varname></term>
333 <listitem>
334 <para>Configures the integrity protection root hash for the root file system, and other related
335 parameters. For details, see
336 <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
337 </listitem>
338 </varlistentry>
339
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340 <varlistentry>
341 <term><varname>systemd.gpt_auto=</varname></term>
342 <term><varname>rd.systemd.gpt_auto=</varname></term>
343
344 <listitem>
345 <para>Configures whether GPT based partition auto-discovery
346 shall be attempted. For details, see
347 <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
348 </listitem>
349 </varlistentry>
350
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351 <varlistentry>
352 <term><varname>systemd.default_timeout_start_sec=</varname></term>
353
354 <listitem>
355 <para>Overwrites the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at boot. For details,
356 see <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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357 </listitem>
358 </varlistentry>
359
360 <varlistentry>
361 <term><varname>systemd.watchdog_device=</varname></term>
362
363 <listitem>
364 <para>Overwrites the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
365 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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366 </listitem>
367 </varlistentry>
368
798d3a52 369 <varlistentry>
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370 <term><varname>modules_load=</varname></term>
371 <term><varname>rd.modules_load=</varname></term>
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372
373 <listitem>
374 <para>Load a specific kernel module early at boot. For
375 details, see
376 <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
377 </listitem>
378 </varlistentry>
379
380 <varlistentry>
381 <term><varname>resume=</varname></term>
382
383 <listitem>
384 <para>Enables resume from hibernation using the specified
385 device. All
3ba3a79d 386 <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-like
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387 paths are supported. For details, see
388 <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
389 </listitem>
390 </varlistentry>
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391
392 <varlistentry>
393 <term><varname>systemd.firstboot=</varname></term>
394
395 <listitem><para>Takes a boolean argument, defaults to on. If off,
396 <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
397 will not query the user for basic system settings, even if the system boots up for the first time and the
398 relevant settings are not initialized yet.</para></listitem>
399 </varlistentry>
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400 </variablelist>
401
402 </refsect1>
403
404 <refsect1>
405 <title>See Also</title>
406 <para>
407 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
408 <citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
af105d03 409 <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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410 <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
411 <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
412 <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
413 <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
414 <citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
415 <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
416 <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
417 <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
2f3dfc6f 418 <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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419 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
420 <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
91214a37 421 <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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422 <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
423 <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
af105d03 424 <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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425 <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
426 <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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427 </para>
428 </refsect1>
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429
430</refentry>