1<?xml version='1.0'?> <!--*-nxml-*-->
2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
5
6<refentry id="kernel-command-line">
7
8  <refentryinfo>
9    <title>kernel-command-line</title>
10    <productname>systemd</productname>
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
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>
36
37    <para>For command line parameters understood by the kernel, please
38    see
39    <ulink url="https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html"><filename>kernel-parameters.html</filename></ulink>
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
45    <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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>
57        <term><varname>systemd.dump_core</varname></term>
58        <term><varname>systemd.early_core_pattern=</varname></term>
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>
63        <term><varname>systemd.service_watchdogs</varname></term>
64        <term><varname>systemd.show_status</varname></term>
65        <term><varname>systemd.status_unit_format=</varname></term>
66        <term><varname>systemd.log_target=</varname></term>
67        <term><varname>systemd.log_level=</varname></term>
68        <term><varname>systemd.log_location=</varname></term>
69        <term><varname>systemd.log_color</varname></term>
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>
73        <term><varname>systemd.machine_id=</varname></term>
74        <term><varname>systemd.unified_cgroup_hierarchy</varname></term>
75        <term><varname>systemd.legacy_systemd_cgroup_controller</varname></term>
76        <term><varname>systemd.set_credential=</varname></term>
77        <term><varname>systemd.import_credentials=</varname></term>
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>
88        <term><varname>systemd.debug_shell</varname></term>
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
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
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)
112          takes over. This parameter allows specifying an absolute path where core dump files should be stored until
113          a handler is installed. The path should be absolute and may contain specifiers, see
114          <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details.</para>
115        </listitem>
116      </varlistentry>
117
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
126          <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
127          </para>
128        </listitem>
129      </varlistentry>
130
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
136          directory and <filename>/var/</filename> are mounted as specified on the kernel command line or
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
139          <filename>/usr/</filename> is mounted from the file system configured as root device, in read-only mode. This
140          enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
141          configuration and no stored state in effect, as <filename>/etc/</filename> and <filename>/var/</filename> (as
142          well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
143          setting is set to <literal>state</literal> the root file system is mounted read-only, however
144          <filename>/var/</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
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
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
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>
178        <term><varname>rd.emergency</varname></term>
179        <term><varname>emergency</varname></term>
180        <term><varname>rd.rescue</varname></term>
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
192          manager, as compatibility and convenience options. For details, see
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>
256        <term><varname>vconsole.keymap_toggle=</varname></term>
257        <term><varname>vconsole.font=</varname></term>
258        <term><varname>vconsole.font_map=</varname></term>
259        <term><varname>vconsole.font_unimap=</varname></term>
260
261        <listitem>
262          <para>Parameters understood by the virtual console setup logic. For details, see
263          <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
264        </listitem>
265      </varlistentry>
266
267      <varlistentry>
268        <term><varname>udev.log_level=</varname></term>
269        <term><varname>rd.udev.log_level=</varname></term>
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>
276        <term><varname>udev.timeout_signal=</varname></term>
277        <term><varname>rd.udev.timeout_signal=</varname></term>
278        <term><varname>udev.blockdev_read_only</varname></term>
279        <term><varname>rd.udev.blockdev_read_only</varname></term>
280        <term><varname>net.ifnames=</varname></term>
281        <term><varname>net.naming-scheme=</varname></term>
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>
335        <term><varname>rootflags=</varname></term>
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
342          mounted read-only or read-write initially. For details,
343          see
344          <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
345        </listitem>
346      </varlistentry>
347
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
360      <varlistentry>
361        <term><varname>veritytab=</varname></term>
362        <term><varname>rd.veritytab=</varname></term>
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>
368        <term><varname>systemd.verity.root_options=</varname></term>
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>
373        <listitem>
374          <para>Configures the integrity protection root hash for the root and <filename>/usr</filename> file systems, and other related
375          parameters. For details, see
376          <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
377        </listitem>
378      </varlistentry>
379
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
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
401      <varlistentry>
402        <term><varname>systemd.default_timeout_start_sec=</varname></term>
403
404        <listitem>
405          <para>Overrides the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at
406          boot. For details, see
407          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
408        </listitem>
409      </varlistentry>
410
411      <varlistentry>
412        <term><varname>systemd.watchdog_device=</varname></term>
413
414        <listitem>
415          <para>Overrides the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
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>
424          <para>Overrides the watchdog timeout settings otherwise configured with
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
429          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
430        </listitem>
431      </varlistentry>
432
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
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
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
466      <varlistentry>
467        <term><varname>modules_load=</varname></term>
468        <term><varname>rd.modules_load=</varname></term>
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>
479        <term><varname>resumeflags=</varname></term>
480
481        <listitem>
482          <para>Enables resume from hibernation using the specified
483          device and mount options. All
484          <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-like
485          paths are supported. For details, see
486          <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
487        </listitem>
488      </varlistentry>
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>
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>
500      </varlistentry>
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>
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>
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
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>
552      </varlistentry>
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>
561    </variablelist>
562
563  </refsect1>
564
565  <refsect1>
566      <title>See Also</title>
567      <para>
568        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
569        <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
570        <citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
571        <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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>,
580        <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
581        <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
582        <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
583        <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
584        <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
585        <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
586        <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
587        <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
588        <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
589        <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
590        <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
591      </para>
592  </refsect1>
593
594</refentry>
595