man/kernel-command-line.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="kernel-command-line" xmlns:xi="http://www.w3.org/2001/XInclude">
   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 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
  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://docs.kernel.org/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 initrd, see
  44     <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
  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>
  56         <term><varname>systemd.dump_core</varname></term>
  57         <term><varname>systemd.crash_chvt</varname></term>
  58         <term><varname>systemd.crash_shell</varname></term>
  59         <term><varname>systemd.crash_reboot</varname></term>
  60         <term><varname>systemd.confirm_spawn</varname></term>
  61         <term><varname>systemd.service_watchdogs</varname></term>
  62         <term><varname>systemd.show_status</varname></term>
  63         <term><varname>systemd.status_unit_format=</varname></term>
  64         <term><varname>systemd.log_target=</varname></term>
  65         <term><varname>systemd.log_level=</varname></term>
  66         <term><varname>systemd.log_location=</varname></term>
  67         <term><varname>systemd.log_color</varname></term>
  68         <term><varname>systemd.log_ratelimit_kmsg</varname></term>
  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>
  72         <term><varname>systemd.machine_id=</varname></term>
  73         <term><varname>systemd.set_credential=</varname></term>
  74         <term><varname>systemd.set_credential_binary=</varname></term>
  75         <term><varname>systemd.import_credentials=</varname></term>
  76         <term><varname>systemd.reload_limit_interval_sec=</varname></term>
  77         <term><varname>systemd.reload_limit_burst=</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
  83           <xi:include href="version-info.xml" xpointer="v186"/>
  84         </listitem>
  85       </varlistentry>
  86
  87       <varlistentry>
  88         <term><varname>systemd.mask=</varname></term>
  89         <term><varname>systemd.wants=</varname></term>
  90         <term><varname>systemd.debug_shell</varname></term>
  91         <listitem>
  92           <para>Additional parameters understood by
  93           <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  94           to mask or start specific units at boot, or invoke a debug
  95           shell on tty9.</para>
  96
  97           <xi:include href="version-info.xml" xpointer="v215"/>
  98         </listitem>
  99       </varlistentry>
 100
 101       <varlistentry>
 102         <term><varname>systemd.run=</varname></term>
 103         <term><varname>systemd.run_success_action=</varname></term>
 104         <term><varname>systemd.run_failure_action=</varname></term>
 105         <listitem>
 106           <para>Additional parameters understood by
 107           <citerefentry><refentrytitle>systemd-run-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, to
 108           run a command line specified on the kernel command line as system service after booting up.</para>
 109
 110           <xi:include href="version-info.xml" xpointer="v240"/>
 111         </listitem>
 112       </varlistentry>
 113
 114       <varlistentry>
 115         <term><varname>systemd.early_core_pattern=</varname></term>
 116         <listitem>
 117           <para>During early boot, the generation of core dump files is disabled until a core dump handler (if any)
 118           takes over. This parameter allows specifying an absolute path where core dump files should be stored until
 119           a handler is installed. The path should be absolute and may contain specifiers, see
 120           <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details.</para>
 121
 122           <xi:include href="version-info.xml" xpointer="v240"/>
 123         </listitem>
 124       </varlistentry>
 125
 126       <varlistentry>
 127         <term><varname>systemd.restore_state=</varname></term>
 128         <listitem>
 129           <para>This parameter is understood by several system tools
 130           to control whether or not they should restore system state
 131           from the previous boot. For details, see
 132           <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 133           and
 134           <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 135           </para>
 136
 137           <xi:include href="version-info.xml" xpointer="v209"/>
 138         </listitem>
 139       </varlistentry>
 140
 141       <varlistentry>
 142         <term><varname>systemd.volatile=</varname></term>
 143         <listitem>
 144           <para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
 145           the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
 146           directory and <filename>/var/</filename> are mounted as specified on the kernel command line or
 147           <filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
 148           this case the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
 149           <filename>/usr/</filename> is mounted from the file system configured as root device, in read-only mode. This
 150           enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
 151           configuration and no stored state in effect, as <filename>/etc/</filename> and <filename>/var/</filename> (as
 152           well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
 153           setting is set to <literal>state</literal> the root file system is mounted read-only, however
 154           <filename>/var/</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
 155           system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. If
 156           this setting is set to <literal>overlay</literal> the root file system is set up as
 157           <literal>overlayfs</literal> mount combining the read-only root directory with a writable
 158           <literal>tmpfs</literal>, so that no modifications are made to disk, but the file system may be modified
 159           nonetheless with all changes being lost at reboot. For details, see
 160           <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 161           and
 162           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 163
 164           <xi:include href="version-info.xml" xpointer="v233"/>
 165         </listitem>
 166       </varlistentry>
 167
 168       <varlistentry>
 169         <term><varname>quiet</varname></term>
 170         <listitem>
 171           <para>Parameter understood by both the kernel and the system
 172           and service manager to control console log verbosity. For
 173           details, see
 174           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 175
 176           <xi:include href="version-info.xml" xpointer="v186"/>
 177         </listitem>
 178       </varlistentry>
 179
 180       <varlistentry>
 181         <term><varname>debug</varname></term>
 182         <listitem>
 183           <para>Parameter understood by both the kernel and the system
 184           and service manager to control console log verbosity. For
 185           details, see
 186           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 187
 188           <xi:include href="version-info.xml" xpointer="v205"/>
 189         </listitem>
 190       </varlistentry>
 191
 192       <varlistentry>
 193         <term><varname>-b</varname></term>
 194         <term><varname>rd.emergency</varname></term>
 195         <term><varname>emergency</varname></term>
 196         <term><varname>rd.rescue</varname></term>
 197         <term><varname>rescue</varname></term>
 198         <term><varname>single</varname></term>
 199         <term><varname>s</varname></term>
 200         <term><varname>S</varname></term>
 201         <term><varname>1</varname></term>
 202         <term><varname>2</varname></term>
 203         <term><varname>3</varname></term>
 204         <term><varname>4</varname></term>
 205         <term><varname>5</varname></term>
 206         <listitem>
 207           <para>Parameters understood by the system and service
 208           manager, as compatibility and convenience options. For details, see
 209           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 210
 211           <xi:include href="version-info.xml" xpointer="v186"/>
 212         </listitem>
 213       </varlistentry>
 214
 215       <varlistentry>
 216         <term><varname>locale.LANG=</varname></term>
 217         <term><varname>locale.LANGUAGE=</varname></term>
 218         <term><varname>locale.LC_CTYPE=</varname></term>
 219         <term><varname>locale.LC_NUMERIC=</varname></term>
 220         <term><varname>locale.LC_TIME=</varname></term>
 221         <term><varname>locale.LC_COLLATE=</varname></term>
 222         <term><varname>locale.LC_MONETARY=</varname></term>
 223         <term><varname>locale.LC_MESSAGES=</varname></term>
 224         <term><varname>locale.LC_PAPER=</varname></term>
 225         <term><varname>locale.LC_NAME=</varname></term>
 226         <term><varname>locale.LC_ADDRESS=</varname></term>
 227         <term><varname>locale.LC_TELEPHONE=</varname></term>
 228         <term><varname>locale.LC_MEASUREMENT=</varname></term>
 229         <term><varname>locale.LC_IDENTIFICATION=</varname></term>
 230         <listitem>
 231           <para>Parameters understood by the system and service
 232           manager to control locale and language settings. For
 233           details, see
 234           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 235
 236           <xi:include href="version-info.xml" xpointer="v186"/>
 237         </listitem>
 238       </varlistentry>
 239
 240       <varlistentry>
 241         <term><varname>fsck.mode=</varname></term>
 242         <term><varname>fsck.repair=</varname></term>
 243
 244         <listitem>
 245           <para>Parameters understood by the file system checker
 246           services. For details, see
 247           <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 248
 249           <xi:include href="version-info.xml" xpointer="v186"/>
 250         </listitem>
 251       </varlistentry>
 252
 253       <varlistentry>
 254         <term><varname>quotacheck.mode=</varname></term>
 255
 256         <listitem>
 257           <para>Parameter understood by the file quota checker
 258           service. For details, see
 259           <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 260
 261           <xi:include href="version-info.xml" xpointer="v186"/>
 262         </listitem>
 263       </varlistentry>
 264
 265       <varlistentry>
 266         <term><varname>systemd.journald.forward_to_syslog=</varname></term>
 267         <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
 268         <term><varname>systemd.journald.forward_to_console=</varname></term>
 269         <term><varname>systemd.journald.forward_to_wall=</varname></term>
 270
 271         <listitem>
 272           <para>Parameters understood by the journal service. For
 273           details, see
 274           <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 275
 276           <xi:include href="version-info.xml" xpointer="v186"/>
 277         </listitem>
 278       </varlistentry>
 279
 280       <varlistentry>
 281         <term><varname>vconsole.keymap=</varname></term>
 282         <term><varname>vconsole.keymap_toggle=</varname></term>
 283         <term><varname>vconsole.font=</varname></term>
 284         <term><varname>vconsole.font_map=</varname></term>
 285         <term><varname>vconsole.font_unimap=</varname></term>
 286
 287         <listitem>
 288           <para>Parameters understood by the virtual console setup logic. For details, see
 289           <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 290
 291           <xi:include href="version-info.xml" xpointer="v186"/>
 292         </listitem>
 293       </varlistentry>
 294
 295       <varlistentry>
 296         <term><varname>udev.log_level=</varname></term>
 297         <term><varname>rd.udev.log_level=</varname></term>
 298         <term><varname>udev.children_max=</varname></term>
 299         <term><varname>rd.udev.children_max=</varname></term>
 300         <term><varname>udev.exec_delay=</varname></term>
 301         <term><varname>rd.udev.exec_delay=</varname></term>
 302         <term><varname>udev.event_timeout=</varname></term>
 303         <term><varname>rd.udev.event_timeout=</varname></term>
 304         <term><varname>udev.timeout_signal=</varname></term>
 305         <term><varname>rd.udev.timeout_signal=</varname></term>
 306         <term><varname>udev.blockdev_read_only</varname></term>
 307         <term><varname>rd.udev.blockdev_read_only</varname></term>
 308         <term><varname>net.ifnames=</varname></term>
 309         <term><varname>net.naming-scheme=</varname></term>
 310
 311         <listitem>
 312           <para>Parameters understood by the device event managing
 313           daemon. For details, see
 314           <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 315
 316           <xi:include href="version-info.xml" xpointer="v186"/>
 317         </listitem>
 318       </varlistentry>
 319
 320       <varlistentry>
 321         <term><varname>plymouth.enable=</varname></term>
 322
 323         <listitem>
 324           <para>May be used to disable the Plymouth boot splash. For
 325           details, see
 326           <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 327
 328           <xi:include href="version-info.xml" xpointer="v186"/>
 329         </listitem>
 330       </varlistentry>
 331
 332       <varlistentry>
 333         <term><varname>luks=</varname></term>
 334         <term><varname>rd.luks=</varname></term>
 335         <term><varname>luks.crypttab=</varname></term>
 336         <term><varname>rd.luks.crypttab=</varname></term>
 337         <term><varname>luks.name=</varname></term>
 338         <term><varname>rd.luks.name=</varname></term>
 339         <term><varname>luks.uuid=</varname></term>
 340         <term><varname>rd.luks.uuid=</varname></term>
 341         <term><varname>luks.options=</varname></term>
 342         <term><varname>rd.luks.options=</varname></term>
 343         <term><varname>luks.key=</varname></term>
 344         <term><varname>rd.luks.key=</varname></term>
 345
 346         <listitem>
 347           <para>Configures the LUKS full-disk encryption logic at
 348           boot. For details, see
 349           <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 350
 351           <xi:include href="version-info.xml" xpointer="v186"/>
 352         </listitem>
 353       </varlistentry>
 354
 355       <varlistentry>
 356         <term><varname>fstab=</varname></term>
 357         <term><varname>rd.fstab=</varname></term>
 358
 359         <listitem>
 360           <para>Configures the <filename>/etc/fstab</filename> logic
 361           at boot. For details, see
 362           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 363
 364         <xi:include href="version-info.xml" xpointer="v186"/>
 365         </listitem>
 366       </varlistentry>
 367
 368       <varlistentry>
 369         <term><varname>root=</varname></term>
 370         <term><varname>rootfstype=</varname></term>
 371         <term><varname>rootflags=</varname></term>
 372         <term><varname>ro</varname></term>
 373         <term><varname>rw</varname></term>
 374
 375         <listitem>
 376           <para>Configures the root file system and its file system type and mount options, as well as
 377           whether it shall be mounted read-only or read-write initially. For details, see
 378           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 379
 380           <para>If <varname>root=</varname> is not set (or set to <literal>gpt-auto</literal>) the automatic
 381           root partition discovery implemented by
 382           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 383           will be in effect. In this case <varname>rootfstype=</varname>, <varname>rootflags=</varname>,
 384           <varname>ro</varname>, <varname>rw</varname> will be interpreted by
 385           <command>systemd-gpt-auto-generator</command>.</para>
 386
 387           <xi:include href="version-info.xml" xpointer="v215"/>
 388         </listitem>
 389       </varlistentry>
 390
 391       <varlistentry>
 392         <term><varname>mount.usr=</varname></term>
 393         <term><varname>mount.usrfstype=</varname></term>
 394         <term><varname>mount.usrflags=</varname></term>
 395
 396         <listitem>
 397           <para>Configures the /usr file system (if required) and
 398           its file system type and mount options. For details, see
 399           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 400
 401           <xi:include href="version-info.xml" xpointer="v235"/>
 402         </listitem>
 403       </varlistentry>
 404
 405       <varlistentry>
 406         <term><varname>veritytab=</varname></term>
 407         <term><varname>rd.veritytab=</varname></term>
 408         <term><varname>roothash=</varname></term>
 409         <term><varname>systemd.verity=</varname></term>
 410         <term><varname>rd.systemd.verity=</varname></term>
 411         <term><varname>systemd.verity_root_data=</varname></term>
 412         <term><varname>systemd.verity_root_hash=</varname></term>
 413         <term><varname>systemd.verity.root_options=</varname></term>
 414         <term><varname>usrhash=</varname></term>
 415         <term><varname>systemd.verity_usr_data=</varname></term>
 416         <term><varname>systemd.verity_usr_hash=</varname></term>
 417         <term><varname>systemd.verity_usr_options=</varname></term>
 418         <listitem>
 419           <para>Configures the integrity protection root hash for the root and <filename>/usr</filename> file systems, and other related
 420           parameters. For details, see
 421           <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 422
 423         <xi:include href="version-info.xml" xpointer="v233"/>
 424         </listitem>
 425       </varlistentry>
 426
 427       <varlistentry>
 428         <term><varname>systemd.getty_auto=</varname></term>
 429
 430         <listitem>
 431           <para>Configures whether the <filename>serial-getty@.service</filename> will run.
 432           For details, see
 433           <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 434
 435         <xi:include href="version-info.xml" xpointer="v250"/>
 436         </listitem>
 437       </varlistentry>
 438
 439       <varlistentry>
 440         <term><varname>systemd.gpt_auto=</varname></term>
 441         <term><varname>rd.systemd.gpt_auto=</varname></term>
 442
 443         <listitem>
 444           <para>Configures whether GPT-based partition auto-discovery shall be attempted. For details, see
 445           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 446
 447           <xi:include href="version-info.xml" xpointer="v215"/>
 448         </listitem>
 449       </varlistentry>
 450
 451       <varlistentry>
 452         <term><varname>systemd.image_policy=</varname></term>
 453         <term><varname>rd.systemd.image_policy=</varname></term>
 454
 455         <listitem><para>When GPT-based partition auto-discovery is used, configures the image dissection
 456         policy string to apply, as per
 457         <citerefentry><refentrytitle>systemd.image-policy</refentrytitle><manvolnum>7</manvolnum></citerefentry>. For
 458         details see
 459         <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 460
 461         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 462       </varlistentry>
 463
 464       <varlistentry>
 465         <term><varname>systemd.default_timeout_start_sec=</varname></term>
 466
 467         <listitem>
 468           <para>Overrides the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at
 469           boot. For details, see
 470           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 471
 472         <xi:include href="version-info.xml" xpointer="v230"/>
 473         </listitem>
 474       </varlistentry>
 475
 476       <varlistentry>
 477         <term><varname>systemd.default_device_timeout_sec=</varname></term>
 478
 479         <listitem>
 480           <para>Overrides the default device timeout <varname>DefaultDeviceTimeoutSec=</varname> at boot. For
 481           details, see
 482           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 483
 484         <xi:include href="version-info.xml" xpointer="v254"/>
 485         </listitem>
 486       </varlistentry>
 487
 488       <varlistentry>
 489         <term><varname>systemd.watchdog_device=</varname></term>
 490
 491         <listitem>
 492           <para>Overrides the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
 493           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 494
 495         <xi:include href="version-info.xml" xpointer="v236"/>
 496         </listitem>
 497       </varlistentry>
 498
 499       <varlistentry>
 500         <term><varname>systemd.watchdog_sec=</varname></term>
 501
 502         <listitem>
 503           <para>Overrides the watchdog timeout settings otherwise configured with
 504           <varname>RuntimeWatchdog=</varname>, <varname>RebootWatchdog=</varname> and
 505           <varname>KExecWatchdogSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 506           implicitly assumed time unit) or the special strings <literal>off</literal> or
 507           <literal>default</literal>. For details, see
 508           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 509
 510           <xi:include href="version-info.xml" xpointer="v250"/>
 511         </listitem>
 512       </varlistentry>
 513
 514       <varlistentry>
 515         <term><varname>systemd.watchdog_pre_sec=</varname></term>
 516
 517         <listitem>
 518           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 519           <varname>RuntimeWatchdogPreSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 520           implicitly assumed time unit) or the special strings <literal>off</literal> or
 521           <literal>default</literal>. For details, see
 522           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 523
 524           <xi:include href="version-info.xml" xpointer="v251"/>
 525         </listitem>
 526       </varlistentry>
 527
 528       <varlistentry>
 529         <term><varname>systemd.watchdog_pretimeout_governor=</varname></term>
 530
 531         <listitem>
 532           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 533           <varname>RuntimeWatchdogPreGovernor=</varname>. Takes a string value. For details, see
 534           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 535
 536           <xi:include href="version-info.xml" xpointer="v251"/>
 537         </listitem>
 538       </varlistentry>
 539
 540       <varlistentry>
 541         <term><varname>systemd.cpu_affinity=</varname></term>
 542
 543         <listitem>
 544           <para>Overrides the CPU affinity mask for the service manager and the default for all child
 545           processes it forks. This takes precedence over <varname>CPUAffinity=</varname>, see
 546           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 547           for details.</para>
 548
 549           <xi:include href="version-info.xml" xpointer="v245"/>
 550         </listitem>
 551       </varlistentry>
 552
 553       <varlistentry>
 554         <term><varname>modules_load=</varname></term>
 555         <term><varname>rd.modules_load=</varname></term>
 556
 557         <listitem>
 558           <para>Load a specific kernel module early at boot. For
 559           details, see
 560           <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 561
 562           <xi:include href="version-info.xml" xpointer="v187"/>
 563         </listitem>
 564       </varlistentry>
 565
 566       <varlistentry>
 567         <term><varname>nameserver=</varname></term>
 568         <term><varname>domain=</varname></term>
 569
 570         <listitem><para>Configures DNS server information and search domains, see
 571         <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 572         for details.</para>
 573
 574         <xi:include href="version-info.xml" xpointer="v253"/></listitem>
 575       </varlistentry>
 576
 577       <varlistentry>
 578         <term><varname>resume=</varname></term>
 579         <term><varname>resumeflags=</varname></term>
 580
 581         <listitem>
 582           <para>Enables resume from hibernation using the specified
 583           device and mount options. All
 584           <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-like
 585           paths are supported. For details, see
 586           <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 587
 588           <xi:include href="version-info.xml" xpointer="v217"/>
 589         </listitem>
 590       </varlistentry>
 591
 592       <varlistentry>
 593         <term><varname>systemd.firstboot=</varname></term>
 594
 595         <listitem><para>Takes a boolean argument, defaults to on. If off,
 596         <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 597         and
 598         <citerefentry><refentrytitle>systemd-homed-firstboot.service</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 599         will not query the user for basic system settings, even if the system boots up for the first time and
 600         the relevant settings are not initialized yet. Not to be confused with
 601         <varname>systemd.condition-first-boot=</varname> (see below), which overrides the result of the
 602         <varname>ConditionFirstBoot=</varname> unit file condition, and thus controls more than just
 603         <filename>systemd-firstboot.service</filename> behaviour.</para>
 604
 605         <xi:include href="version-info.xml" xpointer="v233"/></listitem>
 606       </varlistentry>
 607
 608       <varlistentry>
 609         <term><varname>systemd.condition-needs-update=</varname></term>
 610
 611         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 612         <varname>ConditionNeedsUpdate=</varname> unit condition checks. See
 613         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 614         details.</para>
 615
 616         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 617       </varlistentry>
 618
 619       <varlistentry>
 620         <term><varname>systemd.condition-first-boot=</varname></term>
 621
 622         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 623         <varname>ConditionFirstBoot=</varname> unit condition checks. See
 624         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 625         details. Not to be confused with <varname>systemd.firstboot=</varname> which only controls behaviour
 626         of the <filename>systemd-firstboot.service</filename> system service but has no effect on the
 627         condition check (see above).</para>
 628
 629         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 630       </varlistentry>
 631
 632       <varlistentry>
 633         <term><varname>systemd.clock-usec=</varname></term>
 634
 635         <listitem><para>Takes a decimal, numeric timestamp in μs since January 1st 1970, 00:00am, to set the
 636         system clock to. The system time is set to the specified timestamp early during boot. It is not
 637         propagated to the hardware clock (RTC).</para>
 638
 639         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 640       </varlistentry>
 641
 642       <varlistentry>
 643         <term><varname>systemd.random-seed=</varname></term>
 644
 645         <listitem><para>Takes a base64 encoded random seed value to credit with full entropy to the kernel's
 646         random pool during early service manager initialization. This option is useful in testing
 647         environments where delays due to random pool initialization in entropy starved virtual machines shall
 648         be avoided.</para>
 649
 650         <para>Note that if this option is used the seed is accessible to unprivileged programs from
 651         <filename>/proc/cmdline</filename>. This option is hence a security risk when used outside of test
 652         systems, since the (possibly) only seed used for initialization of the kernel's entropy pool might be
 653         easily acquired by unprivileged programs.</para>
 654
 655         <para>It is recommended to pass 512 bytes of randomized data (as that matches the Linux kernel pool
 656         size), which may be generated with a command like the following:</para>
 657
 658         <programlisting>dd if=/dev/urandom bs=512 count=1 status=none | base64 -w 0</programlisting>
 659
 660         <para>Again: do not use this option outside of testing environments, it's a security risk elsewhere,
 661         as secret key material derived from the entropy pool can possibly be reconstructed by unprivileged
 662         programs.</para>
 663
 664         <xi:include href="version-info.xml" xpointer="v246"/>
 665         </listitem>
 666       </varlistentry>
 667
 668       <varlistentry>
 669         <term><varname>systemd.hostname=</varname></term>
 670
 671         <listitem><para>Accepts a hostname to set during early boot. If specified takes precedence over what
 672         is set in <filename>/etc/hostname</filename>. Note that this does not bar later runtime changes to
 673         the hostname, it simply controls the initial hostname set during early boot.</para>
 674
 675         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 676       </varlistentry>
 677
 678       <varlistentry>
 679         <term><varname>systemd.tty.term.<replaceable>tty</replaceable>=</varname></term>
 680         <term><varname>systemd.tty.rows.<replaceable>tty</replaceable>=</varname></term>
 681         <term><varname>systemd.tty.columns.<replaceable>tty</replaceable>=</varname></term>
 682
 683         <listitem><para>These arguments allow configuring default values for <varname>$TERM</varname>,
 684         <varname>TTYRows=</varname>, and <varname>TTYColumns=</varname> for tty
 685         <replaceable>tty</replaceable>. Additionally, <varname>systemd.tty.term.console</varname> will
 686         configure the <varname>$TERM</varname> value used by <command>systemd</command> if not set explicitly
 687         using <varname>TERM</varname> on the kernel command line. The tty name should be specified without
 688         the <filename>/dev/</filename> prefix (e.g. <literal>systemd.tty.rows.ttyS0=80</literal>).
 689         </para>
 690
 691         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 692       </varlistentry>
 693     </variablelist>
 694   </refsect1>
 695
 696   <refsect1>
 697       <title>History</title>
 698
 699       <variablelist>
 700         <varlistentry>
 701           <term>systemd 252</term>
 702           <listitem><para>Kernel command-line arguments <varname>systemd.unified_cgroup_hierarchy</varname>
 703           and <varname>systemd.legacy_systemd_cgroup_controller</varname> were deprecated. Please switch to
 704           the unified cgroup hierarchy.</para>
 705
 706           <xi:include href="version-info.xml" xpointer="v252"/></listitem>
 707         </varlistentry>
 708       </variablelist>
 709   </refsect1>
 710
 711   <refsect1>
 712       <title>See Also</title>
 713       <para>
 714         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 715         <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 716         <citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 717         <citerefentry><refentrytitle>systemd.system-credentials</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 718         <citerefentry><refentrytitle>smbios-type-11</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 719         <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 720         <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 721         <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 722         <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 723         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 724         <citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 725         <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 726         <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 727         <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 728         <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 729         <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 730         <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 731         <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 732         <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 733         <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 734         <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 735         <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 736         <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 737         <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 738         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 739       </para>
 740   </refsect1>
 741
 742 </refentry>