man/kernel-command-line.xml

   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/4.5/docbookx.dtd">
   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.ssh_auto=</varname></term>
 143         <term><varname>systemd.ssh_listen=</varname></term>
 144         <listitem>
 145           <para>These parameters are interpreted by
 146           <citerefentry><refentrytitle>systemd-ssh-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 147           and may be used to control SSH sockets the system shall be reachable on.</para>
 148
 149           <xi:include href="version-info.xml" xpointer="v256"/>
 150         </listitem>
 151       </varlistentry>
 152
 153       <varlistentry>
 154         <term><varname>systemd.volatile=</varname></term>
 155         <listitem>
 156           <para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
 157           the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
 158           directory and <filename>/var/</filename> are mounted as specified on the kernel command line or
 159           <filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
 160           this case the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
 161           <filename>/usr/</filename> is mounted from the file system configured as root device, in read-only mode. This
 162           enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
 163           configuration and no stored state in effect, as <filename>/etc/</filename> and <filename>/var/</filename> (as
 164           well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
 165           setting is set to <literal>state</literal> the root file system is mounted read-only, however
 166           <filename>/var/</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
 167           system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. If
 168           this setting is set to <literal>overlay</literal> the root file system is set up as
 169           <literal>overlayfs</literal> mount combining the read-only root directory with a writable
 170           <literal>tmpfs</literal>, so that no modifications are made to disk, but the file system may be modified
 171           nonetheless with all changes being lost at reboot. For details, see
 172           <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 173           and
 174           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 175
 176           <xi:include href="version-info.xml" xpointer="v233"/>
 177         </listitem>
 178       </varlistentry>
 179
 180       <varlistentry>
 181         <term><varname>quiet</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="v186"/>
 189         </listitem>
 190       </varlistentry>
 191
 192       <varlistentry>
 193         <term><varname>debug</varname></term>
 194         <listitem>
 195           <para>Parameter understood by both the kernel and the system
 196           and service manager to control console log verbosity. For
 197           details, see
 198           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 199
 200           <xi:include href="version-info.xml" xpointer="v205"/>
 201         </listitem>
 202       </varlistentry>
 203
 204       <varlistentry>
 205         <term><varname>-b</varname></term>
 206         <term><varname>rd.emergency</varname></term>
 207         <term><varname>emergency</varname></term>
 208         <term><varname>rd.rescue</varname></term>
 209         <term><varname>rescue</varname></term>
 210         <term><varname>single</varname></term>
 211         <term><varname>s</varname></term>
 212         <term><varname>S</varname></term>
 213         <term><varname>1</varname></term>
 214         <term><varname>2</varname></term>
 215         <term><varname>3</varname></term>
 216         <term><varname>4</varname></term>
 217         <term><varname>5</varname></term>
 218         <listitem>
 219           <para>Parameters understood by the system and service
 220           manager, as compatibility and convenience options. For details, see
 221           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 222
 223           <xi:include href="version-info.xml" xpointer="v186"/>
 224         </listitem>
 225       </varlistentry>
 226
 227       <varlistentry>
 228         <term><varname>locale.LANG=</varname></term>
 229         <term><varname>locale.LANGUAGE=</varname></term>
 230         <term><varname>locale.LC_CTYPE=</varname></term>
 231         <term><varname>locale.LC_NUMERIC=</varname></term>
 232         <term><varname>locale.LC_TIME=</varname></term>
 233         <term><varname>locale.LC_COLLATE=</varname></term>
 234         <term><varname>locale.LC_MONETARY=</varname></term>
 235         <term><varname>locale.LC_MESSAGES=</varname></term>
 236         <term><varname>locale.LC_PAPER=</varname></term>
 237         <term><varname>locale.LC_NAME=</varname></term>
 238         <term><varname>locale.LC_ADDRESS=</varname></term>
 239         <term><varname>locale.LC_TELEPHONE=</varname></term>
 240         <term><varname>locale.LC_MEASUREMENT=</varname></term>
 241         <term><varname>locale.LC_IDENTIFICATION=</varname></term>
 242         <listitem>
 243           <para>Parameters understood by the system and service
 244           manager to control locale and language settings. For
 245           details, see
 246           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 247
 248           <xi:include href="version-info.xml" xpointer="v186"/>
 249         </listitem>
 250       </varlistentry>
 251
 252       <varlistentry>
 253         <term><varname>fsck.mode=</varname></term>
 254         <term><varname>fsck.repair=</varname></term>
 255
 256         <listitem>
 257           <para>Parameters understood by the file system checker
 258           services. For details, see
 259           <citerefentry><refentrytitle>systemd-fsck@.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>quotacheck.mode=</varname></term>
 267
 268         <listitem>
 269           <para>Parameter understood by the file quota checker
 270           service. For details, see
 271           <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 272
 273           <xi:include href="version-info.xml" xpointer="v186"/>
 274         </listitem>
 275       </varlistentry>
 276
 277       <varlistentry>
 278         <term><varname>systemd.journald.forward_to_syslog=</varname></term>
 279         <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
 280         <term><varname>systemd.journald.forward_to_console=</varname></term>
 281         <term><varname>systemd.journald.forward_to_wall=</varname></term>
 282
 283         <listitem>
 284           <para>Parameters understood by the journal service. For
 285           details, see
 286           <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 287
 288           <xi:include href="version-info.xml" xpointer="v186"/>
 289         </listitem>
 290       </varlistentry>
 291
 292       <varlistentry>
 293         <term><varname>vconsole.keymap=</varname></term>
 294         <term><varname>vconsole.keymap_toggle=</varname></term>
 295         <term><varname>vconsole.font=</varname></term>
 296         <term><varname>vconsole.font_map=</varname></term>
 297         <term><varname>vconsole.font_unimap=</varname></term>
 298
 299         <listitem>
 300           <para>Parameters understood by the virtual console setup logic. For details, see
 301           <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 302
 303           <xi:include href="version-info.xml" xpointer="v186"/>
 304         </listitem>
 305       </varlistentry>
 306
 307       <varlistentry>
 308         <term><varname>udev.log_level=</varname></term>
 309         <term><varname>rd.udev.log_level=</varname></term>
 310         <term><varname>udev.children_max=</varname></term>
 311         <term><varname>rd.udev.children_max=</varname></term>
 312         <term><varname>udev.exec_delay=</varname></term>
 313         <term><varname>rd.udev.exec_delay=</varname></term>
 314         <term><varname>udev.event_timeout=</varname></term>
 315         <term><varname>rd.udev.event_timeout=</varname></term>
 316         <term><varname>udev.timeout_signal=</varname></term>
 317         <term><varname>rd.udev.timeout_signal=</varname></term>
 318         <term><varname>udev.blockdev_read_only</varname></term>
 319         <term><varname>rd.udev.blockdev_read_only</varname></term>
 320         <term><varname>net.ifnames=</varname></term>
 321         <term><varname>net.naming-scheme=</varname></term>
 322
 323         <listitem>
 324           <para>Parameters understood by the device event managing
 325           daemon. For details, see
 326           <citerefentry><refentrytitle>systemd-udevd.service</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>plymouth.enable=</varname></term>
 334
 335         <listitem>
 336           <para>May be used to disable the Plymouth boot splash. For
 337           details, see
 338           <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 339
 340           <xi:include href="version-info.xml" xpointer="v186"/>
 341         </listitem>
 342       </varlistentry>
 343
 344       <varlistentry>
 345         <term><varname>luks=</varname></term>
 346         <term><varname>rd.luks=</varname></term>
 347         <term><varname>luks.crypttab=</varname></term>
 348         <term><varname>rd.luks.crypttab=</varname></term>
 349         <term><varname>luks.name=</varname></term>
 350         <term><varname>rd.luks.name=</varname></term>
 351         <term><varname>luks.uuid=</varname></term>
 352         <term><varname>rd.luks.uuid=</varname></term>
 353         <term><varname>luks.options=</varname></term>
 354         <term><varname>rd.luks.options=</varname></term>
 355         <term><varname>luks.key=</varname></term>
 356         <term><varname>rd.luks.key=</varname></term>
 357
 358         <listitem>
 359           <para>Configures the LUKS full-disk encryption logic at
 360           boot. For details, see
 361           <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 362
 363           <xi:include href="version-info.xml" xpointer="v186"/>
 364         </listitem>
 365       </varlistentry>
 366
 367       <varlistentry>
 368         <term><varname>fstab=</varname></term>
 369         <term><varname>rd.fstab=</varname></term>
 370
 371         <listitem>
 372           <para>Configures the <filename>/etc/fstab</filename> logic
 373           at boot. For details, see
 374           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 375
 376         <xi:include href="version-info.xml" xpointer="v186"/>
 377         </listitem>
 378       </varlistentry>
 379
 380       <varlistentry>
 381         <term><varname>root=</varname></term>
 382         <term><varname>rootfstype=</varname></term>
 383         <term><varname>rootflags=</varname></term>
 384         <term><varname>ro</varname></term>
 385         <term><varname>rw</varname></term>
 386
 387         <listitem>
 388           <para>Configures the root file system and its file system type and mount options, as well as
 389           whether it shall be mounted read-only or read-write initially. For details, see
 390           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 391
 392           <para>If <varname>root=</varname> is not set (or set to <literal>gpt-auto</literal>) the automatic
 393           root partition discovery implemented by
 394           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 395           will be in effect. In this case <varname>rootfstype=</varname>, <varname>rootflags=</varname>,
 396           <varname>ro</varname>, <varname>rw</varname> will be interpreted by
 397           <command>systemd-gpt-auto-generator</command>.</para>
 398
 399           <xi:include href="version-info.xml" xpointer="v215"/>
 400         </listitem>
 401       </varlistentry>
 402
 403       <varlistentry>
 404         <term><varname>mount.usr=</varname></term>
 405         <term><varname>mount.usrfstype=</varname></term>
 406         <term><varname>mount.usrflags=</varname></term>
 407
 408         <listitem>
 409           <para>Configures the /usr file system (if required) and
 410           its file system type and mount options. For details, see
 411           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 412
 413           <xi:include href="version-info.xml" xpointer="v235"/>
 414         </listitem>
 415       </varlistentry>
 416
 417       <varlistentry>
 418         <term><varname>veritytab=</varname></term>
 419         <term><varname>rd.veritytab=</varname></term>
 420         <term><varname>roothash=</varname></term>
 421         <term><varname>systemd.verity=</varname></term>
 422         <term><varname>rd.systemd.verity=</varname></term>
 423         <term><varname>systemd.verity_root_data=</varname></term>
 424         <term><varname>systemd.verity_root_hash=</varname></term>
 425         <term><varname>systemd.verity.root_options=</varname></term>
 426         <term><varname>usrhash=</varname></term>
 427         <term><varname>systemd.verity_usr_data=</varname></term>
 428         <term><varname>systemd.verity_usr_hash=</varname></term>
 429         <term><varname>systemd.verity_usr_options=</varname></term>
 430         <listitem>
 431           <para>Configures the integrity protection root hash for the root and <filename>/usr</filename> file systems, and other related
 432           parameters. For details, see
 433           <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 434
 435         <xi:include href="version-info.xml" xpointer="v233"/>
 436         </listitem>
 437       </varlistentry>
 438
 439       <varlistentry>
 440         <term><varname>systemd.getty_auto=</varname></term>
 441
 442         <listitem>
 443           <para>Configures whether the <filename>serial-getty@.service</filename> will run.
 444           For details, see
 445           <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 446
 447         <xi:include href="version-info.xml" xpointer="v250"/>
 448         </listitem>
 449       </varlistentry>
 450
 451       <varlistentry>
 452         <term><varname>systemd.gpt_auto=</varname></term>
 453         <term><varname>rd.systemd.gpt_auto=</varname></term>
 454
 455         <listitem>
 456           <para>Configures whether GPT-based partition auto-discovery shall be attempted. For details, see
 457           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 458
 459           <xi:include href="version-info.xml" xpointer="v215"/>
 460         </listitem>
 461       </varlistentry>
 462
 463       <varlistentry>
 464         <term><varname>systemd.image_policy=</varname></term>
 465         <term><varname>rd.systemd.image_policy=</varname></term>
 466
 467         <listitem><para>When GPT-based partition auto-discovery is used, configures the image dissection
 468         policy string to apply, as per
 469         <citerefentry><refentrytitle>systemd.image-policy</refentrytitle><manvolnum>7</manvolnum></citerefentry>. For
 470         details see
 471         <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 472
 473         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 474       </varlistentry>
 475
 476       <varlistentry>
 477         <term><varname>systemd.default_timeout_start_sec=</varname></term>
 478
 479         <listitem>
 480           <para>Overrides the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at
 481           boot. For details, see
 482           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 483
 484         <xi:include href="version-info.xml" xpointer="v230"/>
 485         </listitem>
 486       </varlistentry>
 487
 488       <varlistentry>
 489         <term><varname>systemd.default_device_timeout_sec=</varname></term>
 490
 491         <listitem>
 492           <para>Overrides the default device timeout <varname>DefaultDeviceTimeoutSec=</varname> at boot. For
 493           details, see
 494           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 495
 496         <xi:include href="version-info.xml" xpointer="v254"/>
 497         </listitem>
 498       </varlistentry>
 499
 500       <varlistentry>
 501         <term><varname>systemd.watchdog_device=</varname></term>
 502
 503         <listitem>
 504           <para>Overrides the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
 505           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 506
 507         <xi:include href="version-info.xml" xpointer="v236"/>
 508         </listitem>
 509       </varlistentry>
 510
 511       <varlistentry>
 512         <term><varname>systemd.watchdog_sec=</varname></term>
 513
 514         <listitem>
 515           <para>Overrides the watchdog timeout settings otherwise configured with
 516           <varname>RuntimeWatchdog=</varname>, <varname>RebootWatchdog=</varname> and
 517           <varname>KExecWatchdogSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 518           implicitly assumed time unit) or the special strings <literal>off</literal> or
 519           <literal>default</literal>. For details, see
 520           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 521
 522           <xi:include href="version-info.xml" xpointer="v250"/>
 523         </listitem>
 524       </varlistentry>
 525
 526       <varlistentry>
 527         <term><varname>systemd.watchdog_pre_sec=</varname></term>
 528
 529         <listitem>
 530           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 531           <varname>RuntimeWatchdogPreSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 532           implicitly assumed time unit) or the special strings <literal>off</literal> or
 533           <literal>default</literal>. 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.watchdog_pretimeout_governor=</varname></term>
 542
 543         <listitem>
 544           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 545           <varname>RuntimeWatchdogPreGovernor=</varname>. Takes a string value. For details, see
 546           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 547
 548           <xi:include href="version-info.xml" xpointer="v251"/>
 549         </listitem>
 550       </varlistentry>
 551
 552       <varlistentry>
 553         <term><varname>systemd.cpu_affinity=</varname></term>
 554
 555         <listitem>
 556           <para>Overrides the CPU affinity mask for the service manager and the default for all child
 557           processes it forks. This takes precedence over <varname>CPUAffinity=</varname>, see
 558           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 559           for details.</para>
 560
 561           <xi:include href="version-info.xml" xpointer="v245"/>
 562         </listitem>
 563       </varlistentry>
 564
 565       <varlistentry>
 566         <term><varname>modules_load=</varname></term>
 567         <term><varname>rd.modules_load=</varname></term>
 568
 569         <listitem>
 570           <para>Load a specific kernel module early at boot. For
 571           details, see
 572           <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 573
 574           <xi:include href="version-info.xml" xpointer="v187"/>
 575         </listitem>
 576       </varlistentry>
 577
 578       <varlistentry>
 579         <term><varname>nameserver=</varname></term>
 580         <term><varname>domain=</varname></term>
 581
 582         <listitem><para>Configures DNS server information and search domains, see
 583         <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 584         for details.</para>
 585
 586         <xi:include href="version-info.xml" xpointer="v253"/></listitem>
 587       </varlistentry>
 588
 589       <varlistentry>
 590         <term><varname>resume=</varname></term>
 591         <term><varname>resumeflags=</varname></term>
 592
 593         <listitem>
 594           <para>Enables resume from hibernation using the specified
 595           device and mount options. All
 596           <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-like
 597           paths are supported. For details, see
 598           <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 599
 600           <xi:include href="version-info.xml" xpointer="v217"/>
 601         </listitem>
 602       </varlistentry>
 603
 604       <varlistentry>
 605         <term><varname>systemd.firstboot=</varname></term>
 606
 607         <listitem><para>Takes a boolean argument, defaults to on. If off,
 608         <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 609         and
 610         <citerefentry><refentrytitle>systemd-homed-firstboot.service</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 611         will not query the user for basic system settings, even if the system boots up for the first time and
 612         the relevant settings are not initialized yet. Not to be confused with
 613         <varname>systemd.condition-first-boot=</varname> (see below), which overrides the result of the
 614         <varname>ConditionFirstBoot=</varname> unit file condition, and thus controls more than just
 615         <filename>systemd-firstboot.service</filename> behaviour.</para>
 616
 617         <xi:include href="version-info.xml" xpointer="v233"/></listitem>
 618       </varlistentry>
 619
 620       <varlistentry>
 621         <term><varname>systemd.condition-needs-update=</varname></term>
 622
 623         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 624         <varname>ConditionNeedsUpdate=</varname> unit condition checks. See
 625         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 626         details.</para>
 627
 628         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 629       </varlistentry>
 630
 631       <varlistentry>
 632         <term><varname>systemd.condition-first-boot=</varname></term>
 633
 634         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 635         <varname>ConditionFirstBoot=</varname> unit condition checks. See
 636         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 637         details. Not to be confused with <varname>systemd.firstboot=</varname> which only controls behaviour
 638         of the <filename>systemd-firstboot.service</filename> system service but has no effect on the
 639         condition check (see above).</para>
 640
 641         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 642       </varlistentry>
 643
 644       <varlistentry>
 645         <term><varname>systemd.clock-usec=</varname></term>
 646
 647         <listitem><para>Takes a decimal, numeric timestamp in μs since January 1st 1970, 00:00am, to set the
 648         system clock to. The system time is set to the specified timestamp early during boot. It is not
 649         propagated to the hardware clock (RTC).</para>
 650
 651         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 652       </varlistentry>
 653
 654       <varlistentry>
 655         <term><varname>systemd.random-seed=</varname></term>
 656
 657         <listitem><para>Takes a base64 encoded random seed value to credit with full entropy to the kernel's
 658         random pool during early service manager initialization. This option is useful in testing
 659         environments where delays due to random pool initialization in entropy starved virtual machines shall
 660         be avoided.</para>
 661
 662         <para>Note that if this option is used the seed is accessible to unprivileged programs from
 663         <filename>/proc/cmdline</filename>. This option is hence a security risk when used outside of test
 664         systems, since the (possibly) only seed used for initialization of the kernel's entropy pool might be
 665         easily acquired by unprivileged programs.</para>
 666
 667         <para>It is recommended to pass 512 bytes of randomized data (as that matches the Linux kernel pool
 668         size), which may be generated with a command like the following:</para>
 669
 670         <programlisting>dd if=/dev/urandom bs=512 count=1 status=none | base64 -w 0</programlisting>
 671
 672         <para>Again: do not use this option outside of testing environments, it's a security risk elsewhere,
 673         as secret key material derived from the entropy pool can possibly be reconstructed by unprivileged
 674         programs.</para>
 675
 676         <xi:include href="version-info.xml" xpointer="v246"/>
 677         </listitem>
 678       </varlistentry>
 679
 680       <varlistentry>
 681         <term><varname>systemd.hostname=</varname></term>
 682
 683         <listitem><para>Accepts a hostname to set during early boot. If specified takes precedence over what
 684         is set in <filename>/etc/hostname</filename>. Note that this does not bar later runtime changes to
 685         the hostname, it simply controls the initial hostname set during early boot.</para>
 686
 687         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 688       </varlistentry>
 689
 690       <varlistentry>
 691         <term><varname>systemd.tty.term.<replaceable>tty</replaceable>=</varname></term>
 692         <term><varname>systemd.tty.rows.<replaceable>tty</replaceable>=</varname></term>
 693         <term><varname>systemd.tty.columns.<replaceable>tty</replaceable>=</varname></term>
 694
 695         <listitem><para>These arguments allow configuring default values for <varname>$TERM</varname>,
 696         <varname>TTYRows=</varname>, and <varname>TTYColumns=</varname> for tty
 697         <replaceable>tty</replaceable>. Additionally, <varname>systemd.tty.term.console</varname> will
 698         configure the <varname>$TERM</varname> value used by <command>systemd</command> if not set explicitly
 699         using <varname>TERM</varname> on the kernel command line. The tty name should be specified without
 700         the <filename>/dev/</filename> prefix (e.g. <literal>systemd.tty.rows.ttyS0=80</literal>).
 701         </para>
 702
 703         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 704       </varlistentry>
 705     </variablelist>
 706   </refsect1>
 707
 708   <refsect1>
 709       <title>History</title>
 710
 711       <variablelist>
 712         <varlistentry>
 713           <term>systemd 252</term>
 714           <listitem><para>Kernel command-line arguments <varname>systemd.unified_cgroup_hierarchy</varname>
 715           and <varname>systemd.legacy_systemd_cgroup_controller</varname> were deprecated. Please switch to
 716           the unified cgroup hierarchy.</para>
 717
 718           <xi:include href="version-info.xml" xpointer="v252"/></listitem>
 719         </varlistentry>
 720       </variablelist>
 721   </refsect1>
 722
 723   <refsect1>
 724       <title>See Also</title>
 725       <para><simplelist type="inline">
 726         <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 727         <member><citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 728         <member><citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 729         <member><citerefentry><refentrytitle>systemd.system-credentials</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 730         <member><citerefentry><refentrytitle>smbios-type-11</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 731         <member><citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 732         <member><citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 733         <member><citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 734         <member><citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 735         <member><citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 736         <member><citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 737         <member><citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 738         <member><citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 739         <member><citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 740         <member><citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 741         <member><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 742         <member><citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 743         <member><citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 744         <member><citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 745         <member><citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 746         <member><citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 747         <member><citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 748         <member><citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 749         <member><citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 750         <member><citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 751       </simplelist></para>
 752   </refsect1>
 753
 754 </refentry>