man/kernel-command-line.xml

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   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 the documentation of the specific initrd
  44     implementation of your installation.</para>
  45   </refsect1>
  46
  47   <refsect1>
  48     <title>Core OS Command Line Arguments</title>
  49
  50     <variablelist class='kernel-commandline-options'>
  51       <varlistentry>
  52         <term><varname>systemd.unit=</varname></term>
  53         <term><varname>rd.systemd.unit=</varname></term>
  54         <term><varname>systemd.dump_core</varname></term>
  55         <term><varname>systemd.crash_chvt</varname></term>
  56         <term><varname>systemd.crash_shell</varname></term>
  57         <term><varname>systemd.crash_reboot</varname></term>
  58         <term><varname>systemd.confirm_spawn</varname></term>
  59         <term><varname>systemd.service_watchdogs</varname></term>
  60         <term><varname>systemd.show_status</varname></term>
  61         <term><varname>systemd.status_unit_format=</varname></term>
  62         <term><varname>systemd.log_target=</varname></term>
  63         <term><varname>systemd.log_level=</varname></term>
  64         <term><varname>systemd.log_location=</varname></term>
  65         <term><varname>systemd.log_color</varname></term>
  66         <term><varname>systemd.log_ratelimit_kmsg</varname></term>
  67         <term><varname>systemd.default_standard_output=</varname></term>
  68         <term><varname>systemd.default_standard_error=</varname></term>
  69         <term><varname>systemd.setenv=</varname></term>
  70         <term><varname>systemd.machine_id=</varname></term>
  71         <term><varname>systemd.set_credential=</varname></term>
  72         <term><varname>systemd.set_credential_binary=</varname></term>
  73         <term><varname>systemd.import_credentials=</varname></term>
  74         <term><varname>systemd.reload_limit_interval_sec=</varname></term>
  75         <term><varname>systemd.reload_limit_burst=</varname></term>
  76         <listitem>
  77           <para>Parameters understood by the system and service
  78           manager to control system behavior. For details, see
  79           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
  80
  81           <xi:include href="version-info.xml" xpointer="v186"/>
  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
  95           <xi:include href="version-info.xml" xpointer="v215"/>
  96         </listitem>
  97       </varlistentry>
  98
  99       <varlistentry>
 100         <term><varname>systemd.run=</varname></term>
 101         <term><varname>systemd.run_success_action=</varname></term>
 102         <term><varname>systemd.run_failure_action=</varname></term>
 103         <listitem>
 104           <para>Additional parameters understood by
 105           <citerefentry><refentrytitle>systemd-run-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, to
 106           run a command line specified on the kernel command line as system service after booting up.</para>
 107
 108           <xi:include href="version-info.xml" xpointer="v240"/>
 109         </listitem>
 110       </varlistentry>
 111
 112       <varlistentry>
 113         <term><varname>systemd.early_core_pattern=</varname></term>
 114         <listitem>
 115           <para>During early boot, the generation of core dump files is disabled until a core dump handler (if any)
 116           takes over. This parameter allows specifying an absolute path where core dump files should be stored until
 117           a handler is installed. The path should be absolute and may contain specifiers, see
 118           <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details.</para>
 119
 120           <xi:include href="version-info.xml" xpointer="v240"/>
 121         </listitem>
 122       </varlistentry>
 123
 124       <varlistentry>
 125         <term><varname>systemd.restore_state=</varname></term>
 126         <listitem>
 127           <para>This parameter is understood by several system tools
 128           to control whether or not they should restore system state
 129           from the previous boot. For details, see
 130           <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 131           and
 132           <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 133           </para>
 134
 135           <xi:include href="version-info.xml" xpointer="v209"/>
 136         </listitem>
 137       </varlistentry>
 138
 139       <varlistentry>
 140         <term><varname>systemd.ssh_auto=</varname></term>
 141         <term><varname>systemd.ssh_listen=</varname></term>
 142         <listitem>
 143           <para>These parameters are interpreted by
 144           <citerefentry><refentrytitle>systemd-ssh-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 145           and may be used to control SSH sockets the system shall be reachable on.</para>
 146
 147           <xi:include href="version-info.xml" xpointer="v256"/>
 148         </listitem>
 149       </varlistentry>
 150
 151       <varlistentry>
 152         <term><varname>systemd.volatile=</varname></term>
 153         <listitem>
 154           <para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
 155           the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
 156           directory and <filename>/var/</filename> are mounted as specified on the kernel command line or
 157           <filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
 158           this case the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
 159           <filename>/usr/</filename> is mounted from the file system configured as root device, in read-only mode. This
 160           enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
 161           configuration and no stored state in effect, as <filename>/etc/</filename> and <filename>/var/</filename> (as
 162           well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
 163           setting is set to <literal>state</literal> the root file system is mounted read-only, however
 164           <filename>/var/</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
 165           system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. If
 166           this setting is set to <literal>overlay</literal> the root file system is set up as
 167           <literal>overlayfs</literal> mount combining the read-only root directory with a writable
 168           <literal>tmpfs</literal>, so that no modifications are made to disk, but the file system may be modified
 169           nonetheless with all changes being lost at reboot. For details, see
 170           <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 171           and
 172           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 173
 174           <xi:include href="version-info.xml" xpointer="v233"/>
 175         </listitem>
 176       </varlistentry>
 177
 178       <varlistentry>
 179         <term><varname>quiet</varname></term>
 180         <listitem>
 181           <para>Parameter understood by both the kernel and the system
 182           and service manager to control console log verbosity. For
 183           details, see
 184           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 185
 186           <xi:include href="version-info.xml" xpointer="v186"/>
 187         </listitem>
 188       </varlistentry>
 189
 190       <varlistentry>
 191         <term><varname>debug</varname></term>
 192         <listitem>
 193           <para>Parameter understood by both the kernel and the system
 194           and service manager to control console log verbosity. For
 195           details, see
 196           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 197
 198           <xi:include href="version-info.xml" xpointer="v205"/>
 199         </listitem>
 200       </varlistentry>
 201
 202       <varlistentry>
 203         <term><varname>-b</varname></term>
 204         <term><varname>rd.emergency</varname></term>
 205         <term><varname>emergency</varname></term>
 206         <term><varname>rd.rescue</varname></term>
 207         <term><varname>rescue</varname></term>
 208         <term><varname>single</varname></term>
 209         <term><varname>s</varname></term>
 210         <term><varname>S</varname></term>
 211         <term><varname>1</varname></term>
 212         <term><varname>2</varname></term>
 213         <term><varname>3</varname></term>
 214         <term><varname>4</varname></term>
 215         <term><varname>5</varname></term>
 216         <listitem>
 217           <para>Parameters understood by the system and service
 218           manager, as compatibility and convenience options. For details, see
 219           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 220
 221           <xi:include href="version-info.xml" xpointer="v186"/>
 222         </listitem>
 223       </varlistentry>
 224
 225       <varlistentry>
 226         <term><varname>locale.LANG=</varname></term>
 227         <term><varname>locale.LANGUAGE=</varname></term>
 228         <term><varname>locale.LC_CTYPE=</varname></term>
 229         <term><varname>locale.LC_NUMERIC=</varname></term>
 230         <term><varname>locale.LC_TIME=</varname></term>
 231         <term><varname>locale.LC_COLLATE=</varname></term>
 232         <term><varname>locale.LC_MONETARY=</varname></term>
 233         <term><varname>locale.LC_MESSAGES=</varname></term>
 234         <term><varname>locale.LC_PAPER=</varname></term>
 235         <term><varname>locale.LC_NAME=</varname></term>
 236         <term><varname>locale.LC_ADDRESS=</varname></term>
 237         <term><varname>locale.LC_TELEPHONE=</varname></term>
 238         <term><varname>locale.LC_MEASUREMENT=</varname></term>
 239         <term><varname>locale.LC_IDENTIFICATION=</varname></term>
 240         <listitem>
 241           <para>Parameters understood by the system and service
 242           manager to control locale and language settings. For
 243           details, see
 244           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 245
 246           <xi:include href="version-info.xml" xpointer="v186"/>
 247         </listitem>
 248       </varlistentry>
 249
 250       <varlistentry>
 251         <term><varname>fsck.mode=</varname></term>
 252         <term><varname>fsck.repair=</varname></term>
 253
 254         <listitem>
 255           <para>Parameters understood by the file system checker
 256           services. For details, see
 257           <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 258
 259           <xi:include href="version-info.xml" xpointer="v186"/>
 260         </listitem>
 261       </varlistentry>
 262
 263       <varlistentry>
 264         <term><varname>quotacheck.mode=</varname></term>
 265
 266         <listitem>
 267           <para>Parameter understood by the file quota checker
 268           service. For details, see
 269           <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 270
 271           <xi:include href="version-info.xml" xpointer="v186"/>
 272         </listitem>
 273       </varlistentry>
 274
 275       <varlistentry>
 276         <term><varname>systemd.journald.forward_to_syslog=</varname></term>
 277         <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
 278         <term><varname>systemd.journald.forward_to_console=</varname></term>
 279         <term><varname>systemd.journald.forward_to_wall=</varname></term>
 280
 281         <listitem>
 282           <para>Parameters understood by the journal service. For
 283           details, see
 284           <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 285
 286           <xi:include href="version-info.xml" xpointer="v186"/>
 287         </listitem>
 288       </varlistentry>
 289
 290       <varlistentry>
 291         <term><varname>vconsole.keymap=</varname></term>
 292         <term><varname>vconsole.keymap_toggle=</varname></term>
 293         <term><varname>vconsole.font=</varname></term>
 294         <term><varname>vconsole.font_map=</varname></term>
 295         <term><varname>vconsole.font_unimap=</varname></term>
 296
 297         <listitem>
 298           <para>Parameters understood by the virtual console setup logic. For details, see
 299           <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 300
 301           <xi:include href="version-info.xml" xpointer="v186"/>
 302         </listitem>
 303       </varlistentry>
 304
 305       <varlistentry>
 306         <term><varname>udev.log_level=</varname></term>
 307         <term><varname>rd.udev.log_level=</varname></term>
 308         <term><varname>udev.children_max=</varname></term>
 309         <term><varname>rd.udev.children_max=</varname></term>
 310         <term><varname>udev.exec_delay=</varname></term>
 311         <term><varname>rd.udev.exec_delay=</varname></term>
 312         <term><varname>udev.event_timeout=</varname></term>
 313         <term><varname>rd.udev.event_timeout=</varname></term>
 314         <term><varname>udev.timeout_signal=</varname></term>
 315         <term><varname>rd.udev.timeout_signal=</varname></term>
 316         <term><varname>udev.blockdev_read_only</varname></term>
 317         <term><varname>rd.udev.blockdev_read_only</varname></term>
 318         <term><varname>net.ifnames=</varname></term>
 319         <term><varname>net.naming-scheme=</varname></term>
 320
 321         <listitem>
 322           <para>Parameters understood by the device event managing
 323           daemon. For details, see
 324           <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 325
 326           <xi:include href="version-info.xml" xpointer="v186"/>
 327         </listitem>
 328       </varlistentry>
 329
 330       <varlistentry>
 331         <term><varname>plymouth.enable=</varname></term>
 332
 333         <listitem>
 334           <para>May be used to disable the Plymouth boot splash. For
 335           details, see
 336           <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 337
 338           <xi:include href="version-info.xml" xpointer="v186"/>
 339         </listitem>
 340       </varlistentry>
 341
 342       <varlistentry>
 343         <term><varname>luks=</varname></term>
 344         <term><varname>rd.luks=</varname></term>
 345         <term><varname>luks.crypttab=</varname></term>
 346         <term><varname>rd.luks.crypttab=</varname></term>
 347         <term><varname>luks.name=</varname></term>
 348         <term><varname>rd.luks.name=</varname></term>
 349         <term><varname>luks.uuid=</varname></term>
 350         <term><varname>rd.luks.uuid=</varname></term>
 351         <term><varname>luks.options=</varname></term>
 352         <term><varname>rd.luks.options=</varname></term>
 353         <term><varname>luks.key=</varname></term>
 354         <term><varname>rd.luks.key=</varname></term>
 355
 356         <listitem>
 357           <para>Configures the LUKS full-disk encryption logic at
 358           boot. For details, see
 359           <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 360
 361           <xi:include href="version-info.xml" xpointer="v186"/>
 362         </listitem>
 363       </varlistentry>
 364
 365       <varlistentry>
 366         <term><varname>fstab=</varname></term>
 367         <term><varname>rd.fstab=</varname></term>
 368
 369         <listitem>
 370           <para>Configures the <filename>/etc/fstab</filename> logic
 371           at boot. For details, see
 372           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 373
 374         <xi:include href="version-info.xml" xpointer="v186"/>
 375         </listitem>
 376       </varlistentry>
 377
 378       <varlistentry>
 379         <term><varname>root=</varname></term>
 380         <term><varname>rootfstype=</varname></term>
 381         <term><varname>rootflags=</varname></term>
 382         <term><varname>ro</varname></term>
 383         <term><varname>rw</varname></term>
 384
 385         <listitem>
 386           <para>Configures the root file system and its file system type and mount options, as well as
 387           whether it shall be mounted read-only or read-write initially. For details, see
 388           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 389
 390           <para>If <varname>root=</varname> is not set (or set to <literal>gpt-auto</literal>) the automatic
 391           root partition discovery implemented by
 392           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 393           will be in effect. In this case <varname>rootfstype=</varname>, <varname>rootflags=</varname>,
 394           <varname>ro</varname>, <varname>rw</varname> will be interpreted by
 395           <command>systemd-gpt-auto-generator</command>.</para>
 396
 397           <xi:include href="version-info.xml" xpointer="v215"/>
 398         </listitem>
 399       </varlistentry>
 400
 401       <varlistentry>
 402         <term><varname>mount.usr=</varname></term>
 403         <term><varname>mount.usrfstype=</varname></term>
 404         <term><varname>mount.usrflags=</varname></term>
 405
 406         <listitem>
 407           <para>Configures the /usr file system (if required) and
 408           its file system type and mount options. For details, see
 409           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 410
 411           <xi:include href="version-info.xml" xpointer="v235"/>
 412         </listitem>
 413       </varlistentry>
 414
 415       <varlistentry>
 416         <term><varname>veritytab=</varname></term>
 417         <term><varname>rd.veritytab=</varname></term>
 418         <term><varname>roothash=</varname></term>
 419         <term><varname>systemd.verity=</varname></term>
 420         <term><varname>rd.systemd.verity=</varname></term>
 421         <term><varname>systemd.verity_root_data=</varname></term>
 422         <term><varname>systemd.verity_root_hash=</varname></term>
 423         <term><varname>systemd.verity.root_options=</varname></term>
 424         <term><varname>usrhash=</varname></term>
 425         <term><varname>systemd.verity_usr_data=</varname></term>
 426         <term><varname>systemd.verity_usr_hash=</varname></term>
 427         <term><varname>systemd.verity_usr_options=</varname></term>
 428         <listitem>
 429           <para>Configures the integrity protection root hash for the root and <filename>/usr</filename> file systems, and other related
 430           parameters. For details, see
 431           <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 432
 433         <xi:include href="version-info.xml" xpointer="v233"/>
 434         </listitem>
 435       </varlistentry>
 436
 437       <varlistentry>
 438         <term><varname>systemd.getty_auto=</varname></term>
 439
 440         <listitem>
 441           <para>Configures whether the <filename>serial-getty@.service</filename> will run.
 442           For details, see
 443           <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 444
 445         <xi:include href="version-info.xml" xpointer="v250"/>
 446         </listitem>
 447       </varlistentry>
 448
 449       <varlistentry>
 450         <term><varname>systemd.gpt_auto=</varname></term>
 451         <term><varname>rd.systemd.gpt_auto=</varname></term>
 452
 453         <listitem>
 454           <para>Configures whether GPT-based partition auto-discovery shall be attempted. For details, see
 455           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 456
 457           <xi:include href="version-info.xml" xpointer="v215"/>
 458         </listitem>
 459       </varlistentry>
 460
 461       <varlistentry>
 462         <term><varname>systemd.image_policy=</varname></term>
 463         <term><varname>rd.systemd.image_policy=</varname></term>
 464
 465         <listitem><para>When GPT-based partition auto-discovery is used, configures the image dissection
 466         policy string to apply, as per
 467         <citerefentry><refentrytitle>systemd.image-policy</refentrytitle><manvolnum>7</manvolnum></citerefentry>. For
 468         details see
 469         <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 470
 471         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 472       </varlistentry>
 473
 474       <varlistentry>
 475         <term><varname>systemd.default_timeout_start_sec=</varname></term>
 476
 477         <listitem>
 478           <para>Overrides the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at
 479           boot. For details, see
 480           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 481
 482         <xi:include href="version-info.xml" xpointer="v230"/>
 483         </listitem>
 484       </varlistentry>
 485
 486       <varlistentry>
 487         <term><varname>systemd.default_device_timeout_sec=</varname></term>
 488
 489         <listitem>
 490           <para>Overrides the default device timeout <varname>DefaultDeviceTimeoutSec=</varname> at boot. For
 491           details, see
 492           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 493
 494         <xi:include href="version-info.xml" xpointer="v254"/>
 495         </listitem>
 496       </varlistentry>
 497
 498       <varlistentry>
 499         <term><varname>systemd.watchdog_device=</varname></term>
 500
 501         <listitem>
 502           <para>Overrides the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
 503           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 504
 505         <xi:include href="version-info.xml" xpointer="v236"/>
 506         </listitem>
 507       </varlistentry>
 508
 509       <varlistentry>
 510         <term><varname>systemd.watchdog_sec=</varname></term>
 511
 512         <listitem>
 513           <para>Overrides the watchdog timeout settings otherwise configured with
 514           <varname>RuntimeWatchdog=</varname>, <varname>RebootWatchdog=</varname> and
 515           <varname>KExecWatchdogSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 516           implicitly assumed time unit) or the special strings <literal>off</literal> or
 517           <literal>default</literal>. For details, see
 518           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 519
 520           <xi:include href="version-info.xml" xpointer="v250"/>
 521         </listitem>
 522       </varlistentry>
 523
 524       <varlistentry>
 525         <term><varname>systemd.watchdog_pre_sec=</varname></term>
 526
 527         <listitem>
 528           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 529           <varname>RuntimeWatchdogPreSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 530           implicitly assumed time unit) or the special strings <literal>off</literal> or
 531           <literal>default</literal>. For details, see
 532           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 533
 534           <xi:include href="version-info.xml" xpointer="v251"/>
 535         </listitem>
 536       </varlistentry>
 537
 538       <varlistentry>
 539         <term><varname>systemd.watchdog_pretimeout_governor=</varname></term>
 540
 541         <listitem>
 542           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 543           <varname>RuntimeWatchdogPreGovernor=</varname>. Takes a string value. For details, see
 544           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 545
 546           <xi:include href="version-info.xml" xpointer="v251"/>
 547         </listitem>
 548       </varlistentry>
 549
 550       <varlistentry>
 551         <term><varname>systemd.cpu_affinity=</varname></term>
 552
 553         <listitem>
 554           <para>Overrides the CPU affinity mask for the service manager and the default for all child
 555           processes it forks. This takes precedence over <varname>CPUAffinity=</varname>, see
 556           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 557           for details.</para>
 558
 559           <xi:include href="version-info.xml" xpointer="v245"/>
 560         </listitem>
 561       </varlistentry>
 562
 563       <varlistentry>
 564         <term><varname>modules_load=</varname></term>
 565         <term><varname>rd.modules_load=</varname></term>
 566
 567         <listitem>
 568           <para>Load a specific kernel module early at boot. For
 569           details, see
 570           <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 571
 572           <xi:include href="version-info.xml" xpointer="v187"/>
 573         </listitem>
 574       </varlistentry>
 575
 576       <varlistentry>
 577         <term><varname>nameserver=</varname></term>
 578         <term><varname>domain=</varname></term>
 579
 580         <listitem><para>Configures DNS server information and search domains, see
 581         <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 582         for details.</para>
 583
 584         <xi:include href="version-info.xml" xpointer="v253"/></listitem>
 585       </varlistentry>
 586
 587       <varlistentry>
 588         <term><varname>resume=</varname></term>
 589         <term><varname>resumeflags=</varname></term>
 590
 591         <listitem>
 592           <para>Enables resume from hibernation using the specified
 593           device and mount options. All
 594           <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-like
 595           paths are supported. For details, see
 596           <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 597
 598           <xi:include href="version-info.xml" xpointer="v217"/>
 599         </listitem>
 600       </varlistentry>
 601
 602       <varlistentry>
 603         <term><varname>systemd.firstboot=</varname></term>
 604
 605         <listitem><para>Takes a boolean argument, defaults to on. If off,
 606         <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 607         and
 608         <citerefentry><refentrytitle>systemd-homed-firstboot.service</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 609         will not query the user for basic system settings, even if the system boots up for the first time and
 610         the relevant settings are not initialized yet. Not to be confused with
 611         <varname>systemd.condition-first-boot=</varname> (see below), which overrides the result of the
 612         <varname>ConditionFirstBoot=</varname> unit file condition, and thus controls more than just
 613         <filename>systemd-firstboot.service</filename> behaviour.</para>
 614
 615         <xi:include href="version-info.xml" xpointer="v233"/></listitem>
 616       </varlistentry>
 617
 618       <varlistentry>
 619         <term><varname>systemd.condition-needs-update=</varname></term>
 620
 621         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 622         <varname>ConditionNeedsUpdate=</varname> unit condition checks. See
 623         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 624         details.</para>
 625
 626         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 627       </varlistentry>
 628
 629       <varlistentry>
 630         <term><varname>systemd.condition-first-boot=</varname></term>
 631
 632         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 633         <varname>ConditionFirstBoot=</varname> unit condition checks. See
 634         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 635         details. Not to be confused with <varname>systemd.firstboot=</varname> which only controls behaviour
 636         of the <filename>systemd-firstboot.service</filename> system service but has no effect on the
 637         condition check (see above).</para>
 638
 639         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 640       </varlistentry>
 641
 642       <varlistentry>
 643         <term><varname>systemd.clock-usec=</varname></term>
 644
 645         <listitem><para>Takes a decimal, numeric timestamp in μs since January 1st 1970, 00:00am, to set the
 646         system clock to. The system time is set to the specified timestamp early during boot. It is not
 647         propagated to the hardware clock (RTC).</para>
 648
 649         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 650       </varlistentry>
 651
 652       <varlistentry>
 653         <term><varname>systemd.random-seed=</varname></term>
 654
 655         <listitem><para>Takes a base64 encoded random seed value to credit with full entropy to the kernel's
 656         random pool during early service manager initialization. This option is useful in testing
 657         environments where delays due to random pool initialization in entropy starved virtual machines shall
 658         be avoided.</para>
 659
 660         <para>Note that if this option is used the seed is accessible to unprivileged programs from
 661         <filename>/proc/cmdline</filename>. This option is hence a security risk when used outside of test
 662         systems, since the (possibly) only seed used for initialization of the kernel's entropy pool might be
 663         easily acquired by unprivileged programs.</para>
 664
 665         <para>It is recommended to pass 512 bytes of randomized data (as that matches the Linux kernel pool
 666         size), which may be generated with a command like the following:</para>
 667
 668         <programlisting>dd if=/dev/urandom bs=512 count=1 status=none | base64 -w 0</programlisting>
 669
 670         <para>Again: do not use this option outside of testing environments, it's a security risk elsewhere,
 671         as secret key material derived from the entropy pool can possibly be reconstructed by unprivileged
 672         programs.</para>
 673
 674         <xi:include href="version-info.xml" xpointer="v246"/>
 675         </listitem>
 676       </varlistentry>
 677
 678       <varlistentry>
 679         <term><varname>systemd.hostname=</varname></term>
 680
 681         <listitem><para>Accepts a hostname to set during early boot. If specified takes precedence over what
 682         is set in <filename>/etc/hostname</filename>. Note that this does not bar later runtime changes to
 683         the hostname, it simply controls the initial hostname set during early boot.</para>
 684
 685         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 686       </varlistentry>
 687
 688       <varlistentry>
 689         <term><varname>systemd.tty.term.<replaceable>tty</replaceable>=</varname></term>
 690         <term><varname>systemd.tty.rows.<replaceable>tty</replaceable>=</varname></term>
 691         <term><varname>systemd.tty.columns.<replaceable>tty</replaceable>=</varname></term>
 692
 693         <listitem><para>These arguments allow configuring default values for <varname>$TERM</varname>,
 694         <varname>TTYRows=</varname>, and <varname>TTYColumns=</varname> for tty
 695         <replaceable>tty</replaceable>. Additionally, <varname>systemd.tty.term.console</varname> will
 696         configure the <varname>$TERM</varname> value used by <command>systemd</command> if not set explicitly
 697         using <varname>TERM</varname> on the kernel command line. The tty name should be specified without
 698         the <filename>/dev/</filename> prefix (e.g. <literal>systemd.tty.rows.ttyS0=80</literal>).
 699         </para>
 700
 701         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 702       </varlistentry>
 703     </variablelist>
 704   </refsect1>
 705
 706   <refsect1>
 707       <title>History</title>
 708
 709       <variablelist>
 710         <varlistentry>
 711           <term>systemd 252</term>
 712           <listitem><para>Kernel command-line arguments <varname>systemd.unified_cgroup_hierarchy</varname>
 713           and <varname>systemd.legacy_systemd_cgroup_controller</varname> were deprecated. Please switch to
 714           the unified cgroup hierarchy.</para>
 715
 716           <xi:include href="version-info.xml" xpointer="v252"/></listitem>
 717         </varlistentry>
 718       </variablelist>
 719   </refsect1>
 720
 721   <refsect1>
 722       <title>See Also</title>
 723       <para><simplelist type="inline">
 724         <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 725         <member><citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 726         <member><citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 727         <member><citerefentry><refentrytitle>systemd.system-credentials</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 728         <member><citerefentry><refentrytitle>smbios-type-11</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 729         <member><citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 730         <member><citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 731         <member><citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 732         <member><citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 733         <member><citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 734         <member><citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 735         <member><citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 736         <member><citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 737         <member><citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 738         <member><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 739         <member><citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 740         <member><citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 741         <member><citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 742         <member><citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 743         <member><citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 744         <member><citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 745         <member><citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 746         <member><citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 747         <member><citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 748       </simplelist></para>
 749   </refsect1>
 750
 751 </refentry>