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 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_action=</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         <term><varname>systemd.default_debug_tty=</varname></term>
  90         <listitem>
  91           <para>Additional parameters understood by
  92           <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  93           to mask or start specific units at boot, or invoke a debug
  94           shell on tty9.</para>
  95
  96           <xi:include href="version-info.xml" xpointer="v215"/>
  97         </listitem>
  98       </varlistentry>
  99
 100       <varlistentry>
 101         <term><varname>systemd.run=</varname></term>
 102         <term><varname>systemd.run_success_action=</varname></term>
 103         <term><varname>systemd.run_failure_action=</varname></term>
 104         <listitem>
 105           <para>Additional parameters understood by
 106           <citerefentry><refentrytitle>systemd-run-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, to
 107           run a command line specified on the kernel command line as system service after booting up.</para>
 108
 109           <xi:include href="version-info.xml" xpointer="v240"/>
 110         </listitem>
 111       </varlistentry>
 112
 113       <varlistentry>
 114         <term><varname>systemd.early_core_pattern=</varname></term>
 115         <listitem>
 116           <para>During early boot, the generation of core dump files is disabled until a core dump handler (if any)
 117           takes over. This parameter allows specifying an absolute path where core dump files should be stored until
 118           a handler is installed. The path should be absolute and may contain specifiers, see
 119           <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details.</para>
 120
 121           <xi:include href="version-info.xml" xpointer="v240"/>
 122         </listitem>
 123       </varlistentry>
 124
 125       <varlistentry>
 126         <term><varname>systemd.restore_state=</varname></term>
 127         <listitem>
 128           <para>This parameter is understood by several system tools
 129           to control whether or not they should restore system state
 130           from the previous boot. For details, see
 131           <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 132           and
 133           <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 134           </para>
 135
 136           <xi:include href="version-info.xml" xpointer="v209"/>
 137         </listitem>
 138       </varlistentry>
 139
 140       <varlistentry>
 141         <term><varname>systemd.ssh_auto=</varname></term>
 142         <term><varname>systemd.ssh_listen=</varname></term>
 143         <listitem>
 144           <para>These parameters are interpreted by
 145           <citerefentry><refentrytitle>systemd-ssh-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 146           and may be used to control SSH sockets the system shall be reachable on.</para>
 147
 148           <xi:include href="version-info.xml" xpointer="v256"/>
 149         </listitem>
 150       </varlistentry>
 151
 152       <varlistentry>
 153         <term><varname>systemd.volatile=</varname></term>
 154         <listitem>
 155           <para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
 156           the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
 157           directory and <filename>/var/</filename> are mounted as specified on the kernel command line or
 158           <filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
 159           this case the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
 160           <filename>/usr/</filename> is mounted from the file system configured as root device, in read-only mode. This
 161           enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
 162           configuration and no stored state in effect, as <filename>/etc/</filename> and <filename>/var/</filename> (as
 163           well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
 164           setting is set to <literal>state</literal> the root file system is mounted read-only, however
 165           <filename>/var/</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
 166           system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. If
 167           this setting is set to <literal>overlay</literal> the root file system is set up as
 168           <literal>overlayfs</literal> mount combining the read-only root directory with a writable
 169           <literal>tmpfs</literal>, so that no modifications are made to disk, but the file system may be modified
 170           nonetheless with all changes being lost at reboot. For details, see
 171           <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 172           and
 173           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 174
 175           <xi:include href="version-info.xml" xpointer="v233"/>
 176         </listitem>
 177       </varlistentry>
 178
 179       <varlistentry>
 180         <term><varname>quiet</varname></term>
 181         <listitem>
 182           <para>Parameter understood by both the kernel and the system
 183           and service manager to control console log verbosity. For
 184           details, see
 185           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 186
 187           <xi:include href="version-info.xml" xpointer="v186"/>
 188         </listitem>
 189       </varlistentry>
 190
 191       <varlistentry>
 192         <term><varname>debug</varname></term>
 193         <listitem>
 194           <para>Parameter understood by both the kernel and the system
 195           and service manager to control console log verbosity. For
 196           details, see
 197           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 198
 199           <xi:include href="version-info.xml" xpointer="v205"/>
 200         </listitem>
 201       </varlistentry>
 202
 203       <varlistentry>
 204         <term><varname>-b</varname></term>
 205         <term><varname>rd.emergency</varname></term>
 206         <term><varname>emergency</varname></term>
 207         <term><varname>rd.rescue</varname></term>
 208         <term><varname>rescue</varname></term>
 209         <term><varname>single</varname></term>
 210         <term><varname>s</varname></term>
 211         <term><varname>S</varname></term>
 212         <term><varname>1</varname></term>
 213         <term><varname>2</varname></term>
 214         <term><varname>3</varname></term>
 215         <term><varname>4</varname></term>
 216         <term><varname>5</varname></term>
 217         <listitem>
 218           <para>Parameters understood by the system and service
 219           manager, as compatibility and convenience options. For details, see
 220           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 221
 222           <xi:include href="version-info.xml" xpointer="v186"/>
 223         </listitem>
 224       </varlistentry>
 225
 226       <varlistentry>
 227         <term><varname>locale.LANG=</varname></term>
 228         <term><varname>locale.LANGUAGE=</varname></term>
 229         <term><varname>locale.LC_CTYPE=</varname></term>
 230         <term><varname>locale.LC_NUMERIC=</varname></term>
 231         <term><varname>locale.LC_TIME=</varname></term>
 232         <term><varname>locale.LC_COLLATE=</varname></term>
 233         <term><varname>locale.LC_MONETARY=</varname></term>
 234         <term><varname>locale.LC_MESSAGES=</varname></term>
 235         <term><varname>locale.LC_PAPER=</varname></term>
 236         <term><varname>locale.LC_NAME=</varname></term>
 237         <term><varname>locale.LC_ADDRESS=</varname></term>
 238         <term><varname>locale.LC_TELEPHONE=</varname></term>
 239         <term><varname>locale.LC_MEASUREMENT=</varname></term>
 240         <term><varname>locale.LC_IDENTIFICATION=</varname></term>
 241         <listitem>
 242           <para>Parameters understood by the system and service
 243           manager to control locale and language settings. For
 244           details, see
 245           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 246
 247           <xi:include href="version-info.xml" xpointer="v186"/>
 248         </listitem>
 249       </varlistentry>
 250
 251       <varlistentry>
 252         <term><varname>fsck.mode=</varname></term>
 253         <term><varname>fsck.repair=</varname></term>
 254
 255         <listitem>
 256           <para>Parameters understood by the file system checker
 257           services. For details, see
 258           <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 259
 260           <xi:include href="version-info.xml" xpointer="v186"/>
 261         </listitem>
 262       </varlistentry>
 263
 264       <varlistentry>
 265         <term><varname>quotacheck.mode=</varname></term>
 266
 267         <listitem>
 268           <para>Parameter understood by the file quota checker
 269           service. For details, see
 270           <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 271
 272           <xi:include href="version-info.xml" xpointer="v186"/>
 273         </listitem>
 274       </varlistentry>
 275
 276       <varlistentry>
 277         <term><varname>systemd.journald.forward_to_syslog=</varname></term>
 278         <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
 279         <term><varname>systemd.journald.forward_to_console=</varname></term>
 280         <term><varname>systemd.journald.forward_to_wall=</varname></term>
 281
 282         <listitem>
 283           <para>Parameters understood by the journal service. For
 284           details, see
 285           <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 286
 287           <xi:include href="version-info.xml" xpointer="v186"/>
 288         </listitem>
 289       </varlistentry>
 290
 291       <varlistentry>
 292         <term><varname>vconsole.keymap=</varname></term>
 293         <term><varname>vconsole.keymap_toggle=</varname></term>
 294         <term><varname>vconsole.font=</varname></term>
 295         <term><varname>vconsole.font_map=</varname></term>
 296         <term><varname>vconsole.font_unimap=</varname></term>
 297
 298         <listitem>
 299           <para>Parameters understood by the virtual console setup logic. For details, see
 300           <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 301
 302           <xi:include href="version-info.xml" xpointer="v186"/>
 303         </listitem>
 304       </varlistentry>
 305
 306       <varlistentry>
 307         <term><varname>udev.log_level=</varname></term>
 308         <term><varname>rd.udev.log_level=</varname></term>
 309         <term><varname>udev.children_max=</varname></term>
 310         <term><varname>rd.udev.children_max=</varname></term>
 311         <term><varname>udev.exec_delay=</varname></term>
 312         <term><varname>rd.udev.exec_delay=</varname></term>
 313         <term><varname>udev.event_timeout=</varname></term>
 314         <term><varname>rd.udev.event_timeout=</varname></term>
 315         <term><varname>udev.timeout_signal=</varname></term>
 316         <term><varname>rd.udev.timeout_signal=</varname></term>
 317         <term><varname>udev.blockdev_read_only</varname></term>
 318         <term><varname>rd.udev.blockdev_read_only</varname></term>
 319         <term><varname>net.ifnames=</varname></term>
 320         <term><varname>net.naming_scheme=</varname></term>
 321
 322         <listitem>
 323           <para>Parameters understood by the device event managing
 324           daemon. For details, see
 325           <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 326
 327           <xi:include href="version-info.xml" xpointer="v186"/>
 328         </listitem>
 329       </varlistentry>
 330
 331       <varlistentry>
 332         <term><varname>plymouth.enable=</varname></term>
 333
 334         <listitem>
 335           <para>May be used to disable the Plymouth boot splash. For
 336           details, see
 337           <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 338
 339           <xi:include href="version-info.xml" xpointer="v186"/>
 340         </listitem>
 341       </varlistentry>
 342
 343       <varlistentry>
 344         <term><varname>luks=</varname></term>
 345         <term><varname>rd.luks=</varname></term>
 346         <term><varname>luks.crypttab=</varname></term>
 347         <term><varname>rd.luks.crypttab=</varname></term>
 348         <term><varname>luks.name=</varname></term>
 349         <term><varname>rd.luks.name=</varname></term>
 350         <term><varname>luks.uuid=</varname></term>
 351         <term><varname>rd.luks.uuid=</varname></term>
 352         <term><varname>luks.options=</varname></term>
 353         <term><varname>rd.luks.options=</varname></term>
 354         <term><varname>luks.key=</varname></term>
 355         <term><varname>rd.luks.key=</varname></term>
 356
 357         <listitem>
 358           <para>Configures the LUKS full-disk encryption logic at
 359           boot. For details, see
 360           <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 361
 362           <xi:include href="version-info.xml" xpointer="v186"/>
 363         </listitem>
 364       </varlistentry>
 365
 366       <varlistentry>
 367         <term><varname>fstab=</varname></term>
 368         <term><varname>rd.fstab=</varname></term>
 369
 370         <listitem>
 371           <para>Configures the <filename>/etc/fstab</filename> logic
 372           at boot. For details, see
 373           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 374
 375         <xi:include href="version-info.xml" xpointer="v186"/>
 376         </listitem>
 377       </varlistentry>
 378
 379       <varlistentry>
 380         <term><varname>root=</varname></term>
 381         <term><varname>rootfstype=</varname></term>
 382         <term><varname>rootflags=</varname></term>
 383         <term><varname>ro</varname></term>
 384         <term><varname>rw</varname></term>
 385
 386         <listitem>
 387           <para>Configures the root file system and its file system type and mount options, as well as
 388           whether it shall be mounted read-only or read-write initially. For details, see
 389           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 390
 391           <para>If <varname>root=</varname> is not set (or set to <literal>gpt-auto</literal>) the automatic
 392           root partition discovery implemented by
 393           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 394           will be in effect. In this case <varname>rootfstype=</varname>, <varname>rootflags=</varname>,
 395           <varname>ro</varname>, <varname>rw</varname> will be interpreted by
 396           <command>systemd-gpt-auto-generator</command>.</para>
 397
 398           <xi:include href="version-info.xml" xpointer="v215"/>
 399         </listitem>
 400       </varlistentry>
 401
 402       <varlistentry>
 403         <term><varname>mount.usr=</varname></term>
 404         <term><varname>mount.usrfstype=</varname></term>
 405         <term><varname>mount.usrflags=</varname></term>
 406
 407         <listitem>
 408           <para>Configures the /usr file system (if required) and
 409           its file system type and mount options. For details, see
 410           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 411
 412           <xi:include href="version-info.xml" xpointer="v235"/>
 413         </listitem>
 414       </varlistentry>
 415
 416       <varlistentry>
 417         <term><varname>veritytab=</varname></term>
 418         <term><varname>rd.veritytab=</varname></term>
 419         <term><varname>roothash=</varname></term>
 420         <term><varname>systemd.verity=</varname></term>
 421         <term><varname>rd.systemd.verity=</varname></term>
 422         <term><varname>systemd.verity_root_data=</varname></term>
 423         <term><varname>systemd.verity_root_hash=</varname></term>
 424         <term><varname>systemd.verity.root_options=</varname></term>
 425         <term><varname>usrhash=</varname></term>
 426         <term><varname>systemd.verity_usr_data=</varname></term>
 427         <term><varname>systemd.verity_usr_hash=</varname></term>
 428         <term><varname>systemd.verity_usr_options=</varname></term>
 429         <listitem>
 430           <para>Configures the integrity protection root hash for the root and <filename>/usr</filename> file systems, and other related
 431           parameters. For details, see
 432           <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 433
 434         <xi:include href="version-info.xml" xpointer="v233"/>
 435         </listitem>
 436       </varlistentry>
 437
 438       <varlistentry>
 439         <term><varname>systemd.getty_auto=</varname></term>
 440
 441         <listitem>
 442           <para>Configures whether the <filename>serial-getty@.service</filename> will run.
 443           For details, see
 444           <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 445
 446         <xi:include href="version-info.xml" xpointer="v250"/>
 447         </listitem>
 448       </varlistentry>
 449
 450       <varlistentry>
 451         <term><varname>systemd.gpt_auto=</varname></term>
 452         <term><varname>rd.systemd.gpt_auto=</varname></term>
 453
 454         <listitem>
 455           <para>Configures whether GPT-based partition auto-discovery shall be attempted. For details, see
 456           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 457
 458           <xi:include href="version-info.xml" xpointer="v215"/>
 459         </listitem>
 460       </varlistentry>
 461
 462       <varlistentry>
 463         <term><varname>systemd.image_policy=</varname></term>
 464         <term><varname>rd.systemd.image_policy=</varname></term>
 465
 466         <listitem><para>When GPT-based partition auto-discovery is used, configures the image dissection
 467         policy string to apply, as per
 468         <citerefentry><refentrytitle>systemd.image-policy</refentrytitle><manvolnum>7</manvolnum></citerefentry>. For
 469         details see
 470         <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 471
 472         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 473       </varlistentry>
 474
 475       <varlistentry>
 476         <term><varname>systemd.default_timeout_start_sec=</varname></term>
 477
 478         <listitem>
 479           <para>Overrides the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at
 480           boot. For details, see
 481           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 482
 483         <xi:include href="version-info.xml" xpointer="v230"/>
 484         </listitem>
 485       </varlistentry>
 486
 487       <varlistentry>
 488         <term><varname>systemd.default_device_timeout_sec=</varname></term>
 489
 490         <listitem>
 491           <para>Overrides the default device timeout <varname>DefaultDeviceTimeoutSec=</varname> at boot. For
 492           details, see
 493           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 494
 495         <xi:include href="version-info.xml" xpointer="v254"/>
 496         </listitem>
 497       </varlistentry>
 498
 499       <varlistentry>
 500         <term><varname>systemd.watchdog_device=</varname></term>
 501
 502         <listitem>
 503           <para>Overrides the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
 504           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 505
 506         <xi:include href="version-info.xml" xpointer="v236"/>
 507         </listitem>
 508       </varlistentry>
 509
 510       <varlistentry>
 511         <term><varname>systemd.watchdog_sec=</varname></term>
 512
 513         <listitem>
 514           <para>Overrides the watchdog timeout settings otherwise configured with
 515           <varname>RuntimeWatchdog=</varname>, <varname>RebootWatchdog=</varname> and
 516           <varname>KExecWatchdogSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 517           implicitly assumed time unit) or the special strings <literal>off</literal> or
 518           <literal>default</literal>. For details, see
 519           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 520
 521           <xi:include href="version-info.xml" xpointer="v250"/>
 522         </listitem>
 523       </varlistentry>
 524
 525       <varlistentry>
 526         <term><varname>systemd.watchdog_pre_sec=</varname></term>
 527
 528         <listitem>
 529           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 530           <varname>RuntimeWatchdogPreSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 531           implicitly assumed time unit) or the special strings <literal>off</literal> or
 532           <literal>default</literal>. For details, see
 533           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 534
 535           <xi:include href="version-info.xml" xpointer="v251"/>
 536         </listitem>
 537       </varlistentry>
 538
 539       <varlistentry>
 540         <term><varname>systemd.watchdog_pretimeout_governor=</varname></term>
 541
 542         <listitem>
 543           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 544           <varname>RuntimeWatchdogPreGovernor=</varname>. Takes a string value. For details, see
 545           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 546
 547           <xi:include href="version-info.xml" xpointer="v251"/>
 548         </listitem>
 549       </varlistentry>
 550
 551       <varlistentry>
 552         <term><varname>systemd.cpu_affinity=</varname></term>
 553
 554         <listitem>
 555           <para>Overrides the CPU affinity mask for the service manager and the default for all child
 556           processes it forks. This takes precedence over <varname>CPUAffinity=</varname>, see
 557           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 558           for details.</para>
 559
 560           <xi:include href="version-info.xml" xpointer="v245"/>
 561         </listitem>
 562       </varlistentry>
 563
 564       <varlistentry>
 565         <term><varname>modules_load=</varname></term>
 566         <term><varname>rd.modules_load=</varname></term>
 567
 568         <listitem>
 569           <para>Load a specific kernel module early at boot. For
 570           details, see
 571           <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 572
 573           <xi:include href="version-info.xml" xpointer="v187"/>
 574         </listitem>
 575       </varlistentry>
 576
 577       <varlistentry>
 578         <term><varname>nameserver=</varname></term>
 579         <term><varname>domain=</varname></term>
 580
 581         <listitem><para>Configures DNS server information and search domains, see
 582         <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 583         for details.</para>
 584
 585         <xi:include href="version-info.xml" xpointer="v253"/></listitem>
 586       </varlistentry>
 587
 588       <varlistentry>
 589         <term><varname>resume=</varname></term>
 590         <term><varname>resumeflags=</varname></term>
 591
 592         <listitem>
 593           <para>Enable resume from hibernation using the specified device and timeout options. All
 594           <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-style
 595           device identifiers 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>resume_offset=</varname></term>
 604
 605         <listitem><para>Configure the page offset of the swap space from the resume device. For details, see
 606         <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 607         </para>
 608
 609         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 610       </varlistentry>
 611
 612       <varlistentry>
 613         <term><varname>systemd.firstboot=</varname></term>
 614
 615         <listitem><para>Takes a boolean argument, defaults to on. If off,
 616         <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 617         and
 618         <citerefentry><refentrytitle>systemd-homed-firstboot.service</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 619         will not query the user for basic system settings, even if the system boots up for the first time and
 620         the relevant settings are not initialized yet. Not to be confused with
 621         <varname>systemd.condition_first_boot=</varname> (see below), which overrides the result of the
 622         <varname>ConditionFirstBoot=</varname> unit file condition, and thus controls more than just
 623         <filename>systemd-firstboot.service</filename> behaviour.</para>
 624
 625         <xi:include href="version-info.xml" xpointer="v233"/></listitem>
 626       </varlistentry>
 627
 628       <varlistentry>
 629         <term><varname>systemd.condition_needs_update=</varname></term>
 630
 631         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 632         <varname>ConditionNeedsUpdate=</varname> unit condition checks. See
 633         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 634         details.</para>
 635
 636         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 637       </varlistentry>
 638
 639       <varlistentry>
 640         <term><varname>systemd.condition_first_boot=</varname></term>
 641
 642         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 643         <varname>ConditionFirstBoot=</varname> unit condition checks. See
 644         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 645         details. Not to be confused with <varname>systemd.firstboot=</varname> which only controls behaviour
 646         of the <filename>systemd-firstboot.service</filename> system service but has no effect on the
 647         condition check (see above).</para>
 648
 649         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 650       </varlistentry>
 651
 652       <varlistentry>
 653         <term><varname>systemd.clock_usec=</varname></term>
 654
 655         <listitem><para>Takes a decimal, numeric timestamp in μs since January 1st 1970, 00:00am, to set the
 656         system clock to. The system time is set to the specified timestamp early during boot. It is not
 657         propagated to the hardware clock (RTC).</para>
 658
 659         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 660       </varlistentry>
 661
 662       <varlistentry>
 663         <term><varname>systemd.random_seed=</varname></term>
 664
 665         <listitem><para>Takes a base64 encoded random seed value to credit with full entropy to the kernel's
 666         random pool during early service manager initialization. This option is useful in testing
 667         environments where delays due to random pool initialization in entropy starved virtual machines shall
 668         be avoided.</para>
 669
 670         <para>Note that if this option is used the seed is accessible to unprivileged programs from
 671         <filename>/proc/cmdline</filename>. This option is hence a security risk when used outside of test
 672         systems, since the (possibly) only seed used for initialization of the kernel's entropy pool might be
 673         easily acquired by unprivileged programs.</para>
 674
 675         <para>It is recommended to pass 512 bytes of randomized data (as that matches the Linux kernel pool
 676         size), which may be generated with a command like the following:</para>
 677
 678         <programlisting>dd if=/dev/urandom bs=512 count=1 status=none | base64 -w 0</programlisting>
 679
 680         <para>Again: do not use this option outside of testing environments, it's a security risk elsewhere,
 681         as secret key material derived from the entropy pool can possibly be reconstructed by unprivileged
 682         programs.</para>
 683
 684         <xi:include href="version-info.xml" xpointer="v246"/>
 685         </listitem>
 686       </varlistentry>
 687
 688       <varlistentry>
 689         <term><varname>systemd.allow_userspace_verity=</varname></term>
 690
 691         <listitem><para>Takes a boolean argument. Controls whether disk images that are Verity protected may
 692         be authenticated in userspace signature checks via <filename>/etc/verity.d/</filename> (and related
 693         directories) public key drop-ins, or whether in-kernel signature checking only. Defaults to
 694         on.</para>
 695
 696         <xi:include href="version-info.xml" xpointer="v256"/></listitem>
 697       </varlistentry>
 698
 699       <varlistentry>
 700         <term><varname>systemd.hostname=</varname></term>
 701
 702         <listitem><para>Accepts a hostname to set during early boot. If specified takes precedence over what
 703         is set in <filename>/etc/hostname</filename>. Note that this does not bar later runtime changes to
 704         the hostname, it simply controls the initial hostname set during early boot.</para>
 705
 706         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 707       </varlistentry>
 708
 709       <varlistentry>
 710         <term><varname>systemd.tty.term.<replaceable>tty</replaceable>=</varname></term>
 711         <term><varname>systemd.tty.rows.<replaceable>tty</replaceable>=</varname></term>
 712         <term><varname>systemd.tty.columns.<replaceable>tty</replaceable>=</varname></term>
 713
 714         <listitem><para>These arguments allow configuring default values for <varname>$TERM</varname>,
 715         <varname>TTYRows=</varname>, and <varname>TTYColumns=</varname> for tty
 716         <replaceable>tty</replaceable>. Additionally, <varname>systemd.tty.term.console</varname> will
 717         configure the <varname>$TERM</varname> value used by <command>systemd</command> if not set explicitly
 718         using <varname>TERM</varname> on the kernel command line. The tty name should be specified without
 719         the <filename>/dev/</filename> prefix (e.g. <literal>systemd.tty.rows.ttyS0=80</literal>).
 720         </para>
 721
 722         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 723       </varlistentry>
 724
 725       <varlistentry>
 726         <term><varname>systemd.battery_check=</varname></term>
 727
 728         <listitem><para>Accepts a boolean argument. If false the boot-time battery charge check implemented
 729         by
 730         <citerefentry><refentrytitle>systemd-battery-check.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 731         is disabled.</para>
 732
 733         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 734       </varlistentry>
 735
 736       <varlistentry>
 737         <term><varname>ifname=</varname></term>
 738         <term><varname>net.ifname_policy=</varname></term>
 739
 740         <listitem><para>Controls interface naming policies, implemented by
 741         <citerefentry><refentrytitle>systemd-network-generator.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 742
 743         <xi:include href="version-info.xml" xpointer="v245"/></listitem>
 744       </varlistentry>
 745
 746       <varlistentry>
 747         <term><varname>systemd.tpm2_wait=</varname></term>
 748
 749         <listitem><para>Controls whether to wait for a TPM2 device at boot, implemented by
 750         <citerefentry><refentrytitle>systemd-tpm2-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 751
 752         <xi:include href="version-info.xml" xpointer="v256"/></listitem>
 753       </varlistentry>
 754
 755     </variablelist>
 756   </refsect1>
 757
 758   <refsect1>
 759       <title>History</title>
 760
 761       <variablelist>
 762         <varlistentry>
 763           <term>systemd 252</term>
 764           <listitem><para>Kernel command-line arguments <varname>systemd.unified_cgroup_hierarchy</varname>
 765           and <varname>systemd.legacy_systemd_cgroup_controller</varname> were deprecated. Please switch to
 766           the unified cgroup hierarchy.</para>
 767
 768           <xi:include href="version-info.xml" xpointer="v252"/></listitem>
 769         </varlistentry>
 770       </variablelist>
 771   </refsect1>
 772
 773   <refsect1>
 774       <title>See Also</title>
 775       <para><simplelist type="inline">
 776         <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 777         <member><citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 778         <member><citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 779         <member><citerefentry><refentrytitle>systemd.system-credentials</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 780         <member><citerefentry><refentrytitle>smbios-type-11</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 781         <member><citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 782         <member><citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 783         <member><citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 784         <member><citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 785         <member><citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 786         <member><citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 787         <member><citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 788         <member><citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 789         <member><citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 790         <member><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 791         <member><citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 792         <member><citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 793         <member><citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 794         <member><citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 795         <member><citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 796         <member><citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 797         <member><citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 798         <member><citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 799         <member><citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 800       </simplelist></para>
 801   </refsect1>
 802
 803 </refentry>