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.break=</varname></term>
 102         <term><varname>rd.systemd.break=</varname></term>
 103         <listitem>
 104           <para>Parameters understood by
 105           <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 106           to pause the boot process at a certain point and spawn a debug shell.</para>
 107
 108           <xi:include href="version-info.xml" xpointer="v258"/>
 109         </listitem>
 110       </varlistentry>
 111
 112       <varlistentry>
 113         <term><varname>systemd.run=</varname></term>
 114         <term><varname>systemd.run_success_action=</varname></term>
 115         <term><varname>systemd.run_failure_action=</varname></term>
 116         <listitem>
 117           <para>Additional parameters understood by
 118           <citerefentry><refentrytitle>systemd-run-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, to
 119           run a command line specified on the kernel command line as system service after booting up.</para>
 120
 121           <xi:include href="version-info.xml" xpointer="v240"/>
 122         </listitem>
 123       </varlistentry>
 124
 125       <varlistentry>
 126         <term><varname>systemd.early_core_pattern=</varname></term>
 127         <listitem>
 128           <para>During early boot, the generation of core dump files is disabled until a core dump handler (if any)
 129           takes over. This parameter allows specifying an absolute path where core dump files should be stored until
 130           a handler is installed. The path should be absolute and may contain specifiers, see
 131           <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details.</para>
 132
 133           <xi:include href="version-info.xml" xpointer="v240"/>
 134         </listitem>
 135       </varlistentry>
 136
 137       <varlistentry>
 138         <term><varname>systemd.restore_state=</varname></term>
 139         <listitem>
 140           <para>This parameter is understood by several system tools
 141           to control whether or not they should restore system state
 142           from the previous boot. For details, see
 143           <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 144           and
 145           <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 146           </para>
 147
 148           <xi:include href="version-info.xml" xpointer="v209"/>
 149         </listitem>
 150       </varlistentry>
 151
 152       <varlistentry>
 153         <term><varname>systemd.ssh_auto=</varname></term>
 154         <term><varname>systemd.ssh_listen=</varname></term>
 155         <listitem>
 156           <para>These parameters are interpreted by
 157           <citerefentry><refentrytitle>systemd-ssh-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 158           and may be used to control SSH sockets the system shall be reachable on.</para>
 159
 160           <xi:include href="version-info.xml" xpointer="v256"/>
 161         </listitem>
 162       </varlistentry>
 163
 164       <varlistentry>
 165         <term><varname>systemd.volatile=</varname></term>
 166         <listitem>
 167           <para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
 168           the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
 169           directory and <filename>/var/</filename> are mounted as specified on the kernel command line or
 170           <filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
 171           this case, the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
 172           <filename>/usr/</filename> is mounted from the file system configured as root device, in read-only mode. This
 173           enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
 174           configuration and no stored state in effect, as <filename>/etc/</filename> and <filename>/var/</filename> (as
 175           well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
 176           setting is set to <literal>state</literal> the root file system is mounted read-only, however
 177           <filename>/var/</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
 178           system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. If
 179           this setting is set to <literal>overlay</literal> the root file system is set up as
 180           <literal>overlayfs</literal> mount combining the read-only root directory with a writable
 181           <literal>tmpfs</literal>, so that no modifications are made to disk, but the file system may be modified
 182           nonetheless with all changes being lost at reboot. For details, see
 183           <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 184           and
 185           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 186
 187           <xi:include href="version-info.xml" xpointer="v233"/>
 188         </listitem>
 189       </varlistentry>
 190
 191       <varlistentry>
 192         <term><varname>quiet</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="v186"/>
 200         </listitem>
 201       </varlistentry>
 202
 203       <varlistentry>
 204         <term><varname>debug</varname></term>
 205         <listitem>
 206           <para>Parameter understood by both the kernel and the system
 207           and service manager to control console log verbosity. For
 208           details, see
 209           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 210
 211           <xi:include href="version-info.xml" xpointer="v205"/>
 212         </listitem>
 213       </varlistentry>
 214
 215       <varlistentry>
 216         <term><varname>-b</varname></term>
 217         <term><varname>rd.emergency</varname></term>
 218         <term><varname>emergency</varname></term>
 219         <term><varname>rd.rescue</varname></term>
 220         <term><varname>rescue</varname></term>
 221         <term><varname>single</varname></term>
 222         <term><varname>s</varname></term>
 223         <term><varname>S</varname></term>
 224         <term><varname>1</varname></term>
 225         <term><varname>2</varname></term>
 226         <term><varname>3</varname></term>
 227         <term><varname>4</varname></term>
 228         <term><varname>5</varname></term>
 229         <listitem>
 230           <para>Parameters understood by the system and service
 231           manager, as compatibility and convenience options. For details, see
 232           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 233
 234           <xi:include href="version-info.xml" xpointer="v186"/>
 235         </listitem>
 236       </varlistentry>
 237
 238       <varlistentry>
 239         <term><varname>locale.LANG=</varname></term>
 240         <term><varname>locale.LANGUAGE=</varname></term>
 241         <term><varname>locale.LC_CTYPE=</varname></term>
 242         <term><varname>locale.LC_NUMERIC=</varname></term>
 243         <term><varname>locale.LC_TIME=</varname></term>
 244         <term><varname>locale.LC_COLLATE=</varname></term>
 245         <term><varname>locale.LC_MONETARY=</varname></term>
 246         <term><varname>locale.LC_MESSAGES=</varname></term>
 247         <term><varname>locale.LC_PAPER=</varname></term>
 248         <term><varname>locale.LC_NAME=</varname></term>
 249         <term><varname>locale.LC_ADDRESS=</varname></term>
 250         <term><varname>locale.LC_TELEPHONE=</varname></term>
 251         <term><varname>locale.LC_MEASUREMENT=</varname></term>
 252         <term><varname>locale.LC_IDENTIFICATION=</varname></term>
 253         <listitem>
 254           <para>Parameters understood by the system and service
 255           manager to control locale and language settings. For
 256           details, see
 257           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 258
 259           <xi:include href="version-info.xml" xpointer="v186"/>
 260         </listitem>
 261       </varlistentry>
 262
 263       <varlistentry>
 264         <term><varname>fsck.mode=</varname></term>
 265         <term><varname>fsck.repair=</varname></term>
 266
 267         <listitem>
 268           <para>Parameters understood by the file system checker
 269           services. For details, see
 270           <citerefentry><refentrytitle>systemd-fsck@.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>quotacheck.mode=</varname></term>
 278
 279         <listitem>
 280           <para>Parameter understood by the file quota checker
 281           service. For details, see
 282           <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 283
 284           <xi:include href="version-info.xml" xpointer="v186"/>
 285         </listitem>
 286       </varlistentry>
 287
 288       <varlistentry>
 289         <term><varname>systemd.journald.forward_to_syslog=</varname></term>
 290         <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
 291         <term><varname>systemd.journald.forward_to_console=</varname></term>
 292         <term><varname>systemd.journald.forward_to_wall=</varname></term>
 293
 294         <listitem>
 295           <para>Parameters understood by the journal service. For
 296           details, see
 297           <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 298
 299           <xi:include href="version-info.xml" xpointer="v186"/>
 300         </listitem>
 301       </varlistentry>
 302
 303       <varlistentry>
 304         <term><varname>vconsole.keymap=</varname></term>
 305         <term><varname>vconsole.keymap_toggle=</varname></term>
 306         <term><varname>vconsole.font=</varname></term>
 307         <term><varname>vconsole.font_map=</varname></term>
 308         <term><varname>vconsole.font_unimap=</varname></term>
 309
 310         <listitem>
 311           <para>Parameters understood by the virtual console setup logic. For details, see
 312           <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 313
 314           <xi:include href="version-info.xml" xpointer="v186"/>
 315         </listitem>
 316       </varlistentry>
 317
 318       <varlistentry>
 319         <term><varname>udev.log_level=</varname></term>
 320         <term><varname>rd.udev.log_level=</varname></term>
 321         <term><varname>udev.trace=</varname></term>
 322         <term><varname>rd.udev.trace=</varname></term>
 323         <term><varname>udev.children_max=</varname></term>
 324         <term><varname>rd.udev.children_max=</varname></term>
 325         <term><varname>udev.exec_delay=</varname></term>
 326         <term><varname>rd.udev.exec_delay=</varname></term>
 327         <term><varname>udev.event_timeout=</varname></term>
 328         <term><varname>rd.udev.event_timeout=</varname></term>
 329         <term><varname>udev.timeout_signal=</varname></term>
 330         <term><varname>rd.udev.timeout_signal=</varname></term>
 331         <term><varname>udev.blockdev_read_only</varname></term>
 332         <term><varname>rd.udev.blockdev_read_only</varname></term>
 333         <term><varname>net.ifnames=</varname></term>
 334         <term><varname>net.naming_scheme=</varname></term>
 335
 336         <listitem>
 337           <para>Parameters understood by the device event managing
 338           daemon. For details, see
 339           <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 340
 341           <xi:include href="version-info.xml" xpointer="v186"/>
 342         </listitem>
 343       </varlistentry>
 344
 345       <varlistentry>
 346         <term><varname>plymouth.enable=</varname></term>
 347
 348         <listitem>
 349           <para>May be used to disable the Plymouth boot splash. For
 350           details, see
 351           <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 352
 353           <xi:include href="version-info.xml" xpointer="v186"/>
 354         </listitem>
 355       </varlistentry>
 356
 357       <varlistentry>
 358         <term><varname>luks=</varname></term>
 359         <term><varname>rd.luks=</varname></term>
 360         <term><varname>luks.crypttab=</varname></term>
 361         <term><varname>rd.luks.crypttab=</varname></term>
 362         <term><varname>luks.name=</varname></term>
 363         <term><varname>rd.luks.name=</varname></term>
 364         <term><varname>luks.uuid=</varname></term>
 365         <term><varname>rd.luks.uuid=</varname></term>
 366         <term><varname>luks.options=</varname></term>
 367         <term><varname>rd.luks.options=</varname></term>
 368         <term><varname>luks.key=</varname></term>
 369         <term><varname>rd.luks.key=</varname></term>
 370
 371         <listitem>
 372           <para>Configures the LUKS full-disk encryption logic at
 373           boot. For details, see
 374           <citerefentry><refentrytitle>systemd-cryptsetup-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>fstab=</varname></term>
 382         <term><varname>rd.fstab=</varname></term>
 383
 384         <listitem>
 385           <para>Configures the <filename>/etc/fstab</filename> logic
 386           at boot. For details, see
 387           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 388
 389         <xi:include href="version-info.xml" xpointer="v186"/>
 390         </listitem>
 391       </varlistentry>
 392
 393       <varlistentry>
 394         <term><varname>root=</varname></term>
 395         <term><varname>rootfstype=</varname></term>
 396         <term><varname>rootflags=</varname></term>
 397         <term><varname>ro</varname></term>
 398         <term><varname>rw</varname></term>
 399
 400         <listitem>
 401           <para>Configures the root file system and its file system type and mount options, as well as
 402           whether it shall be mounted read-only or read-write initially. For details, see
 403           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 404
 405           <para>If <varname>root=</varname> is not set (or set to <literal>gpt-auto</literal>) the automatic
 406           root partition discovery implemented by
 407           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 408           will be in effect. In this case, <varname>rootfstype=</varname>, <varname>rootflags=</varname>,
 409           <varname>ro</varname>, <varname>rw</varname> will be interpreted by
 410           <command>systemd-gpt-auto-generator</command>.</para>
 411
 412           <xi:include href="version-info.xml" xpointer="v215"/>
 413         </listitem>
 414       </varlistentry>
 415
 416       <varlistentry>
 417         <term><varname>mount.usr=</varname></term>
 418         <term><varname>mount.usrfstype=</varname></term>
 419         <term><varname>mount.usrflags=</varname></term>
 420
 421         <listitem>
 422           <para>Configures the /usr file system (if required) and
 423           its file system type and mount options. For details, see
 424           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 425
 426           <xi:include href="version-info.xml" xpointer="v235"/>
 427         </listitem>
 428       </varlistentry>
 429
 430       <varlistentry>
 431         <term><varname>veritytab=</varname></term>
 432         <term><varname>rd.veritytab=</varname></term>
 433         <term><varname>roothash=</varname></term>
 434         <term><varname>systemd.verity=</varname></term>
 435         <term><varname>rd.systemd.verity=</varname></term>
 436         <term><varname>systemd.verity_root_data=</varname></term>
 437         <term><varname>systemd.verity_root_hash=</varname></term>
 438         <term><varname>systemd.verity_root_options=</varname></term>
 439         <term><varname>usrhash=</varname></term>
 440         <term><varname>systemd.verity_usr_data=</varname></term>
 441         <term><varname>systemd.verity_usr_hash=</varname></term>
 442         <term><varname>systemd.verity_usr_options=</varname></term>
 443         <listitem>
 444           <para>Configures the integrity protection root hash for the root and <filename>/usr</filename> file systems, and other related
 445           parameters. For details, see
 446           <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 447
 448         <xi:include href="version-info.xml" xpointer="v233"/>
 449         </listitem>
 450       </varlistentry>
 451
 452       <varlistentry>
 453         <term><varname>systemd.getty_auto=</varname></term>
 454
 455         <listitem>
 456           <para>Configures whether the <filename>serial-getty@.service</filename> will run.
 457           For details, see
 458           <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 459
 460         <xi:include href="version-info.xml" xpointer="v250"/>
 461         </listitem>
 462       </varlistentry>
 463
 464       <varlistentry>
 465         <term><varname>systemd.gpt_auto=</varname></term>
 466         <term><varname>rd.systemd.gpt_auto=</varname></term>
 467
 468         <listitem>
 469           <para>Configures whether GPT-based partition auto-discovery shall be attempted. For details, see
 470           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 471
 472           <xi:include href="version-info.xml" xpointer="v215"/>
 473         </listitem>
 474       </varlistentry>
 475
 476       <varlistentry>
 477         <term><varname>systemd.image_policy=</varname></term>
 478
 479         <listitem><para>When GPT-based partition auto-discovery is used, configures the image dissection
 480         policy string to apply, as per
 481         <citerefentry><refentrytitle>systemd.image-policy</refentrytitle><manvolnum>7</manvolnum></citerefentry>. For
 482         details see
 483         <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 484
 485         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 486       </varlistentry>
 487
 488       <varlistentry>
 489         <term><varname>systemd.default_timeout_start_sec=</varname></term>
 490
 491         <listitem>
 492           <para>Overrides the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at
 493           boot. For details, see
 494           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 495
 496         <xi:include href="version-info.xml" xpointer="v230"/>
 497         </listitem>
 498       </varlistentry>
 499
 500       <varlistentry>
 501         <term><varname>systemd.default_device_timeout_sec=</varname></term>
 502
 503         <listitem>
 504           <para>Overrides the default device timeout <varname>DefaultDeviceTimeoutSec=</varname> at boot. For
 505           details, see
 506           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 507
 508         <xi:include href="version-info.xml" xpointer="v254"/>
 509         </listitem>
 510       </varlistentry>
 511
 512       <varlistentry>
 513         <term><varname>systemd.watchdog_device=</varname></term>
 514
 515         <listitem>
 516           <para>Overrides the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
 517           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 518
 519         <xi:include href="version-info.xml" xpointer="v236"/>
 520         </listitem>
 521       </varlistentry>
 522
 523       <varlistentry>
 524         <term><varname>systemd.watchdog_sec=</varname></term>
 525
 526         <listitem>
 527           <para>Overrides the watchdog timeout settings otherwise configured with
 528           <varname>RuntimeWatchdog=</varname>, <varname>RebootWatchdog=</varname> and
 529           <varname>KExecWatchdogSec=</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="v250"/>
 535         </listitem>
 536       </varlistentry>
 537
 538       <varlistentry>
 539         <term><varname>systemd.watchdog_pre_sec=</varname></term>
 540
 541         <listitem>
 542           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 543           <varname>RuntimeWatchdogPreSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 544           implicitly assumed time unit) or the special strings <literal>off</literal> or
 545           <literal>default</literal>. 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.watchdog_pretimeout_governor=</varname></term>
 554
 555         <listitem>
 556           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 557           <varname>RuntimeWatchdogPreGovernor=</varname>. Takes a string value. For details, see
 558           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 559
 560           <xi:include href="version-info.xml" xpointer="v251"/>
 561         </listitem>
 562       </varlistentry>
 563
 564       <varlistentry>
 565         <term><varname>systemd.cpu_affinity=</varname></term>
 566
 567         <listitem>
 568           <para>Overrides the CPU affinity mask for the service manager and the default for all child
 569           processes it forks. This takes precedence over <varname>CPUAffinity=</varname>, see
 570           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 571           for details.</para>
 572
 573           <xi:include href="version-info.xml" xpointer="v245"/>
 574         </listitem>
 575       </varlistentry>
 576
 577       <varlistentry>
 578         <term><varname>modules_load=</varname></term>
 579         <term><varname>rd.modules_load=</varname></term>
 580
 581         <listitem>
 582           <para>Load a specific kernel module early at boot. For
 583           details, see
 584           <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 585
 586           <xi:include href="version-info.xml" xpointer="v187"/>
 587         </listitem>
 588       </varlistentry>
 589
 590       <varlistentry>
 591         <term><varname>nameserver=</varname></term>
 592         <term><varname>domain=</varname></term>
 593
 594         <listitem><para>Configures DNS server information and search domains, see
 595         <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 596         for details.</para>
 597
 598         <xi:include href="version-info.xml" xpointer="v253"/></listitem>
 599       </varlistentry>
 600
 601       <varlistentry>
 602         <term><varname>resume=</varname></term>
 603         <term><varname>resumeflags=</varname></term>
 604
 605         <listitem>
 606           <para>Enable resume from hibernation using the specified device and timeout options. All
 607           <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-style
 608           device identifiers are supported. For details, see
 609           <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 610
 611           <xi:include href="version-info.xml" xpointer="v217"/>
 612         </listitem>
 613       </varlistentry>
 614
 615       <varlistentry>
 616         <term><varname>resume_offset=</varname></term>
 617
 618         <listitem><para>Configure the page offset of the swap space from the resume device. For details, see
 619         <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 620         </para>
 621
 622         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 623       </varlistentry>
 624
 625       <varlistentry>
 626         <term><varname>systemd.firstboot=</varname></term>
 627
 628         <listitem><para>Takes a boolean argument, defaults to on. If off,
 629         <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 630         and
 631         <citerefentry><refentrytitle>systemd-homed-firstboot.service</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 632         will not query the user for basic system settings, even if the system boots up for the first time and
 633         the relevant settings are not initialized yet. Not to be confused with
 634         <varname>systemd.condition_first_boot=</varname> (see below), which overrides the result of the
 635         <varname>ConditionFirstBoot=</varname> unit file condition, and thus controls more than just
 636         <filename>systemd-firstboot.service</filename> behaviour.</para>
 637
 638         <xi:include href="version-info.xml" xpointer="v233"/></listitem>
 639       </varlistentry>
 640
 641       <varlistentry>
 642         <term><varname>systemd.condition_needs_update=</varname></term>
 643
 644         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 645         <varname>ConditionNeedsUpdate=</varname> unit condition checks. See
 646         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 647         details.</para>
 648
 649         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 650       </varlistentry>
 651
 652       <varlistentry>
 653         <term><varname>systemd.condition_first_boot=</varname></term>
 654
 655         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 656         <varname>ConditionFirstBoot=</varname> unit condition checks. See
 657         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 658         details. Not to be confused with <varname>systemd.firstboot=</varname> which only controls behaviour
 659         of the <filename>systemd-firstboot.service</filename> system service but has no effect on the
 660         condition check (see above).</para>
 661
 662         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 663       </varlistentry>
 664
 665       <varlistentry>
 666         <term><varname>systemd.clock_usec=</varname></term>
 667
 668         <listitem><para>Takes a decimal, numeric timestamp in μs since January 1st 1970, 00:00am, to set the
 669         system clock to. The system time is set to the specified timestamp early during boot. It is not
 670         propagated to the hardware clock (RTC).</para>
 671
 672         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 673       </varlistentry>
 674
 675       <varlistentry>
 676         <term><varname>systemd.random_seed=</varname></term>
 677
 678         <listitem><para>Takes a base64 encoded random seed value to credit with full entropy to the kernel's
 679         random pool during early service manager initialization. This option is useful in testing
 680         environments where delays due to random pool initialization in entropy starved virtual machines shall
 681         be avoided.</para>
 682
 683         <para>Note that if this option is used the seed is accessible to unprivileged programs from
 684         <filename>/proc/cmdline</filename>. This option is hence a security risk when used outside of test
 685         systems, since the (possibly) only seed used for initialization of the kernel's entropy pool might be
 686         easily acquired by unprivileged programs.</para>
 687
 688         <para>It is recommended to pass 512 bytes of randomized data (as that matches the Linux kernel pool
 689         size), which may be generated with a command like the following:</para>
 690
 691         <programlisting>dd if=/dev/urandom bs=512 count=1 status=none | base64 -w 0</programlisting>
 692
 693         <para>Again: do not use this option outside of testing environments, it is a security risk elsewhere,
 694         as secret key material derived from the entropy pool can possibly be reconstructed by unprivileged
 695         programs.</para>
 696
 697         <xi:include href="version-info.xml" xpointer="v246"/>
 698         </listitem>
 699       </varlistentry>
 700
 701       <varlistentry>
 702         <term><varname>systemd.allow_userspace_verity=</varname></term>
 703
 704         <listitem><para>Takes a boolean argument. Controls whether disk images that are Verity protected may
 705         be authenticated in userspace signature checks via <filename>/etc/verity.d/</filename> (and related
 706         directories) public key drop-ins, or whether in-kernel signature checking only. Defaults to
 707         on.</para>
 708
 709         <xi:include href="version-info.xml" xpointer="v256"/></listitem>
 710       </varlistentry>
 711
 712       <varlistentry>
 713         <term><varname>systemd.hostname=</varname></term>
 714
 715         <listitem><para>Accepts a hostname to set during early boot. If specified takes precedence over what
 716         is set in <filename>/etc/hostname</filename>. Note that this does not bar later runtime changes to
 717         the hostname, it simply controls the initial hostname set during early boot.</para>
 718
 719         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 720       </varlistentry>
 721
 722       <varlistentry>
 723         <term><varname>systemd.tty.term.<replaceable>tty</replaceable>=</varname></term>
 724         <term><varname>systemd.tty.rows.<replaceable>tty</replaceable>=</varname></term>
 725         <term><varname>systemd.tty.columns.<replaceable>tty</replaceable>=</varname></term>
 726
 727         <listitem><para>These arguments allow configuring default values for <varname>$TERM</varname>,
 728         <varname>TTYRows=</varname>, and <varname>TTYColumns=</varname> for tty
 729         <replaceable>tty</replaceable>. Additionally, <varname>systemd.tty.term.console</varname> will
 730         configure the <varname>$TERM</varname> value used by <command>systemd</command> if not set explicitly
 731         using <varname>TERM</varname> on the kernel command line. The tty name should be specified without
 732         the <filename>/dev/</filename> prefix (e.g. <literal>systemd.tty.rows.ttyS0=80</literal>).
 733         </para>
 734
 735         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 736       </varlistentry>
 737
 738       <varlistentry>
 739         <term><varname>systemd.battery_check=</varname></term>
 740
 741         <listitem><para>Accepts a boolean argument. If false the boot-time battery charge check implemented
 742         by
 743         <citerefentry><refentrytitle>systemd-battery-check.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 744         is disabled.</para>
 745
 746         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 747       </varlistentry>
 748
 749       <varlistentry>
 750         <term><varname>ifname=</varname></term>
 751         <term><varname>net.ifname_policy=</varname></term>
 752
 753         <listitem><para>Controls interface naming policies, implemented by
 754         <citerefentry><refentrytitle>systemd-network-generator.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 755
 756         <xi:include href="version-info.xml" xpointer="v245"/></listitem>
 757       </varlistentry>
 758
 759       <varlistentry>
 760         <term><varname>systemd.tpm2_wait=</varname></term>
 761
 762         <listitem><para>Controls whether to wait for a TPM2 device at boot, implemented by
 763         <citerefentry><refentrytitle>systemd-tpm2-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 764
 765         <xi:include href="version-info.xml" xpointer="v256"/></listitem>
 766       </varlistentry>
 767
 768     </variablelist>
 769   </refsect1>
 770
 771   <refsect1>
 772       <title>History</title>
 773
 774       <variablelist>
 775         <varlistentry>
 776           <term>systemd 252</term>
 777           <listitem><para>Kernel command-line arguments <varname>systemd.unified_cgroup_hierarchy</varname>
 778           and <varname>systemd.legacy_systemd_cgroup_controller</varname> were deprecated. Please switch to
 779           the unified cgroup hierarchy.</para>
 780
 781           <xi:include href="version-info.xml" xpointer="v252"/></listitem>
 782         </varlistentry>
 783       </variablelist>
 784   </refsect1>
 785
 786   <refsect1>
 787       <title>See Also</title>
 788       <para><simplelist type="inline">
 789         <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 790         <member><citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 791         <member><citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 792         <member><citerefentry><refentrytitle>systemd.system-credentials</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 793         <member><citerefentry><refentrytitle>smbios-type-11</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
 794         <member><citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 795         <member><citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 796         <member><citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 797         <member><citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 798         <member><citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 799         <member><citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 800         <member><citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 801         <member><citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 802         <member><citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 803         <member><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 804         <member><citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 805         <member><citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 806         <member><citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 807         <member><citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 808         <member><citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 809         <member><citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 810         <member><citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 811         <member><citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 812         <member><citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 813       </simplelist></para>
 814   </refsect1>
 815
 816 </refentry>