man/kernel-command-line.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="kernel-command-line" xmlns:xi="http://www.w3.org/2001/XInclude">
   7
   8   <refentryinfo>
   9     <title>kernel-command-line</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>kernel-command-line</refentrytitle>
  15     <manvolnum>7</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>kernel-command-line</refname>
  20     <refpurpose>Kernel command line parameters</refpurpose>
  21   </refnamediv>
  22
  23   <refsynopsisdiv>
  24     <para><filename>/proc/cmdline</filename></para>
  25   </refsynopsisdiv>
  26
  27   <refsect1>
  28     <title>Description</title>
  29
  30     <para>The kernel, the programs running in the initrd and in the host system may be configured at boot via
  31     kernel command line arguments. In addition, various systemd tools look at the EFI variable
  32     <literal>SystemdOptions</literal> (if available). Both sources are combined, but the kernel command line
  33     has higher priority. Please note that <emphasis>the EFI variable is only used by systemd tools, and is
  34     ignored by the kernel and other user space tools</emphasis>, so it is not a replacement for the kernel
  35     command line.</para>
  36
  37     <para>For command line parameters understood by the kernel, please
  38     see
  39     <ulink url="https://docs.kernel.org/admin-guide/kernel-parameters.html"><filename>kernel-parameters.html</filename></ulink>
  40     and
  41     <citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
  42
  43     <para>For command line parameters understood by the initrd, see
  44     <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
  45     or the documentation of the specific initrd implementation of your
  46     installation.</para>
  47   </refsect1>
  48
  49   <refsect1>
  50     <title>Core OS Command Line Arguments</title>
  51
  52     <variablelist class='kernel-commandline-options'>
  53       <varlistentry>
  54         <term><varname>systemd.unit=</varname></term>
  55         <term><varname>rd.systemd.unit=</varname></term>
  56         <term><varname>systemd.dump_core</varname></term>
  57         <term><varname>systemd.early_core_pattern=</varname></term>
  58         <term><varname>systemd.crash_chvt</varname></term>
  59         <term><varname>systemd.crash_shell</varname></term>
  60         <term><varname>systemd.crash_reboot</varname></term>
  61         <term><varname>systemd.confirm_spawn</varname></term>
  62         <term><varname>systemd.service_watchdogs</varname></term>
  63         <term><varname>systemd.show_status</varname></term>
  64         <term><varname>systemd.status_unit_format=</varname></term>
  65         <term><varname>systemd.log_target=</varname></term>
  66         <term><varname>systemd.log_level=</varname></term>
  67         <term><varname>systemd.log_location=</varname></term>
  68         <term><varname>systemd.log_color</varname></term>
  69         <term><varname>systemd.log_ratelimit_kmsg</varname></term>
  70         <term><varname>systemd.default_standard_output=</varname></term>
  71         <term><varname>systemd.default_standard_error=</varname></term>
  72         <term><varname>systemd.setenv=</varname></term>
  73         <term><varname>systemd.machine_id=</varname></term>
  74         <term><varname>systemd.set_credential=</varname></term>
  75         <term><varname>systemd.set_credential_binary=</varname></term>
  76         <term><varname>systemd.import_credentials=</varname></term>
  77         <term><varname>systemd.reload_limit_interval_sec=</varname></term>
  78         <term><varname>systemd.reload_limit_burst=</varname></term>
  79         <listitem>
  80           <para>Parameters understood by the system and service
  81           manager to control system behavior. For details, see
  82           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
  83
  84           <xi:include href="version-info.xml" xpointer="v186"/>
  85         </listitem>
  86       </varlistentry>
  87
  88       <varlistentry>
  89         <term><varname>systemd.mask=</varname></term>
  90         <term><varname>systemd.wants=</varname></term>
  91         <term><varname>systemd.debug_shell</varname></term>
  92         <listitem>
  93           <para>Additional parameters understood by
  94           <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  95           to mask or start specific units at boot, or invoke a debug
  96           shell on tty9.</para>
  97
  98           <xi:include href="version-info.xml" xpointer="v215"/>
  99         </listitem>
 100       </varlistentry>
 101
 102       <varlistentry>
 103         <term><varname>systemd.run=</varname></term>
 104         <term><varname>systemd.run_success_action=</varname></term>
 105         <term><varname>systemd.run_failure_action=</varname></term>
 106         <listitem>
 107           <para>Additional parameters understood by
 108           <citerefentry><refentrytitle>systemd-run-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, to
 109           run a command line specified on the kernel command line as system service after booting up.</para>
 110
 111           <xi:include href="version-info.xml" xpointer="v240"/>
 112         </listitem>
 113       </varlistentry>
 114
 115       <varlistentry>
 116         <term><varname>systemd.early_core_pattern=</varname></term>
 117         <listitem>
 118           <para>During early boot, the generation of core dump files is disabled until a core dump handler (if any)
 119           takes over. This parameter allows specifying an absolute path where core dump files should be stored until
 120           a handler is installed. The path should be absolute and may contain specifiers, see
 121           <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details.</para>
 122
 123           <xi:include href="version-info.xml" xpointer="v240"/>
 124         </listitem>
 125       </varlistentry>
 126
 127       <varlistentry>
 128         <term><varname>systemd.restore_state=</varname></term>
 129         <listitem>
 130           <para>This parameter is understood by several system tools
 131           to control whether or not they should restore system state
 132           from the previous boot. For details, see
 133           <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 134           and
 135           <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 136           </para>
 137
 138           <xi:include href="version-info.xml" xpointer="v209"/>
 139         </listitem>
 140       </varlistentry>
 141
 142       <varlistentry>
 143         <term><varname>systemd.volatile=</varname></term>
 144         <listitem>
 145           <para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
 146           the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
 147           directory and <filename>/var/</filename> are mounted as specified on the kernel command line or
 148           <filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
 149           this case the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
 150           <filename>/usr/</filename> is mounted from the file system configured as root device, in read-only mode. This
 151           enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
 152           configuration and no stored state in effect, as <filename>/etc/</filename> and <filename>/var/</filename> (as
 153           well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
 154           setting is set to <literal>state</literal> the root file system is mounted read-only, however
 155           <filename>/var/</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
 156           system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. If
 157           this setting is set to <literal>overlay</literal> the root file system is set up as
 158           <literal>overlayfs</literal> mount combining the read-only root directory with a writable
 159           <literal>tmpfs</literal>, so that no modifications are made to disk, but the file system may be modified
 160           nonetheless with all changes being lost at reboot. For details, see
 161           <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 162           and
 163           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 164
 165           <xi:include href="version-info.xml" xpointer="v233"/>
 166         </listitem>
 167       </varlistentry>
 168
 169       <varlistentry>
 170         <term><varname>quiet</varname></term>
 171         <listitem>
 172           <para>Parameter understood by both the kernel and the system
 173           and service manager to control console log verbosity. For
 174           details, see
 175           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 176
 177           <xi:include href="version-info.xml" xpointer="v186"/>
 178         </listitem>
 179       </varlistentry>
 180
 181       <varlistentry>
 182         <term><varname>debug</varname></term>
 183         <listitem>
 184           <para>Parameter understood by both the kernel and the system
 185           and service manager to control console log verbosity. For
 186           details, see
 187           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 188
 189           <xi:include href="version-info.xml" xpointer="v205"/>
 190         </listitem>
 191       </varlistentry>
 192
 193       <varlistentry>
 194         <term><varname>-b</varname></term>
 195         <term><varname>rd.emergency</varname></term>
 196         <term><varname>emergency</varname></term>
 197         <term><varname>rd.rescue</varname></term>
 198         <term><varname>rescue</varname></term>
 199         <term><varname>single</varname></term>
 200         <term><varname>s</varname></term>
 201         <term><varname>S</varname></term>
 202         <term><varname>1</varname></term>
 203         <term><varname>2</varname></term>
 204         <term><varname>3</varname></term>
 205         <term><varname>4</varname></term>
 206         <term><varname>5</varname></term>
 207         <listitem>
 208           <para>Parameters understood by the system and service
 209           manager, as compatibility and convenience options. For details, see
 210           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 211
 212           <xi:include href="version-info.xml" xpointer="v186"/>
 213         </listitem>
 214       </varlistentry>
 215
 216       <varlistentry>
 217         <term><varname>locale.LANG=</varname></term>
 218         <term><varname>locale.LANGUAGE=</varname></term>
 219         <term><varname>locale.LC_CTYPE=</varname></term>
 220         <term><varname>locale.LC_NUMERIC=</varname></term>
 221         <term><varname>locale.LC_TIME=</varname></term>
 222         <term><varname>locale.LC_COLLATE=</varname></term>
 223         <term><varname>locale.LC_MONETARY=</varname></term>
 224         <term><varname>locale.LC_MESSAGES=</varname></term>
 225         <term><varname>locale.LC_PAPER=</varname></term>
 226         <term><varname>locale.LC_NAME=</varname></term>
 227         <term><varname>locale.LC_ADDRESS=</varname></term>
 228         <term><varname>locale.LC_TELEPHONE=</varname></term>
 229         <term><varname>locale.LC_MEASUREMENT=</varname></term>
 230         <term><varname>locale.LC_IDENTIFICATION=</varname></term>
 231         <listitem>
 232           <para>Parameters understood by the system and service
 233           manager to control locale and language settings. For
 234           details, see
 235           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 236
 237           <xi:include href="version-info.xml" xpointer="v186"/>
 238         </listitem>
 239       </varlistentry>
 240
 241       <varlistentry>
 242         <term><varname>fsck.mode=</varname></term>
 243         <term><varname>fsck.repair=</varname></term>
 244
 245         <listitem>
 246           <para>Parameters understood by the file system checker
 247           services. For details, see
 248           <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 249
 250           <xi:include href="version-info.xml" xpointer="v186"/>
 251         </listitem>
 252       </varlistentry>
 253
 254       <varlistentry>
 255         <term><varname>quotacheck.mode=</varname></term>
 256
 257         <listitem>
 258           <para>Parameter understood by the file quota checker
 259           service. For details, see
 260           <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 261
 262           <xi:include href="version-info.xml" xpointer="v186"/>
 263         </listitem>
 264       </varlistentry>
 265
 266       <varlistentry>
 267         <term><varname>systemd.journald.forward_to_syslog=</varname></term>
 268         <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
 269         <term><varname>systemd.journald.forward_to_console=</varname></term>
 270         <term><varname>systemd.journald.forward_to_wall=</varname></term>
 271
 272         <listitem>
 273           <para>Parameters understood by the journal service. For
 274           details, see
 275           <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 276
 277           <xi:include href="version-info.xml" xpointer="v186"/>
 278         </listitem>
 279       </varlistentry>
 280
 281       <varlistentry>
 282         <term><varname>vconsole.keymap=</varname></term>
 283         <term><varname>vconsole.keymap_toggle=</varname></term>
 284         <term><varname>vconsole.font=</varname></term>
 285         <term><varname>vconsole.font_map=</varname></term>
 286         <term><varname>vconsole.font_unimap=</varname></term>
 287
 288         <listitem>
 289           <para>Parameters understood by the virtual console setup logic. For details, see
 290           <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 291
 292           <xi:include href="version-info.xml" xpointer="v186"/>
 293         </listitem>
 294       </varlistentry>
 295
 296       <varlistentry>
 297         <term><varname>udev.log_level=</varname></term>
 298         <term><varname>rd.udev.log_level=</varname></term>
 299         <term><varname>udev.children_max=</varname></term>
 300         <term><varname>rd.udev.children_max=</varname></term>
 301         <term><varname>udev.exec_delay=</varname></term>
 302         <term><varname>rd.udev.exec_delay=</varname></term>
 303         <term><varname>udev.event_timeout=</varname></term>
 304         <term><varname>rd.udev.event_timeout=</varname></term>
 305         <term><varname>udev.timeout_signal=</varname></term>
 306         <term><varname>rd.udev.timeout_signal=</varname></term>
 307         <term><varname>udev.blockdev_read_only</varname></term>
 308         <term><varname>rd.udev.blockdev_read_only</varname></term>
 309         <term><varname>net.ifnames=</varname></term>
 310         <term><varname>net.naming-scheme=</varname></term>
 311
 312         <listitem>
 313           <para>Parameters understood by the device event managing
 314           daemon. For details, see
 315           <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 316
 317           <xi:include href="version-info.xml" xpointer="v186"/>
 318         </listitem>
 319       </varlistentry>
 320
 321       <varlistentry>
 322         <term><varname>plymouth.enable=</varname></term>
 323
 324         <listitem>
 325           <para>May be used to disable the Plymouth boot splash. For
 326           details, see
 327           <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 328
 329           <xi:include href="version-info.xml" xpointer="v186"/>
 330         </listitem>
 331       </varlistentry>
 332
 333       <varlistentry>
 334         <term><varname>luks=</varname></term>
 335         <term><varname>rd.luks=</varname></term>
 336         <term><varname>luks.crypttab=</varname></term>
 337         <term><varname>rd.luks.crypttab=</varname></term>
 338         <term><varname>luks.name=</varname></term>
 339         <term><varname>rd.luks.name=</varname></term>
 340         <term><varname>luks.uuid=</varname></term>
 341         <term><varname>rd.luks.uuid=</varname></term>
 342         <term><varname>luks.options=</varname></term>
 343         <term><varname>rd.luks.options=</varname></term>
 344         <term><varname>luks.key=</varname></term>
 345         <term><varname>rd.luks.key=</varname></term>
 346
 347         <listitem>
 348           <para>Configures the LUKS full-disk encryption logic at
 349           boot. For details, see
 350           <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 351
 352           <xi:include href="version-info.xml" xpointer="v186"/>
 353         </listitem>
 354       </varlistentry>
 355
 356       <varlistentry>
 357         <term><varname>fstab=</varname></term>
 358         <term><varname>rd.fstab=</varname></term>
 359
 360         <listitem>
 361           <para>Configures the <filename>/etc/fstab</filename> logic
 362           at boot. For details, see
 363           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 364
 365         <xi:include href="version-info.xml" xpointer="v186"/>
 366         </listitem>
 367       </varlistentry>
 368
 369       <varlistentry>
 370         <term><varname>root=</varname></term>
 371         <term><varname>rootfstype=</varname></term>
 372         <term><varname>rootflags=</varname></term>
 373         <term><varname>ro</varname></term>
 374         <term><varname>rw</varname></term>
 375
 376         <listitem>
 377           <para>Configures the root file system and its file system type and mount options, as well as
 378           whether it shall be mounted read-only or read-write initially. For details, see
 379           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 380
 381           <para>If <varname>root=</varname> is not set (or set to <literal>gpt-auto</literal>) the automatic
 382           root partition discovery implemented by
 383           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 384           will be in effect. In this case <varname>rootfstype=</varname>, <varname>rootflags=</varname>,
 385           <varname>ro</varname>, <varname>rw</varname> will be interpreted by
 386           <command>systemd-gpt-auto-generator</command>.</para>
 387
 388           <xi:include href="version-info.xml" xpointer="v215"/>
 389         </listitem>
 390       </varlistentry>
 391
 392       <varlistentry>
 393         <term><varname>mount.usr=</varname></term>
 394         <term><varname>mount.usrfstype=</varname></term>
 395         <term><varname>mount.usrflags=</varname></term>
 396
 397         <listitem>
 398           <para>Configures the /usr file system (if required) and
 399           its file system type and mount options. For details, see
 400           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 401
 402           <xi:include href="version-info.xml" xpointer="v235"/>
 403         </listitem>
 404       </varlistentry>
 405
 406       <varlistentry>
 407         <term><varname>veritytab=</varname></term>
 408         <term><varname>rd.veritytab=</varname></term>
 409         <term><varname>roothash=</varname></term>
 410         <term><varname>systemd.verity=</varname></term>
 411         <term><varname>rd.systemd.verity=</varname></term>
 412         <term><varname>systemd.verity_root_data=</varname></term>
 413         <term><varname>systemd.verity_root_hash=</varname></term>
 414         <term><varname>systemd.verity.root_options=</varname></term>
 415         <term><varname>usrhash=</varname></term>
 416         <term><varname>systemd.verity_usr_data=</varname></term>
 417         <term><varname>systemd.verity_usr_hash=</varname></term>
 418         <term><varname>systemd.verity_usr_options=</varname></term>
 419         <listitem>
 420           <para>Configures the integrity protection root hash for the root and <filename>/usr</filename> file systems, and other related
 421           parameters. For details, see
 422           <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 423
 424         <xi:include href="version-info.xml" xpointer="v233"/>
 425         </listitem>
 426       </varlistentry>
 427
 428       <varlistentry>
 429         <term><varname>systemd.getty_auto=</varname></term>
 430
 431         <listitem>
 432           <para>Configures whether the <filename>serial-getty@.service</filename> will run.
 433           For details, see
 434           <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 435
 436         <xi:include href="version-info.xml" xpointer="v250"/>
 437         </listitem>
 438       </varlistentry>
 439
 440       <varlistentry>
 441         <term><varname>systemd.gpt_auto=</varname></term>
 442         <term><varname>rd.systemd.gpt_auto=</varname></term>
 443
 444         <listitem>
 445           <para>Configures whether GPT-based partition auto-discovery shall be attempted. For details, see
 446           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 447
 448           <xi:include href="version-info.xml" xpointer="v215"/>
 449         </listitem>
 450       </varlistentry>
 451
 452       <varlistentry>
 453         <term><varname>systemd.image_policy=</varname></term>
 454         <term><varname>rd.systemd.image_policy=</varname></term>
 455
 456         <listitem><para>When GPT-based partition auto-discovery is used, configures the image dissection
 457         policy string to apply, as per
 458         <citerefentry><refentrytitle>systemd.image-policy</refentrytitle><manvolnum>7</manvolnum></citerefentry>. For
 459         details see
 460         <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 461
 462         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 463       </varlistentry>
 464
 465       <varlistentry>
 466         <term><varname>systemd.default_timeout_start_sec=</varname></term>
 467
 468         <listitem>
 469           <para>Overrides the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at
 470           boot. For details, see
 471           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 472
 473         <xi:include href="version-info.xml" xpointer="v230"/>
 474         </listitem>
 475       </varlistentry>
 476
 477       <varlistentry>
 478         <term><varname>systemd.default_device_timeout_sec=</varname></term>
 479
 480         <listitem>
 481           <para>Overrides the default device timeout <varname>DefaultDeviceTimeoutSec=</varname> at boot. For
 482           details, see
 483           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 484
 485         <xi:include href="version-info.xml" xpointer="v254"/>
 486         </listitem>
 487       </varlistentry>
 488
 489       <varlistentry>
 490         <term><varname>systemd.watchdog_device=</varname></term>
 491
 492         <listitem>
 493           <para>Overrides the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
 494           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 495
 496         <xi:include href="version-info.xml" xpointer="v236"/>
 497         </listitem>
 498       </varlistentry>
 499
 500       <varlistentry>
 501         <term><varname>systemd.watchdog_sec=</varname></term>
 502
 503         <listitem>
 504           <para>Overrides the watchdog timeout settings otherwise configured with
 505           <varname>RuntimeWatchdog=</varname>, <varname>RebootWatchdog=</varname> and
 506           <varname>KExecWatchdogSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 507           implicitly assumed time unit) or the special strings <literal>off</literal> or
 508           <literal>default</literal>. For details, see
 509           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 510
 511           <xi:include href="version-info.xml" xpointer="v250"/>
 512         </listitem>
 513       </varlistentry>
 514
 515       <varlistentry>
 516         <term><varname>systemd.watchdog_pre_sec=</varname></term>
 517
 518         <listitem>
 519           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 520           <varname>RuntimeWatchdogPreSec=</varname>. Takes a time value (if no unit is specified, seconds is the
 521           implicitly assumed time unit) or the special strings <literal>off</literal> or
 522           <literal>default</literal>. For details, see
 523           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 524
 525           <xi:include href="version-info.xml" xpointer="v251"/>
 526         </listitem>
 527       </varlistentry>
 528
 529       <varlistentry>
 530         <term><varname>systemd.watchdog_pretimeout_governor=</varname></term>
 531
 532         <listitem>
 533           <para>Overrides the watchdog pre-timeout settings otherwise configured with
 534           <varname>RuntimeWatchdogPreGovernor=</varname>. Takes a string value. For details, see
 535           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 536
 537           <xi:include href="version-info.xml" xpointer="v251"/>
 538         </listitem>
 539       </varlistentry>
 540
 541       <varlistentry>
 542         <term><varname>systemd.cpu_affinity=</varname></term>
 543
 544         <listitem>
 545           <para>Overrides the CPU affinity mask for the service manager and the default for all child
 546           processes it forks. This takes precedence over <varname>CPUAffinity=</varname>, see
 547           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 548           for details.</para>
 549
 550           <xi:include href="version-info.xml" xpointer="v245"/>
 551         </listitem>
 552       </varlistentry>
 553
 554       <varlistentry>
 555         <term><varname>modules_load=</varname></term>
 556         <term><varname>rd.modules_load=</varname></term>
 557
 558         <listitem>
 559           <para>Load a specific kernel module early at boot. For
 560           details, see
 561           <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 562
 563           <xi:include href="version-info.xml" xpointer="v187"/>
 564         </listitem>
 565       </varlistentry>
 566
 567       <varlistentry>
 568         <term><varname>nameserver=</varname></term>
 569         <term><varname>domain=</varname></term>
 570
 571         <listitem><para>Configures DNS server information and search domains, see
 572         <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 573         for details.</para>
 574
 575         <xi:include href="version-info.xml" xpointer="v253"/></listitem>
 576       </varlistentry>
 577
 578       <varlistentry>
 579         <term><varname>resume=</varname></term>
 580         <term><varname>resumeflags=</varname></term>
 581
 582         <listitem>
 583           <para>Enables resume from hibernation using the specified
 584           device and mount options. All
 585           <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-like
 586           paths are supported. For details, see
 587           <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 588
 589           <xi:include href="version-info.xml" xpointer="v217"/>
 590         </listitem>
 591       </varlistentry>
 592
 593       <varlistentry>
 594         <term><varname>systemd.firstboot=</varname></term>
 595
 596         <listitem><para>Takes a boolean argument, defaults to on. If off,
 597         <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 598         will not query the user for basic system settings, even if the system boots up for the first time and
 599         the relevant settings are not initialized yet. Not to be confused with
 600         <varname>systemd.condition-first-boot=</varname> (see below), which overrides the result of the
 601         <varname>ConditionFirstBoot=</varname> unit file condition, and thus controls more than just
 602         <filename>systemd-firstboot.service</filename> behaviour.</para>
 603
 604         <xi:include href="version-info.xml" xpointer="v233"/></listitem>
 605       </varlistentry>
 606
 607       <varlistentry>
 608         <term><varname>systemd.condition-needs-update=</varname></term>
 609
 610         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 611         <varname>ConditionNeedsUpdate=</varname> unit condition checks. See
 612         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 613         details.</para>
 614
 615         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 616       </varlistentry>
 617
 618       <varlistentry>
 619         <term><varname>systemd.condition-first-boot=</varname></term>
 620
 621         <listitem><para>Takes a boolean argument. If specified, overrides the result of
 622         <varname>ConditionFirstBoot=</varname> unit condition checks. See
 623         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 624         details. Not to be confused with <varname>systemd.firstboot=</varname> which only controls behaviour
 625         of the <filename>systemd-firstboot.service</filename> system service but has no effect on the
 626         condition check (see above).</para>
 627
 628         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 629       </varlistentry>
 630
 631       <varlistentry>
 632         <term><varname>systemd.clock-usec=</varname></term>
 633
 634         <listitem><para>Takes a decimal, numeric timestamp in μs since January 1st 1970, 00:00am, to set the
 635         system clock to. The system time is set to the specified timestamp early during boot. It is not
 636         propagated to the hardware clock (RTC).</para>
 637
 638         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 639       </varlistentry>
 640
 641       <varlistentry>
 642         <term><varname>systemd.random-seed=</varname></term>
 643
 644         <listitem><para>Takes a base64 encoded random seed value to credit with full entropy to the kernel's
 645         random pool during early service manager initialization. This option is useful in testing
 646         environments where delays due to random pool initialization in entropy starved virtual machines shall
 647         be avoided.</para>
 648
 649         <para>Note that if this option is used the seed is accessible to unprivileged programs from
 650         <filename>/proc/cmdline</filename>. This option is hence a security risk when used outside of test
 651         systems, since the (possibly) only seed used for initialization of the kernel's entropy pool might be
 652         easily acquired by unprivileged programs.</para>
 653
 654         <para>It is recommended to pass 512 bytes of randomized data (as that matches the Linux kernel pool
 655         size), which may be generated with a command like the following:</para>
 656
 657         <programlisting>dd if=/dev/urandom bs=512 count=1 status=none | base64 -w 0</programlisting>
 658
 659         <para>Again: do not use this option outside of testing environments, it's a security risk elsewhere,
 660         as secret key material derived from the entropy pool can possibly be reconstructed by unprivileged
 661         programs.</para>
 662
 663         <xi:include href="version-info.xml" xpointer="v246"/>
 664         </listitem>
 665       </varlistentry>
 666
 667       <varlistentry>
 668         <term><varname>systemd.hostname=</varname></term>
 669
 670         <listitem><para>Accepts a hostname to set during early boot. If specified takes precedence over what
 671         is set in <filename>/etc/hostname</filename>. Note that this does not bar later runtime changes to
 672         the hostname, it simply controls the initial hostname set during early boot.</para>
 673
 674         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 675       </varlistentry>
 676
 677       <varlistentry>
 678         <term><varname>systemd.tty.term.<replaceable>tty</replaceable>=</varname></term>
 679         <term><varname>systemd.tty.rows.<replaceable>tty</replaceable>=</varname></term>
 680         <term><varname>systemd.tty.columns.<replaceable>tty</replaceable>=</varname></term>
 681
 682         <listitem><para>These arguments allow configuring default values for <varname>$TERM</varname>,
 683         <varname>TTYRows=</varname>, and <varname>TTYColumns=</varname> for tty
 684         <replaceable>tty</replaceable>. Additionally, <varname>systemd.tty.term.console</varname> will
 685         configure the <varname>$TERM</varname> value used by <command>systemd</command> if not set explicitly
 686         using <varname>TERM</varname> on the kernel command line. The tty name should be specified without
 687         the <filename>/dev/</filename> prefix (e.g. <literal>systemd.tty.rows.ttyS0=80</literal>).
 688         </para>
 689
 690         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 691       </varlistentry>
 692     </variablelist>
 693   </refsect1>
 694
 695   <refsect1>
 696       <title>History</title>
 697
 698       <variablelist>
 699         <varlistentry>
 700           <term>systemd 252</term>
 701           <listitem><para>Kernel command-line arguments <varname>systemd.unified_cgroup_hierarchy</varname>
 702           and <varname>systemd.legacy_systemd_cgroup_controller</varname> were deprecated. Please switch to
 703           the unified cgroup hierarchy.</para>
 704
 705           <xi:include href="version-info.xml" xpointer="v252"/></listitem>
 706         </varlistentry>
 707       </variablelist>
 708   </refsect1>
 709
 710   <refsect1>
 711       <title>See Also</title>
 712       <para>
 713         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 714         <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 715         <citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 716         <citerefentry><refentrytitle>systemd.system-credentials</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 717         <citerefentry><refentrytitle>smbios-type-11</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 718         <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 719         <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 720         <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 721         <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 722         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 723         <citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 724         <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 725         <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 726         <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 727         <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 728         <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 729         <citerefentry><refentrytitle>systemd-getty-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 730         <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 731         <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 732         <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 733         <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 734         <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 735         <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 736         <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 737         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 738       </para>
 739   </refsect1>
 740
 741 </refentry>