man/kernel-command-line.xml

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