man/kernel-command-line.xml

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