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