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 initial RAM disk (initrd) and basic userspace functionality may be configured at
  31     boot via 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://www.kernel.org/doc/html/latest/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 initial RAM
  44     disk, please see
  45     <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
  46     or the documentation of the specific initrd implementation of your
  47     installation.</para>
  48   </refsect1>
  49
  50   <refsect1>
  51     <title>Core OS Command Line Arguments</title>
  52
  53     <variablelist class='kernel-commandline-options'>
  54       <varlistentry>
  55         <term><varname>systemd.unit=</varname></term>
  56         <term><varname>rd.systemd.unit=</varname></term>
  57         <term><varname>systemd.dump_core</varname></term>
  58         <term><varname>systemd.early_core_pattern=</varname></term>
  59         <term><varname>systemd.crash_chvt</varname></term>
  60         <term><varname>systemd.crash_shell</varname></term>
  61         <term><varname>systemd.crash_reboot</varname></term>
  62         <term><varname>systemd.confirm_spawn</varname></term>
  63         <term><varname>systemd.service_watchdogs</varname></term>
  64         <term><varname>systemd.show_status</varname></term>
  65         <term><varname>systemd.status_unit_format=</varname></term>
  66         <term><varname>systemd.log_target=</varname></term>
  67         <term><varname>systemd.log_level=</varname></term>
  68         <term><varname>systemd.log_location=</varname></term>
  69         <term><varname>systemd.log_color</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.unified_cgroup_hierarchy</varname></term>
  75         <term><varname>systemd.legacy_systemd_cgroup_controller</varname></term>
  76         <listitem>
  77           <para>Parameters understood by the system and service
  78           manager to control system behavior. For details, see
  79           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
  80         </listitem>
  81       </varlistentry>
  82
  83       <varlistentry>
  84         <term><varname>systemd.mask=</varname></term>
  85         <term><varname>systemd.wants=</varname></term>
  86         <term><varname>systemd.debug_shell</varname></term>
  87         <listitem>
  88           <para>Additional parameters understood by
  89           <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  90           to mask or start specific units at boot, or invoke a debug
  91           shell on tty9.</para>
  92         </listitem>
  93       </varlistentry>
  94
  95       <varlistentry>
  96         <term><varname>systemd.run=</varname></term>
  97         <term><varname>systemd.run_success_action=</varname></term>
  98         <term><varname>systemd.run_failure_action=</varname></term>
  99         <listitem>
 100           <para>Additional parameters understood by
 101           <citerefentry><refentrytitle>systemd-run-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, to
 102           run a command line specified on the kernel command line as system service after booting up.</para>
 103         </listitem>
 104       </varlistentry>
 105
 106       <varlistentry>
 107         <term><varname>systemd.early_core_pattern=</varname></term>
 108         <listitem>
 109           <para>During early boot, the generation of core dump files is disabled until a core dump handler (if any)
 110           takes over. This parameter allows to specifies an absolute path where core dump files should be stored until
 111           a handler is installed. The path should be absolute and may contain specifiers, see
 112           <citerefentry><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details.</para>
 113         </listitem>
 114       </varlistentry>
 115
 116       <varlistentry>
 117         <term><varname>systemd.restore_state=</varname></term>
 118         <listitem>
 119           <para>This parameter is understood by several system tools
 120           to control whether or not they should restore system state
 121           from the previous boot. For details, see
 122           <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 123           and
 124           <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 125           </para>
 126         </listitem>
 127       </varlistentry>
 128
 129       <varlistentry>
 130         <term><varname>systemd.volatile=</varname></term>
 131         <listitem>
 132           <para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
 133           the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
 134           directory and <filename>/var</filename> are mounted as specified on the kernel command line or
 135           <filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
 136           this case the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
 137           <filename>/usr</filename> is mounted from the file system configured as root device, in read-only mode. This
 138           enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
 139           configuration and no stored state in effect, as <filename>/etc</filename> and <filename>/var</filename> (as
 140           well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
 141           setting is set to <literal>state</literal> the root file system is mounted read-only, however
 142           <filename>/var</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
 143           system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. If
 144           this setting is set to <literal>overlay</literal> the root file system is set up as
 145           <literal>overlayfs</literal> mount combining the read-only root directory with a writable
 146           <literal>tmpfs</literal>, so that no modifications are made to disk, but the file system may be modified
 147           nonetheless with all changes being lost at reboot. For details, see
 148           <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 149           and
 150           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 151         </listitem>
 152       </varlistentry>
 153
 154       <varlistentry>
 155         <term><varname>quiet</varname></term>
 156         <listitem>
 157           <para>Parameter understood by both the kernel and the system
 158           and service manager to control console log verbosity. For
 159           details, see
 160           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 161         </listitem>
 162       </varlistentry>
 163
 164       <varlistentry>
 165         <term><varname>debug</varname></term>
 166         <listitem>
 167           <para>Parameter understood by both the kernel and the system
 168           and service manager to control console log verbosity. For
 169           details, see
 170           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 171         </listitem>
 172       </varlistentry>
 173
 174       <varlistentry>
 175         <term><varname>-b</varname></term>
 176         <term><varname>rd.emergency</varname></term>
 177         <term><varname>emergency</varname></term>
 178         <term><varname>rd.rescue</varname></term>
 179         <term><varname>rescue</varname></term>
 180         <term><varname>single</varname></term>
 181         <term><varname>s</varname></term>
 182         <term><varname>S</varname></term>
 183         <term><varname>1</varname></term>
 184         <term><varname>2</varname></term>
 185         <term><varname>3</varname></term>
 186         <term><varname>4</varname></term>
 187         <term><varname>5</varname></term>
 188         <listitem>
 189           <para>Parameters understood by the system and service
 190           manager, as compatibility and convenience options. For details, see
 191           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 192         </listitem>
 193       </varlistentry>
 194
 195       <varlistentry>
 196         <term><varname>locale.LANG=</varname></term>
 197         <term><varname>locale.LANGUAGE=</varname></term>
 198         <term><varname>locale.LC_CTYPE=</varname></term>
 199         <term><varname>locale.LC_NUMERIC=</varname></term>
 200         <term><varname>locale.LC_TIME=</varname></term>
 201         <term><varname>locale.LC_COLLATE=</varname></term>
 202         <term><varname>locale.LC_MONETARY=</varname></term>
 203         <term><varname>locale.LC_MESSAGES=</varname></term>
 204         <term><varname>locale.LC_PAPER=</varname></term>
 205         <term><varname>locale.LC_NAME=</varname></term>
 206         <term><varname>locale.LC_ADDRESS=</varname></term>
 207         <term><varname>locale.LC_TELEPHONE=</varname></term>
 208         <term><varname>locale.LC_MEASUREMENT=</varname></term>
 209         <term><varname>locale.LC_IDENTIFICATION=</varname></term>
 210         <listitem>
 211           <para>Parameters understood by the system and service
 212           manager to control locale and language settings. For
 213           details, see
 214           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 215         </listitem>
 216       </varlistentry>
 217
 218       <varlistentry>
 219         <term><varname>fsck.mode=</varname></term>
 220         <term><varname>fsck.repair=</varname></term>
 221
 222         <listitem>
 223           <para>Parameters understood by the file system checker
 224           services. For details, see
 225           <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 226         </listitem>
 227       </varlistentry>
 228
 229       <varlistentry>
 230         <term><varname>quotacheck.mode=</varname></term>
 231
 232         <listitem>
 233           <para>Parameter understood by the file quota checker
 234           service. For details, see
 235           <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 236         </listitem>
 237       </varlistentry>
 238
 239       <varlistentry>
 240         <term><varname>systemd.journald.forward_to_syslog=</varname></term>
 241         <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
 242         <term><varname>systemd.journald.forward_to_console=</varname></term>
 243         <term><varname>systemd.journald.forward_to_wall=</varname></term>
 244
 245         <listitem>
 246           <para>Parameters understood by the journal service. For
 247           details, see
 248           <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 249         </listitem>
 250       </varlistentry>
 251
 252       <varlistentry>
 253         <term><varname>vconsole.keymap=</varname></term>
 254         <term><varname>vconsole.keymap_toggle=</varname></term>
 255         <term><varname>vconsole.font=</varname></term>
 256         <term><varname>vconsole.font_map=</varname></term>
 257         <term><varname>vconsole.font_unimap=</varname></term>
 258
 259         <listitem>
 260           <para>Parameters understood by the virtual console setup logic. For details, see
 261           <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 262         </listitem>
 263       </varlistentry>
 264
 265       <varlistentry>
 266         <term><varname>udev.log_priority=</varname></term>
 267         <term><varname>rd.udev.log_priority=</varname></term>
 268         <term><varname>udev.children_max=</varname></term>
 269         <term><varname>rd.udev.children_max=</varname></term>
 270         <term><varname>udev.exec_delay=</varname></term>
 271         <term><varname>rd.udev.exec_delay=</varname></term>
 272         <term><varname>udev.event_timeout=</varname></term>
 273         <term><varname>rd.udev.event_timeout=</varname></term>
 274         <term><varname>net.ifnames=</varname></term>
 275         <term><varname>net.naming-scheme=</varname></term>
 276
 277         <listitem>
 278           <para>Parameters understood by the device event managing
 279           daemon. For details, see
 280           <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 281         </listitem>
 282       </varlistentry>
 283
 284       <varlistentry>
 285         <term><varname>plymouth.enable=</varname></term>
 286
 287         <listitem>
 288           <para>May be used to disable the Plymouth boot splash. For
 289           details, see
 290           <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 291         </listitem>
 292       </varlistentry>
 293
 294       <varlistentry>
 295         <term><varname>luks=</varname></term>
 296         <term><varname>rd.luks=</varname></term>
 297         <term><varname>luks.crypttab=</varname></term>
 298         <term><varname>rd.luks.crypttab=</varname></term>
 299         <term><varname>luks.name=</varname></term>
 300         <term><varname>rd.luks.name=</varname></term>
 301         <term><varname>luks.uuid=</varname></term>
 302         <term><varname>rd.luks.uuid=</varname></term>
 303         <term><varname>luks.options=</varname></term>
 304         <term><varname>rd.luks.options=</varname></term>
 305         <term><varname>luks.key=</varname></term>
 306         <term><varname>rd.luks.key=</varname></term>
 307
 308         <listitem>
 309           <para>Configures the LUKS full-disk encryption logic at
 310           boot. For details, see
 311           <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 312         </listitem>
 313       </varlistentry>
 314
 315       <varlistentry>
 316         <term><varname>fstab=</varname></term>
 317         <term><varname>rd.fstab=</varname></term>
 318
 319         <listitem>
 320           <para>Configures the <filename>/etc/fstab</filename> logic
 321           at boot. For details, see
 322           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 323         </listitem>
 324       </varlistentry>
 325
 326       <varlistentry>
 327         <term><varname>root=</varname></term>
 328         <term><varname>rootfstype=</varname></term>
 329         <term><varname>rootflags=</varname></term>
 330         <term><varname>ro</varname></term>
 331         <term><varname>rw</varname></term>
 332
 333         <listitem>
 334           <para>Configures the root file system and its file system
 335           type and mount options, as well as whether it shall be
 336           mounted read-only or read-write initially. For details,
 337           see
 338           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 339         </listitem>
 340       </varlistentry>
 341
 342       <varlistentry>
 343         <term><varname>mount.usr=</varname></term>
 344         <term><varname>mount.usrfstype=</varname></term>
 345         <term><varname>mount.usrflags=</varname></term>
 346
 347         <listitem>
 348           <para>Configures the /usr file system (if required) and
 349           its file system type and mount options. For details, see
 350           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 351         </listitem>
 352       </varlistentry>
 353
 354       <varlistentry>
 355         <term><varname>roothash=</varname></term>
 356         <term><varname>systemd.verity=</varname></term>
 357         <term><varname>rd.systemd.verity=</varname></term>
 358         <term><varname>systemd.verity_root_data=</varname></term>
 359         <term><varname>systemd.verity_root_hash=</varname></term>
 360         <listitem>
 361           <para>Configures the integrity protection root hash for the root file system, and other related
 362           parameters. For details, see
 363           <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 364         </listitem>
 365       </varlistentry>
 366
 367       <varlistentry>
 368         <term><varname>systemd.gpt_auto=</varname></term>
 369         <term><varname>rd.systemd.gpt_auto=</varname></term>
 370
 371         <listitem>
 372           <para>Configures whether GPT based partition auto-discovery
 373           shall be attempted. For details, see
 374           <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 375         </listitem>
 376       </varlistentry>
 377
 378       <varlistentry>
 379         <term><varname>systemd.default_timeout_start_sec=</varname></term>
 380
 381         <listitem>
 382           <para>Overwrites the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at boot. For details,
 383           see <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 384         </listitem>
 385       </varlistentry>
 386
 387       <varlistentry>
 388         <term><varname>systemd.watchdog_device=</varname></term>
 389
 390         <listitem>
 391           <para>Overwrites the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
 392           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 393         </listitem>
 394       </varlistentry>
 395
 396       <varlistentry>
 397         <term><varname>modules_load=</varname></term>
 398         <term><varname>rd.modules_load=</varname></term>
 399
 400         <listitem>
 401           <para>Load a specific kernel module early at boot. For
 402           details, see
 403           <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 404         </listitem>
 405       </varlistentry>
 406
 407       <varlistentry>
 408         <term><varname>resume=</varname></term>
 409         <term><varname>resumeflags=</varname></term>
 410
 411         <listitem>
 412           <para>Enables resume from hibernation using the specified
 413           device and mount options. All
 414           <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-like
 415           paths are supported. For details, see
 416           <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 417         </listitem>
 418       </varlistentry>
 419
 420       <varlistentry>
 421         <term><varname>systemd.firstboot=</varname></term>
 422
 423         <listitem><para>Takes a boolean argument, defaults to on. If off,
 424         <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 425         will not query the user for basic system settings, even if the system boots up for the first time and the
 426         relevant settings are not initialized yet.</para></listitem>
 427       </varlistentry>
 428     </variablelist>
 429
 430   </refsect1>
 431
 432   <refsect1>
 433       <title>See Also</title>
 434       <para>
 435         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 436         <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 437         <citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 438         <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 439         <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 440         <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 441         <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 442         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 443         <citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 444         <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 445         <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 446         <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 447         <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 448         <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 449         <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 450         <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 451         <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 452         <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 453         <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 454         <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 455         <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 456         <citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 457       </para>
 458   </refsect1>
 459
 460 </refentry>