Documentation/kernel-parameters.txt

   1                           Kernel Parameters
   2                           ~~~~~~~~~~~~~~~~~
   3
   4 The following is a consolidated list of the kernel parameters as implemented
   5 (mostly) by the __setup() macro and sorted into English Dictionary order
   6 (defined as ignoring all punctuation and sorting digits before letters in a
   7 case insensitive manner), and with descriptions where known.
   8
   9 Module parameters for loadable modules are specified only as the
  10 parameter name with optional '=' and value as appropriate, such as:
  11
  12         modprobe usbcore blinkenlights=1
  13
  14 Module parameters for modules that are built into the kernel image
  15 are specified on the kernel command line with the module name plus
  16 '.' plus parameter name, with '=' and value if appropriate, such as:
  17
  18         usbcore.blinkenlights=1
  19
  20 This document may not be entirely up to date and comprehensive. The command
  21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  22 module. Loadable modules, after being loaded into the running kernel, also
  23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  24 parameters may be changed at runtime by the command
  25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  26
  27 The parameters listed below are only valid if certain kernel build options were
  28 enabled and if respective hardware is present. The text in square brackets at
  29 the beginning of each description states the restrictions within which a
  30 parameter is applicable:
  31
  32         ACPI    ACPI support is enabled.
  33         ALSA    ALSA sound support is enabled.
  34         APIC    APIC support is enabled.
  35         APM     Advanced Power Management support is enabled.
  36         AX25    Appropriate AX.25 support is enabled.
  37         CD      Appropriate CD support is enabled.
  38         DRM     Direct Rendering Management support is enabled.
  39         EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
  40         EFI     EFI Partitioning (GPT) is enabled
  41         EIDE    EIDE/ATAPI support is enabled.
  42         FB      The frame buffer device is enabled.
  43         HW      Appropriate hardware is enabled.
  44         IA-32   IA-32 aka i386 architecture is enabled.
  45         IA-64   IA-64 architecture is enabled.
  46         IOSCHED More than one I/O scheduler is enabled.
  47         IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
  48         ISAPNP  ISA PnP code is enabled.
  49         ISDN    Appropriate ISDN support is enabled.
  50         JOY     Appropriate joystick support is enabled.
  51         LP      Printer support is enabled.
  52         LOOP    Loopback device support is enabled.
  53         M68k    M68k architecture is enabled.
  54                         These options have more detailed description inside of
  55                         Documentation/m68k/kernel-options.txt.
  56         MCA     MCA bus support is enabled.
  57         MDA     MDA console support is enabled.
  58         MOUSE   Appropriate mouse support is enabled.
  59         MSI     Message Signaled Interrupts (PCI).
  60         MTD     MTD support is enabled.
  61         NET     Appropriate network support is enabled.
  62         NUMA    NUMA support is enabled.
  63         GENERIC_TIME The generic timeofday code is enabled.
  64         NFS     Appropriate NFS support is enabled.
  65         OSS     OSS sound support is enabled.
  66         PARIDE  The ParIDE subsystem is enabled.
  67         PARISC  The PA-RISC architecture is enabled.
  68         PCI     PCI bus support is enabled.
  69         PCMCIA  The PCMCIA subsystem is enabled.
  70         PNP     Plug & Play support is enabled.
  71         PPC     PowerPC architecture is enabled.
  72         PPT     Parallel port support is enabled.
  73         PS2     Appropriate PS/2 support is enabled.
  74         RAM     RAM disk support is enabled.
  75         S390    S390 architecture is enabled.
  76         SCSI    Appropriate SCSI support is enabled.
  77                         A lot of drivers has their options described inside of
  78                         Documentation/scsi/.
  79         SELINUX SELinux support is enabled.
  80         SERIAL  Serial support is enabled.
  81         SMP     The kernel is an SMP kernel.
  82         SPARC   Sparc architecture is enabled.
  83         SWSUSP  Software suspend is enabled.
  84         TS      Appropriate touchscreen support is enabled.
  85         USB     USB support is enabled.
  86         USBHID  USB Human Interface Device support is enabled.
  87         V4L     Video For Linux support is enabled.
  88         VGA     The VGA console has been enabled.
  89         VT      Virtual terminal support is enabled.
  90         WDT     Watchdog support is enabled.
  91         XT      IBM PC/XT MFM hard disk support is enabled.
  92         X86-64  X86-64 architecture is enabled.
  93                         More X86-64 boot options can be found in
  94                         Documentation/x86_64/boot-options.txt .
  95
  96 In addition, the following text indicates that the option:
  97
  98         BUGS=   Relates to possible processor bugs on the said processor.
  99         KNL     Is a kernel start-up parameter.
 100         BOOT    Is a boot loader parameter.
 101
 102 Parameters denoted with BOOT are actually interpreted by the boot
 103 loader, and have no meaning to the kernel directly.
 104 Do not modify the syntax of boot loader parameters without extreme
 105 need or coordination with <Documentation/i386/boot.txt>.
 106
 107 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
 108 a trailing = on the name of any parameter states that that parameter will
 109 be entered as an environment variable, whereas its absence indicates that
 110 it will appear as a kernel argument readable via /proc/cmdline by programs
 111 running once the system is up.
 112
 113 The number of kernel parameters is not limited, but the length of the
 114 complete command line (parameters including spaces etc.) is limited to
 115 a fixed number of characters. This limit depends on the architecture
 116 and is between 256 and 4096 characters. It is defined in the file
 117 ./include/asm/setup.h as COMMAND_LINE_SIZE.
 118
 119
 120         53c7xx=         [HW,SCSI] Amiga SCSI controllers
 121                         See header of drivers/scsi/53c7xx.c.
 122                         See also Documentation/scsi/ncr53c7xx.txt.
 123
 124         acpi=           [HW,ACPI] Advanced Configuration and Power Interface
 125                         Format: { force | off | ht | strict | noirq }
 126                         force -- enable ACPI if default was off
 127                         off -- disable ACPI if default was on
 128                         noirq -- do not use ACPI for IRQ routing
 129                         ht -- run only enough ACPI to enable Hyper Threading
 130                         strict -- Be less tolerant of platforms that are not
 131                                 strictly ACPI specification compliant.
 132
 133                         See also Documentation/pm.txt, pci=noacpi
 134
 135         acpi_sleep=     [HW,ACPI] Sleep options
 136                         Format: { s3_bios, s3_mode }
 137                         See Documentation/power/video.txt
 138
 139         acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
 140                         Format: { level | edge | high | low }
 141
 142         acpi_irq_balance [HW,ACPI]
 143                         ACPI will balance active IRQs
 144                         default in APIC mode
 145
 146         acpi_irq_nobalance [HW,ACPI]
 147                         ACPI will not move active IRQs (default)
 148                         default in PIC mode
 149
 150         acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
 151                         use by PCI
 152                         Format: <irq>,<irq>...
 153
 154         acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 155                         Format: <irq>,<irq>...
 156
 157         acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
 158                         Format: To spoof as Windows 98: ="Microsoft Windows"
 159
 160         acpi_osi=       [HW,ACPI] empty param disables _OSI
 161
 162         acpi_serialize  [HW,ACPI] force serialization of AML methods
 163
 164         acpi_skip_timer_override [HW,ACPI]
 165                         Recognize and ignore IRQ0/pin2 Interrupt Override.
 166                         For broken nForce2 BIOS resulting in XT-PIC timer.
 167         acpi_use_timer_override [HW,ACPI}
 168                         Use timer override. For some broken Nvidia NF5 boards
 169                         that require a timer override, but don't have
 170                         HPET
 171
 172         acpi_dbg_layer= [HW,ACPI]
 173                         Format: <int>
 174                         Each bit of the <int> indicates an ACPI debug layer,
 175                         1: enable, 0: disable. It is useful for boot time
 176                         debugging. After system has booted up, it can be set
 177                         via /proc/acpi/debug_layer.
 178
 179         acpi_dbg_level= [HW,ACPI]
 180                         Format: <int>
 181                         Each bit of the <int> indicates an ACPI debug level,
 182                         1: enable, 0: disable. It is useful for boot time
 183                         debugging. After system has booted up, it can be set
 184                         via /proc/acpi/debug_level.
 185
 186         acpi_fake_ecdt  [HW,ACPI] Workaround failure due to BIOS lacking ECDT
 187
 188         acpi_generic_hotkey [HW,ACPI]
 189                         Allow consolidated generic hotkey driver to
 190                         override platform specific driver.
 191                         See also Documentation/acpi-hotkey.txt.
 192
 193         acpi_pm_good    [IA-32,X86-64]
 194                         Override the pmtimer bug detection: force the kernel
 195                         to assume that this machine's pmtimer latches its value
 196                         and always returns good values.
 197
 198         enable_timer_pin_1 [i386,x86-64]
 199                         Enable PIN 1 of APIC timer
 200                         Can be useful to work around chipset bugs
 201                         (in particular on some ATI chipsets).
 202                         The kernel tries to set a reasonable default.
 203
 204         disable_timer_pin_1 [i386,x86-64]
 205                         Disable PIN 1 of APIC timer
 206                         Can be useful to work around chipset bugs.
 207
 208         ad1816=         [HW,OSS]
 209                         Format: <io>,<irq>,<dma>,<dma2>
 210                         See also Documentation/sound/oss/AD1816.
 211
 212         ad1848=         [HW,OSS]
 213                         Format: <io>,<irq>,<dma>,<dma2>,<type>
 214
 215         adlib=          [HW,OSS]
 216                         Format: <io>
 217
 218         advansys=       [HW,SCSI]
 219                         See header of drivers/scsi/advansys.c.
 220
 221         advwdt=         [HW,WDT] Advantech WDT
 222                         Format: <iostart>,<iostop>
 223
 224         aedsp16=        [HW,OSS] Audio Excel DSP 16
 225                         Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
 226                         See also header of sound/oss/aedsp16.c.
 227
 228         aha152x=        [HW,SCSI]
 229                         See Documentation/scsi/aha152x.txt.
 230
 231         aha1542=        [HW,SCSI]
 232                         Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
 233
 234         aic7xxx=        [HW,SCSI]
 235                         See Documentation/scsi/aic7xxx.txt.
 236
 237         aic79xx=        [HW,SCSI]
 238                         See Documentation/scsi/aic79xx.txt.
 239
 240         amijoy.map=     [HW,JOY] Amiga joystick support
 241                         Map of devices attached to JOY0DAT and JOY1DAT
 242                         Format: <a>,<b>
 243                         See also Documentation/kernel/input/joystick.txt
 244
 245         analog.map=     [HW,JOY] Analog joystick and gamepad support
 246                         Specifies type or capabilities of an analog joystick
 247                         connected to one of 16 gameports
 248                         Format: <type1>,<type2>,..<type16>
 249
 250         apc=            [HW,SPARC]
 251                         Power management functions (SPARCstation-4/5 + deriv.)
 252                         Format: noidle
 253                         Disable APC CPU standby support. SPARCstation-Fox does
 254                         not play well with APC CPU idle - disable it if you have
 255                         APC and your system crashes randomly.
 256
 257         apic=           [APIC,i386] Change the output verbosity whilst booting
 258                         Format: { quiet (default) | verbose | debug }
 259                         Change the amount of debugging information output
 260                         when initialising the APIC and IO-APIC components.
 261
 262         apm=            [APM] Advanced Power Management
 263                         See header of arch/i386/kernel/apm.c.
 264
 265         applicom=       [HW]
 266                         Format: <mem>,<irq>
 267
 268         arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 269                         Format: <io>,<irq>,<nodeID>
 270
 271         ataflop=        [HW,M68k]
 272
 273         atarimouse=     [HW,MOUSE] Atari Mouse
 274
 275         atascsi=        [HW,SCSI] Atari SCSI
 276
 277         atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 278                         EzKey and similar keyboards
 279
 280         atkbd.reset=    [HW] Reset keyboard during initialization
 281
 282         atkbd.set=      [HW] Select keyboard code set
 283                         Format: <int> (2 = AT (default), 3 = PS/2)
 284
 285         atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 286                         keyboards
 287
 288         atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 289                         Format: <bool> (0 = real, 1 = synthetic (default))
 290
 291         atkbd.softrepeat= [HW]
 292                         Use software keyboard repeat
 293
 294         autotest        [IA64]
 295
 296         aztcd=          [HW,CD] Aztech CD268 CDROM driver
 297                         Format: <io>,0x79 (?)
 298
 299         baycom_epp=     [HW,AX25]
 300                         Format: <io>,<mode>
 301
 302         baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 303                         Format: <io>,<mode>
 304                         See header of drivers/net/hamradio/baycom_par.c.
 305
 306         baycom_ser_fdx= [HW,AX25]
 307                         BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 308                         Format: <io>,<irq>,<mode>[,<baud>]
 309                         See header of drivers/net/hamradio/baycom_ser_fdx.c.
 310
 311         baycom_ser_hdx= [HW,AX25]
 312                         BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 313                         Format: <io>,<irq>,<mode>
 314                         See header of drivers/net/hamradio/baycom_ser_hdx.c.
 315
 316         blkmtd_device=  [HW,MTD]
 317         blkmtd_erasesz=
 318         blkmtd_ro=
 319         blkmtd_bs=
 320         blkmtd_count=
 321
 322         bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 323         bttv.radio=     Most important insmod options are available as
 324                         kernel args too.
 325         bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 326         bttv.tuner=     and Documentation/video4linux/bttv/CARDLIST
 327
 328         BusLogic=       [HW,SCSI]
 329                         See drivers/scsi/BusLogic.c, comment before function
 330                         BusLogic_ParseDriverOptions().
 331
 332         c101=           [NET] Moxa C101 synchronous serial card
 333
 334         cachesize=      [BUGS=IA-32] Override level 2 CPU cache size detection.
 335                         Sometimes CPU hardware bugs make them report the cache
 336                         size incorrectly. The kernel will attempt work arounds
 337                         to fix known problems, but for some CPUs it is not
 338                         possible to determine what the correct size should be.
 339                         This option provides an override for these situations.
 340
 341         cdu31a=         [HW,CD]
 342                         Format: <io>,<irq>[,PAS]
 343                         See header of drivers/cdrom/cdu31a.c.
 344
 345         chandev=        [HW,NET] Generic channel device initialisation
 346
 347         checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 348                         Format: { "0" | "1" }
 349                         See security/selinux/Kconfig help text.
 350                         0 -- check protection applied by kernel (includes
 351                                 any implied execute protection).
 352                         1 -- check protection requested by application.
 353                         Default value is set via a kernel config option.
 354                         Value can be changed at runtime via
 355                                 /selinux/checkreqprot.
 356
 357         clock=          [BUGS=IA-32, HW] gettimeofday clocksource override.
 358                         [Deprecated]
 359                         Forces specified clocksource (if available) to be used
 360                         when calculating gettimeofday(). If specified
 361                         clocksource is not available, it defaults to PIT.
 362                         Format: { pit | tsc | cyclone | pmtmr }
 363
 364         disable_8254_timer
 365         enable_8254_timer
 366                         [IA32/X86_64] Disable/Enable interrupt 0 timer routing
 367                         over the 8254 in addition to over the IO-APIC. The
 368                         kernel tries to set a sensible default.
 369
 370         hpet=           [IA-32,HPET] option to disable HPET and use PIT.
 371                         Format: disable
 372
 373         cm206=          [HW,CD]
 374                         Format: { auto | [<io>,][<irq>] }
 375
 376         com20020=       [HW,NET] ARCnet - COM20020 chipset
 377                         Format:
 378                         <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 379
 380         com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 381                         Format: <io>[,<irq>]
 382
 383         com90xx=        [HW,NET]
 384                         ARCnet - COM90xx chipset (memory-mapped buffers)
 385                         Format: <io>[,<irq>[,<memstart>]]
 386
 387         condev=         [HW,S390] console device
 388         conmode=
 389
 390         console=        [KNL] Output console device and options.
 391
 392                 tty<n>  Use the virtual console device <n>.
 393
 394                 ttyS<n>[,options]
 395                 ttyUSB0[,options]
 396                         Use the specified serial port.  The options are of
 397                         the form "bbbbpnf", where "bbbb" is the baud rate,
 398                         "p" is parity ("n", "o", or "e"), "n" is number of
 399                         bits, and "f" is flow control ("r" for RTS or
 400                         omit it).  Default is "9600n8".
 401
 402                         See Documentation/serial-console.txt for more
 403                         information.  See
 404                         Documentation/networking/netconsole.txt for an
 405                         alternative.
 406
 407                 uart,io,<addr>[,options]
 408                 uart,mmio,<addr>[,options]
 409                         Start an early, polled-mode console on the 8250/16550
 410                         UART at the specified I/O port or MMIO address,
 411                         switching to the matching ttyS device later.  The
 412                         options are the same as for ttyS, above.
 413
 414         cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 415                         Format:
 416                         <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 417
 418         cpia_pp=        [HW,PPT]
 419                         Format: { parport<nr> | auto | none }
 420
 421         crashkernel=nn[KMG]@ss[KMG]
 422                         [KNL] Reserve a chunk of physical memory to
 423                         hold a kernel to switch to with kexec on panic.
 424
 425         cs4232=         [HW,OSS]
 426                         Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
 427
 428         cs89x0_dma=     [HW,NET]
 429                         Format: <dma>
 430
 431         cs89x0_media=   [HW,NET]
 432                         Format: { rj45 | aui | bnc }
 433
 434         cyclades=       [HW,SERIAL] Cyclades multi-serial port adapter.
 435
 436         dasd=           [HW,NET]
 437                         See header of drivers/s390/block/dasd_devmap.c.
 438
 439         db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 440                         (one device per port)
 441                         Format: <port#>,<type>
 442                         See also Documentation/input/joystick-parport.txt
 443
 444         debug           [KNL] Enable kernel debugging (events log level).
 445
 446         debug_locks_verbose=
 447                         [KNL] verbose self-tests
 448                         Format=<0|1>
 449                         Print debugging info while doing the locking API
 450                         self-tests.
 451                         We default to 0 (no extra messages), setting it to
 452                         1 will print _a lot_ more information - normally
 453                         only useful to kernel developers.
 454
 455         decnet=         [HW,NET]
 456                         Format: <area>[,<node>]
 457                         See also Documentation/networking/decnet.txt.
 458
 459         dhash_entries=  [KNL]
 460                         Set number of hash buckets for dentry cache.
 461
 462         digi=           [HW,SERIAL]
 463                         IO parameters + enable/disable command.
 464
 465         digiepca=       [HW,SERIAL]
 466                         See drivers/char/README.epca and
 467                         Documentation/digiepca.txt.
 468
 469         dmascc=         [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
 470                         support available.
 471                         Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
 472
 473         dmasound=       [HW,OSS] Sound subsystem buffers
 474
 475         dscc4.setup=    [NET]
 476
 477         dtc3181e=       [HW,SCSI]
 478
 479         earlyprintk=    [IA-32,X86-64]
 480                         earlyprintk=vga
 481                         earlyprintk=serial[,ttySn[,baudrate]]
 482
 483                         Append ",keep" to not disable it when the real console
 484                         takes over.
 485
 486                         Only vga or serial at a time, not both.
 487
 488                         Currently only ttyS0 and ttyS1 are supported.
 489
 490                         Interaction with the standard serial driver is not
 491                         very good.
 492
 493                         The VGA output is eventually overwritten by the real
 494                         console.
 495
 496         eata=           [HW,SCSI]
 497
 498         ec_intr=        [HW,ACPI] ACPI Embedded Controller interrupt mode
 499                         Format: <int>
 500                         0: polling mode
 501                         non-0: interrupt mode (default)
 502
 503         eda=            [HW,PS2]
 504
 505         edb=            [HW,PS2]
 506
 507         edd=            [EDD]
 508                         Format: {"of[f]" | "sk[ipmbr]"}
 509                         See comment in arch/i386/boot/edd.S
 510
 511         eicon=          [HW,ISDN]
 512                         Format: <id>,<membase>,<irq>
 513
 514         eisa_irq_edge=  [PARISC,HW]
 515                         See header of drivers/parisc/eisa.c.
 516
 517         elanfreq=       [IA-32]
 518                         See comment before function elanfreq_setup() in
 519                         arch/i386/kernel/cpu/cpufreq/elanfreq.c.
 520
 521         elevator=       [IOSCHED]
 522                         Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
 523                         See Documentation/block/as-iosched.txt and
 524                         Documentation/block/deadline-iosched.txt for details.
 525
 526         elfcorehdr=     [IA-32, X86_64]
 527                         Specifies physical address of start of kernel core
 528                         image elf header. Generally kexec loader will
 529                         pass this option to capture kernel.
 530                         See Documentation/kdump/kdump.txt for details.
 531
 532         enforcing       [SELINUX] Set initial enforcing status.
 533                         Format: {"0" | "1"}
 534                         See security/selinux/Kconfig help text.
 535                         0 -- permissive (log only, no denials).
 536                         1 -- enforcing (deny and log).
 537                         Default value is 0.
 538                         Value can be changed at runtime via /selinux/enforce.
 539
 540         es1371=         [HW,OSS]
 541                         Format: <spdif>,[<nomix>,[<amplifier>]]
 542                         See also header of sound/oss/es1371.c.
 543
 544         ether=          [HW,NET] Ethernet cards parameters
 545                         This option is obsoleted by the "netdev=" option, which
 546                         has equivalent usage. See its documentation for details.
 547
 548         eurwdt=         [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
 549                         Format: <io>[,<irq>]
 550
 551         fd_mcs=         [HW,SCSI]
 552                         See header of drivers/scsi/fd_mcs.c.
 553
 554         fdomain=        [HW,SCSI]
 555                         See header of drivers/scsi/fdomain.c.
 556
 557         floppy=         [HW]
 558                         See Documentation/floppy.txt.
 559
 560         ftape=          [HW] Floppy Tape subsystem debugging options.
 561                         See Documentation/ftape.txt.
 562
 563         gamecon.map[2|3]=
 564                         [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 565                         support via parallel port (up to 5 devices per port)
 566                         Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 567                         See also Documentation/input/joystick-parport.txt
 568
 569         gamma=          [HW,DRM]
 570
 571         gdth=           [HW,SCSI]
 572                         See header of drivers/scsi/gdth.c.
 573
 574         gpt             [EFI] Forces disk with valid GPT signature but
 575                         invalid Protective MBR to be treated as GPT.
 576
 577         gscd=           [HW,CD]
 578                         Format: <io>
 579
 580         gvp11=          [HW,SCSI]
 581
 582         hashdist=       [KNL,NUMA] Large hashes allocated during boot
 583                         are distributed across NUMA nodes.  Defaults on
 584                         for IA-64, off otherwise.
 585                         Format: 0 | 1 (for off | on)
 586
 587         hcl=            [IA-64] SGI's Hardware Graph compatibility layer
 588
 589         hd=             [EIDE] (E)IDE hard drive subsystem geometry
 590                         Format: <cyl>,<head>,<sect>
 591
 592         hd?=            [HW] (E)IDE subsystem
 593         hd?lun=         See Documentation/ide.txt.
 594
 595         highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
 596                         size of <nn>. This works even on boxes that have no
 597                         highmem otherwise. This also works to reduce highmem
 598                         size on bigger boxes.
 599
 600         hisax=          [HW,ISDN]
 601                         See Documentation/isdn/README.HiSax.
 602
 603         hugepages=      [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
 604
 605         noirqbalance    [IA-32,SMP,KNL] Disable kernel irq balancing
 606
 607         i8042.direct    [HW] Put keyboard port into non-translated mode
 608         i8042.dumbkbd   [HW] Pretend that controller can only read data from
 609                              keyboard and cannot control its state
 610                              (Don't attempt to blink the leds)
 611         i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
 612         i8042.nokbd     [HW] Don't check/create keyboard port
 613         i8042.nomux     [HW] Don't check presence of an active multiplexing
 614                              controller
 615         i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
 616                              controllers
 617         i8042.panicblink=
 618                         [HW] Frequency with which keyboard LEDs should blink
 619                              when kernel panics (default is 0.5 sec)
 620         i8042.reset     [HW] Reset the controller during init and cleanup
 621         i8042.unlock    [HW] Unlock (ignore) the keylock
 622
 623         i810=           [HW,DRM]
 624
 625         i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
 626                         indicates that the driver is running on unsupported
 627                         hardware.
 628         i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
 629                         does not match list of supported models.
 630         i8k.power_status
 631                         [HW] Report power status in /proc/i8k
 632                         (disabled by default)
 633         i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
 634                         capability is set.
 635
 636         ibmmcascsi=     [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
 637                         See Documentation/mca.txt.
 638
 639         icn=            [HW,ISDN]
 640                         Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
 641
 642         ide=            [HW] (E)IDE subsystem
 643                         Format: ide=nodma or ide=doubler or ide=reverse
 644                         See Documentation/ide.txt.
 645
 646         ide?=           [HW] (E)IDE subsystem
 647                         Format: ide?=noprobe or chipset specific parameters.
 648                         See Documentation/ide.txt.
 649
 650         idebus=         [HW] (E)IDE subsystem - VLB/PCI bus speed
 651                         See Documentation/ide.txt.
 652
 653         idle=           [HW]
 654                         Format: idle=poll or idle=halt
 655
 656         ihash_entries=  [KNL]
 657                         Set number of hash buckets for inode cache.
 658
 659         in2000=         [HW,SCSI]
 660                         See header of drivers/scsi/in2000.c.
 661
 662         init=           [KNL]
 663                         Format: <full_path>
 664                         Run specified binary instead of /sbin/init as init
 665                         process.
 666
 667         initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
 668                         for working out where the kernel is dying during
 669                         startup.
 670
 671         initrd=         [BOOT] Specify the location of the initial ramdisk
 672
 673         inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
 674                         Format: <irq>
 675
 676         combined_mode=  [HW] control which driver uses IDE ports in combined
 677                         mode: legacy IDE driver, libata, or both
 678                         (in the libata case, libata.atapi_enabled=1 may be
 679                         useful as well).  Note that using the ide or libata
 680                         options may affect your device naming (e.g. by
 681                         changing hdc to sdb).
 682                         Format: combined (default), ide, or libata
 683
 684         inttest=        [IA64]
 685
 686         io7=            [HW] IO7 for Marvel based alpha systems
 687                         See comment before marvel_specify_io7 in
 688                         arch/alpha/kernel/core_marvel.c.
 689
 690         ip=             [IP_PNP]
 691                         See Documentation/nfsroot.txt.
 692
 693         ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
 694                         See comment before ip2_setup() in drivers/char/ip2.c.
 695
 696         ips=            [HW,SCSI] Adaptec / IBM ServeRAID controller
 697                         See header of drivers/scsi/ips.c.
 698
 699         ports=          [IP_VS_FTP] IPVS ftp helper module
 700                         Default is 21.
 701                         Up to 8 (IP_VS_APP_MAX_PORTS) ports
 702                         may be specified.
 703                         Format: <port>,<port>....
 704
 705         irqfixup        [HW]
 706                         When an interrupt is not handled search all handlers
 707                         for it. Intended to get systems with badly broken
 708                         firmware running.
 709
 710         irqpoll         [HW]
 711                         When an interrupt is not handled search all handlers
 712                         for it. Also check all handlers each timer
 713                         interrupt. Intended to get systems with badly broken
 714                         firmware running.
 715
 716         isapnp=         [ISAPNP]
 717                         Format: <RDP>,<reset>,<pci_scan>,<verbosity>
 718
 719         isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
 720                         Format: <cpu number>,...,<cpu number>
 721                         This option can be used to specify one or more CPUs
 722                         to isolate from the general SMP balancing and scheduling
 723                         algorithms. The only way to move a process onto or off
 724                         an "isolated" CPU is via the CPU affinity syscalls.
 725                         <cpu number> begins at 0 and the maximum value is
 726                         "number of CPUs in system - 1".
 727
 728                         This option is the preferred way to isolate CPUs. The
 729                         alternative -- manually setting the CPU mask of all
 730                         tasks in the system -- can cause problems and
 731                         suboptimal load balancer performance.
 732
 733         isp16=          [HW,CD]
 734                         Format: <io>,<irq>,<dma>,<setup>
 735
 736         iucv=           [HW,NET]
 737
 738         js=             [HW,JOY] Analog joystick
 739                         See Documentation/input/joystick.txt.
 740
 741         keepinitrd      [HW,ARM]
 742
 743         kstack=N        [IA-32,X86-64] Print N words from the kernel stack
 744                         in oops dumps.
 745
 746         l2cr=           [PPC]
 747
 748         lapic           [IA-32,APIC] Enable the local APIC even if BIOS
 749                         disabled it.
 750
 751         lasi=           [HW,SCSI] PARISC LASI driver for the 53c700 chip
 752                         Format: addr:<io>,irq:<irq>
 753
 754         llsc*=          [IA64] See function print_params() in
 755                         arch/ia64/sn/kernel/llsc4.c.
 756
 757         load_ramdisk=   [RAM] List of ramdisks to load from floppy
 758                         See Documentation/ramdisk.txt.
 759
 760         lockd.nlm_grace_period=P  [NFS] Assign grace period.
 761                         Format: <integer>
 762
 763         lockd.nlm_tcpport=N     [NFS] Assign TCP port.
 764                         Format: <integer>
 765
 766         lockd.nlm_timeout=T     [NFS] Assign timeout value.
 767                         Format: <integer>
 768
 769         lockd.nlm_udpport=M     [NFS] Assign UDP port.
 770                         Format: <integer>
 771
 772         logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
 773                         Format: <irq>
 774
 775         loglevel=       All Kernel Messages with a loglevel smaller than the
 776                         console loglevel will be printed to the console. It can
 777                         also be changed with klogd or other programs. The
 778                         loglevels are defined as follows:
 779
 780                         0 (KERN_EMERG)          system is unusable
 781                         1 (KERN_ALERT)          action must be taken immediately
 782                         2 (KERN_CRIT)           critical conditions
 783                         3 (KERN_ERR)            error conditions
 784                         4 (KERN_WARNING)        warning conditions
 785                         5 (KERN_NOTICE)         normal but significant condition
 786                         6 (KERN_INFO)           informational
 787                         7 (KERN_DEBUG)          debug-level messages
 788
 789         log_buf_len=n   Sets the size of the printk ring buffer, in bytes.
 790                         Format: { n | nk | nM }
 791                         n must be a power of two.  The default size
 792                         is set in the kernel config file.
 793
 794         lp=0            [LP]    Specify parallel ports to use, e.g,
 795         lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
 796         lp=reset                first parallel port). 'lp=0' disables the
 797         lp=auto                 printer driver. 'lp=reset' (which can be
 798                                 specified in addition to the ports) causes
 799                                 attached printers to be reset. Using
 800                                 lp=port1,port2,... specifies the parallel ports
 801                                 to associate lp devices with, starting with
 802                                 lp0. A port specification may be 'none' to skip
 803                                 that lp device, or a parport name such as
 804                                 'parport0'. Specifying 'lp=auto' instead of a
 805                                 port specification list means that device IDs
 806                                 from each port should be examined, to see if
 807                                 an IEEE 1284-compliant printer is attached; if
 808                                 so, the driver will manage that printer.
 809                                 See also header of drivers/char/lp.c.
 810
 811         lpj=n           [KNL]
 812                         Sets loops_per_jiffy to given constant, thus avoiding
 813                         time-consuming boot-time autodetection (up to 250 ms per
 814                         CPU). 0 enables autodetection (default). To determine
 815                         the correct value for your kernel, boot with normal
 816                         autodetection and see what value is printed. Note that
 817                         on SMP systems the preset will be applied to all CPUs,
 818                         which is likely to cause problems if your CPUs need
 819                         significantly divergent settings. An incorrect value
 820                         will cause delays in the kernel to be wrong, leading to
 821                         unpredictable I/O errors and other breakage. Although
 822                         unlikely, in the extreme case this might damage your
 823                         hardware.
 824
 825         ltpc=           [NET]
 826                         Format: <io>,<irq>,<dma>
 827
 828         mac5380=        [HW,SCSI] Format:
 829                         <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
 830
 831         mac53c9x=       [HW,SCSI] Format:
 832                         <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
 833
 834         machvec=        [IA64] Force the use of a particular machine-vector
 835                         (machvec) in a generic kernel.
 836                         Example: machvec=hpzx1_swiotlb
 837
 838         max_loop=       [LOOP] Maximum number of loopback devices that can
 839                         be mounted
 840                         Format: <1-256>
 841
 842         maxcpus=        [SMP] Maximum number of processors that an SMP kernel
 843                         should make use of
 844
 845         max_addr=[KMG]  [KNL,BOOT,ia64] All physical memory greater than or
 846                         equal to this physical address is ignored.
 847
 848         max_luns=       [SCSI] Maximum number of LUNs to probe.
 849                         Should be between 1 and 2^32-1.
 850
 851         max_report_luns=
 852                         [SCSI] Maximum number of LUNs received.
 853                         Should be between 1 and 16384.
 854
 855         mca-pentium     [BUGS=IA-32]
 856
 857         mcatest=        [IA-64]
 858
 859         mcd=            [HW,CD]
 860                         Format: <port>,<irq>,<mitsumi_bug_93_wait>
 861
 862         mcdx=           [HW,CD]
 863
 864         mce             [IA-32] Machine Check Exception
 865
 866         md=             [HW] RAID subsystems devices and level
 867                         See Documentation/md.txt.
 868
 869         mdacon=         [MDA]
 870                         Format: <first>,<last>
 871                         Specifies range of consoles to be captured by the MDA.
 872
 873         mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
 874                         Amount of memory to be used when the kernel is not able
 875                         to see the whole system memory or for test.
 876                         [IA-32] Use together with memmap= to avoid physical
 877                         address space collisions. Without memmap= PCI devices
 878                         could be placed at addresses belonging to unused RAM.
 879
 880         mem=nopentium   [BUGS=IA-32] Disable usage of 4MB pages for kernel
 881                         memory.
 882
 883         memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
 884                         E820 memory map, as specified by the user.
 885                         Such memmap=exactmap lines can be constructed based on
 886                         BIOS output or other requirements. See the memmap=nn@ss
 887                         option description.
 888
 889         memmap=nn[KMG]@ss[KMG]
 890                         [KNL] Force usage of a specific region of memory
 891                         Region of memory to be used, from ss to ss+nn.
 892
 893         memmap=nn[KMG]#ss[KMG]
 894                         [KNL,ACPI] Mark specific memory as ACPI data.
 895                         Region of memory to be used, from ss to ss+nn.
 896
 897         memmap=nn[KMG]$ss[KMG]
 898                         [KNL,ACPI] Mark specific memory as reserved.
 899                         Region of memory to be used, from ss to ss+nn.
 900
 901         meye.*=         [HW] Set MotionEye Camera parameters
 902                         See Documentation/video4linux/meye.txt.
 903
 904         mga=            [HW,DRM]
 905
 906         migration_cost=
 907                         [KNL,SMP] debug: override scheduler migration costs
 908                         Format: <level-1-usecs>,<level-2-usecs>,...
 909                         This debugging option can be used to override the
 910                         default scheduler migration cost matrix. The numbers
 911                         are indexed by 'CPU domain distance'.
 912                         E.g. migration_cost=1000,2000,3000 on an SMT NUMA
 913                         box will set up an intra-core migration cost of
 914                         1 msec, an inter-core migration cost of 2 msecs,
 915                         and an inter-node migration cost of 3 msecs.
 916
 917                         WARNING: using the wrong values here can break
 918                         scheduler performance, so it's only for scheduler
 919                         development purposes, not production environments.
 920
 921         migration_debug=
 922                         [KNL,SMP] migration cost auto-detect verbosity
 923                         Format=<0|1|2>
 924                         If a system's migration matrix reported at bootup
 925                         seems erroneous then this option can be used to
 926                         increase verbosity of the detection process.
 927                         We default to 0 (no extra messages), 1 will print
 928                         some more information, and 2 will be really
 929                         verbose (probably only useful if you also have a
 930                         serial console attached to the system).
 931
 932         migration_factor=
 933                         [KNL,SMP] multiply/divide migration costs by a factor
 934                         Format=<percent>
 935                         This debug option can be used to proportionally
 936                         increase or decrease the auto-detected migration
 937                         costs for all entries of the migration matrix.
 938                         E.g. migration_factor=150 will increase migration
 939                         costs by 50%. (and thus the scheduler will be less
 940                         eager migrating cache-hot tasks)
 941                         migration_factor=80 will decrease migration costs
 942                         by 20%. (thus the scheduler will be more eager to
 943                         migrate tasks)
 944
 945                         WARNING: using the wrong values here can break
 946                         scheduler performance, so it's only for scheduler
 947                         development purposes, not production environments.
 948
 949         mousedev.tap_time=
 950                         [MOUSE] Maximum time between finger touching and
 951                         leaving touchpad surface for touch to be considered
 952                         a tap and be reported as a left button click (for
 953                         touchpads working in absolute mode only).
 954                         Format: <msecs>
 955         mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
 956                         reporting absolute coordinates, such as tablets
 957         mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
 958                         reporting absolute coordinates, such as tablets
 959
 960         mpu401=         [HW,OSS]
 961                         Format: <io>,<irq>
 962
 963         MTD_Partition=  [MTD]
 964                         Format: <name>,<region-number>,<size>,<offset>
 965
 966         MTD_Region=     [MTD] Format:
 967                         <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
 968
 969         mtdparts=       [MTD]
 970                         See drivers/mtd/cmdline.c.
 971
 972         mtouchusb.raw_coordinates=
 973                         [HW] Make the MicroTouch USB driver use raw coordinates
 974                         ('y', default) or cooked coordinates ('n')
 975
 976         n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
 977
 978         NCR_D700=       [HW,SCSI]
 979                         See header of drivers/scsi/NCR_D700.c.
 980
 981         ncr5380=        [HW,SCSI]
 982
 983         ncr53c400=      [HW,SCSI]
 984
 985         ncr53c400a=     [HW,SCSI]
 986
 987         ncr53c406a=     [HW,SCSI]
 988
 989         ncr53c8xx=      [HW,SCSI]
 990
 991         netdev=         [NET] Network devices parameters
 992                         Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
 993                         Note that mem_start is often overloaded to mean
 994                         something different and driver-specific.
 995                         This usage is only documented in each driver source
 996                         file if at all.
 997
 998         nfsaddrs=       [NFS]
 999                         See Documentation/nfsroot.txt.
1000
1001         nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
1002                         See Documentation/nfsroot.txt.
1003
1004         nfs.callback_tcpport=
1005                         [NFS] set the TCP port on which the NFSv4 callback
1006                         channel should listen.
1007
1008         nfs.idmap_cache_timeout=
1009                         [NFS] set the maximum lifetime for idmapper cache
1010                         entries.
1011
1012         nmi_watchdog=   [KNL,BUGS=IA-32] Debugging features for SMP kernels
1013
1014         no387           [BUGS=IA-32] Tells the kernel to use the 387 maths
1015                         emulation library even if a 387 maths coprocessor
1016                         is present.
1017
1018         noalign         [KNL,ARM]
1019
1020         noapic          [SMP,APIC] Tells the kernel to not make use of any
1021                         IOAPICs that may be present in the system.
1022
1023         noasync         [HW,M68K] Disables async and sync negotiation for
1024                         all devices.
1025
1026         nobats          [PPC] Do not use BATs for mapping kernel lowmem
1027                         on "Classic" PPC cores.
1028
1029         nocache         [ARM]
1030
1031         nodelayacct     [KNL] Disable per-task delay accounting
1032
1033         nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1034
1035         noexec          [IA-64]
1036
1037         noexec          [IA-32,X86-64]
1038                         noexec=on: enable non-executable mappings (default)
1039                         noexec=off: disable nn-executable mappings
1040
1041         nofxsr          [BUGS=IA-32] Disables x86 floating point extended
1042                         register save and restore. The kernel will only save
1043                         legacy floating-point registers on task switch.
1044
1045         nohlt           [BUGS=ARM]
1046
1047         no-hlt          [BUGS=IA-32] Tells the kernel that the hlt
1048                         instruction doesn't work correctly and not to
1049                         use it.
1050
1051         nohalt          [IA-64] Tells the kernel not to use the power saving
1052                         function PAL_HALT_LIGHT when idle. This increases
1053                         power-consumption. On the positive side, it reduces
1054                         interrupt wake-up latency, which may improve performance
1055                         in certain environments such as networked servers or
1056                         real-time systems.
1057
1058         noirqdebug      [IA-32] Disables the code which attempts to detect and
1059                         disable unhandled interrupt sources.
1060
1061         noisapnp        [ISAPNP] Disables ISA PnP code.
1062
1063         noinitrd        [RAM] Tells the kernel not to load any configured
1064                         initial RAM disk.
1065
1066         nointroute      [IA-64]
1067
1068         nolapic         [IA-32,APIC] Do not enable or use the local APIC.
1069
1070         noltlbs         [PPC] Do not use large page/tlb entries for kernel
1071                         lowmem mapping on PPC40x.
1072
1073         nomca           [IA-64] Disable machine check abort handling
1074
1075         nomce           [IA-32] Machine Check Exception
1076
1077         noresidual      [PPC] Don't use residual data on PReP machines.
1078
1079         noresume        [SWSUSP] Disables resume and restores original swap
1080                         space.
1081
1082         no-scroll       [VGA] Disables scrollback.
1083                         This is required for the Braillex ib80-piezo Braille
1084                         reader made by F.H. Papenmeier (Germany).
1085
1086         nosbagart       [IA-64]
1087
1088         nosep           [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1089
1090         nosmp           [SMP] Tells an SMP kernel to act as a UP kernel.
1091
1092         nosync          [HW,M68K] Disables sync negotiation for all devices.
1093
1094         notsc           [BUGS=IA-32] Disable Time Stamp Counter
1095
1096         nousb           [USB] Disable the USB subsystem
1097
1098         nowb            [ARM]
1099
1100         nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1101
1102         opl3=           [HW,OSS]
1103                         Format: <io>
1104
1105         opl3sa2=        [HW,OSS] Format:
1106                         <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
1107
1108         oprofile.timer= [HW]
1109                         Use timer interrupt instead of performance counters
1110
1111         optcd=          [HW,CD]
1112                         Format: <io>
1113
1114         osst=           [HW,SCSI] SCSI Tape Driver
1115                         Format: <buffer_size>,<write_threshold>
1116                         See also Documentation/scsi/st.txt.
1117
1118         panic=          [KNL] Kernel behaviour on panic
1119                         Format: <timeout>
1120
1121         parkbd.port=    [HW] Parallel port number the keyboard adapter is
1122                         connected to, default is 0.
1123                         Format: <parport#>
1124         parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
1125                         0 for XT, 1 for AT (default is AT).
1126                         Format: <mode>
1127
1128         parport=        [HW,PPT] Specify parallel ports. 0 disables.
1129                         Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1130                         Use 'auto' to force the driver to use any
1131                         IRQ/DMA settings detected (the default is to
1132                         ignore detected IRQ/DMA settings because of
1133                         possible conflicts). You can specify the base
1134                         address, IRQ, and DMA settings; IRQ and DMA
1135                         should be numbers, or 'auto' (for using detected
1136                         settings on that particular port), or 'nofifo'
1137                         (to avoid using a FIFO even if it is detected).
1138                         Parallel ports are assigned in the order they
1139                         are specified on the command line, starting
1140                         with parport0.
1141
1142         parport_init_mode=      [HW,PPT]
1143                         Configure VIA parallel port to operate in
1144                         a specific mode. This is necessary on Pegasos
1145                         computer where firmware has no options for setting
1146                         up parallel port mode and sets it to spp.
1147                         Currently this function knows 686a and 8231 chips.
1148                         Format: [spp|ps2|epp|ecp|ecpepp]
1149
1150         pas2=           [HW,OSS] Format:
1151                         <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1152
1153         pas16=          [HW,SCSI]
1154                         See header of drivers/scsi/pas16.c.
1155
1156         pause_on_oops=
1157                         Halt all CPUs after the first oops has been printed for
1158                         the specified number of seconds.  This is to be used if
1159                         your oopses keep scrolling off the screen.
1160
1161         pcbit=          [HW,ISDN]
1162
1163         pcd.            [PARIDE]
1164                         See header of drivers/block/paride/pcd.c.
1165                         See also Documentation/paride.txt.
1166
1167         pci=option[,option...]  [PCI] various PCI subsystem options:
1168                 off             [IA-32] don't probe for the PCI bus
1169                 bios            [IA-32] force use of PCI BIOS, don't access
1170                                 the hardware directly. Use this if your machine
1171                                 has a non-standard PCI host bridge.
1172                 nobios          [IA-32] disallow use of PCI BIOS, only direct
1173                                 hardware access methods are allowed. Use this
1174                                 if you experience crashes upon bootup and you
1175                                 suspect they are caused by the BIOS.
1176                 conf1           [IA-32] Force use of PCI Configuration
1177                                 Mechanism 1.
1178                 conf2           [IA-32] Force use of PCI Configuration
1179                                 Mechanism 2.
1180                 nommconf        [IA-32,X86_64] Disable use of MMCONFIG for PCI
1181                                 Configuration
1182                 nomsi           [MSI] If the PCI_MSI kernel config parameter is
1183                                 enabled, this kernel boot option can be used to
1184                                 disable the use of MSI interrupts system-wide.
1185                 nosort          [IA-32] Don't sort PCI devices according to
1186                                 order given by the PCI BIOS. This sorting is
1187                                 done to get a device order compatible with
1188                                 older kernels.
1189                 biosirq         [IA-32] Use PCI BIOS calls to get the interrupt
1190                                 routing table. These calls are known to be buggy
1191                                 on several machines and they hang the machine
1192                                 when used, but on other computers it's the only
1193                                 way to get the interrupt routing table. Try
1194                                 this option if the kernel is unable to allocate
1195                                 IRQs or discover secondary PCI buses on your
1196                                 motherboard.
1197                 rom             [IA-32] Assign address space to expansion ROMs.
1198                                 Use with caution as certain devices share
1199                                 address decoders between ROMs and other
1200                                 resources.
1201                 irqmask=0xMMMM  [IA-32] Set a bit mask of IRQs allowed to be
1202                                 assigned automatically to PCI devices. You can
1203                                 make the kernel exclude IRQs of your ISA cards
1204                                 this way.
1205                 pirqaddr=0xAAAAA        [IA-32] Specify the physical address
1206                                 of the PIRQ table (normally generated
1207                                 by the BIOS) if it is outside the
1208                                 F0000h-100000h range.
1209                 lastbus=N       [IA-32] Scan all buses thru bus #N. Can be
1210                                 useful if the kernel is unable to find your
1211                                 secondary buses and you want to tell it
1212                                 explicitly which ones they are.
1213                 assign-busses   [IA-32] Always assign all PCI bus
1214                                 numbers ourselves, overriding
1215                                 whatever the firmware may have done.
1216                 usepirqmask     [IA-32] Honor the possible IRQ mask stored
1217                                 in the BIOS $PIR table. This is needed on
1218                                 some systems with broken BIOSes, notably
1219                                 some HP Pavilion N5400 and Omnibook XE3
1220                                 notebooks. This will have no effect if ACPI
1221                                 IRQ routing is enabled.
1222                 noacpi          [IA-32] Do not use ACPI for IRQ routing
1223                                 or for PCI scanning.
1224                 routeirq        Do IRQ routing for all PCI devices.
1225                                 This is normally done in pci_enable_device(),
1226                                 so this option is a temporary workaround
1227                                 for broken drivers that don't call it.
1228                 firmware        [ARM] Do not re-enumerate the bus but instead
1229                                 just use the configuration from the
1230                                 bootloader. This is currently used on
1231                                 IXP2000 systems where the bus has to be
1232                                 configured a certain way for adjunct CPUs.
1233                 noearly         [X86] Don't do any early type 1 scanning.
1234                                 This might help on some broken boards which
1235                                 machine check when some devices' config space
1236                                 is read. But various workarounds are disabled
1237                                 and some IOMMU drivers will not work.
1238                 bfsort          Sort PCI devices into breadth-first order.
1239                                 This sorting is done to get a device
1240                                 order compatible with older (<= 2.4) kernels.
1241                 nobfsort        Don't sort PCI devices into breadth-first order.
1242
1243         pcmv=           [HW,PCMCIA] BadgePAD 4
1244
1245         pd.             [PARIDE]
1246                         See Documentation/paride.txt.
1247
1248         pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1249                         boot time.
1250                         Format: { 0 | 1 }
1251                         See arch/parisc/kernel/pdc_chassis.c
1252
1253         pf.             [PARIDE]
1254                         See Documentation/paride.txt.
1255
1256         pg.             [PARIDE]
1257                         See Documentation/paride.txt.
1258
1259         pirq=           [SMP,APIC] Manual mp-table setup
1260                         See Documentation/i386/IO-APIC.txt.
1261
1262         plip=           [PPT,NET] Parallel port network link
1263                         Format: { parport<nr> | timid | 0 }
1264                         See also Documentation/parport.txt.
1265
1266         pnpacpi=        [ACPI]
1267                         { off }
1268
1269         pnpbios=        [ISAPNP]
1270                         { on | off | curr | res | no-curr | no-res }
1271
1272         pnp_reserve_irq=
1273                         [ISAPNP] Exclude IRQs for the autoconfiguration
1274
1275         pnp_reserve_dma=
1276                         [ISAPNP] Exclude DMAs for the autoconfiguration
1277
1278         pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1279                         Ranges are in pairs (I/O port base and size).
1280
1281         pnp_reserve_mem=
1282                         [ISAPNP] Exclude memory regions for the
1283                         autoconfiguration.
1284                         Ranges are in pairs (memory base and size).
1285
1286         profile=        [KNL] Enable kernel profiling via /proc/profile
1287                         Format: [schedule,]<number>
1288                         Param: "schedule" - profile schedule points.
1289                         Param: <number> - step/bucket size as a power of 2 for
1290                                 statistical time based profiling.
1291
1292         processor.max_cstate=   [HW,ACPI]
1293                         Limit processor to maximum C-state
1294                         max_cstate=9 overrides any DMI blacklist limit.
1295
1296         processor.nocst [HW,ACPI]
1297                         Ignore the _CST method to determine C-states,
1298                         instead using the legacy FADT method
1299
1300         prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1301                         before loading.
1302                         See Documentation/ramdisk.txt.
1303
1304         psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
1305                         probe for; one of (bare|imps|exps|lifebook|any).
1306         psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
1307                         per second.
1308         psmouse.resetafter=     [HW,MOUSE]
1309                         Try to reset the device after so many bad packets
1310                         (0 = never).
1311         psmouse.resolution=
1312                         [HW,MOUSE] Set desired mouse resolution, in dpi.
1313         psmouse.smartscroll=
1314                         [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1315                         0 = disabled, 1 = enabled (default).
1316
1317         pss=            [HW,OSS] Personal Sound System (ECHO ESC614)
1318                         Format:
1319                         <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1320
1321         pt.             [PARIDE]
1322                         See Documentation/paride.txt.
1323
1324         quiet           [KNL] Disable most log messages
1325
1326         r128=           [HW,DRM]
1327
1328         raid=           [HW,RAID]
1329                         See Documentation/md.txt.
1330
1331         ramdisk=        [RAM] Sizes of RAM disks in kilobytes [deprecated]
1332                         See Documentation/ramdisk.txt.
1333
1334         ramdisk_blocksize=      [RAM]
1335                         See Documentation/ramdisk.txt.
1336
1337         ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
1338                         New name for the ramdisk parameter.
1339                         See Documentation/ramdisk.txt.
1340
1341         rcu.blimit=     [KNL,BOOT] Set maximum number of finished
1342                         RCU callbacks to process in one batch.
1343
1344         rcu.qhimark=    [KNL,BOOT] Set threshold of queued
1345                         RCU callbacks over which batch limiting is disabled.
1346
1347         rcu.qlowmark=   [KNL,BOOT] Set threshold of queued
1348                         RCU callbacks below which batch limiting is re-enabled.
1349
1350         rdinit=         [KNL]
1351                         Format: <full_path>
1352                         Run specified binary instead of /init from the ramdisk,
1353                         used for early userspace startup. See initrd.
1354
1355         reboot=         [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1356                         Format: <reboot_mode>[,<reboot_mode2>[,...]]
1357                         See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1358
1359         reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
1360
1361         reservetop=     [IA-32]
1362                         Format: nn[KMG]
1363                         Reserves a hole at the top of the kernel virtual
1364                         address space.
1365
1366         reset_devices   [KNL] Force drivers to reset the underlying device
1367                         during initialization.
1368
1369         resume=         [SWSUSP]
1370                         Specify the partition device for software suspend
1371
1372         rhash_entries=  [KNL,NET]
1373                         Set number of hash buckets for route cache
1374
1375         riscom8=        [HW,SERIAL]
1376                         Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1377
1378         ro              [KNL] Mount root device read-only on boot
1379
1380         root=           [KNL] Root filesystem
1381
1382         rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
1383                         mount the root filesystem
1384
1385         rootflags=      [KNL] Set root filesystem mount option string
1386
1387         rootfstype=     [KNL] Set root filesystem type
1388
1389         rw              [KNL] Mount root device read-write on boot
1390
1391         S               [KNL] Run init in single mode
1392
1393         sa1100ir        [NET]
1394                         See drivers/net/irda/sa1100_ir.c.
1395
1396         sb=             [HW,OSS]
1397                         Format: <io>,<irq>,<dma>,<dma2>
1398
1399         sbni=           [NET] Granch SBNI12 leased line adapter
1400
1401         sbpcd=          [HW,CD] Soundblaster CD adapter
1402                         Format: <io>,<type>
1403                         See a comment before function sbpcd_setup() in
1404                         drivers/cdrom/sbpcd.c.
1405
1406         sc1200wdt=      [HW,WDT] SC1200 WDT (watchdog) driver
1407                         Format: <io>[,<timeout>[,<isapnp>]]
1408
1409         scsi_debug_*=   [SCSI]
1410                         See drivers/scsi/scsi_debug.c.
1411
1412         scsi_default_dev_flags=
1413                         [SCSI] SCSI default device flags
1414                         Format: <integer>
1415
1416         scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1417                         Format: <vendor>:<model>:<flags>
1418                         (flags are integer value)
1419
1420         scsi_logging=   [SCSI]
1421
1422         selinux         [SELINUX] Disable or enable SELinux at boot time.
1423                         Format: { "0" | "1" }
1424                         See security/selinux/Kconfig help text.
1425                         0 -- disable.
1426                         1 -- enable.
1427                         Default value is set via kernel config option.
1428                         If enabled at boot time, /selinux/disable can be used
1429                         later to disable prior to initial policy load.
1430
1431         selinux_compat_net =
1432                         [SELINUX] Set initial selinux_compat_net flag value.
1433                         Format: { "0" | "1" }
1434                         0 -- use new secmark-based packet controls
1435                         1 -- use legacy packet controls
1436                         Default value is 0 (preferred).
1437                         Value can be changed at runtime via
1438                         /selinux/compat_net.
1439
1440         serialnumber    [BUGS=IA-32]
1441
1442         sg_def_reserved_size=   [SCSI]
1443
1444         shapers=        [NET]
1445                         Maximal number of shapers.
1446
1447         sim710=         [SCSI,HW]
1448                         See header of drivers/scsi/sim710.c.
1449
1450         simeth=         [IA-64]
1451         simscsi=
1452
1453         sjcd=           [HW,CD]
1454                         Format: <io>,<irq>,<dma>
1455                         See header of drivers/cdrom/sjcd.c.
1456
1457         slram=          [HW,MTD]
1458
1459         smart2=         [HW]
1460                         Format: <io1>[,<io2>[,...,<io8>]]
1461
1462         snd-ad1816a=    [HW,ALSA]
1463
1464         snd-ad1848=     [HW,ALSA]
1465
1466         snd-ali5451=    [HW,ALSA]
1467
1468         snd-als100=     [HW,ALSA]
1469
1470         snd-als4000=    [HW,ALSA]
1471
1472         snd-azt2320=    [HW,ALSA]
1473
1474         snd-cmi8330=    [HW,ALSA]
1475
1476         snd-cmipci=     [HW,ALSA]
1477
1478         snd-cs4231=     [HW,ALSA]
1479
1480         snd-cs4232=     [HW,ALSA]
1481
1482         snd-cs4236=     [HW,ALSA]
1483
1484         snd-cs4281=     [HW,ALSA]
1485
1486         snd-cs46xx=     [HW,ALSA]
1487
1488         snd-dt019x=     [HW,ALSA]
1489
1490         snd-dummy=      [HW,ALSA]
1491
1492         snd-emu10k1=    [HW,ALSA]
1493
1494         snd-ens1370=    [HW,ALSA]
1495
1496         snd-ens1371=    [HW,ALSA]
1497
1498         snd-es968=      [HW,ALSA]
1499
1500         snd-es1688=     [HW,ALSA]
1501
1502         snd-es18xx=     [HW,ALSA]
1503
1504         snd-es1938=     [HW,ALSA]
1505
1506         snd-es1968=     [HW,ALSA]
1507
1508         snd-fm801=      [HW,ALSA]
1509
1510         snd-gusclassic= [HW,ALSA]
1511
1512         snd-gusextreme= [HW,ALSA]
1513
1514         snd-gusmax=     [HW,ALSA]
1515
1516         snd-hdsp=       [HW,ALSA]
1517
1518         snd-ice1712=    [HW,ALSA]
1519
1520         snd-intel8x0=   [HW,ALSA]
1521
1522         snd-interwave=  [HW,ALSA]
1523
1524         snd-interwave-stb=
1525                         [HW,ALSA]
1526
1527         snd-korg1212=   [HW,ALSA]
1528
1529         snd-maestro3=   [HW,ALSA]
1530
1531         snd-mpu401=     [HW,ALSA]
1532
1533         snd-mtpav=      [HW,ALSA]
1534
1535         snd-nm256=      [HW,ALSA]
1536
1537         snd-opl3sa2=    [HW,ALSA]
1538
1539         snd-opti92x-ad1848=
1540                         [HW,ALSA]
1541
1542         snd-opti92x-cs4231=
1543                         [HW,ALSA]
1544
1545         snd-opti93x=    [HW,ALSA]
1546
1547         snd-pmac=       [HW,ALSA]
1548
1549         snd-rme32=      [HW,ALSA]
1550
1551         snd-rme96=      [HW,ALSA]
1552
1553         snd-rme9652=    [HW,ALSA]
1554
1555         snd-sb8=        [HW,ALSA]
1556
1557         snd-sb16=       [HW,ALSA]
1558
1559         snd-sbawe=      [HW,ALSA]
1560
1561         snd-serial=     [HW,ALSA]
1562
1563         snd-sgalaxy=    [HW,ALSA]
1564
1565         snd-sonicvibes= [HW,ALSA]
1566
1567         snd-sun-amd7930=
1568                         [HW,ALSA]
1569
1570         snd-sun-cs4231= [HW,ALSA]
1571
1572         snd-trident=    [HW,ALSA]
1573
1574         snd-usb-audio=  [HW,ALSA,USB]
1575
1576         snd-via82xx=    [HW,ALSA]
1577
1578         snd-virmidi=    [HW,ALSA]
1579
1580         snd-wavefront=  [HW,ALSA]
1581
1582         snd-ymfpci=     [HW,ALSA]
1583
1584         sonycd535=      [HW,CD]
1585                         Format: <io>[,<irq>]
1586
1587         sonypi.*=       [HW] Sony Programmable I/O Control Device driver
1588                         See Documentation/sonypi.txt
1589
1590         specialix=      [HW,SERIAL] Specialix multi-serial port adapter
1591                         See Documentation/specialix.txt.
1592
1593         spia_io_base=   [HW,MTD]
1594         spia_fio_base=
1595         spia_pedr=
1596         spia_peddr=
1597
1598         sscape=         [HW,OSS]
1599                         Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1600
1601         st=             [HW,SCSI] SCSI tape parameters (buffers, etc.)
1602                         See Documentation/scsi/st.txt.
1603
1604         st0x=           [HW,SCSI]
1605                         See header of drivers/scsi/seagate.c.
1606
1607         sti=            [PARISC,HW]
1608                         Format: <num>
1609                         Set the STI (builtin display/keyboard on the HP-PARISC
1610                         machines) console (graphic card) which should be used
1611                         as the initial boot-console.
1612                         See also comment in drivers/video/console/sticore.c.
1613
1614         sti_font=       [HW]
1615                         See comment in drivers/video/console/sticore.c.
1616
1617         stifb=          [HW]
1618                         Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1619
1620         swiotlb=        [IA-64] Number of I/O TLB slabs
1621
1622         switches=       [HW,M68k]
1623
1624         sym53c416=      [HW,SCSI]
1625                         See header of drivers/scsi/sym53c416.c.
1626
1627         t128=           [HW,SCSI]
1628                         See header of drivers/scsi/t128.c.
1629
1630         tdfx=           [HW,DRM]
1631
1632         thash_entries=  [KNL,NET]
1633                         Set number of hash buckets for TCP connection
1634
1635         time            Show timing data prefixed to each printk message line
1636
1637         clocksource=    [GENERIC_TIME] Override the default clocksource
1638                         Override the default clocksource and use the clocksource
1639                         with the name specified.
1640
1641         tipar.timeout=  [HW,PPT]
1642                         Set communications timeout in tenths of a second
1643                         (default 15).
1644
1645         tipar.delay=    [HW,PPT]
1646                         Set inter-bit delay in microseconds (default 10).
1647
1648         tmc8xx=         [HW,SCSI]
1649                         See header of drivers/scsi/seagate.c.
1650
1651         tmscsim=        [HW,SCSI]
1652                         See comment before function dc390_setup() in
1653                         drivers/scsi/tmscsim.c.
1654
1655         tp720=          [HW,PS2]
1656
1657         trix=           [HW,OSS] MediaTrix AudioTrix Pro
1658                         Format:
1659                         <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1660
1661         tsdev.xres=     [TS] Horizontal screen resolution.
1662         tsdev.yres=     [TS] Vertical screen resolution.
1663
1664         turbografx.map[2|3]=    [HW,JOY]
1665                         TurboGraFX parallel port interface
1666                         Format:
1667                         <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1668                         See also Documentation/input/joystick-parport.txt
1669
1670         u14-34f=        [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1671                         See header of drivers/scsi/u14-34f.c.
1672
1673         uart401=        [HW,OSS]
1674                         Format: <io>,<irq>
1675
1676         uart6850=       [HW,OSS]
1677                         Format: <io>,<irq>
1678
1679         usbhid.mousepoll=
1680                         [USBHID] The interval which mice are to be polled at.
1681
1682         vdso=           [IA-32]
1683                         vdso=1: enable VDSO (default)
1684                         vdso=0: disable VDSO mapping
1685
1686         video=          [FB] Frame buffer configuration
1687                         See Documentation/fb/modedb.txt.
1688
1689         vga=            [BOOT,IA-32] Select a particular video mode
1690                         See Documentation/i386/boot.txt and
1691                         Documentation/svga.txt.
1692                         Use vga=ask for menu.
1693                         This is actually a boot loader parameter; the value is
1694                         passed to the kernel using a special protocol.
1695
1696         vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1697                         size of <nn>. This can be used to increase the
1698                         minimum size (128MB on x86). It can also be used to
1699                         decrease the size and leave more room for directly
1700                         mapped kernel RAM.
1701
1702         vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
1703                         Format: <command>
1704
1705         vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
1706                         Format: <command>
1707
1708         vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
1709                         Format: <command>
1710
1711         waveartist=     [HW,OSS]
1712                         Format: <io>,<irq>,<dma>,<dma2>
1713
1714         wd33c93=        [HW,SCSI]
1715                         See header of drivers/scsi/wd33c93.c.
1716
1717         wd7000=         [HW,SCSI]
1718                         See header of drivers/scsi/wd7000.c.
1719
1720         wdt=            [WDT] Watchdog
1721                         See Documentation/watchdog/watchdog.txt.
1722
1723         xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1724         xd_geo=         See header of drivers/block/xd.c.
1725
1726         xirc2ps_cs=     [NET,PCMCIA]
1727                         Format:
1728                         <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1729
1730         norandmaps      Don't use address space randomization
1731                         Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1732
1733
1734 ______________________________________________________________________
1735
1736 TODO:
1737
1738         Add documentation for ALSA options.
1739         Add more DRM drivers.