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         DEVFS   devfs support is enabled.
  39         DRM     Direct Rendering Management support is enabled.
  40         EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
  41         EFI     EFI Partitioning (GPT) is enabled
  42         EIDE    EIDE/ATAPI support is enabled.
  43         FB      The frame buffer device is enabled.
  44         HW      Appropriate hardware is enabled.
  45         IA-32   IA-32 aka i386 architecture is enabled.
  46         IA-64   IA-64 architecture is enabled.
  47         IOSCHED More than one I/O scheduler is enabled.
  48         IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
  49         ISAPNP  ISA PnP code is enabled.
  50         ISDN    Appropriate ISDN support is enabled.
  51         JOY     Appropriate joystick support is enabled.
  52         LP      Printer support is enabled.
  53         LOOP    Loopback device support is enabled.
  54         M68k    M68k architecture is enabled.
  55                         These options have more detailed description inside of
  56                         Documentation/m68k/kernel-options.txt.
  57         MCA     MCA bus support is enabled.
  58         MDA     MDA console support is enabled.
  59         MOUSE   Appropriate mouse support is enabled.
  60         MSI     Message Signaled Interrupts (PCI).
  61         MTD     MTD support is enabled.
  62         NET     Appropriate network support is enabled.
  63         NUMA    NUMA support is enabled.
  64         GENERIC_TIME The generic timeofday code is enabled.
  65         NFS     Appropriate NFS support is enabled.
  66         OSS     OSS sound support is enabled.
  67         PARIDE  The ParIDE subsystem is enabled.
  68         PARISC  The PA-RISC architecture is enabled.
  69         PCI     PCI bus support is enabled.
  70         PCMCIA  The PCMCIA subsystem is enabled.
  71         PNP     Plug & Play support is enabled.
  72         PPC     PowerPC architecture is enabled.
  73         PPT     Parallel port support is enabled.
  74         PS2     Appropriate PS/2 support is enabled.
  75         RAM     RAM disk support is enabled.
  76         S390    S390 architecture is enabled.
  77         SCSI    Appropriate SCSI support is enabled.
  78                         A lot of drivers has their options described inside of
  79                         Documentation/scsi/.
  80         SELINUX SELinux support is enabled.
  81         SERIAL  Serial support is enabled.
  82         SMP     The kernel is an SMP kernel.
  83         SPARC   Sparc architecture is enabled.
  84         SWSUSP  Software suspend is enabled.
  85         TS      Appropriate touchscreen support is enabled.
  86         USB     USB support is enabled.
  87         USBHID  USB Human Interface Device support is enabled.
  88         V4L     Video For Linux support is enabled.
  89         VGA     The VGA console has been enabled.
  90         VT      Virtual terminal support is enabled.
  91         WDT     Watchdog support is enabled.
  92         XT      IBM PC/XT MFM hard disk support is enabled.
  93         X86-64  X86-64 architecture is enabled.
  94                         More X86-64 boot options can be found in
  95                         Documentation/x86_64/boot-options.txt .
  96
  97 In addition, the following text indicates that the option:
  98
  99         BUGS=   Relates to possible processor bugs on the said processor.
 100         KNL     Is a kernel start-up parameter.
 101         BOOT    Is a boot loader parameter.
 102
 103 Parameters denoted with BOOT are actually interpreted by the boot
 104 loader, and have no meaning to the kernel directly.
 105 Do not modify the syntax of boot loader parameters without extreme
 106 need or coordination with <Documentation/i386/boot.txt>.
 107
 108 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
 109 a trailing = on the name of any parameter states that that parameter will
 110 be entered as an environment variable, whereas its absence indicates that
 111 it will appear as a kernel argument readable via /proc/cmdline by programs
 112 running once the system is up.
 113
 114         53c7xx=         [HW,SCSI] Amiga SCSI controllers
 115                         See header of drivers/scsi/53c7xx.c.
 116                         See also Documentation/scsi/ncr53c7xx.txt.
 117
 118         acpi=           [HW,ACPI] Advanced Configuration and Power Interface
 119                         Format: { force | off | ht | strict | noirq }
 120                         force -- enable ACPI if default was off
 121                         off -- disable ACPI if default was on
 122                         noirq -- do not use ACPI for IRQ routing
 123                         ht -- run only enough ACPI to enable Hyper Threading
 124                         strict -- Be less tolerant of platforms that are not
 125                                 strictly ACPI specification compliant.
 126
 127                         See also Documentation/pm.txt, pci=noacpi
 128
 129         acpi_sleep=     [HW,ACPI] Sleep options
 130                         Format: { s3_bios, s3_mode }
 131                         See Documentation/power/video.txt
 132
 133         acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
 134                         Format: { level | edge | high | low }
 135
 136         acpi_irq_balance [HW,ACPI]
 137                         ACPI will balance active IRQs
 138                         default in APIC mode
 139
 140         acpi_irq_nobalance [HW,ACPI]
 141                         ACPI will not move active IRQs (default)
 142                         default in PIC mode
 143
 144         acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
 145                         use by PCI
 146                         Format: <irq>,<irq>...
 147
 148         acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 149                         Format: <irq>,<irq>...
 150
 151         acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
 152                         Format: To spoof as Windows 98: ="Microsoft Windows"
 153
 154         acpi_osi=       [HW,ACPI] empty param disables _OSI
 155
 156         acpi_serialize  [HW,ACPI] force serialization of AML methods
 157
 158         acpi_skip_timer_override [HW,ACPI]
 159                         Recognize and ignore IRQ0/pin2 Interrupt Override.
 160                         For broken nForce2 BIOS resulting in XT-PIC timer.
 161
 162         acpi_dbg_layer= [HW,ACPI]
 163                         Format: <int>
 164                         Each bit of the <int> indicates an ACPI debug layer,
 165                         1: enable, 0: disable. It is useful for boot time
 166                         debugging. After system has booted up, it can be set
 167                         via /proc/acpi/debug_layer.
 168
 169         acpi_dbg_level= [HW,ACPI]
 170                         Format: <int>
 171                         Each bit of the <int> indicates an ACPI debug level,
 172                         1: enable, 0: disable. It is useful for boot time
 173                         debugging. After system has booted up, it can be set
 174                         via /proc/acpi/debug_level.
 175
 176         acpi_fake_ecdt  [HW,ACPI] Workaround failure due to BIOS lacking ECDT
 177
 178         acpi_generic_hotkey [HW,ACPI]
 179                         Allow consolidated generic hotkey driver to
 180                         override platform specific driver.
 181                         See also Documentation/acpi-hotkey.txt.
 182
 183         acpi_pm_good    [IA-32,X86-64]
 184                         Override the pmtimer bug detection: force the kernel
 185                         to assume that this machine's pmtimer latches its value
 186                         and always returns good values.
 187
 188         enable_timer_pin_1 [i386,x86-64]
 189                         Enable PIN 1 of APIC timer
 190                         Can be useful to work around chipset bugs
 191                         (in particular on some ATI chipsets).
 192                         The kernel tries to set a reasonable default.
 193
 194         disable_timer_pin_1 [i386,x86-64]
 195                         Disable PIN 1 of APIC timer
 196                         Can be useful to work around chipset bugs.
 197
 198         ad1816=         [HW,OSS]
 199                         Format: <io>,<irq>,<dma>,<dma2>
 200                         See also Documentation/sound/oss/AD1816.
 201
 202         ad1848=         [HW,OSS]
 203                         Format: <io>,<irq>,<dma>,<dma2>,<type>
 204
 205         adlib=          [HW,OSS]
 206                         Format: <io>
 207
 208         advansys=       [HW,SCSI]
 209                         See header of drivers/scsi/advansys.c.
 210
 211         advwdt=         [HW,WDT] Advantech WDT
 212                         Format: <iostart>,<iostop>
 213
 214         aedsp16=        [HW,OSS] Audio Excel DSP 16
 215                         Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
 216                         See also header of sound/oss/aedsp16.c.
 217
 218         aha152x=        [HW,SCSI]
 219                         See Documentation/scsi/aha152x.txt.
 220
 221         aha1542=        [HW,SCSI]
 222                         Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
 223
 224         aic7xxx=        [HW,SCSI]
 225                         See Documentation/scsi/aic7xxx.txt.
 226
 227         aic79xx=        [HW,SCSI]
 228                         See Documentation/scsi/aic79xx.txt.
 229
 230         amijoy.map=     [HW,JOY] Amiga joystick support
 231                         Map of devices attached to JOY0DAT and JOY1DAT
 232                         Format: <a>,<b>
 233                         See also Documentation/kernel/input/joystick.txt
 234
 235         analog.map=     [HW,JOY] Analog joystick and gamepad support
 236                         Specifies type or capabilities of an analog joystick
 237                         connected to one of 16 gameports
 238                         Format: <type1>,<type2>,..<type16>
 239
 240         apc=            [HW,SPARC]
 241                         Power management functions (SPARCstation-4/5 + deriv.)
 242                         Format: noidle
 243                         Disable APC CPU standby support. SPARCstation-Fox does
 244                         not play well with APC CPU idle - disable it if you have
 245                         APC and your system crashes randomly.
 246
 247         apic=           [APIC,i386] Change the output verbosity whilst booting
 248                         Format: { quiet (default) | verbose | debug }
 249                         Change the amount of debugging information output
 250                         when initialising the APIC and IO-APIC components.
 251
 252         apm=            [APM] Advanced Power Management
 253                         See header of arch/i386/kernel/apm.c.
 254
 255         applicom=       [HW]
 256                         Format: <mem>,<irq>
 257
 258         arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 259                         Format: <io>,<irq>,<nodeID>
 260
 261         ataflop=        [HW,M68k]
 262
 263         atarimouse=     [HW,MOUSE] Atari Mouse
 264
 265         atascsi=        [HW,SCSI] Atari SCSI
 266
 267         atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 268                         EzKey and similar keyboards
 269
 270         atkbd.reset=    [HW] Reset keyboard during initialization
 271
 272         atkbd.set=      [HW] Select keyboard code set
 273                         Format: <int> (2 = AT (default), 3 = PS/2)
 274
 275         atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 276                         keyboards
 277
 278         atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 279                         Format: <bool> (0 = real, 1 = synthetic (default))
 280
 281         atkbd.softrepeat= [HW]
 282                         Use software keyboard repeat
 283
 284         autotest        [IA64]
 285
 286         awe=            [HW,OSS] AWE32/SB32/AWE64 wave table synth
 287                         Format: <io>,<memsize>,<isapnp>
 288
 289         aztcd=          [HW,CD] Aztech CD268 CDROM driver
 290                         Format: <io>,0x79 (?)
 291
 292         baycom_epp=     [HW,AX25]
 293                         Format: <io>,<mode>
 294
 295         baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 296                         Format: <io>,<mode>
 297                         See header of drivers/net/hamradio/baycom_par.c.
 298
 299         baycom_ser_fdx= [HW,AX25]
 300                         BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 301                         Format: <io>,<irq>,<mode>[,<baud>]
 302                         See header of drivers/net/hamradio/baycom_ser_fdx.c.
 303
 304         baycom_ser_hdx= [HW,AX25]
 305                         BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 306                         Format: <io>,<irq>,<mode>
 307                         See header of drivers/net/hamradio/baycom_ser_hdx.c.
 308
 309         blkmtd_device=  [HW,MTD]
 310         blkmtd_erasesz=
 311         blkmtd_ro=
 312         blkmtd_bs=
 313         blkmtd_count=
 314
 315         bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 316         bttv.radio=     Most important insmod options are available as
 317                         kernel args too.
 318         bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 319         bttv.tuner=     and Documentation/video4linux/bttv/CARDLIST
 320
 321         BusLogic=       [HW,SCSI]
 322                         See drivers/scsi/BusLogic.c, comment before function
 323                         BusLogic_ParseDriverOptions().
 324
 325         c101=           [NET] Moxa C101 synchronous serial card
 326
 327         cachesize=      [BUGS=IA-32] Override level 2 CPU cache size detection.
 328                         Sometimes CPU hardware bugs make them report the cache
 329                         size incorrectly. The kernel will attempt work arounds
 330                         to fix known problems, but for some CPUs it is not
 331                         possible to determine what the correct size should be.
 332                         This option provides an override for these situations.
 333
 334         cdu31a=         [HW,CD]
 335                         Format: <io>,<irq>[,PAS]
 336                         See header of drivers/cdrom/cdu31a.c.
 337
 338         chandev=        [HW,NET] Generic channel device initialisation
 339
 340         checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 341                         Format: { "0" | "1" }
 342                         See security/selinux/Kconfig help text.
 343                         0 -- check protection applied by kernel (includes
 344                                 any implied execute protection).
 345                         1 -- check protection requested by application.
 346                         Default value is set via a kernel config option.
 347                         Value can be changed at runtime via
 348                                 /selinux/checkreqprot.
 349
 350         clock=          [BUGS=IA-32, HW] gettimeofday clocksource override.
 351                         [Deprecated]
 352                         Forces specified clocksource (if avaliable) to be used
 353                         when calculating gettimeofday(). If specified
 354                         clocksource is not avalible, it defaults to PIT.
 355                         Format: { pit | tsc | cyclone | pmtmr }
 356
 357         disable_8254_timer
 358         enable_8254_timer
 359                         [IA32/X86_64] Disable/Enable interrupt 0 timer routing
 360                         over the 8254 in addition to over the IO-APIC. The
 361                         kernel tries to set a sensible default.
 362
 363         hpet=           [IA-32,HPET] option to disable HPET and use PIT.
 364                         Format: disable
 365
 366         cm206=          [HW,CD]
 367                         Format: { auto | [<io>,][<irq>] }
 368
 369         com20020=       [HW,NET] ARCnet - COM20020 chipset
 370                         Format:
 371                         <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 372
 373         com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 374                         Format: <io>[,<irq>]
 375
 376         com90xx=        [HW,NET]
 377                         ARCnet - COM90xx chipset (memory-mapped buffers)
 378                         Format: <io>[,<irq>[,<memstart>]]
 379
 380         condev=         [HW,S390] console device
 381         conmode=
 382
 383         console=        [KNL] Output console device and options.
 384
 385                 tty<n>  Use the virtual console device <n>.
 386
 387                 ttyS<n>[,options]
 388                 ttyUSB0[,options]
 389                         Use the specified serial port.  The options are of
 390                         the form "bbbbpnf", where "bbbb" is the baud rate,
 391                         "p" is parity ("n", "o", or "e"), "n" is number of
 392                         bits, and "f" is flow control ("r" for RTS or
 393                         omit it).  Default is "9600n8".
 394
 395                         See Documentation/serial-console.txt for more
 396                         information.  See
 397                         Documentation/networking/netconsole.txt for an
 398                         alternative.
 399
 400                 uart,io,<addr>[,options]
 401                 uart,mmio,<addr>[,options]
 402                         Start an early, polled-mode console on the 8250/16550
 403                         UART at the specified I/O port or MMIO address,
 404                         switching to the matching ttyS device later.  The
 405                         options are the same as for ttyS, above.
 406
 407         cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 408                         Format:
 409                         <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 410
 411         cpia_pp=        [HW,PPT]
 412                         Format: { parport<nr> | auto | none }
 413
 414         crashkernel=nn[KMG]@ss[KMG]
 415                         [KNL] Reserve a chunk of physical memory to
 416                         hold a kernel to switch to with kexec on panic.
 417
 418         cs4232=         [HW,OSS]
 419                         Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
 420
 421         cs89x0_dma=     [HW,NET]
 422                         Format: <dma>
 423
 424         cs89x0_media=   [HW,NET]
 425                         Format: { rj45 | aui | bnc }
 426
 427         cyclades=       [HW,SERIAL] Cyclades multi-serial port adapter.
 428
 429         dasd=           [HW,NET]
 430                         See header of drivers/s390/block/dasd_devmap.c.
 431
 432         db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 433                         (one device per port)
 434                         Format: <port#>,<type>
 435                         See also Documentation/input/joystick-parport.txt
 436
 437         debug           [KNL] Enable kernel debugging (events log level).
 438
 439         decnet=         [HW,NET]
 440                         Format: <area>[,<node>]
 441                         See also Documentation/networking/decnet.txt.
 442
 443         devfs=          [DEVFS]
 444                         See Documentation/filesystems/devfs/boot-options.
 445
 446         dhash_entries=  [KNL]
 447                         Set number of hash buckets for dentry cache.
 448
 449         digi=           [HW,SERIAL]
 450                         IO parameters + enable/disable command.
 451
 452         digiepca=       [HW,SERIAL]
 453                         See drivers/char/README.epca and
 454                         Documentation/digiepca.txt.
 455
 456         dmascc=         [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
 457                         support available.
 458                         Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
 459
 460         dmasound=       [HW,OSS] Sound subsystem buffers
 461
 462         dscc4.setup=    [NET]
 463
 464         dtc3181e=       [HW,SCSI]
 465
 466         earlyprintk=    [IA-32,X86-64]
 467                         earlyprintk=vga
 468                         earlyprintk=serial[,ttySn[,baudrate]]
 469
 470                         Append ",keep" to not disable it when the real console
 471                         takes over.
 472
 473                         Only vga or serial at a time, not both.
 474
 475                         Currently only ttyS0 and ttyS1 are supported.
 476
 477                         Interaction with the standard serial driver is not
 478                         very good.
 479
 480                         The VGA output is eventually overwritten by the real
 481                         console.
 482
 483         eata=           [HW,SCSI]
 484
 485         ec_intr=        [HW,ACPI] ACPI Embedded Controller interrupt mode
 486                         Format: <int>
 487                         0: polling mode
 488                         non-0: interrupt mode (default)
 489
 490         eda=            [HW,PS2]
 491
 492         edb=            [HW,PS2]
 493
 494         edd=            [EDD]
 495                         Format: {"of[f]" | "sk[ipmbr]"}
 496                         See comment in arch/i386/boot/edd.S
 497
 498         eicon=          [HW,ISDN]
 499                         Format: <id>,<membase>,<irq>
 500
 501         eisa_irq_edge=  [PARISC,HW]
 502                         See header of drivers/parisc/eisa.c.
 503
 504         elanfreq=       [IA-32]
 505                         See comment before function elanfreq_setup() in
 506                         arch/i386/kernel/cpu/cpufreq/elanfreq.c.
 507
 508         elevator=       [IOSCHED]
 509                         Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
 510                         See Documentation/block/as-iosched.txt and
 511                         Documentation/block/deadline-iosched.txt for details.
 512
 513         elfcorehdr=     [IA-32, X86_64]
 514                         Specifies physical address of start of kernel core
 515                         image elf header. Generally kexec loader will
 516                         pass this option to capture kernel.
 517                         See Documentation/kdump/kdump.txt for details.
 518
 519         enforcing       [SELINUX] Set initial enforcing status.
 520                         Format: {"0" | "1"}
 521                         See security/selinux/Kconfig help text.
 522                         0 -- permissive (log only, no denials).
 523                         1 -- enforcing (deny and log).
 524                         Default value is 0.
 525                         Value can be changed at runtime via /selinux/enforce.
 526
 527         es1370=         [HW,OSS]
 528                         Format: <lineout>[,<micbias>]
 529                         See also header of sound/oss/es1370.c.
 530
 531         es1371=         [HW,OSS]
 532                         Format: <spdif>,[<nomix>,[<amplifier>]]
 533                         See also header of sound/oss/es1371.c.
 534
 535         ether=          [HW,NET] Ethernet cards parameters
 536                         This option is obsoleted by the "netdev=" option, which
 537                         has equivalent usage. See its documentation for details.
 538
 539         eurwdt=         [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
 540                         Format: <io>[,<irq>]
 541
 542         fd_mcs=         [HW,SCSI]
 543                         See header of drivers/scsi/fd_mcs.c.
 544
 545         fdomain=        [HW,SCSI]
 546                         See header of drivers/scsi/fdomain.c.
 547
 548         floppy=         [HW]
 549                         See Documentation/floppy.txt.
 550
 551         ftape=          [HW] Floppy Tape subsystem debugging options.
 552                         See Documentation/ftape.txt.
 553
 554         gamecon.map[2|3]=
 555                         [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 556                         support via parallel port (up to 5 devices per port)
 557                         Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 558                         See also Documentation/input/joystick-parport.txt
 559
 560         gamma=          [HW,DRM]
 561
 562         gdth=           [HW,SCSI]
 563                         See header of drivers/scsi/gdth.c.
 564
 565         gpt             [EFI] Forces disk with valid GPT signature but
 566                         invalid Protective MBR to be treated as GPT.
 567
 568         gscd=           [HW,CD]
 569                         Format: <io>
 570
 571         gt96100eth=     [NET] MIPS GT96100 Advanced Communication Controller
 572
 573         gus=            [HW,OSS]
 574                         Format: <io>,<irq>,<dma>,<dma16>
 575
 576         gvp11=          [HW,SCSI]
 577
 578         hashdist=       [KNL,NUMA] Large hashes allocated during boot
 579                         are distributed across NUMA nodes.  Defaults on
 580                         for IA-64, off otherwise.
 581                         Format: 0 | 1 (for off | on)
 582
 583         hcl=            [IA-64] SGI's Hardware Graph compatibility layer
 584
 585         hd=             [EIDE] (E)IDE hard drive subsystem geometry
 586                         Format: <cyl>,<head>,<sect>
 587
 588         hd?=            [HW] (E)IDE subsystem
 589         hd?lun=         See Documentation/ide.txt.
 590
 591         highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
 592                         size of <nn>. This works even on boxes that have no
 593                         highmem otherwise. This also works to reduce highmem
 594                         size on bigger boxes.
 595
 596         hisax=          [HW,ISDN]
 597                         See Documentation/isdn/README.HiSax.
 598
 599         hugepages=      [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
 600
 601         noirqbalance    [IA-32,SMP,KNL] Disable kernel irq balancing
 602
 603         i8042.direct    [HW] Put keyboard port into non-translated mode
 604         i8042.dumbkbd   [HW] Pretend that controlled can only read data from
 605                              keyboard and can not control its state
 606                              (Don't attempt to blink the leds)
 607         i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
 608         i8042.nokbd     [HW] Don't check/create keyboard port
 609         i8042.nomux     [HW] Don't check presence of an active multiplexing
 610                              controller
 611         i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
 612                              controllers
 613         i8042.panicblink=
 614                         [HW] Frequency with which keyboard LEDs should blink
 615                              when kernel panics (default is 0.5 sec)
 616         i8042.reset     [HW] Reset the controller during init and cleanup
 617         i8042.unlock    [HW] Unlock (ignore) the keylock
 618
 619         i810=           [HW,DRM]
 620
 621         i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
 622                         indicates that the driver is running on unsupported
 623                         hardware.
 624         i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
 625                         does not match list of supported models.
 626         i8k.power_status
 627                         [HW] Report power status in /proc/i8k
 628                         (disabled by default)
 629         i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
 630                         capability is set.
 631
 632         ibmmcascsi=     [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
 633                         See Documentation/mca.txt.
 634
 635         icn=            [HW,ISDN]
 636                         Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
 637
 638         ide=            [HW] (E)IDE subsystem
 639                         Format: ide=nodma or ide=doubler or ide=reverse
 640                         See Documentation/ide.txt.
 641
 642         ide?=           [HW] (E)IDE subsystem
 643                         Format: ide?=noprobe or chipset specific parameters.
 644                         See Documentation/ide.txt.
 645
 646         idebus=         [HW] (E)IDE subsystem - VLB/PCI bus speed
 647                         See Documentation/ide.txt.
 648
 649         idle=           [HW]
 650                         Format: idle=poll or idle=halt
 651
 652         ihash_entries=  [KNL]
 653                         Set number of hash buckets for inode cache.
 654
 655         in2000=         [HW,SCSI]
 656                         See header of drivers/scsi/in2000.c.
 657
 658         init=           [KNL]
 659                         Format: <full_path>
 660                         Run specified binary instead of /sbin/init as init
 661                         process.
 662
 663         initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
 664                         for working out where the kernel is dying during
 665                         startup.
 666
 667         initrd=         [BOOT] Specify the location of the initial ramdisk
 668
 669         inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
 670                         Format: <irq>
 671
 672         combined_mode=  [HW] control which driver uses IDE ports in combined
 673                         mode: legacy IDE driver, libata, or both
 674                         (in the libata case, libata.atapi_enabled=1 may be
 675                         useful as well).  Note that using the ide or libata
 676                         options may affect your device naming (e.g. by
 677                         changing hdc to sdb).
 678                         Format: combined (default), ide, or libata
 679
 680         inttest=        [IA64]
 681
 682         io7=            [HW] IO7 for Marvel based alpha systems
 683                         See comment before marvel_specify_io7 in
 684                         arch/alpha/kernel/core_marvel.c.
 685
 686         ip=             [IP_PNP]
 687                         See Documentation/nfsroot.txt.
 688
 689         ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
 690                         See comment before ip2_setup() in drivers/char/ip2.c.
 691
 692         ips=            [HW,SCSI] Adaptec / IBM ServeRAID controller
 693                         See header of drivers/scsi/ips.c.
 694
 695         irqfixup        [HW]
 696                         When an interrupt is not handled search all handlers
 697                         for it. Intended to get systems with badly broken
 698                         firmware running.
 699
 700         irqpoll         [HW]
 701                         When an interrupt is not handled search all handlers
 702                         for it. Also check all handlers each timer
 703                         interrupt. Intended to get systems with badly broken
 704                         firmware running.
 705
 706         isapnp=         [ISAPNP]
 707                         Format: <RDP>,<reset>,<pci_scan>,<verbosity>
 708
 709         isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
 710                         Format: <cpu number>,...,<cpu number>
 711                         This option can be used to specify one or more CPUs
 712                         to isolate from the general SMP balancing and scheduling
 713                         algorithms. The only way to move a process onto or off
 714                         an "isolated" CPU is via the CPU affinity syscalls.
 715                         <cpu number> begins at 0 and the maximum value is
 716                         "number of CPUs in system - 1".
 717
 718                         This option is the preferred way to isolate CPUs. The
 719                         alternative -- manually setting the CPU mask of all
 720                         tasks in the system -- can cause problems and
 721                         suboptimal load balancer performance.
 722
 723         isp16=          [HW,CD]
 724                         Format: <io>,<irq>,<dma>,<setup>
 725
 726         iucv=           [HW,NET]
 727
 728         js=             [HW,JOY] Analog joystick
 729                         See Documentation/input/joystick.txt.
 730
 731         keepinitrd      [HW,ARM]
 732
 733         kstack=N        [IA-32,X86-64] Print N words from the kernel stack
 734                         in oops dumps.
 735
 736         l2cr=           [PPC]
 737
 738         lapic           [IA-32,APIC] Enable the local APIC even if BIOS
 739                         disabled it.
 740
 741         lasi=           [HW,SCSI] PARISC LASI driver for the 53c700 chip
 742                         Format: addr:<io>,irq:<irq>
 743
 744         llsc*=          [IA64] See function print_params() in
 745                         arch/ia64/sn/kernel/llsc4.c.
 746
 747         load_ramdisk=   [RAM] List of ramdisks to load from floppy
 748                         See Documentation/ramdisk.txt.
 749
 750         lockd.nlm_grace_period=P  [NFS] Assign grace period.
 751                         Format: <integer>
 752
 753         lockd.nlm_tcpport=N     [NFS] Assign TCP port.
 754                         Format: <integer>
 755
 756         lockd.nlm_timeout=T     [NFS] Assign timeout value.
 757                         Format: <integer>
 758
 759         lockd.nlm_udpport=M     [NFS] Assign UDP port.
 760                         Format: <integer>
 761
 762         logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
 763                         Format: <irq>
 764
 765         loglevel=       All Kernel Messages with a loglevel smaller than the
 766                         console loglevel will be printed to the console. It can
 767                         also be changed with klogd or other programs. The
 768                         loglevels are defined as follows:
 769
 770                         0 (KERN_EMERG)          system is unusable
 771                         1 (KERN_ALERT)          action must be taken immediately
 772                         2 (KERN_CRIT)           critical conditions
 773                         3 (KERN_ERR)            error conditions
 774                         4 (KERN_WARNING)        warning conditions
 775                         5 (KERN_NOTICE)         normal but significant condition
 776                         6 (KERN_INFO)           informational
 777                         7 (KERN_DEBUG)          debug-level messages
 778
 779         log_buf_len=n   Sets the size of the printk ring buffer, in bytes.
 780                         Format: { n | nk | nM }
 781                         n must be a power of two.  The default size
 782                         is set in the kernel config file.
 783
 784         lp=0            [LP]    Specify parallel ports to use, e.g,
 785         lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
 786         lp=reset                first parallel port). 'lp=0' disables the
 787         lp=auto                 printer driver. 'lp=reset' (which can be
 788                                 specified in addition to the ports) causes
 789                                 attached printers to be reset. Using
 790                                 lp=port1,port2,... specifies the parallel ports
 791                                 to associate lp devices with, starting with
 792                                 lp0. A port specification may be 'none' to skip
 793                                 that lp device, or a parport name such as
 794                                 'parport0'. Specifying 'lp=auto' instead of a
 795                                 port specification list means that device IDs
 796                                 from each port should be examined, to see if
 797                                 an IEEE 1284-compliant printer is attached; if
 798                                 so, the driver will manage that printer.
 799                                 See also header of drivers/char/lp.c.
 800
 801         lpj=n           [KNL]
 802                         Sets loops_per_jiffy to given constant, thus avoiding
 803                         time-consuming boot-time autodetection (up to 250 ms per
 804                         CPU). 0 enables autodetection (default). To determine
 805                         the correct value for your kernel, boot with normal
 806                         autodetection and see what value is printed. Note that
 807                         on SMP systems the preset will be applied to all CPUs,
 808                         which is likely to cause problems if your CPUs need
 809                         significantly divergent settings. An incorrect value
 810                         will cause delays in the kernel to be wrong, leading to
 811                         unpredictable I/O errors and other breakage. Although
 812                         unlikely, in the extreme case this might damage your
 813                         hardware.
 814
 815         ltpc=           [NET]
 816                         Format: <io>,<irq>,<dma>
 817
 818         mac5380=        [HW,SCSI] Format:
 819                         <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
 820
 821         mac53c9x=       [HW,SCSI] Format:
 822                         <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
 823
 824         machvec=        [IA64] Force the use of a particular machine-vector
 825                         (machvec) in a generic kernel.
 826                         Example: machvec=hpzx1_swiotlb
 827
 828         mad16=          [HW,OSS] Format:
 829                         <io>,<irq>,<dma>,<dma16>,<mpu_io>,<mpu_irq>,<joystick>
 830
 831         maui=           [HW,OSS]
 832                         Format: <io>,<irq>
 833
 834         max_loop=       [LOOP] Maximum number of loopback devices that can
 835                         be mounted
 836                         Format: <1-256>
 837
 838         maxcpus=        [SMP] Maximum number of processors that an SMP kernel
 839                         should make use of
 840
 841         max_addr=[KMG]  [KNL,BOOT,ia64] All physical memory greater than or
 842                         equal to this physical address is ignored.
 843
 844         max_luns=       [SCSI] Maximum number of LUNs to probe.
 845                         Should be between 1 and 2^32-1.
 846
 847         max_report_luns=
 848                         [SCSI] Maximum number of LUNs received.
 849                         Should be between 1 and 16384.
 850
 851         mca-pentium     [BUGS=IA-32]
 852
 853         mcatest=        [IA-64]
 854
 855         mcd=            [HW,CD]
 856                         Format: <port>,<irq>,<mitsumi_bug_93_wait>
 857
 858         mcdx=           [HW,CD]
 859
 860         mce             [IA-32] Machine Check Exception
 861
 862         md=             [HW] RAID subsystems devices and level
 863                         See Documentation/md.txt.
 864
 865         mdacon=         [MDA]
 866                         Format: <first>,<last>
 867                         Specifies range of consoles to be captured by the MDA.
 868
 869         mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
 870                         Amount of memory to be used when the kernel is not able
 871                         to see the whole system memory or for test.
 872                         [IA-32] Use together with memmap= to avoid physical
 873                         address space collisions. Without memmap= PCI devices
 874                         could be placed at addresses belonging to unused RAM.
 875
 876         mem=nopentium   [BUGS=IA-32] Disable usage of 4MB pages for kernel
 877                         memory.
 878
 879         memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
 880                         E820 memory map, as specified by the user.
 881                         Such memmap=exactmap lines can be constructed based on
 882                         BIOS output or other requirements. See the memmap=nn@ss
 883                         option description.
 884
 885         memmap=nn[KMG]@ss[KMG]
 886                         [KNL] Force usage of a specific region of memory
 887                         Region of memory to be used, from ss to ss+nn.
 888
 889         memmap=nn[KMG]#ss[KMG]
 890                         [KNL,ACPI] Mark specific memory as ACPI data.
 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 reserved.
 895                         Region of memory to be used, from ss to ss+nn.
 896
 897         meye.*=         [HW] Set MotionEye Camera parameters
 898                         See Documentation/video4linux/meye.txt.
 899
 900         mga=            [HW,DRM]
 901
 902         migration_cost=
 903                         [KNL,SMP] debug: override scheduler migration costs
 904                         Format: <level-1-usecs>,<level-2-usecs>,...
 905                         This debugging option can be used to override the
 906                         default scheduler migration cost matrix. The numbers
 907                         are indexed by 'CPU domain distance'.
 908                         E.g. migration_cost=1000,2000,3000 on an SMT NUMA
 909                         box will set up an intra-core migration cost of
 910                         1 msec, an inter-core migration cost of 2 msecs,
 911                         and an inter-node migration cost of 3 msecs.
 912
 913                         WARNING: using the wrong values here can break
 914                         scheduler performance, so it's only for scheduler
 915                         development purposes, not production environments.
 916
 917         migration_debug=
 918                         [KNL,SMP] migration cost auto-detect verbosity
 919                         Format=<0|1|2>
 920                         If a system's migration matrix reported at bootup
 921                         seems erroneous then this option can be used to
 922                         increase verbosity of the detection process.
 923                         We default to 0 (no extra messages), 1 will print
 924                         some more information, and 2 will be really
 925                         verbose (probably only useful if you also have a
 926                         serial console attached to the system).
 927
 928         migration_factor=
 929                         [KNL,SMP] multiply/divide migration costs by a factor
 930                         Format=<percent>
 931                         This debug option can be used to proportionally
 932                         increase or decrease the auto-detected migration
 933                         costs for all entries of the migration matrix.
 934                         E.g. migration_factor=150 will increase migration
 935                         costs by 50%. (and thus the scheduler will be less
 936                         eager migrating cache-hot tasks)
 937                         migration_factor=80 will decrease migration costs
 938                         by 20%. (thus the scheduler will be more eager to
 939                         migrate tasks)
 940
 941                         WARNING: using the wrong values here can break
 942                         scheduler performance, so it's only for scheduler
 943                         development purposes, not production environments.
 944
 945         mousedev.tap_time=
 946                         [MOUSE] Maximum time between finger touching and
 947                         leaving touchpad surface for touch to be considered
 948                         a tap and be reported as a left button click (for
 949                         touchpads working in absolute mode only).
 950                         Format: <msecs>
 951         mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
 952                         reporting absolute coordinates, such as tablets
 953         mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
 954                         reporting absolute coordinates, such as tablets
 955
 956         mpu401=         [HW,OSS]
 957                         Format: <io>,<irq>
 958
 959         MTD_Partition=  [MTD]
 960                         Format: <name>,<region-number>,<size>,<offset>
 961
 962         MTD_Region=     [MTD] Format:
 963                         <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
 964
 965         mtdparts=       [MTD]
 966                         See drivers/mtd/cmdline.c.
 967
 968         mtouchusb.raw_coordinates=
 969                         [HW] Make the MicroTouch USB driver use raw coordinates
 970                         ('y', default) or cooked coordinates ('n')
 971
 972         n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
 973
 974         NCR_D700=       [HW,SCSI]
 975                         See header of drivers/scsi/NCR_D700.c.
 976
 977         ncr5380=        [HW,SCSI]
 978
 979         ncr53c400=      [HW,SCSI]
 980
 981         ncr53c400a=     [HW,SCSI]
 982
 983         ncr53c406a=     [HW,SCSI]
 984
 985         ncr53c8xx=      [HW,SCSI]
 986
 987         netdev=         [NET] Network devices parameters
 988                         Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
 989                         Note that mem_start is often overloaded to mean
 990                         something different and driver-specific.
 991                         This usage is only documented in each driver source
 992                         file if at all.
 993
 994         nfsaddrs=       [NFS]
 995                         See Documentation/nfsroot.txt.
 996
 997         nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
 998                         See Documentation/nfsroot.txt.
 999
1000         nfs.callback_tcpport=
1001                         [NFS] set the TCP port on which the NFSv4 callback
1002                         channel should listen.
1003
1004         nfs.idmap_cache_timeout=
1005                         [NFS] set the maximum lifetime for idmapper cache
1006                         entries.
1007
1008         nmi_watchdog=   [KNL,BUGS=IA-32] Debugging features for SMP kernels
1009
1010         no387           [BUGS=IA-32] Tells the kernel to use the 387 maths
1011                         emulation library even if a 387 maths coprocessor
1012                         is present.
1013
1014         noalign         [KNL,ARM]
1015
1016         noapic          [SMP,APIC] Tells the kernel to not make use of any
1017                         IOAPICs that may be present in the system.
1018
1019         noasync         [HW,M68K] Disables async and sync negotiation for
1020                         all devices.
1021
1022         nobats          [PPC] Do not use BATs for mapping kernel lowmem
1023                         on "Classic" PPC cores.
1024
1025         nocache         [ARM]
1026
1027         nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1028
1029         noexec          [IA-64]
1030
1031         noexec          [IA-32,X86-64]
1032                         noexec=on: enable non-executable mappings (default)
1033                         noexec=off: disable nn-executable mappings
1034
1035         nofxsr          [BUGS=IA-32] Disables x86 floating point extended
1036                         register save and restore. The kernel will only save
1037                         legacy floating-point registers on task switch.
1038
1039         nohlt           [BUGS=ARM]
1040
1041         no-hlt          [BUGS=IA-32] Tells the kernel that the hlt
1042                         instruction doesn't work correctly and not to
1043                         use it.
1044
1045         nohalt          [IA-64] Tells the kernel not to use the power saving
1046                         function PAL_HALT_LIGHT when idle. This increases
1047                         power-consumption. On the positive side, it reduces
1048                         interrupt wake-up latency, which may improve performance
1049                         in certain environments such as networked servers or
1050                         real-time systems.
1051
1052         noirqdebug      [IA-32] Disables the code which attempts to detect and
1053                         disable unhandled interrupt sources.
1054
1055         noisapnp        [ISAPNP] Disables ISA PnP code.
1056
1057         noinitrd        [RAM] Tells the kernel not to load any configured
1058                         initial RAM disk.
1059
1060         nointroute      [IA-64]
1061
1062         nolapic         [IA-32,APIC] Do not enable or use the local APIC.
1063
1064         noltlbs         [PPC] Do not use large page/tlb entries for kernel
1065                         lowmem mapping on PPC40x.
1066
1067         nomca           [IA-64] Disable machine check abort handling
1068
1069         nomce           [IA-32] Machine Check Exception
1070
1071         noresidual      [PPC] Don't use residual data on PReP machines.
1072
1073         noresume        [SWSUSP] Disables resume and restores original swap
1074                         space.
1075
1076         no-scroll       [VGA] Disables scrollback.
1077                         This is required for the Braillex ib80-piezo Braille
1078                         reader made by F.H. Papenmeier (Germany).
1079
1080         nosbagart       [IA-64]
1081
1082         nosep           [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1083
1084         nosmp           [SMP] Tells an SMP kernel to act as a UP kernel.
1085
1086         nosync          [HW,M68K] Disables sync negotiation for all devices.
1087
1088         notsc           [BUGS=IA-32] Disable Time Stamp Counter
1089
1090         nousb           [USB] Disable the USB subsystem
1091
1092         nowb            [ARM]
1093
1094         nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1095
1096         opl3=           [HW,OSS]
1097                         Format: <io>
1098
1099         opl3sa=         [HW,OSS]
1100                         Format: <io>,<irq>,<dma>,<dma2>,<mpu_io>,<mpu_irq>
1101
1102         opl3sa2=        [HW,OSS] Format:
1103                         <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
1104
1105         oprofile.timer= [HW]
1106                         Use timer interrupt instead of performance counters
1107
1108         optcd=          [HW,CD]
1109                         Format: <io>
1110
1111         osst=           [HW,SCSI] SCSI Tape Driver
1112                         Format: <buffer_size>,<write_threshold>
1113                         See also Documentation/scsi/st.txt.
1114
1115         panic=          [KNL] Kernel behaviour on panic
1116                         Format: <timeout>
1117
1118         parkbd.port=    [HW] Parallel port number the keyboard adapter is
1119                         connected to, default is 0.
1120                         Format: <parport#>
1121         parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
1122                         0 for XT, 1 for AT (default is AT).
1123                         Format: <mode>
1124
1125         parport=        [HW,PPT] Specify parallel ports. 0 disables.
1126                         Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1127                         Use 'auto' to force the driver to use any
1128                         IRQ/DMA settings detected (the default is to
1129                         ignore detected IRQ/DMA settings because of
1130                         possible conflicts). You can specify the base
1131                         address, IRQ, and DMA settings; IRQ and DMA
1132                         should be numbers, or 'auto' (for using detected
1133                         settings on that particular port), or 'nofifo'
1134                         (to avoid using a FIFO even if it is detected).
1135                         Parallel ports are assigned in the order they
1136                         are specified on the command line, starting
1137                         with parport0.
1138
1139         parport_init_mode=      [HW,PPT]
1140                         Configure VIA parallel port to operate in
1141                         a specific mode. This is necessary on Pegasos
1142                         computer where firmware has no options for setting
1143                         up parallel port mode and sets it to spp.
1144                         Currently this function knows 686a and 8231 chips.
1145                         Format: [spp|ps2|epp|ecp|ecpepp]
1146
1147         pas2=           [HW,OSS] Format:
1148                         <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1149
1150         pas16=          [HW,SCSI]
1151                         See header of drivers/scsi/pas16.c.
1152
1153         pause_on_oops=
1154                         Halt all CPUs after the first oops has been printed for
1155                         the specified number of seconds.  This is to be used if
1156                         your oopses keep scrolling off the screen.
1157
1158         pcbit=          [HW,ISDN]
1159
1160         pcd.            [PARIDE]
1161                         See header of drivers/block/paride/pcd.c.
1162                         See also Documentation/paride.txt.
1163
1164         pci=option[,option...]  [PCI] various PCI subsystem options:
1165                 off             [IA-32] don't probe for the PCI bus
1166                 bios            [IA-32] force use of PCI BIOS, don't access
1167                                 the hardware directly. Use this if your machine
1168                                 has a non-standard PCI host bridge.
1169                 nobios          [IA-32] disallow use of PCI BIOS, only direct
1170                                 hardware access methods are allowed. Use this
1171                                 if you experience crashes upon bootup and you
1172                                 suspect they are caused by the BIOS.
1173                 conf1           [IA-32] Force use of PCI Configuration
1174                                 Mechanism 1.
1175                 conf2           [IA-32] Force use of PCI Configuration
1176                                 Mechanism 2.
1177                 nommconf        [IA-32,X86_64] Disable use of MMCONFIG for PCI
1178                                 Configuration
1179                 nomsi           [MSI] If the PCI_MSI kernel config parameter is
1180                                 enabled, this kernel boot option can be used to
1181                                 disable the use of MSI interrupts system-wide.
1182                 nosort          [IA-32] Don't sort PCI devices according to
1183                                 order given by the PCI BIOS. This sorting is
1184                                 done to get a device order compatible with
1185                                 older kernels.
1186                 biosirq         [IA-32] Use PCI BIOS calls to get the interrupt
1187                                 routing table. These calls are known to be buggy
1188                                 on several machines and they hang the machine
1189                                 when used, but on other computers it's the only
1190                                 way to get the interrupt routing table. Try
1191                                 this option if the kernel is unable to allocate
1192                                 IRQs or discover secondary PCI buses on your
1193                                 motherboard.
1194                 rom             [IA-32] Assign address space to expansion ROMs.
1195                                 Use with caution as certain devices share
1196                                 address decoders between ROMs and other
1197                                 resources.
1198                 irqmask=0xMMMM  [IA-32] Set a bit mask of IRQs allowed to be
1199                                 assigned automatically to PCI devices. You can
1200                                 make the kernel exclude IRQs of your ISA cards
1201                                 this way.
1202                 pirqaddr=0xAAAAA        [IA-32] Specify the physical address
1203                                 of the PIRQ table (normally generated
1204                                 by the BIOS) if it is outside the
1205                                 F0000h-100000h range.
1206                 lastbus=N       [IA-32] Scan all buses thru bus #N. Can be
1207                                 useful if the kernel is unable to find your
1208                                 secondary buses and you want to tell it
1209                                 explicitly which ones they are.
1210                 assign-busses   [IA-32] Always assign all PCI bus
1211                                 numbers ourselves, overriding
1212                                 whatever the firmware may have done.
1213                 usepirqmask     [IA-32] Honor the possible IRQ mask stored
1214                                 in the BIOS $PIR table. This is needed on
1215                                 some systems with broken BIOSes, notably
1216                                 some HP Pavilion N5400 and Omnibook XE3
1217                                 notebooks. This will have no effect if ACPI
1218                                 IRQ routing is enabled.
1219                 noacpi          [IA-32] Do not use ACPI for IRQ routing
1220                                 or for PCI scanning.
1221                 routeirq        Do IRQ routing for all PCI devices.
1222                                 This is normally done in pci_enable_device(),
1223                                 so this option is a temporary workaround
1224                                 for broken drivers that don't call it.
1225                 firmware        [ARM] Do not re-enumerate the bus but instead
1226                                 just use the configuration from the
1227                                 bootloader. This is currently used on
1228                                 IXP2000 systems where the bus has to be
1229                                 configured a certain way for adjunct CPUs.
1230
1231         pcmv=           [HW,PCMCIA] BadgePAD 4
1232
1233         pd.             [PARIDE]
1234                         See Documentation/paride.txt.
1235
1236         pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1237                         boot time.
1238                         Format: { 0 | 1 }
1239                         See arch/parisc/kernel/pdc_chassis.c
1240
1241         pf.             [PARIDE]
1242                         See Documentation/paride.txt.
1243
1244         pg.             [PARIDE]
1245                         See Documentation/paride.txt.
1246
1247         pirq=           [SMP,APIC] Manual mp-table setup
1248                         See Documentation/i386/IO-APIC.txt.
1249
1250         plip=           [PPT,NET] Parallel port network link
1251                         Format: { parport<nr> | timid | 0 }
1252                         See also Documentation/parport.txt.
1253
1254         pnpacpi=        [ACPI]
1255                         { off }
1256
1257         pnpbios=        [ISAPNP]
1258                         { on | off | curr | res | no-curr | no-res }
1259
1260         pnp_reserve_irq=
1261                         [ISAPNP] Exclude IRQs for the autoconfiguration
1262
1263         pnp_reserve_dma=
1264                         [ISAPNP] Exclude DMAs for the autoconfiguration
1265
1266         pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1267                         Ranges are in pairs (I/O port base and size).
1268
1269         pnp_reserve_mem=
1270                         [ISAPNP] Exclude memory regions for the
1271                         autoconfiguration.
1272                         Ranges are in pairs (memory base and size).
1273
1274         profile=        [KNL] Enable kernel profiling via /proc/profile
1275                         Format: [schedule,]<number>
1276                         Param: "schedule" - profile schedule points.
1277                         Param: <number> - step/bucket size as a power of 2 for
1278                                 statistical time based profiling.
1279
1280         processor.max_cstate=   [HW,ACPI]
1281                         Limit processor to maximum C-state
1282                         max_cstate=9 overrides any DMI blacklist limit.
1283
1284         processor.nocst [HW,ACPI]
1285                         Ignore the _CST method to determine C-states,
1286                         instead using the legacy FADT method
1287
1288         prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1289                         before loading.
1290                         See Documentation/ramdisk.txt.
1291
1292         psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
1293                         probe for; one of (bare|imps|exps|lifebook|any).
1294         psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
1295                         per second.
1296         psmouse.resetafter=     [HW,MOUSE]
1297                         Try to reset the device after so many bad packets
1298                         (0 = never).
1299         psmouse.resolution=
1300                         [HW,MOUSE] Set desired mouse resolution, in dpi.
1301         psmouse.smartscroll=
1302                         [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1303                         0 = disabled, 1 = enabled (default).
1304
1305         pss=            [HW,OSS] Personal Sound System (ECHO ESC614)
1306                         Format:
1307                         <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1308
1309         pt.             [PARIDE]
1310                         See Documentation/paride.txt.
1311
1312         quiet=          [KNL] Disable log messages
1313
1314         r128=           [HW,DRM]
1315
1316         raid=           [HW,RAID]
1317                         See Documentation/md.txt.
1318
1319         ramdisk=        [RAM] Sizes of RAM disks in kilobytes [deprecated]
1320                         See Documentation/ramdisk.txt.
1321
1322         ramdisk_blocksize=      [RAM]
1323                         See Documentation/ramdisk.txt.
1324
1325         ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
1326                         New name for the ramdisk parameter.
1327                         See Documentation/ramdisk.txt.
1328
1329         rcu.blimit=     [KNL,BOOT] Set maximum number of finished
1330                         RCU callbacks to process in one batch.
1331
1332         rcu.qhimark=    [KNL,BOOT] Set threshold of queued
1333                         RCU callbacks over which batch limiting is disabled.
1334
1335         rcu.qlowmark=   [KNL,BOOT] Set threshold of queued
1336                         RCU callbacks below which batch limiting is re-enabled.
1337
1338         rcu.rsinterval= [KNL,BOOT,SMP] Set the number of additional
1339                         RCU callbacks to queued before forcing reschedule
1340                         on all cpus.
1341
1342         rdinit=         [KNL]
1343                         Format: <full_path>
1344                         Run specified binary instead of /init from the ramdisk,
1345                         used for early userspace startup. See initrd.
1346
1347         reboot=         [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1348                         Format: <reboot_mode>[,<reboot_mode2>[,...]]
1349                         See arch/*/kernel/reboot.c.
1350
1351         reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
1352
1353         resume=         [SWSUSP]
1354                         Specify the partition device for software suspend
1355
1356         rhash_entries=  [KNL,NET]
1357                         Set number of hash buckets for route cache
1358
1359         riscom8=        [HW,SERIAL]
1360                         Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1361
1362         ro              [KNL] Mount root device read-only on boot
1363
1364         root=           [KNL] Root filesystem
1365
1366         rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
1367                         mount the root filesystem
1368
1369         rootflags=      [KNL] Set root filesystem mount option string
1370
1371         rootfstype=     [KNL] Set root filesystem type
1372
1373         rw              [KNL] Mount root device read-write on boot
1374
1375         S               [KNL] Run init in single mode
1376
1377         sa1100ir        [NET]
1378                         See drivers/net/irda/sa1100_ir.c.
1379
1380         sb=             [HW,OSS]
1381                         Format: <io>,<irq>,<dma>,<dma2>
1382
1383         sbni=           [NET] Granch SBNI12 leased line adapter
1384
1385         sbpcd=          [HW,CD] Soundblaster CD adapter
1386                         Format: <io>,<type>
1387                         See a comment before function sbpcd_setup() in
1388                         drivers/cdrom/sbpcd.c.
1389
1390         sc1200wdt=      [HW,WDT] SC1200 WDT (watchdog) driver
1391                         Format: <io>[,<timeout>[,<isapnp>]]
1392
1393         scsi_debug_*=   [SCSI]
1394                         See drivers/scsi/scsi_debug.c.
1395
1396         scsi_default_dev_flags=
1397                         [SCSI] SCSI default device flags
1398                         Format: <integer>
1399
1400         scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1401                         Format: <vendor>:<model>:<flags>
1402                         (flags are integer value)
1403
1404         scsi_logging=   [SCSI]
1405
1406         selinux         [SELINUX] Disable or enable SELinux at boot time.
1407                         Format: { "0" | "1" }
1408                         See security/selinux/Kconfig help text.
1409                         0 -- disable.
1410                         1 -- enable.
1411                         Default value is set via kernel config option.
1412                         If enabled at boot time, /selinux/disable can be used
1413                         later to disable prior to initial policy load.
1414
1415         selinux_compat_net =
1416                         [SELINUX] Set initial selinux_compat_net flag value.
1417                         Format: { "0" | "1" }
1418                         0 -- use new secmark-based packet controls
1419                         1 -- use legacy packet controls
1420                         Default value is 0 (preferred).
1421                         Value can be changed at runtime via
1422                         /selinux/compat_net.
1423
1424         serialnumber    [BUGS=IA-32]
1425
1426         sg_def_reserved_size=   [SCSI]
1427
1428         sgalaxy=        [HW,OSS]
1429                         Format: <io>,<irq>,<dma>,<dma2>,<sgbase>
1430
1431         shapers=        [NET]
1432                         Maximal number of shapers.
1433
1434         sim710=         [SCSI,HW]
1435                         See header of drivers/scsi/sim710.c.
1436
1437         simeth=         [IA-64]
1438         simscsi=
1439
1440         sjcd=           [HW,CD]
1441                         Format: <io>,<irq>,<dma>
1442                         See header of drivers/cdrom/sjcd.c.
1443
1444         slram=          [HW,MTD]
1445
1446         smart2=         [HW]
1447                         Format: <io1>[,<io2>[,...,<io8>]]
1448
1449         snd-ad1816a=    [HW,ALSA]
1450
1451         snd-ad1848=     [HW,ALSA]
1452
1453         snd-ali5451=    [HW,ALSA]
1454
1455         snd-als100=     [HW,ALSA]
1456
1457         snd-als4000=    [HW,ALSA]
1458
1459         snd-azt2320=    [HW,ALSA]
1460
1461         snd-cmi8330=    [HW,ALSA]
1462
1463         snd-cmipci=     [HW,ALSA]
1464
1465         snd-cs4231=     [HW,ALSA]
1466
1467         snd-cs4232=     [HW,ALSA]
1468
1469         snd-cs4236=     [HW,ALSA]
1470
1471         snd-cs4281=     [HW,ALSA]
1472
1473         snd-cs46xx=     [HW,ALSA]
1474
1475         snd-dt019x=     [HW,ALSA]
1476
1477         snd-dummy=      [HW,ALSA]
1478
1479         snd-emu10k1=    [HW,ALSA]
1480
1481         snd-ens1370=    [HW,ALSA]
1482
1483         snd-ens1371=    [HW,ALSA]
1484
1485         snd-es968=      [HW,ALSA]
1486
1487         snd-es1688=     [HW,ALSA]
1488
1489         snd-es18xx=     [HW,ALSA]
1490
1491         snd-es1938=     [HW,ALSA]
1492
1493         snd-es1968=     [HW,ALSA]
1494
1495         snd-fm801=      [HW,ALSA]
1496
1497         snd-gusclassic= [HW,ALSA]
1498
1499         snd-gusextreme= [HW,ALSA]
1500
1501         snd-gusmax=     [HW,ALSA]
1502
1503         snd-hdsp=       [HW,ALSA]
1504
1505         snd-ice1712=    [HW,ALSA]
1506
1507         snd-intel8x0=   [HW,ALSA]
1508
1509         snd-interwave=  [HW,ALSA]
1510
1511         snd-interwave-stb=
1512                         [HW,ALSA]
1513
1514         snd-korg1212=   [HW,ALSA]
1515
1516         snd-maestro3=   [HW,ALSA]
1517
1518         snd-mpu401=     [HW,ALSA]
1519
1520         snd-mtpav=      [HW,ALSA]
1521
1522         snd-nm256=      [HW,ALSA]
1523
1524         snd-opl3sa2=    [HW,ALSA]
1525
1526         snd-opti92x-ad1848=
1527                         [HW,ALSA]
1528
1529         snd-opti92x-cs4231=
1530                         [HW,ALSA]
1531
1532         snd-opti93x=    [HW,ALSA]
1533
1534         snd-pmac=       [HW,ALSA]
1535
1536         snd-rme32=      [HW,ALSA]
1537
1538         snd-rme96=      [HW,ALSA]
1539
1540         snd-rme9652=    [HW,ALSA]
1541
1542         snd-sb8=        [HW,ALSA]
1543
1544         snd-sb16=       [HW,ALSA]
1545
1546         snd-sbawe=      [HW,ALSA]
1547
1548         snd-serial=     [HW,ALSA]
1549
1550         snd-sgalaxy=    [HW,ALSA]
1551
1552         snd-sonicvibes= [HW,ALSA]
1553
1554         snd-sun-amd7930=
1555                         [HW,ALSA]
1556
1557         snd-sun-cs4231= [HW,ALSA]
1558
1559         snd-trident=    [HW,ALSA]
1560
1561         snd-usb-audio=  [HW,ALSA,USB]
1562
1563         snd-via82xx=    [HW,ALSA]
1564
1565         snd-virmidi=    [HW,ALSA]
1566
1567         snd-wavefront=  [HW,ALSA]
1568
1569         snd-ymfpci=     [HW,ALSA]
1570
1571         sonicvibes=     [HW,OSS]
1572                         Format: <reverb>
1573
1574         sonycd535=      [HW,CD]
1575                         Format: <io>[,<irq>]
1576
1577         sonypi.*=       [HW] Sony Programmable I/O Control Device driver
1578                         See Documentation/sonypi.txt
1579
1580         specialix=      [HW,SERIAL] Specialix multi-serial port adapter
1581                         See Documentation/specialix.txt.
1582
1583         spia_io_base=   [HW,MTD]
1584         spia_fio_base=
1585         spia_pedr=
1586         spia_peddr=
1587
1588         sscape=         [HW,OSS]
1589                         Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1590
1591         st=             [HW,SCSI] SCSI tape parameters (buffers, etc.)
1592                         See Documentation/scsi/st.txt.
1593
1594         st0x=           [HW,SCSI]
1595                         See header of drivers/scsi/seagate.c.
1596
1597         sti=            [PARISC,HW]
1598                         Format: <num>
1599                         Set the STI (builtin display/keyboard on the HP-PARISC
1600                         machines) console (graphic card) which should be used
1601                         as the initial boot-console.
1602                         See also comment in drivers/video/console/sticore.c.
1603
1604         sti_font=       [HW]
1605                         See comment in drivers/video/console/sticore.c.
1606
1607         stifb=          [HW]
1608                         Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1609
1610         swiotlb=        [IA-64] Number of I/O TLB slabs
1611
1612         switches=       [HW,M68k]
1613
1614         sym53c416=      [HW,SCSI]
1615                         See header of drivers/scsi/sym53c416.c.
1616
1617         t128=           [HW,SCSI]
1618                         See header of drivers/scsi/t128.c.
1619
1620         tdfx=           [HW,DRM]
1621
1622         thash_entries=  [KNL,NET]
1623                         Set number of hash buckets for TCP connection
1624
1625         time            Show timing data prefixed to each printk message line
1626
1627         clocksource=    [GENERIC_TIME] Override the default clocksource
1628                         Override the default clocksource and use the clocksource
1629                         with the name specified.
1630
1631         tipar.timeout=  [HW,PPT]
1632                         Set communications timeout in tenths of a second
1633                         (default 15).
1634
1635         tipar.delay=    [HW,PPT]
1636                         Set inter-bit delay in microseconds (default 10).
1637
1638         tmc8xx=         [HW,SCSI]
1639                         See header of drivers/scsi/seagate.c.
1640
1641         tmscsim=        [HW,SCSI]
1642                         See comment before function dc390_setup() in
1643                         drivers/scsi/tmscsim.c.
1644
1645         tp720=          [HW,PS2]
1646
1647         trix=           [HW,OSS] MediaTrix AudioTrix Pro
1648                         Format:
1649                         <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1650
1651         tsdev.xres=     [TS] Horizontal screen resolution.
1652         tsdev.yres=     [TS] Vertical screen resolution.
1653
1654         turbografx.map[2|3]=    [HW,JOY]
1655                         TurboGraFX parallel port interface
1656                         Format:
1657                         <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1658                         See also Documentation/input/joystick-parport.txt
1659
1660         u14-34f=        [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1661                         See header of drivers/scsi/u14-34f.c.
1662
1663         uart401=        [HW,OSS]
1664                         Format: <io>,<irq>
1665
1666         uart6850=       [HW,OSS]
1667                         Format: <io>,<irq>
1668
1669         usbhid.mousepoll=
1670                         [USBHID] The interval which mice are to be polled at.
1671
1672         video=          [FB] Frame buffer configuration
1673                         See Documentation/fb/modedb.txt.
1674
1675         vga=            [BOOT,IA-32] Select a particular video mode
1676                         See Documentation/i386/boot.txt and
1677                         Documentation/svga.txt.
1678                         Use vga=ask for menu.
1679                         This is actually a boot loader parameter; the value is
1680                         passed to the kernel using a special protocol.
1681
1682         vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1683                         size of <nn>. This can be used to increase the
1684                         minimum size (128MB on x86). It can also be used to
1685                         decrease the size and leave more room for directly
1686                         mapped kernel RAM.
1687
1688         vmhalt=         [KNL,S390]
1689
1690         vmpoff=         [KNL,S390]
1691
1692         waveartist=     [HW,OSS]
1693                         Format: <io>,<irq>,<dma>,<dma2>
1694
1695         wd33c93=        [HW,SCSI]
1696                         See header of drivers/scsi/wd33c93.c.
1697
1698         wd7000=         [HW,SCSI]
1699                         See header of drivers/scsi/wd7000.c.
1700
1701         wdt=            [WDT] Watchdog
1702                         See Documentation/watchdog/watchdog.txt.
1703
1704         xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1705         xd_geo=         See header of drivers/block/xd.c.
1706
1707         xirc2ps_cs=     [NET,PCMCIA]
1708                         Format:
1709                         <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1710
1711         norandmaps      Don't use address space randomization
1712                         Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1713
1714
1715 ______________________________________________________________________
1716
1717 TODO:
1718
1719         Add documentation for ALSA options.
1720         Add more DRM drivers.