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
 168         acpi_dbg_layer= [HW,ACPI]
 169                         Format: <int>
 170                         Each bit of the <int> indicates an ACPI debug layer,
 171                         1: enable, 0: disable. It is useful for boot time
 172                         debugging. After system has booted up, it can be set
 173                         via /proc/acpi/debug_layer.
 174
 175         acpi_dbg_level= [HW,ACPI]
 176                         Format: <int>
 177                         Each bit of the <int> indicates an ACPI debug level,
 178                         1: enable, 0: disable. It is useful for boot time
 179                         debugging. After system has booted up, it can be set
 180                         via /proc/acpi/debug_level.
 181
 182         acpi_fake_ecdt  [HW,ACPI] Workaround failure due to BIOS lacking ECDT
 183
 184         acpi_generic_hotkey [HW,ACPI]
 185                         Allow consolidated generic hotkey driver to
 186                         override platform specific driver.
 187                         See also Documentation/acpi-hotkey.txt.
 188
 189         acpi_pm_good    [IA-32,X86-64]
 190                         Override the pmtimer bug detection: force the kernel
 191                         to assume that this machine's pmtimer latches its value
 192                         and always returns good values.
 193
 194         enable_timer_pin_1 [i386,x86-64]
 195                         Enable PIN 1 of APIC timer
 196                         Can be useful to work around chipset bugs
 197                         (in particular on some ATI chipsets).
 198                         The kernel tries to set a reasonable default.
 199
 200         disable_timer_pin_1 [i386,x86-64]
 201                         Disable PIN 1 of APIC timer
 202                         Can be useful to work around chipset bugs.
 203
 204         ad1816=         [HW,OSS]
 205                         Format: <io>,<irq>,<dma>,<dma2>
 206                         See also Documentation/sound/oss/AD1816.
 207
 208         ad1848=         [HW,OSS]
 209                         Format: <io>,<irq>,<dma>,<dma2>,<type>
 210
 211         adlib=          [HW,OSS]
 212                         Format: <io>
 213
 214         advansys=       [HW,SCSI]
 215                         See header of drivers/scsi/advansys.c.
 216
 217         advwdt=         [HW,WDT] Advantech WDT
 218                         Format: <iostart>,<iostop>
 219
 220         aedsp16=        [HW,OSS] Audio Excel DSP 16
 221                         Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
 222                         See also header of sound/oss/aedsp16.c.
 223
 224         aha152x=        [HW,SCSI]
 225                         See Documentation/scsi/aha152x.txt.
 226
 227         aha1542=        [HW,SCSI]
 228                         Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
 229
 230         aic7xxx=        [HW,SCSI]
 231                         See Documentation/scsi/aic7xxx.txt.
 232
 233         aic79xx=        [HW,SCSI]
 234                         See Documentation/scsi/aic79xx.txt.
 235
 236         amijoy.map=     [HW,JOY] Amiga joystick support
 237                         Map of devices attached to JOY0DAT and JOY1DAT
 238                         Format: <a>,<b>
 239                         See also Documentation/kernel/input/joystick.txt
 240
 241         analog.map=     [HW,JOY] Analog joystick and gamepad support
 242                         Specifies type or capabilities of an analog joystick
 243                         connected to one of 16 gameports
 244                         Format: <type1>,<type2>,..<type16>
 245
 246         apc=            [HW,SPARC]
 247                         Power management functions (SPARCstation-4/5 + deriv.)
 248                         Format: noidle
 249                         Disable APC CPU standby support. SPARCstation-Fox does
 250                         not play well with APC CPU idle - disable it if you have
 251                         APC and your system crashes randomly.
 252
 253         apic=           [APIC,i386] Change the output verbosity whilst booting
 254                         Format: { quiet (default) | verbose | debug }
 255                         Change the amount of debugging information output
 256                         when initialising the APIC and IO-APIC components.
 257
 258         apm=            [APM] Advanced Power Management
 259                         See header of arch/i386/kernel/apm.c.
 260
 261         applicom=       [HW]
 262                         Format: <mem>,<irq>
 263
 264         arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 265                         Format: <io>,<irq>,<nodeID>
 266
 267         ataflop=        [HW,M68k]
 268
 269         atarimouse=     [HW,MOUSE] Atari Mouse
 270
 271         atascsi=        [HW,SCSI] Atari SCSI
 272
 273         atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 274                         EzKey and similar keyboards
 275
 276         atkbd.reset=    [HW] Reset keyboard during initialization
 277
 278         atkbd.set=      [HW] Select keyboard code set
 279                         Format: <int> (2 = AT (default), 3 = PS/2)
 280
 281         atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 282                         keyboards
 283
 284         atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 285                         Format: <bool> (0 = real, 1 = synthetic (default))
 286
 287         atkbd.softrepeat= [HW]
 288                         Use software keyboard repeat
 289
 290         autotest        [IA64]
 291
 292         aztcd=          [HW,CD] Aztech CD268 CDROM driver
 293                         Format: <io>,0x79 (?)
 294
 295         baycom_epp=     [HW,AX25]
 296                         Format: <io>,<mode>
 297
 298         baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 299                         Format: <io>,<mode>
 300                         See header of drivers/net/hamradio/baycom_par.c.
 301
 302         baycom_ser_fdx= [HW,AX25]
 303                         BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 304                         Format: <io>,<irq>,<mode>[,<baud>]
 305                         See header of drivers/net/hamradio/baycom_ser_fdx.c.
 306
 307         baycom_ser_hdx= [HW,AX25]
 308                         BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 309                         Format: <io>,<irq>,<mode>
 310                         See header of drivers/net/hamradio/baycom_ser_hdx.c.
 311
 312         blkmtd_device=  [HW,MTD]
 313         blkmtd_erasesz=
 314         blkmtd_ro=
 315         blkmtd_bs=
 316         blkmtd_count=
 317
 318         bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 319         bttv.radio=     Most important insmod options are available as
 320                         kernel args too.
 321         bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 322         bttv.tuner=     and Documentation/video4linux/bttv/CARDLIST
 323
 324         BusLogic=       [HW,SCSI]
 325                         See drivers/scsi/BusLogic.c, comment before function
 326                         BusLogic_ParseDriverOptions().
 327
 328         c101=           [NET] Moxa C101 synchronous serial card
 329
 330         cachesize=      [BUGS=IA-32] Override level 2 CPU cache size detection.
 331                         Sometimes CPU hardware bugs make them report the cache
 332                         size incorrectly. The kernel will attempt work arounds
 333                         to fix known problems, but for some CPUs it is not
 334                         possible to determine what the correct size should be.
 335                         This option provides an override for these situations.
 336
 337         cdu31a=         [HW,CD]
 338                         Format: <io>,<irq>[,PAS]
 339                         See header of drivers/cdrom/cdu31a.c.
 340
 341         chandev=        [HW,NET] Generic channel device initialisation
 342
 343         checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 344                         Format: { "0" | "1" }
 345                         See security/selinux/Kconfig help text.
 346                         0 -- check protection applied by kernel (includes
 347                                 any implied execute protection).
 348                         1 -- check protection requested by application.
 349                         Default value is set via a kernel config option.
 350                         Value can be changed at runtime via
 351                                 /selinux/checkreqprot.
 352
 353         clock=          [BUGS=IA-32, HW] gettimeofday clocksource override.
 354                         [Deprecated]
 355                         Forces specified clocksource (if available) to be used
 356                         when calculating gettimeofday(). If specified
 357                         clocksource is not available, it defaults to PIT.
 358                         Format: { pit | tsc | cyclone | pmtmr }
 359
 360         disable_8254_timer
 361         enable_8254_timer
 362                         [IA32/X86_64] Disable/Enable interrupt 0 timer routing
 363                         over the 8254 in addition to over the IO-APIC. The
 364                         kernel tries to set a sensible default.
 365
 366         hpet=           [IA-32,HPET] option to disable HPET and use PIT.
 367                         Format: disable
 368
 369         cm206=          [HW,CD]
 370                         Format: { auto | [<io>,][<irq>] }
 371
 372         com20020=       [HW,NET] ARCnet - COM20020 chipset
 373                         Format:
 374                         <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 375
 376         com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 377                         Format: <io>[,<irq>]
 378
 379         com90xx=        [HW,NET]
 380                         ARCnet - COM90xx chipset (memory-mapped buffers)
 381                         Format: <io>[,<irq>[,<memstart>]]
 382
 383         condev=         [HW,S390] console device
 384         conmode=
 385
 386         console=        [KNL] Output console device and options.
 387
 388                 tty<n>  Use the virtual console device <n>.
 389
 390                 ttyS<n>[,options]
 391                 ttyUSB0[,options]
 392                         Use the specified serial port.  The options are of
 393                         the form "bbbbpnf", where "bbbb" is the baud rate,
 394                         "p" is parity ("n", "o", or "e"), "n" is number of
 395                         bits, and "f" is flow control ("r" for RTS or
 396                         omit it).  Default is "9600n8".
 397
 398                         See Documentation/serial-console.txt for more
 399                         information.  See
 400                         Documentation/networking/netconsole.txt for an
 401                         alternative.
 402
 403                 uart,io,<addr>[,options]
 404                 uart,mmio,<addr>[,options]
 405                         Start an early, polled-mode console on the 8250/16550
 406                         UART at the specified I/O port or MMIO address,
 407                         switching to the matching ttyS device later.  The
 408                         options are the same as for ttyS, above.
 409
 410         cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 411                         Format:
 412                         <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 413
 414         cpia_pp=        [HW,PPT]
 415                         Format: { parport<nr> | auto | none }
 416
 417         crashkernel=nn[KMG]@ss[KMG]
 418                         [KNL] Reserve a chunk of physical memory to
 419                         hold a kernel to switch to with kexec on panic.
 420
 421         cs4232=         [HW,OSS]
 422                         Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
 423
 424         cs89x0_dma=     [HW,NET]
 425                         Format: <dma>
 426
 427         cs89x0_media=   [HW,NET]
 428                         Format: { rj45 | aui | bnc }
 429
 430         cyclades=       [HW,SERIAL] Cyclades multi-serial port adapter.
 431
 432         dasd=           [HW,NET]
 433                         See header of drivers/s390/block/dasd_devmap.c.
 434
 435         db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 436                         (one device per port)
 437                         Format: <port#>,<type>
 438                         See also Documentation/input/joystick-parport.txt
 439
 440         debug           [KNL] Enable kernel debugging (events log level).
 441
 442         debug_locks_verbose=
 443                         [KNL] verbose self-tests
 444                         Format=<0|1>
 445                         Print debugging info while doing the locking API
 446                         self-tests.
 447                         We default to 0 (no extra messages), setting it to
 448                         1 will print _a lot_ more information - normally
 449                         only useful to kernel developers.
 450
 451         decnet=         [HW,NET]
 452                         Format: <area>[,<node>]
 453                         See also Documentation/networking/decnet.txt.
 454
 455         dhash_entries=  [KNL]
 456                         Set number of hash buckets for dentry cache.
 457
 458         digi=           [HW,SERIAL]
 459                         IO parameters + enable/disable command.
 460
 461         digiepca=       [HW,SERIAL]
 462                         See drivers/char/README.epca and
 463                         Documentation/digiepca.txt.
 464
 465         dmascc=         [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
 466                         support available.
 467                         Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
 468
 469         dmasound=       [HW,OSS] Sound subsystem buffers
 470
 471         dscc4.setup=    [NET]
 472
 473         dtc3181e=       [HW,SCSI]
 474
 475         earlyprintk=    [IA-32,X86-64]
 476                         earlyprintk=vga
 477                         earlyprintk=serial[,ttySn[,baudrate]]
 478
 479                         Append ",keep" to not disable it when the real console
 480                         takes over.
 481
 482                         Only vga or serial at a time, not both.
 483
 484                         Currently only ttyS0 and ttyS1 are supported.
 485
 486                         Interaction with the standard serial driver is not
 487                         very good.
 488
 489                         The VGA output is eventually overwritten by the real
 490                         console.
 491
 492         eata=           [HW,SCSI]
 493
 494         ec_intr=        [HW,ACPI] ACPI Embedded Controller interrupt mode
 495                         Format: <int>
 496                         0: polling mode
 497                         non-0: interrupt mode (default)
 498
 499         eda=            [HW,PS2]
 500
 501         edb=            [HW,PS2]
 502
 503         edd=            [EDD]
 504                         Format: {"of[f]" | "sk[ipmbr]"}
 505                         See comment in arch/i386/boot/edd.S
 506
 507         eicon=          [HW,ISDN]
 508                         Format: <id>,<membase>,<irq>
 509
 510         eisa_irq_edge=  [PARISC,HW]
 511                         See header of drivers/parisc/eisa.c.
 512
 513         elanfreq=       [IA-32]
 514                         See comment before function elanfreq_setup() in
 515                         arch/i386/kernel/cpu/cpufreq/elanfreq.c.
 516
 517         elevator=       [IOSCHED]
 518                         Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
 519                         See Documentation/block/as-iosched.txt and
 520                         Documentation/block/deadline-iosched.txt for details.
 521
 522         elfcorehdr=     [IA-32, X86_64]
 523                         Specifies physical address of start of kernel core
 524                         image elf header. Generally kexec loader will
 525                         pass this option to capture kernel.
 526                         See Documentation/kdump/kdump.txt for details.
 527
 528         enforcing       [SELINUX] Set initial enforcing status.
 529                         Format: {"0" | "1"}
 530                         See security/selinux/Kconfig help text.
 531                         0 -- permissive (log only, no denials).
 532                         1 -- enforcing (deny and log).
 533                         Default value is 0.
 534                         Value can be changed at runtime via /selinux/enforce.
 535
 536         es1371=         [HW,OSS]
 537                         Format: <spdif>,[<nomix>,[<amplifier>]]
 538                         See also header of sound/oss/es1371.c.
 539
 540         ether=          [HW,NET] Ethernet cards parameters
 541                         This option is obsoleted by the "netdev=" option, which
 542                         has equivalent usage. See its documentation for details.
 543
 544         eurwdt=         [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
 545                         Format: <io>[,<irq>]
 546
 547         fd_mcs=         [HW,SCSI]
 548                         See header of drivers/scsi/fd_mcs.c.
 549
 550         fdomain=        [HW,SCSI]
 551                         See header of drivers/scsi/fdomain.c.
 552
 553         floppy=         [HW]
 554                         See Documentation/floppy.txt.
 555
 556         ftape=          [HW] Floppy Tape subsystem debugging options.
 557                         See Documentation/ftape.txt.
 558
 559         gamecon.map[2|3]=
 560                         [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 561                         support via parallel port (up to 5 devices per port)
 562                         Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 563                         See also Documentation/input/joystick-parport.txt
 564
 565         gamma=          [HW,DRM]
 566
 567         gdth=           [HW,SCSI]
 568                         See header of drivers/scsi/gdth.c.
 569
 570         gpt             [EFI] Forces disk with valid GPT signature but
 571                         invalid Protective MBR to be treated as GPT.
 572
 573         gscd=           [HW,CD]
 574                         Format: <io>
 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 controller can only read data from
 605                              keyboard and cannot 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         ports=          [IP_VS_FTP] IPVS ftp helper module
 696                         Default is 21.
 697                         Up to 8 (IP_VS_APP_MAX_PORTS) ports
 698                         may be specified.
 699                         Format: <port>,<port>....
 700
 701         irqfixup        [HW]
 702                         When an interrupt is not handled search all handlers
 703                         for it. Intended to get systems with badly broken
 704                         firmware running.
 705
 706         irqpoll         [HW]
 707                         When an interrupt is not handled search all handlers
 708                         for it. Also check all handlers each timer
 709                         interrupt. Intended to get systems with badly broken
 710                         firmware running.
 711
 712         isapnp=         [ISAPNP]
 713                         Format: <RDP>,<reset>,<pci_scan>,<verbosity>
 714
 715         isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
 716                         Format: <cpu number>,...,<cpu number>
 717                         This option can be used to specify one or more CPUs
 718                         to isolate from the general SMP balancing and scheduling
 719                         algorithms. The only way to move a process onto or off
 720                         an "isolated" CPU is via the CPU affinity syscalls.
 721                         <cpu number> begins at 0 and the maximum value is
 722                         "number of CPUs in system - 1".
 723
 724                         This option is the preferred way to isolate CPUs. The
 725                         alternative -- manually setting the CPU mask of all
 726                         tasks in the system -- can cause problems and
 727                         suboptimal load balancer performance.
 728
 729         isp16=          [HW,CD]
 730                         Format: <io>,<irq>,<dma>,<setup>
 731
 732         iucv=           [HW,NET]
 733
 734         js=             [HW,JOY] Analog joystick
 735                         See Documentation/input/joystick.txt.
 736
 737         keepinitrd      [HW,ARM]
 738
 739         kstack=N        [IA-32,X86-64] Print N words from the kernel stack
 740                         in oops dumps.
 741
 742         l2cr=           [PPC]
 743
 744         lapic           [IA-32,APIC] Enable the local APIC even if BIOS
 745                         disabled it.
 746
 747         lasi=           [HW,SCSI] PARISC LASI driver for the 53c700 chip
 748                         Format: addr:<io>,irq:<irq>
 749
 750         llsc*=          [IA64] See function print_params() in
 751                         arch/ia64/sn/kernel/llsc4.c.
 752
 753         load_ramdisk=   [RAM] List of ramdisks to load from floppy
 754                         See Documentation/ramdisk.txt.
 755
 756         lockd.nlm_grace_period=P  [NFS] Assign grace period.
 757                         Format: <integer>
 758
 759         lockd.nlm_tcpport=N     [NFS] Assign TCP port.
 760                         Format: <integer>
 761
 762         lockd.nlm_timeout=T     [NFS] Assign timeout value.
 763                         Format: <integer>
 764
 765         lockd.nlm_udpport=M     [NFS] Assign UDP port.
 766                         Format: <integer>
 767
 768         logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
 769                         Format: <irq>
 770
 771         loglevel=       All Kernel Messages with a loglevel smaller than the
 772                         console loglevel will be printed to the console. It can
 773                         also be changed with klogd or other programs. The
 774                         loglevels are defined as follows:
 775
 776                         0 (KERN_EMERG)          system is unusable
 777                         1 (KERN_ALERT)          action must be taken immediately
 778                         2 (KERN_CRIT)           critical conditions
 779                         3 (KERN_ERR)            error conditions
 780                         4 (KERN_WARNING)        warning conditions
 781                         5 (KERN_NOTICE)         normal but significant condition
 782                         6 (KERN_INFO)           informational
 783                         7 (KERN_DEBUG)          debug-level messages
 784
 785         log_buf_len=n   Sets the size of the printk ring buffer, in bytes.
 786                         Format: { n | nk | nM }
 787                         n must be a power of two.  The default size
 788                         is set in the kernel config file.
 789
 790         lp=0            [LP]    Specify parallel ports to use, e.g,
 791         lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
 792         lp=reset                first parallel port). 'lp=0' disables the
 793         lp=auto                 printer driver. 'lp=reset' (which can be
 794                                 specified in addition to the ports) causes
 795                                 attached printers to be reset. Using
 796                                 lp=port1,port2,... specifies the parallel ports
 797                                 to associate lp devices with, starting with
 798                                 lp0. A port specification may be 'none' to skip
 799                                 that lp device, or a parport name such as
 800                                 'parport0'. Specifying 'lp=auto' instead of a
 801                                 port specification list means that device IDs
 802                                 from each port should be examined, to see if
 803                                 an IEEE 1284-compliant printer is attached; if
 804                                 so, the driver will manage that printer.
 805                                 See also header of drivers/char/lp.c.
 806
 807         lpj=n           [KNL]
 808                         Sets loops_per_jiffy to given constant, thus avoiding
 809                         time-consuming boot-time autodetection (up to 250 ms per
 810                         CPU). 0 enables autodetection (default). To determine
 811                         the correct value for your kernel, boot with normal
 812                         autodetection and see what value is printed. Note that
 813                         on SMP systems the preset will be applied to all CPUs,
 814                         which is likely to cause problems if your CPUs need
 815                         significantly divergent settings. An incorrect value
 816                         will cause delays in the kernel to be wrong, leading to
 817                         unpredictable I/O errors and other breakage. Although
 818                         unlikely, in the extreme case this might damage your
 819                         hardware.
 820
 821         ltpc=           [NET]
 822                         Format: <io>,<irq>,<dma>
 823
 824         mac5380=        [HW,SCSI] Format:
 825                         <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
 826
 827         mac53c9x=       [HW,SCSI] Format:
 828                         <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
 829
 830         machvec=        [IA64] Force the use of a particular machine-vector
 831                         (machvec) in a generic kernel.
 832                         Example: machvec=hpzx1_swiotlb
 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         nodelayacct     [KNL] Disable per-task delay accounting
1028
1029         nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1030
1031         noexec          [IA-64]
1032
1033         noexec          [IA-32,X86-64]
1034                         noexec=on: enable non-executable mappings (default)
1035                         noexec=off: disable nn-executable mappings
1036
1037         nofxsr          [BUGS=IA-32] Disables x86 floating point extended
1038                         register save and restore. The kernel will only save
1039                         legacy floating-point registers on task switch.
1040
1041         nohlt           [BUGS=ARM]
1042
1043         no-hlt          [BUGS=IA-32] Tells the kernel that the hlt
1044                         instruction doesn't work correctly and not to
1045                         use it.
1046
1047         nohalt          [IA-64] Tells the kernel not to use the power saving
1048                         function PAL_HALT_LIGHT when idle. This increases
1049                         power-consumption. On the positive side, it reduces
1050                         interrupt wake-up latency, which may improve performance
1051                         in certain environments such as networked servers or
1052                         real-time systems.
1053
1054         noirqdebug      [IA-32] Disables the code which attempts to detect and
1055                         disable unhandled interrupt sources.
1056
1057         noisapnp        [ISAPNP] Disables ISA PnP code.
1058
1059         noinitrd        [RAM] Tells the kernel not to load any configured
1060                         initial RAM disk.
1061
1062         nointroute      [IA-64]
1063
1064         nolapic         [IA-32,APIC] Do not enable or use the local APIC.
1065
1066         noltlbs         [PPC] Do not use large page/tlb entries for kernel
1067                         lowmem mapping on PPC40x.
1068
1069         nomca           [IA-64] Disable machine check abort handling
1070
1071         nomce           [IA-32] Machine Check Exception
1072
1073         noresidual      [PPC] Don't use residual data on PReP machines.
1074
1075         noresume        [SWSUSP] Disables resume and restores original swap
1076                         space.
1077
1078         no-scroll       [VGA] Disables scrollback.
1079                         This is required for the Braillex ib80-piezo Braille
1080                         reader made by F.H. Papenmeier (Germany).
1081
1082         nosbagart       [IA-64]
1083
1084         nosep           [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1085
1086         nosmp           [SMP] Tells an SMP kernel to act as a UP kernel.
1087
1088         nosync          [HW,M68K] Disables sync negotiation for all devices.
1089
1090         notsc           [BUGS=IA-32] Disable Time Stamp Counter
1091
1092         nousb           [USB] Disable the USB subsystem
1093
1094         nowb            [ARM]
1095
1096         nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1097
1098         opl3=           [HW,OSS]
1099                         Format: <io>
1100
1101         opl3sa2=        [HW,OSS] Format:
1102                         <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
1103
1104         oprofile.timer= [HW]
1105                         Use timer interrupt instead of performance counters
1106
1107         optcd=          [HW,CD]
1108                         Format: <io>
1109
1110         osst=           [HW,SCSI] SCSI Tape Driver
1111                         Format: <buffer_size>,<write_threshold>
1112                         See also Documentation/scsi/st.txt.
1113
1114         panic=          [KNL] Kernel behaviour on panic
1115                         Format: <timeout>
1116
1117         parkbd.port=    [HW] Parallel port number the keyboard adapter is
1118                         connected to, default is 0.
1119                         Format: <parport#>
1120         parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
1121                         0 for XT, 1 for AT (default is AT).
1122                         Format: <mode>
1123
1124         parport=        [HW,PPT] Specify parallel ports. 0 disables.
1125                         Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1126                         Use 'auto' to force the driver to use any
1127                         IRQ/DMA settings detected (the default is to
1128                         ignore detected IRQ/DMA settings because of
1129                         possible conflicts). You can specify the base
1130                         address, IRQ, and DMA settings; IRQ and DMA
1131                         should be numbers, or 'auto' (for using detected
1132                         settings on that particular port), or 'nofifo'
1133                         (to avoid using a FIFO even if it is detected).
1134                         Parallel ports are assigned in the order they
1135                         are specified on the command line, starting
1136                         with parport0.
1137
1138         parport_init_mode=      [HW,PPT]
1139                         Configure VIA parallel port to operate in
1140                         a specific mode. This is necessary on Pegasos
1141                         computer where firmware has no options for setting
1142                         up parallel port mode and sets it to spp.
1143                         Currently this function knows 686a and 8231 chips.
1144                         Format: [spp|ps2|epp|ecp|ecpepp]
1145
1146         pas2=           [HW,OSS] Format:
1147                         <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1148
1149         pas16=          [HW,SCSI]
1150                         See header of drivers/scsi/pas16.c.
1151
1152         pause_on_oops=
1153                         Halt all CPUs after the first oops has been printed for
1154                         the specified number of seconds.  This is to be used if
1155                         your oopses keep scrolling off the screen.
1156
1157         pcbit=          [HW,ISDN]
1158
1159         pcd.            [PARIDE]
1160                         See header of drivers/block/paride/pcd.c.
1161                         See also Documentation/paride.txt.
1162
1163         pci=option[,option...]  [PCI] various PCI subsystem options:
1164                 off             [IA-32] don't probe for the PCI bus
1165                 bios            [IA-32] force use of PCI BIOS, don't access
1166                                 the hardware directly. Use this if your machine
1167                                 has a non-standard PCI host bridge.
1168                 nobios          [IA-32] disallow use of PCI BIOS, only direct
1169                                 hardware access methods are allowed. Use this
1170                                 if you experience crashes upon bootup and you
1171                                 suspect they are caused by the BIOS.
1172                 conf1           [IA-32] Force use of PCI Configuration
1173                                 Mechanism 1.
1174                 conf2           [IA-32] Force use of PCI Configuration
1175                                 Mechanism 2.
1176                 nommconf        [IA-32,X86_64] Disable use of MMCONFIG for PCI
1177                                 Configuration
1178                 nomsi           [MSI] If the PCI_MSI kernel config parameter is
1179                                 enabled, this kernel boot option can be used to
1180                                 disable the use of MSI interrupts system-wide.
1181                 nosort          [IA-32] Don't sort PCI devices according to
1182                                 order given by the PCI BIOS. This sorting is
1183                                 done to get a device order compatible with
1184                                 older kernels.
1185                 biosirq         [IA-32] Use PCI BIOS calls to get the interrupt
1186                                 routing table. These calls are known to be buggy
1187                                 on several machines and they hang the machine
1188                                 when used, but on other computers it's the only
1189                                 way to get the interrupt routing table. Try
1190                                 this option if the kernel is unable to allocate
1191                                 IRQs or discover secondary PCI buses on your
1192                                 motherboard.
1193                 rom             [IA-32] Assign address space to expansion ROMs.
1194                                 Use with caution as certain devices share
1195                                 address decoders between ROMs and other
1196                                 resources.
1197                 irqmask=0xMMMM  [IA-32] Set a bit mask of IRQs allowed to be
1198                                 assigned automatically to PCI devices. You can
1199                                 make the kernel exclude IRQs of your ISA cards
1200                                 this way.
1201                 pirqaddr=0xAAAAA        [IA-32] Specify the physical address
1202                                 of the PIRQ table (normally generated
1203                                 by the BIOS) if it is outside the
1204                                 F0000h-100000h range.
1205                 lastbus=N       [IA-32] Scan all buses thru bus #N. Can be
1206                                 useful if the kernel is unable to find your
1207                                 secondary buses and you want to tell it
1208                                 explicitly which ones they are.
1209                 assign-busses   [IA-32] Always assign all PCI bus
1210                                 numbers ourselves, overriding
1211                                 whatever the firmware may have done.
1212                 usepirqmask     [IA-32] Honor the possible IRQ mask stored
1213                                 in the BIOS $PIR table. This is needed on
1214                                 some systems with broken BIOSes, notably
1215                                 some HP Pavilion N5400 and Omnibook XE3
1216                                 notebooks. This will have no effect if ACPI
1217                                 IRQ routing is enabled.
1218                 noacpi          [IA-32] Do not use ACPI for IRQ routing
1219                                 or for PCI scanning.
1220                 routeirq        Do IRQ routing for all PCI devices.
1221                                 This is normally done in pci_enable_device(),
1222                                 so this option is a temporary workaround
1223                                 for broken drivers that don't call it.
1224                 firmware        [ARM] Do not re-enumerate the bus but instead
1225                                 just use the configuration from the
1226                                 bootloader. This is currently used on
1227                                 IXP2000 systems where the bus has to be
1228                                 configured a certain way for adjunct CPUs.
1229                 noearly         [X86] Don't do any early type 1 scanning.
1230                                 This might help on some broken boards which
1231                                 machine check when some devices' config space
1232                                 is read. But various workarounds are disabled
1233                                 and some IOMMU drivers will not work.
1234                 bfsort          Sort PCI devices into breadth-first order.
1235                                 This sorting is done to get a device
1236                                 order compatible with older (<= 2.4) kernels.
1237                 nobfsort        Don't sort PCI devices into breadth-first order.
1238
1239         pcmv=           [HW,PCMCIA] BadgePAD 4
1240
1241         pd.             [PARIDE]
1242                         See Documentation/paride.txt.
1243
1244         pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1245                         boot time.
1246                         Format: { 0 | 1 }
1247                         See arch/parisc/kernel/pdc_chassis.c
1248
1249         pf.             [PARIDE]
1250                         See Documentation/paride.txt.
1251
1252         pg.             [PARIDE]
1253                         See Documentation/paride.txt.
1254
1255         pirq=           [SMP,APIC] Manual mp-table setup
1256                         See Documentation/i386/IO-APIC.txt.
1257
1258         plip=           [PPT,NET] Parallel port network link
1259                         Format: { parport<nr> | timid | 0 }
1260                         See also Documentation/parport.txt.
1261
1262         pnpacpi=        [ACPI]
1263                         { off }
1264
1265         pnpbios=        [ISAPNP]
1266                         { on | off | curr | res | no-curr | no-res }
1267
1268         pnp_reserve_irq=
1269                         [ISAPNP] Exclude IRQs for the autoconfiguration
1270
1271         pnp_reserve_dma=
1272                         [ISAPNP] Exclude DMAs for the autoconfiguration
1273
1274         pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1275                         Ranges are in pairs (I/O port base and size).
1276
1277         pnp_reserve_mem=
1278                         [ISAPNP] Exclude memory regions for the
1279                         autoconfiguration.
1280                         Ranges are in pairs (memory base and size).
1281
1282         profile=        [KNL] Enable kernel profiling via /proc/profile
1283                         Format: [schedule,]<number>
1284                         Param: "schedule" - profile schedule points.
1285                         Param: <number> - step/bucket size as a power of 2 for
1286                                 statistical time based profiling.
1287
1288         processor.max_cstate=   [HW,ACPI]
1289                         Limit processor to maximum C-state
1290                         max_cstate=9 overrides any DMI blacklist limit.
1291
1292         processor.nocst [HW,ACPI]
1293                         Ignore the _CST method to determine C-states,
1294                         instead using the legacy FADT method
1295
1296         prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1297                         before loading.
1298                         See Documentation/ramdisk.txt.
1299
1300         psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
1301                         probe for; one of (bare|imps|exps|lifebook|any).
1302         psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
1303                         per second.
1304         psmouse.resetafter=     [HW,MOUSE]
1305                         Try to reset the device after so many bad packets
1306                         (0 = never).
1307         psmouse.resolution=
1308                         [HW,MOUSE] Set desired mouse resolution, in dpi.
1309         psmouse.smartscroll=
1310                         [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1311                         0 = disabled, 1 = enabled (default).
1312
1313         pss=            [HW,OSS] Personal Sound System (ECHO ESC614)
1314                         Format:
1315                         <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1316
1317         pt.             [PARIDE]
1318                         See Documentation/paride.txt.
1319
1320         quiet           [KNL] Disable most log messages
1321
1322         r128=           [HW,DRM]
1323
1324         raid=           [HW,RAID]
1325                         See Documentation/md.txt.
1326
1327         ramdisk=        [RAM] Sizes of RAM disks in kilobytes [deprecated]
1328                         See Documentation/ramdisk.txt.
1329
1330         ramdisk_blocksize=      [RAM]
1331                         See Documentation/ramdisk.txt.
1332
1333         ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
1334                         New name for the ramdisk parameter.
1335                         See Documentation/ramdisk.txt.
1336
1337         rcu.blimit=     [KNL,BOOT] Set maximum number of finished
1338                         RCU callbacks to process in one batch.
1339
1340         rcu.qhimark=    [KNL,BOOT] Set threshold of queued
1341                         RCU callbacks over which batch limiting is disabled.
1342
1343         rcu.qlowmark=   [KNL,BOOT] Set threshold of queued
1344                         RCU callbacks below which batch limiting is re-enabled.
1345
1346         rdinit=         [KNL]
1347                         Format: <full_path>
1348                         Run specified binary instead of /init from the ramdisk,
1349                         used for early userspace startup. See initrd.
1350
1351         reboot=         [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1352                         Format: <reboot_mode>[,<reboot_mode2>[,...]]
1353                         See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1354
1355         reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
1356
1357         reservetop=     [IA-32]
1358                         Format: nn[KMG]
1359                         Reserves a hole at the top of the kernel virtual
1360                         address space.
1361
1362         reset_devices   [KNL] Force drivers to reset the underlying device
1363                         during initialization.
1364
1365         resume=         [SWSUSP]
1366                         Specify the partition device for software suspend
1367
1368         rhash_entries=  [KNL,NET]
1369                         Set number of hash buckets for route cache
1370
1371         riscom8=        [HW,SERIAL]
1372                         Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1373
1374         ro              [KNL] Mount root device read-only on boot
1375
1376         root=           [KNL] Root filesystem
1377
1378         rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
1379                         mount the root filesystem
1380
1381         rootflags=      [KNL] Set root filesystem mount option string
1382
1383         rootfstype=     [KNL] Set root filesystem type
1384
1385         rw              [KNL] Mount root device read-write on boot
1386
1387         S               [KNL] Run init in single mode
1388
1389         sa1100ir        [NET]
1390                         See drivers/net/irda/sa1100_ir.c.
1391
1392         sb=             [HW,OSS]
1393                         Format: <io>,<irq>,<dma>,<dma2>
1394
1395         sbni=           [NET] Granch SBNI12 leased line adapter
1396
1397         sbpcd=          [HW,CD] Soundblaster CD adapter
1398                         Format: <io>,<type>
1399                         See a comment before function sbpcd_setup() in
1400                         drivers/cdrom/sbpcd.c.
1401
1402         sc1200wdt=      [HW,WDT] SC1200 WDT (watchdog) driver
1403                         Format: <io>[,<timeout>[,<isapnp>]]
1404
1405         scsi_debug_*=   [SCSI]
1406                         See drivers/scsi/scsi_debug.c.
1407
1408         scsi_default_dev_flags=
1409                         [SCSI] SCSI default device flags
1410                         Format: <integer>
1411
1412         scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1413                         Format: <vendor>:<model>:<flags>
1414                         (flags are integer value)
1415
1416         scsi_logging=   [SCSI]
1417
1418         selinux         [SELINUX] Disable or enable SELinux at boot time.
1419                         Format: { "0" | "1" }
1420                         See security/selinux/Kconfig help text.
1421                         0 -- disable.
1422                         1 -- enable.
1423                         Default value is set via kernel config option.
1424                         If enabled at boot time, /selinux/disable can be used
1425                         later to disable prior to initial policy load.
1426
1427         selinux_compat_net =
1428                         [SELINUX] Set initial selinux_compat_net flag value.
1429                         Format: { "0" | "1" }
1430                         0 -- use new secmark-based packet controls
1431                         1 -- use legacy packet controls
1432                         Default value is 0 (preferred).
1433                         Value can be changed at runtime via
1434                         /selinux/compat_net.
1435
1436         serialnumber    [BUGS=IA-32]
1437
1438         sg_def_reserved_size=   [SCSI]
1439
1440         shapers=        [NET]
1441                         Maximal number of shapers.
1442
1443         sim710=         [SCSI,HW]
1444                         See header of drivers/scsi/sim710.c.
1445
1446         simeth=         [IA-64]
1447         simscsi=
1448
1449         sjcd=           [HW,CD]
1450                         Format: <io>,<irq>,<dma>
1451                         See header of drivers/cdrom/sjcd.c.
1452
1453         slram=          [HW,MTD]
1454
1455         smart2=         [HW]
1456                         Format: <io1>[,<io2>[,...,<io8>]]
1457
1458         snd-ad1816a=    [HW,ALSA]
1459
1460         snd-ad1848=     [HW,ALSA]
1461
1462         snd-ali5451=    [HW,ALSA]
1463
1464         snd-als100=     [HW,ALSA]
1465
1466         snd-als4000=    [HW,ALSA]
1467
1468         snd-azt2320=    [HW,ALSA]
1469
1470         snd-cmi8330=    [HW,ALSA]
1471
1472         snd-cmipci=     [HW,ALSA]
1473
1474         snd-cs4231=     [HW,ALSA]
1475
1476         snd-cs4232=     [HW,ALSA]
1477
1478         snd-cs4236=     [HW,ALSA]
1479
1480         snd-cs4281=     [HW,ALSA]
1481
1482         snd-cs46xx=     [HW,ALSA]
1483
1484         snd-dt019x=     [HW,ALSA]
1485
1486         snd-dummy=      [HW,ALSA]
1487
1488         snd-emu10k1=    [HW,ALSA]
1489
1490         snd-ens1370=    [HW,ALSA]
1491
1492         snd-ens1371=    [HW,ALSA]
1493
1494         snd-es968=      [HW,ALSA]
1495
1496         snd-es1688=     [HW,ALSA]
1497
1498         snd-es18xx=     [HW,ALSA]
1499
1500         snd-es1938=     [HW,ALSA]
1501
1502         snd-es1968=     [HW,ALSA]
1503
1504         snd-fm801=      [HW,ALSA]
1505
1506         snd-gusclassic= [HW,ALSA]
1507
1508         snd-gusextreme= [HW,ALSA]
1509
1510         snd-gusmax=     [HW,ALSA]
1511
1512         snd-hdsp=       [HW,ALSA]
1513
1514         snd-ice1712=    [HW,ALSA]
1515
1516         snd-intel8x0=   [HW,ALSA]
1517
1518         snd-interwave=  [HW,ALSA]
1519
1520         snd-interwave-stb=
1521                         [HW,ALSA]
1522
1523         snd-korg1212=   [HW,ALSA]
1524
1525         snd-maestro3=   [HW,ALSA]
1526
1527         snd-mpu401=     [HW,ALSA]
1528
1529         snd-mtpav=      [HW,ALSA]
1530
1531         snd-nm256=      [HW,ALSA]
1532
1533         snd-opl3sa2=    [HW,ALSA]
1534
1535         snd-opti92x-ad1848=
1536                         [HW,ALSA]
1537
1538         snd-opti92x-cs4231=
1539                         [HW,ALSA]
1540
1541         snd-opti93x=    [HW,ALSA]
1542
1543         snd-pmac=       [HW,ALSA]
1544
1545         snd-rme32=      [HW,ALSA]
1546
1547         snd-rme96=      [HW,ALSA]
1548
1549         snd-rme9652=    [HW,ALSA]
1550
1551         snd-sb8=        [HW,ALSA]
1552
1553         snd-sb16=       [HW,ALSA]
1554
1555         snd-sbawe=      [HW,ALSA]
1556
1557         snd-serial=     [HW,ALSA]
1558
1559         snd-sgalaxy=    [HW,ALSA]
1560
1561         snd-sonicvibes= [HW,ALSA]
1562
1563         snd-sun-amd7930=
1564                         [HW,ALSA]
1565
1566         snd-sun-cs4231= [HW,ALSA]
1567
1568         snd-trident=    [HW,ALSA]
1569
1570         snd-usb-audio=  [HW,ALSA,USB]
1571
1572         snd-via82xx=    [HW,ALSA]
1573
1574         snd-virmidi=    [HW,ALSA]
1575
1576         snd-wavefront=  [HW,ALSA]
1577
1578         snd-ymfpci=     [HW,ALSA]
1579
1580         sonycd535=      [HW,CD]
1581                         Format: <io>[,<irq>]
1582
1583         sonypi.*=       [HW] Sony Programmable I/O Control Device driver
1584                         See Documentation/sonypi.txt
1585
1586         specialix=      [HW,SERIAL] Specialix multi-serial port adapter
1587                         See Documentation/specialix.txt.
1588
1589         spia_io_base=   [HW,MTD]
1590         spia_fio_base=
1591         spia_pedr=
1592         spia_peddr=
1593
1594         sscape=         [HW,OSS]
1595                         Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1596
1597         st=             [HW,SCSI] SCSI tape parameters (buffers, etc.)
1598                         See Documentation/scsi/st.txt.
1599
1600         st0x=           [HW,SCSI]
1601                         See header of drivers/scsi/seagate.c.
1602
1603         sti=            [PARISC,HW]
1604                         Format: <num>
1605                         Set the STI (builtin display/keyboard on the HP-PARISC
1606                         machines) console (graphic card) which should be used
1607                         as the initial boot-console.
1608                         See also comment in drivers/video/console/sticore.c.
1609
1610         sti_font=       [HW]
1611                         See comment in drivers/video/console/sticore.c.
1612
1613         stifb=          [HW]
1614                         Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1615
1616         swiotlb=        [IA-64] Number of I/O TLB slabs
1617
1618         switches=       [HW,M68k]
1619
1620         sym53c416=      [HW,SCSI]
1621                         See header of drivers/scsi/sym53c416.c.
1622
1623         t128=           [HW,SCSI]
1624                         See header of drivers/scsi/t128.c.
1625
1626         tdfx=           [HW,DRM]
1627
1628         thash_entries=  [KNL,NET]
1629                         Set number of hash buckets for TCP connection
1630
1631         time            Show timing data prefixed to each printk message line
1632
1633         clocksource=    [GENERIC_TIME] Override the default clocksource
1634                         Override the default clocksource and use the clocksource
1635                         with the name specified.
1636
1637         tipar.timeout=  [HW,PPT]
1638                         Set communications timeout in tenths of a second
1639                         (default 15).
1640
1641         tipar.delay=    [HW,PPT]
1642                         Set inter-bit delay in microseconds (default 10).
1643
1644         tmc8xx=         [HW,SCSI]
1645                         See header of drivers/scsi/seagate.c.
1646
1647         tmscsim=        [HW,SCSI]
1648                         See comment before function dc390_setup() in
1649                         drivers/scsi/tmscsim.c.
1650
1651         tp720=          [HW,PS2]
1652
1653         trix=           [HW,OSS] MediaTrix AudioTrix Pro
1654                         Format:
1655                         <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1656
1657         tsdev.xres=     [TS] Horizontal screen resolution.
1658         tsdev.yres=     [TS] Vertical screen resolution.
1659
1660         turbografx.map[2|3]=    [HW,JOY]
1661                         TurboGraFX parallel port interface
1662                         Format:
1663                         <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1664                         See also Documentation/input/joystick-parport.txt
1665
1666         u14-34f=        [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1667                         See header of drivers/scsi/u14-34f.c.
1668
1669         uart401=        [HW,OSS]
1670                         Format: <io>,<irq>
1671
1672         uart6850=       [HW,OSS]
1673                         Format: <io>,<irq>
1674
1675         usbhid.mousepoll=
1676                         [USBHID] The interval which mice are to be polled at.
1677
1678         vdso=           [IA-32]
1679                         vdso=1: enable VDSO (default)
1680                         vdso=0: disable VDSO mapping
1681
1682         video=          [FB] Frame buffer configuration
1683                         See Documentation/fb/modedb.txt.
1684
1685         vga=            [BOOT,IA-32] Select a particular video mode
1686                         See Documentation/i386/boot.txt and
1687                         Documentation/svga.txt.
1688                         Use vga=ask for menu.
1689                         This is actually a boot loader parameter; the value is
1690                         passed to the kernel using a special protocol.
1691
1692         vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1693                         size of <nn>. This can be used to increase the
1694                         minimum size (128MB on x86). It can also be used to
1695                         decrease the size and leave more room for directly
1696                         mapped kernel RAM.
1697
1698         vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
1699                         Format: <command>
1700
1701         vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
1702                         Format: <command>
1703
1704         vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
1705                         Format: <command>
1706
1707         waveartist=     [HW,OSS]
1708                         Format: <io>,<irq>,<dma>,<dma2>
1709
1710         wd33c93=        [HW,SCSI]
1711                         See header of drivers/scsi/wd33c93.c.
1712
1713         wd7000=         [HW,SCSI]
1714                         See header of drivers/scsi/wd7000.c.
1715
1716         wdt=            [WDT] Watchdog
1717                         See Documentation/watchdog/watchdog.txt.
1718
1719         xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1720         xd_geo=         See header of drivers/block/xd.c.
1721
1722         xirc2ps_cs=     [NET,PCMCIA]
1723                         Format:
1724                         <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1725
1726         norandmaps      Don't use address space randomization
1727                         Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1728
1729
1730 ______________________________________________________________________
1731
1732 TODO:
1733
1734         Add documentation for ALSA options.
1735         Add more DRM drivers.