linux/Documentation/kernel-parameters.txt
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   1                          Kernel Parameters
   2                          ~~~~~~~~~~~~~~~~~
   3
   4The 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
   7case insensitive manner), and with descriptions where known.
   8
   9Module parameters for loadable modules are specified only as the
  10parameter name with optional '=' and value as appropriate, such as:
  11
  12        modprobe usbcore blinkenlights=1
  13
  14Module parameters for modules that are built into the kernel image
  15are 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
  20Hyphens (dashes) and underscores are equivalent in parameter names, so
  21        log_buf_len=1M print-fatal-signals=1
  22can also be entered as
  23        log-buf-len=1M print_fatal_signals=1
  24
  25
  26This document may not be entirely up to date and comprehensive. The command
  27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  28module. Loadable modules, after being loaded into the running kernel, also
  29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  30parameters may be changed at runtime by the command
  31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  32
  33The parameters listed below are only valid if certain kernel build options were
  34enabled and if respective hardware is present. The text in square brackets at
  35the beginning of each description states the restrictions within which a
  36parameter is applicable:
  37
  38        ACPI    ACPI support is enabled.
  39        AGP     AGP (Accelerated Graphics Port) is enabled.
  40        ALSA    ALSA sound support is enabled.
  41        APIC    APIC support is enabled.
  42        APM     Advanced Power Management support is enabled.
  43        AVR32   AVR32 architecture is enabled.
  44        AX25    Appropriate AX.25 support is enabled.
  45        BLACKFIN Blackfin architecture is enabled.
  46        DRM     Direct Rendering Management support is enabled.
  47        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
  48        EFI     EFI Partitioning (GPT) is enabled
  49        EIDE    EIDE/ATAPI support is enabled.
  50        FB      The frame buffer device is enabled.
  51        HW      Appropriate hardware is enabled.
  52        IA-64   IA-64 architecture is enabled.
  53        IMA     Integrity measurement architecture is enabled.
  54        IOSCHED More than one I/O scheduler is enabled.
  55        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
  56        ISAPNP  ISA PnP code is enabled.
  57        ISDN    Appropriate ISDN support is enabled.
  58        JOY     Appropriate joystick support is enabled.
  59        KMEMTRACE kmemtrace is enabled.
  60        LIBATA  Libata driver is enabled
  61        LP      Printer support is enabled.
  62        LOOP    Loopback device support is enabled.
  63        M68k    M68k architecture is enabled.
  64                        These options have more detailed description inside of
  65                        Documentation/m68k/kernel-options.txt.
  66        MCA     MCA bus support is enabled.
  67        MDA     MDA console support is enabled.
  68        MOUSE   Appropriate mouse support is enabled.
  69        MSI     Message Signaled Interrupts (PCI).
  70        MTD     MTD (Memory Technology Device) support is enabled.
  71        NET     Appropriate network support is enabled.
  72        NUMA    NUMA support is enabled.
  73        GENERIC_TIME The generic timeofday code is enabled.
  74        NFS     Appropriate NFS support is enabled.
  75        OSS     OSS sound support is enabled.
  76        PV_OPS  A paravirtualized kernel is enabled.
  77        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
  78        PARISC  The PA-RISC architecture is enabled.
  79        PCI     PCI bus support is enabled.
  80        PCIE    PCI Express support is enabled.
  81        PCMCIA  The PCMCIA subsystem is enabled.
  82        PNP     Plug & Play support is enabled.
  83        PPC     PowerPC architecture is enabled.
  84        PPT     Parallel port support is enabled.
  85        PS2     Appropriate PS/2 support is enabled.
  86        RAM     RAM disk support is enabled.
  87        ROOTPLUG The example Root Plug LSM is enabled.
  88        S390    S390 architecture is enabled.
  89        SCSI    Appropriate SCSI support is enabled.
  90                        A lot of drivers has their options described inside of
  91                        Documentation/scsi/.
  92        SECURITY Different security models are enabled.
  93        SELINUX SELinux support is enabled.
  94        SERIAL  Serial support is enabled.
  95        SH      SuperH architecture is enabled.
  96        SMP     The kernel is an SMP kernel.
  97        SPARC   Sparc architecture is enabled.
  98        SWSUSP  Software suspend (hibernation) is enabled.
  99        SUSPEND System suspend states are enabled.
 100        FTRACE  Function tracing enabled.
 101        TS      Appropriate touchscreen support is enabled.
 102        UMS     USB Mass Storage support is enabled.
 103        USB     USB support is enabled.
 104        USBHID  USB Human Interface Device support is enabled.
 105        V4L     Video For Linux support is enabled.
 106        VGA     The VGA console has been enabled.
 107        VT      Virtual terminal support is enabled.
 108        WDT     Watchdog support is enabled.
 109        XT      IBM PC/XT MFM hard disk support is enabled.
 110        X86-32  X86-32, aka i386 architecture is enabled.
 111        X86-64  X86-64 architecture is enabled.
 112                        More X86-64 boot options can be found in
 113                        Documentation/x86/x86_64/boot-options.txt .
 114        X86     Either 32bit or 64bit x86 (same as X86-32+X86-64)
 115
 116In addition, the following text indicates that the option:
 117
 118        BUGS=   Relates to possible processor bugs on the said processor.
 119        KNL     Is a kernel start-up parameter.
 120        BOOT    Is a boot loader parameter.
 121
 122Parameters denoted with BOOT are actually interpreted by the boot
 123loader, and have no meaning to the kernel directly.
 124Do not modify the syntax of boot loader parameters without extreme
 125need or coordination with <Documentation/x86/boot.txt>.
 126
 127There are also arch-specific kernel-parameters not documented here.
 128See for example <Documentation/x86/x86_64/boot-options.txt>.
 129
 130Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
 131a trailing = on the name of any parameter states that that parameter will
 132be entered as an environment variable, whereas its absence indicates that
 133it will appear as a kernel argument readable via /proc/cmdline by programs
 134running once the system is up.
 135
 136The number of kernel parameters is not limited, but the length of the
 137complete command line (parameters including spaces etc.) is limited to
 138a fixed number of characters. This limit depends on the architecture
 139and is between 256 and 4096 characters. It is defined in the file
 140./include/asm/setup.h as COMMAND_LINE_SIZE.
 141
 142
 143        acpi=           [HW,ACPI,X86]
 144                        Advanced Configuration and Power Interface
 145                        Format: { force | off | ht | strict | noirq | rsdt }
 146                        force -- enable ACPI if default was off
 147                        off -- disable ACPI if default was on
 148                        noirq -- do not use ACPI for IRQ routing
 149                        ht -- run only enough ACPI to enable Hyper Threading
 150                        strict -- Be less tolerant of platforms that are not
 151                                strictly ACPI specification compliant.
 152                        rsdt -- prefer RSDT over (default) XSDT
 153
 154                        See also Documentation/power/pm.txt, pci=noacpi
 155
 156        acpi_apic_instance=     [ACPI, IOAPIC]
 157                        Format: <int>
 158                        2: use 2nd APIC table, if available
 159                        1,0: use 1st APIC table
 160                        default: 0
 161
 162        acpi_backlight= [HW,ACPI]
 163                        acpi_backlight=vendor
 164                        acpi_backlight=video
 165                        If set to vendor, prefer vendor specific driver
 166                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
 167                        of the ACPI video.ko driver.
 168
 169        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
 170        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
 171                        Format: <int>
 172                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
 173                        debug output.  Bits in debug_layer correspond to a
 174                        _COMPONENT in an ACPI source file, e.g.,
 175                            #define _COMPONENT ACPI_PCI_COMPONENT
 176                        Bits in debug_level correspond to a level in
 177                        ACPI_DEBUG_PRINT statements, e.g.,
 178                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
 179                        The debug_level mask defaults to "info".  See
 180                        Documentation/acpi/debug.txt for more information about
 181                        debug layers and levels.
 182
 183                        Enable processor driver info messages:
 184                            acpi.debug_layer=0x20000000
 185                        Enable PCI/PCI interrupt routing info messages:
 186                            acpi.debug_layer=0x400000
 187                        Enable AML "Debug" output, i.e., stores to the Debug
 188                        object while interpreting AML:
 189                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
 190                        Enable all messages related to ACPI hardware:
 191                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
 192
 193                        Some values produce so much output that the system is
 194                        unusable.  The "log_buf_len" parameter may be useful
 195                        if you need to capture more output.
 196
 197        acpi_display_output=    [HW,ACPI]
 198                        acpi_display_output=vendor
 199                        acpi_display_output=video
 200                        See above.
 201
 202        acpi_irq_balance [HW,ACPI]
 203                        ACPI will balance active IRQs
 204                        default in APIC mode
 205
 206        acpi_irq_nobalance [HW,ACPI]
 207                        ACPI will not move active IRQs (default)
 208                        default in PIC mode
 209
 210        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 211                        Format: <irq>,<irq>...
 212
 213        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
 214                        use by PCI
 215                        Format: <irq>,<irq>...
 216
 217        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT
 218
 219        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
 220                        Format: To spoof as Windows 98: ="Microsoft Windows"
 221
 222        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
 223                        acpi_osi="string1"      # add string1 -- only one string
 224                        acpi_osi="!string2"     # remove built-in string2
 225                        acpi_osi=               # disable all strings
 226
 227        acpi_pm_good    [X86]
 228                        Override the pmtimer bug detection: force the kernel
 229                        to assume that this machine's pmtimer latches its value
 230                        and always returns good values.
 231
 232        acpi.power_nocheck=     [HW,ACPI]
 233                        Format: 1/0 enable/disable the check of power state.
 234                        On some bogus BIOS the _PSC object/_STA object of
 235                        power resource can't return the correct device power
 236                        state. In such case it is unneccessary to check its
 237                        power state again in power transition.
 238                        1 : disable the power state check
 239
 240        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
 241                        Format: { level | edge | high | low }
 242
 243        acpi_serialize  [HW,ACPI] force serialization of AML methods
 244
 245        acpi_skip_timer_override [HW,ACPI]
 246                        Recognize and ignore IRQ0/pin2 Interrupt Override.
 247                        For broken nForce2 BIOS resulting in XT-PIC timer.
 248
 249        acpi_sleep=     [HW,ACPI] Sleep options
 250                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
 251                                  old_ordering, s4_nonvs }
 252                        See Documentation/power/video.txt for information on
 253                        s3_bios and s3_mode.
 254                        s3_beep is for debugging; it makes the PC's speaker beep
 255                        as soon as the kernel's real-mode entry point is called.
 256                        s4_nohwsig prevents ACPI hardware signature from being
 257                        used during resume from hibernation.
 258                        old_ordering causes the ACPI 1.0 ordering of the _PTS
 259                        control method, with respect to putting devices into
 260                        low power states, to be enforced (the ACPI 2.0 ordering
 261                        of _PTS is used by default).
 262                        s4_nonvs prevents the kernel from saving/restoring the
 263                        ACPI NVS memory during hibernation.
 264
 265        acpi_use_timer_override [HW,ACPI]
 266                        Use timer override. For some broken Nvidia NF5 boards
 267                        that require a timer override, but don't have HPET
 268
 269        acpi_enforce_resources= [ACPI]
 270                        { strict | lax | no }
 271                        Check for resource conflicts between native drivers
 272                        and ACPI OperationRegions (SystemIO and SystemMemory
 273                        only). IO ports and memory declared in ACPI might be
 274                        used by the ACPI subsystem in arbitrary AML code and
 275                        can interfere with legacy drivers.
 276                        strict (default): access to resources claimed by ACPI
 277                        is denied; legacy drivers trying to access reserved
 278                        resources will fail to bind to device using them.
 279                        lax: access to resources claimed by ACPI is allowed;
 280                        legacy drivers trying to access reserved resources
 281                        will bind successfully but a warning message is logged.
 282                        no: ACPI OperationRegions are not marked as reserved,
 283                        no further checks are performed.
 284
 285        ad1848=         [HW,OSS]
 286                        Format: <io>,<irq>,<dma>,<dma2>,<type>
 287
 288        add_efi_memmap  [EFI; X86] Include EFI memory map in
 289                        kernel's map of available physical RAM.
 290
 291        advansys=       [HW,SCSI]
 292                        See header of drivers/scsi/advansys.c.
 293
 294        advwdt=         [HW,WDT] Advantech WDT
 295                        Format: <iostart>,<iostop>
 296
 297        aedsp16=        [HW,OSS] Audio Excel DSP 16
 298                        Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
 299                        See also header of sound/oss/aedsp16.c.
 300
 301        agp=            [AGP]
 302                        { off | try_unsupported }
 303                        off: disable AGP support
 304                        try_unsupported: try to drive unsupported chipsets
 305                                (may crash computer or cause data corruption)
 306
 307        aha152x=        [HW,SCSI]
 308                        See Documentation/scsi/aha152x.txt.
 309
 310        aha1542=        [HW,SCSI]
 311                        Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
 312
 313        aic7xxx=        [HW,SCSI]
 314                        See Documentation/scsi/aic7xxx.txt.
 315
 316        aic79xx=        [HW,SCSI]
 317                        See Documentation/scsi/aic79xx.txt.
 318
 319        amd_iommu=      [HW,X86-84]
 320                        Pass parameters to the AMD IOMMU driver in the system.
 321                        Possible values are:
 322                        isolate - enable device isolation (each device, as far
 323                                  as possible, will get its own protection
 324                                  domain) [default]
 325                        share - put every device behind one IOMMU into the
 326                                same protection domain
 327                        fullflush - enable flushing of IO/TLB entries when
 328                                    they are unmapped. Otherwise they are
 329                                    flushed before they will be reused, which
 330                                    is a lot of faster
 331
 332        amd_iommu_size= [HW,X86-64]
 333                        Define the size of the aperture for the AMD IOMMU
 334                        driver. Possible values are:
 335                        '32M', '64M' (default), '128M', '256M', '512M', '1G'
 336
 337        amijoy.map=     [HW,JOY] Amiga joystick support
 338                        Map of devices attached to JOY0DAT and JOY1DAT
 339                        Format: <a>,<b>
 340                        See also Documentation/kernel/input/joystick.txt
 341
 342        analog.map=     [HW,JOY] Analog joystick and gamepad support
 343                        Specifies type or capabilities of an analog joystick
 344                        connected to one of 16 gameports
 345                        Format: <type1>,<type2>,..<type16>
 346
 347        apc=            [HW,SPARC]
 348                        Power management functions (SPARCstation-4/5 + deriv.)
 349                        Format: noidle
 350                        Disable APC CPU standby support. SPARCstation-Fox does
 351                        not play well with APC CPU idle - disable it if you have
 352                        APC and your system crashes randomly.
 353
 354        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
 355                        Change the output verbosity whilst booting
 356                        Format: { quiet (default) | verbose | debug }
 357                        Change the amount of debugging information output
 358                        when initialising the APIC and IO-APIC components.
 359
 360        apm=            [APM] Advanced Power Management
 361                        See header of arch/x86/kernel/apm_32.c.
 362
 363        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 364                        Format: <io>,<irq>,<nodeID>
 365
 366        ataflop=        [HW,M68k]
 367
 368        atarimouse=     [HW,MOUSE] Atari Mouse
 369
 370        atascsi=        [HW,SCSI] Atari SCSI
 371
 372        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 373                        EzKey and similar keyboards
 374
 375        atkbd.reset=    [HW] Reset keyboard during initialization
 376
 377        atkbd.set=      [HW] Select keyboard code set
 378                        Format: <int> (2 = AT (default), 3 = PS/2)
 379
 380        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 381                        keyboards
 382
 383        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 384                        Format: <bool> (0 = real, 1 = synthetic (default))
 385
 386        atkbd.softrepeat= [HW]
 387                        Use software keyboard repeat
 388
 389        autotest        [IA64]
 390
 391        baycom_epp=     [HW,AX25]
 392                        Format: <io>,<mode>
 393
 394        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 395                        Format: <io>,<mode>
 396                        See header of drivers/net/hamradio/baycom_par.c.
 397
 398        baycom_ser_fdx= [HW,AX25]
 399                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 400                        Format: <io>,<irq>,<mode>[,<baud>]
 401                        See header of drivers/net/hamradio/baycom_ser_fdx.c.
 402
 403        baycom_ser_hdx= [HW,AX25]
 404                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 405                        Format: <io>,<irq>,<mode>
 406                        See header of drivers/net/hamradio/baycom_ser_hdx.c.
 407
 408        boot_delay=     Milliseconds to delay each printk during boot.
 409                        Values larger than 10 seconds (10000) are changed to
 410                        no delay (0).
 411                        Format: integer
 412
 413        bootmem_debug   [KNL] Enable bootmem allocator debug messages.
 414
 415        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 416        bttv.radio=     Most important insmod options are available as
 417                        kernel args too.
 418        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 419        bttv.tuner=     and Documentation/video4linux/bttv/CARDLIST
 420
 421        BusLogic=       [HW,SCSI]
 422                        See drivers/scsi/BusLogic.c, comment before function
 423                        BusLogic_ParseDriverOptions().
 424
 425        c101=           [NET] Moxa C101 synchronous serial card
 426
 427        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
 428                        Sometimes CPU hardware bugs make them report the cache
 429                        size incorrectly. The kernel will attempt work arounds
 430                        to fix known problems, but for some CPUs it is not
 431                        possible to determine what the correct size should be.
 432                        This option provides an override for these situations.
 433
 434        capability.disable=
 435                        [SECURITY] Disable capabilities.  This would normally
 436                        be used only if an alternative security model is to be
 437                        configured.  Potentially dangerous and should only be
 438                        used if you are entirely sure of the consequences.
 439
 440        ccw_timeout_log [S390]
 441                        See Documentation/s390/CommonIO for details.
 442
 443        cgroup_disable= [KNL] Disable a particular controller
 444                        Format: {name of the controller(s) to disable}
 445                                {Currently supported controllers - "memory"}
 446
 447        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 448                        Format: { "0" | "1" }
 449                        See security/selinux/Kconfig help text.
 450                        0 -- check protection applied by kernel (includes
 451                                any implied execute protection).
 452                        1 -- check protection requested by application.
 453                        Default value is set via a kernel config option.
 454                        Value can be changed at runtime via
 455                                /selinux/checkreqprot.
 456
 457        cio_ignore=     [S390]
 458                        See Documentation/s390/CommonIO for details.
 459
 460        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
 461                        [Deprecated]
 462                        Forces specified clocksource (if available) to be used
 463                        when calculating gettimeofday(). If specified
 464                        clocksource is not available, it defaults to PIT.
 465                        Format: { pit | tsc | cyclone | pmtmr }
 466
 467        clocksource=    [GENERIC_TIME] Override the default clocksource
 468                        Format: <string>
 469                        Override the default clocksource and use the clocksource
 470                        with the name specified.
 471                        Some clocksource names to choose from, depending on
 472                        the platform:
 473                        [all] jiffies (this is the base, fallback clocksource)
 474                        [ACPI] acpi_pm
 475                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
 476                                pxa_timer,timer3,32k_counter,timer0_1
 477                        [AVR32] avr32
 478                        [X86-32] pit,hpet,tsc,vmi-timer;
 479                                scx200_hrt on Geode; cyclone on IBM x440
 480                        [MIPS] MIPS
 481                        [PARISC] cr16
 482                        [S390] tod
 483                        [SH] SuperH
 484                        [SPARC64] tick
 485                        [X86-64] hpet,tsc
 486
 487        clearcpuid=BITNUM [X86]
 488                        Disable CPUID feature X for the kernel. See
 489                        arch/x86/include/asm/cpufeature.h for the valid bit
 490                        numbers. Note the Linux specific bits are not necessarily
 491                        stable over kernel options, but the vendor specific
 492                        ones should be.
 493                        Also note that user programs calling CPUID directly
 494                        or using the feature without checking anything
 495                        will still see it. This just prevents it from
 496                        being used by the kernel or shown in /proc/cpuinfo.
 497                        Also note the kernel might malfunction if you disable
 498                        some critical bits.
 499
 500        code_bytes      [X86] How many bytes of object code to print
 501                        in an oops report.
 502                        Range: 0 - 8192
 503                        Default: 64
 504
 505        com20020=       [HW,NET] ARCnet - COM20020 chipset
 506                        Format:
 507                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 508
 509        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 510                        Format: <io>[,<irq>]
 511
 512        com90xx=        [HW,NET]
 513                        ARCnet - COM90xx chipset (memory-mapped buffers)
 514                        Format: <io>[,<irq>[,<memstart>]]
 515
 516        condev=         [HW,S390] console device
 517        conmode=
 518
 519        console=        [KNL] Output console device and options.
 520
 521                tty<n>  Use the virtual console device <n>.
 522
 523                ttyS<n>[,options]
 524                ttyUSB0[,options]
 525                        Use the specified serial port.  The options are of
 526                        the form "bbbbpnf", where "bbbb" is the baud rate,
 527                        "p" is parity ("n", "o", or "e"), "n" is number of
 528                        bits, and "f" is flow control ("r" for RTS or
 529                        omit it).  Default is "9600n8".
 530
 531                        See Documentation/serial-console.txt for more
 532                        information.  See
 533                        Documentation/networking/netconsole.txt for an
 534                        alternative.
 535
 536                uart[8250],io,<addr>[,options]
 537                uart[8250],mmio,<addr>[,options]
 538                        Start an early, polled-mode console on the 8250/16550
 539                        UART at the specified I/O port or MMIO address,
 540                        switching to the matching ttyS device later.  The
 541                        options are the same as for ttyS, above.
 542
 543                If the device connected to the port is not a TTY but a braille
 544                device, prepend "brl," before the device type, for instance
 545                        console=brl,ttyS0
 546                For now, only VisioBraille is supported.
 547
 548        coredump_filter=
 549                        [KNL] Change the default value for
 550                        /proc/<pid>/coredump_filter.
 551                        See also Documentation/filesystems/proc.txt.
 552
 553        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 554                        Format:
 555                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 556
 557        crashkernel=nn[KMG]@ss[KMG]
 558                        [KNL] Reserve a chunk of physical memory to
 559                        hold a kernel to switch to with kexec on panic.
 560
 561        crashkernel=range1:size1[,range2:size2,...][@offset]
 562                        [KNL] Same as above, but depends on the memory
 563                        in the running system. The syntax of range is
 564                        start-[end] where start and end are both
 565                        a memory unit (amount[KMG]). See also
 566                        Documentation/kdump/kdump.txt for a example.
 567
 568        cs89x0_dma=     [HW,NET]
 569                        Format: <dma>
 570
 571        cs89x0_media=   [HW,NET]
 572                        Format: { rj45 | aui | bnc }
 573
 574        dasd=           [HW,NET]
 575                        See header of drivers/s390/block/dasd_devmap.c.
 576
 577        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 578                        (one device per port)
 579                        Format: <port#>,<type>
 580                        See also Documentation/input/joystick-parport.txt
 581
 582        debug           [KNL] Enable kernel debugging (events log level).
 583
 584        debug_locks_verbose=
 585                        [KNL] verbose self-tests
 586                        Format=<0|1>
 587                        Print debugging info while doing the locking API
 588                        self-tests.
 589                        We default to 0 (no extra messages), setting it to
 590                        1 will print _a lot_ more information - normally
 591                        only useful to kernel developers.
 592
 593        debug_objects   [KNL] Enable object debugging
 594
 595        no_debug_objects
 596                        [KNL] Disable object debugging
 597
 598        debugpat        [X86] Enable PAT debugging
 599
 600        decnet.addr=    [HW,NET]
 601                        Format: <area>[,<node>]
 602                        See also Documentation/networking/decnet.txt.
 603
 604        default_hugepagesz=
 605                        [same as hugepagesz=] The size of the default
 606                        HugeTLB page size. This is the size represented by
 607                        the legacy /proc/ hugepages APIs, used for SHM, and
 608                        default size when mounting hugetlbfs filesystems.
 609                        Defaults to the default architecture's huge page size
 610                        if not specified.
 611
 612        dhash_entries=  [KNL]
 613                        Set number of hash buckets for dentry cache.
 614
 615        digi=           [HW,SERIAL]
 616                        IO parameters + enable/disable command.
 617
 618        digiepca=       [HW,SERIAL]
 619                        See drivers/char/README.epca and
 620                        Documentation/serial/digiepca.txt.
 621
 622        disable_mtrr_cleanup [X86]
 623                        The kernel tries to adjust MTRR layout from continuous
 624                        to discrete, to make X server driver able to add WB
 625                        entry later. This parameter disables that.
 626
 627        disable_mtrr_trim [X86, Intel and AMD only]
 628                        By default the kernel will trim any uncacheable
 629                        memory out of your available memory pool based on
 630                        MTRR settings.  This parameter disables that behavior,
 631                        possibly causing your machine to run very slowly.
 632
 633        disable_timer_pin_1 [X86]
 634                        Disable PIN 1 of APIC timer
 635                        Can be useful to work around chipset bugs.
 636
 637        dmasound=       [HW,OSS] Sound subsystem buffers
 638
 639        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
 640                        this option disables the debugging code at boot.
 641
 642        dma_debug_entries=<number>
 643                        This option allows to tune the number of preallocated
 644                        entries for DMA-API debugging code. One entry is
 645                        required per DMA-API allocation. Use this if the
 646                        DMA-API debugging code disables itself because the
 647                        architectural default is too low.
 648
 649        dscc4.setup=    [NET]
 650
 651        dtc3181e=       [HW,SCSI]
 652
 653        dynamic_printk  Enables pr_debug()/dev_dbg() calls if
 654                        CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
 655                        These can also be switched on/off via
 656                        <debugfs>/dynamic_printk/modules
 657
 658        earlycon=       [KNL] Output early console device and options.
 659                uart[8250],io,<addr>[,options]
 660                uart[8250],mmio,<addr>[,options]
 661                        Start an early, polled-mode console on the 8250/16550
 662                        UART at the specified I/O port or MMIO address.
 663                        The options are the same as for ttyS, above.
 664
 665        earlyprintk=    [X86,SH,BLACKFIN]
 666                        earlyprintk=vga
 667                        earlyprintk=serial[,ttySn[,baudrate]]
 668                        earlyprintk=dbgp
 669
 670                        Append ",keep" to not disable it when the real console
 671                        takes over.
 672
 673                        Only vga or serial or usb debug port at a time.
 674
 675                        Currently only ttyS0 and ttyS1 are supported.
 676
 677                        Interaction with the standard serial driver is not
 678                        very good.
 679
 680                        The VGA output is eventually overwritten by the real
 681                        console.
 682
 683        eata=           [HW,SCSI]
 684
 685        edd=            [EDD]
 686                        Format: {"off" | "on" | "skip[mbr]"}
 687
 688        eisa_irq_edge=  [PARISC,HW]
 689                        See header of drivers/parisc/eisa.c.
 690
 691        elanfreq=       [X86-32]
 692                        See comment before function elanfreq_setup() in
 693                        arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 694
 695        elevator=       [IOSCHED]
 696                        Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
 697                        See Documentation/block/as-iosched.txt and
 698                        Documentation/block/deadline-iosched.txt for details.
 699
 700        elfcorehdr=     [IA64,PPC,SH,X86]
 701                        Specifies physical address of start of kernel core
 702                        image elf header. Generally kexec loader will
 703                        pass this option to capture kernel.
 704                        See Documentation/kdump/kdump.txt for details.
 705
 706        enable_mtrr_cleanup [X86]
 707                        The kernel tries to adjust MTRR layout from continuous
 708                        to discrete, to make X server driver able to add WB
 709                        entry later. This parameter enables that.
 710
 711        enable_timer_pin_1 [X86]
 712                        Enable PIN 1 of APIC timer
 713                        Can be useful to work around chipset bugs
 714                        (in particular on some ATI chipsets).
 715                        The kernel tries to set a reasonable default.
 716
 717        enforcing       [SELINUX] Set initial enforcing status.
 718                        Format: {"0" | "1"}
 719                        See security/selinux/Kconfig help text.
 720                        0 -- permissive (log only, no denials).
 721                        1 -- enforcing (deny and log).
 722                        Default value is 0.
 723                        Value can be changed at runtime via /selinux/enforce.
 724
 725        ether=          [HW,NET] Ethernet cards parameters
 726                        This option is obsoleted by the "netdev=" option, which
 727                        has equivalent usage. See its documentation for details.
 728
 729        eurwdt=         [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
 730                        Format: <io>[,<irq>]
 731
 732        failslab=
 733        fail_page_alloc=
 734        fail_make_request=[KNL]
 735                        General fault injection mechanism.
 736                        Format: <interval>,<probability>,<space>,<times>
 737                        See also /Documentation/fault-injection/.
 738
 739        fd_mcs=         [HW,SCSI]
 740                        See header of drivers/scsi/fd_mcs.c.
 741
 742        fdomain=        [HW,SCSI]
 743                        See header of drivers/scsi/fdomain.c.
 744
 745        floppy=         [HW]
 746                        See Documentation/blockdev/floppy.txt.
 747
 748        force_pal_cache_flush
 749                        [IA-64] Avoid check_sal_cache_flush which may hang on
 750                        buggy SAL_CACHE_FLUSH implementations. Using this
 751                        parameter will force ia64_sal_cache_flush to call
 752                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
 753
 754        ftrace=[tracer]
 755                        [ftrace] will set and start the specified tracer
 756                        as early as possible in order to facilitate early
 757                        boot debugging.
 758
 759        ftrace_dump_on_oops
 760                        [ftrace] will dump the trace buffers on oops.
 761
 762        gamecon.map[2|3]=
 763                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 764                        support via parallel port (up to 5 devices per port)
 765                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 766                        See also Documentation/input/joystick-parport.txt
 767
 768        gamma=          [HW,DRM]
 769
 770        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
 771                        Format: off | on
 772                        default: on
 773
 774        gdth=           [HW,SCSI]
 775                        See header of drivers/scsi/gdth.c.
 776
 777        gpt             [EFI] Forces disk with valid GPT signature but
 778                        invalid Protective MBR to be treated as GPT.
 779
 780        gvp11=          [HW,SCSI]
 781
 782        hashdist=       [KNL,NUMA] Large hashes allocated during boot
 783                        are distributed across NUMA nodes.  Defaults on
 784                        for 64bit NUMA, off otherwise.
 785                        Format: 0 | 1 (for off | on)
 786
 787        hcl=            [IA-64] SGI's Hardware Graph compatibility layer
 788
 789        hd=             [EIDE] (E)IDE hard drive subsystem geometry
 790                        Format: <cyl>,<head>,<sect>
 791
 792        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
 793                        size of <nn>. This works even on boxes that have no
 794                        highmem otherwise. This also works to reduce highmem
 795                        size on bigger boxes.
 796
 797        highres=        [KNL] Enable/disable high resolution timer mode.
 798                        Valid parameters: "on", "off"
 799                        Default: "on"
 800
 801        hisax=          [HW,ISDN]
 802                        See Documentation/isdn/README.HiSax.
 803
 804        hlt             [BUGS=ARM,SH]
 805
 806        hpet=           [X86-32,HPET] option to control HPET usage
 807                        Format: { enable (default) | disable | force |
 808                                verbose }
 809                        disable: disable HPET and use PIT instead
 810                        force: allow force enabled of undocumented chips (ICH4,
 811                                VIA, nVidia)
 812                        verbose: show contents of HPET registers during setup
 813
 814        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
 815        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
 816                        On x86-64 and powerpc, this option can be specified
 817                        multiple times interleaved with hugepages= to reserve
 818                        huge pages of different sizes. Valid pages sizes on
 819                        x86-64 are 2M (when the CPU supports "pse") and 1G
 820                        (when the CPU supports the "pdpe1gb" cpuinfo flag)
 821                        Note that 1GB pages can only be allocated at boot time
 822                        using hugepages= and not freed afterwards.
 823
 824        hvc_iucv=       [S390] Number of z/VM IUCV hypervisor console (HVC)
 825                               terminal devices. Valid values: 0..8
 826        hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
 827                               If specified, z/VM IUCV HVC accepts connections
 828                               from listed z/VM user IDs only.
 829
 830        i2c_bus=        [HW] Override the default board specific I2C bus speed
 831                             or register an additional I2C bus that is not
 832                             registered from board initialization code.
 833                             Format:
 834                             <bus_id>,<clkrate>
 835
 836        i8042.debug     [HW] Toggle i8042 debug mode
 837        i8042.direct    [HW] Put keyboard port into non-translated mode
 838        i8042.dumbkbd   [HW] Pretend that controller can only read data from
 839                             keyboard and cannot control its state
 840                             (Don't attempt to blink the leds)
 841        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
 842        i8042.nokbd     [HW] Don't check/create keyboard port
 843        i8042.noloop    [HW] Disable the AUX Loopback command while probing
 844                             for the AUX port
 845        i8042.nomux     [HW] Don't check presence of an active multiplexing
 846                             controller
 847        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
 848                             controllers
 849        i8042.panicblink=
 850                        [HW] Frequency with which keyboard LEDs should blink
 851                             when kernel panics (default is 0.5 sec)
 852        i8042.reset     [HW] Reset the controller during init and cleanup
 853        i8042.unlock    [HW] Unlock (ignore) the keylock
 854
 855        i810=           [HW,DRM]
 856
 857        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
 858                        indicates that the driver is running on unsupported
 859                        hardware.
 860        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
 861                        does not match list of supported models.
 862        i8k.power_status
 863                        [HW] Report power status in /proc/i8k
 864                        (disabled by default)
 865        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
 866                        capability is set.
 867
 868        ibmmcascsi=     [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
 869                        See Documentation/mca.txt.
 870
 871        icn=            [HW,ISDN]
 872                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
 873
 874        ide-core.nodma= [HW] (E)IDE subsystem
 875                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
 876                        .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
 877                        .chs .ignore_cable are additional options
 878                        See Documentation/ide/ide.txt.
 879
 880        idebus=         [HW] (E)IDE subsystem - VLB/PCI bus speed
 881                        See Documentation/ide/ide.txt.
 882
 883        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
 884                        Claim all unknown PCI IDE storage controllers.
 885
 886        idle=           [X86]
 887                        Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
 888                        Poll forces a polling idle loop that can slightly
 889                        improve the performance of waking up a idle CPU, but
 890                        will use a lot of power and make the system run hot.
 891                        Not recommended.
 892                        idle=mwait: On systems which support MONITOR/MWAIT but
 893                        the kernel chose to not use it because it doesn't save
 894                        as much power as a normal idle loop, use the
 895                        MONITOR/MWAIT idle loop anyways. Performance should be
 896                        the same as idle=poll.
 897                        idle=halt: Halt is forced to be used for CPU idle.
 898                        In such case C2/C3 won't be used again.
 899                        idle=nomwait: Disable mwait for CPU C-states
 900
 901        ignore_loglevel [KNL]
 902                        Ignore loglevel setting - this will print /all/
 903                        kernel messages to the console. Useful for debugging.
 904
 905        ihash_entries=  [KNL]
 906                        Set number of hash buckets for inode cache.
 907
 908        ima_audit=      [IMA]
 909                        Format: { "0" | "1" }
 910                        0 -- integrity auditing messages. (Default)
 911                        1 -- enable informational integrity auditing messages.
 912
 913        ima_hash=       [IMA]
 914                        Formt: { "sha1" | "md5" }
 915                        default: "sha1"
 916
 917        in2000=         [HW,SCSI]
 918                        See header of drivers/scsi/in2000.c.
 919
 920        init=           [KNL]
 921                        Format: <full_path>
 922                        Run specified binary instead of /sbin/init as init
 923                        process.
 924
 925        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
 926                        for working out where the kernel is dying during
 927                        startup.
 928
 929        initrd=         [BOOT] Specify the location of the initial ramdisk
 930
 931        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
 932                        Format: <irq>
 933
 934        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
 935                on
 936                        Enable intel iommu driver.
 937                off
 938                        Disable intel iommu driver.
 939                igfx_off [Default Off]
 940                        By default, gfx is mapped as normal device. If a gfx
 941                        device has a dedicated DMAR unit, the DMAR unit is
 942                        bypassed by not enabling DMAR with this option. In
 943                        this case, gfx device will use physical address for
 944                        DMA.
 945                forcedac [x86_64]
 946                        With this option iommu will not optimize to look
 947                        for io virtual address below 32 bit forcing dual
 948                        address cycle on pci bus for cards supporting greater
 949                        than 32 bit addressing. The default is to look
 950                        for translation below 32 bit and if not available
 951                        then look in the higher range.
 952                strict [Default Off]
 953                        With this option on every unmap_single operation will
 954                        result in a hardware IOTLB flush operation as opposed
 955                        to batching them for performance.
 956
 957        inttest=        [IA64]
 958
 959        iomem=          Disable strict checking of access to MMIO memory
 960                strict  regions from userspace.
 961                relaxed
 962
 963        iommu=          [x86]
 964                off
 965                force
 966                noforce
 967                biomerge
 968                panic
 969                nopanic
 970                merge
 971                nomerge
 972                forcesac
 973                soft
 974
 975        io7=            [HW] IO7 for Marvel based alpha systems
 976                        See comment before marvel_specify_io7 in
 977                        arch/alpha/kernel/core_marvel.c.
 978
 979        io_delay=       [X86] I/O delay method
 980                0x80
 981                        Standard port 0x80 based delay
 982                0xed
 983                        Alternate port 0xed based delay (needed on some systems)
 984                udelay
 985                        Simple two microseconds delay
 986                none
 987                        No delay
 988
 989        ip=             [IP_PNP]
 990                        See Documentation/filesystems/nfsroot.txt.
 991
 992        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
 993                        See comment before ip2_setup() in
 994                        drivers/char/ip2/ip2base.c.
 995
 996        ips=            [HW,SCSI] Adaptec / IBM ServeRAID controller
 997                        See header of drivers/scsi/ips.c.
 998
 999        irqfixup        [HW]
1000                        When an interrupt is not handled search all handlers
1001                        for it. Intended to get systems with badly broken
1002                        firmware running.
1003
1004        irqpoll         [HW]
1005                        When an interrupt is not handled search all handlers
1006                        for it. Also check all handlers each timer
1007                        interrupt. Intended to get systems with badly broken
1008                        firmware running.
1009
1010        isapnp=         [ISAPNP]
1011                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1012
1013        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
1014                        Format:
1015                        <cpu number>,...,<cpu number>
1016                        or
1017                        <cpu number>-<cpu number>
1018                        (must be a positive range in ascending order)
1019                        or a mixture
1020                        <cpu number>,...,<cpu number>-<cpu number>
1021
1022                        This option can be used to specify one or more CPUs
1023                        to isolate from the general SMP balancing and scheduling
1024                        algorithms. You can move a process onto or off an
1025                        "isolated" CPU via the CPU affinity syscalls or cpuset.
1026                        <cpu number> begins at 0 and the maximum value is
1027                        "number of CPUs in system - 1".
1028
1029                        This option is the preferred way to isolate CPUs. The
1030                        alternative -- manually setting the CPU mask of all
1031                        tasks in the system -- can cause problems and
1032                        suboptimal load balancer performance.
1033
1034        iucv=           [HW,NET]
1035
1036        js=             [HW,JOY] Analog joystick
1037                        See Documentation/input/joystick.txt.
1038
1039        keepinitrd      [HW,ARM]
1040
1041        kernelcore=nn[KMG]      [KNL,X86,IA-64,PPC] This parameter
1042                        specifies the amount of memory usable by the kernel
1043                        for non-movable allocations.  The requested amount is
1044                        spread evenly throughout all nodes in the system. The
1045                        remaining memory in each node is used for Movable
1046                        pages. In the event, a node is too small to have both
1047                        kernelcore and Movable pages, kernelcore pages will
1048                        take priority and other nodes will have a larger number
1049                        of kernelcore pages.  The Movable zone is used for the
1050                        allocation of pages that may be reclaimed or moved
1051                        by the page migration subsystem.  This means that
1052                        HugeTLB pages may not be allocated from this zone.
1053                        Note that allocations like PTEs-from-HighMem still
1054                        use the HighMem zone if it exists, and the Normal
1055                        zone if it does not.
1056
1057        kmemtrace.enable=       [KNL,KMEMTRACE] Format: { yes | no }
1058                                Controls whether kmemtrace is enabled
1059                                at boot-time.
1060
1061        kmemtrace.subbufs=n     [KNL,KMEMTRACE] Overrides the number of
1062                        subbufs kmemtrace's relay channel has. Set this
1063                        higher than default (KMEMTRACE_N_SUBBUFS in code) if
1064                        you experience buffer overruns.
1065
1066        kgdboc=         [HW] kgdb over consoles.
1067                        Requires a tty driver that supports console polling.
1068                        (only serial suported for now)
1069                        Format: <serial_device>[,baud]
1070
1071        kmac=           [MIPS] korina ethernet MAC address.
1072                        Configure the RouterBoard 532 series on-chip
1073                        Ethernet adapter MAC address.
1074
1075        kstack=N        [X86] Print N words from the kernel stack
1076                        in oops dumps.
1077
1078        l2cr=           [PPC]
1079
1080        l3cr=           [PPC]
1081
1082        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
1083                        disabled it.
1084
1085        lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
1086                        in C2 power state.
1087
1088        libata.dma=     [LIBATA] DMA control
1089                        libata.dma=0      Disable all PATA and SATA DMA
1090                        libata.dma=1      PATA and SATA Disk DMA only
1091                        libata.dma=2      ATAPI (CDROM) DMA only
1092                        libata.dma=4      Compact Flash DMA only 
1093                        Combinations also work, so libata.dma=3 enables DMA
1094                        for disks and CDROMs, but not CFs.
1095
1096        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
1097                        when set.
1098                        Format: <int>
1099
1100        libata.force=   [LIBATA] Force configurations.  The format is comma
1101                        separated list of "[ID:]VAL" where ID is
1102                        PORT[:DEVICE].  PORT and DEVICE are decimal numbers
1103                        matching port, link or device.  Basically, it matches
1104                        the ATA ID string printed on console by libata.  If
1105                        the whole ID part is omitted, the last PORT and DEVICE
1106                        values are used.  If ID hasn't been specified yet, the
1107                        configuration applies to all ports, links and devices.
1108
1109                        If only DEVICE is omitted, the parameter applies to
1110                        the port and all links and devices behind it.  DEVICE
1111                        number of 0 either selects the first device or the
1112                        first fan-out link behind PMP device.  It does not
1113                        select the host link.  DEVICE number of 15 selects the
1114                        host link and device attached to it.
1115
1116                        The VAL specifies the configuration to force.  As long
1117                        as there's no ambiguity shortcut notation is allowed.
1118                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
1119                        The following configurations can be forced.
1120
1121                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
1122                          Any ID with matching PORT is used.
1123
1124                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1125
1126                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1127                          udma[/][16,25,33,44,66,100,133] notation is also
1128                          allowed.
1129
1130                        * [no]ncq: Turn on or off NCQ.
1131
1132                        * nohrst, nosrst, norst: suppress hard, soft
1133                          and both resets.
1134
1135                        If there are multiple matching configurations changing
1136                        the same attribute, the last one is used.
1137
1138        lmb=debug       [KNL] Enable lmb debug messages.
1139
1140        load_ramdisk=   [RAM] List of ramdisks to load from floppy
1141                        See Documentation/blockdev/ramdisk.txt.
1142
1143        lockd.nlm_grace_period=P  [NFS] Assign grace period.
1144                        Format: <integer>
1145
1146        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
1147                        Format: <integer>
1148
1149        lockd.nlm_timeout=T     [NFS] Assign timeout value.
1150                        Format: <integer>
1151
1152        lockd.nlm_udpport=M     [NFS] Assign UDP port.
1153                        Format: <integer>
1154
1155        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
1156                        Format: <irq>
1157
1158        loglevel=       All Kernel Messages with a loglevel smaller than the
1159                        console loglevel will be printed to the console. It can
1160                        also be changed with klogd or other programs. The
1161                        loglevels are defined as follows:
1162
1163                        0 (KERN_EMERG)          system is unusable
1164                        1 (KERN_ALERT)          action must be taken immediately
1165                        2 (KERN_CRIT)           critical conditions
1166                        3 (KERN_ERR)            error conditions
1167                        4 (KERN_WARNING)        warning conditions
1168                        5 (KERN_NOTICE)         normal but significant condition
1169                        6 (KERN_INFO)           informational
1170                        7 (KERN_DEBUG)          debug-level messages
1171
1172        log_buf_len=n   Sets the size of the printk ring buffer, in bytes.
1173                        Format: { n | nk | nM }
1174                        n must be a power of two.  The default size
1175                        is set in the kernel config file.
1176
1177        logo.nologo     [FB] Disables display of the built-in Linux logo.
1178                        This may be used to provide more screen space for
1179                        kernel log messages and is useful when debugging
1180                        kernel boot problems.
1181
1182        lp=0            [LP]    Specify parallel ports to use, e.g,
1183        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
1184        lp=reset                first parallel port). 'lp=0' disables the
1185        lp=auto                 printer driver. 'lp=reset' (which can be
1186                                specified in addition to the ports) causes
1187                                attached printers to be reset. Using
1188                                lp=port1,port2,... specifies the parallel ports
1189                                to associate lp devices with, starting with
1190                                lp0. A port specification may be 'none' to skip
1191                                that lp device, or a parport name such as
1192                                'parport0'. Specifying 'lp=auto' instead of a
1193                                port specification list means that device IDs
1194                                from each port should be examined, to see if
1195                                an IEEE 1284-compliant printer is attached; if
1196                                so, the driver will manage that printer.
1197                                See also header of drivers/char/lp.c.
1198
1199        lpj=n           [KNL]
1200                        Sets loops_per_jiffy to given constant, thus avoiding
1201                        time-consuming boot-time autodetection (up to 250 ms per
1202                        CPU). 0 enables autodetection (default). To determine
1203                        the correct value for your kernel, boot with normal
1204                        autodetection and see what value is printed. Note that
1205                        on SMP systems the preset will be applied to all CPUs,
1206                        which is likely to cause problems if your CPUs need
1207                        significantly divergent settings. An incorrect value
1208                        will cause delays in the kernel to be wrong, leading to
1209                        unpredictable I/O errors and other breakage. Although
1210                        unlikely, in the extreme case this might damage your
1211                        hardware.
1212
1213        ltpc=           [NET]
1214                        Format: <io>,<irq>,<dma>
1215
1216        mac5380=        [HW,SCSI] Format:
1217                        <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1218
1219        machvec=        [IA64] Force the use of a particular machine-vector
1220                        (machvec) in a generic kernel.
1221                        Example: machvec=hpzx1_swiotlb
1222
1223        max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater
1224                        than or equal to this physical address is ignored.
1225
1226        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
1227                        should make use of.  maxcpus=n : n >= 0 limits the
1228                        kernel to using 'n' processors.  n=0 is a special case,
1229                        it is equivalent to "nosmp", which also disables
1230                        the IO APIC.
1231
1232        max_loop=       [LOOP] Maximum number of loopback devices that can
1233                        be mounted
1234                        Format: <1-256>
1235
1236        max_luns=       [SCSI] Maximum number of LUNs to probe.
1237                        Should be between 1 and 2^32-1.
1238
1239        max_report_luns=
1240                        [SCSI] Maximum number of LUNs received.
1241                        Should be between 1 and 16384.
1242
1243        mcatest=        [IA-64]
1244
1245        mce             [X86-32] Machine Check Exception
1246
1247        mce=option      [X86-64] See Documentation/x86/x86_64/boot-options.txt
1248
1249        md=             [HW] RAID subsystems devices and level
1250                        See Documentation/md.txt.
1251
1252        mdacon=         [MDA]
1253                        Format: <first>,<last>
1254                        Specifies range of consoles to be captured by the MDA.
1255
1256        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
1257                        Amount of memory to be used when the kernel is not able
1258                        to see the whole system memory or for test.
1259                        [X86-32] Use together with memmap= to avoid physical
1260                        address space collisions. Without memmap= PCI devices
1261                        could be placed at addresses belonging to unused RAM.
1262
1263        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
1264                        memory.
1265
1266        memchunk=nn[KMG]
1267                        [KNL,SH] Allow user to override the default size for
1268                        per-device physically contiguous DMA buffers.
1269
1270        memmap=exactmap [KNL,X86] Enable setting of an exact
1271                        E820 memory map, as specified by the user.
1272                        Such memmap=exactmap lines can be constructed based on
1273                        BIOS output or other requirements. See the memmap=nn@ss
1274                        option description.
1275
1276        memmap=nn[KMG]@ss[KMG]
1277                        [KNL] Force usage of a specific region of memory
1278                        Region of memory to be used, from ss to ss+nn.
1279
1280        memmap=nn[KMG]#ss[KMG]
1281                        [KNL,ACPI] Mark specific memory as ACPI data.
1282                        Region of memory to be used, from ss to ss+nn.
1283
1284        memmap=nn[KMG]$ss[KMG]
1285                        [KNL,ACPI] Mark specific memory as reserved.
1286                        Region of memory to be used, from ss to ss+nn.
1287                        Example: Exclude memory from 0x18690000-0x1869ffff
1288                                 memmap=64K$0x18690000
1289                                 or
1290                                 memmap=0x10000$0x18690000
1291
1292        memory_corruption_check=0/1 [X86]
1293                        Some BIOSes seem to corrupt the first 64k of
1294                        memory when doing things like suspend/resume.
1295                        Setting this option will scan the memory
1296                        looking for corruption.  Enabling this will
1297                        both detect corruption and prevent the kernel
1298                        from using the memory being corrupted.
1299                        However, its intended as a diagnostic tool; if
1300                        repeatable BIOS-originated corruption always
1301                        affects the same memory, you can use memmap=
1302                        to prevent the kernel from using that memory.
1303
1304        memory_corruption_check_size=size [X86]
1305                        By default it checks for corruption in the low
1306                        64k, making this memory unavailable for normal
1307                        use.  Use this parameter to scan for
1308                        corruption in more or less memory.
1309
1310        memory_corruption_check_period=seconds [X86]
1311                        By default it checks for corruption every 60
1312                        seconds.  Use this parameter to check at some
1313                        other rate.  0 disables periodic checking.
1314
1315        memtest=        [KNL,X86] Enable memtest
1316                        Format: <integer>
1317                        default : 0 <disable>
1318                        Specifies the number of memtest passes to be
1319                        performed. Each pass selects another test
1320                        pattern from a given set of patterns. Memtest
1321                        fills the memory with this pattern, validates
1322                        memory contents and reserves bad memory
1323                        regions that are detected.
1324
1325        meye.*=         [HW] Set MotionEye Camera parameters
1326                        See Documentation/video4linux/meye.txt.
1327
1328        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
1329                        Multi-Function General Purpose Timers on AMD Geode
1330                        platforms.
1331
1332        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
1333                        the BIOS has incorrectly applied a workaround. TinyBIOS
1334                        version 0.98 is known to be affected, 0.99 fixes the
1335                        problem by letting the user disable the workaround.
1336
1337        mga=            [HW,DRM]
1338
1339        min_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory below this
1340                        physical address is ignored.
1341
1342        mminit_loglevel=
1343                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1344                        parameter allows control of the logging verbosity for
1345                        the additional memory initialisation checks. A value
1346                        of 0 disables mminit logging and a level of 4 will
1347                        log everything. Information is printed at KERN_DEBUG
1348                        so loglevel=8 may also need to be specified.
1349
1350        mousedev.tap_time=
1351                        [MOUSE] Maximum time between finger touching and
1352                        leaving touchpad surface for touch to be considered
1353                        a tap and be reported as a left button click (for
1354                        touchpads working in absolute mode only).
1355                        Format: <msecs>
1356        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
1357                        reporting absolute coordinates, such as tablets
1358        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
1359                        reporting absolute coordinates, such as tablets
1360
1361        movablecore=nn[KMG]     [KNL,X86,IA-64,PPC] This parameter
1362                        is similar to kernelcore except it specifies the
1363                        amount of memory used for migratable allocations.
1364                        If both kernelcore and movablecore is specified,
1365                        then kernelcore will be at *least* the specified
1366                        value but may be more. If movablecore on its own
1367                        is specified, the administrator must be careful
1368                        that the amount of memory usable for all allocations
1369                        is not too small.
1370
1371        mpu401=         [HW,OSS]
1372                        Format: <io>,<irq>
1373
1374        MTD_Partition=  [MTD]
1375                        Format: <name>,<region-number>,<size>,<offset>
1376
1377        MTD_Region=     [MTD] Format:
1378                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1379
1380        mtdparts=       [MTD]
1381                        See drivers/mtd/cmdlinepart.c.
1382
1383        mtdset=         [ARM]
1384                        ARM/S3C2412 JIVE boot control
1385
1386                        See arch/arm/mach-s3c2412/mach-jive.c
1387
1388        mtouchusb.raw_coordinates=
1389                        [HW] Make the MicroTouch USB driver use raw coordinates
1390                        ('y', default) or cooked coordinates ('n')
1391
1392        mtrr_chunk_size=nn[KMG] [X86]
1393                        used for mtrr cleanup. It is largest continous chunk
1394                        that could hold holes aka. UC entries.
1395
1396        mtrr_gran_size=nn[KMG] [X86]
1397                        Used for mtrr cleanup. It is granularity of mtrr block.
1398                        Default is 1.
1399                        Large value could prevent small alignment from
1400                        using up MTRRs.
1401
1402        mtrr_spare_reg_nr=n [X86]
1403                        Format: <integer>
1404                        Range: 0,7 : spare reg number
1405                        Default : 1
1406                        Used for mtrr cleanup. It is spare mtrr entries number.
1407                        Set to 2 or more if your graphical card needs more.
1408
1409        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
1410
1411        NCR_D700=       [HW,SCSI]
1412                        See header of drivers/scsi/NCR_D700.c.
1413
1414        ncr5380=        [HW,SCSI]
1415
1416        ncr53c400=      [HW,SCSI]
1417
1418        ncr53c400a=     [HW,SCSI]
1419
1420        ncr53c406a=     [HW,SCSI]
1421
1422        ncr53c8xx=      [HW,SCSI]
1423
1424        netdev=         [NET] Network devices parameters
1425                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1426                        Note that mem_start is often overloaded to mean
1427                        something different and driver-specific.
1428                        This usage is only documented in each driver source
1429                        file if at all.
1430
1431        nf_conntrack.acct=
1432                        [NETFILTER] Enable connection tracking flow accounting
1433                        0 to disable accounting
1434                        1 to enable accounting
1435                        Default value depends on CONFIG_NF_CT_ACCT that is
1436                        going to be removed in 2.6.29.
1437
1438        nfsaddrs=       [NFS]
1439                        See Documentation/filesystems/nfsroot.txt.
1440
1441        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
1442                        See Documentation/filesystems/nfsroot.txt.
1443
1444        nfs.callback_tcpport=
1445                        [NFS] set the TCP port on which the NFSv4 callback
1446                        channel should listen.
1447
1448        nfs.idmap_cache_timeout=
1449                        [NFS] set the maximum lifetime for idmapper cache
1450                        entries.
1451
1452        nfs.enable_ino64=
1453                        [NFS] enable 64-bit inode numbers.
1454                        If zero, the NFS client will fake up a 32-bit inode
1455                        number for the readdir() and stat() syscalls instead
1456                        of returning the full 64-bit number.
1457                        The default is to return 64-bit inode numbers.
1458
1459        nmi_debug=      [KNL,AVR32] Specify one or more actions to take
1460                        when a NMI is triggered.
1461                        Format: [state][,regs][,debounce][,die]
1462
1463        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
1464                        Format: [panic,][num]
1465                        Valid num: 0,1,2
1466                        0 - turn nmi_watchdog off
1467                        1 - use the IO-APIC timer for the NMI watchdog
1468                        2 - use the local APIC for the NMI watchdog using
1469                        a performance counter. Note: This will use one
1470                        performance counter and the local APIC's performance
1471                        vector.
1472                        When panic is specified, panic when an NMI watchdog
1473                        timeout occurs.
1474                        This is useful when you use a panic=... timeout and
1475                        need the box quickly up again.
1476                        Instead of 1 and 2 it is possible to use the following
1477                        symbolic names: lapic and ioapic
1478                        Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1479
1480        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
1481                        emulation library even if a 387 maths coprocessor
1482                        is present.
1483
1484        no_console_suspend
1485                        [HW] Never suspend the console
1486                        Disable suspending of consoles during suspend and
1487                        hibernate operations.  Once disabled, debugging
1488                        messages can reach various consoles while the rest
1489                        of the system is being put to sleep (ie, while
1490                        debugging driver suspend/resume hooks).  This may
1491                        not work reliably with all consoles, but is known
1492                        to work with serial and VGA consoles.
1493
1494        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
1495                        caches in the slab allocator.  Saves per-node memory,
1496                        but will impact performance.
1497
1498        noalign         [KNL,ARM]
1499
1500        noapic          [SMP,APIC] Tells the kernel to not make use of any
1501                        IOAPICs that may be present in the system.
1502
1503        nobats          [PPC] Do not use BATs for mapping kernel lowmem
1504                        on "Classic" PPC cores.
1505
1506        nocache         [ARM]
1507
1508        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction
1509
1510        nodelayacct     [KNL] Disable per-task delay accounting
1511
1512        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1513
1514        nodsp           [SH] Disable hardware DSP at boot time.
1515
1516        noefi           [X86] Disable EFI runtime services support.
1517
1518        noexec          [IA-64]
1519
1520        noexec          [X86]
1521                        On X86-32 available only on PAE configured kernels.
1522                        noexec=on: enable non-executable mappings (default)
1523                        noexec=off: disable non-executable mappings
1524
1525        noexec32        [X86-64]
1526                        This affects only 32-bit executables.
1527                        noexec32=on: enable non-executable mappings (default)
1528                                read doesn't imply executable mappings
1529                        noexec32=off: disable non-executable mappings
1530                                read implies executable mappings
1531
1532        nofpu           [SH] Disable hardware FPU at boot time.
1533
1534        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
1535                        register save and restore. The kernel will only save
1536                        legacy floating-point registers on task switch.
1537
1538        noxsave         [BUGS=X86] Disables x86 extended register state save
1539                        and restore using xsave. The kernel will fallback to
1540                        enabling legacy floating-point and sse state.
1541
1542        nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1543                        wfi(ARM) instruction doesn't work correctly and not to
1544                        use it. This is also useful when using JTAG debugger.
1545
1546        no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
1547                        instruction doesn't work correctly and not to
1548                        use it.
1549
1550        no_file_caps    Tells the kernel not to honor file capabilities.  The
1551                        only way then for a file to be executed with privilege
1552                        is to be setuid root or executed by root.
1553
1554        nohalt          [IA-64] Tells the kernel not to use the power saving
1555                        function PAL_HALT_LIGHT when idle. This increases
1556                        power-consumption. On the positive side, it reduces
1557                        interrupt wake-up latency, which may improve performance
1558                        in certain environments such as networked servers or
1559                        real-time systems.
1560
1561        nohz=           [KNL] Boottime enable/disable dynamic ticks
1562                        Valid arguments: on, off
1563                        Default: on
1564
1565        noiotrap        [SH] Disables trapped I/O port accesses.
1566
1567        noirqdebug      [X86-32] Disables the code which attempts to detect and
1568                        disable unhandled interrupt sources.
1569
1570        no_timer_check  [X86,APIC] Disables the code which tests for
1571                        broken timer IRQ sources.
1572
1573        noisapnp        [ISAPNP] Disables ISA PnP code.
1574
1575        noinitrd        [RAM] Tells the kernel not to load any configured
1576                        initial RAM disk.
1577
1578        nointroute      [IA-64]
1579
1580        nojitter        [IA64] Disables jitter checking for ITC timers.
1581
1582        nolapic         [X86-32,APIC] Do not enable or use the local APIC.
1583
1584        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.
1585
1586        noltlbs         [PPC] Do not use large page/tlb entries for kernel
1587                        lowmem mapping on PPC40x.
1588
1589        nomca           [IA-64] Disable machine check abort handling
1590
1591        nomce           [X86-32] Machine Check Exception
1592
1593        nomfgpt         [X86-32] Disable Multi-Function General Purpose
1594                        Timer usage (for AMD Geode machines).
1595
1596        norandmaps      Don't use address space randomization.  Equivalent to
1597                        echo 0 > /proc/sys/kernel/randomize_va_space
1598
1599        noreplace-paravirt      [X86-32,PV_OPS] Don't patch paravirt_ops
1600
1601        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
1602                        with UP alternatives
1603
1604        noresidual      [PPC] Don't use residual data on PReP machines.
1605
1606        noresume        [SWSUSP] Disables resume and restores original swap
1607                        space.
1608
1609        no-scroll       [VGA] Disables scrollback.
1610                        This is required for the Braillex ib80-piezo Braille
1611                        reader made by F.H. Papenmeier (Germany).
1612
1613        nosbagart       [IA-64]
1614
1615        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1616
1617        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
1618                        and disable the IO APIC.  legacy for "maxcpus=0".
1619
1620        nosoftlockup    [KNL] Disable the soft-lockup detector.
1621
1622        noswapaccount   [KNL] Disable accounting of swap in memory resource
1623                        controller. (See Documentation/cgroups/memory.txt)
1624
1625        nosync          [HW,M68K] Disables sync negotiation for all devices.
1626
1627        notsc           [BUGS=X86-32] Disable Time Stamp Counter
1628
1629        nousb           [USB] Disable the USB subsystem
1630
1631        nowb            [ARM]
1632
1633        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
1634
1635        nptcg=          [IA64] Override max number of concurrent global TLB
1636                        purges which is reported from either PAL_VM_SUMMARY or
1637                        SAL PALO.
1638
1639        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1640
1641        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1642                        one of ['zone', 'node', 'default'] can be specified
1643                        This can be set from sysctl after boot.
1644                        See Documentation/sysctl/vm.txt for details.
1645
1646        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
1647                        See Documentation/debugging-via-ohci1394.txt for more
1648                        info.
1649
1650        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1651                        Rather than timing out after 20 ms if an EC
1652                        command is not properly ACKed, override the length
1653                        of the timeout.  We have interrupts disabled while
1654                        waiting for the ACK, so if this is set too high
1655                        interrupts *may* be lost!
1656
1657        opl3=           [HW,OSS]
1658                        Format: <io>
1659
1660        oprofile.timer= [HW]
1661                        Use timer interrupt instead of performance counters
1662
1663        osst=           [HW,SCSI] SCSI Tape Driver
1664                        Format: <buffer_size>,<write_threshold>
1665                        See also Documentation/scsi/st.txt.
1666
1667        panic=          [KNL] Kernel behaviour on panic
1668                        Format: <timeout>
1669
1670        parkbd.port=    [HW] Parallel port number the keyboard adapter is
1671                        connected to, default is 0.
1672                        Format: <parport#>
1673        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
1674                        0 for XT, 1 for AT (default is AT).
1675                        Format: <mode>
1676
1677        parport=        [HW,PPT] Specify parallel ports. 0 disables.
1678                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1679                        Use 'auto' to force the driver to use any
1680                        IRQ/DMA settings detected (the default is to
1681                        ignore detected IRQ/DMA settings because of
1682                        possible conflicts). You can specify the base
1683                        address, IRQ, and DMA settings; IRQ and DMA
1684                        should be numbers, or 'auto' (for using detected
1685                        settings on that particular port), or 'nofifo'
1686                        (to avoid using a FIFO even if it is detected).
1687                        Parallel ports are assigned in the order they
1688                        are specified on the command line, starting
1689                        with parport0.
1690
1691        parport_init_mode=      [HW,PPT]
1692                        Configure VIA parallel port to operate in
1693                        a specific mode. This is necessary on Pegasos
1694                        computer where firmware has no options for setting
1695                        up parallel port mode and sets it to spp.
1696                        Currently this function knows 686a and 8231 chips.
1697                        Format: [spp|ps2|epp|ecp|ecpepp]
1698
1699        pas2=           [HW,OSS] Format:
1700                        <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1701
1702        pas16=          [HW,SCSI]
1703                        See header of drivers/scsi/pas16.c.
1704
1705        pause_on_oops=
1706                        Halt all CPUs after the first oops has been printed for
1707                        the specified number of seconds.  This is to be used if
1708                        your oopses keep scrolling off the screen.
1709
1710        pcbit=          [HW,ISDN]
1711
1712        pcd.            [PARIDE]
1713                        See header of drivers/block/paride/pcd.c.
1714                        See also Documentation/blockdev/paride.txt.
1715
1716        pci=option[,option...]  [PCI] various PCI subsystem options:
1717                earlydump       [X86] dump PCI config space before the kernel
1718                                changes anything
1719                off             [X86] don't probe for the PCI bus
1720                bios            [X86-32] force use of PCI BIOS, don't access
1721                                the hardware directly. Use this if your machine
1722                                has a non-standard PCI host bridge.
1723                nobios          [X86-32] disallow use of PCI BIOS, only direct
1724                                hardware access methods are allowed. Use this
1725                                if you experience crashes upon bootup and you
1726                                suspect they are caused by the BIOS.
1727                conf1           [X86] Force use of PCI Configuration
1728                                Mechanism 1.
1729                conf2           [X86] Force use of PCI Configuration
1730                                Mechanism 2.
1731                noaer           [PCIE] If the PCIEAER kernel config parameter is
1732                                enabled, this kernel boot option can be used to
1733                                disable the use of PCIE advanced error reporting.
1734                nodomains       [PCI] Disable support for multiple PCI
1735                                root domains (aka PCI segments, in ACPI-speak).
1736                nommconf        [X86] Disable use of MMCONFIG for PCI
1737                                Configuration
1738                nomsi           [MSI] If the PCI_MSI kernel config parameter is
1739                                enabled, this kernel boot option can be used to
1740                                disable the use of MSI interrupts system-wide.
1741                noioapicquirk   [APIC] Disable all boot interrupt quirks.
1742                                Safety option to keep boot IRQs enabled. This
1743                                should never be necessary.
1744                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
1745                                primary IO-APIC for bridges that cannot disable
1746                                boot IRQs. This fixes a source of spurious IRQs
1747                                when the system masks IRQs.
1748                noioapicreroute [APIC] Disable workaround that uses the
1749                                boot IRQ equivalent of an IRQ that connects to
1750                                a chipset where boot IRQs cannot be disabled.
1751                                The opposite of ioapicreroute.
1752                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
1753                                routing table. These calls are known to be buggy
1754                                on several machines and they hang the machine
1755                                when used, but on other computers it's the only
1756                                way to get the interrupt routing table. Try
1757                                this option if the kernel is unable to allocate
1758                                IRQs or discover secondary PCI buses on your
1759                                motherboard.
1760                rom             [X86] Assign address space to expansion ROMs.
1761                                Use with caution as certain devices share
1762                                address decoders between ROMs and other
1763                                resources.
1764                norom           [X86] Do not assign address space to
1765                                expansion ROMs that do not already have
1766                                BIOS assigned address ranges.
1767                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
1768                                assigned automatically to PCI devices. You can
1769                                make the kernel exclude IRQs of your ISA cards
1770                                this way.
1771                pirqaddr=0xAAAAA        [X86] Specify the physical address
1772                                of the PIRQ table (normally generated
1773                                by the BIOS) if it is outside the
1774                                F0000h-100000h range.
1775                lastbus=N       [X86] Scan all buses thru bus #N. Can be
1776                                useful if the kernel is unable to find your
1777                                secondary buses and you want to tell it
1778                                explicitly which ones they are.
1779                assign-busses   [X86] Always assign all PCI bus
1780                                numbers ourselves, overriding
1781                                whatever the firmware may have done.
1782                usepirqmask     [X86] Honor the possible IRQ mask stored
1783                                in the BIOS $PIR table. This is needed on
1784                                some systems with broken BIOSes, notably
1785                                some HP Pavilion N5400 and Omnibook XE3
1786                                notebooks. This will have no effect if ACPI
1787                                IRQ routing is enabled.
1788                noacpi          [X86] Do not use ACPI for IRQ routing
1789                                or for PCI scanning.
1790                use_crs         [X86] Use _CRS for PCI resource
1791                                allocation.
1792                routeirq        Do IRQ routing for all PCI devices.
1793                                This is normally done in pci_enable_device(),
1794                                so this option is a temporary workaround
1795                                for broken drivers that don't call it.
1796                skip_isa_align  [X86] do not align io start addr, so can
1797                                handle more pci cards
1798                firmware        [ARM] Do not re-enumerate the bus but instead
1799                                just use the configuration from the
1800                                bootloader. This is currently used on
1801                                IXP2000 systems where the bus has to be
1802                                configured a certain way for adjunct CPUs.
1803                noearly         [X86] Don't do any early type 1 scanning.
1804                                This might help on some broken boards which
1805                                machine check when some devices' config space
1806                                is read. But various workarounds are disabled
1807                                and some IOMMU drivers will not work.
1808                bfsort          Sort PCI devices into breadth-first order.
1809                                This sorting is done to get a device
1810                                order compatible with older (<= 2.4) kernels.
1811                nobfsort        Don't sort PCI devices into breadth-first order.
1812                cbiosize=nn[KMG]        The fixed amount of bus space which is
1813                                reserved for the CardBus bridge's IO window.
1814                                The default value is 256 bytes.
1815                cbmemsize=nn[KMG]       The fixed amount of bus space which is
1816                                reserved for the CardBus bridge's memory
1817                                window. The default value is 64 megabytes.
1818                resource_alignment=
1819                                Format:
1820                                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1821                                Specifies alignment and device to reassign
1822                                aligned memory resources.
1823                                If <order of align> is not specified,
1824                                PAGE_SIZE is used as alignment.
1825                                PCI-PCI bridge can be specified, if resource
1826                                windows need to be expanded.
1827
1828        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
1829                        Management.
1830                off     Disable ASPM.
1831                force   Enable ASPM even on devices that claim not to support it.
1832                        WARNING: Forcing ASPM on may cause system lockups.
1833
1834        pcmv=           [HW,PCMCIA] BadgePAD 4
1835
1836        pd.             [PARIDE]
1837                        See Documentation/blockdev/paride.txt.
1838
1839        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1840                        boot time.
1841                        Format: { 0 | 1 }
1842                        See arch/parisc/kernel/pdc_chassis.c
1843
1844        pf.             [PARIDE]
1845                        See Documentation/blockdev/paride.txt.
1846
1847        pg.             [PARIDE]
1848                        See Documentation/blockdev/paride.txt.
1849
1850        pirq=           [SMP,APIC] Manual mp-table setup
1851                        See Documentation/x86/i386/IO-APIC.txt.
1852
1853        plip=           [PPT,NET] Parallel port network link
1854                        Format: { parport<nr> | timid | 0 }
1855                        See also Documentation/parport.txt.
1856
1857        pmtmr=          [X86] Manual setup of pmtmr I/O Port. 
1858                        Override pmtimer IOPort with a hex value.
1859                        e.g. pmtmr=0x508
1860
1861        pnp.debug       [PNP]
1862                        Enable PNP debug messages.  This depends on the
1863                        CONFIG_PNP_DEBUG_MESSAGES option.
1864
1865        pnpacpi=        [ACPI]
1866                        { off }
1867
1868        pnpbios=        [ISAPNP]
1869                        { on | off | curr | res | no-curr | no-res }
1870
1871        pnp_reserve_irq=
1872                        [ISAPNP] Exclude IRQs for the autoconfiguration
1873
1874        pnp_reserve_dma=
1875                        [ISAPNP] Exclude DMAs for the autoconfiguration
1876
1877        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1878                        Ranges are in pairs (I/O port base and size).
1879
1880        pnp_reserve_mem=
1881                        [ISAPNP] Exclude memory regions for the
1882                        autoconfiguration.
1883                        Ranges are in pairs (memory base and size).
1884
1885        ports=          [IP_VS_FTP] IPVS ftp helper module
1886                        Default is 21.
1887                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
1888                        may be specified.
1889                        Format: <port>,<port>....
1890
1891        print-fatal-signals=
1892                        [KNL] debug: print fatal signals
1893                        print-fatal-signals=1: print segfault info to
1894                        the kernel console.
1895                        default: off.
1896
1897        printk.time=    Show timing data prefixed to each printk message line
1898                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
1899
1900        processor.max_cstate=   [HW,ACPI]
1901                        Limit processor to maximum C-state
1902                        max_cstate=9 overrides any DMI blacklist limit.
1903
1904        processor.nocst [HW,ACPI]
1905                        Ignore the _CST method to determine C-states,
1906                        instead using the legacy FADT method
1907
1908        profile=        [KNL] Enable kernel profiling via /proc/profile
1909                        Format: [schedule,]<number>
1910                        Param: "schedule" - profile schedule points.
1911                        Param: <number> - step/bucket size as a power of 2 for
1912                                statistical time based profiling.
1913                        Param: "sleep" - profile D-state sleeping (millisecs).
1914                                Requires CONFIG_SCHEDSTATS
1915                        Param: "kvm" - profile VM exits.
1916
1917        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1918                        before loading.
1919                        See Documentation/blockdev/ramdisk.txt.
1920
1921        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
1922                        probe for; one of (bare|imps|exps|lifebook|any).
1923        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
1924                        per second.
1925        psmouse.resetafter=     [HW,MOUSE]
1926                        Try to reset the device after so many bad packets
1927                        (0 = never).
1928        psmouse.resolution=
1929                        [HW,MOUSE] Set desired mouse resolution, in dpi.
1930        psmouse.smartscroll=
1931                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1932                        0 = disabled, 1 = enabled (default).
1933
1934        pss=            [HW,OSS] Personal Sound System (ECHO ESC614)
1935                        Format:
1936                        <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1937
1938        pt.             [PARIDE]
1939                        See Documentation/blockdev/paride.txt.
1940
1941        pty.legacy_count=
1942                        [KNL] Number of legacy pty's. Overwrites compiled-in
1943                        default number.
1944
1945        quiet           [KNL] Disable most log messages
1946
1947        r128=           [HW,DRM]
1948
1949        raid=           [HW,RAID]
1950                        See Documentation/md.txt.
1951
1952        ramdisk_blocksize=      [RAM]
1953                        See Documentation/blockdev/ramdisk.txt.
1954
1955        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
1956                        See Documentation/blockdev/ramdisk.txt.
1957
1958        rcupdate.blimit=        [KNL,BOOT]
1959                        Set maximum number of finished RCU callbacks to process
1960                        in one batch.
1961
1962        rcupdate.qhimark=       [KNL,BOOT]
1963                        Set threshold of queued
1964                        RCU callbacks over which batch limiting is disabled.
1965
1966        rcupdate.qlowmark=      [KNL,BOOT]
1967                        Set threshold of queued RCU callbacks below which
1968                        batch limiting is re-enabled.
1969
1970        rdinit=         [KNL]
1971                        Format: <full_path>
1972                        Run specified binary instead of /init from the ramdisk,
1973                        used for early userspace startup. See initrd.
1974
1975        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1976                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
1977                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1978
1979        relax_domain_level=
1980                        [KNL, SMP] Set scheduler's default relax_domain_level.
1981                        See Documentation/cgroups/cpusets.txt.
1982
1983        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
1984
1985        reservetop=     [X86-32]
1986                        Format: nn[KMG]
1987                        Reserves a hole at the top of the kernel virtual
1988                        address space.
1989
1990        reset_devices   [KNL] Force drivers to reset the underlying device
1991                        during initialization.
1992
1993        resume=         [SWSUSP]
1994                        Specify the partition device for software suspend
1995
1996        resume_offset=  [SWSUSP]
1997                        Specify the offset from the beginning of the partition
1998                        given by "resume=" at which the swap header is located,
1999                        in <PAGE_SIZE> units (needed only for swap files).
2000                        See  Documentation/power/swsusp-and-swap-files.txt
2001
2002        retain_initrd   [RAM] Keep initrd memory after extraction
2003
2004        rhash_entries=  [KNL,NET]
2005                        Set number of hash buckets for route cache
2006
2007        riscom8=        [HW,SERIAL]
2008                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2009
2010        ro              [KNL] Mount root device read-only on boot
2011
2012        root=           [KNL] Root filesystem
2013
2014        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
2015                        mount the root filesystem
2016
2017        rootflags=      [KNL] Set root filesystem mount option string
2018
2019        rootfstype=     [KNL] Set root filesystem type
2020
2021        rootwait        [KNL] Wait (indefinitely) for root device to show up.
2022                        Useful for devices that are detected asynchronously
2023                        (e.g. USB and MMC devices).
2024
2025        root_plug.vendor_id=
2026                        [ROOTPLUG] Override the default vendor ID
2027
2028        root_plug.product_id=
2029                        [ROOTPLUG] Override the default product ID
2030
2031        root_plug.debug=
2032                        [ROOTPLUG] Enable debugging output
2033
2034        rw              [KNL] Mount root device read-write on boot
2035
2036        S               [KNL] Run init in single mode
2037
2038        sa1100ir        [NET]
2039                        See drivers/net/irda/sa1100_ir.c.
2040
2041        sbni=           [NET] Granch SBNI12 leased line adapter
2042
2043        sc1200wdt=      [HW,WDT] SC1200 WDT (watchdog) driver
2044                        Format: <io>[,<timeout>[,<isapnp>]]
2045
2046        scsi_debug_*=   [SCSI]
2047                        See drivers/scsi/scsi_debug.c.
2048
2049        scsi_default_dev_flags=
2050                        [SCSI] SCSI default device flags
2051                        Format: <integer>
2052
2053        scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2054                        Format: <vendor>:<model>:<flags>
2055                        (flags are integer value)
2056
2057        scsi_logging_level=     [SCSI] a bit mask of logging levels
2058                        See drivers/scsi/scsi_logging.h for bits.  Also
2059                        settable via sysctl at dev.scsi.logging_level
2060                        (/proc/sys/dev/scsi/logging_level).
2061                        There is also a nice 'scsi_logging_level' script in the
2062                        S390-tools package, available for download at
2063                        http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2064
2065        scsi_mod.scan=  [SCSI] sync (default) scans SCSI busses as they are
2066                        discovered.  async scans them in kernel threads,
2067                        allowing boot to proceed.  none ignores them, expecting
2068                        user space to do the scan.
2069
2070        security=       [SECURITY] Choose a security module to enable at boot.
2071                        If this boot parameter is not specified, only the first
2072                        security module asking for security registration will be
2073                        loaded. An invalid security module name will be treated
2074                        as if no module has been chosen.
2075
2076        selinux=        [SELINUX] Disable or enable SELinux at boot time.
2077                        Format: { "0" | "1" }
2078                        See security/selinux/Kconfig help text.
2079                        0 -- disable.
2080                        1 -- enable.
2081                        Default value is set via kernel config option.
2082                        If enabled at boot time, /selinux/disable can be used
2083                        later to disable prior to initial policy load.
2084
2085        serialnumber    [BUGS=X86-32]
2086
2087        shapers=        [NET]
2088                        Maximal number of shapers.
2089
2090        show_msr=       [x86] show boot-time MSR settings
2091                        Format: { <integer> }
2092                        Show boot-time (BIOS-initialized) MSR settings.
2093                        The parameter means the number of CPUs to show,
2094                        for example 1 means boot CPU only.
2095
2096        sim710=         [SCSI,HW]
2097                        See header of drivers/scsi/sim710.c.
2098
2099        simeth=         [IA-64]
2100        simscsi=
2101
2102        slram=          [HW,MTD]
2103
2104        slub_debug[=options[,slabs]]    [MM, SLUB]
2105                        Enabling slub_debug allows one to determine the
2106                        culprit if slab objects become corrupted. Enabling
2107                        slub_debug can create guard zones around objects and
2108                        may poison objects when not in use. Also tracks the
2109                        last alloc / free. For more information see
2110                        Documentation/vm/slub.txt.
2111
2112        slub_max_order= [MM, SLUB]
2113                        Determines the maximum allowed order for slabs.
2114                        A high setting may cause OOMs due to memory
2115                        fragmentation. For more information see
2116                        Documentation/vm/slub.txt.
2117
2118        slub_min_objects=       [MM, SLUB]
2119                        The minimum number of objects per slab. SLUB will
2120                        increase the slab order up to slub_max_order to
2121                        generate a sufficiently large slab able to contain
2122                        the number of objects indicated. The higher the number
2123                        of objects the smaller the overhead of tracking slabs
2124                        and the less frequently locks need to be acquired.
2125                        For more information see Documentation/vm/slub.txt.
2126
2127        slub_min_order= [MM, SLUB]
2128                        Determines the mininum page order for slabs. Must be
2129                        lower than slub_max_order.
2130                        For more information see Documentation/vm/slub.txt.
2131
2132        slub_nomerge    [MM, SLUB]
2133                        Disable merging of slabs with similar size. May be
2134                        necessary if there is some reason to distinguish
2135                        allocs to different slabs. Debug options disable
2136                        merging on their own.
2137                        For more information see Documentation/vm/slub.txt.
2138
2139        smart2=         [HW]
2140                        Format: <io1>[,<io2>[,...,<io8>]]
2141
2142        smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
2143                        attempt to substitute SMP alternatives once at boot.
2144
2145        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
2146        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
2147        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
2148        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
2149        smsc-ircc2.ircc_irq=    [HW] IRQ line
2150        smsc-ircc2.ircc_dma=    [HW] DMA channel
2151        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2152                                0: Toshiba Satellite 1800 (GP data pin select)
2153                                1: Fast pin select (default)
2154                                2: ATC IRMode
2155
2156        snd-ad1816a=    [HW,ALSA]
2157
2158        snd-ad1848=     [HW,ALSA]
2159
2160        snd-ali5451=    [HW,ALSA]
2161
2162        snd-als100=     [HW,ALSA]
2163
2164        snd-als4000=    [HW,ALSA]
2165
2166        snd-azt2320=    [HW,ALSA]
2167
2168        snd-cmi8330=    [HW,ALSA]
2169
2170        snd-cmipci=     [HW,ALSA]
2171
2172        snd-cs4231=     [HW,ALSA]
2173
2174        snd-cs4232=     [HW,ALSA]
2175
2176        snd-cs4236=     [HW,ALSA]
2177
2178        snd-cs4281=     [HW,ALSA]
2179
2180        snd-cs46xx=     [HW,ALSA]
2181
2182        snd-dt019x=     [HW,ALSA]
2183
2184        snd-dummy=      [HW,ALSA]
2185
2186        snd-emu10k1=    [HW,ALSA]
2187
2188        snd-ens1370=    [HW,ALSA]
2189
2190        snd-ens1371=    [HW,ALSA]
2191
2192        snd-es968=      [HW,ALSA]
2193
2194        snd-es1688=     [HW,ALSA]
2195
2196        snd-es18xx=     [HW,ALSA]
2197
2198        snd-es1938=     [HW,ALSA]
2199
2200        snd-es1968=     [HW,ALSA]
2201
2202        snd-fm801=      [HW,ALSA]
2203
2204        snd-gusclassic= [HW,ALSA]
2205
2206        snd-gusextreme= [HW,ALSA]
2207
2208        snd-gusmax=     [HW,ALSA]
2209
2210        snd-hdsp=       [HW,ALSA]
2211
2212        snd-ice1712=    [HW,ALSA]
2213
2214        snd-intel8x0=   [HW,ALSA]
2215
2216        snd-interwave=  [HW,ALSA]
2217
2218        snd-interwave-stb=
2219                        [HW,ALSA]
2220
2221        snd-korg1212=   [HW,ALSA]
2222
2223        snd-maestro3=   [HW,ALSA]
2224
2225        snd-mpu401=     [HW,ALSA]
2226
2227        snd-mtpav=      [HW,ALSA]
2228
2229        snd-nm256=      [HW,ALSA]
2230
2231        snd-opl3sa2=    [HW,ALSA]
2232
2233        snd-opti92x-ad1848=
2234                        [HW,ALSA]
2235
2236        snd-opti92x-cs4231=
2237                        [HW,ALSA]
2238
2239        snd-opti93x=    [HW,ALSA]
2240
2241        snd-pmac=       [HW,ALSA]
2242
2243        snd-rme32=      [HW,ALSA]
2244
2245        snd-rme96=      [HW,ALSA]
2246
2247        snd-rme9652=    [HW,ALSA]
2248
2249        snd-sb8=        [HW,ALSA]
2250
2251        snd-sb16=       [HW,ALSA]
2252
2253        snd-sbawe=      [HW,ALSA]
2254
2255        snd-serial=     [HW,ALSA]
2256
2257        snd-sgalaxy=    [HW,ALSA]
2258
2259        snd-sonicvibes= [HW,ALSA]
2260
2261        snd-sun-amd7930=
2262                        [HW,ALSA]
2263
2264        snd-sun-cs4231= [HW,ALSA]
2265
2266        snd-trident=    [HW,ALSA]
2267
2268        snd-usb-audio=  [HW,ALSA,USB]
2269
2270        snd-via82xx=    [HW,ALSA]
2271
2272        snd-virmidi=    [HW,ALSA]
2273
2274        snd-wavefront=  [HW,ALSA]
2275
2276        snd-ymfpci=     [HW,ALSA]
2277
2278        softlockup_panic=
2279                        [KNL] Should the soft-lockup detector generate panics.
2280
2281        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
2282                        See Documentation/sonypi.txt
2283
2284        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
2285                        See Documentation/serial/specialix.txt.
2286
2287        spia_io_base=   [HW,MTD]
2288        spia_fio_base=
2289        spia_pedr=
2290        spia_peddr=
2291
2292        sscape=         [HW,OSS]
2293                        Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2294
2295        st=             [HW,SCSI] SCSI tape parameters (buffers, etc.)
2296                        See Documentation/scsi/st.txt.
2297
2298        stacktrace      [FTRACE]
2299                        Enabled the stack tracer on boot up.
2300
2301        sti=            [PARISC,HW]
2302                        Format: <num>
2303                        Set the STI (builtin display/keyboard on the HP-PARISC
2304                        machines) console (graphic card) which should be used
2305                        as the initial boot-console.
2306                        See also comment in drivers/video/console/sticore.c.
2307
2308        sti_font=       [HW]
2309                        See comment in drivers/video/console/sticore.c.
2310
2311        stifb=          [HW]
2312                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2313
2314        sunrpc.pool_mode=
2315                        [NFS]
2316                        Control how the NFS server code allocates CPUs to
2317                        service thread pools.  Depending on how many NICs
2318                        you have and where their interrupts are bound, this
2319                        option will affect which CPUs will do NFS serving.
2320                        Note: this parameter cannot be changed while the
2321                        NFS server is running.
2322
2323                        auto        the server chooses an appropriate mode
2324                                    automatically using heuristics
2325                        global      a single global pool contains all CPUs
2326                        percpu      one pool for each CPU
2327                        pernode     one pool for each NUMA node (equivalent
2328                                    to global on non-NUMA machines)
2329
2330        swiotlb=        [IA-64] Number of I/O TLB slabs
2331
2332        switches=       [HW,M68k]
2333
2334        sym53c416=      [HW,SCSI]
2335                        See header of drivers/scsi/sym53c416.c.
2336
2337        sysrq_always_enabled
2338                        [KNL]
2339                        Ignore sysrq setting - this boot parameter will
2340                        neutralize any effect of /proc/sys/kernel/sysrq.
2341                        Useful for debugging.
2342
2343        t128=           [HW,SCSI]
2344                        See header of drivers/scsi/t128.c.
2345
2346        tdfx=           [HW,DRM]
2347
2348        test_suspend=   [SUSPEND]
2349                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
2350                        standby suspend) as the system sleep state to briefly
2351                        enter during system startup.  The system is woken from
2352                        this state using a wakeup-capable RTC alarm.
2353
2354        thash_entries=  [KNL,NET]
2355                        Set number of hash buckets for TCP connection
2356
2357        thermal.act=    [HW,ACPI]
2358                        -1: disable all active trip points in all thermal zones
2359                        <degrees C>: override all lowest active trip points
2360
2361        thermal.crt=    [HW,ACPI]
2362                        -1: disable all critical trip points in all thermal zones
2363                        <degrees C>: override all critical trip points
2364
2365        thermal.nocrt=  [HW,ACPI]
2366                        Set to disable actions on ACPI thermal zone
2367                        critical and hot trip points.
2368
2369        thermal.off=    [HW,ACPI]
2370                        1: disable ACPI thermal control
2371
2372        thermal.psv=    [HW,ACPI]
2373                        -1: disable all passive trip points
2374                        <degrees C>: override all passive trip points to this
2375                        value
2376
2377        thermal.tzp=    [HW,ACPI]
2378                        Specify global default ACPI thermal zone polling rate
2379                        <deci-seconds>: poll all this frequency
2380                        0: no polling (default)
2381
2382        tmscsim=        [HW,SCSI]
2383                        See comment before function dc390_setup() in
2384                        drivers/scsi/tmscsim.c.
2385
2386        topology=       [S390]
2387                        Format: {off | on}
2388                        Specify if the kernel should make use of the cpu
2389                        topology informations if the hardware supports these.
2390                        The scheduler will make use of these informations and
2391                        e.g. base its process migration decisions on it.
2392                        Default is off.
2393
2394        tp720=          [HW,PS2]
2395
2396        trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2397
2398        trix=           [HW,OSS] MediaTrix AudioTrix Pro
2399                        Format:
2400                        <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2401
2402        tsc=            Disable clocksource-must-verify flag for TSC.
2403                        Format: <string>
2404                        [x86] reliable: mark tsc clocksource as reliable, this
2405                        disables clocksource verification at runtime.
2406                        Used to enable high-resolution timer mode on older
2407                        hardware, and in virtualized environment.
2408
2409        turbografx.map[2|3]=    [HW,JOY]
2410                        TurboGraFX parallel port interface
2411                        Format:
2412                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2413                        See also Documentation/input/joystick-parport.txt
2414
2415        u14-34f=        [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2416                        See header of drivers/scsi/u14-34f.c.
2417
2418        uart401=        [HW,OSS]
2419                        Format: <io>,<irq>
2420
2421        uart6850=       [HW,OSS]
2422                        Format: <io>,<irq>
2423
2424        uhci-hcd.ignore_oc=
2425                        [USB] Ignore overcurrent events (default N).
2426                        Some badly-designed motherboards generate lots of
2427                        bogus events, for ports that aren't wired to
2428                        anything.  Set this parameter to avoid log spamming.
2429                        Note that genuine overcurrent events won't be
2430                        reported either.
2431
2432        unknown_nmi_panic
2433                        [X86]
2434                        Set unknown_nmi_panic=1 early on boot.
2435
2436        usbcore.autosuspend=
2437                        [USB] The autosuspend time delay (in seconds) used
2438                        for newly-detected USB devices (default 2).  This
2439                        is the time required before an idle device will be
2440                        autosuspended.  Devices for which the delay is set
2441                        to a negative value won't be autosuspended at all.
2442
2443        usbcore.usbfs_snoop=
2444                        [USB] Set to log all usbfs traffic (default 0 = off).
2445
2446        usbcore.blinkenlights=
2447                        [USB] Set to cycle leds on hubs (default 0 = off).
2448
2449        usbcore.old_scheme_first=
2450                        [USB] Start with the old device initialization
2451                        scheme (default 0 = off).
2452
2453        usbcore.use_both_schemes=
2454                        [USB] Try the other device initialization scheme
2455                        if the first one fails (default 1 = enabled).
2456
2457        usbcore.initial_descriptor_timeout=
2458                        [USB] Specifies timeout for the initial 64-byte
2459                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2460                        (default 5000 = 5.0 seconds).
2461
2462        usbhid.mousepoll=
2463                        [USBHID] The interval which mice are to be polled at.
2464
2465        usb-storage.delay_use=
2466                        [UMS] The delay in seconds before a new device is
2467                        scanned for Logical Units (default 5).
2468
2469        usb-storage.quirks=
2470                        [UMS] A list of quirks entries to supplement or
2471                        override the built-in unusual_devs list.  List
2472                        entries are separated by commas.  Each entry has
2473                        the form VID:PID:Flags where VID and PID are Vendor
2474                        and Product ID values (4-digit hex numbers) and
2475                        Flags is a set of characters, each corresponding
2476                        to a common usb-storage quirk flag as follows:
2477                                a = SANE_SENSE (collect more than 18 bytes
2478                                        of sense data);
2479                                c = FIX_CAPACITY (decrease the reported
2480                                        device capacity by one sector);
2481                                h = CAPACITY_HEURISTICS (decrease the
2482                                        reported device capacity by one
2483                                        sector if the number is odd);
2484                                i = IGNORE_DEVICE (don't bind to this
2485                                        device);
2486                                l = NOT_LOCKABLE (don't try to lock and
2487                                        unlock ejectable media);
2488                                m = MAX_SECTORS_64 (don't transfer more
2489                                        than 64 sectors = 32 KB at a time);
2490                                o = CAPACITY_OK (accept the capacity
2491                                        reported by the device);
2492                                r = IGNORE_RESIDUE (the device reports
2493                                        bogus residue values);
2494                                s = SINGLE_LUN (the device has only one
2495                                        Logical Unit);
2496                                w = NO_WP_DETECT (don't test whether the
2497                                        medium is write-protected).
2498                        Example: quirks=0419:aaf5:rl,0421:0433:rc
2499
2500        vdso=           [X86,SH]
2501                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2502                        vdso=1: enable VDSO (default)
2503                        vdso=0: disable VDSO mapping
2504
2505        vdso32=         [X86]
2506                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2507                        vdso32=1: enable 32-bit VDSO (default)
2508                        vdso32=0: disable 32-bit VDSO mapping
2509
2510        vector=         [IA-64,SMP]
2511                        vector=percpu: enable percpu vector domain
2512
2513        video=          [FB] Frame buffer configuration
2514                        See Documentation/fb/modedb.txt.
2515
2516        vga=            [BOOT,X86-32] Select a particular video mode
2517                        See Documentation/x86/boot.txt and
2518                        Documentation/svga.txt.
2519                        Use vga=ask for menu.
2520                        This is actually a boot loader parameter; the value is
2521                        passed to the kernel using a special protocol.
2522
2523        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2524                        size of <nn>. This can be used to increase the
2525                        minimum size (128MB on x86). It can also be used to
2526                        decrease the size and leave more room for directly
2527                        mapped kernel RAM.
2528
2529        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
2530                        Format: <command>
2531
2532        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
2533                        Format: <command>
2534
2535        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
2536                        Format: <command>
2537
2538        vt.default_blu= [VT]
2539                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2540                        Change the default blue palette of the console.
2541                        This is a 16-member array composed of values
2542                        ranging from 0-255.
2543
2544        vt.default_grn= [VT]
2545                        Format: <green0>,<green1>,<green2>,...,<green15>
2546                        Change the default green palette of the console.
2547                        This is a 16-member array composed of values
2548                        ranging from 0-255.
2549
2550        vt.default_red= [VT]
2551                        Format: <red0>,<red1>,<red2>,...,<red15>
2552                        Change the default red palette of the console.
2553                        This is a 16-member array composed of values
2554                        ranging from 0-255.
2555
2556        vt.default_utf8=
2557                        [VT]
2558                        Format=<0|1>
2559                        Set system-wide default UTF-8 mode for all tty's.
2560                        Default is 1, i.e. UTF-8 mode is enabled for all
2561                        newly opened terminals.
2562
2563        waveartist=     [HW,OSS]
2564                        Format: <io>,<irq>,<dma>,<dma2>
2565
2566        wd33c93=        [HW,SCSI]
2567                        See header of drivers/scsi/wd33c93.c.
2568
2569        wd7000=         [HW,SCSI]
2570                        See header of drivers/scsi/wd7000.c.
2571
2572        wdt=            [WDT] Watchdog
2573                        See Documentation/watchdog/wdt.txt.
2574
2575        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
2576                        default x2apic cluster mode on platforms
2577                        supporting x2apic.
2578
2579        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2580        xd_geo=         See header of drivers/block/xd.c.
2581
2582        xirc2ps_cs=     [NET,PCMCIA]
2583                        Format:
2584                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2585
2586______________________________________________________________________
2587
2588TODO:
2589
2590        Add documentation for ALSA options.
2591        Add more DRM drivers.
2592
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