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        GCOV    GCOV profiling is enabled.
  52        HW      Appropriate hardware is enabled.
  53        IA-64   IA-64 architecture is enabled.
  54        IMA     Integrity measurement architecture is enabled.
  55        IOSCHED More than one I/O scheduler is enabled.
  56        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
  57        IPV6    IPv6 support is enabled.
  58        ISAPNP  ISA PnP code is enabled.
  59        ISDN    Appropriate ISDN support is enabled.
  60        JOY     Appropriate joystick support is enabled.
  61        KGDB    Kernel debugger support is enabled.
  62        KVM     Kernel Virtual Machine support is enabled.
  63        LIBATA  Libata driver is enabled
  64        LP      Printer support is enabled.
  65        LOOP    Loopback device support is enabled.
  66        M68k    M68k architecture is enabled.
  67                        These options have more detailed description inside of
  68                        Documentation/m68k/kernel-options.txt.
  69        MCA     MCA bus support is enabled.
  70        MDA     MDA console support is enabled.
  71        MOUSE   Appropriate mouse support is enabled.
  72        MSI     Message Signaled Interrupts (PCI).
  73        MTD     MTD (Memory Technology Device) support is enabled.
  74        NET     Appropriate network support is enabled.
  75        NUMA    NUMA support is enabled.
  76        NFS     Appropriate NFS support is enabled.
  77        OSS     OSS sound support is enabled.
  78        PV_OPS  A paravirtualized kernel is enabled.
  79        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
  80        PARISC  The PA-RISC architecture is enabled.
  81        PCI     PCI bus support is enabled.
  82        PCIE    PCI Express support is enabled.
  83        PCMCIA  The PCMCIA subsystem is enabled.
  84        PNP     Plug & Play support is enabled.
  85        PPC     PowerPC architecture is enabled.
  86        PPT     Parallel port support is enabled.
  87        PS2     Appropriate PS/2 support is enabled.
  88        RAM     RAM disk support is enabled.
  89        S390    S390 architecture is enabled.
  90        SCSI    Appropriate SCSI support is enabled.
  91                        A lot of drivers have their options described inside
  92                        the Documentation/scsi/ sub-directory.
  93        SECURITY Different security models are enabled.
  94        SELINUX SELinux support is enabled.
  95        APPARMOR AppArmor support is enabled.
  96        SERIAL  Serial support is enabled.
  97        SH      SuperH architecture is enabled.
  98        SMP     The kernel is an SMP kernel.
  99        SPARC   Sparc architecture is enabled.
 100        SWSUSP  Software suspend (hibernation) is enabled.
 101        SUSPEND System suspend states are enabled.
 102        FTRACE  Function tracing enabled.
 103        TPM     TPM drivers are enabled.
 104        TS      Appropriate touchscreen support is enabled.
 105        UMS     USB Mass Storage support is enabled.
 106        USB     USB support is enabled.
 107        USBHID  USB Human Interface Device support is enabled.
 108        V4L     Video For Linux support is enabled.
 109        VGA     The VGA console has been enabled.
 110        VT      Virtual terminal support is enabled.
 111        WDT     Watchdog support is enabled.
 112        XT      IBM PC/XT MFM hard disk support is enabled.
 113        X86-32  X86-32, aka i386 architecture is enabled.
 114        X86-64  X86-64 architecture is enabled.
 115                        More X86-64 boot options can be found in
 116                        Documentation/x86/x86_64/boot-options.txt .
 117        X86     Either 32bit or 64bit x86 (same as X86-32+X86-64)
 118        XEN     Xen support is enabled
 119
 120In addition, the following text indicates that the option:
 121
 122        BUGS=   Relates to possible processor bugs on the said processor.
 123        KNL     Is a kernel start-up parameter.
 124        BOOT    Is a boot loader parameter.
 125
 126Parameters denoted with BOOT are actually interpreted by the boot
 127loader, and have no meaning to the kernel directly.
 128Do not modify the syntax of boot loader parameters without extreme
 129need or coordination with <Documentation/x86/boot.txt>.
 130
 131There are also arch-specific kernel-parameters not documented here.
 132See for example <Documentation/x86/x86_64/boot-options.txt>.
 133
 134Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
 135a trailing = on the name of any parameter states that that parameter will
 136be entered as an environment variable, whereas its absence indicates that
 137it will appear as a kernel argument readable via /proc/cmdline by programs
 138running once the system is up.
 139
 140The number of kernel parameters is not limited, but the length of the
 141complete command line (parameters including spaces etc.) is limited to
 142a fixed number of characters. This limit depends on the architecture
 143and is between 256 and 4096 characters. It is defined in the file
 144./include/asm/setup.h as COMMAND_LINE_SIZE.
 145
 146
 147        acpi=           [HW,ACPI,X86]
 148                        Advanced Configuration and Power Interface
 149                        Format: { force | off | strict | noirq | rsdt }
 150                        force -- enable ACPI if default was off
 151                        off -- disable ACPI if default was on
 152                        noirq -- do not use ACPI for IRQ routing
 153                        strict -- Be less tolerant of platforms that are not
 154                                strictly ACPI specification compliant.
 155                        rsdt -- prefer RSDT over (default) XSDT
 156                        copy_dsdt -- copy DSDT to memory
 157
 158                        See also Documentation/power/pm.txt, pci=noacpi
 159
 160        acpi_apic_instance=     [ACPI, IOAPIC]
 161                        Format: <int>
 162                        2: use 2nd APIC table, if available
 163                        1,0: use 1st APIC table
 164                        default: 0
 165
 166        acpi_backlight= [HW,ACPI]
 167                        acpi_backlight=vendor
 168                        acpi_backlight=video
 169                        If set to vendor, prefer vendor specific driver
 170                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
 171                        of the ACPI video.ko driver.
 172
 173        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
 174        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
 175                        Format: <int>
 176                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
 177                        debug output.  Bits in debug_layer correspond to a
 178                        _COMPONENT in an ACPI source file, e.g.,
 179                            #define _COMPONENT ACPI_PCI_COMPONENT
 180                        Bits in debug_level correspond to a level in
 181                        ACPI_DEBUG_PRINT statements, e.g.,
 182                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
 183                        The debug_level mask defaults to "info".  See
 184                        Documentation/acpi/debug.txt for more information about
 185                        debug layers and levels.
 186
 187                        Enable processor driver info messages:
 188                            acpi.debug_layer=0x20000000
 189                        Enable PCI/PCI interrupt routing info messages:
 190                            acpi.debug_layer=0x400000
 191                        Enable AML "Debug" output, i.e., stores to the Debug
 192                        object while interpreting AML:
 193                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
 194                        Enable all messages related to ACPI hardware:
 195                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
 196
 197                        Some values produce so much output that the system is
 198                        unusable.  The "log_buf_len" parameter may be useful
 199                        if you need to capture more output.
 200
 201        acpi_display_output=    [HW,ACPI]
 202                        acpi_display_output=vendor
 203                        acpi_display_output=video
 204                        See above.
 205
 206        acpi_irq_balance [HW,ACPI]
 207                        ACPI will balance active IRQs
 208                        default in APIC mode
 209
 210        acpi_irq_nobalance [HW,ACPI]
 211                        ACPI will not move active IRQs (default)
 212                        default in PIC mode
 213
 214        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 215                        Format: <irq>,<irq>...
 216
 217        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
 218                        use by PCI
 219                        Format: <irq>,<irq>...
 220
 221        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT
 222
 223        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
 224                        Format: To spoof as Windows 98: ="Microsoft Windows"
 225
 226        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
 227                        acpi_osi="string1"      # add string1 -- only one string
 228                        acpi_osi="!string2"     # remove built-in string2
 229                        acpi_osi=               # disable all strings
 230
 231        acpi_pm_good    [X86]
 232                        Override the pmtimer bug detection: force the kernel
 233                        to assume that this machine's pmtimer latches its value
 234                        and always returns good values.
 235
 236        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
 237                        Format: { level | edge | high | low }
 238
 239        acpi_serialize  [HW,ACPI] force serialization of AML methods
 240
 241        acpi_skip_timer_override [HW,ACPI]
 242                        Recognize and ignore IRQ0/pin2 Interrupt Override.
 243                        For broken nForce2 BIOS resulting in XT-PIC timer.
 244
 245        acpi_sleep=     [HW,ACPI] Sleep options
 246                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
 247                                  old_ordering, s4_nonvs, sci_force_enable }
 248                        See Documentation/power/video.txt for information on
 249                        s3_bios and s3_mode.
 250                        s3_beep is for debugging; it makes the PC's speaker beep
 251                        as soon as the kernel's real-mode entry point is called.
 252                        s4_nohwsig prevents ACPI hardware signature from being
 253                        used during resume from hibernation.
 254                        old_ordering causes the ACPI 1.0 ordering of the _PTS
 255                        control method, with respect to putting devices into
 256                        low power states, to be enforced (the ACPI 2.0 ordering
 257                        of _PTS is used by default).
 258                        nonvs prevents the kernel from saving/restoring the
 259                        ACPI NVS memory during suspend/hibernation and resume.
 260                        sci_force_enable causes the kernel to set SCI_EN directly
 261                        on resume from S1/S3 (which is against the ACPI spec,
 262                        but some broken systems don't work without it).
 263
 264        acpi_use_timer_override [HW,ACPI]
 265                        Use timer override. For some broken Nvidia NF5 boards
 266                        that require a timer override, but don't have HPET
 267
 268        acpi_enforce_resources= [ACPI]
 269                        { strict | lax | no }
 270                        Check for resource conflicts between native drivers
 271                        and ACPI OperationRegions (SystemIO and SystemMemory
 272                        only). IO ports and memory declared in ACPI might be
 273                        used by the ACPI subsystem in arbitrary AML code and
 274                        can interfere with legacy drivers.
 275                        strict (default): access to resources claimed by ACPI
 276                        is denied; legacy drivers trying to access reserved
 277                        resources will fail to bind to device using them.
 278                        lax: access to resources claimed by ACPI is allowed;
 279                        legacy drivers trying to access reserved resources
 280                        will bind successfully but a warning message is logged.
 281                        no: ACPI OperationRegions are not marked as reserved,
 282                        no further checks are performed.
 283
 284        add_efi_memmap  [EFI; X86] Include EFI memory map in
 285                        kernel's map of available physical RAM.
 286
 287        agp=            [AGP]
 288                        { off | try_unsupported }
 289                        off: disable AGP support
 290                        try_unsupported: try to drive unsupported chipsets
 291                                (may crash computer or cause data corruption)
 292
 293        ALSA            [HW,ALSA]
 294                        See Documentation/sound/alsa/alsa-parameters.txt
 295
 296        alignment=      [KNL,ARM]
 297                        Allow the default userspace alignment fault handler
 298                        behaviour to be specified.  Bit 0 enables warnings,
 299                        bit 1 enables fixups, and bit 2 sends a segfault.
 300
 301        amd_iommu=      [HW,X86-84]
 302                        Pass parameters to the AMD IOMMU driver in the system.
 303                        Possible values are:
 304                        fullflush - enable flushing of IO/TLB entries when
 305                                    they are unmapped. Otherwise they are
 306                                    flushed before they will be reused, which
 307                                    is a lot of faster
 308                        off       - do not initialize any AMD IOMMU found in
 309                                    the system
 310
 311        amijoy.map=     [HW,JOY] Amiga joystick support
 312                        Map of devices attached to JOY0DAT and JOY1DAT
 313                        Format: <a>,<b>
 314                        See also Documentation/kernel/input/joystick.txt
 315
 316        analog.map=     [HW,JOY] Analog joystick and gamepad support
 317                        Specifies type or capabilities of an analog joystick
 318                        connected to one of 16 gameports
 319                        Format: <type1>,<type2>,..<type16>
 320
 321        apc=            [HW,SPARC]
 322                        Power management functions (SPARCstation-4/5 + deriv.)
 323                        Format: noidle
 324                        Disable APC CPU standby support. SPARCstation-Fox does
 325                        not play well with APC CPU idle - disable it if you have
 326                        APC and your system crashes randomly.
 327
 328        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
 329                        Change the output verbosity whilst booting
 330                        Format: { quiet (default) | verbose | debug }
 331                        Change the amount of debugging information output
 332                        when initialising the APIC and IO-APIC components.
 333
 334        autoconf=       [IPV6]
 335                        See Documentation/networking/ipv6.txt.
 336
 337        show_lapic=     [APIC,X86] Advanced Programmable Interrupt Controller
 338                        Limit apic dumping. The parameter defines the maximal
 339                        number of local apics being dumped. Also it is possible
 340                        to set it to "all" by meaning -- no limit here.
 341                        Format: { 1 (default) | 2 | ... | all }.
 342                        The parameter valid if only apic=debug or
 343                        apic=verbose is specified.
 344                        Example: apic=debug show_lapic=all
 345
 346        apm=            [APM] Advanced Power Management
 347                        See header of arch/x86/kernel/apm_32.c.
 348
 349        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 350                        Format: <io>,<irq>,<nodeID>
 351
 352        ataflop=        [HW,M68k]
 353
 354        atarimouse=     [HW,MOUSE] Atari Mouse
 355
 356        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 357                        EzKey and similar keyboards
 358
 359        atkbd.reset=    [HW] Reset keyboard during initialization
 360
 361        atkbd.set=      [HW] Select keyboard code set
 362                        Format: <int> (2 = AT (default), 3 = PS/2)
 363
 364        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 365                        keyboards
 366
 367        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 368                        Format: <bool> (0 = real, 1 = synthetic (default))
 369
 370        atkbd.softrepeat= [HW]
 371                        Use software keyboard repeat
 372
 373        autotest        [IA64]
 374
 375        baycom_epp=     [HW,AX25]
 376                        Format: <io>,<mode>
 377
 378        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 379                        Format: <io>,<mode>
 380                        See header of drivers/net/hamradio/baycom_par.c.
 381
 382        baycom_ser_fdx= [HW,AX25]
 383                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 384                        Format: <io>,<irq>,<mode>[,<baud>]
 385                        See header of drivers/net/hamradio/baycom_ser_fdx.c.
 386
 387        baycom_ser_hdx= [HW,AX25]
 388                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 389                        Format: <io>,<irq>,<mode>
 390                        See header of drivers/net/hamradio/baycom_ser_hdx.c.
 391
 392        boot_delay=     Milliseconds to delay each printk during boot.
 393                        Values larger than 10 seconds (10000) are changed to
 394                        no delay (0).
 395                        Format: integer
 396
 397        bootmem_debug   [KNL] Enable bootmem allocator debug messages.
 398
 399        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 400        bttv.radio=     Most important insmod options are available as
 401                        kernel args too.
 402        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 403        bttv.tuner=     and Documentation/video4linux/bttv/CARDLIST
 404
 405        c101=           [NET] Moxa C101 synchronous serial card
 406
 407        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
 408                        Sometimes CPU hardware bugs make them report the cache
 409                        size incorrectly. The kernel will attempt work arounds
 410                        to fix known problems, but for some CPUs it is not
 411                        possible to determine what the correct size should be.
 412                        This option provides an override for these situations.
 413
 414        capability.disable=
 415                        [SECURITY] Disable capabilities.  This would normally
 416                        be used only if an alternative security model is to be
 417                        configured.  Potentially dangerous and should only be
 418                        used if you are entirely sure of the consequences.
 419
 420        ccw_timeout_log [S390]
 421                        See Documentation/s390/CommonIO for details.
 422
 423        cgroup_disable= [KNL] Disable a particular controller
 424                        Format: {name of the controller(s) to disable}
 425                                {Currently supported controllers - "memory"}
 426
 427        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 428                        Format: { "0" | "1" }
 429                        See security/selinux/Kconfig help text.
 430                        0 -- check protection applied by kernel (includes
 431                                any implied execute protection).
 432                        1 -- check protection requested by application.
 433                        Default value is set via a kernel config option.
 434                        Value can be changed at runtime via
 435                                /selinux/checkreqprot.
 436
 437        cio_ignore=     [S390]
 438                        See Documentation/s390/CommonIO for details.
 439
 440        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
 441                        [Deprecated]
 442                        Forces specified clocksource (if available) to be used
 443                        when calculating gettimeofday(). If specified
 444                        clocksource is not available, it defaults to PIT.
 445                        Format: { pit | tsc | cyclone | pmtmr }
 446
 447        clocksource=    Override the default clocksource
 448                        Format: <string>
 449                        Override the default clocksource and use the clocksource
 450                        with the name specified.
 451                        Some clocksource names to choose from, depending on
 452                        the platform:
 453                        [all] jiffies (this is the base, fallback clocksource)
 454                        [ACPI] acpi_pm
 455                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
 456                                pxa_timer,timer3,32k_counter,timer0_1
 457                        [AVR32] avr32
 458                        [X86-32] pit,hpet,tsc,vmi-timer;
 459                                scx200_hrt on Geode; cyclone on IBM x440
 460                        [MIPS] MIPS
 461                        [PARISC] cr16
 462                        [S390] tod
 463                        [SH] SuperH
 464                        [SPARC64] tick
 465                        [X86-64] hpet,tsc
 466
 467        clearcpuid=BITNUM [X86]
 468                        Disable CPUID feature X for the kernel. See
 469                        arch/x86/include/asm/cpufeature.h for the valid bit
 470                        numbers. Note the Linux specific bits are not necessarily
 471                        stable over kernel options, but the vendor specific
 472                        ones should be.
 473                        Also note that user programs calling CPUID directly
 474                        or using the feature without checking anything
 475                        will still see it. This just prevents it from
 476                        being used by the kernel or shown in /proc/cpuinfo.
 477                        Also note the kernel might malfunction if you disable
 478                        some critical bits.
 479
 480        cmo_free_hint=  [PPC] Format: { yes | no }
 481                        Specify whether pages are marked as being inactive
 482                        when they are freed.  This is used in CMO environments
 483                        to determine OS memory pressure for page stealing by
 484                        a hypervisor.
 485                        Default: yes
 486
 487        code_bytes      [X86] How many bytes of object code to print
 488                        in an oops report.
 489                        Range: 0 - 8192
 490                        Default: 64
 491
 492        com20020=       [HW,NET] ARCnet - COM20020 chipset
 493                        Format:
 494                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 495
 496        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 497                        Format: <io>[,<irq>]
 498
 499        com90xx=        [HW,NET]
 500                        ARCnet - COM90xx chipset (memory-mapped buffers)
 501                        Format: <io>[,<irq>[,<memstart>]]
 502
 503        condev=         [HW,S390] console device
 504        conmode=
 505
 506        console=        [KNL] Output console device and options.
 507
 508                tty<n>  Use the virtual console device <n>.
 509
 510                ttyS<n>[,options]
 511                ttyUSB0[,options]
 512                        Use the specified serial port.  The options are of
 513                        the form "bbbbpnf", where "bbbb" is the baud rate,
 514                        "p" is parity ("n", "o", or "e"), "n" is number of
 515                        bits, and "f" is flow control ("r" for RTS or
 516                        omit it).  Default is "9600n8".
 517
 518                        See Documentation/serial-console.txt for more
 519                        information.  See
 520                        Documentation/networking/netconsole.txt for an
 521                        alternative.
 522
 523                uart[8250],io,<addr>[,options]
 524                uart[8250],mmio,<addr>[,options]
 525                        Start an early, polled-mode console on the 8250/16550
 526                        UART at the specified I/O port or MMIO address,
 527                        switching to the matching ttyS device later.  The
 528                        options are the same as for ttyS, above.
 529
 530                If the device connected to the port is not a TTY but a braille
 531                device, prepend "brl," before the device type, for instance
 532                        console=brl,ttyS0
 533                For now, only VisioBraille is supported.
 534
 535        consoleblank=   [KNL] The console blank (screen saver) timeout in
 536                        seconds. Defaults to 10*60 = 10mins. A value of 0
 537                        disables the blank timer.
 538
 539        coredump_filter=
 540                        [KNL] Change the default value for
 541                        /proc/<pid>/coredump_filter.
 542                        See also Documentation/filesystems/proc.txt.
 543
 544        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 545                        Format:
 546                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 547
 548        crashkernel=nn[KMG]@ss[KMG]
 549                        [KNL] Reserve a chunk of physical memory to
 550                        hold a kernel to switch to with kexec on panic.
 551
 552        crashkernel=range1:size1[,range2:size2,...][@offset]
 553                        [KNL] Same as above, but depends on the memory
 554                        in the running system. The syntax of range is
 555                        start-[end] where start and end are both
 556                        a memory unit (amount[KMG]). See also
 557                        Documentation/kdump/kdump.txt for a example.
 558
 559        cs89x0_dma=     [HW,NET]
 560                        Format: <dma>
 561
 562        cs89x0_media=   [HW,NET]
 563                        Format: { rj45 | aui | bnc }
 564
 565        dasd=           [HW,NET]
 566                        See header of drivers/s390/block/dasd_devmap.c.
 567
 568        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 569                        (one device per port)
 570                        Format: <port#>,<type>
 571                        See also Documentation/input/joystick-parport.txt
 572
 573        debug           [KNL] Enable kernel debugging (events log level).
 574
 575        debug_locks_verbose=
 576                        [KNL] verbose self-tests
 577                        Format=<0|1>
 578                        Print debugging info while doing the locking API
 579                        self-tests.
 580                        We default to 0 (no extra messages), setting it to
 581                        1 will print _a lot_ more information - normally
 582                        only useful to kernel developers.
 583
 584        debug_objects   [KNL] Enable object debugging
 585
 586        no_debug_objects
 587                        [KNL] Disable object debugging
 588
 589        debugpat        [X86] Enable PAT debugging
 590
 591        decnet.addr=    [HW,NET]
 592                        Format: <area>[,<node>]
 593                        See also Documentation/networking/decnet.txt.
 594
 595        default_hugepagesz=
 596                        [same as hugepagesz=] The size of the default
 597                        HugeTLB page size. This is the size represented by
 598                        the legacy /proc/ hugepages APIs, used for SHM, and
 599                        default size when mounting hugetlbfs filesystems.
 600                        Defaults to the default architecture's huge page size
 601                        if not specified.
 602
 603        dhash_entries=  [KNL]
 604                        Set number of hash buckets for dentry cache.
 605
 606        digi=           [HW,SERIAL]
 607                        IO parameters + enable/disable command.
 608
 609        digiepca=       [HW,SERIAL]
 610                        See drivers/char/README.epca and
 611                        Documentation/serial/digiepca.txt.
 612
 613        disable=        [IPV6]
 614                        See Documentation/networking/ipv6.txt.
 615
 616        disable_ipv6=   [IPV6]
 617                        See Documentation/networking/ipv6.txt.
 618
 619        disable_mtrr_cleanup [X86]
 620                        The kernel tries to adjust MTRR layout from continuous
 621                        to discrete, to make X server driver able to add WB
 622                        entry later. This parameter disables that.
 623
 624        disable_mtrr_trim [X86, Intel and AMD only]
 625                        By default the kernel will trim any uncacheable
 626                        memory out of your available memory pool based on
 627                        MTRR settings.  This parameter disables that behavior,
 628                        possibly causing your machine to run very slowly.
 629
 630        disable_timer_pin_1 [X86]
 631                        Disable PIN 1 of APIC timer
 632                        Can be useful to work around chipset bugs.
 633
 634        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
 635                        this option disables the debugging code at boot.
 636
 637        dma_debug_entries=<number>
 638                        This option allows to tune the number of preallocated
 639                        entries for DMA-API debugging code. One entry is
 640                        required per DMA-API allocation. Use this if the
 641                        DMA-API debugging code disables itself because the
 642                        architectural default is too low.
 643
 644        dma_debug_driver=<driver_name>
 645                        With this option the DMA-API debugging driver
 646                        filter feature can be enabled at boot time. Just
 647                        pass the driver to filter for as the parameter.
 648                        The filter can be disabled or changed to another
 649                        driver later using sysfs.
 650
 651        dscc4.setup=    [NET]
 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                uart[8250],mmio32,<addr>[,options]
 662                        Start an early, polled-mode console on the 8250/16550
 663                        UART at the specified I/O port or MMIO address.
 664                        MMIO inter-register address stride is either 8bit (mmio)
 665                        or 32bit (mmio32).
 666                        The options are the same as for ttyS, above.
 667
 668        earlyprintk=    [X86,SH,BLACKFIN]
 669                        earlyprintk=vga
 670                        earlyprintk=serial[,ttySn[,baudrate]]
 671                        earlyprintk=ttySn[,baudrate]
 672                        earlyprintk=dbgp[debugController#]
 673
 674                        Append ",keep" to not disable it when the real console
 675                        takes over.
 676
 677                        Only vga or serial or usb debug port at a time.
 678
 679                        Currently only ttyS0 and ttyS1 are supported.
 680
 681                        Interaction with the standard serial driver is not
 682                        very good.
 683
 684                        The VGA output is eventually overwritten by the real
 685                        console.
 686
 687        ekgdboc=        [X86,KGDB] Allow early kernel console debugging
 688                        ekgdboc=kbd
 689
 690                        This is desgined to be used in conjunction with
 691                        the boot argument: earlyprintk=vga
 692
 693        edd=            [EDD]
 694                        Format: {"off" | "on" | "skip[mbr]"}
 695
 696        eisa_irq_edge=  [PARISC,HW]
 697                        See header of drivers/parisc/eisa.c.
 698
 699        elanfreq=       [X86-32]
 700                        See comment before function elanfreq_setup() in
 701                        arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 702
 703        elevator=       [IOSCHED]
 704                        Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
 705                        See Documentation/block/as-iosched.txt and
 706                        Documentation/block/deadline-iosched.txt for details.
 707
 708        elfcorehdr=     [IA64,PPC,SH,X86]
 709                        Specifies physical address of start of kernel core
 710                        image elf header. Generally kexec loader will
 711                        pass this option to capture kernel.
 712                        See Documentation/kdump/kdump.txt for details.
 713
 714        enable_mtrr_cleanup [X86]
 715                        The kernel tries to adjust MTRR layout from continuous
 716                        to discrete, to make X server driver able to add WB
 717                        entry later. This parameter enables that.
 718
 719        enable_timer_pin_1 [X86]
 720                        Enable PIN 1 of APIC timer
 721                        Can be useful to work around chipset bugs
 722                        (in particular on some ATI chipsets).
 723                        The kernel tries to set a reasonable default.
 724
 725        enforcing       [SELINUX] Set initial enforcing status.
 726                        Format: {"0" | "1"}
 727                        See security/selinux/Kconfig help text.
 728                        0 -- permissive (log only, no denials).
 729                        1 -- enforcing (deny and log).
 730                        Default value is 0.
 731                        Value can be changed at runtime via /selinux/enforce.
 732
 733        erst_disable    [ACPI]
 734                        Disable Error Record Serialization Table (ERST)
 735                        support.
 736
 737        ether=          [HW,NET] Ethernet cards parameters
 738                        This option is obsoleted by the "netdev=" option, which
 739                        has equivalent usage. See its documentation for details.
 740
 741        failslab=
 742        fail_page_alloc=
 743        fail_make_request=[KNL]
 744                        General fault injection mechanism.
 745                        Format: <interval>,<probability>,<space>,<times>
 746                        See also /Documentation/fault-injection/.
 747
 748        floppy=         [HW]
 749                        See Documentation/blockdev/floppy.txt.
 750
 751        force_pal_cache_flush
 752                        [IA-64] Avoid check_sal_cache_flush which may hang on
 753                        buggy SAL_CACHE_FLUSH implementations. Using this
 754                        parameter will force ia64_sal_cache_flush to call
 755                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
 756
 757        ftrace=[tracer]
 758                        [FTRACE] will set and start the specified tracer
 759                        as early as possible in order to facilitate early
 760                        boot debugging.
 761
 762        ftrace_dump_on_oops[=orig_cpu]
 763                        [FTRACE] will dump the trace buffers on oops.
 764                        If no parameter is passed, ftrace will dump
 765                        buffers of all CPUs, but if you pass orig_cpu, it will
 766                        dump only the buffer of the CPU that triggered the
 767                        oops.
 768
 769        ftrace_filter=[function-list]
 770                        [FTRACE] Limit the functions traced by the function
 771                        tracer at boot up. function-list is a comma separated
 772                        list of functions. This list can be changed at run
 773                        time by the set_ftrace_filter file in the debugfs
 774                        tracing directory. 
 775
 776        ftrace_notrace=[function-list]
 777                        [FTRACE] Do not trace the functions specified in
 778                        function-list. This list can be changed at run time
 779                        by the set_ftrace_notrace file in the debugfs
 780                        tracing directory.
 781
 782        ftrace_graph_filter=[function-list]
 783                        [FTRACE] Limit the top level callers functions traced
 784                        by the function graph tracer at boot up.
 785                        function-list is a comma separated list of functions
 786                        that can be changed at run time by the
 787                        set_graph_function file in the debugfs tracing directory.
 788
 789        gamecon.map[2|3]=
 790                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 791                        support via parallel port (up to 5 devices per port)
 792                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 793                        See also Documentation/input/joystick-parport.txt
 794
 795        gamma=          [HW,DRM]
 796
 797        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
 798                        Format: off | on
 799                        default: on
 800
 801        gcov_persist=   [GCOV] When non-zero (default), profiling data for
 802                        kernel modules is saved and remains accessible via
 803                        debugfs, even when the module is unloaded/reloaded.
 804                        When zero, profiling data is discarded and associated
 805                        debugfs files are removed at module unload time.
 806
 807        gpt             [EFI] Forces disk with valid GPT signature but
 808                        invalid Protective MBR to be treated as GPT.
 809
 810        hashdist=       [KNL,NUMA] Large hashes allocated during boot
 811                        are distributed across NUMA nodes.  Defaults on
 812                        for 64bit NUMA, off otherwise.
 813                        Format: 0 | 1 (for off | on)
 814
 815        hcl=            [IA-64] SGI's Hardware Graph compatibility layer
 816
 817        hd=             [EIDE] (E)IDE hard drive subsystem geometry
 818                        Format: <cyl>,<head>,<sect>
 819
 820        hest_disable    [ACPI]
 821                        Disable Hardware Error Source Table (HEST) support;
 822                        corresponding firmware-first mode error processing
 823                        logic will be disabled.
 824
 825        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
 826                        size of <nn>. This works even on boxes that have no
 827                        highmem otherwise. This also works to reduce highmem
 828                        size on bigger boxes.
 829
 830        highres=        [KNL] Enable/disable high resolution timer mode.
 831                        Valid parameters: "on", "off"
 832                        Default: "on"
 833
 834        hisax=          [HW,ISDN]
 835                        See Documentation/isdn/README.HiSax.
 836
 837        hlt             [BUGS=ARM,SH]
 838
 839        hpet=           [X86-32,HPET] option to control HPET usage
 840                        Format: { enable (default) | disable | force |
 841                                verbose }
 842                        disable: disable HPET and use PIT instead
 843                        force: allow force enabled of undocumented chips (ICH4,
 844                                VIA, nVidia)
 845                        verbose: show contents of HPET registers during setup
 846
 847        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
 848        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
 849                        On x86-64 and powerpc, this option can be specified
 850                        multiple times interleaved with hugepages= to reserve
 851                        huge pages of different sizes. Valid pages sizes on
 852                        x86-64 are 2M (when the CPU supports "pse") and 1G
 853                        (when the CPU supports the "pdpe1gb" cpuinfo flag)
 854                        Note that 1GB pages can only be allocated at boot time
 855                        using hugepages= and not freed afterwards.
 856
 857        hvc_iucv=       [S390] Number of z/VM IUCV hypervisor console (HVC)
 858                               terminal devices. Valid values: 0..8
 859        hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
 860                               If specified, z/VM IUCV HVC accepts connections
 861                               from listed z/VM user IDs only.
 862
 863        i2c_bus=        [HW] Override the default board specific I2C bus speed
 864                             or register an additional I2C bus that is not
 865                             registered from board initialization code.
 866                             Format:
 867                             <bus_id>,<clkrate>
 868
 869        i8042.debug     [HW] Toggle i8042 debug mode
 870        i8042.direct    [HW] Put keyboard port into non-translated mode
 871        i8042.dumbkbd   [HW] Pretend that controller can only read data from
 872                             keyboard and cannot control its state
 873                             (Don't attempt to blink the leds)
 874        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
 875        i8042.nokbd     [HW] Don't check/create keyboard port
 876        i8042.noloop    [HW] Disable the AUX Loopback command while probing
 877                             for the AUX port
 878        i8042.nomux     [HW] Don't check presence of an active multiplexing
 879                             controller
 880        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
 881                             controllers
 882        i8042.notimeout [HW] Ignore timeout condition signalled by conroller
 883        i8042.reset     [HW] Reset the controller during init and cleanup
 884        i8042.unlock    [HW] Unlock (ignore) the keylock
 885
 886        i810=           [HW,DRM]
 887
 888        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
 889                        indicates that the driver is running on unsupported
 890                        hardware.
 891        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
 892                        does not match list of supported models.
 893        i8k.power_status
 894                        [HW] Report power status in /proc/i8k
 895                        (disabled by default)
 896        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
 897                        capability is set.
 898
 899        icn=            [HW,ISDN]
 900                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
 901
 902        ide-core.nodma= [HW] (E)IDE subsystem
 903                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
 904                        .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
 905                        .cdrom .chs .ignore_cable are additional options
 906                        See Documentation/ide/ide.txt.
 907
 908        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
 909                        Claim all unknown PCI IDE storage controllers.
 910
 911        idle=           [X86]
 912                        Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
 913                        Poll forces a polling idle loop that can slightly
 914                        improve the performance of waking up a idle CPU, but
 915                        will use a lot of power and make the system run hot.
 916                        Not recommended.
 917                        idle=mwait: On systems which support MONITOR/MWAIT but
 918                        the kernel chose to not use it because it doesn't save
 919                        as much power as a normal idle loop, use the
 920                        MONITOR/MWAIT idle loop anyways. Performance should be
 921                        the same as idle=poll.
 922                        idle=halt: Halt is forced to be used for CPU idle.
 923                        In such case C2/C3 won't be used again.
 924                        idle=nomwait: Disable mwait for CPU C-states
 925
 926        ignore_loglevel [KNL]
 927                        Ignore loglevel setting - this will print /all/
 928                        kernel messages to the console. Useful for debugging.
 929
 930        ihash_entries=  [KNL]
 931                        Set number of hash buckets for inode cache.
 932
 933        ima_audit=      [IMA]
 934                        Format: { "0" | "1" }
 935                        0 -- integrity auditing messages. (Default)
 936                        1 -- enable informational integrity auditing messages.
 937
 938        ima_hash=       [IMA]
 939                        Format: { "sha1" | "md5" }
 940                        default: "sha1"
 941
 942        ima_tcb         [IMA]
 943                        Load a policy which meets the needs of the Trusted
 944                        Computing Base.  This means IMA will measure all
 945                        programs exec'd, files mmap'd for exec, and all files
 946                        opened for read by uid=0.
 947
 948        init=           [KNL]
 949                        Format: <full_path>
 950                        Run specified binary instead of /sbin/init as init
 951                        process.
 952
 953        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
 954                        for working out where the kernel is dying during
 955                        startup.
 956
 957        initrd=         [BOOT] Specify the location of the initial ramdisk
 958
 959        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
 960                        Format: <irq>
 961
 962        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
 963                on
 964                        Enable intel iommu driver.
 965                off
 966                        Disable intel iommu driver.
 967                igfx_off [Default Off]
 968                        By default, gfx is mapped as normal device. If a gfx
 969                        device has a dedicated DMAR unit, the DMAR unit is
 970                        bypassed by not enabling DMAR with this option. In
 971                        this case, gfx device will use physical address for
 972                        DMA.
 973                forcedac [x86_64]
 974                        With this option iommu will not optimize to look
 975                        for io virtual address below 32 bit forcing dual
 976                        address cycle on pci bus for cards supporting greater
 977                        than 32 bit addressing. The default is to look
 978                        for translation below 32 bit and if not available
 979                        then look in the higher range.
 980                strict [Default Off]
 981                        With this option on every unmap_single operation will
 982                        result in a hardware IOTLB flush operation as opposed
 983                        to batching them for performance.
 984
 985        intremap=       [X86-64, Intel-IOMMU]
 986                        Format: { on (default) | off | nosid }
 987                        on      enable Interrupt Remapping (default)
 988                        off     disable Interrupt Remapping
 989                        nosid   disable Source ID checking
 990
 991        inttest=        [IA64]
 992
 993        iomem=          Disable strict checking of access to MMIO memory
 994                strict  regions from userspace.
 995                relaxed
 996
 997        iommu=          [x86]
 998                off
 999                force
1000                noforce
1001                biomerge
1002                panic
1003                nopanic
1004                merge
1005                nomerge
1006                forcesac
1007                soft
1008                pt      [x86, IA64]
1009
1010        io7=            [HW] IO7 for Marvel based alpha systems
1011                        See comment before marvel_specify_io7 in
1012                        arch/alpha/kernel/core_marvel.c.
1013
1014        io_delay=       [X86] I/O delay method
1015                0x80
1016                        Standard port 0x80 based delay
1017                0xed
1018                        Alternate port 0xed based delay (needed on some systems)
1019                udelay
1020                        Simple two microseconds delay
1021                none
1022                        No delay
1023
1024        ip=             [IP_PNP]
1025                        See Documentation/filesystems/nfs/nfsroot.txt.
1026
1027        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1028                        See comment before ip2_setup() in
1029                        drivers/char/ip2/ip2base.c.
1030
1031        irqfixup        [HW]
1032                        When an interrupt is not handled search all handlers
1033                        for it. Intended to get systems with badly broken
1034                        firmware running.
1035
1036        irqpoll         [HW]
1037                        When an interrupt is not handled search all handlers
1038                        for it. Also check all handlers each timer
1039                        interrupt. Intended to get systems with badly broken
1040                        firmware running.
1041
1042        isapnp=         [ISAPNP]
1043                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1044
1045        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
1046                        Format:
1047                        <cpu number>,...,<cpu number>
1048                        or
1049                        <cpu number>-<cpu number>
1050                        (must be a positive range in ascending order)
1051                        or a mixture
1052                        <cpu number>,...,<cpu number>-<cpu number>
1053
1054                        This option can be used to specify one or more CPUs
1055                        to isolate from the general SMP balancing and scheduling
1056                        algorithms. You can move a process onto or off an
1057                        "isolated" CPU via the CPU affinity syscalls or cpuset.
1058                        <cpu number> begins at 0 and the maximum value is
1059                        "number of CPUs in system - 1".
1060
1061                        This option is the preferred way to isolate CPUs. The
1062                        alternative -- manually setting the CPU mask of all
1063                        tasks in the system -- can cause problems and
1064                        suboptimal load balancer performance.
1065
1066        iucv=           [HW,NET]
1067
1068        js=             [HW,JOY] Analog joystick
1069                        See Documentation/input/joystick.txt.
1070
1071        keepinitrd      [HW,ARM]
1072
1073        kernelcore=nn[KMG]      [KNL,X86,IA-64,PPC] This parameter
1074                        specifies the amount of memory usable by the kernel
1075                        for non-movable allocations.  The requested amount is
1076                        spread evenly throughout all nodes in the system. The
1077                        remaining memory in each node is used for Movable
1078                        pages. In the event, a node is too small to have both
1079                        kernelcore and Movable pages, kernelcore pages will
1080                        take priority and other nodes will have a larger number
1081                        of kernelcore pages.  The Movable zone is used for the
1082                        allocation of pages that may be reclaimed or moved
1083                        by the page migration subsystem.  This means that
1084                        HugeTLB pages may not be allocated from this zone.
1085                        Note that allocations like PTEs-from-HighMem still
1086                        use the HighMem zone if it exists, and the Normal
1087                        zone if it does not.
1088
1089        kgdbdbgp=       [KGDB,HW] kgdb over EHCI usb debug port.
1090                        Format: <Controller#>[,poll interval]
1091                        The controller # is the number of the ehci usb debug
1092                        port as it is probed via PCI.  The poll interval is
1093                        optional and is the number seconds in between
1094                        each poll cycle to the debug port in case you need
1095                        the functionality for interrupting the kernel with
1096                        gdb or control-c on the dbgp connection.  When
1097                        not using this parameter you use sysrq-g to break into
1098                        the kernel debugger.
1099
1100        kgdboc=         [KGDB,HW] kgdb over consoles.
1101                        Requires a tty driver that supports console polling,
1102                        or a supported polling keyboard driver (non-usb).
1103                         Serial only format: <serial_device>[,baud]
1104                         keyboard only format: kbd
1105                         keyboard and serial format: kbd,<serial_device>[,baud]
1106                        Optional Kernel mode setting:
1107                         kms, kbd format: kms,kbd
1108                         kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1109
1110        kgdbwait        [KGDB] Stop kernel execution and enter the
1111                        kernel debugger at the earliest opportunity.
1112
1113        kmac=           [MIPS] korina ethernet MAC address.
1114                        Configure the RouterBoard 532 series on-chip
1115                        Ethernet adapter MAC address.
1116
1117        kmemleak=       [KNL] Boot-time kmemleak enable/disable
1118                        Valid arguments: on, off
1119                        Default: on
1120
1121        kstack=N        [X86] Print N words from the kernel stack
1122                        in oops dumps.
1123
1124        kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1125                        Default is 0 (don't ignore, but inject #GP)
1126
1127        kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1128                        Default is 1 (enabled)
1129
1130        kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1131                        Default is 0 (off)
1132
1133        kvm-amd.npt=    [KVM,AMD] Disable nested paging (virtualized MMU)
1134                        for all guests.
1135                        Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1136
1137        kvm-intel.bypass_guest_pf=
1138                        [KVM,Intel] Disables bypassing of guest page faults
1139                        on Intel chips. Default is 1 (enabled)
1140
1141        kvm-intel.ept=  [KVM,Intel] Disable extended page tables
1142                        (virtualized MMU) support on capable Intel chips.
1143                        Default is 1 (enabled)
1144
1145        kvm-intel.emulate_invalid_guest_state=
1146                        [KVM,Intel] Enable emulation of invalid guest states
1147                        Default is 0 (disabled)
1148
1149        kvm-intel.flexpriority=
1150                        [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1151                        Default is 1 (enabled)
1152
1153        kvm-intel.unrestricted_guest=
1154                        [KVM,Intel] Disable unrestricted guest feature
1155                        (virtualized real and unpaged mode) on capable
1156                        Intel chips. Default is 1 (enabled)
1157
1158        kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1159                        feature (tagged TLBs) on capable Intel chips.
1160                        Default is 1 (enabled)
1161
1162        l2cr=           [PPC]
1163
1164        l3cr=           [PPC]
1165
1166        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
1167                        disabled it.
1168
1169        lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
1170                        in C2 power state.
1171
1172        libata.dma=     [LIBATA] DMA control
1173                        libata.dma=0      Disable all PATA and SATA DMA
1174                        libata.dma=1      PATA and SATA Disk DMA only
1175                        libata.dma=2      ATAPI (CDROM) DMA only
1176                        libata.dma=4      Compact Flash DMA only 
1177                        Combinations also work, so libata.dma=3 enables DMA
1178                        for disks and CDROMs, but not CFs.
1179        
1180        libata.ignore_hpa=      [LIBATA] Ignore HPA limit
1181                        libata.ignore_hpa=0       keep BIOS limits (default)
1182                        libata.ignore_hpa=1       ignore limits, using full disk
1183
1184        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
1185                        when set.
1186                        Format: <int>
1187
1188        libata.force=   [LIBATA] Force configurations.  The format is comma
1189                        separated list of "[ID:]VAL" where ID is
1190                        PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1191                        matching port, link or device.  Basically, it matches
1192                        the ATA ID string printed on console by libata.  If
1193                        the whole ID part is omitted, the last PORT and DEVICE
1194                        values are used.  If ID hasn't been specified yet, the
1195                        configuration applies to all ports, links and devices.
1196
1197                        If only DEVICE is omitted, the parameter applies to
1198                        the port and all links and devices behind it.  DEVICE
1199                        number of 0 either selects the first device or the
1200                        first fan-out link behind PMP device.  It does not
1201                        select the host link.  DEVICE number of 15 selects the
1202                        host link and device attached to it.
1203
1204                        The VAL specifies the configuration to force.  As long
1205                        as there's no ambiguity shortcut notation is allowed.
1206                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
1207                        The following configurations can be forced.
1208
1209                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
1210                          Any ID with matching PORT is used.
1211
1212                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1213
1214                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1215                          udma[/][16,25,33,44,66,100,133] notation is also
1216                          allowed.
1217
1218                        * [no]ncq: Turn on or off NCQ.
1219
1220                        * nohrst, nosrst, norst: suppress hard, soft
1221                          and both resets.
1222
1223                        * dump_id: dump IDENTIFY data.
1224
1225                        If there are multiple matching configurations changing
1226                        the same attribute, the last one is used.
1227
1228        memblock=debug  [KNL] Enable memblock debug messages.
1229
1230        load_ramdisk=   [RAM] List of ramdisks to load from floppy
1231                        See Documentation/blockdev/ramdisk.txt.
1232
1233        lockd.nlm_grace_period=P  [NFS] Assign grace period.
1234                        Format: <integer>
1235
1236        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
1237                        Format: <integer>
1238
1239        lockd.nlm_timeout=T     [NFS] Assign timeout value.
1240                        Format: <integer>
1241
1242        lockd.nlm_udpport=M     [NFS] Assign UDP port.
1243                        Format: <integer>
1244
1245        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
1246                        Format: <irq>
1247
1248        loglevel=       All Kernel Messages with a loglevel smaller than the
1249                        console loglevel will be printed to the console. It can
1250                        also be changed with klogd or other programs. The
1251                        loglevels are defined as follows:
1252
1253                        0 (KERN_EMERG)          system is unusable
1254                        1 (KERN_ALERT)          action must be taken immediately
1255                        2 (KERN_CRIT)           critical conditions
1256                        3 (KERN_ERR)            error conditions
1257                        4 (KERN_WARNING)        warning conditions
1258                        5 (KERN_NOTICE)         normal but significant condition
1259                        6 (KERN_INFO)           informational
1260                        7 (KERN_DEBUG)          debug-level messages
1261
1262        log_buf_len=n   Sets the size of the printk ring buffer, in bytes.
1263                        Format: { n | nk | nM }
1264                        n must be a power of two.  The default size
1265                        is set in the kernel config file.
1266
1267        logo.nologo     [FB] Disables display of the built-in Linux logo.
1268                        This may be used to provide more screen space for
1269                        kernel log messages and is useful when debugging
1270                        kernel boot problems.
1271
1272        lp=0            [LP]    Specify parallel ports to use, e.g,
1273        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
1274        lp=reset                first parallel port). 'lp=0' disables the
1275        lp=auto                 printer driver. 'lp=reset' (which can be
1276                                specified in addition to the ports) causes
1277                                attached printers to be reset. Using
1278                                lp=port1,port2,... specifies the parallel ports
1279                                to associate lp devices with, starting with
1280                                lp0. A port specification may be 'none' to skip
1281                                that lp device, or a parport name such as
1282                                'parport0'. Specifying 'lp=auto' instead of a
1283                                port specification list means that device IDs
1284                                from each port should be examined, to see if
1285                                an IEEE 1284-compliant printer is attached; if
1286                                so, the driver will manage that printer.
1287                                See also header of drivers/char/lp.c.
1288
1289        lpj=n           [KNL]
1290                        Sets loops_per_jiffy to given constant, thus avoiding
1291                        time-consuming boot-time autodetection (up to 250 ms per
1292                        CPU). 0 enables autodetection (default). To determine
1293                        the correct value for your kernel, boot with normal
1294                        autodetection and see what value is printed. Note that
1295                        on SMP systems the preset will be applied to all CPUs,
1296                        which is likely to cause problems if your CPUs need
1297                        significantly divergent settings. An incorrect value
1298                        will cause delays in the kernel to be wrong, leading to
1299                        unpredictable I/O errors and other breakage. Although
1300                        unlikely, in the extreme case this might damage your
1301                        hardware.
1302
1303        ltpc=           [NET]
1304                        Format: <io>,<irq>,<dma>
1305
1306        machvec=        [IA64] Force the use of a particular machine-vector
1307                        (machvec) in a generic kernel.
1308                        Example: machvec=hpzx1_swiotlb
1309
1310        machtype=       [Loongson] Share the same kernel image file between different
1311                         yeeloong laptop.
1312                        Example: machtype=lemote-yeeloong-2f-7inch
1313
1314        max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater
1315                        than or equal to this physical address is ignored.
1316
1317        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
1318                        should make use of.  maxcpus=n : n >= 0 limits the
1319                        kernel to using 'n' processors.  n=0 is a special case,
1320                        it is equivalent to "nosmp", which also disables
1321                        the IO APIC.
1322
1323        max_loop=       [LOOP] Maximum number of loopback devices that can
1324                        be mounted
1325                        Format: <1-256>
1326
1327        mcatest=        [IA-64]
1328
1329        mce             [X86-32] Machine Check Exception
1330
1331        mce=option      [X86-64] See Documentation/x86/x86_64/boot-options.txt
1332
1333        md=             [HW] RAID subsystems devices and level
1334                        See Documentation/md.txt.
1335
1336        mdacon=         [MDA]
1337                        Format: <first>,<last>
1338                        Specifies range of consoles to be captured by the MDA.
1339
1340        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
1341                        Amount of memory to be used when the kernel is not able
1342                        to see the whole system memory or for test.
1343                        [X86-32] Use together with memmap= to avoid physical
1344                        address space collisions. Without memmap= PCI devices
1345                        could be placed at addresses belonging to unused RAM.
1346
1347        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
1348                        memory.
1349
1350        memchunk=nn[KMG]
1351                        [KNL,SH] Allow user to override the default size for
1352                        per-device physically contiguous DMA buffers.
1353
1354        memmap=exactmap [KNL,X86] Enable setting of an exact
1355                        E820 memory map, as specified by the user.
1356                        Such memmap=exactmap lines can be constructed based on
1357                        BIOS output or other requirements. See the memmap=nn@ss
1358                        option description.
1359
1360        memmap=nn[KMG]@ss[KMG]
1361                        [KNL] Force usage of a specific region of memory
1362                        Region of memory to be used, from ss to ss+nn.
1363
1364        memmap=nn[KMG]#ss[KMG]
1365                        [KNL,ACPI] Mark specific memory as ACPI data.
1366                        Region of memory to be used, from ss to ss+nn.
1367
1368        memmap=nn[KMG]$ss[KMG]
1369                        [KNL,ACPI] Mark specific memory as reserved.
1370                        Region of memory to be used, from ss to ss+nn.
1371                        Example: Exclude memory from 0x18690000-0x1869ffff
1372                                 memmap=64K$0x18690000
1373                                 or
1374                                 memmap=0x10000$0x18690000
1375
1376        memory_corruption_check=0/1 [X86]
1377                        Some BIOSes seem to corrupt the first 64k of
1378                        memory when doing things like suspend/resume.
1379                        Setting this option will scan the memory
1380                        looking for corruption.  Enabling this will
1381                        both detect corruption and prevent the kernel
1382                        from using the memory being corrupted.
1383                        However, its intended as a diagnostic tool; if
1384                        repeatable BIOS-originated corruption always
1385                        affects the same memory, you can use memmap=
1386                        to prevent the kernel from using that memory.
1387
1388        memory_corruption_check_size=size [X86]
1389                        By default it checks for corruption in the low
1390                        64k, making this memory unavailable for normal
1391                        use.  Use this parameter to scan for
1392                        corruption in more or less memory.
1393
1394        memory_corruption_check_period=seconds [X86]
1395                        By default it checks for corruption every 60
1396                        seconds.  Use this parameter to check at some
1397                        other rate.  0 disables periodic checking.
1398
1399        memtest=        [KNL,X86] Enable memtest
1400                        Format: <integer>
1401                        default : 0 <disable>
1402                        Specifies the number of memtest passes to be
1403                        performed. Each pass selects another test
1404                        pattern from a given set of patterns. Memtest
1405                        fills the memory with this pattern, validates
1406                        memory contents and reserves bad memory
1407                        regions that are detected.
1408
1409        meye.*=         [HW] Set MotionEye Camera parameters
1410                        See Documentation/video4linux/meye.txt.
1411
1412        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
1413                        Multi-Function General Purpose Timers on AMD Geode
1414                        platforms.
1415
1416        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
1417                        the BIOS has incorrectly applied a workaround. TinyBIOS
1418                        version 0.98 is known to be affected, 0.99 fixes the
1419                        problem by letting the user disable the workaround.
1420
1421        mga=            [HW,DRM]
1422
1423        min_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory below this
1424                        physical address is ignored.
1425
1426        mini2440=       [ARM,HW,KNL]
1427                        Format:[0..2][b][c][t]
1428                        Default: "0tb"
1429                        MINI2440 configuration specification:
1430                        0 - The attached screen is the 3.5" TFT
1431                        1 - The attached screen is the 7" TFT
1432                        2 - The VGA Shield is attached (1024x768)
1433                        Leaving out the screen size parameter will not load
1434                        the TFT driver, and the framebuffer will be left
1435                        unconfigured.
1436                        b - Enable backlight. The TFT backlight pin will be
1437                        linked to the kernel VESA blanking code and a GPIO
1438                        LED. This parameter is not necessary when using the
1439                        VGA shield.
1440                        c - Enable the s3c camera interface.
1441                        t - Reserved for enabling touchscreen support. The
1442                        touchscreen support is not enabled in the mainstream
1443                        kernel as of 2.6.30, a preliminary port can be found
1444                        in the "bleeding edge" mini2440 support kernel at
1445                        http://repo.or.cz/w/linux-2.6/mini2440.git
1446
1447        mminit_loglevel=
1448                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1449                        parameter allows control of the logging verbosity for
1450                        the additional memory initialisation checks. A value
1451                        of 0 disables mminit logging and a level of 4 will
1452                        log everything. Information is printed at KERN_DEBUG
1453                        so loglevel=8 may also need to be specified.
1454
1455        mousedev.tap_time=
1456                        [MOUSE] Maximum time between finger touching and
1457                        leaving touchpad surface for touch to be considered
1458                        a tap and be reported as a left button click (for
1459                        touchpads working in absolute mode only).
1460                        Format: <msecs>
1461        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
1462                        reporting absolute coordinates, such as tablets
1463        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
1464                        reporting absolute coordinates, such as tablets
1465
1466        movablecore=nn[KMG]     [KNL,X86,IA-64,PPC] This parameter
1467                        is similar to kernelcore except it specifies the
1468                        amount of memory used for migratable allocations.
1469                        If both kernelcore and movablecore is specified,
1470                        then kernelcore will be at *least* the specified
1471                        value but may be more. If movablecore on its own
1472                        is specified, the administrator must be careful
1473                        that the amount of memory usable for all allocations
1474                        is not too small.
1475
1476        MTD_Partition=  [MTD]
1477                        Format: <name>,<region-number>,<size>,<offset>
1478
1479        MTD_Region=     [MTD] Format:
1480                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1481
1482        mtdparts=       [MTD]
1483                        See drivers/mtd/cmdlinepart.c.
1484
1485        onenand.bdry=   [HW,MTD] Flex-OneNAND Boundary Configuration
1486
1487                        Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1488
1489                        boundary - index of last SLC block on Flex-OneNAND.
1490                                   The remaining blocks are configured as MLC blocks.
1491                        lock     - Configure if Flex-OneNAND boundary should be locked.
1492                                   Once locked, the boundary cannot be changed.
1493                                   1 indicates lock status, 0 indicates unlock status.
1494
1495        mtdset=         [ARM]
1496                        ARM/S3C2412 JIVE boot control
1497
1498                        See arch/arm/mach-s3c2412/mach-jive.c
1499
1500        mtouchusb.raw_coordinates=
1501                        [HW] Make the MicroTouch USB driver use raw coordinates
1502                        ('y', default) or cooked coordinates ('n')
1503
1504        mtrr_chunk_size=nn[KMG] [X86]
1505                        used for mtrr cleanup. It is largest continuous chunk
1506                        that could hold holes aka. UC entries.
1507
1508        mtrr_gran_size=nn[KMG] [X86]
1509                        Used for mtrr cleanup. It is granularity of mtrr block.
1510                        Default is 1.
1511                        Large value could prevent small alignment from
1512                        using up MTRRs.
1513
1514        mtrr_spare_reg_nr=n [X86]
1515                        Format: <integer>
1516                        Range: 0,7 : spare reg number
1517                        Default : 1
1518                        Used for mtrr cleanup. It is spare mtrr entries number.
1519                        Set to 2 or more if your graphical card needs more.
1520
1521        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
1522
1523        netdev=         [NET] Network devices parameters
1524                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1525                        Note that mem_start is often overloaded to mean
1526                        something different and driver-specific.
1527                        This usage is only documented in each driver source
1528                        file if at all.
1529
1530        nf_conntrack.acct=
1531                        [NETFILTER] Enable connection tracking flow accounting
1532                        0 to disable accounting
1533                        1 to enable accounting
1534                        Default value is 0.
1535
1536        nfsaddrs=       [NFS]
1537                        See Documentation/filesystems/nfs/nfsroot.txt.
1538
1539        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
1540                        See Documentation/filesystems/nfs/nfsroot.txt.
1541
1542        nfs.callback_tcpport=
1543                        [NFS] set the TCP port on which the NFSv4 callback
1544                        channel should listen.
1545
1546        nfs.cache_getent=
1547                        [NFS] sets the pathname to the program which is used
1548                        to update the NFS client cache entries.
1549
1550        nfs.cache_getent_timeout=
1551                        [NFS] sets the timeout after which an attempt to
1552                        update a cache entry is deemed to have failed.
1553
1554        nfs.idmap_cache_timeout=
1555                        [NFS] set the maximum lifetime for idmapper cache
1556                        entries.
1557
1558        nfs.enable_ino64=
1559                        [NFS] enable 64-bit inode numbers.
1560                        If zero, the NFS client will fake up a 32-bit inode
1561                        number for the readdir() and stat() syscalls instead
1562                        of returning the full 64-bit number.
1563                        The default is to return 64-bit inode numbers.
1564
1565        nmi_debug=      [KNL,AVR32,SH] Specify one or more actions to take
1566                        when a NMI is triggered.
1567                        Format: [state][,regs][,debounce][,die]
1568
1569        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
1570                        Format: [panic,][num]
1571                        Valid num: 0,1,2
1572                        0 - turn nmi_watchdog off
1573                        1 - use the IO-APIC timer for the NMI watchdog
1574                        2 - use the local APIC for the NMI watchdog using
1575                        a performance counter. Note: This will use one
1576                        performance counter and the local APIC's performance
1577                        vector.
1578                        When panic is specified, panic when an NMI watchdog
1579                        timeout occurs.
1580                        This is useful when you use a panic=... timeout and
1581                        need the box quickly up again.
1582                        Instead of 1 and 2 it is possible to use the following
1583                        symbolic names: lapic and ioapic
1584                        Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1585
1586        netpoll.carrier_timeout=
1587                        [NET] Specifies amount of time (in seconds) that
1588                        netpoll should wait for a carrier. By default netpoll
1589                        waits 4 seconds.
1590
1591        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
1592                        emulation library even if a 387 maths coprocessor
1593                        is present.
1594
1595        no_console_suspend
1596                        [HW] Never suspend the console
1597                        Disable suspending of consoles during suspend and
1598                        hibernate operations.  Once disabled, debugging
1599                        messages can reach various consoles while the rest
1600                        of the system is being put to sleep (ie, while
1601                        debugging driver suspend/resume hooks).  This may
1602                        not work reliably with all consoles, but is known
1603                        to work with serial and VGA consoles.
1604
1605        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
1606                        caches in the slab allocator.  Saves per-node memory,
1607                        but will impact performance.
1608
1609        noalign         [KNL,ARM]
1610
1611        noapic          [SMP,APIC] Tells the kernel to not make use of any
1612                        IOAPICs that may be present in the system.
1613
1614        nobats          [PPC] Do not use BATs for mapping kernel lowmem
1615                        on "Classic" PPC cores.
1616
1617        nocache         [ARM]
1618
1619        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction
1620
1621        nodelayacct     [KNL] Disable per-task delay accounting
1622
1623        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1624
1625        nodsp           [SH] Disable hardware DSP at boot time.
1626
1627        noefi           [X86] Disable EFI runtime services support.
1628
1629        noexec          [IA-64]
1630
1631        noexec          [X86]
1632                        On X86-32 available only on PAE configured kernels.
1633                        noexec=on: enable non-executable mappings (default)
1634                        noexec=off: disable non-executable mappings
1635
1636        noexec32        [X86-64]
1637                        This affects only 32-bit executables.
1638                        noexec32=on: enable non-executable mappings (default)
1639                                read doesn't imply executable mappings
1640                        noexec32=off: disable non-executable mappings
1641                                read implies executable mappings
1642
1643        nofpu           [SH] Disable hardware FPU at boot time.
1644
1645        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
1646                        register save and restore. The kernel will only save
1647                        legacy floating-point registers on task switch.
1648
1649        noxsave         [BUGS=X86] Disables x86 extended register state save
1650                        and restore using xsave. The kernel will fallback to
1651                        enabling legacy floating-point and sse state.
1652
1653        nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1654                        wfi(ARM) instruction doesn't work correctly and not to
1655                        use it. This is also useful when using JTAG debugger.
1656
1657        no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
1658                        instruction doesn't work correctly and not to
1659                        use it.
1660
1661        no_file_caps    Tells the kernel not to honor file capabilities.  The
1662                        only way then for a file to be executed with privilege
1663                        is to be setuid root or executed by root.
1664
1665        nohalt          [IA-64] Tells the kernel not to use the power saving
1666                        function PAL_HALT_LIGHT when idle. This increases
1667                        power-consumption. On the positive side, it reduces
1668                        interrupt wake-up latency, which may improve performance
1669                        in certain environments such as networked servers or
1670                        real-time systems.
1671
1672        nohz=           [KNL] Boottime enable/disable dynamic ticks
1673                        Valid arguments: on, off
1674                        Default: on
1675
1676        noiotrap        [SH] Disables trapped I/O port accesses.
1677
1678        noirqdebug      [X86-32] Disables the code which attempts to detect and
1679                        disable unhandled interrupt sources.
1680
1681        no_timer_check  [X86,APIC] Disables the code which tests for
1682                        broken timer IRQ sources.
1683
1684        noisapnp        [ISAPNP] Disables ISA PnP code.
1685
1686        noinitrd        [RAM] Tells the kernel not to load any configured
1687                        initial RAM disk.
1688
1689        nointremap      [X86-64, Intel-IOMMU] Do not enable interrupt
1690                        remapping.
1691                        [Deprecated - use intremap=off]
1692
1693        nointroute      [IA-64]
1694
1695        nojitter        [IA64] Disables jitter checking for ITC timers.
1696
1697        nolapic         [X86-32,APIC] Do not enable or use the local APIC.
1698
1699        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.
1700
1701        noltlbs         [PPC] Do not use large page/tlb entries for kernel
1702                        lowmem mapping on PPC40x.
1703
1704        nomca           [IA-64] Disable machine check abort handling
1705
1706        nomce           [X86-32] Machine Check Exception
1707
1708        nomfgpt         [X86-32] Disable Multi-Function General Purpose
1709                        Timer usage (for AMD Geode machines).
1710
1711        nopat           [X86] Disable PAT (page attribute table extension of
1712                        pagetables) support.
1713
1714        norandmaps      Don't use address space randomization.  Equivalent to
1715                        echo 0 > /proc/sys/kernel/randomize_va_space
1716
1717        noreplace-paravirt      [X86-32,PV_OPS] Don't patch paravirt_ops
1718
1719        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
1720                        with UP alternatives
1721
1722        noresidual      [PPC] Don't use residual data on PReP machines.
1723
1724        noresume        [SWSUSP] Disables resume and restores original swap
1725                        space.
1726
1727        no-scroll       [VGA] Disables scrollback.
1728                        This is required for the Braillex ib80-piezo Braille
1729                        reader made by F.H. Papenmeier (Germany).
1730
1731        nosbagart       [IA-64]
1732
1733        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1734
1735        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
1736                        and disable the IO APIC.  legacy for "maxcpus=0".
1737
1738        nosoftlockup    [KNL] Disable the soft-lockup detector.
1739
1740        noswapaccount   [KNL] Disable accounting of swap in memory resource
1741                        controller. (See Documentation/cgroups/memory.txt)
1742
1743        nosync          [HW,M68K] Disables sync negotiation for all devices.
1744
1745        notsc           [BUGS=X86-32] Disable Time Stamp Counter
1746
1747        nousb           [USB] Disable the USB subsystem
1748
1749        nowatchdog      [KNL] Disable the lockup detector (NMI watchdog).
1750
1751        nowb            [ARM]
1752
1753        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
1754
1755        nptcg=          [IA64] Override max number of concurrent global TLB
1756                        purges which is reported from either PAL_VM_SUMMARY or
1757                        SAL PALO.
1758
1759        nr_cpus=        [SMP] Maximum number of processors that an SMP kernel
1760                        could support.  nr_cpus=n : n >= 1 limits the kernel to
1761                        supporting 'n' processors. Later in runtime you can not
1762                        use hotplug cpu feature to put more cpu back to online.
1763                        just like you compile the kernel NR_CPUS=n
1764
1765        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1766
1767        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1768                        one of ['zone', 'node', 'default'] can be specified
1769                        This can be set from sysctl after boot.
1770                        See Documentation/sysctl/vm.txt for details.
1771
1772        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
1773                        See Documentation/debugging-via-ohci1394.txt for more
1774                        info.
1775
1776        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1777                        Rather than timing out after 20 ms if an EC
1778                        command is not properly ACKed, override the length
1779                        of the timeout.  We have interrupts disabled while
1780                        waiting for the ACK, so if this is set too high
1781                        interrupts *may* be lost!
1782
1783        omap_mux=       [OMAP] Override bootloader pin multiplexing.
1784                        Format: <mux_mode0.mode_name=value>...
1785                        For example, to override I2C bus2:
1786                        omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1787
1788        oprofile.timer= [HW]
1789                        Use timer interrupt instead of performance counters
1790
1791        oprofile.cpu_type=      Force an oprofile cpu type
1792                        This might be useful if you have an older oprofile
1793                        userland or if you want common events.
1794                        Format: { arch_perfmon }
1795                        arch_perfmon: [X86] Force use of architectural
1796                                perfmon on Intel CPUs instead of the
1797                                CPU specific event set.
1798
1799        OSS             [HW,OSS]
1800                        See Documentation/sound/oss/oss-parameters.txt
1801
1802        panic=          [KNL] Kernel behaviour on panic
1803                        Format: <timeout>
1804
1805        parkbd.port=    [HW] Parallel port number the keyboard adapter is
1806                        connected to, default is 0.
1807                        Format: <parport#>
1808        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
1809                        0 for XT, 1 for AT (default is AT).
1810                        Format: <mode>
1811
1812        parport=        [HW,PPT] Specify parallel ports. 0 disables.
1813                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1814                        Use 'auto' to force the driver to use any
1815                        IRQ/DMA settings detected (the default is to
1816                        ignore detected IRQ/DMA settings because of
1817                        possible conflicts). You can specify the base
1818                        address, IRQ, and DMA settings; IRQ and DMA
1819                        should be numbers, or 'auto' (for using detected
1820                        settings on that particular port), or 'nofifo'
1821                        (to avoid using a FIFO even if it is detected).
1822                        Parallel ports are assigned in the order they
1823                        are specified on the command line, starting
1824                        with parport0.
1825
1826        parport_init_mode=      [HW,PPT]
1827                        Configure VIA parallel port to operate in
1828                        a specific mode. This is necessary on Pegasos
1829                        computer where firmware has no options for setting
1830                        up parallel port mode and sets it to spp.
1831                        Currently this function knows 686a and 8231 chips.
1832                        Format: [spp|ps2|epp|ecp|ecpepp]
1833
1834        pause_on_oops=
1835                        Halt all CPUs after the first oops has been printed for
1836                        the specified number of seconds.  This is to be used if
1837                        your oopses keep scrolling off the screen.
1838
1839        pcbit=          [HW,ISDN]
1840
1841        pcd.            [PARIDE]
1842                        See header of drivers/block/paride/pcd.c.
1843                        See also Documentation/blockdev/paride.txt.
1844
1845        pci=option[,option...]  [PCI] various PCI subsystem options:
1846                earlydump       [X86] dump PCI config space before the kernel
1847                                changes anything
1848                off             [X86] don't probe for the PCI bus
1849                bios            [X86-32] force use of PCI BIOS, don't access
1850                                the hardware directly. Use this if your machine
1851                                has a non-standard PCI host bridge.
1852                nobios          [X86-32] disallow use of PCI BIOS, only direct
1853                                hardware access methods are allowed. Use this
1854                                if you experience crashes upon bootup and you
1855                                suspect they are caused by the BIOS.
1856                conf1           [X86] Force use of PCI Configuration
1857                                Mechanism 1.
1858                conf2           [X86] Force use of PCI Configuration
1859                                Mechanism 2.
1860                noaer           [PCIE] If the PCIEAER kernel config parameter is
1861                                enabled, this kernel boot option can be used to
1862                                disable the use of PCIE advanced error reporting.
1863                nodomains       [PCI] Disable support for multiple PCI
1864                                root domains (aka PCI segments, in ACPI-speak).
1865                nommconf        [X86] Disable use of MMCONFIG for PCI
1866                                Configuration
1867                check_enable_amd_mmconf [X86] check for and enable
1868                                properly configured MMIO access to PCI
1869                                config space on AMD family 10h CPU
1870                nomsi           [MSI] If the PCI_MSI kernel config parameter is
1871                                enabled, this kernel boot option can be used to
1872                                disable the use of MSI interrupts system-wide.
1873                noioapicquirk   [APIC] Disable all boot interrupt quirks.
1874                                Safety option to keep boot IRQs enabled. This
1875                                should never be necessary.
1876                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
1877                                primary IO-APIC for bridges that cannot disable
1878                                boot IRQs. This fixes a source of spurious IRQs
1879                                when the system masks IRQs.
1880                noioapicreroute [APIC] Disable workaround that uses the
1881                                boot IRQ equivalent of an IRQ that connects to
1882                                a chipset where boot IRQs cannot be disabled.
1883                                The opposite of ioapicreroute.
1884                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
1885                                routing table. These calls are known to be buggy
1886                                on several machines and they hang the machine
1887                                when used, but on other computers it's the only
1888                                way to get the interrupt routing table. Try
1889                                this option if the kernel is unable to allocate
1890                                IRQs or discover secondary PCI buses on your
1891                                motherboard.
1892                rom             [X86] Assign address space to expansion ROMs.
1893                                Use with caution as certain devices share
1894                                address decoders between ROMs and other
1895                                resources.
1896                norom           [X86] Do not assign address space to
1897                                expansion ROMs that do not already have
1898                                BIOS assigned address ranges.
1899                nobar           [X86] Do not assign address space to the
1900                                BARs that weren't assigned by the BIOS.
1901                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
1902                                assigned automatically to PCI devices. You can
1903                                make the kernel exclude IRQs of your ISA cards
1904                                this way.
1905                pirqaddr=0xAAAAA        [X86] Specify the physical address
1906                                of the PIRQ table (normally generated
1907                                by the BIOS) if it is outside the
1908                                F0000h-100000h range.
1909                lastbus=N       [X86] Scan all buses thru bus #N. Can be
1910                                useful if the kernel is unable to find your
1911                                secondary buses and you want to tell it
1912                                explicitly which ones they are.
1913                assign-busses   [X86] Always assign all PCI bus
1914                                numbers ourselves, overriding
1915                                whatever the firmware may have done.
1916                usepirqmask     [X86] Honor the possible IRQ mask stored
1917                                in the BIOS $PIR table. This is needed on
1918                                some systems with broken BIOSes, notably
1919                                some HP Pavilion N5400 and Omnibook XE3
1920                                notebooks. This will have no effect if ACPI
1921                                IRQ routing is enabled.
1922                noacpi          [X86] Do not use ACPI for IRQ routing
1923                                or for PCI scanning.
1924                use_crs         [X86] Use PCI host bridge window information
1925                                from ACPI.  On BIOSes from 2008 or later, this
1926                                is enabled by default.  If you need to use this,
1927                                please report a bug.
1928                nocrs           [X86] Ignore PCI host bridge windows from ACPI.
1929                                If you need to use this, please report a bug.
1930                routeirq        Do IRQ routing for all PCI devices.
1931                                This is normally done in pci_enable_device(),
1932                                so this option is a temporary workaround
1933                                for broken drivers that don't call it.
1934                skip_isa_align  [X86] do not align io start addr, so can
1935                                handle more pci cards
1936                firmware        [ARM] Do not re-enumerate the bus but instead
1937                                just use the configuration from the
1938                                bootloader. This is currently used on
1939                                IXP2000 systems where the bus has to be
1940                                configured a certain way for adjunct CPUs.
1941                noearly         [X86] Don't do any early type 1 scanning.
1942                                This might help on some broken boards which
1943                                machine check when some devices' config space
1944                                is read. But various workarounds are disabled
1945                                and some IOMMU drivers will not work.
1946                bfsort          Sort PCI devices into breadth-first order.
1947                                This sorting is done to get a device
1948                                order compatible with older (<= 2.4) kernels.
1949                nobfsort        Don't sort PCI devices into breadth-first order.
1950                cbiosize=nn[KMG]        The fixed amount of bus space which is
1951                                reserved for the CardBus bridge's IO window.
1952                                The default value is 256 bytes.
1953                cbmemsize=nn[KMG]       The fixed amount of bus space which is
1954                                reserved for the CardBus bridge's memory
1955                                window. The default value is 64 megabytes.
1956                resource_alignment=
1957                                Format:
1958                                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1959                                Specifies alignment and device to reassign
1960                                aligned memory resources.
1961                                If <order of align> is not specified,
1962                                PAGE_SIZE is used as alignment.
1963                                PCI-PCI bridge can be specified, if resource
1964                                windows need to be expanded.
1965                ecrc=           Enable/disable PCIe ECRC (transaction layer
1966                                end-to-end CRC checking).
1967                                bios: Use BIOS/firmware settings. This is the
1968                                the default.
1969                                off: Turn ECRC off
1970                                on: Turn ECRC on.
1971
1972        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
1973                        Management.
1974                off     Disable ASPM.
1975                force   Enable ASPM even on devices that claim not to support it.
1976                        WARNING: Forcing ASPM on may cause system lockups.
1977
1978        pcie_ports=     [PCIE] PCIe ports handling:
1979                auto    Ask the BIOS whether or not to use native PCIe services
1980                        associated with PCIe ports (PME, hot-plug, AER).  Use
1981                        them only if that is allowed by the BIOS.
1982                native  Use native PCIe services associated with PCIe ports
1983                        unconditionally.
1984                compat  Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1985                        ports driver.
1986
1987        pcie_pme=       [PCIE,PM] Native PCIe PME signaling options:
1988                nomsi   Do not use MSI for native PCIe PME signaling (this makes
1989                        all PCIe root ports use INTx for all services).
1990
1991        pcmv=           [HW,PCMCIA] BadgePAD 4
1992
1993        pd.             [PARIDE]
1994                        See Documentation/blockdev/paride.txt.
1995
1996        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1997                        boot time.
1998                        Format: { 0 | 1 }
1999                        See arch/parisc/kernel/pdc_chassis.c
2000
2001        percpu_alloc=   Select which percpu first chunk allocator to use.
2002                        Currently supported values are "embed" and "page".
2003                        Archs may support subset or none of the selections.
2004                        See comments in mm/percpu.c for details on each
2005                        allocator.  This parameter is primarily for debugging
2006                        and performance comparison.
2007
2008        pf.             [PARIDE]
2009                        See Documentation/blockdev/paride.txt.
2010
2011        pg.             [PARIDE]
2012                        See Documentation/blockdev/paride.txt.
2013
2014        pirq=           [SMP,APIC] Manual mp-table setup
2015                        See Documentation/x86/i386/IO-APIC.txt.
2016
2017        plip=           [PPT,NET] Parallel port network link
2018                        Format: { parport<nr> | timid | 0 }
2019                        See also Documentation/parport.txt.
2020
2021        pmtmr=          [X86] Manual setup of pmtmr I/O Port. 
2022                        Override pmtimer IOPort with a hex value.
2023                        e.g. pmtmr=0x508
2024
2025        pnp.debug       [PNP]
2026                        Enable PNP debug messages.  This depends on the
2027                        CONFIG_PNP_DEBUG_MESSAGES option.
2028
2029        pnpacpi=        [ACPI]
2030                        { off }
2031
2032        pnpbios=        [ISAPNP]
2033                        { on | off | curr | res | no-curr | no-res }
2034
2035        pnp_reserve_irq=
2036                        [ISAPNP] Exclude IRQs for the autoconfiguration
2037
2038        pnp_reserve_dma=
2039                        [ISAPNP] Exclude DMAs for the autoconfiguration
2040
2041        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2042                        Ranges are in pairs (I/O port base and size).
2043
2044        pnp_reserve_mem=
2045                        [ISAPNP] Exclude memory regions for the
2046                        autoconfiguration.
2047                        Ranges are in pairs (memory base and size).
2048
2049        ports=          [IP_VS_FTP] IPVS ftp helper module
2050                        Default is 21.
2051                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
2052                        may be specified.
2053                        Format: <port>,<port>....
2054
2055        print-fatal-signals=
2056                        [KNL] debug: print fatal signals
2057
2058                        If enabled, warn about various signal handling
2059                        related application anomalies: too many signals,
2060                        too many POSIX.1 timers, fatal signals causing a
2061                        coredump - etc.
2062
2063                        If you hit the warning due to signal overflow,
2064                        you might want to try "ulimit -i unlimited".
2065
2066                        default: off.
2067
2068        printk.time=    Show timing data prefixed to each printk message line
2069                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2070
2071        processor.max_cstate=   [HW,ACPI]
2072                        Limit processor to maximum C-state
2073                        max_cstate=9 overrides any DMI blacklist limit.
2074
2075        processor.nocst [HW,ACPI]
2076                        Ignore the _CST method to determine C-states,
2077                        instead using the legacy FADT method
2078
2079        profile=        [KNL] Enable kernel profiling via /proc/profile
2080                        Format: [schedule,]<number>
2081                        Param: "schedule" - profile schedule points.
2082                        Param: <number> - step/bucket size as a power of 2 for
2083                                statistical time based profiling.
2084                        Param: "sleep" - profile D-state sleeping (millisecs).
2085                                Requires CONFIG_SCHEDSTATS
2086                        Param: "kvm" - profile VM exits.
2087
2088        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2089                        before loading.
2090                        See Documentation/blockdev/ramdisk.txt.
2091
2092        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
2093                        probe for; one of (bare|imps|exps|lifebook|any).
2094        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
2095                        per second.
2096        psmouse.resetafter=     [HW,MOUSE]
2097                        Try to reset the device after so many bad packets
2098                        (0 = never).
2099        psmouse.resolution=
2100                        [HW,MOUSE] Set desired mouse resolution, in dpi.
2101        psmouse.smartscroll=
2102                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2103                        0 = disabled, 1 = enabled (default).
2104
2105        pt.             [PARIDE]
2106                        See Documentation/blockdev/paride.txt.
2107
2108        pty.legacy_count=
2109                        [KNL] Number of legacy pty's. Overwrites compiled-in
2110                        default number.
2111
2112        quiet           [KNL] Disable most log messages
2113
2114        r128=           [HW,DRM]
2115
2116        raid=           [HW,RAID]
2117                        See Documentation/md.txt.
2118
2119        ramdisk_blocksize=      [RAM]
2120                        See Documentation/blockdev/ramdisk.txt.
2121
2122        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
2123                        See Documentation/blockdev/ramdisk.txt.
2124
2125        rcupdate.blimit=        [KNL,BOOT]
2126                        Set maximum number of finished RCU callbacks to process
2127                        in one batch.
2128
2129        rcupdate.qhimark=       [KNL,BOOT]
2130                        Set threshold of queued
2131                        RCU callbacks over which batch limiting is disabled.
2132
2133        rcupdate.qlowmark=      [KNL,BOOT]
2134                        Set threshold of queued RCU callbacks below which
2135                        batch limiting is re-enabled.
2136
2137        rdinit=         [KNL]
2138                        Format: <full_path>
2139                        Run specified binary instead of /init from the ramdisk,
2140                        used for early userspace startup. See initrd.
2141
2142        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2143                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
2144                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2145
2146        relax_domain_level=
2147                        [KNL, SMP] Set scheduler's default relax_domain_level.
2148                        See Documentation/cgroups/cpusets.txt.
2149
2150        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
2151
2152        reservetop=     [X86-32]
2153                        Format: nn[KMG]
2154                        Reserves a hole at the top of the kernel virtual
2155                        address space.
2156
2157        reset_devices   [KNL] Force drivers to reset the underlying device
2158                        during initialization.
2159
2160        resume=         [SWSUSP]
2161                        Specify the partition device for software suspend
2162
2163        resume_offset=  [SWSUSP]
2164                        Specify the offset from the beginning of the partition
2165                        given by "resume=" at which the swap header is located,
2166                        in <PAGE_SIZE> units (needed only for swap files).
2167                        See  Documentation/power/swsusp-and-swap-files.txt
2168
2169        retain_initrd   [RAM] Keep initrd memory after extraction
2170
2171        rhash_entries=  [KNL,NET]
2172                        Set number of hash buckets for route cache
2173
2174        riscom8=        [HW,SERIAL]
2175                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2176
2177        ro              [KNL] Mount root device read-only on boot
2178
2179        root=           [KNL] Root filesystem
2180
2181        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
2182                        mount the root filesystem
2183
2184        rootflags=      [KNL] Set root filesystem mount option string
2185
2186        rootfstype=     [KNL] Set root filesystem type
2187
2188        rootwait        [KNL] Wait (indefinitely) for root device to show up.
2189                        Useful for devices that are detected asynchronously
2190                        (e.g. USB and MMC devices).
2191
2192        rw              [KNL] Mount root device read-write on boot
2193
2194        S               [KNL] Run init in single mode
2195
2196        sa1100ir        [NET]
2197                        See drivers/net/irda/sa1100_ir.c.
2198
2199        sbni=           [NET] Granch SBNI12 leased line adapter
2200
2201        sched_debug     [KNL] Enables verbose scheduler debug messages.
2202
2203        security=       [SECURITY] Choose a security module to enable at boot.
2204                        If this boot parameter is not specified, only the first
2205                        security module asking for security registration will be
2206                        loaded. An invalid security module name will be treated
2207                        as if no module has been chosen.
2208
2209        selinux=        [SELINUX] Disable or enable SELinux at boot time.
2210                        Format: { "0" | "1" }
2211                        See security/selinux/Kconfig help text.
2212                        0 -- disable.
2213                        1 -- enable.
2214                        Default value is set via kernel config option.
2215                        If enabled at boot time, /selinux/disable can be used
2216                        later to disable prior to initial policy load.
2217
2218        apparmor=       [APPARMOR] Disable or enable AppArmor at boot time
2219                        Format: { "0" | "1" }
2220                        See security/apparmor/Kconfig help text
2221                        0 -- disable.
2222                        1 -- enable.
2223                        Default value is set via kernel config option.
2224
2225        serialnumber    [BUGS=X86-32]
2226
2227        shapers=        [NET]
2228                        Maximal number of shapers.
2229
2230        show_msr=       [x86] show boot-time MSR settings
2231                        Format: { <integer> }
2232                        Show boot-time (BIOS-initialized) MSR settings.
2233                        The parameter means the number of CPUs to show,
2234                        for example 1 means boot CPU only.
2235
2236        simeth=         [IA-64]
2237        simscsi=
2238
2239        slram=          [HW,MTD]
2240
2241        slub_debug[=options[,slabs]]    [MM, SLUB]
2242                        Enabling slub_debug allows one to determine the
2243                        culprit if slab objects become corrupted. Enabling
2244                        slub_debug can create guard zones around objects and
2245                        may poison objects when not in use. Also tracks the
2246                        last alloc / free. For more information see
2247                        Documentation/vm/slub.txt.
2248
2249        slub_max_order= [MM, SLUB]
2250                        Determines the maximum allowed order for slabs.
2251                        A high setting may cause OOMs due to memory
2252                        fragmentation. For more information see
2253                        Documentation/vm/slub.txt.
2254
2255        slub_min_objects=       [MM, SLUB]
2256                        The minimum number of objects per slab. SLUB will
2257                        increase the slab order up to slub_max_order to
2258                        generate a sufficiently large slab able to contain
2259                        the number of objects indicated. The higher the number
2260                        of objects the smaller the overhead of tracking slabs
2261                        and the less frequently locks need to be acquired.
2262                        For more information see Documentation/vm/slub.txt.
2263
2264        slub_min_order= [MM, SLUB]
2265                        Determines the mininum page order for slabs. Must be
2266                        lower than slub_max_order.
2267                        For more information see Documentation/vm/slub.txt.
2268
2269        slub_nomerge    [MM, SLUB]
2270                        Disable merging of slabs with similar size. May be
2271                        necessary if there is some reason to distinguish
2272                        allocs to different slabs. Debug options disable
2273                        merging on their own.
2274                        For more information see Documentation/vm/slub.txt.
2275
2276        smart2=         [HW]
2277                        Format: <io1>[,<io2>[,...,<io8>]]
2278
2279        smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
2280                        attempt to substitute SMP alternatives once at boot.
2281
2282        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
2283        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
2284        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
2285        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
2286        smsc-ircc2.ircc_irq=    [HW] IRQ line
2287        smsc-ircc2.ircc_dma=    [HW] DMA channel
2288        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2289                                0: Toshiba Satellite 1800 (GP data pin select)
2290                                1: Fast pin select (default)
2291                                2: ATC IRMode
2292
2293        softlockup_panic=
2294                        [KNL] Should the soft-lockup detector generate panics.
2295
2296        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
2297                        See Documentation/sonypi.txt
2298
2299        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
2300                        See Documentation/serial/specialix.txt.
2301
2302        spia_io_base=   [HW,MTD]
2303        spia_fio_base=
2304        spia_pedr=
2305        spia_peddr=
2306
2307        stacktrace      [FTRACE]
2308                        Enabled the stack tracer on boot up.
2309
2310        sti=            [PARISC,HW]
2311                        Format: <num>
2312                        Set the STI (builtin display/keyboard on the HP-PARISC
2313                        machines) console (graphic card) which should be used
2314                        as the initial boot-console.
2315                        See also comment in drivers/video/console/sticore.c.
2316
2317        sti_font=       [HW]
2318                        See comment in drivers/video/console/sticore.c.
2319
2320        stifb=          [HW]
2321                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2322
2323        sunrpc.min_resvport=
2324        sunrpc.max_resvport=
2325                        [NFS,SUNRPC]
2326                        SunRPC servers often require that client requests
2327                        originate from a privileged port (i.e. a port in the
2328                        range 0 < portnr < 1024).
2329                        An administrator who wishes to reserve some of these
2330                        ports for other uses may adjust the range that the
2331                        kernel's sunrpc client considers to be privileged
2332                        using these two parameters to set the minimum and
2333                        maximum port values.
2334
2335        sunrpc.pool_mode=
2336                        [NFS]
2337                        Control how the NFS server code allocates CPUs to
2338                        service thread pools.  Depending on how many NICs
2339                        you have and where their interrupts are bound, this
2340                        option will affect which CPUs will do NFS serving.
2341                        Note: this parameter cannot be changed while the
2342                        NFS server is running.
2343
2344                        auto        the server chooses an appropriate mode
2345                                    automatically using heuristics
2346                        global      a single global pool contains all CPUs
2347                        percpu      one pool for each CPU
2348                        pernode     one pool for each NUMA node (equivalent
2349                                    to global on non-NUMA machines)
2350
2351        sunrpc.tcp_slot_table_entries=
2352        sunrpc.udp_slot_table_entries=
2353                        [NFS,SUNRPC]
2354                        Sets the upper limit on the number of simultaneous
2355                        RPC calls that can be sent from the client to a
2356                        server. Increasing these values may allow you to
2357                        improve throughput, but will also increase the
2358                        amount of memory reserved for use by the client.
2359
2360        swiotlb=        [IA-64] Number of I/O TLB slabs
2361
2362        switches=       [HW,M68k]
2363
2364        sysrq_always_enabled
2365                        [KNL]
2366                        Ignore sysrq setting - this boot parameter will
2367                        neutralize any effect of /proc/sys/kernel/sysrq.
2368                        Useful for debugging.
2369
2370        tdfx=           [HW,DRM]
2371
2372        test_suspend=   [SUSPEND]
2373                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
2374                        standby suspend) as the system sleep state to briefly
2375                        enter during system startup.  The system is woken from
2376                        this state using a wakeup-capable RTC alarm.
2377
2378        thash_entries=  [KNL,NET]
2379                        Set number of hash buckets for TCP connection
2380
2381        thermal.act=    [HW,ACPI]
2382                        -1: disable all active trip points in all thermal zones
2383                        <degrees C>: override all lowest active trip points
2384
2385        thermal.crt=    [HW,ACPI]
2386                        -1: disable all critical trip points in all thermal zones
2387                        <degrees C>: override all critical trip points
2388
2389        thermal.nocrt=  [HW,ACPI]
2390                        Set to disable actions on ACPI thermal zone
2391                        critical and hot trip points.
2392
2393        thermal.off=    [HW,ACPI]
2394                        1: disable ACPI thermal control
2395
2396        thermal.psv=    [HW,ACPI]
2397                        -1: disable all passive trip points
2398                        <degrees C>: override all passive trip points to this
2399                        value
2400
2401        thermal.tzp=    [HW,ACPI]
2402                        Specify global default ACPI thermal zone polling rate
2403                        <deci-seconds>: poll all this frequency
2404                        0: no polling (default)
2405
2406        topology=       [S390]
2407                        Format: {off | on}
2408                        Specify if the kernel should make use of the cpu
2409                        topology informations if the hardware supports these.
2410                        The scheduler will make use of these informations and
2411                        e.g. base its process migration decisions on it.
2412                        Default is off.
2413
2414        tp720=          [HW,PS2]
2415
2416        tpm_suspend_pcr=[HW,TPM]
2417                        Format: integer pcr id
2418                        Specify that at suspend time, the tpm driver
2419                        should extend the specified pcr with zeros,
2420                        as a workaround for some chips which fail to
2421                        flush the last written pcr on TPM_SaveState.
2422                        This will guarantee that all the other pcrs
2423                        are saved.
2424
2425        trace_buf_size=nn[KMG]
2426                        [FTRACE] will set tracing buffer size.
2427
2428        trace_event=[event-list]
2429                        [FTRACE] Set and start specified trace events in order
2430                        to facilitate early boot debugging.
2431                        See also Documentation/trace/events.txt
2432
2433        tsc=            Disable clocksource-must-verify flag for TSC.
2434                        Format: <string>
2435                        [x86] reliable: mark tsc clocksource as reliable, this
2436                        disables clocksource verification at runtime.
2437                        Used to enable high-resolution timer mode on older
2438                        hardware, and in virtualized environment.
2439
2440        turbografx.map[2|3]=    [HW,JOY]
2441                        TurboGraFX parallel port interface
2442                        Format:
2443                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2444                        See also Documentation/input/joystick-parport.txt
2445
2446        uhash_entries=  [KNL,NET]
2447                        Set number of hash buckets for UDP/UDP-Lite connections
2448
2449        uhci-hcd.ignore_oc=
2450                        [USB] Ignore overcurrent events (default N).
2451                        Some badly-designed motherboards generate lots of
2452                        bogus events, for ports that aren't wired to
2453                        anything.  Set this parameter to avoid log spamming.
2454                        Note that genuine overcurrent events won't be
2455                        reported either.
2456
2457        unknown_nmi_panic
2458                        [X86]
2459                        Set unknown_nmi_panic=1 early on boot.
2460
2461        usbcore.autosuspend=
2462                        [USB] The autosuspend time delay (in seconds) used
2463                        for newly-detected USB devices (default 2).  This
2464                        is the time required before an idle device will be
2465                        autosuspended.  Devices for which the delay is set
2466                        to a negative value won't be autosuspended at all.
2467
2468        usbcore.usbfs_snoop=
2469                        [USB] Set to log all usbfs traffic (default 0 = off).
2470
2471        usbcore.blinkenlights=
2472                        [USB] Set to cycle leds on hubs (default 0 = off).
2473
2474        usbcore.old_scheme_first=
2475                        [USB] Start with the old device initialization
2476                        scheme (default 0 = off).
2477
2478        usbcore.use_both_schemes=
2479                        [USB] Try the other device initialization scheme
2480                        if the first one fails (default 1 = enabled).
2481
2482        usbcore.initial_descriptor_timeout=
2483                        [USB] Specifies timeout for the initial 64-byte
2484                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2485                        (default 5000 = 5.0 seconds).
2486
2487        usbhid.mousepoll=
2488                        [USBHID] The interval which mice are to be polled at.
2489
2490        usb-storage.delay_use=
2491                        [UMS] The delay in seconds before a new device is
2492                        scanned for Logical Units (default 5).
2493
2494        usb-storage.quirks=
2495                        [UMS] A list of quirks entries to supplement or
2496                        override the built-in unusual_devs list.  List
2497                        entries are separated by commas.  Each entry has
2498                        the form VID:PID:Flags where VID and PID are Vendor
2499                        and Product ID values (4-digit hex numbers) and
2500                        Flags is a set of characters, each corresponding
2501                        to a common usb-storage quirk flag as follows:
2502                                a = SANE_SENSE (collect more than 18 bytes
2503                                        of sense data);
2504                                b = BAD_SENSE (don't collect more than 18
2505                                        bytes of sense data);
2506                                c = FIX_CAPACITY (decrease the reported
2507                                        device capacity by one sector);
2508                                h = CAPACITY_HEURISTICS (decrease the
2509                                        reported device capacity by one
2510                                        sector if the number is odd);
2511                                i = IGNORE_DEVICE (don't bind to this
2512                                        device);
2513                                l = NOT_LOCKABLE (don't try to lock and
2514                                        unlock ejectable media);
2515                                m = MAX_SECTORS_64 (don't transfer more
2516                                        than 64 sectors = 32 KB at a time);
2517                                o = CAPACITY_OK (accept the capacity
2518                                        reported by the device);
2519                                r = IGNORE_RESIDUE (the device reports
2520                                        bogus residue values);
2521                                s = SINGLE_LUN (the device has only one
2522                                        Logical Unit);
2523                                w = NO_WP_DETECT (don't test whether the
2524                                        medium is write-protected).
2525                        Example: quirks=0419:aaf5:rl,0421:0433:rc
2526
2527        userpte=
2528                        [X86] Flags controlling user PTE allocations.
2529
2530                                nohigh = do not allocate PTE pages in
2531                                        HIGHMEM regardless of setting
2532                                        of CONFIG_HIGHPTE.
2533
2534        vdso=           [X86,SH]
2535                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2536                        vdso=1: enable VDSO (default)
2537                        vdso=0: disable VDSO mapping
2538
2539        vdso32=         [X86]
2540                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2541                        vdso32=1: enable 32-bit VDSO (default)
2542                        vdso32=0: disable 32-bit VDSO mapping
2543
2544        vector=         [IA-64,SMP]
2545                        vector=percpu: enable percpu vector domain
2546
2547        video=          [FB] Frame buffer configuration
2548                        See Documentation/fb/modedb.txt.
2549
2550        vga=            [BOOT,X86-32] Select a particular video mode
2551                        See Documentation/x86/boot.txt and
2552                        Documentation/svga.txt.
2553                        Use vga=ask for menu.
2554                        This is actually a boot loader parameter; the value is
2555                        passed to the kernel using a special protocol.
2556
2557        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2558                        size of <nn>. This can be used to increase the
2559                        minimum size (128MB on x86). It can also be used to
2560                        decrease the size and leave more room for directly
2561                        mapped kernel RAM.
2562
2563        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
2564                        Format: <command>
2565
2566        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
2567                        Format: <command>
2568
2569        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
2570                        Format: <command>
2571
2572        vt.cur_default= [VT] Default cursor shape.
2573                        Format: 0xCCBBAA, where AA, BB, and CC are the same as
2574                        the parameters of the <Esc>[?A;B;Cc escape sequence;
2575                        see VGA-softcursor.txt. Default: 2 = underline.
2576
2577        vt.default_blu= [VT]
2578                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2579                        Change the default blue palette of the console.
2580                        This is a 16-member array composed of values
2581                        ranging from 0-255.
2582
2583        vt.default_grn= [VT]
2584                        Format: <green0>,<green1>,<green2>,...,<green15>
2585                        Change the default green palette of the console.
2586                        This is a 16-member array composed of values
2587                        ranging from 0-255.
2588
2589        vt.default_red= [VT]
2590                        Format: <red0>,<red1>,<red2>,...,<red15>
2591                        Change the default red palette of the console.
2592                        This is a 16-member array composed of values
2593                        ranging from 0-255.
2594
2595        vt.default_utf8=
2596                        [VT]
2597                        Format=<0|1>
2598                        Set system-wide default UTF-8 mode for all tty's.
2599                        Default is 1, i.e. UTF-8 mode is enabled for all
2600                        newly opened terminals.
2601
2602        vt.global_cursor_default=
2603                        [VT]
2604                        Format=<-1|0|1>
2605                        Set system-wide default for whether a cursor
2606                        is shown on new VTs. Default is -1,
2607                        i.e. cursors will be created by default unless
2608                        overridden by individual drivers. 0 will hide
2609                        cursors, 1 will display them.
2610
2611        watchdog timers [HW,WDT] For information on watchdog timers,
2612                        see Documentation/watchdog/watchdog-parameters.txt
2613                        or other driver-specific files in the
2614                        Documentation/watchdog/ directory.
2615
2616        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
2617                        default x2apic cluster mode on platforms
2618                        supporting x2apic.
2619
2620        x86_mrst_timer= [X86-32,APBT]
2621                        Choose timer option for x86 Moorestown MID platform.
2622                        Two valid options are apbt timer only and lapic timer
2623                        plus one apbt timer for broadcast timer.
2624                        x86_mrst_timer=apbt_only | lapic_and_apbt
2625
2626        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2627        xd_geo=         See header of drivers/block/xd.c.
2628
2629        xen_emul_unplug=                [HW,X86,XEN]
2630                        Unplug Xen emulated devices
2631                        Format: [unplug0,][unplug1]
2632                        ide-disks -- unplug primary master IDE devices
2633                        aux-ide-disks -- unplug non-primary-master IDE devices
2634                        nics -- unplug network devices
2635                        all -- unplug all emulated devices (NICs and IDE disks)
2636                        unnecessary -- unplugging emulated devices is
2637                                unnecessary even if the host did not respond to
2638                                the unplug protocol
2639                        never -- do not unplug even if version check succeeds
2640
2641        xirc2ps_cs=     [NET,PCMCIA]
2642                        Format:
2643                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2644
2645______________________________________________________________________
2646
2647TODO:
2648
2649        Add more DRM drivers.
2650
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