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        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
  47        EFI     EFI Partitioning (GPT) is enabled
  48        EIDE    EIDE/ATAPI support is enabled.
  49        DRM     Direct Rendering Management support is enabled.
  50        DYNAMIC_DEBUG Build in debug messages and enable them at runtime
  51        FB      The frame buffer device is enabled.
  52        GCOV    GCOV profiling is enabled.
  53        HW      Appropriate hardware is enabled.
  54        IA-64   IA-64 architecture is enabled.
  55        IMA     Integrity measurement architecture is enabled.
  56        IOSCHED More than one I/O scheduler is enabled.
  57        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
  58        IPV6    IPv6 support is enabled.
  59        ISAPNP  ISA PnP code is enabled.
  60        ISDN    Appropriate ISDN support is enabled.
  61        JOY     Appropriate joystick support is enabled.
  62        KGDB    Kernel debugger support is enabled.
  63        KVM     Kernel Virtual Machine support is enabled.
  64        LIBATA  Libata driver is enabled
  65        LP      Printer support is enabled.
  66        LOOP    Loopback device support is enabled.
  67        M68k    M68k architecture is enabled.
  68                        These options have more detailed description inside of
  69                        Documentation/m68k/kernel-options.txt.
  70        MCA     MCA bus support is enabled.
  71        MDA     MDA console support is enabled.
  72        MOUSE   Appropriate mouse support is enabled.
  73        MSI     Message Signaled Interrupts (PCI).
  74        MTD     MTD (Memory Technology Device) support is enabled.
  75        NET     Appropriate network support is enabled.
  76        NUMA    NUMA support is enabled.
  77        NFS     Appropriate NFS support is enabled.
  78        OSS     OSS sound support is enabled.
  79        PV_OPS  A paravirtualized kernel is enabled.
  80        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
  81        PARISC  The PA-RISC architecture is enabled.
  82        PCI     PCI bus support is enabled.
  83        PCIE    PCI Express support is enabled.
  84        PCMCIA  The PCMCIA subsystem is enabled.
  85        PNP     Plug & Play support is enabled.
  86        PPC     PowerPC architecture is enabled.
  87        PPT     Parallel port support is enabled.
  88        PS2     Appropriate PS/2 support is enabled.
  89        RAM     RAM disk support is enabled.
  90        S390    S390 architecture is enabled.
  91        SCSI    Appropriate SCSI support is enabled.
  92                        A lot of drivers have their options described inside
  93                        the Documentation/scsi/ sub-directory.
  94        SECURITY Different security models are enabled.
  95        SELINUX SELinux support is enabled.
  96        APPARMOR AppArmor support is enabled.
  97        SERIAL  Serial support is enabled.
  98        SH      SuperH architecture is enabled.
  99        SMP     The kernel is an SMP kernel.
 100        SPARC   Sparc architecture is enabled.
 101        SWSUSP  Software suspend (hibernation) is enabled.
 102        SUSPEND System suspend states are enabled.
 103        FTRACE  Function tracing enabled.
 104        TPM     TPM drivers are enabled.
 105        TS      Appropriate touchscreen support is enabled.
 106        UMS     USB Mass Storage support is enabled.
 107        USB     USB support is enabled.
 108        USBHID  USB Human Interface Device support is enabled.
 109        V4L     Video For Linux support is enabled.
 110        VGA     The VGA console has been enabled.
 111        VT      Virtual terminal support is enabled.
 112        WDT     Watchdog support is enabled.
 113        XT      IBM PC/XT MFM hard disk support is enabled.
 114        X86-32  X86-32, aka i386 architecture is enabled.
 115        X86-64  X86-64 architecture is enabled.
 116                        More X86-64 boot options can be found in
 117                        Documentation/x86/x86_64/boot-options.txt .
 118        X86     Either 32bit or 64bit x86 (same as X86-32+X86-64)
 119        XEN     Xen support is enabled
 120
 121In addition, the following text indicates that the option:
 122
 123        BUGS=   Relates to possible processor bugs on the said processor.
 124        KNL     Is a kernel start-up parameter.
 125        BOOT    Is a boot loader parameter.
 126
 127Parameters denoted with BOOT are actually interpreted by the boot
 128loader, and have no meaning to the kernel directly.
 129Do not modify the syntax of boot loader parameters without extreme
 130need or coordination with <Documentation/x86/boot.txt>.
 131
 132There are also arch-specific kernel-parameters not documented here.
 133See for example <Documentation/x86/x86_64/boot-options.txt>.
 134
 135Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
 136a trailing = on the name of any parameter states that that parameter will
 137be entered as an environment variable, whereas its absence indicates that
 138it will appear as a kernel argument readable via /proc/cmdline by programs
 139running once the system is up.
 140
 141The number of kernel parameters is not limited, but the length of the
 142complete command line (parameters including spaces etc.) is limited to
 143a fixed number of characters. This limit depends on the architecture
 144and is between 256 and 4096 characters. It is defined in the file
 145./include/asm/setup.h as COMMAND_LINE_SIZE.
 146
 147
 148        acpi=           [HW,ACPI,X86]
 149                        Advanced Configuration and Power Interface
 150                        Format: { force | off | strict | noirq | rsdt }
 151                        force -- enable ACPI if default was off
 152                        off -- disable ACPI if default was on
 153                        noirq -- do not use ACPI for IRQ routing
 154                        strict -- Be less tolerant of platforms that are not
 155                                strictly ACPI specification compliant.
 156                        rsdt -- prefer RSDT over (default) XSDT
 157                        copy_dsdt -- copy DSDT to memory
 158
 159                        See also Documentation/power/pm.txt, pci=noacpi
 160
 161        acpi_apic_instance=     [ACPI, IOAPIC]
 162                        Format: <int>
 163                        2: use 2nd APIC table, if available
 164                        1,0: use 1st APIC table
 165                        default: 0
 166
 167        acpi_backlight= [HW,ACPI]
 168                        acpi_backlight=vendor
 169                        acpi_backlight=video
 170                        If set to vendor, prefer vendor specific driver
 171                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
 172                        of the ACPI video.ko driver.
 173
 174        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
 175        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
 176                        Format: <int>
 177                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
 178                        debug output.  Bits in debug_layer correspond to a
 179                        _COMPONENT in an ACPI source file, e.g.,
 180                            #define _COMPONENT ACPI_PCI_COMPONENT
 181                        Bits in debug_level correspond to a level in
 182                        ACPI_DEBUG_PRINT statements, e.g.,
 183                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
 184                        The debug_level mask defaults to "info".  See
 185                        Documentation/acpi/debug.txt for more information about
 186                        debug layers and levels.
 187
 188                        Enable processor driver info messages:
 189                            acpi.debug_layer=0x20000000
 190                        Enable PCI/PCI interrupt routing info messages:
 191                            acpi.debug_layer=0x400000
 192                        Enable AML "Debug" output, i.e., stores to the Debug
 193                        object while interpreting AML:
 194                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
 195                        Enable all messages related to ACPI hardware:
 196                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
 197
 198                        Some values produce so much output that the system is
 199                        unusable.  The "log_buf_len" parameter may be useful
 200                        if you need to capture more output.
 201
 202        acpi_display_output=    [HW,ACPI]
 203                        acpi_display_output=vendor
 204                        acpi_display_output=video
 205                        See above.
 206
 207        acpi_irq_balance [HW,ACPI]
 208                        ACPI will balance active IRQs
 209                        default in APIC mode
 210
 211        acpi_irq_nobalance [HW,ACPI]
 212                        ACPI will not move active IRQs (default)
 213                        default in PIC mode
 214
 215        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 216                        Format: <irq>,<irq>...
 217
 218        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
 219                        use by PCI
 220                        Format: <irq>,<irq>...
 221
 222        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT
 223
 224        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
 225                        Format: To spoof as Windows 98: ="Microsoft Windows"
 226
 227        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
 228                        acpi_osi="string1"      # add string1 -- only one string
 229                        acpi_osi="!string2"     # remove built-in string2
 230                        acpi_osi=               # disable all strings
 231
 232        acpi_pm_good    [X86]
 233                        Override the pmtimer bug detection: force the kernel
 234                        to assume that this machine's pmtimer latches its value
 235                        and always returns good values.
 236
 237        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
 238                        Format: { level | edge | high | low }
 239
 240        acpi_serialize  [HW,ACPI] force serialization of AML methods
 241
 242        acpi_skip_timer_override [HW,ACPI]
 243                        Recognize and ignore IRQ0/pin2 Interrupt Override.
 244                        For broken nForce2 BIOS resulting in XT-PIC timer.
 245
 246        acpi_sleep=     [HW,ACPI] Sleep options
 247                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
 248                                  old_ordering, s4_nonvs, sci_force_enable }
 249                        See Documentation/power/video.txt for information on
 250                        s3_bios and s3_mode.
 251                        s3_beep is for debugging; it makes the PC's speaker beep
 252                        as soon as the kernel's real-mode entry point is called.
 253                        s4_nohwsig prevents ACPI hardware signature from being
 254                        used during resume from hibernation.
 255                        old_ordering causes the ACPI 1.0 ordering of the _PTS
 256                        control method, with respect to putting devices into
 257                        low power states, to be enforced (the ACPI 2.0 ordering
 258                        of _PTS is used by default).
 259                        nonvs prevents the kernel from saving/restoring the
 260                        ACPI NVS memory during suspend/hibernation and resume.
 261                        sci_force_enable causes the kernel to set SCI_EN directly
 262                        on resume from S1/S3 (which is against the ACPI spec,
 263                        but some broken systems don't work without it).
 264
 265        acpi_use_timer_override [HW,ACPI]
 266                        Use timer override. For some broken Nvidia NF5 boards
 267                        that require a timer override, but don't have HPET
 268
 269        acpi_enforce_resources= [ACPI]
 270                        { strict | lax | no }
 271                        Check for resource conflicts between native drivers
 272                        and ACPI OperationRegions (SystemIO and SystemMemory
 273                        only). IO ports and memory declared in ACPI might be
 274                        used by the ACPI subsystem in arbitrary AML code and
 275                        can interfere with legacy drivers.
 276                        strict (default): access to resources claimed by ACPI
 277                        is denied; legacy drivers trying to access reserved
 278                        resources will fail to bind to device using them.
 279                        lax: access to resources claimed by ACPI is allowed;
 280                        legacy drivers trying to access reserved resources
 281                        will bind successfully but a warning message is logged.
 282                        no: ACPI OperationRegions are not marked as reserved,
 283                        no further checks are performed.
 284
 285        add_efi_memmap  [EFI; X86] Include EFI memory map in
 286                        kernel's map of available physical RAM.
 287
 288        agp=            [AGP]
 289                        { off | try_unsupported }
 290                        off: disable AGP support
 291                        try_unsupported: try to drive unsupported chipsets
 292                                (may crash computer or cause data corruption)
 293
 294        ALSA            [HW,ALSA]
 295                        See Documentation/sound/alsa/alsa-parameters.txt
 296
 297        alignment=      [KNL,ARM]
 298                        Allow the default userspace alignment fault handler
 299                        behaviour to be specified.  Bit 0 enables warnings,
 300                        bit 1 enables fixups, and bit 2 sends a segfault.
 301
 302        amd_iommu=      [HW,X86-84]
 303                        Pass parameters to the AMD IOMMU driver in the system.
 304                        Possible values are:
 305                        fullflush - enable flushing of IO/TLB entries when
 306                                    they are unmapped. Otherwise they are
 307                                    flushed before they will be reused, which
 308                                    is a lot of faster
 309                        off       - do not initialize any AMD IOMMU found in
 310                                    the system
 311
 312        amijoy.map=     [HW,JOY] Amiga joystick support
 313                        Map of devices attached to JOY0DAT and JOY1DAT
 314                        Format: <a>,<b>
 315                        See also Documentation/kernel/input/joystick.txt
 316
 317        analog.map=     [HW,JOY] Analog joystick and gamepad support
 318                        Specifies type or capabilities of an analog joystick
 319                        connected to one of 16 gameports
 320                        Format: <type1>,<type2>,..<type16>
 321
 322        apc=            [HW,SPARC]
 323                        Power management functions (SPARCstation-4/5 + deriv.)
 324                        Format: noidle
 325                        Disable APC CPU standby support. SPARCstation-Fox does
 326                        not play well with APC CPU idle - disable it if you have
 327                        APC and your system crashes randomly.
 328
 329        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
 330                        Change the output verbosity whilst booting
 331                        Format: { quiet (default) | verbose | debug }
 332                        Change the amount of debugging information output
 333                        when initialising the APIC and IO-APIC components.
 334
 335        autoconf=       [IPV6]
 336                        See Documentation/networking/ipv6.txt.
 337
 338        show_lapic=     [APIC,X86] Advanced Programmable Interrupt Controller
 339                        Limit apic dumping. The parameter defines the maximal
 340                        number of local apics being dumped. Also it is possible
 341                        to set it to "all" by meaning -- no limit here.
 342                        Format: { 1 (default) | 2 | ... | all }.
 343                        The parameter valid if only apic=debug or
 344                        apic=verbose is specified.
 345                        Example: apic=debug show_lapic=all
 346
 347        apm=            [APM] Advanced Power Management
 348                        See header of arch/x86/kernel/apm_32.c.
 349
 350        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 351                        Format: <io>,<irq>,<nodeID>
 352
 353        ataflop=        [HW,M68k]
 354
 355        atarimouse=     [HW,MOUSE] Atari Mouse
 356
 357        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 358                        EzKey and similar keyboards
 359
 360        atkbd.reset=    [HW] Reset keyboard during initialization
 361
 362        atkbd.set=      [HW] Select keyboard code set
 363                        Format: <int> (2 = AT (default), 3 = PS/2)
 364
 365        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 366                        keyboards
 367
 368        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 369                        Format: <bool> (0 = real, 1 = synthetic (default))
 370
 371        atkbd.softrepeat= [HW]
 372                        Use software keyboard repeat
 373
 374        autotest        [IA64]
 375
 376        baycom_epp=     [HW,AX25]
 377                        Format: <io>,<mode>
 378
 379        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 380                        Format: <io>,<mode>
 381                        See header of drivers/net/hamradio/baycom_par.c.
 382
 383        baycom_ser_fdx= [HW,AX25]
 384                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 385                        Format: <io>,<irq>,<mode>[,<baud>]
 386                        See header of drivers/net/hamradio/baycom_ser_fdx.c.
 387
 388        baycom_ser_hdx= [HW,AX25]
 389                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 390                        Format: <io>,<irq>,<mode>
 391                        See header of drivers/net/hamradio/baycom_ser_hdx.c.
 392
 393        boot_delay=     Milliseconds to delay each printk during boot.
 394                        Values larger than 10 seconds (10000) are changed to
 395                        no delay (0).
 396                        Format: integer
 397
 398        bootmem_debug   [KNL] Enable bootmem allocator debug messages.
 399
 400        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 401        bttv.radio=     Most important insmod options are available as
 402                        kernel args too.
 403        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 404        bttv.tuner=     and Documentation/video4linux/bttv/CARDLIST
 405
 406        c101=           [NET] Moxa C101 synchronous serial card
 407
 408        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
 409                        Sometimes CPU hardware bugs make them report the cache
 410                        size incorrectly. The kernel will attempt work arounds
 411                        to fix known problems, but for some CPUs it is not
 412                        possible to determine what the correct size should be.
 413                        This option provides an override for these situations.
 414
 415        capability.disable=
 416                        [SECURITY] Disable capabilities.  This would normally
 417                        be used only if an alternative security model is to be
 418                        configured.  Potentially dangerous and should only be
 419                        used if you are entirely sure of the consequences.
 420
 421        ccw_timeout_log [S390]
 422                        See Documentation/s390/CommonIO for details.
 423
 424        cgroup_disable= [KNL] Disable a particular controller
 425                        Format: {name of the controller(s) to disable}
 426                                {Currently supported controllers - "memory"}
 427
 428        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 429                        Format: { "0" | "1" }
 430                        See security/selinux/Kconfig help text.
 431                        0 -- check protection applied by kernel (includes
 432                                any implied execute protection).
 433                        1 -- check protection requested by application.
 434                        Default value is set via a kernel config option.
 435                        Value can be changed at runtime via
 436                                /selinux/checkreqprot.
 437
 438        cio_ignore=     [S390]
 439                        See Documentation/s390/CommonIO for details.
 440
 441        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
 442                        [Deprecated]
 443                        Forces specified clocksource (if available) to be used
 444                        when calculating gettimeofday(). If specified
 445                        clocksource is not available, it defaults to PIT.
 446                        Format: { pit | tsc | cyclone | pmtmr }
 447
 448        clocksource=    Override the default clocksource
 449                        Format: <string>
 450                        Override the default clocksource and use the clocksource
 451                        with the name specified.
 452                        Some clocksource names to choose from, depending on
 453                        the platform:
 454                        [all] jiffies (this is the base, fallback clocksource)
 455                        [ACPI] acpi_pm
 456                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
 457                                pxa_timer,timer3,32k_counter,timer0_1
 458                        [AVR32] avr32
 459                        [X86-32] pit,hpet,tsc;
 460                                scx200_hrt on Geode; cyclone on IBM x440
 461                        [MIPS] MIPS
 462                        [PARISC] cr16
 463                        [S390] tod
 464                        [SH] SuperH
 465                        [SPARC64] tick
 466                        [X86-64] hpet,tsc
 467
 468        clearcpuid=BITNUM [X86]
 469                        Disable CPUID feature X for the kernel. See
 470                        arch/x86/include/asm/cpufeature.h for the valid bit
 471                        numbers. Note the Linux specific bits are not necessarily
 472                        stable over kernel options, but the vendor specific
 473                        ones should be.
 474                        Also note that user programs calling CPUID directly
 475                        or using the feature without checking anything
 476                        will still see it. This just prevents it from
 477                        being used by the kernel or shown in /proc/cpuinfo.
 478                        Also note the kernel might malfunction if you disable
 479                        some critical bits.
 480
 481        cmo_free_hint=  [PPC] Format: { yes | no }
 482                        Specify whether pages are marked as being inactive
 483                        when they are freed.  This is used in CMO environments
 484                        to determine OS memory pressure for page stealing by
 485                        a hypervisor.
 486                        Default: yes
 487
 488        code_bytes      [X86] How many bytes of object code to print
 489                        in an oops report.
 490                        Range: 0 - 8192
 491                        Default: 64
 492
 493        com20020=       [HW,NET] ARCnet - COM20020 chipset
 494                        Format:
 495                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 496
 497        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 498                        Format: <io>[,<irq>]
 499
 500        com90xx=        [HW,NET]
 501                        ARCnet - COM90xx chipset (memory-mapped buffers)
 502                        Format: <io>[,<irq>[,<memstart>]]
 503
 504        condev=         [HW,S390] console device
 505        conmode=
 506
 507        console=        [KNL] Output console device and options.
 508
 509                tty<n>  Use the virtual console device <n>.
 510
 511                ttyS<n>[,options]
 512                ttyUSB0[,options]
 513                        Use the specified serial port.  The options are of
 514                        the form "bbbbpnf", where "bbbb" is the baud rate,
 515                        "p" is parity ("n", "o", or "e"), "n" is number of
 516                        bits, and "f" is flow control ("r" for RTS or
 517                        omit it).  Default is "9600n8".
 518
 519                        See Documentation/serial-console.txt for more
 520                        information.  See
 521                        Documentation/networking/netconsole.txt for an
 522                        alternative.
 523
 524                uart[8250],io,<addr>[,options]
 525                uart[8250],mmio,<addr>[,options]
 526                        Start an early, polled-mode console on the 8250/16550
 527                        UART at the specified I/O port or MMIO address,
 528                        switching to the matching ttyS device later.  The
 529                        options are the same as for ttyS, above.
 530
 531                If the device connected to the port is not a TTY but a braille
 532                device, prepend "brl," before the device type, for instance
 533                        console=brl,ttyS0
 534                For now, only VisioBraille is supported.
 535
 536        consoleblank=   [KNL] The console blank (screen saver) timeout in
 537                        seconds. Defaults to 10*60 = 10mins. A value of 0
 538                        disables the blank timer.
 539
 540        coredump_filter=
 541                        [KNL] Change the default value for
 542                        /proc/<pid>/coredump_filter.
 543                        See also Documentation/filesystems/proc.txt.
 544
 545        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 546                        Format:
 547                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 548
 549        crashkernel=nn[KMG]@ss[KMG]
 550                        [KNL] Reserve a chunk of physical memory to
 551                        hold a kernel to switch to with kexec on panic.
 552
 553        crashkernel=range1:size1[,range2:size2,...][@offset]
 554                        [KNL] Same as above, but depends on the memory
 555                        in the running system. The syntax of range is
 556                        start-[end] where start and end are both
 557                        a memory unit (amount[KMG]). See also
 558                        Documentation/kdump/kdump.txt for a example.
 559
 560        cs89x0_dma=     [HW,NET]
 561                        Format: <dma>
 562
 563        cs89x0_media=   [HW,NET]
 564                        Format: { rj45 | aui | bnc }
 565
 566        dasd=           [HW,NET]
 567                        See header of drivers/s390/block/dasd_devmap.c.
 568
 569        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 570                        (one device per port)
 571                        Format: <port#>,<type>
 572                        See also Documentation/input/joystick-parport.txt
 573
 574        ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
 575                        time. See Documentation/dynamic-debug-howto.txt for
 576                        details.
 577
 578        debug           [KNL] Enable kernel debugging (events log level).
 579
 580        debug_locks_verbose=
 581                        [KNL] verbose self-tests
 582                        Format=<0|1>
 583                        Print debugging info while doing the locking API
 584                        self-tests.
 585                        We default to 0 (no extra messages), setting it to
 586                        1 will print _a lot_ more information - normally
 587                        only useful to kernel developers.
 588
 589        debug_objects   [KNL] Enable object debugging
 590
 591        no_debug_objects
 592                        [KNL] Disable object debugging
 593
 594        debugpat        [X86] Enable PAT debugging
 595
 596        decnet.addr=    [HW,NET]
 597                        Format: <area>[,<node>]
 598                        See also Documentation/networking/decnet.txt.
 599
 600        default_hugepagesz=
 601                        [same as hugepagesz=] The size of the default
 602                        HugeTLB page size. This is the size represented by
 603                        the legacy /proc/ hugepages APIs, used for SHM, and
 604                        default size when mounting hugetlbfs filesystems.
 605                        Defaults to the default architecture's huge page size
 606                        if not specified.
 607
 608        dhash_entries=  [KNL]
 609                        Set number of hash buckets for dentry cache.
 610
 611        digi=           [HW,SERIAL]
 612                        IO parameters + enable/disable command.
 613
 614        digiepca=       [HW,SERIAL]
 615                        See drivers/char/README.epca and
 616                        Documentation/serial/digiepca.txt.
 617
 618        disable=        [IPV6]
 619                        See Documentation/networking/ipv6.txt.
 620
 621        disable_ipv6=   [IPV6]
 622                        See Documentation/networking/ipv6.txt.
 623
 624        disable_mtrr_cleanup [X86]
 625                        The kernel tries to adjust MTRR layout from continuous
 626                        to discrete, to make X server driver able to add WB
 627                        entry later. This parameter disables that.
 628
 629        disable_mtrr_trim [X86, Intel and AMD only]
 630                        By default the kernel will trim any uncacheable
 631                        memory out of your available memory pool based on
 632                        MTRR settings.  This parameter disables that behavior,
 633                        possibly causing your machine to run very slowly.
 634
 635        disable_timer_pin_1 [X86]
 636                        Disable PIN 1 of APIC timer
 637                        Can be useful to work around chipset bugs.
 638
 639        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
 640                        this option disables the debugging code at boot.
 641
 642        dma_debug_entries=<number>
 643                        This option allows to tune the number of preallocated
 644                        entries for DMA-API debugging code. One entry is
 645                        required per DMA-API allocation. Use this if the
 646                        DMA-API debugging code disables itself because the
 647                        architectural default is too low.
 648
 649        dma_debug_driver=<driver_name>
 650                        With this option the DMA-API debugging driver
 651                        filter feature can be enabled at boot time. Just
 652                        pass the driver to filter for as the parameter.
 653                        The filter can be disabled or changed to another
 654                        driver later using sysfs.
 655
 656        dscc4.setup=    [NET]
 657
 658        dynamic_printk  Enables pr_debug()/dev_dbg() calls if
 659                        CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
 660                        These can also be switched on/off via
 661                        <debugfs>/dynamic_printk/modules
 662
 663        earlycon=       [KNL] Output early console device and options.
 664                uart[8250],io,<addr>[,options]
 665                uart[8250],mmio,<addr>[,options]
 666                uart[8250],mmio32,<addr>[,options]
 667                        Start an early, polled-mode console on the 8250/16550
 668                        UART at the specified I/O port or MMIO address.
 669                        MMIO inter-register address stride is either 8bit (mmio)
 670                        or 32bit (mmio32).
 671                        The options are the same as for ttyS, above.
 672
 673        earlyprintk=    [X86,SH,BLACKFIN]
 674                        earlyprintk=vga
 675                        earlyprintk=serial[,ttySn[,baudrate]]
 676                        earlyprintk=ttySn[,baudrate]
 677                        earlyprintk=dbgp[debugController#]
 678
 679                        Append ",keep" to not disable it when the real console
 680                        takes over.
 681
 682                        Only vga or serial or usb debug port at a time.
 683
 684                        Currently only ttyS0 and ttyS1 are supported.
 685
 686                        Interaction with the standard serial driver is not
 687                        very good.
 688
 689                        The VGA output is eventually overwritten by the real
 690                        console.
 691
 692        ekgdboc=        [X86,KGDB] Allow early kernel console debugging
 693                        ekgdboc=kbd
 694
 695                        This is desgined to be used in conjunction with
 696                        the boot argument: earlyprintk=vga
 697
 698        edd=            [EDD]
 699                        Format: {"off" | "on" | "skip[mbr]"}
 700
 701        eisa_irq_edge=  [PARISC,HW]
 702                        See header of drivers/parisc/eisa.c.
 703
 704        elanfreq=       [X86-32]
 705                        See comment before function elanfreq_setup() in
 706                        arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 707
 708        elevator=       [IOSCHED]
 709                        Format: {"cfq" | "deadline" | "noop"}
 710                        See Documentation/block/as-iosched.txt and
 711                        Documentation/block/deadline-iosched.txt for details.
 712
 713        elfcorehdr=     [IA64,PPC,SH,X86]
 714                        Specifies physical address of start of kernel core
 715                        image elf header. Generally kexec loader will
 716                        pass this option to capture kernel.
 717                        See Documentation/kdump/kdump.txt for details.
 718
 719        enable_mtrr_cleanup [X86]
 720                        The kernel tries to adjust MTRR layout from continuous
 721                        to discrete, to make X server driver able to add WB
 722                        entry later. This parameter enables that.
 723
 724        enable_timer_pin_1 [X86]
 725                        Enable PIN 1 of APIC timer
 726                        Can be useful to work around chipset bugs
 727                        (in particular on some ATI chipsets).
 728                        The kernel tries to set a reasonable default.
 729
 730        enforcing       [SELINUX] Set initial enforcing status.
 731                        Format: {"0" | "1"}
 732                        See security/selinux/Kconfig help text.
 733                        0 -- permissive (log only, no denials).
 734                        1 -- enforcing (deny and log).
 735                        Default value is 0.
 736                        Value can be changed at runtime via /selinux/enforce.
 737
 738        erst_disable    [ACPI]
 739                        Disable Error Record Serialization Table (ERST)
 740                        support.
 741
 742        ether=          [HW,NET] Ethernet cards parameters
 743                        This option is obsoleted by the "netdev=" option, which
 744                        has equivalent usage. See its documentation for details.
 745
 746        failslab=
 747        fail_page_alloc=
 748        fail_make_request=[KNL]
 749                        General fault injection mechanism.
 750                        Format: <interval>,<probability>,<space>,<times>
 751                        See also /Documentation/fault-injection/.
 752
 753        floppy=         [HW]
 754                        See Documentation/blockdev/floppy.txt.
 755
 756        force_pal_cache_flush
 757                        [IA-64] Avoid check_sal_cache_flush which may hang on
 758                        buggy SAL_CACHE_FLUSH implementations. Using this
 759                        parameter will force ia64_sal_cache_flush to call
 760                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
 761
 762        ftrace=[tracer]
 763                        [FTRACE] will set and start the specified tracer
 764                        as early as possible in order to facilitate early
 765                        boot debugging.
 766
 767        ftrace_dump_on_oops[=orig_cpu]
 768                        [FTRACE] will dump the trace buffers on oops.
 769                        If no parameter is passed, ftrace will dump
 770                        buffers of all CPUs, but if you pass orig_cpu, it will
 771                        dump only the buffer of the CPU that triggered the
 772                        oops.
 773
 774        ftrace_filter=[function-list]
 775                        [FTRACE] Limit the functions traced by the function
 776                        tracer at boot up. function-list is a comma separated
 777                        list of functions. This list can be changed at run
 778                        time by the set_ftrace_filter file in the debugfs
 779                        tracing directory. 
 780
 781        ftrace_notrace=[function-list]
 782                        [FTRACE] Do not trace the functions specified in
 783                        function-list. This list can be changed at run time
 784                        by the set_ftrace_notrace file in the debugfs
 785                        tracing directory.
 786
 787        ftrace_graph_filter=[function-list]
 788                        [FTRACE] Limit the top level callers functions traced
 789                        by the function graph tracer at boot up.
 790                        function-list is a comma separated list of functions
 791                        that can be changed at run time by the
 792                        set_graph_function file in the debugfs tracing directory.
 793
 794        gamecon.map[2|3]=
 795                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 796                        support via parallel port (up to 5 devices per port)
 797                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 798                        See also Documentation/input/joystick-parport.txt
 799
 800        gamma=          [HW,DRM]
 801
 802        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
 803                        Format: off | on
 804                        default: on
 805
 806        gcov_persist=   [GCOV] When non-zero (default), profiling data for
 807                        kernel modules is saved and remains accessible via
 808                        debugfs, even when the module is unloaded/reloaded.
 809                        When zero, profiling data is discarded and associated
 810                        debugfs files are removed at module unload time.
 811
 812        gpt             [EFI] Forces disk with valid GPT signature but
 813                        invalid Protective MBR to be treated as GPT.
 814
 815        hashdist=       [KNL,NUMA] Large hashes allocated during boot
 816                        are distributed across NUMA nodes.  Defaults on
 817                        for 64bit NUMA, off otherwise.
 818                        Format: 0 | 1 (for off | on)
 819
 820        hcl=            [IA-64] SGI's Hardware Graph compatibility layer
 821
 822        hd=             [EIDE] (E)IDE hard drive subsystem geometry
 823                        Format: <cyl>,<head>,<sect>
 824
 825        hest_disable    [ACPI]
 826                        Disable Hardware Error Source Table (HEST) support;
 827                        corresponding firmware-first mode error processing
 828                        logic will be disabled.
 829
 830        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
 831                        size of <nn>. This works even on boxes that have no
 832                        highmem otherwise. This also works to reduce highmem
 833                        size on bigger boxes.
 834
 835        highres=        [KNL] Enable/disable high resolution timer mode.
 836                        Valid parameters: "on", "off"
 837                        Default: "on"
 838
 839        hisax=          [HW,ISDN]
 840                        See Documentation/isdn/README.HiSax.
 841
 842        hlt             [BUGS=ARM,SH]
 843
 844        hpet=           [X86-32,HPET] option to control HPET usage
 845                        Format: { enable (default) | disable | force |
 846                                verbose }
 847                        disable: disable HPET and use PIT instead
 848                        force: allow force enabled of undocumented chips (ICH4,
 849                                VIA, nVidia)
 850                        verbose: show contents of HPET registers during setup
 851
 852        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
 853        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
 854                        On x86-64 and powerpc, this option can be specified
 855                        multiple times interleaved with hugepages= to reserve
 856                        huge pages of different sizes. Valid pages sizes on
 857                        x86-64 are 2M (when the CPU supports "pse") and 1G
 858                        (when the CPU supports the "pdpe1gb" cpuinfo flag)
 859                        Note that 1GB pages can only be allocated at boot time
 860                        using hugepages= and not freed afterwards.
 861
 862        hvc_iucv=       [S390] Number of z/VM IUCV hypervisor console (HVC)
 863                               terminal devices. Valid values: 0..8
 864        hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
 865                               If specified, z/VM IUCV HVC accepts connections
 866                               from listed z/VM user IDs only.
 867
 868        i2c_bus=        [HW] Override the default board specific I2C bus speed
 869                             or register an additional I2C bus that is not
 870                             registered from board initialization code.
 871                             Format:
 872                             <bus_id>,<clkrate>
 873
 874        i8042.debug     [HW] Toggle i8042 debug mode
 875        i8042.direct    [HW] Put keyboard port into non-translated mode
 876        i8042.dumbkbd   [HW] Pretend that controller can only read data from
 877                             keyboard and cannot control its state
 878                             (Don't attempt to blink the leds)
 879        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
 880        i8042.nokbd     [HW] Don't check/create keyboard port
 881        i8042.noloop    [HW] Disable the AUX Loopback command while probing
 882                             for the AUX port
 883        i8042.nomux     [HW] Don't check presence of an active multiplexing
 884                             controller
 885        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
 886                             controllers
 887        i8042.reset     [HW] Reset the controller during init and cleanup
 888        i8042.unlock    [HW] Unlock (ignore) the keylock
 889
 890        i810=           [HW,DRM]
 891
 892        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
 893                        indicates that the driver is running on unsupported
 894                        hardware.
 895        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
 896                        does not match list of supported models.
 897        i8k.power_status
 898                        [HW] Report power status in /proc/i8k
 899                        (disabled by default)
 900        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
 901                        capability is set.
 902
 903        icn=            [HW,ISDN]
 904                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
 905
 906        ide-core.nodma= [HW] (E)IDE subsystem
 907                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
 908                        .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
 909                        .cdrom .chs .ignore_cable are additional options
 910                        See Documentation/ide/ide.txt.
 911
 912        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
 913                        Claim all unknown PCI IDE storage controllers.
 914
 915        idle=           [X86]
 916                        Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
 917                        Poll forces a polling idle loop that can slightly
 918                        improve the performance of waking up a idle CPU, but
 919                        will use a lot of power and make the system run hot.
 920                        Not recommended.
 921                        idle=mwait: On systems which support MONITOR/MWAIT but
 922                        the kernel chose to not use it because it doesn't save
 923                        as much power as a normal idle loop, use the
 924                        MONITOR/MWAIT idle loop anyways. Performance should be
 925                        the same as idle=poll.
 926                        idle=halt: Halt is forced to be used for CPU idle.
 927                        In such case C2/C3 won't be used again.
 928                        idle=nomwait: Disable mwait for CPU C-states
 929
 930        ignore_loglevel [KNL]
 931                        Ignore loglevel setting - this will print /all/
 932                        kernel messages to the console. Useful for debugging.
 933
 934        ihash_entries=  [KNL]
 935                        Set number of hash buckets for inode cache.
 936
 937        ima_audit=      [IMA]
 938                        Format: { "0" | "1" }
 939                        0 -- integrity auditing messages. (Default)
 940                        1 -- enable informational integrity auditing messages.
 941
 942        ima_hash=       [IMA]
 943                        Format: { "sha1" | "md5" }
 944                        default: "sha1"
 945
 946        ima_tcb         [IMA]
 947                        Load a policy which meets the needs of the Trusted
 948                        Computing Base.  This means IMA will measure all
 949                        programs exec'd, files mmap'd for exec, and all files
 950                        opened for read by uid=0.
 951
 952        init=           [KNL]
 953                        Format: <full_path>
 954                        Run specified binary instead of /sbin/init as init
 955                        process.
 956
 957        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
 958                        for working out where the kernel is dying during
 959                        startup.
 960
 961        initrd=         [BOOT] Specify the location of the initial ramdisk
 962
 963        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
 964                        Format: <irq>
 965
 966        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
 967                on
 968                        Enable intel iommu driver.
 969                off
 970                        Disable intel iommu driver.
 971                igfx_off [Default Off]
 972                        By default, gfx is mapped as normal device. If a gfx
 973                        device has a dedicated DMAR unit, the DMAR unit is
 974                        bypassed by not enabling DMAR with this option. In
 975                        this case, gfx device will use physical address for
 976                        DMA.
 977                forcedac [x86_64]
 978                        With this option iommu will not optimize to look
 979                        for io virtual address below 32 bit forcing dual
 980                        address cycle on pci bus for cards supporting greater
 981                        than 32 bit addressing. The default is to look
 982                        for translation below 32 bit and if not available
 983                        then look in the higher range.
 984                strict [Default Off]
 985                        With this option on every unmap_single operation will
 986                        result in a hardware IOTLB flush operation as opposed
 987                        to batching them for performance.
 988
 989        intremap=       [X86-64, Intel-IOMMU]
 990                        Format: { on (default) | off | nosid }
 991                        on      enable Interrupt Remapping (default)
 992                        off     disable Interrupt Remapping
 993                        nosid   disable Source ID checking
 994
 995        inttest=        [IA64]
 996
 997        iomem=          Disable strict checking of access to MMIO memory
 998                strict  regions from userspace.
 999                relaxed
1000
1001        iommu=          [x86]
1002                off
1003                force
1004                noforce
1005                biomerge
1006                panic
1007                nopanic
1008                merge
1009                nomerge
1010                forcesac
1011                soft
1012                pt      [x86, IA64]
1013
1014        io7=            [HW] IO7 for Marvel based alpha systems
1015                        See comment before marvel_specify_io7 in
1016                        arch/alpha/kernel/core_marvel.c.
1017
1018        io_delay=       [X86] I/O delay method
1019                0x80
1020                        Standard port 0x80 based delay
1021                0xed
1022                        Alternate port 0xed based delay (needed on some systems)
1023                udelay
1024                        Simple two microseconds delay
1025                none
1026                        No delay
1027
1028        ip=             [IP_PNP]
1029                        See Documentation/filesystems/nfs/nfsroot.txt.
1030
1031        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1032                        See comment before ip2_setup() in
1033                        drivers/char/ip2/ip2base.c.
1034
1035        irqfixup        [HW]
1036                        When an interrupt is not handled search all handlers
1037                        for it. Intended to get systems with badly broken
1038                        firmware running.
1039
1040        irqpoll         [HW]
1041                        When an interrupt is not handled search all handlers
1042                        for it. Also check all handlers each timer
1043                        interrupt. Intended to get systems with badly broken
1044                        firmware running.
1045
1046        isapnp=         [ISAPNP]
1047                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1048
1049        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
1050                        Format:
1051                        <cpu number>,...,<cpu number>
1052                        or
1053                        <cpu number>-<cpu number>
1054                        (must be a positive range in ascending order)
1055                        or a mixture
1056                        <cpu number>,...,<cpu number>-<cpu number>
1057
1058                        This option can be used to specify one or more CPUs
1059                        to isolate from the general SMP balancing and scheduling
1060                        algorithms. You can move a process onto or off an
1061                        "isolated" CPU via the CPU affinity syscalls or cpuset.
1062                        <cpu number> begins at 0 and the maximum value is
1063                        "number of CPUs in system - 1".
1064
1065                        This option is the preferred way to isolate CPUs. The
1066                        alternative -- manually setting the CPU mask of all
1067                        tasks in the system -- can cause problems and
1068                        suboptimal load balancer performance.
1069
1070        iucv=           [HW,NET]
1071
1072        js=             [HW,JOY] Analog joystick
1073                        See Documentation/input/joystick.txt.
1074
1075        keepinitrd      [HW,ARM]
1076
1077        kernelcore=nn[KMG]      [KNL,X86,IA-64,PPC] This parameter
1078                        specifies the amount of memory usable by the kernel
1079                        for non-movable allocations.  The requested amount is
1080                        spread evenly throughout all nodes in the system. The
1081                        remaining memory in each node is used for Movable
1082                        pages. In the event, a node is too small to have both
1083                        kernelcore and Movable pages, kernelcore pages will
1084                        take priority and other nodes will have a larger number
1085                        of kernelcore pages.  The Movable zone is used for the
1086                        allocation of pages that may be reclaimed or moved
1087                        by the page migration subsystem.  This means that
1088                        HugeTLB pages may not be allocated from this zone.
1089                        Note that allocations like PTEs-from-HighMem still
1090                        use the HighMem zone if it exists, and the Normal
1091                        zone if it does not.
1092
1093        kgdbdbgp=       [KGDB,HW] kgdb over EHCI usb debug port.
1094                        Format: <Controller#>[,poll interval]
1095                        The controller # is the number of the ehci usb debug
1096                        port as it is probed via PCI.  The poll interval is
1097                        optional and is the number seconds in between
1098                        each poll cycle to the debug port in case you need
1099                        the functionality for interrupting the kernel with
1100                        gdb or control-c on the dbgp connection.  When
1101                        not using this parameter you use sysrq-g to break into
1102                        the kernel debugger.
1103
1104        kgdboc=         [KGDB,HW] kgdb over consoles.
1105                        Requires a tty driver that supports console polling,
1106                        or a supported polling keyboard driver (non-usb).
1107                         Serial only format: <serial_device>[,baud]
1108                         keyboard only format: kbd
1109                         keyboard and serial format: kbd,<serial_device>[,baud]
1110                        Optional Kernel mode setting:
1111                         kms, kbd format: kms,kbd
1112                         kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1113
1114        kgdbwait        [KGDB] Stop kernel execution and enter the
1115                        kernel debugger at the earliest opportunity.
1116
1117        kmac=           [MIPS] korina ethernet MAC address.
1118                        Configure the RouterBoard 532 series on-chip
1119                        Ethernet adapter MAC address.
1120
1121        kmemleak=       [KNL] Boot-time kmemleak enable/disable
1122                        Valid arguments: on, off
1123                        Default: on
1124
1125        kstack=N        [X86] Print N words from the kernel stack
1126                        in oops dumps.
1127
1128        kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1129                        Default is 0 (don't ignore, but inject #GP)
1130
1131        kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1132                        Default is 1 (enabled)
1133
1134        kvm.mmu_audit=  [KVM] This is a R/W parameter which allows audit
1135                        KVM MMU at runtime.
1136                        Default is 0 (off)
1137
1138        kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1139                        Default is 1 (enabled)
1140
1141        kvm-amd.npt=    [KVM,AMD] Disable nested paging (virtualized MMU)
1142                        for all guests.
1143                        Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1144
1145        kvm-intel.bypass_guest_pf=
1146                        [KVM,Intel] Disables bypassing of guest page faults
1147                        on Intel chips. Default is 1 (enabled)
1148
1149        kvm-intel.ept=  [KVM,Intel] Disable extended page tables
1150                        (virtualized MMU) support on capable Intel chips.
1151                        Default is 1 (enabled)
1152
1153        kvm-intel.emulate_invalid_guest_state=
1154                        [KVM,Intel] Enable emulation of invalid guest states
1155                        Default is 0 (disabled)
1156
1157        kvm-intel.flexpriority=
1158                        [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1159                        Default is 1 (enabled)
1160
1161        kvm-intel.unrestricted_guest=
1162                        [KVM,Intel] Disable unrestricted guest feature
1163                        (virtualized real and unpaged mode) on capable
1164                        Intel chips. Default is 1 (enabled)
1165
1166        kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1167                        feature (tagged TLBs) on capable Intel chips.
1168                        Default is 1 (enabled)
1169
1170        l2cr=           [PPC]
1171
1172        l3cr=           [PPC]
1173
1174        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
1175                        disabled it.
1176
1177        lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
1178                        in C2 power state.
1179
1180        libata.dma=     [LIBATA] DMA control
1181                        libata.dma=0      Disable all PATA and SATA DMA
1182                        libata.dma=1      PATA and SATA Disk DMA only
1183                        libata.dma=2      ATAPI (CDROM) DMA only
1184                        libata.dma=4      Compact Flash DMA only 
1185                        Combinations also work, so libata.dma=3 enables DMA
1186                        for disks and CDROMs, but not CFs.
1187        
1188        libata.ignore_hpa=      [LIBATA] Ignore HPA limit
1189                        libata.ignore_hpa=0       keep BIOS limits (default)
1190                        libata.ignore_hpa=1       ignore limits, using full disk
1191
1192        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
1193                        when set.
1194                        Format: <int>
1195
1196        libata.force=   [LIBATA] Force configurations.  The format is comma
1197                        separated list of "[ID:]VAL" where ID is
1198                        PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1199                        matching port, link or device.  Basically, it matches
1200                        the ATA ID string printed on console by libata.  If
1201                        the whole ID part is omitted, the last PORT and DEVICE
1202                        values are used.  If ID hasn't been specified yet, the
1203                        configuration applies to all ports, links and devices.
1204
1205                        If only DEVICE is omitted, the parameter applies to
1206                        the port and all links and devices behind it.  DEVICE
1207                        number of 0 either selects the first device or the
1208                        first fan-out link behind PMP device.  It does not
1209                        select the host link.  DEVICE number of 15 selects the
1210                        host link and device attached to it.
1211
1212                        The VAL specifies the configuration to force.  As long
1213                        as there's no ambiguity shortcut notation is allowed.
1214                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
1215                        The following configurations can be forced.
1216
1217                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
1218                          Any ID with matching PORT is used.
1219
1220                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1221
1222                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1223                          udma[/][16,25,33,44,66,100,133] notation is also
1224                          allowed.
1225
1226                        * [no]ncq: Turn on or off NCQ.
1227
1228                        * nohrst, nosrst, norst: suppress hard, soft
1229                          and both resets.
1230
1231                        * dump_id: dump IDENTIFY data.
1232
1233                        If there are multiple matching configurations changing
1234                        the same attribute, the last one is used.
1235
1236        memblock=debug  [KNL] Enable memblock debug messages.
1237
1238        load_ramdisk=   [RAM] List of ramdisks to load from floppy
1239                        See Documentation/blockdev/ramdisk.txt.
1240
1241        lockd.nlm_grace_period=P  [NFS] Assign grace period.
1242                        Format: <integer>
1243
1244        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
1245                        Format: <integer>
1246
1247        lockd.nlm_timeout=T     [NFS] Assign timeout value.
1248                        Format: <integer>
1249
1250        lockd.nlm_udpport=M     [NFS] Assign UDP port.
1251                        Format: <integer>
1252
1253        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
1254                        Format: <irq>
1255
1256        loglevel=       All Kernel Messages with a loglevel smaller than the
1257                        console loglevel will be printed to the console. It can
1258                        also be changed with klogd or other programs. The
1259                        loglevels are defined as follows:
1260
1261                        0 (KERN_EMERG)          system is unusable
1262                        1 (KERN_ALERT)          action must be taken immediately
1263                        2 (KERN_CRIT)           critical conditions
1264                        3 (KERN_ERR)            error conditions
1265                        4 (KERN_WARNING)        warning conditions
1266                        5 (KERN_NOTICE)         normal but significant condition
1267                        6 (KERN_INFO)           informational
1268                        7 (KERN_DEBUG)          debug-level messages
1269
1270        log_buf_len=n   Sets the size of the printk ring buffer, in bytes.
1271                        Format: { n | nk | nM }
1272                        n must be a power of two.  The default size
1273                        is set in the kernel config file.
1274
1275        logo.nologo     [FB] Disables display of the built-in Linux logo.
1276                        This may be used to provide more screen space for
1277                        kernel log messages and is useful when debugging
1278                        kernel boot problems.
1279
1280        lp=0            [LP]    Specify parallel ports to use, e.g,
1281        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
1282        lp=reset                first parallel port). 'lp=0' disables the
1283        lp=auto                 printer driver. 'lp=reset' (which can be
1284                                specified in addition to the ports) causes
1285                                attached printers to be reset. Using
1286                                lp=port1,port2,... specifies the parallel ports
1287                                to associate lp devices with, starting with
1288                                lp0. A port specification may be 'none' to skip
1289                                that lp device, or a parport name such as
1290                                'parport0'. Specifying 'lp=auto' instead of a
1291                                port specification list means that device IDs
1292                                from each port should be examined, to see if
1293                                an IEEE 1284-compliant printer is attached; if
1294                                so, the driver will manage that printer.
1295                                See also header of drivers/char/lp.c.
1296
1297        lpj=n           [KNL]
1298                        Sets loops_per_jiffy to given constant, thus avoiding
1299                        time-consuming boot-time autodetection (up to 250 ms per
1300                        CPU). 0 enables autodetection (default). To determine
1301                        the correct value for your kernel, boot with normal
1302                        autodetection and see what value is printed. Note that
1303                        on SMP systems the preset will be applied to all CPUs,
1304                        which is likely to cause problems if your CPUs need
1305                        significantly divergent settings. An incorrect value
1306                        will cause delays in the kernel to be wrong, leading to
1307                        unpredictable I/O errors and other breakage. Although
1308                        unlikely, in the extreme case this might damage your
1309                        hardware.
1310
1311        ltpc=           [NET]
1312                        Format: <io>,<irq>,<dma>
1313
1314        machvec=        [IA64] Force the use of a particular machine-vector
1315                        (machvec) in a generic kernel.
1316                        Example: machvec=hpzx1_swiotlb
1317
1318        machtype=       [Loongson] Share the same kernel image file between different
1319                         yeeloong laptop.
1320                        Example: machtype=lemote-yeeloong-2f-7inch
1321
1322        max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater
1323                        than or equal to this physical address is ignored.
1324
1325        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
1326                        should make use of.  maxcpus=n : n >= 0 limits the
1327                        kernel to using 'n' processors.  n=0 is a special case,
1328                        it is equivalent to "nosmp", which also disables
1329                        the IO APIC.
1330
1331        max_loop=       [LOOP] Maximum number of loopback devices that can
1332                        be mounted
1333                        Format: <1-256>
1334
1335        mcatest=        [IA-64]
1336
1337        mce             [X86-32] Machine Check Exception
1338
1339        mce=option      [X86-64] See Documentation/x86/x86_64/boot-options.txt
1340
1341        md=             [HW] RAID subsystems devices and level
1342                        See Documentation/md.txt.
1343
1344        mdacon=         [MDA]
1345                        Format: <first>,<last>
1346                        Specifies range of consoles to be captured by the MDA.
1347
1348        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
1349                        Amount of memory to be used when the kernel is not able
1350                        to see the whole system memory or for test.
1351                        [X86-32] Use together with memmap= to avoid physical
1352                        address space collisions. Without memmap= PCI devices
1353                        could be placed at addresses belonging to unused RAM.
1354
1355        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
1356                        memory.
1357
1358        memchunk=nn[KMG]
1359                        [KNL,SH] Allow user to override the default size for
1360                        per-device physically contiguous DMA buffers.
1361
1362        memmap=exactmap [KNL,X86] Enable setting of an exact
1363                        E820 memory map, as specified by the user.
1364                        Such memmap=exactmap lines can be constructed based on
1365                        BIOS output or other requirements. See the memmap=nn@ss
1366                        option description.
1367
1368        memmap=nn[KMG]@ss[KMG]
1369                        [KNL] Force usage of a specific region of memory
1370                        Region of memory to be used, from ss to ss+nn.
1371
1372        memmap=nn[KMG]#ss[KMG]
1373                        [KNL,ACPI] Mark specific memory as ACPI data.
1374                        Region of memory to be used, from ss to ss+nn.
1375
1376        memmap=nn[KMG]$ss[KMG]
1377                        [KNL,ACPI] Mark specific memory as reserved.
1378                        Region of memory to be used, from ss to ss+nn.
1379                        Example: Exclude memory from 0x18690000-0x1869ffff
1380                                 memmap=64K$0x18690000
1381                                 or
1382                                 memmap=0x10000$0x18690000
1383
1384        memory_corruption_check=0/1 [X86]
1385                        Some BIOSes seem to corrupt the first 64k of
1386                        memory when doing things like suspend/resume.
1387                        Setting this option will scan the memory
1388                        looking for corruption.  Enabling this will
1389                        both detect corruption and prevent the kernel
1390                        from using the memory being corrupted.
1391                        However, its intended as a diagnostic tool; if
1392                        repeatable BIOS-originated corruption always
1393                        affects the same memory, you can use memmap=
1394                        to prevent the kernel from using that memory.
1395
1396        memory_corruption_check_size=size [X86]
1397                        By default it checks for corruption in the low
1398                        64k, making this memory unavailable for normal
1399                        use.  Use this parameter to scan for
1400                        corruption in more or less memory.
1401
1402        memory_corruption_check_period=seconds [X86]
1403                        By default it checks for corruption every 60
1404                        seconds.  Use this parameter to check at some
1405                        other rate.  0 disables periodic checking.
1406
1407        memtest=        [KNL,X86] Enable memtest
1408                        Format: <integer>
1409                        default : 0 <disable>
1410                        Specifies the number of memtest passes to be
1411                        performed. Each pass selects another test
1412                        pattern from a given set of patterns. Memtest
1413                        fills the memory with this pattern, validates
1414                        memory contents and reserves bad memory
1415                        regions that are detected.
1416
1417        meye.*=         [HW] Set MotionEye Camera parameters
1418                        See Documentation/video4linux/meye.txt.
1419
1420        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
1421                        Multi-Function General Purpose Timers on AMD Geode
1422                        platforms.
1423
1424        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
1425                        the BIOS has incorrectly applied a workaround. TinyBIOS
1426                        version 0.98 is known to be affected, 0.99 fixes the
1427                        problem by letting the user disable the workaround.
1428
1429        mga=            [HW,DRM]
1430
1431        min_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory below this
1432                        physical address is ignored.
1433
1434        mini2440=       [ARM,HW,KNL]
1435                        Format:[0..2][b][c][t]
1436                        Default: "0tb"
1437                        MINI2440 configuration specification:
1438                        0 - The attached screen is the 3.5" TFT
1439                        1 - The attached screen is the 7" TFT
1440                        2 - The VGA Shield is attached (1024x768)
1441                        Leaving out the screen size parameter will not load
1442                        the TFT driver, and the framebuffer will be left
1443                        unconfigured.
1444                        b - Enable backlight. The TFT backlight pin will be
1445                        linked to the kernel VESA blanking code and a GPIO
1446                        LED. This parameter is not necessary when using the
1447                        VGA shield.
1448                        c - Enable the s3c camera interface.
1449                        t - Reserved for enabling touchscreen support. The
1450                        touchscreen support is not enabled in the mainstream
1451                        kernel as of 2.6.30, a preliminary port can be found
1452                        in the "bleeding edge" mini2440 support kernel at
1453                        http://repo.or.cz/w/linux-2.6/mini2440.git
1454
1455        mminit_loglevel=
1456                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1457                        parameter allows control of the logging verbosity for
1458                        the additional memory initialisation checks. A value
1459                        of 0 disables mminit logging and a level of 4 will
1460                        log everything. Information is printed at KERN_DEBUG
1461                        so loglevel=8 may also need to be specified.
1462
1463        mousedev.tap_time=
1464                        [MOUSE] Maximum time between finger touching and
1465                        leaving touchpad surface for touch to be considered
1466                        a tap and be reported as a left button click (for
1467                        touchpads working in absolute mode only).
1468                        Format: <msecs>
1469        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
1470                        reporting absolute coordinates, such as tablets
1471        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
1472                        reporting absolute coordinates, such as tablets
1473
1474        movablecore=nn[KMG]     [KNL,X86,IA-64,PPC] This parameter
1475                        is similar to kernelcore except it specifies the
1476                        amount of memory used for migratable allocations.
1477                        If both kernelcore and movablecore is specified,
1478                        then kernelcore will be at *least* the specified
1479                        value but may be more. If movablecore on its own
1480                        is specified, the administrator must be careful
1481                        that the amount of memory usable for all allocations
1482                        is not too small.
1483
1484        MTD_Partition=  [MTD]
1485                        Format: <name>,<region-number>,<size>,<offset>
1486
1487        MTD_Region=     [MTD] Format:
1488                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1489
1490        mtdparts=       [MTD]
1491                        See drivers/mtd/cmdlinepart.c.
1492
1493        onenand.bdry=   [HW,MTD] Flex-OneNAND Boundary Configuration
1494
1495                        Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1496
1497                        boundary - index of last SLC block on Flex-OneNAND.
1498                                   The remaining blocks are configured as MLC blocks.
1499                        lock     - Configure if Flex-OneNAND boundary should be locked.
1500                                   Once locked, the boundary cannot be changed.
1501                                   1 indicates lock status, 0 indicates unlock status.
1502
1503        mtdset=         [ARM]
1504                        ARM/S3C2412 JIVE boot control
1505
1506                        See arch/arm/mach-s3c2412/mach-jive.c
1507
1508        mtouchusb.raw_coordinates=
1509                        [HW] Make the MicroTouch USB driver use raw coordinates
1510                        ('y', default) or cooked coordinates ('n')
1511
1512        mtrr_chunk_size=nn[KMG] [X86]
1513                        used for mtrr cleanup. It is largest continuous chunk
1514                        that could hold holes aka. UC entries.
1515
1516        mtrr_gran_size=nn[KMG] [X86]
1517                        Used for mtrr cleanup. It is granularity of mtrr block.
1518                        Default is 1.
1519                        Large value could prevent small alignment from
1520                        using up MTRRs.
1521
1522        mtrr_spare_reg_nr=n [X86]
1523                        Format: <integer>
1524                        Range: 0,7 : spare reg number
1525                        Default : 1
1526                        Used for mtrr cleanup. It is spare mtrr entries number.
1527                        Set to 2 or more if your graphical card needs more.
1528
1529        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
1530
1531        netdev=         [NET] Network devices parameters
1532                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1533                        Note that mem_start is often overloaded to mean
1534                        something different and driver-specific.
1535                        This usage is only documented in each driver source
1536                        file if at all.
1537
1538        nf_conntrack.acct=
1539                        [NETFILTER] Enable connection tracking flow accounting
1540                        0 to disable accounting
1541                        1 to enable accounting
1542                        Default value is 0.
1543
1544        nfsaddrs=       [NFS] Deprecated.  Use ip= instead.
1545                        See Documentation/filesystems/nfs/nfsroot.txt.
1546
1547        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
1548                        See Documentation/filesystems/nfs/nfsroot.txt.
1549
1550        nfsrootdebug    [NFS] enable nfsroot debugging messages.
1551                        See Documentation/filesystems/nfs/nfsroot.txt.
1552
1553        nfs.callback_tcpport=
1554                        [NFS] set the TCP port on which the NFSv4 callback
1555                        channel should listen.
1556
1557        nfs.cache_getent=
1558                        [NFS] sets the pathname to the program which is used
1559                        to update the NFS client cache entries.
1560
1561        nfs.cache_getent_timeout=
1562                        [NFS] sets the timeout after which an attempt to
1563                        update a cache entry is deemed to have failed.
1564
1565        nfs.idmap_cache_timeout=
1566                        [NFS] set the maximum lifetime for idmapper cache
1567                        entries.
1568
1569        nfs.enable_ino64=
1570                        [NFS] enable 64-bit inode numbers.
1571                        If zero, the NFS client will fake up a 32-bit inode
1572                        number for the readdir() and stat() syscalls instead
1573                        of returning the full 64-bit number.
1574                        The default is to return 64-bit inode numbers.
1575
1576        nmi_debug=      [KNL,AVR32,SH] Specify one or more actions to take
1577                        when a NMI is triggered.
1578                        Format: [state][,regs][,debounce][,die]
1579
1580        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
1581                        Format: [panic,][num]
1582                        Valid num: 0,1,2
1583                        0 - turn nmi_watchdog off
1584                        1 - use the IO-APIC timer for the NMI watchdog
1585                        2 - use the local APIC for the NMI watchdog using
1586                        a performance counter. Note: This will use one
1587                        performance counter and the local APIC's performance
1588                        vector.
1589                        When panic is specified, panic when an NMI watchdog
1590                        timeout occurs.
1591                        This is useful when you use a panic=... timeout and
1592                        need the box quickly up again.
1593                        Instead of 1 and 2 it is possible to use the following
1594                        symbolic names: lapic and ioapic
1595                        Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1596
1597        netpoll.carrier_timeout=
1598                        [NET] Specifies amount of time (in seconds) that
1599                        netpoll should wait for a carrier. By default netpoll
1600                        waits 4 seconds.
1601
1602        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
1603                        emulation library even if a 387 maths coprocessor
1604                        is present.
1605
1606        no_console_suspend
1607                        [HW] Never suspend the console
1608                        Disable suspending of consoles during suspend and
1609                        hibernate operations.  Once disabled, debugging
1610                        messages can reach various consoles while the rest
1611                        of the system is being put to sleep (ie, while
1612                        debugging driver suspend/resume hooks).  This may
1613                        not work reliably with all consoles, but is known
1614                        to work with serial and VGA consoles.
1615
1616        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
1617                        caches in the slab allocator.  Saves per-node memory,
1618                        but will impact performance.
1619
1620        noalign         [KNL,ARM]
1621
1622        noapic          [SMP,APIC] Tells the kernel to not make use of any
1623                        IOAPICs that may be present in the system.
1624
1625        nobats          [PPC] Do not use BATs for mapping kernel lowmem
1626                        on "Classic" PPC cores.
1627
1628        nocache         [ARM]
1629
1630        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction
1631
1632        nodelayacct     [KNL] Disable per-task delay accounting
1633
1634        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1635
1636        nodsp           [SH] Disable hardware DSP at boot time.
1637
1638        noefi           [X86] Disable EFI runtime services support.
1639
1640        noexec          [IA-64]
1641
1642        noexec          [X86]
1643                        On X86-32 available only on PAE configured kernels.
1644                        noexec=on: enable non-executable mappings (default)
1645                        noexec=off: disable non-executable mappings
1646
1647        noexec32        [X86-64]
1648                        This affects only 32-bit executables.
1649                        noexec32=on: enable non-executable mappings (default)
1650                                read doesn't imply executable mappings
1651                        noexec32=off: disable non-executable mappings
1652                                read implies executable mappings
1653
1654        nofpu           [SH] Disable hardware FPU at boot time.
1655
1656        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
1657                        register save and restore. The kernel will only save
1658                        legacy floating-point registers on task switch.
1659
1660        noxsave         [BUGS=X86] Disables x86 extended register state save
1661                        and restore using xsave. The kernel will fallback to
1662                        enabling legacy floating-point and sse state.
1663
1664        nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1665                        wfi(ARM) instruction doesn't work correctly and not to
1666                        use it. This is also useful when using JTAG debugger.
1667
1668        no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
1669                        instruction doesn't work correctly and not to
1670                        use it.
1671
1672        no_file_caps    Tells the kernel not to honor file capabilities.  The
1673                        only way then for a file to be executed with privilege
1674                        is to be setuid root or executed by root.
1675
1676        nohalt          [IA-64] Tells the kernel not to use the power saving
1677                        function PAL_HALT_LIGHT when idle. This increases
1678                        power-consumption. On the positive side, it reduces
1679                        interrupt wake-up latency, which may improve performance
1680                        in certain environments such as networked servers or
1681                        real-time systems.
1682
1683        nohz=           [KNL] Boottime enable/disable dynamic ticks
1684                        Valid arguments: on, off
1685                        Default: on
1686
1687        noiotrap        [SH] Disables trapped I/O port accesses.
1688
1689        noirqdebug      [X86-32] Disables the code which attempts to detect and
1690                        disable unhandled interrupt sources.
1691
1692        no_timer_check  [X86,APIC] Disables the code which tests for
1693                        broken timer IRQ sources.
1694
1695        noisapnp        [ISAPNP] Disables ISA PnP code.
1696
1697        noinitrd        [RAM] Tells the kernel not to load any configured
1698                        initial RAM disk.
1699
1700        nointremap      [X86-64, Intel-IOMMU] Do not enable interrupt
1701                        remapping.
1702                        [Deprecated - use intremap=off]
1703
1704        nointroute      [IA-64]
1705
1706        nojitter        [IA64] Disables jitter checking for ITC timers.
1707
1708        no-kvmclock     [X86,KVM] Disable paravirtualized KVM clock driver
1709
1710        nolapic         [X86-32,APIC] Do not enable or use the local APIC.
1711
1712        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.
1713
1714        noltlbs         [PPC] Do not use large page/tlb entries for kernel
1715                        lowmem mapping on PPC40x.
1716
1717        nomca           [IA-64] Disable machine check abort handling
1718
1719        nomce           [X86-32] Machine Check Exception
1720
1721        nomfgpt         [X86-32] Disable Multi-Function General Purpose
1722                        Timer usage (for AMD Geode machines).
1723
1724        nopat           [X86] Disable PAT (page attribute table extension of
1725                        pagetables) support.
1726
1727        norandmaps      Don't use address space randomization.  Equivalent to
1728                        echo 0 > /proc/sys/kernel/randomize_va_space
1729
1730        noreplace-paravirt      [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1731
1732        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
1733                        with UP alternatives
1734
1735        noresidual      [PPC] Don't use residual data on PReP machines.
1736
1737        noresume        [SWSUSP] Disables resume and restores original swap
1738                        space.
1739
1740        no-scroll       [VGA] Disables scrollback.
1741                        This is required for the Braillex ib80-piezo Braille
1742                        reader made by F.H. Papenmeier (Germany).
1743
1744        nosbagart       [IA-64]
1745
1746        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1747
1748        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
1749                        and disable the IO APIC.  legacy for "maxcpus=0".
1750
1751        nosoftlockup    [KNL] Disable the soft-lockup detector.
1752
1753        noswapaccount   [KNL] Disable accounting of swap in memory resource
1754                        controller. (See Documentation/cgroups/memory.txt)
1755
1756        nosync          [HW,M68K] Disables sync negotiation for all devices.
1757
1758        notsc           [BUGS=X86-32] Disable Time Stamp Counter
1759
1760        nousb           [USB] Disable the USB subsystem
1761
1762        nowatchdog      [KNL] Disable the lockup detector (NMI watchdog).
1763
1764        nowb            [ARM]
1765
1766        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
1767
1768        nptcg=          [IA64] Override max number of concurrent global TLB
1769                        purges which is reported from either PAL_VM_SUMMARY or
1770                        SAL PALO.
1771
1772        nr_cpus=        [SMP] Maximum number of processors that an SMP kernel
1773                        could support.  nr_cpus=n : n >= 1 limits the kernel to
1774                        supporting 'n' processors. Later in runtime you can not
1775                        use hotplug cpu feature to put more cpu back to online.
1776                        just like you compile the kernel NR_CPUS=n
1777
1778        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1779
1780        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1781                        one of ['zone', 'node', 'default'] can be specified
1782                        This can be set from sysctl after boot.
1783                        See Documentation/sysctl/vm.txt for details.
1784
1785        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
1786                        See Documentation/debugging-via-ohci1394.txt for more
1787                        info.
1788
1789        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1790                        Rather than timing out after 20 ms if an EC
1791                        command is not properly ACKed, override the length
1792                        of the timeout.  We have interrupts disabled while
1793                        waiting for the ACK, so if this is set too high
1794                        interrupts *may* be lost!
1795
1796        omap_mux=       [OMAP] Override bootloader pin multiplexing.
1797                        Format: <mux_mode0.mode_name=value>...
1798                        For example, to override I2C bus2:
1799                        omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1800
1801        oprofile.timer= [HW]
1802                        Use timer interrupt instead of performance counters
1803
1804        oprofile.cpu_type=      Force an oprofile cpu type
1805                        This might be useful if you have an older oprofile
1806                        userland or if you want common events.
1807                        Format: { arch_perfmon }
1808                        arch_perfmon: [X86] Force use of architectural
1809                                perfmon on Intel CPUs instead of the
1810                                CPU specific event set.
1811
1812        OSS             [HW,OSS]
1813                        See Documentation/sound/oss/oss-parameters.txt
1814
1815        panic=          [KNL] Kernel behaviour on panic
1816                        Format: <timeout>
1817
1818        parkbd.port=    [HW] Parallel port number the keyboard adapter is
1819                        connected to, default is 0.
1820                        Format: <parport#>
1821        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
1822                        0 for XT, 1 for AT (default is AT).
1823                        Format: <mode>
1824
1825        parport=        [HW,PPT] Specify parallel ports. 0 disables.
1826                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1827                        Use 'auto' to force the driver to use any
1828                        IRQ/DMA settings detected (the default is to
1829                        ignore detected IRQ/DMA settings because of
1830                        possible conflicts). You can specify the base
1831                        address, IRQ, and DMA settings; IRQ and DMA
1832                        should be numbers, or 'auto' (for using detected
1833                        settings on that particular port), or 'nofifo'
1834                        (to avoid using a FIFO even if it is detected).
1835                        Parallel ports are assigned in the order they
1836                        are specified on the command line, starting
1837                        with parport0.
1838
1839        parport_init_mode=      [HW,PPT]
1840                        Configure VIA parallel port to operate in
1841                        a specific mode. This is necessary on Pegasos
1842                        computer where firmware has no options for setting
1843                        up parallel port mode and sets it to spp.
1844                        Currently this function knows 686a and 8231 chips.
1845                        Format: [spp|ps2|epp|ecp|ecpepp]
1846
1847        pause_on_oops=
1848                        Halt all CPUs after the first oops has been printed for
1849                        the specified number of seconds.  This is to be used if
1850                        your oopses keep scrolling off the screen.
1851
1852        pcbit=          [HW,ISDN]
1853
1854        pcd.            [PARIDE]
1855                        See header of drivers/block/paride/pcd.c.
1856                        See also Documentation/blockdev/paride.txt.
1857
1858        pci=option[,option...]  [PCI] various PCI subsystem options:
1859                earlydump       [X86] dump PCI config space before the kernel
1860                                changes anything
1861                off             [X86] don't probe for the PCI bus
1862                bios            [X86-32] force use of PCI BIOS, don't access
1863                                the hardware directly. Use this if your machine
1864                                has a non-standard PCI host bridge.
1865                nobios          [X86-32] disallow use of PCI BIOS, only direct
1866                                hardware access methods are allowed. Use this
1867                                if you experience crashes upon bootup and you
1868                                suspect they are caused by the BIOS.
1869                conf1           [X86] Force use of PCI Configuration
1870                                Mechanism 1.
1871                conf2           [X86] Force use of PCI Configuration
1872                                Mechanism 2.
1873                noaer           [PCIE] If the PCIEAER kernel config parameter is
1874                                enabled, this kernel boot option can be used to
1875                                disable the use of PCIE advanced error reporting.
1876                nodomains       [PCI] Disable support for multiple PCI
1877                                root domains (aka PCI segments, in ACPI-speak).
1878                nommconf        [X86] Disable use of MMCONFIG for PCI
1879                                Configuration
1880                check_enable_amd_mmconf [X86] check for and enable
1881                                properly configured MMIO access to PCI
1882                                config space on AMD family 10h CPU
1883                nomsi           [MSI] If the PCI_MSI kernel config parameter is
1884                                enabled, this kernel boot option can be used to
1885                                disable the use of MSI interrupts system-wide.
1886                noioapicquirk   [APIC] Disable all boot interrupt quirks.
1887                                Safety option to keep boot IRQs enabled. This
1888                                should never be necessary.
1889                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
1890                                primary IO-APIC for bridges that cannot disable
1891                                boot IRQs. This fixes a source of spurious IRQs
1892                                when the system masks IRQs.
1893                noioapicreroute [APIC] Disable workaround that uses the
1894                                boot IRQ equivalent of an IRQ that connects to
1895                                a chipset where boot IRQs cannot be disabled.
1896                                The opposite of ioapicreroute.
1897                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
1898                                routing table. These calls are known to be buggy
1899                                on several machines and they hang the machine
1900                                when used, but on other computers it's the only
1901                                way to get the interrupt routing table. Try
1902                                this option if the kernel is unable to allocate
1903                                IRQs or discover secondary PCI buses on your
1904                                motherboard.
1905                rom             [X86] Assign address space to expansion ROMs.
1906                                Use with caution as certain devices share
1907                                address decoders between ROMs and other
1908                                resources.
1909                norom           [X86] Do not assign address space to
1910                                expansion ROMs that do not already have
1911                                BIOS assigned address ranges.
1912                nobar           [X86] Do not assign address space to the
1913                                BARs that weren't assigned by the BIOS.
1914                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
1915                                assigned automatically to PCI devices. You can
1916                                make the kernel exclude IRQs of your ISA cards
1917                                this way.
1918                pirqaddr=0xAAAAA        [X86] Specify the physical address
1919                                of the PIRQ table (normally generated
1920                                by the BIOS) if it is outside the
1921                                F0000h-100000h range.
1922                lastbus=N       [X86] Scan all buses thru bus #N. Can be
1923                                useful if the kernel is unable to find your
1924                                secondary buses and you want to tell it
1925                                explicitly which ones they are.
1926                assign-busses   [X86] Always assign all PCI bus
1927                                numbers ourselves, overriding
1928                                whatever the firmware may have done.
1929                usepirqmask     [X86] Honor the possible IRQ mask stored
1930                                in the BIOS $PIR table. This is needed on
1931                                some systems with broken BIOSes, notably
1932                                some HP Pavilion N5400 and Omnibook XE3
1933                                notebooks. This will have no effect if ACPI
1934                                IRQ routing is enabled.
1935                noacpi          [X86] Do not use ACPI for IRQ routing
1936                                or for PCI scanning.
1937                use_crs         [X86] Use PCI host bridge window information
1938                                from ACPI.  On BIOSes from 2008 or later, this
1939                                is enabled by default.  If you need to use this,
1940                                please report a bug.
1941                nocrs           [X86] Ignore PCI host bridge windows from ACPI.
1942                                If you need to use this, please report a bug.
1943                routeirq        Do IRQ routing for all PCI devices.
1944                                This is normally done in pci_enable_device(),
1945                                so this option is a temporary workaround
1946                                for broken drivers that don't call it.
1947                skip_isa_align  [X86] do not align io start addr, so can
1948                                handle more pci cards
1949                firmware        [ARM] Do not re-enumerate the bus but instead
1950                                just use the configuration from the
1951                                bootloader. This is currently used on
1952                                IXP2000 systems where the bus has to be
1953                                configured a certain way for adjunct CPUs.
1954                noearly         [X86] Don't do any early type 1 scanning.
1955                                This might help on some broken boards which
1956                                machine check when some devices' config space
1957                                is read. But various workarounds are disabled
1958                                and some IOMMU drivers will not work.
1959                bfsort          Sort PCI devices into breadth-first order.
1960                                This sorting is done to get a device
1961                                order compatible with older (<= 2.4) kernels.
1962                nobfsort        Don't sort PCI devices into breadth-first order.
1963                cbiosize=nn[KMG]        The fixed amount of bus space which is
1964                                reserved for the CardBus bridge's IO window.
1965                                The default value is 256 bytes.
1966                cbmemsize=nn[KMG]       The fixed amount of bus space which is
1967                                reserved for the CardBus bridge's memory
1968                                window. The default value is 64 megabytes.
1969                resource_alignment=
1970                                Format:
1971                                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1972                                Specifies alignment and device to reassign
1973                                aligned memory resources.
1974                                If <order of align> is not specified,
1975                                PAGE_SIZE is used as alignment.
1976                                PCI-PCI bridge can be specified, if resource
1977                                windows need to be expanded.
1978                ecrc=           Enable/disable PCIe ECRC (transaction layer
1979                                end-to-end CRC checking).
1980                                bios: Use BIOS/firmware settings. This is the
1981                                the default.
1982                                off: Turn ECRC off
1983                                on: Turn ECRC on.
1984
1985        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
1986                        Management.
1987                off     Disable ASPM.
1988                force   Enable ASPM even on devices that claim not to support it.
1989                        WARNING: Forcing ASPM on may cause system lockups.
1990
1991        pcie_ports=     [PCIE] PCIe ports handling:
1992                auto    Ask the BIOS whether or not to use native PCIe services
1993                        associated with PCIe ports (PME, hot-plug, AER).  Use
1994                        them only if that is allowed by the BIOS.
1995                native  Use native PCIe services associated with PCIe ports
1996                        unconditionally.
1997                compat  Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1998                        ports driver.
1999
2000        pcie_pme=       [PCIE,PM] Native PCIe PME signaling options:
2001                nomsi   Do not use MSI for native PCIe PME signaling (this makes
2002                        all PCIe root ports use INTx for all services).
2003
2004        pcmv=           [HW,PCMCIA] BadgePAD 4
2005
2006        pd.             [PARIDE]
2007                        See Documentation/blockdev/paride.txt.
2008
2009        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2010                        boot time.
2011                        Format: { 0 | 1 }
2012                        See arch/parisc/kernel/pdc_chassis.c
2013
2014        percpu_alloc=   Select which percpu first chunk allocator to use.
2015                        Currently supported values are "embed" and "page".
2016                        Archs may support subset or none of the selections.
2017                        See comments in mm/percpu.c for details on each
2018                        allocator.  This parameter is primarily for debugging
2019                        and performance comparison.
2020
2021        pf.             [PARIDE]
2022                        See Documentation/blockdev/paride.txt.
2023
2024        pg.             [PARIDE]
2025                        See Documentation/blockdev/paride.txt.
2026
2027        pirq=           [SMP,APIC] Manual mp-table setup
2028                        See Documentation/x86/i386/IO-APIC.txt.
2029
2030        plip=           [PPT,NET] Parallel port network link
2031                        Format: { parport<nr> | timid | 0 }
2032                        See also Documentation/parport.txt.
2033
2034        pmtmr=          [X86] Manual setup of pmtmr I/O Port. 
2035                        Override pmtimer IOPort with a hex value.
2036                        e.g. pmtmr=0x508
2037
2038        pnp.debug       [PNP]
2039                        Enable PNP debug messages.  This depends on the
2040                        CONFIG_PNP_DEBUG_MESSAGES option.
2041
2042        pnpacpi=        [ACPI]
2043                        { off }
2044
2045        pnpbios=        [ISAPNP]
2046                        { on | off | curr | res | no-curr | no-res }
2047
2048        pnp_reserve_irq=
2049                        [ISAPNP] Exclude IRQs for the autoconfiguration
2050
2051        pnp_reserve_dma=
2052                        [ISAPNP] Exclude DMAs for the autoconfiguration
2053
2054        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2055                        Ranges are in pairs (I/O port base and size).
2056
2057        pnp_reserve_mem=
2058                        [ISAPNP] Exclude memory regions for the
2059                        autoconfiguration.
2060                        Ranges are in pairs (memory base and size).
2061
2062        ports=          [IP_VS_FTP] IPVS ftp helper module
2063                        Default is 21.
2064                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
2065                        may be specified.
2066                        Format: <port>,<port>....
2067
2068        print-fatal-signals=
2069                        [KNL] debug: print fatal signals
2070
2071                        If enabled, warn about various signal handling
2072                        related application anomalies: too many signals,
2073                        too many POSIX.1 timers, fatal signals causing a
2074                        coredump - etc.
2075
2076                        If you hit the warning due to signal overflow,
2077                        you might want to try "ulimit -i unlimited".
2078
2079                        default: off.
2080
2081        printk.time=    Show timing data prefixed to each printk message line
2082                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2083
2084        processor.max_cstate=   [HW,ACPI]
2085                        Limit processor to maximum C-state
2086                        max_cstate=9 overrides any DMI blacklist limit.
2087
2088        processor.nocst [HW,ACPI]
2089                        Ignore the _CST method to determine C-states,
2090                        instead using the legacy FADT method
2091
2092        profile=        [KNL] Enable kernel profiling via /proc/profile
2093                        Format: [schedule,]<number>
2094                        Param: "schedule" - profile schedule points.
2095                        Param: <number> - step/bucket size as a power of 2 for
2096                                statistical time based profiling.
2097                        Param: "sleep" - profile D-state sleeping (millisecs).
2098                                Requires CONFIG_SCHEDSTATS
2099                        Param: "kvm" - profile VM exits.
2100
2101        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2102                        before loading.
2103                        See Documentation/blockdev/ramdisk.txt.
2104
2105        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
2106                        probe for; one of (bare|imps|exps|lifebook|any).
2107        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
2108                        per second.
2109        psmouse.resetafter=     [HW,MOUSE]
2110                        Try to reset the device after so many bad packets
2111                        (0 = never).
2112        psmouse.resolution=
2113                        [HW,MOUSE] Set desired mouse resolution, in dpi.
2114        psmouse.smartscroll=
2115                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2116                        0 = disabled, 1 = enabled (default).
2117
2118        pt.             [PARIDE]
2119                        See Documentation/blockdev/paride.txt.
2120
2121        pty.legacy_count=
2122                        [KNL] Number of legacy pty's. Overwrites compiled-in
2123                        default number.
2124
2125        quiet           [KNL] Disable most log messages
2126
2127        r128=           [HW,DRM]
2128
2129        raid=           [HW,RAID]
2130                        See Documentation/md.txt.
2131
2132        ramdisk_blocksize=      [RAM]
2133                        See Documentation/blockdev/ramdisk.txt.
2134
2135        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
2136                        See Documentation/blockdev/ramdisk.txt.
2137
2138        rcupdate.blimit=        [KNL,BOOT]
2139                        Set maximum number of finished RCU callbacks to process
2140                        in one batch.
2141
2142        rcupdate.qhimark=       [KNL,BOOT]
2143                        Set threshold of queued
2144                        RCU callbacks over which batch limiting is disabled.
2145
2146        rcupdate.qlowmark=      [KNL,BOOT]
2147                        Set threshold of queued RCU callbacks below which
2148                        batch limiting is re-enabled.
2149
2150        rdinit=         [KNL]
2151                        Format: <full_path>
2152                        Run specified binary instead of /init from the ramdisk,
2153                        used for early userspace startup. See initrd.
2154
2155        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2156                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
2157                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2158
2159        relax_domain_level=
2160                        [KNL, SMP] Set scheduler's default relax_domain_level.
2161                        See Documentation/cgroups/cpusets.txt.
2162
2163        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
2164
2165        reservetop=     [X86-32]
2166                        Format: nn[KMG]
2167                        Reserves a hole at the top of the kernel virtual
2168                        address space.
2169
2170        reservelow=     [X86]
2171                        Format: nn[K]
2172                        Set the amount of memory to reserve for BIOS at
2173                        the bottom of the address space.
2174
2175        reset_devices   [KNL] Force drivers to reset the underlying device
2176                        during initialization.
2177
2178        resume=         [SWSUSP]
2179                        Specify the partition device for software suspend
2180
2181        resume_offset=  [SWSUSP]
2182                        Specify the offset from the beginning of the partition
2183                        given by "resume=" at which the swap header is located,
2184                        in <PAGE_SIZE> units (needed only for swap files).
2185                        See  Documentation/power/swsusp-and-swap-files.txt
2186
2187        hibernate=      [HIBERNATION]
2188                noresume        Don't check if there's a hibernation image
2189                                present during boot.
2190                nocompress      Don't compress/decompress hibernation images.
2191
2192        retain_initrd   [RAM] Keep initrd memory after extraction
2193
2194        rhash_entries=  [KNL,NET]
2195                        Set number of hash buckets for route cache
2196
2197        riscom8=        [HW,SERIAL]
2198                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2199
2200        ro              [KNL] Mount root device read-only on boot
2201
2202        root=           [KNL] Root filesystem
2203
2204        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
2205                        mount the root filesystem
2206
2207        rootflags=      [KNL] Set root filesystem mount option string
2208
2209        rootfstype=     [KNL] Set root filesystem type
2210
2211        rootwait        [KNL] Wait (indefinitely) for root device to show up.
2212                        Useful for devices that are detected asynchronously
2213                        (e.g. USB and MMC devices).
2214
2215        rw              [KNL] Mount root device read-write on boot
2216
2217        S               [KNL] Run init in single mode
2218
2219        sa1100ir        [NET]
2220                        See drivers/net/irda/sa1100_ir.c.
2221
2222        sbni=           [NET] Granch SBNI12 leased line adapter
2223
2224        sched_debug     [KNL] Enables verbose scheduler debug messages.
2225
2226        security=       [SECURITY] Choose a security module to enable at boot.
2227                        If this boot parameter is not specified, only the first
2228                        security module asking for security registration will be
2229                        loaded. An invalid security module name will be treated
2230                        as if no module has been chosen.
2231
2232        selinux=        [SELINUX] Disable or enable SELinux at boot time.
2233                        Format: { "0" | "1" }
2234                        See security/selinux/Kconfig help text.
2235                        0 -- disable.
2236                        1 -- enable.
2237                        Default value is set via kernel config option.
2238                        If enabled at boot time, /selinux/disable can be used
2239                        later to disable prior to initial policy load.
2240
2241        apparmor=       [APPARMOR] Disable or enable AppArmor at boot time
2242                        Format: { "0" | "1" }
2243                        See security/apparmor/Kconfig help text
2244                        0 -- disable.
2245                        1 -- enable.
2246                        Default value is set via kernel config option.
2247
2248        serialnumber    [BUGS=X86-32]
2249
2250        shapers=        [NET]
2251                        Maximal number of shapers.
2252
2253        show_msr=       [x86] show boot-time MSR settings
2254                        Format: { <integer> }
2255                        Show boot-time (BIOS-initialized) MSR settings.
2256                        The parameter means the number of CPUs to show,
2257                        for example 1 means boot CPU only.
2258
2259        simeth=         [IA-64]
2260        simscsi=
2261
2262        slram=          [HW,MTD]
2263
2264        slub_debug[=options[,slabs]]    [MM, SLUB]
2265                        Enabling slub_debug allows one to determine the
2266                        culprit if slab objects become corrupted. Enabling
2267                        slub_debug can create guard zones around objects and
2268                        may poison objects when not in use. Also tracks the
2269                        last alloc / free. For more information see
2270                        Documentation/vm/slub.txt.
2271
2272        slub_max_order= [MM, SLUB]
2273                        Determines the maximum allowed order for slabs.
2274                        A high setting may cause OOMs due to memory
2275                        fragmentation. For more information see
2276                        Documentation/vm/slub.txt.
2277
2278        slub_min_objects=       [MM, SLUB]
2279                        The minimum number of objects per slab. SLUB will
2280                        increase the slab order up to slub_max_order to
2281                        generate a sufficiently large slab able to contain
2282                        the number of objects indicated. The higher the number
2283                        of objects the smaller the overhead of tracking slabs
2284                        and the less frequently locks need to be acquired.
2285                        For more information see Documentation/vm/slub.txt.
2286
2287        slub_min_order= [MM, SLUB]
2288                        Determines the mininum page order for slabs. Must be
2289                        lower than slub_max_order.
2290                        For more information see Documentation/vm/slub.txt.
2291
2292        slub_nomerge    [MM, SLUB]
2293                        Disable merging of slabs with similar size. May be
2294                        necessary if there is some reason to distinguish
2295                        allocs to different slabs. Debug options disable
2296                        merging on their own.
2297                        For more information see Documentation/vm/slub.txt.
2298
2299        smart2=         [HW]
2300                        Format: <io1>[,<io2>[,...,<io8>]]
2301
2302        smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
2303                        attempt to substitute SMP alternatives once at boot.
2304
2305        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
2306        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
2307        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
2308        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
2309        smsc-ircc2.ircc_irq=    [HW] IRQ line
2310        smsc-ircc2.ircc_dma=    [HW] DMA channel
2311        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2312                                0: Toshiba Satellite 1800 (GP data pin select)
2313                                1: Fast pin select (default)
2314                                2: ATC IRMode
2315
2316        softlockup_panic=
2317                        [KNL] Should the soft-lockup detector generate panics.
2318
2319        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
2320                        See Documentation/sonypi.txt
2321
2322        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
2323                        See Documentation/serial/specialix.txt.
2324
2325        spia_io_base=   [HW,MTD]
2326        spia_fio_base=
2327        spia_pedr=
2328        spia_peddr=
2329
2330        stacktrace      [FTRACE]
2331                        Enabled the stack tracer on boot up.
2332
2333        sti=            [PARISC,HW]
2334                        Format: <num>
2335                        Set the STI (builtin display/keyboard on the HP-PARISC
2336                        machines) console (graphic card) which should be used
2337                        as the initial boot-console.
2338                        See also comment in drivers/video/console/sticore.c.
2339
2340        sti_font=       [HW]
2341                        See comment in drivers/video/console/sticore.c.
2342
2343        stifb=          [HW]
2344                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2345
2346        sunrpc.min_resvport=
2347        sunrpc.max_resvport=
2348                        [NFS,SUNRPC]
2349                        SunRPC servers often require that client requests
2350                        originate from a privileged port (i.e. a port in the
2351                        range 0 < portnr < 1024).
2352                        An administrator who wishes to reserve some of these
2353                        ports for other uses may adjust the range that the
2354                        kernel's sunrpc client considers to be privileged
2355                        using these two parameters to set the minimum and
2356                        maximum port values.
2357
2358        sunrpc.pool_mode=
2359                        [NFS]
2360                        Control how the NFS server code allocates CPUs to
2361                        service thread pools.  Depending on how many NICs
2362                        you have and where their interrupts are bound, this
2363                        option will affect which CPUs will do NFS serving.
2364                        Note: this parameter cannot be changed while the
2365                        NFS server is running.
2366
2367                        auto        the server chooses an appropriate mode
2368                                    automatically using heuristics
2369                        global      a single global pool contains all CPUs
2370                        percpu      one pool for each CPU
2371                        pernode     one pool for each NUMA node (equivalent
2372                                    to global on non-NUMA machines)
2373
2374        sunrpc.tcp_slot_table_entries=
2375        sunrpc.udp_slot_table_entries=
2376                        [NFS,SUNRPC]
2377                        Sets the upper limit on the number of simultaneous
2378                        RPC calls that can be sent from the client to a
2379                        server. Increasing these values may allow you to
2380                        improve throughput, but will also increase the
2381                        amount of memory reserved for use by the client.
2382
2383        swapaccount[=0|1]
2384                        [KNL] Enable accounting of swap in memory resource
2385                        controller if no parameter or 1 is given or disable
2386                        it if 0 is given (See Documentation/cgroups/memory.txt)
2387
2388        swiotlb=        [IA-64] Number of I/O TLB slabs
2389
2390        switches=       [HW,M68k]
2391
2392        sysfs.deprecated=0|1 [KNL]
2393                        Enable/disable old style sysfs layout for old udev
2394                        on older distributions. When this option is enabled
2395                        very new udev will not work anymore. When this option
2396                        is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2397                        in older udev will not work anymore.
2398                        Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2399                        the kernel configuration.
2400
2401        sysrq_always_enabled
2402                        [KNL]
2403                        Ignore sysrq setting - this boot parameter will
2404                        neutralize any effect of /proc/sys/kernel/sysrq.
2405                        Useful for debugging.
2406
2407        tdfx=           [HW,DRM]
2408
2409        test_suspend=   [SUSPEND]
2410                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
2411                        standby suspend) as the system sleep state to briefly
2412                        enter during system startup.  The system is woken from
2413                        this state using a wakeup-capable RTC alarm.
2414
2415        thash_entries=  [KNL,NET]
2416                        Set number of hash buckets for TCP connection
2417
2418        thermal.act=    [HW,ACPI]
2419                        -1: disable all active trip points in all thermal zones
2420                        <degrees C>: override all lowest active trip points
2421
2422        thermal.crt=    [HW,ACPI]
2423                        -1: disable all critical trip points in all thermal zones
2424                        <degrees C>: override all critical trip points
2425
2426        thermal.nocrt=  [HW,ACPI]
2427                        Set to disable actions on ACPI thermal zone
2428                        critical and hot trip points.
2429
2430        thermal.off=    [HW,ACPI]
2431                        1: disable ACPI thermal control
2432
2433        thermal.psv=    [HW,ACPI]
2434                        -1: disable all passive trip points
2435                        <degrees C>: override all passive trip points to this
2436                        value
2437
2438        thermal.tzp=    [HW,ACPI]
2439                        Specify global default ACPI thermal zone polling rate
2440                        <deci-seconds>: poll all this frequency
2441                        0: no polling (default)
2442
2443        topology=       [S390]
2444                        Format: {off | on}
2445                        Specify if the kernel should make use of the cpu
2446                        topology informations if the hardware supports these.
2447                        The scheduler will make use of these informations and
2448                        e.g. base its process migration decisions on it.
2449                        Default is on.
2450
2451        tp720=          [HW,PS2]
2452
2453        tpm_suspend_pcr=[HW,TPM]
2454                        Format: integer pcr id
2455                        Specify that at suspend time, the tpm driver
2456                        should extend the specified pcr with zeros,
2457                        as a workaround for some chips which fail to
2458                        flush the last written pcr on TPM_SaveState.
2459                        This will guarantee that all the other pcrs
2460                        are saved.
2461
2462        trace_buf_size=nn[KMG]
2463                        [FTRACE] will set tracing buffer size.
2464
2465        trace_event=[event-list]
2466                        [FTRACE] Set and start specified trace events in order
2467                        to facilitate early boot debugging.
2468                        See also Documentation/trace/events.txt
2469
2470        tsc=            Disable clocksource-must-verify flag for TSC.
2471                        Format: <string>
2472                        [x86] reliable: mark tsc clocksource as reliable, this
2473                        disables clocksource verification at runtime.
2474                        Used to enable high-resolution timer mode on older
2475                        hardware, and in virtualized environment.
2476                        [x86] noirqtime: Do not use TSC to do irq accounting.
2477                        Used to run time disable IRQ_TIME_ACCOUNTING on any
2478                        platforms where RDTSC is slow and this accounting
2479                        can add overhead.
2480
2481        turbografx.map[2|3]=    [HW,JOY]
2482                        TurboGraFX parallel port interface
2483                        Format:
2484                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2485                        See also Documentation/input/joystick-parport.txt
2486
2487        uhash_entries=  [KNL,NET]
2488                        Set number of hash buckets for UDP/UDP-Lite connections
2489
2490        uhci-hcd.ignore_oc=
2491                        [USB] Ignore overcurrent events (default N).
2492                        Some badly-designed motherboards generate lots of
2493                        bogus events, for ports that aren't wired to
2494                        anything.  Set this parameter to avoid log spamming.
2495                        Note that genuine overcurrent events won't be
2496                        reported either.
2497
2498        unknown_nmi_panic
2499                        [X86]
2500                        Set unknown_nmi_panic=1 early on boot.
2501
2502        usbcore.autosuspend=
2503                        [USB] The autosuspend time delay (in seconds) used
2504                        for newly-detected USB devices (default 2).  This
2505                        is the time required before an idle device will be
2506                        autosuspended.  Devices for which the delay is set
2507                        to a negative value won't be autosuspended at all.
2508
2509        usbcore.usbfs_snoop=
2510                        [USB] Set to log all usbfs traffic (default 0 = off).
2511
2512        usbcore.blinkenlights=
2513                        [USB] Set to cycle leds on hubs (default 0 = off).
2514
2515        usbcore.old_scheme_first=
2516                        [USB] Start with the old device initialization
2517                        scheme (default 0 = off).
2518
2519        usbcore.use_both_schemes=
2520                        [USB] Try the other device initialization scheme
2521                        if the first one fails (default 1 = enabled).
2522
2523        usbcore.initial_descriptor_timeout=
2524                        [USB] Specifies timeout for the initial 64-byte
2525                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2526                        (default 5000 = 5.0 seconds).
2527
2528        usbhid.mousepoll=
2529                        [USBHID] The interval which mice are to be polled at.
2530
2531        usb-storage.delay_use=
2532                        [UMS] The delay in seconds before a new device is
2533                        scanned for Logical Units (default 5).
2534
2535        usb-storage.quirks=
2536                        [UMS] A list of quirks entries to supplement or
2537                        override the built-in unusual_devs list.  List
2538                        entries are separated by commas.  Each entry has
2539                        the form VID:PID:Flags where VID and PID are Vendor
2540                        and Product ID values (4-digit hex numbers) and
2541                        Flags is a set of characters, each corresponding
2542                        to a common usb-storage quirk flag as follows:
2543                                a = SANE_SENSE (collect more than 18 bytes
2544                                        of sense data);
2545                                b = BAD_SENSE (don't collect more than 18
2546                                        bytes of sense data);
2547                                c = FIX_CAPACITY (decrease the reported
2548                                        device capacity by one sector);
2549                                h = CAPACITY_HEURISTICS (decrease the
2550                                        reported device capacity by one
2551                                        sector if the number is odd);
2552                                i = IGNORE_DEVICE (don't bind to this
2553                                        device);
2554                                l = NOT_LOCKABLE (don't try to lock and
2555                                        unlock ejectable media);
2556                                m = MAX_SECTORS_64 (don't transfer more
2557                                        than 64 sectors = 32 KB at a time);
2558                                o = CAPACITY_OK (accept the capacity
2559                                        reported by the device);
2560                                r = IGNORE_RESIDUE (the device reports
2561                                        bogus residue values);
2562                                s = SINGLE_LUN (the device has only one
2563                                        Logical Unit);
2564                                w = NO_WP_DETECT (don't test whether the
2565                                        medium is write-protected).
2566                        Example: quirks=0419:aaf5:rl,0421:0433:rc
2567
2568        userpte=
2569                        [X86] Flags controlling user PTE allocations.
2570
2571                                nohigh = do not allocate PTE pages in
2572                                        HIGHMEM regardless of setting
2573                                        of CONFIG_HIGHPTE.
2574
2575        vdso=           [X86,SH]
2576                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2577                        vdso=1: enable VDSO (default)
2578                        vdso=0: disable VDSO mapping
2579
2580        vdso32=         [X86]
2581                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2582                        vdso32=1: enable 32-bit VDSO (default)
2583                        vdso32=0: disable 32-bit VDSO mapping
2584
2585        vector=         [IA-64,SMP]
2586                        vector=percpu: enable percpu vector domain
2587
2588        video=          [FB] Frame buffer configuration
2589                        See Documentation/fb/modedb.txt.
2590
2591        vga=            [BOOT,X86-32] Select a particular video mode
2592                        See Documentation/x86/boot.txt and
2593                        Documentation/svga.txt.
2594                        Use vga=ask for menu.
2595                        This is actually a boot loader parameter; the value is
2596                        passed to the kernel using a special protocol.
2597
2598        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2599                        size of <nn>. This can be used to increase the
2600                        minimum size (128MB on x86). It can also be used to
2601                        decrease the size and leave more room for directly
2602                        mapped kernel RAM.
2603
2604        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
2605                        Format: <command>
2606
2607        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
2608                        Format: <command>
2609
2610        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
2611                        Format: <command>
2612
2613        vt.cur_default= [VT] Default cursor shape.
2614                        Format: 0xCCBBAA, where AA, BB, and CC are the same as
2615                        the parameters of the <Esc>[?A;B;Cc escape sequence;
2616                        see VGA-softcursor.txt. Default: 2 = underline.
2617
2618        vt.default_blu= [VT]
2619                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2620                        Change the default blue palette of the console.
2621                        This is a 16-member array composed of values
2622                        ranging from 0-255.
2623
2624        vt.default_grn= [VT]
2625                        Format: <green0>,<green1>,<green2>,...,<green15>
2626                        Change the default green palette of the console.
2627                        This is a 16-member array composed of values
2628                        ranging from 0-255.
2629
2630        vt.default_red= [VT]
2631                        Format: <red0>,<red1>,<red2>,...,<red15>
2632                        Change the default red palette of the console.
2633                        This is a 16-member array composed of values
2634                        ranging from 0-255.
2635
2636        vt.default_utf8=
2637                        [VT]
2638                        Format=<0|1>
2639                        Set system-wide default UTF-8 mode for all tty's.
2640                        Default is 1, i.e. UTF-8 mode is enabled for all
2641                        newly opened terminals.
2642
2643        vt.global_cursor_default=
2644                        [VT]
2645                        Format=<-1|0|1>
2646                        Set system-wide default for whether a cursor
2647                        is shown on new VTs. Default is -1,
2648                        i.e. cursors will be created by default unless
2649                        overridden by individual drivers. 0 will hide
2650                        cursors, 1 will display them.
2651
2652        watchdog timers [HW,WDT] For information on watchdog timers,
2653                        see Documentation/watchdog/watchdog-parameters.txt
2654                        or other driver-specific files in the
2655                        Documentation/watchdog/ directory.
2656
2657        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
2658                        default x2apic cluster mode on platforms
2659                        supporting x2apic.
2660
2661        x86_mrst_timer= [X86-32,APBT]
2662                        Choose timer option for x86 Moorestown MID platform.
2663                        Two valid options are apbt timer only and lapic timer
2664                        plus one apbt timer for broadcast timer.
2665                        x86_mrst_timer=apbt_only | lapic_and_apbt
2666
2667        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2668        xd_geo=         See header of drivers/block/xd.c.
2669
2670        xen_emul_unplug=                [HW,X86,XEN]
2671                        Unplug Xen emulated devices
2672                        Format: [unplug0,][unplug1]
2673                        ide-disks -- unplug primary master IDE devices
2674                        aux-ide-disks -- unplug non-primary-master IDE devices
2675                        nics -- unplug network devices
2676                        all -- unplug all emulated devices (NICs and IDE disks)
2677                        unnecessary -- unplugging emulated devices is
2678                                unnecessary even if the host did not respond to
2679                                the unplug protocol
2680                        never -- do not unplug even if version check succeeds
2681
2682        xirc2ps_cs=     [NET,PCMCIA]
2683                        Format:
2684                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2685
2686______________________________________________________________________
2687
2688TODO:
2689
2690        Add more DRM drivers.
2691
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