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.notimeout [HW] Ignore timeout condition signalled by conroller
 888        i8042.reset     [HW] Reset the controller during init and cleanup
 889        i8042.unlock    [HW] Unlock (ignore) the keylock
 890
 891        i810=           [HW,DRM]
 892
 893        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
 894                        indicates that the driver is running on unsupported
 895                        hardware.
 896        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
 897                        does not match list of supported models.
 898        i8k.power_status
 899                        [HW] Report power status in /proc/i8k
 900                        (disabled by default)
 901        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
 902                        capability is set.
 903
 904        icn=            [HW,ISDN]
 905                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
 906
 907        ide-core.nodma= [HW] (E)IDE subsystem
 908                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
 909                        .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
 910                        .cdrom .chs .ignore_cable are additional options
 911                        See Documentation/ide/ide.txt.
 912
 913        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
 914                        Claim all unknown PCI IDE storage controllers.
 915
 916        idle=           [X86]
 917                        Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
 918                        Poll forces a polling idle loop that can slightly
 919                        improve the performance of waking up a idle CPU, but
 920                        will use a lot of power and make the system run hot.
 921                        Not recommended.
 922                        idle=mwait: On systems which support MONITOR/MWAIT but
 923                        the kernel chose to not use it because it doesn't save
 924                        as much power as a normal idle loop, use the
 925                        MONITOR/MWAIT idle loop anyways. Performance should be
 926                        the same as idle=poll.
 927                        idle=halt: Halt is forced to be used for CPU idle.
 928                        In such case C2/C3 won't be used again.
 929                        idle=nomwait: Disable mwait for CPU C-states
 930
 931        ignore_loglevel [KNL]
 932                        Ignore loglevel setting - this will print /all/
 933                        kernel messages to the console. Useful for debugging.
 934
 935        ihash_entries=  [KNL]
 936                        Set number of hash buckets for inode cache.
 937
 938        ima_audit=      [IMA]
 939                        Format: { "0" | "1" }
 940                        0 -- integrity auditing messages. (Default)
 941                        1 -- enable informational integrity auditing messages.
 942
 943        ima_hash=       [IMA]
 944                        Format: { "sha1" | "md5" }
 945                        default: "sha1"
 946
 947        ima_tcb         [IMA]
 948                        Load a policy which meets the needs of the Trusted
 949                        Computing Base.  This means IMA will measure all
 950                        programs exec'd, files mmap'd for exec, and all files
 951                        opened for read by uid=0.
 952
 953        init=           [KNL]
 954                        Format: <full_path>
 955                        Run specified binary instead of /sbin/init as init
 956                        process.
 957
 958        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
 959                        for working out where the kernel is dying during
 960                        startup.
 961
 962        initrd=         [BOOT] Specify the location of the initial ramdisk
 963
 964        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
 965                        Format: <irq>
 966
 967        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
 968                on
 969                        Enable intel iommu driver.
 970                off
 971                        Disable intel iommu driver.
 972                igfx_off [Default Off]
 973                        By default, gfx is mapped as normal device. If a gfx
 974                        device has a dedicated DMAR unit, the DMAR unit is
 975                        bypassed by not enabling DMAR with this option. In
 976                        this case, gfx device will use physical address for
 977                        DMA.
 978                forcedac [x86_64]
 979                        With this option iommu will not optimize to look
 980                        for io virtual address below 32 bit forcing dual
 981                        address cycle on pci bus for cards supporting greater
 982                        than 32 bit addressing. The default is to look
 983                        for translation below 32 bit and if not available
 984                        then look in the higher range.
 985                strict [Default Off]
 986                        With this option on every unmap_single operation will
 987                        result in a hardware IOTLB flush operation as opposed
 988                        to batching them for performance.
 989
 990        intremap=       [X86-64, Intel-IOMMU]
 991                        Format: { on (default) | off | nosid }
 992                        on      enable Interrupt Remapping (default)
 993                        off     disable Interrupt Remapping
 994                        nosid   disable Source ID checking
 995
 996        inttest=        [IA64]
 997
 998        iomem=          Disable strict checking of access to MMIO memory
 999                strict  regions from userspace.
1000                relaxed
1001
1002        iommu=          [x86]
1003                off
1004                force
1005                noforce
1006                biomerge
1007                panic
1008                nopanic
1009                merge
1010                nomerge
1011                forcesac
1012                soft
1013                pt      [x86, IA64]
1014
1015        io7=            [HW] IO7 for Marvel based alpha systems
1016                        See comment before marvel_specify_io7 in
1017                        arch/alpha/kernel/core_marvel.c.
1018
1019        io_delay=       [X86] I/O delay method
1020                0x80
1021                        Standard port 0x80 based delay
1022                0xed
1023                        Alternate port 0xed based delay (needed on some systems)
1024                udelay
1025                        Simple two microseconds delay
1026                none
1027                        No delay
1028
1029        ip=             [IP_PNP]
1030                        See Documentation/filesystems/nfs/nfsroot.txt.
1031
1032        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1033                        See comment before ip2_setup() in
1034                        drivers/char/ip2/ip2base.c.
1035
1036        irqfixup        [HW]
1037                        When an interrupt is not handled search all handlers
1038                        for it. Intended to get systems with badly broken
1039                        firmware running.
1040
1041        irqpoll         [HW]
1042                        When an interrupt is not handled search all handlers
1043                        for it. Also check all handlers each timer
1044                        interrupt. Intended to get systems with badly broken
1045                        firmware running.
1046
1047        isapnp=         [ISAPNP]
1048                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1049
1050        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
1051                        Format:
1052                        <cpu number>,...,<cpu number>
1053                        or
1054                        <cpu number>-<cpu number>
1055                        (must be a positive range in ascending order)
1056                        or a mixture
1057                        <cpu number>,...,<cpu number>-<cpu number>
1058
1059                        This option can be used to specify one or more CPUs
1060                        to isolate from the general SMP balancing and scheduling
1061                        algorithms. You can move a process onto or off an
1062                        "isolated" CPU via the CPU affinity syscalls or cpuset.
1063                        <cpu number> begins at 0 and the maximum value is
1064                        "number of CPUs in system - 1".
1065
1066                        This option is the preferred way to isolate CPUs. The
1067                        alternative -- manually setting the CPU mask of all
1068                        tasks in the system -- can cause problems and
1069                        suboptimal load balancer performance.
1070
1071        iucv=           [HW,NET]
1072
1073        js=             [HW,JOY] Analog joystick
1074                        See Documentation/input/joystick.txt.
1075
1076        keepinitrd      [HW,ARM]
1077
1078        kernelcore=nn[KMG]      [KNL,X86,IA-64,PPC] This parameter
1079                        specifies the amount of memory usable by the kernel
1080                        for non-movable allocations.  The requested amount is
1081                        spread evenly throughout all nodes in the system. The
1082                        remaining memory in each node is used for Movable
1083                        pages. In the event, a node is too small to have both
1084                        kernelcore and Movable pages, kernelcore pages will
1085                        take priority and other nodes will have a larger number
1086                        of kernelcore pages.  The Movable zone is used for the
1087                        allocation of pages that may be reclaimed or moved
1088                        by the page migration subsystem.  This means that
1089                        HugeTLB pages may not be allocated from this zone.
1090                        Note that allocations like PTEs-from-HighMem still
1091                        use the HighMem zone if it exists, and the Normal
1092                        zone if it does not.
1093
1094        kgdbdbgp=       [KGDB,HW] kgdb over EHCI usb debug port.
1095                        Format: <Controller#>[,poll interval]
1096                        The controller # is the number of the ehci usb debug
1097                        port as it is probed via PCI.  The poll interval is
1098                        optional and is the number seconds in between
1099                        each poll cycle to the debug port in case you need
1100                        the functionality for interrupting the kernel with
1101                        gdb or control-c on the dbgp connection.  When
1102                        not using this parameter you use sysrq-g to break into
1103                        the kernel debugger.
1104
1105        kgdboc=         [KGDB,HW] kgdb over consoles.
1106                        Requires a tty driver that supports console polling,
1107                        or a supported polling keyboard driver (non-usb).
1108                         Serial only format: <serial_device>[,baud]
1109                         keyboard only format: kbd
1110                         keyboard and serial format: kbd,<serial_device>[,baud]
1111                        Optional Kernel mode setting:
1112                         kms, kbd format: kms,kbd
1113                         kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1114
1115        kgdbwait        [KGDB] Stop kernel execution and enter the
1116                        kernel debugger at the earliest opportunity.
1117
1118        kmac=           [MIPS] korina ethernet MAC address.
1119                        Configure the RouterBoard 532 series on-chip
1120                        Ethernet adapter MAC address.
1121
1122        kmemleak=       [KNL] Boot-time kmemleak enable/disable
1123                        Valid arguments: on, off
1124                        Default: on
1125
1126        kstack=N        [X86] Print N words from the kernel stack
1127                        in oops dumps.
1128
1129        kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1130                        Default is 0 (don't ignore, but inject #GP)
1131
1132        kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1133                        Default is 1 (enabled)
1134
1135        kvm.mmu_audit=  [KVM] This is a R/W parameter which allows audit
1136                        KVM MMU at runtime.
1137                        Default is 0 (off)
1138
1139        kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1140                        Default is 1 (enabled)
1141
1142        kvm-amd.npt=    [KVM,AMD] Disable nested paging (virtualized MMU)
1143                        for all guests.
1144                        Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1145
1146        kvm-intel.bypass_guest_pf=
1147                        [KVM,Intel] Disables bypassing of guest page faults
1148                        on Intel chips. Default is 1 (enabled)
1149
1150        kvm-intel.ept=  [KVM,Intel] Disable extended page tables
1151                        (virtualized MMU) support on capable Intel chips.
1152                        Default is 1 (enabled)
1153
1154        kvm-intel.emulate_invalid_guest_state=
1155                        [KVM,Intel] Enable emulation of invalid guest states
1156                        Default is 0 (disabled)
1157
1158        kvm-intel.flexpriority=
1159                        [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1160                        Default is 1 (enabled)
1161
1162        kvm-intel.unrestricted_guest=
1163                        [KVM,Intel] Disable unrestricted guest feature
1164                        (virtualized real and unpaged mode) on capable
1165                        Intel chips. Default is 1 (enabled)
1166
1167        kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1168                        feature (tagged TLBs) on capable Intel chips.
1169                        Default is 1 (enabled)
1170
1171        l2cr=           [PPC]
1172
1173        l3cr=           [PPC]
1174
1175        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
1176                        disabled it.
1177
1178        lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
1179                        in C2 power state.
1180
1181        libata.dma=     [LIBATA] DMA control
1182                        libata.dma=0      Disable all PATA and SATA DMA
1183                        libata.dma=1      PATA and SATA Disk DMA only
1184                        libata.dma=2      ATAPI (CDROM) DMA only
1185                        libata.dma=4      Compact Flash DMA only 
1186                        Combinations also work, so libata.dma=3 enables DMA
1187                        for disks and CDROMs, but not CFs.
1188        
1189        libata.ignore_hpa=      [LIBATA] Ignore HPA limit
1190                        libata.ignore_hpa=0       keep BIOS limits (default)
1191                        libata.ignore_hpa=1       ignore limits, using full disk
1192
1193        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
1194                        when set.
1195                        Format: <int>
1196
1197        libata.force=   [LIBATA] Force configurations.  The format is comma
1198                        separated list of "[ID:]VAL" where ID is
1199                        PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1200                        matching port, link or device.  Basically, it matches
1201                        the ATA ID string printed on console by libata.  If
1202                        the whole ID part is omitted, the last PORT and DEVICE
1203                        values are used.  If ID hasn't been specified yet, the
1204                        configuration applies to all ports, links and devices.
1205
1206                        If only DEVICE is omitted, the parameter applies to
1207                        the port and all links and devices behind it.  DEVICE
1208                        number of 0 either selects the first device or the
1209                        first fan-out link behind PMP device.  It does not
1210                        select the host link.  DEVICE number of 15 selects the
1211                        host link and device attached to it.
1212
1213                        The VAL specifies the configuration to force.  As long
1214                        as there's no ambiguity shortcut notation is allowed.
1215                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
1216                        The following configurations can be forced.
1217
1218                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
1219                          Any ID with matching PORT is used.
1220
1221                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1222
1223                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1224                          udma[/][16,25,33,44,66,100,133] notation is also
1225                          allowed.
1226
1227                        * [no]ncq: Turn on or off NCQ.
1228
1229                        * nohrst, nosrst, norst: suppress hard, soft
1230                          and both resets.
1231
1232                        * dump_id: dump IDENTIFY data.
1233
1234                        If there are multiple matching configurations changing
1235                        the same attribute, the last one is used.
1236
1237        memblock=debug  [KNL] Enable memblock debug messages.
1238
1239        load_ramdisk=   [RAM] List of ramdisks to load from floppy
1240                        See Documentation/blockdev/ramdisk.txt.
1241
1242        lockd.nlm_grace_period=P  [NFS] Assign grace period.
1243                        Format: <integer>
1244
1245        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
1246                        Format: <integer>
1247
1248        lockd.nlm_timeout=T     [NFS] Assign timeout value.
1249                        Format: <integer>
1250
1251        lockd.nlm_udpport=M     [NFS] Assign UDP port.
1252                        Format: <integer>
1253
1254        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
1255                        Format: <irq>
1256
1257        loglevel=       All Kernel Messages with a loglevel smaller than the
1258                        console loglevel will be printed to the console. It can
1259                        also be changed with klogd or other programs. The
1260                        loglevels are defined as follows:
1261
1262                        0 (KERN_EMERG)          system is unusable
1263                        1 (KERN_ALERT)          action must be taken immediately
1264                        2 (KERN_CRIT)           critical conditions
1265                        3 (KERN_ERR)            error conditions
1266                        4 (KERN_WARNING)        warning conditions
1267                        5 (KERN_NOTICE)         normal but significant condition
1268                        6 (KERN_INFO)           informational
1269                        7 (KERN_DEBUG)          debug-level messages
1270
1271        log_buf_len=n   Sets the size of the printk ring buffer, in bytes.
1272                        Format: { n | nk | nM }
1273                        n must be a power of two.  The default size
1274                        is set in the kernel config file.
1275
1276        logo.nologo     [FB] Disables display of the built-in Linux logo.
1277                        This may be used to provide more screen space for
1278                        kernel log messages and is useful when debugging
1279                        kernel boot problems.
1280
1281        lp=0            [LP]    Specify parallel ports to use, e.g,
1282        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
1283        lp=reset                first parallel port). 'lp=0' disables the
1284        lp=auto                 printer driver. 'lp=reset' (which can be
1285                                specified in addition to the ports) causes
1286                                attached printers to be reset. Using
1287                                lp=port1,port2,... specifies the parallel ports
1288                                to associate lp devices with, starting with
1289                                lp0. A port specification may be 'none' to skip
1290                                that lp device, or a parport name such as
1291                                'parport0'. Specifying 'lp=auto' instead of a
1292                                port specification list means that device IDs
1293                                from each port should be examined, to see if
1294                                an IEEE 1284-compliant printer is attached; if
1295                                so, the driver will manage that printer.
1296                                See also header of drivers/char/lp.c.
1297
1298        lpj=n           [KNL]
1299                        Sets loops_per_jiffy to given constant, thus avoiding
1300                        time-consuming boot-time autodetection (up to 250 ms per
1301                        CPU). 0 enables autodetection (default). To determine
1302                        the correct value for your kernel, boot with normal
1303                        autodetection and see what value is printed. Note that
1304                        on SMP systems the preset will be applied to all CPUs,
1305                        which is likely to cause problems if your CPUs need
1306                        significantly divergent settings. An incorrect value
1307                        will cause delays in the kernel to be wrong, leading to
1308                        unpredictable I/O errors and other breakage. Although
1309                        unlikely, in the extreme case this might damage your
1310                        hardware.
1311
1312        ltpc=           [NET]
1313                        Format: <io>,<irq>,<dma>
1314
1315        machvec=        [IA64] Force the use of a particular machine-vector
1316                        (machvec) in a generic kernel.
1317                        Example: machvec=hpzx1_swiotlb
1318
1319        machtype=       [Loongson] Share the same kernel image file between different
1320                         yeeloong laptop.
1321                        Example: machtype=lemote-yeeloong-2f-7inch
1322
1323        max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater
1324                        than or equal to this physical address is ignored.
1325
1326        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
1327                        should make use of.  maxcpus=n : n >= 0 limits the
1328                        kernel to using 'n' processors.  n=0 is a special case,
1329                        it is equivalent to "nosmp", which also disables
1330                        the IO APIC.
1331
1332        max_loop=       [LOOP] Maximum number of loopback devices that can
1333                        be mounted
1334                        Format: <1-256>
1335
1336        mcatest=        [IA-64]
1337
1338        mce             [X86-32] Machine Check Exception
1339
1340        mce=option      [X86-64] See Documentation/x86/x86_64/boot-options.txt
1341
1342        md=             [HW] RAID subsystems devices and level
1343                        See Documentation/md.txt.
1344
1345        mdacon=         [MDA]
1346                        Format: <first>,<last>
1347                        Specifies range of consoles to be captured by the MDA.
1348
1349        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
1350                        Amount of memory to be used when the kernel is not able
1351                        to see the whole system memory or for test.
1352                        [X86-32] Use together with memmap= to avoid physical
1353                        address space collisions. Without memmap= PCI devices
1354                        could be placed at addresses belonging to unused RAM.
1355
1356        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
1357                        memory.
1358
1359        memchunk=nn[KMG]
1360                        [KNL,SH] Allow user to override the default size for
1361                        per-device physically contiguous DMA buffers.
1362
1363        memmap=exactmap [KNL,X86] Enable setting of an exact
1364                        E820 memory map, as specified by the user.
1365                        Such memmap=exactmap lines can be constructed based on
1366                        BIOS output or other requirements. See the memmap=nn@ss
1367                        option description.
1368
1369        memmap=nn[KMG]@ss[KMG]
1370                        [KNL] Force usage of a specific region of memory
1371                        Region of memory to be used, from ss to ss+nn.
1372
1373        memmap=nn[KMG]#ss[KMG]
1374                        [KNL,ACPI] Mark specific memory as ACPI data.
1375                        Region of memory to be used, from ss to ss+nn.
1376
1377        memmap=nn[KMG]$ss[KMG]
1378                        [KNL,ACPI] Mark specific memory as reserved.
1379                        Region of memory to be used, from ss to ss+nn.
1380                        Example: Exclude memory from 0x18690000-0x1869ffff
1381                                 memmap=64K$0x18690000
1382                                 or
1383                                 memmap=0x10000$0x18690000
1384
1385        memory_corruption_check=0/1 [X86]
1386                        Some BIOSes seem to corrupt the first 64k of
1387                        memory when doing things like suspend/resume.
1388                        Setting this option will scan the memory
1389                        looking for corruption.  Enabling this will
1390                        both detect corruption and prevent the kernel
1391                        from using the memory being corrupted.
1392                        However, its intended as a diagnostic tool; if
1393                        repeatable BIOS-originated corruption always
1394                        affects the same memory, you can use memmap=
1395                        to prevent the kernel from using that memory.
1396
1397        memory_corruption_check_size=size [X86]
1398                        By default it checks for corruption in the low
1399                        64k, making this memory unavailable for normal
1400                        use.  Use this parameter to scan for
1401                        corruption in more or less memory.
1402
1403        memory_corruption_check_period=seconds [X86]
1404                        By default it checks for corruption every 60
1405                        seconds.  Use this parameter to check at some
1406                        other rate.  0 disables periodic checking.
1407
1408        memtest=        [KNL,X86] Enable memtest
1409                        Format: <integer>
1410                        default : 0 <disable>
1411                        Specifies the number of memtest passes to be
1412                        performed. Each pass selects another test
1413                        pattern from a given set of patterns. Memtest
1414                        fills the memory with this pattern, validates
1415                        memory contents and reserves bad memory
1416                        regions that are detected.
1417
1418        meye.*=         [HW] Set MotionEye Camera parameters
1419                        See Documentation/video4linux/meye.txt.
1420
1421        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
1422                        Multi-Function General Purpose Timers on AMD Geode
1423                        platforms.
1424
1425        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
1426                        the BIOS has incorrectly applied a workaround. TinyBIOS
1427                        version 0.98 is known to be affected, 0.99 fixes the
1428                        problem by letting the user disable the workaround.
1429
1430        mga=            [HW,DRM]
1431
1432        min_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory below this
1433                        physical address is ignored.
1434
1435        mini2440=       [ARM,HW,KNL]
1436                        Format:[0..2][b][c][t]
1437                        Default: "0tb"
1438                        MINI2440 configuration specification:
1439                        0 - The attached screen is the 3.5" TFT
1440                        1 - The attached screen is the 7" TFT
1441                        2 - The VGA Shield is attached (1024x768)
1442                        Leaving out the screen size parameter will not load
1443                        the TFT driver, and the framebuffer will be left
1444                        unconfigured.
1445                        b - Enable backlight. The TFT backlight pin will be
1446                        linked to the kernel VESA blanking code and a GPIO
1447                        LED. This parameter is not necessary when using the
1448                        VGA shield.
1449                        c - Enable the s3c camera interface.
1450                        t - Reserved for enabling touchscreen support. The
1451                        touchscreen support is not enabled in the mainstream
1452                        kernel as of 2.6.30, a preliminary port can be found
1453                        in the "bleeding edge" mini2440 support kernel at
1454                        http://repo.or.cz/w/linux-2.6/mini2440.git
1455
1456        mminit_loglevel=
1457                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1458                        parameter allows control of the logging verbosity for
1459                        the additional memory initialisation checks. A value
1460                        of 0 disables mminit logging and a level of 4 will
1461                        log everything. Information is printed at KERN_DEBUG
1462                        so loglevel=8 may also need to be specified.
1463
1464        mousedev.tap_time=
1465                        [MOUSE] Maximum time between finger touching and
1466                        leaving touchpad surface for touch to be considered
1467                        a tap and be reported as a left button click (for
1468                        touchpads working in absolute mode only).
1469                        Format: <msecs>
1470        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
1471                        reporting absolute coordinates, such as tablets
1472        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
1473                        reporting absolute coordinates, such as tablets
1474
1475        movablecore=nn[KMG]     [KNL,X86,IA-64,PPC] This parameter
1476                        is similar to kernelcore except it specifies the
1477                        amount of memory used for migratable allocations.
1478                        If both kernelcore and movablecore is specified,
1479                        then kernelcore will be at *least* the specified
1480                        value but may be more. If movablecore on its own
1481                        is specified, the administrator must be careful
1482                        that the amount of memory usable for all allocations
1483                        is not too small.
1484
1485        MTD_Partition=  [MTD]
1486                        Format: <name>,<region-number>,<size>,<offset>
1487
1488        MTD_Region=     [MTD] Format:
1489                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1490
1491        mtdparts=       [MTD]
1492                        See drivers/mtd/cmdlinepart.c.
1493
1494        onenand.bdry=   [HW,MTD] Flex-OneNAND Boundary Configuration
1495
1496                        Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1497
1498                        boundary - index of last SLC block on Flex-OneNAND.
1499                                   The remaining blocks are configured as MLC blocks.
1500                        lock     - Configure if Flex-OneNAND boundary should be locked.
1501                                   Once locked, the boundary cannot be changed.
1502                                   1 indicates lock status, 0 indicates unlock status.
1503
1504        mtdset=         [ARM]
1505                        ARM/S3C2412 JIVE boot control
1506
1507                        See arch/arm/mach-s3c2412/mach-jive.c
1508
1509        mtouchusb.raw_coordinates=
1510                        [HW] Make the MicroTouch USB driver use raw coordinates
1511                        ('y', default) or cooked coordinates ('n')
1512
1513        mtrr_chunk_size=nn[KMG] [X86]
1514                        used for mtrr cleanup. It is largest continuous chunk
1515                        that could hold holes aka. UC entries.
1516
1517        mtrr_gran_size=nn[KMG] [X86]
1518                        Used for mtrr cleanup. It is granularity of mtrr block.
1519                        Default is 1.
1520                        Large value could prevent small alignment from
1521                        using up MTRRs.
1522
1523        mtrr_spare_reg_nr=n [X86]
1524                        Format: <integer>
1525                        Range: 0,7 : spare reg number
1526                        Default : 1
1527                        Used for mtrr cleanup. It is spare mtrr entries number.
1528                        Set to 2 or more if your graphical card needs more.
1529
1530        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
1531
1532        netdev=         [NET] Network devices parameters
1533                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1534                        Note that mem_start is often overloaded to mean
1535                        something different and driver-specific.
1536                        This usage is only documented in each driver source
1537                        file if at all.
1538
1539        nf_conntrack.acct=
1540                        [NETFILTER] Enable connection tracking flow accounting
1541                        0 to disable accounting
1542                        1 to enable accounting
1543                        Default value is 0.
1544
1545        nfsaddrs=       [NFS] Deprecated.  Use ip= instead.
1546                        See Documentation/filesystems/nfs/nfsroot.txt.
1547
1548        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
1549                        See Documentation/filesystems/nfs/nfsroot.txt.
1550
1551        nfsrootdebug    [NFS] enable nfsroot debugging messages.
1552                        See Documentation/filesystems/nfs/nfsroot.txt.
1553
1554        nfs.callback_tcpport=
1555                        [NFS] set the TCP port on which the NFSv4 callback
1556                        channel should listen.
1557
1558        nfs.cache_getent=
1559                        [NFS] sets the pathname to the program which is used
1560                        to update the NFS client cache entries.
1561
1562        nfs.cache_getent_timeout=
1563                        [NFS] sets the timeout after which an attempt to
1564                        update a cache entry is deemed to have failed.
1565
1566        nfs.idmap_cache_timeout=
1567                        [NFS] set the maximum lifetime for idmapper cache
1568                        entries.
1569
1570        nfs.enable_ino64=
1571                        [NFS] enable 64-bit inode numbers.
1572                        If zero, the NFS client will fake up a 32-bit inode
1573                        number for the readdir() and stat() syscalls instead
1574                        of returning the full 64-bit number.
1575                        The default is to return 64-bit inode numbers.
1576
1577        nmi_debug=      [KNL,AVR32,SH] Specify one or more actions to take
1578                        when a NMI is triggered.
1579                        Format: [state][,regs][,debounce][,die]
1580
1581        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
1582                        Format: [panic,][num]
1583                        Valid num: 0,1,2
1584                        0 - turn nmi_watchdog off
1585                        1 - use the IO-APIC timer for the NMI watchdog
1586                        2 - use the local APIC for the NMI watchdog using
1587                        a performance counter. Note: This will use one
1588                        performance counter and the local APIC's performance
1589                        vector.
1590                        When panic is specified, panic when an NMI watchdog
1591                        timeout occurs.
1592                        This is useful when you use a panic=... timeout and
1593                        need the box quickly up again.
1594                        Instead of 1 and 2 it is possible to use the following
1595                        symbolic names: lapic and ioapic
1596                        Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1597
1598        netpoll.carrier_timeout=
1599                        [NET] Specifies amount of time (in seconds) that
1600                        netpoll should wait for a carrier. By default netpoll
1601                        waits 4 seconds.
1602
1603        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
1604                        emulation library even if a 387 maths coprocessor
1605                        is present.
1606
1607        no_console_suspend
1608                        [HW] Never suspend the console
1609                        Disable suspending of consoles during suspend and
1610                        hibernate operations.  Once disabled, debugging
1611                        messages can reach various consoles while the rest
1612                        of the system is being put to sleep (ie, while
1613                        debugging driver suspend/resume hooks).  This may
1614                        not work reliably with all consoles, but is known
1615                        to work with serial and VGA consoles.
1616
1617        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
1618                        caches in the slab allocator.  Saves per-node memory,
1619                        but will impact performance.
1620
1621        noalign         [KNL,ARM]
1622
1623        noapic          [SMP,APIC] Tells the kernel to not make use of any
1624                        IOAPICs that may be present in the system.
1625
1626        nobats          [PPC] Do not use BATs for mapping kernel lowmem
1627                        on "Classic" PPC cores.
1628
1629        nocache         [ARM]
1630
1631        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction
1632
1633        nodelayacct     [KNL] Disable per-task delay accounting
1634
1635        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1636
1637        nodsp           [SH] Disable hardware DSP at boot time.
1638
1639        noefi           [X86] Disable EFI runtime services support.
1640
1641        noexec          [IA-64]
1642
1643        noexec          [X86]
1644                        On X86-32 available only on PAE configured kernels.
1645                        noexec=on: enable non-executable mappings (default)
1646                        noexec=off: disable non-executable mappings
1647
1648        noexec32        [X86-64]
1649                        This affects only 32-bit executables.
1650                        noexec32=on: enable non-executable mappings (default)
1651                                read doesn't imply executable mappings
1652                        noexec32=off: disable non-executable mappings
1653                                read implies executable mappings
1654
1655        nofpu           [SH] Disable hardware FPU at boot time.
1656
1657        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
1658                        register save and restore. The kernel will only save
1659                        legacy floating-point registers on task switch.
1660
1661        noxsave         [BUGS=X86] Disables x86 extended register state save
1662                        and restore using xsave. The kernel will fallback to
1663                        enabling legacy floating-point and sse state.
1664
1665        nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1666                        wfi(ARM) instruction doesn't work correctly and not to
1667                        use it. This is also useful when using JTAG debugger.
1668
1669        no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
1670                        instruction doesn't work correctly and not to
1671                        use it.
1672
1673        no_file_caps    Tells the kernel not to honor file capabilities.  The
1674                        only way then for a file to be executed with privilege
1675                        is to be setuid root or executed by root.
1676
1677        nohalt          [IA-64] Tells the kernel not to use the power saving
1678                        function PAL_HALT_LIGHT when idle. This increases
1679                        power-consumption. On the positive side, it reduces
1680                        interrupt wake-up latency, which may improve performance
1681                        in certain environments such as networked servers or
1682                        real-time systems.
1683
1684        nohz=           [KNL] Boottime enable/disable dynamic ticks
1685                        Valid arguments: on, off
1686                        Default: on
1687
1688        noiotrap        [SH] Disables trapped I/O port accesses.
1689
1690        noirqdebug      [X86-32] Disables the code which attempts to detect and
1691                        disable unhandled interrupt sources.
1692
1693        no_timer_check  [X86,APIC] Disables the code which tests for
1694                        broken timer IRQ sources.
1695
1696        noisapnp        [ISAPNP] Disables ISA PnP code.
1697
1698        noinitrd        [RAM] Tells the kernel not to load any configured
1699                        initial RAM disk.
1700
1701        nointremap      [X86-64, Intel-IOMMU] Do not enable interrupt
1702                        remapping.
1703                        [Deprecated - use intremap=off]
1704
1705        nointroute      [IA-64]
1706
1707        nojitter        [IA64] Disables jitter checking for ITC timers.
1708
1709        no-kvmclock     [X86,KVM] Disable paravirtualized KVM clock driver
1710
1711        nolapic         [X86-32,APIC] Do not enable or use the local APIC.
1712
1713        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.
1714
1715        noltlbs         [PPC] Do not use large page/tlb entries for kernel
1716                        lowmem mapping on PPC40x.
1717
1718        nomca           [IA-64] Disable machine check abort handling
1719
1720        nomce           [X86-32] Machine Check Exception
1721
1722        nomfgpt         [X86-32] Disable Multi-Function General Purpose
1723                        Timer usage (for AMD Geode machines).
1724
1725        nopat           [X86] Disable PAT (page attribute table extension of
1726                        pagetables) support.
1727
1728        norandmaps      Don't use address space randomization.  Equivalent to
1729                        echo 0 > /proc/sys/kernel/randomize_va_space
1730
1731        noreplace-paravirt      [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1732
1733        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
1734                        with UP alternatives
1735
1736        noresidual      [PPC] Don't use residual data on PReP machines.
1737
1738        noresume        [SWSUSP] Disables resume and restores original swap
1739                        space.
1740
1741        no-scroll       [VGA] Disables scrollback.
1742                        This is required for the Braillex ib80-piezo Braille
1743                        reader made by F.H. Papenmeier (Germany).
1744
1745        nosbagart       [IA-64]
1746
1747        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1748
1749        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
1750                        and disable the IO APIC.  legacy for "maxcpus=0".
1751
1752        nosoftlockup    [KNL] Disable the soft-lockup detector.
1753
1754        noswapaccount   [KNL] Disable accounting of swap in memory resource
1755                        controller. (See Documentation/cgroups/memory.txt)
1756
1757        nosync          [HW,M68K] Disables sync negotiation for all devices.
1758
1759        notsc           [BUGS=X86-32] Disable Time Stamp Counter
1760
1761        nousb           [USB] Disable the USB subsystem
1762
1763        nowatchdog      [KNL] Disable the lockup detector (NMI watchdog).
1764
1765        nowb            [ARM]
1766
1767        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
1768
1769        nptcg=          [IA64] Override max number of concurrent global TLB
1770                        purges which is reported from either PAL_VM_SUMMARY or
1771                        SAL PALO.
1772
1773        nr_cpus=        [SMP] Maximum number of processors that an SMP kernel
1774                        could support.  nr_cpus=n : n >= 1 limits the kernel to
1775                        supporting 'n' processors. Later in runtime you can not
1776                        use hotplug cpu feature to put more cpu back to online.
1777                        just like you compile the kernel NR_CPUS=n
1778
1779        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1780
1781        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1782                        one of ['zone', 'node', 'default'] can be specified
1783                        This can be set from sysctl after boot.
1784                        See Documentation/sysctl/vm.txt for details.
1785
1786        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
1787                        See Documentation/debugging-via-ohci1394.txt for more
1788                        info.
1789
1790        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1791                        Rather than timing out after 20 ms if an EC
1792                        command is not properly ACKed, override the length
1793                        of the timeout.  We have interrupts disabled while
1794                        waiting for the ACK, so if this is set too high
1795                        interrupts *may* be lost!
1796
1797        omap_mux=       [OMAP] Override bootloader pin multiplexing.
1798                        Format: <mux_mode0.mode_name=value>...
1799                        For example, to override I2C bus2:
1800                        omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1801
1802        oprofile.timer= [HW]
1803                        Use timer interrupt instead of performance counters
1804
1805        oprofile.cpu_type=      Force an oprofile cpu type
1806                        This might be useful if you have an older oprofile
1807                        userland or if you want common events.
1808                        Format: { arch_perfmon }
1809                        arch_perfmon: [X86] Force use of architectural
1810                                perfmon on Intel CPUs instead of the
1811                                CPU specific event set.
1812
1813        OSS             [HW,OSS]
1814                        See Documentation/sound/oss/oss-parameters.txt
1815
1816        panic=          [KNL] Kernel behaviour on panic
1817                        Format: <timeout>
1818
1819        parkbd.port=    [HW] Parallel port number the keyboard adapter is
1820                        connected to, default is 0.
1821                        Format: <parport#>
1822        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
1823                        0 for XT, 1 for AT (default is AT).
1824                        Format: <mode>
1825
1826        parport=        [HW,PPT] Specify parallel ports. 0 disables.
1827                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1828                        Use 'auto' to force the driver to use any
1829                        IRQ/DMA settings detected (the default is to
1830                        ignore detected IRQ/DMA settings because of
1831                        possible conflicts). You can specify the base
1832                        address, IRQ, and DMA settings; IRQ and DMA
1833                        should be numbers, or 'auto' (for using detected
1834                        settings on that particular port), or 'nofifo'
1835                        (to avoid using a FIFO even if it is detected).
1836                        Parallel ports are assigned in the order they
1837                        are specified on the command line, starting
1838                        with parport0.
1839
1840        parport_init_mode=      [HW,PPT]
1841                        Configure VIA parallel port to operate in
1842                        a specific mode. This is necessary on Pegasos
1843                        computer where firmware has no options for setting
1844                        up parallel port mode and sets it to spp.
1845                        Currently this function knows 686a and 8231 chips.
1846                        Format: [spp|ps2|epp|ecp|ecpepp]
1847
1848        pause_on_oops=
1849                        Halt all CPUs after the first oops has been printed for
1850                        the specified number of seconds.  This is to be used if
1851                        your oopses keep scrolling off the screen.
1852
1853        pcbit=          [HW,ISDN]
1854
1855        pcd.            [PARIDE]
1856                        See header of drivers/block/paride/pcd.c.
1857                        See also Documentation/blockdev/paride.txt.
1858
1859        pci=option[,option...]  [PCI] various PCI subsystem options:
1860                earlydump       [X86] dump PCI config space before the kernel
1861                                changes anything
1862                off             [X86] don't probe for the PCI bus
1863                bios            [X86-32] force use of PCI BIOS, don't access
1864                                the hardware directly. Use this if your machine
1865                                has a non-standard PCI host bridge.
1866                nobios          [X86-32] disallow use of PCI BIOS, only direct
1867                                hardware access methods are allowed. Use this
1868                                if you experience crashes upon bootup and you
1869                                suspect they are caused by the BIOS.
1870                conf1           [X86] Force use of PCI Configuration
1871                                Mechanism 1.
1872                conf2           [X86] Force use of PCI Configuration
1873                                Mechanism 2.
1874                noaer           [PCIE] If the PCIEAER kernel config parameter is
1875                                enabled, this kernel boot option can be used to
1876                                disable the use of PCIE advanced error reporting.
1877                nodomains       [PCI] Disable support for multiple PCI
1878                                root domains (aka PCI segments, in ACPI-speak).
1879                nommconf        [X86] Disable use of MMCONFIG for PCI
1880                                Configuration
1881                check_enable_amd_mmconf [X86] check for and enable
1882                                properly configured MMIO access to PCI
1883                                config space on AMD family 10h CPU
1884                nomsi           [MSI] If the PCI_MSI kernel config parameter is
1885                                enabled, this kernel boot option can be used to
1886                                disable the use of MSI interrupts system-wide.
1887                noioapicquirk   [APIC] Disable all boot interrupt quirks.
1888                                Safety option to keep boot IRQs enabled. This
1889                                should never be necessary.
1890                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
1891                                primary IO-APIC for bridges that cannot disable
1892                                boot IRQs. This fixes a source of spurious IRQs
1893                                when the system masks IRQs.
1894                noioapicreroute [APIC] Disable workaround that uses the
1895                                boot IRQ equivalent of an IRQ that connects to
1896                                a chipset where boot IRQs cannot be disabled.
1897                                The opposite of ioapicreroute.
1898                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
1899                                routing table. These calls are known to be buggy
1900                                on several machines and they hang the machine
1901                                when used, but on other computers it's the only
1902                                way to get the interrupt routing table. Try
1903                                this option if the kernel is unable to allocate
1904                                IRQs or discover secondary PCI buses on your
1905                                motherboard.
1906                rom             [X86] Assign address space to expansion ROMs.
1907                                Use with caution as certain devices share
1908                                address decoders between ROMs and other
1909                                resources.
1910                norom           [X86] Do not assign address space to
1911                                expansion ROMs that do not already have
1912                                BIOS assigned address ranges.
1913                nobar           [X86] Do not assign address space to the
1914                                BARs that weren't assigned by the BIOS.
1915                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
1916                                assigned automatically to PCI devices. You can
1917                                make the kernel exclude IRQs of your ISA cards
1918                                this way.
1919                pirqaddr=0xAAAAA        [X86] Specify the physical address
1920                                of the PIRQ table (normally generated
1921                                by the BIOS) if it is outside the
1922                                F0000h-100000h range.
1923                lastbus=N       [X86] Scan all buses thru bus #N. Can be
1924                                useful if the kernel is unable to find your
1925                                secondary buses and you want to tell it
1926                                explicitly which ones they are.
1927                assign-busses   [X86] Always assign all PCI bus
1928                                numbers ourselves, overriding
1929                                whatever the firmware may have done.
1930                usepirqmask     [X86] Honor the possible IRQ mask stored
1931                                in the BIOS $PIR table. This is needed on
1932                                some systems with broken BIOSes, notably
1933                                some HP Pavilion N5400 and Omnibook XE3
1934                                notebooks. This will have no effect if ACPI
1935                                IRQ routing is enabled.
1936                noacpi          [X86] Do not use ACPI for IRQ routing
1937                                or for PCI scanning.
1938                use_crs         [X86] Use PCI host bridge window information
1939                                from ACPI.  On BIOSes from 2008 or later, this
1940                                is enabled by default.  If you need to use this,
1941                                please report a bug.
1942                nocrs           [X86] Ignore PCI host bridge windows from ACPI.
1943                                If you need to use this, please report a bug.
1944                routeirq        Do IRQ routing for all PCI devices.
1945                                This is normally done in pci_enable_device(),
1946                                so this option is a temporary workaround
1947                                for broken drivers that don't call it.
1948                skip_isa_align  [X86] do not align io start addr, so can
1949                                handle more pci cards
1950                firmware        [ARM] Do not re-enumerate the bus but instead
1951                                just use the configuration from the
1952                                bootloader. This is currently used on
1953                                IXP2000 systems where the bus has to be
1954                                configured a certain way for adjunct CPUs.
1955                noearly         [X86] Don't do any early type 1 scanning.
1956                                This might help on some broken boards which
1957                                machine check when some devices' config space
1958                                is read. But various workarounds are disabled
1959                                and some IOMMU drivers will not work.
1960                bfsort          Sort PCI devices into breadth-first order.
1961                                This sorting is done to get a device
1962                                order compatible with older (<= 2.4) kernels.
1963                nobfsort        Don't sort PCI devices into breadth-first order.
1964                cbiosize=nn[KMG]        The fixed amount of bus space which is
1965                                reserved for the CardBus bridge's IO window.
1966                                The default value is 256 bytes.
1967                cbmemsize=nn[KMG]       The fixed amount of bus space which is
1968                                reserved for the CardBus bridge's memory
1969                                window. The default value is 64 megabytes.
1970                resource_alignment=
1971                                Format:
1972                                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1973                                Specifies alignment and device to reassign
1974                                aligned memory resources.
1975                                If <order of align> is not specified,
1976                                PAGE_SIZE is used as alignment.
1977                                PCI-PCI bridge can be specified, if resource
1978                                windows need to be expanded.
1979                ecrc=           Enable/disable PCIe ECRC (transaction layer
1980                                end-to-end CRC checking).
1981                                bios: Use BIOS/firmware settings. This is the
1982                                the default.
1983                                off: Turn ECRC off
1984                                on: Turn ECRC on.
1985
1986        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
1987                        Management.
1988                off     Disable ASPM.
1989                force   Enable ASPM even on devices that claim not to support it.
1990                        WARNING: Forcing ASPM on may cause system lockups.
1991
1992        pcie_ports=     [PCIE] PCIe ports handling:
1993                auto    Ask the BIOS whether or not to use native PCIe services
1994                        associated with PCIe ports (PME, hot-plug, AER).  Use
1995                        them only if that is allowed by the BIOS.
1996                native  Use native PCIe services associated with PCIe ports
1997                        unconditionally.
1998                compat  Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1999                        ports driver.
2000
2001        pcie_pme=       [PCIE,PM] Native PCIe PME signaling options:
2002                nomsi   Do not use MSI for native PCIe PME signaling (this makes
2003                        all PCIe root ports use INTx for all services).
2004
2005        pcmv=           [HW,PCMCIA] BadgePAD 4
2006
2007        pd.             [PARIDE]
2008                        See Documentation/blockdev/paride.txt.
2009
2010        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2011                        boot time.
2012                        Format: { 0 | 1 }
2013                        See arch/parisc/kernel/pdc_chassis.c
2014
2015        percpu_alloc=   Select which percpu first chunk allocator to use.
2016                        Currently supported values are "embed" and "page".
2017                        Archs may support subset or none of the selections.
2018                        See comments in mm/percpu.c for details on each
2019                        allocator.  This parameter is primarily for debugging
2020                        and performance comparison.
2021
2022        pf.             [PARIDE]
2023                        See Documentation/blockdev/paride.txt.
2024
2025        pg.             [PARIDE]
2026                        See Documentation/blockdev/paride.txt.
2027
2028        pirq=           [SMP,APIC] Manual mp-table setup
2029                        See Documentation/x86/i386/IO-APIC.txt.
2030
2031        plip=           [PPT,NET] Parallel port network link
2032                        Format: { parport<nr> | timid | 0 }
2033                        See also Documentation/parport.txt.
2034
2035        pmtmr=          [X86] Manual setup of pmtmr I/O Port. 
2036                        Override pmtimer IOPort with a hex value.
2037                        e.g. pmtmr=0x508
2038
2039        pnp.debug       [PNP]
2040                        Enable PNP debug messages.  This depends on the
2041                        CONFIG_PNP_DEBUG_MESSAGES option.
2042
2043        pnpacpi=        [ACPI]
2044                        { off }
2045
2046        pnpbios=        [ISAPNP]
2047                        { on | off | curr | res | no-curr | no-res }
2048
2049        pnp_reserve_irq=
2050                        [ISAPNP] Exclude IRQs for the autoconfiguration
2051
2052        pnp_reserve_dma=
2053                        [ISAPNP] Exclude DMAs for the autoconfiguration
2054
2055        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2056                        Ranges are in pairs (I/O port base and size).
2057
2058        pnp_reserve_mem=
2059                        [ISAPNP] Exclude memory regions for the
2060                        autoconfiguration.
2061                        Ranges are in pairs (memory base and size).
2062
2063        ports=          [IP_VS_FTP] IPVS ftp helper module
2064                        Default is 21.
2065                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
2066                        may be specified.
2067                        Format: <port>,<port>....
2068
2069        print-fatal-signals=
2070                        [KNL] debug: print fatal signals
2071
2072                        If enabled, warn about various signal handling
2073                        related application anomalies: too many signals,
2074                        too many POSIX.1 timers, fatal signals causing a
2075                        coredump - etc.
2076
2077                        If you hit the warning due to signal overflow,
2078                        you might want to try "ulimit -i unlimited".
2079
2080                        default: off.
2081
2082        printk.time=    Show timing data prefixed to each printk message line
2083                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2084
2085        processor.max_cstate=   [HW,ACPI]
2086                        Limit processor to maximum C-state
2087                        max_cstate=9 overrides any DMI blacklist limit.
2088
2089        processor.nocst [HW,ACPI]
2090                        Ignore the _CST method to determine C-states,
2091                        instead using the legacy FADT method
2092
2093        profile=        [KNL] Enable kernel profiling via /proc/profile
2094                        Format: [schedule,]<number>
2095                        Param: "schedule" - profile schedule points.
2096                        Param: <number> - step/bucket size as a power of 2 for
2097                                statistical time based profiling.
2098                        Param: "sleep" - profile D-state sleeping (millisecs).
2099                                Requires CONFIG_SCHEDSTATS
2100                        Param: "kvm" - profile VM exits.
2101
2102        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2103                        before loading.
2104                        See Documentation/blockdev/ramdisk.txt.
2105
2106        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
2107                        probe for; one of (bare|imps|exps|lifebook|any).
2108        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
2109                        per second.
2110        psmouse.resetafter=     [HW,MOUSE]
2111                        Try to reset the device after so many bad packets
2112                        (0 = never).
2113        psmouse.resolution=
2114                        [HW,MOUSE] Set desired mouse resolution, in dpi.
2115        psmouse.smartscroll=
2116                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2117                        0 = disabled, 1 = enabled (default).
2118
2119        pt.             [PARIDE]
2120                        See Documentation/blockdev/paride.txt.
2121
2122        pty.legacy_count=
2123                        [KNL] Number of legacy pty's. Overwrites compiled-in
2124                        default number.
2125
2126        quiet           [KNL] Disable most log messages
2127
2128        r128=           [HW,DRM]
2129
2130        raid=           [HW,RAID]
2131                        See Documentation/md.txt.
2132
2133        ramdisk_blocksize=      [RAM]
2134                        See Documentation/blockdev/ramdisk.txt.
2135
2136        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
2137                        See Documentation/blockdev/ramdisk.txt.
2138
2139        rcupdate.blimit=        [KNL,BOOT]
2140                        Set maximum number of finished RCU callbacks to process
2141                        in one batch.
2142
2143        rcupdate.qhimark=       [KNL,BOOT]
2144                        Set threshold of queued
2145                        RCU callbacks over which batch limiting is disabled.
2146
2147        rcupdate.qlowmark=      [KNL,BOOT]
2148                        Set threshold of queued RCU callbacks below which
2149                        batch limiting is re-enabled.
2150
2151        rdinit=         [KNL]
2152                        Format: <full_path>
2153                        Run specified binary instead of /init from the ramdisk,
2154                        used for early userspace startup. See initrd.
2155
2156        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2157                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
2158                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2159
2160        relax_domain_level=
2161                        [KNL, SMP] Set scheduler's default relax_domain_level.
2162                        See Documentation/cgroups/cpusets.txt.
2163
2164        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
2165
2166        reservetop=     [X86-32]
2167                        Format: nn[KMG]
2168                        Reserves a hole at the top of the kernel virtual
2169                        address space.
2170
2171        reservelow=     [X86]
2172                        Format: nn[K]
2173                        Set the amount of memory to reserve for BIOS at
2174                        the bottom of the address space.
2175
2176        reset_devices   [KNL] Force drivers to reset the underlying device
2177                        during initialization.
2178
2179        resume=         [SWSUSP]
2180                        Specify the partition device for software suspend
2181
2182        resume_offset=  [SWSUSP]
2183                        Specify the offset from the beginning of the partition
2184                        given by "resume=" at which the swap header is located,
2185                        in <PAGE_SIZE> units (needed only for swap files).
2186                        See  Documentation/power/swsusp-and-swap-files.txt
2187
2188        hibernate=      [HIBERNATION]
2189                noresume        Don't check if there's a hibernation image
2190                                present during boot.
2191                nocompress      Don't compress/decompress hibernation images.
2192
2193        retain_initrd   [RAM] Keep initrd memory after extraction
2194
2195        rhash_entries=  [KNL,NET]
2196                        Set number of hash buckets for route cache
2197
2198        riscom8=        [HW,SERIAL]
2199                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2200
2201        ro              [KNL] Mount root device read-only on boot
2202
2203        root=           [KNL] Root filesystem
2204
2205        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
2206                        mount the root filesystem
2207
2208        rootflags=      [KNL] Set root filesystem mount option string
2209
2210        rootfstype=     [KNL] Set root filesystem type
2211
2212        rootwait        [KNL] Wait (indefinitely) for root device to show up.
2213                        Useful for devices that are detected asynchronously
2214                        (e.g. USB and MMC devices).
2215
2216        rw              [KNL] Mount root device read-write on boot
2217
2218        S               [KNL] Run init in single mode
2219
2220        sa1100ir        [NET]
2221                        See drivers/net/irda/sa1100_ir.c.
2222
2223        sbni=           [NET] Granch SBNI12 leased line adapter
2224
2225        sched_debug     [KNL] Enables verbose scheduler debug messages.
2226
2227        security=       [SECURITY] Choose a security module to enable at boot.
2228                        If this boot parameter is not specified, only the first
2229                        security module asking for security registration will be
2230                        loaded. An invalid security module name will be treated
2231                        as if no module has been chosen.
2232
2233        selinux=        [SELINUX] Disable or enable SELinux at boot time.
2234                        Format: { "0" | "1" }
2235                        See security/selinux/Kconfig help text.
2236                        0 -- disable.
2237                        1 -- enable.
2238                        Default value is set via kernel config option.
2239                        If enabled at boot time, /selinux/disable can be used
2240                        later to disable prior to initial policy load.
2241
2242        apparmor=       [APPARMOR] Disable or enable AppArmor at boot time
2243                        Format: { "0" | "1" }
2244                        See security/apparmor/Kconfig help text
2245                        0 -- disable.
2246                        1 -- enable.
2247                        Default value is set via kernel config option.
2248
2249        serialnumber    [BUGS=X86-32]
2250
2251        shapers=        [NET]
2252                        Maximal number of shapers.
2253
2254        show_msr=       [x86] show boot-time MSR settings
2255                        Format: { <integer> }
2256                        Show boot-time (BIOS-initialized) MSR settings.
2257                        The parameter means the number of CPUs to show,
2258                        for example 1 means boot CPU only.
2259
2260        simeth=         [IA-64]
2261        simscsi=
2262
2263        slram=          [HW,MTD]
2264
2265        slub_debug[=options[,slabs]]    [MM, SLUB]
2266                        Enabling slub_debug allows one to determine the
2267                        culprit if slab objects become corrupted. Enabling
2268                        slub_debug can create guard zones around objects and
2269                        may poison objects when not in use. Also tracks the
2270                        last alloc / free. For more information see
2271                        Documentation/vm/slub.txt.
2272
2273        slub_max_order= [MM, SLUB]
2274                        Determines the maximum allowed order for slabs.
2275                        A high setting may cause OOMs due to memory
2276                        fragmentation. For more information see
2277                        Documentation/vm/slub.txt.
2278
2279        slub_min_objects=       [MM, SLUB]
2280                        The minimum number of objects per slab. SLUB will
2281                        increase the slab order up to slub_max_order to
2282                        generate a sufficiently large slab able to contain
2283                        the number of objects indicated. The higher the number
2284                        of objects the smaller the overhead of tracking slabs
2285                        and the less frequently locks need to be acquired.
2286                        For more information see Documentation/vm/slub.txt.
2287
2288        slub_min_order= [MM, SLUB]
2289                        Determines the mininum page order for slabs. Must be
2290                        lower than slub_max_order.
2291                        For more information see Documentation/vm/slub.txt.
2292
2293        slub_nomerge    [MM, SLUB]
2294                        Disable merging of slabs with similar size. May be
2295                        necessary if there is some reason to distinguish
2296                        allocs to different slabs. Debug options disable
2297                        merging on their own.
2298                        For more information see Documentation/vm/slub.txt.
2299
2300        smart2=         [HW]
2301                        Format: <io1>[,<io2>[,...,<io8>]]
2302
2303        smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
2304                        attempt to substitute SMP alternatives once at boot.
2305
2306        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
2307        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
2308        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
2309        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
2310        smsc-ircc2.ircc_irq=    [HW] IRQ line
2311        smsc-ircc2.ircc_dma=    [HW] DMA channel
2312        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2313                                0: Toshiba Satellite 1800 (GP data pin select)
2314                                1: Fast pin select (default)
2315                                2: ATC IRMode
2316
2317        softlockup_panic=
2318                        [KNL] Should the soft-lockup detector generate panics.
2319
2320        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
2321                        See Documentation/sonypi.txt
2322
2323        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
2324                        See Documentation/serial/specialix.txt.
2325
2326        spia_io_base=   [HW,MTD]
2327        spia_fio_base=
2328        spia_pedr=
2329        spia_peddr=
2330
2331        stacktrace      [FTRACE]
2332                        Enabled the stack tracer on boot up.
2333
2334        sti=            [PARISC,HW]
2335                        Format: <num>
2336                        Set the STI (builtin display/keyboard on the HP-PARISC
2337                        machines) console (graphic card) which should be used
2338                        as the initial boot-console.
2339                        See also comment in drivers/video/console/sticore.c.
2340
2341        sti_font=       [HW]
2342                        See comment in drivers/video/console/sticore.c.
2343
2344        stifb=          [HW]
2345                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2346
2347        sunrpc.min_resvport=
2348        sunrpc.max_resvport=
2349                        [NFS,SUNRPC]
2350                        SunRPC servers often require that client requests
2351                        originate from a privileged port (i.e. a port in the
2352                        range 0 < portnr < 1024).
2353                        An administrator who wishes to reserve some of these
2354                        ports for other uses may adjust the range that the
2355                        kernel's sunrpc client considers to be privileged
2356                        using these two parameters to set the minimum and
2357                        maximum port values.
2358
2359        sunrpc.pool_mode=
2360                        [NFS]
2361                        Control how the NFS server code allocates CPUs to
2362                        service thread pools.  Depending on how many NICs
2363                        you have and where their interrupts are bound, this
2364                        option will affect which CPUs will do NFS serving.
2365                        Note: this parameter cannot be changed while the
2366                        NFS server is running.
2367
2368                        auto        the server chooses an appropriate mode
2369                                    automatically using heuristics
2370                        global      a single global pool contains all CPUs
2371                        percpu      one pool for each CPU
2372                        pernode     one pool for each NUMA node (equivalent
2373                                    to global on non-NUMA machines)
2374
2375        sunrpc.tcp_slot_table_entries=
2376        sunrpc.udp_slot_table_entries=
2377                        [NFS,SUNRPC]
2378                        Sets the upper limit on the number of simultaneous
2379                        RPC calls that can be sent from the client to a
2380                        server. Increasing these values may allow you to
2381                        improve throughput, but will also increase the
2382                        amount of memory reserved for use by the client.
2383
2384        swapaccount[=0|1]
2385                        [KNL] Enable accounting of swap in memory resource
2386                        controller if no parameter or 1 is given or disable
2387                        it if 0 is given (See Documentation/cgroups/memory.txt)
2388
2389        swiotlb=        [IA-64] Number of I/O TLB slabs
2390
2391        switches=       [HW,M68k]
2392
2393        sysfs.deprecated=0|1 [KNL]
2394                        Enable/disable old style sysfs layout for old udev
2395                        on older distributions. When this option is enabled
2396                        very new udev will not work anymore. When this option
2397                        is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2398                        in older udev will not work anymore.
2399                        Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2400                        the kernel configuration.
2401
2402        sysrq_always_enabled
2403                        [KNL]
2404                        Ignore sysrq setting - this boot parameter will
2405                        neutralize any effect of /proc/sys/kernel/sysrq.
2406                        Useful for debugging.
2407
2408        tdfx=           [HW,DRM]
2409
2410        test_suspend=   [SUSPEND]
2411                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
2412                        standby suspend) as the system sleep state to briefly
2413                        enter during system startup.  The system is woken from
2414                        this state using a wakeup-capable RTC alarm.
2415
2416        thash_entries=  [KNL,NET]
2417                        Set number of hash buckets for TCP connection
2418
2419        thermal.act=    [HW,ACPI]
2420                        -1: disable all active trip points in all thermal zones
2421                        <degrees C>: override all lowest active trip points
2422
2423        thermal.crt=    [HW,ACPI]
2424                        -1: disable all critical trip points in all thermal zones
2425                        <degrees C>: override all critical trip points
2426
2427        thermal.nocrt=  [HW,ACPI]
2428                        Set to disable actions on ACPI thermal zone
2429                        critical and hot trip points.
2430
2431        thermal.off=    [HW,ACPI]
2432                        1: disable ACPI thermal control
2433
2434        thermal.psv=    [HW,ACPI]
2435                        -1: disable all passive trip points
2436                        <degrees C>: override all passive trip points to this
2437                        value
2438
2439        thermal.tzp=    [HW,ACPI]
2440                        Specify global default ACPI thermal zone polling rate
2441                        <deci-seconds>: poll all this frequency
2442                        0: no polling (default)
2443
2444        topology=       [S390]
2445                        Format: {off | on}
2446                        Specify if the kernel should make use of the cpu
2447                        topology informations if the hardware supports these.
2448                        The scheduler will make use of these informations and
2449                        e.g. base its process migration decisions on it.
2450                        Default is on.
2451
2452        tp720=          [HW,PS2]
2453
2454        tpm_suspend_pcr=[HW,TPM]
2455                        Format: integer pcr id
2456                        Specify that at suspend time, the tpm driver
2457                        should extend the specified pcr with zeros,
2458                        as a workaround for some chips which fail to
2459                        flush the last written pcr on TPM_SaveState.
2460                        This will guarantee that all the other pcrs
2461                        are saved.
2462
2463        trace_buf_size=nn[KMG]
2464                        [FTRACE] will set tracing buffer size.
2465
2466        trace_event=[event-list]
2467                        [FTRACE] Set and start specified trace events in order
2468                        to facilitate early boot debugging.
2469                        See also Documentation/trace/events.txt
2470
2471        tsc=            Disable clocksource-must-verify flag for TSC.
2472                        Format: <string>
2473                        [x86] reliable: mark tsc clocksource as reliable, this
2474                        disables clocksource verification at runtime.
2475                        Used to enable high-resolution timer mode on older
2476                        hardware, and in virtualized environment.
2477                        [x86] noirqtime: Do not use TSC to do irq accounting.
2478                        Used to run time disable IRQ_TIME_ACCOUNTING on any
2479                        platforms where RDTSC is slow and this accounting
2480                        can add overhead.
2481
2482        turbografx.map[2|3]=    [HW,JOY]
2483                        TurboGraFX parallel port interface
2484                        Format:
2485                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2486                        See also Documentation/input/joystick-parport.txt
2487
2488        uhash_entries=  [KNL,NET]
2489                        Set number of hash buckets for UDP/UDP-Lite connections
2490
2491        uhci-hcd.ignore_oc=
2492                        [USB] Ignore overcurrent events (default N).
2493                        Some badly-designed motherboards generate lots of
2494                        bogus events, for ports that aren't wired to
2495                        anything.  Set this parameter to avoid log spamming.
2496                        Note that genuine overcurrent events won't be
2497                        reported either.
2498
2499        unknown_nmi_panic
2500                        [X86]
2501                        Set unknown_nmi_panic=1 early on boot.
2502
2503        usbcore.autosuspend=
2504                        [USB] The autosuspend time delay (in seconds) used
2505                        for newly-detected USB devices (default 2).  This
2506                        is the time required before an idle device will be
2507                        autosuspended.  Devices for which the delay is set
2508                        to a negative value won't be autosuspended at all.
2509
2510        usbcore.usbfs_snoop=
2511                        [USB] Set to log all usbfs traffic (default 0 = off).
2512
2513        usbcore.blinkenlights=
2514                        [USB] Set to cycle leds on hubs (default 0 = off).
2515
2516        usbcore.old_scheme_first=
2517                        [USB] Start with the old device initialization
2518                        scheme (default 0 = off).
2519
2520        usbcore.use_both_schemes=
2521                        [USB] Try the other device initialization scheme
2522                        if the first one fails (default 1 = enabled).
2523
2524        usbcore.initial_descriptor_timeout=
2525                        [USB] Specifies timeout for the initial 64-byte
2526                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2527                        (default 5000 = 5.0 seconds).
2528
2529        usbhid.mousepoll=
2530                        [USBHID] The interval which mice are to be polled at.
2531
2532        usb-storage.delay_use=
2533                        [UMS] The delay in seconds before a new device is
2534                        scanned for Logical Units (default 5).
2535
2536        usb-storage.quirks=
2537                        [UMS] A list of quirks entries to supplement or
2538                        override the built-in unusual_devs list.  List
2539                        entries are separated by commas.  Each entry has
2540                        the form VID:PID:Flags where VID and PID are Vendor
2541                        and Product ID values (4-digit hex numbers) and
2542                        Flags is a set of characters, each corresponding
2543                        to a common usb-storage quirk flag as follows:
2544                                a = SANE_SENSE (collect more than 18 bytes
2545                                        of sense data);
2546                                b = BAD_SENSE (don't collect more than 18
2547                                        bytes of sense data);
2548                                c = FIX_CAPACITY (decrease the reported
2549                                        device capacity by one sector);
2550                                h = CAPACITY_HEURISTICS (decrease the
2551                                        reported device capacity by one
2552                                        sector if the number is odd);
2553                                i = IGNORE_DEVICE (don't bind to this
2554                                        device);
2555                                l = NOT_LOCKABLE (don't try to lock and
2556                                        unlock ejectable media);
2557                                m = MAX_SECTORS_64 (don't transfer more
2558                                        than 64 sectors = 32 KB at a time);
2559                                o = CAPACITY_OK (accept the capacity
2560                                        reported by the device);
2561                                r = IGNORE_RESIDUE (the device reports
2562                                        bogus residue values);
2563                                s = SINGLE_LUN (the device has only one
2564                                        Logical Unit);
2565                                w = NO_WP_DETECT (don't test whether the
2566                                        medium is write-protected).
2567                        Example: quirks=0419:aaf5:rl,0421:0433:rc
2568
2569        userpte=
2570                        [X86] Flags controlling user PTE allocations.
2571
2572                                nohigh = do not allocate PTE pages in
2573                                        HIGHMEM regardless of setting
2574                                        of CONFIG_HIGHPTE.
2575
2576        vdso=           [X86,SH]
2577                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2578                        vdso=1: enable VDSO (default)
2579                        vdso=0: disable VDSO mapping
2580
2581        vdso32=         [X86]
2582                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2583                        vdso32=1: enable 32-bit VDSO (default)
2584                        vdso32=0: disable 32-bit VDSO mapping
2585
2586        vector=         [IA-64,SMP]
2587                        vector=percpu: enable percpu vector domain
2588
2589        video=          [FB] Frame buffer configuration
2590                        See Documentation/fb/modedb.txt.
2591
2592        vga=            [BOOT,X86-32] Select a particular video mode
2593                        See Documentation/x86/boot.txt and
2594                        Documentation/svga.txt.
2595                        Use vga=ask for menu.
2596                        This is actually a boot loader parameter; the value is
2597                        passed to the kernel using a special protocol.
2598
2599        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2600                        size of <nn>. This can be used to increase the
2601                        minimum size (128MB on x86). It can also be used to
2602                        decrease the size and leave more room for directly
2603                        mapped kernel RAM.
2604
2605        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
2606                        Format: <command>
2607
2608        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
2609                        Format: <command>
2610
2611        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
2612                        Format: <command>
2613
2614        vt.cur_default= [VT] Default cursor shape.
2615                        Format: 0xCCBBAA, where AA, BB, and CC are the same as
2616                        the parameters of the <Esc>[?A;B;Cc escape sequence;
2617                        see VGA-softcursor.txt. Default: 2 = underline.
2618
2619        vt.default_blu= [VT]
2620                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2621                        Change the default blue palette of the console.
2622                        This is a 16-member array composed of values
2623                        ranging from 0-255.
2624
2625        vt.default_grn= [VT]
2626                        Format: <green0>,<green1>,<green2>,...,<green15>
2627                        Change the default green palette of the console.
2628                        This is a 16-member array composed of values
2629                        ranging from 0-255.
2630
2631        vt.default_red= [VT]
2632                        Format: <red0>,<red1>,<red2>,...,<red15>
2633                        Change the default red palette of the console.
2634                        This is a 16-member array composed of values
2635                        ranging from 0-255.
2636
2637        vt.default_utf8=
2638                        [VT]
2639                        Format=<0|1>
2640                        Set system-wide default UTF-8 mode for all tty's.
2641                        Default is 1, i.e. UTF-8 mode is enabled for all
2642                        newly opened terminals.
2643
2644        vt.global_cursor_default=
2645                        [VT]
2646                        Format=<-1|0|1>
2647                        Set system-wide default for whether a cursor
2648                        is shown on new VTs. Default is -1,
2649                        i.e. cursors will be created by default unless
2650                        overridden by individual drivers. 0 will hide
2651                        cursors, 1 will display them.
2652
2653        watchdog timers [HW,WDT] For information on watchdog timers,
2654                        see Documentation/watchdog/watchdog-parameters.txt
2655                        or other driver-specific files in the
2656                        Documentation/watchdog/ directory.
2657
2658        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
2659                        default x2apic cluster mode on platforms
2660                        supporting x2apic.
2661
2662        x86_mrst_timer= [X86-32,APBT]
2663                        Choose timer option for x86 Moorestown MID platform.
2664                        Two valid options are apbt timer only and lapic timer
2665                        plus one apbt timer for broadcast timer.
2666                        x86_mrst_timer=apbt_only | lapic_and_apbt
2667
2668        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2669        xd_geo=         See header of drivers/block/xd.c.
2670
2671        xen_emul_unplug=                [HW,X86,XEN]
2672                        Unplug Xen emulated devices
2673                        Format: [unplug0,][unplug1]
2674                        ide-disks -- unplug primary master IDE devices
2675                        aux-ide-disks -- unplug non-primary-master IDE devices
2676                        nics -- unplug network devices
2677                        all -- unplug all emulated devices (NICs and IDE disks)
2678                        unnecessary -- unplugging emulated devices is
2679                                unnecessary even if the host did not respond to
2680                                the unplug protocol
2681                        never -- do not unplug even if version check succeeds
2682
2683        xirc2ps_cs=     [NET,PCMCIA]
2684                        Format:
2685                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2686
2687______________________________________________________________________
2688
2689TODO:
2690
2691        Add more DRM drivers.
2692
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