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        ARM     ARM architecture is enabled.
  44        AVR32   AVR32 architecture is enabled.
  45        AX25    Appropriate AX.25 support is enabled.
  46        BLACKFIN Blackfin architecture is enabled.
  47        DRM     Direct Rendering Management support is enabled.
  48        DYNAMIC_DEBUG Build in debug messages and enable them at runtime
  49        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
  50        EFI     EFI Partitioning (GPT) is enabled
  51        EIDE    EIDE/ATAPI support is enabled.
  52        EVM     Extended Verification Module
  53        FB      The frame buffer device is enabled.
  54        FTRACE  Function tracing enabled.
  55        GCOV    GCOV profiling is enabled.
  56        HW      Appropriate hardware is enabled.
  57        IA-64   IA-64 architecture is enabled.
  58        IMA     Integrity measurement architecture is enabled.
  59        IOSCHED More than one I/O scheduler is enabled.
  60        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
  61        IPV6    IPv6 support is enabled.
  62        ISAPNP  ISA PnP code is enabled.
  63        ISDN    Appropriate ISDN support is enabled.
  64        JOY     Appropriate joystick support is enabled.
  65        KGDB    Kernel debugger support is enabled.
  66        KVM     Kernel Virtual Machine support is enabled.
  67        LIBATA  Libata driver is enabled
  68        LP      Printer support is enabled.
  69        LOOP    Loopback device support is enabled.
  70        M68k    M68k architecture is enabled.
  71                        These options have more detailed description inside of
  72                        Documentation/m68k/kernel-options.txt.
  73        MDA     MDA console support is enabled.
  74        MIPS    MIPS architecture is enabled.
  75        MOUSE   Appropriate mouse support is enabled.
  76        MSI     Message Signaled Interrupts (PCI).
  77        MTD     MTD (Memory Technology Device) support is enabled.
  78        NET     Appropriate network support is enabled.
  79        NUMA    NUMA support is enabled.
  80        NFS     Appropriate NFS support is enabled.
  81        OSS     OSS sound support is enabled.
  82        PV_OPS  A paravirtualized kernel is enabled.
  83        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
  84        PARISC  The PA-RISC architecture is enabled.
  85        PCI     PCI bus support is enabled.
  86        PCIE    PCI Express support is enabled.
  87        PCMCIA  The PCMCIA subsystem is enabled.
  88        PNP     Plug & Play support is enabled.
  89        PPC     PowerPC architecture is enabled.
  90        PPT     Parallel port support is enabled.
  91        PS2     Appropriate PS/2 support is enabled.
  92        RAM     RAM disk support is enabled.
  93        S390    S390 architecture is enabled.
  94        SCSI    Appropriate SCSI support is enabled.
  95                        A lot of drivers have their options described inside
  96                        the Documentation/scsi/ sub-directory.
  97        SECURITY Different security models are enabled.
  98        SELINUX SELinux support is enabled.
  99        APPARMOR AppArmor support is enabled.
 100        SERIAL  Serial support is enabled.
 101        SH      SuperH architecture is enabled.
 102        SMP     The kernel is an SMP kernel.
 103        SPARC   Sparc architecture is enabled.
 104        SWSUSP  Software suspend (hibernation) is enabled.
 105        SUSPEND System suspend states are enabled.
 106        TPM     TPM drivers are enabled.
 107        TS      Appropriate touchscreen support is enabled.
 108        UMS     USB Mass Storage support is enabled.
 109        USB     USB support is enabled.
 110        USBHID  USB Human Interface Device support is enabled.
 111        V4L     Video For Linux support is enabled.
 112        VMMIO   Driver for memory mapped virtio devices is enabled.
 113        VGA     The VGA console has been enabled.
 114        VT      Virtual terminal support is enabled.
 115        WDT     Watchdog support is enabled.
 116        XT      IBM PC/XT MFM hard disk support is enabled.
 117        X86-32  X86-32, aka i386 architecture is enabled.
 118        X86-64  X86-64 architecture is enabled.
 119                        More X86-64 boot options can be found in
 120                        Documentation/x86/x86_64/boot-options.txt .
 121        X86     Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
 122        XEN     Xen support is enabled
 123
 124In addition, the following text indicates that the option:
 125
 126        BUGS=   Relates to possible processor bugs on the said processor.
 127        KNL     Is a kernel start-up parameter.
 128        BOOT    Is a boot loader parameter.
 129
 130Parameters denoted with BOOT are actually interpreted by the boot
 131loader, and have no meaning to the kernel directly.
 132Do not modify the syntax of boot loader parameters without extreme
 133need or coordination with <Documentation/x86/boot.txt>.
 134
 135There are also arch-specific kernel-parameters not documented here.
 136See for example <Documentation/x86/x86_64/boot-options.txt>.
 137
 138Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
 139a trailing = on the name of any parameter states that that parameter will
 140be entered as an environment variable, whereas its absence indicates that
 141it will appear as a kernel argument readable via /proc/cmdline by programs
 142running once the system is up.
 143
 144The number of kernel parameters is not limited, but the length of the
 145complete command line (parameters including spaces etc.) is limited to
 146a fixed number of characters. This limit depends on the architecture
 147and is between 256 and 4096 characters. It is defined in the file
 148./include/asm/setup.h as COMMAND_LINE_SIZE.
 149
 150Finally, the [KMG] suffix is commonly described after a number of kernel
 151parameter values. These 'K', 'M', and 'G' letters represent the _binary_
 152multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
 153bytes respectively. Such letter suffixes can also be entirely omitted.
 154
 155
 156        acpi=           [HW,ACPI,X86]
 157                        Advanced Configuration and Power Interface
 158                        Format: { force | off | strict | noirq | rsdt }
 159                        force -- enable ACPI if default was off
 160                        off -- disable ACPI if default was on
 161                        noirq -- do not use ACPI for IRQ routing
 162                        strict -- Be less tolerant of platforms that are not
 163                                strictly ACPI specification compliant.
 164                        rsdt -- prefer RSDT over (default) XSDT
 165                        copy_dsdt -- copy DSDT to memory
 166
 167                        See also Documentation/power/runtime_pm.txt, pci=noacpi
 168
 169        acpi_rsdp=      [ACPI,EFI,KEXEC]
 170                        Pass the RSDP address to the kernel, mostly used
 171                        on machines running EFI runtime service to boot the
 172                        second kernel for kdump.
 173
 174        acpi_apic_instance=     [ACPI, IOAPIC]
 175                        Format: <int>
 176                        2: use 2nd APIC table, if available
 177                        1,0: use 1st APIC table
 178                        default: 0
 179
 180        acpi_backlight= [HW,ACPI]
 181                        acpi_backlight=vendor
 182                        acpi_backlight=video
 183                        If set to vendor, prefer vendor specific driver
 184                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
 185                        of the ACPI video.ko driver.
 186
 187        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
 188        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
 189                        Format: <int>
 190                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
 191                        debug output.  Bits in debug_layer correspond to a
 192                        _COMPONENT in an ACPI source file, e.g.,
 193                            #define _COMPONENT ACPI_PCI_COMPONENT
 194                        Bits in debug_level correspond to a level in
 195                        ACPI_DEBUG_PRINT statements, e.g.,
 196                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
 197                        The debug_level mask defaults to "info".  See
 198                        Documentation/acpi/debug.txt for more information about
 199                        debug layers and levels.
 200
 201                        Enable processor driver info messages:
 202                            acpi.debug_layer=0x20000000
 203                        Enable PCI/PCI interrupt routing info messages:
 204                            acpi.debug_layer=0x400000
 205                        Enable AML "Debug" output, i.e., stores to the Debug
 206                        object while interpreting AML:
 207                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
 208                        Enable all messages related to ACPI hardware:
 209                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
 210
 211                        Some values produce so much output that the system is
 212                        unusable.  The "log_buf_len" parameter may be useful
 213                        if you need to capture more output.
 214
 215        acpi_irq_balance [HW,ACPI]
 216                        ACPI will balance active IRQs
 217                        default in APIC mode
 218
 219        acpi_irq_nobalance [HW,ACPI]
 220                        ACPI will not move active IRQs (default)
 221                        default in PIC mode
 222
 223        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 224                        Format: <irq>,<irq>...
 225
 226        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
 227                        use by PCI
 228                        Format: <irq>,<irq>...
 229
 230        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT
 231
 232        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
 233                        Format: To spoof as Windows 98: ="Microsoft Windows"
 234
 235        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
 236                        acpi_osi="string1"      # add string1 -- only one string
 237                        acpi_osi="!string2"     # remove built-in string2
 238                        acpi_osi=               # disable all strings
 239
 240        acpi_pm_good    [X86]
 241                        Override the pmtimer bug detection: force the kernel
 242                        to assume that this machine's pmtimer latches its value
 243                        and always returns good values.
 244
 245        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
 246                        Format: { level | edge | high | low }
 247
 248        acpi_serialize  [HW,ACPI] force serialization of AML methods
 249
 250        acpi_skip_timer_override [HW,ACPI]
 251                        Recognize and ignore IRQ0/pin2 Interrupt Override.
 252                        For broken nForce2 BIOS resulting in XT-PIC timer.
 253
 254        acpi_sleep=     [HW,ACPI] Sleep options
 255                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
 256                                  old_ordering, nonvs, sci_force_enable }
 257                        See Documentation/power/video.txt for information on
 258                        s3_bios and s3_mode.
 259                        s3_beep is for debugging; it makes the PC's speaker beep
 260                        as soon as the kernel's real-mode entry point is called.
 261                        s4_nohwsig prevents ACPI hardware signature from being
 262                        used during resume from hibernation.
 263                        old_ordering causes the ACPI 1.0 ordering of the _PTS
 264                        control method, with respect to putting devices into
 265                        low power states, to be enforced (the ACPI 2.0 ordering
 266                        of _PTS is used by default).
 267                        nonvs prevents the kernel from saving/restoring the
 268                        ACPI NVS memory during suspend/hibernation and resume.
 269                        sci_force_enable causes the kernel to set SCI_EN directly
 270                        on resume from S1/S3 (which is against the ACPI spec,
 271                        but some broken systems don't work without it).
 272
 273        acpi_use_timer_override [HW,ACPI]
 274                        Use timer override. For some broken Nvidia NF5 boards
 275                        that require a timer override, but don't have HPET
 276
 277        acpi_enforce_resources= [ACPI]
 278                        { strict | lax | no }
 279                        Check for resource conflicts between native drivers
 280                        and ACPI OperationRegions (SystemIO and SystemMemory
 281                        only). IO ports and memory declared in ACPI might be
 282                        used by the ACPI subsystem in arbitrary AML code and
 283                        can interfere with legacy drivers.
 284                        strict (default): access to resources claimed by ACPI
 285                        is denied; legacy drivers trying to access reserved
 286                        resources will fail to bind to device using them.
 287                        lax: access to resources claimed by ACPI is allowed;
 288                        legacy drivers trying to access reserved resources
 289                        will bind successfully but a warning message is logged.
 290                        no: ACPI OperationRegions are not marked as reserved,
 291                        no further checks are performed.
 292
 293        add_efi_memmap  [EFI; X86] Include EFI memory map in
 294                        kernel's map of available physical RAM.
 295
 296        agp=            [AGP]
 297                        { off | try_unsupported }
 298                        off: disable AGP support
 299                        try_unsupported: try to drive unsupported chipsets
 300                                (may crash computer or cause data corruption)
 301
 302        ALSA            [HW,ALSA]
 303                        See Documentation/sound/alsa/alsa-parameters.txt
 304
 305        alignment=      [KNL,ARM]
 306                        Allow the default userspace alignment fault handler
 307                        behaviour to be specified.  Bit 0 enables warnings,
 308                        bit 1 enables fixups, and bit 2 sends a segfault.
 309
 310        align_va_addr=  [X86-64]
 311                        Align virtual addresses by clearing slice [14:12] when
 312                        allocating a VMA at process creation time. This option
 313                        gives you up to 3% performance improvement on AMD F15h
 314                        machines (where it is enabled by default) for a
 315                        CPU-intensive style benchmark, and it can vary highly in
 316                        a microbenchmark depending on workload and compiler.
 317
 318                        32: only for 32-bit processes
 319                        64: only for 64-bit processes
 320                        on: enable for both 32- and 64-bit processes
 321                        off: disable for both 32- and 64-bit processes
 322
 323        amd_iommu=      [HW,X86-64]
 324                        Pass parameters to the AMD IOMMU driver in the system.
 325                        Possible values are:
 326                        fullflush - enable flushing of IO/TLB entries when
 327                                    they are unmapped. Otherwise they are
 328                                    flushed before they will be reused, which
 329                                    is a lot of faster
 330                        off       - do not initialize any AMD IOMMU found in
 331                                    the system
 332                        force_isolation - Force device isolation for all
 333                                          devices. The IOMMU driver is not
 334                                          allowed anymore to lift isolation
 335                                          requirements as needed. This option
 336                                          does not override iommu=pt
 337
 338        amd_iommu_dump= [HW,X86-64]
 339                        Enable AMD IOMMU driver option to dump the ACPI table
 340                        for AMD IOMMU. With this option enabled, AMD IOMMU
 341                        driver will print ACPI tables for AMD IOMMU during
 342                        IOMMU initialization.
 343
 344        amijoy.map=     [HW,JOY] Amiga joystick support
 345                        Map of devices attached to JOY0DAT and JOY1DAT
 346                        Format: <a>,<b>
 347                        See also Documentation/input/joystick.txt
 348
 349        analog.map=     [HW,JOY] Analog joystick and gamepad support
 350                        Specifies type or capabilities of an analog joystick
 351                        connected to one of 16 gameports
 352                        Format: <type1>,<type2>,..<type16>
 353
 354        apc=            [HW,SPARC]
 355                        Power management functions (SPARCstation-4/5 + deriv.)
 356                        Format: noidle
 357                        Disable APC CPU standby support. SPARCstation-Fox does
 358                        not play well with APC CPU idle - disable it if you have
 359                        APC and your system crashes randomly.
 360
 361        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
 362                        Change the output verbosity whilst booting
 363                        Format: { quiet (default) | verbose | debug }
 364                        Change the amount of debugging information output
 365                        when initialising the APIC and IO-APIC components.
 366
 367        autoconf=       [IPV6]
 368                        See Documentation/networking/ipv6.txt.
 369
 370        show_lapic=     [APIC,X86] Advanced Programmable Interrupt Controller
 371                        Limit apic dumping. The parameter defines the maximal
 372                        number of local apics being dumped. Also it is possible
 373                        to set it to "all" by meaning -- no limit here.
 374                        Format: { 1 (default) | 2 | ... | all }.
 375                        The parameter valid if only apic=debug or
 376                        apic=verbose is specified.
 377                        Example: apic=debug show_lapic=all
 378
 379        apm=            [APM] Advanced Power Management
 380                        See header of arch/x86/kernel/apm_32.c.
 381
 382        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 383                        Format: <io>,<irq>,<nodeID>
 384
 385        ataflop=        [HW,M68k]
 386
 387        atarimouse=     [HW,MOUSE] Atari Mouse
 388
 389        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 390                        EzKey and similar keyboards
 391
 392        atkbd.reset=    [HW] Reset keyboard during initialization
 393
 394        atkbd.set=      [HW] Select keyboard code set
 395                        Format: <int> (2 = AT (default), 3 = PS/2)
 396
 397        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 398                        keyboards
 399
 400        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 401                        Format: <bool> (0 = real, 1 = synthetic (default))
 402
 403        atkbd.softrepeat= [HW]
 404                        Use software keyboard repeat
 405
 406        baycom_epp=     [HW,AX25]
 407                        Format: <io>,<mode>
 408
 409        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 410                        Format: <io>,<mode>
 411                        See header of drivers/net/hamradio/baycom_par.c.
 412
 413        baycom_ser_fdx= [HW,AX25]
 414                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 415                        Format: <io>,<irq>,<mode>[,<baud>]
 416                        See header of drivers/net/hamradio/baycom_ser_fdx.c.
 417
 418        baycom_ser_hdx= [HW,AX25]
 419                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 420                        Format: <io>,<irq>,<mode>
 421                        See header of drivers/net/hamradio/baycom_ser_hdx.c.
 422
 423        boot_delay=     Milliseconds to delay each printk during boot.
 424                        Values larger than 10 seconds (10000) are changed to
 425                        no delay (0).
 426                        Format: integer
 427
 428        bootmem_debug   [KNL] Enable bootmem allocator debug messages.
 429
 430        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 431        bttv.radio=     Most important insmod options are available as
 432                        kernel args too.
 433        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 434        bttv.tuner=
 435
 436        bulk_remove=off [PPC]  This parameter disables the use of the pSeries
 437                        firmware feature for flushing multiple hpte entries
 438                        at a time.
 439
 440        c101=           [NET] Moxa C101 synchronous serial card
 441
 442        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
 443                        Sometimes CPU hardware bugs make them report the cache
 444                        size incorrectly. The kernel will attempt work arounds
 445                        to fix known problems, but for some CPUs it is not
 446                        possible to determine what the correct size should be.
 447                        This option provides an override for these situations.
 448
 449        capability.disable=
 450                        [SECURITY] Disable capabilities.  This would normally
 451                        be used only if an alternative security model is to be
 452                        configured.  Potentially dangerous and should only be
 453                        used if you are entirely sure of the consequences.
 454
 455        ccw_timeout_log [S390]
 456                        See Documentation/s390/CommonIO for details.
 457
 458        cgroup_disable= [KNL] Disable a particular controller
 459                        Format: {name of the controller(s) to disable}
 460                                {Currently supported controllers - "memory"}
 461
 462        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 463                        Format: { "0" | "1" }
 464                        See security/selinux/Kconfig help text.
 465                        0 -- check protection applied by kernel (includes
 466                                any implied execute protection).
 467                        1 -- check protection requested by application.
 468                        Default value is set via a kernel config option.
 469                        Value can be changed at runtime via
 470                                /selinux/checkreqprot.
 471
 472        cio_ignore=     [S390]
 473                        See Documentation/s390/CommonIO for details.
 474
 475        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
 476                        [Deprecated]
 477                        Forces specified clocksource (if available) to be used
 478                        when calculating gettimeofday(). If specified
 479                        clocksource is not available, it defaults to PIT.
 480                        Format: { pit | tsc | cyclone | pmtmr }
 481
 482        clocksource=    Override the default clocksource
 483                        Format: <string>
 484                        Override the default clocksource and use the clocksource
 485                        with the name specified.
 486                        Some clocksource names to choose from, depending on
 487                        the platform:
 488                        [all] jiffies (this is the base, fallback clocksource)
 489                        [ACPI] acpi_pm
 490                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
 491                                pxa_timer,timer3,32k_counter,timer0_1
 492                        [AVR32] avr32
 493                        [X86-32] pit,hpet,tsc;
 494                                scx200_hrt on Geode; cyclone on IBM x440
 495                        [MIPS] MIPS
 496                        [PARISC] cr16
 497                        [S390] tod
 498                        [SH] SuperH
 499                        [SPARC64] tick
 500                        [X86-64] hpet,tsc
 501
 502        clearcpuid=BITNUM [X86]
 503                        Disable CPUID feature X for the kernel. See
 504                        arch/x86/include/asm/cpufeature.h for the valid bit
 505                        numbers. Note the Linux specific bits are not necessarily
 506                        stable over kernel options, but the vendor specific
 507                        ones should be.
 508                        Also note that user programs calling CPUID directly
 509                        or using the feature without checking anything
 510                        will still see it. This just prevents it from
 511                        being used by the kernel or shown in /proc/cpuinfo.
 512                        Also note the kernel might malfunction if you disable
 513                        some critical bits.
 514
 515        cma=nn[MG]      [ARM,KNL]
 516                        Sets the size of kernel global memory area for contiguous
 517                        memory allocations. For more information, see
 518                        include/linux/dma-contiguous.h
 519
 520        cmo_free_hint=  [PPC] Format: { yes | no }
 521                        Specify whether pages are marked as being inactive
 522                        when they are freed.  This is used in CMO environments
 523                        to determine OS memory pressure for page stealing by
 524                        a hypervisor.
 525                        Default: yes
 526
 527        coherent_pool=nn[KMG]   [ARM,KNL]
 528                        Sets the size of memory pool for coherent, atomic dma
 529                        allocations, by default set to 256K.
 530
 531        code_bytes      [X86] How many bytes of object code to print
 532                        in an oops report.
 533                        Range: 0 - 8192
 534                        Default: 64
 535
 536        com20020=       [HW,NET] ARCnet - COM20020 chipset
 537                        Format:
 538                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 539
 540        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 541                        Format: <io>[,<irq>]
 542
 543        com90xx=        [HW,NET]
 544                        ARCnet - COM90xx chipset (memory-mapped buffers)
 545                        Format: <io>[,<irq>[,<memstart>]]
 546
 547        condev=         [HW,S390] console device
 548        conmode=
 549
 550        console=        [KNL] Output console device and options.
 551
 552                tty<n>  Use the virtual console device <n>.
 553
 554                ttyS<n>[,options]
 555                ttyUSB0[,options]
 556                        Use the specified serial port.  The options are of
 557                        the form "bbbbpnf", where "bbbb" is the baud rate,
 558                        "p" is parity ("n", "o", or "e"), "n" is number of
 559                        bits, and "f" is flow control ("r" for RTS or
 560                        omit it).  Default is "9600n8".
 561
 562                        See Documentation/serial-console.txt for more
 563                        information.  See
 564                        Documentation/networking/netconsole.txt for an
 565                        alternative.
 566
 567                uart[8250],io,<addr>[,options]
 568                uart[8250],mmio,<addr>[,options]
 569                        Start an early, polled-mode console on the 8250/16550
 570                        UART at the specified I/O port or MMIO address,
 571                        switching to the matching ttyS device later.  The
 572                        options are the same as for ttyS, above.
 573
 574                If the device connected to the port is not a TTY but a braille
 575                device, prepend "brl," before the device type, for instance
 576                        console=brl,ttyS0
 577                For now, only VisioBraille is supported.
 578
 579        consoleblank=   [KNL] The console blank (screen saver) timeout in
 580                        seconds. Defaults to 10*60 = 10mins. A value of 0
 581                        disables the blank timer.
 582
 583        coredump_filter=
 584                        [KNL] Change the default value for
 585                        /proc/<pid>/coredump_filter.
 586                        See also Documentation/filesystems/proc.txt.
 587
 588        cpuidle.off=1   [CPU_IDLE]
 589                        disable the cpuidle sub-system
 590
 591        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 592                        Format:
 593                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 594
 595        crashkernel=size[KMG][@offset[KMG]]
 596                        [KNL] Using kexec, Linux can switch to a 'crash kernel'
 597                        upon panic. This parameter reserves the physical
 598                        memory region [offset, offset + size] for that kernel
 599                        image. If '@offset' is omitted, then a suitable offset
 600                        is selected automatically. Check
 601                        Documentation/kdump/kdump.txt for further details.
 602
 603        crashkernel=range1:size1[,range2:size2,...][@offset]
 604                        [KNL] Same as above, but depends on the memory
 605                        in the running system. The syntax of range is
 606                        start-[end] where start and end are both
 607                        a memory unit (amount[KMG]). See also
 608                        Documentation/kdump/kdump.txt for an example.
 609
 610        cs89x0_dma=     [HW,NET]
 611                        Format: <dma>
 612
 613        cs89x0_media=   [HW,NET]
 614                        Format: { rj45 | aui | bnc }
 615
 616        dasd=           [HW,NET]
 617                        See header of drivers/s390/block/dasd_devmap.c.
 618
 619        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 620                        (one device per port)
 621                        Format: <port#>,<type>
 622                        See also Documentation/input/joystick-parport.txt
 623
 624        ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
 625                        time. See Documentation/dynamic-debug-howto.txt for
 626                        details.  Deprecated, see dyndbg.
 627
 628        debug           [KNL] Enable kernel debugging (events log level).
 629
 630        debug_locks_verbose=
 631                        [KNL] verbose self-tests
 632                        Format=<0|1>
 633                        Print debugging info while doing the locking API
 634                        self-tests.
 635                        We default to 0 (no extra messages), setting it to
 636                        1 will print _a lot_ more information - normally
 637                        only useful to kernel developers.
 638
 639        debug_objects   [KNL] Enable object debugging
 640
 641        no_debug_objects
 642                        [KNL] Disable object debugging
 643
 644        debug_guardpage_minorder=
 645                        [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
 646                        parameter allows control of the order of pages that will
 647                        be intentionally kept free (and hence protected) by the
 648                        buddy allocator. Bigger value increase the probability
 649                        of catching random memory corruption, but reduce the
 650                        amount of memory for normal system use. The maximum
 651                        possible value is MAX_ORDER/2.  Setting this parameter
 652                        to 1 or 2 should be enough to identify most random
 653                        memory corruption problems caused by bugs in kernel or
 654                        driver code when a CPU writes to (or reads from) a
 655                        random memory location. Note that there exists a class
 656                        of memory corruptions problems caused by buggy H/W or
 657                        F/W or by drivers badly programing DMA (basically when
 658                        memory is written at bus level and the CPU MMU is
 659                        bypassed) which are not detectable by
 660                        CONFIG_DEBUG_PAGEALLOC, hence this option will not help
 661                        tracking down these problems.
 662
 663        debugpat        [X86] Enable PAT debugging
 664
 665        decnet.addr=    [HW,NET]
 666                        Format: <area>[,<node>]
 667                        See also Documentation/networking/decnet.txt.
 668
 669        default_hugepagesz=
 670                        [same as hugepagesz=] The size of the default
 671                        HugeTLB page size. This is the size represented by
 672                        the legacy /proc/ hugepages APIs, used for SHM, and
 673                        default size when mounting hugetlbfs filesystems.
 674                        Defaults to the default architecture's huge page size
 675                        if not specified.
 676
 677        dhash_entries=  [KNL]
 678                        Set number of hash buckets for dentry cache.
 679
 680        digi=           [HW,SERIAL]
 681                        IO parameters + enable/disable command.
 682
 683        digiepca=       [HW,SERIAL]
 684                        See drivers/char/README.epca and
 685                        Documentation/serial/digiepca.txt.
 686
 687        disable=        [IPV6]
 688                        See Documentation/networking/ipv6.txt.
 689
 690        disable_ddw     [PPC/PSERIES]
 691                        Disable Dynamic DMA Window support. Use this if
 692                        to workaround buggy firmware.
 693
 694        disable_ipv6=   [IPV6]
 695                        See Documentation/networking/ipv6.txt.
 696
 697        disable_mtrr_cleanup [X86]
 698                        The kernel tries to adjust MTRR layout from continuous
 699                        to discrete, to make X server driver able to add WB
 700                        entry later. This parameter disables that.
 701
 702        disable_mtrr_trim [X86, Intel and AMD only]
 703                        By default the kernel will trim any uncacheable
 704                        memory out of your available memory pool based on
 705                        MTRR settings.  This parameter disables that behavior,
 706                        possibly causing your machine to run very slowly.
 707
 708        disable_timer_pin_1 [X86]
 709                        Disable PIN 1 of APIC timer
 710                        Can be useful to work around chipset bugs.
 711
 712        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
 713                        this option disables the debugging code at boot.
 714
 715        dma_debug_entries=<number>
 716                        This option allows to tune the number of preallocated
 717                        entries for DMA-API debugging code. One entry is
 718                        required per DMA-API allocation. Use this if the
 719                        DMA-API debugging code disables itself because the
 720                        architectural default is too low.
 721
 722        dma_debug_driver=<driver_name>
 723                        With this option the DMA-API debugging driver
 724                        filter feature can be enabled at boot time. Just
 725                        pass the driver to filter for as the parameter.
 726                        The filter can be disabled or changed to another
 727                        driver later using sysfs.
 728
 729        drm_kms_helper.edid_firmware=[<connector>:]<file>
 730                        Broken monitors, graphic adapters and KVMs may
 731                        send no or incorrect EDID data sets. This parameter
 732                        allows to specify an EDID data set in the
 733                        /lib/firmware directory that is used instead.
 734                        Generic built-in EDID data sets are used, if one of
 735                        edid/1024x768.bin, edid/1280x1024.bin,
 736                        edid/1680x1050.bin, or edid/1920x1080.bin is given
 737                        and no file with the same name exists. Details and
 738                        instructions how to build your own EDID data are
 739                        available in Documentation/EDID/HOWTO.txt. An EDID
 740                        data set will only be used for a particular connector,
 741                        if its name and a colon are prepended to the EDID
 742                        name.
 743
 744        dscc4.setup=    [NET]
 745
 746        dyndbg[="val"]          [KNL,DYNAMIC_DEBUG]
 747        module.dyndbg[="val"]
 748                        Enable debug messages at boot time.  See
 749                        Documentation/dynamic-debug-howto.txt for details.
 750
 751        earlycon=       [KNL] Output early console device and options.
 752                uart[8250],io,<addr>[,options]
 753                uart[8250],mmio,<addr>[,options]
 754                uart[8250],mmio32,<addr>[,options]
 755                        Start an early, polled-mode console on the 8250/16550
 756                        UART at the specified I/O port or MMIO address.
 757                        MMIO inter-register address stride is either 8-bit
 758                        (mmio) or 32-bit (mmio32).
 759                        The options are the same as for ttyS, above.
 760
 761        earlyprintk=    [X86,SH,BLACKFIN]
 762                        earlyprintk=vga
 763                        earlyprintk=serial[,ttySn[,baudrate]]
 764                        earlyprintk=ttySn[,baudrate]
 765                        earlyprintk=dbgp[debugController#]
 766
 767                        Append ",keep" to not disable it when the real console
 768                        takes over.
 769
 770                        Only vga or serial or usb debug port at a time.
 771
 772                        Currently only ttyS0 and ttyS1 are supported.
 773
 774                        Interaction with the standard serial driver is not
 775                        very good.
 776
 777                        The VGA output is eventually overwritten by the real
 778                        console.
 779
 780        ekgdboc=        [X86,KGDB] Allow early kernel console debugging
 781                        ekgdboc=kbd
 782
 783                        This is designed to be used in conjunction with
 784                        the boot argument: earlyprintk=vga
 785
 786        edd=            [EDD]
 787                        Format: {"off" | "on" | "skip[mbr]"}
 788
 789        eisa_irq_edge=  [PARISC,HW]
 790                        See header of drivers/parisc/eisa.c.
 791
 792        elanfreq=       [X86-32]
 793                        See comment before function elanfreq_setup() in
 794                        arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 795
 796        elevator=       [IOSCHED]
 797                        Format: {"cfq" | "deadline" | "noop"}
 798                        See Documentation/block/cfq-iosched.txt and
 799                        Documentation/block/deadline-iosched.txt for details.
 800
 801        elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
 802                        Specifies physical address of start of kernel core
 803                        image elf header and optionally the size. Generally
 804                        kexec loader will pass this option to capture kernel.
 805                        See Documentation/kdump/kdump.txt for details.
 806
 807        enable_mtrr_cleanup [X86]
 808                        The kernel tries to adjust MTRR layout from continuous
 809                        to discrete, to make X server driver able to add WB
 810                        entry later. This parameter enables that.
 811
 812        enable_timer_pin_1 [X86]
 813                        Enable PIN 1 of APIC timer
 814                        Can be useful to work around chipset bugs
 815                        (in particular on some ATI chipsets).
 816                        The kernel tries to set a reasonable default.
 817
 818        enforcing       [SELINUX] Set initial enforcing status.
 819                        Format: {"0" | "1"}
 820                        See security/selinux/Kconfig help text.
 821                        0 -- permissive (log only, no denials).
 822                        1 -- enforcing (deny and log).
 823                        Default value is 0.
 824                        Value can be changed at runtime via /selinux/enforce.
 825
 826        erst_disable    [ACPI]
 827                        Disable Error Record Serialization Table (ERST)
 828                        support.
 829
 830        ether=          [HW,NET] Ethernet cards parameters
 831                        This option is obsoleted by the "netdev=" option, which
 832                        has equivalent usage. See its documentation for details.
 833
 834        evm=            [EVM]
 835                        Format: { "fix" }
 836                        Permit 'security.evm' to be updated regardless of
 837                        current integrity status.
 838
 839        failslab=
 840        fail_page_alloc=
 841        fail_make_request=[KNL]
 842                        General fault injection mechanism.
 843                        Format: <interval>,<probability>,<space>,<times>
 844                        See also Documentation/fault-injection/.
 845
 846        floppy=         [HW]
 847                        See Documentation/blockdev/floppy.txt.
 848
 849        force_pal_cache_flush
 850                        [IA-64] Avoid check_sal_cache_flush which may hang on
 851                        buggy SAL_CACHE_FLUSH implementations. Using this
 852                        parameter will force ia64_sal_cache_flush to call
 853                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
 854
 855        ftrace=[tracer]
 856                        [FTRACE] will set and start the specified tracer
 857                        as early as possible in order to facilitate early
 858                        boot debugging.
 859
 860        ftrace_dump_on_oops[=orig_cpu]
 861                        [FTRACE] will dump the trace buffers on oops.
 862                        If no parameter is passed, ftrace will dump
 863                        buffers of all CPUs, but if you pass orig_cpu, it will
 864                        dump only the buffer of the CPU that triggered the
 865                        oops.
 866
 867        ftrace_filter=[function-list]
 868                        [FTRACE] Limit the functions traced by the function
 869                        tracer at boot up. function-list is a comma separated
 870                        list of functions. This list can be changed at run
 871                        time by the set_ftrace_filter file in the debugfs
 872                        tracing directory.
 873
 874        ftrace_notrace=[function-list]
 875                        [FTRACE] Do not trace the functions specified in
 876                        function-list. This list can be changed at run time
 877                        by the set_ftrace_notrace file in the debugfs
 878                        tracing directory.
 879
 880        ftrace_graph_filter=[function-list]
 881                        [FTRACE] Limit the top level callers functions traced
 882                        by the function graph tracer at boot up.
 883                        function-list is a comma separated list of functions
 884                        that can be changed at run time by the
 885                        set_graph_function file in the debugfs tracing directory.
 886
 887        gamecon.map[2|3]=
 888                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 889                        support via parallel port (up to 5 devices per port)
 890                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 891                        See also Documentation/input/joystick-parport.txt
 892
 893        gamma=          [HW,DRM]
 894
 895        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
 896                        Format: off | on
 897                        default: on
 898
 899        gcov_persist=   [GCOV] When non-zero (default), profiling data for
 900                        kernel modules is saved and remains accessible via
 901                        debugfs, even when the module is unloaded/reloaded.
 902                        When zero, profiling data is discarded and associated
 903                        debugfs files are removed at module unload time.
 904
 905        gpt             [EFI] Forces disk with valid GPT signature but
 906                        invalid Protective MBR to be treated as GPT.
 907
 908        hashdist=       [KNL,NUMA] Large hashes allocated during boot
 909                        are distributed across NUMA nodes.  Defaults on
 910                        for 64-bit NUMA, off otherwise.
 911                        Format: 0 | 1 (for off | on)
 912
 913        hcl=            [IA-64] SGI's Hardware Graph compatibility layer
 914
 915        hd=             [EIDE] (E)IDE hard drive subsystem geometry
 916                        Format: <cyl>,<head>,<sect>
 917
 918        hest_disable    [ACPI]
 919                        Disable Hardware Error Source Table (HEST) support;
 920                        corresponding firmware-first mode error processing
 921                        logic will be disabled.
 922
 923        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
 924                        size of <nn>. This works even on boxes that have no
 925                        highmem otherwise. This also works to reduce highmem
 926                        size on bigger boxes.
 927
 928        highres=        [KNL] Enable/disable high resolution timer mode.
 929                        Valid parameters: "on", "off"
 930                        Default: "on"
 931
 932        hisax=          [HW,ISDN]
 933                        See Documentation/isdn/README.HiSax.
 934
 935        hlt             [BUGS=ARM,SH]
 936
 937        hpet=           [X86-32,HPET] option to control HPET usage
 938                        Format: { enable (default) | disable | force |
 939                                verbose }
 940                        disable: disable HPET and use PIT instead
 941                        force: allow force enabled of undocumented chips (ICH4,
 942                                VIA, nVidia)
 943                        verbose: show contents of HPET registers during setup
 944
 945        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
 946        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
 947                        On x86-64 and powerpc, this option can be specified
 948                        multiple times interleaved with hugepages= to reserve
 949                        huge pages of different sizes. Valid pages sizes on
 950                        x86-64 are 2M (when the CPU supports "pse") and 1G
 951                        (when the CPU supports the "pdpe1gb" cpuinfo flag)
 952                        Note that 1GB pages can only be allocated at boot time
 953                        using hugepages= and not freed afterwards.
 954
 955        hvc_iucv=       [S390] Number of z/VM IUCV hypervisor console (HVC)
 956                               terminal devices. Valid values: 0..8
 957        hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
 958                               If specified, z/VM IUCV HVC accepts connections
 959                               from listed z/VM user IDs only.
 960
 961        keep_bootcon    [KNL]
 962                        Do not unregister boot console at start. This is only
 963                        useful for debugging when something happens in the window
 964                        between unregistering the boot console and initializing
 965                        the real console.
 966
 967        i2c_bus=        [HW] Override the default board specific I2C bus speed
 968                             or register an additional I2C bus that is not
 969                             registered from board initialization code.
 970                             Format:
 971                             <bus_id>,<clkrate>
 972
 973        i8042.debug     [HW] Toggle i8042 debug mode
 974        i8042.direct    [HW] Put keyboard port into non-translated mode
 975        i8042.dumbkbd   [HW] Pretend that controller can only read data from
 976                             keyboard and cannot control its state
 977                             (Don't attempt to blink the leds)
 978        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
 979        i8042.nokbd     [HW] Don't check/create keyboard port
 980        i8042.noloop    [HW] Disable the AUX Loopback command while probing
 981                             for the AUX port
 982        i8042.nomux     [HW] Don't check presence of an active multiplexing
 983                             controller
 984        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
 985                             controllers
 986        i8042.notimeout [HW] Ignore timeout condition signalled by controller
 987        i8042.reset     [HW] Reset the controller during init and cleanup
 988        i8042.unlock    [HW] Unlock (ignore) the keylock
 989
 990        i810=           [HW,DRM]
 991
 992        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
 993                        indicates that the driver is running on unsupported
 994                        hardware.
 995        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
 996                        does not match list of supported models.
 997        i8k.power_status
 998                        [HW] Report power status in /proc/i8k
 999                        (disabled by default)
1000        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
1001                        capability is set.
1002
1003        i915.invert_brightness=
1004                        [DRM] Invert the sense of the variable that is used to
1005                        set the brightness of the panel backlight. Normally a
1006                        brightness value of 0 indicates backlight switched off,
1007                        and the maximum of the brightness value sets the backlight
1008                        to maximum brightness. If this parameter is set to 0
1009                        (default) and the machine requires it, or this parameter
1010                        is set to 1, a brightness value of 0 sets the backlight
1011                        to maximum brightness, and the maximum of the brightness
1012                        value switches the backlight off.
1013                        -1 -- never invert brightness
1014                         0 -- machine default
1015                         1 -- force brightness inversion
1016
1017        icn=            [HW,ISDN]
1018                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1019
1020        ide-core.nodma= [HW] (E)IDE subsystem
1021                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1022                        .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1023                        .cdrom .chs .ignore_cable are additional options
1024                        See Documentation/ide/ide.txt.
1025
1026        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1027                        Claim all unknown PCI IDE storage controllers.
1028
1029        idle=           [X86]
1030                        Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1031                        Poll forces a polling idle loop that can slightly
1032                        improve the performance of waking up a idle CPU, but
1033                        will use a lot of power and make the system run hot.
1034                        Not recommended.
1035                        idle=mwait: On systems which support MONITOR/MWAIT but
1036                        the kernel chose to not use it because it doesn't save
1037                        as much power as a normal idle loop, use the
1038                        MONITOR/MWAIT idle loop anyways. Performance should be
1039                        the same as idle=poll.
1040                        idle=halt: Halt is forced to be used for CPU idle.
1041                        In such case C2/C3 won't be used again.
1042                        idle=nomwait: Disable mwait for CPU C-states
1043
1044        ignore_loglevel [KNL]
1045                        Ignore loglevel setting - this will print /all/
1046                        kernel messages to the console. Useful for debugging.
1047                        We also add it as printk module parameter, so users
1048                        could change it dynamically, usually by
1049                        /sys/module/printk/parameters/ignore_loglevel.
1050
1051        ihash_entries=  [KNL]
1052                        Set number of hash buckets for inode cache.
1053
1054        ima_audit=      [IMA]
1055                        Format: { "0" | "1" }
1056                        0 -- integrity auditing messages. (Default)
1057                        1 -- enable informational integrity auditing messages.
1058
1059        ima_hash=       [IMA]
1060                        Format: { "sha1" | "md5" }
1061                        default: "sha1"
1062
1063        ima_tcb         [IMA]
1064                        Load a policy which meets the needs of the Trusted
1065                        Computing Base.  This means IMA will measure all
1066                        programs exec'd, files mmap'd for exec, and all files
1067                        opened for read by uid=0.
1068
1069        init=           [KNL]
1070                        Format: <full_path>
1071                        Run specified binary instead of /sbin/init as init
1072                        process.
1073
1074        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
1075                        for working out where the kernel is dying during
1076                        startup.
1077
1078        initrd=         [BOOT] Specify the location of the initial ramdisk
1079
1080        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
1081                        Format: <irq>
1082
1083        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
1084                on
1085                        Enable intel iommu driver.
1086                off
1087                        Disable intel iommu driver.
1088                igfx_off [Default Off]
1089                        By default, gfx is mapped as normal device. If a gfx
1090                        device has a dedicated DMAR unit, the DMAR unit is
1091                        bypassed by not enabling DMAR with this option. In
1092                        this case, gfx device will use physical address for
1093                        DMA.
1094                forcedac [x86_64]
1095                        With this option iommu will not optimize to look
1096                        for io virtual address below 32-bit forcing dual
1097                        address cycle on pci bus for cards supporting greater
1098                        than 32-bit addressing. The default is to look
1099                        for translation below 32-bit and if not available
1100                        then look in the higher range.
1101                strict [Default Off]
1102                        With this option on every unmap_single operation will
1103                        result in a hardware IOTLB flush operation as opposed
1104                        to batching them for performance.
1105                sp_off [Default Off]
1106                        By default, super page will be supported if Intel IOMMU
1107                        has the capability. With this option, super page will
1108                        not be supported.
1109
1110        intel_idle.max_cstate=  [KNL,HW,ACPI,X86]
1111                        0       disables intel_idle and fall back on acpi_idle.
1112                        1 to 6  specify maximum depth of C-state.
1113
1114        intremap=       [X86-64, Intel-IOMMU]
1115                        on      enable Interrupt Remapping (default)
1116                        off     disable Interrupt Remapping
1117                        nosid   disable Source ID checking
1118                        no_x2apic_optout
1119                                BIOS x2APIC opt-out request will be ignored
1120
1121        iomem=          Disable strict checking of access to MMIO memory
1122                strict  regions from userspace.
1123                relaxed
1124
1125        iommu=          [x86]
1126                off
1127                force
1128                noforce
1129                biomerge
1130                panic
1131                nopanic
1132                merge
1133                nomerge
1134                forcesac
1135                soft
1136                pt              [x86, IA-64]
1137
1138
1139        io7=            [HW] IO7 for Marvel based alpha systems
1140                        See comment before marvel_specify_io7 in
1141                        arch/alpha/kernel/core_marvel.c.
1142
1143        io_delay=       [X86] I/O delay method
1144                0x80
1145                        Standard port 0x80 based delay
1146                0xed
1147                        Alternate port 0xed based delay (needed on some systems)
1148                udelay
1149                        Simple two microseconds delay
1150                none
1151                        No delay
1152
1153        ip=             [IP_PNP]
1154                        See Documentation/filesystems/nfs/nfsroot.txt.
1155
1156        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1157                        See comment before ip2_setup() in
1158                        drivers/char/ip2/ip2base.c.
1159
1160        irqfixup        [HW]
1161                        When an interrupt is not handled search all handlers
1162                        for it. Intended to get systems with badly broken
1163                        firmware running.
1164
1165        irqpoll         [HW]
1166                        When an interrupt is not handled search all handlers
1167                        for it. Also check all handlers each timer
1168                        interrupt. Intended to get systems with badly broken
1169                        firmware running.
1170
1171        isapnp=         [ISAPNP]
1172                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1173
1174        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
1175                        Format:
1176                        <cpu number>,...,<cpu number>
1177                        or
1178                        <cpu number>-<cpu number>
1179                        (must be a positive range in ascending order)
1180                        or a mixture
1181                        <cpu number>,...,<cpu number>-<cpu number>
1182
1183                        This option can be used to specify one or more CPUs
1184                        to isolate from the general SMP balancing and scheduling
1185                        algorithms. You can move a process onto or off an
1186                        "isolated" CPU via the CPU affinity syscalls or cpuset.
1187                        <cpu number> begins at 0 and the maximum value is
1188                        "number of CPUs in system - 1".
1189
1190                        This option is the preferred way to isolate CPUs. The
1191                        alternative -- manually setting the CPU mask of all
1192                        tasks in the system -- can cause problems and
1193                        suboptimal load balancer performance.
1194
1195        iucv=           [HW,NET]
1196
1197        js=             [HW,JOY] Analog joystick
1198                        See Documentation/input/joystick.txt.
1199
1200        keepinitrd      [HW,ARM]
1201
1202        kernelcore=nn[KMG]      [KNL,X86,IA-64,PPC] This parameter
1203                        specifies the amount of memory usable by the kernel
1204                        for non-movable allocations.  The requested amount is
1205                        spread evenly throughout all nodes in the system. The
1206                        remaining memory in each node is used for Movable
1207                        pages. In the event, a node is too small to have both
1208                        kernelcore and Movable pages, kernelcore pages will
1209                        take priority and other nodes will have a larger number
1210                        of kernelcore pages.  The Movable zone is used for the
1211                        allocation of pages that may be reclaimed or moved
1212                        by the page migration subsystem.  This means that
1213                        HugeTLB pages may not be allocated from this zone.
1214                        Note that allocations like PTEs-from-HighMem still
1215                        use the HighMem zone if it exists, and the Normal
1216                        zone if it does not.
1217
1218        kgdbdbgp=       [KGDB,HW] kgdb over EHCI usb debug port.
1219                        Format: <Controller#>[,poll interval]
1220                        The controller # is the number of the ehci usb debug
1221                        port as it is probed via PCI.  The poll interval is
1222                        optional and is the number seconds in between
1223                        each poll cycle to the debug port in case you need
1224                        the functionality for interrupting the kernel with
1225                        gdb or control-c on the dbgp connection.  When
1226                        not using this parameter you use sysrq-g to break into
1227                        the kernel debugger.
1228
1229        kgdboc=         [KGDB,HW] kgdb over consoles.
1230                        Requires a tty driver that supports console polling,
1231                        or a supported polling keyboard driver (non-usb).
1232                         Serial only format: <serial_device>[,baud]
1233                         keyboard only format: kbd
1234                         keyboard and serial format: kbd,<serial_device>[,baud]
1235                        Optional Kernel mode setting:
1236                         kms, kbd format: kms,kbd
1237                         kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1238
1239        kgdbwait        [KGDB] Stop kernel execution and enter the
1240                        kernel debugger at the earliest opportunity.
1241
1242        kmac=           [MIPS] korina ethernet MAC address.
1243                        Configure the RouterBoard 532 series on-chip
1244                        Ethernet adapter MAC address.
1245
1246        kmemleak=       [KNL] Boot-time kmemleak enable/disable
1247                        Valid arguments: on, off
1248                        Default: on
1249
1250        kstack=N        [X86] Print N words from the kernel stack
1251                        in oops dumps.
1252
1253        kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1254                        Default is 0 (don't ignore, but inject #GP)
1255
1256        kvm.mmu_audit=  [KVM] This is a R/W parameter which allows audit
1257                        KVM MMU at runtime.
1258                        Default is 0 (off)
1259
1260        kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1261                        Default is 1 (enabled)
1262
1263        kvm-amd.npt=    [KVM,AMD] Disable nested paging (virtualized MMU)
1264                        for all guests.
1265                        Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1266
1267        kvm-intel.ept=  [KVM,Intel] Disable extended page tables
1268                        (virtualized MMU) support on capable Intel chips.
1269                        Default is 1 (enabled)
1270
1271        kvm-intel.emulate_invalid_guest_state=
1272                        [KVM,Intel] Enable emulation of invalid guest states
1273                        Default is 0 (disabled)
1274
1275        kvm-intel.flexpriority=
1276                        [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1277                        Default is 1 (enabled)
1278
1279        kvm-intel.nested=
1280                        [KVM,Intel] Enable VMX nesting (nVMX).
1281                        Default is 0 (disabled)
1282
1283        kvm-intel.unrestricted_guest=
1284                        [KVM,Intel] Disable unrestricted guest feature
1285                        (virtualized real and unpaged mode) on capable
1286                        Intel chips. Default is 1 (enabled)
1287
1288        kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1289                        feature (tagged TLBs) on capable Intel chips.
1290                        Default is 1 (enabled)
1291
1292        l2cr=           [PPC]
1293
1294        l3cr=           [PPC]
1295
1296        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
1297                        disabled it.
1298
1299        lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
1300                        in C2 power state.
1301
1302        libata.dma=     [LIBATA] DMA control
1303                        libata.dma=0      Disable all PATA and SATA DMA
1304                        libata.dma=1      PATA and SATA Disk DMA only
1305                        libata.dma=2      ATAPI (CDROM) DMA only
1306                        libata.dma=4      Compact Flash DMA only
1307                        Combinations also work, so libata.dma=3 enables DMA
1308                        for disks and CDROMs, but not CFs.
1309
1310        libata.ignore_hpa=      [LIBATA] Ignore HPA limit
1311                        libata.ignore_hpa=0       keep BIOS limits (default)
1312                        libata.ignore_hpa=1       ignore limits, using full disk
1313
1314        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
1315                        when set.
1316                        Format: <int>
1317
1318        libata.force=   [LIBATA] Force configurations.  The format is comma
1319                        separated list of "[ID:]VAL" where ID is
1320                        PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1321                        matching port, link or device.  Basically, it matches
1322                        the ATA ID string printed on console by libata.  If
1323                        the whole ID part is omitted, the last PORT and DEVICE
1324                        values are used.  If ID hasn't been specified yet, the
1325                        configuration applies to all ports, links and devices.
1326
1327                        If only DEVICE is omitted, the parameter applies to
1328                        the port and all links and devices behind it.  DEVICE
1329                        number of 0 either selects the first device or the
1330                        first fan-out link behind PMP device.  It does not
1331                        select the host link.  DEVICE number of 15 selects the
1332                        host link and device attached to it.
1333
1334                        The VAL specifies the configuration to force.  As long
1335                        as there's no ambiguity shortcut notation is allowed.
1336                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
1337                        The following configurations can be forced.
1338
1339                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
1340                          Any ID with matching PORT is used.
1341
1342                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1343
1344                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1345                          udma[/][16,25,33,44,66,100,133] notation is also
1346                          allowed.
1347
1348                        * [no]ncq: Turn on or off NCQ.
1349
1350                        * nohrst, nosrst, norst: suppress hard, soft
1351                          and both resets.
1352
1353                        * dump_id: dump IDENTIFY data.
1354
1355                        If there are multiple matching configurations changing
1356                        the same attribute, the last one is used.
1357
1358        memblock=debug  [KNL] Enable memblock debug messages.
1359
1360        load_ramdisk=   [RAM] List of ramdisks to load from floppy
1361                        See Documentation/blockdev/ramdisk.txt.
1362
1363        lockd.nlm_grace_period=P  [NFS] Assign grace period.
1364                        Format: <integer>
1365
1366        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
1367                        Format: <integer>
1368
1369        lockd.nlm_timeout=T     [NFS] Assign timeout value.
1370                        Format: <integer>
1371
1372        lockd.nlm_udpport=M     [NFS] Assign UDP port.
1373                        Format: <integer>
1374
1375        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
1376                        Format: <irq>
1377
1378        loglevel=       All Kernel Messages with a loglevel smaller than the
1379                        console loglevel will be printed to the console. It can
1380                        also be changed with klogd or other programs. The
1381                        loglevels are defined as follows:
1382
1383                        0 (KERN_EMERG)          system is unusable
1384                        1 (KERN_ALERT)          action must be taken immediately
1385                        2 (KERN_CRIT)           critical conditions
1386                        3 (KERN_ERR)            error conditions
1387                        4 (KERN_WARNING)        warning conditions
1388                        5 (KERN_NOTICE)         normal but significant condition
1389                        6 (KERN_INFO)           informational
1390                        7 (KERN_DEBUG)          debug-level messages
1391
1392        log_buf_len=n[KMG]      Sets the size of the printk ring buffer,
1393                        in bytes.  n must be a power of two.  The default
1394                        size is set in the kernel config file.
1395
1396        logo.nologo     [FB] Disables display of the built-in Linux logo.
1397                        This may be used to provide more screen space for
1398                        kernel log messages and is useful when debugging
1399                        kernel boot problems.
1400
1401        lp=0            [LP]    Specify parallel ports to use, e.g,
1402        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
1403        lp=reset                first parallel port). 'lp=0' disables the
1404        lp=auto                 printer driver. 'lp=reset' (which can be
1405                                specified in addition to the ports) causes
1406                                attached printers to be reset. Using
1407                                lp=port1,port2,... specifies the parallel ports
1408                                to associate lp devices with, starting with
1409                                lp0. A port specification may be 'none' to skip
1410                                that lp device, or a parport name such as
1411                                'parport0'. Specifying 'lp=auto' instead of a
1412                                port specification list means that device IDs
1413                                from each port should be examined, to see if
1414                                an IEEE 1284-compliant printer is attached; if
1415                                so, the driver will manage that printer.
1416                                See also header of drivers/char/lp.c.
1417
1418        lpj=n           [KNL]
1419                        Sets loops_per_jiffy to given constant, thus avoiding
1420                        time-consuming boot-time autodetection (up to 250 ms per
1421                        CPU). 0 enables autodetection (default). To determine
1422                        the correct value for your kernel, boot with normal
1423                        autodetection and see what value is printed. Note that
1424                        on SMP systems the preset will be applied to all CPUs,
1425                        which is likely to cause problems if your CPUs need
1426                        significantly divergent settings. An incorrect value
1427                        will cause delays in the kernel to be wrong, leading to
1428                        unpredictable I/O errors and other breakage. Although
1429                        unlikely, in the extreme case this might damage your
1430                        hardware.
1431
1432        ltpc=           [NET]
1433                        Format: <io>,<irq>,<dma>
1434
1435        machvec=        [IA-64] Force the use of a particular machine-vector
1436                        (machvec) in a generic kernel.
1437                        Example: machvec=hpzx1_swiotlb
1438
1439        machtype=       [Loongson] Share the same kernel image file between different
1440                         yeeloong laptop.
1441                        Example: machtype=lemote-yeeloong-2f-7inch
1442
1443        max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater
1444                        than or equal to this physical address is ignored.
1445
1446        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
1447                        should make use of.  maxcpus=n : n >= 0 limits the
1448                        kernel to using 'n' processors.  n=0 is a special case,
1449                        it is equivalent to "nosmp", which also disables
1450                        the IO APIC.
1451
1452        max_loop=       [LOOP] The number of loop block devices that get
1453        (loop.max_loop) unconditionally pre-created at init time. The default
1454                        number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1455                        of statically allocating a predefined number, loop
1456                        devices can be requested on-demand with the
1457                        /dev/loop-control interface.
1458
1459        mce             [X86-32] Machine Check Exception
1460
1461        mce=option      [X86-64] See Documentation/x86/x86_64/boot-options.txt
1462
1463        md=             [HW] RAID subsystems devices and level
1464                        See Documentation/md.txt.
1465
1466        mdacon=         [MDA]
1467                        Format: <first>,<last>
1468                        Specifies range of consoles to be captured by the MDA.
1469
1470        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
1471                        Amount of memory to be used when the kernel is not able
1472                        to see the whole system memory or for test.
1473                        [X86-32] Use together with memmap= to avoid physical
1474                        address space collisions. Without memmap= PCI devices
1475                        could be placed at addresses belonging to unused RAM.
1476
1477        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
1478                        memory.
1479
1480        memchunk=nn[KMG]
1481                        [KNL,SH] Allow user to override the default size for
1482                        per-device physically contiguous DMA buffers.
1483
1484        memmap=exactmap [KNL,X86] Enable setting of an exact
1485                        E820 memory map, as specified by the user.
1486                        Such memmap=exactmap lines can be constructed based on
1487                        BIOS output or other requirements. See the memmap=nn@ss
1488                        option description.
1489
1490        memmap=nn[KMG]@ss[KMG]
1491                        [KNL] Force usage of a specific region of memory
1492                        Region of memory to be used, from ss to ss+nn.
1493
1494        memmap=nn[KMG]#ss[KMG]
1495                        [KNL,ACPI] Mark specific memory as ACPI data.
1496                        Region of memory to be used, from ss to ss+nn.
1497
1498        memmap=nn[KMG]$ss[KMG]
1499                        [KNL,ACPI] Mark specific memory as reserved.
1500                        Region of memory to be used, from ss to ss+nn.
1501                        Example: Exclude memory from 0x18690000-0x1869ffff
1502                                 memmap=64K$0x18690000
1503                                 or
1504                                 memmap=0x10000$0x18690000
1505
1506        memory_corruption_check=0/1 [X86]
1507                        Some BIOSes seem to corrupt the first 64k of
1508                        memory when doing things like suspend/resume.
1509                        Setting this option will scan the memory
1510                        looking for corruption.  Enabling this will
1511                        both detect corruption and prevent the kernel
1512                        from using the memory being corrupted.
1513                        However, its intended as a diagnostic tool; if
1514                        repeatable BIOS-originated corruption always
1515                        affects the same memory, you can use memmap=
1516                        to prevent the kernel from using that memory.
1517
1518        memory_corruption_check_size=size [X86]
1519                        By default it checks for corruption in the low
1520                        64k, making this memory unavailable for normal
1521                        use.  Use this parameter to scan for
1522                        corruption in more or less memory.
1523
1524        memory_corruption_check_period=seconds [X86]
1525                        By default it checks for corruption every 60
1526                        seconds.  Use this parameter to check at some
1527                        other rate.  0 disables periodic checking.
1528
1529        memtest=        [KNL,X86] Enable memtest
1530                        Format: <integer>
1531                        default : 0 <disable>
1532                        Specifies the number of memtest passes to be
1533                        performed. Each pass selects another test
1534                        pattern from a given set of patterns. Memtest
1535                        fills the memory with this pattern, validates
1536                        memory contents and reserves bad memory
1537                        regions that are detected.
1538
1539        meye.*=         [HW] Set MotionEye Camera parameters
1540                        See Documentation/video4linux/meye.txt.
1541
1542        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
1543                        Multi-Function General Purpose Timers on AMD Geode
1544                        platforms.
1545
1546        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
1547                        the BIOS has incorrectly applied a workaround. TinyBIOS
1548                        version 0.98 is known to be affected, 0.99 fixes the
1549                        problem by letting the user disable the workaround.
1550
1551        mga=            [HW,DRM]
1552
1553        min_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory below this
1554                        physical address is ignored.
1555
1556        mini2440=       [ARM,HW,KNL]
1557                        Format:[0..2][b][c][t]
1558                        Default: "0tb"
1559                        MINI2440 configuration specification:
1560                        0 - The attached screen is the 3.5" TFT
1561                        1 - The attached screen is the 7" TFT
1562                        2 - The VGA Shield is attached (1024x768)
1563                        Leaving out the screen size parameter will not load
1564                        the TFT driver, and the framebuffer will be left
1565                        unconfigured.
1566                        b - Enable backlight. The TFT backlight pin will be
1567                        linked to the kernel VESA blanking code and a GPIO
1568                        LED. This parameter is not necessary when using the
1569                        VGA shield.
1570                        c - Enable the s3c camera interface.
1571                        t - Reserved for enabling touchscreen support. The
1572                        touchscreen support is not enabled in the mainstream
1573                        kernel as of 2.6.30, a preliminary port can be found
1574                        in the "bleeding edge" mini2440 support kernel at
1575                        http://repo.or.cz/w/linux-2.6/mini2440.git
1576
1577        mminit_loglevel=
1578                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1579                        parameter allows control of the logging verbosity for
1580                        the additional memory initialisation checks. A value
1581                        of 0 disables mminit logging and a level of 4 will
1582                        log everything. Information is printed at KERN_DEBUG
1583                        so loglevel=8 may also need to be specified.
1584
1585        mousedev.tap_time=
1586                        [MOUSE] Maximum time between finger touching and
1587                        leaving touchpad surface for touch to be considered
1588                        a tap and be reported as a left button click (for
1589                        touchpads working in absolute mode only).
1590                        Format: <msecs>
1591        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
1592                        reporting absolute coordinates, such as tablets
1593        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
1594                        reporting absolute coordinates, such as tablets
1595
1596        movablecore=nn[KMG]     [KNL,X86,IA-64,PPC] This parameter
1597                        is similar to kernelcore except it specifies the
1598                        amount of memory used for migratable allocations.
1599                        If both kernelcore and movablecore is specified,
1600                        then kernelcore will be at *least* the specified
1601                        value but may be more. If movablecore on its own
1602                        is specified, the administrator must be careful
1603                        that the amount of memory usable for all allocations
1604                        is not too small.
1605
1606        MTD_Partition=  [MTD]
1607                        Format: <name>,<region-number>,<size>,<offset>
1608
1609        MTD_Region=     [MTD] Format:
1610                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1611
1612        mtdparts=       [MTD]
1613                        See drivers/mtd/cmdlinepart.c.
1614
1615        multitce=off    [PPC]  This parameter disables the use of the pSeries
1616                        firmware feature for updating multiple TCE entries
1617                        at a time.
1618
1619        onenand.bdry=   [HW,MTD] Flex-OneNAND Boundary Configuration
1620
1621                        Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1622
1623                        boundary - index of last SLC block on Flex-OneNAND.
1624                                   The remaining blocks are configured as MLC blocks.
1625                        lock     - Configure if Flex-OneNAND boundary should be locked.
1626                                   Once locked, the boundary cannot be changed.
1627                                   1 indicates lock status, 0 indicates unlock status.
1628
1629        mtdset=         [ARM]
1630                        ARM/S3C2412 JIVE boot control
1631
1632                        See arch/arm/mach-s3c2412/mach-jive.c
1633
1634        mtouchusb.raw_coordinates=
1635                        [HW] Make the MicroTouch USB driver use raw coordinates
1636                        ('y', default) or cooked coordinates ('n')
1637
1638        mtrr_chunk_size=nn[KMG] [X86]
1639                        used for mtrr cleanup. It is largest continuous chunk
1640                        that could hold holes aka. UC entries.
1641
1642        mtrr_gran_size=nn[KMG] [X86]
1643                        Used for mtrr cleanup. It is granularity of mtrr block.
1644                        Default is 1.
1645                        Large value could prevent small alignment from
1646                        using up MTRRs.
1647
1648        mtrr_spare_reg_nr=n [X86]
1649                        Format: <integer>
1650                        Range: 0,7 : spare reg number
1651                        Default : 1
1652                        Used for mtrr cleanup. It is spare mtrr entries number.
1653                        Set to 2 or more if your graphical card needs more.
1654
1655        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
1656
1657        netdev=         [NET] Network devices parameters
1658                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1659                        Note that mem_start is often overloaded to mean
1660                        something different and driver-specific.
1661                        This usage is only documented in each driver source
1662                        file if at all.
1663
1664        nf_conntrack.acct=
1665                        [NETFILTER] Enable connection tracking flow accounting
1666                        0 to disable accounting
1667                        1 to enable accounting
1668                        Default value is 0.
1669
1670        nfsaddrs=       [NFS] Deprecated.  Use ip= instead.
1671                        See Documentation/filesystems/nfs/nfsroot.txt.
1672
1673        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
1674                        See Documentation/filesystems/nfs/nfsroot.txt.
1675
1676        nfsrootdebug    [NFS] enable nfsroot debugging messages.
1677                        See Documentation/filesystems/nfs/nfsroot.txt.
1678
1679        nfs.callback_tcpport=
1680                        [NFS] set the TCP port on which the NFSv4 callback
1681                        channel should listen.
1682
1683        nfs.cache_getent=
1684                        [NFS] sets the pathname to the program which is used
1685                        to update the NFS client cache entries.
1686
1687        nfs.cache_getent_timeout=
1688                        [NFS] sets the timeout after which an attempt to
1689                        update a cache entry is deemed to have failed.
1690
1691        nfs.idmap_cache_timeout=
1692                        [NFS] set the maximum lifetime for idmapper cache
1693                        entries.
1694
1695        nfs.enable_ino64=
1696                        [NFS] enable 64-bit inode numbers.
1697                        If zero, the NFS client will fake up a 32-bit inode
1698                        number for the readdir() and stat() syscalls instead
1699                        of returning the full 64-bit number.
1700                        The default is to return 64-bit inode numbers.
1701
1702        nfs.max_session_slots=
1703                        [NFSv4.1] Sets the maximum number of session slots
1704                        the client will attempt to negotiate with the server.
1705                        This limits the number of simultaneous RPC requests
1706                        that the client can send to the NFSv4.1 server.
1707                        Note that there is little point in setting this
1708                        value higher than the max_tcp_slot_table_limit.
1709
1710        nfs.nfs4_disable_idmapping=
1711                        [NFSv4] When set to the default of '1', this option
1712                        ensures that both the RPC level authentication
1713                        scheme and the NFS level operations agree to use
1714                        numeric uids/gids if the mount is using the
1715                        'sec=sys' security flavour. In effect it is
1716                        disabling idmapping, which can make migration from
1717                        legacy NFSv2/v3 systems to NFSv4 easier.
1718                        Servers that do not support this mode of operation
1719                        will be autodetected by the client, and it will fall
1720                        back to using the idmapper.
1721                        To turn off this behaviour, set the value to '0'.
1722
1723        nfs.send_implementation_id =
1724                        [NFSv4.1] Send client implementation identification
1725                        information in exchange_id requests.
1726                        If zero, no implementation identification information
1727                        will be sent.
1728                        The default is to send the implementation identification
1729                        information.
1730
1731        nfsd.nfs4_disable_idmapping=
1732                        [NFSv4] When set to the default of '1', the NFSv4
1733                        server will return only numeric uids and gids to
1734                        clients using auth_sys, and will accept numeric uids
1735                        and gids from such clients.  This is intended to ease
1736                        migration from NFSv2/v3.
1737
1738        objlayoutdriver.osd_login_prog=
1739                        [NFS] [OBJLAYOUT] sets the pathname to the program which
1740                        is used to automatically discover and login into new
1741                        osd-targets. Please see:
1742                        Documentation/filesystems/pnfs.txt for more explanations
1743
1744        nmi_debug=      [KNL,AVR32,SH] Specify one or more actions to take
1745                        when a NMI is triggered.
1746                        Format: [state][,regs][,debounce][,die]
1747
1748        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
1749                        Format: [panic,][nopanic,][num]
1750                        Valid num: 0
1751                        0 - turn nmi_watchdog off
1752                        When panic is specified, panic when an NMI watchdog
1753                        timeout occurs (or 'nopanic' to override the opposite
1754                        default).
1755                        This is useful when you use a panic=... timeout and
1756                        need the box quickly up again.
1757
1758        netpoll.carrier_timeout=
1759                        [NET] Specifies amount of time (in seconds) that
1760                        netpoll should wait for a carrier. By default netpoll
1761                        waits 4 seconds.
1762
1763        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
1764                        emulation library even if a 387 maths coprocessor
1765                        is present.
1766
1767        no_console_suspend
1768                        [HW] Never suspend the console
1769                        Disable suspending of consoles during suspend and
1770                        hibernate operations.  Once disabled, debugging
1771                        messages can reach various consoles while the rest
1772                        of the system is being put to sleep (ie, while
1773                        debugging driver suspend/resume hooks).  This may
1774                        not work reliably with all consoles, but is known
1775                        to work with serial and VGA consoles.
1776                        To facilitate more flexible debugging, we also add
1777                        console_suspend, a printk module parameter to control
1778                        it. Users could use console_suspend (usually
1779                        /sys/module/printk/parameters/console_suspend) to
1780                        turn on/off it dynamically.
1781
1782        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
1783                        caches in the slab allocator.  Saves per-node memory,
1784                        but will impact performance.
1785
1786        noalign         [KNL,ARM]
1787
1788        noapic          [SMP,APIC] Tells the kernel to not make use of any
1789                        IOAPICs that may be present in the system.
1790
1791        noautogroup     Disable scheduler automatic task group creation.
1792
1793        nobats          [PPC] Do not use BATs for mapping kernel lowmem
1794                        on "Classic" PPC cores.
1795
1796        nocache         [ARM]
1797
1798        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction
1799
1800        nodelayacct     [KNL] Disable per-task delay accounting
1801
1802        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1803
1804        nodsp           [SH] Disable hardware DSP at boot time.
1805
1806        noefi           [X86] Disable EFI runtime services support.
1807
1808        noexec          [IA-64]
1809
1810        noexec          [X86]
1811                        On X86-32 available only on PAE configured kernels.
1812                        noexec=on: enable non-executable mappings (default)
1813                        noexec=off: disable non-executable mappings
1814
1815        nosmep          [X86]
1816                        Disable SMEP (Supervisor Mode Execution Protection)
1817                        even if it is supported by processor.
1818
1819        noexec32        [X86-64]
1820                        This affects only 32-bit executables.
1821                        noexec32=on: enable non-executable mappings (default)
1822                                read doesn't imply executable mappings
1823                        noexec32=off: disable non-executable mappings
1824                                read implies executable mappings
1825
1826        nofpu           [SH] Disable hardware FPU at boot time.
1827
1828        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
1829                        register save and restore. The kernel will only save
1830                        legacy floating-point registers on task switch.
1831
1832        noxsave         [BUGS=X86] Disables x86 extended register state save
1833                        and restore using xsave. The kernel will fallback to
1834                        enabling legacy floating-point and sse state.
1835
1836        nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1837                        wfi(ARM) instruction doesn't work correctly and not to
1838                        use it. This is also useful when using JTAG debugger.
1839
1840        no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
1841                        instruction doesn't work correctly and not to
1842                        use it.
1843
1844        no_file_caps    Tells the kernel not to honor file capabilities.  The
1845                        only way then for a file to be executed with privilege
1846                        is to be setuid root or executed by root.
1847
1848        nohalt          [IA-64] Tells the kernel not to use the power saving
1849                        function PAL_HALT_LIGHT when idle. This increases
1850                        power-consumption. On the positive side, it reduces
1851                        interrupt wake-up latency, which may improve performance
1852                        in certain environments such as networked servers or
1853                        real-time systems.
1854
1855        nohz=           [KNL] Boottime enable/disable dynamic ticks
1856                        Valid arguments: on, off
1857                        Default: on
1858
1859        noiotrap        [SH] Disables trapped I/O port accesses.
1860
1861        noirqdebug      [X86-32] Disables the code which attempts to detect and
1862                        disable unhandled interrupt sources.
1863
1864        no_timer_check  [X86,APIC] Disables the code which tests for
1865                        broken timer IRQ sources.
1866
1867        noisapnp        [ISAPNP] Disables ISA PnP code.
1868
1869        noinitrd        [RAM] Tells the kernel not to load any configured
1870                        initial RAM disk.
1871
1872        nointremap      [X86-64, Intel-IOMMU] Do not enable interrupt
1873                        remapping.
1874                        [Deprecated - use intremap=off]
1875
1876        nointroute      [IA-64]
1877
1878        nojitter        [IA-64] Disables jitter checking for ITC timers.
1879
1880        no-kvmclock     [X86,KVM] Disable paravirtualized KVM clock driver
1881
1882        no-kvmapf       [X86,KVM] Disable paravirtualized asynchronous page
1883                        fault handling.
1884
1885        no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
1886                        steal time is computed, but won't influence scheduler
1887                        behaviour
1888
1889        nolapic         [X86-32,APIC] Do not enable or use the local APIC.
1890
1891        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.
1892
1893        noltlbs         [PPC] Do not use large page/tlb entries for kernel
1894                        lowmem mapping on PPC40x.
1895
1896        nomca           [IA-64] Disable machine check abort handling
1897
1898        nomce           [X86-32] Machine Check Exception
1899
1900        nomfgpt         [X86-32] Disable Multi-Function General Purpose
1901                        Timer usage (for AMD Geode machines).
1902
1903        nonmi_ipi       [X86] Disable using NMI IPIs during panic/reboot to
1904                        shutdown the other cpus.  Instead use the REBOOT_VECTOR
1905                        irq.
1906
1907        nomodule        Disable module load
1908
1909        nopat           [X86] Disable PAT (page attribute table extension of
1910                        pagetables) support.
1911
1912        norandmaps      Don't use address space randomization.  Equivalent to
1913                        echo 0 > /proc/sys/kernel/randomize_va_space
1914
1915        noreplace-paravirt      [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1916
1917        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
1918                        with UP alternatives
1919
1920        noresidual      [PPC] Don't use residual data on PReP machines.
1921
1922        nordrand        [X86] Disable the direct use of the RDRAND
1923                        instruction even if it is supported by the
1924                        processor.  RDRAND is still available to user
1925                        space applications.
1926
1927        noresume        [SWSUSP] Disables resume and restores original swap
1928                        space.
1929
1930        no-scroll       [VGA] Disables scrollback.
1931                        This is required for the Braillex ib80-piezo Braille
1932                        reader made by F.H. Papenmeier (Germany).
1933
1934        nosbagart       [IA-64]
1935
1936        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1937
1938        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
1939                        and disable the IO APIC.  legacy for "maxcpus=0".
1940
1941        nosoftlockup    [KNL] Disable the soft-lockup detector.
1942
1943        nosync          [HW,M68K] Disables sync negotiation for all devices.
1944
1945        notsc           [BUGS=X86-32] Disable Time Stamp Counter
1946
1947        nousb           [USB] Disable the USB subsystem
1948
1949        nowatchdog      [KNL] Disable the lockup detector (NMI watchdog).
1950
1951        nowb            [ARM]
1952
1953        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
1954
1955        nptcg=          [IA-64] Override max number of concurrent global TLB
1956                        purges which is reported from either PAL_VM_SUMMARY or
1957                        SAL PALO.
1958
1959        nr_cpus=        [SMP] Maximum number of processors that an SMP kernel
1960                        could support.  nr_cpus=n : n >= 1 limits the kernel to
1961                        supporting 'n' processors. Later in runtime you can not
1962                        use hotplug cpu feature to put more cpu back to online.
1963                        just like you compile the kernel NR_CPUS=n
1964
1965        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1966
1967        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1968                        one of ['zone', 'node', 'default'] can be specified
1969                        This can be set from sysctl after boot.
1970                        See Documentation/sysctl/vm.txt for details.
1971
1972        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
1973                        See Documentation/debugging-via-ohci1394.txt for more
1974                        info.
1975
1976        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1977                        Rather than timing out after 20 ms if an EC
1978                        command is not properly ACKed, override the length
1979                        of the timeout.  We have interrupts disabled while
1980                        waiting for the ACK, so if this is set too high
1981                        interrupts *may* be lost!
1982
1983        omap_mux=       [OMAP] Override bootloader pin multiplexing.
1984                        Format: <mux_mode0.mode_name=value>...
1985                        For example, to override I2C bus2:
1986                        omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1987
1988        oprofile.timer= [HW]
1989                        Use timer interrupt instead of performance counters
1990
1991        oprofile.cpu_type=      Force an oprofile cpu type
1992                        This might be useful if you have an older oprofile
1993                        userland or if you want common events.
1994                        Format: { arch_perfmon }
1995                        arch_perfmon: [X86] Force use of architectural
1996                                perfmon on Intel CPUs instead of the
1997                                CPU specific event set.
1998                        timer: [X86] Force use of architectural NMI
1999                                timer mode (see also oprofile.timer
2000                                for generic hr timer mode)
2001                                [s390] Force legacy basic mode sampling
2002                                (report cpu_type "timer")
2003
2004        oops=panic      Always panic on oopses. Default is to just kill the
2005                        process, but there is a small probability of
2006                        deadlocking the machine.
2007                        This will also cause panics on machine check exceptions.
2008                        Useful together with panic=30 to trigger a reboot.
2009
2010        OSS             [HW,OSS]
2011                        See Documentation/sound/oss/oss-parameters.txt
2012
2013        panic=          [KNL] Kernel behaviour on panic: delay <timeout>
2014                        timeout > 0: seconds before rebooting
2015                        timeout = 0: wait forever
2016                        timeout < 0: reboot immediately
2017                        Format: <timeout>
2018
2019        parkbd.port=    [HW] Parallel port number the keyboard adapter is
2020                        connected to, default is 0.
2021                        Format: <parport#>
2022        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
2023                        0 for XT, 1 for AT (default is AT).
2024                        Format: <mode>
2025
2026        parport=        [HW,PPT] Specify parallel ports. 0 disables.
2027                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2028                        Use 'auto' to force the driver to use any
2029                        IRQ/DMA settings detected (the default is to
2030                        ignore detected IRQ/DMA settings because of
2031                        possible conflicts). You can specify the base
2032                        address, IRQ, and DMA settings; IRQ and DMA
2033                        should be numbers, or 'auto' (for using detected
2034                        settings on that particular port), or 'nofifo'
2035                        (to avoid using a FIFO even if it is detected).
2036                        Parallel ports are assigned in the order they
2037                        are specified on the command line, starting
2038                        with parport0.
2039
2040        parport_init_mode=      [HW,PPT]
2041                        Configure VIA parallel port to operate in
2042                        a specific mode. This is necessary on Pegasos
2043                        computer where firmware has no options for setting
2044                        up parallel port mode and sets it to spp.
2045                        Currently this function knows 686a and 8231 chips.
2046                        Format: [spp|ps2|epp|ecp|ecpepp]
2047
2048        pause_on_oops=
2049                        Halt all CPUs after the first oops has been printed for
2050                        the specified number of seconds.  This is to be used if
2051                        your oopses keep scrolling off the screen.
2052
2053        pcbit=          [HW,ISDN]
2054
2055        pcd.            [PARIDE]
2056                        See header of drivers/block/paride/pcd.c.
2057                        See also Documentation/blockdev/paride.txt.
2058
2059        pci=option[,option...]  [PCI] various PCI subsystem options:
2060                earlydump       [X86] dump PCI config space before the kernel
2061                                changes anything
2062                off             [X86] don't probe for the PCI bus
2063                bios            [X86-32] force use of PCI BIOS, don't access
2064                                the hardware directly. Use this if your machine
2065                                has a non-standard PCI host bridge.
2066                nobios          [X86-32] disallow use of PCI BIOS, only direct
2067                                hardware access methods are allowed. Use this
2068                                if you experience crashes upon bootup and you
2069                                suspect they are caused by the BIOS.
2070                conf1           [X86] Force use of PCI Configuration
2071                                Mechanism 1.
2072                conf2           [X86] Force use of PCI Configuration
2073                                Mechanism 2.
2074                noaer           [PCIE] If the PCIEAER kernel config parameter is
2075                                enabled, this kernel boot option can be used to
2076                                disable the use of PCIE advanced error reporting.
2077                nodomains       [PCI] Disable support for multiple PCI
2078                                root domains (aka PCI segments, in ACPI-speak).
2079                nommconf        [X86] Disable use of MMCONFIG for PCI
2080                                Configuration
2081                check_enable_amd_mmconf [X86] check for and enable
2082                                properly configured MMIO access to PCI
2083                                config space on AMD family 10h CPU
2084                nomsi           [MSI] If the PCI_MSI kernel config parameter is
2085                                enabled, this kernel boot option can be used to
2086                                disable the use of MSI interrupts system-wide.
2087                noioapicquirk   [APIC] Disable all boot interrupt quirks.
2088                                Safety option to keep boot IRQs enabled. This
2089                                should never be necessary.
2090                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
2091                                primary IO-APIC for bridges that cannot disable
2092                                boot IRQs. This fixes a source of spurious IRQs
2093                                when the system masks IRQs.
2094                noioapicreroute [APIC] Disable workaround that uses the
2095                                boot IRQ equivalent of an IRQ that connects to
2096                                a chipset where boot IRQs cannot be disabled.
2097                                The opposite of ioapicreroute.
2098                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
2099                                routing table. These calls are known to be buggy
2100                                on several machines and they hang the machine
2101                                when used, but on other computers it's the only
2102                                way to get the interrupt routing table. Try
2103                                this option if the kernel is unable to allocate
2104                                IRQs or discover secondary PCI buses on your
2105                                motherboard.
2106                rom             [X86] Assign address space to expansion ROMs.
2107                                Use with caution as certain devices share
2108                                address decoders between ROMs and other
2109                                resources.
2110                norom           [X86] Do not assign address space to
2111                                expansion ROMs that do not already have
2112                                BIOS assigned address ranges.
2113                nobar           [X86] Do not assign address space to the
2114                                BARs that weren't assigned by the BIOS.
2115                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
2116                                assigned automatically to PCI devices. You can
2117                                make the kernel exclude IRQs of your ISA cards
2118                                this way.
2119                pirqaddr=0xAAAAA        [X86] Specify the physical address
2120                                of the PIRQ table (normally generated
2121                                by the BIOS) if it is outside the
2122                                F0000h-100000h range.
2123                lastbus=N       [X86] Scan all buses thru bus #N. Can be
2124                                useful if the kernel is unable to find your
2125                                secondary buses and you want to tell it
2126                                explicitly which ones they are.
2127                assign-busses   [X86] Always assign all PCI bus
2128                                numbers ourselves, overriding
2129                                whatever the firmware may have done.
2130                usepirqmask     [X86] Honor the possible IRQ mask stored
2131                                in the BIOS $PIR table. This is needed on
2132                                some systems with broken BIOSes, notably
2133                                some HP Pavilion N5400 and Omnibook XE3
2134                                notebooks. This will have no effect if ACPI
2135                                IRQ routing is enabled.
2136                noacpi          [X86] Do not use ACPI for IRQ routing
2137                                or for PCI scanning.
2138                use_crs         [X86] Use PCI host bridge window information
2139                                from ACPI.  On BIOSes from 2008 or later, this
2140                                is enabled by default.  If you need to use this,
2141                                please report a bug.
2142                nocrs           [X86] Ignore PCI host bridge windows from ACPI.
2143                                If you need to use this, please report a bug.
2144                routeirq        Do IRQ routing for all PCI devices.
2145                                This is normally done in pci_enable_device(),
2146                                so this option is a temporary workaround
2147                                for broken drivers that don't call it.
2148                skip_isa_align  [X86] do not align io start addr, so can
2149                                handle more pci cards
2150                firmware        [ARM] Do not re-enumerate the bus but instead
2151                                just use the configuration from the
2152                                bootloader. This is currently used on
2153                                IXP2000 systems where the bus has to be
2154                                configured a certain way for adjunct CPUs.
2155                noearly         [X86] Don't do any early type 1 scanning.
2156                                This might help on some broken boards which
2157                                machine check when some devices' config space
2158                                is read. But various workarounds are disabled
2159                                and some IOMMU drivers will not work.
2160                bfsort          Sort PCI devices into breadth-first order.
2161                                This sorting is done to get a device
2162                                order compatible with older (<= 2.4) kernels.
2163                nobfsort        Don't sort PCI devices into breadth-first order.
2164                cbiosize=nn[KMG]        The fixed amount of bus space which is
2165                                reserved for the CardBus bridge's IO window.
2166                                The default value is 256 bytes.
2167                cbmemsize=nn[KMG]       The fixed amount of bus space which is
2168                                reserved for the CardBus bridge's memory
2169                                window. The default value is 64 megabytes.
2170                resource_alignment=
2171                                Format:
2172                                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2173                                Specifies alignment and device to reassign
2174                                aligned memory resources.
2175                                If <order of align> is not specified,
2176                                PAGE_SIZE is used as alignment.
2177                                PCI-PCI bridge can be specified, if resource
2178                                windows need to be expanded.
2179                ecrc=           Enable/disable PCIe ECRC (transaction layer
2180                                end-to-end CRC checking).
2181                                bios: Use BIOS/firmware settings. This is the
2182                                the default.
2183                                off: Turn ECRC off
2184                                on: Turn ECRC on.
2185                realloc=        Enable/disable reallocating PCI bridge resources
2186                                if allocations done by BIOS are too small to
2187                                accommodate resources required by all child
2188                                devices.
2189                                off: Turn realloc off
2190                                on: Turn realloc on
2191                realloc         same as realloc=on
2192                noari           do not use PCIe ARI.
2193                pcie_scan_all   Scan all possible PCIe devices.  Otherwise we
2194                                only look for one device below a PCIe downstream
2195                                port.
2196
2197        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
2198                        Management.
2199                off     Disable ASPM.
2200                force   Enable ASPM even on devices that claim not to support it.
2201                        WARNING: Forcing ASPM on may cause system lockups.
2202
2203        pcie_hp=        [PCIE] PCI Express Hotplug driver options:
2204                nomsi   Do not use MSI for PCI Express Native Hotplug (this
2205                        makes all PCIe ports use INTx for hotplug services).
2206
2207        pcie_ports=     [PCIE] PCIe ports handling:
2208                auto    Ask the BIOS whether or not to use native PCIe services
2209                        associated with PCIe ports (PME, hot-plug, AER).  Use
2210                        them only if that is allowed by the BIOS.
2211                native  Use native PCIe services associated with PCIe ports
2212                        unconditionally.
2213                compat  Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2214                        ports driver.
2215
2216        pcie_pme=       [PCIE,PM] Native PCIe PME signaling options:
2217                nomsi   Do not use MSI for native PCIe PME signaling (this makes
2218                        all PCIe root ports use INTx for all services).
2219
2220        pcmv=           [HW,PCMCIA] BadgePAD 4
2221
2222        pd.             [PARIDE]
2223                        See Documentation/blockdev/paride.txt.
2224
2225        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2226                        boot time.
2227                        Format: { 0 | 1 }
2228                        See arch/parisc/kernel/pdc_chassis.c
2229
2230        percpu_alloc=   Select which percpu first chunk allocator to use.
2231                        Currently supported values are "embed" and "page".
2232                        Archs may support subset or none of the selections.
2233                        See comments in mm/percpu.c for details on each
2234                        allocator.  This parameter is primarily for debugging
2235                        and performance comparison.
2236
2237        pf.             [PARIDE]
2238                        See Documentation/blockdev/paride.txt.
2239
2240        pg.             [PARIDE]
2241                        See Documentation/blockdev/paride.txt.
2242
2243        pirq=           [SMP,APIC] Manual mp-table setup
2244                        See Documentation/x86/i386/IO-APIC.txt.
2245
2246        plip=           [PPT,NET] Parallel port network link
2247                        Format: { parport<nr> | timid | 0 }
2248                        See also Documentation/parport.txt.
2249
2250        pmtmr=          [X86] Manual setup of pmtmr I/O Port.
2251                        Override pmtimer IOPort with a hex value.
2252                        e.g. pmtmr=0x508
2253
2254        pnp.debug=1     [PNP]
2255                        Enable PNP debug messages (depends on the
2256                        CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
2257                        via /sys/module/pnp/parameters/debug.  We always show
2258                        current resource usage; turning this on also shows
2259                        possible settings and some assignment information.
2260
2261        pnpacpi=        [ACPI]
2262                        { off }
2263
2264        pnpbios=        [ISAPNP]
2265                        { on | off | curr | res | no-curr | no-res }
2266
2267        pnp_reserve_irq=
2268                        [ISAPNP] Exclude IRQs for the autoconfiguration
2269
2270        pnp_reserve_dma=
2271                        [ISAPNP] Exclude DMAs for the autoconfiguration
2272
2273        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2274                        Ranges are in pairs (I/O port base and size).
2275
2276        pnp_reserve_mem=
2277                        [ISAPNP] Exclude memory regions for the
2278                        autoconfiguration.
2279                        Ranges are in pairs (memory base and size).
2280
2281        ports=          [IP_VS_FTP] IPVS ftp helper module
2282                        Default is 21.
2283                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
2284                        may be specified.
2285                        Format: <port>,<port>....
2286
2287        print-fatal-signals=
2288                        [KNL] debug: print fatal signals
2289
2290                        If enabled, warn about various signal handling
2291                        related application anomalies: too many signals,
2292                        too many POSIX.1 timers, fatal signals causing a
2293                        coredump - etc.
2294
2295                        If you hit the warning due to signal overflow,
2296                        you might want to try "ulimit -i unlimited".
2297
2298                        default: off.
2299
2300        printk.always_kmsg_dump=
2301                        Trigger kmsg_dump for cases other than kernel oops or
2302                        panics
2303                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2304                        default: disabled
2305
2306        printk.time=    Show timing data prefixed to each printk message line
2307                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2308
2309        processor.max_cstate=   [HW,ACPI]
2310                        Limit processor to maximum C-state
2311                        max_cstate=9 overrides any DMI blacklist limit.
2312
2313        processor.nocst [HW,ACPI]
2314                        Ignore the _CST method to determine C-states,
2315                        instead using the legacy FADT method
2316
2317        profile=        [KNL] Enable kernel profiling via /proc/profile
2318                        Format: [schedule,]<number>
2319                        Param: "schedule" - profile schedule points.
2320                        Param: <number> - step/bucket size as a power of 2 for
2321                                statistical time based profiling.
2322                        Param: "sleep" - profile D-state sleeping (millisecs).
2323                                Requires CONFIG_SCHEDSTATS
2324                        Param: "kvm" - profile VM exits.
2325
2326        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2327                        before loading.
2328                        See Documentation/blockdev/ramdisk.txt.
2329
2330        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
2331                        probe for; one of (bare|imps|exps|lifebook|any).
2332        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
2333                        per second.
2334        psmouse.resetafter=     [HW,MOUSE]
2335                        Try to reset the device after so many bad packets
2336                        (0 = never).
2337        psmouse.resolution=
2338                        [HW,MOUSE] Set desired mouse resolution, in dpi.
2339        psmouse.smartscroll=
2340                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2341                        0 = disabled, 1 = enabled (default).
2342
2343        pstore.backend= Specify the name of the pstore backend to use
2344
2345        pt.             [PARIDE]
2346                        See Documentation/blockdev/paride.txt.
2347
2348        pty.legacy_count=
2349                        [KNL] Number of legacy pty's. Overwrites compiled-in
2350                        default number.
2351
2352        quiet           [KNL] Disable most log messages
2353
2354        r128=           [HW,DRM]
2355
2356        raid=           [HW,RAID]
2357                        See Documentation/md.txt.
2358
2359        ramdisk_blocksize=      [RAM]
2360                        See Documentation/blockdev/ramdisk.txt.
2361
2362        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
2363                        See Documentation/blockdev/ramdisk.txt.
2364
2365        rcutree.blimit= [KNL,BOOT]
2366                        Set maximum number of finished RCU callbacks to process
2367                        in one batch.
2368
2369        rcutree.fanout_leaf=    [KNL,BOOT]
2370                        Increase the number of CPUs assigned to each
2371                        leaf rcu_node structure.  Useful for very large
2372                        systems.
2373
2374        rcutree.qhimark=        [KNL,BOOT]
2375                        Set threshold of queued
2376                        RCU callbacks over which batch limiting is disabled.
2377
2378        rcutree.qlowmark=       [KNL,BOOT]
2379                        Set threshold of queued RCU callbacks below which
2380                        batch limiting is re-enabled.
2381
2382        rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2383                        Suppress RCU CPU stall warning messages.
2384
2385        rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2386                        Set timeout for RCU CPU stall warning messages.
2387
2388        rcutorture.fqs_duration= [KNL,BOOT]
2389                        Set duration of force_quiescent_state bursts.
2390
2391        rcutorture.fqs_holdoff= [KNL,BOOT]
2392                        Set holdoff time within force_quiescent_state bursts.
2393
2394        rcutorture.fqs_stutter= [KNL,BOOT]
2395                        Set wait time between force_quiescent_state bursts.
2396
2397        rcutorture.irqreader= [KNL,BOOT]
2398                        Test RCU readers from irq handlers.
2399
2400        rcutorture.n_barrier_cbs= [KNL,BOOT]
2401                        Set callbacks/threads for rcu_barrier() testing.
2402
2403        rcutorture.nfakewriters= [KNL,BOOT]
2404                        Set number of concurrent RCU writers.  These just
2405                        stress RCU, they don't participate in the actual
2406                        test, hence the "fake".
2407
2408        rcutorture.nreaders= [KNL,BOOT]
2409                        Set number of RCU readers.
2410
2411        rcutorture.onoff_holdoff= [KNL,BOOT]
2412                        Set time (s) after boot for CPU-hotplug testing.
2413
2414        rcutorture.onoff_interval= [KNL,BOOT]
2415                        Set time (s) between CPU-hotplug operations, or
2416                        zero to disable CPU-hotplug testing.
2417
2418        rcutorture.shuffle_interval= [KNL,BOOT]
2419                        Set task-shuffle interval (s).  Shuffling tasks
2420                        allows some CPUs to go into dyntick-idle mode
2421                        during the rcutorture test.
2422
2423        rcutorture.shutdown_secs= [KNL,BOOT]
2424                        Set time (s) after boot system shutdown.  This
2425                        is useful for hands-off automated testing.
2426
2427        rcutorture.stall_cpu= [KNL,BOOT]
2428                        Duration of CPU stall (s) to test RCU CPU stall
2429                        warnings, zero to disable.
2430
2431        rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2432                        Time to wait (s) after boot before inducing stall.
2433
2434        rcutorture.stat_interval= [KNL,BOOT]
2435                        Time (s) between statistics printk()s.
2436
2437        rcutorture.stutter= [KNL,BOOT]
2438                        Time (s) to stutter testing, for example, specifying
2439                        five seconds causes the test to run for five seconds,
2440                        wait for five seconds, and so on.  This tests RCU's
2441                        ability to transition abruptly to and from idle.
2442
2443        rcutorture.test_boost= [KNL,BOOT]
2444                        Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
2445                        "Maybe" means test if the RCU implementation
2446                        under test support RCU priority boosting.
2447
2448        rcutorture.test_boost_duration= [KNL,BOOT]
2449                        Duration (s) of each individual boost test.
2450
2451        rcutorture.test_boost_interval= [KNL,BOOT]
2452                        Interval (s) between each boost test.
2453
2454        rcutorture.test_no_idle_hz= [KNL,BOOT]
2455                        Test RCU's dyntick-idle handling.  See also the
2456                        rcutorture.shuffle_interval parameter.
2457
2458        rcutorture.torture_type= [KNL,BOOT]
2459                        Specify the RCU implementation to test.
2460
2461        rcutorture.verbose= [KNL,BOOT]
2462                        Enable additional printk() statements.
2463
2464        rdinit=         [KNL]
2465                        Format: <full_path>
2466                        Run specified binary instead of /init from the ramdisk,
2467                        used for early userspace startup. See initrd.
2468
2469        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2470                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
2471                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2472
2473        relax_domain_level=
2474                        [KNL, SMP] Set scheduler's default relax_domain_level.
2475                        See Documentation/cgroups/cpusets.txt.
2476
2477        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
2478
2479        reservetop=     [X86-32]
2480                        Format: nn[KMG]
2481                        Reserves a hole at the top of the kernel virtual
2482                        address space.
2483
2484        reservelow=     [X86]
2485                        Format: nn[K]
2486                        Set the amount of memory to reserve for BIOS at
2487                        the bottom of the address space.
2488
2489        reset_devices   [KNL] Force drivers to reset the underlying device
2490                        during initialization.
2491
2492        resume=         [SWSUSP]
2493                        Specify the partition device for software suspend
2494                        Format:
2495                        {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2496
2497        resume_offset=  [SWSUSP]
2498                        Specify the offset from the beginning of the partition
2499                        given by "resume=" at which the swap header is located,
2500                        in <PAGE_SIZE> units (needed only for swap files).
2501                        See  Documentation/power/swsusp-and-swap-files.txt
2502
2503        resumedelay=    [HIBERNATION] Delay (in seconds) to pause before attempting to
2504                        read the resume files
2505
2506        resumewait      [HIBERNATION] Wait (indefinitely) for resume device to show up.
2507                        Useful for devices that are detected asynchronously
2508                        (e.g. USB and MMC devices).
2509
2510        hibernate=      [HIBERNATION]
2511                noresume        Don't check if there's a hibernation image
2512                                present during boot.
2513                nocompress      Don't compress/decompress hibernation images.
2514
2515        retain_initrd   [RAM] Keep initrd memory after extraction
2516
2517        rhash_entries=  [KNL,NET]
2518                        Set number of hash buckets for route cache
2519
2520        riscom8=        [HW,SERIAL]
2521                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2522
2523        ro              [KNL] Mount root device read-only on boot
2524
2525        root=           [KNL] Root filesystem
2526                        See name_to_dev_t comment in init/do_mounts.c.
2527
2528        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
2529                        mount the root filesystem
2530
2531        rootflags=      [KNL] Set root filesystem mount option string
2532
2533        rootfstype=     [KNL] Set root filesystem type
2534
2535        rootwait        [KNL] Wait (indefinitely) for root device to show up.
2536                        Useful for devices that are detected asynchronously
2537                        (e.g. USB and MMC devices).
2538
2539        rw              [KNL] Mount root device read-write on boot
2540
2541        S               [KNL] Run init in single mode
2542
2543        sa1100ir        [NET]
2544                        See drivers/net/irda/sa1100_ir.c.
2545
2546        sbni=           [NET] Granch SBNI12 leased line adapter
2547
2548        sched_debug     [KNL] Enables verbose scheduler debug messages.
2549
2550        skew_tick=      [KNL] Offset the periodic timer tick per cpu to mitigate
2551                        xtime_lock contention on larger systems, and/or RCU lock
2552                        contention on all systems with CONFIG_MAXSMP set.
2553                        Format: { "0" | "1" }
2554                        0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2555                        1 -- enable.
2556                        Note: increases power consumption, thus should only be
2557                        enabled if running jitter sensitive (HPC/RT) workloads.
2558
2559        security=       [SECURITY] Choose a security module to enable at boot.
2560                        If this boot parameter is not specified, only the first
2561                        security module asking for security registration will be
2562                        loaded. An invalid security module name will be treated
2563                        as if no module has been chosen.
2564
2565        selinux=        [SELINUX] Disable or enable SELinux at boot time.
2566                        Format: { "0" | "1" }
2567                        See security/selinux/Kconfig help text.
2568                        0 -- disable.
2569                        1 -- enable.
2570                        Default value is set via kernel config option.
2571                        If enabled at boot time, /selinux/disable can be used
2572                        later to disable prior to initial policy load.
2573
2574        apparmor=       [APPARMOR] Disable or enable AppArmor at boot time
2575                        Format: { "0" | "1" }
2576                        See security/apparmor/Kconfig help text
2577                        0 -- disable.
2578                        1 -- enable.
2579                        Default value is set via kernel config option.
2580
2581        serialnumber    [BUGS=X86-32]
2582
2583        shapers=        [NET]
2584                        Maximal number of shapers.
2585
2586        show_msr=       [x86] show boot-time MSR settings
2587                        Format: { <integer> }
2588                        Show boot-time (BIOS-initialized) MSR settings.
2589                        The parameter means the number of CPUs to show,
2590                        for example 1 means boot CPU only.
2591
2592        simeth=         [IA-64]
2593        simscsi=
2594
2595        slram=          [HW,MTD]
2596
2597        slab_max_order= [MM, SLAB]
2598                        Determines the maximum allowed order for slabs.
2599                        A high setting may cause OOMs due to memory
2600                        fragmentation.  Defaults to 1 for systems with
2601                        more than 32MB of RAM, 0 otherwise.
2602
2603        slub_debug[=options[,slabs]]    [MM, SLUB]
2604                        Enabling slub_debug allows one to determine the
2605                        culprit if slab objects become corrupted. Enabling
2606                        slub_debug can create guard zones around objects and
2607                        may poison objects when not in use. Also tracks the
2608                        last alloc / free. For more information see
2609                        Documentation/vm/slub.txt.
2610
2611        slub_max_order= [MM, SLUB]
2612                        Determines the maximum allowed order for slabs.
2613                        A high setting may cause OOMs due to memory
2614                        fragmentation. For more information see
2615                        Documentation/vm/slub.txt.
2616
2617        slub_min_objects=       [MM, SLUB]
2618                        The minimum number of objects per slab. SLUB will
2619                        increase the slab order up to slub_max_order to
2620                        generate a sufficiently large slab able to contain
2621                        the number of objects indicated. The higher the number
2622                        of objects the smaller the overhead of tracking slabs
2623                        and the less frequently locks need to be acquired.
2624                        For more information see Documentation/vm/slub.txt.
2625
2626        slub_min_order= [MM, SLUB]
2627                        Determines the minimum page order for slabs. Must be
2628                        lower than slub_max_order.
2629                        For more information see Documentation/vm/slub.txt.
2630
2631        slub_nomerge    [MM, SLUB]
2632                        Disable merging of slabs with similar size. May be
2633                        necessary if there is some reason to distinguish
2634                        allocs to different slabs. Debug options disable
2635                        merging on their own.
2636                        For more information see Documentation/vm/slub.txt.
2637
2638        smart2=         [HW]
2639                        Format: <io1>[,<io2>[,...,<io8>]]
2640
2641        smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
2642                        attempt to substitute SMP alternatives once at boot.
2643
2644        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
2645        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
2646        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
2647        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
2648        smsc-ircc2.ircc_irq=    [HW] IRQ line
2649        smsc-ircc2.ircc_dma=    [HW] DMA channel
2650        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2651                                0: Toshiba Satellite 1800 (GP data pin select)
2652                                1: Fast pin select (default)
2653                                2: ATC IRMode
2654
2655        softlockup_panic=
2656                        [KNL] Should the soft-lockup detector generate panics.
2657                        Format: <integer>
2658
2659        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
2660                        See Documentation/laptops/sonypi.txt
2661
2662        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
2663                        See Documentation/serial/specialix.txt.
2664
2665        spia_io_base=   [HW,MTD]
2666        spia_fio_base=
2667        spia_pedr=
2668        spia_peddr=
2669
2670        stacktrace      [FTRACE]
2671                        Enabled the stack tracer on boot up.
2672
2673        stacktrace_filter=[function-list]
2674                        [FTRACE] Limit the functions that the stack tracer
2675                        will trace at boot up. function-list is a comma separated
2676                        list of functions. This list can be changed at run
2677                        time by the stack_trace_filter file in the debugfs
2678                        tracing directory. Note, this enables stack tracing
2679                        and the stacktrace above is not needed.
2680
2681        sti=            [PARISC,HW]
2682                        Format: <num>
2683                        Set the STI (builtin display/keyboard on the HP-PARISC
2684                        machines) console (graphic card) which should be used
2685                        as the initial boot-console.
2686                        See also comment in drivers/video/console/sticore.c.
2687
2688        sti_font=       [HW]
2689                        See comment in drivers/video/console/sticore.c.
2690
2691        stifb=          [HW]
2692                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2693
2694        sunrpc.min_resvport=
2695        sunrpc.max_resvport=
2696                        [NFS,SUNRPC]
2697                        SunRPC servers often require that client requests
2698                        originate from a privileged port (i.e. a port in the
2699                        range 0 < portnr < 1024).
2700                        An administrator who wishes to reserve some of these
2701                        ports for other uses may adjust the range that the
2702                        kernel's sunrpc client considers to be privileged
2703                        using these two parameters to set the minimum and
2704                        maximum port values.
2705
2706        sunrpc.pool_mode=
2707                        [NFS]
2708                        Control how the NFS server code allocates CPUs to
2709                        service thread pools.  Depending on how many NICs
2710                        you have and where their interrupts are bound, this
2711                        option will affect which CPUs will do NFS serving.
2712                        Note: this parameter cannot be changed while the
2713                        NFS server is running.
2714
2715                        auto        the server chooses an appropriate mode
2716                                    automatically using heuristics
2717                        global      a single global pool contains all CPUs
2718                        percpu      one pool for each CPU
2719                        pernode     one pool for each NUMA node (equivalent
2720                                    to global on non-NUMA machines)
2721
2722        sunrpc.tcp_slot_table_entries=
2723        sunrpc.udp_slot_table_entries=
2724                        [NFS,SUNRPC]
2725                        Sets the upper limit on the number of simultaneous
2726                        RPC calls that can be sent from the client to a
2727                        server. Increasing these values may allow you to
2728                        improve throughput, but will also increase the
2729                        amount of memory reserved for use by the client.
2730
2731        swapaccount[=0|1]
2732                        [KNL] Enable accounting of swap in memory resource
2733                        controller if no parameter or 1 is given or disable
2734                        it if 0 is given (See Documentation/cgroups/memory.txt)
2735
2736        swiotlb=        [IA-64] Number of I/O TLB slabs
2737
2738        switches=       [HW,M68k]
2739
2740        sysfs.deprecated=0|1 [KNL]
2741                        Enable/disable old style sysfs layout for old udev
2742                        on older distributions. When this option is enabled
2743                        very new udev will not work anymore. When this option
2744                        is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2745                        in older udev will not work anymore.
2746                        Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2747                        the kernel configuration.
2748
2749        sysrq_always_enabled
2750                        [KNL]
2751                        Ignore sysrq setting - this boot parameter will
2752                        neutralize any effect of /proc/sys/kernel/sysrq.
2753                        Useful for debugging.
2754
2755        tdfx=           [HW,DRM]
2756
2757        test_suspend=   [SUSPEND]
2758                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
2759                        standby suspend) as the system sleep state to briefly
2760                        enter during system startup.  The system is woken from
2761                        this state using a wakeup-capable RTC alarm.
2762
2763        thash_entries=  [KNL,NET]
2764                        Set number of hash buckets for TCP connection
2765
2766        thermal.act=    [HW,ACPI]
2767                        -1: disable all active trip points in all thermal zones
2768                        <degrees C>: override all lowest active trip points
2769
2770        thermal.crt=    [HW,ACPI]
2771                        -1: disable all critical trip points in all thermal zones
2772                        <degrees C>: override all critical trip points
2773
2774        thermal.nocrt=  [HW,ACPI]
2775                        Set to disable actions on ACPI thermal zone
2776                        critical and hot trip points.
2777
2778        thermal.off=    [HW,ACPI]
2779                        1: disable ACPI thermal control
2780
2781        thermal.psv=    [HW,ACPI]
2782                        -1: disable all passive trip points
2783                        <degrees C>: override all passive trip points to this
2784                        value
2785
2786        thermal.tzp=    [HW,ACPI]
2787                        Specify global default ACPI thermal zone polling rate
2788                        <deci-seconds>: poll all this frequency
2789                        0: no polling (default)
2790
2791        threadirqs      [KNL]
2792                        Force threading of all interrupt handlers except those
2793                        marked explicitly IRQF_NO_THREAD.
2794
2795        topology=       [S390]
2796                        Format: {off | on}
2797                        Specify if the kernel should make use of the cpu
2798                        topology information if the hardware supports this.
2799                        The scheduler will make use of this information and
2800                        e.g. base its process migration decisions on it.
2801                        Default is on.
2802
2803        tp720=          [HW,PS2]
2804
2805        tpm_suspend_pcr=[HW,TPM]
2806                        Format: integer pcr id
2807                        Specify that at suspend time, the tpm driver
2808                        should extend the specified pcr with zeros,
2809                        as a workaround for some chips which fail to
2810                        flush the last written pcr on TPM_SaveState.
2811                        This will guarantee that all the other pcrs
2812                        are saved.
2813
2814        trace_buf_size=nn[KMG]
2815                        [FTRACE] will set tracing buffer size.
2816
2817        trace_event=[event-list]
2818                        [FTRACE] Set and start specified trace events in order
2819                        to facilitate early boot debugging.
2820                        See also Documentation/trace/events.txt
2821
2822        transparent_hugepage=
2823                        [KNL]
2824                        Format: [always|madvise|never]
2825                        Can be used to control the default behavior of the system
2826                        with respect to transparent hugepages.
2827                        See Documentation/vm/transhuge.txt for more details.
2828
2829        tsc=            Disable clocksource stability checks for TSC.
2830                        Format: <string>
2831                        [x86] reliable: mark tsc clocksource as reliable, this
2832                        disables clocksource verification at runtime, as well
2833                        as the stability checks done at bootup. Used to enable
2834                        high-resolution timer mode on older hardware, and in
2835                        virtualized environment.
2836                        [x86] noirqtime: Do not use TSC to do irq accounting.
2837                        Used to run time disable IRQ_TIME_ACCOUNTING on any
2838                        platforms where RDTSC is slow and this accounting
2839                        can add overhead.
2840
2841        turbografx.map[2|3]=    [HW,JOY]
2842                        TurboGraFX parallel port interface
2843                        Format:
2844                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2845                        See also Documentation/input/joystick-parport.txt
2846
2847        udbg-immortal   [PPC] When debugging early kernel crashes that
2848                        happen after console_init() and before a proper 
2849                        console driver takes over, this boot options might
2850                        help "seeing" what's going on.
2851
2852        uhash_entries=  [KNL,NET]
2853                        Set number of hash buckets for UDP/UDP-Lite connections
2854
2855        uhci-hcd.ignore_oc=
2856                        [USB] Ignore overcurrent events (default N).
2857                        Some badly-designed motherboards generate lots of
2858                        bogus events, for ports that aren't wired to
2859                        anything.  Set this parameter to avoid log spamming.
2860                        Note that genuine overcurrent events won't be
2861                        reported either.
2862
2863        unknown_nmi_panic
2864                        [X86] Cause panic on unknown NMI.
2865
2866        usbcore.authorized_default=
2867                        [USB] Default USB device authorization:
2868                        (default -1 = authorized except for wireless USB,
2869                        0 = not authorized, 1 = authorized)
2870
2871        usbcore.autosuspend=
2872                        [USB] The autosuspend time delay (in seconds) used
2873                        for newly-detected USB devices (default 2).  This
2874                        is the time required before an idle device will be
2875                        autosuspended.  Devices for which the delay is set
2876                        to a negative value won't be autosuspended at all.
2877
2878        usbcore.usbfs_snoop=
2879                        [USB] Set to log all usbfs traffic (default 0 = off).
2880
2881        usbcore.blinkenlights=
2882                        [USB] Set to cycle leds on hubs (default 0 = off).
2883
2884        usbcore.old_scheme_first=
2885                        [USB] Start with the old device initialization
2886                        scheme (default 0 = off).
2887
2888        usbcore.usbfs_memory_mb=
2889                        [USB] Memory limit (in MB) for buffers allocated by
2890                        usbfs (default = 16, 0 = max = 2047).
2891
2892        usbcore.use_both_schemes=
2893                        [USB] Try the other device initialization scheme
2894                        if the first one fails (default 1 = enabled).
2895
2896        usbcore.initial_descriptor_timeout=
2897                        [USB] Specifies timeout for the initial 64-byte
2898                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2899                        (default 5000 = 5.0 seconds).
2900
2901        usbhid.mousepoll=
2902                        [USBHID] The interval which mice are to be polled at.
2903
2904        usb-storage.delay_use=
2905                        [UMS] The delay in seconds before a new device is
2906                        scanned for Logical Units (default 5).
2907
2908        usb-storage.quirks=
2909                        [UMS] A list of quirks entries to supplement or
2910                        override the built-in unusual_devs list.  List
2911                        entries are separated by commas.  Each entry has
2912                        the form VID:PID:Flags where VID and PID are Vendor
2913                        and Product ID values (4-digit hex numbers) and
2914                        Flags is a set of characters, each corresponding
2915                        to a common usb-storage quirk flag as follows:
2916                                a = SANE_SENSE (collect more than 18 bytes
2917                                        of sense data);
2918                                b = BAD_SENSE (don't collect more than 18
2919                                        bytes of sense data);
2920                                c = FIX_CAPACITY (decrease the reported
2921                                        device capacity by one sector);
2922                                d = NO_READ_DISC_INFO (don't use
2923                                        READ_DISC_INFO command);
2924                                e = NO_READ_CAPACITY_16 (don't use
2925                                        READ_CAPACITY_16 command);
2926                                h = CAPACITY_HEURISTICS (decrease the
2927                                        reported device capacity by one
2928                                        sector if the number is odd);
2929                                i = IGNORE_DEVICE (don't bind to this
2930                                        device);
2931                                l = NOT_LOCKABLE (don't try to lock and
2932                                        unlock ejectable media);
2933                                m = MAX_SECTORS_64 (don't transfer more
2934                                        than 64 sectors = 32 KB at a time);
2935                                n = INITIAL_READ10 (force a retry of the
2936                                        initial READ(10) command);
2937                                o = CAPACITY_OK (accept the capacity
2938                                        reported by the device);
2939                                p = WRITE_CACHE (the device cache is ON
2940                                        by default);
2941                                r = IGNORE_RESIDUE (the device reports
2942                                        bogus residue values);
2943                                s = SINGLE_LUN (the device has only one
2944                                        Logical Unit);
2945                                w = NO_WP_DETECT (don't test whether the
2946                                        medium is write-protected).
2947                        Example: quirks=0419:aaf5:rl,0421:0433:rc
2948
2949        user_debug=     [KNL,ARM]
2950                        Format: <int>
2951                        See arch/arm/Kconfig.debug help text.
2952                                 1 - undefined instruction events
2953                                 2 - system calls
2954                                 4 - invalid data aborts
2955                                 8 - SIGSEGV faults
2956                                16 - SIGBUS faults
2957                        Example: user_debug=31
2958
2959        userpte=
2960                        [X86] Flags controlling user PTE allocations.
2961
2962                                nohigh = do not allocate PTE pages in
2963                                        HIGHMEM regardless of setting
2964                                        of CONFIG_HIGHPTE.
2965
2966        vdso=           [X86,SH]
2967                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2968                        vdso=1: enable VDSO (default)
2969                        vdso=0: disable VDSO mapping
2970
2971        vdso32=         [X86]
2972                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2973                        vdso32=1: enable 32-bit VDSO (default)
2974                        vdso32=0: disable 32-bit VDSO mapping
2975
2976        vector=         [IA-64,SMP]
2977                        vector=percpu: enable percpu vector domain
2978
2979        video=          [FB] Frame buffer configuration
2980                        See Documentation/fb/modedb.txt.
2981
2982        virtio_mmio.device=
2983                        [VMMIO] Memory mapped virtio (platform) device.
2984
2985                                <size>@<baseaddr>:<irq>[:<id>]
2986                        where:
2987                                <size>     := size (can use standard suffixes
2988                                                like K, M and G)
2989                                <baseaddr> := physical base address
2990                                <irq>      := interrupt number (as passed to
2991                                                request_irq())
2992                                <id>       := (optional) platform device id
2993                        example:
2994                                virtio_mmio.device=1K@0x100b0000:48:7
2995
2996                        Can be used multiple times for multiple devices.
2997
2998        vga=            [BOOT,X86-32] Select a particular video mode
2999                        See Documentation/x86/boot.txt and
3000                        Documentation/svga.txt.
3001                        Use vga=ask for menu.
3002                        This is actually a boot loader parameter; the value is
3003                        passed to the kernel using a special protocol.
3004
3005        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3006                        size of <nn>. This can be used to increase the
3007                        minimum size (128MB on x86). It can also be used to
3008                        decrease the size and leave more room for directly
3009                        mapped kernel RAM.
3010
3011        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
3012                        Format: <command>
3013
3014        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
3015                        Format: <command>
3016
3017        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
3018                        Format: <command>
3019
3020        vsyscall=       [X86-64]
3021                        Controls the behavior of vsyscalls (i.e. calls to
3022                        fixed addresses of 0xffffffffff600x00 from legacy
3023                        code).  Most statically-linked binaries and older
3024                        versions of glibc use these calls.  Because these
3025                        functions are at fixed addresses, they make nice
3026                        targets for exploits that can control RIP.
3027
3028                        emulate     [default] Vsyscalls turn into traps and are
3029                                    emulated reasonably safely.
3030
3031                        native      Vsyscalls are native syscall instructions.
3032                                    This is a little bit faster than trapping
3033                                    and makes a few dynamic recompilers work
3034                                    better than they would in emulation mode.
3035                                    It also makes exploits much easier to write.
3036
3037                        none        Vsyscalls don't work at all.  This makes
3038                                    them quite hard to use for exploits but
3039                                    might break your system.
3040
3041        vt.cur_default= [VT] Default cursor shape.
3042                        Format: 0xCCBBAA, where AA, BB, and CC are the same as
3043                        the parameters of the <Esc>[?A;B;Cc escape sequence;
3044                        see VGA-softcursor.txt. Default: 2 = underline.
3045
3046        vt.default_blu= [VT]
3047                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3048                        Change the default blue palette of the console.
3049                        This is a 16-member array composed of values
3050                        ranging from 0-255.
3051
3052        vt.default_grn= [VT]
3053                        Format: <green0>,<green1>,<green2>,...,<green15>
3054                        Change the default green palette of the console.
3055                        This is a 16-member array composed of values
3056                        ranging from 0-255.
3057
3058        vt.default_red= [VT]
3059                        Format: <red0>,<red1>,<red2>,...,<red15>
3060                        Change the default red palette of the console.
3061                        This is a 16-member array composed of values
3062                        ranging from 0-255.
3063
3064        vt.default_utf8=
3065                        [VT]
3066                        Format=<0|1>
3067                        Set system-wide default UTF-8 mode for all tty's.
3068                        Default is 1, i.e. UTF-8 mode is enabled for all
3069                        newly opened terminals.
3070
3071        vt.global_cursor_default=
3072                        [VT]
3073                        Format=<-1|0|1>
3074                        Set system-wide default for whether a cursor
3075                        is shown on new VTs. Default is -1,
3076                        i.e. cursors will be created by default unless
3077                        overridden by individual drivers. 0 will hide
3078                        cursors, 1 will display them.
3079
3080        watchdog timers [HW,WDT] For information on watchdog timers,
3081                        see Documentation/watchdog/watchdog-parameters.txt
3082                        or other driver-specific files in the
3083                        Documentation/watchdog/ directory.
3084
3085        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
3086                        default x2apic cluster mode on platforms
3087                        supporting x2apic.
3088
3089        x86_mrst_timer= [X86-32,APBT]
3090                        Choose timer option for x86 Moorestown MID platform.
3091                        Two valid options are apbt timer only and lapic timer
3092                        plus one apbt timer for broadcast timer.
3093                        x86_mrst_timer=apbt_only | lapic_and_apbt
3094
3095        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3096        xd_geo=         See header of drivers/block/xd.c.
3097
3098        xen_emul_unplug=                [HW,X86,XEN]
3099                        Unplug Xen emulated devices
3100                        Format: [unplug0,][unplug1]
3101                        ide-disks -- unplug primary master IDE devices
3102                        aux-ide-disks -- unplug non-primary-master IDE devices
3103                        nics -- unplug network devices
3104                        all -- unplug all emulated devices (NICs and IDE disks)
3105                        unnecessary -- unplugging emulated devices is
3106                                unnecessary even if the host did not respond to
3107                                the unplug protocol
3108                        never -- do not unplug even if version check succeeds
3109
3110        xirc2ps_cs=     [NET,PCMCIA]
3111                        Format:
3112                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3113
3114______________________________________________________________________
3115
3116TODO:
3117
3118        Add more DRM drivers.
3119
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