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