linux/Documentation/kernel-parameters.txt
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   1                          Kernel Parameters
   2                          ~~~~~~~~~~~~~~~~~
   3
   4The following is a consolidated list of the kernel parameters as implemented
   5(mostly) by the __setup() macro and sorted into English Dictionary order
   6(defined as ignoring all punctuation and sorting digits before letters in a
   7case insensitive manner), and with descriptions where known.
   8
   9Module parameters for loadable modules are specified only as the
  10parameter name with optional '=' and value as appropriate, such as:
  11
  12        modprobe usbcore blinkenlights=1
  13
  14Module parameters for modules that are built into the kernel image
  15are specified on the kernel command line with the module name plus
  16'.' plus parameter name, with '=' and value if appropriate, such as:
  17
  18        usbcore.blinkenlights=1
  19
  20Hyphens (dashes) and underscores are equivalent in parameter names, so
  21        log_buf_len=1M print-fatal-signals=1
  22can also be entered as
  23        log-buf-len=1M print_fatal_signals=1
  24
  25
  26This document may not be entirely up to date and comprehensive. The command
  27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  28module. Loadable modules, after being loaded into the running kernel, also
  29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  30parameters may be changed at runtime by the command
  31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  32
  33The parameters listed below are only valid if certain kernel build options were
  34enabled and if respective hardware is present. The text in square brackets at
  35the beginning of each description states the restrictions within which a
  36parameter is applicable:
  37
  38        ACPI    ACPI support is enabled.
  39        AGP     AGP (Accelerated Graphics Port) is enabled.
  40        ALSA    ALSA sound support is enabled.
  41        APIC    APIC support is enabled.
  42        APM     Advanced Power Management support is enabled.
  43        ARM     ARM architecture is enabled.
  44        AVR32   AVR32 architecture is enabled.
  45        AX25    Appropriate AX.25 support is enabled.
  46        BLACKFIN Blackfin architecture is enabled.
  47        DRM     Direct Rendering Management support is enabled.
  48        DYNAMIC_DEBUG Build in debug messages and enable them at runtime
  49        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
  50        EFI     EFI Partitioning (GPT) is enabled
  51        EIDE    EIDE/ATAPI support is enabled.
  52        EVM     Extended Verification Module
  53        FB      The frame buffer device is enabled.
  54        FTRACE  Function tracing enabled.
  55        GCOV    GCOV profiling is enabled.
  56        HW      Appropriate hardware is enabled.
  57        IA-64   IA-64 architecture is enabled.
  58        IMA     Integrity measurement architecture is enabled.
  59        IOSCHED More than one I/O scheduler is enabled.
  60        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
  61        IPV6    IPv6 support is enabled.
  62        ISAPNP  ISA PnP code is enabled.
  63        ISDN    Appropriate ISDN support is enabled.
  64        JOY     Appropriate joystick support is enabled.
  65        KGDB    Kernel debugger support is enabled.
  66        KVM     Kernel Virtual Machine support is enabled.
  67        LIBATA  Libata driver is enabled
  68        LP      Printer support is enabled.
  69        LOOP    Loopback device support is enabled.
  70        M68k    M68k architecture is enabled.
  71                        These options have more detailed description inside of
  72                        Documentation/m68k/kernel-options.txt.
  73        MDA     MDA console support is enabled.
  74        MIPS    MIPS architecture is enabled.
  75        MOUSE   Appropriate mouse support is enabled.
  76        MSI     Message Signaled Interrupts (PCI).
  77        MTD     MTD (Memory Technology Device) support is enabled.
  78        NET     Appropriate network support is enabled.
  79        NUMA    NUMA support is enabled.
  80        NFS     Appropriate NFS support is enabled.
  81        OSS     OSS sound support is enabled.
  82        PV_OPS  A paravirtualized kernel is enabled.
  83        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
  84        PARISC  The PA-RISC architecture is enabled.
  85        PCI     PCI bus support is enabled.
  86        PCIE    PCI Express support is enabled.
  87        PCMCIA  The PCMCIA subsystem is enabled.
  88        PNP     Plug & Play support is enabled.
  89        PPC     PowerPC architecture is enabled.
  90        PPT     Parallel port support is enabled.
  91        PS2     Appropriate PS/2 support is enabled.
  92        RAM     RAM disk support is enabled.
  93        S390    S390 architecture is enabled.
  94        SCSI    Appropriate SCSI support is enabled.
  95                        A lot of drivers have their options described inside
  96                        the Documentation/scsi/ sub-directory.
  97        SECURITY Different security models are enabled.
  98        SELINUX SELinux support is enabled.
  99        APPARMOR AppArmor support is enabled.
 100        SERIAL  Serial support is enabled.
 101        SH      SuperH architecture is enabled.
 102        SMP     The kernel is an SMP kernel.
 103        SPARC   Sparc architecture is enabled.
 104        SWSUSP  Software suspend (hibernation) is enabled.
 105        SUSPEND System suspend states are enabled.
 106        TPM     TPM drivers are enabled.
 107        TS      Appropriate touchscreen support is enabled.
 108        UMS     USB Mass Storage support is enabled.
 109        USB     USB support is enabled.
 110        USBHID  USB Human Interface Device support is enabled.
 111        V4L     Video For Linux support is enabled.
 112        VMMIO   Driver for memory mapped virtio devices is enabled.
 113        VGA     The VGA console has been enabled.
 114        VT      Virtual terminal support is enabled.
 115        WDT     Watchdog support is enabled.
 116        XT      IBM PC/XT MFM hard disk support is enabled.
 117        X86-32  X86-32, aka i386 architecture is enabled.
 118        X86-64  X86-64 architecture is enabled.
 119                        More X86-64 boot options can be found in
 120                        Documentation/x86/x86_64/boot-options.txt .
 121        X86     Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
 122        XEN     Xen support is enabled
 123
 124In addition, the following text indicates that the option:
 125
 126        BUGS=   Relates to possible processor bugs on the said processor.
 127        KNL     Is a kernel start-up parameter.
 128        BOOT    Is a boot loader parameter.
 129
 130Parameters denoted with BOOT are actually interpreted by the boot
 131loader, and have no meaning to the kernel directly.
 132Do not modify the syntax of boot loader parameters without extreme
 133need or coordination with <Documentation/x86/boot.txt>.
 134
 135There are also arch-specific kernel-parameters not documented here.
 136See for example <Documentation/x86/x86_64/boot-options.txt>.
 137
 138Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
 139a trailing = on the name of any parameter states that that parameter will
 140be entered as an environment variable, whereas its absence indicates that
 141it will appear as a kernel argument readable via /proc/cmdline by programs
 142running once the system is up.
 143
 144The number of kernel parameters is not limited, but the length of the
 145complete command line (parameters including spaces etc.) is limited to
 146a fixed number of characters. This limit depends on the architecture
 147and is between 256 and 4096 characters. It is defined in the file
 148./include/asm/setup.h as COMMAND_LINE_SIZE.
 149
 150Finally, the [KMG] suffix is commonly described after a number of kernel
 151parameter values. These 'K', 'M', and 'G' letters represent the _binary_
 152multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
 153bytes respectively. Such letter suffixes can also be entirely omitted.
 154
 155
 156        acpi=           [HW,ACPI,X86]
 157                        Advanced Configuration and Power Interface
 158                        Format: { force | off | strict | noirq | rsdt }
 159                        force -- enable ACPI if default was off
 160                        off -- disable ACPI if default was on
 161                        noirq -- do not use ACPI for IRQ routing
 162                        strict -- Be less tolerant of platforms that are not
 163                                strictly ACPI specification compliant.
 164                        rsdt -- prefer RSDT over (default) XSDT
 165                        copy_dsdt -- copy DSDT to memory
 166
 167                        See also Documentation/power/runtime_pm.txt, pci=noacpi
 168
 169        acpi_rsdp=      [ACPI,EFI,KEXEC]
 170                        Pass the RSDP address to the kernel, mostly used
 171                        on machines running EFI runtime service to boot the
 172                        second kernel for kdump.
 173
 174        acpi_apic_instance=     [ACPI, IOAPIC]
 175                        Format: <int>
 176                        2: use 2nd APIC table, if available
 177                        1,0: use 1st APIC table
 178                        default: 0
 179
 180        acpi_backlight= [HW,ACPI]
 181                        acpi_backlight=vendor
 182                        acpi_backlight=video
 183                        If set to vendor, prefer vendor specific driver
 184                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
 185                        of the ACPI video.ko driver.
 186
 187        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
 188        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
 189                        Format: <int>
 190                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
 191                        debug output.  Bits in debug_layer correspond to a
 192                        _COMPONENT in an ACPI source file, e.g.,
 193                            #define _COMPONENT ACPI_PCI_COMPONENT
 194                        Bits in debug_level correspond to a level in
 195                        ACPI_DEBUG_PRINT statements, e.g.,
 196                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
 197                        The debug_level mask defaults to "info".  See
 198                        Documentation/acpi/debug.txt for more information about
 199                        debug layers and levels.
 200
 201                        Enable processor driver info messages:
 202                            acpi.debug_layer=0x20000000
 203                        Enable PCI/PCI interrupt routing info messages:
 204                            acpi.debug_layer=0x400000
 205                        Enable AML "Debug" output, i.e., stores to the Debug
 206                        object while interpreting AML:
 207                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
 208                        Enable all messages related to ACPI hardware:
 209                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
 210
 211                        Some values produce so much output that the system is
 212                        unusable.  The "log_buf_len" parameter may be useful
 213                        if you need to capture more output.
 214
 215        acpi_irq_balance [HW,ACPI]
 216                        ACPI will balance active IRQs
 217                        default in APIC mode
 218
 219        acpi_irq_nobalance [HW,ACPI]
 220                        ACPI will not move active IRQs (default)
 221                        default in PIC mode
 222
 223        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 224                        Format: <irq>,<irq>...
 225
 226        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
 227                        use by PCI
 228                        Format: <irq>,<irq>...
 229
 230        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT
 231
 232        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
 233                        Format: To spoof as Windows 98: ="Microsoft Windows"
 234
 235        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
 236                        acpi_osi="string1"      # add string1 -- only one string
 237                        acpi_osi="!string2"     # remove built-in string2
 238                        acpi_osi=               # disable all strings
 239
 240        acpi_pm_good    [X86]
 241                        Override the pmtimer bug detection: force the kernel
 242                        to assume that this machine's pmtimer latches its value
 243                        and always returns good values.
 244
 245        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
 246                        Format: { level | edge | high | low }
 247
 248        acpi_serialize  [HW,ACPI] force serialization of AML methods
 249
 250        acpi_skip_timer_override [HW,ACPI]
 251                        Recognize and ignore IRQ0/pin2 Interrupt Override.
 252                        For broken nForce2 BIOS resulting in XT-PIC timer.
 253
 254        acpi_sleep=     [HW,ACPI] Sleep options
 255                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
 256                                  old_ordering, nonvs, sci_force_enable }
 257                        See Documentation/power/video.txt for information on
 258                        s3_bios and s3_mode.
 259                        s3_beep is for debugging; it makes the PC's speaker beep
 260                        as soon as the kernel's real-mode entry point is called.
 261                        s4_nohwsig prevents ACPI hardware signature from being
 262                        used during resume from hibernation.
 263                        old_ordering causes the ACPI 1.0 ordering of the _PTS
 264                        control method, with respect to putting devices into
 265                        low power states, to be enforced (the ACPI 2.0 ordering
 266                        of _PTS is used by default).
 267                        nonvs prevents the kernel from saving/restoring the
 268                        ACPI NVS memory during suspend/hibernation and resume.
 269                        sci_force_enable causes the kernel to set SCI_EN directly
 270                        on resume from S1/S3 (which is against the ACPI spec,
 271                        but some broken systems don't work without it).
 272
 273        acpi_use_timer_override [HW,ACPI]
 274                        Use timer override. For some broken Nvidia NF5 boards
 275                        that require a timer override, but don't have HPET
 276
 277        acpi_enforce_resources= [ACPI]
 278                        { strict | lax | no }
 279                        Check for resource conflicts between native drivers
 280                        and ACPI OperationRegions (SystemIO and SystemMemory
 281                        only). IO ports and memory declared in ACPI might be
 282                        used by the ACPI subsystem in arbitrary AML code and
 283                        can interfere with legacy drivers.
 284                        strict (default): access to resources claimed by ACPI
 285                        is denied; legacy drivers trying to access reserved
 286                        resources will fail to bind to device using them.
 287                        lax: access to resources claimed by ACPI is allowed;
 288                        legacy drivers trying to access reserved resources
 289                        will bind successfully but a warning message is logged.
 290                        no: ACPI OperationRegions are not marked as reserved,
 291                        no further checks are performed.
 292
 293        add_efi_memmap  [EFI; X86] Include EFI memory map in
 294                        kernel's map of available physical RAM.
 295
 296        agp=            [AGP]
 297                        { off | try_unsupported }
 298                        off: disable AGP support
 299                        try_unsupported: try to drive unsupported chipsets
 300                                (may crash computer or cause data corruption)
 301
 302        ALSA            [HW,ALSA]
 303                        See Documentation/sound/alsa/alsa-parameters.txt
 304
 305        alignment=      [KNL,ARM]
 306                        Allow the default userspace alignment fault handler
 307                        behaviour to be specified.  Bit 0 enables warnings,
 308                        bit 1 enables fixups, and bit 2 sends a segfault.
 309
 310        align_va_addr=  [X86-64]
 311                        Align virtual addresses by clearing slice [14:12] when
 312                        allocating a VMA at process creation time. This option
 313                        gives you up to 3% performance improvement on AMD F15h
 314                        machines (where it is enabled by default) for a
 315                        CPU-intensive style benchmark, and it can vary highly in
 316                        a microbenchmark depending on workload and compiler.
 317
 318                        32: only for 32-bit processes
 319                        64: only for 64-bit processes
 320                        on: enable for both 32- and 64-bit processes
 321                        off: disable for both 32- and 64-bit processes
 322
 323        amd_iommu=      [HW,X86-64]
 324                        Pass parameters to the AMD IOMMU driver in the system.
 325                        Possible values are:
 326                        fullflush - enable flushing of IO/TLB entries when
 327                                    they are unmapped. Otherwise they are
 328                                    flushed before they will be reused, which
 329                                    is a lot of faster
 330                        off       - do not initialize any AMD IOMMU found in
 331                                    the system
 332                        force_isolation - Force device isolation for all
 333                                          devices. The IOMMU driver is not
 334                                          allowed anymore to lift isolation
 335                                          requirements as needed. This option
 336                                          does not override iommu=pt
 337
 338        amd_iommu_dump= [HW,X86-64]
 339                        Enable AMD IOMMU driver option to dump the ACPI table
 340                        for AMD IOMMU. With this option enabled, AMD IOMMU
 341                        driver will print ACPI tables for AMD IOMMU during
 342                        IOMMU initialization.
 343
 344        amijoy.map=     [HW,JOY] Amiga joystick support
 345                        Map of devices attached to JOY0DAT and JOY1DAT
 346                        Format: <a>,<b>
 347                        See also Documentation/input/joystick.txt
 348
 349        analog.map=     [HW,JOY] Analog joystick and gamepad support
 350                        Specifies type or capabilities of an analog joystick
 351                        connected to one of 16 gameports
 352                        Format: <type1>,<type2>,..<type16>
 353
 354        apc=            [HW,SPARC]
 355                        Power management functions (SPARCstation-4/5 + deriv.)
 356                        Format: noidle
 357                        Disable APC CPU standby support. SPARCstation-Fox does
 358                        not play well with APC CPU idle - disable it if you have
 359                        APC and your system crashes randomly.
 360
 361        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
 362                        Change the output verbosity whilst booting
 363                        Format: { quiet (default) | verbose | debug }
 364                        Change the amount of debugging information output
 365                        when initialising the APIC and IO-APIC components.
 366
 367        autoconf=       [IPV6]
 368                        See Documentation/networking/ipv6.txt.
 369
 370        show_lapic=     [APIC,X86] Advanced Programmable Interrupt Controller
 371                        Limit apic dumping. The parameter defines the maximal
 372                        number of local apics being dumped. Also it is possible
 373                        to set it to "all" by meaning -- no limit here.
 374                        Format: { 1 (default) | 2 | ... | all }.
 375                        The parameter valid if only apic=debug or
 376                        apic=verbose is specified.
 377                        Example: apic=debug show_lapic=all
 378
 379        apm=            [APM] Advanced Power Management
 380                        See header of arch/x86/kernel/apm_32.c.
 381
 382        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 383                        Format: <io>,<irq>,<nodeID>
 384
 385        ataflop=        [HW,M68k]
 386
 387        atarimouse=     [HW,MOUSE] Atari Mouse
 388
 389        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 390                        EzKey and similar keyboards
 391
 392        atkbd.reset=    [HW] Reset keyboard during initialization
 393
 394        atkbd.set=      [HW] Select keyboard code set
 395                        Format: <int> (2 = AT (default), 3 = PS/2)
 396
 397        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 398                        keyboards
 399
 400        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 401                        Format: <bool> (0 = real, 1 = synthetic (default))
 402
 403        atkbd.softrepeat= [HW]
 404                        Use software keyboard repeat
 405
 406        baycom_epp=     [HW,AX25]
 407                        Format: <io>,<mode>
 408
 409        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 410                        Format: <io>,<mode>
 411                        See header of drivers/net/hamradio/baycom_par.c.
 412
 413        baycom_ser_fdx= [HW,AX25]
 414                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 415                        Format: <io>,<irq>,<mode>[,<baud>]
 416                        See header of drivers/net/hamradio/baycom_ser_fdx.c.
 417
 418        baycom_ser_hdx= [HW,AX25]
 419                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 420                        Format: <io>,<irq>,<mode>
 421                        See header of drivers/net/hamradio/baycom_ser_hdx.c.
 422
 423        boot_delay=     Milliseconds to delay each printk during boot.
 424                        Values larger than 10 seconds (10000) are changed to
 425                        no delay (0).
 426                        Format: integer
 427
 428        bootmem_debug   [KNL] Enable bootmem allocator debug messages.
 429
 430        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 431        bttv.radio=     Most important insmod options are available as
 432                        kernel args too.
 433        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 434        bttv.tuner=
 435
 436        bulk_remove=off [PPC]  This parameter disables the use of the pSeries
 437                        firmware feature for flushing multiple hpte entries
 438                        at a time.
 439
 440        c101=           [NET] Moxa C101 synchronous serial card
 441
 442        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
 443                        Sometimes CPU hardware bugs make them report the cache
 444                        size incorrectly. The kernel will attempt work arounds
 445                        to fix known problems, but for some CPUs it is not
 446                        possible to determine what the correct size should be.
 447                        This option provides an override for these situations.
 448
 449        ccw_timeout_log [S390]
 450                        See Documentation/s390/CommonIO for details.
 451
 452        cgroup_disable= [KNL] Disable a particular controller
 453                        Format: {name of the controller(s) to disable}
 454                                {Currently supported controllers - "memory"}
 455
 456        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 457                        Format: { "0" | "1" }
 458                        See security/selinux/Kconfig help text.
 459                        0 -- check protection applied by kernel (includes
 460                                any implied execute protection).
 461                        1 -- check protection requested by application.
 462                        Default value is set via a kernel config option.
 463                        Value can be changed at runtime via
 464                                /selinux/checkreqprot.
 465
 466        cio_ignore=     [S390]
 467                        See Documentation/s390/CommonIO for details.
 468
 469        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
 470                        [Deprecated]
 471                        Forces specified clocksource (if available) to be used
 472                        when calculating gettimeofday(). If specified
 473                        clocksource is not available, it defaults to PIT.
 474                        Format: { pit | tsc | cyclone | pmtmr }
 475
 476        clocksource=    Override the default clocksource
 477                        Format: <string>
 478                        Override the default clocksource and use the clocksource
 479                        with the name specified.
 480                        Some clocksource names to choose from, depending on
 481                        the platform:
 482                        [all] jiffies (this is the base, fallback clocksource)
 483                        [ACPI] acpi_pm
 484                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
 485                                pxa_timer,timer3,32k_counter,timer0_1
 486                        [AVR32] avr32
 487                        [X86-32] pit,hpet,tsc;
 488                                scx200_hrt on Geode; cyclone on IBM x440
 489                        [MIPS] MIPS
 490                        [PARISC] cr16
 491                        [S390] tod
 492                        [SH] SuperH
 493                        [SPARC64] tick
 494                        [X86-64] hpet,tsc
 495
 496        clearcpuid=BITNUM [X86]
 497                        Disable CPUID feature X for the kernel. See
 498                        arch/x86/include/asm/cpufeature.h for the valid bit
 499                        numbers. Note the Linux specific bits are not necessarily
 500                        stable over kernel options, but the vendor specific
 501                        ones should be.
 502                        Also note that user programs calling CPUID directly
 503                        or using the feature without checking anything
 504                        will still see it. This just prevents it from
 505                        being used by the kernel or shown in /proc/cpuinfo.
 506                        Also note the kernel might malfunction if you disable
 507                        some critical bits.
 508
 509        cma=nn[MG]      [ARM,KNL]
 510                        Sets the size of kernel global memory area for contiguous
 511                        memory allocations. For more information, see
 512                        include/linux/dma-contiguous.h
 513
 514        cmo_free_hint=  [PPC] Format: { yes | no }
 515                        Specify whether pages are marked as being inactive
 516                        when they are freed.  This is used in CMO environments
 517                        to determine OS memory pressure for page stealing by
 518                        a hypervisor.
 519                        Default: yes
 520
 521        coherent_pool=nn[KMG]   [ARM,KNL]
 522                        Sets the size of memory pool for coherent, atomic dma
 523                        allocations, by default set to 256K.
 524
 525        code_bytes      [X86] How many bytes of object code to print
 526                        in an oops report.
 527                        Range: 0 - 8192
 528                        Default: 64
 529
 530        com20020=       [HW,NET] ARCnet - COM20020 chipset
 531                        Format:
 532                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 533
 534        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 535                        Format: <io>[,<irq>]
 536
 537        com90xx=        [HW,NET]
 538                        ARCnet - COM90xx chipset (memory-mapped buffers)
 539                        Format: <io>[,<irq>[,<memstart>]]
 540
 541        condev=         [HW,S390] console device
 542        conmode=
 543
 544        console=        [KNL] Output console device and options.
 545
 546                tty<n>  Use the virtual console device <n>.
 547
 548                ttyS<n>[,options]
 549                ttyUSB0[,options]
 550                        Use the specified serial port.  The options are of
 551                        the form "bbbbpnf", where "bbbb" is the baud rate,
 552                        "p" is parity ("n", "o", or "e"), "n" is number of
 553                        bits, and "f" is flow control ("r" for RTS or
 554                        omit it).  Default is "9600n8".
 555
 556                        See Documentation/serial-console.txt for more
 557                        information.  See
 558                        Documentation/networking/netconsole.txt for an
 559                        alternative.
 560
 561                uart[8250],io,<addr>[,options]
 562                uart[8250],mmio,<addr>[,options]
 563                        Start an early, polled-mode console on the 8250/16550
 564                        UART at the specified I/O port or MMIO address,
 565                        switching to the matching ttyS device later.  The
 566                        options are the same as for ttyS, above.
 567                hvc<n>  Use the hypervisor console device <n>. This is for
 568                        both Xen and PowerPC hypervisors.
 569
 570                If the device connected to the port is not a TTY but a braille
 571                device, prepend "brl," before the device type, for instance
 572                        console=brl,ttyS0
 573                For now, only VisioBraille is supported.
 574
 575        consoleblank=   [KNL] The console blank (screen saver) timeout in
 576                        seconds. Defaults to 10*60 = 10mins. A value of 0
 577                        disables the blank timer.
 578
 579        coredump_filter=
 580                        [KNL] Change the default value for
 581                        /proc/<pid>/coredump_filter.
 582                        See also Documentation/filesystems/proc.txt.
 583
 584        cpuidle.off=1   [CPU_IDLE]
 585                        disable the cpuidle sub-system
 586
 587        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 588                        Format:
 589                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 590
 591        crashkernel=size[KMG][@offset[KMG]]
 592                        [KNL] Using kexec, Linux can switch to a 'crash kernel'
 593                        upon panic. This parameter reserves the physical
 594                        memory region [offset, offset + size] for that kernel
 595                        image. If '@offset' is omitted, then a suitable offset
 596                        is selected automatically. Check
 597                        Documentation/kdump/kdump.txt for further details.
 598
 599        crashkernel=range1:size1[,range2:size2,...][@offset]
 600                        [KNL] Same as above, but depends on the memory
 601                        in the running system. The syntax of range is
 602                        start-[end] where start and end are both
 603                        a memory unit (amount[KMG]). See also
 604                        Documentation/kdump/kdump.txt for an example.
 605
 606        crashkernel=size[KMG],high
 607                        [KNL, x86_64] range could be above 4G. Allow kernel
 608                        to allocate physical memory region from top, so could
 609                        be above 4G if system have more than 4G ram installed.
 610                        Otherwise memory region will be allocated below 4G, if
 611                        available.
 612                        It will be ignored if crashkernel=X is specified.
 613        crashkernel=size[KMG],low
 614                        [KNL, x86_64] range under 4G. When crashkernel=X,high
 615                        is passed, kernel could allocate physical memory region
 616                        above 4G, that cause second kernel crash on system
 617                        that require some amount of low memory, e.g. swiotlb
 618                        requires at least 64M+32K low memory.  Kernel would
 619                        try to allocate 72M below 4G automatically.
 620                        This one let user to specify own low range under 4G
 621                        for second kernel instead.
 622                        0: to disable low allocation.
 623                        It will be ignored when crashkernel=X,high is not used
 624                        or memory reserved is below 4G.
 625
 626        cs89x0_dma=     [HW,NET]
 627                        Format: <dma>
 628
 629        cs89x0_media=   [HW,NET]
 630                        Format: { rj45 | aui | bnc }
 631
 632        dasd=           [HW,NET]
 633                        See header of drivers/s390/block/dasd_devmap.c.
 634
 635        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 636                        (one device per port)
 637                        Format: <port#>,<type>
 638                        See also Documentation/input/joystick-parport.txt
 639
 640        ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
 641                        time. See Documentation/dynamic-debug-howto.txt for
 642                        details.  Deprecated, see dyndbg.
 643
 644        debug           [KNL] Enable kernel debugging (events log level).
 645
 646        debug_locks_verbose=
 647                        [KNL] verbose self-tests
 648                        Format=<0|1>
 649                        Print debugging info while doing the locking API
 650                        self-tests.
 651                        We default to 0 (no extra messages), setting it to
 652                        1 will print _a lot_ more information - normally
 653                        only useful to kernel developers.
 654
 655        debug_objects   [KNL] Enable object debugging
 656
 657        no_debug_objects
 658                        [KNL] Disable object debugging
 659
 660        debug_guardpage_minorder=
 661                        [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
 662                        parameter allows control of the order of pages that will
 663                        be intentionally kept free (and hence protected) by the
 664                        buddy allocator. Bigger value increase the probability
 665                        of catching random memory corruption, but reduce the
 666                        amount of memory for normal system use. The maximum
 667                        possible value is MAX_ORDER/2.  Setting this parameter
 668                        to 1 or 2 should be enough to identify most random
 669                        memory corruption problems caused by bugs in kernel or
 670                        driver code when a CPU writes to (or reads from) a
 671                        random memory location. Note that there exists a class
 672                        of memory corruptions problems caused by buggy H/W or
 673                        F/W or by drivers badly programing DMA (basically when
 674                        memory is written at bus level and the CPU MMU is
 675                        bypassed) which are not detectable by
 676                        CONFIG_DEBUG_PAGEALLOC, hence this option will not help
 677                        tracking down these problems.
 678
 679        debugpat        [X86] Enable PAT debugging
 680
 681        decnet.addr=    [HW,NET]
 682                        Format: <area>[,<node>]
 683                        See also Documentation/networking/decnet.txt.
 684
 685        default_hugepagesz=
 686                        [same as hugepagesz=] The size of the default
 687                        HugeTLB page size. This is the size represented by
 688                        the legacy /proc/ hugepages APIs, used for SHM, and
 689                        default size when mounting hugetlbfs filesystems.
 690                        Defaults to the default architecture's huge page size
 691                        if not specified.
 692
 693        dhash_entries=  [KNL]
 694                        Set number of hash buckets for dentry cache.
 695
 696        digi=           [HW,SERIAL]
 697                        IO parameters + enable/disable command.
 698
 699        digiepca=       [HW,SERIAL]
 700                        See drivers/char/README.epca and
 701                        Documentation/serial/digiepca.txt.
 702
 703        disable=        [IPV6]
 704                        See Documentation/networking/ipv6.txt.
 705
 706        disable_ddw     [PPC/PSERIES]
 707                        Disable Dynamic DMA Window support. Use this if
 708                        to workaround buggy firmware.
 709
 710        disable_ipv6=   [IPV6]
 711                        See Documentation/networking/ipv6.txt.
 712
 713        disable_mtrr_cleanup [X86]
 714                        The kernel tries to adjust MTRR layout from continuous
 715                        to discrete, to make X server driver able to add WB
 716                        entry later. This parameter disables that.
 717
 718        disable_mtrr_trim [X86, Intel and AMD only]
 719                        By default the kernel will trim any uncacheable
 720                        memory out of your available memory pool based on
 721                        MTRR settings.  This parameter disables that behavior,
 722                        possibly causing your machine to run very slowly.
 723
 724        disable_timer_pin_1 [X86]
 725                        Disable PIN 1 of APIC timer
 726                        Can be useful to work around chipset bugs.
 727
 728        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
 729                        this option disables the debugging code at boot.
 730
 731        dma_debug_entries=<number>
 732                        This option allows to tune the number of preallocated
 733                        entries for DMA-API debugging code. One entry is
 734                        required per DMA-API allocation. Use this if the
 735                        DMA-API debugging code disables itself because the
 736                        architectural default is too low.
 737
 738        dma_debug_driver=<driver_name>
 739                        With this option the DMA-API debugging driver
 740                        filter feature can be enabled at boot time. Just
 741                        pass the driver to filter for as the parameter.
 742                        The filter can be disabled or changed to another
 743                        driver later using sysfs.
 744
 745        drm_kms_helper.edid_firmware=[<connector>:]<file>
 746                        Broken monitors, graphic adapters and KVMs may
 747                        send no or incorrect EDID data sets. This parameter
 748                        allows to specify an EDID data set in the
 749                        /lib/firmware directory that is used instead.
 750                        Generic built-in EDID data sets are used, if one of
 751                        edid/1024x768.bin, edid/1280x1024.bin,
 752                        edid/1680x1050.bin, or edid/1920x1080.bin is given
 753                        and no file with the same name exists. Details and
 754                        instructions how to build your own EDID data are
 755                        available in Documentation/EDID/HOWTO.txt. An EDID
 756                        data set will only be used for a particular connector,
 757                        if its name and a colon are prepended to the EDID
 758                        name.
 759
 760        dscc4.setup=    [NET]
 761
 762        dyndbg[="val"]          [KNL,DYNAMIC_DEBUG]
 763        module.dyndbg[="val"]
 764                        Enable debug messages at boot time.  See
 765                        Documentation/dynamic-debug-howto.txt for details.
 766
 767        earlycon=       [KNL] Output early console device and options.
 768                uart[8250],io,<addr>[,options]
 769                uart[8250],mmio,<addr>[,options]
 770                uart[8250],mmio32,<addr>[,options]
 771                        Start an early, polled-mode console on the 8250/16550
 772                        UART at the specified I/O port or MMIO address.
 773                        MMIO inter-register address stride is either 8-bit
 774                        (mmio) or 32-bit (mmio32).
 775                        The options are the same as for ttyS, above.
 776
 777        earlyprintk=    [X86,SH,BLACKFIN]
 778                        earlyprintk=vga
 779                        earlyprintk=xen
 780                        earlyprintk=serial[,ttySn[,baudrate]]
 781                        earlyprintk=ttySn[,baudrate]
 782                        earlyprintk=dbgp[debugController#]
 783
 784                        Append ",keep" to not disable it when the real console
 785                        takes over.
 786
 787                        Only vga or serial or usb debug port at a time.
 788
 789                        Currently only ttyS0 and ttyS1 are supported.
 790
 791                        Interaction with the standard serial driver is not
 792                        very good.
 793
 794                        The VGA output is eventually overwritten by the real
 795                        console.
 796
 797                        The xen output can only be used by Xen PV guests.
 798
 799        ekgdboc=        [X86,KGDB] Allow early kernel console debugging
 800                        ekgdboc=kbd
 801
 802                        This is designed to be used in conjunction with
 803                        the boot argument: earlyprintk=vga
 804
 805        edd=            [EDD]
 806                        Format: {"off" | "on" | "skip[mbr]"}
 807
 808        efi_no_storage_paranoia [EFI; X86]
 809                        Using this parameter you can use more than 50% of
 810                        your efi variable storage. Use this parameter only if
 811                        you are really sure that your UEFI does sane gc and
 812                        fulfills the spec otherwise your board may brick.
 813
 814        eisa_irq_edge=  [PARISC,HW]
 815                        See header of drivers/parisc/eisa.c.
 816
 817        elanfreq=       [X86-32]
 818                        See comment before function elanfreq_setup() in
 819                        arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 820
 821        elevator=       [IOSCHED]
 822                        Format: {"cfq" | "deadline" | "noop"}
 823                        See Documentation/block/cfq-iosched.txt and
 824                        Documentation/block/deadline-iosched.txt for details.
 825
 826        elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
 827                        Specifies physical address of start of kernel core
 828                        image elf header and optionally the size. Generally
 829                        kexec loader will pass this option to capture kernel.
 830                        See Documentation/kdump/kdump.txt for details.
 831
 832        enable_mtrr_cleanup [X86]
 833                        The kernel tries to adjust MTRR layout from continuous
 834                        to discrete, to make X server driver able to add WB
 835                        entry later. This parameter enables that.
 836
 837        enable_timer_pin_1 [X86]
 838                        Enable PIN 1 of APIC timer
 839                        Can be useful to work around chipset bugs
 840                        (in particular on some ATI chipsets).
 841                        The kernel tries to set a reasonable default.
 842
 843        enforcing       [SELINUX] Set initial enforcing status.
 844                        Format: {"0" | "1"}
 845                        See security/selinux/Kconfig help text.
 846                        0 -- permissive (log only, no denials).
 847                        1 -- enforcing (deny and log).
 848                        Default value is 0.
 849                        Value can be changed at runtime via /selinux/enforce.
 850
 851        erst_disable    [ACPI]
 852                        Disable Error Record Serialization Table (ERST)
 853                        support.
 854
 855        ether=          [HW,NET] Ethernet cards parameters
 856                        This option is obsoleted by the "netdev=" option, which
 857                        has equivalent usage. See its documentation for details.
 858
 859        evm=            [EVM]
 860                        Format: { "fix" }
 861                        Permit 'security.evm' to be updated regardless of
 862                        current integrity status.
 863
 864        failslab=
 865        fail_page_alloc=
 866        fail_make_request=[KNL]
 867                        General fault injection mechanism.
 868                        Format: <interval>,<probability>,<space>,<times>
 869                        See also Documentation/fault-injection/.
 870
 871        floppy=         [HW]
 872                        See Documentation/blockdev/floppy.txt.
 873
 874        force_pal_cache_flush
 875                        [IA-64] Avoid check_sal_cache_flush which may hang on
 876                        buggy SAL_CACHE_FLUSH implementations. Using this
 877                        parameter will force ia64_sal_cache_flush to call
 878                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
 879
 880        ftrace=[tracer]
 881                        [FTRACE] will set and start the specified tracer
 882                        as early as possible in order to facilitate early
 883                        boot debugging.
 884
 885        ftrace_dump_on_oops[=orig_cpu]
 886                        [FTRACE] will dump the trace buffers on oops.
 887                        If no parameter is passed, ftrace will dump
 888                        buffers of all CPUs, but if you pass orig_cpu, it will
 889                        dump only the buffer of the CPU that triggered the
 890                        oops.
 891
 892        ftrace_filter=[function-list]
 893                        [FTRACE] Limit the functions traced by the function
 894                        tracer at boot up. function-list is a comma separated
 895                        list of functions. This list can be changed at run
 896                        time by the set_ftrace_filter file in the debugfs
 897                        tracing directory.
 898
 899        ftrace_notrace=[function-list]
 900                        [FTRACE] Do not trace the functions specified in
 901                        function-list. This list can be changed at run time
 902                        by the set_ftrace_notrace file in the debugfs
 903                        tracing directory.
 904
 905        ftrace_graph_filter=[function-list]
 906                        [FTRACE] Limit the top level callers functions traced
 907                        by the function graph tracer at boot up.
 908                        function-list is a comma separated list of functions
 909                        that can be changed at run time by the
 910                        set_graph_function file in the debugfs tracing directory.
 911
 912        gamecon.map[2|3]=
 913                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 914                        support via parallel port (up to 5 devices per port)
 915                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 916                        See also Documentation/input/joystick-parport.txt
 917
 918        gamma=          [HW,DRM]
 919
 920        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
 921                        Format: off | on
 922                        default: on
 923
 924        gcov_persist=   [GCOV] When non-zero (default), profiling data for
 925                        kernel modules is saved and remains accessible via
 926                        debugfs, even when the module is unloaded/reloaded.
 927                        When zero, profiling data is discarded and associated
 928                        debugfs files are removed at module unload time.
 929
 930        gpt             [EFI] Forces disk with valid GPT signature but
 931                        invalid Protective MBR to be treated as GPT.
 932
 933        grcan.enable0=  [HW] Configuration of physical interface 0. Determines
 934                        the "Enable 0" bit of the configuration register.
 935                        Format: 0 | 1
 936                        Default: 0
 937        grcan.enable1=  [HW] Configuration of physical interface 1. Determines
 938                        the "Enable 0" bit of the configuration register.
 939                        Format: 0 | 1
 940                        Default: 0
 941        grcan.select=   [HW] Select which physical interface to use.
 942                        Format: 0 | 1
 943                        Default: 0
 944        grcan.txsize=   [HW] Sets the size of the tx buffer.
 945                        Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
 946                        Default: 1024
 947        grcan.rxsize=   [HW] Sets the size of the rx buffer.
 948                        Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
 949                        Default: 1024
 950
 951        hashdist=       [KNL,NUMA] Large hashes allocated during boot
 952                        are distributed across NUMA nodes.  Defaults on
 953                        for 64-bit NUMA, off otherwise.
 954                        Format: 0 | 1 (for off | on)
 955
 956        hcl=            [IA-64] SGI's Hardware Graph compatibility layer
 957
 958        hd=             [EIDE] (E)IDE hard drive subsystem geometry
 959                        Format: <cyl>,<head>,<sect>
 960
 961        hest_disable    [ACPI]
 962                        Disable Hardware Error Source Table (HEST) support;
 963                        corresponding firmware-first mode error processing
 964                        logic will be disabled.
 965
 966        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
 967                        size of <nn>. This works even on boxes that have no
 968                        highmem otherwise. This also works to reduce highmem
 969                        size on bigger boxes.
 970
 971        highres=        [KNL] Enable/disable high resolution timer mode.
 972                        Valid parameters: "on", "off"
 973                        Default: "on"
 974
 975        hisax=          [HW,ISDN]
 976                        See Documentation/isdn/README.HiSax.
 977
 978        hlt             [BUGS=ARM,SH]
 979
 980        hpet=           [X86-32,HPET] option to control HPET usage
 981                        Format: { enable (default) | disable | force |
 982                                verbose }
 983                        disable: disable HPET and use PIT instead
 984                        force: allow force enabled of undocumented chips (ICH4,
 985                                VIA, nVidia)
 986                        verbose: show contents of HPET registers during setup
 987
 988        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
 989        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
 990                        On x86-64 and powerpc, this option can be specified
 991                        multiple times interleaved with hugepages= to reserve
 992                        huge pages of different sizes. Valid pages sizes on
 993                        x86-64 are 2M (when the CPU supports "pse") and 1G
 994                        (when the CPU supports the "pdpe1gb" cpuinfo flag)
 995                        Note that 1GB pages can only be allocated at boot time
 996                        using hugepages= and not freed afterwards.
 997
 998        hvc_iucv=       [S390] Number of z/VM IUCV hypervisor console (HVC)
 999                               terminal devices. Valid values: 0..8
1000        hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1001                               If specified, z/VM IUCV HVC accepts connections
1002                               from listed z/VM user IDs only.
1003
1004        hwthread_map=   [METAG] Comma-separated list of Linux cpu id to
1005                                hardware thread id mappings.
1006                                Format: <cpu>:<hwthread>
1007
1008        keep_bootcon    [KNL]
1009                        Do not unregister boot console at start. This is only
1010                        useful for debugging when something happens in the window
1011                        between unregistering the boot console and initializing
1012                        the real console.
1013
1014        i2c_bus=        [HW] Override the default board specific I2C bus speed
1015                             or register an additional I2C bus that is not
1016                             registered from board initialization code.
1017                             Format:
1018                             <bus_id>,<clkrate>
1019
1020        i8042.debug     [HW] Toggle i8042 debug mode
1021        i8042.direct    [HW] Put keyboard port into non-translated mode
1022        i8042.dumbkbd   [HW] Pretend that controller can only read data from
1023                             keyboard and cannot control its state
1024                             (Don't attempt to blink the leds)
1025        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
1026        i8042.nokbd     [HW] Don't check/create keyboard port
1027        i8042.noloop    [HW] Disable the AUX Loopback command while probing
1028                             for the AUX port
1029        i8042.nomux     [HW] Don't check presence of an active multiplexing
1030                             controller
1031        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1032                             controllers
1033        i8042.notimeout [HW] Ignore timeout condition signalled by controller
1034        i8042.reset     [HW] Reset the controller during init and cleanup
1035        i8042.unlock    [HW] Unlock (ignore) the keylock
1036
1037        i810=           [HW,DRM]
1038
1039        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
1040                        indicates that the driver is running on unsupported
1041                        hardware.
1042        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
1043                        does not match list of supported models.
1044        i8k.power_status
1045                        [HW] Report power status in /proc/i8k
1046                        (disabled by default)
1047        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
1048                        capability is set.
1049
1050        i915.invert_brightness=
1051                        [DRM] Invert the sense of the variable that is used to
1052                        set the brightness of the panel backlight. Normally a
1053                        brightness value of 0 indicates backlight switched off,
1054                        and the maximum of the brightness value sets the backlight
1055                        to maximum brightness. If this parameter is set to 0
1056                        (default) and the machine requires it, or this parameter
1057                        is set to 1, a brightness value of 0 sets the backlight
1058                        to maximum brightness, and the maximum of the brightness
1059                        value switches the backlight off.
1060                        -1 -- never invert brightness
1061                         0 -- machine default
1062                         1 -- force brightness inversion
1063
1064        icn=            [HW,ISDN]
1065                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1066
1067        ide-core.nodma= [HW] (E)IDE subsystem
1068                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1069                        .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1070                        .cdrom .chs .ignore_cable are additional options
1071                        See Documentation/ide/ide.txt.
1072
1073        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1074                        Claim all unknown PCI IDE storage controllers.
1075
1076        idle=           [X86]
1077                        Format: idle=poll, idle=halt, idle=nomwait
1078                        Poll forces a polling idle loop that can slightly
1079                        improve the performance of waking up a idle CPU, but
1080                        will use a lot of power and make the system run hot.
1081                        Not recommended.
1082                        idle=halt: Halt is forced to be used for CPU idle.
1083                        In such case C2/C3 won't be used again.
1084                        idle=nomwait: Disable mwait for CPU C-states
1085
1086        ignore_loglevel [KNL]
1087                        Ignore loglevel setting - this will print /all/
1088                        kernel messages to the console. Useful for debugging.
1089                        We also add it as printk module parameter, so users
1090                        could change it dynamically, usually by
1091                        /sys/module/printk/parameters/ignore_loglevel.
1092
1093        ihash_entries=  [KNL]
1094                        Set number of hash buckets for inode cache.
1095
1096        ima_appraise=   [IMA] appraise integrity measurements
1097                        Format: { "off" | "enforce" | "fix" }
1098                        default: "enforce"
1099
1100        ima_appraise_tcb [IMA]
1101                        The builtin appraise policy appraises all files
1102                        owned by uid=0.
1103
1104        ima_audit=      [IMA]
1105                        Format: { "0" | "1" }
1106                        0 -- integrity auditing messages. (Default)
1107                        1 -- enable informational integrity auditing messages.
1108
1109        ima_hash=       [IMA]
1110                        Format: { "sha1" | "md5" }
1111                        default: "sha1"
1112
1113        ima_tcb         [IMA]
1114                        Load a policy which meets the needs of the Trusted
1115                        Computing Base.  This means IMA will measure all
1116                        programs exec'd, files mmap'd for exec, and all files
1117                        opened for read by uid=0.
1118
1119        init=           [KNL]
1120                        Format: <full_path>
1121                        Run specified binary instead of /sbin/init as init
1122                        process.
1123
1124        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
1125                        for working out where the kernel is dying during
1126                        startup.
1127
1128        initrd=         [BOOT] Specify the location of the initial ramdisk
1129
1130        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
1131                        Format: <irq>
1132
1133        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
1134                on
1135                        Enable intel iommu driver.
1136                off
1137                        Disable intel iommu driver.
1138                igfx_off [Default Off]
1139                        By default, gfx is mapped as normal device. If a gfx
1140                        device has a dedicated DMAR unit, the DMAR unit is
1141                        bypassed by not enabling DMAR with this option. In
1142                        this case, gfx device will use physical address for
1143                        DMA.
1144                forcedac [x86_64]
1145                        With this option iommu will not optimize to look
1146                        for io virtual address below 32-bit forcing dual
1147                        address cycle on pci bus for cards supporting greater
1148                        than 32-bit addressing. The default is to look
1149                        for translation below 32-bit and if not available
1150                        then look in the higher range.
1151                strict [Default Off]
1152                        With this option on every unmap_single operation will
1153                        result in a hardware IOTLB flush operation as opposed
1154                        to batching them for performance.
1155                sp_off [Default Off]
1156                        By default, super page will be supported if Intel IOMMU
1157                        has the capability. With this option, super page will
1158                        not be supported.
1159
1160        intel_idle.max_cstate=  [KNL,HW,ACPI,X86]
1161                        0       disables intel_idle and fall back on acpi_idle.
1162                        1 to 6  specify maximum depth of C-state.
1163
1164        intel_pstate=  [X86]
1165                       disable
1166                         Do not enable intel_pstate as the default
1167                         scaling driver for the supported processors
1168
1169        intremap=       [X86-64, Intel-IOMMU]
1170                        on      enable Interrupt Remapping (default)
1171                        off     disable Interrupt Remapping
1172                        nosid   disable Source ID checking
1173                        no_x2apic_optout
1174                                BIOS x2APIC opt-out request will be ignored
1175
1176        iomem=          Disable strict checking of access to MMIO memory
1177                strict  regions from userspace.
1178                relaxed
1179
1180        iommu=          [x86]
1181                off
1182                force
1183                noforce
1184                biomerge
1185                panic
1186                nopanic
1187                merge
1188                nomerge
1189                forcesac
1190                soft
1191                pt              [x86, IA-64]
1192
1193
1194        io7=            [HW] IO7 for Marvel based alpha systems
1195                        See comment before marvel_specify_io7 in
1196                        arch/alpha/kernel/core_marvel.c.
1197
1198        io_delay=       [X86] I/O delay method
1199                0x80
1200                        Standard port 0x80 based delay
1201                0xed
1202                        Alternate port 0xed based delay (needed on some systems)
1203                udelay
1204                        Simple two microseconds delay
1205                none
1206                        No delay
1207
1208        ip=             [IP_PNP]
1209                        See Documentation/filesystems/nfs/nfsroot.txt.
1210
1211        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1212                        See comment before ip2_setup() in
1213                        drivers/char/ip2/ip2base.c.
1214
1215        irqfixup        [HW]
1216                        When an interrupt is not handled search all handlers
1217                        for it. Intended to get systems with badly broken
1218                        firmware running.
1219
1220        irqpoll         [HW]
1221                        When an interrupt is not handled search all handlers
1222                        for it. Also check all handlers each timer
1223                        interrupt. Intended to get systems with badly broken
1224                        firmware running.
1225
1226        isapnp=         [ISAPNP]
1227                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1228
1229        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
1230                        Format:
1231                        <cpu number>,...,<cpu number>
1232                        or
1233                        <cpu number>-<cpu number>
1234                        (must be a positive range in ascending order)
1235                        or a mixture
1236                        <cpu number>,...,<cpu number>-<cpu number>
1237
1238                        This option can be used to specify one or more CPUs
1239                        to isolate from the general SMP balancing and scheduling
1240                        algorithms. You can move a process onto or off an
1241                        "isolated" CPU via the CPU affinity syscalls or cpuset.
1242                        <cpu number> begins at 0 and the maximum value is
1243                        "number of CPUs in system - 1".
1244
1245                        This option is the preferred way to isolate CPUs. The
1246                        alternative -- manually setting the CPU mask of all
1247                        tasks in the system -- can cause problems and
1248                        suboptimal load balancer performance.
1249
1250        iucv=           [HW,NET]
1251
1252        js=             [HW,JOY] Analog joystick
1253                        See Documentation/input/joystick.txt.
1254
1255        keepinitrd      [HW,ARM]
1256
1257        kernelcore=nn[KMG]      [KNL,X86,IA-64,PPC] This parameter
1258                        specifies the amount of memory usable by the kernel
1259                        for non-movable allocations.  The requested amount is
1260                        spread evenly throughout all nodes in the system. The
1261                        remaining memory in each node is used for Movable
1262                        pages. In the event, a node is too small to have both
1263                        kernelcore and Movable pages, kernelcore pages will
1264                        take priority and other nodes will have a larger number
1265                        of kernelcore pages.  The Movable zone is used for the
1266                        allocation of pages that may be reclaimed or moved
1267                        by the page migration subsystem.  This means that
1268                        HugeTLB pages may not be allocated from this zone.
1269                        Note that allocations like PTEs-from-HighMem still
1270                        use the HighMem zone if it exists, and the Normal
1271                        zone if it does not.
1272
1273        kgdbdbgp=       [KGDB,HW] kgdb over EHCI usb debug port.
1274                        Format: <Controller#>[,poll interval]
1275                        The controller # is the number of the ehci usb debug
1276                        port as it is probed via PCI.  The poll interval is
1277                        optional and is the number seconds in between
1278                        each poll cycle to the debug port in case you need
1279                        the functionality for interrupting the kernel with
1280                        gdb or control-c on the dbgp connection.  When
1281                        not using this parameter you use sysrq-g to break into
1282                        the kernel debugger.
1283
1284        kgdboc=         [KGDB,HW] kgdb over consoles.
1285                        Requires a tty driver that supports console polling,
1286                        or a supported polling keyboard driver (non-usb).
1287                         Serial only format: <serial_device>[,baud]
1288                         keyboard only format: kbd
1289                         keyboard and serial format: kbd,<serial_device>[,baud]
1290                        Optional Kernel mode setting:
1291                         kms, kbd format: kms,kbd
1292                         kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1293
1294        kgdbwait        [KGDB] Stop kernel execution and enter the
1295                        kernel debugger at the earliest opportunity.
1296
1297        kmac=           [MIPS] korina ethernet MAC address.
1298                        Configure the RouterBoard 532 series on-chip
1299                        Ethernet adapter MAC address.
1300
1301        kmemleak=       [KNL] Boot-time kmemleak enable/disable
1302                        Valid arguments: on, off
1303                        Default: on
1304
1305        kstack=N        [X86] Print N words from the kernel stack
1306                        in oops dumps.
1307
1308        kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1309                        Default is 0 (don't ignore, but inject #GP)
1310
1311        kvm.mmu_audit=  [KVM] This is a R/W parameter which allows audit
1312                        KVM MMU at runtime.
1313                        Default is 0 (off)
1314
1315        kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1316                        Default is 1 (enabled)
1317
1318        kvm-amd.npt=    [KVM,AMD] Disable nested paging (virtualized MMU)
1319                        for all guests.
1320                        Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1321
1322        kvm-intel.ept=  [KVM,Intel] Disable extended page tables
1323                        (virtualized MMU) support on capable Intel chips.
1324                        Default is 1 (enabled)
1325
1326        kvm-intel.emulate_invalid_guest_state=
1327                        [KVM,Intel] Enable emulation of invalid guest states
1328                        Default is 0 (disabled)
1329
1330        kvm-intel.flexpriority=
1331                        [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1332                        Default is 1 (enabled)
1333
1334        kvm-intel.nested=
1335                        [KVM,Intel] Enable VMX nesting (nVMX).
1336                        Default is 0 (disabled)
1337
1338        kvm-intel.unrestricted_guest=
1339                        [KVM,Intel] Disable unrestricted guest feature
1340                        (virtualized real and unpaged mode) on capable
1341                        Intel chips. Default is 1 (enabled)
1342
1343        kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1344                        feature (tagged TLBs) on capable Intel chips.
1345                        Default is 1 (enabled)
1346
1347        l2cr=           [PPC]
1348
1349        l3cr=           [PPC]
1350
1351        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
1352                        disabled it.
1353
1354        lapic=          [x86,APIC] "notscdeadline" Do not use TSC deadline
1355                        value for LAPIC timer one-shot implementation. Default
1356                        back to the programmable timer unit in the LAPIC.
1357
1358        lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
1359                        in C2 power state.
1360
1361        libata.dma=     [LIBATA] DMA control
1362                        libata.dma=0      Disable all PATA and SATA DMA
1363                        libata.dma=1      PATA and SATA Disk DMA only
1364                        libata.dma=2      ATAPI (CDROM) DMA only
1365                        libata.dma=4      Compact Flash DMA only
1366                        Combinations also work, so libata.dma=3 enables DMA
1367                        for disks and CDROMs, but not CFs.
1368
1369        libata.ignore_hpa=      [LIBATA] Ignore HPA limit
1370                        libata.ignore_hpa=0       keep BIOS limits (default)
1371                        libata.ignore_hpa=1       ignore limits, using full disk
1372
1373        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
1374                        when set.
1375                        Format: <int>
1376
1377        libata.force=   [LIBATA] Force configurations.  The format is comma
1378                        separated list of "[ID:]VAL" where ID is
1379                        PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1380                        matching port, link or device.  Basically, it matches
1381                        the ATA ID string printed on console by libata.  If
1382                        the whole ID part is omitted, the last PORT and DEVICE
1383                        values are used.  If ID hasn't been specified yet, the
1384                        configuration applies to all ports, links and devices.
1385
1386                        If only DEVICE is omitted, the parameter applies to
1387                        the port and all links and devices behind it.  DEVICE
1388                        number of 0 either selects the first device or the
1389                        first fan-out link behind PMP device.  It does not
1390                        select the host link.  DEVICE number of 15 selects the
1391                        host link and device attached to it.
1392
1393                        The VAL specifies the configuration to force.  As long
1394                        as there's no ambiguity shortcut notation is allowed.
1395                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
1396                        The following configurations can be forced.
1397
1398                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
1399                          Any ID with matching PORT is used.
1400
1401                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1402
1403                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1404                          udma[/][16,25,33,44,66,100,133] notation is also
1405                          allowed.
1406
1407                        * [no]ncq: Turn on or off NCQ.
1408
1409                        * nohrst, nosrst, norst: suppress hard, soft
1410                          and both resets.
1411
1412                        * rstonce: only attempt one reset during
1413                          hot-unplug link recovery
1414
1415                        * dump_id: dump IDENTIFY data.
1416
1417                        If there are multiple matching configurations changing
1418                        the same attribute, the last one is used.
1419
1420        memblock=debug  [KNL] Enable memblock debug messages.
1421
1422        load_ramdisk=   [RAM] List of ramdisks to load from floppy
1423                        See Documentation/blockdev/ramdisk.txt.
1424
1425        lockd.nlm_grace_period=P  [NFS] Assign grace period.
1426                        Format: <integer>
1427
1428        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
1429                        Format: <integer>
1430
1431        lockd.nlm_timeout=T     [NFS] Assign timeout value.
1432                        Format: <integer>
1433
1434        lockd.nlm_udpport=M     [NFS] Assign UDP port.
1435                        Format: <integer>
1436
1437        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
1438                        Format: <irq>
1439
1440        loglevel=       All Kernel Messages with a loglevel smaller than the
1441                        console loglevel will be printed to the console. It can
1442                        also be changed with klogd or other programs. The
1443                        loglevels are defined as follows:
1444
1445                        0 (KERN_EMERG)          system is unusable
1446                        1 (KERN_ALERT)          action must be taken immediately
1447                        2 (KERN_CRIT)           critical conditions
1448                        3 (KERN_ERR)            error conditions
1449                        4 (KERN_WARNING)        warning conditions
1450                        5 (KERN_NOTICE)         normal but significant condition
1451                        6 (KERN_INFO)           informational
1452                        7 (KERN_DEBUG)          debug-level messages
1453
1454        log_buf_len=n[KMG]      Sets the size of the printk ring buffer,
1455                        in bytes.  n must be a power of two.  The default
1456                        size is set in the kernel config file.
1457
1458        logo.nologo     [FB] Disables display of the built-in Linux logo.
1459                        This may be used to provide more screen space for
1460                        kernel log messages and is useful when debugging
1461                        kernel boot problems.
1462
1463        lp=0            [LP]    Specify parallel ports to use, e.g,
1464        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
1465        lp=reset                first parallel port). 'lp=0' disables the
1466        lp=auto                 printer driver. 'lp=reset' (which can be
1467                                specified in addition to the ports) causes
1468                                attached printers to be reset. Using
1469                                lp=port1,port2,... specifies the parallel ports
1470                                to associate lp devices with, starting with
1471                                lp0. A port specification may be 'none' to skip
1472                                that lp device, or a parport name such as
1473                                'parport0'. Specifying 'lp=auto' instead of a
1474                                port specification list means that device IDs
1475                                from each port should be examined, to see if
1476                                an IEEE 1284-compliant printer is attached; if
1477                                so, the driver will manage that printer.
1478                                See also header of drivers/char/lp.c.
1479
1480        lpj=n           [KNL]
1481                        Sets loops_per_jiffy to given constant, thus avoiding
1482                        time-consuming boot-time autodetection (up to 250 ms per
1483                        CPU). 0 enables autodetection (default). To determine
1484                        the correct value for your kernel, boot with normal
1485                        autodetection and see what value is printed. Note that
1486                        on SMP systems the preset will be applied to all CPUs,
1487                        which is likely to cause problems if your CPUs need
1488                        significantly divergent settings. An incorrect value
1489                        will cause delays in the kernel to be wrong, leading to
1490                        unpredictable I/O errors and other breakage. Although
1491                        unlikely, in the extreme case this might damage your
1492                        hardware.
1493
1494        ltpc=           [NET]
1495                        Format: <io>,<irq>,<dma>
1496
1497        machvec=        [IA-64] Force the use of a particular machine-vector
1498                        (machvec) in a generic kernel.
1499                        Example: machvec=hpzx1_swiotlb
1500
1501        machtype=       [Loongson] Share the same kernel image file between different
1502                         yeeloong laptop.
1503                        Example: machtype=lemote-yeeloong-2f-7inch
1504
1505        max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater
1506                        than or equal to this physical address is ignored.
1507
1508        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
1509                        should make use of.  maxcpus=n : n >= 0 limits the
1510                        kernel to using 'n' processors.  n=0 is a special case,
1511                        it is equivalent to "nosmp", which also disables
1512                        the IO APIC.
1513
1514        max_loop=       [LOOP] The number of loop block devices that get
1515        (loop.max_loop) unconditionally pre-created at init time. The default
1516                        number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1517                        of statically allocating a predefined number, loop
1518                        devices can be requested on-demand with the
1519                        /dev/loop-control interface.
1520
1521        mce             [X86-32] Machine Check Exception
1522
1523        mce=option      [X86-64] See Documentation/x86/x86_64/boot-options.txt
1524
1525        md=             [HW] RAID subsystems devices and level
1526                        See Documentation/md.txt.
1527
1528        mdacon=         [MDA]
1529                        Format: <first>,<last>
1530                        Specifies range of consoles to be captured by the MDA.
1531
1532        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
1533                        Amount of memory to be used when the kernel is not able
1534                        to see the whole system memory or for test.
1535                        [X86] Work as limiting max address. Use together
1536                        with memmap= to avoid physical address space collisions.
1537                        Without memmap= PCI devices could be placed at addresses
1538                        belonging to unused RAM.
1539
1540        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
1541                        memory.
1542
1543        memchunk=nn[KMG]
1544                        [KNL,SH] Allow user to override the default size for
1545                        per-device physically contiguous DMA buffers.
1546
1547        memmap=exactmap [KNL,X86] Enable setting of an exact
1548                        E820 memory map, as specified by the user.
1549                        Such memmap=exactmap lines can be constructed based on
1550                        BIOS output or other requirements. See the memmap=nn@ss
1551                        option description.
1552
1553        memmap=nn[KMG]@ss[KMG]
1554                        [KNL] Force usage of a specific region of memory
1555                        Region of memory to be used, from ss to ss+nn.
1556
1557        memmap=nn[KMG]#ss[KMG]
1558                        [KNL,ACPI] Mark specific memory as ACPI data.
1559                        Region of memory to be used, from ss to ss+nn.
1560
1561        memmap=nn[KMG]$ss[KMG]
1562                        [KNL,ACPI] Mark specific memory as reserved.
1563                        Region of memory to be used, from ss to ss+nn.
1564                        Example: Exclude memory from 0x18690000-0x1869ffff
1565                                 memmap=64K$0x18690000
1566                                 or
1567                                 memmap=0x10000$0x18690000
1568
1569        memory_corruption_check=0/1 [X86]
1570                        Some BIOSes seem to corrupt the first 64k of
1571                        memory when doing things like suspend/resume.
1572                        Setting this option will scan the memory
1573                        looking for corruption.  Enabling this will
1574                        both detect corruption and prevent the kernel
1575                        from using the memory being corrupted.
1576                        However, its intended as a diagnostic tool; if
1577                        repeatable BIOS-originated corruption always
1578                        affects the same memory, you can use memmap=
1579                        to prevent the kernel from using that memory.
1580
1581        memory_corruption_check_size=size [X86]
1582                        By default it checks for corruption in the low
1583                        64k, making this memory unavailable for normal
1584                        use.  Use this parameter to scan for
1585                        corruption in more or less memory.
1586
1587        memory_corruption_check_period=seconds [X86]
1588                        By default it checks for corruption every 60
1589                        seconds.  Use this parameter to check at some
1590                        other rate.  0 disables periodic checking.
1591
1592        memtest=        [KNL,X86] Enable memtest
1593                        Format: <integer>
1594                        default : 0 <disable>
1595                        Specifies the number of memtest passes to be
1596                        performed. Each pass selects another test
1597                        pattern from a given set of patterns. Memtest
1598                        fills the memory with this pattern, validates
1599                        memory contents and reserves bad memory
1600                        regions that are detected.
1601
1602        meye.*=         [HW] Set MotionEye Camera parameters
1603                        See Documentation/video4linux/meye.txt.
1604
1605        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
1606                        Multi-Function General Purpose Timers on AMD Geode
1607                        platforms.
1608
1609        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
1610                        the BIOS has incorrectly applied a workaround. TinyBIOS
1611                        version 0.98 is known to be affected, 0.99 fixes the
1612                        problem by letting the user disable the workaround.
1613
1614        mga=            [HW,DRM]
1615
1616        min_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory below this
1617                        physical address is ignored.
1618
1619        mini2440=       [ARM,HW,KNL]
1620                        Format:[0..2][b][c][t]
1621                        Default: "0tb"
1622                        MINI2440 configuration specification:
1623                        0 - The attached screen is the 3.5" TFT
1624                        1 - The attached screen is the 7" TFT
1625                        2 - The VGA Shield is attached (1024x768)
1626                        Leaving out the screen size parameter will not load
1627                        the TFT driver, and the framebuffer will be left
1628                        unconfigured.
1629                        b - Enable backlight. The TFT backlight pin will be
1630                        linked to the kernel VESA blanking code and a GPIO
1631                        LED. This parameter is not necessary when using the
1632                        VGA shield.
1633                        c - Enable the s3c camera interface.
1634                        t - Reserved for enabling touchscreen support. The
1635                        touchscreen support is not enabled in the mainstream
1636                        kernel as of 2.6.30, a preliminary port can be found
1637                        in the "bleeding edge" mini2440 support kernel at
1638                        http://repo.or.cz/w/linux-2.6/mini2440.git
1639
1640        mminit_loglevel=
1641                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1642                        parameter allows control of the logging verbosity for
1643                        the additional memory initialisation checks. A value
1644                        of 0 disables mminit logging and a level of 4 will
1645                        log everything. Information is printed at KERN_DEBUG
1646                        so loglevel=8 may also need to be specified.
1647
1648        module.sig_enforce
1649                        [KNL] When CONFIG_MODULE_SIG is set, this means that
1650                        modules without (valid) signatures will fail to load.
1651                        Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1652                        is always true, so this option does nothing.
1653
1654        mousedev.tap_time=
1655                        [MOUSE] Maximum time between finger touching and
1656                        leaving touchpad surface for touch to be considered
1657                        a tap and be reported as a left button click (for
1658                        touchpads working in absolute mode only).
1659                        Format: <msecs>
1660        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
1661                        reporting absolute coordinates, such as tablets
1662        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
1663                        reporting absolute coordinates, such as tablets
1664
1665        movablecore=nn[KMG]     [KNL,X86,IA-64,PPC] This parameter
1666                        is similar to kernelcore except it specifies the
1667                        amount of memory used for migratable allocations.
1668                        If both kernelcore and movablecore is specified,
1669                        then kernelcore will be at *least* the specified
1670                        value but may be more. If movablecore on its own
1671                        is specified, the administrator must be careful
1672                        that the amount of memory usable for all allocations
1673                        is not too small.
1674
1675        MTD_Partition=  [MTD]
1676                        Format: <name>,<region-number>,<size>,<offset>
1677
1678        MTD_Region=     [MTD] Format:
1679                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1680
1681        mtdparts=       [MTD]
1682                        See drivers/mtd/cmdlinepart.c.
1683
1684        multitce=off    [PPC]  This parameter disables the use of the pSeries
1685                        firmware feature for updating multiple TCE entries
1686                        at a time.
1687
1688        onenand.bdry=   [HW,MTD] Flex-OneNAND Boundary Configuration
1689
1690                        Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1691
1692                        boundary - index of last SLC block on Flex-OneNAND.
1693                                   The remaining blocks are configured as MLC blocks.
1694                        lock     - Configure if Flex-OneNAND boundary should be locked.
1695                                   Once locked, the boundary cannot be changed.
1696                                   1 indicates lock status, 0 indicates unlock status.
1697
1698        mtdset=         [ARM]
1699                        ARM/S3C2412 JIVE boot control
1700
1701                        See arch/arm/mach-s3c2412/mach-jive.c
1702
1703        mtouchusb.raw_coordinates=
1704                        [HW] Make the MicroTouch USB driver use raw coordinates
1705                        ('y', default) or cooked coordinates ('n')
1706
1707        mtrr_chunk_size=nn[KMG] [X86]
1708                        used for mtrr cleanup. It is largest continuous chunk
1709                        that could hold holes aka. UC entries.
1710
1711        mtrr_gran_size=nn[KMG] [X86]
1712                        Used for mtrr cleanup. It is granularity of mtrr block.
1713                        Default is 1.
1714                        Large value could prevent small alignment from
1715                        using up MTRRs.
1716
1717        mtrr_spare_reg_nr=n [X86]
1718                        Format: <integer>
1719                        Range: 0,7 : spare reg number
1720                        Default : 1
1721                        Used for mtrr cleanup. It is spare mtrr entries number.
1722                        Set to 2 or more if your graphical card needs more.
1723
1724        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
1725
1726        netdev=         [NET] Network devices parameters
1727                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1728                        Note that mem_start is often overloaded to mean
1729                        something different and driver-specific.
1730                        This usage is only documented in each driver source
1731                        file if at all.
1732
1733        nf_conntrack.acct=
1734                        [NETFILTER] Enable connection tracking flow accounting
1735                        0 to disable accounting
1736                        1 to enable accounting
1737                        Default value is 0.
1738
1739        nfsaddrs=       [NFS] Deprecated.  Use ip= instead.
1740                        See Documentation/filesystems/nfs/nfsroot.txt.
1741
1742        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
1743                        See Documentation/filesystems/nfs/nfsroot.txt.
1744
1745        nfsrootdebug    [NFS] enable nfsroot debugging messages.
1746                        See Documentation/filesystems/nfs/nfsroot.txt.
1747
1748        nfs.callback_tcpport=
1749                        [NFS] set the TCP port on which the NFSv4 callback
1750                        channel should listen.
1751
1752        nfs.cache_getent=
1753                        [NFS] sets the pathname to the program which is used
1754                        to update the NFS client cache entries.
1755
1756        nfs.cache_getent_timeout=
1757                        [NFS] sets the timeout after which an attempt to
1758                        update a cache entry is deemed to have failed.
1759
1760        nfs.idmap_cache_timeout=
1761                        [NFS] set the maximum lifetime for idmapper cache
1762                        entries.
1763
1764        nfs.enable_ino64=
1765                        [NFS] enable 64-bit inode numbers.
1766                        If zero, the NFS client will fake up a 32-bit inode
1767                        number for the readdir() and stat() syscalls instead
1768                        of returning the full 64-bit number.
1769                        The default is to return 64-bit inode numbers.
1770
1771        nfs.max_session_slots=
1772                        [NFSv4.1] Sets the maximum number of session slots
1773                        the client will attempt to negotiate with the server.
1774                        This limits the number of simultaneous RPC requests
1775                        that the client can send to the NFSv4.1 server.
1776                        Note that there is little point in setting this
1777                        value higher than the max_tcp_slot_table_limit.
1778
1779        nfs.nfs4_disable_idmapping=
1780                        [NFSv4] When set to the default of '1', this option
1781                        ensures that both the RPC level authentication
1782                        scheme and the NFS level operations agree to use
1783                        numeric uids/gids if the mount is using the
1784                        'sec=sys' security flavour. In effect it is
1785                        disabling idmapping, which can make migration from
1786                        legacy NFSv2/v3 systems to NFSv4 easier.
1787                        Servers that do not support this mode of operation
1788                        will be autodetected by the client, and it will fall
1789                        back to using the idmapper.
1790                        To turn off this behaviour, set the value to '0'.
1791        nfs.nfs4_unique_id=
1792                        [NFS4] Specify an additional fixed unique ident-
1793                        ification string that NFSv4 clients can insert into
1794                        their nfs_client_id4 string.  This is typically a
1795                        UUID that is generated at system install time.
1796
1797        nfs.send_implementation_id =
1798                        [NFSv4.1] Send client implementation identification
1799                        information in exchange_id requests.
1800                        If zero, no implementation identification information
1801                        will be sent.
1802                        The default is to send the implementation identification
1803                        information.
1804
1805        nfsd.nfs4_disable_idmapping=
1806                        [NFSv4] When set to the default of '1', the NFSv4
1807                        server will return only numeric uids and gids to
1808                        clients using auth_sys, and will accept numeric uids
1809                        and gids from such clients.  This is intended to ease
1810                        migration from NFSv2/v3.
1811
1812        objlayoutdriver.osd_login_prog=
1813                        [NFS] [OBJLAYOUT] sets the pathname to the program which
1814                        is used to automatically discover and login into new
1815                        osd-targets. Please see:
1816                        Documentation/filesystems/pnfs.txt for more explanations
1817
1818        nmi_debug=      [KNL,AVR32,SH] Specify one or more actions to take
1819                        when a NMI is triggered.
1820                        Format: [state][,regs][,debounce][,die]
1821
1822        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
1823                        Format: [panic,][nopanic,][num]
1824                        Valid num: 0
1825                        0 - turn nmi_watchdog off
1826                        When panic is specified, panic when an NMI watchdog
1827                        timeout occurs (or 'nopanic' to override the opposite
1828                        default).
1829                        This is useful when you use a panic=... timeout and
1830                        need the box quickly up again.
1831
1832        netpoll.carrier_timeout=
1833                        [NET] Specifies amount of time (in seconds) that
1834                        netpoll should wait for a carrier. By default netpoll
1835                        waits 4 seconds.
1836
1837        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
1838                        emulation library even if a 387 maths coprocessor
1839                        is present.
1840
1841        no_console_suspend
1842                        [HW] Never suspend the console
1843                        Disable suspending of consoles during suspend and
1844                        hibernate operations.  Once disabled, debugging
1845                        messages can reach various consoles while the rest
1846                        of the system is being put to sleep (ie, while
1847                        debugging driver suspend/resume hooks).  This may
1848                        not work reliably with all consoles, but is known
1849                        to work with serial and VGA consoles.
1850                        To facilitate more flexible debugging, we also add
1851                        console_suspend, a printk module parameter to control
1852                        it. Users could use console_suspend (usually
1853                        /sys/module/printk/parameters/console_suspend) to
1854                        turn on/off it dynamically.
1855
1856        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
1857                        caches in the slab allocator.  Saves per-node memory,
1858                        but will impact performance.
1859
1860        noalign         [KNL,ARM]
1861
1862        noapic          [SMP,APIC] Tells the kernel to not make use of any
1863                        IOAPICs that may be present in the system.
1864
1865        noautogroup     Disable scheduler automatic task group creation.
1866
1867        nobats          [PPC] Do not use BATs for mapping kernel lowmem
1868                        on "Classic" PPC cores.
1869
1870        nocache         [ARM]
1871
1872        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction
1873
1874        nodelayacct     [KNL] Disable per-task delay accounting
1875
1876        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1877
1878        nodsp           [SH] Disable hardware DSP at boot time.
1879
1880        noefi           [X86] Disable EFI runtime services support.
1881
1882        noexec          [IA-64]
1883
1884        noexec          [X86]
1885                        On X86-32 available only on PAE configured kernels.
1886                        noexec=on: enable non-executable mappings (default)
1887                        noexec=off: disable non-executable mappings
1888
1889        nosmap          [X86]
1890                        Disable SMAP (Supervisor Mode Access Prevention)
1891                        even if it is supported by processor.
1892
1893        nosmep          [X86]
1894                        Disable SMEP (Supervisor Mode Execution Prevention)
1895                        even if it is supported by processor.
1896
1897        noexec32        [X86-64]
1898                        This affects only 32-bit executables.
1899                        noexec32=on: enable non-executable mappings (default)
1900                                read doesn't imply executable mappings
1901                        noexec32=off: disable non-executable mappings
1902                                read implies executable mappings
1903
1904        nofpu           [SH] Disable hardware FPU at boot time.
1905
1906        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
1907                        register save and restore. The kernel will only save
1908                        legacy floating-point registers on task switch.
1909
1910        noxsave         [BUGS=X86] Disables x86 extended register state save
1911                        and restore using xsave. The kernel will fallback to
1912                        enabling legacy floating-point and sse state.
1913
1914        eagerfpu=       [X86]
1915                        on      enable eager fpu restore
1916                        off     disable eager fpu restore
1917                        auto    selects the default scheme, which automatically
1918                                enables eagerfpu restore for xsaveopt.
1919
1920        nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1921                        wfi(ARM) instruction doesn't work correctly and not to
1922                        use it. This is also useful when using JTAG debugger.
1923
1924        no_file_caps    Tells the kernel not to honor file capabilities.  The
1925                        only way then for a file to be executed with privilege
1926                        is to be setuid root or executed by root.
1927
1928        nohalt          [IA-64] Tells the kernel not to use the power saving
1929                        function PAL_HALT_LIGHT when idle. This increases
1930                        power-consumption. On the positive side, it reduces
1931                        interrupt wake-up latency, which may improve performance
1932                        in certain environments such as networked servers or
1933                        real-time systems.
1934
1935        nohz=           [KNL] Boottime enable/disable dynamic ticks
1936                        Valid arguments: on, off
1937                        Default: on
1938
1939        noiotrap        [SH] Disables trapped I/O port accesses.
1940
1941        noirqdebug      [X86-32] Disables the code which attempts to detect and
1942                        disable unhandled interrupt sources.
1943
1944        no_timer_check  [X86,APIC] Disables the code which tests for
1945                        broken timer IRQ sources.
1946
1947        noisapnp        [ISAPNP] Disables ISA PnP code.
1948
1949        noinitrd        [RAM] Tells the kernel not to load any configured
1950                        initial RAM disk.
1951
1952        nointremap      [X86-64, Intel-IOMMU] Do not enable interrupt
1953                        remapping.
1954                        [Deprecated - use intremap=off]
1955
1956        nointroute      [IA-64]
1957
1958        nojitter        [IA-64] Disables jitter checking for ITC timers.
1959
1960        no-kvmclock     [X86,KVM] Disable paravirtualized KVM clock driver
1961
1962        no-kvmapf       [X86,KVM] Disable paravirtualized asynchronous page
1963                        fault handling.
1964
1965        no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
1966                        steal time is computed, but won't influence scheduler
1967                        behaviour
1968
1969        nolapic         [X86-32,APIC] Do not enable or use the local APIC.
1970
1971        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.
1972
1973        noltlbs         [PPC] Do not use large page/tlb entries for kernel
1974                        lowmem mapping on PPC40x.
1975
1976        nomca           [IA-64] Disable machine check abort handling
1977
1978        nomce           [X86-32] Machine Check Exception
1979
1980        nomfgpt         [X86-32] Disable Multi-Function General Purpose
1981                        Timer usage (for AMD Geode machines).
1982
1983        nonmi_ipi       [X86] Disable using NMI IPIs during panic/reboot to
1984                        shutdown the other cpus.  Instead use the REBOOT_VECTOR
1985                        irq.
1986
1987        nomodule        Disable module load
1988
1989        nopat           [X86] Disable PAT (page attribute table extension of
1990                        pagetables) support.
1991
1992        norandmaps      Don't use address space randomization.  Equivalent to
1993                        echo 0 > /proc/sys/kernel/randomize_va_space
1994
1995        noreplace-paravirt      [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1996
1997        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
1998                        with UP alternatives
1999
2000        noresidual      [PPC] Don't use residual data on PReP machines.
2001
2002        nordrand        [X86] Disable the direct use of the RDRAND
2003                        instruction even if it is supported by the
2004                        processor.  RDRAND is still available to user
2005                        space applications.
2006
2007        noresume        [SWSUSP] Disables resume and restores original swap
2008                        space.
2009
2010        no-scroll       [VGA] Disables scrollback.
2011                        This is required for the Braillex ib80-piezo Braille
2012                        reader made by F.H. Papenmeier (Germany).
2013
2014        nosbagart       [IA-64]
2015
2016        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2017
2018        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
2019                        and disable the IO APIC.  legacy for "maxcpus=0".
2020
2021        nosoftlockup    [KNL] Disable the soft-lockup detector.
2022
2023        nosync          [HW,M68K] Disables sync negotiation for all devices.
2024
2025        notsc           [BUGS=X86-32] Disable Time Stamp Counter
2026
2027        nousb           [USB] Disable the USB subsystem
2028
2029        nowatchdog      [KNL] Disable the lockup detector (NMI watchdog).
2030
2031        nowb            [ARM]
2032
2033        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
2034
2035        cpu0_hotplug    [X86] Turn on CPU0 hotplug feature when
2036                        CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2037                        Some features depend on CPU0. Known dependencies are:
2038                        1. Resume from suspend/hibernate depends on CPU0.
2039                        Suspend/hibernate will fail if CPU0 is offline and you
2040                        need to online CPU0 before suspend/hibernate.
2041                        2. PIC interrupts also depend on CPU0. CPU0 can't be
2042                        removed if a PIC interrupt is detected.
2043                        It's said poweroff/reboot may depend on CPU0 on some
2044                        machines although I haven't seen such issues so far
2045                        after CPU0 is offline on a few tested machines.
2046                        If the dependencies are under your control, you can
2047                        turn on cpu0_hotplug.
2048
2049        nptcg=          [IA-64] Override max number of concurrent global TLB
2050                        purges which is reported from either PAL_VM_SUMMARY or
2051                        SAL PALO.
2052
2053        nr_cpus=        [SMP] Maximum number of processors that an SMP kernel
2054                        could support.  nr_cpus=n : n >= 1 limits the kernel to
2055                        supporting 'n' processors. Later in runtime you can not
2056                        use hotplug cpu feature to put more cpu back to online.
2057                        just like you compile the kernel NR_CPUS=n
2058
2059        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
2060
2061        numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2062                        Allowed values are enable and disable
2063
2064        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2065                        one of ['zone', 'node', 'default'] can be specified
2066                        This can be set from sysctl after boot.
2067                        See Documentation/sysctl/vm.txt for details.
2068
2069        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
2070                        See Documentation/debugging-via-ohci1394.txt for more
2071                        info.
2072
2073        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2074                        Rather than timing out after 20 ms if an EC
2075                        command is not properly ACKed, override the length
2076                        of the timeout.  We have interrupts disabled while
2077                        waiting for the ACK, so if this is set too high
2078                        interrupts *may* be lost!
2079
2080        omap_mux=       [OMAP] Override bootloader pin multiplexing.
2081                        Format: <mux_mode0.mode_name=value>...
2082                        For example, to override I2C bus2:
2083                        omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2084
2085        oprofile.timer= [HW]
2086                        Use timer interrupt instead of performance counters
2087
2088        oprofile.cpu_type=      Force an oprofile cpu type
2089                        This might be useful if you have an older oprofile
2090                        userland or if you want common events.
2091                        Format: { arch_perfmon }
2092                        arch_perfmon: [X86] Force use of architectural
2093                                perfmon on Intel CPUs instead of the
2094                                CPU specific event set.
2095                        timer: [X86] Force use of architectural NMI
2096                                timer mode (see also oprofile.timer
2097                                for generic hr timer mode)
2098                                [s390] Force legacy basic mode sampling
2099                                (report cpu_type "timer")
2100
2101        oops=panic      Always panic on oopses. Default is to just kill the
2102                        process, but there is a small probability of
2103                        deadlocking the machine.
2104                        This will also cause panics on machine check exceptions.
2105                        Useful together with panic=30 to trigger a reboot.
2106
2107        OSS             [HW,OSS]
2108                        See Documentation/sound/oss/oss-parameters.txt
2109
2110        panic=          [KNL] Kernel behaviour on panic: delay <timeout>
2111                        timeout > 0: seconds before rebooting
2112                        timeout = 0: wait forever
2113                        timeout < 0: reboot immediately
2114                        Format: <timeout>
2115
2116        parkbd.port=    [HW] Parallel port number the keyboard adapter is
2117                        connected to, default is 0.
2118                        Format: <parport#>
2119        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
2120                        0 for XT, 1 for AT (default is AT).
2121                        Format: <mode>
2122
2123        parport=        [HW,PPT] Specify parallel ports. 0 disables.
2124                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2125                        Use 'auto' to force the driver to use any
2126                        IRQ/DMA settings detected (the default is to
2127                        ignore detected IRQ/DMA settings because of
2128                        possible conflicts). You can specify the base
2129                        address, IRQ, and DMA settings; IRQ and DMA
2130                        should be numbers, or 'auto' (for using detected
2131                        settings on that particular port), or 'nofifo'
2132                        (to avoid using a FIFO even if it is detected).
2133                        Parallel ports are assigned in the order they
2134                        are specified on the command line, starting
2135                        with parport0.
2136
2137        parport_init_mode=      [HW,PPT]
2138                        Configure VIA parallel port to operate in
2139                        a specific mode. This is necessary on Pegasos
2140                        computer where firmware has no options for setting
2141                        up parallel port mode and sets it to spp.
2142                        Currently this function knows 686a and 8231 chips.
2143                        Format: [spp|ps2|epp|ecp|ecpepp]
2144
2145        pause_on_oops=
2146                        Halt all CPUs after the first oops has been printed for
2147                        the specified number of seconds.  This is to be used if
2148                        your oopses keep scrolling off the screen.
2149
2150        pcbit=          [HW,ISDN]
2151
2152        pcd.            [PARIDE]
2153                        See header of drivers/block/paride/pcd.c.
2154                        See also Documentation/blockdev/paride.txt.
2155
2156        pci=option[,option...]  [PCI] various PCI subsystem options:
2157                earlydump       [X86] dump PCI config space before the kernel
2158                                changes anything
2159                off             [X86] don't probe for the PCI bus
2160                bios            [X86-32] force use of PCI BIOS, don't access
2161                                the hardware directly. Use this if your machine
2162                                has a non-standard PCI host bridge.
2163                nobios          [X86-32] disallow use of PCI BIOS, only direct
2164                                hardware access methods are allowed. Use this
2165                                if you experience crashes upon bootup and you
2166                                suspect they are caused by the BIOS.
2167                conf1           [X86] Force use of PCI Configuration
2168                                Mechanism 1.
2169                conf2           [X86] Force use of PCI Configuration
2170                                Mechanism 2.
2171                noaer           [PCIE] If the PCIEAER kernel config parameter is
2172                                enabled, this kernel boot option can be used to
2173                                disable the use of PCIE advanced error reporting.
2174                nodomains       [PCI] Disable support for multiple PCI
2175                                root domains (aka PCI segments, in ACPI-speak).
2176                nommconf        [X86] Disable use of MMCONFIG for PCI
2177                                Configuration
2178                check_enable_amd_mmconf [X86] check for and enable
2179                                properly configured MMIO access to PCI
2180                                config space on AMD family 10h CPU
2181                nomsi           [MSI] If the PCI_MSI kernel config parameter is
2182                                enabled, this kernel boot option can be used to
2183                                disable the use of MSI interrupts system-wide.
2184                noioapicquirk   [APIC] Disable all boot interrupt quirks.
2185                                Safety option to keep boot IRQs enabled. This
2186                                should never be necessary.
2187                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
2188                                primary IO-APIC for bridges that cannot disable
2189                                boot IRQs. This fixes a source of spurious IRQs
2190                                when the system masks IRQs.
2191                noioapicreroute [APIC] Disable workaround that uses the
2192                                boot IRQ equivalent of an IRQ that connects to
2193                                a chipset where boot IRQs cannot be disabled.
2194                                The opposite of ioapicreroute.
2195                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
2196                                routing table. These calls are known to be buggy
2197                                on several machines and they hang the machine
2198                                when used, but on other computers it's the only
2199                                way to get the interrupt routing table. Try
2200                                this option if the kernel is unable to allocate
2201                                IRQs or discover secondary PCI buses on your
2202                                motherboard.
2203                rom             [X86] Assign address space to expansion ROMs.
2204                                Use with caution as certain devices share
2205                                address decoders between ROMs and other
2206                                resources.
2207                norom           [X86] Do not assign address space to
2208                                expansion ROMs that do not already have
2209                                BIOS assigned address ranges.
2210                nobar           [X86] Do not assign address space to the
2211                                BARs that weren't assigned by the BIOS.
2212                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
2213                                assigned automatically to PCI devices. You can
2214                                make the kernel exclude IRQs of your ISA cards
2215                                this way.
2216                pirqaddr=0xAAAAA        [X86] Specify the physical address
2217                                of the PIRQ table (normally generated
2218                                by the BIOS) if it is outside the
2219                                F0000h-100000h range.
2220                lastbus=N       [X86] Scan all buses thru bus #N. Can be
2221                                useful if the kernel is unable to find your
2222                                secondary buses and you want to tell it
2223                                explicitly which ones they are.
2224                assign-busses   [X86] Always assign all PCI bus
2225                                numbers ourselves, overriding
2226                                whatever the firmware may have done.
2227                usepirqmask     [X86] Honor the possible IRQ mask stored
2228                                in the BIOS $PIR table. This is needed on
2229                                some systems with broken BIOSes, notably
2230                                some HP Pavilion N5400 and Omnibook XE3
2231                                notebooks. This will have no effect if ACPI
2232                                IRQ routing is enabled.
2233                noacpi          [X86] Do not use ACPI for IRQ routing
2234                                or for PCI scanning.
2235                use_crs         [X86] Use PCI host bridge window information
2236                                from ACPI.  On BIOSes from 2008 or later, this
2237                                is enabled by default.  If you need to use this,
2238                                please report a bug.
2239                nocrs           [X86] Ignore PCI host bridge windows from ACPI.
2240                                If you need to use this, please report a bug.
2241                routeirq        Do IRQ routing for all PCI devices.
2242                                This is normally done in pci_enable_device(),
2243                                so this option is a temporary workaround
2244                                for broken drivers that don't call it.
2245                skip_isa_align  [X86] do not align io start addr, so can
2246                                handle more pci cards
2247                firmware        [ARM] Do not re-enumerate the bus but instead
2248                                just use the configuration from the
2249                                bootloader. This is currently used on
2250                                IXP2000 systems where the bus has to be
2251                                configured a certain way for adjunct CPUs.
2252                noearly         [X86] Don't do any early type 1 scanning.
2253                                This might help on some broken boards which
2254                                machine check when some devices' config space
2255                                is read. But various workarounds are disabled
2256                                and some IOMMU drivers will not work.
2257                bfsort          Sort PCI devices into breadth-first order.
2258                                This sorting is done to get a device
2259                                order compatible with older (<= 2.4) kernels.
2260                nobfsort        Don't sort PCI devices into breadth-first order.
2261                pcie_bus_tune_off       Disable PCIe MPS (Max Payload Size)
2262                                tuning and use the BIOS-configured MPS defaults.
2263                pcie_bus_safe   Set every device's MPS to the largest value
2264                                supported by all devices below the root complex.
2265                pcie_bus_perf   Set device MPS to the largest allowable MPS
2266                                based on its parent bus. Also set MRRS (Max
2267                                Read Request Size) to the largest supported
2268                                value (no larger than the MPS that the device
2269                                or bus can support) for best performance.
2270                pcie_bus_peer2peer      Set every device's MPS to 128B, which
2271                                every device is guaranteed to support. This
2272                                configuration allows peer-to-peer DMA between
2273                                any pair of devices, possibly at the cost of
2274                                reduced performance.  This also guarantees
2275                                that hot-added devices will work.
2276                cbiosize=nn[KMG]        The fixed amount of bus space which is
2277                                reserved for the CardBus bridge's IO window.
2278                                The default value is 256 bytes.
2279                cbmemsize=nn[KMG]       The fixed amount of bus space which is
2280                                reserved for the CardBus bridge's memory
2281                                window. The default value is 64 megabytes.
2282                resource_alignment=
2283                                Format:
2284                                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2285                                Specifies alignment and device to reassign
2286                                aligned memory resources.
2287                                If <order of align> is not specified,
2288                                PAGE_SIZE is used as alignment.
2289                                PCI-PCI bridge can be specified, if resource
2290                                windows need to be expanded.
2291                ecrc=           Enable/disable PCIe ECRC (transaction layer
2292                                end-to-end CRC checking).
2293                                bios: Use BIOS/firmware settings. This is the
2294                                the default.
2295                                off: Turn ECRC off
2296                                on: Turn ECRC on.
2297                hpiosize=nn[KMG]        The fixed amount of bus space which is
2298                                reserved for hotplug bridge's IO window.
2299                                Default size is 256 bytes.
2300                hpmemsize=nn[KMG]       The fixed amount of bus space which is
2301                                reserved for hotplug bridge's memory window.
2302                                Default size is 2 megabytes.
2303                realloc=        Enable/disable reallocating PCI bridge resources
2304                                if allocations done by BIOS are too small to
2305                                accommodate resources required by all child
2306                                devices.
2307                                off: Turn realloc off
2308                                on: Turn realloc on
2309                realloc         same as realloc=on
2310                noari           do not use PCIe ARI.
2311                pcie_scan_all   Scan all possible PCIe devices.  Otherwise we
2312                                only look for one device below a PCIe downstream
2313                                port.
2314
2315        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
2316                        Management.
2317                off     Disable ASPM.
2318                force   Enable ASPM even on devices that claim not to support it.
2319                        WARNING: Forcing ASPM on may cause system lockups.
2320
2321        pcie_hp=        [PCIE] PCI Express Hotplug driver options:
2322                nomsi   Do not use MSI for PCI Express Native Hotplug (this
2323                        makes all PCIe ports use INTx for hotplug services).
2324
2325        pcie_ports=     [PCIE] PCIe ports handling:
2326                auto    Ask the BIOS whether or not to use native PCIe services
2327                        associated with PCIe ports (PME, hot-plug, AER).  Use
2328                        them only if that is allowed by the BIOS.
2329                native  Use native PCIe services associated with PCIe ports
2330                        unconditionally.
2331                compat  Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2332                        ports driver.
2333
2334        pcie_pme=       [PCIE,PM] Native PCIe PME signaling options:
2335                nomsi   Do not use MSI for native PCIe PME signaling (this makes
2336                        all PCIe root ports use INTx for all services).
2337
2338        pcmv=           [HW,PCMCIA] BadgePAD 4
2339
2340        pd.             [PARIDE]
2341                        See Documentation/blockdev/paride.txt.
2342
2343        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2344                        boot time.
2345                        Format: { 0 | 1 }
2346                        See arch/parisc/kernel/pdc_chassis.c
2347
2348        percpu_alloc=   Select which percpu first chunk allocator to use.
2349                        Currently supported values are "embed" and "page".
2350                        Archs may support subset or none of the selections.
2351                        See comments in mm/percpu.c for details on each
2352                        allocator.  This parameter is primarily for debugging
2353                        and performance comparison.
2354
2355        pf.             [PARIDE]
2356                        See Documentation/blockdev/paride.txt.
2357
2358        pg.             [PARIDE]
2359                        See Documentation/blockdev/paride.txt.
2360
2361        pirq=           [SMP,APIC] Manual mp-table setup
2362                        See Documentation/x86/i386/IO-APIC.txt.
2363
2364        plip=           [PPT,NET] Parallel port network link
2365                        Format: { parport<nr> | timid | 0 }
2366                        See also Documentation/parport.txt.
2367
2368        pmtmr=          [X86] Manual setup of pmtmr I/O Port.
2369                        Override pmtimer IOPort with a hex value.
2370                        e.g. pmtmr=0x508
2371
2372        pnp.debug=1     [PNP]
2373                        Enable PNP debug messages (depends on the
2374                        CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
2375                        via /sys/module/pnp/parameters/debug.  We always show
2376                        current resource usage; turning this on also shows
2377                        possible settings and some assignment information.
2378
2379        pnpacpi=        [ACPI]
2380                        { off }
2381
2382        pnpbios=        [ISAPNP]
2383                        { on | off | curr | res | no-curr | no-res }
2384
2385        pnp_reserve_irq=
2386                        [ISAPNP] Exclude IRQs for the autoconfiguration
2387
2388        pnp_reserve_dma=
2389                        [ISAPNP] Exclude DMAs for the autoconfiguration
2390
2391        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2392                        Ranges are in pairs (I/O port base and size).
2393
2394        pnp_reserve_mem=
2395                        [ISAPNP] Exclude memory regions for the
2396                        autoconfiguration.
2397                        Ranges are in pairs (memory base and size).
2398
2399        ports=          [IP_VS_FTP] IPVS ftp helper module
2400                        Default is 21.
2401                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
2402                        may be specified.
2403                        Format: <port>,<port>....
2404
2405        print-fatal-signals=
2406                        [KNL] debug: print fatal signals
2407
2408                        If enabled, warn about various signal handling
2409                        related application anomalies: too many signals,
2410                        too many POSIX.1 timers, fatal signals causing a
2411                        coredump - etc.
2412
2413                        If you hit the warning due to signal overflow,
2414                        you might want to try "ulimit -i unlimited".
2415
2416                        default: off.
2417
2418        printk.always_kmsg_dump=
2419                        Trigger kmsg_dump for cases other than kernel oops or
2420                        panics
2421                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2422                        default: disabled
2423
2424        printk.time=    Show timing data prefixed to each printk message line
2425                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2426
2427        processor.max_cstate=   [HW,ACPI]
2428                        Limit processor to maximum C-state
2429                        max_cstate=9 overrides any DMI blacklist limit.
2430
2431        processor.nocst [HW,ACPI]
2432                        Ignore the _CST method to determine C-states,
2433                        instead using the legacy FADT method
2434
2435        profile=        [KNL] Enable kernel profiling via /proc/profile
2436                        Format: [schedule,]<number>
2437                        Param: "schedule" - profile schedule points.
2438                        Param: <number> - step/bucket size as a power of 2 for
2439                                statistical time based profiling.
2440                        Param: "sleep" - profile D-state sleeping (millisecs).
2441                                Requires CONFIG_SCHEDSTATS
2442                        Param: "kvm" - profile VM exits.
2443
2444        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2445                        before loading.
2446                        See Documentation/blockdev/ramdisk.txt.
2447
2448        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
2449                        probe for; one of (bare|imps|exps|lifebook|any).
2450        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
2451                        per second.
2452        psmouse.resetafter=     [HW,MOUSE]
2453                        Try to reset the device after so many bad packets
2454                        (0 = never).
2455        psmouse.resolution=
2456                        [HW,MOUSE] Set desired mouse resolution, in dpi.
2457        psmouse.smartscroll=
2458                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2459                        0 = disabled, 1 = enabled (default).
2460
2461        pstore.backend= Specify the name of the pstore backend to use
2462
2463        pt.             [PARIDE]
2464                        See Documentation/blockdev/paride.txt.
2465
2466        pty.legacy_count=
2467                        [KNL] Number of legacy pty's. Overwrites compiled-in
2468                        default number.
2469
2470        quiet           [KNL] Disable most log messages
2471
2472        r128=           [HW,DRM]
2473
2474        raid=           [HW,RAID]
2475                        See Documentation/md.txt.
2476
2477        ramdisk_blocksize=      [RAM]
2478                        See Documentation/blockdev/ramdisk.txt.
2479
2480        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
2481                        See Documentation/blockdev/ramdisk.txt.
2482
2483        rcu_nocbs=      [KNL,BOOT]
2484                        In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2485                        the specified list of CPUs to be no-callback CPUs.
2486                        Invocation of these CPUs' RCU callbacks will
2487                        be offloaded to "rcuoN" kthreads created for
2488                        that purpose.  This reduces OS jitter on the
2489                        offloaded CPUs, which can be useful for HPC and
2490                        real-time workloads.  It can also improve energy
2491                        efficiency for asymmetric multiprocessors.
2492
2493        rcu_nocb_poll   [KNL,BOOT]
2494                        Rather than requiring that offloaded CPUs
2495                        (specified by rcu_nocbs= above) explicitly
2496                        awaken the corresponding "rcuoN" kthreads,
2497                        make these kthreads poll for callbacks.
2498                        This improves the real-time response for the
2499                        offloaded CPUs by relieving them of the need to
2500                        wake up the corresponding kthread, but degrades
2501                        energy efficiency by requiring that the kthreads
2502                        periodically wake up to do the polling.
2503
2504        rcutree.blimit= [KNL,BOOT]
2505                        Set maximum number of finished RCU callbacks to process
2506                        in one batch.
2507
2508        rcutree.fanout_leaf=    [KNL,BOOT]
2509                        Increase the number of CPUs assigned to each
2510                        leaf rcu_node structure.  Useful for very large
2511                        systems.
2512
2513        rcutree.qhimark=        [KNL,BOOT]
2514                        Set threshold of queued
2515                        RCU callbacks over which batch limiting is disabled.
2516
2517        rcutree.qlowmark=       [KNL,BOOT]
2518                        Set threshold of queued RCU callbacks below which
2519                        batch limiting is re-enabled.
2520
2521        rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2522                        Suppress RCU CPU stall warning messages.
2523
2524        rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2525                        Set timeout for RCU CPU stall warning messages.
2526
2527        rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2528                        Set delay from grace-period initialization to
2529                        first attempt to force quiescent states.
2530                        Units are jiffies, minimum value is zero,
2531                        and maximum value is HZ.
2532
2533        rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2534                        Set delay between subsequent attempts to force
2535                        quiescent states.  Units are jiffies, minimum
2536                        value is one, and maximum value is HZ.
2537
2538        rcutorture.fqs_duration= [KNL,BOOT]
2539                        Set duration of force_quiescent_state bursts.
2540
2541        rcutorture.fqs_holdoff= [KNL,BOOT]
2542                        Set holdoff time within force_quiescent_state bursts.
2543
2544        rcutorture.fqs_stutter= [KNL,BOOT]
2545                        Set wait time between force_quiescent_state bursts.
2546
2547        rcutorture.irqreader= [KNL,BOOT]
2548                        Test RCU readers from irq handlers.
2549
2550        rcutorture.n_barrier_cbs= [KNL,BOOT]
2551                        Set callbacks/threads for rcu_barrier() testing.
2552
2553        rcutorture.nfakewriters= [KNL,BOOT]
2554                        Set number of concurrent RCU writers.  These just
2555                        stress RCU, they don't participate in the actual
2556                        test, hence the "fake".
2557
2558        rcutorture.nreaders= [KNL,BOOT]
2559                        Set number of RCU readers.
2560
2561        rcutorture.onoff_holdoff= [KNL,BOOT]
2562                        Set time (s) after boot for CPU-hotplug testing.
2563
2564        rcutorture.onoff_interval= [KNL,BOOT]
2565                        Set time (s) between CPU-hotplug operations, or
2566                        zero to disable CPU-hotplug testing.
2567
2568        rcutorture.shuffle_interval= [KNL,BOOT]
2569                        Set task-shuffle interval (s).  Shuffling tasks
2570                        allows some CPUs to go into dyntick-idle mode
2571                        during the rcutorture test.
2572
2573        rcutorture.shutdown_secs= [KNL,BOOT]
2574                        Set time (s) after boot system shutdown.  This
2575                        is useful for hands-off automated testing.
2576
2577        rcutorture.stall_cpu= [KNL,BOOT]
2578                        Duration of CPU stall (s) to test RCU CPU stall
2579                        warnings, zero to disable.
2580
2581        rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2582                        Time to wait (s) after boot before inducing stall.
2583
2584        rcutorture.stat_interval= [KNL,BOOT]
2585                        Time (s) between statistics printk()s.
2586
2587        rcutorture.stutter= [KNL,BOOT]
2588                        Time (s) to stutter testing, for example, specifying
2589                        five seconds causes the test to run for five seconds,
2590                        wait for five seconds, and so on.  This tests RCU's
2591                        ability to transition abruptly to and from idle.
2592
2593        rcutorture.test_boost= [KNL,BOOT]
2594                        Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
2595                        "Maybe" means test if the RCU implementation
2596                        under test support RCU priority boosting.
2597
2598        rcutorture.test_boost_duration= [KNL,BOOT]
2599                        Duration (s) of each individual boost test.
2600
2601        rcutorture.test_boost_interval= [KNL,BOOT]
2602                        Interval (s) between each boost test.
2603
2604        rcutorture.test_no_idle_hz= [KNL,BOOT]
2605                        Test RCU's dyntick-idle handling.  See also the
2606                        rcutorture.shuffle_interval parameter.
2607
2608        rcutorture.torture_type= [KNL,BOOT]
2609                        Specify the RCU implementation to test.
2610
2611        rcutorture.verbose= [KNL,BOOT]
2612                        Enable additional printk() statements.
2613
2614        rdinit=         [KNL]
2615                        Format: <full_path>
2616                        Run specified binary instead of /init from the ramdisk,
2617                        used for early userspace startup. See initrd.
2618
2619        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2620                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
2621                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2622
2623        relax_domain_level=
2624                        [KNL, SMP] Set scheduler's default relax_domain_level.
2625                        See Documentation/cgroups/cpusets.txt.
2626
2627        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
2628
2629        reservetop=     [X86-32]
2630                        Format: nn[KMG]
2631                        Reserves a hole at the top of the kernel virtual
2632                        address space.
2633
2634        reservelow=     [X86]
2635                        Format: nn[K]
2636                        Set the amount of memory to reserve for BIOS at
2637                        the bottom of the address space.
2638
2639        reset_devices   [KNL] Force drivers to reset the underlying device
2640                        during initialization.
2641
2642        resume=         [SWSUSP]
2643                        Specify the partition device for software suspend
2644                        Format:
2645                        {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2646
2647        resume_offset=  [SWSUSP]
2648                        Specify the offset from the beginning of the partition
2649                        given by "resume=" at which the swap header is located,
2650                        in <PAGE_SIZE> units (needed only for swap files).
2651                        See  Documentation/power/swsusp-and-swap-files.txt
2652
2653        resumedelay=    [HIBERNATION] Delay (in seconds) to pause before attempting to
2654                        read the resume files
2655
2656        resumewait      [HIBERNATION] Wait (indefinitely) for resume device to show up.
2657                        Useful for devices that are detected asynchronously
2658                        (e.g. USB and MMC devices).
2659
2660        hibernate=      [HIBERNATION]
2661                noresume        Don't check if there's a hibernation image
2662                                present during boot.
2663                nocompress      Don't compress/decompress hibernation images.
2664
2665        retain_initrd   [RAM] Keep initrd memory after extraction
2666
2667        rhash_entries=  [KNL,NET]
2668                        Set number of hash buckets for route cache
2669
2670        riscom8=        [HW,SERIAL]
2671                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2672
2673        ro              [KNL] Mount root device read-only on boot
2674
2675        root=           [KNL] Root filesystem
2676                        See name_to_dev_t comment in init/do_mounts.c.
2677
2678        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
2679                        mount the root filesystem
2680
2681        rootflags=      [KNL] Set root filesystem mount option string
2682
2683        rootfstype=     [KNL] Set root filesystem type
2684
2685        rootwait        [KNL] Wait (indefinitely) for root device to show up.
2686                        Useful for devices that are detected asynchronously
2687                        (e.g. USB and MMC devices).
2688
2689        rw              [KNL] Mount root device read-write on boot
2690
2691        S               [KNL] Run init in single mode
2692
2693        sa1100ir        [NET]
2694                        See drivers/net/irda/sa1100_ir.c.
2695
2696        sbni=           [NET] Granch SBNI12 leased line adapter
2697
2698        sched_debug     [KNL] Enables verbose scheduler debug messages.
2699
2700        skew_tick=      [KNL] Offset the periodic timer tick per cpu to mitigate
2701                        xtime_lock contention on larger systems, and/or RCU lock
2702                        contention on all systems with CONFIG_MAXSMP set.
2703                        Format: { "0" | "1" }
2704                        0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2705                        1 -- enable.
2706                        Note: increases power consumption, thus should only be
2707                        enabled if running jitter sensitive (HPC/RT) workloads.
2708
2709        security=       [SECURITY] Choose a security module to enable at boot.
2710                        If this boot parameter is not specified, only the first
2711                        security module asking for security registration will be
2712                        loaded. An invalid security module name will be treated
2713                        as if no module has been chosen.
2714
2715        selinux=        [SELINUX] Disable or enable SELinux at boot time.
2716                        Format: { "0" | "1" }
2717                        See security/selinux/Kconfig help text.
2718                        0 -- disable.
2719                        1 -- enable.
2720                        Default value is set via kernel config option.
2721                        If enabled at boot time, /selinux/disable can be used
2722                        later to disable prior to initial policy load.
2723
2724        apparmor=       [APPARMOR] Disable or enable AppArmor at boot time
2725                        Format: { "0" | "1" }
2726                        See security/apparmor/Kconfig help text
2727                        0 -- disable.
2728                        1 -- enable.
2729                        Default value is set via kernel config option.
2730
2731        serialnumber    [BUGS=X86-32]
2732
2733        shapers=        [NET]
2734                        Maximal number of shapers.
2735
2736        show_msr=       [x86] show boot-time MSR settings
2737                        Format: { <integer> }
2738                        Show boot-time (BIOS-initialized) MSR settings.
2739                        The parameter means the number of CPUs to show,
2740                        for example 1 means boot CPU only.
2741
2742        simeth=         [IA-64]
2743        simscsi=
2744
2745        slram=          [HW,MTD]
2746
2747        slab_max_order= [MM, SLAB]
2748                        Determines the maximum allowed order for slabs.
2749                        A high setting may cause OOMs due to memory
2750                        fragmentation.  Defaults to 1 for systems with
2751                        more than 32MB of RAM, 0 otherwise.
2752
2753        slub_debug[=options[,slabs]]    [MM, SLUB]
2754                        Enabling slub_debug allows one to determine the
2755                        culprit if slab objects become corrupted. Enabling
2756                        slub_debug can create guard zones around objects and
2757                        may poison objects when not in use. Also tracks the
2758                        last alloc / free. For more information see
2759                        Documentation/vm/slub.txt.
2760
2761        slub_max_order= [MM, SLUB]
2762                        Determines the maximum allowed order for slabs.
2763                        A high setting may cause OOMs due to memory
2764                        fragmentation. For more information see
2765                        Documentation/vm/slub.txt.
2766
2767        slub_min_objects=       [MM, SLUB]
2768                        The minimum number of objects per slab. SLUB will
2769                        increase the slab order up to slub_max_order to
2770                        generate a sufficiently large slab able to contain
2771                        the number of objects indicated. The higher the number
2772                        of objects the smaller the overhead of tracking slabs
2773                        and the less frequently locks need to be acquired.
2774                        For more information see Documentation/vm/slub.txt.
2775
2776        slub_min_order= [MM, SLUB]
2777                        Determines the minimum page order for slabs. Must be
2778                        lower than slub_max_order.
2779                        For more information see Documentation/vm/slub.txt.
2780
2781        slub_nomerge    [MM, SLUB]
2782                        Disable merging of slabs with similar size. May be
2783                        necessary if there is some reason to distinguish
2784                        allocs to different slabs. Debug options disable
2785                        merging on their own.
2786                        For more information see Documentation/vm/slub.txt.
2787
2788        smart2=         [HW]
2789                        Format: <io1>[,<io2>[,...,<io8>]]
2790
2791        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
2792        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
2793        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
2794        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
2795        smsc-ircc2.ircc_irq=    [HW] IRQ line
2796        smsc-ircc2.ircc_dma=    [HW] DMA channel
2797        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2798                                0: Toshiba Satellite 1800 (GP data pin select)
2799                                1: Fast pin select (default)
2800                                2: ATC IRMode
2801
2802        softlockup_panic=
2803                        [KNL] Should the soft-lockup detector generate panics.
2804                        Format: <integer>
2805
2806        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
2807                        See Documentation/laptops/sonypi.txt
2808
2809        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
2810                        See Documentation/serial/specialix.txt.
2811
2812        spia_io_base=   [HW,MTD]
2813        spia_fio_base=
2814        spia_pedr=
2815        spia_peddr=
2816
2817        stacktrace      [FTRACE]
2818                        Enabled the stack tracer on boot up.
2819
2820        stacktrace_filter=[function-list]
2821                        [FTRACE] Limit the functions that the stack tracer
2822                        will trace at boot up. function-list is a comma separated
2823                        list of functions. This list can be changed at run
2824                        time by the stack_trace_filter file in the debugfs
2825                        tracing directory. Note, this enables stack tracing
2826                        and the stacktrace above is not needed.
2827
2828        sti=            [PARISC,HW]
2829                        Format: <num>
2830                        Set the STI (builtin display/keyboard on the HP-PARISC
2831                        machines) console (graphic card) which should be used
2832                        as the initial boot-console.
2833                        See also comment in drivers/video/console/sticore.c.
2834
2835        sti_font=       [HW]
2836                        See comment in drivers/video/console/sticore.c.
2837
2838        stifb=          [HW]
2839                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2840
2841        sunrpc.min_resvport=
2842        sunrpc.max_resvport=
2843                        [NFS,SUNRPC]
2844                        SunRPC servers often require that client requests
2845                        originate from a privileged port (i.e. a port in the
2846                        range 0 < portnr < 1024).
2847                        An administrator who wishes to reserve some of these
2848                        ports for other uses may adjust the range that the
2849                        kernel's sunrpc client considers to be privileged
2850                        using these two parameters to set the minimum and
2851                        maximum port values.
2852
2853        sunrpc.pool_mode=
2854                        [NFS]
2855                        Control how the NFS server code allocates CPUs to
2856                        service thread pools.  Depending on how many NICs
2857                        you have and where their interrupts are bound, this
2858                        option will affect which CPUs will do NFS serving.
2859                        Note: this parameter cannot be changed while the
2860                        NFS server is running.
2861
2862                        auto        the server chooses an appropriate mode
2863                                    automatically using heuristics
2864                        global      a single global pool contains all CPUs
2865                        percpu      one pool for each CPU
2866                        pernode     one pool for each NUMA node (equivalent
2867                                    to global on non-NUMA machines)
2868
2869        sunrpc.tcp_slot_table_entries=
2870        sunrpc.udp_slot_table_entries=
2871                        [NFS,SUNRPC]
2872                        Sets the upper limit on the number of simultaneous
2873                        RPC calls that can be sent from the client to a
2874                        server. Increasing these values may allow you to
2875                        improve throughput, but will also increase the
2876                        amount of memory reserved for use by the client.
2877
2878        swapaccount[=0|1]
2879                        [KNL] Enable accounting of swap in memory resource
2880                        controller if no parameter or 1 is given or disable
2881                        it if 0 is given (See Documentation/cgroups/memory.txt)
2882
2883        swiotlb=        [IA-64] Number of I/O TLB slabs
2884
2885        switches=       [HW,M68k]
2886
2887        sysfs.deprecated=0|1 [KNL]
2888                        Enable/disable old style sysfs layout for old udev
2889                        on older distributions. When this option is enabled
2890                        very new udev will not work anymore. When this option
2891                        is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2892                        in older udev will not work anymore.
2893                        Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2894                        the kernel configuration.
2895
2896        sysrq_always_enabled
2897                        [KNL]
2898                        Ignore sysrq setting - this boot parameter will
2899                        neutralize any effect of /proc/sys/kernel/sysrq.
2900                        Useful for debugging.
2901
2902        tdfx=           [HW,DRM]
2903
2904        test_suspend=   [SUSPEND]
2905                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
2906                        standby suspend) as the system sleep state to briefly
2907                        enter during system startup.  The system is woken from
2908                        this state using a wakeup-capable RTC alarm.
2909
2910        thash_entries=  [KNL,NET]
2911                        Set number of hash buckets for TCP connection
2912
2913        thermal.act=    [HW,ACPI]
2914                        -1: disable all active trip points in all thermal zones
2915                        <degrees C>: override all lowest active trip points
2916
2917        thermal.crt=    [HW,ACPI]
2918                        -1: disable all critical trip points in all thermal zones
2919                        <degrees C>: override all critical trip points
2920
2921        thermal.nocrt=  [HW,ACPI]
2922                        Set to disable actions on ACPI thermal zone
2923                        critical and hot trip points.
2924
2925        thermal.off=    [HW,ACPI]
2926                        1: disable ACPI thermal control
2927
2928        thermal.psv=    [HW,ACPI]
2929                        -1: disable all passive trip points
2930                        <degrees C>: override all passive trip points to this
2931                        value
2932
2933        thermal.tzp=    [HW,ACPI]
2934                        Specify global default ACPI thermal zone polling rate
2935                        <deci-seconds>: poll all this frequency
2936                        0: no polling (default)
2937
2938        threadirqs      [KNL]
2939                        Force threading of all interrupt handlers except those
2940                        marked explicitly IRQF_NO_THREAD.
2941
2942        topology=       [S390]
2943                        Format: {off | on}
2944                        Specify if the kernel should make use of the cpu
2945                        topology information if the hardware supports this.
2946                        The scheduler will make use of this information and
2947                        e.g. base its process migration decisions on it.
2948                        Default is on.
2949
2950        tp720=          [HW,PS2]
2951
2952        tpm_suspend_pcr=[HW,TPM]
2953                        Format: integer pcr id
2954                        Specify that at suspend time, the tpm driver
2955                        should extend the specified pcr with zeros,
2956                        as a workaround for some chips which fail to
2957                        flush the last written pcr on TPM_SaveState.
2958                        This will guarantee that all the other pcrs
2959                        are saved.
2960
2961        trace_buf_size=nn[KMG]
2962                        [FTRACE] will set tracing buffer size.
2963
2964        trace_event=[event-list]
2965                        [FTRACE] Set and start specified trace events in order
2966                        to facilitate early boot debugging.
2967                        See also Documentation/trace/events.txt
2968
2969        trace_options=[option-list]
2970                        [FTRACE] Enable or disable tracer options at boot.
2971                        The option-list is a comma delimited list of options
2972                        that can be enabled or disabled just as if you were
2973                        to echo the option name into
2974
2975                            /sys/kernel/debug/tracing/trace_options
2976
2977                        For example, to enable stacktrace option (to dump the
2978                        stack trace of each event), add to the command line:
2979
2980                              trace_options=stacktrace
2981
2982                        See also Documentation/trace/ftrace.txt "trace options"
2983                        section.
2984
2985        transparent_hugepage=
2986                        [KNL]
2987                        Format: [always|madvise|never]
2988                        Can be used to control the default behavior of the system
2989                        with respect to transparent hugepages.
2990                        See Documentation/vm/transhuge.txt for more details.
2991
2992        tsc=            Disable clocksource stability checks for TSC.
2993                        Format: <string>
2994                        [x86] reliable: mark tsc clocksource as reliable, this
2995                        disables clocksource verification at runtime, as well
2996                        as the stability checks done at bootup. Used to enable
2997                        high-resolution timer mode on older hardware, and in
2998                        virtualized environment.
2999                        [x86] noirqtime: Do not use TSC to do irq accounting.
3000                        Used to run time disable IRQ_TIME_ACCOUNTING on any
3001                        platforms where RDTSC is slow and this accounting
3002                        can add overhead.
3003
3004        turbografx.map[2|3]=    [HW,JOY]
3005                        TurboGraFX parallel port interface
3006                        Format:
3007                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3008                        See also Documentation/input/joystick-parport.txt
3009
3010        udbg-immortal   [PPC] When debugging early kernel crashes that
3011                        happen after console_init() and before a proper 
3012                        console driver takes over, this boot options might
3013                        help "seeing" what's going on.
3014
3015        uhash_entries=  [KNL,NET]
3016                        Set number of hash buckets for UDP/UDP-Lite connections
3017
3018        uhci-hcd.ignore_oc=
3019                        [USB] Ignore overcurrent events (default N).
3020                        Some badly-designed motherboards generate lots of
3021                        bogus events, for ports that aren't wired to
3022                        anything.  Set this parameter to avoid log spamming.
3023                        Note that genuine overcurrent events won't be
3024                        reported either.
3025
3026        unknown_nmi_panic
3027                        [X86] Cause panic on unknown NMI.
3028
3029        usbcore.authorized_default=
3030                        [USB] Default USB device authorization:
3031                        (default -1 = authorized except for wireless USB,
3032                        0 = not authorized, 1 = authorized)
3033
3034        usbcore.autosuspend=
3035                        [USB] The autosuspend time delay (in seconds) used
3036                        for newly-detected USB devices (default 2).  This
3037                        is the time required before an idle device will be
3038                        autosuspended.  Devices for which the delay is set
3039                        to a negative value won't be autosuspended at all.
3040
3041        usbcore.usbfs_snoop=
3042                        [USB] Set to log all usbfs traffic (default 0 = off).
3043
3044        usbcore.blinkenlights=
3045                        [USB] Set to cycle leds on hubs (default 0 = off).
3046
3047        usbcore.old_scheme_first=
3048                        [USB] Start with the old device initialization
3049                        scheme (default 0 = off).
3050
3051        usbcore.usbfs_memory_mb=
3052                        [USB] Memory limit (in MB) for buffers allocated by
3053                        usbfs (default = 16, 0 = max = 2047).
3054
3055        usbcore.use_both_schemes=
3056                        [USB] Try the other device initialization scheme
3057                        if the first one fails (default 1 = enabled).
3058
3059        usbcore.initial_descriptor_timeout=
3060                        [USB] Specifies timeout for the initial 64-byte
3061                        USB_REQ_GET_DESCRIPTOR request in milliseconds
3062                        (default 5000 = 5.0 seconds).
3063
3064        usbhid.mousepoll=
3065                        [USBHID] The interval which mice are to be polled at.
3066
3067        usb-storage.delay_use=
3068                        [UMS] The delay in seconds before a new device is
3069                        scanned for Logical Units (default 5).
3070
3071        usb-storage.quirks=
3072                        [UMS] A list of quirks entries to supplement or
3073                        override the built-in unusual_devs list.  List
3074                        entries are separated by commas.  Each entry has
3075                        the form VID:PID:Flags where VID and PID are Vendor
3076                        and Product ID values (4-digit hex numbers) and
3077                        Flags is a set of characters, each corresponding
3078                        to a common usb-storage quirk flag as follows:
3079                                a = SANE_SENSE (collect more than 18 bytes
3080                                        of sense data);
3081                                b = BAD_SENSE (don't collect more than 18
3082                                        bytes of sense data);
3083                                c = FIX_CAPACITY (decrease the reported
3084                                        device capacity by one sector);
3085                                d = NO_READ_DISC_INFO (don't use
3086                                        READ_DISC_INFO command);
3087                                e = NO_READ_CAPACITY_16 (don't use
3088                                        READ_CAPACITY_16 command);
3089                                h = CAPACITY_HEURISTICS (decrease the
3090                                        reported device capacity by one
3091                                        sector if the number is odd);
3092                                i = IGNORE_DEVICE (don't bind to this
3093                                        device);
3094                                l = NOT_LOCKABLE (don't try to lock and
3095                                        unlock ejectable media);
3096                                m = MAX_SECTORS_64 (don't transfer more
3097                                        than 64 sectors = 32 KB at a time);
3098                                n = INITIAL_READ10 (force a retry of the
3099                                        initial READ(10) command);
3100                                o = CAPACITY_OK (accept the capacity
3101                                        reported by the device);
3102                                p = WRITE_CACHE (the device cache is ON
3103                                        by default);
3104                                r = IGNORE_RESIDUE (the device reports
3105                                        bogus residue values);
3106                                s = SINGLE_LUN (the device has only one
3107                                        Logical Unit);
3108                                w = NO_WP_DETECT (don't test whether the
3109                                        medium is write-protected).
3110                        Example: quirks=0419:aaf5:rl,0421:0433:rc
3111
3112        user_debug=     [KNL,ARM]
3113                        Format: <int>
3114                        See arch/arm/Kconfig.debug help text.
3115                                 1 - undefined instruction events
3116                                 2 - system calls
3117                                 4 - invalid data aborts
3118                                 8 - SIGSEGV faults
3119                                16 - SIGBUS faults
3120                        Example: user_debug=31
3121
3122        userpte=
3123                        [X86] Flags controlling user PTE allocations.
3124
3125                                nohigh = do not allocate PTE pages in
3126                                        HIGHMEM regardless of setting
3127                                        of CONFIG_HIGHPTE.
3128
3129        vdso=           [X86,SH]
3130                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3131                        vdso=1: enable VDSO (default)
3132                        vdso=0: disable VDSO mapping
3133
3134        vdso32=         [X86]
3135                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3136                        vdso32=1: enable 32-bit VDSO (default)
3137                        vdso32=0: disable 32-bit VDSO mapping
3138
3139        vector=         [IA-64,SMP]
3140                        vector=percpu: enable percpu vector domain
3141
3142        video=          [FB] Frame buffer configuration
3143                        See Documentation/fb/modedb.txt.
3144
3145        virtio_mmio.device=
3146                        [VMMIO] Memory mapped virtio (platform) device.
3147
3148                                <size>@<baseaddr>:<irq>[:<id>]
3149                        where:
3150                                <size>     := size (can use standard suffixes
3151                                                like K, M and G)
3152                                <baseaddr> := physical base address
3153                                <irq>      := interrupt number (as passed to
3154                                                request_irq())
3155                                <id>       := (optional) platform device id
3156                        example:
3157                                virtio_mmio.device=1K@0x100b0000:48:7
3158
3159                        Can be used multiple times for multiple devices.
3160
3161        vga=            [BOOT,X86-32] Select a particular video mode
3162                        See Documentation/x86/boot.txt and
3163                        Documentation/svga.txt.
3164                        Use vga=ask for menu.
3165                        This is actually a boot loader parameter; the value is
3166                        passed to the kernel using a special protocol.
3167
3168        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3169                        size of <nn>. This can be used to increase the
3170                        minimum size (128MB on x86). It can also be used to
3171                        decrease the size and leave more room for directly
3172                        mapped kernel RAM.
3173
3174        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
3175                        Format: <command>
3176
3177        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
3178                        Format: <command>
3179
3180        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
3181                        Format: <command>
3182
3183        vsyscall=       [X86-64]
3184                        Controls the behavior of vsyscalls (i.e. calls to
3185                        fixed addresses of 0xffffffffff600x00 from legacy
3186                        code).  Most statically-linked binaries and older
3187                        versions of glibc use these calls.  Because these
3188                        functions are at fixed addresses, they make nice
3189                        targets for exploits that can control RIP.
3190
3191                        emulate     [default] Vsyscalls turn into traps and are
3192                                    emulated reasonably safely.
3193
3194                        native      Vsyscalls are native syscall instructions.
3195                                    This is a little bit faster than trapping
3196                                    and makes a few dynamic recompilers work
3197                                    better than they would in emulation mode.
3198                                    It also makes exploits much easier to write.
3199
3200                        none        Vsyscalls don't work at all.  This makes
3201                                    them quite hard to use for exploits but
3202                                    might break your system.
3203
3204        vt.cur_default= [VT] Default cursor shape.
3205                        Format: 0xCCBBAA, where AA, BB, and CC are the same as
3206                        the parameters of the <Esc>[?A;B;Cc escape sequence;
3207                        see VGA-softcursor.txt. Default: 2 = underline.
3208
3209        vt.default_blu= [VT]
3210                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3211                        Change the default blue palette of the console.
3212                        This is a 16-member array composed of values
3213                        ranging from 0-255.
3214
3215        vt.default_grn= [VT]
3216                        Format: <green0>,<green1>,<green2>,...,<green15>
3217                        Change the default green palette of the console.
3218                        This is a 16-member array composed of values
3219                        ranging from 0-255.
3220
3221        vt.default_red= [VT]
3222                        Format: <red0>,<red1>,<red2>,...,<red15>
3223                        Change the default red palette of the console.
3224                        This is a 16-member array composed of values
3225                        ranging from 0-255.
3226
3227        vt.default_utf8=
3228                        [VT]
3229                        Format=<0|1>
3230                        Set system-wide default UTF-8 mode for all tty's.
3231                        Default is 1, i.e. UTF-8 mode is enabled for all
3232                        newly opened terminals.
3233
3234        vt.global_cursor_default=
3235                        [VT]
3236                        Format=<-1|0|1>
3237                        Set system-wide default for whether a cursor
3238                        is shown on new VTs. Default is -1,
3239                        i.e. cursors will be created by default unless
3240                        overridden by individual drivers. 0 will hide
3241                        cursors, 1 will display them.
3242
3243        watchdog timers [HW,WDT] For information on watchdog timers,
3244                        see Documentation/watchdog/watchdog-parameters.txt
3245                        or other driver-specific files in the
3246                        Documentation/watchdog/ directory.
3247
3248        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
3249                        default x2apic cluster mode on platforms
3250                        supporting x2apic.
3251
3252        x86_mrst_timer= [X86-32,APBT]
3253                        Choose timer option for x86 Moorestown MID platform.
3254                        Two valid options are apbt timer only and lapic timer
3255                        plus one apbt timer for broadcast timer.
3256                        x86_mrst_timer=apbt_only | lapic_and_apbt
3257
3258        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3259        xd_geo=         See header of drivers/block/xd.c.
3260
3261        xen_emul_unplug=                [HW,X86,XEN]
3262                        Unplug Xen emulated devices
3263                        Format: [unplug0,][unplug1]
3264                        ide-disks -- unplug primary master IDE devices
3265                        aux-ide-disks -- unplug non-primary-master IDE devices
3266                        nics -- unplug network devices
3267                        all -- unplug all emulated devices (NICs and IDE disks)
3268                        unnecessary -- unplugging emulated devices is
3269                                unnecessary even if the host did not respond to
3270                                the unplug protocol
3271                        never -- do not unplug even if version check succeeds
3272
3273        xirc2ps_cs=     [NET,PCMCIA]
3274                        Format:
3275                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3276
3277______________________________________________________________________
3278
3279TODO:
3280
3281        Add more DRM drivers.
3282
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