The following is a consolidated list of the kernel parameters as implemented (mostly) by the __setup() macro and sorted into English Dictionary order (defined as ignoring all punctuation and sorting digits before letters in a case insensitive manner), and with descriptions where known.

Module parameters for loadable modules are specified only as the parameter name with optional '=' and value as appropriate, such as:

modprobe usbcore blinkenlights=1

Module parameters for modules that are built into the kernel image are specified on the kernel command line with the module name plus '.' plus parameter name, with '=' and value if appropriate, such as:

usbcore.blinkenlights=1

Hyphens (dashes) and underscores are equivalent in parameter names, so

log_buf_len=1M print-fatal-signals=1 can also be entered as

log-buf-len=1M print_fatal_signals=1

This document may not be entirely up to date and comprehensive. The command "modinfo -p ${modulename}" shows a current list of all parameters of a loadable module. Loadable modules, after being loaded into the running kernel, also reveal their parameters in /sys/module/${modulename}/parameters/. Some of these parameters may be changed at runtime by the command "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".

The parameters listed below are only valid if certain kernel build options were enabled and if respective hardware is present. The text in square brackets at the beginning of each description states the restrictions within which a parameter is applicable:

        ACPI    ACPI support is enabled.
        AGP     AGP (Accelerated Graphics Port) is enabled.
        ALSA    ALSA sound support is enabled.
        APIC    APIC support is enabled.
        APM     Advanced Power Management support is enabled.
        AVR32   AVR32 architecture is enabled.
        AX25    Appropriate AX.25 support is enabled.
        BLACKFIN Blackfin architecture is enabled.
        DRM     Direct Rendering Management support is enabled.
        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
        EFI     EFI Partitioning (GPT) is enabled
        EIDE    EIDE/ATAPI support is enabled.
        FB      The frame buffer device is enabled.
        GCOV    GCOV profiling is enabled.
        HW      Appropriate hardware is enabled.
        IA-64   IA-64 architecture is enabled.
        IMA     Integrity measurement architecture is enabled.
        IOSCHED More than one I/O scheduler is enabled.
        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
        IPV6    IPv6 support is enabled.
        ISAPNP  ISA PnP code is enabled.
        ISDN    Appropriate ISDN support is enabled.
        JOY     Appropriate joystick support is enabled.
        KGDB    Kernel debugger support is enabled.
        KVM     Kernel Virtual Machine support is enabled.
        LIBATA  Libata driver is enabled
        LP      Printer support is enabled.
        LOOP    Loopback device support is enabled.
        M68k    M68k architecture is enabled.
                        These options have more detailed description inside of
                        Documentation/m68k/kernel-options.txt.
        MCA     MCA bus support is enabled.
        MDA     MDA console support is enabled.
        MOUSE   Appropriate mouse support is enabled.
        MSI     Message Signaled Interrupts (PCI).
        MTD     MTD (Memory Technology Device) support is enabled.
        NET     Appropriate network support is enabled.
        NUMA    NUMA support is enabled.
        GENERIC_TIME The generic timeofday code is enabled.
        NFS     Appropriate NFS support is enabled.
        OSS     OSS sound support is enabled.
        PV_OPS  A paravirtualized kernel is enabled.
        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
        PARISC  The PA-RISC architecture is enabled.
        PCI     PCI bus support is enabled.
        PCIE    PCI Express support is enabled.
        PCMCIA  The PCMCIA subsystem is enabled.
        PNP     Plug & Play support is enabled.
        PPC     PowerPC architecture is enabled.
        PPT     Parallel port support is enabled.
        PS2     Appropriate PS/2 support is enabled.
        RAM     RAM disk support is enabled.
        S390    S390 architecture is enabled.
        SCSI    Appropriate SCSI support is enabled.
                        A lot of drivers has their options described inside of
                        Documentation/scsi/.
        SECURITY Different security models are enabled.
        SELINUX SELinux support is enabled.
        SERIAL  Serial support is enabled.
        SH      SuperH architecture is enabled.
        SMP     The kernel is an SMP kernel.
        SPARC   Sparc architecture is enabled.
        SWSUSP  Software suspend (hibernation) is enabled.
        SUSPEND System suspend states are enabled.
        FTRACE  Function tracing enabled.
        TPM     TPM drivers are enabled.
        TS      Appropriate touchscreen support is enabled.
        UMS     USB Mass Storage support is enabled.
        USB     USB support is enabled.
        USBHID  USB Human Interface Device support is enabled.
        V4L     Video For Linux support is enabled.
        VGA     The VGA console has been enabled.
        VT      Virtual terminal support is enabled.
        WDT     Watchdog support is enabled.
        XT      IBM PC/XT MFM hard disk support is enabled.
        X86-32  X86-32, aka i386 architecture is enabled.
        X86-64  X86-64 architecture is enabled.
                        More X86-64 boot options can be found in
                        Documentation/x86/x86_64/boot-options.txt .
        X86     Either 32bit or 64bit x86 (same as X86-32+X86-64)
In addition, the following text indicates that the option:

        BUGS=   Relates to possible processor bugs on the said processor.
        KNL     Is a kernel start-up parameter.
        BOOT    Is a boot loader parameter.
Parameters denoted with BOOT are actually interpreted by the boot loader, and have no meaning to the kernel directly. Do not modify the syntax of boot loader parameters without extreme need or coordination with <Documentation/x86/boot.txt>.

There are also arch-specific kernel-parameters not documented here. See for example <Documentation/x86/x86_64/boot-options.txt>.

Note that ALL kernel parameters listed below are CASE SENSITIVE, and that a trailing = on the name of any parameter states that that parameter will be entered as an environment variable, whereas its absence indicates that it will appear as a kernel argument readable via /proc/cmdline by programs running once the system is up.

The number of kernel parameters is not limited, but the length of the complete command line (parameters including spaces etc.) is limited to a fixed number of characters. This limit depends on the architecture and is between 256 and 4096 characters. It is defined in the file ./include/asm/setup.h as COMMAND_LINE_SIZE.

        acpi=           [HW,ACPI,X86]
                        Advanced Configuration and Power Interface
                        Format: { force | off | strict | noirq | rsdt }
                        force -- enable ACPI if default was off
                        off -- disable ACPI if default was on
                        noirq -- do not use ACPI for IRQ routing
                        strict -- Be less tolerant of platforms that are not
                                strictly ACPI specification compliant.
                        rsdt -- prefer RSDT over (default) XSDT
                        copy_dsdt -- copy DSDT to memory

                        See also Documentation/power/pm.txt, pci=noacpi

        acpi_apic_instance=     [ACPI, IOAPIC]
                        Format: <int>
                        2: use 2nd APIC table, if available
                        1,0: use 1st APIC table
                        default: 0

        acpi_backlight= [HW,ACPI]
                        acpi_backlight=vendor
                        acpi_backlight=video
                        If set to vendor, prefer vendor specific driver
                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
                        of the ACPI video.ko driver.

        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
                        Format: <int>
                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
                        debug output.  Bits in debug_layer correspond to a
                        _COMPONENT in an ACPI source file, e.g.,
                            #define COMPONENT ACPIPCI_COMPONENT
                        Bits in debug_level correspond to a level in
                        ACPI_DEBUG_PRINT statements, e.g.,
                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
                        The debug_level mask defaults to "info".  See
                        Documentation/acpi/debug.txt for more information about
                        debug layers and levels.

                        Enable processor driver info messages:
                            acpi.debug_layer=0x20000000
                        Enable PCI/PCI interrupt routing info messages:
                            acpi.debug_layer=0x400000
                        Enable AML "Debug" output, i.e., stores to the Debug
                        object while interpreting AML:
                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
                        Enable all messages related to ACPI hardware:
                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff

                        Some values produce so much output that the system is
                        unusable.  The "log_buf_len" parameter may be useful
                        if you need to capture more output.

        acpi_display_output=    [HW,ACPI]
                        acpi_display_output=vendor
                        acpi_display_output=video
                        See above.

        acpi_irq_balance [HW,ACPI]
                        ACPI will balance active IRQs
                        default in APIC mode

        acpi_irq_nobalance [HW,ACPI]
                        ACPI will not move active IRQs (default)
                        default in PIC mode

        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
                        Format: <irq>,<irq>...

        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
                        use by PCI
                        Format: <irq>,<irq>...

        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT

        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
                        Format: To spoof as Windows 98: ="Microsoft Windows"

        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
                        acpi_osi="string1"      # add string1 -- only one string
                        acpi_osi="!string2"     # remove built-in string2
                        acpi_osi=               # disable all strings

        acpi_pm_good    [X86]
                        Override the pmtimer bug detection: force the kernel
                        to assume that this machine's pmtimer latches its value
                        and always returns good values.

        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
                        Format: { level | edge | high | low }

        acpi_serialize  [HW,ACPI] force serialization of AML methods

        acpi_skip_timer_override [HW,ACPI]
                        Recognize and ignore IRQ0/pin2 Interrupt Override.
                        For broken nForce2 BIOS resulting in XT-PIC timer.

        acpi_sleep=     [HW,ACPI] Sleep options
                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
                                  old_ordering, s4_nonvs, sci_force_enable }
                        See Documentation/power/video.txt for information on
                        s3_bios and s3_mode.
                        s3_beep is for debugging; it makes the PC's speaker beep
                        as soon as the kernel's real-mode entry point is called.
                        s4_nohwsig prevents ACPI hardware signature from being
                        used during resume from hibernation.
                        old_ordering causes the ACPI 1.0 ordering of the _PTS
                        control method, with respect to putting devices into
                        low power states, to be enforced (the ACPI 2.0 ordering
                        of PTS is used by default).
                        nonvs prevents the kernel from saving/restoring the
                        ACPI NVS memory during suspend/hibernation and resume.
                        sciforce_enable causes the kernel to set SCI_EN directly
                        on resume from S1/S3 (which is against the ACPI spec,
                        but some broken systems don't work without it).

        acpi_use_timer_override [HW,ACPI]
                        Use timer override. For some broken Nvidia NF5 boards
                        that require a timer override, but don't have HPET

        acpi_enforce_resources= [ACPI]
                        { strict | lax | no }
                        Check for resource conflicts between native drivers
                        and ACPI OperationRegions (SystemIO and SystemMemory
                        only). IO ports and memory declared in ACPI might be
                        used by the ACPI subsystem in arbitrary AML code and
                        can interfere with legacy drivers.
                        strict (default): access to resources claimed by ACPI
                        is denied; legacy drivers trying to access reserved
                        resources will fail to bind to device using them.
                        lax: access to resources claimed by ACPI is allowed;
                        legacy drivers trying to access reserved resources
                        will bind successfully but a warning message is logged.
                        no: ACPI OperationRegions are not marked as reserved,
                        no further checks are performed.

        ad1848=         [HW,OSS]
                        Format: <io>,<irq>,<dma>,<dma2>,<type>

        add_efi_memmap  [EFI; X86] Include EFI memory map in
                        kernel's map of available physical RAM.

        advansys=       [HW,SCSI]
                        See header of drivers/scsi/advansys.c.

        aedsp16=        [HW,OSS] Audio Excel DSP 16
                        Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
                        See also header of sound/oss/aedsp16.c.

        agp=            [AGP]
                        { off | try_unsupported }
                        off: disable AGP support
                        try_unsupported: try to drive unsupported chipsets
                                (may crash computer or cause data corruption)

        aha152x=        [HW,SCSI]
                        See Documentation/scsi/aha152x.txt.

        aha1542=        [HW,SCSI]
                        Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]

        aic7xxx=        [HW,SCSI]
                        See Documentation/scsi/aic7xxx.txt.

        aic79xx=        [HW,SCSI]
                        See Documentation/scsi/aic79xx.txt.

        alignment=      [KNL,ARM]
                        Allow the default userspace alignment fault handler
                        behaviour to be specified.  Bit 0 enables warnings,
                        bit 1 enables fixups, and bit 2 sends a segfault.

        amd_iommu=      [HW,X86-84]
                        Pass parameters to the AMD IOMMU driver in the system.
                        Possible values are:
                        fullflush - enable flushing of IO/TLB entries when
                                    they are unmapped. Otherwise they are
                                    flushed before they will be reused, which
                                    is a lot of faster
                        off       - do not initialize any AMD IOMMU found in
                                    the system

        amijoy.map=     [HW,JOY] Amiga joystick support
                        Map of devices attached to JOY0DAT and JOY1DAT
                        Format: <a>,<b>
                        See also Documentation/kernel/input/joystick.txt

        analog.map=     [HW,JOY] Analog joystick and gamepad support
                        Specifies type or capabilities of an analog joystick
                        connected to one of 16 gameports
                        Format: <type1>,<type2>,..<type16>

        apc=            [HW,SPARC]
                        Power management functions (SPARCstation-4/5 + deriv.)
                        Format: noidle
                        Disable APC CPU standby support. SPARCstation-Fox does
                        not play well with APC CPU idle - disable it if you have
                        APC and your system crashes randomly.

        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
                        Change the output verbosity whilst booting
                        Format: { quiet (default) | verbose | debug }
                        Change the amount of debugging information output
                        when initialising the APIC and IO-APIC components.

        autoconf=       [IPV6]
                        See Documentation/networking/ipv6.txt.

        show_lapic=     [APIC,X86] Advanced Programmable Interrupt Controller
                        Limit apic dumping. The parameter defines the maximal
                        number of local apics being dumped. Also it is possible
                        to set it to "all" by meaning -- no limit here.
                        Format: { 1 (default) | 2 | ... | all }.
                        The parameter valid if only apic=debug or
                        apic=verbose is specified.
                        Example: apic=debug show_lapic=all

        apm=            [APM] Advanced Power Management
                        See header of arch/x86/kernel/apm_32.c.

        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
                        Format: <io>,<irq>,<nodeID>

        ataflop=        [HW,M68k]

        atarimouse=     [HW,MOUSE] Atari Mouse

        atascsi=        [HW,SCSI] Atari SCSI

        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
                        EzKey and similar keyboards

        atkbd.reset=    [HW] Reset keyboard during initialization

        atkbd.set=      [HW] Select keyboard code set
                        Format: <int> (2 = AT (default), 3 = PS/2)

        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
                        keyboards

        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
                        Format: <bool> (0 = real, 1 = synthetic (default))

        atkbd.softrepeat= [HW]
                        Use software keyboard repeat

        autotest        [IA64]

        baycom_epp=     [HW,AX25]
                        Format: <io>,<mode>

        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
                        Format: <io>,<mode>
                        See header of drivers/net/hamradio/baycom_par.c.

        baycom_ser_fdx= [HW,AX25]
                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
                        Format: <io>,<irq>,<mode>[,<baud>]
                        See header of drivers/net/hamradio/baycom_ser_fdx.c.

        baycom_ser_hdx= [HW,AX25]
                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
                        Format: <io>,<irq>,<mode>
                        See header of drivers/net/hamradio/baycom_ser_hdx.c.

        boot_delay=     Milliseconds to delay each printk during boot.
                        Values larger than 10 seconds (10000) are changed to
                        no delay (0).
                        Format: integer

        bootmem_debug   [KNL] Enable bootmem allocator debug messages.

        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
        bttv.radio=     Most important insmod options are available as
                        kernel args too.
        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
        bttv.tuner=     and Documentation/video4linux/bttv/CARDLIST

        BusLogic=       [HW,SCSI]
                        See drivers/scsi/BusLogic.c, comment before function
                        BusLogic_ParseDriverOptions().

        c101=           [NET] Moxa C101 synchronous serial card

        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
                        Sometimes CPU hardware bugs make them report the cache
                        size incorrectly. The kernel will attempt work arounds
                        to fix known problems, but for some CPUs it is not
                        possible to determine what the correct size should be.
                        This option provides an override for these situations.

        capability.disable=
                        [SECURITY] Disable capabilities.  This would normally
                        be used only if an alternative security model is to be
                        configured.  Potentially dangerous and should only be
                        used if you are entirely sure of the consequences.

        ccw_timeout_log [S390]
                        See Documentation/s390/CommonIO for details.

        cgroup_disable= [KNL] Disable a particular controller
                        Format: {name of the controller(s) to disable}
                                {Currently supported controllers - "memory"}

        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
                        Format: { "0" | "1" }
                        See security/selinux/Kconfig help text.
                        0 -- check protection applied by kernel (includes
                                any implied execute protection).
                        1 -- check protection requested by application.
                        Default value is set via a kernel config option.
                        Value can be changed at runtime via
                                /selinux/checkreqprot.

        cio_ignore=     [S390]
                        See Documentation/s390/CommonIO for details.

        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
                        [Deprecated]
                        Forces specified clocksource (if available) to be used
                        when calculating gettimeofday(). If specified
                        clocksource is not available, it defaults to PIT.
                        Format: { pit | tsc | cyclone | pmtmr }

        clocksource=    [GENERIC_TIME] Override the default clocksource
                        Format: <string>
                        Override the default clocksource and use the clocksource
                        with the name specified.
                        Some clocksource names to choose from, depending on
                        the platform:
                        [all] jiffies (this is the base, fallback clocksource)
                        [ACPI] acpi_pm
                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
                                pxa_timer,timer3,32k_counter,timer0_1
                        [AVR32] avr32
                        [X86-32] pit,hpet,tsc,vmi-timer;
                                scx200_hrt on Geode; cyclone on IBM x440
                        [MIPS] MIPS
                        [PARISC] cr16
                        [S390] tod
                        [SH] SuperH
                        [SPARC64] tick
                        [X86-64] hpet,tsc

        clearcpuid=BITNUM [X86]
                        Disable CPUID feature X for the kernel. See
                        arch/x86/include/asm/cpufeature.h for the valid bit
                        numbers. Note the Linux specific bits are not necessarily
                        stable over kernel options, but the vendor specific
                        ones should be.
                        Also note that user programs calling CPUID directly
                        or using the feature without checking anything
                        will still see it. This just prevents it from
                        being used by the kernel or shown in /proc/cpuinfo.
                        Also note the kernel might malfunction if you disable
                        some critical bits.

        cmo_free_hint=  [PPC] Format: { yes | no }
                        Specify whether pages are marked as being inactive
                        when they are freed.  This is used in CMO environments
                        to determine OS memory pressure for page stealing by
                        a hypervisor.
                        Default: yes

        code_bytes      [X86] How many bytes of object code to print
                        in an oops report.
                        Range: 0 - 8192
                        Default: 64

        com20020=       [HW,NET] ARCnet - COM20020 chipset
                        Format:
                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]

        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
                        Format: <io>[,<irq>]

        com90xx=        [HW,NET]
                        ARCnet - COM90xx chipset (memory-mapped buffers)
                        Format: <io>[,<irq>[,<memstart>]]

        condev=         [HW,S390] console device
        conmode=

        console=        [KNL] Output console device and options.

                tty<n>  Use the virtual console device <n>.

                ttyS<n>[,options]
                ttyUSB0[,options]
                        Use the specified serial port.  The options are of
                        the form "bbbbpnf", where "bbbb" is the baud rate,
                        "p" is parity ("n", "o", or "e"), "n" is number of
                        bits, and "f" is flow control ("r" for RTS or
                        omit it).  Default is "9600n8".

                        See Documentation/serial-console.txt for more
                        information.  See
                        Documentation/networking/netconsole.txt for an
                        alternative.

                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                        Start an early, polled-mode console on the 8250/16550
                        UART at the specified I/O port or MMIO address,
                        switching to the matching ttyS device later.  The
                        options are the same as for ttyS, above.

                If the device connected to the port is not a TTY but a braille
                device, prepend "brl," before the device type, for instance
                        console=brl,ttyS0
                For now, only VisioBraille is supported.

        consoleblank=   [KNL] The console blank (screen saver) timeout in
                        seconds. Defaults to 10*60 = 10mins. A value of 0
                        disables the blank timer.

        coredump_filter=
                        [KNL] Change the default value for
                        /proc/<pid>/coredump_filter.
                        See also Documentation/filesystems/proc.txt.

        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
                        Format:
                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]

        crashkernel=nn[KMG]@ss[KMG]
                        [KNL] Reserve a chunk of physical memory to
                        hold a kernel to switch to with kexec on panic.

        crashkernel=range1:size1[,range2:size2,...][@offset]
                        [KNL] Same as above, but depends on the memory
                        in the running system. The syntax of range is
                        start-[end] where start and end are both
                        a memory unit (amount[KMG]). See also
                        Documentation/kdump/kdump.txt for a example.

        cs89x0_dma=     [HW,NET]
                        Format: <dma>

        cs89x0_media=   [HW,NET]
                        Format: { rj45 | aui | bnc }

        dasd=           [HW,NET]
                        See header of drivers/s390/block/dasd_devmap.c.

        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
                        (one device per port)
                        Format: <port#>,<type>
                        See also Documentation/input/joystick-parport.txt

        debug           [KNL] Enable kernel debugging (events log level).

        debug_locks_verbose=
                        [KNL] verbose self-tests
                        Format=<0|1>
                        Print debugging info while doing the locking API
                        self-tests.
                        We default to 0 (no extra messages), setting it to
                        1 will print a lot more information - normally
                        only useful to kernel developers.

        debug_objects   [KNL] Enable object debugging

        no_debug_objects
                        [KNL] Disable object debugging

        debugpat        [X86] Enable PAT debugging

        decnet.addr=    [HW,NET]
                        Format: <area>[,<node>]
                        See also Documentation/networking/decnet.txt.

        default_hugepagesz=
                        [same as hugepagesz=] The size of the default
                        HugeTLB page size. This is the size represented by
                        the legacy /proc/ hugepages APIs, used for SHM, and
                        default size when mounting hugetlbfs filesystems.
                        Defaults to the default architecture's huge page size
                        if not specified.

        dhash_entries=  [KNL]
                        Set number of hash buckets for dentry cache.

        digi=           [HW,SERIAL]
                        IO parameters + enable/disable command.

        digiepca=       [HW,SERIAL]
                        See drivers/char/README.epca and
                        Documentation/serial/digiepca.txt.

        disable=        [IPV6]
                        See Documentation/networking/ipv6.txt.

        disable_ipv6=   [IPV6]
                        See Documentation/networking/ipv6.txt.

        disable_mtrr_cleanup [X86]
                        The kernel tries to adjust MTRR layout from continuous
                        to discrete, to make X server driver able to add WB
                        entry later. This parameter disables that.

        disable_mtrr_trim [X86, Intel and AMD only]
                        By default the kernel will trim any uncacheable
                        memory out of your available memory pool based on
                        MTRR settings.  This parameter disables that behavior,
                        possibly causing your machine to run very slowly.

        disable_timer_pin_1 [X86]
                        Disable PIN 1 of APIC timer
                        Can be useful to work around chipset bugs.

        dmasound=       [HW,OSS] Sound subsystem buffers

        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
                        this option disables the debugging code at boot.

        dma_debug_entries=<number>
                        This option allows to tune the number of preallocated
                        entries for DMA-API debugging code. One entry is
                        required per DMA-API allocation. Use this if the
                        DMA-API debugging code disables itself because the
                        architectural default is too low.

        dma_debug_driver=<driver_name>
                        With this option the DMA-API debugging driver
                        filter feature can be enabled at boot time. Just
                        pass the driver to filter for as the parameter.
                        The filter can be disabled or changed to another
                        driver later using sysfs.

        dscc4.setup=    [NET]

        dtc3181e=       [HW,SCSI]

        dynamic_printk  Enables pr_debug()/dev_dbg() calls if
                        CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
                        These can also be switched on/off via
                        <debugfs>/dynamic_printk/modules

        earlycon=       [KNL] Output early console device and options.
                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                        Start an early, polled-mode console on the 8250/16550
                        UART at the specified I/O port or MMIO address.
                        The options are the same as for ttyS, above.

        earlyprintk=    [X86,SH,BLACKFIN]
                        earlyprintk=vga
                        earlyprintk=serial[,ttySn[,baudrate]]
                        earlyprintk=ttySn[,baudrate]
                        earlyprintk=dbgp[debugController#]

                        Append ",keep" to not disable it when the real console
                        takes over.

                        Only vga or serial or usb debug port at a time.

                        Currently only ttyS0 and ttyS1 are supported.

                        Interaction with the standard serial driver is not
                        very good.

                        The VGA output is eventually overwritten by the real
                        console.

        ekgdboc=        [X86,KGDB] Allow early kernel console debugging
                        ekgdboc=kbd

                        This is desgined to be used in conjunction with
                        the boot argument: earlyprintk=vga

        eata=           [HW,SCSI]

        edd=            [EDD]
                        Format: {"off" | "on" | "skip[mbr]"}

        eisa_irq_edge=  [PARISC,HW]
                        See header of drivers/parisc/eisa.c.

        elanfreq=       [X86-32]
                        See comment before function elanfreq_setup() in
                        arch/x86/kernel/cpu/cpufreq/elanfreq.c.

        elevator=       [IOSCHED]
                        Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
                        See Documentation/block/as-iosched.txt and
                        Documentation/block/deadline-iosched.txt for details.

        elfcorehdr=     [IA64,PPC,SH,X86]
                        Specifies physical address of start of kernel core
                        image elf header. Generally kexec loader will
                        pass this option to capture kernel.
                        See Documentation/kdump/kdump.txt for details.

        enable_mtrr_cleanup [X86]
                        The kernel tries to adjust MTRR layout from continuous
                        to discrete, to make X server driver able to add WB
                        entry later. This parameter enables that.

        enable_timer_pin_1 [X86]
                        Enable PIN 1 of APIC timer
                        Can be useful to work around chipset bugs
                        (in particular on some ATI chipsets).
                        The kernel tries to set a reasonable default.

        enforcing       [SELINUX] Set initial enforcing status.
                        Format: {"0" | "1"}
                        See security/selinux/Kconfig help text.
                        0 -- permissive (log only, no denials).
                        1 -- enforcing (deny and log).
                        Default value is 0.
                        Value can be changed at runtime via /selinux/enforce.

        erst_disable    [ACPI]
                        Disable Error Record Serialization Table (ERST)
                        support.

        ether=          [HW,NET] Ethernet cards parameters
                        This option is obsoleted by the "netdev=" option, which
                        has equivalent usage. See its documentation for details.

        failslab=
        fail_page_alloc=
        fail_make_request=[KNL]
                        General fault injection mechanism.
                        Format: <interval>,<probability>,<space>,<times>
                        See also /Documentation/fault-injection/.

        fd_mcs=         [HW,SCSI]
                        See header of drivers/scsi/fd_mcs.c.

        fdomain=        [HW,SCSI]
                        See header of drivers/scsi/fdomain.c.

        floppy=         [HW]
                        See Documentation/blockdev/floppy.txt.

        force_pal_cache_flush
                        [IA-64] Avoid check_sal_cache_flush which may hang on
                        buggy SAL_CACHE_FLUSH implementations. Using this
                        parameter will force ia64_sal_cache_flush to call
                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.

        ftrace=[tracer]
                        [FTRACE] will set and start the specified tracer
                        as early as possible in order to facilitate early
                        boot debugging.

        ftrace_dump_on_oops[=orig_cpu]
                        [FTRACE] will dump the trace buffers on oops.
                        If no parameter is passed, ftrace will dump
                        buffers of all CPUs, but if you pass orig_cpu, it will
                        dump only the buffer of the CPU that triggered the
                        oops.

        ftrace_filter=[function-list]
                        [FTRACE] Limit the functions traced by the function
                        tracer at boot up. function-list is a comma separated
                        list of functions. This list can be changed at run
                        time by the set_ftrace_filter file in the debugfs
                        tracing directory.

        ftrace_notrace=[function-list]
                        [FTRACE] Do not trace the functions specified in
                        function-list. This list can be changed at run time
                        by the set_ftrace_notrace file in the debugfs
                        tracing directory.

        ftrace_graph_filter=[function-list]
                        [FTRACE] Limit the top level callers functions traced
                        by the function graph tracer at boot up.
                        function-list is a comma separated list of functions
                        that can be changed at run time by the
                        set_graph_function file in the debugfs tracing directory.

        gamecon.map[2|3]=
                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
                        support via parallel port (up to 5 devices per port)
                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
                        See also Documentation/input/joystick-parport.txt

        gamma=          [HW,DRM]

        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
                        Format: off | on
                        default: on

        gcov_persist=   [GCOV] When non-zero (default), profiling data for
                        kernel modules is saved and remains accessible via
                        debugfs, even when the module is unloaded/reloaded.
                        When zero, profiling data is discarded and associated
                        debugfs files are removed at module unload time.

        gdth=           [HW,SCSI]
                        See header of drivers/scsi/gdth.c.

        gpt             [EFI] Forces disk with valid GPT signature but
                        invalid Protective MBR to be treated as GPT.

        gvp11=          [HW,SCSI]

        hashdist=       [KNL,NUMA] Large hashes allocated during boot
                        are distributed across NUMA nodes.  Defaults on
                        for 64bit NUMA, off otherwise.
                        Format: 0 | 1 (for off | on)

        hcl=            [IA-64] SGI's Hardware Graph compatibility layer

        hd=             [EIDE] (E)IDE hard drive subsystem geometry
                        Format: <cyl>,<head>,<sect>

        hest_disable    [ACPI]
                        Disable Hardware Error Source Table (HEST) support;
                        corresponding firmware-first mode error processing
                        logic will be disabled.

        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
                        size of <nn>. This works even on boxes that have no
                        highmem otherwise. This also works to reduce highmem
                        size on bigger boxes.

        highres=        [KNL] Enable/disable high resolution timer mode.
                        Valid parameters: "on", "off"
                        Default: "on"

        hisax=          [HW,ISDN]
                        See Documentation/isdn/README.HiSax.

        hlt             [BUGS=ARM,SH]

        hpet=           [X86-32,HPET] option to control HPET usage
                        Format: { enable (default) | disable | force |
                                verbose }
                        disable: disable HPET and use PIT instead
                        force: allow force enabled of undocumented chips (ICH4,
                                VIA, nVidia)
                        verbose: show contents of HPET registers during setup

        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
                        On x86-64 and powerpc, this option can be specified
                        multiple times interleaved with hugepages= to reserve
                        huge pages of different sizes. Valid pages sizes on
                        x86-64 are 2M (when the CPU supports "pse") and 1G
                        (when the CPU supports the "pdpe1gb" cpuinfo flag)
                        Note that 1GB pages can only be allocated at boot time
                        using hugepages= and not freed afterwards.

        hvc_iucv=       [S390] Number of z/VM IUCV hypervisor console (HVC)
                               terminal devices. Valid values: 0..8
        hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
                               If specified, z/VM IUCV HVC accepts connections
                               from listed z/VM user IDs only.

        i2c_bus=        [HW] Override the default board specific I2C bus speed
                             or register an additional I2C bus that is not
                             registered from board initialization code.
                             Format:
                             <bus_id>,<clkrate>

        i8042.debug     [HW] Toggle i8042 debug mode
        i8042.direct    [HW] Put keyboard port into non-translated mode
        i8042.dumbkbd   [HW] Pretend that controller can only read data from
                             keyboard and cannot control its state
                             (Don't attempt to blink the leds)
        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
        i8042.nokbd     [HW] Don't check/create keyboard port
        i8042.noloop    [HW] Disable the AUX Loopback command while probing
                             for the AUX port
        i8042.nomux     [HW] Don't check presence of an active multiplexing
                             controller
        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
                             controllers
        i8042.panicblink=
                        [HW] Frequency with which keyboard LEDs should blink
                             when kernel panics (default is 0.5 sec)
        i8042.reset     [HW] Reset the controller during init and cleanup
        i8042.unlock    [HW] Unlock (ignore) the keylock

        i810=           [HW,DRM]

        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
                        indicates that the driver is running on unsupported
                        hardware.
        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
                        does not match list of supported models.
        i8k.power_status
                        [HW] Report power status in /proc/i8k
                        (disabled by default)
        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
                        capability is set.

        ibmmcascsi=     [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
                        See Documentation/mca.txt.

        icn=            [HW,ISDN]
                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]

        ide-core.nodma= [HW] (E)IDE subsystem
                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
                        .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
                        .cdrom .chs .ignore_cable are additional options
                        See Documentation/ide/ide.txt.

        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
                        Claim all unknown PCI IDE storage controllers.

        idle=           [X86]
                        Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
                        Poll forces a polling idle loop that can slightly
                        improve the performance of waking up a idle CPU, but
                        will use a lot of power and make the system run hot.
                        Not recommended.
                        idle=mwait: On systems which support MONITOR/MWAIT but
                        the kernel chose to not use it because it doesn't save
                        as much power as a normal idle loop, use the
                        MONITOR/MWAIT idle loop anyways. Performance should be
                        the same as idle=poll.
                        idle=halt: Halt is forced to be used for CPU idle.
                        In such case C2/C3 won't be used again.