This is a non-complete but fairly verbose alphabetically organized list of possible kernel boot-time parameters. Anyone requiring more than what is provided here should refer to their vendor, sysadmin or the official Red Hat documentation located at

Kernel Boot-Time Parameters

Advanced Configuration and Power Interface Format: { force | off | ht | strict | noirq } force — enable ACPI if default was off off — disable ACPI if default was on noirq — do not use ACPI for IRQ routing ht — run only enough ACPI to enable Hyper Threading strict — Be less tolerant of platforms that are not strictly ACPI specification compliant.

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

Format: <int> 2: use 2nd APIC table, if available 1,0: use 1st APIC table default: 0

Sleep options Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering } See Documentation/power/video.txt for 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, wrt putting devices into low power states, to be enforced (the ACPI 2.0 ordering of _PTS is used by default).

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

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

    acpi_irq_isa=    [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
            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_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_use_timer_override [HW,ACPI}
            Use timer override. For some broken Nvidia NF5 boards
            that require a timer override, but don’t have

    acpi.debug_layer=    [HW,ACPI]
            Format: <int>
            Each bit of the <int> indicates an ACPI debug layer,
            1: enable, 0: disable. It is useful for boot time
            debugging. After system has booted up, it can be set
            via /sys/module/acpi/parameters/debug_layer.
            CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
            Available bits (add the numbers together) to enable debug output
            for specific parts of the ACPI subsystem:
            0x01 utilities 0x02 hardware 0x04 events 0x08 tables
            0x10 namespace 0x20 parser 0x40 dispatcher
            0x80 executer 0x100 resources 0x200 acpica debugger
            0x400 os services 0x800 acpica disassembler.
            The number can be in decimal or prefixed with 0x in hex.
            Warning: Many of these options can produce a lot of
            output and make your system unusable. Be very careful.

    acpi.debug_level=    [HW,ACPI]
            Format: <int>
            Each bit of the <int> indicates an ACPI debug level,
            1: enable, 0: disable. It is useful for boot time
            debugging. After system has booted up, it can be set
            via /sys/module/acpi/parameters/debug_level.
            CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
            Available bits (add the numbers together) to enable different
            debug output levels of the ACPI subsystem:
            0x01 error 0x02 warn 0x04 init 0x08 debug object
            0x10 info 0x20 init names 0x40 parse 0x80 load
            0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
            0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
            0x10000 resources 0x20000 user requests 0x40000 package.
            The number can be in decimal or prefixed with 0x in hex.
            Warning: Many of these options can produce a lot of
            output and make your system unusable. Be very careful.

    acpi_pm_good    [X86-32,X86-64]
            Override the pmtimer bug detection: force the kernel
            to assume that this machine’s pmtimer latches its value
            and always returns good values.

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

    enable_timer_pin_1 [i386,x86-64]
            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.

    disable_timer_pin_1 [i386,x86-64]
            Disable PIN 1 of APIC timer
            Can be useful to work around chipset bugs.

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

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

    advwdt=        [HW,WDT] Advantech WDT
            Format: <iostart>,<iostop>

    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.

    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.

    amd_iommu=    [HW,X86-84]
            Pass parameters to the AMD IOMMU driver in the system.
            Possible values are:
            isolate – enable device isolation (each device, as far
                      as possible, will get its own protection
    amd_iommu_size= [HW,X86-64]
            Define the size of the aperture for the AMD IOMMU
            driver. Possible values are:
            ’32M’, ’64M’ (default), ‘128M’, ‘256M’, ‘512M’, ‘1G’    [HW,JOY] Amiga joystick support
            Map of devices attached to JOY0DAT and JOY1DAT
            Format: <a>,<b>
            See also Documentation/kernel/input/joystick.txt    [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,i386] 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.

    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

    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

    bttv.card=    [HW,V4L] bttv (bt848 + bt878 based grabber cards)    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

    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.

    security=    [SECURITY] Choose a security module to enable at boot.
            If this boot parameter is not specified, only the first
            security module asking for security registration will be
            loaded. An invalid security module name will be treated
            as if no module has been chosen.

            [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

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

    clock=        [BUGS=X86-32, HW] gettimeofday clocksource override.
            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,
            [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
            include/asm-x86/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.

    code_bytes    [IA32/X86_64] How many bytes of object code to print
            in an oops report.
            Range: 0 – 8192
            Default: 64

            [IA32/X86_64] Disable/Enable interrupt 0 timer routing
            over the 8254 in addition to over the IO-APIC. The
            kernel tries to set a sensible default.

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

    com20020=    [HW,NET] ARCnet – COM20020 chipset

    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

    console=    [KNL] Output console device and options.

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

            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

            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
        For now, only VisioBraille is supported.

    earlycon=    [KNL] Output early console device and 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.

            [HW] Never suspend the console
            Disable suspending of consoles during suspend and
            hibernate operations.  Once disabled, debugging
            messages can reach various consoles while the rest
            of the system is being put to sleep (ie, while
            debugging driver suspend/resume hooks).  This may
            not work reliably with all consoles, but is known
            to work with serial and VGA consoles.

    cpcihp_generic=    [HW,PCI] Generic port I/O CompactPCI driver

            [KNL] Reserve a chunk of physical memory to
            hold a kernel to switch to with kexec on panic.

            [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.

    cs4232=        [HW,OSS]
            Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>

    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.[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).

            [KNL] verbose self-tests
            Print debugging info while doing the locking API
            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

    debugpat    [X86] Enable PAT debugging

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

    vt.default_blu=    [VT]
            Format: <blue0>,<blue1>,<blue2>,…,<blue15>
            Change the default blue palette of the console.
            This is a 16-member array composed of values
            ranging from 0-255.

    vt.default_grn=    [VT]
            Format: <green0>,<green1>,<green2>,…,<green15>
            Change the default green palette of the console.
            This is a 16-member array composed of values
            ranging from 0-255.

    vt.default_red=    [VT]
            Format: <red0>,<red1>,<red2>,…,<red15>
            Change the default red palette of the console.
            This is a 16-member array composed of values
            ranging from 0-255.

            Set system-wide default UTF-8 mode for all tty’s.
            Default is 1, i.e. UTF-8 mode is enabled for all
            newly opened terminals.

    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

    disable_mtrr_cleanup [X86]
    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/disables that.

    mtrr_chunk_size=nn[KMG] [X86]
            used for mtrr cleanup. It is largest continous chunk
            that could hold holes aka. UC entries.

    mtrr_gran_size=nn[KMG] [X86]
            Used for mtrr cleanup. It is granularity of mtrr block.
            Default is 1.
            Large value could prevent small alignment from
            using up MTRRs.

    mtrr_spare_reg_nr=n [X86]
            Format: <integer>
            Range: 0,7 : spare reg number
            Default : 1
            Used for mtrr cleanup. It is spare mtrr entries number.
            Set to 2 or more if your graphical card needs more.

    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.

    dmasound=    [HW,OSS] Sound subsystem buffers

    dscc4.setup=    [NET]

    dtc3181e=    [HW,SCSI]

    earlyprintk=    [X86-32,X86-64,SH,BLACKFIN]

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

            Only vga or serial at a time, not both.

            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

    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

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

    elfcorehdr=    [X86-32, X86_64]
            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.

    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.

    es1371=        [HW,OSS]
            Format: <spdif>,[<nomix>,[<amplifier>]]
            See also header of sound/oss/es1371.c.

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

    eurwdt=        [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
            Format: <io>[,<irq>]

            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/floppy.txt.

            [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.[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

    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 IA-64, 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>

    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.

    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.
            [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.    [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
    i8042.nopnp    [HW] Don’t use ACPIPnP / PnPBIOS to discover KBD/AUX
            [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
    i8k.force    [HW] Activate i8k driver even if SMM BIOS signature
            does not match list of supported models.
            [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=        [HW] (E)IDE subsystem
            Format: ide=nodma or ide=doubler
            See Documentation/ide/ide.txt.

    idebus=        [HW] (E)IDE subsystem – VLB/PCI bus speed
            See Documentation/ide/ide.txt.

    idle=        [X86]
            Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
            Poll forces a polling idle loop that can slightly improves 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.
            idle=nomwait. Disable mwait for CPU C-states

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

    ignore_loglevel    [KNL]
            Ignore loglevel setting – this will print /all/
            kernel messages to the console. Useful for debugging.

    ihash_entries=    [KNL]
            Set number of hash buckets for inode cache.

    in2000=        [HW,SCSI]
            See header of drivers/scsi/in2000.c.

    init=        [KNL]
            Format: <full_path>
            Run specified binary instead of /sbin/init as init

    initcall_debug    [KNL] Trace initcalls as they are executed.  Useful
            for working out where the kernel is dying during

    initrd=        [BOOT] Specify the location of the initial ramdisk

    inport.irq=    [HW] Inport (ATI XL and Microsoft) busmouse driver
            Format: <irq>

    inttest=    [IA64]

    iommu=        [x86]

    intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
            Disable intel iommu driver.
        igfx_off [Default Off]
            By default, gfx is mapped as normal device. If a gfx
            device has a dedicated DMAR unit, the DMAR unit is
            bypassed by not enabling DMAR with this option. In
            this case, gfx device will use physical address for
        forcedac [x86_64]
            With this option iommu will not optimize to look
            for io virtual address below 32 bit forcing dual
            address cycle on pci bus for cards supporting greater
            than 32 bit addressing. The default is to look
            for translation below 32 bit and if not available
            then look in the higher range.
        strict [Default Off]
            With this option on every unmap_single operation will
            result in a hardware IOTLB flush operation as opposed
            to batching them for performance.

    io_delay=    [X86-32,X86-64] I/O delay method
            Standard port 0x80 based delay
            Alternate port 0xed based delay (needed on some systems)
            Simple two microseconds delay
            No delay

    io7=        [HW] IO7 for Marvel based alpha systems
            See comment before marvel_specify_io7 in

    ip=        [IP_PNP]
            See Documentation/filesystems/nfsroot.txt.

    ip2=        [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
            See comment before ip2_setup() in

    ips=        [HW,SCSI] Adaptec / IBM ServeRAID controller
            See header of drivers/scsi/ips.c.

    ports=        [IP_VS_FTP] IPVS ftp helper module
            Default is 21.
            Up to 8 (IP_VS_APP_MAX_PORTS) ports
            may be specified.
            Format: <port>,<port>….

    irqfixup    [HW]
            When an interrupt is not handled search all handlers
            for it. Intended to get systems with badly broken
            firmware running.

    irqpoll        [HW]
            When an interrupt is not handled search all handlers
            for it. Also check all handlers each timer
            interrupt. Intended to get systems with badly broken
            firmware running.

    isapnp=        [ISAPNP]
            Format: <RDP>,<reset>,<pci_scan>,<verbosity>

    isolcpus=    [KNL,SMP] Isolate CPUs from the general scheduler.
            <cpu number>,…,<cpu number>
            <cpu number>-<cpu number>  (must be a positive range in ascending order)
            or a mixture
            <cpu number>,…,<cpu number>-<cpu number>
            This option can be used to specify one or more CPUs
            to isolate from the general SMP balancing and scheduling
            algorithms. The only way to move a process onto or off
            an “isolated” CPU is via the CPU affinity syscalls.
            <cpu number> begins at 0 and the maximum value is
            “number of CPUs in system – 1”.

            This option is the preferred way to isolate CPUs. The
            alternative — manually setting the CPU mask of all
            tasks in the system — can cause problems and
            suboptimal load balancer performance.

    iucv=        [HW,NET]

    js=        [HW,JOY] Analog joystick
            See Documentation/input/joystick.txt.

    kernelcore=nn[KMG]    [KNL,X86-32,IA-64,PPC,X86-64] This parameter
            specifies the amount of memory usable by the kernel
            for non-movable allocations.  The requested amount is
            spread evenly throughout all nodes in the system. The
            remaining memory in each node is used for Movable
            pages. In the event, a node is too small to have both
            kernelcore and Movable pages, kernelcore pages will
            take priority and other nodes will have a larger number
            of kernelcore pages.  The Movable zone is used for the
            allocation of pages that may be reclaimed or moved
            by the page migration subsystem.  This means that
            HugeTLB pages may not be allocated from this zone.
            Note that allocations like PTEs-from-HighMem still
            use the HighMem zone if it exists, and the Normal
            zone if it does not.

    movablecore=nn[KMG]    [KNL,X86-32,IA-64,PPC,X86-64] This parameter
            is similar to kernelcore except it specifies the
            amount of memory used for migratable allocations.
            If both kernelcore and movablecore is specified,
            then kernelcore will be at *least* the specified
            value but may be more. If movablecore on its own
            is specified, the administrator must be careful
            that the amount of memory usable for all allocations
            is not too small.

    keepinitrd    [HW,ARM]

    kstack=N    [X86-32,X86-64] Print N words from the kernel stack
            in oops dumps.

    kgdboc=        [HW] kgdb over consoles.
            Requires a tty driver that supports console polling.
            (only serial suported for now)
            Format: <serial_device>[,baud]

    l2cr=        [PPC]

    l3cr=        [PPC]

    lapic        [X86-32,APIC] Enable the local APIC even if BIOS
            disabled it.

    lapic_timer_c2_ok    [X86-32,x86-64,APIC] trust the local apic timer in
            C2 power state.

    libata.dma=    [LIBATA] DMA control
            libata.dma=0      Disable all PATA and SATA DMA
            libata.dma=1      PATA and SATA Disk DMA only
            libata.dma=2      ATAPI (CDROM) DMA only
            libata.dma=4      Compact Flash DMA only
            Combinations also work, so libata.dma=3 enables DMA
            for disks and CDROMs, but not CFs.

    libata.noacpi    [LIBATA] Disables use of ACPI in libata suspend/resume
            when set.
            Format: <int>

    libata.force=    [LIBATA] Force configurations.  The format is comma
            separated list of “[ID:]VAL” where ID is
            PORT[:DEVICE].  PORT and DEVICE are decimal numbers
            matching port, link or device.  Basically, it matches
            the ATA ID string printed on console by libata.  If
            the whole ID part is omitted, the last PORT and DEVICE
            values are used.  If ID hasn’t been specified yet, the
            configuration applies to all ports, links and devices.

            If only DEVICE is omitted, the parameter applies to
            the port and all links and devices behind it.  DEVICE
            number of 0 either selects the first device or the
            first fan-out link behind PMP device.  It does not
            select the host link.  DEVICE number of 15 selects the
            host link and device attached to it.

            The VAL specifies the configuration to force.  As long
            as there’s no ambiguity shortcut notation is allowed.
            For example, both 1.5 and 1.5G would work for 1.5Gbps.
            The following configurations can be forced.

            * Cable type: 40c, 80c, short40c, unk, ign or sata.
              Any ID with matching PORT is used.

            * SATA link speed limit: 1.5Gbps or 3.0Gbps.

            * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
              udma[/][16,25,33,44,66,100,133] notation is also

            * [no]ncq: Turn on or off NCQ.

            If there are multiple matching configurations changing
            the same attribute, the last one is used.

    load_ramdisk=    [RAM] List of ramdisks to load from floppy
            See Documentation/ramdisk.txt.

    lockd.nlm_grace_period=P  [NFS] Assign grace period.
            Format: <integer>

    lockd.nlm_tcpport=N    [NFS] Assign TCP port.
            Format: <integer>

    lockd.nlm_timeout=T    [NFS] Assign timeout value.
            Format: <integer>

    lockd.nlm_udpport=M    [NFS] Assign UDP port.
            Format: <integer>

    logibm.irq=    [HW,MOUSE] Logitech Bus Mouse Driver
            Format: <irq>

    loglevel=    All Kernel Messages with a loglevel smaller than the
            console loglevel will be printed to the console. It can
            also be changed with klogd or other programs. The
            loglevels are defined as follows:

            0 (KERN_EMERG)        system is unusable
            1 (KERN_ALERT)        action must be taken immediately
            2 (KERN_CRIT)        critical conditions
            3 (KERN_ERR)        error conditions
            4 (KERN_WARNING)    warning conditions
            5 (KERN_NOTICE)        normal but significant condition
            6 (KERN_INFO)        informational
            7 (KERN_DEBUG)        debug-level messages

    log_buf_len=n    Sets the size of the printk ring buffer, in bytes.
            Format: { n | nk | nM }
            n must be a power of two.  The default size
            is set in the kernel config file.

    logo.nologo    [FB] Disables display of the built-in Linux logo.
            This may be used to provide more screen space for
            kernel log messages and is useful when debugging
            kernel boot problems.

    lp=0        [LP]    Specify parallel ports to use, e.g,
    lp=port[,port…]    lp=none,parport0 (lp0 not configured, lp1 uses
    lp=reset        first parallel port). ‘lp=0’ disables the
    lp=auto            printer driver. ‘lp=reset’ (which can be
                specified in addition to the ports) causes
                attached printers to be reset. Using
                lp=port1,port2,… specifies the parallel ports
                to associate lp devices with, starting with
                lp0. A port specification may be ‘none’ to skip
                that lp device, or a parport name such as
                ‘parport0’. Specifying ‘lp=auto’ instead of a
                port specification list means that device IDs
                from each port should be examined, to see if
                an IEEE 1284-compliant printer is attached; if
                so, the driver will manage that printer.
                See also header of drivers/char/lp.c.

    lpj=n        [KNL]
            Sets loops_per_jiffy to given constant, thus avoiding
            time-consuming boot-time autodetection (up to 250 ms per
            CPU). 0 enables autodetection (default). To determine
            the correct value for your kernel, boot with normal
            autodetection and see what value is printed. Note that
            on SMP systems the preset will be applied to all CPUs,
            which is likely to cause problems if your CPUs need
            significantly divergent settings. An incorrect value
            will cause delays in the kernel to be wrong, leading to
            unpredictable I/O errors and other breakage. Although
            unlikely, in the extreme case this might damage your

    ltpc=        [NET]
            Format: <io>,<irq>,<dma>

    mac5380=    [HW,SCSI] Format:

    machvec=    [IA64] Force the use of a particular machine-vector
            (machvec) in a generic kernel.
            Example: machvec=hpzx1_swiotlb

    max_loop=    [LOOP] Maximum number of loopback devices that can
            be mounted
            Format: <1-256>

    maxcpus=    [SMP] Maximum number of processors that    an SMP kernel
            should make use of.  maxcpus=n : n >= 0 limits the
            kernel to using ‘n’ processors.  n=0 is a special case,
            it is equivalent to “nosmp”, which also disables
            the IO APIC.

    max_addr=[KMG]    [KNL,BOOT,ia64] All physical memory greater than or
            equal to this physical address is ignored.

    max_luns=    [SCSI] Maximum number of LUNs to probe.
            Should be between 1 and 2^32-1.

            [SCSI] Maximum number of LUNs received.
            Should be between 1 and 16384.

    mcatest=    [IA-64]

    mce        [X86-32] Machine Check Exception

    mce=option    [X86-64] See Documentation/x86_64/boot-options.txt

    md=        [HW] RAID subsystems devices and level
            See Documentation/md.txt.

    mdacon=        [MDA]
            Format: <first>,<last>
            Specifies range of consoles to be captured by the MDA.

    mem=nn[KMG]    [KNL,BOOT] Force usage of a specific amount of memory
            Amount of memory to be used when the kernel is not able
            to see the whole system memory or for test.
            [X86-32] Use together with memmap= to avoid physical
            address space collisions. Without memmap= PCI devices
            could be placed at addresses belonging to unused RAM.

    mem=nopentium    [BUGS=X86-32] Disable usage of 4MB pages for kernel

    memmap=exactmap    [KNL,X86-32,X86_64] Enable setting of an exact
            E820 memory map, as specified by the user.
            Such memmap=exactmap lines can be constructed based on
            BIOS output or other requirements. See the memmap=nn@ss
            option description.

            [KNL] Force usage of a specific region of memory
            Region of memory to be used, from ss to ss+nn.

            [KNL,ACPI] Mark specific memory as ACPI data.
            Region of memory to be used, from ss to ss+nn.

            [KNL,ACPI] Mark specific memory as reserved.
            Region of memory to be used, from ss to ss+nn.
            Example: Exclude memory from 0x18690000-0x1869ffff

    memtest=    [KNL,X86] Enable memtest
            Format: <integer>
            range: 0,4 : pattern number
            default : 0 <disable>

    meye.*=        [HW] Set MotionEye Camera parameters
            See Documentation/video4linux/meye.txt.

    mfgpt_irq=    [IA-32] Specify the IRQ to use for the
            Multi-Function General Purpose Timers on AMD Geode

    mfgptfix    [X86-32] Fix MFGPT timers on AMD Geode platforms when
            the BIOS has incorrectly applied a workaround. TinyBIOS
            version 0.98 is known to be affected, 0.99 fixes the
            problem by letting the user disable the workaround.

    mga=        [HW,DRM]

            [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
            parameter allows control of the logging verbosity for
            the additional memory initialisation checks. A value
            of 0 disables mminit logging and a level of 4 will
            log everything. Information is printed at KERN_DEBUG
            so loglevel=8 may also need to be specified.

            [MOUSE] Maximum time between finger touching and
            leaving touchpad surface for touch to be considered
            a tap and be reported as a left button click (for
            touchpads working in absolute mode only).
            Format: <msecs>
    mousedev.xres=    [MOUSE] Horizontal screen resolution, used for devices
            reporting absolute coordinates, such as tablets
    mousedev.yres=    [MOUSE] Vertical screen resolution, used for devices
            reporting absolute coordinates, such as tablets

    mpu401=        [HW,OSS]
            Format: <io>,<irq>

    MTD_Partition=    [MTD]
            Format: <name>,<region-number>,<size>,<offset>

    MTD_Region=    [MTD] Format:

    mtdparts=    [MTD]
            See drivers/mtd/cmdlinepart.c.

    mtdset=        [ARM]
            ARM/S3C2412 JIVE boot control

            See arch/arm/mach-s3c2412/mach-jive.c

            [HW] Make the MicroTouch USB driver use raw coordinates
            (‘y’, default) or cooked coordinates (‘n’)

    n2=        [NET] SDL Inc. RISCom/N2 synchronous serial card

    NCR_D700=    [HW,SCSI]
            See header of drivers/scsi/NCR_D700.c.

    ncr5380=    [HW,SCSI]

    ncr53c400=    [HW,SCSI]

    ncr53c400a=    [HW,SCSI]

    ncr53c406a=    [HW,SCSI]

    ncr53c8xx=    [HW,SCSI]

    netdev=        [NET] Network devices parameters
            Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
            Note that mem_start is often overloaded to mean
            something different and driver-specific.
            This usage is only documented in each driver source
            file if at all.

            [NETFILTER] Enable connection tracking flow accounting
            0 to disable accounting
            1 to enable accounting
            Default value depends on CONFIG_NF_CT_ACCT that is
            going to be removed in 2.6.29.

    nfsaddrs=    [NFS]
            See Documentation/filesystems/nfsroot.txt.

    nfsroot=    [NFS] nfs root filesystem for disk-less boxes.
            See Documentation/filesystems/nfsroot.txt.

            [NFS] set the TCP port on which the NFSv4 callback
            channel should listen.

            [NFS] set the maximum lifetime for idmapper cache

            [NFS] enable 64-bit inode numbers.
            If zero, the NFS client will fake up a 32-bit inode
            number for the readdir() and stat() syscalls instead
            of returning the full 64-bit number.
            The default is to return 64-bit inode numbers.

    nmi_debug=    [KNL,AVR32] Specify one or more actions to take
            when a NMI is triggered.
            Format: [state][,regs][,debounce][,die]

    nmi_watchdog=    [KNL,BUGS=X86-32] Debugging features for SMP kernels

    no387        [BUGS=X86-32] Tells the kernel to use the 387 maths
            emulation library even if a 387 maths coprocessor
            is present.

    noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
            caches in the slab allocator.  Saves per-node memory,
            but will impact performance.

    noalign        [KNL,ARM]

    noapic        [SMP,APIC] Tells the kernel to not make use of any
            IOAPICs that may be present in the system.

    nobats        [PPC] Do not use BATs for mapping kernel lowmem
            on “Classic” PPC cores.

    nocache        [ARM]

    nodelayacct    [KNL] Disable per-task delay accounting

    nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.

    noefi        [X86-32,X86-64] Disable EFI runtime services support.

    noexec        [IA-64]

    noexec        [X86-32,X86-64]
            On X86-32 available only on PAE configured kernels.
            noexec=on: enable non-executable mappings (default)
            noexec=off: disable non-executable mappings

    noexec32    [X86-64]
            This affects only 32-bit executables.
            noexec32=on: enable non-executable mappings (default)
                read doesn’t imply executable mappings
            noexec32=off: disable non-executable mappings
                read implies executable mappings

    nofxsr        [BUGS=X86-32] Disables x86 floating point extended
            register save and restore. The kernel will only save
            legacy floating-point registers on task switch.

    noclflush    [BUGS=X86] Don’t use the CLFLUSH instruction

    nohlt        [BUGS=ARM]

    no-hlt        [BUGS=X86-32] Tells the kernel that the hlt
            instruction doesn’t work correctly and not to
            use it.

    nohalt        [IA-64] Tells the kernel not to use the power saving
            function PAL_HALT_LIGHT when idle. This increases
            power-consumption. On the positive side, it reduces
            interrupt wake-up latency, which may improve performance
            in certain environments such as networked servers or
            real-time systems.

    nohz=        [KNL] Boottime enable/disable dynamic ticks
            Valid arguments: on, off
            Default: on

    noirqbalance    [X86-32,SMP,KNL] Disable kernel irq balancing

    noirqdebug    [X86-32] Disables the code which attempts to detect and
            disable unhandled interrupt sources.

    no_timer_check    [X86-32,X86_64,APIC] Disables the code which tests for
            broken timer IRQ sources.

    noisapnp    [ISAPNP] Disables ISA PnP code.

    noinitrd    [RAM] Tells the kernel not to load any configured
            initial RAM disk.

    nointroute    [IA-64]

    nojitter    [IA64] Disables jitter checking for ITC timers.

    nolapic        [X86-32,APIC] Do not enable or use the local APIC.

    nolapic_timer    [X86-32,APIC] Do not use the local APIC timer.

    noltlbs        [PPC] Do not use large page/tlb entries for kernel
            lowmem mapping on PPC40x.

    nomca        [IA-64] Disable machine check abort handling

    nomce        [X86-32] Machine Check Exception

    nomfgpt        [X86-32] Disable Multi-Function General Purpose
            Timer usage (for AMD Geode machines).

    noreplace-paravirt    [X86-32,PV_OPS] Don’t patch paravirt_ops

    noreplace-smp    [X86-32,SMP] Don’t replace SMP instructions
            with UP alternatives

    noresidual    [PPC] Don’t use residual data on PReP machines.

    noresume    [SWSUSP] Disables resume and restores original swap

    no-scroll    [VGA] Disables scrollback.
            This is required for the Braillex ib80-piezo Braille
            reader made by F.H. Papenmeier (Germany).

    nosbagart    [IA-64]

    nosep        [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.

    nosmp        [SMP] Tells an SMP kernel to act as a UP kernel,
            and disable the IO APIC.  legacy for “maxcpus=0”.

    nosoftlockup    [KNL] Disable the soft-lockup detector.

    nosync        [HW,M68K] Disables sync negotiation for all devices.

    notsc        [BUGS=X86-32] Disable Time Stamp Counter

    nousb        [USB] Disable the USB subsystem

    nowb        [ARM]

    nptcg=        [IA64] Override max number of concurrent global TLB
            purges which is reported from either PAL_VM_SUMMARY or
            SAL PALO.

    numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
            one of [‘zone’, ‘node’, ‘default’] can be specified
            This can be set from sysctl after boot.
            See Documentation/sysctl/vm.txt for details.

    nr_uarts=    [SERIAL] maximum number of UARTs to be registered.

    olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
            Rather than timing out after 20 ms if an EC
            command is not properly ACKed, override the length
            of the timeout.  We have interrupts disabled while
            waiting for the ACK, so if this is set too high
            interrupts *may* be lost!

    opl3=        [HW,OSS]
            Format: <io>

    oprofile.timer=    [HW]
            Use timer interrupt instead of performance counters

    osst=        [HW,SCSI] SCSI Tape Driver
            Format: <buffer_size>,<write_threshold>
            See also Documentation/scsi/st.txt.

    panic=        [KNL] Kernel behaviour on panic
            Format: <timeout>

    parkbd.port=    [HW] Parallel port number the keyboard adapter is
            connected to, default is 0.
            Format: <parport#>
    parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
            0 for XT, 1 for AT (default is AT).
            Format: <mode>

    parport=    [HW,PPT] Specify parallel ports. 0 disables.
            Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
            Use ‘auto’ to force the driver to use any
            IRQ/DMA settings detected (the default is to
            ignore detected IRQ/DMA settings because of
            possible conflicts). You can specify the base
            address, IRQ, and DMA settings; IRQ and DMA
            should be numbers, or ‘auto’ (for using detected
            settings on that particular port), or ‘nofifo’
            (to avoid using a FIFO even if it is detected).
            Parallel ports are assigned in the order they
            are specified on the command line, starting
            with parport0.

    parport_init_mode=    [HW,PPT]
            Configure VIA parallel port to operate in
            a specific mode. This is necessary on Pegasos
            computer where firmware has no options for setting
            up parallel port mode and sets it to spp.
            Currently this function knows 686a and 8231 chips.
            Format: [spp|ps2|epp|ecp|ecpepp]

    pas2=        [HW,OSS] Format:

    pas16=        [HW,SCSI]
            See header of drivers/scsi/pas16.c.

            Halt all CPUs after the first oops has been printed for
            the specified number of seconds.  This is to be used if
            your oopses keep scrolling off the screen.

    pcbit=        [HW,ISDN]

    pcd.        [PARIDE]
            See header of drivers/block/paride/pcd.c.
            See also Documentation/paride.txt.

    pci=option[,option…]    [PCI] various PCI subsystem options:
        off        [X86-32] don’t probe for the PCI bus
        bios        [X86-32] force use of PCI BIOS, don’t access
                the hardware directly. Use this if your machine
                has a non-standard PCI host bridge.
        nobios        [X86-32] disallow use of PCI BIOS, only direct
                hardware access methods are allowed. Use this
                if you experience crashes upon bootup and you
                suspect they are caused by the BIOS.
        conf1        [X86-32] Force use of PCI Configuration
                Mechanism 1.
        conf2        [X86-32] Force use of PCI Configuration
                Mechanism 2.
        noaer        [PCIE] If the PCIEAER kernel config parameter is
                enabled, this kernel boot option can be used to
                disable the use of PCIE advanced error reporting.
        nodomains    [PCI] Disable support for multiple PCI
                root domains (aka PCI segments, in ACPI-speak).
        nommconf    [X86-32,X86_64] Disable use of MMCONFIG for PCI
        nomsi        [MSI] If the PCI_MSI kernel config parameter is
                enabled, this kernel boot option can be used to
                disable the use of MSI interrupts system-wide.
        biosirq        [X86-32] Use PCI BIOS calls to get the interrupt
                routing table. These calls are known to be buggy
                on several machines and they hang the machine
                when used, but on other computers it’s the only
                way to get the interrupt routing table. Try
                this option if the kernel is unable to allocate
                IRQs or discover secondary PCI buses on your
        rom        [X86-32] Assign address space to expansion ROMs.
                Use with caution as certain devices share
                address decoders between ROMs and other
        norom        [X86-32,X86_64] Do not assign address space to
                expansion ROMs that do not already have
                BIOS assigned address ranges.
        irqmask=0xMMMM    [X86-32] Set a bit mask of IRQs allowed to be
                assigned automatically to PCI devices. You can
                make the kernel exclude IRQs of your ISA cards
                this way.
        pirqaddr=0xAAAAA    [X86-32] Specify the physical address
                of the PIRQ table (normally generated
                by the BIOS) if it is outside the
                F0000h-100000h range.
        lastbus=N    [X86-32] Scan all buses thru bus #N. Can be
                useful if the kernel is unable to find your
                secondary buses and you want to tell it
                explicitly which ones they are.
        assign-busses    [X86-32] Always assign all PCI bus
                numbers ourselves, overriding
                whatever the firmware may have done.
        usepirqmask    [X86-32] Honor the possible IRQ mask stored
                in the BIOS $PIR table. This is needed on
                some systems with broken BIOSes, notably
                some HP Pavilion N5400 and Omnibook XE3
                notebooks. This will have no effect if ACPI
                IRQ routing is enabled.
        noacpi        [X86-32] Do not use ACPI for IRQ routing
                or for PCI scanning.
        use_crs        [X86-32] Use _CRS for PCI resource
        routeirq    Do IRQ routing for all PCI devices.
                This is normally done in pci_enable_device(),
                so this option is a temporary workaround
                for broken drivers that don’t call it.
        skip_isa_align    [X86] do not align io start addr, so can
                handle more pci cards
        firmware    [ARM] Do not re-enumerate the bus but instead
                just use the configuration from the
                bootloader. This is currently used on
                IXP2000 systems where the bus has to be
                configured a certain way for adjunct CPUs.
        noearly        [X86] Don’t do any early type 1 scanning.
                This might help on some broken boards which
                machine check when some devices’ config space
                is read. But various workarounds are disabled
                and some IOMMU drivers will not work.
        bfsort        Sort PCI devices into breadth-first order.
                This sorting is done to get a device
                order compatible with older (<= 2.4) kernels.
        nobfsort    Don’t sort PCI devices into breadth-first order.
        cbiosize=nn[KMG]    The fixed amount of bus space which is
                reserved for the CardBus bridge’s IO window.
                The default value is 256 bytes.
        cbmemsize=nn[KMG]    The fixed amount of bus space which is
                reserved for the CardBus bridge’s memory
                window. The default value is 64 megabytes.

    pcmv=        [HW,PCMCIA] BadgePAD 4

    pd.        [PARIDE]
            See Documentation/paride.txt.

    pdcchassis=    [PARISC,HW] Disable/Enable PDC Chassis Status codes at
            boot time.
            Format: { 0 | 1 }
            See arch/parisc/kernel/pdc_chassis.c

    pf.        [PARIDE]
            See Documentation/paride.txt.

    pg.        [PARIDE]
            See Documentation/paride.txt.

    pirq=        [SMP,APIC] Manual mp-table setup
            See Documentation/i386/IO-APIC.txt.

    plip=        [PPT,NET] Parallel port network link
            Format: { parport<nr> | timid | 0 }
            See also Documentation/parport.txt.

    pmtmr=        [X86] Manual setup of pmtmr I/O Port.
            Override pmtimer IOPort with a hex value.
            e.g. pmtmr=0x508

    pnpacpi=    [ACPI]
            { off }

    pnpbios=    [ISAPNP]
            { on | off | curr | res | no-curr | no-res }

            [ISAPNP] Exclude IRQs for the autoconfiguration

            [ISAPNP] Exclude DMAs for the autoconfiguration

    pnp_reserve_io=    [ISAPNP] Exclude I/O ports for the autoconfiguration
            Ranges are in pairs (I/O port base and size).

            [ISAPNP] Exclude memory regions for the
            Ranges are in pairs (memory base and size).

            [KNL] debug: print fatal signals
            print-fatal-signals=1: print segfault info to
            the kernel console.
            default: off.

    printk.time=    Show timing data prefixed to each printk message line
            Format: <bool>  (1/Y/y=enable, 0/N/n=disable)

    profile=    [KNL] Enable kernel profiling via /proc/profile
            Format: [schedule,]<number>
            Param: “schedule” – profile schedule points.
            Param: <number> – step/bucket size as a power of 2 for
                statistical time based profiling.
            Param: “sleep” – profile D-state sleeping (millisecs).
                Requires CONFIG_SCHEDSTATS
            Param: “kvm” – profile VM exits.

    processor.max_cstate=    [HW,ACPI]
            Limit processor to maximum C-state
            max_cstate=9 overrides any DMI blacklist limit.

    processor.nocst    [HW,ACPI]
            Ignore the _CST method to determine C-states,
            instead using the legacy FADT method

    prompt_ramdisk=    [RAM] List of RAM disks to prompt for floppy disk
            before loading.
            See Documentation/ramdisk.txt.

    psmouse.proto=    [HW,MOUSE] Highest PS2 mouse protocol extension to
            probe for; one of (bare|imps|exps|lifebook|any).
    psmouse.rate=    [HW,MOUSE] Set desired mouse report rate, in reports
            per second.
    psmouse.resetafter=    [HW,MOUSE]
            Try to reset the device after so many bad packets
            (0 = never).
            [HW,MOUSE] Set desired mouse resolution, in dpi.
            [HW,MOUSE] Controls Logitech smartscroll autorepeat.
            0 = disabled, 1 = enabled (default).

    pss=        [HW,OSS] Personal Sound System (ECHO ESC614)

    pt.        [PARIDE]
            See Documentation/paride.txt.

            [KNL] Number of legacy pty’s. Overwrites compiled-in
            default number.

    quiet        [KNL] Disable most log messages

    r128=        [HW,DRM]

    raid=        [HW,RAID]
            See Documentation/md.txt.

    ramdisk_blocksize=    [RAM]
            See Documentation/ramdisk.txt.

    ramdisk_size=    [RAM] Sizes of RAM disks in kilobytes
            See Documentation/ramdisk.txt.

    rcupdate.blimit=    [KNL,BOOT]
            Set maximum number of finished RCU callbacks to process
            in one batch.

    rcupdate.qhimark=    [KNL,BOOT]
            Set threshold of queued
            RCU callbacks over which batch limiting is disabled.

    rcupdate.qlowmark=    [KNL,BOOT]
            Set threshold of queued RCU callbacks below which
            batch limiting is re-enabled.

    rdinit=        [KNL]
            Format: <full_path>
            Run specified binary instead of /init from the ramdisk,
            used for early userspace startup. See initrd.

    reboot=        [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
            Format: <reboot_mode>[,<reboot_mode2>[,…]]
            See arch/*/kernel/reboot.c or arch/*/kernel/process.c           

            [KNL, SMP] Set scheduler’s default relax_domain_level.
            See Documentation/cpusets.txt.

    reserve=    [KNL,BUGS] Force the kernel to ignore some iomem area

    reservetop=    [X86-32]
            Format: nn[KMG]
            Reserves a hole at the top of the kernel virtual
            address space.

    reset_devices    [KNL] Force drivers to reset the underlying device
            during initialization.

    resume=        [SWSUSP]
            Specify the partition device for software suspend

    resume_offset=    [SWSUSP]
            Specify the offset from the beginning of the partition
            given by “resume=” at which the swap header is located,
            in <PAGE_SIZE> units (needed only for swap files).
            See  Documentation/power/swsusp-and-swap-files.txt

    retain_initrd    [RAM] Keep initrd memory after extraction

    rhash_entries=    [KNL,NET]
            Set number of hash buckets for route cache

    riscom8=    [HW,SERIAL]
            Format: <io_board1>[,<io_board2>[,…<io_boardN>]]

    ro        [KNL] Mount root device read-only on boot

    root=        [KNL] Root filesystem

    rootdelay=    [KNL] Delay (in seconds) to pause before attempting to
            mount the root filesystem

    rootflags=    [KNL] Set root filesystem mount option string

    rootfstype=    [KNL] Set root filesystem type

    rootwait    [KNL] Wait (indefinitely) for root device to show up.
            Useful for devices that are detected asynchronously
            (e.g. USB and MMC devices).

            [ROOTPLUG] Override the default vendor ID

            [ROOTPLUG] Override the default product ID

            [ROOTPLUG] Enable debugging output

    rw        [KNL] Mount root device read-write on boot

    S        [KNL] Run init in single mode

    sa1100ir    [NET]
            See drivers/net/irda/sa1100_ir.c.

    sbni=        [NET] Granch SBNI12 leased line adapter

    sc1200wdt=    [HW,WDT] SC1200 WDT (watchdog) driver
            Format: <io>[,<timeout>[,<isapnp>]]

    scsi_debug_*=    [SCSI]
            See drivers/scsi/scsi_debug.c.

            [SCSI] SCSI default device flags
            Format: <integer>

    scsi_dev_flags=    [SCSI] Black/white list entry for vendor and model
            Format: <vendor>:<model>:<flags>
            (flags are integer value)

    scsi_logging_level=    [SCSI] a bit mask of logging levels
            See drivers/scsi/scsi_logging.h for bits.  Also
            settable via sysctl at dev.scsi.logging_level
            There is also a nice ‘scsi_logging_level’ script in the
            S390-tools package, available for download at

    scsi_mod.scan=    [SCSI] sync (default) scans SCSI busses as they are
            discovered.  async scans them in kernel threads,
            allowing boot to proceed.  none ignores them, expecting
            user space to do the scan.

    selinux        [SELINUX] Disable or enable SELinux at boot time.
            Format: { “0” | “1” }
            See security/selinux/Kconfig help text.
            0 — disable.
            1 — enable.
            Default value is set via kernel config option.
            If enabled at boot time, /selinux/disable can be used
            later to disable prior to initial policy load.

    selinux_compat_net =
            [SELINUX] Set initial selinux_compat_net flag value.
                        Format: { “0” | “1” }
                        0 — use new secmark-based packet controls
                        1 — use legacy packet controls
                        Default value is 0 (preferred).
                        Value can be changed at runtime via

    serialnumber    [BUGS=X86-32]

    shapers=    [NET]
            Maximal number of shapers.

    sim710=        [SCSI,HW]
            See header of drivers/scsi/sim710.c.

    simeth=        [IA-64]

    slram=        [HW,MTD]

    slub_debug[=options[,slabs]]    [MM, SLUB]
            Enabling slub_debug allows one to determine the
            culprit if slab objects become corrupted. Enabling
            slub_debug can create guard zones around objects and
            may poison objects when not in use. Also tracks the
            last alloc / free. For more information see

    slub_max_order= [MM, SLUB]
            Determines the maximum allowed order for slabs.
            A high setting may cause OOMs due to memory
            fragmentation. For more information see

    slub_min_objects=    [MM, SLUB]
            The minimum number of objects per slab. SLUB will
            increase the slab order up to slub_max_order to
            generate a sufficiently large slab able to contain
            the number of objects indicated. The higher the number
            of objects the smaller the overhead of tracking slabs
            and the less frequently locks need to be acquired.
            For more information see Documentation/vm/slub.txt.

    slub_min_order=    [MM, SLUB]
            Determines the mininum page order for slabs. Must be
            lower than slub_max_order.
            For more information see Documentation/vm/slub.txt.

    slub_nomerge    [MM, SLUB]
            Disable merging of slabs with similar size. May be
            necessary if there is some reason to distinguish
            allocs to different slabs. Debug options disable
            merging on their own.
            For more information see Documentation/vm/slub.txt.

    smart2=        [HW]
            Format: <io1>[,<io2>[,…,<io8>]]

    smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
            attempt to substitute SMP alternatives once at boot.

    smsc-ircc2.nopnp    [HW] Don’t use PNP to discover SMC devices
    smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
    smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
    smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
    smsc-ircc2.ircc_irq=    [HW] IRQ line
    smsc-ircc2.ircc_dma=    [HW] DMA channel
    smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
                0: Toshiba Satellite 1800 (GP data pin select)
                1: Fast pin select (default)
                2: ATC IRMode

    snd-ad1816a=    [HW,ALSA]

    snd-ad1848=    [HW,ALSA]

    snd-ali5451=    [HW,ALSA]

    snd-als100=    [HW,ALSA]

    snd-als4000=    [HW,ALSA]

    snd-azt2320=    [HW,ALSA]

    snd-cmi8330=    [HW,ALSA]

    snd-cmipci=    [HW,ALSA]

    snd-cs4231=    [HW,ALSA]

    snd-cs4232=    [HW,ALSA]

    snd-cs4236=    [HW,ALSA]

    snd-cs4281=    [HW,ALSA]

    snd-cs46xx=    [HW,ALSA]

    snd-dt019x=    [HW,ALSA]

    snd-dummy=    [HW,ALSA]

    snd-emu10k1=    [HW,ALSA]

    snd-ens1370=    [HW,ALSA]

    snd-ens1371=    [HW,ALSA]

    snd-es968=    [HW,ALSA]

    snd-es1688=    [HW,ALSA]

    snd-es18xx=    [HW,ALSA]

    snd-es1938=    [HW,ALSA]

    snd-es1968=    [HW,ALSA]

    snd-fm801=    [HW,ALSA]

    snd-gusclassic=    [HW,ALSA]

    snd-gusextreme=    [HW,ALSA]

    snd-gusmax=    [HW,ALSA]

    snd-hdsp=    [HW,ALSA]

    snd-ice1712=    [HW,ALSA]

    snd-intel8x0=    [HW,ALSA]

    snd-interwave=    [HW,ALSA]


    snd-korg1212=    [HW,ALSA]

    snd-maestro3=    [HW,ALSA]

    snd-mpu401=    [HW,ALSA]

    snd-mtpav=    [HW,ALSA]

    snd-nm256=    [HW,ALSA]

    snd-opl3sa2=    [HW,ALSA]



    snd-opti93x=    [HW,ALSA]

    snd-pmac=    [HW,ALSA]

    snd-rme32=    [HW,ALSA]

    snd-rme96=    [HW,ALSA]

    snd-rme9652=    [HW,ALSA]

    snd-sb8=    [HW,ALSA]

    snd-sb16=    [HW,ALSA]

    snd-sbawe=    [HW,ALSA]

    snd-serial=    [HW,ALSA]

    snd-sgalaxy=    [HW,ALSA]

    snd-sonicvibes=    [HW,ALSA]


    snd-sun-cs4231=    [HW,ALSA]

    snd-trident=    [HW,ALSA]

    snd-usb-audio=    [HW,ALSA,USB]

    snd-via82xx=    [HW,ALSA]

    snd-virmidi=    [HW,ALSA]

    snd-wavefront=    [HW,ALSA]

    snd-ymfpci=    [HW,ALSA]

            [KNL] Should the soft-lockup detector generate panics.

    sonypi.*=    [HW] Sony Programmable I/O Control Device driver
            See Documentation/sonypi.txt

    specialix=    [HW,SERIAL] Specialix multi-serial port adapter
            See Documentation/specialix.txt.

    spia_io_base=    [HW,MTD]

    sscape=        [HW,OSS]
            Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>

    st=        [HW,SCSI] SCSI tape parameters (buffers, etc.)
            See Documentation/scsi/st.txt.

    sti=        [PARISC,HW]
            Format: <num>
            Set the STI (builtin display/keyboard on the HP-PARISC
            machines) console (graphic card) which should be used
            as the initial boot-console.
            See also comment in drivers/video/console/sticore.c.

    sti_font=    [HW]
            See comment in drivers/video/console/sticore.c.

    stifb=        [HW]
            Format: bpp:<bpp1>[:<bpp2>[:<bpp3>…]]

            Control how the NFS server code allocates CPUs to
            service thread pools.  Depending on how many NICs
            you have and where their interrupts are bound, this
            option will affect which CPUs will do NFS serving.
            Note: this parameter cannot be changed while the
            NFS server is running.

            auto        the server chooses an appropriate mode
                    automatically using heuristics
            global        a single global pool contains all CPUs
            percpu        one pool for each CPU
            pernode        one pool for each NUMA node (equivalent
                    to global on non-NUMA machines)

    swiotlb=    [IA-64] Number of I/O TLB slabs

    switches=    [HW,M68k]

    sym53c416=    [HW,SCSI]
            See header of drivers/scsi/sym53c416.c.

            Ignore sysrq setting – this boot parameter will
            neutralize any effect of /proc/sys/kernel/sysrq.
            Useful for debugging.

    t128=        [HW,SCSI]
            See header of drivers/scsi/t128.c.

    tdfx=        [HW,DRM]

    test_suspend=    [SUSPEND]
            Specify “mem” (for Suspend-to-RAM) or “standby” (for
            standby suspend) as the system sleep state to briefly
            enter during system startup.  The system is woken from
            this state using a wakeup-capable RTC alarm.

    thash_entries=    [KNL,NET]
            Set number of hash buckets for TCP connection

    thermal.act=    [HW,ACPI]
            -1: disable all active trip points in all thermal zones
            <degrees C>: override all lowest active trip points

    thermal.crt=    [HW,ACPI]
            -1: disable all critical trip points in all thermal zones
            <degrees C>: lower all critical trip points

    thermal.nocrt=    [HW,ACPI]
            Set to disable actions on ACPI thermal zone
            critical and hot trip points.    [HW,ACPI]
            1: disable ACPI thermal control

    thermal.psv=    [HW,ACPI]
            -1: disable all passive trip points
            <degrees C>: override all passive trip points to this value

    thermal.tzp=    [HW,ACPI]
            Specify global default ACPI thermal zone polling rate
            <deci-seconds>: poll all this frequency
            0: no polling (default)

    tmscsim=    [HW,SCSI]
            See comment before function dc390_setup() in

    tp720=        [HW,PS2]

    trix=        [HW,OSS] MediaTrix AudioTrix Pro
            <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>[2|3]=    [HW,JOY]
            TurboGraFX parallel port interface
            See also Documentation/input/joystick-parport.txt

    u14-34f=    [HW,SCSI] UltraStor 14F/34F SCSI host adapter
            See header of drivers/scsi/u14-34f.c.

    uart401=    [HW,OSS]
            Format: <io>,<irq>

    uart6850=    [HW,OSS]
            Format: <io>,<irq>

            [USB] Ignore overcurrent events (default N).
            Some badly-designed motherboards generate lots of
            bogus events, for ports that aren’t wired to
            anything.  Set this parameter to avoid log spamming.
            Note that genuine overcurrent events won’t be
            reported either.

            Set unknown_nmi_panic=1 early on boot.

            [USB] The autosuspend time delay (in seconds) used
            for newly-detected USB devices (default 2).  This
            is the time required before an idle device will be
            autosuspended.  Devices for which the delay is set
            to a negative value won’t be autosuspended at all.

            [USBHID] The interval which mice are to be polled at.

    add_efi_memmap    [EFI; x86-32,X86-64] Include EFI memory map in
            kernel’s map of available physical RAM.

    vdso=        [X86-32,SH,x86-64]
            vdso=2: enable compat VDSO (default with COMPAT_VDSO)
            vdso=1: enable VDSO (default)
            vdso=0: disable VDSO mapping

    vdso32=        [X86-32,X86-64]
            vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
            vdso32=1: enable 32-bit VDSO (default)
            vdso32=0: disable 32-bit VDSO mapping

    vector=        [IA-64,SMP]
            vector=percpu: enable percpu vector domain

    video=        [FB] Frame buffer configuration
            See Documentation/fb/modedb.txt.

    vga=        [BOOT,X86-32] Select a particular video mode
            See Documentation/i386/boot.txt and
            Use vga=ask for menu.
            This is actually a boot loader parameter; the value is
            passed to the kernel using a special protocol.

    vmalloc=nn[KMG]    [KNL,BOOT] Forces the vmalloc area to have an exact
            size of <nn>. This can be used to increase the
            minimum size (128MB on x86). It can also be used to
            decrease the size and leave more room for directly
            mapped kernel RAM.

    vmhalt=        [KNL,S390] Perform z/VM CP command after system halt.
            Format: <command>

    vmpanic=    [KNL,S390] Perform z/VM CP command after kernel panic.
            Format: <command>

    vmpoff=        [KNL,S390] Perform z/VM CP command after power off.
            Format: <command>

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

    wd33c93=    [HW,SCSI]
            See header of drivers/scsi/wd33c93.c.

    wd7000=        [HW,SCSI]
            See header of drivers/scsi/wd7000.c.

    wdt=        [WDT] Watchdog
            See Documentation/watchdog/wdt.txt.

    xd=        [HW,XT] Original XT pre-IDE (RLL encoded) disks.
    xd_geo=        See header of drivers/block/xd.c.

    xirc2ps_cs=    [NET,PCMCIA]

    norandmaps    Don’t use address space randomization
            Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space


Last Modified: 15 Dec, 2011 at 17:54:14