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July 2000                 Kernel Parameters                     v2.4.0
                          ~~~~~~~~~~~~~~~~~

The following is a consolidated list of the kernel parameters as implemented
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.

The text in square brackets at the beginning of the description state the
restrictions on the kernel for the said kernel parameter to be valid. The
restrictions referred to are that the relevant option is valid if:

        ACPI    ACPI support is enabled.
        APIC    APIC support is enabled.
        APM     Advanced Power Management support is enabled.
        AX25    Appropriate AX.25 support is enabled.
        CD      Appropriate CD support is enabled.
        DEVFS   devfs support is enabled. 
        DRM     Direct Rendering Management support is enabled. 
        EFI     EFI Partitioning (GPT) is enabled
        EIDE    EIDE/ATAPI support is enabled.
        FB      The frame buffer device is enabled.
        HW      Appropriate hardware is enabled.
        IA-32   IA-32 aka i386 architecture is enabled.
        IA-64   IA-64 architecture is enabled.
        IP_PNP  IP DCHP, BOOTP, or RARP is enabled.
        ISAPNP  ISA PnP code is enabled.
        ISDN    Appropriate ISDN support is enabled.
        JOY     Appropriate joystick support is enabled.
        LP      Printer support is enabled.
        LOOP    Loopback device support is enabled.
        M68k    M68k architecture is enabled. 
        MCA     MCA bus support is enabled.
        MDA     MDA console support is enabled.
        MOUSE   Appropriate mouse support is enabled.
        NET     Appropriate network support is enabled.
        NFS     Appropriate NFS support is enabled.
        PARIDE  The ParIDE subsystem is enabled.
        PCI     PCI bus support is enabled.
        PCMCIA  The PCMCIA subsystem is enabled.
        PNP     Plug & Play support is enabled.
        PPT     Parallel port support is enabled.
        PS2     Appropriate PS/2 support is enabled.
        RAM     RAM disk support is enabled.
        SCSI    Appropriate SCSI support is enabled.
        SERIAL  Serial support is enabled.
        SMP     The kernel is an SMP kernel.
        SOUND   Appropriate sound system support is enabled.
        V4L     Video For Linux support is enabled.
        VGA     The VGA console has been enabled.
        VT      Virtual terminal support is enabled.
        XT      IBM PC/XT MFM hard disk support is enabled.

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.

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.

        53c7xx=         [HW,SCSI] Amiga SCSI controllers.

        acpi=           [HW,ACPI] Advanced Configuration and Power Interface 
                force   Force ACPI on, even if blacklisted platform
                off     Disable ACPI
                ht      Limit ACPI to boot-time LAPIC enumeration for HT,
                        disabling the run-time AML interpreter.
                strict  Be less tolerant of platforms that are not
                        strictly ACPI specification compliant.

        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
                        Format: { level | edge |  high | low }
 
        acpi_irq_balance        ACPI will balance active IRQs
        acpi_irq_nobalance      ACPI will not move active IRQs
        acpi_irq_pci=   If irq_balance, Clear listed IRQs for use by PCI
        acpi_irq_isa=   If irq_balance, Mark listed IRQs used by ISA

        acpi_osi=       [HW,ACPI] empty param disables _OSI

        acpi_serialize  [HW,ACPI] force serialization of AML methods

        ad1816=         [HW,SOUND]

        ad1848=         [HW,SOUND]
 
        adb_buttons=    [HW,MOUSE]

        adlib=          [HW,SOUND]
 
        advansys=       [HW,SCSI]

        aedsp16=        [HW,SOUND]
 
        aha152x=        [HW,SCSI]

        aha1542=        [HW,SCSI]

        aic7xxx=        [HW,SCSI]

        AM53C974=       [HW,SCSI]

        amijoy=         [HW,JOY] Amiga joystick support 
 
        apm=            [APM] Advanced Power Management.

        applicom=       [HW]
 
        arcrimi=        [HW,NET]

        ataflop=        [HW,M68k]

        atarimouse=     [HW,MOUSE] Atari Mouse.

        atascsi=        [HW,SCSI] Atari SCSI.

        awe=            [HW,SOUND]
 
        aztcd=          [HW,CD] Aztec CD driver.

        baycom_epp=     [HW,AX25]
 
        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem.

        baycom_ser_fdx= [HW,AX25] BayCom Serial Port AX.25 Modem in Full
                        Duplex Mode.

        baycom_ser_hdx= [HW,AX25] BayCom Serial Port AX.25 Modem in Half
                        Duplex Mode.

        bmouse=         [HW,MOUSE,PS2] Bus mouse.

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

        cdu31a=         [HW,CD]

        chandev=        [HW,NET] 
 
        cm206=          [HW,CD]

        com20020=       [HW,NET]

        com90io=        [HW,NET]

        com90xx=        [HW,NET]

        condev=         [HW]
 
        console=        [KNL] output console + comm spec (speed, control,
                        parity).

        cpia_pp=        [HW,PPT]

        cs4232=         [HW,SOUND]

        cs89x0_dma=     [HW,NET]

        ctc=            [HW,NET]
 
        cyclades=       [HW,SERIAL] Cyclades multi-serial port adapter.
 
        dasd=           [HW,NET]    

        db9=            [HW,JOY]

        db9_2=          [HW,JOY]

        db9_3=          [HW,JOY]
 
        debug           [KNL] Enable kernel debugging (events log level).

        decnet=         [HW,NET]

        devfs=          [DEVFS]
 
        digi=           [HW,SERIAL] io parameters + enable/disable command.

        digiepca=       [HW,SERIAL]

        dmascc=         [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
                        support available.

        dmasound=       [HW,SOUND] (sound subsystem buffers).

        dtc3181e=       [HW,SCSI]

        eata=           [HW,SCSI]

        eda=            [HW,PS2]

        edb=            [HW,PS2]

        eicon=          [HW,ISDN] 

        es1370=         [HW,SOUND]

        es1371=         [HW,SOUND]
 
        ether=          [HW,NET] Ethernet cards parameters (irq,
                        base_io_addr, mem_start, mem_end, name.
                        (mem_start is often overloaded to mean something
                        different and driver-specific).

        fd_mcs=         [HW,SCSI]

        fdomain=        [HW,SCSI]

        floppy=         [HW]

        ftape=          [HW] Floppy Tape subsystem debugging options.

        gamma=          [HW,DRM]

        gc=             [HW,JOY]

        gc_2=           [HW,JOY]
         
        gc_3=           [HW,JOY]
 
        gdth=           [HW,SCSI]

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

        gscd=           [HW,CD]

        gus=            [HW,SOUND] 
 
        gvp11=          [HW,SCSI]

        hd=             [EIDE] (E)IDE hard drive subsystem geometry
                        (Cyl/heads/sectors) or tune parameters.

        hfmodem=        [HW,AX25]

        hisax=          [HW,ISDN]

        i810=           [HW,DRM]

        ibmmcascsi=     [HW,MCA,SCSI] IBM MicroChannel SCSI adapter.

        icn=            [HW,ISDN]

        ide?=           [HW] (E)IDE subsystem : config (iomem/irq), tuning or
                        debugging (serialize,reset,no{dma,tune,probe}) or
                        chipset specific parameters.
        
        idebus=         [HW] (E)IDE subsystem : VLB/PCI bus speed.

        idle=           [HW]
 
        in2000=         [HW,SCSI]

        init=           [KNL]

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

        ip=             [IP_PNP]

        isapnp=         [ISAPNP] Specify RDP, reset, pci_scan and verbosity.

        isapnp_reserve_irq= [ISAPNP] Exclude IRQs for the autoconfiguration.

        isapnp_reserve_dma= [ISAPNP] Exclude DMAs for the autoconfiguration.

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

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

        isp16=          [HW,CD]

        iucv=           [HW,NET] 

        js=             [HW,JOY] Analog joystick
 
        kbd-reset       [VT]

        keepinitrd      [HW, ARM]

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

        load_ramdisk=   [RAM] List of ramdisks to load from floppy.

        lockd.udpport=  [NFS]

        lockd.tcpport=  [NFS]

        logi_busmouse=  [HW, MOUSE]

        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.

        ltpc=           [HW]

        mac5380=        [HW,SCSI]

        mac53c9x=       [HW,SCSI]
        
        mad16=          [HW,SOUND]

        maui=           [HW,SOUND]
 
        max_loop=[0-255] [LOOP] Set the maximum number of loopback devices
                                that can be mounted.

        maxcpus=        [SMP] States the maximum number of processors that
                        an SMP kernel should make use of.

        max_scsi_luns=  [SCSI]

        mca-pentium     [BUGS=IA-32]

        mcd=            [HW,CD]

        mcdx=           [HW,CD]

        md=             [HW] RAID subsystems devices and level.

        mdisk=          [HW]
 
        mdacon=         [MDA]

        megaraid=       [HW,SCSI]
 
        mem=exactmap    [KNL,BOOT,IA-32] enable setting of an exact
                        e820 memory map, as specified by the user.
                        Such mem=exactmap lines can be constructed
                        based on BIOS output or other requirements.

        mem=nn[KMG]     [KNL,BOOT] force use of a specific amount of
                        memory; to be used when the kernel is not able
                        to see the whole system memory or for test.

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

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

        mem=nn[KMG]$ss[KMG]
                        [KNL,BOOT,ACPI] Mark specific memory as reserved.
                        Region of memory to be used, from ss to ss+nn.

        memfrac=        [KNL]

        mga=            [HW,DRM]

        mpu401=         [HW,SOUND]
 
        msmouse=        [HW,MOUSE] Microsoft Mouse.

        ncr5380=        [HW,SCSI]

        ncr53c400=      [HW,SCSI]

        ncr53c400a=     [HW,SCSI]

        ncr53c406a=     [HW,SCSI]

        ncr53c8xx=      [HW,SCSI]

        netdev=         [NET] Ethernet cards parameters (irq,
                        base_io_addr, mem_start, mem_end, name.
                        (mem_start is often overloaded to mean something
                        different and driver-specific).
                        (cf: ether=)
 
        nfsaddrs=       [NFS]

        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.

        nmi_watchdog=   [KNL,BUGS=IA-32] debugging features for SMP kernels.

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

        noalign         [KNL,ARM] 
 
        noapic          [SMP,APIC] Tells the kernel not to make use of any
                        APIC that may be present on the system.

        noasync         [HW, M68K] Disables async and sync negotiation for
                        all devices.

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

        nohlt           [BUGS=ARM]
 
        no-hlt          [BUGS=IA-32] Tells the kernel that the hlt
                        instruction doesn't work correctly and not to
                        use it.

        noisapnp        [ISAPNP] Disables ISA PnP code.

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

        nointroute      [IA-64]
 
        nolapic         [IA-32,APIC] Do not enable or use the local APIC.

        no-scroll       [VGA]

        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel.

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

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

        nowb            [ARM]
 
        opl3=           [HW,SOUND]

        opl3sa=         [HW,SOUND]

        opl3sa2=        [HW,SOUND]
 
        optcd=          [HW,CD]

        panic=          [KNL] kernel behaviour on panic.

        parport=0       [HW,PPT]        Specify parallel ports. 0 disables.
        parport=auto                    Use 'auto' to force the driver to use
        parport=0xBBB[,IRQ[,DMA]]       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.

        pas2=           [HW,SOUND]
 
        pas16=          [HW,SCSI]

        pcbit=          [HW,ISDN]

        pcd.            [PARIDE]

        pci=option[,option...]          [PCI] various PCI subsystem options:
                off                     [IA-32] don't probe for the PCI bus
                bios                    [IA-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                  [IA-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                   [IA-32] Force use of PCI Configuration Mechanism 1.
                conf2                   [IA-32] Force use of PCI Configuration Mechanism 2.
                nosort                  [IA-32] Don't sort PCI devices according to
                                        order given by the PCI BIOS. This sorting is done
                                        to get a device order compatible with older kernels.
                biosirq                 [IA-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 motherboard.
                rom                     [IA-32] Assign address space to expansion ROMs.
                                        Use with caution as certain devices share address
                                        decoders between ROMs and other resources.
                irqmask=0xMMMM          [IA-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.
                lastbus=N               [IA-32] Scan all buses till 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           [IA-32] Always assign all PCI bus
                                        numbers ourselves, overriding
                                        whatever the firmware may have
                                        done.

        pd.             [PARIDE]

        pf.             [PARIDE]

        pg.             [PARIDE]

        pirq=           [SMP,APIC] mp-table.

        plip=           [PPT,NET] Parallel port network link.

        profile=        [KNL] enable kernel profiling via /proc/profile
                        (param: profile step/bucket size as a power of 2)

        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
                        before loading.

        pss=            [HW,SOUND] 
 
        pt.             [PARIDE]

        quiet=          [KNL] Disable log messages.
 
        r128=           [HW,DRM]

        raid=           [HW,RAID]

        ramdisk=        [RAM] Sizes of RAM disks in kilobytes [deprecated].

        ramdisk_blocksize=
                        [RAM]
 
        ramdisk_size=   [RAM] New name for the ramdisk parameter.

        ramdisk_start=  [RAM] Starting block of RAM disk image (so you can
                        place it after the kernel image on a boot floppy).

        reboot=         [BUGS=IA-32]

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

        riscom8=        [HW,SERIAL]

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

        root=           [KNL] root filesystem.

        rootflags=      [KNL] set root filesystem mount option string

        rootfstype=     [KNL] set root filesystem type

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

        S               [KNL] run init in single mode.

        sb=             [HW,SOUND]
 
        sbpcd=          [HW,CD] Soundblaster CD adapter.

        scsi_logging=   [SCSI]

        scsihosts=      [SCSI]

        sg_def_reserved_size=
                        [SCSI]
 
        sgalaxy=        [HW,SOUND]
 
        sim710=         [SCSI,HW]
 
        sjcd=           [HW,CD]

        smart2=         [HW]
 
        sonicvibes=     [HW,SOUND]
 
        sonycd535=      [HW,CD]

        sound=          [SOUND]

        soundmodem=     [HW,AX25,SOUND] Use sound card as packet radio modem.

        specialix=      [HW,SERIAL] Specialix multi-serial port adapter.

        sscape=         [HW,SOUND]
 
        st=             [HW,SCSI] SCSI tape parameters (buffers, etc.).

        st0x=           [HW,SCSI]

        stram_swap=     [HW]

        swiotlb=        [IA-64] Number of I/O TLB slabs.
 
        switches=       [HW, M68K]

        sym53c416=      [HW,SCSI]

        sym53c8xx=      [HW,SCSI]

        t128=           [HW,SCSI]

        tdfx=           [HW,DRM]
 
        tgfx=           [HW,JOY]

        tgfx_2=         [HW,JOY]

        tgfx_3=         [HW,JOY]
 
        tmc8xx=         [HW,SCSI]

        tmscsim=        [HW,SCSI]

        tp720=          [HW,PS2]

        trix=           [HW,SOUND]
 
        u14-34f=        [HW,SCSI]

        uart401=        [HW,SOUND]

        uart6850=       [HW,SOUND]
 
        usbfix          [BUGS=IA-64] 
 
        video=          [FB] frame buffer configuration.

        vga=            [BOOT] on ix386, select a particular video mode
                        (use vga=ask for menu).  This is actually a
                        boot loader parameter; the value is passed to
                        the kernel using a special protocol.  See
                        linux/Documentation/i386/boot.txt for information.

        vmhalt=         [KNL,S390]

        vmpoff=         [KNL,S390] 
 
        waveartist=     [HW,SOUND]
 
        wd33c93=        [HW,SCSI]

        wd7000=         [HW,SCSI]

        wdt=            [HW]

        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.

        xd_geo=         [HW,XT]