kernel-parameters.txt

February 2003             Kernel Parameters                     v2.5.59
                          ~~~~~~~~~~~~~~~~~

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

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

	modprobe usbcore blinkenlights=1

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

	usbcore.blinkenlights=1

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.
	ALSA	ALSA sound 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. 
	EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
	EFI	EFI Partitioning (GPT) is enabled
	EIDE	EIDE/ATAPI support is enabled.
	FB	The frame buffer device is enabled.
	HW	Appropriate hardware is enabled.
	IA-32	IA-32 aka i386 architecture is enabled.
	IA-64	IA-64 architecture is enabled.
	IOSCHED	More than one I/O scheduler is enabled.
	IP_PNP	IP DHCP, 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.
			These options have more detailed description inside of
			Documentation/m68k/kernel-options.txt.
	MCA	MCA bus support is enabled.
	MDA	MDA console support is enabled.
	MOUSE	Appropriate mouse support is enabled.
	MTD	MTD support is enabled.
	NET	Appropriate network support is enabled.
	NUMA	NUMA support is enabled.
	NFS	Appropriate NFS support is enabled.
	OSS	OSS sound support is enabled.
	PARIDE	The ParIDE subsystem is enabled.
	PARISC	The PA-RISC architecture is enabled.
	PCI	PCI bus support is enabled.
	PCMCIA	The PCMCIA subsystem is enabled.
	PNP	Plug & Play support is enabled.
	PPC	PowerPC architecture is enabled.
	PPT	Parallel port support is enabled.
	PS2	Appropriate PS/2 support is enabled.
	RAM	RAM disk support is enabled.
	S390	S390 architecture is enabled.
	SCSI	Appropriate SCSI support is enabled.
			A lot of drivers has their options described inside of
			Documentation/scsi/.
	SELINUX SELinux support is enabled.
	SERIAL	Serial support is enabled.
	SMP	The kernel is an SMP kernel.
	SPARC	Sparc architecture is enabled.
	SWSUSP	Software suspension is enabled.
	TS	Appropriate touchscreen support is enabled.
	USB	USB support is enabled.
	USBHID	USB Human Interface Device support is enabled.
	V4L	Video For Linux support is enabled.
	VGA	The VGA console has been enabled.
	VT	Virtual terminal support is enabled.
	WDT	Watchdog support is enabled.
	XT	IBM PC/XT MFM hard disk support is enabled.
	X86-64	X86-64 architecture is enabled.
			More X86-64 boot options can be found in
			Documentation/x86_64/boot-options.txt .

In addition, the following text indicates that the option:

	BUGS=	Relates to possible processor bugs on the said processor.
	KNL	Is a kernel start-up parameter.
	BOOT	Is a boot loader parameter.

Parameters denoted with BOOT are actually interpreted by the boot
loader, and have no meaning to the kernel directly.
Do not modify the syntax of boot loader parameters without extreme
need or coordination with <Documentation/i386/boot.txt>.

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

	53c7xx=		[HW,SCSI] Amiga SCSI controllers
			See header of drivers/scsi/53c7xx.c.
			See also Documentation/scsi/ncr53c7xx.txt.

	acpi=		[HW,ACPI] Advanced Configuration and Power Interface 
			Format: { force | off | ht | strict }
			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/pm.txt, pci=noacpi

	acpi_sleep=	[HW,ACPI] Sleep options
			Format: { s3_bios, s3_mode }
			See Documentation/power/video.txt
 
	acpi_sci=	[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_osi=	[HW,ACPI] empty param disables _OSI

	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_dbg_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 /proc/acpi/debug_layer.

	acpi_dbg_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 /proc/acpi/debug_level.

	acpi_fake_ecdt	[HW,ACPI] Workaround failure due to BIOS lacking ECDT

	acpi_generic_hotkey [HW,ACPI]
			Allow consolidated generic hotkey driver to
			over-ride platform specific driver.
			See also Documentation/acpi-hotkey.txt.

	ad1816=		[HW,OSS]
			Format: <io>,<irq>,<dma>,<dma2>
			See also Documentation/sound/oss/AD1816.

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

	adlib=		[HW,OSS]
			Format: <io>
 
	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.

	AM53C974=	[HW,SCSI]
			Format: <host-scsi-id>,<target-scsi-id>,<max-rate>,<max-offset>
			See also header of drivers/scsi/AM53C974.c.

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

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

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

	apic=		[APIC,i386] 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/i386/kernel/apm.c.

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

	ataflop=	[HW,M68k]

	atarimouse=	[HW,MOUSE] Atari Mouse

	atascsi=	[HW,SCSI] Atari SCSI

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

	atkbd.reset=	[HW] Reset keyboard during initialization

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

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

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

	autotest	[IA64]

	awe=		[HW,OSS] AWE32/SB32/AWE64 wave table synth
			Format: <io>,<memsize>,<isapnp>
 
	aztcd=		[HW,CD] Aztech CD268 CDROM driver
			Format: <io>,0x79 (?)

	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.

	blkmtd_device=	[HW,MTD]
	blkmtd_erasesz=
	blkmtd_ro=
	blkmtd_bs=
	blkmtd_count=

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

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

	c101=		[NET] Moxa C101 synchronous serial card

	cachesize=	[BUGS=IA-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.

	cdu31a=		[HW,CD]
			Format: <io>,<irq>[,PAS]
			See header of drivers/cdrom/cdu31a.c.

	chandev=	[HW,NET] Generic channel device initialisation

	checkreqprot	[SELINUX] Set initial checkreqprot flag value.
			Format: { "0" | "1" }
			See security/selinux/Kconfig help text.
			0 -- check protection applied by kernel (includes any implied execute protection).
			1 -- check protection requested by application.
			Default value is set via a kernel config option.
			Value can be changed at runtime via /selinux/checkreqprot.
 
 	clock=		[BUGS=IA-32, HW] gettimeofday timesource override. 
			Forces specified timesource (if avaliable) to be used
			when calculating gettimeofday(). If specicified timesource
			is not avalible, it defaults to PIT. 
			Format: { pit | tsc | cyclone | pmtmr }

	hpet=		[IA-32,HPET] option to disable HPET and use PIT.
			Format: disable

	cm206=		[HW,CD]
			Format: { auto | [<io>,][<irq>] }

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

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

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

	condev=		[HW,S390] console device
	conmode=
 
	console=	[KNL] Output console device and options.

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

		ttyS<n>[,options]
			Use the specified serial port.  The options are of
			the form "bbbbpn", where "bbbb" is the baud rate,
			"p" is parity ("n", "o", or "e"), and "n" is bits.
			Default is "9600n8".

			See also Documentation/serial-console.txt.

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

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

	cpia_pp=	[HW,PPT]
			Format: { parport<nr> | auto | none }

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

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

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

	cs89x0_media=	[HW,NET]
			Format: { rj45 | aui | bnc }
 
	cyclades=	[HW,SERIAL] Cyclades multi-serial port adapter.
 
	dasd=		[HW,NET]    
			See header of drivers/s390/block/dasd_devmap.c.

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

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

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

	devfs=		[DEVFS]
			See Documentation/filesystems/devfs/boot-options.

	dhash_entries=	[KNL]
			Set number of hash buckets for dentry cache.
 
	digi=		[HW,SERIAL]
			IO parameters + enable/disable command.

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

	dmascc=		[HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
			support available.
			Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]

	dmasound=	[HW,OSS] Sound subsystem buffers

	dscc4.setup=	[NET]

	dtc3181e=	[HW,SCSI]

	earlyprintk=	[IA-32, X86-64]
			earlyprintk=vga
			earlyprintk=serial[,ttySn[,baudrate]]

			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
			console.

	eata=		[HW,SCSI]

	eda=		[HW,PS2]

	edb=		[HW,PS2]

	edd=		[EDD]
			Format: {"of[f]" | "sk[ipmbr]"}
			See comment in arch/i386/boot/edd.S

	eicon=		[HW,ISDN] 
			Format: <id>,<membase>,<irq>

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

	elanfreq=	[IA-32]
			See comment before function elanfreq_setup() in
			arch/i386/kernel/cpu/cpufreq/elanfreq.c.

	elevator=	[IOSCHED]
			Format: {"as"|"cfq"|"deadline"|"noop"}
			See Documentation/block/as-iosched.txt
			and Documentation/block/deadline-iosched.txt for details.
	elfcorehdr=	[IA-32]
			Specifies physical address of start of kernel core image
			elf header.
			See Documentation/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.

	es1370=		[HW,OSS]
			Format: <lineout>[,<micbias>]
			See also header of sound/oss/es1370.c.

	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>]

	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.

	ftape=		[HW] Floppy Tape subsystem debugging options.
			See Documentation/ftape.txt.

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

	gamma=		[HW,DRM]

	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.

	gscd=		[HW,CD]
			Format: <io>

	gt96100eth=	[NET] MIPS GT96100 Advanced Communication Controller

	gus=		[HW,OSS]
			Format: <io>,<irq>,<dma>,<dma16>
 
	gvp11=		[HW,SCSI]

	hashdist=	[KNL,NUMA] Large hashes allocated during boot
			are distributed across NUMA nodes.  Defaults on
			for IA-64, off otherwise.

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

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

	hd?=		[HW] (E)IDE subsystem
	hd?lun=		See Documentation/ide.txt.

	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.

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

	hugepages=	[HW,IA-32,IA-64] Maximal number of HugeTLB pages.

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

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

	i810=		[HW,DRM]

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

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

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

	ide=		[HW] (E)IDE subsystem
			Format: ide=nodma or ide=doubler or ide=reverse
			See Documentation/ide.txt.

	ide?=		[HW] (E)IDE subsystem
			Format: ide?=noprobe or chipset specific parameters.
			See Documentation/ide.txt.
	
	idebus=		[HW] (E)IDE subsystem - VLB/PCI bus speed
			See Documentation/ide.txt.

	idle=		[HW]
			Format: idle=poll or idle=halt
 
	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
			process.

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

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

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

	inttest=	[IA64]

	io7=		[HW] IO7 for Marvel based alpha systems
			See comment before marvel_specify_io7 in
			arch/alpha/kernel/core_marvel.c.

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

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

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

	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.
			Format: <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.

	isp16=		[HW,CD]
			Format: <io>,<irq>,<dma>,<setup>

	iucv=		[HW,NET] 

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

	keepinitrd	[HW,ARM]

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

	l2cr=		[PPC]

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

	lasi=		[HW,SCSI] PARISC LASI driver for the 53c700 chip
			Format: addr:<io>,irq:<irq>

	llsc*=		[IA64]
			See function print_params() in arch/ia64/sn/kernel/llsc4.c.

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

	lockd.udpport=	[NFS]

	lockd.tcpport=	[NFS]

	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 is n, nk, nM.  n must be a power of two.  The
			default is set in kernel config.

	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
			hardware.

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

	mac5380=	[HW,SCSI]
			Format: <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>

	mac53c9x=	[HW,SCSI]
			Format: <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>

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

	mad16=		[HW,OSS]
			Format: <io>,<irq>,<dma>,<dma16>,<mpu_io>,<mpu_irq>,<joystick>

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

	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.

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

	mca-pentium	[BUGS=IA-32]

	mcatest=	[IA-64]

	mcd=		[HW,CD]
			Format: <port>,<irq>,<mitsumi_bug_93_wait>

	mcdx=		[HW,CD]

	mce		[IA-32] Machine Check Exception

	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.
			[IA-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=IA-32] Disable usage of 4MB pages for kernel
			memory.

	memmap=exactmap	[KNL,IA-32] 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.

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

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

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

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

	mga=		[HW,DRM]

	mousedev.tap_time=
			[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: <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]

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

	mtouchusb.raw_coordinates=
			[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.
 
	nfsaddrs=	[NFS]
			See Documentation/nfsroot.txt.

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

	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 to not make use of any
			IOAPICs that may be present in the system.

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

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

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

	noexec		[IA-64]

	noexec		[IA-32, X86-64]
			noexec=on: enable non-executable mappings (default)
			noexec=off: disable nn-executable mappings

	nofxsr		[BUGS=IA-32]

	nohlt		[BUGS=ARM]
 
	no-hlt		[BUGS=IA-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.

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

	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.

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

	nomce		[IA-32] Machine Check Exception

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

	noresume	[SWSUSP] Disables resume and restore original swap space.
 
	no-scroll	[VGA] Disables scrollback.
			This is required for the Braillex ib80-piezo Braille
			reader made by F.H. Papenmeier (Germany).

	nosbagart	[IA-64]

	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

	nousb		[USB] Disable the USB subsystem

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

	opl3sa=		[HW,OSS]
			Format: <io>,<irq>,<dma>,<dma2>,<mpu_io>,<mpu_irq>

	opl3sa2=	[HW,OSS]
			Format: <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
 
	oprofile.timer=	[HW]
			Use timer interrupt instead of performance counters

	optcd=		[HW,CD]
			Format: <io>

	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=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