path: root/Documentation/kernel-parameters.txt

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. 
	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.
	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 
 
	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 (iomem, irq,
			dev_name).

	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]

	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=		[PNP]

	isp16=		[HW,CD]

	iucv=		[HW,NET] 

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

	keep_initrd	[HW, ARM]

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

	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=ix86]

	mcd=		[HW,CD]

	mcdx=		[HW,CD]

	md=		[HW] RAID subsystems devices and level.

	mdisk=		[HW]
 
	mdacon=		[MDA]

	megaraid=	[HW,SCSI]
 
	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.

	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]
 
	nfsaddrs=	[NFS]

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

	nmi_watchdog=	[KNL,BUGS=ix86] debugging features for SMP kernels.

	no387		[BUGS=ix86] 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=ix86]

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

	nointroute	[IA-64]
 
	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=ix86] 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.

	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:log level).

	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=ix86]

	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.

	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]