kernel-parameters.txt

                          Kernel Parameters
                          ~~~~~~~~~~~~~~~~~

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

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

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

	ACPI	ACPI support is enabled.
	AGP	AGP (Accelerated Graphics Port) is enabled.
	ALSA	ALSA sound support is enabled.
	APIC	APIC support is enabled.
	APM	Advanced Power Management support is enabled.
	AX25	Appropriate AX.25 support is enabled.
	BLACKFIN Blackfin architecture is enabled.
	DRM	Direct Rendering Management support is enabled.
	EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
	EFI	EFI Partitioning (GPT) is enabled
	EIDE	EIDE/ATAPI support is enabled.
	FB	The frame buffer device is enabled.
	HW	Appropriate hardware 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.
	LIBATA  Libata driver is enabled
	LP	Printer support is enabled.
	LOOP	Loopback device support is enabled.
	M68k	M68k architecture is enabled.
			These options have more detailed description inside of
			Documentation/m68k/kernel-options.txt.
	MCA	MCA bus support is enabled.
	MDA	MDA console support is enabled.
	MOUSE	Appropriate mouse support is enabled.
	MSI	Message Signaled Interrupts (PCI).
	MTD	MTD (Memory Technology Device) support is enabled.
	NET	Appropriate network support is enabled.
	NUMA	NUMA support is enabled.
	GENERIC_TIME The generic timeofday code is enabled.
	NFS	Appropriate NFS support is enabled.
	OSS	OSS sound support is enabled.
	PV_OPS	A paravirtualized kernel is enabled.
	PARIDE	The ParIDE (parallel port IDE) subsystem is enabled.
	PARISC	The PA-RISC architecture is enabled.
	PCI	PCI bus support is enabled.
	PCIE	PCI Express support is enabled.
	PCMCIA	The PCMCIA subsystem is enabled.
	PNP	Plug & Play support is enabled.
	PPC	PowerPC architecture is enabled.
	PPT	Parallel port support is enabled.
	PS2	Appropriate PS/2 support is enabled.
	RAM	RAM disk support is enabled.
	ROOTPLUG The example Root Plug LSM is enabled.
	S390	S390 architecture is enabled.
	SCSI	Appropriate SCSI support is enabled.
			A lot of drivers has their options described inside of
			Documentation/scsi/.
	SECURITY Different security models are enabled.
	SELINUX SELinux support is enabled.
	SERIAL	Serial support is enabled.
	SH	SuperH architecture is enabled.
	SMP	The kernel is an SMP kernel.
	SPARC	Sparc architecture is enabled.
	SWSUSP	Software suspend 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.
	X86-32	X86-32, aka i386 architecture is enabled.
	X86-64	X86-64 architecture is enabled.
			More X86-64 boot options can be found in
			Documentation/x86_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>.

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

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

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


	acpi=		[HW,ACPI,X86-64,i386]
			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/pm.txt, pci=noacpi

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

	acpi_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_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
			HPET

	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.

	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] 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/i386/kernel/apm.c.

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

	ataflop=	[HW,M68k]

	atarimouse=	[HW,MOUSE] Atari Mouse

	atascsi=	[HW,SCSI] Atari SCSI

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

	atkbd.reset=	[HW] Reset keyboard during initialization

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

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

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

	atkbd.softrepeat= [HW]
			Use software keyboard repeat

	autotest	[IA64]

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

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

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

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

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

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

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

	c101=		[NET] Moxa C101 synchronous serial card

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

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

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

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

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

	disable_8254_timer
	enable_8254_timer
			[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
			Format:
			<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]

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

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

	condev=		[HW,S390] console device
	conmode=

	console=	[KNL] Output console device and options.

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

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

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

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

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

	no_console_suspend
			[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
			Format:
			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]

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

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

	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.

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

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

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

	decnet=		[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.

	vt.default_utf8=
			[VT]
			Format=<0|1>
			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
			Documentation/digiepca.txt.

	dmasound=	[HW,OSS] Sound subsystem buffers

	dscc4.setup=	[NET]

	dtc3181e=	[HW,SCSI]

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

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

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

	elanfreq=	[X86-32]
			See comment before function elanfreq_setup() in
			arch/i386/kernel/cpu/cpufreq/elanfreq.c.

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

	elfcorehdr=	[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>]

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

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

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

	floppy=		[HW]
			See Documentation/floppy.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.

	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>

	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.

	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] Maximal number of HugeTLB pages.

	i8042.direct	[HW] Put keyboard port into non-translated mode
	i8042.dumbkbd	[HW] Pretend that controller can only read data from
			     keyboard and cannot control its state
			     (Don't attempt to blink the leds)
	i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
	i8042.nokbd	[HW] Don't check/create keyboard port
	i8042.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=		[X86]
			Format: idle=poll or idle=mwait
			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.

	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
			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]

	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
		off
			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
			DMA.
		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.

	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/ip2base.c.

	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.
			Format:
			<cpu number>,...,<cpu number>
			or
			<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.

	l2cr=		[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.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
			when set.
			Format: <int>

	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
			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

	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.

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

	mca-pentium	[BUGS=X86-32]

	mcatest=	[IA-64]

	mce		[X86-32] Machine Check Exception