kernel-parameters.txt 108.3 KB
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                          Kernel Parameters
                          ~~~~~~~~~~~~~~~~~
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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

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Hyphens (dashes) and underscores are equivalent in parameter names, so
	log_buf_len=1M print-fatal-signals=1
can also be entered as
	log-buf-len=1M print_fatal_signals=1


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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}".

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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:
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	ACPI	ACPI support is enabled.
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	AGP	AGP (Accelerated Graphics Port) is enabled.
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	ALSA	ALSA sound support is enabled.
	APIC	APIC support is enabled.
	APM	Advanced Power Management support is enabled.
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	ARM	ARM architecture is enabled.
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	AVR32	AVR32 architecture is enabled.
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	AX25	Appropriate AX.25 support is enabled.
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	BLACKFIN Blackfin architecture is enabled.
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	DRM	Direct Rendering Management support is enabled.
	DYNAMIC_DEBUG Build in debug messages and enable them at runtime
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	EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
	EFI	EFI Partitioning (GPT) is enabled
	EIDE	EIDE/ATAPI support is enabled.
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	EVM	Extended Verification Module
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	FB	The frame buffer device is enabled.
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	FTRACE	Function tracing enabled.
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	GCOV	GCOV profiling is enabled.
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	HW	Appropriate hardware is enabled.
	IA-64	IA-64 architecture is enabled.
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	IMA     Integrity measurement architecture is enabled.
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	IOSCHED	More than one I/O scheduler is enabled.
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	IP_PNP	IP DHCP, BOOTP, or RARP is enabled.
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	IPV6	IPv6 support is enabled.
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	ISAPNP	ISA PnP code is enabled.
	ISDN	Appropriate ISDN support is enabled.
	JOY	Appropriate joystick support is enabled.
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	KGDB	Kernel debugger support is enabled.
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	KVM	Kernel Virtual Machine support is enabled.
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	LIBATA  Libata driver is enabled
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	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.
	MDA	MDA console support is enabled.
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	MIPS	MIPS architecture is enabled.
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	MOUSE	Appropriate mouse support is enabled.
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	MSI	Message Signaled Interrupts (PCI).
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	MTD	MTD (Memory Technology Device) support is enabled.
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	NET	Appropriate network support is enabled.
	NUMA	NUMA support is enabled.
	NFS	Appropriate NFS support is enabled.
	OSS	OSS sound support is enabled.
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	PV_OPS	A paravirtualized kernel is enabled.
	PARIDE	The ParIDE (parallel port IDE) subsystem is enabled.
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	PARISC	The PA-RISC architecture is enabled.
	PCI	PCI bus support is enabled.
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	PCIE	PCI Express support is enabled.
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	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.
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			A lot of drivers have their options described inside
			the Documentation/scsi/ sub-directory.
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	SECURITY Different security models are enabled.
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	SELINUX SELinux support is enabled.
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	APPARMOR AppArmor support is enabled.
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	SERIAL	Serial support is enabled.
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	SH	SuperH architecture is enabled.
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	SMP	The kernel is an SMP kernel.
	SPARC	Sparc architecture is enabled.
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	SWSUSP	Software suspend (hibernation) is enabled.
	SUSPEND	System suspend states are enabled.
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	TPM	TPM drivers are enabled.
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	TS	Appropriate touchscreen support is enabled.
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	UMS	USB Mass Storage support is enabled.
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	USB	USB support is enabled.
	USBHID	USB Human Interface Device support is enabled.
	V4L	Video For Linux support is enabled.
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	VMMIO   Driver for memory mapped virtio devices is enabled.
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	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.
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	X86-32	X86-32, aka i386 architecture is enabled.
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	X86-64	X86-64 architecture is enabled.
			More X86-64 boot options can be found in
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			Documentation/x86/x86_64/boot-options.txt .
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	X86	Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
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	XEN	Xen support is enabled
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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
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need or coordination with <Documentation/x86/boot.txt>.
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There are also arch-specific kernel-parameters not documented here.
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See for example <Documentation/x86/x86_64/boot-options.txt>.
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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.

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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.

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Finally, the [KMG] suffix is commonly described after a number of kernel
parameter values. These 'K', 'M', and 'G' letters represent the _binary_
multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
bytes respectively. Such letter suffixes can also be entirely omitted.

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	acpi=		[HW,ACPI,X86]
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			Advanced Configuration and Power Interface
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			Format: { force | off | strict | noirq | rsdt }
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			force -- enable ACPI if default was off
			off -- disable ACPI if default was on
			noirq -- do not use ACPI for IRQ routing
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			strict -- Be less tolerant of platforms that are not
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				strictly ACPI specification compliant.
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			rsdt -- prefer RSDT over (default) XSDT
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			copy_dsdt -- copy DSDT to memory
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			See also Documentation/power/runtime_pm.txt, pci=noacpi
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	acpi_rsdp=	[ACPI,EFI,KEXEC]
			Pass the RSDP address to the kernel, mostly used
			on machines running EFI runtime service to boot the
			second kernel for kdump.

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	acpi_apic_instance=	[ACPI, IOAPIC]
			Format: <int>
			2: use 2nd APIC table, if available
			1,0: use 1st APIC table
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			default: 0
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	acpi_backlight=	[HW,ACPI]
			acpi_backlight=vendor
			acpi_backlight=video
			If set to vendor, prefer vendor specific driver
			(e.g. thinkpad_acpi, sony_acpi, etc.) instead
			of the ACPI video.ko driver.

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	acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
	acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
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			Format: <int>
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			CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
			debug output.  Bits in debug_layer correspond to a
			_COMPONENT in an ACPI source file, e.g.,
			    #define _COMPONENT ACPI_PCI_COMPONENT
			Bits in debug_level correspond to a level in
			ACPI_DEBUG_PRINT statements, e.g.,
			    ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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			The debug_level mask defaults to "info".  See
			Documentation/acpi/debug.txt for more information about
			debug layers and levels.
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			Enable processor driver info messages:
			    acpi.debug_layer=0x20000000
			Enable PCI/PCI interrupt routing info messages:
			    acpi.debug_layer=0x400000
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			Enable AML "Debug" output, i.e., stores to the Debug
			object while interpreting AML:
			    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
			Enable all messages related to ACPI hardware:
			    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff

			Some values produce so much output that the system is
			unusable.  The "log_buf_len" parameter may be useful
			if you need to capture more output.
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	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_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
			Format: <irq>,<irq>...

	acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
			use by PCI
			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

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

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

	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_sleep=	[HW,ACPI] Sleep options
			Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
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				  old_ordering, nonvs, sci_force_enable }
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			See Documentation/power/video.txt for information on
			s3_bios and s3_mode.
			s3_beep is for debugging; it makes the PC's speaker beep
			as soon as the kernel's real-mode entry point is called.
			s4_nohwsig prevents ACPI hardware signature from being
			used during resume from hibernation.
			old_ordering causes the ACPI 1.0 ordering of the _PTS
			control method, with respect to putting devices into
			low power states, to be enforced (the ACPI 2.0 ordering
			of _PTS is used by default).
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			nonvs prevents the kernel from saving/restoring the
			ACPI NVS memory during suspend/hibernation and resume.
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			sci_force_enable causes the kernel to set SCI_EN directly
			on resume from S1/S3 (which is against the ACPI spec,
			but some broken systems don't work without it).
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	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

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	acpi_enforce_resources=	[ACPI]
			{ strict | lax | no }
			Check for resource conflicts between native drivers
			and ACPI OperationRegions (SystemIO and SystemMemory
			only). IO ports and memory declared in ACPI might be
			used by the ACPI subsystem in arbitrary AML code and
			can interfere with legacy drivers.
			strict (default): access to resources claimed by ACPI
			is denied; legacy drivers trying to access reserved
			resources will fail to bind to device using them.
			lax: access to resources claimed by ACPI is allowed;
			legacy drivers trying to access reserved resources
			will bind successfully but a warning message is logged.
			no: ACPI OperationRegions are not marked as reserved,
			no further checks are performed.

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	add_efi_memmap	[EFI; X86] Include EFI memory map in
			kernel's map of available physical RAM.

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

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	ALSA		[HW,ALSA]
			See Documentation/sound/alsa/alsa-parameters.txt

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	alignment=	[KNL,ARM]
			Allow the default userspace alignment fault handler
			behaviour to be specified.  Bit 0 enables warnings,
			bit 1 enables fixups, and bit 2 sends a segfault.

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	align_va_addr=	[X86-64]
			Align virtual addresses by clearing slice [14:12] when
			allocating a VMA at process creation time. This option
			gives you up to 3% performance improvement on AMD F15h
			machines (where it is enabled by default) for a
			CPU-intensive style benchmark, and it can vary highly in
			a microbenchmark depending on workload and compiler.

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			32: only for 32-bit processes
			64: only for 64-bit processes
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			on: enable for both 32- and 64-bit processes
			off: disable for both 32- and 64-bit processes

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	amd_iommu=	[HW,X86-64]
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			Pass parameters to the AMD IOMMU driver in the system.
			Possible values are:
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			fullflush - enable flushing of IO/TLB entries when
				    they are unmapped. Otherwise they are
				    flushed before they will be reused, which
				    is a lot of faster
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			off	  - do not initialize any AMD IOMMU found in
				    the system
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			force_isolation - Force device isolation for all
					  devices. The IOMMU driver is not
					  allowed anymore to lift isolation
					  requirements as needed. This option
					  does not override iommu=pt
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	amd_iommu_dump=	[HW,X86-64]
			Enable AMD IOMMU driver option to dump the ACPI table
			for AMD IOMMU. With this option enabled, AMD IOMMU
			driver will print ACPI tables for AMD IOMMU during
			IOMMU initialization.

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

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	apc=		[HW,SPARC]
			Power management functions (SPARCstation-4/5 + deriv.)
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			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.

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	apic=		[APIC,X86-32] Advanced Programmable Interrupt Controller
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			Change the output verbosity whilst booting
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			Format: { quiet (default) | verbose | debug }
			Change the amount of debugging information output
			when initialising the APIC and IO-APIC components.
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	autoconf=	[IPV6]
			See Documentation/networking/ipv6.txt.

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	show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
			Limit apic dumping. The parameter defines the maximal
			number of local apics being dumped. Also it is possible
			to set it to "all" by meaning -- no limit here.
			Format: { 1 (default) | 2 | ... | all }.
			The parameter valid if only apic=debug or
			apic=verbose is specified.
			Example: apic=debug show_lapic=all

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	apm=		[APM] Advanced Power Management
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			See header of arch/x86/kernel/apm_32.c.
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	arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
			Format: <io>,<irq>,<nodeID>

	ataflop=	[HW,M68k]

	atarimouse=	[HW,MOUSE] Atari Mouse

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

	atkbd.reset=	[HW] Reset keyboard during initialization

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	atkbd.set=	[HW] Select keyboard code set
			Format: <int> (2 = AT (default), 3 = PS/2)
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	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))
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	atkbd.softrepeat= [HW]
			Use software keyboard repeat
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	baycom_epp=	[HW,AX25]
			Format: <io>,<mode>
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	baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
			Format: <io>,<mode>
			See header of drivers/net/hamradio/baycom_par.c.

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

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

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

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	bootmem_debug	[KNL] Enable bootmem allocator debug messages.

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	bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
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	bttv.radio=	Most important insmod options are available as
			kernel args too.
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	bttv.pll=	See Documentation/video4linux/bttv/Insmod-options
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	bttv.tuner=
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	bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
			firmware feature for flushing multiple hpte entries
			at a time.

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	c101=		[NET] Moxa C101 synchronous serial card

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	cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
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			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.

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	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.

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	ccw_timeout_log [S390]
			See Documentation/s390/CommonIO for details.
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	cgroup_disable= [KNL] Disable a particular controller
			Format: {name of the controller(s) to disable}
				{Currently supported controllers - "memory"}

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	checkreqprot	[SELINUX] Set initial checkreqprot flag value.
			Format: { "0" | "1" }
			See security/selinux/Kconfig help text.
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			0 -- check protection applied by kernel (includes
				any implied execute protection).
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			1 -- check protection requested by application.
			Default value is set via a kernel config option.
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			Value can be changed at runtime via
				/selinux/checkreqprot.

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

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

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	clocksource=	Override the default clocksource
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			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
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			[X86-32] pit,hpet,tsc;
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				scx200_hrt on Geode; cyclone on IBM x440
			[MIPS] MIPS
			[PARISC] cr16
			[S390] tod
			[SH] SuperH
			[SPARC64] tick
			[X86-64] hpet,tsc

502 503
	clearcpuid=BITNUM [X86]
			Disable CPUID feature X for the kernel. See
504 505
			arch/x86/include/asm/cpufeature.h for the valid bit
			numbers. Note the Linux specific bits are not necessarily
506 507 508 509 510 511 512 513 514
			stable over kernel options, but the vendor specific
			ones should be.
			Also note that user programs calling CPUID directly
			or using the feature without checking anything
			will still see it. This just prevents it from
			being used by the kernel or shown in /proc/cpuinfo.
			Also note the kernel might malfunction if you disable
			some critical bits.

515 516 517 518 519
	cma=nn[MG]	[ARM,KNL]
			Sets the size of kernel global memory area for contiguous
			memory allocations. For more information, see
			include/linux/dma-contiguous.h

520 521 522 523 524 525 526
	cmo_free_hint=	[PPC] Format: { yes | no }
			Specify whether pages are marked as being inactive
			when they are freed.  This is used in CMO environments
			to determine OS memory pressure for page stealing by
			a hypervisor.
			Default: yes

527 528
	coherent_pool=nn[KMG]	[ARM,KNL]
			Sets the size of memory pool for coherent, atomic dma
529
			allocations, by default set to 256K.
530

531
	code_bytes	[X86] How many bytes of object code to print
532
			in an oops report.
533 534 535
			Range: 0 - 8192
			Default: 64

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	com20020=	[HW,NET] ARCnet - COM20020 chipset
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			Format:
			<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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	com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
			Format: <io>[,<irq>]

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

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

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

		ttyS<n>[,options]
555
		ttyUSB0[,options]
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			Use the specified serial port.  The options are of
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			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.
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567 568
		uart[8250],io,<addr>[,options]
		uart[8250],mmio,<addr>[,options]
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			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.

574 575 576 577 578
                If the device connected to the port is not a TTY but a braille
                device, prepend "brl," before the device type, for instance
			console=brl,ttyS0
		For now, only VisioBraille is supported.

579 580 581 582
	consoleblank=	[KNL] The console blank (screen saver) timeout in
			seconds. Defaults to 10*60 = 10mins. A value of 0
			disables the blank timer.

583 584 585 586 587
	coredump_filter=
			[KNL] Change the default value for
			/proc/<pid>/coredump_filter.
			See also Documentation/filesystems/proc.txt.

588 589 590
	cpuidle.off=1	[CPU_IDLE]
			disable the cpuidle sub-system

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	cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
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			Format:
			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
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	crashkernel=size[KMG][@offset[KMG]]
			[KNL] Using kexec, Linux can switch to a 'crash kernel'
			upon panic. This parameter reserves the physical
			memory region [offset, offset + size] for that kernel
			image. If '@offset' is omitted, then a suitable offset
			is selected automatically. Check
			Documentation/kdump/kdump.txt for further details.
602

603 604 605 606 607
	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
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			Documentation/kdump/kdump.txt for an example.
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	cs89x0_dma=	[HW,NET]
			Format: <dma>

	cs89x0_media=	[HW,NET]
			Format: { rj45 | aui | bnc }
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	dasd=		[HW,NET]
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			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

624 625
	ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
			time. See Documentation/dynamic-debug-howto.txt for
626
			details.  Deprecated, see dyndbg.
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	debug		[KNL] Enable kernel debugging (events log level).

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	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.

639 640
	debug_objects	[KNL] Enable object debugging

641 642 643
	no_debug_objects
			[KNL] Disable object debugging

644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662
	debug_guardpage_minorder=
			[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
			parameter allows control of the order of pages that will
			be intentionally kept free (and hence protected) by the
			buddy allocator. Bigger value increase the probability
			of catching random memory corruption, but reduce the
			amount of memory for normal system use. The maximum
			possible value is MAX_ORDER/2.  Setting this parameter
			to 1 or 2 should be enough to identify most random
			memory corruption problems caused by bugs in kernel or
			driver code when a CPU writes to (or reads from) a
			random memory location. Note that there exists a class
			of memory corruptions problems caused by buggy H/W or
			F/W or by drivers badly programing DMA (basically when
			memory is written at bus level and the CPU MMU is
			bypassed) which are not detectable by
			CONFIG_DEBUG_PAGEALLOC, hence this option will not help
			tracking down these problems.

663 664
	debugpat	[X86] Enable PAT debugging

665
	decnet.addr=	[HW,NET]
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			Format: <area>[,<node>]
			See also Documentation/networking/decnet.txt.

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	default_hugepagesz=
			[same as hugepagesz=] The size of the default
			HugeTLB page size. This is the size represented by
			the legacy /proc/ hugepages APIs, used for SHM, and
			default size when mounting hugetlbfs filesystems.
			Defaults to the default architecture's huge page size
			if not specified.
676

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

	digiepca=	[HW,SERIAL]
			See drivers/char/README.epca and
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			Documentation/serial/digiepca.txt.
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	disable=	[IPV6]
			See Documentation/networking/ipv6.txt.

690 691 692 693
	disable_ddw     [PPC/PSERIES]
			Disable Dynamic DMA Window support. Use this if
			to workaround buggy firmware.

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	disable_ipv6=	[IPV6]
			See Documentation/networking/ipv6.txt.

697 698 699
	disable_mtrr_cleanup [X86]
			The kernel tries to adjust MTRR layout from continuous
			to discrete, to make X server driver able to add WB
700
			entry later. This parameter disables that.
701

702
	disable_mtrr_trim [X86, Intel and AMD only]
703 704 705 706 707
			By default the kernel will trim any uncacheable
			memory out of your available memory pool based on
			MTRR settings.  This parameter disables that behavior,
			possibly causing your machine to run very slowly.

708
	disable_timer_pin_1 [X86]
709 710 711 712 713 714 715 716 717 718 719 720 721
			Disable PIN 1 of APIC timer
			Can be useful to work around chipset bugs.

	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
			this option disables the debugging code at boot.

	dma_debug_entries=<number>
			This option allows to tune the number of preallocated
			entries for DMA-API debugging code. One entry is
			required per DMA-API allocation. Use this if the
			DMA-API debugging code disables itself because the
			architectural default is too low.

722 723 724 725 726 727 728
	dma_debug_driver=<driver_name>
			With this option the DMA-API debugging driver
			filter feature can be enabled at boot time. Just
			pass the driver to filter for as the parameter.
			The filter can be disabled or changed to another
			driver later using sysfs.

729 730 731 732 733 734 735 736 737 738 739 740 741 742 743
	drm_kms_helper.edid_firmware=[<connector>:]<file>
			Broken monitors, graphic adapters and KVMs may
			send no or incorrect EDID data sets. This parameter
			allows to specify an EDID data set in the
			/lib/firmware directory that is used instead.
			Generic built-in EDID data sets are used, if one of
			edid/1024x768.bin, edid/1280x1024.bin,
			edid/1680x1050.bin, or edid/1920x1080.bin is given
			and no file with the same name exists. Details and
			instructions how to build your own EDID data are
			available in Documentation/EDID/HOWTO.txt. An EDID
			data set will only be used for a particular connector,
			if its name and a colon are prepended to the EDID
			name.

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	dscc4.setup=	[NET]

746 747 748 749 750
	dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
	module.dyndbg[="val"]
			Enable debug messages at boot time.  See
			Documentation/dynamic-debug-howto.txt for details.

751 752 753
	earlycon=	[KNL] Output early console device and options.
		uart[8250],io,<addr>[,options]
		uart[8250],mmio,<addr>[,options]
754
		uart[8250],mmio32,<addr>[,options]
755 756
			Start an early, polled-mode console on the 8250/16550
			UART at the specified I/O port or MMIO address.
757 758
			MMIO inter-register address stride is either 8-bit
			(mmio) or 32-bit (mmio32).
759 760
			The options are the same as for ttyS, above.

761
	earlyprintk=	[X86,SH,BLACKFIN]
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			earlyprintk=vga
			earlyprintk=serial[,ttySn[,baudrate]]
764
			earlyprintk=ttySn[,baudrate]
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			earlyprintk=dbgp[debugController#]
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			Append ",keep" to not disable it when the real console
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			takes over.

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			Only vga or serial or usb debug port at a time.
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			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.

780 781 782
	ekgdboc=	[X86,KGDB] Allow early kernel console debugging
			ekgdboc=kbd

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			This is designed to be used in conjunction with
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			the boot argument: earlyprintk=vga

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	edd=		[EDD]
787
			Format: {"off" | "on" | "skip[mbr]"}
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	eisa_irq_edge=	[PARISC,HW]
			See header of drivers/parisc/eisa.c.

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	elanfreq=	[X86-32]
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			See comment before function elanfreq_setup() in
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			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
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	elevator=	[IOSCHED]
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			Format: {"cfq" | "deadline" | "noop"}
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			See Documentation/block/cfq-iosched.txt and
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			Documentation/block/deadline-iosched.txt for details.

801
	elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
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			Specifies physical address of start of kernel core
803 804
			image elf header and optionally the size. Generally
			kexec loader will pass this option to capture kernel.
805
			See Documentation/kdump/kdump.txt for details.
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	enable_mtrr_cleanup [X86]
			The kernel tries to adjust MTRR layout from continuous
			to discrete, to make X server driver able to add WB
			entry later. This parameter enables that.

812
	enable_timer_pin_1 [X86]
813 814 815 816 817
			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.

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	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.

826 827 828 829
	erst_disable	[ACPI]
			Disable Error Record Serialization Table (ERST)
			support.

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

834 835 836 837 838
	evm=		[EVM]
			Format: { "fix" }
			Permit 'security.evm' to be updated regardless of
			current integrity status.

839 840 841 842 843
	failslab=
	fail_page_alloc=
	fail_make_request=[KNL]
			General fault injection mechanism.
			Format: <interval>,<probability>,<space>,<times>
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			See also Documentation/fault-injection/.
845

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	floppy=		[HW]
847
			See Documentation/blockdev/floppy.txt.
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849 850 851 852 853 854
	force_pal_cache_flush
			[IA-64] Avoid check_sal_cache_flush which may hang on
			buggy SAL_CACHE_FLUSH implementations. Using this
			parameter will force ia64_sal_cache_flush to call
			ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.

855
	ftrace=[tracer]
856
			[FTRACE] will set and start the specified tracer
857 858 859
			as early as possible in order to facilitate early
			boot debugging.

860
	ftrace_dump_on_oops[=orig_cpu]
861
			[FTRACE] will dump the trace buffers on oops.
862 863 864 865
			If no parameter is passed, ftrace will dump
			buffers of all CPUs, but if you pass orig_cpu, it will
			dump only the buffer of the CPU that triggered the
			oops.
866 867 868 869 870 871

	ftrace_filter=[function-list]
			[FTRACE] Limit the functions traced by the function
			tracer at boot up. function-list is a comma separated
			list of functions. This list can be changed at run
			time by the set_ftrace_filter file in the debugfs
872
			tracing directory.
873 874 875 876 877 878

	ftrace_notrace=[function-list]
			[FTRACE] Do not trace the functions specified in
			function-list. This list can be changed at run time
			by the set_ftrace_notrace file in the debugfs
			tracing directory.
879

880 881 882 883 884 885 886
	ftrace_graph_filter=[function-list]
			[FTRACE] Limit the top level callers functions traced
			by the function graph tracer at boot up.
			function-list is a comma separated list of functions
			that can be changed at run time by the
			set_graph_function file in the debugfs tracing directory.

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	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]

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	gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
			Format: off | on
			default: on

899 900 901 902 903 904
	gcov_persist=	[GCOV] When non-zero (default), profiling data for
			kernel modules is saved and remains accessible via
			debugfs, even when the module is unloaded/reloaded.
			When zero, profiling data is discarded and associated
			debugfs files are removed at module unload time.

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

	hashdist=	[KNL,NUMA] Large hashes allocated during boot
			are distributed across NUMA nodes.  Defaults on
910
			for 64-bit NUMA, off otherwise.
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			Format: 0 | 1 (for off | on)
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	hcl=		[IA-64] SGI's Hardware Graph compatibility layer

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

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	hest_disable	[ACPI]
			Disable Hardware Error Source Table (HEST) support;
			corresponding firmware-first mode error processing
			logic will be disabled.

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	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.

928 929 930 931
	highres=	[KNL] Enable/disable high resolution timer mode.
			Valid parameters: "on", "off"
			Default: "on"

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

935 936 937 938 939 940 941 942 943 944
	hlt		[BUGS=ARM,SH]

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

945 946
	hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
	hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
947 948 949 950 951
			On x86-64 and powerpc, this option can be specified
			multiple times interleaved with hugepages= to reserve
			huge pages of different sizes. Valid pages sizes on
			x86-64 are 2M (when the CPU supports "pse") and 1G
			(when the CPU supports the "pdpe1gb" cpuinfo flag)
952 953
			Note that 1GB pages can only be allocated at boot time
			using hugepages= and not freed afterwards.
954

955 956
	hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
			       terminal devices. Valid values: 0..8
957 958 959
	hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
			       If specified, z/VM IUCV HVC accepts connections
			       from listed z/VM user IDs only.
960

961 962 963 964 965 966
	keep_bootcon	[KNL]
			Do not unregister boot console at start. This is only
			useful for debugging when something happens in the window
			between unregistering the boot console and initializing
			the real console.

967
	i2c_bus=	[HW] Override the default board specific I2C bus speed
968 969
			     or register an additional I2C bus that is not
			     registered from board initialization code.
970 971 972
			     Format:
			     <bus_id>,<clkrate>

973
	i8042.debug	[HW] Toggle i8042 debug mode
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	i8042.direct	[HW] Put keyboard port into non-translated mode
975 976
	i8042.dumbkbd	[HW] Pretend that controller can only read data from
			     keyboard and cannot control its state
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			     (Don't attempt to blink the leds)
	i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
979
	i8042.nokbd	[HW] Don't check/create keyboard port
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	i8042.noloop	[HW] Disable the AUX Loopback command while probing
			     for the AUX port
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	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
986
	i8042.notimeout	[HW] Ignore timeout condition signalled by controller
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	i8042.reset	[HW] Reset the controller during init and cleanup
	i8042.unlock	[HW] Unlock (ignore) the keylock

	i810=		[HW,DRM]

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	i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
			indicates that the driver is running on unsupported
			hardware.
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	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.

1003
	i915.invert_brightness=
1004 1005
			[DRM] Invert the sense of the variable that is used to
			set the brightness of the panel backlight. Normally a
1006 1007 1008 1009 1010 1011 1012 1013 1014 1015
			brightness value of 0 indicates backlight switched off,
			and the maximum of the brightness value sets the backlight
			to maximum brightness. If this parameter is set to 0
			(default) and the machine requires it, or this parameter
			is set to 1, a brightness value of 0 sets the backlight
			to maximum brightness, and the maximum of the brightness
			value switches the backlight off.
			-1 -- never invert brightness
			 0 -- machine default
			 1 -- force brightness inversion
1016

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

1020 1021
	ide-core.nodma=	[HW] (E)IDE subsystem
			Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1022 1023
			.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
			.cdrom .chs .ignore_cable are additional options
1024
			See Documentation/ide/ide.txt.
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1026 1027 1028
	ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
			Claim all unknown PCI IDE storage controllers.

1029
	idle=		[X86]
1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040
			Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
			Poll forces a polling idle loop that can slightly
			improve the performance of waking up a idle CPU, but
			will use a lot of power and make the system run hot.
			Not recommended.
			idle=mwait: On systems which support MONITOR/MWAIT but
			the kernel chose to not use it because it doesn't save
			as much power as a normal idle loop, use the
			MONITOR/MWAIT idle loop anyways. Performance should be
			the same as idle=poll.
			idle=halt: Halt is forced to be used for CPU idle.
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			In such case C2/C3 won't be used again.
1042
			idle=nomwait: Disable mwait for CPU C-states
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1044 1045 1046
	ignore_loglevel	[KNL]
			Ignore loglevel setting - this will print /all/
			kernel messages to the console. Useful for debugging.
1047 1048 1049
			We also add it as printk module parameter, so users
			could change it dynamically, usually by
			/sys/module/printk/parameters/ignore_loglevel.
1050

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

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	ima_appraise=	[IMA] appraise integrity measurements
			Format: { "off" | "enforce" | "fix" }
			default: "enforce"

1058 1059 1060 1061
	ima_appraise_tcb [IMA]
			The builtin appraise policy appraises all files
			owned by uid=0.

1062 1063 1064 1065 1066 1067
	ima_audit=	[IMA]
			Format: { "0" | "1" }
			0 -- integrity auditing messages. (Default)
			1 -- enable informational integrity auditing messages.

	ima_hash=	[IMA]
1068
			Format: { "sha1" | "md5" }
1069 1070
			default: "sha1"

1071 1072 1073 1074 1075 1076
	ima_tcb		[IMA]
			Load a policy which meets the needs of the Trusted
			Computing Base.  This means IMA will measure all
			programs exec'd, files mmap'd for exec, and all files
			opened for read by uid=0.

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	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>

1091
	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1092 1093
		on
			Enable intel iommu driver.
1094 1095 1096 1097 1098 1099 1100 1101
		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.
1102 1103
		forcedac [x86_64]
			With this option iommu will not optimize to look
1104
			for io virtual address below 32-bit forcing dual
1105
			address cycle on pci bus for cards supporting greater
1106 1107
			than 32-bit addressing. The default is to look
			for translation below 32-bit and if not available
1108
			then look in the higher range.
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		strict [Default Off]
			With this option on every unmap_single operation will
			result in a hardware IOTLB flush operation as opposed
			to batching them for performance.
1113 1114 1115 1116
		sp_off [Default Off]
			By default, super page will be supported if Intel IOMMU
			has the capability. With this option, super page will
			not be supported.
1117 1118 1119 1120 1121

	intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
			0	disables intel_idle and fall back on acpi_idle.
			1 to 6	specify maximum depth of C-state.

1122 1123 1124 1125
	intremap=	[X86-64, Intel-IOMMU]
			on	enable Interrupt Remapping (default)
			off	disable Interrupt Remapping
			nosid	disable Source ID checking
1126 1127
			no_x2apic_optout
				BIOS x2APIC opt-out request will be ignored
1128

1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143
	iomem=		Disable strict checking of access to MMIO memory
		strict	regions from userspace.
		relaxed

	iommu=		[x86]
		off
		force
		noforce
		biomerge
		panic
		nopanic
		merge
		nomerge
		forcesac
		soft
1144 1145
		pt		[x86, IA-64]

1146 1147 1148 1149 1150

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

1151
	io_delay=	[X86] I/O delay method
1152 1153 1154 1155
		0x80
			Standard port 0x80 based delay
		0xed
			Alternate port 0xed based delay (needed on some systems)
1156
		udelay
1157 1158 1159
			Simple two microseconds delay
		none
			No delay
1160

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	ip=		[IP_PNP]
1162
			See Documentation/filesystems/nfs/nfsroot.txt.
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	ip2=		[HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1165 1166
			See comment before ip2_setup() in
			drivers/char/ip2/ip2base.c.
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	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.

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	isapnp=		[ISAPNP]
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			Format: <RDP>,<reset>,<pci_scan>,<verbosity>
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	isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1183 1184 1185
			Format:
			<cpu number>,...,<cpu number>
			or
1186 1187
			<cpu number>-<cpu number>
			(must be a positive range in ascending order)
1188 1189
			or a mixture
			<cpu number>,...,<cpu number>-<cpu number>
1190

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			This option can be used to specify one or more CPUs
			to isolate from the general SMP balancing and scheduling
1193 1194
			algorithms. You can move a process onto or off an
			"isolated" CPU via the CPU affinity syscalls or cpuset.
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			<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
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			alternative -- manually setting the CPU mask of all
			tasks in the system -- can cause problems and
			suboptimal load balancer performance.
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	iucv=		[HW,NET]
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	js=		[HW,JOY] Analog joystick
			See Documentation/input/joystick.txt.

1208 1209
	keepinitrd	[HW,ARM]

1210
	kernelcore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
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			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.

1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236
	kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
			Format: <Controller#>[,poll interval]
			The controller # is the number of the ehci usb debug
			port as it is probed via PCI.  The poll interval is
			optional and is the number seconds in between
			each poll cycle to the debug port in case you need
			the functionality for interrupting the kernel with
			gdb or control-c on the dbgp connection.  When
			not using this parameter you use sysrq-g to break into
			the kernel debugger.

1237
	kgdboc=		[KGDB,HW] kgdb over consoles.
1238 1239
			Requires a tty driver that supports console polling,
			or a supported polling keyboard driver (non-usb).
1240 1241 1242 1243 1244 1245
			 Serial only format: <serial_device>[,baud]
			 keyboard only format: kbd
			 keyboard and serial format: kbd,<serial_device>[,baud]
			Optional Kernel mode setting:
			 kms, kbd format: kms,kbd
			 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
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1247 1248 1249
	kgdbwait	[KGDB] Stop kernel execution and enter the
			kernel debugger at the earliest opportunity.

1250 1251 1252 1253
	kmac=		[MIPS] korina ethernet MAC address.
			Configure the RouterBoard 532 series on-chip
			Ethernet adapter MAC address.

1254 1255 1256 1257
	kmemleak=	[KNL] Boot-time kmemleak enable/disable
			Valid arguments: on, off
			Default: on

1258
	kstack=N	[X86] Print N words from the kernel stack
1259 1260
			in oops dumps.

1261 1262 1263
	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
			Default is 0 (don't ignore, but inject #GP)

1264 1265
	kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
			KVM MMU at runtime.
1266 1267 1268
			Default is 0 (off)

	kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1269
			Default is 1 (enabled)
1270 1271 1272

	kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
			for all guests.
1273
			Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286

	kvm-intel.ept=	[KVM,Intel] Disable extended page tables
			(virtualized MMU) support on capable Intel chips.
			Default is 1 (enabled)

	kvm-intel.emulate_invalid_guest_state=
			[KVM,Intel] Enable emulation of invalid guest states
			Default is 0 (disabled)

	kvm-intel.flexpriority=
			[KVM,Intel] Disable FlexPriority feature (TPR shadow).
			Default is 1 (enabled)

1287 1288 1289 1290
	kvm-intel.nested=
			[KVM,Intel] Enable VMX nesting (nVMX).
			Default is 0 (disabled)

1291 1292 1293 1294 1295 1296 1297 1298 1299
	kvm-intel.unrestricted_guest=
			[KVM,Intel] Disable unrestricted guest feature
			(virtualized real and unpaged mode) on capable
			Intel chips. Default is 1 (enabled)

	kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
			feature (tagged TLBs) on capable Intel chips.
			Default is 1 (enabled)

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	l2cr=		[PPC]

1302 1303
	l3cr=		[PPC]

1304
	lapic		[X86-32,APIC] Enable the local APIC even if BIOS
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			disabled it.
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1307
	lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
1308
			in C2 power state.
1309

1310 1311 1312 1313
	libata.dma=	[LIBATA] DMA control
			libata.dma=0	  Disable all PATA and SATA DMA
			libata.dma=1	  PATA and SATA Disk DMA only
			libata.dma=2	  ATAPI (CDROM) DMA only
1314
			libata.dma=4	  Compact Flash DMA only
1315 1316
			Combinations also work, so libata.dma=3 enables DMA
			for disks and CDROMs, but not CFs.
1317

1318 1319 1320
	libata.ignore_hpa=	[LIBATA] Ignore HPA limit
			libata.ignore_hpa=0	  keep BIOS limits (default)
			libata.ignore_hpa=1	  ignore limits, using full disk
1321

1322 1323 1324 1325
	libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
			when set.
			Format: <int>

1326 1327
	libata.force=	[LIBATA] Force configurations.  The format is comma
			separated list of "[ID:]VAL" where ID is
1328
			PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357
			matching port, link or device.  Basically, it matches
			the ATA ID string printed on console by libata.  If
			the whole ID part is omitted, the last PORT and DEVICE
			values are used.  If ID hasn't been specified yet, the
			configuration applies to all ports, links and devices.

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

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

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

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

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

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

1358 1359 1360
			* nohrst, nosrst, norst: suppress hard, soft
                          and both resets.

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			* rstonce: only attempt one reset during
			  hot-unplug link recovery

1364 1365
			* dump_id: dump IDENTIFY data.

1366 1367 1368
			If there are multiple matching configurations changing
			the same attribute, the last one is used.

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	memblock=debug	[KNL] Enable memblock debug messages.
1370

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	load_ramdisk=	[RAM] List of ramdisks to load from floppy
1372
			See Documentation/blockdev/ramdisk.txt.
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1374 1375
	lockd.nlm_grace_period=P  [NFS] Assign grace period.
			Format: <integer>
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1377 1378 1379 1380 1381 1382 1383 1384
	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>
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	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

1403 1404 1405
	log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
			in bytes.  n must be a power of two.  The default
			size is set in the kernel config file.
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	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.

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	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>

1446
	machvec=	[IA-64] Force the use of a particular machine-vector
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			(machvec) in a generic kernel.
			Example: machvec=hpzx1_swiotlb
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1450 1451 1452 1453
	machtype=	[Loongson] Share the same kernel image file between different
			 yeeloong laptop.
			Example: machtype=lemote-yeeloong-2f-7inch

1454 1455
	max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
			than or equal to this physical address is ignored.
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	maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
1458 1459 1460 1461
			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.
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	max_loop=	[LOOP] The number of loop block devices that get
	(loop.max_loop)	unconditionally pre-created at init time. The default
			number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
			of statically allocating a predefined number, loop
			devices can be requested on-demand with the
			/dev/loop-control interface.
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	mce		[X86-32] Machine Check Exception
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	mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
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	md=		[HW] RAID subsystems devices and level
			See Documentation/md.txt.
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	mdacon=		[MDA]
			Format: <first>,<last>
			Specifies range of consoles to be captured by the MDA.
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	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.
1484
			[X86-32] Use together with memmap= to avoid physical
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			address space collisions. Without memmap= PCI devices
			could be placed at addresses belonging to unused RAM.

1488
	mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
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			memory.

1491 1492 1493 1494
	memchunk=nn[KMG]
			[KNL,SH] Allow user to override the default size for
			per-device physically contiguous DMA buffers.

1495
	memmap=exactmap	[KNL,X86] Enable setting of an exact
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			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.
1512 1513 1514 1515
			Example: Exclude memory from 0x18690000-0x1869ffff
			         memmap=64K$0x18690000
			         or
			         memmap=0x10000$0x18690000
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1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539
	memory_corruption_check=0/1 [X86]
			Some BIOSes seem to corrupt the first 64k of
			memory when doing things like suspend/resume.
			Setting this option will scan the memory
			looking for corruption.  Enabling this will
			both detect corruption and prevent the kernel
			from using the memory being corrupted.
			However, its intended as a diagnostic tool; if
			repeatable BIOS-originated corruption always
			affects the same memory, you can use memmap=
			to prevent the kernel from using that memory.

	memory_corruption_check_size=size [X86]
			By default it checks for corruption in the low
			64k, making this memory unavailable for normal
			use.  Use this parameter to scan for
			corruption in more or less memory.

	memory_corruption_check_period=seconds [X86]
			By default it checks for corruption every 60
			seconds.  Use this parameter to check at some
			other rate.  0 disables periodic checking.

1540
	memtest=	[KNL,X86] Enable memtest
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			Format: <integer>
			default : 0 <disable>
1543 1544 1545 1546 1547 1548
			Specifies the number of memtest passes to be
			performed. Each pass selects another test
			pattern from a given set of patterns. Memtest
			fills the memory with this pattern, validates
			memory contents and reserves bad memory
			regions that are detected.
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	meye.*=		[HW] Set MotionEye Camera parameters
			See Documentation/video4linux/meye.txt.

1553 1554 1555 1556
	mfgpt_irq=	[IA-32] Specify the IRQ to use for the
			Multi-Function General Purpose Timers on AMD Geode
			platforms.

1557 1558 1559 1560 1561
	mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
			the BIOS has incorrectly applied a workaround. TinyBIOS
			version 0.98 is known to be affected, 0.99 fixes the
			problem by letting the user disable the workaround.

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	mga=		[HW,DRM]

1564 1565 1566
	min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
			physical address is ignored.

1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587
	mini2440=	[ARM,HW,KNL]
			Format:[0..2][b][c][t]
			Default: "0tb"
			MINI2440 configuration specification:
			0 - The attached screen is the 3.5" TFT
			1 - The attached screen is the 7" TFT
			2 - The VGA Shield is attached (1024x768)
			Leaving out the screen size parameter will not load
			the TFT driver, and the framebuffer will be left
			unconfigured.
			b - Enable backlight. The TFT backlight pin will be
			linked to the kernel VESA blanking code and a GPIO
			LED. This parameter is not necessary when using the
			VGA shield.
			c - Enable the s3c camera interface.
			t - Reserved for enabling touchscreen support. The
			touchscreen support is not enabled in the mainstream
			kernel as of 2.6.30, a preliminary port can be found
			in the "bleeding edge" mini2440 support kernel at
			http://repo.or.cz/w/linux-2.6/mini2440.git

1588 1589 1590 1591 1592 1593 1594 1595
	mminit_loglevel=
			[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
			parameter allows control of the logging verbosity for
			the additional memory initialisation checks. A value
			of 0 disables mminit logging and a level of 4 will
			log everything. Information is printed at KERN_DEBUG
			so loglevel=8 may also need to be specified.

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	module.sig_enforce
			[KNL] When CONFIG_MODULE_SIG is set, this means that
			modules without (valid) signatures will fail to load.
			Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
			is always true, so this option does nothing.

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	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

1613
	movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
1614 1615 1616 1617 1618 1619 1620 1621 1622
			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.

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

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	MTD_Region=	[MTD] Format:
			<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
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	mtdparts=	[MTD]
1630
			See drivers/mtd/cmdlinepart.c.
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1632 1633 1634 1635
	multitce=off	[PPC]  This parameter disables the use of the pSeries
			firmware feature for updating multiple TCE entries
			at a time.

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	onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration

			Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]

			boundary - index of last SLC block on Flex-OneNAND.
				   The remaining blocks are configured as MLC blocks.
			lock	 - Configure if Flex-OneNAND boundary should be locked.
				   Once locked, the boundary cannot be changed.
				   1 indicates lock status, 0 indicates unlock status.

1646 1647 1648 1649 1650
	mtdset=		[ARM]
			ARM/S3C2412 JIVE boot control

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

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	mtouchusb.raw_coordinates=
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			[HW] Make the MicroTouch USB driver use raw coordinates
			('y', default) or cooked coordinates ('n')
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1655
	mtrr_chunk_size=nn[KMG] [X86]
1656
			used for mtrr cleanup. It is largest continuous chunk
1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671
			that could hold holes aka. UC entries.

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

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

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

	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.
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			This usage is only documented in each driver source
			file if at all.

1681 1682 1683 1684
	nf_conntrack.acct=
			[NETFILTER] Enable connection tracking flow accounting
			0 to disable accounting
			1 to enable accounting
1685
			Default value is 0.
1686

1687
	nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
1688
			See Documentation/filesystems/nfs/nfsroot.txt.
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	nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
1691
			See Documentation/filesystems/nfs/nfsroot.txt.
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1693 1694 1695
	nfsrootdebug	[NFS] enable nfsroot debugging messages.
			See Documentation/filesystems/nfs/nfsroot.txt.

1696 1697 1698 1699
	nfs.callback_tcpport=
			[NFS] set the TCP port on which the NFSv4 callback
			channel should listen.

1700 1701 1702 1703 1704 1705 1706 1707
	nfs.cache_getent=
			[NFS] sets the pathname to the program which is used
			to update the NFS client cache entries.

	nfs.cache_getent_timeout=
			[NFS] sets the timeout after which an attempt to
			update a cache entry is deemed to have failed.

1708 1709 1710 1711
	nfs.idmap_cache_timeout=
			[NFS] set the maximum lifetime for idmapper cache
			entries.

1712 1713 1714 1715 1716 1717 1718
	nfs.enable_ino64=
			[NFS] enable 64-bit inode numbers.
			If zero, the NFS client will fake up a 32-bit inode
			number for the readdir() and stat() syscalls instead
			of returning the full 64-bit number.
			The default is to return 64-bit inode numbers.

1719 1720 1721 1722 1723 1724 1725 1726
	nfs.max_session_slots=
			[NFSv4.1] Sets the maximum number of session slots
			the client will attempt to negotiate with the server.
			This limits the number of simultaneous RPC requests
			that the client can send to the NFSv4.1 server.
			Note that there is little point in setting this
			value higher than the max_tcp_slot_table_limit.

1727
	nfs.nfs4_disable_idmapping=
1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738
			[NFSv4] When set to the default of '1', this option
			ensures that both the RPC level authentication
			scheme and the NFS level operations agree to use
			numeric uids/gids if the mount is using the
			'sec=sys' security flavour. In effect it is
			disabling idmapping, which can make migration from
			legacy NFSv2/v3 systems to NFSv4 easier.
			Servers that do not support this mode of operation
			will be autodetected by the client, and it will fall
			back to using the idmapper.
			To turn off this behaviour, set the value to '0'.
1739 1740 1741 1742 1743
	nfs.nfs4_unique_id=
			[NFS4] Specify an additional fixed unique ident-
			ification string that NFSv4 clients can insert into
			their nfs_client_id4 string.  This is typically a
			UUID that is generated at system install time.
1744

1745 1746 1747 1748 1749 1750 1751 1752
	nfs.send_implementation_id =
			[NFSv4.1] Send client implementation identification
			information in exchange_id requests.
			If zero, no implementation identification information
			will be sent.
			The default is to send the implementation identification
			information.

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	nfsd.nfs4_disable_idmapping=
			[NFSv4] When set to the default of '1', the NFSv4
			server will return only numeric uids and gids to
			clients using auth_sys, and will accept numeric uids
			and gids from such clients.  This is intended to ease
			migration from NFSv2/v3.
1759

1760 1761 1762 1763 1764 1765
	objlayoutdriver.osd_login_prog=
			[NFS] [OBJLAYOUT] sets the pathname to the program which
			is used to automatically discover and login into new
			osd-targets. Please see:
			Documentation/filesystems/pnfs.txt for more explanations

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

1770
	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
1771
			Format: [panic,][nopanic,][num]
1772
			Valid num: 0
1773
			0 - turn nmi_watchdog off
1774
			When panic is specified, panic when an NMI watchdog
1775 1776
			timeout occurs (or 'nopanic' to override the opposite
			default).
1777 1778
			This is useful when you use a panic=... timeout and
			need the box quickly up again.
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1780 1781 1782 1783 1784
	netpoll.carrier_timeout=
			[NET] Specifies amount of time (in seconds) that
			netpoll should wait for a carrier. By default netpoll
			waits 4 seconds.

1785
	no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
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			emulation library even if a 387 maths coprocessor
			is present.

1789 1790 1791 1792 1793 1794 1795 1796 1797
	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.
1798 1799 1800 1801 1802
			To facilitate more flexible debugging, we also add
			console_suspend, a printk module parameter to control
			it. Users could use console_suspend (usually
			/sys/module/printk/parameters/console_suspend) to
			turn on/off it dynamically.
1803

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	noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
			caches in the slab allocator.  Saves per-node memory,
			but will impact performance.
1807

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	noalign		[KNL,ARM]

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

1813 1814
	noautogroup	Disable scheduler automatic task group creation.

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

	nocache		[ARM]
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1820 1821
	noclflush	[BUGS=X86] Don't use the CLFLUSH instruction

1822 1823
	nodelayacct	[KNL] Disable per-task delay accounting

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

1826 1827
	nodsp		[SH] Disable hardware DSP at boot time.

1828
	noefi		[X86] Disable EFI runtime services support.
1829

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	noexec		[IA-64]

1832
	noexec		[X86]
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			On X86-32 available only on PAE configured kernels.
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			noexec=on: enable non-executable mappings (default)
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			noexec=off: disable non-executable mappings

1837 1838 1839 1840
	nosmap		[X86]
			Disable SMAP (Supervisor Mode Access Prevention)
			even if it is supported by processor.

1841
	nosmep		[X86]
1842
			Disable SMEP (Supervisor Mode Execution Prevention)
1843 1844
			even if it is supported by processor.

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	noexec32	[X86-64]
			This affects only 32-bit executables.
			noexec32=on: enable non-executable mappings (default)
				read doesn't imply executable mappings
			noexec32=off: disable non-executable mappings
				read implies executable mappings
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1852 1853
	nofpu		[SH] Disable hardware FPU at boot time.

1854
	nofxsr		[BUGS=X86-32] Disables x86 floating point extended
1855 1856
			register save and restore. The kernel will only save
			legacy floating-point registers on task switch.
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1858 1859 1860 1861
	noxsave		[BUGS=X86] Disables x86 extended register state save
			and restore using xsave. The kernel will fallback to
			enabling legacy floating-point and sse state.

1862
	eagerfpu=	[X86]
1863
			on	enable eager fpu restore
1864
			off	disable eager fpu restore
1865 1866
			auto	selects the default scheme, which automatically
				enables eagerfpu restore for xsaveopt.
1867

1868 1869 1870
	nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
			wfi(ARM) instruction doesn't work correctly and not to
			use it. This is also useful when using JTAG debugger.
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1872
	no-hlt		[BUGS=X86-32] Tells the kernel that the hlt
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			instruction doesn't work correctly and not to
			use it.

1876 1877 1878 1879
	no_file_caps	Tells the kernel not to honor file capabilities.  The
			only way then for a file to be executed with privilege
			is to be setuid root or executed by root.

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	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.

1887 1888 1889 1890
	nohz=		[KNL] Boottime enable/disable dynamic ticks
			Valid arguments: on, off
			Default: on

1891 1892
	noiotrap	[SH] Disables trapped I/O port accesses.

1893
	noirqdebug	[X86-32] Disables the code which attempts to detect and
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			disable unhandled interrupt sources.

1896
	no_timer_check	[X86,APIC] Disables the code which tests for
1897 1898
			broken timer IRQ sources.

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	noisapnp	[ISAPNP] Disables ISA PnP code.

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

1904 1905
	nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
			remapping.
1906
			[Deprecated - use intremap=off]
1907

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	nointroute	[IA-64]

1910
	nojitter	[IA-64] Disables jitter checking for ITC timers.
1911

1912 1913
	no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver

1914 1915 1916
	no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
			fault handling.

1917 1918 1919 1920
	no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
			steal time is computed, but won't influence scheduler
			behaviour

1921
	nolapic		[X86-32,APIC] Do not enable or use the local APIC.
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1923
	nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
1924

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1925 1926 1927
	noltlbs		[PPC] Do not use large page/tlb entries for kernel
			lowmem mapping on PPC40x.

1928 1929
	nomca		[IA-64] Disable machine check abort handling

1930
	nomce		[X86-32] Machine Check Exception
1931

1932 1933 1934
	nomfgpt		[X86-32] Disable Multi-Function General Purpose
			Timer usage (for AMD Geode machines).

1935 1936 1937 1938
	nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
			shutdown the other cpus.  Instead use the REBOOT_VECTOR
			irq.

1939 1940
	nomodule	Disable module load

1941 1942 1943
	nopat		[X86] Disable PAT (page attribute table extension of
			pagetables) support.

1944 1945 1946
	norandmaps	Don't use address space randomization.  Equivalent to
			echo 0 > /proc/sys/kernel/randomize_va_space

1947
	noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
1948

1949
	noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
1950 1951
			with UP alternatives

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

1954 1955 1956 1957 1958
	nordrand	[X86] Disable the direct use of the RDRAND
			instruction even if it is supported by the
			processor.  RDRAND is still available to user
			space applications.

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	noresume	[SWSUSP] Disables resume and restores original swap
			space.

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

	nosbagart	[IA-64]

1968
	nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1969

1970 1971
	nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
			and disable the IO APIC.  legacy for "maxcpus=0".
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1973 1974
	nosoftlockup	[KNL] Disable the soft-lockup detector.

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

1977
	notsc		[BUGS=X86-32] Disable Time Stamp Counter
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	nousb		[USB] Disable the USB subsystem

1981
	nowatchdog	[KNL] Disable the lockup detector (NMI watchdog).
1982

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1983
	nowb		[ARM]
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1985 1986
	nox2apic	[X86-64,APIC] Do not enable x2APIC mode.

1987
	nptcg=		[IA-64] Override max number of concurrent global TLB
1988 1989 1990
			purges which is reported from either PAL_VM_SUMMARY or
			SAL PALO.

1991 1992 1993 1994 1995 1996
	nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
			could support.  nr_cpus=n : n >= 1 limits the kernel to
			supporting 'n' processors. Later in runtime you can not
			use hotplug cpu feature to put more cpu back to online.
			just like you compile the kernel NR_CPUS=n

1997 1998
	nr_uarts=	[SERIAL] maximum number of UARTs to be registered.

1999 2000 2001 2002 2003
	numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
			one of ['zone', 'node', 'default'] can be specified
			This can be set from sysctl after boot.
			See Documentation/sysctl/vm.txt for details.

2004 2005 2006 2007
	ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
			See Documentation/debugging-via-ohci1394.txt for more
			info.

2008 2009 2010 2011 2012 2013 2014
	olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
			Rather than timing out after 20 ms if an EC
			command is not properly ACKed, override the length
			of the timeout.  We have interrupts disabled while
			waiting for the ACK, so if this is set too high
			interrupts *may* be lost!

2015 2016 2017 2018 2019
	omap_mux=	[OMAP] Override bootloader pin multiplexing.
			Format: <mux_mode0.mode_name=value>...
			For example, to override I2C bus2:
			omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100

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

2023 2024 2025
	oprofile.cpu_type=	Force an oprofile cpu type
			This might be useful if you have an older oprofile
			userland or if you want common events.
2026 2027
			Format: { arch_perfmon }
			arch_perfmon: [X86] Force use of architectural
2028 2029
				perfmon on Intel CPUs instead of the
				CPU specific event set.
2030 2031 2032
			timer: [X86] Force use of architectural NMI
				timer mode (see also oprofile.timer
				for generic hr timer mode)
2033 2034
				[s390] Force legacy basic mode sampling
                                (report cpu_type "timer")
2035

2036 2037 2038
	oops=panic	Always panic on oopses. Default is to just kill the
			process, but there is a small probability of
			deadlocking the machine.
2039 2040 2041
			This will also cause panics on machine check exceptions.
			Useful together with panic=30 to trigger a reboot.

2042 2043 2044
	OSS		[HW,OSS]
			See Documentation/sound/oss/oss-parameters.txt

2045
	panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2046 2047 2048
			timeout > 0: seconds before rebooting
			timeout = 0: wait forever
			timeout < 0: reboot immediately
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			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).
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			Format: <mode>

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

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

2080 2081 2082 2083 2084
	pause_on_oops=
			Halt all CPUs after the first oops has been printed for
			the specified number of seconds.  This is to be used if
			your oopses keep scrolling off the screen.

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	pcbit=		[HW,ISDN]

	pcd.		[PARIDE]
			See header of drivers/block/paride/pcd.c.
2089
			See also Documentation/blockdev/paride.txt.
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	pci=option[,option...]	[PCI] various PCI subsystem options:
2092 2093
		earlydump	[X86] dump PCI config space before the kernel
			        changes anything
2094
		off		[X86] don't probe for the PCI bus
2095
		bios		[X86-32] force use of PCI BIOS, don't access
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				the hardware directly. Use this if your machine
				has a non-standard PCI host bridge.
2098
		nobios		[X86-32] disallow use of PCI BIOS, only direct
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				hardware access methods are allowed. Use this
				if you experience crashes upon bootup and you
				suspect they are caused by the BIOS.
2102
		conf1		[X86] Force use of PCI Configuration
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				Mechanism 1.
2104
		conf2		[X86] Force use of PCI Configuration
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				Mechanism 2.
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		noaer		[PCIE] If the PCIEAER kernel config parameter is
				enabled, this kernel boot option can be used to
				disable the use of PCIE advanced error reporting.
2109 2110
		nodomains	[PCI] Disable support for multiple PCI
				root domains (aka PCI segments, in ACPI-speak).
2111
		nommconf	[X86] Disable use of MMCONFIG for PCI
2112
				Configuration
2113 2114 2115
		check_enable_amd_mmconf [X86] check for and enable
				properly configured MMIO access to PCI
				config space on AMD family 10h CPU
2116 2117 2118
		nomsi		[MSI] If the PCI_MSI kernel config parameter is
				enabled, this kernel boot option can be used to
				disable the use of MSI interrupts system-wide.
2119 2120 2121
		noioapicquirk	[APIC] Disable all boot interrupt quirks.
				Safety option to keep boot IRQs enabled. This
				should never be necessary.
2122 2123 2124 2125
		ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
				primary IO-APIC for bridges that cannot disable
				boot IRQs. This fixes a source of spurious IRQs
				when the system masks IRQs.
2126 2127 2128 2129
		noioapicreroute	[APIC] Disable workaround that uses the
				boot IRQ equivalent of an IRQ that connects to
				a chipset where boot IRQs cannot be disabled.
				The opposite of ioapicreroute.
2130
		biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
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				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.
2138
		rom		[X86] Assign address space to expansion ROMs.
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				Use with caution as certain devices share
				address decoders between ROMs and other
				resources.
2142
		norom		[X86] Do not assign address space to
2143 2144
				expansion ROMs that do not already have
				BIOS assigned address ranges.
2145 2146
		nobar		[X86] Do not assign address space to the
				BARs that weren't assigned by the BIOS.
2147
		irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
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				assigned automatically to PCI devices. You can
				make the kernel exclude IRQs of your ISA cards
				this way.
2151
		pirqaddr=0xAAAAA	[X86] Specify the physical address
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				of the PIRQ table (normally generated
				by the BIOS) if it is outside the
				F0000h-100000h range.
2155
		lastbus=N	[X86] Scan all buses thru bus #N. Can be
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				useful if the kernel is unable to find your
				secondary buses and you want to tell it
				explicitly which ones they are.
2159
		assign-busses	[X86] Always assign all PCI bus
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				numbers ourselves, overriding
				whatever the firmware may have done.
2162
		usepirqmask	[X86] Honor the possible IRQ mask stored
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				in the BIOS $PIR table. This is needed on
				some systems with broken BIOSes, notably
				some HP Pavilion N5400 and Omnibook XE3
				notebooks. This will have no effect if ACPI
				IRQ routing is enabled.
2168
		noacpi		[X86] Do not use ACPI for IRQ routing
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				or for PCI scanning.
2170 2171 2172 2173 2174 2175
		use_crs		[X86] Use PCI host bridge window information
				from ACPI.  On BIOSes from 2008 or later, this
				is enabled by default.  If you need to use this,
				please report a bug.
		nocrs		[X86] Ignore PCI host bridge windows from ACPI.
			        If you need to use this, please report a bug.
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		routeirq	Do IRQ routing for all PCI devices.
				This is normally done in pci_enable_device(),
				so this option is a temporary workaround
				for broken drivers that don't call it.
2180 2181
		skip_isa_align	[X86] do not align io start addr, so can
				handle more pci cards
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		firmware	[ARM] Do not re-enumerate the bus but instead
				just use the configuration from the
				bootloader. This is currently used on
				IXP2000 systems where the bus has to be
				configured a certain way for adjunct CPUs.
2187 2188 2189 2190 2191
		noearly		[X86] Don't do any early type 1 scanning.
				This might help on some broken boards which
				machine check when some devices' config space
				is read. But various workarounds are disabled
				and some IOMMU drivers will not work.
2192 2193 2194 2195
		bfsort		Sort PCI devices into breadth-first order.
				This sorting is done to get a device
				order compatible with older (<= 2.4) kernels.
		nobfsort	Don't sort PCI devices into breadth-first order.
2196 2197 2198 2199 2200 2201
		cbiosize=nn[KMG]	The fixed amount of bus space which is
				reserved for the CardBus bridge's IO window.
				The default value is 256 bytes.
		cbmemsize=nn[KMG]	The fixed amount of bus space which is
				reserved for the CardBus bridge's memory
				window. The default value is 64 megabytes.
2202 2203 2204 2205 2206 2207 2208 2209 2210
		resource_alignment=
				Format:
				[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
				Specifies alignment and device to reassign
				aligned memory resources.
				If <order of align> is not specified,
				PAGE_SIZE is used as alignment.
				PCI-PCI bridge can be specified, if resource
				windows need to be expanded.
2211 2212 2213 2214 2215 2216
		ecrc=		Enable/disable PCIe ECRC (transaction layer
				end-to-end CRC checking).
				bios: Use BIOS/firmware settings. This is the
				the default.
				off: Turn ECRC off
				on: Turn ECRC on.
2217 2218 2219 2220 2221 2222 2223
		realloc=	Enable/disable reallocating PCI bridge resources
				if allocations done by BIOS are too small to
				accommodate resources required by all child
				devices.
				off: Turn realloc off
				on: Turn realloc on
		realloc		same as realloc=on
2224
		noari		do not use PCIe ARI.
2225 2226 2227
		pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
				only look for one device below a PCIe downstream
				port.
2228

2229 2230 2231 2232 2233 2234
	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
			Management.
		off	Disable ASPM.
		force	Enable ASPM even on devices that claim not to support it.
			WARNING: Forcing ASPM on may cause system lockups.

2235 2236 2237 2238
	pcie_hp=	[PCIE] PCI Express Hotplug driver options:
		nomsi	Do not use MSI for PCI Express Native Hotplug (this
			makes all PCIe ports use INTx for hotplug services).

2239
	pcie_ports=	[PCIE] PCIe ports handling:
2240 2241 2242 2243 2244
		auto	Ask the BIOS whether or not to use native PCIe services
			associated with PCIe ports (PME, hot-plug, AER).  Use
			them only if that is allowed by the BIOS.
		native	Use native PCIe services associated with PCIe ports
			unconditionally.
2245 2246 2247
		compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
			ports driver.

2248
	pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
2249
		nomsi	Do not use MSI for native PCIe PME signaling (this makes
2250
			all PCIe root ports use INTx for all services).
2251

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	pcmv=		[HW,PCMCIA] BadgePAD 4

	pd.		[PARIDE]
2255
			See Documentation/blockdev/paride.txt.
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	pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
			boot time.
			Format: { 0 | 1 }
			See arch/parisc/kernel/pdc_chassis.c

2262
	percpu_alloc=	Select which percpu first chunk allocator to use.
2263 2264 2265 2266 2267
			Currently supported values are "embed" and "page".
			Archs may support subset or none of the	selections.
			See comments in mm/percpu.c for details on each
			allocator.  This parameter is primarily	for debugging
			and performance comparison.
2268

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	pf.		[PARIDE]
2270
			See Documentation/blockdev/paride.txt.
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	pg.		[PARIDE]
2273
			See Documentation/blockdev/paride.txt.
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	pirq=		[SMP,APIC] Manual mp-table setup
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			See Documentation/x86/i386/IO-APIC.txt.
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	plip=		[PPT,NET] Parallel port network link
			Format: { parport<nr> | timid | 0 }
			See also Documentation/parport.txt.

2282
	pmtmr=		[X86] Manual setup of pmtmr I/O Port.
2283 2284 2285
			Override pmtimer IOPort with a hex value.
			e.g. pmtmr=0x508

2286 2287 2288 2289 2290 2291
	pnp.debug=1	[PNP]
			Enable PNP debug messages (depends on the
			CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
			via /sys/module/pnp/parameters/debug.  We always show
			current resource usage; turning this on also shows
			possible settings and some assignment information.
2292

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	pnpacpi=	[ACPI]
			{ off }

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

	pnp_reserve_irq=
			[ISAPNP] Exclude IRQs for the autoconfiguration

	pnp_reserve_dma=
			[ISAPNP] Exclude DMAs for the autoconfiguration

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

2313 2314 2315 2316 2317 2318
	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>....

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	print-fatal-signals=
			[KNL] debug: print fatal signals
2321 2322 2323 2324 2325 2326 2327 2328 2329

			If enabled, warn about various signal handling
			related application anomalies: too many signals,
			too many POSIX.1 timers, fatal signals causing a
			coredump - etc.

			If you hit the warning due to signal overflow,
			you might want to try "ulimit -i unlimited".

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			default: off.

2332 2333 2334 2335 2336 2337
	printk.always_kmsg_dump=
			Trigger kmsg_dump for cases other than kernel oops or
			panics
			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
			default: disabled

2338 2339 2340
	printk.time=	Show timing data prefixed to each printk message line
			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)

2341 2342 2343 2344 2345 2346 2347 2348
	processor.max_cstate=	[HW,ACPI]
			Limit processor to maximum C-state
			max_cstate=9 overrides any DMI blacklist limit.

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

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	profile=	[KNL] Enable kernel profiling via /proc/profile
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2350 2351 2352 2353
			Format: [schedule,]<number>
			Param: "schedule" - profile schedule points.
			Param: <number> - step/bucket size as a power of 2 for
				statistical time based profiling.
2354 2355
			Param: "sleep" - profile D-state sleeping (millisecs).
				Requires CONFIG_SCHEDSTATS
2356
			Param: "kvm" - profile VM exits.
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	prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
			before loading.
2360
			See Documentation/blockdev/ramdisk.txt.
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	psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
			probe for; one of (bare|imps|exps|lifebook|any).
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	psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
			per second.
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2366 2367
	psmouse.resetafter=	[HW,MOUSE]
			Try to reset the device after so many bad packets
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			(0 = never).
	psmouse.resolution=
			[HW,MOUSE] Set desired mouse resolution, in dpi.
	psmouse.smartscroll=
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			[HW,MOUSE] Controls Logitech smartscroll autorepeat.
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			0 = disabled, 1 = enabled (default).

2375 2376
	pstore.backend=	Specify the name of the pstore backend to use

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	pt.		[PARIDE]
2378
			See Documentation/blockdev/paride.txt.
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2380 2381 2382 2383
	pty.legacy_count=
			[KNL] Number of legacy pty's. Overwrites compiled-in
			default number.

2384
	quiet		[KNL] Disable most log messages
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	r128=		[HW,DRM]

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

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	ramdisk_blocksize=	[RAM]
2392
			See Documentation/blockdev/ramdisk.txt.
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	ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
2395
			See Documentation/blockdev/ramdisk.txt.
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2397
	rcutree.blimit=	[KNL,BOOT]
2398 2399
			Set maximum number of finished RCU callbacks to process
			in one batch.
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2401 2402 2403 2404 2405
	rcutree.fanout_leaf=	[KNL,BOOT]
			Increase the number of CPUs assigned to each
			leaf rcu_node structure.  Useful for very large
			systems.

2406
	rcutree.qhimark=	[KNL,BOOT]
2407
			Set threshold of queued
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			RCU callbacks over which batch limiting is disabled.

2410
	rcutree.qlowmark=	[KNL,BOOT]
2411 2412
			Set threshold of queued RCU callbacks below which
			batch limiting is re-enabled.
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2414 2415 2416 2417 2418 2419
	rcutree.rcu_cpu_stall_suppress=	[KNL,BOOT]
			Suppress RCU CPU stall warning messages.

	rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
			Set timeout for RCU CPU stall warning messages.

2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430
	rcutree.jiffies_till_first_fqs= [KNL,BOOT]
			Set delay from grace-period initialization to
			first attempt to force quiescent states.
			Units are jiffies, minimum value is zero,
			and maximum value is HZ.

	rcutree.jiffies_till_next_fqs= [KNL,BOOT]
			Set delay between subsequent attempts to force
			quiescent states.  Units are jiffies, minimum
			value is one, and maximum value is HZ.

2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506
	rcutorture.fqs_duration= [KNL,BOOT]
			Set duration of force_quiescent_state bursts.

	rcutorture.fqs_holdoff= [KNL,BOOT]
			Set holdoff time within force_quiescent_state bursts.

	rcutorture.fqs_stutter= [KNL,BOOT]
			Set wait time between force_quiescent_state bursts.

	rcutorture.irqreader= [KNL,BOOT]
			Test RCU readers from irq handlers.

	rcutorture.n_barrier_cbs= [KNL,BOOT]
			Set callbacks/threads for rcu_barrier() testing.

	rcutorture.nfakewriters= [KNL,BOOT]
			Set number of concurrent RCU writers.  These just
			stress RCU, they don't participate in the actual
			test, hence the "fake".

	rcutorture.nreaders= [KNL,BOOT]
			Set number of RCU readers.

	rcutorture.onoff_holdoff= [KNL,BOOT]
			Set time (s) after boot for CPU-hotplug testing.

	rcutorture.onoff_interval= [KNL,BOOT]
			Set time (s) between CPU-hotplug operations, or
			zero to disable CPU-hotplug testing.

	rcutorture.shuffle_interval= [KNL,BOOT]
			Set task-shuffle interval (s).  Shuffling tasks
			allows some CPUs to go into dyntick-idle mode
			during the rcutorture test.

	rcutorture.shutdown_secs= [KNL,BOOT]
			Set time (s) after boot system shutdown.  This
			is useful for hands-off automated testing.

	rcutorture.stall_cpu= [KNL,BOOT]
			Duration of CPU stall (s) to test RCU CPU stall
			warnings, zero to disable.

	rcutorture.stall_cpu_holdoff= [KNL,BOOT]
			Time to wait (s) after boot before inducing stall.

	rcutorture.stat_interval= [KNL,BOOT]
			Time (s) between statistics printk()s.

	rcutorture.stutter= [KNL,BOOT]
			Time (s) to stutter testing, for example, specifying
			five seconds causes the test to run for five seconds,
			wait for five seconds, and so on.  This tests RCU's
			ability to transition abruptly to and from idle.

	rcutorture.test_boost= [KNL,BOOT]
			Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
			"Maybe" means test if the RCU implementation
			under test support RCU priority boosting.

	rcutorture.test_boost_duration= [KNL,BOOT]
			Duration (s) of each individual boost test.

	rcutorture.test_boost_interval= [KNL,BOOT]
			Interval (s) between each boost test.

	rcutorture.test_no_idle_hz= [KNL,BOOT]
			Test RCU's dyntick-idle handling.  See also the
			rcutorture.shuffle_interval parameter.

	rcutorture.torture_type= [KNL,BOOT]
			Specify the RCU implementation to test.

	rcutorture.verbose= [KNL,BOOT]
			Enable additional printk() statements.

2507 2508 2509 2510 2511
	rdinit=		[KNL]
			Format: <full_path>
			Run specified binary instead of /init from the ramdisk,
			used for early userspace startup. See initrd.

2512
	reboot=		[BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
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			Format: <reboot_mode>[,<reboot_mode2>[,...]]
2514
			See arch/*/kernel/reboot.c or arch/*/kernel/process.c
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2516 2517
	relax_domain_level=
			[KNL, SMP] Set scheduler's default relax_domain_level.
2518
			See Documentation/cgroups/cpusets.txt.
2519

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

2522
	reservetop=	[X86-32]
2523 2524 2525 2526
			Format: nn[KMG]
			Reserves a hole at the top of the kernel virtual
			address space.

2527 2528 2529 2530 2531
	reservelow=	[X86]
			Format: nn[K]
			Set the amount of memory to reserve for BIOS at
			the bottom of the address space.

2532 2533 2534
	reset_devices	[KNL] Force drivers to reset the underlying device
			during initialization.

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	resume=		[SWSUSP]
			Specify the partition device for software suspend
2537 2538
			Format:
			{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
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2540 2541 2542 2543 2544 2545
	resume_offset=	[SWSUSP]
			Specify the offset from the beginning of the partition
			given by "resume=" at which the swap header is located,
			in <PAGE_SIZE> units (needed only for swap files).
			See  Documentation/power/swsusp-and-swap-files.txt

2546 2547 2548
	resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
			read the resume files

2549 2550 2551 2552
	resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
			Useful for devices that are detected asynchronously
			(e.g. USB and MMC devices).

2553 2554 2555 2556 2557
	hibernate=	[HIBERNATION]
		noresume	Don't check if there's a hibernation image
				present during boot.
		nocompress	Don't compress/decompress hibernation images.

2558 2559
	retain_initrd	[RAM] Keep initrd memory after extraction

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

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

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

	root=		[KNL] Root filesystem
2569
			See name_to_dev_t comment in init/do_mounts.c.
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	rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
			mount the root filesystem

	rootflags=	[KNL] Set root filesystem mount option string

	rootfstype=	[KNL] Set root filesystem type

2578 2579 2580 2581
	rootwait	[KNL] Wait (indefinitely) for root device to show up.
			Useful for devices that are detected asynchronously
			(e.g. USB and MMC devices).

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

	S		[KNL] Run init in single mode

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

	sbni=		[NET] Granch SBNI12 leased line adapter
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2591 2592
	sched_debug	[KNL] Enables verbose scheduler debug messages.

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	skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
			xtime_lock contention on larger systems, and/or RCU lock
			contention on all systems with CONFIG_MAXSMP set.
			Format: { "0" | "1" }
			0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
			1 -- enable.
			Note: increases power consumption, thus should only be
			enabled if running jitter sensitive (HPC/RT) workloads.

2602 2603 2604 2605 2606 2607 2608
	security=	[SECURITY] Choose a security module to enable at boot.
			If this boot parameter is not specified, only the first
			security module asking for security registration will be
			loaded. An invalid security module name will be treated
			as if no module has been chosen.

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

2617 2618 2619 2620 2621 2622 2623
	apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
			Format: { "0" | "1" }
			See security/apparmor/Kconfig help text
			0 -- disable.
			1 -- enable.
			Default value is set via kernel config option.

2624
	serialnumber	[BUGS=X86-32]
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	shapers=	[NET]
			Maximal number of shapers.
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	show_msr=	[x86] show boot-time MSR settings
			Format: { <integer> }
			Show boot-time (BIOS-initialized) MSR settings.
			The parameter means the number of CPUs to show,
			for example 1 means boot CPU only.

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	simeth=		[IA-64]
	simscsi=
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	slram=		[HW,MTD]

2640 2641 2642 2643 2644 2645
	slab_max_order=	[MM, SLAB]
			Determines the maximum allowed order for slabs.
			A high setting may cause OOMs due to memory
			fragmentation.  Defaults to 1 for systems with
			more than 32MB of RAM, 0 otherwise.

2646 2647 2648 2649 2650 2651 2652
	slub_debug[=options[,slabs]]	[MM, SLUB]
			Enabling slub_debug allows one to determine the
			culprit if slab objects become corrupted. Enabling
			slub_debug can create guard zones around objects and
			may poison objects when not in use. Also tracks the
			last alloc / free. For more information see
			Documentation/vm/slub.txt.
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	slub_max_order= [MM, SLUB]
2655 2656 2657 2658
			Determines the maximum allowed order for slabs.
			A high setting may cause OOMs due to memory
			fragmentation. For more information see
			Documentation/vm/slub.txt.
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	slub_min_objects=	[MM, SLUB]
2661 2662 2663 2664 2665 2666
			The minimum number of objects per slab. SLUB will
			increase the slab order up to slub_max_order to
			generate a sufficiently large slab able to contain
			the number of objects indicated. The higher the number
			of objects the smaller the overhead of tracking slabs
			and the less frequently locks need to be acquired.
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			For more information see Documentation/vm/slub.txt.

	slub_min_order=	[MM, SLUB]
2670
			Determines the minimum page order for slabs. Must be
2671
			lower than slub_max_order.
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			For more information see Documentation/vm/slub.txt.

	slub_nomerge	[MM, SLUB]
2675
			Disable merging of slabs with similar size. May be
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			necessary if there is some reason to distinguish
2677 2678
			allocs to different slabs. Debug options disable
			merging on their own.
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			For more information see Documentation/vm/slub.txt.

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

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

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	softlockup_panic=
			[KNL] Should the soft-lockup detector generate panics.
2697
			Format: <integer>
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	sonypi.*=	[HW] Sony Programmable I/O Control Device driver
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			See Documentation/laptops/sonypi.txt
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	specialix=	[HW,SERIAL] Specialix multi-serial port adapter
2703
			See Documentation/serial/specialix.txt.
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	spia_io_base=	[HW,MTD]
	spia_fio_base=
	spia_pedr=
	spia_peddr=

2710 2711 2712
	stacktrace	[FTRACE]
			Enabled the stack tracer on boot up.

2713 2714 2715 2716 2717 2718 2719 2720
	stacktrace_filter=[function-list]
			[FTRACE] Limit the functions that the stack tracer
			will trace at boot up. function-list is a comma separated
			list of functions. This list can be changed at run
			time by the stack_trace_filter file in the debugfs
			tracing directory. Note, this enables stack tracing
			and the stacktrace above is not needed.

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

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

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

2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745
	sunrpc.min_resvport=
	sunrpc.max_resvport=
			[NFS,SUNRPC]
			SunRPC servers often require that client requests
			originate from a privileged port (i.e. a port in the
			range 0 < portnr < 1024).
			An administrator who wishes to reserve some of these
			ports for other uses may adjust the range that the
			kernel's sunrpc client considers to be privileged
			using these two parameters to set the minimum and
			maximum port values.

2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761
	sunrpc.pool_mode=
			[NFS]
			Control how the NFS server code allocates CPUs to
			service thread pools.  Depending on how many NICs
			you have and where their interrupts are bound, this
			option will affect which CPUs will do NFS serving.
			Note: this parameter cannot be changed while the
			NFS server is running.

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

2762 2763 2764 2765 2766 2767 2768 2769 2770
	sunrpc.tcp_slot_table_entries=
	sunrpc.udp_slot_table_entries=
			[NFS,SUNRPC]
			Sets the upper limit on the number of simultaneous
			RPC calls that can be sent from the client to a
			server. Increasing these values may allow you to
			improve throughput, but will also increase the
			amount of memory reserved for use by the client.

2771 2772 2773 2774 2775
	swapaccount[=0|1]
			[KNL] Enable accounting of swap in memory resource
			controller if no parameter or 1 is given or disable
			it if 0 is given (See Documentation/cgroups/memory.txt)

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	swiotlb=	[IA-64] Number of I/O TLB slabs
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	switches=	[HW,M68k]

2780 2781 2782 2783 2784 2785 2786 2787 2788
	sysfs.deprecated=0|1 [KNL]
			Enable/disable old style sysfs layout for old udev
			on older distributions. When this option is enabled
			very new udev will not work anymore. When this option
			is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
			in older udev will not work anymore.
			Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
			the kernel configuration.

2789 2790 2791 2792 2793 2794
	sysrq_always_enabled
			[KNL]
			Ignore sysrq setting - this boot parameter will
			neutralize any effect of /proc/sys/kernel/sysrq.
			Useful for debugging.

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	tdfx=		[HW,DRM]

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

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

2806 2807 2808 2809
	thermal.act=	[HW,ACPI]
			-1: disable all active trip points in all thermal zones
			<degrees C>: override all lowest active trip points

2810 2811
	thermal.crt=	[HW,ACPI]
			-1: disable all critical trip points in all thermal zones
2812
			<degrees C>: override all critical trip points
2813

2814 2815 2816 2817
	thermal.nocrt=	[HW,ACPI]
			Set to disable actions on ACPI thermal zone
			critical and hot trip points.

2818 2819 2820
	thermal.off=	[HW,ACPI]
			1: disable ACPI thermal control

2821 2822
	thermal.psv=	[HW,ACPI]
			-1: disable all passive trip points
2823 2824
			<degrees C>: override all passive trip points to this
			value
2825

2826 2827 2828 2829 2830
	thermal.tzp=	[HW,ACPI]
			Specify global default ACPI thermal zone polling rate
			<deci-seconds>: poll all this frequency
			0: no polling (default)

2831 2832
	threadirqs	[KNL]
			Force threading of all interrupt handlers except those
2833
			marked explicitly IRQF_NO_THREAD.
2834

2835 2836 2837
	topology=	[S390]
			Format: {off | on}
			Specify if the kernel should make use of the cpu
2838 2839
			topology information if the hardware supports this.
			The scheduler will make use of this information and
2840
			e.g. base its process migration decisions on it.
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			Default is on.
2842

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	tp720=		[HW,PS2]

2845 2846 2847 2848 2849 2850 2851 2852 2853
	tpm_suspend_pcr=[HW,TPM]
			Format: integer pcr id
			Specify that at suspend time, the tpm driver
			should extend the specified pcr with zeros,
			as a workaround for some chips which fail to
			flush the last written pcr on TPM_SaveState.
			This will guarantee that all the other pcrs
			are saved.

2854 2855
	trace_buf_size=nn[KMG]
			[FTRACE] will set tracing buffer size.
2856

2857 2858 2859 2860 2861
	trace_event=[event-list]
			[FTRACE] Set and start specified trace events in order
			to facilitate early boot debugging.
			See also Documentation/trace/events.txt

2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877
	trace_options=[option-list]
			[FTRACE] Enable or disable tracer options at boot.
			The option-list is a comma delimited list of options
			that can be enabled or disabled just as if you were
			to echo the option name into

			    /sys/kernel/debug/tracing/trace_options

			For example, to enable stacktrace option (to dump the
			stack trace of each event), add to the command line:

			      trace_options=stacktrace

			See also Documentation/trace/ftrace.txt "trace options"
			section.

2878 2879 2880 2881 2882 2883 2884
	transparent_hugepage=
			[KNL]
			Format: [always|madvise|never]
			Can be used to control the default behavior of the system
			with respect to transparent hugepages.
			See Documentation/vm/transhuge.txt for more details.

2885
	tsc=		Disable clocksource stability checks for TSC.
2886 2887
			Format: <string>
			[x86] reliable: mark tsc clocksource as reliable, this
2888 2889 2890 2891
			disables clocksource verification at runtime, as well
			as the stability checks done at bootup.	Used to enable
			high-resolution timer mode on older hardware, and in
			virtualized environment.
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			[x86] noirqtime: Do not use TSC to do irq accounting.
			Used to run time disable IRQ_TIME_ACCOUNTING on any
			platforms where RDTSC is slow and this accounting
			can add overhead.
2896

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	turbografx.map[2|3]=	[HW,JOY]
			TurboGraFX parallel port interface
			Format:
			<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
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			See also Documentation/input/joystick-parport.txt

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	udbg-immortal	[PPC] When debugging early kernel crashes that
			happen after console_init() and before a proper 
			console driver takes over, this boot options might
			help "seeing" what's going on.

2908 2909 2910
	uhash_entries=	[KNL,NET]
			Set number of hash buckets for UDP/UDP-Lite connections

2911 2912 2913 2914 2915 2916 2917 2918
	uhci-hcd.ignore_oc=
			[USB] Ignore overcurrent events (default N).
			Some badly-designed motherboards generate lots of
			bogus events, for ports that aren't wired to
			anything.  Set this parameter to avoid log spamming.
			Note that genuine overcurrent events won't be
			reported either.

2919
	unknown_nmi_panic
2920
			[X86] Cause panic on unknown NMI.
2921

2922 2923 2924 2925 2926
	usbcore.authorized_default=
			[USB] Default USB device authorization:
			(default -1 = authorized except for wireless USB,
			0 = not authorized, 1 = authorized)

2927 2928 2929 2930 2931
	usbcore.autosuspend=
			[USB] The autosuspend time delay (in seconds) used
			for newly-detected USB devices (default 2).  This
			is the time required before an idle device will be
			autosuspended.  Devices for which the delay is set
2932
			to a negative value won't be autosuspended at all.
2933

2934 2935 2936 2937 2938 2939 2940 2941 2942 2943
	usbcore.usbfs_snoop=
			[USB] Set to log all usbfs traffic (default 0 = off).

	usbcore.blinkenlights=
			[USB] Set to cycle leds on hubs (default 0 = off).

	usbcore.old_scheme_first=
			[USB] Start with the old device initialization
			scheme (default 0 = off).

2944 2945 2946 2947
	usbcore.usbfs_memory_mb=
			[USB] Memory limit (in MB) for buffers allocated by
			usbfs (default = 16, 0 = max = 2047).

2948 2949 2950 2951 2952 2953 2954 2955 2956
	usbcore.use_both_schemes=
			[USB] Try the other device initialization scheme
			if the first one fails (default 1 = enabled).

	usbcore.initial_descriptor_timeout=
			[USB] Specifies timeout for the initial 64-byte
                        USB_REQ_GET_DESCRIPTOR request in milliseconds
			(default 5000 = 5.0 seconds).

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	usbhid.mousepoll=
			[USBHID] The interval which mice are to be polled at.
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2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971
	usb-storage.delay_use=
			[UMS] The delay in seconds before a new device is
			scanned for Logical Units (default 5).

	usb-storage.quirks=
			[UMS] A list of quirks entries to supplement or
			override the built-in unusual_devs list.  List
			entries are separated by commas.  Each entry has
			the form VID:PID:Flags where VID and PID are Vendor
			and Product ID values (4-digit hex numbers) and
			Flags is a set of characters, each corresponding
			to a common usb-storage quirk flag as follows:
2972 2973
				a = SANE_SENSE (collect more than 18 bytes
					of sense data);
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				b = BAD_SENSE (don't collect more than 18
					bytes of sense data);
2976 2977
				c = FIX_CAPACITY (decrease the reported
					device capacity by one sector);
2978 2979 2980 2981
				d = NO_READ_DISC_INFO (don't use
					READ_DISC_INFO command);
				e = NO_READ_CAPACITY_16 (don't use
					READ_CAPACITY_16 command);
2982 2983 2984
				h = CAPACITY_HEURISTICS (decrease the
					reported device capacity by one
					sector if the number is odd);
2985 2986 2987 2988 2989 2990
				i = IGNORE_DEVICE (don't bind to this
					device);
				l = NOT_LOCKABLE (don't try to lock and
					unlock ejectable media);
				m = MAX_SECTORS_64 (don't transfer more
					than 64 sectors = 32 KB at a time);
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				n = INITIAL_READ10 (force a retry of the
					initial READ(10) command);
2993 2994
				o = CAPACITY_OK (accept the capacity
					reported by the device);
2995 2996
				p = WRITE_CACHE (the device cache is ON
					by default);
2997 2998 2999 3000 3001 3002 3003 3004
				r = IGNORE_RESIDUE (the device reports
					bogus residue values);
				s = SINGLE_LUN (the device has only one
					Logical Unit);
				w = NO_WP_DETECT (don't test whether the
					medium is write-protected).
			Example: quirks=0419:aaf5:rl,0421:0433:rc

3005 3006 3007 3008 3009 3010 3011 3012 3013 3014
	user_debug=	[KNL,ARM]
			Format: <int>
			See arch/arm/Kconfig.debug help text.
				 1 - undefined instruction events
				 2 - system calls
				 4 - invalid data aborts
				 8 - SIGSEGV faults
				16 - SIGBUS faults
			Example: user_debug=31

3015 3016 3017 3018 3019 3020 3021
	userpte=
			[X86] Flags controlling user PTE allocations.

				nohigh = do not allocate PTE pages in
					HIGHMEM regardless of setting
					of CONFIG_HIGHPTE.

3022
	vdso=		[X86,SH]
3023
			vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3024 3025 3026
			vdso=1: enable VDSO (default)
			vdso=0: disable VDSO mapping

3027
	vdso32=		[X86]
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			vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
			vdso32=1: enable 32-bit VDSO (default)
			vdso32=0: disable 32-bit VDSO mapping

3032 3033 3034
	vector=		[IA-64,SMP]
			vector=percpu: enable percpu vector domain

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

3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053
	virtio_mmio.device=
			[VMMIO] Memory mapped virtio (platform) device.

				<size>@<baseaddr>:<irq>[:<id>]
			where:
				<size>     := size (can use standard suffixes
						like K, M and G)
				<baseaddr> := physical base address
				<irq>      := interrupt number (as passed to
						request_irq())
				<id>       := (optional) platform device id
			example:
				virtio_mmio.device=1K@0x100b0000:48:7

			Can be used multiple times for multiple devices.

3054
	vga=		[BOOT,X86-32] Select a particular video mode
3055
			See Documentation/x86/boot.txt and
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			Documentation/svga.txt.
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			Use vga=ask for menu.
			This is actually a boot loader parameter; the value is
			passed to the kernel using a special protocol.

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

3067 3068
	vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
			Format: <command>
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3070 3071 3072 3073 3074
	vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
			Format: <command>

	vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
			Format: <command>
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3076 3077 3078 3079 3080 3081 3082 3083
	vsyscall=	[X86-64]
			Controls the behavior of vsyscalls (i.e. calls to
			fixed addresses of 0xffffffffff600x00 from legacy
			code).  Most statically-linked binaries and older
			versions of glibc use these calls.  Because these
			functions are at fixed addresses, they make nice
			targets for exploits that can control RIP.

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			emulate     [default] Vsyscalls turn into traps and are
			            emulated reasonably safely.
3086

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			native      Vsyscalls are native syscall instructions.
3088 3089 3090 3091 3092 3093 3094 3095 3096
			            This is a little bit faster than trapping
			            and makes a few dynamic recompilers work
			            better than they would in emulation mode.
			            It also makes exploits much easier to write.

			none        Vsyscalls don't work at all.  This makes
			            them quite hard to use for exploits but
			            might break your system.

3097 3098 3099 3100 3101
	vt.cur_default=	[VT] Default cursor shape.
			Format: 0xCCBBAA, where AA, BB, and CC are the same as
			the parameters of the <Esc>[?A;B;Cc escape sequence;
			see VGA-softcursor.txt. Default: 2 = underline.

3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126
	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.

3127 3128 3129 3130 3131 3132 3133 3134 3135
	vt.global_cursor_default=
			[VT]
			Format=<-1|0|1>
			Set system-wide default for whether a cursor
			is shown on new VTs. Default is -1,
			i.e. cursors will be created by default unless
			overridden by individual drivers. 0 will hide
			cursors, 1 will display them.

3136 3137 3138 3139
	watchdog timers	[HW,WDT] For information on watchdog timers,
			see Documentation/watchdog/watchdog-parameters.txt
			or other driver-specific files in the
			Documentation/watchdog/ directory.
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3141 3142 3143 3144
	x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
			default x2apic cluster mode on platforms
			supporting x2apic.

3145 3146 3147 3148 3149 3150
	x86_mrst_timer= [X86-32,APBT]
			Choose timer option for x86 Moorestown MID platform.
			Two valid options are apbt timer only and lapic timer
			plus one apbt timer for broadcast timer.
			x86_mrst_timer=apbt_only | lapic_and_apbt

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

3154 3155 3156 3157 3158 3159 3160
	xen_emul_unplug=		[HW,X86,XEN]
			Unplug Xen emulated devices
			Format: [unplug0,][unplug1]
			ide-disks -- unplug primary master IDE devices
			aux-ide-disks -- unplug non-primary-master IDE devices
			nics -- unplug network devices
			all -- unplug all emulated devices (NICs and IDE disks)
3161 3162 3163
			unnecessary -- unplugging emulated devices is
				unnecessary even if the host did not respond to
				the unplug protocol
3164
			never -- do not unplug even if version check succeeds
3165

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	xirc2ps_cs=	[NET,PCMCIA]
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			Format:
			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
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______________________________________________________________________
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TODO:

	Add more DRM drivers.