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Based on kernel version 4.2. Page generated on 2015-09-09 12:14 EST.

1	                          Kernel Parameters
2	                          ~~~~~~~~~~~~~~~~~
4	The following is a consolidated list of the kernel parameters as
5	implemented by the __setup(), core_param() and module_param() macros
6	and sorted into English Dictionary order (defined as ignoring all
7	punctuation and sorting digits before letters in a case insensitive
8	manner), and with descriptions where known.
10	The kernel parses parameters from the kernel command line up to "--";
11	if it doesn't recognize a parameter and it doesn't contain a '.', the
12	parameter gets passed to init: parameters with '=' go into init's
13	environment, others are passed as command line arguments to init.
14	Everything after "--" is passed as an argument to init.
16	Module parameters can be specified in two ways: via the kernel command
17	line with a module name prefix, or via modprobe, e.g.:
19		(kernel command line) usbcore.blinkenlights=1
20		(modprobe command line) modprobe usbcore blinkenlights=1
22	Parameters for modules which are built into the kernel need to be
23	specified on the kernel command line.  modprobe looks through the
24	kernel command line (/proc/cmdline) and collects module parameters
25	when it loads a module, so the kernel command line can be used for
26	loadable modules too.
28	Hyphens (dashes) and underscores are equivalent in parameter names, so
29		log_buf_len=1M print-fatal-signals=1
30	can also be entered as
31		log-buf-len=1M print_fatal_signals=1
33	Double-quotes can be used to protect spaces in values, e.g.:
34		param="spaces in here"
36	This document may not be entirely up to date and comprehensive. The command
37	"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38	module. Loadable modules, after being loaded into the running kernel, also
39	reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40	parameters may be changed at runtime by the command
41	"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43	The parameters listed below are only valid if certain kernel build options were
44	enabled and if respective hardware is present. The text in square brackets at
45	the beginning of each description states the restrictions within which a
46	parameter is applicable:
48		ACPI	ACPI support is enabled.
49		AGP	AGP (Accelerated Graphics Port) is enabled.
50		ALSA	ALSA sound support is enabled.
51		APIC	APIC support is enabled.
52		APM	Advanced Power Management support is enabled.
53		ARM	ARM architecture is enabled.
54		AVR32	AVR32 architecture is enabled.
55		AX25	Appropriate AX.25 support is enabled.
56		BLACKFIN Blackfin architecture is enabled.
57		CLK	Common clock infrastructure is enabled.
58		CMA	Contiguous Memory Area support is enabled.
59		DRM	Direct Rendering Management support is enabled.
60		DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61		EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
62		EFI	EFI Partitioning (GPT) is enabled
63		EIDE	EIDE/ATAPI support is enabled.
64		EVM	Extended Verification Module
65		FB	The frame buffer device is enabled.
66		FTRACE	Function tracing enabled.
67		GCOV	GCOV profiling is enabled.
68		HW	Appropriate hardware is enabled.
69		IA-64	IA-64 architecture is enabled.
70		IMA     Integrity measurement architecture is enabled.
71		IOSCHED	More than one I/O scheduler is enabled.
72		IP_PNP	IP DHCP, BOOTP, or RARP is enabled.
73		IPV6	IPv6 support is enabled.
74		ISAPNP	ISA PnP code is enabled.
75		ISDN	Appropriate ISDN support is enabled.
76		JOY	Appropriate joystick support is enabled.
77		KGDB	Kernel debugger support is enabled.
78		KVM	Kernel Virtual Machine support is enabled.
79		LIBATA  Libata driver is enabled
80		LP	Printer support is enabled.
81		LOOP	Loopback device support is enabled.
82		M68k	M68k architecture is enabled.
83				These options have more detailed description inside of
84				Documentation/m68k/kernel-options.txt.
85		MDA	MDA console support is enabled.
86		MIPS	MIPS architecture is enabled.
87		MOUSE	Appropriate mouse support is enabled.
88		MSI	Message Signaled Interrupts (PCI).
89		MTD	MTD (Memory Technology Device) support is enabled.
90		NET	Appropriate network support is enabled.
91		NUMA	NUMA support is enabled.
92		NFS	Appropriate NFS support is enabled.
93		OSS	OSS sound support is enabled.
94		PV_OPS	A paravirtualized kernel is enabled.
95		PARIDE	The ParIDE (parallel port IDE) subsystem is enabled.
96		PARISC	The PA-RISC architecture is enabled.
97		PCI	PCI bus support is enabled.
98		PCIE	PCI Express support is enabled.
99		PCMCIA	The PCMCIA subsystem is enabled.
100		PNP	Plug & Play support is enabled.
101		PPC	PowerPC architecture is enabled.
102		PPT	Parallel port support is enabled.
103		PS2	Appropriate PS/2 support is enabled.
104		RAM	RAM disk support is enabled.
105		S390	S390 architecture is enabled.
106		SCSI	Appropriate SCSI support is enabled.
107				A lot of drivers have their options described inside
108				the Documentation/scsi/ sub-directory.
109		SECURITY Different security models are enabled.
110		SELINUX SELinux support is enabled.
111		APPARMOR AppArmor support is enabled.
112		SERIAL	Serial support is enabled.
113		SH	SuperH architecture is enabled.
114		SMP	The kernel is an SMP kernel.
115		SPARC	Sparc architecture is enabled.
116		SWSUSP	Software suspend (hibernation) is enabled.
117		SUSPEND	System suspend states are enabled.
118		TPM	TPM drivers are enabled.
119		TS	Appropriate touchscreen support is enabled.
120		UMS	USB Mass Storage support is enabled.
121		USB	USB support is enabled.
122		USBHID	USB Human Interface Device support is enabled.
123		V4L	Video For Linux support is enabled.
124		VMMIO   Driver for memory mapped virtio devices is enabled.
125		VGA	The VGA console has been enabled.
126		VT	Virtual terminal support is enabled.
127		WDT	Watchdog support is enabled.
128		XT	IBM PC/XT MFM hard disk support is enabled.
129		X86-32	X86-32, aka i386 architecture is enabled.
130		X86-64	X86-64 architecture is enabled.
131				More X86-64 boot options can be found in
132				Documentation/x86/x86_64/boot-options.txt .
133		X86	Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134		XEN	Xen support is enabled
136	In addition, the following text indicates that the option:
138		BUGS=	Relates to possible processor bugs on the said processor.
139		KNL	Is a kernel start-up parameter.
140		BOOT	Is a boot loader parameter.
142	Parameters denoted with BOOT are actually interpreted by the boot
143	loader, and have no meaning to the kernel directly.
144	Do not modify the syntax of boot loader parameters without extreme
145	need or coordination with <Documentation/x86/boot.txt>.
147	There are also arch-specific kernel-parameters not documented here.
148	See for example <Documentation/x86/x86_64/boot-options.txt>.
150	Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151	a trailing = on the name of any parameter states that that parameter will
152	be entered as an environment variable, whereas its absence indicates that
153	it will appear as a kernel argument readable via /proc/cmdline by programs
154	running once the system is up.
156	The number of kernel parameters is not limited, but the length of the
157	complete command line (parameters including spaces etc.) is limited to
158	a fixed number of characters. This limit depends on the architecture
159	and is between 256 and 4096 characters. It is defined in the file
160	./include/asm/setup.h as COMMAND_LINE_SIZE.
162	Finally, the [KMG] suffix is commonly described after a number of kernel
163	parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164	multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165	bytes respectively. Such letter suffixes can also be entirely omitted.
168		acpi=		[HW,ACPI,X86,ARM64]
169				Advanced Configuration and Power Interface
170				Format: { force | off | strict | noirq | rsdt }
171				force -- enable ACPI if default was off
172				off -- disable ACPI if default was on
173				noirq -- do not use ACPI for IRQ routing
174				strict -- Be less tolerant of platforms that are not
175					strictly ACPI specification compliant.
176				rsdt -- prefer RSDT over (default) XSDT
177				copy_dsdt -- copy DSDT to memory
178				For ARM64, ONLY "acpi=off" or "acpi=force" are available
180				See also Documentation/power/runtime_pm.txt, pci=noacpi
182		acpi_apic_instance=	[ACPI, IOAPIC]
183				Format: <int>
184				2: use 2nd APIC table, if available
185				1,0: use 1st APIC table
186				default: 0
188		acpi_backlight=	[HW,ACPI]
189				acpi_backlight=vendor
190				acpi_backlight=video
191				If set to vendor, prefer vendor specific driver
192				(e.g. thinkpad_acpi, sony_acpi, etc.) instead
193				of the ACPI video.ko driver.
195		acpica_no_return_repair [HW, ACPI]
196				Disable AML predefined validation mechanism
197				This mechanism can repair the evaluation result to make
198				the return objects more ACPI specification compliant.
199				This option is useful for developers to identify the
200				root cause of an AML interpreter issue when the issue
201				has something to do with the repair mechanism.
203		acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
204		acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
205				Format: <int>
206				CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
207				debug output.  Bits in debug_layer correspond to a
208				_COMPONENT in an ACPI source file, e.g.,
210				Bits in debug_level correspond to a level in
211				ACPI_DEBUG_PRINT statements, e.g.,
213				The debug_level mask defaults to "info".  See
214				Documentation/acpi/debug.txt for more information about
215				debug layers and levels.
217				Enable processor driver info messages:
218				    acpi.debug_layer=0x20000000
219				Enable PCI/PCI interrupt routing info messages:
220				    acpi.debug_layer=0x400000
221				Enable AML "Debug" output, i.e., stores to the Debug
222				object while interpreting AML:
223				    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
224				Enable all messages related to ACPI hardware:
225				    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
227				Some values produce so much output that the system is
228				unusable.  The "log_buf_len" parameter may be useful
229				if you need to capture more output.
231		acpi_enforce_resources=	[ACPI]
232				{ strict | lax | no }
233				Check for resource conflicts between native drivers
234				and ACPI OperationRegions (SystemIO and SystemMemory
235				only). IO ports and memory declared in ACPI might be
236				used by the ACPI subsystem in arbitrary AML code and
237				can interfere with legacy drivers.
238				strict (default): access to resources claimed by ACPI
239				is denied; legacy drivers trying to access reserved
240				resources will fail to bind to device using them.
241				lax: access to resources claimed by ACPI is allowed;
242				legacy drivers trying to access reserved resources
243				will bind successfully but a warning message is logged.
244				no: ACPI OperationRegions are not marked as reserved,
245				no further checks are performed.
247		acpi_force_table_verification	[HW,ACPI]
248				Enable table checksum verification during early stage.
249				By default, this is disabled due to x86 early mapping
250				size limitation.
252		acpi_irq_balance [HW,ACPI]
253				ACPI will balance active IRQs
254				default in APIC mode
256		acpi_irq_nobalance [HW,ACPI]
257				ACPI will not move active IRQs (default)
258				default in PIC mode
260		acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
261				Format: <irq>,<irq>...
263		acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
264				use by PCI
265				Format: <irq>,<irq>...
267		acpi_no_auto_serialize	[HW,ACPI]
268				Disable auto-serialization of AML methods
269				AML control methods that contain the opcodes to create
270				named objects will be marked as "Serialized" by the
271				auto-serialization feature.
272				This feature is enabled by default.
273				This option allows to turn off the feature.
275		acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
276				   kernels.
278		acpi_no_static_ssdt	[HW,ACPI]
279				Disable installation of static SSDTs at early boot time
280				By default, SSDTs contained in the RSDT/XSDT will be
281				installed automatically and they will appear under
282				/sys/firmware/acpi/tables.
283				This option turns off this feature.
284				Note that specifying this option does not affect
285				dynamic table installation which will install SSDT
286				tables to /sys/firmware/acpi/tables/dynamic.
288		acpi_rsdp=	[ACPI,EFI,KEXEC]
289				Pass the RSDP address to the kernel, mostly used
290				on machines running EFI runtime service to boot the
291				second kernel for kdump.
293		acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
294				Format: To spoof as Windows 98: ="Microsoft Windows"
296		acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
297				of 2 which is mandated by ACPI 6) as the supported ACPI
298				specification revision (when using this switch, it may
299				be necessary to carry out a cold reboot _twice_ in a
300				row to make it take effect on the platform firmware).
302		acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
303				acpi_osi="string1"	# add string1
304				acpi_osi="!string2"	# remove string2
305				acpi_osi=!*		# remove all strings
306				acpi_osi=!		# disable all built-in OS vendor
307							  strings
308				acpi_osi=		# disable all strings
310				'acpi_osi=!' can be used in combination with single or
311				multiple 'acpi_osi="string1"' to support specific OS
312				vendor string(s).  Note that such command can only
313				affect the default state of the OS vendor strings, thus
314				it cannot affect the default state of the feature group
315				strings and the current state of the OS vendor strings,
316				specifying it multiple times through kernel command line
317				is meaningless.  This command is useful when one do not
318				care about the state of the feature group strings which
319				should be controlled by the OSPM.
320				Examples:
321				  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
322				     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
323				     can make '_OSI("Windows 2000")' TRUE.
325				'acpi_osi=' cannot be used in combination with other
326				'acpi_osi=' command lines, the _OSI method will not
327				exist in the ACPI namespace.  NOTE that such command can
328				only affect the _OSI support state, thus specifying it
329				multiple times through kernel command line is also
330				meaningless.
331				Examples:
332				  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
333				     FALSE.
335				'acpi_osi=!*' can be used in combination with single or
336				multiple 'acpi_osi="string1"' to support specific
337				string(s).  Note that such command can affect the
338				current state of both the OS vendor strings and the
339				feature group strings, thus specifying it multiple times
340				through kernel command line is meaningful.  But it may
341				still not able to affect the final state of a string if
342				there are quirks related to this string.  This command
343				is useful when one want to control the state of the
344				feature group strings to debug BIOS issues related to
345				the OSPM features.
346				Examples:
347				  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
348				     '_OSI("Module Device")' FALSE.
349				  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
350				     '_OSI("Module Device")' TRUE.
351				  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
352				     equivalent to
353				     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
354				     and
355				     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
356				     they all will make '_OSI("Windows 2000")' TRUE.
358		acpi_pm_good	[X86]
359				Override the pmtimer bug detection: force the kernel
360				to assume that this machine's pmtimer latches its value
361				and always returns good values.
363		acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
364				Format: { level | edge | high | low }
366		acpi_skip_timer_override [HW,ACPI]
367				Recognize and ignore IRQ0/pin2 Interrupt Override.
368				For broken nForce2 BIOS resulting in XT-PIC timer.
370		acpi_sleep=	[HW,ACPI] Sleep options
371				Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
372					  old_ordering, nonvs, sci_force_enable }
373				See Documentation/power/video.txt for information on
374				s3_bios and s3_mode.
375				s3_beep is for debugging; it makes the PC's speaker beep
376				as soon as the kernel's real-mode entry point is called.
377				s4_nohwsig prevents ACPI hardware signature from being
378				used during resume from hibernation.
379				old_ordering causes the ACPI 1.0 ordering of the _PTS
380				control method, with respect to putting devices into
381				low power states, to be enforced (the ACPI 2.0 ordering
382				of _PTS is used by default).
383				nonvs prevents the kernel from saving/restoring the
384				ACPI NVS memory during suspend/hibernation and resume.
385				sci_force_enable causes the kernel to set SCI_EN directly
386				on resume from S1/S3 (which is against the ACPI spec,
387				but some broken systems don't work without it).
389		acpi_use_timer_override [HW,ACPI]
390				Use timer override. For some broken Nvidia NF5 boards
391				that require a timer override, but don't have HPET
393		add_efi_memmap	[EFI; X86] Include EFI memory map in
394				kernel's map of available physical RAM.
396		agp=		[AGP]
397				{ off | try_unsupported }
398				off: disable AGP support
399				try_unsupported: try to drive unsupported chipsets
400					(may crash computer or cause data corruption)
402		ALSA		[HW,ALSA]
403				See Documentation/sound/alsa/alsa-parameters.txt
405		alignment=	[KNL,ARM]
406				Allow the default userspace alignment fault handler
407				behaviour to be specified.  Bit 0 enables warnings,
408				bit 1 enables fixups, and bit 2 sends a segfault.
410		align_va_addr=	[X86-64]
411				Align virtual addresses by clearing slice [14:12] when
412				allocating a VMA at process creation time. This option
413				gives you up to 3% performance improvement on AMD F15h
414				machines (where it is enabled by default) for a
415				CPU-intensive style benchmark, and it can vary highly in
416				a microbenchmark depending on workload and compiler.
418				32: only for 32-bit processes
419				64: only for 64-bit processes
420				on: enable for both 32- and 64-bit processes
421				off: disable for both 32- and 64-bit processes
423		alloc_snapshot	[FTRACE]
424				Allocate the ftrace snapshot buffer on boot up when the
425				main buffer is allocated. This is handy if debugging
426				and you need to use tracing_snapshot() on boot up, and
427				do not want to use tracing_snapshot_alloc() as it needs
428				to be done where GFP_KERNEL allocations are allowed.
430		amd_iommu=	[HW,X86-64]
431				Pass parameters to the AMD IOMMU driver in the system.
432				Possible values are:
433				fullflush - enable flushing of IO/TLB entries when
434					    they are unmapped. Otherwise they are
435					    flushed before they will be reused, which
436					    is a lot of faster
437				off	  - do not initialize any AMD IOMMU found in
438					    the system
439				force_isolation - Force device isolation for all
440						  devices. The IOMMU driver is not
441						  allowed anymore to lift isolation
442						  requirements as needed. This option
443						  does not override iommu=pt
445		amd_iommu_dump=	[HW,X86-64]
446				Enable AMD IOMMU driver option to dump the ACPI table
447				for AMD IOMMU. With this option enabled, AMD IOMMU
448				driver will print ACPI tables for AMD IOMMU during
449				IOMMU initialization.
451		amijoy.map=	[HW,JOY] Amiga joystick support
452				Map of devices attached to JOY0DAT and JOY1DAT
453				Format: <a>,<b>
454				See also Documentation/input/joystick.txt
456		analog.map=	[HW,JOY] Analog joystick and gamepad support
457				Specifies type or capabilities of an analog joystick
458				connected to one of 16 gameports
459				Format: <type1>,<type2>,..<type16>
461		apc=		[HW,SPARC]
462				Power management functions (SPARCstation-4/5 + deriv.)
463				Format: noidle
464				Disable APC CPU standby support. SPARCstation-Fox does
465				not play well with APC CPU idle - disable it if you have
466				APC and your system crashes randomly.
468		apic=		[APIC,X86-32] Advanced Programmable Interrupt Controller
469				Change the output verbosity whilst booting
470				Format: { quiet (default) | verbose | debug }
471				Change the amount of debugging information output
472				when initialising the APIC and IO-APIC components.
474		autoconf=	[IPV6]
475				See Documentation/networking/ipv6.txt.
477		show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
478				Limit apic dumping. The parameter defines the maximal
479				number of local apics being dumped. Also it is possible
480				to set it to "all" by meaning -- no limit here.
481				Format: { 1 (default) | 2 | ... | all }.
482				The parameter valid if only apic=debug or
483				apic=verbose is specified.
484				Example: apic=debug show_lapic=all
486		apm=		[APM] Advanced Power Management
487				See header of arch/x86/kernel/apm_32.c.
489		arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
490				Format: <io>,<irq>,<nodeID>
492		ataflop=	[HW,M68k]
494		atarimouse=	[HW,MOUSE] Atari Mouse
496		atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
497				EzKey and similar keyboards
499		atkbd.reset=	[HW] Reset keyboard during initialization
501		atkbd.set=	[HW] Select keyboard code set
502				Format: <int> (2 = AT (default), 3 = PS/2)
504		atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
505				keyboards
507		atkbd.softraw=	[HW] Choose between synthetic and real raw mode
508				Format: <bool> (0 = real, 1 = synthetic (default))
510		atkbd.softrepeat= [HW]
511				Use software keyboard repeat
513		audit=		[KNL] Enable the audit sub-system
514				Format: { "0" | "1" } (0 = disabled, 1 = enabled)
515				0 - kernel audit is disabled and can not be enabled
516				    until the next reboot
517				unset - kernel audit is initialized but disabled and
518				    will be fully enabled by the userspace auditd.
519				1 - kernel audit is initialized and partially enabled,
520				    storing at most audit_backlog_limit messages in
521				    RAM until it is fully enabled by the userspace
522				    auditd.
523				Default: unset
525		audit_backlog_limit= [KNL] Set the audit queue size limit.
526				Format: <int> (must be >=0)
527				Default: 64
529		baycom_epp=	[HW,AX25]
530				Format: <io>,<mode>
532		baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
533				Format: <io>,<mode>
534				See header of drivers/net/hamradio/baycom_par.c.
536		baycom_ser_fdx=	[HW,AX25]
537				BayCom Serial Port AX.25 Modem (Full Duplex Mode)
538				Format: <io>,<irq>,<mode>[,<baud>]
539				See header of drivers/net/hamradio/baycom_ser_fdx.c.
541		baycom_ser_hdx=	[HW,AX25]
542				BayCom Serial Port AX.25 Modem (Half Duplex Mode)
543				Format: <io>,<irq>,<mode>
544				See header of drivers/net/hamradio/baycom_ser_hdx.c.
546		blkdevparts=	Manual partition parsing of block device(s) for
547				embedded devices based on command line input.
548				See Documentation/block/cmdline-partition.txt
550		boot_delay=	Milliseconds to delay each printk during boot.
551				Values larger than 10 seconds (10000) are changed to
552				no delay (0).
553				Format: integer
555		bootmem_debug	[KNL] Enable bootmem allocator debug messages.
557		bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
558		bttv.radio=	Most important insmod options are available as
559				kernel args too.
560		bttv.pll=	See Documentation/video4linux/bttv/Insmod-options
561		bttv.tuner=
563		bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
564				firmware feature for flushing multiple hpte entries
565				at a time.
567		c101=		[NET] Moxa C101 synchronous serial card
569		cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
570				Sometimes CPU hardware bugs make them report the cache
571				size incorrectly. The kernel will attempt work arounds
572				to fix known problems, but for some CPUs it is not
573				possible to determine what the correct size should be.
574				This option provides an override for these situations.
576		ca_keys=	[KEYS] This parameter identifies a specific key(s) on
577				the system trusted keyring to be used for certificate
578				trust validation.
579				format: { id:<keyid> | builtin }
581		cca=		[MIPS] Override the kernel pages' cache coherency
582				algorithm.  Accepted values range from 0 to 7
583				inclusive. See arch/mips/include/asm/pgtable-bits.h
584				for platform specific values (SB1, Loongson3 and
585				others).
587		ccw_timeout_log [S390]
588				See Documentation/s390/CommonIO for details.
590		cgroup_disable= [KNL] Disable a particular controller
591				Format: {name of the controller(s) to disable}
592				The effects of cgroup_disable=foo are:
593				- foo isn't auto-mounted if you mount all cgroups in
594				  a single hierarchy
595				- foo isn't visible as an individually mountable
596				  subsystem
597				{Currently only "memory" controller deal with this and
598				cut the overhead, others just disable the usage. So
599				only cgroup_disable=memory is actually worthy}
601		checkreqprot	[SELINUX] Set initial checkreqprot flag value.
602				Format: { "0" | "1" }
603				See security/selinux/Kconfig help text.
604				0 -- check protection applied by kernel (includes
605					any implied execute protection).
606				1 -- check protection requested by application.
607				Default value is set via a kernel config option.
608				Value can be changed at runtime via
609					/selinux/checkreqprot.
611		cio_ignore=	[S390]
612				See Documentation/s390/CommonIO for details.
613		clk_ignore_unused
614				[CLK]
615				Prevents the clock framework from automatically gating
616				clocks that have not been explicitly enabled by a Linux
617				device driver but are enabled in hardware at reset or
618				by the bootloader/firmware. Note that this does not
619				force such clocks to be always-on nor does it reserve
620				those clocks in any way. This parameter is useful for
621				debug and development, but should not be needed on a
622				platform with proper driver support.  For more
623				information, see Documentation/clk.txt.
625		clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
626				[Deprecated]
627				Forces specified clocksource (if available) to be used
628				when calculating gettimeofday(). If specified
629				clocksource is not available, it defaults to PIT.
630				Format: { pit | tsc | cyclone | pmtmr }
632		clocksource=	Override the default clocksource
633				Format: <string>
634				Override the default clocksource and use the clocksource
635				with the name specified.
636				Some clocksource names to choose from, depending on
637				the platform:
638				[all] jiffies (this is the base, fallback clocksource)
639				[ACPI] acpi_pm
640				[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
641					pxa_timer,timer3,32k_counter,timer0_1
642				[AVR32] avr32
643				[X86-32] pit,hpet,tsc;
644					scx200_hrt on Geode; cyclone on IBM x440
645				[MIPS] MIPS
646				[PARISC] cr16
647				[S390] tod
648				[SH] SuperH
649				[SPARC64] tick
650				[X86-64] hpet,tsc
652		clearcpuid=BITNUM [X86]
653				Disable CPUID feature X for the kernel. See
654				arch/x86/include/asm/cpufeature.h for the valid bit
655				numbers. Note the Linux specific bits are not necessarily
656				stable over kernel options, but the vendor specific
657				ones should be.
658				Also note that user programs calling CPUID directly
659				or using the feature without checking anything
660				will still see it. This just prevents it from
661				being used by the kernel or shown in /proc/cpuinfo.
662				Also note the kernel might malfunction if you disable
663				some critical bits.
665		cma=nn[MG]@[start[MG][-end[MG]]]
666				[ARM,X86,KNL]
667				Sets the size of kernel global memory area for
668				contiguous memory allocations and optionally the
669				placement constraint by the physical address range of
670				memory allocations. A value of 0 disables CMA
671				altogether. For more information, see
672				include/linux/dma-contiguous.h
674		cmo_free_hint=	[PPC] Format: { yes | no }
675				Specify whether pages are marked as being inactive
676				when they are freed.  This is used in CMO environments
677				to determine OS memory pressure for page stealing by
678				a hypervisor.
679				Default: yes
681		coherent_pool=nn[KMG]	[ARM,KNL]
682				Sets the size of memory pool for coherent, atomic dma
683				allocations, by default set to 256K.
685		code_bytes	[X86] How many bytes of object code to print
686				in an oops report.
687				Range: 0 - 8192
688				Default: 64
690		com20020=	[HW,NET] ARCnet - COM20020 chipset
691				Format:
692				<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
694		com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
695				Format: <io>[,<irq>]
697		com90xx=	[HW,NET]
698				ARCnet - COM90xx chipset (memory-mapped buffers)
699				Format: <io>[,<irq>[,<memstart>]]
701		condev=		[HW,S390] console device
702		conmode=
704		console=	[KNL] Output console device and options.
706			tty<n>	Use the virtual console device <n>.
708			ttyS<n>[,options]
709			ttyUSB0[,options]
710				Use the specified serial port.  The options are of
711				the form "bbbbpnf", where "bbbb" is the baud rate,
712				"p" is parity ("n", "o", or "e"), "n" is number of
713				bits, and "f" is flow control ("r" for RTS or
714				omit it).  Default is "9600n8".
716				See Documentation/serial-console.txt for more
717				information.  See
718				Documentation/networking/netconsole.txt for an
719				alternative.
721			uart[8250],io,<addr>[,options]
722			uart[8250],mmio,<addr>[,options]
723			uart[8250],mmio32,<addr>[,options]
724			uart[8250],0x<addr>[,options]
725				Start an early, polled-mode console on the 8250/16550
726				UART at the specified I/O port or MMIO address,
727				switching to the matching ttyS device later.
728				MMIO inter-register address stride is either 8-bit
729				(mmio) or 32-bit (mmio32).
730				If none of [io|mmio|mmio32], <addr> is assumed to be
731				equivalent to 'mmio'. 'options' are specified in the
732				same format described for ttyS above; if unspecified,
733				the h/w is not re-initialized.
735			hvc<n>	Use the hypervisor console device <n>. This is for
736				both Xen and PowerPC hypervisors.
738	                If the device connected to the port is not a TTY but a braille
739	                device, prepend "brl," before the device type, for instance
740				console=brl,ttyS0
741			For now, only VisioBraille is supported.
743		consoleblank=	[KNL] The console blank (screen saver) timeout in
744				seconds. Defaults to 10*60 = 10mins. A value of 0
745				disables the blank timer.
747		coredump_filter=
748				[KNL] Change the default value for
749				/proc/<pid>/coredump_filter.
750				See also Documentation/filesystems/proc.txt.
752		cpuidle.off=1	[CPU_IDLE]
753				disable the cpuidle sub-system
755		cpu_init_udelay=N
756				[X86] Delay for N microsec between assert and de-assert
757				of APIC INIT to start processors.  This delay occurs
758				on every CPU online, such as boot, and resume from suspend.
759				Default: 10000
761		cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
762				Format:
763				<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
765		crashkernel=size[KMG][@offset[KMG]]
766				[KNL] Using kexec, Linux can switch to a 'crash kernel'
767				upon panic. This parameter reserves the physical
768				memory region [offset, offset + size] for that kernel
769				image. If '@offset' is omitted, then a suitable offset
770				is selected automatically. Check
771				Documentation/kdump/kdump.txt for further details.
773		crashkernel=range1:size1[,range2:size2,...][@offset]
774				[KNL] Same as above, but depends on the memory
775				in the running system. The syntax of range is
776				start-[end] where start and end are both
777				a memory unit (amount[KMG]). See also
778				Documentation/kdump/kdump.txt for an example.
780		crashkernel=size[KMG],high
781				[KNL, x86_64] range could be above 4G. Allow kernel
782				to allocate physical memory region from top, so could
783				be above 4G if system have more than 4G ram installed.
784				Otherwise memory region will be allocated below 4G, if
785				available.
786				It will be ignored if crashkernel=X is specified.
787		crashkernel=size[KMG],low
788				[KNL, x86_64] range under 4G. When crashkernel=X,high
789				is passed, kernel could allocate physical memory region
790				above 4G, that cause second kernel crash on system
791				that require some amount of low memory, e.g. swiotlb
792				requires at least 64M+32K low memory.  Kernel would
793				try to allocate 72M below 4G automatically.
794				This one let user to specify own low range under 4G
795				for second kernel instead.
796				0: to disable low allocation.
797				It will be ignored when crashkernel=X,high is not used
798				or memory reserved is below 4G.
800		cs89x0_dma=	[HW,NET]
801				Format: <dma>
803		cs89x0_media=	[HW,NET]
804				Format: { rj45 | aui | bnc }
806		dasd=		[HW,NET]
807				See header of drivers/s390/block/dasd_devmap.c.
809		db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
810				(one device per port)
811				Format: <port#>,<type>
812				See also Documentation/input/joystick-parport.txt
814		ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
815				time. See Documentation/dynamic-debug-howto.txt for
816				details.  Deprecated, see dyndbg.
818		debug		[KNL] Enable kernel debugging (events log level).
820		debug_locks_verbose=
821				[KNL] verbose self-tests
822				Format=<0|1>
823				Print debugging info while doing the locking API
824				self-tests.
825				We default to 0 (no extra messages), setting it to
826				1 will print _a lot_ more information - normally
827				only useful to kernel developers.
829		debug_objects	[KNL] Enable object debugging
831		no_debug_objects
832				[KNL] Disable object debugging
834		debug_guardpage_minorder=
835				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
836				parameter allows control of the order of pages that will
837				be intentionally kept free (and hence protected) by the
838				buddy allocator. Bigger value increase the probability
839				of catching random memory corruption, but reduce the
840				amount of memory for normal system use. The maximum
841				possible value is MAX_ORDER/2.  Setting this parameter
842				to 1 or 2 should be enough to identify most random
843				memory corruption problems caused by bugs in kernel or
844				driver code when a CPU writes to (or reads from) a
845				random memory location. Note that there exists a class
846				of memory corruptions problems caused by buggy H/W or
847				F/W or by drivers badly programing DMA (basically when
848				memory is written at bus level and the CPU MMU is
849				bypassed) which are not detectable by
850				CONFIG_DEBUG_PAGEALLOC, hence this option will not help
851				tracking down these problems.
853		debug_pagealloc=
854				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
855				parameter enables the feature at boot time. In
856				default, it is disabled. We can avoid allocating huge
857				chunk of memory for debug pagealloc if we don't enable
858				it at boot time and the system will work mostly same
859				with the kernel built without CONFIG_DEBUG_PAGEALLOC.
860				on: enable the feature
862		debugpat	[X86] Enable PAT debugging
864		decnet.addr=	[HW,NET]
865				Format: <area>[,<node>]
866				See also Documentation/networking/decnet.txt.
868		default_hugepagesz=
869				[same as hugepagesz=] The size of the default
870				HugeTLB page size. This is the size represented by
871				the legacy /proc/ hugepages APIs, used for SHM, and
872				default size when mounting hugetlbfs filesystems.
873				Defaults to the default architecture's huge page size
874				if not specified.
876		dhash_entries=	[KNL]
877				Set number of hash buckets for dentry cache.
879		disable=	[IPV6]
880				See Documentation/networking/ipv6.txt.
882		disable_cpu_apicid= [X86,APIC,SMP]
883				Format: <int>
884				The number of initial APIC ID for the
885				corresponding CPU to be disabled at boot,
886				mostly used for the kdump 2nd kernel to
887				disable BSP to wake up multiple CPUs without
888				causing system reset or hang due to sending
889				INIT from AP to BSP.
891		disable_ddw     [PPC/PSERIES]
892				Disable Dynamic DMA Window support. Use this if
893				to workaround buggy firmware.
895		disable_ipv6=	[IPV6]
896				See Documentation/networking/ipv6.txt.
898		disable_mtrr_cleanup [X86]
899				The kernel tries to adjust MTRR layout from continuous
900				to discrete, to make X server driver able to add WB
901				entry later. This parameter disables that.
903		disable_mtrr_trim [X86, Intel and AMD only]
904				By default the kernel will trim any uncacheable
905				memory out of your available memory pool based on
906				MTRR settings.  This parameter disables that behavior,
907				possibly causing your machine to run very slowly.
909		disable_timer_pin_1 [X86]
910				Disable PIN 1 of APIC timer
911				Can be useful to work around chipset bugs.
913		dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
914				this option disables the debugging code at boot.
916		dma_debug_entries=<number>
917				This option allows to tune the number of preallocated
918				entries for DMA-API debugging code. One entry is
919				required per DMA-API allocation. Use this if the
920				DMA-API debugging code disables itself because the
921				architectural default is too low.
923		dma_debug_driver=<driver_name>
924				With this option the DMA-API debugging driver
925				filter feature can be enabled at boot time. Just
926				pass the driver to filter for as the parameter.
927				The filter can be disabled or changed to another
928				driver later using sysfs.
930		drm_kms_helper.edid_firmware=[<connector>:]<file>
931				Broken monitors, graphic adapters and KVMs may
932				send no or incorrect EDID data sets. This parameter
933				allows to specify an EDID data set in the
934				/lib/firmware directory that is used instead.
935				Generic built-in EDID data sets are used, if one of
936				edid/1024x768.bin, edid/1280x1024.bin,
937				edid/1680x1050.bin, or edid/1920x1080.bin is given
938				and no file with the same name exists. Details and
939				instructions how to build your own EDID data are
940				available in Documentation/EDID/HOWTO.txt. An EDID
941				data set will only be used for a particular connector,
942				if its name and a colon are prepended to the EDID
943				name.
945		dscc4.setup=	[NET]
947		dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
948		module.dyndbg[="val"]
949				Enable debug messages at boot time.  See
950				Documentation/dynamic-debug-howto.txt for details.
952		nompx		[X86] Disables Intel Memory Protection Extensions.
953				See Documentation/x86/intel_mpx.txt for more
954				information about the feature.
956		eagerfpu=	[X86]
957				on	enable eager fpu restore
958				off	disable eager fpu restore
959				auto	selects the default scheme, which automatically
960					enables eagerfpu restore for xsaveopt.
962		module.async_probe [KNL]
963				Enable asynchronous probe on this module.
965		early_ioremap_debug [KNL]
966				Enable debug messages in early_ioremap support. This
967				is useful for tracking down temporary early mappings
968				which are not unmapped.
970		earlycon=	[KNL] Output early console device and options.
972			cdns,<addr>
973				Start an early, polled-mode console on a cadence serial
974				port at the specified address. The cadence serial port
975				must already be setup and configured. Options are not
976				yet supported.
978			uart[8250],io,<addr>[,options]
979			uart[8250],mmio,<addr>[,options]
980			uart[8250],mmio32,<addr>[,options]
981			uart[8250],mmio32be,<addr>[,options]
982			uart[8250],0x<addr>[,options]
983				Start an early, polled-mode console on the 8250/16550
984				UART at the specified I/O port or MMIO address.
985				MMIO inter-register address stride is either 8-bit
986				(mmio) or 32-bit (mmio32 or mmio32be).
987				If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
988				to be equivalent to 'mmio'. 'options' are specified
989				in the same format described for "console=ttyS<n>"; if
990				unspecified, the h/w is not initialized.
992			pl011,<addr>
993				Start an early, polled-mode console on a pl011 serial
994				port at the specified address. The pl011 serial port
995				must already be setup and configured. Options are not
996				yet supported.
998			msm_serial,<addr>
999				Start an early, polled-mode console on an msm serial
1000				port at the specified address. The serial port
1001				must already be setup and configured. Options are not
1002				yet supported.
1004			msm_serial_dm,<addr>
1005				Start an early, polled-mode console on an msm serial
1006				dm port at the specified address. The serial port
1007				must already be setup and configured. Options are not
1008				yet supported.
1010			smh	Use ARM semihosting calls for early console.
1012			s3c2410,<addr>
1013			s3c2412,<addr>
1014			s3c2440,<addr>
1015			s3c6400,<addr>
1016			s5pv210,<addr>
1017			exynos4210,<addr>
1018				Use early console provided by serial driver available
1019				on Samsung SoCs, requires selecting proper type and
1020				a correct base address of the selected UART port. The
1021				serial port must already be setup and configured.
1022				Options are not yet supported.
1024		earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
1025				earlyprintk=vga
1026				earlyprintk=efi
1027				earlyprintk=xen
1028				earlyprintk=serial[,ttySn[,baudrate]]
1029				earlyprintk=serial[,0x...[,baudrate]]
1030				earlyprintk=ttySn[,baudrate]
1031				earlyprintk=dbgp[debugController#]
1032				earlyprintk=pciserial,bus:device.function[,baudrate]
1034				earlyprintk is useful when the kernel crashes before
1035				the normal console is initialized. It is not enabled by
1036				default because it has some cosmetic problems.
1038				Append ",keep" to not disable it when the real console
1039				takes over.
1041				Only one of vga, efi, serial, or usb debug port can
1042				be used at a time.
1044				Currently only ttyS0 and ttyS1 may be specified by
1045				name.  Other I/O ports may be explicitly specified
1046				on some architectures (x86 and arm at least) by
1047				replacing ttySn with an I/O port address, like this:
1048					earlyprintk=serial,0x1008,115200
1049				You can find the port for a given device in
1050				/proc/tty/driver/serial:
1051					2: uart:ST16650V2 port:00001008 irq:18 ...
1053				Interaction with the standard serial driver is not
1054				very good.
1056				The VGA and EFI output is eventually overwritten by
1057				the real console.
1059				The xen output can only be used by Xen PV guests.
1061		edac_report=	[HW,EDAC] Control how to report EDAC event
1062				Format: {"on" | "off" | "force"}
1063				on: enable EDAC to report H/W event. May be overridden
1064				by other higher priority error reporting module.
1065				off: disable H/W event reporting through EDAC.
1066				force: enforce the use of EDAC to report H/W event.
1067				default: on.
1069		ekgdboc=	[X86,KGDB] Allow early kernel console debugging
1070				ekgdboc=kbd
1072				This is designed to be used in conjunction with
1073				the boot argument: earlyprintk=vga
1075		edd=		[EDD]
1076				Format: {"off" | "on" | "skip[mbr]"}
1078		efi=		[EFI]
1079				Format: { "old_map", "nochunk", "noruntime", "debug" }
1080				old_map [X86-64]: switch to the old ioremap-based EFI
1081				runtime services mapping. 32-bit still uses this one by
1082				default.
1083				nochunk: disable reading files in "chunks" in the EFI
1084				boot stub, as chunking can cause problems with some
1085				firmware implementations.
1086				noruntime : disable EFI runtime services support
1087				debug: enable misc debug output
1089		efi_no_storage_paranoia [EFI; X86]
1090				Using this parameter you can use more than 50% of
1091				your efi variable storage. Use this parameter only if
1092				you are really sure that your UEFI does sane gc and
1093				fulfills the spec otherwise your board may brick.
1095		eisa_irq_edge=	[PARISC,HW]
1096				See header of drivers/parisc/eisa.c.
1098		elanfreq=	[X86-32]
1099				See comment before function elanfreq_setup() in
1100				arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1102		elevator=	[IOSCHED]
1103				Format: {"cfq" | "deadline" | "noop"}
1104				See Documentation/block/cfq-iosched.txt and
1105				Documentation/block/deadline-iosched.txt for details.
1107		elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1108				Specifies physical address of start of kernel core
1109				image elf header and optionally the size. Generally
1110				kexec loader will pass this option to capture kernel.
1111				See Documentation/kdump/kdump.txt for details.
1113		enable_mtrr_cleanup [X86]
1114				The kernel tries to adjust MTRR layout from continuous
1115				to discrete, to make X server driver able to add WB
1116				entry later. This parameter enables that.
1118		enable_timer_pin_1 [X86]
1119				Enable PIN 1 of APIC timer
1120				Can be useful to work around chipset bugs
1121				(in particular on some ATI chipsets).
1122				The kernel tries to set a reasonable default.
1124		enforcing	[SELINUX] Set initial enforcing status.
1125				Format: {"0" | "1"}
1126				See security/selinux/Kconfig help text.
1127				0 -- permissive (log only, no denials).
1128				1 -- enforcing (deny and log).
1129				Default value is 0.
1130				Value can be changed at runtime via /selinux/enforce.
1132		erst_disable	[ACPI]
1133				Disable Error Record Serialization Table (ERST)
1134				support.
1136		ether=		[HW,NET] Ethernet cards parameters
1137				This option is obsoleted by the "netdev=" option, which
1138				has equivalent usage. See its documentation for details.
1140		evm=		[EVM]
1141				Format: { "fix" }
1142				Permit 'security.evm' to be updated regardless of
1143				current integrity status.
1145		failslab=
1146		fail_page_alloc=
1147		fail_make_request=[KNL]
1148				General fault injection mechanism.
1149				Format: <interval>,<probability>,<space>,<times>
1150				See also Documentation/fault-injection/.
1152		floppy=		[HW]
1153				See Documentation/blockdev/floppy.txt.
1155		force_pal_cache_flush
1156				[IA-64] Avoid check_sal_cache_flush which may hang on
1157				buggy SAL_CACHE_FLUSH implementations. Using this
1158				parameter will force ia64_sal_cache_flush to call
1159				ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1161		forcepae [X86-32]
1162				Forcefully enable Physical Address Extension (PAE).
1163				Many Pentium M systems disable PAE but may have a
1164				functionally usable PAE implementation.
1165				Warning: use of this parameter will taint the kernel
1166				and may cause unknown problems.
1168		ftrace=[tracer]
1169				[FTRACE] will set and start the specified tracer
1170				as early as possible in order to facilitate early
1171				boot debugging.
1173		ftrace_dump_on_oops[=orig_cpu]
1174				[FTRACE] will dump the trace buffers on oops.
1175				If no parameter is passed, ftrace will dump
1176				buffers of all CPUs, but if you pass orig_cpu, it will
1177				dump only the buffer of the CPU that triggered the
1178				oops.
1180		ftrace_filter=[function-list]
1181				[FTRACE] Limit the functions traced by the function
1182				tracer at boot up. function-list is a comma separated
1183				list of functions. This list can be changed at run
1184				time by the set_ftrace_filter file in the debugfs
1185				tracing directory.
1187		ftrace_notrace=[function-list]
1188				[FTRACE] Do not trace the functions specified in
1189				function-list. This list can be changed at run time
1190				by the set_ftrace_notrace file in the debugfs
1191				tracing directory.
1193		ftrace_graph_filter=[function-list]
1194				[FTRACE] Limit the top level callers functions traced
1195				by the function graph tracer at boot up.
1196				function-list is a comma separated list of functions
1197				that can be changed at run time by the
1198				set_graph_function file in the debugfs tracing directory.
1200		ftrace_graph_notrace=[function-list]
1201				[FTRACE] Do not trace from the functions specified in
1202				function-list.  This list is a comma separated list of
1203				functions that can be changed at run time by the
1204				set_graph_notrace file in the debugfs tracing directory.
1206		gamecon.map[2|3]=
1207				[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1208				support via parallel port (up to 5 devices per port)
1209				Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1210				See also Documentation/input/joystick-parport.txt
1212		gamma=		[HW,DRM]
1214		gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
1215				Format: off | on
1216				default: on
1218		gcov_persist=	[GCOV] When non-zero (default), profiling data for
1219				kernel modules is saved and remains accessible via
1220				debugfs, even when the module is unloaded/reloaded.
1221				When zero, profiling data is discarded and associated
1222				debugfs files are removed at module unload time.
1224		gpt		[EFI] Forces disk with valid GPT signature but
1225				invalid Protective MBR to be treated as GPT. If the
1226				primary GPT is corrupted, it enables the backup/alternate
1227				GPT to be used instead.
1229		grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1230				the "Enable 0" bit of the configuration register.
1231				Format: 0 | 1
1232				Default: 0
1233		grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1234				the "Enable 0" bit of the configuration register.
1235				Format: 0 | 1
1236				Default: 0
1237		grcan.select=	[HW] Select which physical interface to use.
1238				Format: 0 | 1
1239				Default: 0
1240		grcan.txsize=	[HW] Sets the size of the tx buffer.
1241				Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1242				Default: 1024
1243		grcan.rxsize=	[HW] Sets the size of the rx buffer.
1244				Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1245				Default: 1024
1247		hashdist=	[KNL,NUMA] Large hashes allocated during boot
1248				are distributed across NUMA nodes.  Defaults on
1249				for 64-bit NUMA, off otherwise.
1250				Format: 0 | 1 (for off | on)
1252		hcl=		[IA-64] SGI's Hardware Graph compatibility layer
1254		hd=		[EIDE] (E)IDE hard drive subsystem geometry
1255				Format: <cyl>,<head>,<sect>
1257		hest_disable	[ACPI]
1258				Disable Hardware Error Source Table (HEST) support;
1259				corresponding firmware-first mode error processing
1260				logic will be disabled.
1262		highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
1263				size of <nn>. This works even on boxes that have no
1264				highmem otherwise. This also works to reduce highmem
1265				size on bigger boxes.
1267		highres=	[KNL] Enable/disable high resolution timer mode.
1268				Valid parameters: "on", "off"
1269				Default: "on"
1271		hisax=		[HW,ISDN]
1272				See Documentation/isdn/README.HiSax.
1274		hlt		[BUGS=ARM,SH]
1276		hpet=		[X86-32,HPET] option to control HPET usage
1277				Format: { enable (default) | disable | force |
1278					verbose }
1279				disable: disable HPET and use PIT instead
1280				force: allow force enabled of undocumented chips (ICH4,
1281					VIA, nVidia)
1282				verbose: show contents of HPET registers during setup
1284		hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1285				registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1287		hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1288		hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1289				On x86-64 and powerpc, this option can be specified
1290				multiple times interleaved with hugepages= to reserve
1291				huge pages of different sizes. Valid pages sizes on
1292				x86-64 are 2M (when the CPU supports "pse") and 1G
1293				(when the CPU supports the "pdpe1gb" cpuinfo flag).
1295		hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
1296				       terminal devices. Valid values: 0..8
1297		hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
1298				       If specified, z/VM IUCV HVC accepts connections
1299				       from listed z/VM user IDs only.
1301		hwthread_map=	[METAG] Comma-separated list of Linux cpu id to
1302				        hardware thread id mappings.
1303					Format: <cpu>:<hwthread>
1305		keep_bootcon	[KNL]
1306				Do not unregister boot console at start. This is only
1307				useful for debugging when something happens in the window
1308				between unregistering the boot console and initializing
1309				the real console.
1311		i2c_bus=	[HW] Override the default board specific I2C bus speed
1312				     or register an additional I2C bus that is not
1313				     registered from board initialization code.
1314				     Format:
1315				     <bus_id>,<clkrate>
1317		i8042.debug	[HW] Toggle i8042 debug mode
1318		i8042.direct	[HW] Put keyboard port into non-translated mode
1319		i8042.dumbkbd	[HW] Pretend that controller can only read data from
1320				     keyboard and cannot control its state
1321				     (Don't attempt to blink the leds)
1322		i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1323		i8042.nokbd	[HW] Don't check/create keyboard port
1324		i8042.noloop	[HW] Disable the AUX Loopback command while probing
1325				     for the AUX port
1326		i8042.nomux	[HW] Don't check presence of an active multiplexing
1327				     controller
1328		i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1329				     controllers
1330		i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1331		i8042.reset	[HW] Reset the controller during init and cleanup
1332		i8042.unlock	[HW] Unlock (ignore) the keylock
1333		i8042.kbdreset  [HW] Reset device connected to KBD port
1335		i810=		[HW,DRM]
1337		i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
1338				indicates that the driver is running on unsupported
1339				hardware.
1340		i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
1341				does not match list of supported models.
1342		i8k.power_status
1343				[HW] Report power status in /proc/i8k
1344				(disabled by default)
1345		i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
1346				capability is set.
1348		i915.invert_brightness=
1349				[DRM] Invert the sense of the variable that is used to
1350				set the brightness of the panel backlight. Normally a
1351				brightness value of 0 indicates backlight switched off,
1352				and the maximum of the brightness value sets the backlight
1353				to maximum brightness. If this parameter is set to 0
1354				(default) and the machine requires it, or this parameter
1355				is set to 1, a brightness value of 0 sets the backlight
1356				to maximum brightness, and the maximum of the brightness
1357				value switches the backlight off.
1358				-1 -- never invert brightness
1359				 0 -- machine default
1360				 1 -- force brightness inversion
1362		icn=		[HW,ISDN]
1363				Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1365		ide-core.nodma=	[HW] (E)IDE subsystem
1366				Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1367				.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1368				.cdrom .chs .ignore_cable are additional options
1369				See Documentation/ide/ide.txt.
1371		ide-generic.probe-mask= [HW] (E)IDE subsystem
1372				Format: <int>
1373				Probe mask for legacy ISA IDE ports.  Depending on
1374				platform up to 6 ports are supported, enabled by
1375				setting corresponding bits in the mask to 1.  The
1376				default value is 0x0, which has a special meaning.
1377				On systems that have PCI, it triggers scanning the
1378				PCI bus for the first and the second port, which
1379				are then probed.  On systems without PCI the value
1380				of 0x0 enables probing the two first ports as if it
1381				was 0x3.
1383		ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1384				Claim all unknown PCI IDE storage controllers.
1386		idle=		[X86]
1387				Format: idle=poll, idle=halt, idle=nomwait
1388				Poll forces a polling idle loop that can slightly
1389				improve the performance of waking up a idle CPU, but
1390				will use a lot of power and make the system run hot.
1391				Not recommended.
1392				idle=halt: Halt is forced to be used for CPU idle.
1393				In such case C2/C3 won't be used again.
1394				idle=nomwait: Disable mwait for CPU C-states
1396		ignore_loglevel	[KNL]
1397				Ignore loglevel setting - this will print /all/
1398				kernel messages to the console. Useful for debugging.
1399				We also add it as printk module parameter, so users
1400				could change it dynamically, usually by
1401				/sys/module/printk/parameters/ignore_loglevel.
1403		ihash_entries=	[KNL]
1404				Set number of hash buckets for inode cache.
1406		ima_appraise=	[IMA] appraise integrity measurements
1407				Format: { "off" | "enforce" | "fix" | "log" }
1408				default: "enforce"
1410		ima_appraise_tcb [IMA]
1411				The builtin appraise policy appraises all files
1412				owned by uid=0.
1414		ima_hash=	[IMA]
1415				Format: { md5 | sha1 | rmd160 | sha256 | sha384
1416					   | sha512 | ... }
1417				default: "sha1"
1419				The list of supported hash algorithms is defined
1420				in crypto/hash_info.h.
1422		ima_policy=	[IMA]
1423				The builtin measurement policy to load during IMA
1424				setup.  Specyfing "tcb" as the value, measures all
1425				programs exec'd, files mmap'd for exec, and all files
1426				opened with the read mode bit set by either the
1427				effective uid (euid=0) or uid=0.
1428				Format: "tcb"
1430		ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
1431				Load a policy which meets the needs of the Trusted
1432				Computing Base.  This means IMA will measure all
1433				programs exec'd, files mmap'd for exec, and all files
1434				opened for read by uid=0.
1436		ima_template=   [IMA]
1437				Select one of defined IMA measurements template formats.
1438				Formats: { "ima" | "ima-ng" | "ima-sig" }
1439				Default: "ima-ng"
1441		ima_template_fmt=
1442		                [IMA] Define a custom template format.
1443				Format: { "field1|...|fieldN" }
1445		ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1446				Format: <min_file_size>
1447				Set the minimal file size for using asynchronous hash.
1448				If left unspecified, ahash usage is disabled.
1450				ahash performance varies for different data sizes on
1451				different crypto accelerators. This option can be used
1452				to achieve the best performance for a particular HW.
1454		ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1455				Format: <bufsize>
1456				Set hashing buffer size. Default: 4k.
1458				ahash performance varies for different chunk sizes on
1459				different crypto accelerators. This option can be used
1460				to achieve best performance for particular HW.
1462		init=		[KNL]
1463				Format: <full_path>
1464				Run specified binary instead of /sbin/init as init
1465				process.
1467		initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
1468				for working out where the kernel is dying during
1469				startup.
1471		initcall_blacklist=  [KNL] Do not execute a comma-separated list of
1472				initcall functions.  Useful for debugging built-in
1473				modules and initcalls.
1475		initrd=		[BOOT] Specify the location of the initial ramdisk
1477		inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
1478				Format: <irq>
1480		int_pln_enable  [x86] Enable power limit notification interrupt
1482		integrity_audit=[IMA]
1483				Format: { "0" | "1" }
1484				0 -- basic integrity auditing messages. (Default)
1485				1 -- additional integrity auditing messages.
1487		intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1488			on
1489				Enable intel iommu driver.
1490			off
1491				Disable intel iommu driver.
1492			igfx_off [Default Off]
1493				By default, gfx is mapped as normal device. If a gfx
1494				device has a dedicated DMAR unit, the DMAR unit is
1495				bypassed by not enabling DMAR with this option. In
1496				this case, gfx device will use physical address for
1497				DMA.
1498			forcedac [x86_64]
1499				With this option iommu will not optimize to look
1500				for io virtual address below 32-bit forcing dual
1501				address cycle on pci bus for cards supporting greater
1502				than 32-bit addressing. The default is to look
1503				for translation below 32-bit and if not available
1504				then look in the higher range.
1505			strict [Default Off]
1506				With this option on every unmap_single operation will
1507				result in a hardware IOTLB flush operation as opposed
1508				to batching them for performance.
1509			sp_off [Default Off]
1510				By default, super page will be supported if Intel IOMMU
1511				has the capability. With this option, super page will
1512				not be supported.
1513			ecs_off [Default Off]
1514				By default, extended context tables will be supported if
1515				the hardware advertises that it has support both for the
1516				extended tables themselves, and also PASID support. With
1517				this option set, extended tables will not be used even
1518				on hardware which claims to support them.
1520		intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
1521				0	disables intel_idle and fall back on acpi_idle.
1522				1 to 6	specify maximum depth of C-state.
1524		intel_pstate=  [X86]
1525			       disable
1526			         Do not enable intel_pstate as the default
1527			         scaling driver for the supported processors
1528			       force
1529				 Enable intel_pstate on systems that prohibit it by default
1530				 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1531				 instead of acpi-cpufreq may disable platform features, such
1532				 as thermal controls and power capping, that rely on ACPI
1533				 P-States information being indicated to OSPM and therefore
1534				 should be used with caution. This option does not work with
1535				 processors that aren't supported by the intel_pstate driver
1536				 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1537			       no_hwp
1538			         Do not enable hardware P state control (HWP)
1539				 if available.
1540			hwp_only
1541				Only load intel_pstate on systems which support
1542				hardware P state control (HWP) if available.
1544		intremap=	[X86-64, Intel-IOMMU]
1545				on	enable Interrupt Remapping (default)
1546				off	disable Interrupt Remapping
1547				nosid	disable Source ID checking
1548				no_x2apic_optout
1549					BIOS x2APIC opt-out request will be ignored
1551		iomem=		Disable strict checking of access to MMIO memory
1552			strict	regions from userspace.
1553			relaxed
1555		iommu=		[x86]
1556			off
1557			force
1558			noforce
1559			biomerge
1560			panic
1561			nopanic
1562			merge
1563			nomerge
1564			forcesac
1565			soft
1566			pt		[x86, IA-64]
1567			nobypass	[PPC/POWERNV]
1568				Disable IOMMU bypass, using IOMMU for PCI devices.
1571		io7=		[HW] IO7 for Marvel based alpha systems
1572				See comment before marvel_specify_io7 in
1573				arch/alpha/kernel/core_marvel.c.
1575		io_delay=	[X86] I/O delay method
1576			0x80
1577				Standard port 0x80 based delay
1578			0xed
1579				Alternate port 0xed based delay (needed on some systems)
1580			udelay
1581				Simple two microseconds delay
1582			none
1583				No delay
1585		ip=		[IP_PNP]
1586				See Documentation/filesystems/nfs/nfsroot.txt.
1588		irqfixup	[HW]
1589				When an interrupt is not handled search all handlers
1590				for it. Intended to get systems with badly broken
1591				firmware running.
1593		irqpoll		[HW]
1594				When an interrupt is not handled search all handlers
1595				for it. Also check all handlers each timer
1596				interrupt. Intended to get systems with badly broken
1597				firmware running.
1599		isapnp=		[ISAPNP]
1600				Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1602		isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1603				Format:
1604				<cpu number>,...,<cpu number>
1605				or
1606				<cpu number>-<cpu number>
1607				(must be a positive range in ascending order)
1608				or a mixture
1609				<cpu number>,...,<cpu number>-<cpu number>
1611				This option can be used to specify one or more CPUs
1612				to isolate from the general SMP balancing and scheduling
1613				algorithms. You can move a process onto or off an
1614				"isolated" CPU via the CPU affinity syscalls or cpuset.
1615				<cpu number> begins at 0 and the maximum value is
1616				"number of CPUs in system - 1".
1618				This option is the preferred way to isolate CPUs. The
1619				alternative -- manually setting the CPU mask of all
1620				tasks in the system -- can cause problems and
1621				suboptimal load balancer performance.
1623		iucv=		[HW,NET]
1625		ivrs_ioapic	[HW,X86_64]
1626				Provide an override to the IOAPIC-ID<->DEVICE-ID
1627				mapping provided in the IVRS ACPI table. For
1628				example, to map IOAPIC-ID decimal 10 to
1629				PCI device 00:14.0 write the parameter as:
1630					ivrs_ioapic[10]=00:14.0
1632		ivrs_hpet	[HW,X86_64]
1633				Provide an override to the HPET-ID<->DEVICE-ID
1634				mapping provided in the IVRS ACPI table. For
1635				example, to map HPET-ID decimal 0 to
1636				PCI device 00:14.0 write the parameter as:
1637					ivrs_hpet[0]=00:14.0
1639		js=		[HW,JOY] Analog joystick
1640				See Documentation/input/joystick.txt.
1642		kaslr/nokaslr	[X86]
1643				Enable/disable kernel and module base offset ASLR
1644				(Address Space Layout Randomization) if built into
1645				the kernel. When CONFIG_HIBERNATION is selected,
1646				kASLR is disabled by default. When kASLR is enabled,
1647				hibernation will be disabled.
1649		keepinitrd	[HW,ARM]
1651		kernelcore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
1652				specifies the amount of memory usable by the kernel
1653				for non-movable allocations.  The requested amount is
1654				spread evenly throughout all nodes in the system. The
1655				remaining memory in each node is used for Movable
1656				pages. In the event, a node is too small to have both
1657				kernelcore and Movable pages, kernelcore pages will
1658				take priority and other nodes will have a larger number
1659				of Movable pages.  The Movable zone is used for the
1660				allocation of pages that may be reclaimed or moved
1661				by the page migration subsystem.  This means that
1662				HugeTLB pages may not be allocated from this zone.
1663				Note that allocations like PTEs-from-HighMem still
1664				use the HighMem zone if it exists, and the Normal
1665				zone if it does not.
1667		kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
1668				Format: <Controller#>[,poll interval]
1669				The controller # is the number of the ehci usb debug
1670				port as it is probed via PCI.  The poll interval is
1671				optional and is the number seconds in between
1672				each poll cycle to the debug port in case you need
1673				the functionality for interrupting the kernel with
1674				gdb or control-c on the dbgp connection.  When
1675				not using this parameter you use sysrq-g to break into
1676				the kernel debugger.
1678		kgdboc=		[KGDB,HW] kgdb over consoles.
1679				Requires a tty driver that supports console polling,
1680				or a supported polling keyboard driver (non-usb).
1681				 Serial only format: <serial_device>[,baud]
1682				 keyboard only format: kbd
1683				 keyboard and serial format: kbd,<serial_device>[,baud]
1684				Optional Kernel mode setting:
1685				 kms, kbd format: kms,kbd
1686				 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1688		kgdbwait	[KGDB] Stop kernel execution and enter the
1689				kernel debugger at the earliest opportunity.
1691		kmac=		[MIPS] korina ethernet MAC address.
1692				Configure the RouterBoard 532 series on-chip
1693				Ethernet adapter MAC address.
1695		kmemleak=	[KNL] Boot-time kmemleak enable/disable
1696				Valid arguments: on, off
1697				Default: on
1699				the default is off.
1701		kmemcheck=	[X86] Boot-time kmemcheck enable/disable/one-shot mode
1702				Valid arguments: 0, 1, 2
1703				kmemcheck=0 (disabled)
1704				kmemcheck=1 (enabled)
1705				kmemcheck=2 (one-shot mode)
1706				Default: 2 (one-shot mode)
1708		kstack=N	[X86] Print N words from the kernel stack
1709				in oops dumps.
1711		kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1712				Default is 0 (don't ignore, but inject #GP)
1714		kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
1715				KVM MMU at runtime.
1716				Default is 0 (off)
1718		kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1719				Default is 1 (enabled)
1721		kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
1722				for all guests.
1723				Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1725		kvm-intel.ept=	[KVM,Intel] Disable extended page tables
1726				(virtualized MMU) support on capable Intel chips.
1727				Default is 1 (enabled)
1729		kvm-intel.emulate_invalid_guest_state=
1730				[KVM,Intel] Enable emulation of invalid guest states
1731				Default is 0 (disabled)
1733		kvm-intel.flexpriority=
1734				[KVM,Intel] Disable FlexPriority feature (TPR shadow).
1735				Default is 1 (enabled)
1737		kvm-intel.nested=
1738				[KVM,Intel] Enable VMX nesting (nVMX).
1739				Default is 0 (disabled)
1741		kvm-intel.unrestricted_guest=
1742				[KVM,Intel] Disable unrestricted guest feature
1743				(virtualized real and unpaged mode) on capable
1744				Intel chips. Default is 1 (enabled)
1746		kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
1747				feature (tagged TLBs) on capable Intel chips.
1748				Default is 1 (enabled)
1750		l2cr=		[PPC]
1752		l3cr=		[PPC]
1754		lapic		[X86-32,APIC] Enable the local APIC even if BIOS
1755				disabled it.
1757		lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
1758				value for LAPIC timer one-shot implementation. Default
1759				back to the programmable timer unit in the LAPIC.
1761		lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
1762				in C2 power state.
1764		libata.dma=	[LIBATA] DMA control
1765				libata.dma=0	  Disable all PATA and SATA DMA
1766				libata.dma=1	  PATA and SATA Disk DMA only
1767				libata.dma=2	  ATAPI (CDROM) DMA only
1768				libata.dma=4	  Compact Flash DMA only
1769				Combinations also work, so libata.dma=3 enables DMA
1770				for disks and CDROMs, but not CFs.
1772		libata.ignore_hpa=	[LIBATA] Ignore HPA limit
1773				libata.ignore_hpa=0	  keep BIOS limits (default)
1774				libata.ignore_hpa=1	  ignore limits, using full disk
1776		libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
1777				when set.
1778				Format: <int>
1780		libata.force=	[LIBATA] Force configurations.  The format is comma
1781				separated list of "[ID:]VAL" where ID is
1782				PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1783				matching port, link or device.  Basically, it matches
1784				the ATA ID string printed on console by libata.  If
1785				the whole ID part is omitted, the last PORT and DEVICE
1786				values are used.  If ID hasn't been specified yet, the
1787				configuration applies to all ports, links and devices.
1789				If only DEVICE is omitted, the parameter applies to
1790				the port and all links and devices behind it.  DEVICE
1791				number of 0 either selects the first device or the
1792				first fan-out link behind PMP device.  It does not
1793				select the host link.  DEVICE number of 15 selects the
1794				host link and device attached to it.
1796				The VAL specifies the configuration to force.  As long
1797				as there's no ambiguity shortcut notation is allowed.
1798				For example, both 1.5 and 1.5G would work for 1.5Gbps.
1799				The following configurations can be forced.
1801				* Cable type: 40c, 80c, short40c, unk, ign or sata.
1802				  Any ID with matching PORT is used.
1804				* SATA link speed limit: 1.5Gbps or 3.0Gbps.
1806				* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1807				  udma[/][16,25,33,44,66,100,133] notation is also
1808				  allowed.
1810				* [no]ncq: Turn on or off NCQ.
1812				* [no]ncqtrim: Turn off queued DSM TRIM.
1814				* nohrst, nosrst, norst: suppress hard, soft
1815	                          and both resets.
1817				* rstonce: only attempt one reset during
1818				  hot-unplug link recovery
1820				* dump_id: dump IDENTIFY data.
1822				* atapi_dmadir: Enable ATAPI DMADIR bridge support
1824				* disable: Disable this device.
1826				If there are multiple matching configurations changing
1827				the same attribute, the last one is used.
1829		memblock=debug	[KNL] Enable memblock debug messages.
1831		load_ramdisk=	[RAM] List of ramdisks to load from floppy
1832				See Documentation/blockdev/ramdisk.txt.
1834		lockd.nlm_grace_period=P  [NFS] Assign grace period.
1835				Format: <integer>
1837		lockd.nlm_tcpport=N	[NFS] Assign TCP port.
1838				Format: <integer>
1840		lockd.nlm_timeout=T	[NFS] Assign timeout value.
1841				Format: <integer>
1843		lockd.nlm_udpport=M	[NFS] Assign UDP port.
1844				Format: <integer>
1846		locktorture.nreaders_stress= [KNL]
1847				Set the number of locking read-acquisition kthreads.
1848				Defaults to being automatically set based on the
1849				number of online CPUs.
1851		locktorture.nwriters_stress= [KNL]
1852				Set the number of locking write-acquisition kthreads.
1854		locktorture.onoff_holdoff= [KNL]
1855				Set time (s) after boot for CPU-hotplug testing.
1857		locktorture.onoff_interval= [KNL]
1858				Set time (s) between CPU-hotplug operations, or
1859				zero to disable CPU-hotplug testing.
1861		locktorture.shuffle_interval= [KNL]
1862				Set task-shuffle interval (jiffies).  Shuffling
1863				tasks allows some CPUs to go into dyntick-idle
1864				mode during the locktorture test.
1866		locktorture.shutdown_secs= [KNL]
1867				Set time (s) after boot system shutdown.  This
1868				is useful for hands-off automated testing.
1870		locktorture.stat_interval= [KNL]
1871				Time (s) between statistics printk()s.
1873		locktorture.stutter= [KNL]
1874				Time (s) to stutter testing, for example,
1875				specifying five seconds causes the test to run for
1876				five seconds, wait for five seconds, and so on.
1877				This tests the locking primitive's ability to
1878				transition abruptly to and from idle.
1880		locktorture.torture_runnable= [BOOT]
1881				Start locktorture running at boot time.
1883		locktorture.torture_type= [KNL]
1884				Specify the locking implementation to test.
1886		locktorture.verbose= [KNL]
1887				Enable additional printk() statements.
1889		logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
1890				Format: <irq>
1892		loglevel=	All Kernel Messages with a loglevel smaller than the
1893				console loglevel will be printed to the console. It can
1894				also be changed with klogd or other programs. The
1895				loglevels are defined as follows:
1897				0 (KERN_EMERG)		system is unusable
1898				1 (KERN_ALERT)		action must be taken immediately
1899				2 (KERN_CRIT)		critical conditions
1900				3 (KERN_ERR)		error conditions
1901				4 (KERN_WARNING)	warning conditions
1902				5 (KERN_NOTICE)		normal but significant condition
1903				6 (KERN_INFO)		informational
1904				7 (KERN_DEBUG)		debug-level messages
1906		log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
1907				in bytes.  n must be a power of two and greater
1908				than the minimal size. The minimal size is defined
1909				by LOG_BUF_SHIFT kernel config parameter. There is
1910				also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1911				that allows to increase the default size depending on
1912				the number of CPUs. See init/Kconfig for more details.
1914		logo.nologo	[FB] Disables display of the built-in Linux logo.
1915				This may be used to provide more screen space for
1916				kernel log messages and is useful when debugging
1917				kernel boot problems.
1919		lp=0		[LP]	Specify parallel ports to use, e.g,
1920		lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
1921		lp=reset		first parallel port). 'lp=0' disables the
1922		lp=auto			printer driver. 'lp=reset' (which can be
1923					specified in addition to the ports) causes
1924					attached printers to be reset. Using
1925					lp=port1,port2,... specifies the parallel ports
1926					to associate lp devices with, starting with
1927					lp0. A port specification may be 'none' to skip
1928					that lp device, or a parport name such as
1929					'parport0'. Specifying 'lp=auto' instead of a
1930					port specification list means that device IDs
1931					from each port should be examined, to see if
1932					an IEEE 1284-compliant printer is attached; if
1933					so, the driver will manage that printer.
1934					See also header of drivers/char/lp.c.
1936		lpj=n		[KNL]
1937				Sets loops_per_jiffy to given constant, thus avoiding
1938				time-consuming boot-time autodetection (up to 250 ms per
1939				CPU). 0 enables autodetection (default). To determine
1940				the correct value for your kernel, boot with normal
1941				autodetection and see what value is printed. Note that
1942				on SMP systems the preset will be applied to all CPUs,
1943				which is likely to cause problems if your CPUs need
1944				significantly divergent settings. An incorrect value
1945				will cause delays in the kernel to be wrong, leading to
1946				unpredictable I/O errors and other breakage. Although
1947				unlikely, in the extreme case this might damage your
1948				hardware.
1950		ltpc=		[NET]
1951				Format: <io>,<irq>,<dma>
1953		machvec=	[IA-64] Force the use of a particular machine-vector
1954				(machvec) in a generic kernel.
1955				Example: machvec=hpzx1_swiotlb
1957		machtype=	[Loongson] Share the same kernel image file between different
1958				 yeeloong laptop.
1959				Example: machtype=lemote-yeeloong-2f-7inch
1961		max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
1962				than or equal to this physical address is ignored.
1964		maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
1965				should make use of.  maxcpus=n : n >= 0 limits the
1966				kernel to using 'n' processors.  n=0 is a special case,
1967				it is equivalent to "nosmp", which also disables
1968				the IO APIC.
1970		max_loop=	[LOOP] The number of loop block devices that get
1971		(loop.max_loop)	unconditionally pre-created at init time. The default
1972				number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1973				of statically allocating a predefined number, loop
1974				devices can be requested on-demand with the
1975				/dev/loop-control interface.
1977		mce		[X86-32] Machine Check Exception
1979		mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
1981		md=		[HW] RAID subsystems devices and level
1982				See Documentation/md.txt.
1984		mdacon=		[MDA]
1985				Format: <first>,<last>
1986				Specifies range of consoles to be captured by the MDA.
1988		mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
1989				Amount of memory to be used when the kernel is not able
1990				to see the whole system memory or for test.
1991				[X86] Work as limiting max address. Use together
1992				with memmap= to avoid physical address space collisions.
1993				Without memmap= PCI devices could be placed at addresses
1994				belonging to unused RAM.
1996		mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
1997				memory.
1999		memchunk=nn[KMG]
2000				[KNL,SH] Allow user to override the default size for
2001				per-device physically contiguous DMA buffers.
2003		memmap=exactmap	[KNL,X86] Enable setting of an exact
2004				E820 memory map, as specified by the user.
2005				Such memmap=exactmap lines can be constructed based on
2006				BIOS output or other requirements. See the memmap=nn@ss
2007				option description.
2009		memmap=nn[KMG]@ss[KMG]
2010				[KNL] Force usage of a specific region of memory.
2011				Region of memory to be used is from ss to ss+nn.
2013		memmap=nn[KMG]#ss[KMG]
2014				[KNL,ACPI] Mark specific memory as ACPI data.
2015				Region of memory to be marked is from ss to ss+nn.
2017		memmap=nn[KMG]$ss[KMG]
2018				[KNL,ACPI] Mark specific memory as reserved.
2019				Region of memory to be reserved is from ss to ss+nn.
2020				Example: Exclude memory from 0x18690000-0x1869ffff
2021				         memmap=64K$0x18690000
2022				         or
2023				         memmap=0x10000$0x18690000
2025		memmap=nn[KMG]!ss[KMG]
2026				[KNL,X86] Mark specific memory as protected.
2027				Region of memory to be used, from ss to ss+nn.
2028				The memory region may be marked as e820 type 12 (0xc)
2029				and is NVDIMM or ADR memory.
2031		memory_corruption_check=0/1 [X86]
2032				Some BIOSes seem to corrupt the first 64k of
2033				memory when doing things like suspend/resume.
2034				Setting this option will scan the memory
2035				looking for corruption.  Enabling this will
2036				both detect corruption and prevent the kernel
2037				from using the memory being corrupted.
2038				However, its intended as a diagnostic tool; if
2039				repeatable BIOS-originated corruption always
2040				affects the same memory, you can use memmap=
2041				to prevent the kernel from using that memory.
2043		memory_corruption_check_size=size [X86]
2044				By default it checks for corruption in the low
2045				64k, making this memory unavailable for normal
2046				use.  Use this parameter to scan for
2047				corruption in more or less memory.
2049		memory_corruption_check_period=seconds [X86]
2050				By default it checks for corruption every 60
2051				seconds.  Use this parameter to check at some
2052				other rate.  0 disables periodic checking.
2054		memtest=	[KNL,X86,ARM] Enable memtest
2055				Format: <integer>
2056				default : 0 <disable>
2057				Specifies the number of memtest passes to be
2058				performed. Each pass selects another test
2059				pattern from a given set of patterns. Memtest
2060				fills the memory with this pattern, validates
2061				memory contents and reserves bad memory
2062				regions that are detected.
2064		meye.*=		[HW] Set MotionEye Camera parameters
2065				See Documentation/video4linux/meye.txt.
2067		mfgpt_irq=	[IA-32] Specify the IRQ to use for the
2068				Multi-Function General Purpose Timers on AMD Geode
2069				platforms.
2071		mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
2072				the BIOS has incorrectly applied a workaround. TinyBIOS
2073				version 0.98 is known to be affected, 0.99 fixes the
2074				problem by letting the user disable the workaround.
2076		mga=		[HW,DRM]
2078		min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
2079				physical address is ignored.
2081		mini2440=	[ARM,HW,KNL]
2082				Format:[0..2][b][c][t]
2083				Default: "0tb"
2084				MINI2440 configuration specification:
2085				0 - The attached screen is the 3.5" TFT
2086				1 - The attached screen is the 7" TFT
2087				2 - The VGA Shield is attached (1024x768)
2088				Leaving out the screen size parameter will not load
2089				the TFT driver, and the framebuffer will be left
2090				unconfigured.
2091				b - Enable backlight. The TFT backlight pin will be
2092				linked to the kernel VESA blanking code and a GPIO
2093				LED. This parameter is not necessary when using the
2094				VGA shield.
2095				c - Enable the s3c camera interface.
2096				t - Reserved for enabling touchscreen support. The
2097				touchscreen support is not enabled in the mainstream
2098				kernel as of 2.6.30, a preliminary port can be found
2099				in the "bleeding edge" mini2440 support kernel at
2100				http://repo.or.cz/w/linux-2.6/mini2440.git
2102		mminit_loglevel=
2103				[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2104				parameter allows control of the logging verbosity for
2105				the additional memory initialisation checks. A value
2106				of 0 disables mminit logging and a level of 4 will
2107				log everything. Information is printed at KERN_DEBUG
2108				so loglevel=8 may also need to be specified.
2110		module.sig_enforce
2111				[KNL] When CONFIG_MODULE_SIG is set, this means that
2112				modules without (valid) signatures will fail to load.
2113				Note that if CONFIG_MODULE_SIG_FORCE is set, that
2114				is always true, so this option does nothing.
2116		mousedev.tap_time=
2117				[MOUSE] Maximum time between finger touching and
2118				leaving touchpad surface for touch to be considered
2119				a tap and be reported as a left button click (for
2120				touchpads working in absolute mode only).
2121				Format: <msecs>
2122		mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
2123				reporting absolute coordinates, such as tablets
2124		mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
2125				reporting absolute coordinates, such as tablets
2127		movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
2128				is similar to kernelcore except it specifies the
2129				amount of memory used for migratable allocations.
2130				If both kernelcore and movablecore is specified,
2131				then kernelcore will be at *least* the specified
2132				value but may be more. If movablecore on its own
2133				is specified, the administrator must be careful
2134				that the amount of memory usable for all allocations
2135				is not too small.
2137		movable_node	[KNL,X86] Boot-time switch to enable the effects
2138				of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2140		MTD_Partition=	[MTD]
2141				Format: <name>,<region-number>,<size>,<offset>
2143		MTD_Region=	[MTD] Format:
2144				<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2146		mtdparts=	[MTD]
2147				See drivers/mtd/cmdlinepart.c.
2149		multitce=off	[PPC]  This parameter disables the use of the pSeries
2150				firmware feature for updating multiple TCE entries
2151				at a time.
2153		onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
2155				Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2157				boundary - index of last SLC block on Flex-OneNAND.
2158					   The remaining blocks are configured as MLC blocks.
2159				lock	 - Configure if Flex-OneNAND boundary should be locked.
2160					   Once locked, the boundary cannot be changed.
2161					   1 indicates lock status, 0 indicates unlock status.
2163		mtdset=		[ARM]
2164				ARM/S3C2412 JIVE boot control
2166				See arch/arm/mach-s3c2412/mach-jive.c
2168		mtouchusb.raw_coordinates=
2169				[HW] Make the MicroTouch USB driver use raw coordinates
2170				('y', default) or cooked coordinates ('n')
2172		mtrr_chunk_size=nn[KMG] [X86]
2173				used for mtrr cleanup. It is largest continuous chunk
2174				that could hold holes aka. UC entries.
2176		mtrr_gran_size=nn[KMG] [X86]
2177				Used for mtrr cleanup. It is granularity of mtrr block.
2178				Default is 1.
2179				Large value could prevent small alignment from
2180				using up MTRRs.
2182		mtrr_spare_reg_nr=n [X86]
2183				Format: <integer>
2184				Range: 0,7 : spare reg number
2185				Default : 1
2186				Used for mtrr cleanup. It is spare mtrr entries number.
2187				Set to 2 or more if your graphical card needs more.
2189		n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
2191		netdev=		[NET] Network devices parameters
2192				Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2193				Note that mem_start is often overloaded to mean
2194				something different and driver-specific.
2195				This usage is only documented in each driver source
2196				file if at all.
2198		nf_conntrack.acct=
2199				[NETFILTER] Enable connection tracking flow accounting
2200				0 to disable accounting
2201				1 to enable accounting
2202				Default value is 0.
2204		nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
2205				See Documentation/filesystems/nfs/nfsroot.txt.
2207		nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
2208				See Documentation/filesystems/nfs/nfsroot.txt.
2210		nfsrootdebug	[NFS] enable nfsroot debugging messages.
2211				See Documentation/filesystems/nfs/nfsroot.txt.
2213		nfs.callback_tcpport=
2214				[NFS] set the TCP port on which the NFSv4 callback
2215				channel should listen.
2217		nfs.cache_getent=
2218				[NFS] sets the pathname to the program which is used
2219				to update the NFS client cache entries.
2221		nfs.cache_getent_timeout=
2222				[NFS] sets the timeout after which an attempt to
2223				update a cache entry is deemed to have failed.
2225		nfs.idmap_cache_timeout=
2226				[NFS] set the maximum lifetime for idmapper cache
2227				entries.
2229		nfs.enable_ino64=
2230				[NFS] enable 64-bit inode numbers.
2231				If zero, the NFS client will fake up a 32-bit inode
2232				number for the readdir() and stat() syscalls instead
2233				of returning the full 64-bit number.
2234				The default is to return 64-bit inode numbers.
2236		nfs.max_session_slots=
2237				[NFSv4.1] Sets the maximum number of session slots
2238				the client will attempt to negotiate with the server.
2239				This limits the number of simultaneous RPC requests
2240				that the client can send to the NFSv4.1 server.
2241				Note that there is little point in setting this
2242				value higher than the max_tcp_slot_table_limit.
2244		nfs.nfs4_disable_idmapping=
2245				[NFSv4] When set to the default of '1', this option
2246				ensures that both the RPC level authentication
2247				scheme and the NFS level operations agree to use
2248				numeric uids/gids if the mount is using the
2249				'sec=sys' security flavour. In effect it is
2250				disabling idmapping, which can make migration from
2251				legacy NFSv2/v3 systems to NFSv4 easier.
2252				Servers that do not support this mode of operation
2253				will be autodetected by the client, and it will fall
2254				back to using the idmapper.
2255				To turn off this behaviour, set the value to '0'.
2256		nfs.nfs4_unique_id=
2257				[NFS4] Specify an additional fixed unique ident-
2258				ification string that NFSv4 clients can insert into
2259				their nfs_client_id4 string.  This is typically a
2260				UUID that is generated at system install time.
2262		nfs.send_implementation_id =
2263				[NFSv4.1] Send client implementation identification
2264				information in exchange_id requests.
2265				If zero, no implementation identification information
2266				will be sent.
2267				The default is to send the implementation identification
2268				information.
2270		nfs.recover_lost_locks =
2271				[NFSv4] Attempt to recover locks that were lost due
2272				to a lease timeout on the server. Please note that
2273				doing this risks data corruption, since there are
2274				no guarantees that the file will remain unchanged
2275				after the locks are lost.
2276				If you want to enable the kernel legacy behaviour of
2277				attempting to recover these locks, then set this
2278				parameter to '1'.
2279				The default parameter value of '0' causes the kernel
2280				not to attempt recovery of lost locks.
2282		nfsd.nfs4_disable_idmapping=
2283				[NFSv4] When set to the default of '1', the NFSv4
2284				server will return only numeric uids and gids to
2285				clients using auth_sys, and will accept numeric uids
2286				and gids from such clients.  This is intended to ease
2287				migration from NFSv2/v3.
2289		objlayoutdriver.osd_login_prog=
2290				[NFS] [OBJLAYOUT] sets the pathname to the program which
2291				is used to automatically discover and login into new
2292				osd-targets. Please see:
2293				Documentation/filesystems/pnfs.txt for more explanations
2295		nmi_debug=	[KNL,AVR32,SH] Specify one or more actions to take
2296				when a NMI is triggered.
2297				Format: [state][,regs][,debounce][,die]
2299		nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
2300				Format: [panic,][nopanic,][num]
2301				Valid num: 0 or 1
2302				0 - turn nmi_watchdog off
2303				1 - turn nmi_watchdog on
2304				When panic is specified, panic when an NMI watchdog
2305				timeout occurs (or 'nopanic' to override the opposite
2306				default).
2307				This is useful when you use a panic=... timeout and
2308				need the box quickly up again.
2310		netpoll.carrier_timeout=
2311				[NET] Specifies amount of time (in seconds) that
2312				netpoll should wait for a carrier. By default netpoll
2313				waits 4 seconds.
2315		no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
2316				emulation library even if a 387 maths coprocessor
2317				is present.
2319		no_console_suspend
2320				[HW] Never suspend the console
2321				Disable suspending of consoles during suspend and
2322				hibernate operations.  Once disabled, debugging
2323				messages can reach various consoles while the rest
2324				of the system is being put to sleep (ie, while
2325				debugging driver suspend/resume hooks).  This may
2326				not work reliably with all consoles, but is known
2327				to work with serial and VGA consoles.
2328				To facilitate more flexible debugging, we also add
2329				console_suspend, a printk module parameter to control
2330				it. Users could use console_suspend (usually
2331				/sys/module/printk/parameters/console_suspend) to
2332				turn on/off it dynamically.
2334		noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
2335				caches in the slab allocator.  Saves per-node memory,
2336				but will impact performance.
2338		noalign		[KNL,ARM]
2340		noapic		[SMP,APIC] Tells the kernel to not make use of any
2341				IOAPICs that may be present in the system.
2343		noautogroup	Disable scheduler automatic task group creation.
2345		nobats		[PPC] Do not use BATs for mapping kernel lowmem
2346				on "Classic" PPC cores.
2348		nocache		[ARM]
2350		noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
2352		nodelayacct	[KNL] Disable per-task delay accounting
2354		nodisconnect	[HW,SCSI,M68K] Disables SCSI disconnects.
2356		nodsp		[SH] Disable hardware DSP at boot time.
2358		noefi		Disable EFI runtime services support.
2360		noexec		[IA-64]
2362		noexec		[X86]
2363				On X86-32 available only on PAE configured kernels.
2364				noexec=on: enable non-executable mappings (default)
2365				noexec=off: disable non-executable mappings
2367		nosmap		[X86]
2368				Disable SMAP (Supervisor Mode Access Prevention)
2369				even if it is supported by processor.
2371		nosmep		[X86]
2372				Disable SMEP (Supervisor Mode Execution Prevention)
2373				even if it is supported by processor.
2375		noexec32	[X86-64]
2376				This affects only 32-bit executables.
2377				noexec32=on: enable non-executable mappings (default)
2378					read doesn't imply executable mappings
2379				noexec32=off: disable non-executable mappings
2380					read implies executable mappings
2382		nofpu		[MIPS,SH] Disable hardware FPU at boot time.
2384		nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2385				register save and restore. The kernel will only save
2386				legacy floating-point registers on task switch.
2388		nohugeiomap	[KNL,x86] Disable kernel huge I/O mappings.
2390		noxsave		[BUGS=X86] Disables x86 extended register state save
2391				and restore using xsave. The kernel will fallback to
2392				enabling legacy floating-point and sse state.
2394		noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
2395				register states. The kernel will fall back to use
2396				xsave to save the states. By using this parameter,
2397				performance of saving the states is degraded because
2398				xsave doesn't support modified optimization while
2399				xsaveopt supports it on xsaveopt enabled systems.
2401		noxsaves	[X86] Disables xsaves and xrstors used in saving and
2402				restoring x86 extended register state in compacted
2403				form of xsave area. The kernel will fall back to use
2404				xsaveopt and xrstor to save and restore the states
2405				in standard form of xsave area. By using this
2406				parameter, xsave area per process might occupy more
2407				memory on xsaves enabled systems.
2409		nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2410				wfi(ARM) instruction doesn't work correctly and not to
2411				use it. This is also useful when using JTAG debugger.
2413		no_file_caps	Tells the kernel not to honor file capabilities.  The
2414				only way then for a file to be executed with privilege
2415				is to be setuid root or executed by root.
2417		nohalt		[IA-64] Tells the kernel not to use the power saving
2418				function PAL_HALT_LIGHT when idle. This increases
2419				power-consumption. On the positive side, it reduces
2420				interrupt wake-up latency, which may improve performance
2421				in certain environments such as networked servers or
2422				real-time systems.
2424		nohibernate	[HIBERNATION] Disable hibernation and resume.
2426		nohz=		[KNL] Boottime enable/disable dynamic ticks
2427				Valid arguments: on, off
2428				Default: on
2430		nohz_full=	[KNL,BOOT]
2431				In kernels built with CONFIG_NO_HZ_FULL=y, set
2432				the specified list of CPUs whose tick will be stopped
2433				whenever possible. The boot CPU will be forced outside
2434				the range to maintain the timekeeping.
2435				The CPUs in this range must also be included in the
2436				rcu_nocbs= set.
2438		noiotrap	[SH] Disables trapped I/O port accesses.
2440		noirqdebug	[X86-32] Disables the code which attempts to detect and
2441				disable unhandled interrupt sources.
2443		no_timer_check	[X86,APIC] Disables the code which tests for
2444				broken timer IRQ sources.
2446		noisapnp	[ISAPNP] Disables ISA PnP code.
2448		noinitrd	[RAM] Tells the kernel not to load any configured
2449				initial RAM disk.
2451		nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
2452				remapping.
2453				[Deprecated - use intremap=off]
2455		nointroute	[IA-64]
2457		nojitter	[IA-64] Disables jitter checking for ITC timers.
2459		no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
2461		no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
2462				fault handling.
2464		no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
2465				steal time is computed, but won't influence scheduler
2466				behaviour
2468		nolapic		[X86-32,APIC] Do not enable or use the local APIC.
2470		nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
2472		noltlbs		[PPC] Do not use large page/tlb entries for kernel
2473				lowmem mapping on PPC40x.
2475		nomca		[IA-64] Disable machine check abort handling
2477		nomce		[X86-32] Disable Machine Check Exception
2479		nomfgpt		[X86-32] Disable Multi-Function General Purpose
2480				Timer usage (for AMD Geode machines).
2482		nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
2483				shutdown the other cpus.  Instead use the REBOOT_VECTOR
2484				irq.
2486		nomodule	Disable module load
2488		nopat		[X86] Disable PAT (page attribute table extension of
2489				pagetables) support.
2491		norandmaps	Don't use address space randomization.  Equivalent to
2492				echo 0 > /proc/sys/kernel/randomize_va_space
2494		noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
2496		noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
2497				with UP alternatives
2499		nordrand	[X86] Disable kernel use of the RDRAND and
2500				RDSEED instructions even if they are supported
2501				by the processor.  RDRAND and RDSEED are still
2502				available to user space applications.
2504		noresume	[SWSUSP] Disables resume and restores original swap
2505				space.
2507		no-scroll	[VGA] Disables scrollback.
2508				This is required for the Braillex ib80-piezo Braille
2509				reader made by F.H. Papenmeier (Germany).
2511		nosbagart	[IA-64]
2513		nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2515		nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
2516				and disable the IO APIC.  legacy for "maxcpus=0".
2518		nosoftlockup	[KNL] Disable the soft-lockup detector.
2520		nosync		[HW,M68K] Disables sync negotiation for all devices.
2522		notsc		[BUGS=X86-32] Disable Time Stamp Counter
2524		nousb		[USB] Disable the USB subsystem
2526		nowatchdog	[KNL] Disable both lockup detectors, i.e.
2527	                        soft-lockup and NMI watchdog (hard-lockup).
2529		nowb		[ARM]
2531		nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
2533		cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
2535				Some features depend on CPU0. Known dependencies are:
2536				1. Resume from suspend/hibernate depends on CPU0.
2537				Suspend/hibernate will fail if CPU0 is offline and you
2538				need to online CPU0 before suspend/hibernate.
2539				2. PIC interrupts also depend on CPU0. CPU0 can't be
2540				removed if a PIC interrupt is detected.
2541				It's said poweroff/reboot may depend on CPU0 on some
2542				machines although I haven't seen such issues so far
2543				after CPU0 is offline on a few tested machines.
2544				If the dependencies are under your control, you can
2545				turn on cpu0_hotplug.
2547		nptcg=		[IA-64] Override max number of concurrent global TLB
2548				purges which is reported from either PAL_VM_SUMMARY or
2549				SAL PALO.
2551		nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
2552				could support.  nr_cpus=n : n >= 1 limits the kernel to
2553				supporting 'n' processors. Later in runtime you can not
2554				use hotplug cpu feature to put more cpu back to online.
2555				just like you compile the kernel NR_CPUS=n
2557		nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
2559		numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
2560				Allowed values are enable and disable
2562		numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2563				one of ['zone', 'node', 'default'] can be specified
2564				This can be set from sysctl after boot.
2565				See Documentation/sysctl/vm.txt for details.
2567		ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
2568				See Documentation/debugging-via-ohci1394.txt for more
2569				info.
2571		olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2572				Rather than timing out after 20 ms if an EC
2573				command is not properly ACKed, override the length
2574				of the timeout.  We have interrupts disabled while
2575				waiting for the ACK, so if this is set too high
2576				interrupts *may* be lost!
2578		omap_mux=	[OMAP] Override bootloader pin multiplexing.
2579				Format: <mux_mode0.mode_name=value>...
2580				For example, to override I2C bus2:
2581				omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2583		oprofile.timer=	[HW]
2584				Use timer interrupt instead of performance counters
2586		oprofile.cpu_type=	Force an oprofile cpu type
2587				This might be useful if you have an older oprofile
2588				userland or if you want common events.
2589				Format: { arch_perfmon }
2590				arch_perfmon: [X86] Force use of architectural
2591					perfmon on Intel CPUs instead of the
2592					CPU specific event set.
2593				timer: [X86] Force use of architectural NMI
2594					timer mode (see also oprofile.timer
2595					for generic hr timer mode)
2596					[s390] Force legacy basic mode sampling
2597	                                (report cpu_type "timer")
2599		oops=panic	Always panic on oopses. Default is to just kill the
2600				process, but there is a small probability of
2601				deadlocking the machine.
2602				This will also cause panics on machine check exceptions.
2603				Useful together with panic=30 to trigger a reboot.
2605		OSS		[HW,OSS]
2606				See Documentation/sound/oss/oss-parameters.txt
2608		page_owner=	[KNL] Boot-time page_owner enabling option.
2609				Storage of the information about who allocated
2610				each page is disabled in default. With this switch,
2611				we can turn it on.
2612				on: enable the feature
2614		panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2615				timeout > 0: seconds before rebooting
2616				timeout = 0: wait forever
2617				timeout < 0: reboot immediately
2618				Format: <timeout>
2620		panic_on_warn	panic() instead of WARN().  Useful to cause kdump
2621				on a WARN().
2623		crash_kexec_post_notifiers
2624				Run kdump after running panic-notifiers and dumping
2625				kmsg. This only for the users who doubt kdump always
2626				succeeds in any situation.
2627				Note that this also increases risks of kdump failure,
2628				because some panic notifiers can make the crashed
2629				kernel more unstable.
2631		parkbd.port=	[HW] Parallel port number the keyboard adapter is
2632				connected to, default is 0.
2633				Format: <parport#>
2634		parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
2635				0 for XT, 1 for AT (default is AT).
2636				Format: <mode>
2638		parport=	[HW,PPT] Specify parallel ports. 0 disables.
2639				Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2640				Use 'auto' to force the driver to use any
2641				IRQ/DMA settings detected (the default is to
2642				ignore detected IRQ/DMA settings because of
2643				possible conflicts). You can specify the base
2644				address, IRQ, and DMA settings; IRQ and DMA
2645				should be numbers, or 'auto' (for using detected
2646				settings on that particular port), or 'nofifo'
2647				(to avoid using a FIFO even if it is detected).
2648				Parallel ports are assigned in the order they
2649				are specified on the command line, starting
2650				with parport0.
2652		parport_init_mode=	[HW,PPT]
2653				Configure VIA parallel port to operate in
2654				a specific mode. This is necessary on Pegasos
2655				computer where firmware has no options for setting
2656				up parallel port mode and sets it to spp.
2657				Currently this function knows 686a and 8231 chips.
2658				Format: [spp|ps2|epp|ecp|ecpepp]
2660		pause_on_oops=
2661				Halt all CPUs after the first oops has been printed for
2662				the specified number of seconds.  This is to be used if
2663				your oopses keep scrolling off the screen.
2665		pcbit=		[HW,ISDN]
2667		pcd.		[PARIDE]
2668				See header of drivers/block/paride/pcd.c.
2669				See also Documentation/blockdev/paride.txt.
2671		pci=option[,option...]	[PCI] various PCI subsystem options:
2672			earlydump	[X86] dump PCI config space before the kernel
2673				        changes anything
2674			off		[X86] don't probe for the PCI bus
2675			bios		[X86-32] force use of PCI BIOS, don't access
2676					the hardware directly. Use this if your machine
2677					has a non-standard PCI host bridge.
2678			nobios		[X86-32] disallow use of PCI BIOS, only direct
2679					hardware access methods are allowed. Use this
2680					if you experience crashes upon bootup and you
2681					suspect they are caused by the BIOS.
2682			conf1		[X86] Force use of PCI Configuration
2683					Mechanism 1.
2684			conf2		[X86] Force use of PCI Configuration
2685					Mechanism 2.
2686			noaer		[PCIE] If the PCIEAER kernel config parameter is
2687					enabled, this kernel boot option can be used to
2688					disable the use of PCIE advanced error reporting.
2689			nodomains	[PCI] Disable support for multiple PCI
2690					root domains (aka PCI segments, in ACPI-speak).
2691			nommconf	[X86] Disable use of MMCONFIG for PCI
2692					Configuration
2693			check_enable_amd_mmconf [X86] check for and enable
2694					properly configured MMIO access to PCI
2695					config space on AMD family 10h CPU
2696			nomsi		[MSI] If the PCI_MSI kernel config parameter is
2697					enabled, this kernel boot option can be used to
2698					disable the use of MSI interrupts system-wide.
2699			noioapicquirk	[APIC] Disable all boot interrupt quirks.
2700					Safety option to keep boot IRQs enabled. This
2701					should never be necessary.
2702			ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
2703					primary IO-APIC for bridges that cannot disable
2704					boot IRQs. This fixes a source of spurious IRQs
2705					when the system masks IRQs.
2706			noioapicreroute	[APIC] Disable workaround that uses the
2707					boot IRQ equivalent of an IRQ that connects to
2708					a chipset where boot IRQs cannot be disabled.
2709					The opposite of ioapicreroute.
2710			biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
2711					routing table. These calls are known to be buggy
2712					on several machines and they hang the machine
2713					when used, but on other computers it's the only
2714					way to get the interrupt routing table. Try
2715					this option if the kernel is unable to allocate
2716					IRQs or discover secondary PCI buses on your
2717					motherboard.
2718			rom		[X86] Assign address space to expansion ROMs.
2719					Use with caution as certain devices share
2720					address decoders between ROMs and other
2721					resources.
2722			norom		[X86] Do not assign address space to
2723					expansion ROMs that do not already have
2724					BIOS assigned address ranges.
2725			nobar		[X86] Do not assign address space to the
2726					BARs that weren't assigned by the BIOS.
2727			irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
2728					assigned automatically to PCI devices. You can
2729					make the kernel exclude IRQs of your ISA cards
2730					this way.
2731			pirqaddr=0xAAAAA	[X86] Specify the physical address
2732					of the PIRQ table (normally generated
2733					by the BIOS) if it is outside the
2734					F0000h-100000h range.
2735			lastbus=N	[X86] Scan all buses thru bus #N. Can be
2736					useful if the kernel is unable to find your
2737					secondary buses and you want to tell it
2738					explicitly which ones they are.
2739			assign-busses	[X86] Always assign all PCI bus
2740					numbers ourselves, overriding
2741					whatever the firmware may have done.
2742			usepirqmask	[X86] Honor the possible IRQ mask stored
2743					in the BIOS $PIR table. This is needed on
2744					some systems with broken BIOSes, notably
2745					some HP Pavilion N5400 and Omnibook XE3
2746					notebooks. This will have no effect if ACPI
2747					IRQ routing is enabled.
2748			noacpi		[X86] Do not use ACPI for IRQ routing
2749					or for PCI scanning.
2750			use_crs		[X86] Use PCI host bridge window information
2751					from ACPI.  On BIOSes from 2008 or later, this
2752					is enabled by default.  If you need to use this,
2753					please report a bug.
2754			nocrs		[X86] Ignore PCI host bridge windows from ACPI.
2755				        If you need to use this, please report a bug.
2756			routeirq	Do IRQ routing for all PCI devices.
2757					This is normally done in pci_enable_device(),
2758					so this option is a temporary workaround
2759					for broken drivers that don't call it.
2760			skip_isa_align	[X86] do not align io start addr, so can
2761					handle more pci cards
2762			firmware	[ARM] Do not re-enumerate the bus but instead
2763					just use the configuration from the
2764					bootloader. This is currently used on
2765					IXP2000 systems where the bus has to be
2766					configured a certain way for adjunct CPUs.
2767			noearly		[X86] Don't do any early type 1 scanning.
2768					This might help on some broken boards which
2769					machine check when some devices' config space
2770					is read. But various workarounds are disabled
2771					and some IOMMU drivers will not work.
2772			bfsort		Sort PCI devices into breadth-first order.
2773					This sorting is done to get a device
2774					order compatible with older (<= 2.4) kernels.
2775			nobfsort	Don't sort PCI devices into breadth-first order.
2776			pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
2777					tuning and use the BIOS-configured MPS defaults.
2778			pcie_bus_safe	Set every device's MPS to the largest value
2779					supported by all devices below the root complex.
2780			pcie_bus_perf	Set device MPS to the largest allowable MPS
2781					based on its parent bus. Also set MRRS (Max
2782					Read Request Size) to the largest supported
2783					value (no larger than the MPS that the device
2784					or bus can support) for best performance.
2785			pcie_bus_peer2peer	Set every device's MPS to 128B, which
2786					every device is guaranteed to support. This
2787					configuration allows peer-to-peer DMA between
2788					any pair of devices, possibly at the cost of
2789					reduced performance.  This also guarantees
2790					that hot-added devices will work.
2791			cbiosize=nn[KMG]	The fixed amount of bus space which is
2792					reserved for the CardBus bridge's IO window.
2793					The default value is 256 bytes.
2794			cbmemsize=nn[KMG]	The fixed amount of bus space which is
2795					reserved for the CardBus bridge's memory
2796					window. The default value is 64 megabytes.
2797			resource_alignment=
2798					Format:
2799					[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2800					Specifies alignment and device to reassign
2801					aligned memory resources.
2802					If <order of align> is not specified,
2803					PAGE_SIZE is used as alignment.
2804					PCI-PCI bridge can be specified, if resource
2805					windows need to be expanded.
2806			ecrc=		Enable/disable PCIe ECRC (transaction layer
2807					end-to-end CRC checking).
2808					bios: Use BIOS/firmware settings. This is the
2809					the default.
2810					off: Turn ECRC off
2811					on: Turn ECRC on.
2812			hpiosize=nn[KMG]	The fixed amount of bus space which is
2813					reserved for hotplug bridge's IO window.
2814					Default size is 256 bytes.
2815			hpmemsize=nn[KMG]	The fixed amount of bus space which is
2816					reserved for hotplug bridge's memory window.
2817					Default size is 2 megabytes.
2818			realloc=	Enable/disable reallocating PCI bridge resources
2819					if allocations done by BIOS are too small to
2820					accommodate resources required by all child
2821					devices.
2822					off: Turn realloc off
2823					on: Turn realloc on
2824			realloc		same as realloc=on
2825			noari		do not use PCIe ARI.
2826			pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
2827					only look for one device below a PCIe downstream
2828					port.
2830		pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
2831				Management.
2832			off	Disable ASPM.
2833			force	Enable ASPM even on devices that claim not to support it.
2834				WARNING: Forcing ASPM on may cause system lockups.
2836		pcie_hp=	[PCIE] PCI Express Hotplug driver options:
2837			nomsi	Do not use MSI for PCI Express Native Hotplug (this
2838				makes all PCIe ports use INTx for hotplug services).
2840		pcie_ports=	[PCIE] PCIe ports handling:
2841			auto	Ask the BIOS whether or not to use native PCIe services
2842				associated with PCIe ports (PME, hot-plug, AER).  Use
2843				them only if that is allowed by the BIOS.
2844			native	Use native PCIe services associated with PCIe ports
2845				unconditionally.
2846			compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2847				ports driver.
2849		pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
2850			nomsi	Do not use MSI for native PCIe PME signaling (this makes
2851				all PCIe root ports use INTx for all services).
2853		pcmv=		[HW,PCMCIA] BadgePAD 4
2855		pd_ignore_unused
2856				[PM]
2857				Keep all power-domains already enabled by bootloader on,
2858				even if no driver has claimed them. This is useful
2859				for debug and development, but should not be
2860				needed on a platform with proper driver support.
2862		pd.		[PARIDE]
2863				See Documentation/blockdev/paride.txt.
2865		pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
2866				boot time.
2867				Format: { 0 | 1 }
2868				See arch/parisc/kernel/pdc_chassis.c
2870		percpu_alloc=	Select which percpu first chunk allocator to use.
2871				Currently supported values are "embed" and "page".
2872				Archs may support subset or none of the	selections.
2873				See comments in mm/percpu.c for details on each
2874				allocator.  This parameter is primarily	for debugging
2875				and performance comparison.
2877		pf.		[PARIDE]
2878				See Documentation/blockdev/paride.txt.
2880		pg.		[PARIDE]
2881				See Documentation/blockdev/paride.txt.
2883		pirq=		[SMP,APIC] Manual mp-table setup
2884				See Documentation/x86/i386/IO-APIC.txt.
2886		plip=		[PPT,NET] Parallel port network link
2887				Format: { parport<nr> | timid | 0 }
2888				See also Documentation/parport.txt.
2890		pmtmr=		[X86] Manual setup of pmtmr I/O Port.
2891				Override pmtimer IOPort with a hex value.
2892				e.g. pmtmr=0x508
2894		pnp.debug=1	[PNP]
2895				Enable PNP debug messages (depends on the
2896				CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
2897				via /sys/module/pnp/parameters/debug.  We always show
2898				current resource usage; turning this on also shows
2899				possible settings and some assignment information.
2901		pnpacpi=	[ACPI]
2902				{ off }
2904		pnpbios=	[ISAPNP]
2905				{ on | off | curr | res | no-curr | no-res }
2907		pnp_reserve_irq=
2908				[ISAPNP] Exclude IRQs for the autoconfiguration
2910		pnp_reserve_dma=
2911				[ISAPNP] Exclude DMAs for the autoconfiguration
2913		pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
2914				Ranges are in pairs (I/O port base and size).
2916		pnp_reserve_mem=
2917				[ISAPNP] Exclude memory regions for the
2918				autoconfiguration.
2919				Ranges are in pairs (memory base and size).
2921		ports=		[IP_VS_FTP] IPVS ftp helper module
2922				Default is 21.
2923				Up to 8 (IP_VS_APP_MAX_PORTS) ports
2924				may be specified.
2925				Format: <port>,<port>....
2927		print-fatal-signals=
2928				[KNL] debug: print fatal signals
2930				If enabled, warn about various signal handling
2931				related application anomalies: too many signals,
2932				too many POSIX.1 timers, fatal signals causing a
2933				coredump - etc.
2935				If you hit the warning due to signal overflow,
2936				you might want to try "ulimit -i unlimited".
2938				default: off.
2940		printk.always_kmsg_dump=
2941				Trigger kmsg_dump for cases other than kernel oops or
2942				panics
2943				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2944				default: disabled
2946		printk.time=	Show timing data prefixed to each printk message line
2947				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2949		processor.max_cstate=	[HW,ACPI]
2950				Limit processor to maximum C-state
2951				max_cstate=9 overrides any DMI blacklist limit.
2953		processor.nocst	[HW,ACPI]
2954				Ignore the _CST method to determine C-states,
2955				instead using the legacy FADT method
2957		profile=	[KNL] Enable kernel profiling via /proc/profile
2958				Format: [schedule,]<number>
2959				Param: "schedule" - profile schedule points.
2960				Param: <number> - step/bucket size as a power of 2 for
2961					statistical time based profiling.
2962				Param: "sleep" - profile D-state sleeping (millisecs).
2963					Requires CONFIG_SCHEDSTATS
2964				Param: "kvm" - profile VM exits.
2966		prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
2967				before loading.
2968				See Documentation/blockdev/ramdisk.txt.
2970		psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
2971				probe for; one of (bare|imps|exps|lifebook|any).
2972		psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
2973				per second.
2974		psmouse.resetafter=	[HW,MOUSE]
2975				Try to reset the device after so many bad packets
2976				(0 = never).
2977		psmouse.resolution=
2978				[HW,MOUSE] Set desired mouse resolution, in dpi.
2979		psmouse.smartscroll=
2980				[HW,MOUSE] Controls Logitech smartscroll autorepeat.
2981				0 = disabled, 1 = enabled (default).
2983		pstore.backend=	Specify the name of the pstore backend to use
2985		pt.		[PARIDE]
2986				See Documentation/blockdev/paride.txt.
2988		pty.legacy_count=
2989				[KNL] Number of legacy pty's. Overwrites compiled-in
2990				default number.
2992		quiet		[KNL] Disable most log messages
2994		r128=		[HW,DRM]
2996		raid=		[HW,RAID]
2997				See Documentation/md.txt.
2999		ramdisk_blocksize=	[RAM]
3000				See Documentation/blockdev/ramdisk.txt.
3002		ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
3003				See Documentation/blockdev/ramdisk.txt.
3005		rcu_nocbs=	[KNL]
3006				In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3007				the specified list of CPUs to be no-callback CPUs.
3008				Invocation of these CPUs' RCU callbacks will
3009				be offloaded to "rcuox/N" kthreads created for
3010				that purpose, where "x" is "b" for RCU-bh, "p"
3011				for RCU-preempt, and "s" for RCU-sched, and "N"
3012				is the CPU number.  This reduces OS jitter on the
3013				offloaded CPUs, which can be useful for HPC and
3014				real-time workloads.  It can also improve energy
3015				efficiency for asymmetric multiprocessors.
3017		rcu_nocb_poll	[KNL]
3018				Rather than requiring that offloaded CPUs
3019				(specified by rcu_nocbs= above) explicitly
3020				awaken the corresponding "rcuoN" kthreads,
3021				make these kthreads poll for callbacks.
3022				This improves the real-time response for the
3023				offloaded CPUs by relieving them of the need to
3024				wake up the corresponding kthread, but degrades
3025				energy efficiency by requiring that the kthreads
3026				periodically wake up to do the polling.
3028		rcutree.blimit=	[KNL]
3029				Set maximum number of finished RCU callbacks to
3030				process in one batch.
3032		rcutree.dump_tree=	[KNL]
3033				Dump the structure of the rcu_node combining tree
3034				out at early boot.  This is used for diagnostic
3035				purposes, to verify correct tree setup.
3037		rcutree.gp_cleanup_delay=	[KNL]
3038				Set the number of jiffies to delay each step of
3039				RCU grace-period cleanup.  This only has effect
3042		rcutree.gp_init_delay=	[KNL]
3043				Set the number of jiffies to delay each step of
3044				RCU grace-period initialization.  This only has
3046				is set.
3048		rcutree.gp_preinit_delay=	[KNL]
3049				Set the number of jiffies to delay each step of
3050				RCU grace-period pre-initialization, that is,
3051				the propagation of recent CPU-hotplug changes up
3052				the rcu_node combining tree.  This only has effect
3055		rcutree.rcu_fanout_exact= [KNL]
3056				Disable autobalancing of the rcu_node combining
3057				tree.  This is used by rcutorture, and might
3058				possibly be useful for architectures having high
3059				cache-to-cache transfer latencies.
3061		rcutree.rcu_fanout_leaf= [KNL]
3062				Increase the number of CPUs assigned to each
3063				leaf rcu_node structure.  Useful for very large
3064				systems.
3066		rcutree.jiffies_till_sched_qs= [KNL]
3067				Set required age in jiffies for a
3068				given grace period before RCU starts
3069				soliciting quiescent-state help from
3070				rcu_note_context_switch().
3072		rcutree.jiffies_till_first_fqs= [KNL]
3073				Set delay from grace-period initialization to
3074				first attempt to force quiescent states.
3075				Units are jiffies, minimum value is zero,
3076				and maximum value is HZ.
3078		rcutree.jiffies_till_next_fqs= [KNL]
3079				Set delay between subsequent attempts to force
3080				quiescent states.  Units are jiffies, minimum
3081				value is one, and maximum value is HZ.
3083		rcutree.kthread_prio= 	 [KNL,BOOT]
3084				Set the SCHED_FIFO priority of the RCU per-CPU
3085				kthreads (rcuc/N). This value is also used for
3086				the priority of the RCU boost threads (rcub/N)
3087				and for the RCU grace-period kthreads (rcu_bh,
3088				rcu_preempt, and rcu_sched). If RCU_BOOST is
3089				set, valid values are 1-99 and the default is 1
3090				(the least-favored priority).  Otherwise, when
3091				RCU_BOOST is not set, valid values are 0-99 and
3092				the default is zero (non-realtime operation).
3094		rcutree.rcu_nocb_leader_stride= [KNL]
3095				Set the number of NOCB kthread groups, which
3096				defaults to the square root of the number of
3097				CPUs.  Larger numbers reduces the wakeup overhead
3098				on the per-CPU grace-period kthreads, but increases
3099				that same overhead on each group's leader.
3101		rcutree.qhimark= [KNL]
3102				Set threshold of queued RCU callbacks beyond which
3103				batch limiting is disabled.
3105		rcutree.qlowmark= [KNL]
3106				Set threshold of queued RCU callbacks below which
3107				batch limiting is re-enabled.
3109		rcutree.rcu_idle_gp_delay= [KNL]
3110				Set wakeup interval for idle CPUs that have
3111				RCU callbacks (RCU_FAST_NO_HZ=y).
3113		rcutree.rcu_idle_lazy_gp_delay= [KNL]
3114				Set wakeup interval for idle CPUs that have
3115				only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3116				Lazy RCU callbacks are those which RCU can
3117				prove do nothing more than free memory.
3119		rcutorture.cbflood_inter_holdoff= [KNL]
3120				Set holdoff time (jiffies) between successive
3121				callback-flood tests.
3123		rcutorture.cbflood_intra_holdoff= [KNL]
3124				Set holdoff time (jiffies) between successive
3125				bursts of callbacks within a given callback-flood
3126				test.
3128		rcutorture.cbflood_n_burst= [KNL]
3129				Set the number of bursts making up a given
3130				callback-flood test.  Set this to zero to
3131				disable callback-flood testing.
3133		rcutorture.cbflood_n_per_burst= [KNL]
3134				Set the number of callbacks to be registered
3135				in a given burst of a callback-flood test.
3137		rcutorture.fqs_duration= [KNL]
3138				Set duration of force_quiescent_state bursts.
3140		rcutorture.fqs_holdoff= [KNL]
3141				Set holdoff time within force_quiescent_state bursts.
3143		rcutorture.fqs_stutter= [KNL]
3144				Set wait time between force_quiescent_state bursts.
3146		rcutorture.gp_exp= [KNL]
3147				Use expedited update-side primitives.
3149		rcutorture.gp_normal= [KNL]
3150				Use normal (non-expedited) update-side primitives.
3151				If both gp_exp and gp_normal are set, do both.
3152				If neither gp_exp nor gp_normal are set, still
3153				do both.
3155		rcutorture.n_barrier_cbs= [KNL]
3156				Set callbacks/threads for rcu_barrier() testing.
3158		rcutorture.nfakewriters= [KNL]
3159				Set number of concurrent RCU writers.  These just
3160				stress RCU, they don't participate in the actual
3161				test, hence the "fake".
3163		rcutorture.nreaders= [KNL]
3164				Set number of RCU readers.  The value -1 selects
3165				N-1, where N is the number of CPUs.  A value
3166				"n" less than -1 selects N-n-2, where N is again
3167				the number of CPUs.  For example, -2 selects N
3168				(the number of CPUs), -3 selects N+1, and so on.
3170		rcutorture.object_debug= [KNL]
3171				Enable debug-object double-call_rcu() testing.
3173		rcutorture.onoff_holdoff= [KNL]
3174				Set time (s) after boot for CPU-hotplug testing.
3176		rcutorture.onoff_interval= [KNL]
3177				Set time (s) between CPU-hotplug operations, or
3178				zero to disable CPU-hotplug testing.
3180		rcutorture.torture_runnable= [BOOT]
3181				Start rcutorture running at boot time.
3183		rcutorture.shuffle_interval= [KNL]
3184				Set task-shuffle interval (s).  Shuffling tasks
3185				allows some CPUs to go into dyntick-idle mode
3186				during the rcutorture test.
3188		rcutorture.shutdown_secs= [KNL]
3189				Set time (s) after boot system shutdown.  This
3190				is useful for hands-off automated testing.
3192		rcutorture.stall_cpu= [KNL]
3193				Duration of CPU stall (s) to test RCU CPU stall
3194				warnings, zero to disable.
3196		rcutorture.stall_cpu_holdoff= [KNL]
3197				Time to wait (s) after boot before inducing stall.
3199		rcutorture.stat_interval= [KNL]
3200				Time (s) between statistics printk()s.
3202		rcutorture.stutter= [KNL]
3203				Time (s) to stutter testing, for example, specifying
3204				five seconds causes the test to run for five seconds,
3205				wait for five seconds, and so on.  This tests RCU's
3206				ability to transition abruptly to and from idle.
3208		rcutorture.test_boost= [KNL]
3209				Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
3210				"Maybe" means test if the RCU implementation
3211				under test support RCU priority boosting.
3213		rcutorture.test_boost_duration= [KNL]
3214				Duration (s) of each individual boost test.
3216		rcutorture.test_boost_interval= [KNL]
3217				Interval (s) between each boost test.
3219		rcutorture.test_no_idle_hz= [KNL]
3220				Test RCU's dyntick-idle handling.  See also the
3221				rcutorture.shuffle_interval parameter.
3223		rcutorture.torture_type= [KNL]
3224				Specify the RCU implementation to test.
3226		rcutorture.verbose= [KNL]
3227				Enable additional printk() statements.
3229		rcupdate.rcu_expedited= [KNL]
3230				Use expedited grace-period primitives, for
3231				example, synchronize_rcu_expedited() instead
3232				of synchronize_rcu().  This reduces latency,
3233				but can increase CPU utilization, degrade
3234				real-time latency, and degrade energy efficiency.
3236		rcupdate.rcu_cpu_stall_suppress= [KNL]
3237				Suppress RCU CPU stall warning messages.
3239		rcupdate.rcu_cpu_stall_timeout= [KNL]
3240				Set timeout for RCU CPU stall warning messages.
3242		rcupdate.rcu_task_stall_timeout= [KNL]
3243				Set timeout in jiffies for RCU task stall warning
3244				messages.  Disable with a value less than or equal
3245				to zero.
3247		rcupdate.rcu_self_test= [KNL]
3248				Run the RCU early boot self tests
3250		rcupdate.rcu_self_test_bh= [KNL]
3251				Run the RCU bh early boot self tests
3253		rcupdate.rcu_self_test_sched= [KNL]
3254				Run the RCU sched early boot self tests
3256		rdinit=		[KNL]
3257				Format: <full_path>
3258				Run specified binary instead of /init from the ramdisk,
3259				used for early userspace startup. See initrd.
3261		reboot=		[KNL]
3262				Format (x86 or x86_64):
3263					[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3264					[[,]s[mp]#### \
3265					[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3266					[[,]f[orce]
3267				Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3268				      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3269				      reboot_force is either force or not specified,
3270				      reboot_cpu is s[mp]#### with #### being the processor
3271						to be used for rebooting.
3273		relax_domain_level=
3274				[KNL, SMP] Set scheduler's default relax_domain_level.
3275				See Documentation/cgroups/cpusets.txt.
3277		relative_sleep_states=
3278				[SUSPEND] Use sleep state labeling where the deepest
3279				state available other than hibernation is always "mem".
3280				Format: { "0" | "1" }
3281				0 -- Traditional sleep state labels.
3282				1 -- Relative sleep state labels.
3284		reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
3286		reservetop=	[X86-32]
3287				Format: nn[KMG]
3288				Reserves a hole at the top of the kernel virtual
3289				address space.
3291		reservelow=	[X86]
3292				Format: nn[K]
3293				Set the amount of memory to reserve for BIOS at
3294				the bottom of the address space.
3296		reset_devices	[KNL] Force drivers to reset the underlying device
3297				during initialization.
3299		resume=		[SWSUSP]
3300				Specify the partition device for software suspend
3301				Format:
3302				{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3304		resume_offset=	[SWSUSP]
3305				Specify the offset from the beginning of the partition
3306				given by "resume=" at which the swap header is located,
3307				in <PAGE_SIZE> units (needed only for swap files).
3308				See  Documentation/power/swsusp-and-swap-files.txt
3310		resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
3311				read the resume files
3313		resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
3314				Useful for devices that are detected asynchronously
3315				(e.g. USB and MMC devices).
3317		hibernate=	[HIBERNATION]
3318			noresume	Don't check if there's a hibernation image
3319					present during boot.
3320			nocompress	Don't compress/decompress hibernation images.
3321			no		Disable hibernation and resume.
3323		retain_initrd	[RAM] Keep initrd memory after extraction
3325		rfkill.default_state=
3326			0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
3327				etc. communication is blocked by default.
3328			1	Unblocked.
3330		rfkill.master_switch_mode=
3331			0	The "airplane mode" button does nothing.
3332			1	The "airplane mode" button toggles between everything
3333				blocked and the previous configuration.
3334			2	The "airplane mode" button toggles between everything
3335				blocked and everything unblocked.
3337		rhash_entries=	[KNL,NET]
3338				Set number of hash buckets for route cache
3340		ro		[KNL] Mount root device read-only on boot
3342		root=		[KNL] Root filesystem
3343				See name_to_dev_t comment in init/do_mounts.c.
3345		rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
3346				mount the root filesystem
3348		rootflags=	[KNL] Set root filesystem mount option string
3350		rootfstype=	[KNL] Set root filesystem type
3352		rootwait	[KNL] Wait (indefinitely) for root device to show up.
3353				Useful for devices that are detected asynchronously
3354				(e.g. USB and MMC devices).
3356		rproc_mem=nn[KMG][@address]
3357				[KNL,ARM,CMA] Remoteproc physical memory block.
3358				Memory area to be used by remote processor image,
3359				managed by CMA.
3361		rw		[KNL] Mount root device read-write on boot
3363		S		[KNL] Run init in single mode
3365		s390_iommu=	[HW,S390]
3366				Set s390 IOTLB flushing mode
3367			strict
3368				With strict flushing every unmap operation will result in
3369				an IOTLB flush. Default is lazy flushing before reuse,
3370				which is faster.
3372		sa1100ir	[NET]
3373				See drivers/net/irda/sa1100_ir.c.
3375		sbni=		[NET] Granch SBNI12 leased line adapter
3377		sched_debug	[KNL] Enables verbose scheduler debug messages.
3379		skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
3380				xtime_lock contention on larger systems, and/or RCU lock
3381				contention on all systems with CONFIG_MAXSMP set.
3382				Format: { "0" | "1" }
3383				0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3384				1 -- enable.
3385				Note: increases power consumption, thus should only be
3386				enabled if running jitter sensitive (HPC/RT) workloads.
3388		security=	[SECURITY] Choose a security module to enable at boot.
3389				If this boot parameter is not specified, only the first
3390				security module asking for security registration will be
3391				loaded. An invalid security module name will be treated
3392				as if no module has been chosen.
3394		selinux=	[SELINUX] Disable or enable SELinux at boot time.
3395				Format: { "0" | "1" }
3396				See security/selinux/Kconfig help text.
3397				0 -- disable.
3398				1 -- enable.
3399				Default value is set via kernel config option.
3400				If enabled at boot time, /selinux/disable can be used
3401				later to disable prior to initial policy load.
3403		apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
3404				Format: { "0" | "1" }
3405				See security/apparmor/Kconfig help text
3406				0 -- disable.
3407				1 -- enable.
3408				Default value is set via kernel config option.
3410		serialnumber	[BUGS=X86-32]
3412		shapers=	[NET]
3413				Maximal number of shapers.
3415		show_msr=	[x86] show boot-time MSR settings
3416				Format: { <integer> }
3417				Show boot-time (BIOS-initialized) MSR settings.
3418				The parameter means the number of CPUs to show,
3419				for example 1 means boot CPU only.
3421		simeth=		[IA-64]
3422		simscsi=
3424		slram=		[HW,MTD]
3426		slab_nomerge	[MM]
3427				Disable merging of slabs with similar size. May be
3428				necessary if there is some reason to distinguish
3429				allocs to different slabs. Debug options disable
3430				merging on their own.
3431				For more information see Documentation/vm/slub.txt.
3433		slab_max_order=	[MM, SLAB]
3434				Determines the maximum allowed order for slabs.
3435				A high setting may cause OOMs due to memory
3436				fragmentation.  Defaults to 1 for systems with
3437				more than 32MB of RAM, 0 otherwise.
3439		slub_debug[=options[,slabs]]	[MM, SLUB]
3440				Enabling slub_debug allows one to determine the
3441				culprit if slab objects become corrupted. Enabling
3442				slub_debug can create guard zones around objects and
3443				may poison objects when not in use. Also tracks the
3444				last alloc / free. For more information see
3445				Documentation/vm/slub.txt.
3447		slub_max_order= [MM, SLUB]
3448				Determines the maximum allowed order for slabs.
3449				A high setting may cause OOMs due to memory
3450				fragmentation. For more information see
3451				Documentation/vm/slub.txt.
3453		slub_min_objects=	[MM, SLUB]
3454				The minimum number of objects per slab. SLUB will
3455				increase the slab order up to slub_max_order to
3456				generate a sufficiently large slab able to contain
3457				the number of objects indicated. The higher the number
3458				of objects the smaller the overhead of tracking slabs
3459				and the less frequently locks need to be acquired.
3460				For more information see Documentation/vm/slub.txt.
3462		slub_min_order=	[MM, SLUB]
3463				Determines the minimum page order for slabs. Must be
3464				lower than slub_max_order.
3465				For more information see Documentation/vm/slub.txt.
3467		slub_nomerge	[MM, SLUB]
3468				Same with slab_nomerge. This is supported for legacy.
3469				See slab_nomerge for more information.
3471		smart2=		[HW]
3472				Format: <io1>[,<io2>[,...,<io8>]]
3474		smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
3475		smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
3476		smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
3477		smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
3478		smsc-ircc2.ircc_irq=	[HW] IRQ line
3479		smsc-ircc2.ircc_dma=	[HW] DMA channel
3480		smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3481					0: Toshiba Satellite 1800 (GP data pin select)
3482					1: Fast pin select (default)
3483					2: ATC IRMode
3485		softlockup_panic=
3486				[KNL] Should the soft-lockup detector generate panics.
3487				Format: <integer>
3489		softlockup_all_cpu_backtrace=
3490				[KNL] Should the soft-lockup detector generate
3491				backtraces on all cpus.
3492				Format: <integer>
3494		sonypi.*=	[HW] Sony Programmable I/O Control Device driver
3495				See Documentation/laptops/sonypi.txt
3497		spia_io_base=	[HW,MTD]
3498		spia_fio_base=
3499		spia_pedr=
3500		spia_peddr=
3502		stacktrace	[FTRACE]
3503				Enabled the stack tracer on boot up.
3505		stacktrace_filter=[function-list]
3506				[FTRACE] Limit the functions that the stack tracer
3507				will trace at boot up. function-list is a comma separated
3508				list of functions. This list can be changed at run
3509				time by the stack_trace_filter file in the debugfs
3510				tracing directory. Note, this enables stack tracing
3511				and the stacktrace above is not needed.
3513		sti=		[PARISC,HW]
3514				Format: <num>
3515				Set the STI (builtin display/keyboard on the HP-PARISC
3516				machines) console (graphic card) which should be used
3517				as the initial boot-console.
3518				See also comment in drivers/video/console/sticore.c.
3520		sti_font=	[HW]
3521				See comment in drivers/video/console/sticore.c.
3523		stifb=		[HW]
3524				Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3526		sunrpc.min_resvport=
3527		sunrpc.max_resvport=
3528				[NFS,SUNRPC]
3529				SunRPC servers often require that client requests
3530				originate from a privileged port (i.e. a port in the
3531				range 0 < portnr < 1024).
3532				An administrator who wishes to reserve some of these
3533				ports for other uses may adjust the range that the
3534				kernel's sunrpc client considers to be privileged
3535				using these two parameters to set the minimum and
3536				maximum port values.
3538		sunrpc.pool_mode=
3539				[NFS]
3540				Control how the NFS server code allocates CPUs to
3541				service thread pools.  Depending on how many NICs
3542				you have and where their interrupts are bound, this
3543				option will affect which CPUs will do NFS serving.
3544				Note: this parameter cannot be changed while the
3545				NFS server is running.
3547				auto	    the server chooses an appropriate mode
3548					    automatically using heuristics
3549				global	    a single global pool contains all CPUs
3550				percpu	    one pool for each CPU
3551				pernode	    one pool for each NUMA node (equivalent
3552					    to global on non-NUMA machines)
3554		sunrpc.tcp_slot_table_entries=
3555		sunrpc.udp_slot_table_entries=
3556				[NFS,SUNRPC]
3557				Sets the upper limit on the number of simultaneous
3558				RPC calls that can be sent from the client to a
3559				server. Increasing these values may allow you to
3560				improve throughput, but will also increase the
3561				amount of memory reserved for use by the client.
3563		suspend.pm_test_delay=
3564				[SUSPEND]
3565				Sets the number of seconds to remain in a suspend test
3566				mode before resuming the system (see
3567				/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3568				is set. Default value is 5.
3570		swapaccount=[0|1]
3571				[KNL] Enable accounting of swap in memory resource
3572				controller if no parameter or 1 is given or disable
3573				it if 0 is given (See Documentation/cgroups/memory.txt)
3575		swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
3576				Format: { <int> | force }
3577				<int> -- Number of I/O TLB slabs
3578				force -- force using of bounce buffers even if they
3579				         wouldn't be automatically used by the kernel
3581		switches=	[HW,M68k]
3583		sysfs.deprecated=0|1 [KNL]
3584				Enable/disable old style sysfs layout for old udev
3585				on older distributions. When this option is enabled
3586				very new udev will not work anymore. When this option
3587				is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3588				in older udev will not work anymore.
3589				Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3590				the kernel configuration.
3592		sysrq_always_enabled
3593				[KNL]
3594				Ignore sysrq setting - this boot parameter will
3595				neutralize any effect of /proc/sys/kernel/sysrq.
3596				Useful for debugging.
3598		tcpmhash_entries= [KNL,NET]
3599				Set the number of tcp_metrics_hash slots.
3600				Default value is 8192 or 16384 depending on total
3601				ram pages. This is used to specify the TCP metrics
3602				cache size. See Documentation/networking/ip-sysctl.txt
3603				"tcp_no_metrics_save" section for more details.
3605		tdfx=		[HW,DRM]
3607		test_suspend=	[SUSPEND][,N]
3608				Specify "mem" (for Suspend-to-RAM) or "standby" (for
3609				standby suspend) or "freeze" (for suspend type freeze)
3610				as the system sleep state during system startup with
3611				the optional capability to repeat N number of times.
3612				The system is woken from this state using a
3613				wakeup-capable RTC alarm.
3615		thash_entries=	[KNL,NET]
3616				Set number of hash buckets for TCP connection
3618		thermal.act=	[HW,ACPI]
3619				-1: disable all active trip points in all thermal zones
3620				<degrees C>: override all lowest active trip points
3622		thermal.crt=	[HW,ACPI]
3623				-1: disable all critical trip points in all thermal zones
3624				<degrees C>: override all critical trip points
3626		thermal.nocrt=	[HW,ACPI]
3627				Set to disable actions on ACPI thermal zone
3628				critical and hot trip points.
3630		thermal.off=	[HW,ACPI]
3631				1: disable ACPI thermal control
3633		thermal.psv=	[HW,ACPI]
3634				-1: disable all passive trip points
3635				<degrees C>: override all passive trip points to this
3636				value
3638		thermal.tzp=	[HW,ACPI]
3639				Specify global default ACPI thermal zone polling rate
3640				<deci-seconds>: poll all this frequency
3641				0: no polling (default)
3643		threadirqs	[KNL]
3644				Force threading of all interrupt handlers except those
3645				marked explicitly IRQF_NO_THREAD.
3647		tmem		[KNL,XEN]
3648				Enable the Transcendent memory driver if built-in.
3650		tmem.cleancache=0|1 [KNL, XEN]
3651				Default is on (1). Disable the usage of the cleancache
3652				API to send anonymous pages to the hypervisor.
3654		tmem.frontswap=0|1 [KNL, XEN]
3655				Default is on (1). Disable the usage of the frontswap
3656				API to send swap pages to the hypervisor. If disabled
3657				the selfballooning and selfshrinking are force disabled.
3659		tmem.selfballooning=0|1 [KNL, XEN]
3660				Default is on (1). Disable the driving of swap pages
3661				to the hypervisor.
3663		tmem.selfshrinking=0|1 [KNL, XEN]
3664				Default is on (1). Partial swapoff that immediately
3665				transfers pages from Xen hypervisor back to the
3666				kernel based on different criteria.
3668		topology=	[S390]
3669				Format: {off | on}
3670				Specify if the kernel should make use of the cpu
3671				topology information if the hardware supports this.
3672				The scheduler will make use of this information and
3673				e.g. base its process migration decisions on it.
3674				Default is on.
3676		topology_updates= [KNL, PPC, NUMA]
3677				Format: {off}
3678				Specify if the kernel should ignore (off)
3679				topology updates sent by the hypervisor to this
3680				LPAR.
3682		tp720=		[HW,PS2]
3684		tpm_suspend_pcr=[HW,TPM]
3685				Format: integer pcr id
3686				Specify that at suspend time, the tpm driver
3687				should extend the specified pcr with zeros,
3688				as a workaround for some chips which fail to
3689				flush the last written pcr on TPM_SaveState.
3690				This will guarantee that all the other pcrs
3691				are saved.
3693		trace_buf_size=nn[KMG]
3694				[FTRACE] will set tracing buffer size on each cpu.
3696		trace_event=[event-list]
3697				[FTRACE] Set and start specified trace events in order
3698				to facilitate early boot debugging.
3699				See also Documentation/trace/events.txt
3701		trace_options=[option-list]
3702				[FTRACE] Enable or disable tracer options at boot.
3703				The option-list is a comma delimited list of options
3704				that can be enabled or disabled just as if you were
3705				to echo the option name into
3707				    /sys/kernel/debug/tracing/trace_options
3709				For example, to enable stacktrace option (to dump the
3710				stack trace of each event), add to the command line:
3712				      trace_options=stacktrace
3714				See also Documentation/trace/ftrace.txt "trace options"
3715				section.
3717		tp_printk[FTRACE]
3718				Have the tracepoints sent to printk as well as the
3719				tracing ring buffer. This is useful for early boot up
3720				where the system hangs or reboots and does not give the
3721				option for reading the tracing buffer or performing a
3722				ftrace_dump_on_oops.
3724				To turn off having tracepoints sent to printk,
3725				 echo 0 > /proc/sys/kernel/tracepoint_printk
3726				Note, echoing 1 into this file without the
3727				tracepoint_printk kernel cmdline option has no effect.
3729				** CAUTION **
3731				Having tracepoints sent to printk() and activating high
3732				frequency tracepoints such as irq or sched, can cause
3733				the system to live lock.
3735		traceoff_on_warning
3736				[FTRACE] enable this option to disable tracing when a
3737				warning is hit. This turns off "tracing_on". Tracing can
3738				be enabled again by echoing '1' into the "tracing_on"
3739				file located in /sys/kernel/debug/tracing/
3741				This option is useful, as it disables the trace before
3742				the WARNING dump is called, which prevents the trace to
3743				be filled with content caused by the warning output.
3745				This option can also be set at run time via the sysctl
3746				option:  kernel/traceoff_on_warning
3748		transparent_hugepage=
3749				[KNL]
3750				Format: [always|madvise|never]
3751				Can be used to control the default behavior of the system
3752				with respect to transparent hugepages.
3753				See Documentation/vm/transhuge.txt for more details.
3755		tsc=		Disable clocksource stability checks for TSC.
3756				Format: <string>
3757				[x86] reliable: mark tsc clocksource as reliable, this
3758				disables clocksource verification at runtime, as well
3759				as the stability checks done at bootup.	Used to enable
3760				high-resolution timer mode on older hardware, and in
3761				virtualized environment.
3762				[x86] noirqtime: Do not use TSC to do irq accounting.
3763				Used to run time disable IRQ_TIME_ACCOUNTING on any
3764				platforms where RDTSC is slow and this accounting
3765				can add overhead.
3767		turbografx.map[2|3]=	[HW,JOY]
3768				TurboGraFX parallel port interface
3769				Format:
3770				<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3771				See also Documentation/input/joystick-parport.txt
3773		udbg-immortal	[PPC] When debugging early kernel crashes that
3774				happen after console_init() and before a proper 
3775				console driver takes over, this boot options might
3776				help "seeing" what's going on.
3778		uhash_entries=	[KNL,NET]
3779				Set number of hash buckets for UDP/UDP-Lite connections
3781		uhci-hcd.ignore_oc=
3782				[USB] Ignore overcurrent events (default N).
3783				Some badly-designed motherboards generate lots of
3784				bogus events, for ports that aren't wired to
3785				anything.  Set this parameter to avoid log spamming.
3786				Note that genuine overcurrent events won't be
3787				reported either.
3789		unknown_nmi_panic
3790				[X86] Cause panic on unknown NMI.
3792		usbcore.authorized_default=
3793				[USB] Default USB device authorization:
3794				(default -1 = authorized except for wireless USB,
3795				0 = not authorized, 1 = authorized)
3797		usbcore.autosuspend=
3798				[USB] The autosuspend time delay (in seconds) used
3799				for newly-detected USB devices (default 2).  This
3800				is the time required before an idle device will be
3801				autosuspended.  Devices for which the delay is set
3802				to a negative value won't be autosuspended at all.
3804		usbcore.usbfs_snoop=
3805				[USB] Set to log all usbfs traffic (default 0 = off).
3807		usbcore.blinkenlights=
3808				[USB] Set to cycle leds on hubs (default 0 = off).
3810		usbcore.old_scheme_first=
3811				[USB] Start with the old device initialization
3812				scheme (default 0 = off).
3814		usbcore.usbfs_memory_mb=
3815				[USB] Memory limit (in MB) for buffers allocated by
3816				usbfs (default = 16, 0 = max = 2047).
3818		usbcore.use_both_schemes=
3819				[USB] Try the other device initialization scheme
3820				if the first one fails (default 1 = enabled).
3822		usbcore.initial_descriptor_timeout=
3823				[USB] Specifies timeout for the initial 64-byte
3824	                        USB_REQ_GET_DESCRIPTOR request in milliseconds
3825				(default 5000 = 5.0 seconds).
3827		usbhid.mousepoll=
3828				[USBHID] The interval which mice are to be polled at.
3830		usb-storage.delay_use=
3831				[UMS] The delay in seconds before a new device is
3832				scanned for Logical Units (default 1).
3834		usb-storage.quirks=
3835				[UMS] A list of quirks entries to supplement or
3836				override the built-in unusual_devs list.  List
3837				entries are separated by commas.  Each entry has
3838				the form VID:PID:Flags where VID and PID are Vendor
3839				and Product ID values (4-digit hex numbers) and
3840				Flags is a set of characters, each corresponding
3841				to a common usb-storage quirk flag as follows:
3842					a = SANE_SENSE (collect more than 18 bytes
3843						of sense data);
3844					b = BAD_SENSE (don't collect more than 18
3845						bytes of sense data);
3846					c = FIX_CAPACITY (decrease the reported
3847						device capacity by one sector);
3848					d = NO_READ_DISC_INFO (don't use
3849						READ_DISC_INFO command);
3850					e = NO_READ_CAPACITY_16 (don't use
3851						READ_CAPACITY_16 command);
3852					f = NO_REPORT_OPCODES (don't use report opcodes
3853						command, uas only);
3854					g = MAX_SECTORS_240 (don't transfer more than
3855						240 sectors at a time, uas only);
3856					h = CAPACITY_HEURISTICS (decrease the
3857						reported device capacity by one
3858						sector if the number is odd);
3859					i = IGNORE_DEVICE (don't bind to this
3860						device);
3861					l = NOT_LOCKABLE (don't try to lock and
3862						unlock ejectable media);
3863					m = MAX_SECTORS_64 (don't transfer more
3864						than 64 sectors = 32 KB at a time);
3865					n = INITIAL_READ10 (force a retry of the
3866						initial READ(10) command);
3867					o = CAPACITY_OK (accept the capacity
3868						reported by the device);
3869					p = WRITE_CACHE (the device cache is ON
3870						by default);
3871					r = IGNORE_RESIDUE (the device reports
3872						bogus residue values);
3873					s = SINGLE_LUN (the device has only one
3874						Logical Unit);
3875					t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3876						commands, uas only);
3877					u = IGNORE_UAS (don't bind to the uas driver);
3878					w = NO_WP_DETECT (don't test whether the
3879						medium is write-protected).
3880				Example: quirks=0419:aaf5:rl,0421:0433:rc
3882		user_debug=	[KNL,ARM]
3883				Format: <int>
3884				See arch/arm/Kconfig.debug help text.
3885					 1 - undefined instruction events
3886					 2 - system calls
3887					 4 - invalid data aborts
3888					 8 - SIGSEGV faults
3889					16 - SIGBUS faults
3890				Example: user_debug=31
3892		userpte=
3893				[X86] Flags controlling user PTE allocations.
3895					nohigh = do not allocate PTE pages in
3896						HIGHMEM regardless of setting
3897						of CONFIG_HIGHPTE.
3899		vdso=		[X86,SH]
3900				On X86_32, this is an alias for vdso32=.  Otherwise:
3902				vdso=1: enable VDSO (the default)
3903				vdso=0: disable VDSO mapping
3905		vdso32=		[X86] Control the 32-bit vDSO
3906				vdso32=1: enable 32-bit VDSO
3907				vdso32=0 or vdso32=2: disable 32-bit VDSO
3909				See the help text for CONFIG_COMPAT_VDSO for more
3910				details.  If CONFIG_COMPAT_VDSO is set, the default is
3911				vdso32=0; otherwise, the default is vdso32=1.
3913				For compatibility with older kernels, vdso32=2 is an
3914				alias for vdso32=0.
3916				Try vdso32=0 if you encounter an error that says:
3917				dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3919		vector=		[IA-64,SMP]
3920				vector=percpu: enable percpu vector domain
3922		video=		[FB] Frame buffer configuration
3923				See Documentation/fb/modedb.txt.
3925		video.brightness_switch_enabled= [0,1]
3926				If set to 1, on receiving an ACPI notify event
3927				generated by hotkey, video driver will adjust brightness
3928				level and then send out the event to user space through
3929				the allocated input device; If set to 0, video driver
3930				will only send out the event without touching backlight
3931				brightness level.
3932				default: 1
3934		virtio_mmio.device=
3935				[VMMIO] Memory mapped virtio (platform) device.
3937					<size>@<baseaddr>:<irq>[:<id>]
3938				where:
3939					<size>     := size (can use standard suffixes
3940							like K, M and G)
3941					<baseaddr> := physical base address
3942					<irq>      := interrupt number (as passed to
3943							request_irq())
3944					<id>       := (optional) platform device id
3945				example:
3946					virtio_mmio.device=1K@0x100b0000:48:7
3948				Can be used multiple times for multiple devices.
3950		vga=		[BOOT,X86-32] Select a particular video mode
3951				See Documentation/x86/boot.txt and
3952				Documentation/svga.txt.
3953				Use vga=ask for menu.
3954				This is actually a boot loader parameter; the value is
3955				passed to the kernel using a special protocol.
3957		vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
3958				size of <nn>. This can be used to increase the
3959				minimum size (128MB on x86). It can also be used to
3960				decrease the size and leave more room for directly
3961				mapped kernel RAM.
3963		vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
3964				Format: <command>
3966		vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
3967				Format: <command>
3969		vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
3970				Format: <command>
3972		vsyscall=	[X86-64]
3973				Controls the behavior of vsyscalls (i.e. calls to
3974				fixed addresses of 0xffffffffff600x00 from legacy
3975				code).  Most statically-linked binaries and older
3976				versions of glibc use these calls.  Because these
3977				functions are at fixed addresses, they make nice
3978				targets for exploits that can control RIP.
3980				emulate     [default] Vsyscalls turn into traps and are
3981				            emulated reasonably safely.
3983				native      Vsyscalls are native syscall instructions.
3984				            This is a little bit faster than trapping
3985				            and makes a few dynamic recompilers work
3986				            better than they would in emulation mode.
3987				            It also makes exploits much easier to write.
3989				none        Vsyscalls don't work at all.  This makes
3990				            them quite hard to use for exploits but
3991				            might break your system.
3993		vt.color=	[VT] Default text color.
3994				Format: 0xYX, X = foreground, Y = background.
3995				Default: 0x07 = light gray on black.
3997		vt.cur_default=	[VT] Default cursor shape.
3998				Format: 0xCCBBAA, where AA, BB, and CC are the same as
3999				the parameters of the <Esc>[?A;B;Cc escape sequence;
4000				see VGA-softcursor.txt. Default: 2 = underline.
4002		vt.default_blu=	[VT]
4003				Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4004				Change the default blue palette of the console.
4005				This is a 16-member array composed of values
4006				ranging from 0-255.
4008		vt.default_grn=	[VT]
4009				Format: <green0>,<green1>,<green2>,...,<green15>
4010				Change the default green palette of the console.
4011				This is a 16-member array composed of values
4012				ranging from 0-255.
4014		vt.default_red=	[VT]
4015				Format: <red0>,<red1>,<red2>,...,<red15>
4016				Change the default red palette of the console.
4017				This is a 16-member array composed of values
4018				ranging from 0-255.
4020		vt.default_utf8=
4021				[VT]
4022				Format=<0|1>
4023				Set system-wide default UTF-8 mode for all tty's.
4024				Default is 1, i.e. UTF-8 mode is enabled for all
4025				newly opened terminals.
4027		vt.global_cursor_default=
4028				[VT]
4029				Format=<-1|0|1>
4030				Set system-wide default for whether a cursor
4031				is shown on new VTs. Default is -1,
4032				i.e. cursors will be created by default unless
4033				overridden by individual drivers. 0 will hide
4034				cursors, 1 will display them.
4036		vt.italic=	[VT] Default color for italic text; 0-15.
4037				Default: 2 = green.
4039		vt.underline=	[VT] Default color for underlined text; 0-15.
4040				Default: 3 = cyan.
4042		watchdog timers	[HW,WDT] For information on watchdog timers,
4043				see Documentation/watchdog/watchdog-parameters.txt
4044				or other driver-specific files in the
4045				Documentation/watchdog/ directory.
4047		workqueue.disable_numa
4048				By default, all work items queued to unbound
4049				workqueues are affine to the NUMA nodes they're
4050				issued on, which results in better behavior in
4051				general.  If NUMA affinity needs to be disabled for
4052				whatever reason, this option can be used.  Note
4053				that this also can be controlled per-workqueue for
4054				workqueues visible under /sys/bus/workqueue/.
4056		workqueue.power_efficient
4057				Per-cpu workqueues are generally preferred because
4058				they show better performance thanks to cache
4059				locality; unfortunately, per-cpu workqueues tend to
4060				be more power hungry than unbound workqueues.
4062				Enabling this makes the per-cpu workqueues which
4063				were observed to contribute significantly to power
4064				consumption unbound, leading to measurably lower
4065				power usage at the cost of small performance
4066				overhead.
4068				The default value of this parameter is determined by
4069				the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4071		x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
4072				default x2apic cluster mode on platforms
4073				supporting x2apic.
4075		x86_intel_mid_timer= [X86-32,APBT]
4076				Choose timer option for x86 Intel MID platform.
4077				Two valid options are apbt timer only and lapic timer
4078				plus one apbt timer for broadcast timer.
4079				x86_intel_mid_timer=apbt_only | lapic_and_apbt
4081		xen_emul_unplug=		[HW,X86,XEN]
4082				Unplug Xen emulated devices
4083				Format: [unplug0,][unplug1]
4084				ide-disks -- unplug primary master IDE devices
4085				aux-ide-disks -- unplug non-primary-master IDE devices
4086				nics -- unplug network devices
4087				all -- unplug all emulated devices (NICs and IDE disks)
4088				unnecessary -- unplugging emulated devices is
4089					unnecessary even if the host did not respond to
4090					the unplug protocol
4091				never -- do not unplug even if version check succeeds
4093		xen_nopvspin	[X86,XEN]
4094				Disables the ticketlock slowpath using Xen PV
4095				optimizations.
4097		xen_nopv	[X86]
4098				Disables the PV optimizations forcing the HVM guest to
4099				run as generic HVM guest with no PV drivers.
4101		xirc2ps_cs=	[NET,PCMCIA]
4102				Format:
4103				<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4105	______________________________________________________________________
4107	TODO:
4109		Add more DRM drivers.
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