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Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -07003
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
Randy Dunlapca1eda22009-05-06 16:02:58 -070020Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22can also be entered as
23 log-buf-len=1M print_fatal_signals=1
24
25
Stefan Richtera901ebb2006-04-01 01:43:18 +020026This document may not be entirely up to date and comprehensive. The command
27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28module. Loadable modules, after being loaded into the running kernel, also
29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30parameters may be changed at runtime by the command
31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32
Stefan Richter6585fa82006-04-01 01:44:30 +020033The parameters listed below are only valid if certain kernel build options were
34enabled and if respective hardware is present. The text in square brackets at
35the beginning of each description states the restrictions within which a
36parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070037
38 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100039 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070040 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020043 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070044 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080045 BLACKFIN Blackfin architecture is enabled.
Alan Cox9cfe2682011-01-25 14:18:38 +000046 DRM Direct Rendering Management support is enabled.
47 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070048 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49 EFI EFI Partitioning (GPT) is enabled
50 EIDE EIDE/ATAPI support is enabled.
51 FB The frame buffer device is enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070052 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070054 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050055 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070056 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070057 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080058 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050062 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020063 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070064 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070073 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070074 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070075 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070079 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070081 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070083 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -070092 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -070094 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070095 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -070096 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +090098 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
Steven Rostedtf38f1d22008-12-16 23:06:40 -0500103 FTRACE Function tracing enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300104 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500106 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700114 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700117 Documentation/x86/x86_64/boot-options.txt .
Andi Kleenc0115602008-08-22 09:53:39 +0200118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100119 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120
121In addition, the following text indicates that the option:
122
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
126
127Parameters denoted with BOOT are actually interpreted by the boot
128loader, and have no meaning to the kernel directly.
129Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500130need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131
Karsten Weiss55588702007-02-13 13:26:21 +0100132There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700133See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100134
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136a trailing = on the name of any parameter states that that parameter will
137be entered as an environment variable, whereas its absence indicates that
138it will appear as a kernel argument readable via /proc/cmdline by programs
139running once the system is up.
140
jens m. noedler9c4751f2006-09-29 02:00:27 -0700141The number of kernel parameters is not limited, but the length of the
142complete command line (parameters including spaces etc.) is limited to
143a fixed number of characters. This limit depends on the architecture
144and is between 256 and 4096 characters. It is defined in the file
145./include/asm/setup.h as COMMAND_LINE_SIZE.
146
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800147Finally, the [KMG] suffix is commonly described after a number of kernel
148parameter values. These 'K', 'M', and 'G' letters represent the _binary_
149multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
150bytes respectively. Such letter suffixes can also be entirely omitted.
151
jens m. noedler9c4751f2006-09-29 02:00:27 -0700152
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530153 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800154 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500155 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 force -- enable ACPI if default was off
157 off -- disable ACPI if default was on
158 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700159 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800161 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800162 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163
Randy Dunlap53471122008-03-12 18:10:51 -0400164 See also Documentation/power/pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165
Takao Indoh4996c022011-07-14 18:05:21 -0400166 acpi_rsdp= [ACPI,EFI,KEXEC]
167 Pass the RSDP address to the kernel, mostly used
168 on machines running EFI runtime service to boot the
169 second kernel for kdump.
170
Len Browna1fdcc02007-03-11 03:26:14 -0400171 acpi_apic_instance= [ACPI, IOAPIC]
172 Format: <int>
173 2: use 2nd APIC table, if available
174 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400175 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400176
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200177 acpi_backlight= [HW,ACPI]
178 acpi_backlight=vendor
179 acpi_backlight=video
180 If set to vendor, prefer vendor specific driver
181 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
182 of the ACPI video.ko driver.
183
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700184 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
185 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700187 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
188 debug output. Bits in debug_layer correspond to a
189 _COMPONENT in an ACPI source file, e.g.,
190 #define _COMPONENT ACPI_PCI_COMPONENT
191 Bits in debug_level correspond to a level in
192 ACPI_DEBUG_PRINT statements, e.g.,
193 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600194 The debug_level mask defaults to "info". See
195 Documentation/acpi/debug.txt for more information about
196 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600198 Enable processor driver info messages:
199 acpi.debug_layer=0x20000000
200 Enable PCI/PCI interrupt routing info messages:
201 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700202 Enable AML "Debug" output, i.e., stores to the Debug
203 object while interpreting AML:
204 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700205 Enable all messages related to ACPI hardware:
206 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200207
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700208 Some values produce so much output that the system is
209 unusable. The "log_buf_len" parameter may be useful
210 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800211
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700212 acpi_irq_balance [HW,ACPI]
213 ACPI will balance active IRQs
214 default in APIC mode
215
216 acpi_irq_nobalance [HW,ACPI]
217 ACPI will not move active IRQs (default)
218 default in PIC mode
219
220 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
221 Format: <irq>,<irq>...
222
223 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
224 use by PCI
225 Format: <irq>,<irq>...
226
227 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
228
229 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
230 Format: To spoof as Windows 98: ="Microsoft Windows"
231
232 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
233 acpi_osi="string1" # add string1 -- only one string
234 acpi_osi="!string2" # remove built-in string2
235 acpi_osi= # disable all strings
236
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530237 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700238 Override the pmtimer bug detection: force the kernel
239 to assume that this machine's pmtimer latches its value
240 and always returns good values.
241
Randy Dunlap4af94f32009-04-17 18:30:28 -0700242 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
243 Format: { level | edge | high | low }
244
245 acpi_serialize [HW,ACPI] force serialization of AML methods
246
247 acpi_skip_timer_override [HW,ACPI]
248 Recognize and ignore IRQ0/pin2 Interrupt Override.
249 For broken nForce2 BIOS resulting in XT-PIC timer.
250
251 acpi_sleep= [HW,ACPI] Sleep options
252 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200253 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700254 See Documentation/power/video.txt for information on
255 s3_bios and s3_mode.
256 s3_beep is for debugging; it makes the PC's speaker beep
257 as soon as the kernel's real-mode entry point is called.
258 s4_nohwsig prevents ACPI hardware signature from being
259 used during resume from hibernation.
260 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with respect to putting devices into
262 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200264 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800266 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700269
270 acpi_use_timer_override [HW,ACPI]
271 Use timer override. For some broken Nvidia NF5 boards
272 that require a timer override, but don't have HPET
273
Luca Tettamanti7e905602009-03-30 00:01:27 +0200274 acpi_enforce_resources= [ACPI]
275 { strict | lax | no }
276 Check for resource conflicts between native drivers
277 and ACPI OperationRegions (SystemIO and SystemMemory
278 only). IO ports and memory declared in ACPI might be
279 used by the ACPI subsystem in arbitrary AML code and
280 can interfere with legacy drivers.
281 strict (default): access to resources claimed by ACPI
282 is denied; legacy drivers trying to access reserved
283 resources will fail to bind to device using them.
284 lax: access to resources claimed by ACPI is allowed;
285 legacy drivers trying to access reserved resources
286 will bind successfully but a warning message is logged.
287 no: ACPI OperationRegions are not marked as reserved,
288 no further checks are performed.
289
Randy Dunlap4af94f32009-04-17 18:30:28 -0700290 add_efi_memmap [EFI; X86] Include EFI memory map in
291 kernel's map of available physical RAM.
292
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700293 agp= [AGP]
294 { off | try_unsupported }
295 off: disable AGP support
296 try_unsupported: try to drive unsupported chipsets
297 (may crash computer or cause data corruption)
298
Randy Dunlapbcfde332010-06-07 17:10:38 -0700299 ALSA [HW,ALSA]
300 See Documentation/sound/alsa/alsa-parameters.txt
301
Russell Kingd944d542010-02-20 16:13:29 +0000302 alignment= [KNL,ARM]
303 Allow the default userspace alignment fault handler
304 behaviour to be specified. Bit 0 enables warnings,
305 bit 1 enables fixups, and bit 2 sends a segfault.
306
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200307 amd_iommu= [HW,X86-84]
308 Pass parameters to the AMD IOMMU driver in the system.
309 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900310 fullflush - enable flushing of IO/TLB entries when
311 they are unmapped. Otherwise they are
312 flushed before they will be reused, which
313 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200314 off - do not initialize any AMD IOMMU found in
315 the system
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900316
Linus Torvalds1da177e2005-04-16 15:20:36 -0700317 amijoy.map= [HW,JOY] Amiga joystick support
318 Map of devices attached to JOY0DAT and JOY1DAT
319 Format: <a>,<b>
320 See also Documentation/kernel/input/joystick.txt
321
322 analog.map= [HW,JOY] Analog joystick and gamepad support
323 Specifies type or capabilities of an analog joystick
324 connected to one of 16 gameports
325 Format: <type1>,<type2>,..<type16>
326
Randy Dunlapa9913042005-10-23 12:57:11 -0700327 apc= [HW,SPARC]
328 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700329 Format: noidle
330 Disable APC CPU standby support. SPARCstation-Fox does
331 not play well with APC CPU idle - disable it if you have
332 APC and your system crashes randomly.
333
Randy Dunlapca1eda22009-05-06 16:02:58 -0700334 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700335 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700336 Format: { quiet (default) | verbose | debug }
337 Change the amount of debugging information output
338 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700339
Brian Haleyb0f83b22010-02-04 13:36:50 -0800340 autoconf= [IPV6]
341 See Documentation/networking/ipv6.txt.
342
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400343 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
344 Limit apic dumping. The parameter defines the maximal
345 number of local apics being dumped. Also it is possible
346 to set it to "all" by meaning -- no limit here.
347 Format: { 1 (default) | 2 | ... | all }.
348 The parameter valid if only apic=debug or
349 apic=verbose is specified.
350 Example: apic=debug show_lapic=all
351
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700353 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700354
Linus Torvalds1da177e2005-04-16 15:20:36 -0700355 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
356 Format: <io>,<irq>,<nodeID>
357
358 ataflop= [HW,M68k]
359
360 atarimouse= [HW,MOUSE] Atari Mouse
361
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
363 EzKey and similar keyboards
364
365 atkbd.reset= [HW] Reset keyboard during initialization
366
Randy Dunlapa9913042005-10-23 12:57:11 -0700367 atkbd.set= [HW] Select keyboard code set
368 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369
370 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
371 keyboards
372
373 atkbd.softraw= [HW] Choose between synthetic and real raw mode
374 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700375
376 atkbd.softrepeat= [HW]
377 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378
379 autotest [IA64]
380
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381 baycom_epp= [HW,AX25]
382 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700383
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
385 Format: <io>,<mode>
386 See header of drivers/net/hamradio/baycom_par.c.
387
Randy Dunlapa9913042005-10-23 12:57:11 -0700388 baycom_ser_fdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390 Format: <io>,<irq>,<mode>[,<baud>]
391 See header of drivers/net/hamradio/baycom_ser_fdx.c.
392
Randy Dunlapa9913042005-10-23 12:57:11 -0700393 baycom_ser_hdx= [HW,AX25]
394 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700395 Format: <io>,<irq>,<mode>
396 See header of drivers/net/hamradio/baycom_ser_hdx.c.
397
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700398 boot_delay= Milliseconds to delay each printk during boot.
399 Values larger than 10 seconds (10000) are changed to
400 no delay (0).
401 Format: integer
402
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700403 bootmem_debug [KNL] Enable bootmem allocator debug messages.
404
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700406 bttv.radio= Most important insmod options are available as
407 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
409 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
410
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000411 bulk_remove=off [PPC] This parameter disables the use of the pSeries
412 firmware feature for flushing multiple hpte entries
413 at a time.
414
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415 c101= [NET] Moxa C101 synchronous serial card
416
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700417 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700418 Sometimes CPU hardware bugs make them report the cache
419 size incorrectly. The kernel will attempt work arounds
420 to fix known problems, but for some CPUs it is not
421 possible to determine what the correct size should be.
422 This option provides an override for these situations.
423
James Morris20510f22007-10-16 23:31:32 -0700424 capability.disable=
425 [SECURITY] Disable capabilities. This would normally
426 be used only if an alternative security model is to be
427 configured. Potentially dangerous and should only be
428 used if you are entirely sure of the consequences.
429
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100430 ccw_timeout_log [S390]
431 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432
Paul Menage8bab8dd2008-04-04 14:29:57 -0700433 cgroup_disable= [KNL] Disable a particular controller
434 Format: {name of the controller(s) to disable}
435 {Currently supported controllers - "memory"}
436
Linus Torvalds1da177e2005-04-16 15:20:36 -0700437 checkreqprot [SELINUX] Set initial checkreqprot flag value.
438 Format: { "0" | "1" }
439 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700440 0 -- check protection applied by kernel (includes
441 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442 1 -- check protection requested by application.
443 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700444 Value can be changed at runtime via
445 /selinux/checkreqprot.
446
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100447 cio_ignore= [S390]
448 See Documentation/s390/CommonIO for details.
449
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700450 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700451 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200452 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700453 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200454 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700455 Format: { pit | tsc | cyclone | pmtmr }
456
John Stultz592913e2010-07-13 17:56:20 -0700457 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700458 Format: <string>
459 Override the default clocksource and use the clocksource
460 with the name specified.
461 Some clocksource names to choose from, depending on
462 the platform:
463 [all] jiffies (this is the base, fallback clocksource)
464 [ACPI] acpi_pm
465 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
466 pxa_timer,timer3,32k_counter,timer0_1
467 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700468 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700469 scx200_hrt on Geode; cyclone on IBM x440
470 [MIPS] MIPS
471 [PARISC] cr16
472 [S390] tod
473 [SH] SuperH
474 [SPARC64] tick
475 [X86-64] hpet,tsc
476
Andi Kleenac72e782008-01-30 13:33:21 +0100477 clearcpuid=BITNUM [X86]
478 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800479 arch/x86/include/asm/cpufeature.h for the valid bit
480 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100481 stable over kernel options, but the vendor specific
482 ones should be.
483 Also note that user programs calling CPUID directly
484 or using the feature without checking anything
485 will still see it. This just prevents it from
486 being used by the kernel or shown in /proc/cpuinfo.
487 Also note the kernel might malfunction if you disable
488 some critical bits.
489
Robert Jennings14f966e2009-04-15 05:55:32 +0000490 cmo_free_hint= [PPC] Format: { yes | no }
491 Specify whether pages are marked as being inactive
492 when they are freed. This is used in CMO environments
493 to determine OS memory pressure for page stealing by
494 a hypervisor.
495 Default: yes
496
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530497 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100498 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100499 Range: 0 - 8192
500 Default: 64
501
Linus Torvalds1da177e2005-04-16 15:20:36 -0700502 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700503 Format:
504 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700505
506 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
507 Format: <io>[,<irq>]
508
Randy Dunlapa9913042005-10-23 12:57:11 -0700509 com90xx= [HW,NET]
510 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511 Format: <io>[,<irq>[,<memstart>]]
512
513 condev= [HW,S390] console device
514 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700515
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 console= [KNL] Output console device and options.
517
518 tty<n> Use the virtual console device <n>.
519
520 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800521 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800523 the form "bbbbpnf", where "bbbb" is the baud rate,
524 "p" is parity ("n", "o", or "e"), "n" is number of
525 bits, and "f" is flow control ("r" for RTS or
526 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700527
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800528 See Documentation/serial-console.txt for more
529 information. See
530 Documentation/networking/netconsole.txt for an
531 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700533 uart[8250],io,<addr>[,options]
534 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700535 Start an early, polled-mode console on the 8250/16550
536 UART at the specified I/O port or MMIO address,
537 switching to the matching ttyS device later. The
538 options are the same as for ttyS, above.
539
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700540 If the device connected to the port is not a TTY but a braille
541 device, prepend "brl," before the device type, for instance
542 console=brl,ttyS0
543 For now, only VisioBraille is supported.
544
Daniel Mackf324edc2009-06-16 15:33:52 -0700545 consoleblank= [KNL] The console blank (screen saver) timeout in
546 seconds. Defaults to 10*60 = 10mins. A value of 0
547 disables the blank timer.
548
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800549 coredump_filter=
550 [KNL] Change the default value for
551 /proc/<pid>/coredump_filter.
552 See also Documentation/filesystems/proc.txt.
553
Len Brown62027ae2011-04-01 18:13:10 -0400554 cpuidle.off=1 [CPU_IDLE]
555 disable the cpuidle sub-system
556
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700558 Format:
559 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700560
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800561 crashkernel=size[KMG][@offset[KMG]]
562 [KNL] Using kexec, Linux can switch to a 'crash kernel'
563 upon panic. This parameter reserves the physical
564 memory region [offset, offset + size] for that kernel
565 image. If '@offset' is omitted, then a suitable offset
566 is selected automatically. Check
567 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700568
Bernhard Wallefb391592007-10-18 23:41:02 -0700569 crashkernel=range1:size1[,range2:size2,...][@offset]
570 [KNL] Same as above, but depends on the memory
571 in the running system. The syntax of range is
572 start-[end] where start and end are both
573 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800574 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700575
Linus Torvalds1da177e2005-04-16 15:20:36 -0700576 cs89x0_dma= [HW,NET]
577 Format: <dma>
578
579 cs89x0_media= [HW,NET]
580 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700581
Randy Dunlapa9913042005-10-23 12:57:11 -0700582 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700583 See header of drivers/s390/block/dasd_devmap.c.
584
585 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
586 (one device per port)
587 Format: <port#>,<type>
588 See also Documentation/input/joystick-parport.txt
589
Thomas Renningera648ec02010-08-06 16:11:02 +0200590 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
591 time. See Documentation/dynamic-debug-howto.txt for
592 details.
593
Linus Torvalds1da177e2005-04-16 15:20:36 -0700594 debug [KNL] Enable kernel debugging (events log level).
595
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700596 debug_locks_verbose=
597 [KNL] verbose self-tests
598 Format=<0|1>
599 Print debugging info while doing the locking API
600 self-tests.
601 We default to 0 (no extra messages), setting it to
602 1 will print _a lot_ more information - normally
603 only useful to kernel developers.
604
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700605 debug_objects [KNL] Enable object debugging
606
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500607 no_debug_objects
608 [KNL] Disable object debugging
609
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200610 debugpat [X86] Enable PAT debugging
611
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200612 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613 Format: <area>[,<node>]
614 See also Documentation/networking/decnet.txt.
615
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700616 default_hugepagesz=
617 [same as hugepagesz=] The size of the default
618 HugeTLB page size. This is the size represented by
619 the legacy /proc/ hugepages APIs, used for SHM, and
620 default size when mounting hugetlbfs filesystems.
621 Defaults to the default architecture's huge page size
622 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700623
Linus Torvalds1da177e2005-04-16 15:20:36 -0700624 dhash_entries= [KNL]
625 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700626
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627 digi= [HW,SERIAL]
628 IO parameters + enable/disable command.
629
630 digiepca= [HW,SERIAL]
631 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000632 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633
Brian Haleyb0f83b22010-02-04 13:36:50 -0800634 disable= [IPV6]
635 See Documentation/networking/ipv6.txt.
636
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000637 disable_ddw [PPC/PSERIES]
638 Disable Dynamic DMA Window support. Use this if
639 to workaround buggy firmware.
640
Brian Haleyb0f83b22010-02-04 13:36:50 -0800641 disable_ipv6= [IPV6]
642 See Documentation/networking/ipv6.txt.
643
Yinghai Lu95ffa242008-04-29 03:52:33 -0700644 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700645 The kernel tries to adjust MTRR layout from continuous
646 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700647 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700648
Yinghai Lu093af8d2008-01-30 13:33:32 +0100649 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100650 By default the kernel will trim any uncacheable
651 memory out of your available memory pool based on
652 MTRR settings. This parameter disables that behavior,
653 possibly causing your machine to run very slowly.
654
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530655 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700656 Disable PIN 1 of APIC timer
657 Can be useful to work around chipset bugs.
658
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700659 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
660 this option disables the debugging code at boot.
661
662 dma_debug_entries=<number>
663 This option allows to tune the number of preallocated
664 entries for DMA-API debugging code. One entry is
665 required per DMA-API allocation. Use this if the
666 DMA-API debugging code disables itself because the
667 architectural default is too low.
668
Joerg Roedel1745de52009-05-22 21:49:51 +0200669 dma_debug_driver=<driver_name>
670 With this option the DMA-API debugging driver
671 filter feature can be enabled at boot time. Just
672 pass the driver to filter for as the parameter.
673 The filter can be disabled or changed to another
674 driver later using sysfs.
675
Linus Torvalds1da177e2005-04-16 15:20:36 -0700676 dscc4.setup= [NET]
677
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700678 earlycon= [KNL] Output early console device and options.
679 uart[8250],io,<addr>[,options]
680 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700681 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700682 Start an early, polled-mode console on the 8250/16550
683 UART at the specified I/O port or MMIO address.
Samium Gromoff1917ac72010-07-20 15:26:51 -0700684 MMIO inter-register address stride is either 8bit (mmio)
685 or 32bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700686 The options are the same as for ttyS, above.
687
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530688 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700689 earlyprintk=vga
690 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500691 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500692 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693
Randy Dunlapa9913042005-10-23 12:57:11 -0700694 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700695 takes over.
696
Yinghai Lu5c059172008-07-24 17:29:40 -0700697 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698
699 Currently only ttyS0 and ttyS1 are supported.
700
701 Interaction with the standard serial driver is not
702 very good.
703
704 The VGA output is eventually overwritten by the real
705 console.
706
Jason Wessel97311912010-05-20 21:04:30 -0500707 ekgdboc= [X86,KGDB] Allow early kernel console debugging
708 ekgdboc=kbd
709
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300710 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -0500711 the boot argument: earlyprintk=vga
712
Linus Torvalds1da177e2005-04-16 15:20:36 -0700713 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700714 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716 eisa_irq_edge= [PARISC,HW]
717 See header of drivers/parisc/eisa.c.
718
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700719 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700721 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722
723 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +0100724 Format: {"cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700725 See Documentation/block/as-iosched.txt and
726 Documentation/block/deadline-iosched.txt for details.
727
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530728 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700729 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800730 image elf header. Generally kexec loader will
731 pass this option to capture kernel.
732 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700733
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700734 enable_mtrr_cleanup [X86]
735 The kernel tries to adjust MTRR layout from continuous
736 to discrete, to make X server driver able to add WB
737 entry later. This parameter enables that.
738
Randy Dunlapca1eda22009-05-06 16:02:58 -0700739 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700740 Enable PIN 1 of APIC timer
741 Can be useful to work around chipset bugs
742 (in particular on some ATI chipsets).
743 The kernel tries to set a reasonable default.
744
Linus Torvalds1da177e2005-04-16 15:20:36 -0700745 enforcing [SELINUX] Set initial enforcing status.
746 Format: {"0" | "1"}
747 See security/selinux/Kconfig help text.
748 0 -- permissive (log only, no denials).
749 1 -- enforcing (deny and log).
750 Default value is 0.
751 Value can be changed at runtime via /selinux/enforce.
752
Huang Yinga08f82d2010-05-18 14:35:21 +0800753 erst_disable [ACPI]
754 Disable Error Record Serialization Table (ERST)
755 support.
756
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757 ether= [HW,NET] Ethernet cards parameters
758 This option is obsoleted by the "netdev=" option, which
759 has equivalent usage. See its documentation for details.
760
Akinobu Mitade1ba092006-12-08 02:39:42 -0800761 failslab=
762 fail_page_alloc=
763 fail_make_request=[KNL]
764 General fault injection mechanism.
765 Format: <interval>,<probability>,<space>,<times>
766 See also /Documentation/fault-injection/.
767
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000769 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700770
Alex Chiangf13ae302008-05-08 14:03:23 -0600771 force_pal_cache_flush
772 [IA-64] Avoid check_sal_cache_flush which may hang on
773 buggy SAL_CACHE_FLUSH implementations. Using this
774 parameter will force ia64_sal_cache_flush to call
775 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
776
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100777 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400778 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100779 as early as possible in order to facilitate early
780 boot debugging.
781
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200782 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400783 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200784 If no parameter is passed, ftrace will dump
785 buffers of all CPUs, but if you pass orig_cpu, it will
786 dump only the buffer of the CPU that triggered the
787 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400788
789 ftrace_filter=[function-list]
790 [FTRACE] Limit the functions traced by the function
791 tracer at boot up. function-list is a comma separated
792 list of functions. This list can be changed at run
793 time by the set_ftrace_filter file in the debugfs
794 tracing directory.
795
796 ftrace_notrace=[function-list]
797 [FTRACE] Do not trace the functions specified in
798 function-list. This list can be changed at run time
799 by the set_ftrace_notrace file in the debugfs
800 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100801
Stefan Assmann369bc182009-10-12 22:17:21 +0200802 ftrace_graph_filter=[function-list]
803 [FTRACE] Limit the top level callers functions traced
804 by the function graph tracer at boot up.
805 function-list is a comma separated list of functions
806 that can be changed at run time by the
807 set_graph_function file in the debugfs tracing directory.
808
Linus Torvalds1da177e2005-04-16 15:20:36 -0700809 gamecon.map[2|3]=
810 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
811 support via parallel port (up to 5 devices per port)
812 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
813 See also Documentation/input/joystick-parport.txt
814
815 gamma= [HW,DRM]
816
Yinghai Luaaf23042008-01-30 13:33:09 +0100817 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
818 Format: off | on
819 default: on
820
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700821 gcov_persist= [GCOV] When non-zero (default), profiling data for
822 kernel modules is saved and remains accessible via
823 debugfs, even when the module is unloaded/reloaded.
824 When zero, profiling data is discarded and associated
825 debugfs files are removed at module unload time.
826
Linus Torvalds1da177e2005-04-16 15:20:36 -0700827 gpt [EFI] Forces disk with valid GPT signature but
828 invalid Protective MBR to be treated as GPT.
829
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 hashdist= [KNL,NUMA] Large hashes allocated during boot
831 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700832 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700833 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700834
835 hcl= [IA-64] SGI's Hardware Graph compatibility layer
836
837 hd= [EIDE] (E)IDE hard drive subsystem geometry
838 Format: <cyl>,<head>,<sect>
839
Huang Yingea8c0712010-05-18 14:35:15 +0800840 hest_disable [ACPI]
841 Disable Hardware Error Source Table (HEST) support;
842 corresponding firmware-first mode error processing
843 logic will be disabled.
844
Linus Torvalds1da177e2005-04-16 15:20:36 -0700845 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
846 size of <nn>. This works even on boxes that have no
847 highmem otherwise. This also works to reduce highmem
848 size on bigger boxes.
849
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800850 highres= [KNL] Enable/disable high resolution timer mode.
851 Valid parameters: "on", "off"
852 Default: "on"
853
Linus Torvalds1da177e2005-04-16 15:20:36 -0700854 hisax= [HW,ISDN]
855 See Documentation/isdn/README.HiSax.
856
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700857 hlt [BUGS=ARM,SH]
858
859 hpet= [X86-32,HPET] option to control HPET usage
860 Format: { enable (default) | disable | force |
861 verbose }
862 disable: disable HPET and use PIT instead
863 force: allow force enabled of undocumented chips (ICH4,
864 VIA, nVidia)
865 verbose: show contents of HPET registers during setup
866
Andi Kleenb4718e62008-07-23 21:27:51 -0700867 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
868 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700869 On x86-64 and powerpc, this option can be specified
870 multiple times interleaved with hugepages= to reserve
871 huge pages of different sizes. Valid pages sizes on
872 x86-64 are 2M (when the CPU supports "pse") and 1G
873 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700874 Note that 1GB pages can only be allocated at boot time
875 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900876
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100877 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
878 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100879 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
880 If specified, z/VM IUCV HVC accepts connections
881 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100882
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -0700883 keep_bootcon [KNL]
884 Do not unregister boot console at start. This is only
885 useful for debugging when something happens in the window
886 between unregistering the boot console and initializing
887 the real console.
888
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700889 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700890 or register an additional I2C bus that is not
891 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700892 Format:
893 <bus_id>,<clkrate>
894
Jiri Kosina36d95732008-10-06 02:51:09 -0400895 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700896 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200897 i8042.dumbkbd [HW] Pretend that controller can only read data from
898 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700899 (Don't attempt to blink the leds)
900 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500901 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400902 i8042.noloop [HW] Disable the AUX Loopback command while probing
903 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904 i8042.nomux [HW] Don't check presence of an active multiplexing
905 controller
906 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
907 controllers
Jiri Kosinaf8313ef2011-01-08 01:37:26 -0800908 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
Linus Torvalds1da177e2005-04-16 15:20:36 -0700909 i8042.reset [HW] Reset the controller during init and cleanup
910 i8042.unlock [HW] Unlock (ignore) the keylock
911
912 i810= [HW,DRM]
913
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700914 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
915 indicates that the driver is running on unsupported
916 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700917 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
918 does not match list of supported models.
919 i8k.power_status
920 [HW] Report power status in /proc/i8k
921 (disabled by default)
922 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
923 capability is set.
924
Linus Torvalds1da177e2005-04-16 15:20:36 -0700925 icn= [HW,ISDN]
926 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
927
David Fries0af80c02009-02-25 20:28:21 +0100928 ide-core.nodma= [HW] (E)IDE subsystem
929 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200930 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
931 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100932 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700933
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700934 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
935 Claim all unknown PCI IDE storage controllers.
936
Andi Kleenf039b752007-05-02 19:27:12 +0200937 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800938 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
939 Poll forces a polling idle loop that can slightly
940 improve the performance of waking up a idle CPU, but
941 will use a lot of power and make the system run hot.
942 Not recommended.
943 idle=mwait: On systems which support MONITOR/MWAIT but
944 the kernel chose to not use it because it doesn't save
945 as much power as a normal idle loop, use the
946 MONITOR/MWAIT idle loop anyways. Performance should be
947 the same as idle=poll.
948 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800949 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800950 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700951
Ingo Molnar792908222006-12-06 20:40:51 -0800952 ignore_loglevel [KNL]
953 Ignore loglevel setting - this will print /all/
954 kernel messages to the console. Useful for debugging.
955
Linus Torvalds1da177e2005-04-16 15:20:36 -0700956 ihash_entries= [KNL]
957 Set number of hash buckets for inode cache.
958
Mimi Zohar3323eec92009-02-04 09:06:58 -0500959 ima_audit= [IMA]
960 Format: { "0" | "1" }
961 0 -- integrity auditing messages. (Default)
962 1 -- enable informational integrity auditing messages.
963
964 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700965 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -0500966 default: "sha1"
967
Eric Paris5789ba32009-05-21 15:47:06 -0400968 ima_tcb [IMA]
969 Load a policy which meets the needs of the Trusted
970 Computing Base. This means IMA will measure all
971 programs exec'd, files mmap'd for exec, and all files
972 opened for read by uid=0.
973
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974 init= [KNL]
975 Format: <full_path>
976 Run specified binary instead of /sbin/init as init
977 process.
978
979 initcall_debug [KNL] Trace initcalls as they are executed. Useful
980 for working out where the kernel is dying during
981 startup.
982
983 initrd= [BOOT] Specify the location of the initial ramdisk
984
985 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
986 Format: <irq>
987
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700988 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800989 on
990 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700991 off
992 Disable intel iommu driver.
993 igfx_off [Default Off]
994 By default, gfx is mapped as normal device. If a gfx
995 device has a dedicated DMAR unit, the DMAR unit is
996 bypassed by not enabling DMAR with this option. In
997 this case, gfx device will use physical address for
998 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700999 forcedac [x86_64]
1000 With this option iommu will not optimize to look
1001 for io virtual address below 32 bit forcing dual
1002 address cycle on pci bus for cards supporting greater
1003 than 32 bit addressing. The default is to look
1004 for translation below 32 bit and if not available
1005 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001006 strict [Default Off]
1007 With this option on every unmap_single operation will
1008 result in a hardware IOTLB flush operation as opposed
1009 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001010 sp_off [Default Off]
1011 By default, super page will be supported if Intel IOMMU
1012 has the capability. With this option, super page will
1013 not be supported.
Chris Wrightd1423d52010-07-20 11:06:49 -07001014 intremap= [X86-64, Intel-IOMMU]
1015 Format: { on (default) | off | nosid }
1016 on enable Interrupt Remapping (default)
1017 off disable Interrupt Remapping
1018 nosid disable Source ID checking
1019
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001020 inttest= [IA64]
1021
1022 iomem= Disable strict checking of access to MMIO memory
1023 strict regions from userspace.
1024 relaxed
1025
1026 iommu= [x86]
1027 off
1028 force
1029 noforce
1030 biomerge
1031 panic
1032 nopanic
1033 merge
1034 nomerge
1035 forcesac
1036 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001037 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001038
1039 io7= [HW] IO7 for Marvel based alpha systems
1040 See comment before marvel_specify_io7 in
1041 arch/alpha/kernel/core_marvel.c.
1042
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301043 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001044 0x80
1045 Standard port 0x80 based delay
1046 0xed
1047 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001048 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001049 Simple two microseconds delay
1050 none
1051 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001052
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001054 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055
1056 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001057 See comment before ip2_setup() in
1058 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001059
Alan Cox200803d2005-06-28 20:45:18 -07001060 irqfixup [HW]
1061 When an interrupt is not handled search all handlers
1062 for it. Intended to get systems with badly broken
1063 firmware running.
1064
1065 irqpoll [HW]
1066 When an interrupt is not handled search all handlers
1067 for it. Also check all handlers each timer
1068 interrupt. Intended to get systems with badly broken
1069 firmware running.
1070
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001072 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001073
1074 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001075 Format:
1076 <cpu number>,...,<cpu number>
1077 or
Li Zefanb225d442008-11-06 12:53:39 -08001078 <cpu number>-<cpu number>
1079 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001080 or a mixture
1081 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001082
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083 This option can be used to specify one or more CPUs
1084 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001085 algorithms. You can move a process onto or off an
1086 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001087 <cpu number> begins at 0 and the maximum value is
1088 "number of CPUs in system - 1".
1089
1090 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001091 alternative -- manually setting the CPU mask of all
1092 tasks in the system -- can cause problems and
1093 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001094
Randy Dunlapa9913042005-10-23 12:57:11 -07001095 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096
1097 js= [HW,JOY] Analog joystick
1098 See Documentation/input/joystick.txt.
1099
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001100 keepinitrd [HW,ARM]
1101
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301102 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001103 specifies the amount of memory usable by the kernel
1104 for non-movable allocations. The requested amount is
1105 spread evenly throughout all nodes in the system. The
1106 remaining memory in each node is used for Movable
1107 pages. In the event, a node is too small to have both
1108 kernelcore and Movable pages, kernelcore pages will
1109 take priority and other nodes will have a larger number
1110 of kernelcore pages. The Movable zone is used for the
1111 allocation of pages that may be reclaimed or moved
1112 by the page migration subsystem. This means that
1113 HugeTLB pages may not be allocated from this zone.
1114 Note that allocations like PTEs-from-HighMem still
1115 use the HighMem zone if it exists, and the Normal
1116 zone if it does not.
1117
Jason Wessel4fe1da42010-05-20 21:04:31 -05001118 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1119 Format: <Controller#>[,poll interval]
1120 The controller # is the number of the ehci usb debug
1121 port as it is probed via PCI. The poll interval is
1122 optional and is the number seconds in between
1123 each poll cycle to the debug port in case you need
1124 the functionality for interrupting the kernel with
1125 gdb or control-c on the dbgp connection. When
1126 not using this parameter you use sysrq-g to break into
1127 the kernel debugger.
1128
Jason Wessel84c08fd2010-05-20 21:04:24 -05001129 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001130 Requires a tty driver that supports console polling,
1131 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001132 Serial only format: <serial_device>[,baud]
1133 keyboard only format: kbd
1134 keyboard and serial format: kbd,<serial_device>[,baud]
1135 Optional Kernel mode setting:
1136 kms, kbd format: kms,kbd
1137 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001138
Jason Wessel84c08fd2010-05-20 21:04:24 -05001139 kgdbwait [KGDB] Stop kernel execution and enter the
1140 kernel debugger at the earliest opportunity.
1141
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001142 kmac= [MIPS] korina ethernet MAC address.
1143 Configure the RouterBoard 532 series on-chip
1144 Ethernet adapter MAC address.
1145
Catalin Marinas04f70332009-06-11 13:22:39 +01001146 kmemleak= [KNL] Boot-time kmemleak enable/disable
1147 Valid arguments: on, off
1148 Default: on
1149
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301150 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001151 in oops dumps.
1152
Andre Przywarafef07aa2009-07-10 14:20:35 +02001153 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1154 Default is 0 (don't ignore, but inject #GP)
1155
1156 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1157 Default is 1 (enabled)
1158
Xiao Guangronga182d872010-09-20 22:17:48 +08001159 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1160 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001161 Default is 0 (off)
1162
Andre Przywarafef07aa2009-07-10 14:20:35 +02001163 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001164 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001165
1166 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1167 for all guests.
1168 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1169
Andre Przywarafef07aa2009-07-10 14:20:35 +02001170 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1171 (virtualized MMU) support on capable Intel chips.
1172 Default is 1 (enabled)
1173
1174 kvm-intel.emulate_invalid_guest_state=
1175 [KVM,Intel] Enable emulation of invalid guest states
1176 Default is 0 (disabled)
1177
1178 kvm-intel.flexpriority=
1179 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1180 Default is 1 (enabled)
1181
1182 kvm-intel.unrestricted_guest=
1183 [KVM,Intel] Disable unrestricted guest feature
1184 (virtualized real and unpaged mode) on capable
1185 Intel chips. Default is 1 (enabled)
1186
1187 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1188 feature (tagged TLBs) on capable Intel chips.
1189 Default is 1 (enabled)
1190
Linus Torvalds1da177e2005-04-16 15:20:36 -07001191 l2cr= [PPC]
1192
Robert Brosea78bfbf2008-03-29 07:20:23 +11001193 l3cr= [PPC]
1194
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001195 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001196 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001197
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301198 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001199 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001200
FD Camifcb71f62008-01-06 19:08:56 +01001201 libata.dma= [LIBATA] DMA control
1202 libata.dma=0 Disable all PATA and SATA DMA
1203 libata.dma=1 PATA and SATA Disk DMA only
1204 libata.dma=2 ATAPI (CDROM) DMA only
1205 libata.dma=4 Compact Flash DMA only
1206 Combinations also work, so libata.dma=3 enables DMA
1207 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001208
1209 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1210 libata.ignore_hpa=0 keep BIOS limits (default)
1211 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001212
Dave Jones78e70c22007-09-27 11:50:13 -04001213 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1214 when set.
1215 Format: <int>
1216
Tejun Heo33267322008-02-13 09:15:09 +09001217 libata.force= [LIBATA] Force configurations. The format is comma
1218 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001219 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001220 matching port, link or device. Basically, it matches
1221 the ATA ID string printed on console by libata. If
1222 the whole ID part is omitted, the last PORT and DEVICE
1223 values are used. If ID hasn't been specified yet, the
1224 configuration applies to all ports, links and devices.
1225
1226 If only DEVICE is omitted, the parameter applies to
1227 the port and all links and devices behind it. DEVICE
1228 number of 0 either selects the first device or the
1229 first fan-out link behind PMP device. It does not
1230 select the host link. DEVICE number of 15 selects the
1231 host link and device attached to it.
1232
1233 The VAL specifies the configuration to force. As long
1234 as there's no ambiguity shortcut notation is allowed.
1235 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1236 The following configurations can be forced.
1237
1238 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1239 Any ID with matching PORT is used.
1240
1241 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1242
1243 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1244 udma[/][16,25,33,44,66,100,133] notation is also
1245 allowed.
1246
1247 * [no]ncq: Turn on or off NCQ.
1248
Tejun Heo05944bd2008-08-13 20:19:09 +09001249 * nohrst, nosrst, norst: suppress hard, soft
1250 and both resets.
1251
Tejun Heo43c9c592010-05-23 12:59:11 +02001252 * dump_id: dump IDENTIFY data.
1253
Tejun Heo33267322008-02-13 09:15:09 +09001254 If there are multiple matching configurations changing
1255 the same attribute, the last one is used.
1256
Yinghai Lu95f72d12010-07-12 14:36:09 +10001257 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001258
Linus Torvalds1da177e2005-04-16 15:20:36 -07001259 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001260 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001261
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001262 lockd.nlm_grace_period=P [NFS] Assign grace period.
1263 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001265 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1266 Format: <integer>
1267
1268 lockd.nlm_timeout=T [NFS] Assign timeout value.
1269 Format: <integer>
1270
1271 lockd.nlm_udpport=M [NFS] Assign UDP port.
1272 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001273
1274 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1275 Format: <irq>
1276
1277 loglevel= All Kernel Messages with a loglevel smaller than the
1278 console loglevel will be printed to the console. It can
1279 also be changed with klogd or other programs. The
1280 loglevels are defined as follows:
1281
1282 0 (KERN_EMERG) system is unusable
1283 1 (KERN_ALERT) action must be taken immediately
1284 2 (KERN_CRIT) critical conditions
1285 3 (KERN_ERR) error conditions
1286 4 (KERN_WARNING) warning conditions
1287 5 (KERN_NOTICE) normal but significant condition
1288 6 (KERN_INFO) informational
1289 7 (KERN_DEBUG) debug-level messages
1290
Randy Dunlapc756d082011-02-20 20:08:35 -08001291 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1292 in bytes. n must be a power of two. The default
1293 size is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001294
Randy Dunlapaccaa242007-10-16 01:29:37 -07001295 logo.nologo [FB] Disables display of the built-in Linux logo.
1296 This may be used to provide more screen space for
1297 kernel log messages and is useful when debugging
1298 kernel boot problems.
1299
Linus Torvalds1da177e2005-04-16 15:20:36 -07001300 lp=0 [LP] Specify parallel ports to use, e.g,
1301 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1302 lp=reset first parallel port). 'lp=0' disables the
1303 lp=auto printer driver. 'lp=reset' (which can be
1304 specified in addition to the ports) causes
1305 attached printers to be reset. Using
1306 lp=port1,port2,... specifies the parallel ports
1307 to associate lp devices with, starting with
1308 lp0. A port specification may be 'none' to skip
1309 that lp device, or a parport name such as
1310 'parport0'. Specifying 'lp=auto' instead of a
1311 port specification list means that device IDs
1312 from each port should be examined, to see if
1313 an IEEE 1284-compliant printer is attached; if
1314 so, the driver will manage that printer.
1315 See also header of drivers/char/lp.c.
1316
1317 lpj=n [KNL]
1318 Sets loops_per_jiffy to given constant, thus avoiding
1319 time-consuming boot-time autodetection (up to 250 ms per
1320 CPU). 0 enables autodetection (default). To determine
1321 the correct value for your kernel, boot with normal
1322 autodetection and see what value is printed. Note that
1323 on SMP systems the preset will be applied to all CPUs,
1324 which is likely to cause problems if your CPUs need
1325 significantly divergent settings. An incorrect value
1326 will cause delays in the kernel to be wrong, leading to
1327 unpredictable I/O errors and other breakage. Although
1328 unlikely, in the extreme case this might damage your
1329 hardware.
1330
1331 ltpc= [NET]
1332 Format: <io>,<irq>,<dma>
1333
Randy Dunlapa9913042005-10-23 12:57:11 -07001334 machvec= [IA64] Force the use of a particular machine-vector
1335 (machvec) in a generic kernel.
1336 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001337
Wu Zhangjin3209e702009-07-02 23:27:12 +08001338 machtype= [Loongson] Share the same kernel image file between different
1339 yeeloong laptop.
1340 Example: machtype=lemote-yeeloong-2f-7inch
1341
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001342 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1343 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344
1345 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001346 should make use of. maxcpus=n : n >= 0 limits the
1347 kernel to using 'n' processors. n=0 is a special case,
1348 it is equivalent to "nosmp", which also disables
1349 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001350
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001351 max_loop= [LOOP] Maximum number of loopback devices that can
1352 be mounted
1353 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001354
Linus Torvalds1da177e2005-04-16 15:20:36 -07001355 mcatest= [IA-64]
1356
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001357 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001358
Uwe Hermann71cced62008-10-20 09:32:21 -07001359 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001360
Linus Torvalds1da177e2005-04-16 15:20:36 -07001361 md= [HW] RAID subsystems devices and level
1362 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001363
Linus Torvalds1da177e2005-04-16 15:20:36 -07001364 mdacon= [MDA]
1365 Format: <first>,<last>
1366 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001367
Linus Torvalds1da177e2005-04-16 15:20:36 -07001368 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1369 Amount of memory to be used when the kernel is not able
1370 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001371 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001372 address space collisions. Without memmap= PCI devices
1373 could be placed at addresses belonging to unused RAM.
1374
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001375 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001376 memory.
1377
Paul Mundt6902aa82008-09-21 17:14:42 +09001378 memchunk=nn[KMG]
1379 [KNL,SH] Allow user to override the default size for
1380 per-device physically contiguous DMA buffers.
1381
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301382 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001383 E820 memory map, as specified by the user.
1384 Such memmap=exactmap lines can be constructed based on
1385 BIOS output or other requirements. See the memmap=nn@ss
1386 option description.
1387
1388 memmap=nn[KMG]@ss[KMG]
1389 [KNL] Force usage of a specific region of memory
1390 Region of memory to be used, from ss to ss+nn.
1391
1392 memmap=nn[KMG]#ss[KMG]
1393 [KNL,ACPI] Mark specific memory as ACPI data.
1394 Region of memory to be used, from ss to ss+nn.
1395
1396 memmap=nn[KMG]$ss[KMG]
1397 [KNL,ACPI] Mark specific memory as reserved.
1398 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001399 Example: Exclude memory from 0x18690000-0x1869ffff
1400 memmap=64K$0x18690000
1401 or
1402 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001403
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001404 memory_corruption_check=0/1 [X86]
1405 Some BIOSes seem to corrupt the first 64k of
1406 memory when doing things like suspend/resume.
1407 Setting this option will scan the memory
1408 looking for corruption. Enabling this will
1409 both detect corruption and prevent the kernel
1410 from using the memory being corrupted.
1411 However, its intended as a diagnostic tool; if
1412 repeatable BIOS-originated corruption always
1413 affects the same memory, you can use memmap=
1414 to prevent the kernel from using that memory.
1415
1416 memory_corruption_check_size=size [X86]
1417 By default it checks for corruption in the low
1418 64k, making this memory unavailable for normal
1419 use. Use this parameter to scan for
1420 corruption in more or less memory.
1421
1422 memory_corruption_check_period=seconds [X86]
1423 By default it checks for corruption every 60
1424 seconds. Use this parameter to check at some
1425 other rate. 0 disables periodic checking.
1426
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001427 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001428 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001429 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001430 Specifies the number of memtest passes to be
1431 performed. Each pass selects another test
1432 pattern from a given set of patterns. Memtest
1433 fills the memory with this pattern, validates
1434 memory contents and reserves bad memory
1435 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001436
Linus Torvalds1da177e2005-04-16 15:20:36 -07001437 meye.*= [HW] Set MotionEye Camera parameters
1438 See Documentation/video4linux/meye.txt.
1439
Andres Salomon8f368812007-10-12 23:04:06 +02001440 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1441 Multi-Function General Purpose Timers on AMD Geode
1442 platforms.
1443
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001444 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1445 the BIOS has incorrectly applied a workaround. TinyBIOS
1446 version 0.98 is known to be affected, 0.99 fixes the
1447 problem by letting the user disable the workaround.
1448
Linus Torvalds1da177e2005-04-16 15:20:36 -07001449 mga= [HW,DRM]
1450
Randy Dunlap1c207f92008-11-19 15:36:16 -08001451 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1452 physical address is ignored.
1453
Michel Pollet39f45d72009-05-20 11:10:31 +01001454 mini2440= [ARM,HW,KNL]
1455 Format:[0..2][b][c][t]
1456 Default: "0tb"
1457 MINI2440 configuration specification:
1458 0 - The attached screen is the 3.5" TFT
1459 1 - The attached screen is the 7" TFT
1460 2 - The VGA Shield is attached (1024x768)
1461 Leaving out the screen size parameter will not load
1462 the TFT driver, and the framebuffer will be left
1463 unconfigured.
1464 b - Enable backlight. The TFT backlight pin will be
1465 linked to the kernel VESA blanking code and a GPIO
1466 LED. This parameter is not necessary when using the
1467 VGA shield.
1468 c - Enable the s3c camera interface.
1469 t - Reserved for enabling touchscreen support. The
1470 touchscreen support is not enabled in the mainstream
1471 kernel as of 2.6.30, a preliminary port can be found
1472 in the "bleeding edge" mini2440 support kernel at
1473 http://repo.or.cz/w/linux-2.6/mini2440.git
1474
Mel Gorman6b74ab92008-07-23 21:26:49 -07001475 mminit_loglevel=
1476 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1477 parameter allows control of the logging verbosity for
1478 the additional memory initialisation checks. A value
1479 of 0 disables mminit logging and a level of 4 will
1480 log everything. Information is printed at KERN_DEBUG
1481 so loglevel=8 may also need to be specified.
1482
Linus Torvalds1da177e2005-04-16 15:20:36 -07001483 mousedev.tap_time=
1484 [MOUSE] Maximum time between finger touching and
1485 leaving touchpad surface for touch to be considered
1486 a tap and be reported as a left button click (for
1487 touchpads working in absolute mode only).
1488 Format: <msecs>
1489 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1490 reporting absolute coordinates, such as tablets
1491 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1492 reporting absolute coordinates, such as tablets
1493
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301494 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001495 is similar to kernelcore except it specifies the
1496 amount of memory used for migratable allocations.
1497 If both kernelcore and movablecore is specified,
1498 then kernelcore will be at *least* the specified
1499 value but may be more. If movablecore on its own
1500 is specified, the administrator must be careful
1501 that the amount of memory usable for all allocations
1502 is not too small.
1503
Linus Torvalds1da177e2005-04-16 15:20:36 -07001504 MTD_Partition= [MTD]
1505 Format: <name>,<region-number>,<size>,<offset>
1506
Randy Dunlapa9913042005-10-23 12:57:11 -07001507 MTD_Region= [MTD] Format:
1508 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001509
1510 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001511 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001512
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001513 multitce=off [PPC] This parameter disables the use of the pSeries
1514 firmware feature for updating multiple TCE entries
1515 at a time.
1516
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001517 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1518
1519 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1520
1521 boundary - index of last SLC block on Flex-OneNAND.
1522 The remaining blocks are configured as MLC blocks.
1523 lock - Configure if Flex-OneNAND boundary should be locked.
1524 Once locked, the boundary cannot be changed.
1525 1 indicates lock status, 0 indicates unlock status.
1526
Ben Dooks9db829f2008-07-03 11:24:29 +01001527 mtdset= [ARM]
1528 ARM/S3C2412 JIVE boot control
1529
1530 See arch/arm/mach-s3c2412/mach-jive.c
1531
Linus Torvalds1da177e2005-04-16 15:20:36 -07001532 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001533 [HW] Make the MicroTouch USB driver use raw coordinates
1534 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001535
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001536 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001537 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001538 that could hold holes aka. UC entries.
1539
1540 mtrr_gran_size=nn[KMG] [X86]
1541 Used for mtrr cleanup. It is granularity of mtrr block.
1542 Default is 1.
1543 Large value could prevent small alignment from
1544 using up MTRRs.
1545
1546 mtrr_spare_reg_nr=n [X86]
1547 Format: <integer>
1548 Range: 0,7 : spare reg number
1549 Default : 1
1550 Used for mtrr cleanup. It is spare mtrr entries number.
1551 Set to 2 or more if your graphical card needs more.
1552
Linus Torvalds1da177e2005-04-16 15:20:36 -07001553 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1554
Linus Torvalds1da177e2005-04-16 15:20:36 -07001555 netdev= [NET] Network devices parameters
1556 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1557 Note that mem_start is often overloaded to mean
1558 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001559 This usage is only documented in each driver source
1560 file if at all.
1561
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001562 nf_conntrack.acct=
1563 [NETFILTER] Enable connection tracking flow accounting
1564 0 to disable accounting
1565 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001566 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001567
Chuck Lever306a0752010-09-17 10:54:37 -04001568 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001569 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001570
1571 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001572 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001573
Chuck Lever306a0752010-09-17 10:54:37 -04001574 nfsrootdebug [NFS] enable nfsroot debugging messages.
1575 See Documentation/filesystems/nfs/nfsroot.txt.
1576
Trond Myklebusta72b4422006-01-03 09:55:41 +01001577 nfs.callback_tcpport=
1578 [NFS] set the TCP port on which the NFSv4 callback
1579 channel should listen.
1580
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001581 nfs.cache_getent=
1582 [NFS] sets the pathname to the program which is used
1583 to update the NFS client cache entries.
1584
1585 nfs.cache_getent_timeout=
1586 [NFS] sets the timeout after which an attempt to
1587 update a cache entry is deemed to have failed.
1588
Trond Myklebust58df0952006-01-03 09:55:57 +01001589 nfs.idmap_cache_timeout=
1590 [NFS] set the maximum lifetime for idmapper cache
1591 entries.
1592
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001593 nfs.enable_ino64=
1594 [NFS] enable 64-bit inode numbers.
1595 If zero, the NFS client will fake up a 32-bit inode
1596 number for the readdir() and stat() syscalls instead
1597 of returning the full 64-bit number.
1598 The default is to return 64-bit inode numbers.
1599
Trond Myklebustb064eca22011-02-22 15:44:32 -08001600 nfs.nfs4_disable_idmapping=
1601 [NFSv4] When set, this option disables the NFSv4
1602 idmapper on the client, but only if the mount
1603 is using the 'sec=sys' security flavour. This may
1604 make migration from legacy NFSv2/v3 systems easier
1605 provided that the server has the appropriate support.
1606 The default is to always enable NFSv4 idmapping.
1607
Paul Mundt1e1030d2009-09-01 17:38:32 +09001608 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001609 when a NMI is triggered.
1610 Format: [state][,regs][,debounce][,die]
1611
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301612 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07001613 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05001614 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001615 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001616 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07001617 timeout occurs (or 'nopanic' to override the opposite
1618 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001619 This is useful when you use a panic=... timeout and
1620 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001621
Anton Vorontsovbff38772009-07-08 11:10:56 -07001622 netpoll.carrier_timeout=
1623 [NET] Specifies amount of time (in seconds) that
1624 netpoll should wait for a carrier. By default netpoll
1625 waits 4 seconds.
1626
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001627 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001628 emulation library even if a 387 maths coprocessor
1629 is present.
1630
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001631 no_console_suspend
1632 [HW] Never suspend the console
1633 Disable suspending of consoles during suspend and
1634 hibernate operations. Once disabled, debugging
1635 messages can reach various consoles while the rest
1636 of the system is being put to sleep (ie, while
1637 debugging driver suspend/resume hooks). This may
1638 not work reliably with all consoles, but is known
1639 to work with serial and VGA consoles.
1640
Christoph Lameterc1aee212007-05-31 00:40:47 -07001641 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1642 caches in the slab allocator. Saves per-node memory,
1643 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001644
Randy Dunlapa9913042005-10-23 12:57:11 -07001645 noalign [KNL,ARM]
1646
Linus Torvalds1da177e2005-04-16 15:20:36 -07001647 noapic [SMP,APIC] Tells the kernel to not make use of any
1648 IOAPICs that may be present in the system.
1649
Mike Galbraith5091faa2010-11-30 14:18:03 +01001650 noautogroup Disable scheduler automatic task group creation.
1651
Linus Torvalds1da177e2005-04-16 15:20:36 -07001652 nobats [PPC] Do not use BATs for mapping kernel lowmem
1653 on "Classic" PPC cores.
1654
1655 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001656
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001657 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1658
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001659 nodelayacct [KNL] Disable per-task delay accounting
1660
Linus Torvalds1da177e2005-04-16 15:20:36 -07001661 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1662
Paul Mundt6902aa82008-09-21 17:14:42 +09001663 nodsp [SH] Disable hardware DSP at boot time.
1664
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301665 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001666
Linus Torvalds1da177e2005-04-16 15:20:36 -07001667 noexec [IA-64]
1668
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301669 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001670 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001671 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001672 noexec=off: disable non-executable mappings
1673
Fenghua Yude5397a2011-05-11 16:51:05 -07001674 nosmep [X86]
1675 Disable SMEP (Supervisor Mode Execution Protection)
1676 even if it is supported by processor.
1677
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001678 noexec32 [X86-64]
1679 This affects only 32-bit executables.
1680 noexec32=on: enable non-executable mappings (default)
1681 read doesn't imply executable mappings
1682 noexec32=off: disable non-executable mappings
1683 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001684
Paul Mundt6902aa82008-09-21 17:14:42 +09001685 nofpu [SH] Disable hardware FPU at boot time.
1686
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001687 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001688 register save and restore. The kernel will only save
1689 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001690
Suresh Siddha0c752a92009-05-22 12:17:45 -07001691 noxsave [BUGS=X86] Disables x86 extended register state save
1692 and restore using xsave. The kernel will fallback to
1693 enabling legacy floating-point and sse state.
1694
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001695 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1696 wfi(ARM) instruction doesn't work correctly and not to
1697 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001698
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001699 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001700 instruction doesn't work correctly and not to
1701 use it.
1702
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001703 no_file_caps Tells the kernel not to honor file capabilities. The
1704 only way then for a file to be executed with privilege
1705 is to be setuid root or executed by root.
1706
Linus Torvalds1da177e2005-04-16 15:20:36 -07001707 nohalt [IA-64] Tells the kernel not to use the power saving
1708 function PAL_HALT_LIGHT when idle. This increases
1709 power-consumption. On the positive side, it reduces
1710 interrupt wake-up latency, which may improve performance
1711 in certain environments such as networked servers or
1712 real-time systems.
1713
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001714 nohz= [KNL] Boottime enable/disable dynamic ticks
1715 Valid arguments: on, off
1716 Default: on
1717
Paul Mundteeee7852009-04-02 12:31:16 +09001718 noiotrap [SH] Disables trapped I/O port accesses.
1719
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001720 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001721 disable unhandled interrupt sources.
1722
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301723 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001724 broken timer IRQ sources.
1725
Linus Torvalds1da177e2005-04-16 15:20:36 -07001726 noisapnp [ISAPNP] Disables ISA PnP code.
1727
1728 noinitrd [RAM] Tells the kernel not to load any configured
1729 initial RAM disk.
1730
Weidong Han03ea8152009-04-17 16:42:15 +08001731 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1732 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07001733 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08001734
Linus Torvalds1da177e2005-04-16 15:20:36 -07001735 nointroute [IA-64]
1736
Tony Luck0aa366f2007-07-20 11:22:30 -07001737 nojitter [IA64] Disables jitter checking for ITC timers.
1738
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02001739 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1740
Gleb Natapovfd10cde2010-10-14 11:22:51 +02001741 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1742 fault handling.
1743
Glauber Costad910f5c2011-07-11 15:28:19 -04001744 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1745 steal time is computed, but won't influence scheduler
1746 behaviour
1747
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001748 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001749
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001750 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001751
Linus Torvalds1da177e2005-04-16 15:20:36 -07001752 noltlbs [PPC] Do not use large page/tlb entries for kernel
1753 lowmem mapping on PPC40x.
1754
Horms312f1f02006-02-22 09:57:55 +09001755 nomca [IA-64] Disable machine check abort handling
1756
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001757 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001758
Andres Salomon83d73842007-10-12 23:04:06 +02001759 nomfgpt [X86-32] Disable Multi-Function General Purpose
1760 Timer usage (for AMD Geode machines).
1761
Jiri Kosina016ddd92010-01-18 17:05:40 +01001762 nopat [X86] Disable PAT (page attribute table extension of
1763 pagetables) support.
1764
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001765 norandmaps Don't use address space randomization. Equivalent to
1766 echo 0 > /proc/sys/kernel/randomize_va_space
1767
Jiri Kosinabbff2162010-08-11 18:34:09 +02001768 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001769
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001770 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001771 with UP alternatives
1772
Linus Torvalds1da177e2005-04-16 15:20:36 -07001773 noresidual [PPC] Don't use residual data on PReP machines.
1774
Randy Dunlapa9913042005-10-23 12:57:11 -07001775 noresume [SWSUSP] Disables resume and restores original swap
1776 space.
1777
Linus Torvalds1da177e2005-04-16 15:20:36 -07001778 no-scroll [VGA] Disables scrollback.
1779 This is required for the Braillex ib80-piezo Braille
1780 reader made by F.H. Papenmeier (Germany).
1781
1782 nosbagart [IA-64]
1783
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001784 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001785
Len Brown61ec7562007-08-16 03:34:22 -04001786 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1787 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001788
Dave Jones97842212007-07-15 23:41:05 -07001789 nosoftlockup [KNL] Disable the soft-lockup detector.
1790
Linus Torvalds1da177e2005-04-16 15:20:36 -07001791 nosync [HW,M68K] Disables sync negotiation for all devices.
1792
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001793 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001794
1795 nousb [USB] Disable the USB subsystem
1796
Ben Hutchings55142372011-01-02 23:02:42 +00001797 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04001798
Linus Torvalds1da177e2005-04-16 15:20:36 -07001799 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001800
Weidong Han2b2fd872009-04-17 16:42:12 +08001801 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1802
Fenghua Yua6c75b862008-03-14 13:57:08 -07001803 nptcg= [IA64] Override max number of concurrent global TLB
1804 purges which is reported from either PAL_VM_SUMMARY or
1805 SAL PALO.
1806
Yinghai Lu2b633e32010-02-10 01:20:37 -08001807 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1808 could support. nr_cpus=n : n >= 1 limits the kernel to
1809 supporting 'n' processors. Later in runtime you can not
1810 use hotplug cpu feature to put more cpu back to online.
1811 just like you compile the kernel NR_CPUS=n
1812
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001813 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1814
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001815 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1816 one of ['zone', 'node', 'default'] can be specified
1817 This can be set from sysctl after boot.
1818 See Documentation/sysctl/vm.txt for details.
1819
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001820 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1821 See Documentation/debugging-via-ohci1394.txt for more
1822 info.
1823
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001824 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1825 Rather than timing out after 20 ms if an EC
1826 command is not properly ACKed, override the length
1827 of the timeout. We have interrupts disabled while
1828 waiting for the ACK, so if this is set too high
1829 interrupts *may* be lost!
1830
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001831 omap_mux= [OMAP] Override bootloader pin multiplexing.
1832 Format: <mux_mode0.mode_name=value>...
1833 For example, to override I2C bus2:
1834 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1835
Linus Torvalds1da177e2005-04-16 15:20:36 -07001836 oprofile.timer= [HW]
1837 Use timer interrupt instead of performance counters
1838
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001839 oprofile.cpu_type= Force an oprofile cpu type
1840 This might be useful if you have an older oprofile
1841 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001842 Format: { arch_perfmon }
1843 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001844 perfmon on Intel CPUs instead of the
1845 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001846
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07001847 oops=panic Always panic on oopses. Default is to just kill the
1848 process, but there is a small probability of
1849 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07001850 This will also cause panics on machine check exceptions.
1851 Useful together with panic=30 to trigger a reboot.
1852
Randy Dunlapbcfde332010-06-07 17:10:38 -07001853 OSS [HW,OSS]
1854 See Documentation/sound/oss/oss-parameters.txt
1855
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07001856 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07001857 timeout > 0: seconds before rebooting
1858 timeout = 0: wait forever
1859 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07001860 Format: <timeout>
1861
1862 parkbd.port= [HW] Parallel port number the keyboard adapter is
1863 connected to, default is 0.
1864 Format: <parport#>
1865 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1866 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001867 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868
Randy Dunlapa9913042005-10-23 12:57:11 -07001869 parport= [HW,PPT] Specify parallel ports. 0 disables.
1870 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1871 Use 'auto' to force the driver to use any
1872 IRQ/DMA settings detected (the default is to
1873 ignore detected IRQ/DMA settings because of
1874 possible conflicts). You can specify the base
1875 address, IRQ, and DMA settings; IRQ and DMA
1876 should be numbers, or 'auto' (for using detected
1877 settings on that particular port), or 'nofifo'
1878 (to avoid using a FIFO even if it is detected).
1879 Parallel ports are assigned in the order they
1880 are specified on the command line, starting
1881 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001882
Randy Dunlapa9913042005-10-23 12:57:11 -07001883 parport_init_mode= [HW,PPT]
1884 Configure VIA parallel port to operate in
1885 a specific mode. This is necessary on Pegasos
1886 computer where firmware has no options for setting
1887 up parallel port mode and sets it to spp.
1888 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001889 Format: [spp|ps2|epp|ecp|ecpepp]
1890
Andrew Mortondd287792006-03-23 03:00:57 -08001891 pause_on_oops=
1892 Halt all CPUs after the first oops has been printed for
1893 the specified number of seconds. This is to be used if
1894 your oopses keep scrolling off the screen.
1895
Linus Torvalds1da177e2005-04-16 15:20:36 -07001896 pcbit= [HW,ISDN]
1897
1898 pcd. [PARIDE]
1899 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001900 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001901
Randy Dunlapa9913042005-10-23 12:57:11 -07001902 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001903 earlydump [X86] dump PCI config space before the kernel
1904 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001905 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001906 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001907 the hardware directly. Use this if your machine
1908 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001909 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001910 hardware access methods are allowed. Use this
1911 if you experience crashes upon bootup and you
1912 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001913 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001914 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001915 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001916 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001917 noaer [PCIE] If the PCIEAER kernel config parameter is
1918 enabled, this kernel boot option can be used to
1919 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001920 nodomains [PCI] Disable support for multiple PCI
1921 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301922 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001923 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001924 check_enable_amd_mmconf [X86] check for and enable
1925 properly configured MMIO access to PCI
1926 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001927 nomsi [MSI] If the PCI_MSI kernel config parameter is
1928 enabled, this kernel boot option can be used to
1929 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001930 noioapicquirk [APIC] Disable all boot interrupt quirks.
1931 Safety option to keep boot IRQs enabled. This
1932 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001933 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1934 primary IO-APIC for bridges that cannot disable
1935 boot IRQs. This fixes a source of spurious IRQs
1936 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001937 noioapicreroute [APIC] Disable workaround that uses the
1938 boot IRQ equivalent of an IRQ that connects to
1939 a chipset where boot IRQs cannot be disabled.
1940 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001941 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001942 routing table. These calls are known to be buggy
1943 on several machines and they hang the machine
1944 when used, but on other computers it's the only
1945 way to get the interrupt routing table. Try
1946 this option if the kernel is unable to allocate
1947 IRQs or discover secondary PCI buses on your
1948 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001949 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001950 Use with caution as certain devices share
1951 address decoders between ROMs and other
1952 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001953 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001954 expansion ROMs that do not already have
1955 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07001956 nobar [X86] Do not assign address space to the
1957 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001958 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001959 assigned automatically to PCI devices. You can
1960 make the kernel exclude IRQs of your ISA cards
1961 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001962 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001963 of the PIRQ table (normally generated
1964 by the BIOS) if it is outside the
1965 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001966 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001967 useful if the kernel is unable to find your
1968 secondary buses and you want to tell it
1969 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001970 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001971 numbers ourselves, overriding
1972 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001973 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001974 in the BIOS $PIR table. This is needed on
1975 some systems with broken BIOSes, notably
1976 some HP Pavilion N5400 and Omnibook XE3
1977 notebooks. This will have no effect if ACPI
1978 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001979 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001980 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07001981 use_crs [X86] Use PCI host bridge window information
1982 from ACPI. On BIOSes from 2008 or later, this
1983 is enabled by default. If you need to use this,
1984 please report a bug.
1985 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1986 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07001987 routeirq Do IRQ routing for all PCI devices.
1988 This is normally done in pci_enable_device(),
1989 so this option is a temporary workaround
1990 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001991 skip_isa_align [X86] do not align io start addr, so can
1992 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001993 firmware [ARM] Do not re-enumerate the bus but instead
1994 just use the configuration from the
1995 bootloader. This is currently used on
1996 IXP2000 systems where the bus has to be
1997 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001998 noearly [X86] Don't do any early type 1 scanning.
1999 This might help on some broken boards which
2000 machine check when some devices' config space
2001 is read. But various workarounds are disabled
2002 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002003 bfsort Sort PCI devices into breadth-first order.
2004 This sorting is done to get a device
2005 order compatible with older (<= 2.4) kernels.
2006 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002007 cbiosize=nn[KMG] The fixed amount of bus space which is
2008 reserved for the CardBus bridge's IO window.
2009 The default value is 256 bytes.
2010 cbmemsize=nn[KMG] The fixed amount of bus space which is
2011 reserved for the CardBus bridge's memory
2012 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002013 resource_alignment=
2014 Format:
2015 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2016 Specifies alignment and device to reassign
2017 aligned memory resources.
2018 If <order of align> is not specified,
2019 PAGE_SIZE is used as alignment.
2020 PCI-PCI bridge can be specified, if resource
2021 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002022 ecrc= Enable/disable PCIe ECRC (transaction layer
2023 end-to-end CRC checking).
2024 bios: Use BIOS/firmware settings. This is the
2025 the default.
2026 off: Turn ECRC off
2027 on: Turn ECRC on.
Ram Paif483d392011-07-07 11:19:10 -07002028 realloc reallocate PCI resources if allocations done by BIOS
2029 are erroneous.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002030
Chuck Ebberte5665a42008-09-24 20:40:34 -04002031 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2032 Management.
2033 off Disable ASPM.
2034 force Enable ASPM even on devices that claim not to support it.
2035 WARNING: Forcing ASPM on may cause system lockups.
2036
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002037 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002038 auto Ask the BIOS whether or not to use native PCIe services
2039 associated with PCIe ports (PME, hot-plug, AER). Use
2040 them only if that is allowed by the BIOS.
2041 native Use native PCIe services associated with PCIe ports
2042 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002043 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2044 ports driver.
2045
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002046 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002047 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002048 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002049
Linus Torvalds1da177e2005-04-16 15:20:36 -07002050 pcmv= [HW,PCMCIA] BadgePAD 4
2051
2052 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002053 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002054
2055 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2056 boot time.
2057 Format: { 0 | 1 }
2058 See arch/parisc/kernel/pdc_chassis.c
2059
Tejun Heof58dc012009-08-14 15:00:50 +09002060 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002061 Currently supported values are "embed" and "page".
2062 Archs may support subset or none of the selections.
2063 See comments in mm/percpu.c for details on each
2064 allocator. This parameter is primarily for debugging
2065 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002066
Linus Torvalds1da177e2005-04-16 15:20:36 -07002067 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002068 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002069
2070 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002071 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002072
2073 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002074 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002075
2076 plip= [PPT,NET] Parallel port network link
2077 Format: { parport<nr> | timid | 0 }
2078 See also Documentation/parport.txt.
2079
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002080 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2081 Override pmtimer IOPort with a hex value.
2082 e.g. pmtmr=0x508
2083
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002084 pnp.debug [PNP]
2085 Enable PNP debug messages. This depends on the
2086 CONFIG_PNP_DEBUG_MESSAGES option.
2087
Linus Torvalds1da177e2005-04-16 15:20:36 -07002088 pnpacpi= [ACPI]
2089 { off }
2090
2091 pnpbios= [ISAPNP]
2092 { on | off | curr | res | no-curr | no-res }
2093
2094 pnp_reserve_irq=
2095 [ISAPNP] Exclude IRQs for the autoconfiguration
2096
2097 pnp_reserve_dma=
2098 [ISAPNP] Exclude DMAs for the autoconfiguration
2099
2100 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002101 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002102
2103 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002104 [ISAPNP] Exclude memory regions for the
2105 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002106 Ranges are in pairs (memory base and size).
2107
Randy Dunlap4af94f32009-04-17 18:30:28 -07002108 ports= [IP_VS_FTP] IPVS ftp helper module
2109 Default is 21.
2110 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2111 may be specified.
2112 Format: <port>,<port>....
2113
Ingo Molnar45807a12007-07-15 23:40:10 -07002114 print-fatal-signals=
2115 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002116
2117 If enabled, warn about various signal handling
2118 related application anomalies: too many signals,
2119 too many POSIX.1 timers, fatal signals causing a
2120 coredump - etc.
2121
2122 If you hit the warning due to signal overflow,
2123 you might want to try "ulimit -i unlimited".
2124
Ingo Molnar45807a12007-07-15 23:40:10 -07002125 default: off.
2126
Randy Dunlape84845c2007-07-15 23:40:25 -07002127 printk.time= Show timing data prefixed to each printk message line
2128 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2129
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002130 processor.max_cstate= [HW,ACPI]
2131 Limit processor to maximum C-state
2132 max_cstate=9 overrides any DMI blacklist limit.
2133
2134 processor.nocst [HW,ACPI]
2135 Ignore the _CST method to determine C-states,
2136 instead using the legacy FADT method
2137
Linus Torvalds1da177e2005-04-16 15:20:36 -07002138 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002139 Format: [schedule,]<number>
2140 Param: "schedule" - profile schedule points.
2141 Param: <number> - step/bucket size as a power of 2 for
2142 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002143 Param: "sleep" - profile D-state sleeping (millisecs).
2144 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002145 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002146
Linus Torvalds1da177e2005-04-16 15:20:36 -07002147 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2148 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002149 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002150
Randy Dunlapa9913042005-10-23 12:57:11 -07002151 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2152 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002153 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2154 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002155 psmouse.resetafter= [HW,MOUSE]
2156 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002157 (0 = never).
2158 psmouse.resolution=
2159 [HW,MOUSE] Set desired mouse resolution, in dpi.
2160 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002161 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002162 0 = disabled, 1 = enabled (default).
2163
Matthew Garrettdee28e72011-07-21 16:57:55 -04002164 pstore.backend= Specify the name of the pstore backend to use
2165
Linus Torvalds1da177e2005-04-16 15:20:36 -07002166 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002167 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002168
Kay Sieversdc8c8582007-08-15 12:25:38 +02002169 pty.legacy_count=
2170 [KNL] Number of legacy pty's. Overwrites compiled-in
2171 default number.
2172
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002173 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002174
Linus Torvalds1da177e2005-04-16 15:20:36 -07002175 r128= [HW,DRM]
2176
2177 raid= [HW,RAID]
2178 See Documentation/md.txt.
2179
Randy Dunlapa9913042005-10-23 12:57:11 -07002180 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002181 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002182
Linus Torvalds1da177e2005-04-16 15:20:36 -07002183 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002184 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002185
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002186 rcupdate.blimit= [KNL,BOOT]
2187 Set maximum number of finished RCU callbacks to process
2188 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002189
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002190 rcupdate.qhimark= [KNL,BOOT]
2191 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002192 RCU callbacks over which batch limiting is disabled.
2193
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002194 rcupdate.qlowmark= [KNL,BOOT]
2195 Set threshold of queued RCU callbacks below which
2196 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002197
Olof Johanssonffdfc402005-09-06 15:17:19 -07002198 rdinit= [KNL]
2199 Format: <full_path>
2200 Run specified binary instead of /init from the ramdisk,
2201 used for early userspace startup. See initrd.
2202
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002203 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002204 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002205 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002206
Paul Jackson46b6d942008-07-04 10:00:09 -07002207 relax_domain_level=
2208 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002209 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002210
Linus Torvalds1da177e2005-04-16 15:20:36 -07002211 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2212
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002213 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002214 Format: nn[KMG]
2215 Reserves a hole at the top of the kernel virtual
2216 address space.
2217
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002218 reservelow= [X86]
2219 Format: nn[K]
2220 Set the amount of memory to reserve for BIOS at
2221 the bottom of the address space.
2222
Vivek Goyal7e962872006-09-27 01:50:44 -07002223 reset_devices [KNL] Force drivers to reset the underlying device
2224 during initialization.
2225
Randy Dunlapa9913042005-10-23 12:57:11 -07002226 resume= [SWSUSP]
2227 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002228
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002229 resume_offset= [SWSUSP]
2230 Specify the offset from the beginning of the partition
2231 given by "resume=" at which the swap header is located,
2232 in <PAGE_SIZE> units (needed only for swap files).
2233 See Documentation/power/swsusp-and-swap-files.txt
2234
Bojan Smojverf996fc92010-09-09 23:06:23 +02002235 hibernate= [HIBERNATION]
2236 noresume Don't check if there's a hibernation image
2237 present during boot.
2238 nocompress Don't compress/decompress hibernation images.
2239
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002240 retain_initrd [RAM] Keep initrd memory after extraction
2241
Linus Torvalds1da177e2005-04-16 15:20:36 -07002242 rhash_entries= [KNL,NET]
2243 Set number of hash buckets for route cache
2244
2245 riscom8= [HW,SERIAL]
2246 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2247
2248 ro [KNL] Mount root device read-only on boot
2249
2250 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07002251 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002252
2253 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2254 mount the root filesystem
2255
2256 rootflags= [KNL] Set root filesystem mount option string
2257
2258 rootfstype= [KNL] Set root filesystem type
2259
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002260 rootwait [KNL] Wait (indefinitely) for root device to show up.
2261 Useful for devices that are detected asynchronously
2262 (e.g. USB and MMC devices).
2263
Linus Torvalds1da177e2005-04-16 15:20:36 -07002264 rw [KNL] Mount root device read-write on boot
2265
2266 S [KNL] Run init in single mode
2267
2268 sa1100ir [NET]
2269 See drivers/net/irda/sa1100_ir.c.
2270
Linus Torvalds1da177e2005-04-16 15:20:36 -07002271 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002272
Mike Travisf6630112009-11-17 18:22:15 -06002273 sched_debug [KNL] Enables verbose scheduler debug messages.
2274
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002275 security= [SECURITY] Choose a security module to enable at boot.
2276 If this boot parameter is not specified, only the first
2277 security module asking for security registration will be
2278 loaded. An invalid security module name will be treated
2279 as if no module has been chosen.
2280
2281 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002282 Format: { "0" | "1" }
2283 See security/selinux/Kconfig help text.
2284 0 -- disable.
2285 1 -- enable.
2286 Default value is set via kernel config option.
2287 If enabled at boot time, /selinux/disable can be used
2288 later to disable prior to initial policy load.
2289
John Johansenc1c124e2010-07-29 14:48:09 -07002290 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2291 Format: { "0" | "1" }
2292 See security/apparmor/Kconfig help text
2293 0 -- disable.
2294 1 -- enable.
2295 Default value is set via kernel config option.
2296
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002297 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002298
Linus Torvalds1da177e2005-04-16 15:20:36 -07002299 shapers= [NET]
2300 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002301
Yinghai Lub05f78f2008-08-22 01:32:50 -07002302 show_msr= [x86] show boot-time MSR settings
2303 Format: { <integer> }
2304 Show boot-time (BIOS-initialized) MSR settings.
2305 The parameter means the number of CPUs to show,
2306 for example 1 means boot CPU only.
2307
Linus Torvalds1da177e2005-04-16 15:20:36 -07002308 simeth= [IA-64]
2309 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002310
Linus Torvalds1da177e2005-04-16 15:20:36 -07002311 slram= [HW,MTD]
2312
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002313 slub_debug[=options[,slabs]] [MM, SLUB]
2314 Enabling slub_debug allows one to determine the
2315 culprit if slab objects become corrupted. Enabling
2316 slub_debug can create guard zones around objects and
2317 may poison objects when not in use. Also tracks the
2318 last alloc / free. For more information see
2319 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002320
2321 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002322 Determines the maximum allowed order for slabs.
2323 A high setting may cause OOMs due to memory
2324 fragmentation. For more information see
2325 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002326
2327 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002328 The minimum number of objects per slab. SLUB will
2329 increase the slab order up to slub_max_order to
2330 generate a sufficiently large slab able to contain
2331 the number of objects indicated. The higher the number
2332 of objects the smaller the overhead of tracking slabs
2333 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002334 For more information see Documentation/vm/slub.txt.
2335
2336 slub_min_order= [MM, SLUB]
2337 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002338 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002339 For more information see Documentation/vm/slub.txt.
2340
2341 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002342 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002343 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002344 allocs to different slabs. Debug options disable
2345 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002346 For more information see Documentation/vm/slub.txt.
2347
Linus Torvalds1da177e2005-04-16 15:20:36 -07002348 smart2= [HW]
2349 Format: <io1>[,<io2>[,...,<io8>]]
2350
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002351 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002352 attempt to substitute SMP alternatives once at boot.
2353
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002354 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2355 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2356 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2357 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2358 smsc-ircc2.ircc_irq= [HW] IRQ line
2359 smsc-ircc2.ircc_dma= [HW] DMA channel
2360 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2361 0: Toshiba Satellite 1800 (GP data pin select)
2362 1: Fast pin select (default)
2363 2: ATC IRMode
2364
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002365 softlockup_panic=
2366 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002367 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002368
Linus Torvalds1da177e2005-04-16 15:20:36 -07002369 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2370 See Documentation/sonypi.txt
2371
2372 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002373 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002374
2375 spia_io_base= [HW,MTD]
2376 spia_fio_base=
2377 spia_pedr=
2378 spia_peddr=
2379
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002380 stacktrace [FTRACE]
2381 Enabled the stack tracer on boot up.
2382
Linus Torvalds1da177e2005-04-16 15:20:36 -07002383 sti= [PARISC,HW]
2384 Format: <num>
2385 Set the STI (builtin display/keyboard on the HP-PARISC
2386 machines) console (graphic card) which should be used
2387 as the initial boot-console.
2388 See also comment in drivers/video/console/sticore.c.
2389
2390 sti_font= [HW]
2391 See comment in drivers/video/console/sticore.c.
2392
2393 stifb= [HW]
2394 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2395
Trond Myklebustcbf11072009-08-09 15:06:19 -04002396 sunrpc.min_resvport=
2397 sunrpc.max_resvport=
2398 [NFS,SUNRPC]
2399 SunRPC servers often require that client requests
2400 originate from a privileged port (i.e. a port in the
2401 range 0 < portnr < 1024).
2402 An administrator who wishes to reserve some of these
2403 ports for other uses may adjust the range that the
2404 kernel's sunrpc client considers to be privileged
2405 using these two parameters to set the minimum and
2406 maximum port values.
2407
Greg Banks42a7fc42007-03-06 01:42:23 -08002408 sunrpc.pool_mode=
2409 [NFS]
2410 Control how the NFS server code allocates CPUs to
2411 service thread pools. Depending on how many NICs
2412 you have and where their interrupts are bound, this
2413 option will affect which CPUs will do NFS serving.
2414 Note: this parameter cannot be changed while the
2415 NFS server is running.
2416
2417 auto the server chooses an appropriate mode
2418 automatically using heuristics
2419 global a single global pool contains all CPUs
2420 percpu one pool for each CPU
2421 pernode one pool for each NUMA node (equivalent
2422 to global on non-NUMA machines)
2423
Trond Myklebustcbf11072009-08-09 15:06:19 -04002424 sunrpc.tcp_slot_table_entries=
2425 sunrpc.udp_slot_table_entries=
2426 [NFS,SUNRPC]
2427 Sets the upper limit on the number of simultaneous
2428 RPC calls that can be sent from the client to a
2429 server. Increasing these values may allow you to
2430 improve throughput, but will also increase the
2431 amount of memory reserved for use by the client.
2432
Michal Hockoa42c3902010-11-24 12:57:08 -08002433 swapaccount[=0|1]
2434 [KNL] Enable accounting of swap in memory resource
2435 controller if no parameter or 1 is given or disable
2436 it if 0 is given (See Documentation/cgroups/memory.txt)
2437
Linus Torvalds1da177e2005-04-16 15:20:36 -07002438 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002439
Linus Torvalds1da177e2005-04-16 15:20:36 -07002440 switches= [HW,M68k]
2441
Andi Kleene52eec12010-09-08 16:54:17 +02002442 sysfs.deprecated=0|1 [KNL]
2443 Enable/disable old style sysfs layout for old udev
2444 on older distributions. When this option is enabled
2445 very new udev will not work anymore. When this option
2446 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2447 in older udev will not work anymore.
2448 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2449 the kernel configuration.
2450
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002451 sysrq_always_enabled
2452 [KNL]
2453 Ignore sysrq setting - this boot parameter will
2454 neutralize any effect of /proc/sys/kernel/sysrq.
2455 Useful for debugging.
2456
Linus Torvalds1da177e2005-04-16 15:20:36 -07002457 tdfx= [HW,DRM]
2458
David Brownell77437fd2008-07-23 21:28:33 -07002459 test_suspend= [SUSPEND]
2460 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2461 standby suspend) as the system sleep state to briefly
2462 enter during system startup. The system is woken from
2463 this state using a wakeup-capable RTC alarm.
2464
Linus Torvalds1da177e2005-04-16 15:20:36 -07002465 thash_entries= [KNL,NET]
2466 Set number of hash buckets for TCP connection
2467
Len Brownf8707ec2007-08-12 00:12:54 -04002468 thermal.act= [HW,ACPI]
2469 -1: disable all active trip points in all thermal zones
2470 <degrees C>: override all lowest active trip points
2471
Len Brownc52a7412007-08-14 15:49:32 -04002472 thermal.crt= [HW,ACPI]
2473 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002474 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002475
Len Brownf5487142007-08-12 00:12:44 -04002476 thermal.nocrt= [HW,ACPI]
2477 Set to disable actions on ACPI thermal zone
2478 critical and hot trip points.
2479
Len Brown72b33ef2007-08-12 00:12:17 -04002480 thermal.off= [HW,ACPI]
2481 1: disable ACPI thermal control
2482
Len Browna70cdc52007-08-12 00:12:35 -04002483 thermal.psv= [HW,ACPI]
2484 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002485 <degrees C>: override all passive trip points to this
2486 value
Len Browna70cdc52007-08-12 00:12:35 -04002487
Len Brown730ff342007-08-12 00:12:26 -04002488 thermal.tzp= [HW,ACPI]
2489 Specify global default ACPI thermal zone polling rate
2490 <deci-seconds>: poll all this frequency
2491 0: no polling (default)
2492
Thomas Gleixner8d32a302011-02-23 23:52:23 +00002493 threadirqs [KNL]
2494 Force threading of all interrupt handlers except those
2495 marked explicitely IRQF_NO_THREAD.
2496
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002497 topology= [S390]
2498 Format: {off | on}
2499 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07002500 topology information if the hardware supports this.
2501 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002502 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02002503 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002504
Linus Torvalds1da177e2005-04-16 15:20:36 -07002505 tp720= [HW,PS2]
2506
Rajiv Andrade225a9be2010-03-25 00:55:32 -03002507 tpm_suspend_pcr=[HW,TPM]
2508 Format: integer pcr id
2509 Specify that at suspend time, the tpm driver
2510 should extend the specified pcr with zeros,
2511 as a workaround for some chips which fail to
2512 flush the last written pcr on TPM_SaveState.
2513 This will guarantee that all the other pcrs
2514 are saved.
2515
Li Zefan9d612be2009-06-24 17:33:15 +08002516 trace_buf_size=nn[KMG]
2517 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002518
Li Zefan020e5f82009-07-01 10:47:05 +08002519 trace_event=[event-list]
2520 [FTRACE] Set and start specified trace events in order
2521 to facilitate early boot debugging.
2522 See also Documentation/trace/events.txt
2523
john stultzd3b8f882009-08-17 16:40:47 -07002524 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07002525 Format: <string>
2526 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07002527 disables clocksource verification at runtime, as well
2528 as the stability checks done at bootup. Used to enable
2529 high-resolution timer mode on older hardware, and in
2530 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07002531 [x86] noirqtime: Do not use TSC to do irq accounting.
2532 Used to run time disable IRQ_TIME_ACCOUNTING on any
2533 platforms where RDTSC is slow and this accounting
2534 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07002535
Randy Dunlapa9913042005-10-23 12:57:11 -07002536 turbografx.map[2|3]= [HW,JOY]
2537 TurboGraFX parallel port interface
2538 Format:
2539 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002540 See also Documentation/input/joystick-parport.txt
2541
Christian Kujaub6935f82011-05-31 15:22:05 +00002542 udbg-immortal [PPC] When debugging early kernel crashes that
2543 happen after console_init() and before a proper
2544 console driver takes over, this boot options might
2545 help "seeing" what's going on.
2546
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002547 uhash_entries= [KNL,NET]
2548 Set number of hash buckets for UDP/UDP-Lite connections
2549
Alan Stern5f8364b2006-12-05 16:29:55 -05002550 uhci-hcd.ignore_oc=
2551 [USB] Ignore overcurrent events (default N).
2552 Some badly-designed motherboards generate lots of
2553 bogus events, for ports that aren't wired to
2554 anything. Set this parameter to avoid log spamming.
2555 Note that genuine overcurrent events won't be
2556 reported either.
2557
Simon Arlotte3a61b02008-07-19 23:32:54 +01002558 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002559 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01002560
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02002561 usbcore.authorized_default=
2562 [USB] Default USB device authorization:
2563 (default -1 = authorized except for wireless USB,
2564 0 = not authorized, 1 = authorized)
2565
Alan Sternb5e795f2007-02-20 15:00:53 -05002566 usbcore.autosuspend=
2567 [USB] The autosuspend time delay (in seconds) used
2568 for newly-detected USB devices (default 2). This
2569 is the time required before an idle device will be
2570 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002571 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002572
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002573 usbcore.usbfs_snoop=
2574 [USB] Set to log all usbfs traffic (default 0 = off).
2575
2576 usbcore.blinkenlights=
2577 [USB] Set to cycle leds on hubs (default 0 = off).
2578
2579 usbcore.old_scheme_first=
2580 [USB] Start with the old device initialization
2581 scheme (default 0 = off).
2582
2583 usbcore.use_both_schemes=
2584 [USB] Try the other device initialization scheme
2585 if the first one fails (default 1 = enabled).
2586
2587 usbcore.initial_descriptor_timeout=
2588 [USB] Specifies timeout for the initial 64-byte
2589 USB_REQ_GET_DESCRIPTOR request in milliseconds
2590 (default 5000 = 5.0 seconds).
2591
Linus Torvalds1da177e2005-04-16 15:20:36 -07002592 usbhid.mousepoll=
2593 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002594
Alan Sternd4f373e2008-11-10 14:07:45 -05002595 usb-storage.delay_use=
2596 [UMS] The delay in seconds before a new device is
2597 scanned for Logical Units (default 5).
2598
2599 usb-storage.quirks=
2600 [UMS] A list of quirks entries to supplement or
2601 override the built-in unusual_devs list. List
2602 entries are separated by commas. Each entry has
2603 the form VID:PID:Flags where VID and PID are Vendor
2604 and Product ID values (4-digit hex numbers) and
2605 Flags is a set of characters, each corresponding
2606 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002607 a = SANE_SENSE (collect more than 18 bytes
2608 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002609 b = BAD_SENSE (don't collect more than 18
2610 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002611 c = FIX_CAPACITY (decrease the reported
2612 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01002613 d = NO_READ_DISC_INFO (don't use
2614 READ_DISC_INFO command);
2615 e = NO_READ_CAPACITY_16 (don't use
2616 READ_CAPACITY_16 command);
Alan Sternc838ea42008-12-15 10:40:06 -05002617 h = CAPACITY_HEURISTICS (decrease the
2618 reported device capacity by one
2619 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002620 i = IGNORE_DEVICE (don't bind to this
2621 device);
2622 l = NOT_LOCKABLE (don't try to lock and
2623 unlock ejectable media);
2624 m = MAX_SECTORS_64 (don't transfer more
2625 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04002626 n = INITIAL_READ10 (force a retry of the
2627 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05002628 o = CAPACITY_OK (accept the capacity
2629 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002630 r = IGNORE_RESIDUE (the device reports
2631 bogus residue values);
2632 s = SINGLE_LUN (the device has only one
2633 Logical Unit);
2634 w = NO_WP_DETECT (don't test whether the
2635 medium is write-protected).
2636 Example: quirks=0419:aaf5:rl,0421:0433:rc
2637
Ian Campbell14315592010-02-17 10:38:10 +00002638 userpte=
2639 [X86] Flags controlling user PTE allocations.
2640
2641 nohigh = do not allocate PTE pages in
2642 HIGHMEM regardless of setting
2643 of CONFIG_HIGHPTE.
2644
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302645 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002646 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002647 vdso=1: enable VDSO (default)
2648 vdso=0: disable VDSO mapping
2649
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302650 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002651 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2652 vdso32=1: enable 32-bit VDSO (default)
2653 vdso32=0: disable 32-bit VDSO mapping
2654
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002655 vector= [IA-64,SMP]
2656 vector=percpu: enable percpu vector domain
2657
Linus Torvalds1da177e2005-04-16 15:20:36 -07002658 video= [FB] Frame buffer configuration
2659 See Documentation/fb/modedb.txt.
2660
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002661 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002662 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002663 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002664 Use vga=ask for menu.
2665 This is actually a boot loader parameter; the value is
2666 passed to the kernel using a special protocol.
2667
Randy Dunlapa9913042005-10-23 12:57:11 -07002668 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002669 size of <nn>. This can be used to increase the
2670 minimum size (128MB on x86). It can also be used to
2671 decrease the size and leave more room for directly
2672 mapped kernel RAM.
2673
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002674 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2675 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002676
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002677 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2678 Format: <command>
2679
2680 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2681 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002682
Andy Lutomirski3ae36652011-08-10 11:15:32 -04002683 vsyscall= [X86-64]
2684 Controls the behavior of vsyscalls (i.e. calls to
2685 fixed addresses of 0xffffffffff600x00 from legacy
2686 code). Most statically-linked binaries and older
2687 versions of glibc use these calls. Because these
2688 functions are at fixed addresses, they make nice
2689 targets for exploits that can control RIP.
2690
2691 emulate [default] Vsyscalls turn into traps and are
2692 emulated reasonably safely.
2693
2694 native Vsyscalls are native syscall instructions.
2695 This is a little bit faster than trapping
2696 and makes a few dynamic recompilers work
2697 better than they would in emulation mode.
2698 It also makes exploits much easier to write.
2699
2700 none Vsyscalls don't work at all. This makes
2701 them quite hard to use for exploits but
2702 might break your system.
2703
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002704 vt.cur_default= [VT] Default cursor shape.
2705 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2706 the parameters of the <Esc>[?A;B;Cc escape sequence;
2707 see VGA-softcursor.txt. Default: 2 = underline.
2708
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002709 vt.default_blu= [VT]
2710 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2711 Change the default blue palette of the console.
2712 This is a 16-member array composed of values
2713 ranging from 0-255.
2714
2715 vt.default_grn= [VT]
2716 Format: <green0>,<green1>,<green2>,...,<green15>
2717 Change the default green palette of the console.
2718 This is a 16-member array composed of values
2719 ranging from 0-255.
2720
2721 vt.default_red= [VT]
2722 Format: <red0>,<red1>,<red2>,...,<red15>
2723 Change the default red palette of the console.
2724 This is a 16-member array composed of values
2725 ranging from 0-255.
2726
2727 vt.default_utf8=
2728 [VT]
2729 Format=<0|1>
2730 Set system-wide default UTF-8 mode for all tty's.
2731 Default is 1, i.e. UTF-8 mode is enabled for all
2732 newly opened terminals.
2733
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002734 vt.global_cursor_default=
2735 [VT]
2736 Format=<-1|0|1>
2737 Set system-wide default for whether a cursor
2738 is shown on new VTs. Default is -1,
2739 i.e. cursors will be created by default unless
2740 overridden by individual drivers. 0 will hide
2741 cursors, 1 will display them.
2742
Randy Dunlap4724ba572010-05-03 11:42:52 -07002743 watchdog timers [HW,WDT] For information on watchdog timers,
2744 see Documentation/watchdog/watchdog-parameters.txt
2745 or other driver-specific files in the
2746 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002747
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002748 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2749 default x2apic cluster mode on platforms
2750 supporting x2apic.
2751
Jacob Panbb24c472009-09-02 07:37:17 -07002752 x86_mrst_timer= [X86-32,APBT]
2753 Choose timer option for x86 Moorestown MID platform.
2754 Two valid options are apbt timer only and lapic timer
2755 plus one apbt timer for broadcast timer.
2756 x86_mrst_timer=apbt_only | lapic_and_apbt
2757
Linus Torvalds1da177e2005-04-16 15:20:36 -07002758 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2759 xd_geo= See header of drivers/block/xd.c.
2760
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002761 xen_emul_unplug= [HW,X86,XEN]
2762 Unplug Xen emulated devices
2763 Format: [unplug0,][unplug1]
2764 ide-disks -- unplug primary master IDE devices
2765 aux-ide-disks -- unplug non-primary-master IDE devices
2766 nics -- unplug network devices
2767 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01002768 unnecessary -- unplugging emulated devices is
2769 unnecessary even if the host did not respond to
2770 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01002771 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002772
Linus Torvalds1da177e2005-04-16 15:20:36 -07002773 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002774 Format:
2775 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002776
Randy Dunlapa9913042005-10-23 12:57:11 -07002777______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002778
2779TODO:
2780
Linus Torvalds1da177e2005-04-16 15:20:36 -07002781 Add more DRM drivers.