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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.
Randy Dunlapa9913042005-10-23 12:57:11 -070046 DRM Direct Rendering Management support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070047 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070051 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070052 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050054 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070056 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080057 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020061 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070062 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070063 LP Printer support is enabled.
64 LOOP Loopback device support is enabled.
65 M68k M68k architecture is enabled.
66 These options have more detailed description inside of
67 Documentation/m68k/kernel-options.txt.
68 MCA MCA bus support is enabled.
69 MDA MDA console support is enabled.
70 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070071 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070072 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 NET Appropriate network support is enabled.
74 NUMA NUMA support is enabled.
john stultz734efb42006-06-26 00:25:05 -070075 GENERIC_TIME The generic timeofday code is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070076 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070078 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070082 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
92 Documentation/scsi/.
James Morris20510f22007-10-16 23:31:32 -070093 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070094 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +090096 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -070099 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
Steven Rostedtf38f1d22008-12-16 23:06:40 -0500101 FTRACE Function tracing enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300102 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500104 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 USB USB support is enabled.
106 USBHID USB Human Interface Device support is enabled.
107 V4L Video For Linux support is enabled.
108 VGA The VGA console has been enabled.
109 VT Virtual terminal support is enabled.
110 WDT Watchdog support is enabled.
111 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700112 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 X86-64 X86-64 architecture is enabled.
114 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700115 Documentation/x86/x86_64/boot-options.txt .
Andi Kleenc0115602008-08-22 09:53:39 +0200116 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117
118In addition, the following text indicates that the option:
119
120 BUGS= Relates to possible processor bugs on the said processor.
121 KNL Is a kernel start-up parameter.
122 BOOT Is a boot loader parameter.
123
124Parameters denoted with BOOT are actually interpreted by the boot
125loader, and have no meaning to the kernel directly.
126Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500127need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128
Karsten Weiss55588702007-02-13 13:26:21 +0100129There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700130See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100131
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
133a trailing = on the name of any parameter states that that parameter will
134be entered as an environment variable, whereas its absence indicates that
135it will appear as a kernel argument readable via /proc/cmdline by programs
136running once the system is up.
137
jens m. noedler9c4751f2006-09-29 02:00:27 -0700138The number of kernel parameters is not limited, but the length of the
139complete command line (parameters including spaces etc.) is limited to
140a fixed number of characters. This limit depends on the architecture
141and is between 256 and 4096 characters. It is defined in the file
142./include/asm/setup.h as COMMAND_LINE_SIZE.
143
144
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530145 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800146 Advanced Configuration and Power Interface
Randy Dunlapaf23f572009-02-22 17:05:22 -0800147 Format: { force | off | ht | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148 force -- enable ACPI if default was off
149 off -- disable ACPI if default was on
150 noirq -- do not use ACPI for IRQ routing
151 ht -- run only enough ACPI to enable Hyper Threading
Randy Dunlapa9913042005-10-23 12:57:11 -0700152 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800154 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800155 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156
Randy Dunlap53471122008-03-12 18:10:51 -0400157 See also Documentation/power/pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158
Len Browna1fdcc02007-03-11 03:26:14 -0400159 acpi_apic_instance= [ACPI, IOAPIC]
160 Format: <int>
161 2: use 2nd APIC table, if available
162 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400163 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400164
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200165 acpi_backlight= [HW,ACPI]
166 acpi_backlight=vendor
167 acpi_backlight=video
168 If set to vendor, prefer vendor specific driver
169 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
170 of the ACPI video.ko driver.
171
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700172 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
173 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700175 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
176 debug output. Bits in debug_layer correspond to a
177 _COMPONENT in an ACPI source file, e.g.,
178 #define _COMPONENT ACPI_PCI_COMPONENT
179 Bits in debug_level correspond to a level in
180 ACPI_DEBUG_PRINT statements, e.g.,
181 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600182 The debug_level mask defaults to "info". See
183 Documentation/acpi/debug.txt for more information about
184 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600186 Enable processor driver info messages:
187 acpi.debug_layer=0x20000000
188 Enable PCI/PCI interrupt routing info messages:
189 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700190 Enable AML "Debug" output, i.e., stores to the Debug
191 object while interpreting AML:
192 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700193 Enable all messages related to ACPI hardware:
194 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200195
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700196 Some values produce so much output that the system is
197 unusable. The "log_buf_len" parameter may be useful
198 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800199
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700200 acpi_display_output= [HW,ACPI]
201 acpi_display_output=vendor
202 acpi_display_output=video
203 See above.
204
205 acpi_irq_balance [HW,ACPI]
206 ACPI will balance active IRQs
207 default in APIC mode
208
209 acpi_irq_nobalance [HW,ACPI]
210 ACPI will not move active IRQs (default)
211 default in PIC mode
212
213 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
214 Format: <irq>,<irq>...
215
216 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
217 use by PCI
218 Format: <irq>,<irq>...
219
220 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
221
222 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
223 Format: To spoof as Windows 98: ="Microsoft Windows"
224
225 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
226 acpi_osi="string1" # add string1 -- only one string
227 acpi_osi="!string2" # remove built-in string2
228 acpi_osi= # disable all strings
229
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530230 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700231 Override the pmtimer bug detection: force the kernel
232 to assume that this machine's pmtimer latches its value
233 and always returns good values.
234
Randy Dunlap4af94f32009-04-17 18:30:28 -0700235 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge | high | low }
237
238 acpi_serialize [HW,ACPI] force serialization of AML methods
239
240 acpi_skip_timer_override [HW,ACPI]
241 Recognize and ignore IRQ0/pin2 Interrupt Override.
242 For broken nForce2 BIOS resulting in XT-PIC timer.
243
244 acpi_sleep= [HW,ACPI] Sleep options
245 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800246 old_ordering, s4_nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700247 See Documentation/power/video.txt for information on
248 s3_bios and s3_mode.
249 s3_beep is for debugging; it makes the PC's speaker beep
250 as soon as the kernel's real-mode entry point is called.
251 s4_nohwsig prevents ACPI hardware signature from being
252 used during resume from hibernation.
253 old_ordering causes the ACPI 1.0 ordering of the _PTS
254 control method, with respect to putting devices into
255 low power states, to be enforced (the ACPI 2.0 ordering
256 of _PTS is used by default).
257 s4_nonvs prevents the kernel from saving/restoring the
258 ACPI NVS memory during hibernation.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800259 sci_force_enable causes the kernel to set SCI_EN directly
260 on resume from S1/S3 (which is against the ACPI spec,
261 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700262
263 acpi_use_timer_override [HW,ACPI]
264 Use timer override. For some broken Nvidia NF5 boards
265 that require a timer override, but don't have HPET
266
Luca Tettamanti7e905602009-03-30 00:01:27 +0200267 acpi_enforce_resources= [ACPI]
268 { strict | lax | no }
269 Check for resource conflicts between native drivers
270 and ACPI OperationRegions (SystemIO and SystemMemory
271 only). IO ports and memory declared in ACPI might be
272 used by the ACPI subsystem in arbitrary AML code and
273 can interfere with legacy drivers.
274 strict (default): access to resources claimed by ACPI
275 is denied; legacy drivers trying to access reserved
276 resources will fail to bind to device using them.
277 lax: access to resources claimed by ACPI is allowed;
278 legacy drivers trying to access reserved resources
279 will bind successfully but a warning message is logged.
280 no: ACPI OperationRegions are not marked as reserved,
281 no further checks are performed.
282
Linus Torvalds1da177e2005-04-16 15:20:36 -0700283 ad1848= [HW,OSS]
284 Format: <io>,<irq>,<dma>,<dma2>,<type>
285
Randy Dunlap4af94f32009-04-17 18:30:28 -0700286 add_efi_memmap [EFI; X86] Include EFI memory map in
287 kernel's map of available physical RAM.
288
Linus Torvalds1da177e2005-04-16 15:20:36 -0700289 advansys= [HW,SCSI]
290 See header of drivers/scsi/advansys.c.
291
292 advwdt= [HW,WDT] Advantech WDT
293 Format: <iostart>,<iostop>
294
295 aedsp16= [HW,OSS] Audio Excel DSP 16
296 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
297 See also header of sound/oss/aedsp16.c.
Randy Dunlapa9913042005-10-23 12:57:11 -0700298
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700299 agp= [AGP]
300 { off | try_unsupported }
301 off: disable AGP support
302 try_unsupported: try to drive unsupported chipsets
303 (may crash computer or cause data corruption)
304
Linus Torvalds1da177e2005-04-16 15:20:36 -0700305 aha152x= [HW,SCSI]
306 See Documentation/scsi/aha152x.txt.
307
308 aha1542= [HW,SCSI]
309 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
310
311 aic7xxx= [HW,SCSI]
312 See Documentation/scsi/aic7xxx.txt.
313
314 aic79xx= [HW,SCSI]
315 See Documentation/scsi/aic79xx.txt.
316
Russell Kingd944d542010-02-20 16:13:29 +0000317 alignment= [KNL,ARM]
318 Allow the default userspace alignment fault handler
319 behaviour to be specified. Bit 0 enables warnings,
320 bit 1 enables fixups, and bit 2 sends a segfault.
321
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200322 amd_iommu= [HW,X86-84]
323 Pass parameters to the AMD IOMMU driver in the system.
324 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900325 fullflush - enable flushing of IO/TLB entries when
326 they are unmapped. Otherwise they are
327 flushed before they will be reused, which
328 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200329 off - do not initialize any AMD IOMMU found in
330 the system
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900331
Linus Torvalds1da177e2005-04-16 15:20:36 -0700332 amijoy.map= [HW,JOY] Amiga joystick support
333 Map of devices attached to JOY0DAT and JOY1DAT
334 Format: <a>,<b>
335 See also Documentation/kernel/input/joystick.txt
336
337 analog.map= [HW,JOY] Analog joystick and gamepad support
338 Specifies type or capabilities of an analog joystick
339 connected to one of 16 gameports
340 Format: <type1>,<type2>,..<type16>
341
Randy Dunlapa9913042005-10-23 12:57:11 -0700342 apc= [HW,SPARC]
343 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344 Format: noidle
345 Disable APC CPU standby support. SPARCstation-Fox does
346 not play well with APC CPU idle - disable it if you have
347 APC and your system crashes randomly.
348
Randy Dunlapca1eda22009-05-06 16:02:58 -0700349 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700350 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700351 Format: { quiet (default) | verbose | debug }
352 Change the amount of debugging information output
353 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700354
Brian Haleyb0f83b22010-02-04 13:36:50 -0800355 autoconf= [IPV6]
356 See Documentation/networking/ipv6.txt.
357
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400358 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
359 Limit apic dumping. The parameter defines the maximal
360 number of local apics being dumped. Also it is possible
361 to set it to "all" by meaning -- no limit here.
362 Format: { 1 (default) | 2 | ... | all }.
363 The parameter valid if only apic=debug or
364 apic=verbose is specified.
365 Example: apic=debug show_lapic=all
366
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700368 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
371 Format: <io>,<irq>,<nodeID>
372
373 ataflop= [HW,M68k]
374
375 atarimouse= [HW,MOUSE] Atari Mouse
376
377 atascsi= [HW,SCSI] Atari SCSI
378
379 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
380 EzKey and similar keyboards
381
382 atkbd.reset= [HW] Reset keyboard during initialization
383
Randy Dunlapa9913042005-10-23 12:57:11 -0700384 atkbd.set= [HW] Select keyboard code set
385 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386
387 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
388 keyboards
389
390 atkbd.softraw= [HW] Choose between synthetic and real raw mode
391 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700392
393 atkbd.softrepeat= [HW]
394 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700395
396 autotest [IA64]
397
Linus Torvalds1da177e2005-04-16 15:20:36 -0700398 baycom_epp= [HW,AX25]
399 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700400
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
402 Format: <io>,<mode>
403 See header of drivers/net/hamradio/baycom_par.c.
404
Randy Dunlapa9913042005-10-23 12:57:11 -0700405 baycom_ser_fdx= [HW,AX25]
406 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700407 Format: <io>,<irq>,<mode>[,<baud>]
408 See header of drivers/net/hamradio/baycom_ser_fdx.c.
409
Randy Dunlapa9913042005-10-23 12:57:11 -0700410 baycom_ser_hdx= [HW,AX25]
411 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700412 Format: <io>,<irq>,<mode>
413 See header of drivers/net/hamradio/baycom_ser_hdx.c.
414
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700415 boot_delay= Milliseconds to delay each printk during boot.
416 Values larger than 10 seconds (10000) are changed to
417 no delay (0).
418 Format: integer
419
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700420 bootmem_debug [KNL] Enable bootmem allocator debug messages.
421
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700423 bttv.radio= Most important insmod options are available as
424 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700425 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
426 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
427
428 BusLogic= [HW,SCSI]
429 See drivers/scsi/BusLogic.c, comment before function
430 BusLogic_ParseDriverOptions().
431
432 c101= [NET] Moxa C101 synchronous serial card
433
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700434 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435 Sometimes CPU hardware bugs make them report the cache
436 size incorrectly. The kernel will attempt work arounds
437 to fix known problems, but for some CPUs it is not
438 possible to determine what the correct size should be.
439 This option provides an override for these situations.
440
James Morris20510f22007-10-16 23:31:32 -0700441 capability.disable=
442 [SECURITY] Disable capabilities. This would normally
443 be used only if an alternative security model is to be
444 configured. Potentially dangerous and should only be
445 used if you are entirely sure of the consequences.
446
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100447 ccw_timeout_log [S390]
448 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449
Paul Menage8bab8dd2008-04-04 14:29:57 -0700450 cgroup_disable= [KNL] Disable a particular controller
451 Format: {name of the controller(s) to disable}
452 {Currently supported controllers - "memory"}
453
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454 checkreqprot [SELINUX] Set initial checkreqprot flag value.
455 Format: { "0" | "1" }
456 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700457 0 -- check protection applied by kernel (includes
458 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700459 1 -- check protection requested by application.
460 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700461 Value can be changed at runtime via
462 /selinux/checkreqprot.
463
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100464 cio_ignore= [S390]
465 See Documentation/s390/CommonIO for details.
466
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700467 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700468 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200469 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700470 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200471 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472 Format: { pit | tsc | cyclone | pmtmr }
473
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700474 clocksource= [GENERIC_TIME] Override the default clocksource
475 Format: <string>
476 Override the default clocksource and use the clocksource
477 with the name specified.
478 Some clocksource names to choose from, depending on
479 the platform:
480 [all] jiffies (this is the base, fallback clocksource)
481 [ACPI] acpi_pm
482 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
483 pxa_timer,timer3,32k_counter,timer0_1
484 [AVR32] avr32
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700485 [X86-32] pit,hpet,tsc,vmi-timer;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700486 scx200_hrt on Geode; cyclone on IBM x440
487 [MIPS] MIPS
488 [PARISC] cr16
489 [S390] tod
490 [SH] SuperH
491 [SPARC64] tick
492 [X86-64] hpet,tsc
493
Andi Kleenac72e782008-01-30 13:33:21 +0100494 clearcpuid=BITNUM [X86]
495 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800496 arch/x86/include/asm/cpufeature.h for the valid bit
497 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100498 stable over kernel options, but the vendor specific
499 ones should be.
500 Also note that user programs calling CPUID directly
501 or using the feature without checking anything
502 will still see it. This just prevents it from
503 being used by the kernel or shown in /proc/cpuinfo.
504 Also note the kernel might malfunction if you disable
505 some critical bits.
506
Robert Jennings14f966e2009-04-15 05:55:32 +0000507 cmo_free_hint= [PPC] Format: { yes | no }
508 Specify whether pages are marked as being inactive
509 when they are freed. This is used in CMO environments
510 to determine OS memory pressure for page stealing by
511 a hypervisor.
512 Default: yes
513
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530514 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100515 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100516 Range: 0 - 8192
517 Default: 64
518
Linus Torvalds1da177e2005-04-16 15:20:36 -0700519 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700520 Format:
521 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522
523 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
524 Format: <io>[,<irq>]
525
Randy Dunlapa9913042005-10-23 12:57:11 -0700526 com90xx= [HW,NET]
527 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700528 Format: <io>[,<irq>[,<memstart>]]
529
530 condev= [HW,S390] console device
531 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700532
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533 console= [KNL] Output console device and options.
534
535 tty<n> Use the virtual console device <n>.
536
537 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800538 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700539 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800540 the form "bbbbpnf", where "bbbb" is the baud rate,
541 "p" is parity ("n", "o", or "e"), "n" is number of
542 bits, and "f" is flow control ("r" for RTS or
543 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800545 See Documentation/serial-console.txt for more
546 information. See
547 Documentation/networking/netconsole.txt for an
548 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700549
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700550 uart[8250],io,<addr>[,options]
551 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700552 Start an early, polled-mode console on the 8250/16550
553 UART at the specified I/O port or MMIO address,
554 switching to the matching ttyS device later. The
555 options are the same as for ttyS, above.
556
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700557 If the device connected to the port is not a TTY but a braille
558 device, prepend "brl," before the device type, for instance
559 console=brl,ttyS0
560 For now, only VisioBraille is supported.
561
Daniel Mackf324edc2009-06-16 15:33:52 -0700562 consoleblank= [KNL] The console blank (screen saver) timeout in
563 seconds. Defaults to 10*60 = 10mins. A value of 0
564 disables the blank timer.
565
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800566 coredump_filter=
567 [KNL] Change the default value for
568 /proc/<pid>/coredump_filter.
569 See also Documentation/filesystems/proc.txt.
570
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700572 Format:
573 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700574
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700575 crashkernel=nn[KMG]@ss[KMG]
576 [KNL] Reserve a chunk of physical memory to
577 hold a kernel to switch to with kexec on panic.
578
Bernhard Wallefb391592007-10-18 23:41:02 -0700579 crashkernel=range1:size1[,range2:size2,...][@offset]
580 [KNL] Same as above, but depends on the memory
581 in the running system. The syntax of range is
582 start-[end] where start and end are both
583 a memory unit (amount[KMG]). See also
584 Documentation/kdump/kdump.txt for a example.
585
Linus Torvalds1da177e2005-04-16 15:20:36 -0700586 cs89x0_dma= [HW,NET]
587 Format: <dma>
588
589 cs89x0_media= [HW,NET]
590 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700591
Randy Dunlapa9913042005-10-23 12:57:11 -0700592 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593 See header of drivers/s390/block/dasd_devmap.c.
594
595 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
596 (one device per port)
597 Format: <port#>,<type>
598 See also Documentation/input/joystick-parport.txt
599
600 debug [KNL] Enable kernel debugging (events log level).
601
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700602 debug_locks_verbose=
603 [KNL] verbose self-tests
604 Format=<0|1>
605 Print debugging info while doing the locking API
606 self-tests.
607 We default to 0 (no extra messages), setting it to
608 1 will print _a lot_ more information - normally
609 only useful to kernel developers.
610
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700611 debug_objects [KNL] Enable object debugging
612
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500613 no_debug_objects
614 [KNL] Disable object debugging
615
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200616 debugpat [X86] Enable PAT debugging
617
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200618 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700619 Format: <area>[,<node>]
620 See also Documentation/networking/decnet.txt.
621
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700622 default_hugepagesz=
623 [same as hugepagesz=] The size of the default
624 HugeTLB page size. This is the size represented by
625 the legacy /proc/ hugepages APIs, used for SHM, and
626 default size when mounting hugetlbfs filesystems.
627 Defaults to the default architecture's huge page size
628 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700629
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630 dhash_entries= [KNL]
631 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700632
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633 digi= [HW,SERIAL]
634 IO parameters + enable/disable command.
635
636 digiepca= [HW,SERIAL]
637 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000638 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700639
Brian Haleyb0f83b22010-02-04 13:36:50 -0800640 disable= [IPV6]
641 See Documentation/networking/ipv6.txt.
642
643 disable_ipv6= [IPV6]
644 See Documentation/networking/ipv6.txt.
645
Yinghai Lu95ffa242008-04-29 03:52:33 -0700646 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700647 The kernel tries to adjust MTRR layout from continuous
648 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700649 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700650
Yinghai Lu093af8d2008-01-30 13:33:32 +0100651 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100652 By default the kernel will trim any uncacheable
653 memory out of your available memory pool based on
654 MTRR settings. This parameter disables that behavior,
655 possibly causing your machine to run very slowly.
656
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530657 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700658 Disable PIN 1 of APIC timer
659 Can be useful to work around chipset bugs.
660
Linus Torvalds1da177e2005-04-16 15:20:36 -0700661 dmasound= [HW,OSS] Sound subsystem buffers
662
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700663 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
664 this option disables the debugging code at boot.
665
666 dma_debug_entries=<number>
667 This option allows to tune the number of preallocated
668 entries for DMA-API debugging code. One entry is
669 required per DMA-API allocation. Use this if the
670 DMA-API debugging code disables itself because the
671 architectural default is too low.
672
Joerg Roedel1745de52009-05-22 21:49:51 +0200673 dma_debug_driver=<driver_name>
674 With this option the DMA-API debugging driver
675 filter feature can be enabled at boot time. Just
676 pass the driver to filter for as the parameter.
677 The filter can be disabled or changed to another
678 driver later using sysfs.
679
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 dscc4.setup= [NET]
681
682 dtc3181e= [HW,SCSI]
683
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700684 dynamic_printk Enables pr_debug()/dev_dbg() calls if
685 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
686 These can also be switched on/off via
687 <debugfs>/dynamic_printk/modules
688
689 earlycon= [KNL] Output early console device and options.
690 uart[8250],io,<addr>[,options]
691 uart[8250],mmio,<addr>[,options]
692 Start an early, polled-mode console on the 8250/16550
693 UART at the specified I/O port or MMIO address.
694 The options are the same as for ttyS, above.
695
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530696 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700697 earlyprintk=vga
698 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500699 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500700 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700701
Randy Dunlapa9913042005-10-23 12:57:11 -0700702 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703 takes over.
704
Yinghai Lu5c059172008-07-24 17:29:40 -0700705 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700706
707 Currently only ttyS0 and ttyS1 are supported.
708
709 Interaction with the standard serial driver is not
710 very good.
711
712 The VGA output is eventually overwritten by the real
713 console.
714
715 eata= [HW,SCSI]
716
Linus Torvalds1da177e2005-04-16 15:20:36 -0700717 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700718 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700719
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720 eisa_irq_edge= [PARISC,HW]
721 See header of drivers/parisc/eisa.c.
722
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700723 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700725 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700726
727 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800728 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700729 See Documentation/block/as-iosched.txt and
730 Documentation/block/deadline-iosched.txt for details.
731
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530732 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700733 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800734 image elf header. Generally kexec loader will
735 pass this option to capture kernel.
736 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700738 enable_mtrr_cleanup [X86]
739 The kernel tries to adjust MTRR layout from continuous
740 to discrete, to make X server driver able to add WB
741 entry later. This parameter enables that.
742
Randy Dunlapca1eda22009-05-06 16:02:58 -0700743 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700744 Enable PIN 1 of APIC timer
745 Can be useful to work around chipset bugs
746 (in particular on some ATI chipsets).
747 The kernel tries to set a reasonable default.
748
Linus Torvalds1da177e2005-04-16 15:20:36 -0700749 enforcing [SELINUX] Set initial enforcing status.
750 Format: {"0" | "1"}
751 See security/selinux/Kconfig help text.
752 0 -- permissive (log only, no denials).
753 1 -- enforcing (deny and log).
754 Default value is 0.
755 Value can be changed at runtime via /selinux/enforce.
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
761 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
762 Format: <io>[,<irq>]
763
Akinobu Mitade1ba092006-12-08 02:39:42 -0800764 failslab=
765 fail_page_alloc=
766 fail_make_request=[KNL]
767 General fault injection mechanism.
768 Format: <interval>,<probability>,<space>,<times>
769 See also /Documentation/fault-injection/.
770
Linus Torvalds1da177e2005-04-16 15:20:36 -0700771 fd_mcs= [HW,SCSI]
772 See header of drivers/scsi/fd_mcs.c.
773
774 fdomain= [HW,SCSI]
775 See header of drivers/scsi/fdomain.c.
776
777 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000778 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700779
Alex Chiangf13ae302008-05-08 14:03:23 -0600780 force_pal_cache_flush
781 [IA-64] Avoid check_sal_cache_flush which may hang on
782 buggy SAL_CACHE_FLUSH implementations. Using this
783 parameter will force ia64_sal_cache_flush to call
784 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
785
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100786 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400787 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100788 as early as possible in order to facilitate early
789 boot debugging.
790
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200791 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400792 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200793 If no parameter is passed, ftrace will dump
794 buffers of all CPUs, but if you pass orig_cpu, it will
795 dump only the buffer of the CPU that triggered the
796 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400797
798 ftrace_filter=[function-list]
799 [FTRACE] Limit the functions traced by the function
800 tracer at boot up. function-list is a comma separated
801 list of functions. This list can be changed at run
802 time by the set_ftrace_filter file in the debugfs
803 tracing directory.
804
805 ftrace_notrace=[function-list]
806 [FTRACE] Do not trace the functions specified in
807 function-list. This list can be changed at run time
808 by the set_ftrace_notrace file in the debugfs
809 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100810
Stefan Assmann369bc182009-10-12 22:17:21 +0200811 ftrace_graph_filter=[function-list]
812 [FTRACE] Limit the top level callers functions traced
813 by the function graph tracer at boot up.
814 function-list is a comma separated list of functions
815 that can be changed at run time by the
816 set_graph_function file in the debugfs tracing directory.
817
Linus Torvalds1da177e2005-04-16 15:20:36 -0700818 gamecon.map[2|3]=
819 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
820 support via parallel port (up to 5 devices per port)
821 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
822 See also Documentation/input/joystick-parport.txt
823
824 gamma= [HW,DRM]
825
Yinghai Luaaf23042008-01-30 13:33:09 +0100826 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
827 Format: off | on
828 default: on
829
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700830 gcov_persist= [GCOV] When non-zero (default), profiling data for
831 kernel modules is saved and remains accessible via
832 debugfs, even when the module is unloaded/reloaded.
833 When zero, profiling data is discarded and associated
834 debugfs files are removed at module unload time.
835
Linus Torvalds1da177e2005-04-16 15:20:36 -0700836 gdth= [HW,SCSI]
837 See header of drivers/scsi/gdth.c.
838
839 gpt [EFI] Forces disk with valid GPT signature but
840 invalid Protective MBR to be treated as GPT.
841
Linus Torvalds1da177e2005-04-16 15:20:36 -0700842 gvp11= [HW,SCSI]
843
844 hashdist= [KNL,NUMA] Large hashes allocated during boot
845 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700846 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700847 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700848
849 hcl= [IA-64] SGI's Hardware Graph compatibility layer
850
851 hd= [EIDE] (E)IDE hard drive subsystem geometry
852 Format: <cyl>,<head>,<sect>
853
Linus Torvalds1da177e2005-04-16 15:20:36 -0700854 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
855 size of <nn>. This works even on boxes that have no
856 highmem otherwise. This also works to reduce highmem
857 size on bigger boxes.
858
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800859 highres= [KNL] Enable/disable high resolution timer mode.
860 Valid parameters: "on", "off"
861 Default: "on"
862
Linus Torvalds1da177e2005-04-16 15:20:36 -0700863 hisax= [HW,ISDN]
864 See Documentation/isdn/README.HiSax.
865
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700866 hlt [BUGS=ARM,SH]
867
868 hpet= [X86-32,HPET] option to control HPET usage
869 Format: { enable (default) | disable | force |
870 verbose }
871 disable: disable HPET and use PIT instead
872 force: allow force enabled of undocumented chips (ICH4,
873 VIA, nVidia)
874 verbose: show contents of HPET registers during setup
875
Andi Kleenb4718e62008-07-23 21:27:51 -0700876 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
877 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700878 On x86-64 and powerpc, this option can be specified
879 multiple times interleaved with hugepages= to reserve
880 huge pages of different sizes. Valid pages sizes on
881 x86-64 are 2M (when the CPU supports "pse") and 1G
882 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700883 Note that 1GB pages can only be allocated at boot time
884 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900885
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100886 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
887 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100888 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
889 If specified, z/VM IUCV HVC accepts connections
890 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100891
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700892 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700893 or register an additional I2C bus that is not
894 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700895 Format:
896 <bus_id>,<clkrate>
897
Jiri Kosina36d95732008-10-06 02:51:09 -0400898 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700899 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200900 i8042.dumbkbd [HW] Pretend that controller can only read data from
901 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700902 (Don't attempt to blink the leds)
903 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500904 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400905 i8042.noloop [HW] Disable the AUX Loopback command while probing
906 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700907 i8042.nomux [HW] Don't check presence of an active multiplexing
908 controller
909 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
910 controllers
911 i8042.panicblink=
912 [HW] Frequency with which keyboard LEDs should blink
913 when kernel panics (default is 0.5 sec)
914 i8042.reset [HW] Reset the controller during init and cleanup
915 i8042.unlock [HW] Unlock (ignore) the keylock
916
917 i810= [HW,DRM]
918
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700919 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
920 indicates that the driver is running on unsupported
921 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
923 does not match list of supported models.
924 i8k.power_status
925 [HW] Report power status in /proc/i8k
926 (disabled by default)
927 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
928 capability is set.
929
930 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
931 See Documentation/mca.txt.
932
933 icn= [HW,ISDN]
934 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
935
David Fries0af80c02009-02-25 20:28:21 +0100936 ide-core.nodma= [HW] (E)IDE subsystem
937 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200938 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
939 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100940 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700941
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700942 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
943 Claim all unknown PCI IDE storage controllers.
944
Andi Kleenf039b752007-05-02 19:27:12 +0200945 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800946 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
947 Poll forces a polling idle loop that can slightly
948 improve the performance of waking up a idle CPU, but
949 will use a lot of power and make the system run hot.
950 Not recommended.
951 idle=mwait: On systems which support MONITOR/MWAIT but
952 the kernel chose to not use it because it doesn't save
953 as much power as a normal idle loop, use the
954 MONITOR/MWAIT idle loop anyways. Performance should be
955 the same as idle=poll.
956 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800957 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800958 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700959
Ingo Molnar792908222006-12-06 20:40:51 -0800960 ignore_loglevel [KNL]
961 Ignore loglevel setting - this will print /all/
962 kernel messages to the console. Useful for debugging.
963
Linus Torvalds1da177e2005-04-16 15:20:36 -0700964 ihash_entries= [KNL]
965 Set number of hash buckets for inode cache.
966
Mimi Zohar3323eec92009-02-04 09:06:58 -0500967 ima_audit= [IMA]
968 Format: { "0" | "1" }
969 0 -- integrity auditing messages. (Default)
970 1 -- enable informational integrity auditing messages.
971
972 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700973 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -0500974 default: "sha1"
975
Eric Paris5789ba32009-05-21 15:47:06 -0400976 ima_tcb [IMA]
977 Load a policy which meets the needs of the Trusted
978 Computing Base. This means IMA will measure all
979 programs exec'd, files mmap'd for exec, and all files
980 opened for read by uid=0.
981
Linus Torvalds1da177e2005-04-16 15:20:36 -0700982 in2000= [HW,SCSI]
983 See header of drivers/scsi/in2000.c.
984
985 init= [KNL]
986 Format: <full_path>
987 Run specified binary instead of /sbin/init as init
988 process.
989
990 initcall_debug [KNL] Trace initcalls as they are executed. Useful
991 for working out where the kernel is dying during
992 startup.
993
994 initrd= [BOOT] Specify the location of the initial ramdisk
995
996 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
997 Format: <irq>
998
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700999 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001000 on
1001 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001002 off
1003 Disable intel iommu driver.
1004 igfx_off [Default Off]
1005 By default, gfx is mapped as normal device. If a gfx
1006 device has a dedicated DMAR unit, the DMAR unit is
1007 bypassed by not enabling DMAR with this option. In
1008 this case, gfx device will use physical address for
1009 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001010 forcedac [x86_64]
1011 With this option iommu will not optimize to look
1012 for io virtual address below 32 bit forcing dual
1013 address cycle on pci bus for cards supporting greater
1014 than 32 bit addressing. The default is to look
1015 for translation below 32 bit and if not available
1016 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001017 strict [Default Off]
1018 With this option on every unmap_single operation will
1019 result in a hardware IOTLB flush operation as opposed
1020 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001021
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001022 inttest= [IA64]
1023
1024 iomem= Disable strict checking of access to MMIO memory
1025 strict regions from userspace.
1026 relaxed
1027
1028 iommu= [x86]
1029 off
1030 force
1031 noforce
1032 biomerge
1033 panic
1034 nopanic
1035 merge
1036 nomerge
1037 forcesac
1038 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001039 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001040
1041 io7= [HW] IO7 for Marvel based alpha systems
1042 See comment before marvel_specify_io7 in
1043 arch/alpha/kernel/core_marvel.c.
1044
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301045 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001046 0x80
1047 Standard port 0x80 based delay
1048 0xed
1049 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001050 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001051 Simple two microseconds delay
1052 none
1053 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001054
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001056 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001057
1058 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001059 See comment before ip2_setup() in
1060 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001061
1062 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1063 See header of drivers/scsi/ips.c.
1064
Alan Cox200803d2005-06-28 20:45:18 -07001065 irqfixup [HW]
1066 When an interrupt is not handled search all handlers
1067 for it. Intended to get systems with badly broken
1068 firmware running.
1069
1070 irqpoll [HW]
1071 When an interrupt is not handled search all handlers
1072 for it. Also check all handlers each timer
1073 interrupt. Intended to get systems with badly broken
1074 firmware running.
1075
Linus Torvalds1da177e2005-04-16 15:20:36 -07001076 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001077 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078
1079 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001080 Format:
1081 <cpu number>,...,<cpu number>
1082 or
Li Zefanb225d442008-11-06 12:53:39 -08001083 <cpu number>-<cpu number>
1084 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001085 or a mixture
1086 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001087
Linus Torvalds1da177e2005-04-16 15:20:36 -07001088 This option can be used to specify one or more CPUs
1089 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001090 algorithms. You can move a process onto or off an
1091 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001092 <cpu number> begins at 0 and the maximum value is
1093 "number of CPUs in system - 1".
1094
1095 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001096 alternative -- manually setting the CPU mask of all
1097 tasks in the system -- can cause problems and
1098 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001099
Randy Dunlapa9913042005-10-23 12:57:11 -07001100 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001101
1102 js= [HW,JOY] Analog joystick
1103 See Documentation/input/joystick.txt.
1104
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001105 keepinitrd [HW,ARM]
1106
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301107 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001108 specifies the amount of memory usable by the kernel
1109 for non-movable allocations. The requested amount is
1110 spread evenly throughout all nodes in the system. The
1111 remaining memory in each node is used for Movable
1112 pages. In the event, a node is too small to have both
1113 kernelcore and Movable pages, kernelcore pages will
1114 take priority and other nodes will have a larger number
1115 of kernelcore pages. The Movable zone is used for the
1116 allocation of pages that may be reclaimed or moved
1117 by the page migration subsystem. This means that
1118 HugeTLB pages may not be allocated from this zone.
1119 Note that allocations like PTEs-from-HighMem still
1120 use the HighMem zone if it exists, and the Normal
1121 zone if it does not.
1122
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001123 kgdboc= [HW] kgdb over consoles.
1124 Requires a tty driver that supports console polling.
Matt LaPlante19f59462009-04-27 15:06:31 +02001125 (only serial supported for now)
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001126 Format: <serial_device>[,baud]
1127
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001128 kmac= [MIPS] korina ethernet MAC address.
1129 Configure the RouterBoard 532 series on-chip
1130 Ethernet adapter MAC address.
1131
Catalin Marinas04f70332009-06-11 13:22:39 +01001132 kmemleak= [KNL] Boot-time kmemleak enable/disable
1133 Valid arguments: on, off
1134 Default: on
1135
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301136 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001137 in oops dumps.
1138
Andre Przywarafef07aa2009-07-10 14:20:35 +02001139 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1140 Default is 0 (don't ignore, but inject #GP)
1141
1142 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1143 Default is 1 (enabled)
1144
1145 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1146 Default is 0 (off)
1147
1148 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1149 for all guests.
1150 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1151
1152 kvm-intel.bypass_guest_pf=
1153 [KVM,Intel] Disables bypassing of guest page faults
1154 on Intel chips. Default is 1 (enabled)
1155
1156 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1157 (virtualized MMU) support on capable Intel chips.
1158 Default is 1 (enabled)
1159
1160 kvm-intel.emulate_invalid_guest_state=
1161 [KVM,Intel] Enable emulation of invalid guest states
1162 Default is 0 (disabled)
1163
1164 kvm-intel.flexpriority=
1165 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1166 Default is 1 (enabled)
1167
1168 kvm-intel.unrestricted_guest=
1169 [KVM,Intel] Disable unrestricted guest feature
1170 (virtualized real and unpaged mode) on capable
1171 Intel chips. Default is 1 (enabled)
1172
1173 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1174 feature (tagged TLBs) on capable Intel chips.
1175 Default is 1 (enabled)
1176
Linus Torvalds1da177e2005-04-16 15:20:36 -07001177 l2cr= [PPC]
1178
Robert Brosea78bfbf2008-03-29 07:20:23 +11001179 l3cr= [PPC]
1180
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001181 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001182 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001183
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301184 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001185 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001186
FD Camifcb71f62008-01-06 19:08:56 +01001187 libata.dma= [LIBATA] DMA control
1188 libata.dma=0 Disable all PATA and SATA DMA
1189 libata.dma=1 PATA and SATA Disk DMA only
1190 libata.dma=2 ATAPI (CDROM) DMA only
1191 libata.dma=4 Compact Flash DMA only
1192 Combinations also work, so libata.dma=3 enables DMA
1193 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001194
1195 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1196 libata.ignore_hpa=0 keep BIOS limits (default)
1197 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001198
Dave Jones78e70c22007-09-27 11:50:13 -04001199 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1200 when set.
1201 Format: <int>
1202
Tejun Heo33267322008-02-13 09:15:09 +09001203 libata.force= [LIBATA] Force configurations. The format is comma
1204 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001205 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001206 matching port, link or device. Basically, it matches
1207 the ATA ID string printed on console by libata. If
1208 the whole ID part is omitted, the last PORT and DEVICE
1209 values are used. If ID hasn't been specified yet, the
1210 configuration applies to all ports, links and devices.
1211
1212 If only DEVICE is omitted, the parameter applies to
1213 the port and all links and devices behind it. DEVICE
1214 number of 0 either selects the first device or the
1215 first fan-out link behind PMP device. It does not
1216 select the host link. DEVICE number of 15 selects the
1217 host link and device attached to it.
1218
1219 The VAL specifies the configuration to force. As long
1220 as there's no ambiguity shortcut notation is allowed.
1221 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1222 The following configurations can be forced.
1223
1224 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1225 Any ID with matching PORT is used.
1226
1227 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1228
1229 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1230 udma[/][16,25,33,44,66,100,133] notation is also
1231 allowed.
1232
1233 * [no]ncq: Turn on or off NCQ.
1234
Tejun Heo05944bd2008-08-13 20:19:09 +09001235 * nohrst, nosrst, norst: suppress hard, soft
1236 and both resets.
1237
Tejun Heo33267322008-02-13 09:15:09 +09001238 If there are multiple matching configurations changing
1239 the same attribute, the last one is used.
1240
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001241 lmb=debug [KNL] Enable lmb debug messages.
1242
Linus Torvalds1da177e2005-04-16 15:20:36 -07001243 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001244 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001245
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001246 lockd.nlm_grace_period=P [NFS] Assign grace period.
1247 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001248
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001249 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1250 Format: <integer>
1251
1252 lockd.nlm_timeout=T [NFS] Assign timeout value.
1253 Format: <integer>
1254
1255 lockd.nlm_udpport=M [NFS] Assign UDP port.
1256 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001257
1258 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1259 Format: <irq>
1260
1261 loglevel= All Kernel Messages with a loglevel smaller than the
1262 console loglevel will be printed to the console. It can
1263 also be changed with klogd or other programs. The
1264 loglevels are defined as follows:
1265
1266 0 (KERN_EMERG) system is unusable
1267 1 (KERN_ALERT) action must be taken immediately
1268 2 (KERN_CRIT) critical conditions
1269 3 (KERN_ERR) error conditions
1270 4 (KERN_WARNING) warning conditions
1271 5 (KERN_NOTICE) normal but significant condition
1272 6 (KERN_INFO) informational
1273 7 (KERN_DEBUG) debug-level messages
1274
1275 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001276 Format: { n | nk | nM }
1277 n must be a power of two. The default size
1278 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001279
Randy Dunlapaccaa242007-10-16 01:29:37 -07001280 logo.nologo [FB] Disables display of the built-in Linux logo.
1281 This may be used to provide more screen space for
1282 kernel log messages and is useful when debugging
1283 kernel boot problems.
1284
Linus Torvalds1da177e2005-04-16 15:20:36 -07001285 lp=0 [LP] Specify parallel ports to use, e.g,
1286 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1287 lp=reset first parallel port). 'lp=0' disables the
1288 lp=auto printer driver. 'lp=reset' (which can be
1289 specified in addition to the ports) causes
1290 attached printers to be reset. Using
1291 lp=port1,port2,... specifies the parallel ports
1292 to associate lp devices with, starting with
1293 lp0. A port specification may be 'none' to skip
1294 that lp device, or a parport name such as
1295 'parport0'. Specifying 'lp=auto' instead of a
1296 port specification list means that device IDs
1297 from each port should be examined, to see if
1298 an IEEE 1284-compliant printer is attached; if
1299 so, the driver will manage that printer.
1300 See also header of drivers/char/lp.c.
1301
1302 lpj=n [KNL]
1303 Sets loops_per_jiffy to given constant, thus avoiding
1304 time-consuming boot-time autodetection (up to 250 ms per
1305 CPU). 0 enables autodetection (default). To determine
1306 the correct value for your kernel, boot with normal
1307 autodetection and see what value is printed. Note that
1308 on SMP systems the preset will be applied to all CPUs,
1309 which is likely to cause problems if your CPUs need
1310 significantly divergent settings. An incorrect value
1311 will cause delays in the kernel to be wrong, leading to
1312 unpredictable I/O errors and other breakage. Although
1313 unlikely, in the extreme case this might damage your
1314 hardware.
1315
1316 ltpc= [NET]
1317 Format: <io>,<irq>,<dma>
1318
Randy Dunlapa9913042005-10-23 12:57:11 -07001319 mac5380= [HW,SCSI] Format:
1320 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001321
Randy Dunlapa9913042005-10-23 12:57:11 -07001322 machvec= [IA64] Force the use of a particular machine-vector
1323 (machvec) in a generic kernel.
1324 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001325
Wu Zhangjin3209e702009-07-02 23:27:12 +08001326 machtype= [Loongson] Share the same kernel image file between different
1327 yeeloong laptop.
1328 Example: machtype=lemote-yeeloong-2f-7inch
1329
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001330 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1331 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332
1333 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001334 should make use of. maxcpus=n : n >= 0 limits the
1335 kernel to using 'n' processors. n=0 is a special case,
1336 it is equivalent to "nosmp", which also disables
1337 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001338
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001339 max_loop= [LOOP] Maximum number of loopback devices that can
1340 be mounted
1341 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001342
Randy Dunlapa9913042005-10-23 12:57:11 -07001343 max_luns= [SCSI] Maximum number of LUNs to probe.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344 Should be between 1 and 2^32-1.
1345
1346 max_report_luns=
Randy Dunlapa9913042005-10-23 12:57:11 -07001347 [SCSI] Maximum number of LUNs received.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001348 Should be between 1 and 16384.
1349
Linus Torvalds1da177e2005-04-16 15:20:36 -07001350 mcatest= [IA-64]
1351
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001352 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353
Uwe Hermann71cced62008-10-20 09:32:21 -07001354 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001355
Linus Torvalds1da177e2005-04-16 15:20:36 -07001356 md= [HW] RAID subsystems devices and level
1357 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001358
Linus Torvalds1da177e2005-04-16 15:20:36 -07001359 mdacon= [MDA]
1360 Format: <first>,<last>
1361 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001362
Linus Torvalds1da177e2005-04-16 15:20:36 -07001363 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1364 Amount of memory to be used when the kernel is not able
1365 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001366 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367 address space collisions. Without memmap= PCI devices
1368 could be placed at addresses belonging to unused RAM.
1369
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001370 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371 memory.
1372
Paul Mundt6902aa82008-09-21 17:14:42 +09001373 memchunk=nn[KMG]
1374 [KNL,SH] Allow user to override the default size for
1375 per-device physically contiguous DMA buffers.
1376
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301377 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001378 E820 memory map, as specified by the user.
1379 Such memmap=exactmap lines can be constructed based on
1380 BIOS output or other requirements. See the memmap=nn@ss
1381 option description.
1382
1383 memmap=nn[KMG]@ss[KMG]
1384 [KNL] Force usage of a specific region of memory
1385 Region of memory to be used, from ss to ss+nn.
1386
1387 memmap=nn[KMG]#ss[KMG]
1388 [KNL,ACPI] Mark specific memory as ACPI data.
1389 Region of memory to be used, from ss to ss+nn.
1390
1391 memmap=nn[KMG]$ss[KMG]
1392 [KNL,ACPI] Mark specific memory as reserved.
1393 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001394 Example: Exclude memory from 0x18690000-0x1869ffff
1395 memmap=64K$0x18690000
1396 or
1397 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001398
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001399 memory_corruption_check=0/1 [X86]
1400 Some BIOSes seem to corrupt the first 64k of
1401 memory when doing things like suspend/resume.
1402 Setting this option will scan the memory
1403 looking for corruption. Enabling this will
1404 both detect corruption and prevent the kernel
1405 from using the memory being corrupted.
1406 However, its intended as a diagnostic tool; if
1407 repeatable BIOS-originated corruption always
1408 affects the same memory, you can use memmap=
1409 to prevent the kernel from using that memory.
1410
1411 memory_corruption_check_size=size [X86]
1412 By default it checks for corruption in the low
1413 64k, making this memory unavailable for normal
1414 use. Use this parameter to scan for
1415 corruption in more or less memory.
1416
1417 memory_corruption_check_period=seconds [X86]
1418 By default it checks for corruption every 60
1419 seconds. Use this parameter to check at some
1420 other rate. 0 disables periodic checking.
1421
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001422 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001423 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001424 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001425 Specifies the number of memtest passes to be
1426 performed. Each pass selects another test
1427 pattern from a given set of patterns. Memtest
1428 fills the memory with this pattern, validates
1429 memory contents and reserves bad memory
1430 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001431
Linus Torvalds1da177e2005-04-16 15:20:36 -07001432 meye.*= [HW] Set MotionEye Camera parameters
1433 See Documentation/video4linux/meye.txt.
1434
Andres Salomon8f368812007-10-12 23:04:06 +02001435 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1436 Multi-Function General Purpose Timers on AMD Geode
1437 platforms.
1438
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001439 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1440 the BIOS has incorrectly applied a workaround. TinyBIOS
1441 version 0.98 is known to be affected, 0.99 fixes the
1442 problem by letting the user disable the workaround.
1443
Linus Torvalds1da177e2005-04-16 15:20:36 -07001444 mga= [HW,DRM]
1445
Randy Dunlap1c207f92008-11-19 15:36:16 -08001446 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1447 physical address is ignored.
1448
Michel Pollet39f45d72009-05-20 11:10:31 +01001449 mini2440= [ARM,HW,KNL]
1450 Format:[0..2][b][c][t]
1451 Default: "0tb"
1452 MINI2440 configuration specification:
1453 0 - The attached screen is the 3.5" TFT
1454 1 - The attached screen is the 7" TFT
1455 2 - The VGA Shield is attached (1024x768)
1456 Leaving out the screen size parameter will not load
1457 the TFT driver, and the framebuffer will be left
1458 unconfigured.
1459 b - Enable backlight. The TFT backlight pin will be
1460 linked to the kernel VESA blanking code and a GPIO
1461 LED. This parameter is not necessary when using the
1462 VGA shield.
1463 c - Enable the s3c camera interface.
1464 t - Reserved for enabling touchscreen support. The
1465 touchscreen support is not enabled in the mainstream
1466 kernel as of 2.6.30, a preliminary port can be found
1467 in the "bleeding edge" mini2440 support kernel at
1468 http://repo.or.cz/w/linux-2.6/mini2440.git
1469
Mel Gorman6b74ab92008-07-23 21:26:49 -07001470 mminit_loglevel=
1471 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1472 parameter allows control of the logging verbosity for
1473 the additional memory initialisation checks. A value
1474 of 0 disables mminit logging and a level of 4 will
1475 log everything. Information is printed at KERN_DEBUG
1476 so loglevel=8 may also need to be specified.
1477
Linus Torvalds1da177e2005-04-16 15:20:36 -07001478 mousedev.tap_time=
1479 [MOUSE] Maximum time between finger touching and
1480 leaving touchpad surface for touch to be considered
1481 a tap and be reported as a left button click (for
1482 touchpads working in absolute mode only).
1483 Format: <msecs>
1484 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1485 reporting absolute coordinates, such as tablets
1486 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1487 reporting absolute coordinates, such as tablets
1488
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301489 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001490 is similar to kernelcore except it specifies the
1491 amount of memory used for migratable allocations.
1492 If both kernelcore and movablecore is specified,
1493 then kernelcore will be at *least* the specified
1494 value but may be more. If movablecore on its own
1495 is specified, the administrator must be careful
1496 that the amount of memory usable for all allocations
1497 is not too small.
1498
Linus Torvalds1da177e2005-04-16 15:20:36 -07001499 mpu401= [HW,OSS]
1500 Format: <io>,<irq>
1501
1502 MTD_Partition= [MTD]
1503 Format: <name>,<region-number>,<size>,<offset>
1504
Randy Dunlapa9913042005-10-23 12:57:11 -07001505 MTD_Region= [MTD] Format:
1506 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001507
1508 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001509 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001510
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001511 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1512
1513 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1514
1515 boundary - index of last SLC block on Flex-OneNAND.
1516 The remaining blocks are configured as MLC blocks.
1517 lock - Configure if Flex-OneNAND boundary should be locked.
1518 Once locked, the boundary cannot be changed.
1519 1 indicates lock status, 0 indicates unlock status.
1520
Ben Dooks9db829f2008-07-03 11:24:29 +01001521 mtdset= [ARM]
1522 ARM/S3C2412 JIVE boot control
1523
1524 See arch/arm/mach-s3c2412/mach-jive.c
1525
Linus Torvalds1da177e2005-04-16 15:20:36 -07001526 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001527 [HW] Make the MicroTouch USB driver use raw coordinates
1528 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001529
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001530 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001531 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001532 that could hold holes aka. UC entries.
1533
1534 mtrr_gran_size=nn[KMG] [X86]
1535 Used for mtrr cleanup. It is granularity of mtrr block.
1536 Default is 1.
1537 Large value could prevent small alignment from
1538 using up MTRRs.
1539
1540 mtrr_spare_reg_nr=n [X86]
1541 Format: <integer>
1542 Range: 0,7 : spare reg number
1543 Default : 1
1544 Used for mtrr cleanup. It is spare mtrr entries number.
1545 Set to 2 or more if your graphical card needs more.
1546
Linus Torvalds1da177e2005-04-16 15:20:36 -07001547 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1548
1549 NCR_D700= [HW,SCSI]
1550 See header of drivers/scsi/NCR_D700.c.
1551
1552 ncr5380= [HW,SCSI]
1553
1554 ncr53c400= [HW,SCSI]
1555
1556 ncr53c400a= [HW,SCSI]
1557
1558 ncr53c406a= [HW,SCSI]
1559
1560 ncr53c8xx= [HW,SCSI]
1561
1562 netdev= [NET] Network devices parameters
1563 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1564 Note that mem_start is often overloaded to mean
1565 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001566 This usage is only documented in each driver source
1567 file if at all.
1568
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001569 nf_conntrack.acct=
1570 [NETFILTER] Enable connection tracking flow accounting
1571 0 to disable accounting
1572 1 to enable accounting
1573 Default value depends on CONFIG_NF_CT_ACCT that is
1574 going to be removed in 2.6.29.
1575
Linus Torvalds1da177e2005-04-16 15:20:36 -07001576 nfsaddrs= [NFS]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001577 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001578
1579 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001580 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001581
Trond Myklebusta72b4422006-01-03 09:55:41 +01001582 nfs.callback_tcpport=
1583 [NFS] set the TCP port on which the NFSv4 callback
1584 channel should listen.
1585
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001586 nfs.cache_getent=
1587 [NFS] sets the pathname to the program which is used
1588 to update the NFS client cache entries.
1589
1590 nfs.cache_getent_timeout=
1591 [NFS] sets the timeout after which an attempt to
1592 update a cache entry is deemed to have failed.
1593
Trond Myklebust58df0952006-01-03 09:55:57 +01001594 nfs.idmap_cache_timeout=
1595 [NFS] set the maximum lifetime for idmapper cache
1596 entries.
1597
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001598 nfs.enable_ino64=
1599 [NFS] enable 64-bit inode numbers.
1600 If zero, the NFS client will fake up a 32-bit inode
1601 number for the readdir() and stat() syscalls instead
1602 of returning the full 64-bit number.
1603 The default is to return 64-bit inode numbers.
1604
Paul Mundt1e1030d2009-09-01 17:38:32 +09001605 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001606 when a NMI is triggered.
1607 Format: [state][,regs][,debounce][,die]
1608
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301609 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001610 Format: [panic,][num]
1611 Valid num: 0,1,2
1612 0 - turn nmi_watchdog off
1613 1 - use the IO-APIC timer for the NMI watchdog
1614 2 - use the local APIC for the NMI watchdog using
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001615 a performance counter. Note: This will use one
1616 performance counter and the local APIC's performance
1617 vector.
1618 When panic is specified, panic when an NMI watchdog
1619 timeout occurs.
1620 This is useful when you use a panic=... timeout and
1621 need the box quickly up again.
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001622 Instead of 1 and 2 it is possible to use the following
1623 symbolic names: lapic and ioapic
1624 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
Linus Torvalds1da177e2005-04-16 15:20:36 -07001625
Anton Vorontsovbff38772009-07-08 11:10:56 -07001626 netpoll.carrier_timeout=
1627 [NET] Specifies amount of time (in seconds) that
1628 netpoll should wait for a carrier. By default netpoll
1629 waits 4 seconds.
1630
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001631 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001632 emulation library even if a 387 maths coprocessor
1633 is present.
1634
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001635 no_console_suspend
1636 [HW] Never suspend the console
1637 Disable suspending of consoles during suspend and
1638 hibernate operations. Once disabled, debugging
1639 messages can reach various consoles while the rest
1640 of the system is being put to sleep (ie, while
1641 debugging driver suspend/resume hooks). This may
1642 not work reliably with all consoles, but is known
1643 to work with serial and VGA consoles.
1644
Christoph Lameterc1aee212007-05-31 00:40:47 -07001645 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1646 caches in the slab allocator. Saves per-node memory,
1647 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001648
Randy Dunlapa9913042005-10-23 12:57:11 -07001649 noalign [KNL,ARM]
1650
Linus Torvalds1da177e2005-04-16 15:20:36 -07001651 noapic [SMP,APIC] Tells the kernel to not make use of any
1652 IOAPICs that may be present in the system.
1653
Linus Torvalds1da177e2005-04-16 15:20:36 -07001654 nobats [PPC] Do not use BATs for mapping kernel lowmem
1655 on "Classic" PPC cores.
1656
1657 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001658
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001659 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1660
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001661 nodelayacct [KNL] Disable per-task delay accounting
1662
Linus Torvalds1da177e2005-04-16 15:20:36 -07001663 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1664
Paul Mundt6902aa82008-09-21 17:14:42 +09001665 nodsp [SH] Disable hardware DSP at boot time.
1666
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301667 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001668
Linus Torvalds1da177e2005-04-16 15:20:36 -07001669 noexec [IA-64]
1670
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301671 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001672 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001673 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001674 noexec=off: disable non-executable mappings
1675
1676 noexec32 [X86-64]
1677 This affects only 32-bit executables.
1678 noexec32=on: enable non-executable mappings (default)
1679 read doesn't imply executable mappings
1680 noexec32=off: disable non-executable mappings
1681 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001682
Paul Mundt6902aa82008-09-21 17:14:42 +09001683 nofpu [SH] Disable hardware FPU at boot time.
1684
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001685 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001686 register save and restore. The kernel will only save
1687 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001688
Suresh Siddha0c752a92009-05-22 12:17:45 -07001689 noxsave [BUGS=X86] Disables x86 extended register state save
1690 and restore using xsave. The kernel will fallback to
1691 enabling legacy floating-point and sse state.
1692
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001693 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1694 wfi(ARM) instruction doesn't work correctly and not to
1695 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001696
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001697 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001698 instruction doesn't work correctly and not to
1699 use it.
1700
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001701 no_file_caps Tells the kernel not to honor file capabilities. The
1702 only way then for a file to be executed with privilege
1703 is to be setuid root or executed by root.
1704
Linus Torvalds1da177e2005-04-16 15:20:36 -07001705 nohalt [IA-64] Tells the kernel not to use the power saving
1706 function PAL_HALT_LIGHT when idle. This increases
1707 power-consumption. On the positive side, it reduces
1708 interrupt wake-up latency, which may improve performance
1709 in certain environments such as networked servers or
1710 real-time systems.
1711
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001712 nohz= [KNL] Boottime enable/disable dynamic ticks
1713 Valid arguments: on, off
1714 Default: on
1715
Paul Mundteeee7852009-04-02 12:31:16 +09001716 noiotrap [SH] Disables trapped I/O port accesses.
1717
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001718 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001719 disable unhandled interrupt sources.
1720
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301721 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001722 broken timer IRQ sources.
1723
Linus Torvalds1da177e2005-04-16 15:20:36 -07001724 noisapnp [ISAPNP] Disables ISA PnP code.
1725
1726 noinitrd [RAM] Tells the kernel not to load any configured
1727 initial RAM disk.
1728
Weidong Han03ea8152009-04-17 16:42:15 +08001729 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1730 remapping.
1731
Linus Torvalds1da177e2005-04-16 15:20:36 -07001732 nointroute [IA-64]
1733
Tony Luck0aa366f2007-07-20 11:22:30 -07001734 nojitter [IA64] Disables jitter checking for ITC timers.
1735
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001736 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001737
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001738 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001739
Linus Torvalds1da177e2005-04-16 15:20:36 -07001740 noltlbs [PPC] Do not use large page/tlb entries for kernel
1741 lowmem mapping on PPC40x.
1742
Horms312f1f02006-02-22 09:57:55 +09001743 nomca [IA-64] Disable machine check abort handling
1744
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001745 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001746
Andres Salomon83d73842007-10-12 23:04:06 +02001747 nomfgpt [X86-32] Disable Multi-Function General Purpose
1748 Timer usage (for AMD Geode machines).
1749
Jiri Kosina016ddd92010-01-18 17:05:40 +01001750 nopat [X86] Disable PAT (page attribute table extension of
1751 pagetables) support.
1752
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001753 norandmaps Don't use address space randomization. Equivalent to
1754 echo 0 > /proc/sys/kernel/randomize_va_space
1755
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001756 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001757
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001758 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001759 with UP alternatives
1760
Linus Torvalds1da177e2005-04-16 15:20:36 -07001761 noresidual [PPC] Don't use residual data on PReP machines.
1762
Randy Dunlapa9913042005-10-23 12:57:11 -07001763 noresume [SWSUSP] Disables resume and restores original swap
1764 space.
1765
Linus Torvalds1da177e2005-04-16 15:20:36 -07001766 no-scroll [VGA] Disables scrollback.
1767 This is required for the Braillex ib80-piezo Braille
1768 reader made by F.H. Papenmeier (Germany).
1769
1770 nosbagart [IA-64]
1771
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001772 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001773
Len Brown61ec7562007-08-16 03:34:22 -04001774 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1775 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001776
Dave Jones97842212007-07-15 23:41:05 -07001777 nosoftlockup [KNL] Disable the soft-lockup detector.
1778
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001779 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001780 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001781
Linus Torvalds1da177e2005-04-16 15:20:36 -07001782 nosync [HW,M68K] Disables sync negotiation for all devices.
1783
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001784 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001785
1786 nousb [USB] Disable the USB subsystem
1787
1788 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001789
Weidong Han2b2fd872009-04-17 16:42:12 +08001790 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1791
Fenghua Yua6c75b862008-03-14 13:57:08 -07001792 nptcg= [IA64] Override max number of concurrent global TLB
1793 purges which is reported from either PAL_VM_SUMMARY or
1794 SAL PALO.
1795
Yinghai Lu2b633e32010-02-10 01:20:37 -08001796 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1797 could support. nr_cpus=n : n >= 1 limits the kernel to
1798 supporting 'n' processors. Later in runtime you can not
1799 use hotplug cpu feature to put more cpu back to online.
1800 just like you compile the kernel NR_CPUS=n
1801
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001802 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1803
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001804 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1805 one of ['zone', 'node', 'default'] can be specified
1806 This can be set from sysctl after boot.
1807 See Documentation/sysctl/vm.txt for details.
1808
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001809 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1810 See Documentation/debugging-via-ohci1394.txt for more
1811 info.
1812
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001813 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1814 Rather than timing out after 20 ms if an EC
1815 command is not properly ACKed, override the length
1816 of the timeout. We have interrupts disabled while
1817 waiting for the ACK, so if this is set too high
1818 interrupts *may* be lost!
1819
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001820 omap_mux= [OMAP] Override bootloader pin multiplexing.
1821 Format: <mux_mode0.mode_name=value>...
1822 For example, to override I2C bus2:
1823 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1824
Linus Torvalds1da177e2005-04-16 15:20:36 -07001825 opl3= [HW,OSS]
1826 Format: <io>
1827
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828 oprofile.timer= [HW]
1829 Use timer interrupt instead of performance counters
1830
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001831 oprofile.cpu_type= Force an oprofile cpu type
1832 This might be useful if you have an older oprofile
1833 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001834 Format: { arch_perfmon }
1835 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001836 perfmon on Intel CPUs instead of the
1837 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001838
Linus Torvalds1da177e2005-04-16 15:20:36 -07001839 osst= [HW,SCSI] SCSI Tape Driver
1840 Format: <buffer_size>,<write_threshold>
1841 See also Documentation/scsi/st.txt.
1842
1843 panic= [KNL] Kernel behaviour on panic
1844 Format: <timeout>
1845
1846 parkbd.port= [HW] Parallel port number the keyboard adapter is
1847 connected to, default is 0.
1848 Format: <parport#>
1849 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1850 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001851 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001852
Randy Dunlapa9913042005-10-23 12:57:11 -07001853 parport= [HW,PPT] Specify parallel ports. 0 disables.
1854 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1855 Use 'auto' to force the driver to use any
1856 IRQ/DMA settings detected (the default is to
1857 ignore detected IRQ/DMA settings because of
1858 possible conflicts). You can specify the base
1859 address, IRQ, and DMA settings; IRQ and DMA
1860 should be numbers, or 'auto' (for using detected
1861 settings on that particular port), or 'nofifo'
1862 (to avoid using a FIFO even if it is detected).
1863 Parallel ports are assigned in the order they
1864 are specified on the command line, starting
1865 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001866
Randy Dunlapa9913042005-10-23 12:57:11 -07001867 parport_init_mode= [HW,PPT]
1868 Configure VIA parallel port to operate in
1869 a specific mode. This is necessary on Pegasos
1870 computer where firmware has no options for setting
1871 up parallel port mode and sets it to spp.
1872 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001873 Format: [spp|ps2|epp|ecp|ecpepp]
1874
Randy Dunlapa9913042005-10-23 12:57:11 -07001875 pas2= [HW,OSS] Format:
1876 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1877
Linus Torvalds1da177e2005-04-16 15:20:36 -07001878 pas16= [HW,SCSI]
1879 See header of drivers/scsi/pas16.c.
1880
Andrew Mortondd287792006-03-23 03:00:57 -08001881 pause_on_oops=
1882 Halt all CPUs after the first oops has been printed for
1883 the specified number of seconds. This is to be used if
1884 your oopses keep scrolling off the screen.
1885
Linus Torvalds1da177e2005-04-16 15:20:36 -07001886 pcbit= [HW,ISDN]
1887
1888 pcd. [PARIDE]
1889 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001890 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001891
Randy Dunlapa9913042005-10-23 12:57:11 -07001892 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001893 earlydump [X86] dump PCI config space before the kernel
1894 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001895 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001896 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001897 the hardware directly. Use this if your machine
1898 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001899 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001900 hardware access methods are allowed. Use this
1901 if you experience crashes upon bootup and you
1902 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001903 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001904 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001905 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001906 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001907 noaer [PCIE] If the PCIEAER kernel config parameter is
1908 enabled, this kernel boot option can be used to
1909 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001910 nodomains [PCI] Disable support for multiple PCI
1911 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301912 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001913 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001914 check_enable_amd_mmconf [X86] check for and enable
1915 properly configured MMIO access to PCI
1916 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001917 nomsi [MSI] If the PCI_MSI kernel config parameter is
1918 enabled, this kernel boot option can be used to
1919 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001920 noioapicquirk [APIC] Disable all boot interrupt quirks.
1921 Safety option to keep boot IRQs enabled. This
1922 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001923 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1924 primary IO-APIC for bridges that cannot disable
1925 boot IRQs. This fixes a source of spurious IRQs
1926 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001927 noioapicreroute [APIC] Disable workaround that uses the
1928 boot IRQ equivalent of an IRQ that connects to
1929 a chipset where boot IRQs cannot be disabled.
1930 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001931 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001932 routing table. These calls are known to be buggy
1933 on several machines and they hang the machine
1934 when used, but on other computers it's the only
1935 way to get the interrupt routing table. Try
1936 this option if the kernel is unable to allocate
1937 IRQs or discover secondary PCI buses on your
1938 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001939 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001940 Use with caution as certain devices share
1941 address decoders between ROMs and other
1942 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001943 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001944 expansion ROMs that do not already have
1945 BIOS assigned address ranges.
Andi Kleenc0115602008-08-22 09:53:39 +02001946 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001947 assigned automatically to PCI devices. You can
1948 make the kernel exclude IRQs of your ISA cards
1949 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001950 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001951 of the PIRQ table (normally generated
1952 by the BIOS) if it is outside the
1953 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001954 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001955 useful if the kernel is unable to find your
1956 secondary buses and you want to tell it
1957 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001958 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001959 numbers ourselves, overriding
1960 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001961 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001962 in the BIOS $PIR table. This is needed on
1963 some systems with broken BIOSes, notably
1964 some HP Pavilion N5400 and Omnibook XE3
1965 notebooks. This will have no effect if ACPI
1966 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001967 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001968 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07001969 use_crs [X86] Use PCI host bridge window information
1970 from ACPI. On BIOSes from 2008 or later, this
1971 is enabled by default. If you need to use this,
1972 please report a bug.
1973 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1974 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07001975 routeirq Do IRQ routing for all PCI devices.
1976 This is normally done in pci_enable_device(),
1977 so this option is a temporary workaround
1978 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001979 skip_isa_align [X86] do not align io start addr, so can
1980 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001981 firmware [ARM] Do not re-enumerate the bus but instead
1982 just use the configuration from the
1983 bootloader. This is currently used on
1984 IXP2000 systems where the bus has to be
1985 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001986 noearly [X86] Don't do any early type 1 scanning.
1987 This might help on some broken boards which
1988 machine check when some devices' config space
1989 is read. But various workarounds are disabled
1990 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001991 bfsort Sort PCI devices into breadth-first order.
1992 This sorting is done to get a device
1993 order compatible with older (<= 2.4) kernels.
1994 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001995 cbiosize=nn[KMG] The fixed amount of bus space which is
1996 reserved for the CardBus bridge's IO window.
1997 The default value is 256 bytes.
1998 cbmemsize=nn[KMG] The fixed amount of bus space which is
1999 reserved for the CardBus bridge's memory
2000 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002001 resource_alignment=
2002 Format:
2003 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2004 Specifies alignment and device to reassign
2005 aligned memory resources.
2006 If <order of align> is not specified,
2007 PAGE_SIZE is used as alignment.
2008 PCI-PCI bridge can be specified, if resource
2009 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002010 ecrc= Enable/disable PCIe ECRC (transaction layer
2011 end-to-end CRC checking).
2012 bios: Use BIOS/firmware settings. This is the
2013 the default.
2014 off: Turn ECRC off
2015 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002016
Chuck Ebberte5665a42008-09-24 20:40:34 -04002017 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2018 Management.
2019 off Disable ASPM.
2020 force Enable ASPM even on devices that claim not to support it.
2021 WARNING: Forcing ASPM on may cause system lockups.
2022
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002023 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2024 off Do not use native PCIe PME signaling.
2025 force Use native PCIe PME signaling even if the BIOS refuses
2026 to allow the kernel to control the relevant PCIe config
2027 registers.
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002028 nomsi Do not use MSI for native PCIe PME signaling (this makes
2029 all PCIe root ports use INTx for everything).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002030
Linus Torvalds1da177e2005-04-16 15:20:36 -07002031 pcmv= [HW,PCMCIA] BadgePAD 4
2032
2033 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002034 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002035
2036 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2037 boot time.
2038 Format: { 0 | 1 }
2039 See arch/parisc/kernel/pdc_chassis.c
2040
Tejun Heof58dc012009-08-14 15:00:50 +09002041 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002042 Currently supported values are "embed" and "page".
2043 Archs may support subset or none of the selections.
2044 See comments in mm/percpu.c for details on each
2045 allocator. This parameter is primarily for debugging
2046 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002047
Linus Torvalds1da177e2005-04-16 15:20:36 -07002048 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002049 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002050
2051 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002052 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002053
2054 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002055 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002056
2057 plip= [PPT,NET] Parallel port network link
2058 Format: { parport<nr> | timid | 0 }
2059 See also Documentation/parport.txt.
2060
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002061 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2062 Override pmtimer IOPort with a hex value.
2063 e.g. pmtmr=0x508
2064
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002065 pnp.debug [PNP]
2066 Enable PNP debug messages. This depends on the
2067 CONFIG_PNP_DEBUG_MESSAGES option.
2068
Linus Torvalds1da177e2005-04-16 15:20:36 -07002069 pnpacpi= [ACPI]
2070 { off }
2071
2072 pnpbios= [ISAPNP]
2073 { on | off | curr | res | no-curr | no-res }
2074
2075 pnp_reserve_irq=
2076 [ISAPNP] Exclude IRQs for the autoconfiguration
2077
2078 pnp_reserve_dma=
2079 [ISAPNP] Exclude DMAs for the autoconfiguration
2080
2081 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002082 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002083
2084 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002085 [ISAPNP] Exclude memory regions for the
2086 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087 Ranges are in pairs (memory base and size).
2088
Randy Dunlap4af94f32009-04-17 18:30:28 -07002089 ports= [IP_VS_FTP] IPVS ftp helper module
2090 Default is 21.
2091 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2092 may be specified.
2093 Format: <port>,<port>....
2094
Ingo Molnar45807a12007-07-15 23:40:10 -07002095 print-fatal-signals=
2096 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002097
2098 If enabled, warn about various signal handling
2099 related application anomalies: too many signals,
2100 too many POSIX.1 timers, fatal signals causing a
2101 coredump - etc.
2102
2103 If you hit the warning due to signal overflow,
2104 you might want to try "ulimit -i unlimited".
2105
Ingo Molnar45807a12007-07-15 23:40:10 -07002106 default: off.
2107
Randy Dunlape84845c2007-07-15 23:40:25 -07002108 printk.time= Show timing data prefixed to each printk message line
2109 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2110
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002111 processor.max_cstate= [HW,ACPI]
2112 Limit processor to maximum C-state
2113 max_cstate=9 overrides any DMI blacklist limit.
2114
2115 processor.nocst [HW,ACPI]
2116 Ignore the _CST method to determine C-states,
2117 instead using the legacy FADT method
2118
Linus Torvalds1da177e2005-04-16 15:20:36 -07002119 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002120 Format: [schedule,]<number>
2121 Param: "schedule" - profile schedule points.
2122 Param: <number> - step/bucket size as a power of 2 for
2123 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002124 Param: "sleep" - profile D-state sleeping (millisecs).
2125 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002126 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002127
Linus Torvalds1da177e2005-04-16 15:20:36 -07002128 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2129 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002130 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002131
Randy Dunlapa9913042005-10-23 12:57:11 -07002132 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2133 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002134 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2135 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002136 psmouse.resetafter= [HW,MOUSE]
2137 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002138 (0 = never).
2139 psmouse.resolution=
2140 [HW,MOUSE] Set desired mouse resolution, in dpi.
2141 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002142 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002143 0 = disabled, 1 = enabled (default).
2144
2145 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
Randy Dunlapa9913042005-10-23 12:57:11 -07002146 Format:
2147 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002148
2149 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002150 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151
Kay Sieversdc8c8582007-08-15 12:25:38 +02002152 pty.legacy_count=
2153 [KNL] Number of legacy pty's. Overwrites compiled-in
2154 default number.
2155
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002156 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002157
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158 r128= [HW,DRM]
2159
2160 raid= [HW,RAID]
2161 See Documentation/md.txt.
2162
Randy Dunlapa9913042005-10-23 12:57:11 -07002163 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002164 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002165
Linus Torvalds1da177e2005-04-16 15:20:36 -07002166 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002167 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002168
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002169 rcupdate.blimit= [KNL,BOOT]
2170 Set maximum number of finished RCU callbacks to process
2171 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002172
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002173 rcupdate.qhimark= [KNL,BOOT]
2174 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002175 RCU callbacks over which batch limiting is disabled.
2176
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002177 rcupdate.qlowmark= [KNL,BOOT]
2178 Set threshold of queued RCU callbacks below which
2179 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002180
Olof Johanssonffdfc402005-09-06 15:17:19 -07002181 rdinit= [KNL]
2182 Format: <full_path>
2183 Run specified binary instead of /init from the ramdisk,
2184 used for early userspace startup. See initrd.
2185
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002186 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002187 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002188 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002189
Paul Jackson46b6d942008-07-04 10:00:09 -07002190 relax_domain_level=
2191 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002192 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002193
Linus Torvalds1da177e2005-04-16 15:20:36 -07002194 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2195
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002196 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002197 Format: nn[KMG]
2198 Reserves a hole at the top of the kernel virtual
2199 address space.
2200
Vivek Goyal7e962872006-09-27 01:50:44 -07002201 reset_devices [KNL] Force drivers to reset the underlying device
2202 during initialization.
2203
Randy Dunlapa9913042005-10-23 12:57:11 -07002204 resume= [SWSUSP]
2205 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002206
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002207 resume_offset= [SWSUSP]
2208 Specify the offset from the beginning of the partition
2209 given by "resume=" at which the swap header is located,
2210 in <PAGE_SIZE> units (needed only for swap files).
2211 See Documentation/power/swsusp-and-swap-files.txt
2212
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002213 retain_initrd [RAM] Keep initrd memory after extraction
2214
Linus Torvalds1da177e2005-04-16 15:20:36 -07002215 rhash_entries= [KNL,NET]
2216 Set number of hash buckets for route cache
2217
2218 riscom8= [HW,SERIAL]
2219 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2220
2221 ro [KNL] Mount root device read-only on boot
2222
2223 root= [KNL] Root filesystem
2224
2225 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2226 mount the root filesystem
2227
2228 rootflags= [KNL] Set root filesystem mount option string
2229
2230 rootfstype= [KNL] Set root filesystem type
2231
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002232 rootwait [KNL] Wait (indefinitely) for root device to show up.
2233 Useful for devices that are detected asynchronously
2234 (e.g. USB and MMC devices).
2235
Linus Torvalds1da177e2005-04-16 15:20:36 -07002236 rw [KNL] Mount root device read-write on boot
2237
2238 S [KNL] Run init in single mode
2239
2240 sa1100ir [NET]
2241 See drivers/net/irda/sa1100_ir.c.
2242
Linus Torvalds1da177e2005-04-16 15:20:36 -07002243 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002244
Mike Travisf6630112009-11-17 18:22:15 -06002245 sched_debug [KNL] Enables verbose scheduler debug messages.
2246
Linus Torvalds1da177e2005-04-16 15:20:36 -07002247 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2248 Format: <io>[,<timeout>[,<isapnp>]]
2249
2250 scsi_debug_*= [SCSI]
2251 See drivers/scsi/scsi_debug.c.
2252
2253 scsi_default_dev_flags=
2254 [SCSI] SCSI default device flags
2255 Format: <integer>
2256
2257 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2258 Format: <vendor>:<model>:<flags>
2259 (flags are integer value)
2260
Randy Dunlap6af66322007-11-14 16:52:25 -08002261 scsi_logging_level= [SCSI] a bit mask of logging levels
2262 See drivers/scsi/scsi_logging.h for bits. Also
2263 settable via sysctl at dev.scsi.logging_level
2264 (/proc/sys/dev/scsi/logging_level).
2265 There is also a nice 'scsi_logging_level' script in the
2266 S390-tools package, available for download at
2267 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268
Matthew Wilcox3e082a92006-09-28 15:19:20 -06002269 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2270 discovered. async scans them in kernel threads,
2271 allowing boot to proceed. none ignores them, expecting
2272 user space to do the scan.
2273
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002274 security= [SECURITY] Choose a security module to enable at boot.
2275 If this boot parameter is not specified, only the first
2276 security module asking for security registration will be
2277 loaded. An invalid security module name will be treated
2278 as if no module has been chosen.
2279
2280 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002281 Format: { "0" | "1" }
2282 See security/selinux/Kconfig help text.
2283 0 -- disable.
2284 1 -- enable.
2285 Default value is set via kernel config option.
2286 If enabled at boot time, /selinux/disable can be used
2287 later to disable prior to initial policy load.
2288
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002289 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002290
Linus Torvalds1da177e2005-04-16 15:20:36 -07002291 shapers= [NET]
2292 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002293
Yinghai Lub05f78f2008-08-22 01:32:50 -07002294 show_msr= [x86] show boot-time MSR settings
2295 Format: { <integer> }
2296 Show boot-time (BIOS-initialized) MSR settings.
2297 The parameter means the number of CPUs to show,
2298 for example 1 means boot CPU only.
2299
Linus Torvalds1da177e2005-04-16 15:20:36 -07002300 sim710= [SCSI,HW]
2301 See header of drivers/scsi/sim710.c.
2302
2303 simeth= [IA-64]
2304 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002305
Linus Torvalds1da177e2005-04-16 15:20:36 -07002306 slram= [HW,MTD]
2307
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002308 slub_debug[=options[,slabs]] [MM, SLUB]
2309 Enabling slub_debug allows one to determine the
2310 culprit if slab objects become corrupted. Enabling
2311 slub_debug can create guard zones around objects and
2312 may poison objects when not in use. Also tracks the
2313 last alloc / free. For more information see
2314 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002315
2316 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002317 Determines the maximum allowed order for slabs.
2318 A high setting may cause OOMs due to memory
2319 fragmentation. For more information see
2320 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002321
2322 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002323 The minimum number of objects per slab. SLUB will
2324 increase the slab order up to slub_max_order to
2325 generate a sufficiently large slab able to contain
2326 the number of objects indicated. The higher the number
2327 of objects the smaller the overhead of tracking slabs
2328 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002329 For more information see Documentation/vm/slub.txt.
2330
2331 slub_min_order= [MM, SLUB]
2332 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002333 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002334 For more information see Documentation/vm/slub.txt.
2335
2336 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002337 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002338 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002339 allocs to different slabs. Debug options disable
2340 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002341 For more information see Documentation/vm/slub.txt.
2342
Linus Torvalds1da177e2005-04-16 15:20:36 -07002343 smart2= [HW]
2344 Format: <io1>[,<io2>[,...,<io8>]]
2345
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002346 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002347 attempt to substitute SMP alternatives once at boot.
2348
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002349 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2350 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2351 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2352 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2353 smsc-ircc2.ircc_irq= [HW] IRQ line
2354 smsc-ircc2.ircc_dma= [HW] DMA channel
2355 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2356 0: Toshiba Satellite 1800 (GP data pin select)
2357 1: Fast pin select (default)
2358 2: ATC IRMode
2359
Linus Torvalds1da177e2005-04-16 15:20:36 -07002360 snd-ad1816a= [HW,ALSA]
2361
2362 snd-ad1848= [HW,ALSA]
2363
2364 snd-ali5451= [HW,ALSA]
2365
2366 snd-als100= [HW,ALSA]
2367
2368 snd-als4000= [HW,ALSA]
2369
2370 snd-azt2320= [HW,ALSA]
2371
2372 snd-cmi8330= [HW,ALSA]
2373
2374 snd-cmipci= [HW,ALSA]
2375
2376 snd-cs4231= [HW,ALSA]
2377
2378 snd-cs4232= [HW,ALSA]
2379
2380 snd-cs4236= [HW,ALSA]
2381
2382 snd-cs4281= [HW,ALSA]
2383
2384 snd-cs46xx= [HW,ALSA]
2385
2386 snd-dt019x= [HW,ALSA]
2387
2388 snd-dummy= [HW,ALSA]
2389
2390 snd-emu10k1= [HW,ALSA]
2391
2392 snd-ens1370= [HW,ALSA]
2393
2394 snd-ens1371= [HW,ALSA]
2395
2396 snd-es968= [HW,ALSA]
2397
2398 snd-es1688= [HW,ALSA]
2399
2400 snd-es18xx= [HW,ALSA]
2401
2402 snd-es1938= [HW,ALSA]
2403
2404 snd-es1968= [HW,ALSA]
2405
2406 snd-fm801= [HW,ALSA]
2407
2408 snd-gusclassic= [HW,ALSA]
2409
2410 snd-gusextreme= [HW,ALSA]
2411
2412 snd-gusmax= [HW,ALSA]
2413
2414 snd-hdsp= [HW,ALSA]
2415
2416 snd-ice1712= [HW,ALSA]
2417
2418 snd-intel8x0= [HW,ALSA]
2419
2420 snd-interwave= [HW,ALSA]
2421
2422 snd-interwave-stb=
2423 [HW,ALSA]
2424
2425 snd-korg1212= [HW,ALSA]
2426
2427 snd-maestro3= [HW,ALSA]
2428
2429 snd-mpu401= [HW,ALSA]
2430
2431 snd-mtpav= [HW,ALSA]
2432
2433 snd-nm256= [HW,ALSA]
2434
2435 snd-opl3sa2= [HW,ALSA]
2436
2437 snd-opti92x-ad1848=
2438 [HW,ALSA]
2439
2440 snd-opti92x-cs4231=
2441 [HW,ALSA]
2442
2443 snd-opti93x= [HW,ALSA]
2444
2445 snd-pmac= [HW,ALSA]
2446
2447 snd-rme32= [HW,ALSA]
2448
2449 snd-rme96= [HW,ALSA]
2450
2451 snd-rme9652= [HW,ALSA]
2452
2453 snd-sb8= [HW,ALSA]
2454
2455 snd-sb16= [HW,ALSA]
2456
2457 snd-sbawe= [HW,ALSA]
2458
2459 snd-serial= [HW,ALSA]
2460
2461 snd-sgalaxy= [HW,ALSA]
2462
2463 snd-sonicvibes= [HW,ALSA]
2464
2465 snd-sun-amd7930=
2466 [HW,ALSA]
2467
2468 snd-sun-cs4231= [HW,ALSA]
2469
2470 snd-trident= [HW,ALSA]
2471
2472 snd-usb-audio= [HW,ALSA,USB]
2473
2474 snd-via82xx= [HW,ALSA]
2475
2476 snd-virmidi= [HW,ALSA]
2477
2478 snd-wavefront= [HW,ALSA]
2479
2480 snd-ymfpci= [HW,ALSA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002481
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002482 softlockup_panic=
2483 [KNL] Should the soft-lockup detector generate panics.
2484
Linus Torvalds1da177e2005-04-16 15:20:36 -07002485 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2486 See Documentation/sonypi.txt
2487
2488 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002489 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002490
2491 spia_io_base= [HW,MTD]
2492 spia_fio_base=
2493 spia_pedr=
2494 spia_peddr=
2495
2496 sscape= [HW,OSS]
2497 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
Randy Dunlapa9913042005-10-23 12:57:11 -07002498
Linus Torvalds1da177e2005-04-16 15:20:36 -07002499 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2500 See Documentation/scsi/st.txt.
2501
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002502 stacktrace [FTRACE]
2503 Enabled the stack tracer on boot up.
2504
Linus Torvalds1da177e2005-04-16 15:20:36 -07002505 sti= [PARISC,HW]
2506 Format: <num>
2507 Set the STI (builtin display/keyboard on the HP-PARISC
2508 machines) console (graphic card) which should be used
2509 as the initial boot-console.
2510 See also comment in drivers/video/console/sticore.c.
2511
2512 sti_font= [HW]
2513 See comment in drivers/video/console/sticore.c.
2514
2515 stifb= [HW]
2516 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2517
Trond Myklebustcbf11072009-08-09 15:06:19 -04002518 sunrpc.min_resvport=
2519 sunrpc.max_resvport=
2520 [NFS,SUNRPC]
2521 SunRPC servers often require that client requests
2522 originate from a privileged port (i.e. a port in the
2523 range 0 < portnr < 1024).
2524 An administrator who wishes to reserve some of these
2525 ports for other uses may adjust the range that the
2526 kernel's sunrpc client considers to be privileged
2527 using these two parameters to set the minimum and
2528 maximum port values.
2529
Greg Banks42a7fc42007-03-06 01:42:23 -08002530 sunrpc.pool_mode=
2531 [NFS]
2532 Control how the NFS server code allocates CPUs to
2533 service thread pools. Depending on how many NICs
2534 you have and where their interrupts are bound, this
2535 option will affect which CPUs will do NFS serving.
2536 Note: this parameter cannot be changed while the
2537 NFS server is running.
2538
2539 auto the server chooses an appropriate mode
2540 automatically using heuristics
2541 global a single global pool contains all CPUs
2542 percpu one pool for each CPU
2543 pernode one pool for each NUMA node (equivalent
2544 to global on non-NUMA machines)
2545
Trond Myklebustcbf11072009-08-09 15:06:19 -04002546 sunrpc.tcp_slot_table_entries=
2547 sunrpc.udp_slot_table_entries=
2548 [NFS,SUNRPC]
2549 Sets the upper limit on the number of simultaneous
2550 RPC calls that can be sent from the client to a
2551 server. Increasing these values may allow you to
2552 improve throughput, but will also increase the
2553 amount of memory reserved for use by the client.
2554
Linus Torvalds1da177e2005-04-16 15:20:36 -07002555 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002556
Linus Torvalds1da177e2005-04-16 15:20:36 -07002557 switches= [HW,M68k]
2558
2559 sym53c416= [HW,SCSI]
2560 See header of drivers/scsi/sym53c416.c.
2561
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002562 sysrq_always_enabled
2563 [KNL]
2564 Ignore sysrq setting - this boot parameter will
2565 neutralize any effect of /proc/sys/kernel/sysrq.
2566 Useful for debugging.
2567
Linus Torvalds1da177e2005-04-16 15:20:36 -07002568 t128= [HW,SCSI]
2569 See header of drivers/scsi/t128.c.
2570
2571 tdfx= [HW,DRM]
2572
David Brownell77437fd2008-07-23 21:28:33 -07002573 test_suspend= [SUSPEND]
2574 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2575 standby suspend) as the system sleep state to briefly
2576 enter during system startup. The system is woken from
2577 this state using a wakeup-capable RTC alarm.
2578
Linus Torvalds1da177e2005-04-16 15:20:36 -07002579 thash_entries= [KNL,NET]
2580 Set number of hash buckets for TCP connection
2581
Len Brownf8707ec2007-08-12 00:12:54 -04002582 thermal.act= [HW,ACPI]
2583 -1: disable all active trip points in all thermal zones
2584 <degrees C>: override all lowest active trip points
2585
Len Brownc52a7412007-08-14 15:49:32 -04002586 thermal.crt= [HW,ACPI]
2587 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002588 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002589
Len Brownf5487142007-08-12 00:12:44 -04002590 thermal.nocrt= [HW,ACPI]
2591 Set to disable actions on ACPI thermal zone
2592 critical and hot trip points.
2593
Len Brown72b33ef2007-08-12 00:12:17 -04002594 thermal.off= [HW,ACPI]
2595 1: disable ACPI thermal control
2596
Len Browna70cdc52007-08-12 00:12:35 -04002597 thermal.psv= [HW,ACPI]
2598 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002599 <degrees C>: override all passive trip points to this
2600 value
Len Browna70cdc52007-08-12 00:12:35 -04002601
Len Brown730ff342007-08-12 00:12:26 -04002602 thermal.tzp= [HW,ACPI]
2603 Specify global default ACPI thermal zone polling rate
2604 <deci-seconds>: poll all this frequency
2605 0: no polling (default)
2606
Linus Torvalds1da177e2005-04-16 15:20:36 -07002607 tmscsim= [HW,SCSI]
2608 See comment before function dc390_setup() in
2609 drivers/scsi/tmscsim.c.
2610
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002611 topology= [S390]
2612 Format: {off | on}
2613 Specify if the kernel should make use of the cpu
2614 topology informations if the hardware supports these.
2615 The scheduler will make use of these informations and
2616 e.g. base its process migration decisions on it.
2617 Default is off.
2618
Linus Torvalds1da177e2005-04-16 15:20:36 -07002619 tp720= [HW,PS2]
2620
Rajiv Andrade225a9be2010-03-25 00:55:32 -03002621 tpm_suspend_pcr=[HW,TPM]
2622 Format: integer pcr id
2623 Specify that at suspend time, the tpm driver
2624 should extend the specified pcr with zeros,
2625 as a workaround for some chips which fail to
2626 flush the last written pcr on TPM_SaveState.
2627 This will guarantee that all the other pcrs
2628 are saved.
2629
Li Zefan9d612be2009-06-24 17:33:15 +08002630 trace_buf_size=nn[KMG]
2631 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002632
Li Zefan020e5f82009-07-01 10:47:05 +08002633 trace_event=[event-list]
2634 [FTRACE] Set and start specified trace events in order
2635 to facilitate early boot debugging.
2636 See also Documentation/trace/events.txt
2637
Linus Torvalds1da177e2005-04-16 15:20:36 -07002638 trix= [HW,OSS] MediaTrix AudioTrix Pro
Randy Dunlapa9913042005-10-23 12:57:11 -07002639 Format:
2640 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2641
Alok Kataria395628e2008-10-24 17:22:01 -07002642 tsc= Disable clocksource-must-verify flag for TSC.
2643 Format: <string>
2644 [x86] reliable: mark tsc clocksource as reliable, this
2645 disables clocksource verification at runtime.
2646 Used to enable high-resolution timer mode on older
2647 hardware, and in virtualized environment.
2648
Randy Dunlapa9913042005-10-23 12:57:11 -07002649 turbografx.map[2|3]= [HW,JOY]
2650 TurboGraFX parallel port interface
2651 Format:
2652 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002653 See also Documentation/input/joystick-parport.txt
2654
2655 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2656 See header of drivers/scsi/u14-34f.c.
2657
2658 uart401= [HW,OSS]
2659 Format: <io>,<irq>
2660
2661 uart6850= [HW,OSS]
2662 Format: <io>,<irq>
2663
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002664 uhash_entries= [KNL,NET]
2665 Set number of hash buckets for UDP/UDP-Lite connections
2666
Alan Stern5f8364b2006-12-05 16:29:55 -05002667 uhci-hcd.ignore_oc=
2668 [USB] Ignore overcurrent events (default N).
2669 Some badly-designed motherboards generate lots of
2670 bogus events, for ports that aren't wired to
2671 anything. Set this parameter to avoid log spamming.
2672 Note that genuine overcurrent events won't be
2673 reported either.
2674
Simon Arlotte3a61b02008-07-19 23:32:54 +01002675 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302676 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002677 Set unknown_nmi_panic=1 early on boot.
2678
Alan Sternb5e795f2007-02-20 15:00:53 -05002679 usbcore.autosuspend=
2680 [USB] The autosuspend time delay (in seconds) used
2681 for newly-detected USB devices (default 2). This
2682 is the time required before an idle device will be
2683 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002684 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002685
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002686 usbcore.usbfs_snoop=
2687 [USB] Set to log all usbfs traffic (default 0 = off).
2688
2689 usbcore.blinkenlights=
2690 [USB] Set to cycle leds on hubs (default 0 = off).
2691
2692 usbcore.old_scheme_first=
2693 [USB] Start with the old device initialization
2694 scheme (default 0 = off).
2695
2696 usbcore.use_both_schemes=
2697 [USB] Try the other device initialization scheme
2698 if the first one fails (default 1 = enabled).
2699
2700 usbcore.initial_descriptor_timeout=
2701 [USB] Specifies timeout for the initial 64-byte
2702 USB_REQ_GET_DESCRIPTOR request in milliseconds
2703 (default 5000 = 5.0 seconds).
2704
Linus Torvalds1da177e2005-04-16 15:20:36 -07002705 usbhid.mousepoll=
2706 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002707
Alan Sternd4f373e2008-11-10 14:07:45 -05002708 usb-storage.delay_use=
2709 [UMS] The delay in seconds before a new device is
2710 scanned for Logical Units (default 5).
2711
2712 usb-storage.quirks=
2713 [UMS] A list of quirks entries to supplement or
2714 override the built-in unusual_devs list. List
2715 entries are separated by commas. Each entry has
2716 the form VID:PID:Flags where VID and PID are Vendor
2717 and Product ID values (4-digit hex numbers) and
2718 Flags is a set of characters, each corresponding
2719 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002720 a = SANE_SENSE (collect more than 18 bytes
2721 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002722 b = BAD_SENSE (don't collect more than 18
2723 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002724 c = FIX_CAPACITY (decrease the reported
2725 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002726 h = CAPACITY_HEURISTICS (decrease the
2727 reported device capacity by one
2728 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002729 i = IGNORE_DEVICE (don't bind to this
2730 device);
2731 l = NOT_LOCKABLE (don't try to lock and
2732 unlock ejectable media);
2733 m = MAX_SECTORS_64 (don't transfer more
2734 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002735 o = CAPACITY_OK (accept the capacity
2736 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002737 r = IGNORE_RESIDUE (the device reports
2738 bogus residue values);
2739 s = SINGLE_LUN (the device has only one
2740 Logical Unit);
2741 w = NO_WP_DETECT (don't test whether the
2742 medium is write-protected).
2743 Example: quirks=0419:aaf5:rl,0421:0433:rc
2744
Ian Campbell14315592010-02-17 10:38:10 +00002745 userpte=
2746 [X86] Flags controlling user PTE allocations.
2747
2748 nohigh = do not allocate PTE pages in
2749 HIGHMEM regardless of setting
2750 of CONFIG_HIGHPTE.
2751
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302752 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002753 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002754 vdso=1: enable VDSO (default)
2755 vdso=0: disable VDSO mapping
2756
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302757 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002758 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2759 vdso32=1: enable 32-bit VDSO (default)
2760 vdso32=0: disable 32-bit VDSO mapping
2761
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002762 vector= [IA-64,SMP]
2763 vector=percpu: enable percpu vector domain
2764
Linus Torvalds1da177e2005-04-16 15:20:36 -07002765 video= [FB] Frame buffer configuration
2766 See Documentation/fb/modedb.txt.
2767
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002768 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002769 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002770 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002771 Use vga=ask for menu.
2772 This is actually a boot loader parameter; the value is
2773 passed to the kernel using a special protocol.
2774
Randy Dunlapa9913042005-10-23 12:57:11 -07002775 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002776 size of <nn>. This can be used to increase the
2777 minimum size (128MB on x86). It can also be used to
2778 decrease the size and leave more room for directly
2779 mapped kernel RAM.
2780
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002781 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2782 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002783
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002784 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2785 Format: <command>
2786
2787 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2788 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002789
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002790 vt.cur_default= [VT] Default cursor shape.
2791 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2792 the parameters of the <Esc>[?A;B;Cc escape sequence;
2793 see VGA-softcursor.txt. Default: 2 = underline.
2794
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002795 vt.default_blu= [VT]
2796 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2797 Change the default blue palette of the console.
2798 This is a 16-member array composed of values
2799 ranging from 0-255.
2800
2801 vt.default_grn= [VT]
2802 Format: <green0>,<green1>,<green2>,...,<green15>
2803 Change the default green palette of the console.
2804 This is a 16-member array composed of values
2805 ranging from 0-255.
2806
2807 vt.default_red= [VT]
2808 Format: <red0>,<red1>,<red2>,...,<red15>
2809 Change the default red palette of the console.
2810 This is a 16-member array composed of values
2811 ranging from 0-255.
2812
2813 vt.default_utf8=
2814 [VT]
2815 Format=<0|1>
2816 Set system-wide default UTF-8 mode for all tty's.
2817 Default is 1, i.e. UTF-8 mode is enabled for all
2818 newly opened terminals.
2819
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002820 vt.global_cursor_default=
2821 [VT]
2822 Format=<-1|0|1>
2823 Set system-wide default for whether a cursor
2824 is shown on new VTs. Default is -1,
2825 i.e. cursors will be created by default unless
2826 overridden by individual drivers. 0 will hide
2827 cursors, 1 will display them.
2828
Linus Torvalds1da177e2005-04-16 15:20:36 -07002829 waveartist= [HW,OSS]
2830 Format: <io>,<irq>,<dma>,<dma2>
Randy Dunlapa9913042005-10-23 12:57:11 -07002831
Linus Torvalds1da177e2005-04-16 15:20:36 -07002832 wd33c93= [HW,SCSI]
2833 See header of drivers/scsi/wd33c93.c.
2834
2835 wd7000= [HW,SCSI]
2836 See header of drivers/scsi/wd7000.c.
2837
2838 wdt= [WDT] Watchdog
Gabriel C8dfe9c22007-08-10 13:01:00 -07002839 See Documentation/watchdog/wdt.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002840
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002841 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2842 default x2apic cluster mode on platforms
2843 supporting x2apic.
2844
Jacob Panbb24c472009-09-02 07:37:17 -07002845 x86_mrst_timer= [X86-32,APBT]
2846 Choose timer option for x86 Moorestown MID platform.
2847 Two valid options are apbt timer only and lapic timer
2848 plus one apbt timer for broadcast timer.
2849 x86_mrst_timer=apbt_only | lapic_and_apbt
2850
Linus Torvalds1da177e2005-04-16 15:20:36 -07002851 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2852 xd_geo= See header of drivers/block/xd.c.
2853
2854 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002855 Format:
2856 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002857
Randy Dunlapa9913042005-10-23 12:57:11 -07002858______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002859
2860TODO:
2861
2862 Add documentation for ALSA options.
2863 Add more DRM drivers.