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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.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500103 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 USB USB support is enabled.
105 USBHID USB Human Interface Device support is enabled.
106 V4L Video For Linux support is enabled.
107 VGA The VGA console has been enabled.
108 VT Virtual terminal support is enabled.
109 WDT Watchdog support is enabled.
110 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700111 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112 X86-64 X86-64 architecture is enabled.
113 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700114 Documentation/x86/x86_64/boot-options.txt .
Andi Kleenc0115602008-08-22 09:53:39 +0200115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116
117In addition, the following text indicates that the option:
118
119 BUGS= Relates to possible processor bugs on the said processor.
120 KNL Is a kernel start-up parameter.
121 BOOT Is a boot loader parameter.
122
123Parameters denoted with BOOT are actually interpreted by the boot
124loader, and have no meaning to the kernel directly.
125Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500126need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127
Karsten Weiss55588702007-02-13 13:26:21 +0100128There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700129See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100130
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132a trailing = on the name of any parameter states that that parameter will
133be entered as an environment variable, whereas its absence indicates that
134it will appear as a kernel argument readable via /proc/cmdline by programs
135running once the system is up.
136
jens m. noedler9c4751f2006-09-29 02:00:27 -0700137The number of kernel parameters is not limited, but the length of the
138complete command line (parameters including spaces etc.) is limited to
139a fixed number of characters. This limit depends on the architecture
140and is between 256 and 4096 characters. It is defined in the file
141./include/asm/setup.h as COMMAND_LINE_SIZE.
142
143
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530144 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800145 Advanced Configuration and Power Interface
Randy Dunlapaf23f572009-02-22 17:05:22 -0800146 Format: { force | off | ht | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147 force -- enable ACPI if default was off
148 off -- disable ACPI if default was on
149 noirq -- do not use ACPI for IRQ routing
150 ht -- run only enough ACPI to enable Hyper Threading
Randy Dunlapa9913042005-10-23 12:57:11 -0700151 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700152 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800153 rsdt -- prefer RSDT over (default) XSDT
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154
Randy Dunlap53471122008-03-12 18:10:51 -0400155 See also Documentation/power/pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156
Len Browna1fdcc02007-03-11 03:26:14 -0400157 acpi_apic_instance= [ACPI, IOAPIC]
158 Format: <int>
159 2: use 2nd APIC table, if available
160 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400161 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400162
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200163 acpi_backlight= [HW,ACPI]
164 acpi_backlight=vendor
165 acpi_backlight=video
166 If set to vendor, prefer vendor specific driver
167 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
168 of the ACPI video.ko driver.
169
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700170 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
171 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700173 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
174 debug output. Bits in debug_layer correspond to a
175 _COMPONENT in an ACPI source file, e.g.,
176 #define _COMPONENT ACPI_PCI_COMPONENT
177 Bits in debug_level correspond to a level in
178 ACPI_DEBUG_PRINT statements, e.g.,
179 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600180 The debug_level mask defaults to "info". See
181 Documentation/acpi/debug.txt for more information about
182 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600184 Enable processor driver info messages:
185 acpi.debug_layer=0x20000000
186 Enable PCI/PCI interrupt routing info messages:
187 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700188 Enable AML "Debug" output, i.e., stores to the Debug
189 object while interpreting AML:
190 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700191 Enable all messages related to ACPI hardware:
192 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200193
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700194 Some values produce so much output that the system is
195 unusable. The "log_buf_len" parameter may be useful
196 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800197
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700198 acpi_display_output= [HW,ACPI]
199 acpi_display_output=vendor
200 acpi_display_output=video
201 See above.
202
203 acpi_irq_balance [HW,ACPI]
204 ACPI will balance active IRQs
205 default in APIC mode
206
207 acpi_irq_nobalance [HW,ACPI]
208 ACPI will not move active IRQs (default)
209 default in PIC mode
210
211 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
212 Format: <irq>,<irq>...
213
214 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
215 use by PCI
216 Format: <irq>,<irq>...
217
218 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
219
220 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
221 Format: To spoof as Windows 98: ="Microsoft Windows"
222
223 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
224 acpi_osi="string1" # add string1 -- only one string
225 acpi_osi="!string2" # remove built-in string2
226 acpi_osi= # disable all strings
227
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530228 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
232
Randy Dunlap4af94f32009-04-17 18:30:28 -0700233 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
234 Format: { level | edge | high | low }
235
236 acpi_serialize [HW,ACPI] force serialization of AML methods
237
238 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIOS resulting in XT-PIC timer.
241
242 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800244 old_ordering, s4_nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700245 See Documentation/power/video.txt for information on
246 s3_bios and s3_mode.
247 s3_beep is for debugging; it makes the PC's speaker beep
248 as soon as the kernel's real-mode entry point is called.
249 s4_nohwsig prevents ACPI hardware signature from being
250 used during resume from hibernation.
251 old_ordering causes the ACPI 1.0 ordering of the _PTS
252 control method, with respect to putting devices into
253 low power states, to be enforced (the ACPI 2.0 ordering
254 of _PTS is used by default).
255 s4_nonvs prevents the kernel from saving/restoring the
256 ACPI NVS memory during hibernation.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800257 sci_force_enable causes the kernel to set SCI_EN directly
258 on resume from S1/S3 (which is against the ACPI spec,
259 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700260
261 acpi_use_timer_override [HW,ACPI]
262 Use timer override. For some broken Nvidia NF5 boards
263 that require a timer override, but don't have HPET
264
Luca Tettamanti7e905602009-03-30 00:01:27 +0200265 acpi_enforce_resources= [ACPI]
266 { strict | lax | no }
267 Check for resource conflicts between native drivers
268 and ACPI OperationRegions (SystemIO and SystemMemory
269 only). IO ports and memory declared in ACPI might be
270 used by the ACPI subsystem in arbitrary AML code and
271 can interfere with legacy drivers.
272 strict (default): access to resources claimed by ACPI
273 is denied; legacy drivers trying to access reserved
274 resources will fail to bind to device using them.
275 lax: access to resources claimed by ACPI is allowed;
276 legacy drivers trying to access reserved resources
277 will bind successfully but a warning message is logged.
278 no: ACPI OperationRegions are not marked as reserved,
279 no further checks are performed.
280
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281 ad1848= [HW,OSS]
282 Format: <io>,<irq>,<dma>,<dma2>,<type>
283
Randy Dunlap4af94f32009-04-17 18:30:28 -0700284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
286
Linus Torvalds1da177e2005-04-16 15:20:36 -0700287 advansys= [HW,SCSI]
288 See header of drivers/scsi/advansys.c.
289
290 advwdt= [HW,WDT] Advantech WDT
291 Format: <iostart>,<iostop>
292
293 aedsp16= [HW,OSS] Audio Excel DSP 16
294 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
295 See also header of sound/oss/aedsp16.c.
Randy Dunlapa9913042005-10-23 12:57:11 -0700296
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700297 agp= [AGP]
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
302
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303 aha152x= [HW,SCSI]
304 See Documentation/scsi/aha152x.txt.
305
306 aha1542= [HW,SCSI]
307 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
308
309 aic7xxx= [HW,SCSI]
310 See Documentation/scsi/aic7xxx.txt.
311
312 aic79xx= [HW,SCSI]
313 See Documentation/scsi/aic79xx.txt.
314
Russell Kingd944d542010-02-20 16:13:29 +0000315 alignment= [KNL,ARM]
316 Allow the default userspace alignment fault handler
317 behaviour to be specified. Bit 0 enables warnings,
318 bit 1 enables fixups, and bit 2 sends a segfault.
319
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200320 amd_iommu= [HW,X86-84]
321 Pass parameters to the AMD IOMMU driver in the system.
322 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900323 fullflush - enable flushing of IO/TLB entries when
324 they are unmapped. Otherwise they are
325 flushed before they will be reused, which
326 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200327 off - do not initialize any AMD IOMMU found in
328 the system
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900329
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330 amijoy.map= [HW,JOY] Amiga joystick support
331 Map of devices attached to JOY0DAT and JOY1DAT
332 Format: <a>,<b>
333 See also Documentation/kernel/input/joystick.txt
334
335 analog.map= [HW,JOY] Analog joystick and gamepad support
336 Specifies type or capabilities of an analog joystick
337 connected to one of 16 gameports
338 Format: <type1>,<type2>,..<type16>
339
Randy Dunlapa9913042005-10-23 12:57:11 -0700340 apc= [HW,SPARC]
341 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342 Format: noidle
343 Disable APC CPU standby support. SPARCstation-Fox does
344 not play well with APC CPU idle - disable it if you have
345 APC and your system crashes randomly.
346
Randy Dunlapca1eda22009-05-06 16:02:58 -0700347 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700348 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349 Format: { quiet (default) | verbose | debug }
350 Change the amount of debugging information output
351 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700352
Brian Haleyb0f83b22010-02-04 13:36:50 -0800353 autoconf= [IPV6]
354 See Documentation/networking/ipv6.txt.
355
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400356 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
357 Limit apic dumping. The parameter defines the maximal
358 number of local apics being dumped. Also it is possible
359 to set it to "all" by meaning -- no limit here.
360 Format: { 1 (default) | 2 | ... | all }.
361 The parameter valid if only apic=debug or
362 apic=verbose is specified.
363 Example: apic=debug show_lapic=all
364
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700366 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
369 Format: <io>,<irq>,<nodeID>
370
371 ataflop= [HW,M68k]
372
373 atarimouse= [HW,MOUSE] Atari Mouse
374
375 atascsi= [HW,SCSI] Atari SCSI
376
377 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
378 EzKey and similar keyboards
379
380 atkbd.reset= [HW] Reset keyboard during initialization
381
Randy Dunlapa9913042005-10-23 12:57:11 -0700382 atkbd.set= [HW] Select keyboard code set
383 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384
385 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
386 keyboards
387
388 atkbd.softraw= [HW] Choose between synthetic and real raw mode
389 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700390
391 atkbd.softrepeat= [HW]
392 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393
394 autotest [IA64]
395
Linus Torvalds1da177e2005-04-16 15:20:36 -0700396 baycom_epp= [HW,AX25]
397 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700398
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
400 Format: <io>,<mode>
401 See header of drivers/net/hamradio/baycom_par.c.
402
Randy Dunlapa9913042005-10-23 12:57:11 -0700403 baycom_ser_fdx= [HW,AX25]
404 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405 Format: <io>,<irq>,<mode>[,<baud>]
406 See header of drivers/net/hamradio/baycom_ser_fdx.c.
407
Randy Dunlapa9913042005-10-23 12:57:11 -0700408 baycom_ser_hdx= [HW,AX25]
409 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700410 Format: <io>,<irq>,<mode>
411 See header of drivers/net/hamradio/baycom_ser_hdx.c.
412
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700413 boot_delay= Milliseconds to delay each printk during boot.
414 Values larger than 10 seconds (10000) are changed to
415 no delay (0).
416 Format: integer
417
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700418 bootmem_debug [KNL] Enable bootmem allocator debug messages.
419
Linus Torvalds1da177e2005-04-16 15:20:36 -0700420 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700421 bttv.radio= Most important insmod options are available as
422 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
424 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
425
426 BusLogic= [HW,SCSI]
427 See drivers/scsi/BusLogic.c, comment before function
428 BusLogic_ParseDriverOptions().
429
430 c101= [NET] Moxa C101 synchronous serial card
431
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700432 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700433 Sometimes CPU hardware bugs make them report the cache
434 size incorrectly. The kernel will attempt work arounds
435 to fix known problems, but for some CPUs it is not
436 possible to determine what the correct size should be.
437 This option provides an override for these situations.
438
James Morris20510f22007-10-16 23:31:32 -0700439 capability.disable=
440 [SECURITY] Disable capabilities. This would normally
441 be used only if an alternative security model is to be
442 configured. Potentially dangerous and should only be
443 used if you are entirely sure of the consequences.
444
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100445 ccw_timeout_log [S390]
446 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700447
Paul Menage8bab8dd2008-04-04 14:29:57 -0700448 cgroup_disable= [KNL] Disable a particular controller
449 Format: {name of the controller(s) to disable}
450 {Currently supported controllers - "memory"}
451
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 checkreqprot [SELINUX] Set initial checkreqprot flag value.
453 Format: { "0" | "1" }
454 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700455 0 -- check protection applied by kernel (includes
456 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700457 1 -- check protection requested by application.
458 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700459 Value can be changed at runtime via
460 /selinux/checkreqprot.
461
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100462 cio_ignore= [S390]
463 See Documentation/s390/CommonIO for details.
464
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700465 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700466 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200467 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700468 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200469 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700470 Format: { pit | tsc | cyclone | pmtmr }
471
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700472 clocksource= [GENERIC_TIME] Override the default clocksource
473 Format: <string>
474 Override the default clocksource and use the clocksource
475 with the name specified.
476 Some clocksource names to choose from, depending on
477 the platform:
478 [all] jiffies (this is the base, fallback clocksource)
479 [ACPI] acpi_pm
480 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
481 pxa_timer,timer3,32k_counter,timer0_1
482 [AVR32] avr32
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700483 [X86-32] pit,hpet,tsc,vmi-timer;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700484 scx200_hrt on Geode; cyclone on IBM x440
485 [MIPS] MIPS
486 [PARISC] cr16
487 [S390] tod
488 [SH] SuperH
489 [SPARC64] tick
490 [X86-64] hpet,tsc
491
Andi Kleenac72e782008-01-30 13:33:21 +0100492 clearcpuid=BITNUM [X86]
493 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800494 arch/x86/include/asm/cpufeature.h for the valid bit
495 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100496 stable over kernel options, but the vendor specific
497 ones should be.
498 Also note that user programs calling CPUID directly
499 or using the feature without checking anything
500 will still see it. This just prevents it from
501 being used by the kernel or shown in /proc/cpuinfo.
502 Also note the kernel might malfunction if you disable
503 some critical bits.
504
Robert Jennings14f966e2009-04-15 05:55:32 +0000505 cmo_free_hint= [PPC] Format: { yes | no }
506 Specify whether pages are marked as being inactive
507 when they are freed. This is used in CMO environments
508 to determine OS memory pressure for page stealing by
509 a hypervisor.
510 Default: yes
511
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530512 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100513 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100514 Range: 0 - 8192
515 Default: 64
516
Linus Torvalds1da177e2005-04-16 15:20:36 -0700517 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700518 Format:
519 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520
521 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
522 Format: <io>[,<irq>]
523
Randy Dunlapa9913042005-10-23 12:57:11 -0700524 com90xx= [HW,NET]
525 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700526 Format: <io>[,<irq>[,<memstart>]]
527
528 condev= [HW,S390] console device
529 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700530
Linus Torvalds1da177e2005-04-16 15:20:36 -0700531 console= [KNL] Output console device and options.
532
533 tty<n> Use the virtual console device <n>.
534
535 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800536 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800538 the form "bbbbpnf", where "bbbb" is the baud rate,
539 "p" is parity ("n", "o", or "e"), "n" is number of
540 bits, and "f" is flow control ("r" for RTS or
541 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700542
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800543 See Documentation/serial-console.txt for more
544 information. See
545 Documentation/networking/netconsole.txt for an
546 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700548 uart[8250],io,<addr>[,options]
549 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 Start an early, polled-mode console on the 8250/16550
551 UART at the specified I/O port or MMIO address,
552 switching to the matching ttyS device later. The
553 options are the same as for ttyS, above.
554
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700555 If the device connected to the port is not a TTY but a braille
556 device, prepend "brl," before the device type, for instance
557 console=brl,ttyS0
558 For now, only VisioBraille is supported.
559
Daniel Mackf324edc2009-06-16 15:33:52 -0700560 consoleblank= [KNL] The console blank (screen saver) timeout in
561 seconds. Defaults to 10*60 = 10mins. A value of 0
562 disables the blank timer.
563
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800564 coredump_filter=
565 [KNL] Change the default value for
566 /proc/<pid>/coredump_filter.
567 See also Documentation/filesystems/proc.txt.
568
Linus Torvalds1da177e2005-04-16 15:20:36 -0700569 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700570 Format:
571 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700572
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700573 crashkernel=nn[KMG]@ss[KMG]
574 [KNL] Reserve a chunk of physical memory to
575 hold a kernel to switch to with kexec on panic.
576
Bernhard Wallefb391592007-10-18 23:41:02 -0700577 crashkernel=range1:size1[,range2:size2,...][@offset]
578 [KNL] Same as above, but depends on the memory
579 in the running system. The syntax of range is
580 start-[end] where start and end are both
581 a memory unit (amount[KMG]). See also
582 Documentation/kdump/kdump.txt for a example.
583
Linus Torvalds1da177e2005-04-16 15:20:36 -0700584 cs89x0_dma= [HW,NET]
585 Format: <dma>
586
587 cs89x0_media= [HW,NET]
588 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700589
Randy Dunlapa9913042005-10-23 12:57:11 -0700590 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591 See header of drivers/s390/block/dasd_devmap.c.
592
593 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
594 (one device per port)
595 Format: <port#>,<type>
596 See also Documentation/input/joystick-parport.txt
597
598 debug [KNL] Enable kernel debugging (events log level).
599
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700600 debug_locks_verbose=
601 [KNL] verbose self-tests
602 Format=<0|1>
603 Print debugging info while doing the locking API
604 self-tests.
605 We default to 0 (no extra messages), setting it to
606 1 will print _a lot_ more information - normally
607 only useful to kernel developers.
608
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700609 debug_objects [KNL] Enable object debugging
610
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500611 no_debug_objects
612 [KNL] Disable object debugging
613
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200614 debugpat [X86] Enable PAT debugging
615
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200616 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700617 Format: <area>[,<node>]
618 See also Documentation/networking/decnet.txt.
619
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700620 default_hugepagesz=
621 [same as hugepagesz=] The size of the default
622 HugeTLB page size. This is the size represented by
623 the legacy /proc/ hugepages APIs, used for SHM, and
624 default size when mounting hugetlbfs filesystems.
625 Defaults to the default architecture's huge page size
626 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700627
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628 dhash_entries= [KNL]
629 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700630
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 digi= [HW,SERIAL]
632 IO parameters + enable/disable command.
633
634 digiepca= [HW,SERIAL]
635 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000636 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700637
Brian Haleyb0f83b22010-02-04 13:36:50 -0800638 disable= [IPV6]
639 See Documentation/networking/ipv6.txt.
640
641 disable_ipv6= [IPV6]
642 See Documentation/networking/ipv6.txt.
643
Yinghai Lu95ffa242008-04-29 03:52:33 -0700644 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700645 The kernel tries to adjust MTRR layout from continuous
646 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700647 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700648
Yinghai Lu093af8d2008-01-30 13:33:32 +0100649 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100650 By default the kernel will trim any uncacheable
651 memory out of your available memory pool based on
652 MTRR settings. This parameter disables that behavior,
653 possibly causing your machine to run very slowly.
654
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530655 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700656 Disable PIN 1 of APIC timer
657 Can be useful to work around chipset bugs.
658
Linus Torvalds1da177e2005-04-16 15:20:36 -0700659 dmasound= [HW,OSS] Sound subsystem buffers
660
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700661 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
662 this option disables the debugging code at boot.
663
664 dma_debug_entries=<number>
665 This option allows to tune the number of preallocated
666 entries for DMA-API debugging code. One entry is
667 required per DMA-API allocation. Use this if the
668 DMA-API debugging code disables itself because the
669 architectural default is too low.
670
Joerg Roedel1745de52009-05-22 21:49:51 +0200671 dma_debug_driver=<driver_name>
672 With this option the DMA-API debugging driver
673 filter feature can be enabled at boot time. Just
674 pass the driver to filter for as the parameter.
675 The filter can be disabled or changed to another
676 driver later using sysfs.
677
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678 dscc4.setup= [NET]
679
680 dtc3181e= [HW,SCSI]
681
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700682 dynamic_printk Enables pr_debug()/dev_dbg() calls if
683 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
684 These can also be switched on/off via
685 <debugfs>/dynamic_printk/modules
686
687 earlycon= [KNL] Output early console device and options.
688 uart[8250],io,<addr>[,options]
689 uart[8250],mmio,<addr>[,options]
690 Start an early, polled-mode console on the 8250/16550
691 UART at the specified I/O port or MMIO address.
692 The options are the same as for ttyS, above.
693
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530694 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700695 earlyprintk=vga
696 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500697 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500698 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700699
Randy Dunlapa9913042005-10-23 12:57:11 -0700700 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700701 takes over.
702
Yinghai Lu5c059172008-07-24 17:29:40 -0700703 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704
705 Currently only ttyS0 and ttyS1 are supported.
706
707 Interaction with the standard serial driver is not
708 very good.
709
710 The VGA output is eventually overwritten by the real
711 console.
712
713 eata= [HW,SCSI]
714
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700716 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700717
Linus Torvalds1da177e2005-04-16 15:20:36 -0700718 eisa_irq_edge= [PARISC,HW]
719 See header of drivers/parisc/eisa.c.
720
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700721 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700723 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724
725 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800726 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700727 See Documentation/block/as-iosched.txt and
728 Documentation/block/deadline-iosched.txt for details.
729
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530730 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700731 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800732 image elf header. Generally kexec loader will
733 pass this option to capture kernel.
734 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700735
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700736 enable_mtrr_cleanup [X86]
737 The kernel tries to adjust MTRR layout from continuous
738 to discrete, to make X server driver able to add WB
739 entry later. This parameter enables that.
740
Randy Dunlapca1eda22009-05-06 16:02:58 -0700741 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700742 Enable PIN 1 of APIC timer
743 Can be useful to work around chipset bugs
744 (in particular on some ATI chipsets).
745 The kernel tries to set a reasonable default.
746
Linus Torvalds1da177e2005-04-16 15:20:36 -0700747 enforcing [SELINUX] Set initial enforcing status.
748 Format: {"0" | "1"}
749 See security/selinux/Kconfig help text.
750 0 -- permissive (log only, no denials).
751 1 -- enforcing (deny and log).
752 Default value is 0.
753 Value can be changed at runtime via /selinux/enforce.
754
Linus Torvalds1da177e2005-04-16 15:20:36 -0700755 ether= [HW,NET] Ethernet cards parameters
756 This option is obsoleted by the "netdev=" option, which
757 has equivalent usage. See its documentation for details.
758
759 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
760 Format: <io>[,<irq>]
761
Akinobu Mitade1ba092006-12-08 02:39:42 -0800762 failslab=
763 fail_page_alloc=
764 fail_make_request=[KNL]
765 General fault injection mechanism.
766 Format: <interval>,<probability>,<space>,<times>
767 See also /Documentation/fault-injection/.
768
Linus Torvalds1da177e2005-04-16 15:20:36 -0700769 fd_mcs= [HW,SCSI]
770 See header of drivers/scsi/fd_mcs.c.
771
772 fdomain= [HW,SCSI]
773 See header of drivers/scsi/fdomain.c.
774
775 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000776 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700777
Alex Chiangf13ae302008-05-08 14:03:23 -0600778 force_pal_cache_flush
779 [IA-64] Avoid check_sal_cache_flush which may hang on
780 buggy SAL_CACHE_FLUSH implementations. Using this
781 parameter will force ia64_sal_cache_flush to call
782 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
783
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100784 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400785 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100786 as early as possible in order to facilitate early
787 boot debugging.
788
789 ftrace_dump_on_oops
Steven Rostedt2af15d62009-05-28 13:37:24 -0400790 [FTRACE] will dump the trace buffers on oops.
791
792 ftrace_filter=[function-list]
793 [FTRACE] Limit the functions traced by the function
794 tracer at boot up. function-list is a comma separated
795 list of functions. This list can be changed at run
796 time by the set_ftrace_filter file in the debugfs
797 tracing directory.
798
799 ftrace_notrace=[function-list]
800 [FTRACE] Do not trace the functions specified in
801 function-list. This list can be changed at run time
802 by the set_ftrace_notrace file in the debugfs
803 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100804
Stefan Assmann369bc182009-10-12 22:17:21 +0200805 ftrace_graph_filter=[function-list]
806 [FTRACE] Limit the top level callers functions traced
807 by the function graph tracer at boot up.
808 function-list is a comma separated list of functions
809 that can be changed at run time by the
810 set_graph_function file in the debugfs tracing directory.
811
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812 gamecon.map[2|3]=
813 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
814 support via parallel port (up to 5 devices per port)
815 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
816 See also Documentation/input/joystick-parport.txt
817
818 gamma= [HW,DRM]
819
Yinghai Luaaf23042008-01-30 13:33:09 +0100820 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
821 Format: off | on
822 default: on
823
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700824 gcov_persist= [GCOV] When non-zero (default), profiling data for
825 kernel modules is saved and remains accessible via
826 debugfs, even when the module is unloaded/reloaded.
827 When zero, profiling data is discarded and associated
828 debugfs files are removed at module unload time.
829
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 gdth= [HW,SCSI]
831 See header of drivers/scsi/gdth.c.
832
833 gpt [EFI] Forces disk with valid GPT signature but
834 invalid Protective MBR to be treated as GPT.
835
Linus Torvalds1da177e2005-04-16 15:20:36 -0700836 gvp11= [HW,SCSI]
837
838 hashdist= [KNL,NUMA] Large hashes allocated during boot
839 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700840 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700841 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700842
843 hcl= [IA-64] SGI's Hardware Graph compatibility layer
844
845 hd= [EIDE] (E)IDE hard drive subsystem geometry
846 Format: <cyl>,<head>,<sect>
847
Linus Torvalds1da177e2005-04-16 15:20:36 -0700848 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
849 size of <nn>. This works even on boxes that have no
850 highmem otherwise. This also works to reduce highmem
851 size on bigger boxes.
852
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800853 highres= [KNL] Enable/disable high resolution timer mode.
854 Valid parameters: "on", "off"
855 Default: "on"
856
Linus Torvalds1da177e2005-04-16 15:20:36 -0700857 hisax= [HW,ISDN]
858 See Documentation/isdn/README.HiSax.
859
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700860 hlt [BUGS=ARM,SH]
861
862 hpet= [X86-32,HPET] option to control HPET usage
863 Format: { enable (default) | disable | force |
864 verbose }
865 disable: disable HPET and use PIT instead
866 force: allow force enabled of undocumented chips (ICH4,
867 VIA, nVidia)
868 verbose: show contents of HPET registers during setup
869
Andi Kleenb4718e62008-07-23 21:27:51 -0700870 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
871 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700872 On x86-64 and powerpc, this option can be specified
873 multiple times interleaved with hugepages= to reserve
874 huge pages of different sizes. Valid pages sizes on
875 x86-64 are 2M (when the CPU supports "pse") and 1G
876 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700877 Note that 1GB pages can only be allocated at boot time
878 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900879
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100880 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
881 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100882 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
883 If specified, z/VM IUCV HVC accepts connections
884 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100885
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700886 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700887 or register an additional I2C bus that is not
888 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700889 Format:
890 <bus_id>,<clkrate>
891
Jiri Kosina36d95732008-10-06 02:51:09 -0400892 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700893 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200894 i8042.dumbkbd [HW] Pretend that controller can only read data from
895 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700896 (Don't attempt to blink the leds)
897 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500898 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400899 i8042.noloop [HW] Disable the AUX Loopback command while probing
900 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901 i8042.nomux [HW] Don't check presence of an active multiplexing
902 controller
903 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
904 controllers
905 i8042.panicblink=
906 [HW] Frequency with which keyboard LEDs should blink
907 when kernel panics (default is 0.5 sec)
908 i8042.reset [HW] Reset the controller during init and cleanup
909 i8042.unlock [HW] Unlock (ignore) the keylock
910
911 i810= [HW,DRM]
912
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700913 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
914 indicates that the driver is running on unsupported
915 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700916 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
917 does not match list of supported models.
918 i8k.power_status
919 [HW] Report power status in /proc/i8k
920 (disabled by default)
921 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
922 capability is set.
923
924 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
925 See Documentation/mca.txt.
926
927 icn= [HW,ISDN]
928 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
929
David Fries0af80c02009-02-25 20:28:21 +0100930 ide-core.nodma= [HW] (E)IDE subsystem
931 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200932 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
933 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100934 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700935
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700936 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
937 Claim all unknown PCI IDE storage controllers.
938
Andi Kleenf039b752007-05-02 19:27:12 +0200939 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800940 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
941 Poll forces a polling idle loop that can slightly
942 improve the performance of waking up a idle CPU, but
943 will use a lot of power and make the system run hot.
944 Not recommended.
945 idle=mwait: On systems which support MONITOR/MWAIT but
946 the kernel chose to not use it because it doesn't save
947 as much power as a normal idle loop, use the
948 MONITOR/MWAIT idle loop anyways. Performance should be
949 the same as idle=poll.
950 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800951 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800952 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700953
Ingo Molnar792908222006-12-06 20:40:51 -0800954 ignore_loglevel [KNL]
955 Ignore loglevel setting - this will print /all/
956 kernel messages to the console. Useful for debugging.
957
Linus Torvalds1da177e2005-04-16 15:20:36 -0700958 ihash_entries= [KNL]
959 Set number of hash buckets for inode cache.
960
Mimi Zohar3323eec92009-02-04 09:06:58 -0500961 ima_audit= [IMA]
962 Format: { "0" | "1" }
963 0 -- integrity auditing messages. (Default)
964 1 -- enable informational integrity auditing messages.
965
966 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700967 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -0500968 default: "sha1"
969
Eric Paris5789ba32009-05-21 15:47:06 -0400970 ima_tcb [IMA]
971 Load a policy which meets the needs of the Trusted
972 Computing Base. This means IMA will measure all
973 programs exec'd, files mmap'd for exec, and all files
974 opened for read by uid=0.
975
Linus Torvalds1da177e2005-04-16 15:20:36 -0700976 in2000= [HW,SCSI]
977 See header of drivers/scsi/in2000.c.
978
979 init= [KNL]
980 Format: <full_path>
981 Run specified binary instead of /sbin/init as init
982 process.
983
984 initcall_debug [KNL] Trace initcalls as they are executed. Useful
985 for working out where the kernel is dying during
986 startup.
987
988 initrd= [BOOT] Specify the location of the initial ramdisk
989
990 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
991 Format: <irq>
992
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700993 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800994 on
995 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700996 off
997 Disable intel iommu driver.
998 igfx_off [Default Off]
999 By default, gfx is mapped as normal device. If a gfx
1000 device has a dedicated DMAR unit, the DMAR unit is
1001 bypassed by not enabling DMAR with this option. In
1002 this case, gfx device will use physical address for
1003 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001004 forcedac [x86_64]
1005 With this option iommu will not optimize to look
1006 for io virtual address below 32 bit forcing dual
1007 address cycle on pci bus for cards supporting greater
1008 than 32 bit addressing. The default is to look
1009 for translation below 32 bit and if not available
1010 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001011 strict [Default Off]
1012 With this option on every unmap_single operation will
1013 result in a hardware IOTLB flush operation as opposed
1014 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001015
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001016 inttest= [IA64]
1017
1018 iomem= Disable strict checking of access to MMIO memory
1019 strict regions from userspace.
1020 relaxed
1021
1022 iommu= [x86]
1023 off
1024 force
1025 noforce
1026 biomerge
1027 panic
1028 nopanic
1029 merge
1030 nomerge
1031 forcesac
1032 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001033 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001034
1035 io7= [HW] IO7 for Marvel based alpha systems
1036 See comment before marvel_specify_io7 in
1037 arch/alpha/kernel/core_marvel.c.
1038
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301039 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001040 0x80
1041 Standard port 0x80 based delay
1042 0xed
1043 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001044 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001045 Simple two microseconds delay
1046 none
1047 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001048
Linus Torvalds1da177e2005-04-16 15:20:36 -07001049 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001050 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001051
1052 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001053 See comment before ip2_setup() in
1054 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055
1056 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1057 See header of drivers/scsi/ips.c.
1058
Alan Cox200803d2005-06-28 20:45:18 -07001059 irqfixup [HW]
1060 When an interrupt is not handled search all handlers
1061 for it. Intended to get systems with badly broken
1062 firmware running.
1063
1064 irqpoll [HW]
1065 When an interrupt is not handled search all handlers
1066 for it. Also check all handlers each timer
1067 interrupt. Intended to get systems with badly broken
1068 firmware running.
1069
Linus Torvalds1da177e2005-04-16 15:20:36 -07001070 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001071 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001072
1073 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001074 Format:
1075 <cpu number>,...,<cpu number>
1076 or
Li Zefanb225d442008-11-06 12:53:39 -08001077 <cpu number>-<cpu number>
1078 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001079 or a mixture
1080 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001081
Linus Torvalds1da177e2005-04-16 15:20:36 -07001082 This option can be used to specify one or more CPUs
1083 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001084 algorithms. You can move a process onto or off an
1085 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086 <cpu number> begins at 0 and the maximum value is
1087 "number of CPUs in system - 1".
1088
1089 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001090 alternative -- manually setting the CPU mask of all
1091 tasks in the system -- can cause problems and
1092 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001093
Randy Dunlapa9913042005-10-23 12:57:11 -07001094 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095
1096 js= [HW,JOY] Analog joystick
1097 See Documentation/input/joystick.txt.
1098
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001099 keepinitrd [HW,ARM]
1100
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301101 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001102 specifies the amount of memory usable by the kernel
1103 for non-movable allocations. The requested amount is
1104 spread evenly throughout all nodes in the system. The
1105 remaining memory in each node is used for Movable
1106 pages. In the event, a node is too small to have both
1107 kernelcore and Movable pages, kernelcore pages will
1108 take priority and other nodes will have a larger number
1109 of kernelcore pages. The Movable zone is used for the
1110 allocation of pages that may be reclaimed or moved
1111 by the page migration subsystem. This means that
1112 HugeTLB pages may not be allocated from this zone.
1113 Note that allocations like PTEs-from-HighMem still
1114 use the HighMem zone if it exists, and the Normal
1115 zone if it does not.
1116
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001117 kgdboc= [HW] kgdb over consoles.
1118 Requires a tty driver that supports console polling.
Matt LaPlante19f59462009-04-27 15:06:31 +02001119 (only serial supported for now)
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001120 Format: <serial_device>[,baud]
1121
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001122 kmac= [MIPS] korina ethernet MAC address.
1123 Configure the RouterBoard 532 series on-chip
1124 Ethernet adapter MAC address.
1125
Catalin Marinas04f70332009-06-11 13:22:39 +01001126 kmemleak= [KNL] Boot-time kmemleak enable/disable
1127 Valid arguments: on, off
1128 Default: on
1129
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301130 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001131 in oops dumps.
1132
Andre Przywarafef07aa2009-07-10 14:20:35 +02001133 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1134 Default is 0 (don't ignore, but inject #GP)
1135
1136 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1137 Default is 1 (enabled)
1138
1139 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1140 Default is 0 (off)
1141
1142 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1143 for all guests.
1144 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1145
1146 kvm-intel.bypass_guest_pf=
1147 [KVM,Intel] Disables bypassing of guest page faults
1148 on Intel chips. Default is 1 (enabled)
1149
1150 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1151 (virtualized MMU) support on capable Intel chips.
1152 Default is 1 (enabled)
1153
1154 kvm-intel.emulate_invalid_guest_state=
1155 [KVM,Intel] Enable emulation of invalid guest states
1156 Default is 0 (disabled)
1157
1158 kvm-intel.flexpriority=
1159 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1160 Default is 1 (enabled)
1161
1162 kvm-intel.unrestricted_guest=
1163 [KVM,Intel] Disable unrestricted guest feature
1164 (virtualized real and unpaged mode) on capable
1165 Intel chips. Default is 1 (enabled)
1166
1167 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1168 feature (tagged TLBs) on capable Intel chips.
1169 Default is 1 (enabled)
1170
Linus Torvalds1da177e2005-04-16 15:20:36 -07001171 l2cr= [PPC]
1172
Robert Brosea78bfbf2008-03-29 07:20:23 +11001173 l3cr= [PPC]
1174
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001175 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001176 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001177
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301178 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001179 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001180
FD Camifcb71f62008-01-06 19:08:56 +01001181 libata.dma= [LIBATA] DMA control
1182 libata.dma=0 Disable all PATA and SATA DMA
1183 libata.dma=1 PATA and SATA Disk DMA only
1184 libata.dma=2 ATAPI (CDROM) DMA only
1185 libata.dma=4 Compact Flash DMA only
1186 Combinations also work, so libata.dma=3 enables DMA
1187 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001188
1189 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1190 libata.ignore_hpa=0 keep BIOS limits (default)
1191 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001192
Dave Jones78e70c22007-09-27 11:50:13 -04001193 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1194 when set.
1195 Format: <int>
1196
Tejun Heo33267322008-02-13 09:15:09 +09001197 libata.force= [LIBATA] Force configurations. The format is comma
1198 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001199 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001200 matching port, link or device. Basically, it matches
1201 the ATA ID string printed on console by libata. If
1202 the whole ID part is omitted, the last PORT and DEVICE
1203 values are used. If ID hasn't been specified yet, the
1204 configuration applies to all ports, links and devices.
1205
1206 If only DEVICE is omitted, the parameter applies to
1207 the port and all links and devices behind it. DEVICE
1208 number of 0 either selects the first device or the
1209 first fan-out link behind PMP device. It does not
1210 select the host link. DEVICE number of 15 selects the
1211 host link and device attached to it.
1212
1213 The VAL specifies the configuration to force. As long
1214 as there's no ambiguity shortcut notation is allowed.
1215 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1216 The following configurations can be forced.
1217
1218 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1219 Any ID with matching PORT is used.
1220
1221 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1222
1223 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1224 udma[/][16,25,33,44,66,100,133] notation is also
1225 allowed.
1226
1227 * [no]ncq: Turn on or off NCQ.
1228
Tejun Heo05944bd2008-08-13 20:19:09 +09001229 * nohrst, nosrst, norst: suppress hard, soft
1230 and both resets.
1231
Tejun Heo33267322008-02-13 09:15:09 +09001232 If there are multiple matching configurations changing
1233 the same attribute, the last one is used.
1234
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001235 lmb=debug [KNL] Enable lmb debug messages.
1236
Linus Torvalds1da177e2005-04-16 15:20:36 -07001237 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001238 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001239
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001240 lockd.nlm_grace_period=P [NFS] Assign grace period.
1241 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001242
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001243 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1244 Format: <integer>
1245
1246 lockd.nlm_timeout=T [NFS] Assign timeout value.
1247 Format: <integer>
1248
1249 lockd.nlm_udpport=M [NFS] Assign UDP port.
1250 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001251
1252 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1253 Format: <irq>
1254
1255 loglevel= All Kernel Messages with a loglevel smaller than the
1256 console loglevel will be printed to the console. It can
1257 also be changed with klogd or other programs. The
1258 loglevels are defined as follows:
1259
1260 0 (KERN_EMERG) system is unusable
1261 1 (KERN_ALERT) action must be taken immediately
1262 2 (KERN_CRIT) critical conditions
1263 3 (KERN_ERR) error conditions
1264 4 (KERN_WARNING) warning conditions
1265 5 (KERN_NOTICE) normal but significant condition
1266 6 (KERN_INFO) informational
1267 7 (KERN_DEBUG) debug-level messages
1268
1269 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001270 Format: { n | nk | nM }
1271 n must be a power of two. The default size
1272 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001273
Randy Dunlapaccaa242007-10-16 01:29:37 -07001274 logo.nologo [FB] Disables display of the built-in Linux logo.
1275 This may be used to provide more screen space for
1276 kernel log messages and is useful when debugging
1277 kernel boot problems.
1278
Linus Torvalds1da177e2005-04-16 15:20:36 -07001279 lp=0 [LP] Specify parallel ports to use, e.g,
1280 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1281 lp=reset first parallel port). 'lp=0' disables the
1282 lp=auto printer driver. 'lp=reset' (which can be
1283 specified in addition to the ports) causes
1284 attached printers to be reset. Using
1285 lp=port1,port2,... specifies the parallel ports
1286 to associate lp devices with, starting with
1287 lp0. A port specification may be 'none' to skip
1288 that lp device, or a parport name such as
1289 'parport0'. Specifying 'lp=auto' instead of a
1290 port specification list means that device IDs
1291 from each port should be examined, to see if
1292 an IEEE 1284-compliant printer is attached; if
1293 so, the driver will manage that printer.
1294 See also header of drivers/char/lp.c.
1295
1296 lpj=n [KNL]
1297 Sets loops_per_jiffy to given constant, thus avoiding
1298 time-consuming boot-time autodetection (up to 250 ms per
1299 CPU). 0 enables autodetection (default). To determine
1300 the correct value for your kernel, boot with normal
1301 autodetection and see what value is printed. Note that
1302 on SMP systems the preset will be applied to all CPUs,
1303 which is likely to cause problems if your CPUs need
1304 significantly divergent settings. An incorrect value
1305 will cause delays in the kernel to be wrong, leading to
1306 unpredictable I/O errors and other breakage. Although
1307 unlikely, in the extreme case this might damage your
1308 hardware.
1309
1310 ltpc= [NET]
1311 Format: <io>,<irq>,<dma>
1312
Randy Dunlapa9913042005-10-23 12:57:11 -07001313 mac5380= [HW,SCSI] Format:
1314 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001315
Randy Dunlapa9913042005-10-23 12:57:11 -07001316 machvec= [IA64] Force the use of a particular machine-vector
1317 (machvec) in a generic kernel.
1318 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319
Wu Zhangjin3209e702009-07-02 23:27:12 +08001320 machtype= [Loongson] Share the same kernel image file between different
1321 yeeloong laptop.
1322 Example: machtype=lemote-yeeloong-2f-7inch
1323
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001324 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1325 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001326
1327 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001328 should make use of. maxcpus=n : n >= 0 limits the
1329 kernel to using 'n' processors. n=0 is a special case,
1330 it is equivalent to "nosmp", which also disables
1331 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001333 max_loop= [LOOP] Maximum number of loopback devices that can
1334 be mounted
1335 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001336
Randy Dunlapa9913042005-10-23 12:57:11 -07001337 max_luns= [SCSI] Maximum number of LUNs to probe.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001338 Should be between 1 and 2^32-1.
1339
1340 max_report_luns=
Randy Dunlapa9913042005-10-23 12:57:11 -07001341 [SCSI] Maximum number of LUNs received.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342 Should be between 1 and 16384.
1343
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344 mcatest= [IA-64]
1345
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001346 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347
Uwe Hermann71cced62008-10-20 09:32:21 -07001348 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001349
Linus Torvalds1da177e2005-04-16 15:20:36 -07001350 md= [HW] RAID subsystems devices and level
1351 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001352
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353 mdacon= [MDA]
1354 Format: <first>,<last>
1355 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001356
Linus Torvalds1da177e2005-04-16 15:20:36 -07001357 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1358 Amount of memory to be used when the kernel is not able
1359 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001360 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001361 address space collisions. Without memmap= PCI devices
1362 could be placed at addresses belonging to unused RAM.
1363
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001364 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001365 memory.
1366
Paul Mundt6902aa82008-09-21 17:14:42 +09001367 memchunk=nn[KMG]
1368 [KNL,SH] Allow user to override the default size for
1369 per-device physically contiguous DMA buffers.
1370
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301371 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001372 E820 memory map, as specified by the user.
1373 Such memmap=exactmap lines can be constructed based on
1374 BIOS output or other requirements. See the memmap=nn@ss
1375 option description.
1376
1377 memmap=nn[KMG]@ss[KMG]
1378 [KNL] Force usage of a specific region of memory
1379 Region of memory to be used, from ss to ss+nn.
1380
1381 memmap=nn[KMG]#ss[KMG]
1382 [KNL,ACPI] Mark specific memory as ACPI data.
1383 Region of memory to be used, from ss to ss+nn.
1384
1385 memmap=nn[KMG]$ss[KMG]
1386 [KNL,ACPI] Mark specific memory as reserved.
1387 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001388 Example: Exclude memory from 0x18690000-0x1869ffff
1389 memmap=64K$0x18690000
1390 or
1391 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001392
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001393 memory_corruption_check=0/1 [X86]
1394 Some BIOSes seem to corrupt the first 64k of
1395 memory when doing things like suspend/resume.
1396 Setting this option will scan the memory
1397 looking for corruption. Enabling this will
1398 both detect corruption and prevent the kernel
1399 from using the memory being corrupted.
1400 However, its intended as a diagnostic tool; if
1401 repeatable BIOS-originated corruption always
1402 affects the same memory, you can use memmap=
1403 to prevent the kernel from using that memory.
1404
1405 memory_corruption_check_size=size [X86]
1406 By default it checks for corruption in the low
1407 64k, making this memory unavailable for normal
1408 use. Use this parameter to scan for
1409 corruption in more or less memory.
1410
1411 memory_corruption_check_period=seconds [X86]
1412 By default it checks for corruption every 60
1413 seconds. Use this parameter to check at some
1414 other rate. 0 disables periodic checking.
1415
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001416 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001417 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001418 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001419 Specifies the number of memtest passes to be
1420 performed. Each pass selects another test
1421 pattern from a given set of patterns. Memtest
1422 fills the memory with this pattern, validates
1423 memory contents and reserves bad memory
1424 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001425
Linus Torvalds1da177e2005-04-16 15:20:36 -07001426 meye.*= [HW] Set MotionEye Camera parameters
1427 See Documentation/video4linux/meye.txt.
1428
Andres Salomon8f368812007-10-12 23:04:06 +02001429 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1430 Multi-Function General Purpose Timers on AMD Geode
1431 platforms.
1432
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001433 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1434 the BIOS has incorrectly applied a workaround. TinyBIOS
1435 version 0.98 is known to be affected, 0.99 fixes the
1436 problem by letting the user disable the workaround.
1437
Linus Torvalds1da177e2005-04-16 15:20:36 -07001438 mga= [HW,DRM]
1439
Randy Dunlap1c207f92008-11-19 15:36:16 -08001440 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1441 physical address is ignored.
1442
Michel Pollet39f45d72009-05-20 11:10:31 +01001443 mini2440= [ARM,HW,KNL]
1444 Format:[0..2][b][c][t]
1445 Default: "0tb"
1446 MINI2440 configuration specification:
1447 0 - The attached screen is the 3.5" TFT
1448 1 - The attached screen is the 7" TFT
1449 2 - The VGA Shield is attached (1024x768)
1450 Leaving out the screen size parameter will not load
1451 the TFT driver, and the framebuffer will be left
1452 unconfigured.
1453 b - Enable backlight. The TFT backlight pin will be
1454 linked to the kernel VESA blanking code and a GPIO
1455 LED. This parameter is not necessary when using the
1456 VGA shield.
1457 c - Enable the s3c camera interface.
1458 t - Reserved for enabling touchscreen support. The
1459 touchscreen support is not enabled in the mainstream
1460 kernel as of 2.6.30, a preliminary port can be found
1461 in the "bleeding edge" mini2440 support kernel at
1462 http://repo.or.cz/w/linux-2.6/mini2440.git
1463
Mel Gorman6b74ab92008-07-23 21:26:49 -07001464 mminit_loglevel=
1465 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1466 parameter allows control of the logging verbosity for
1467 the additional memory initialisation checks. A value
1468 of 0 disables mminit logging and a level of 4 will
1469 log everything. Information is printed at KERN_DEBUG
1470 so loglevel=8 may also need to be specified.
1471
Linus Torvalds1da177e2005-04-16 15:20:36 -07001472 mousedev.tap_time=
1473 [MOUSE] Maximum time between finger touching and
1474 leaving touchpad surface for touch to be considered
1475 a tap and be reported as a left button click (for
1476 touchpads working in absolute mode only).
1477 Format: <msecs>
1478 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1479 reporting absolute coordinates, such as tablets
1480 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1481 reporting absolute coordinates, such as tablets
1482
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301483 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001484 is similar to kernelcore except it specifies the
1485 amount of memory used for migratable allocations.
1486 If both kernelcore and movablecore is specified,
1487 then kernelcore will be at *least* the specified
1488 value but may be more. If movablecore on its own
1489 is specified, the administrator must be careful
1490 that the amount of memory usable for all allocations
1491 is not too small.
1492
Linus Torvalds1da177e2005-04-16 15:20:36 -07001493 mpu401= [HW,OSS]
1494 Format: <io>,<irq>
1495
1496 MTD_Partition= [MTD]
1497 Format: <name>,<region-number>,<size>,<offset>
1498
Randy Dunlapa9913042005-10-23 12:57:11 -07001499 MTD_Region= [MTD] Format:
1500 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001501
1502 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001503 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001504
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001505 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1506
1507 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1508
1509 boundary - index of last SLC block on Flex-OneNAND.
1510 The remaining blocks are configured as MLC blocks.
1511 lock - Configure if Flex-OneNAND boundary should be locked.
1512 Once locked, the boundary cannot be changed.
1513 1 indicates lock status, 0 indicates unlock status.
1514
Ben Dooks9db829f2008-07-03 11:24:29 +01001515 mtdset= [ARM]
1516 ARM/S3C2412 JIVE boot control
1517
1518 See arch/arm/mach-s3c2412/mach-jive.c
1519
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001521 [HW] Make the MicroTouch USB driver use raw coordinates
1522 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001523
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001524 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001525 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001526 that could hold holes aka. UC entries.
1527
1528 mtrr_gran_size=nn[KMG] [X86]
1529 Used for mtrr cleanup. It is granularity of mtrr block.
1530 Default is 1.
1531 Large value could prevent small alignment from
1532 using up MTRRs.
1533
1534 mtrr_spare_reg_nr=n [X86]
1535 Format: <integer>
1536 Range: 0,7 : spare reg number
1537 Default : 1
1538 Used for mtrr cleanup. It is spare mtrr entries number.
1539 Set to 2 or more if your graphical card needs more.
1540
Linus Torvalds1da177e2005-04-16 15:20:36 -07001541 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1542
1543 NCR_D700= [HW,SCSI]
1544 See header of drivers/scsi/NCR_D700.c.
1545
1546 ncr5380= [HW,SCSI]
1547
1548 ncr53c400= [HW,SCSI]
1549
1550 ncr53c400a= [HW,SCSI]
1551
1552 ncr53c406a= [HW,SCSI]
1553
1554 ncr53c8xx= [HW,SCSI]
1555
1556 netdev= [NET] Network devices parameters
1557 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1558 Note that mem_start is often overloaded to mean
1559 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001560 This usage is only documented in each driver source
1561 file if at all.
1562
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001563 nf_conntrack.acct=
1564 [NETFILTER] Enable connection tracking flow accounting
1565 0 to disable accounting
1566 1 to enable accounting
1567 Default value depends on CONFIG_NF_CT_ACCT that is
1568 going to be removed in 2.6.29.
1569
Linus Torvalds1da177e2005-04-16 15:20:36 -07001570 nfsaddrs= [NFS]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001571 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001572
1573 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001574 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001575
Trond Myklebusta72b4422006-01-03 09:55:41 +01001576 nfs.callback_tcpport=
1577 [NFS] set the TCP port on which the NFSv4 callback
1578 channel should listen.
1579
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001580 nfs.cache_getent=
1581 [NFS] sets the pathname to the program which is used
1582 to update the NFS client cache entries.
1583
1584 nfs.cache_getent_timeout=
1585 [NFS] sets the timeout after which an attempt to
1586 update a cache entry is deemed to have failed.
1587
Trond Myklebust58df0952006-01-03 09:55:57 +01001588 nfs.idmap_cache_timeout=
1589 [NFS] set the maximum lifetime for idmapper cache
1590 entries.
1591
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001592 nfs.enable_ino64=
1593 [NFS] enable 64-bit inode numbers.
1594 If zero, the NFS client will fake up a 32-bit inode
1595 number for the readdir() and stat() syscalls instead
1596 of returning the full 64-bit number.
1597 The default is to return 64-bit inode numbers.
1598
Paul Mundt1e1030d2009-09-01 17:38:32 +09001599 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001600 when a NMI is triggered.
1601 Format: [state][,regs][,debounce][,die]
1602
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301603 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001604 Format: [panic,][num]
1605 Valid num: 0,1,2
1606 0 - turn nmi_watchdog off
1607 1 - use the IO-APIC timer for the NMI watchdog
1608 2 - use the local APIC for the NMI watchdog using
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001609 a performance counter. Note: This will use one
1610 performance counter and the local APIC's performance
1611 vector.
1612 When panic is specified, panic when an NMI watchdog
1613 timeout occurs.
1614 This is useful when you use a panic=... timeout and
1615 need the box quickly up again.
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001616 Instead of 1 and 2 it is possible to use the following
1617 symbolic names: lapic and ioapic
1618 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
Linus Torvalds1da177e2005-04-16 15:20:36 -07001619
Anton Vorontsovbff38772009-07-08 11:10:56 -07001620 netpoll.carrier_timeout=
1621 [NET] Specifies amount of time (in seconds) that
1622 netpoll should wait for a carrier. By default netpoll
1623 waits 4 seconds.
1624
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001625 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001626 emulation library even if a 387 maths coprocessor
1627 is present.
1628
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001629 no_console_suspend
1630 [HW] Never suspend the console
1631 Disable suspending of consoles during suspend and
1632 hibernate operations. Once disabled, debugging
1633 messages can reach various consoles while the rest
1634 of the system is being put to sleep (ie, while
1635 debugging driver suspend/resume hooks). This may
1636 not work reliably with all consoles, but is known
1637 to work with serial and VGA consoles.
1638
Christoph Lameterc1aee212007-05-31 00:40:47 -07001639 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1640 caches in the slab allocator. Saves per-node memory,
1641 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001642
Randy Dunlapa9913042005-10-23 12:57:11 -07001643 noalign [KNL,ARM]
1644
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 noapic [SMP,APIC] Tells the kernel to not make use of any
1646 IOAPICs that may be present in the system.
1647
Linus Torvalds1da177e2005-04-16 15:20:36 -07001648 nobats [PPC] Do not use BATs for mapping kernel lowmem
1649 on "Classic" PPC cores.
1650
1651 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001652
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001653 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1654
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001655 nodelayacct [KNL] Disable per-task delay accounting
1656
Linus Torvalds1da177e2005-04-16 15:20:36 -07001657 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1658
Paul Mundt6902aa82008-09-21 17:14:42 +09001659 nodsp [SH] Disable hardware DSP at boot time.
1660
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301661 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001662
Linus Torvalds1da177e2005-04-16 15:20:36 -07001663 noexec [IA-64]
1664
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301665 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001666 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001667 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001668 noexec=off: disable non-executable mappings
1669
1670 noexec32 [X86-64]
1671 This affects only 32-bit executables.
1672 noexec32=on: enable non-executable mappings (default)
1673 read doesn't imply executable mappings
1674 noexec32=off: disable non-executable mappings
1675 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001676
Paul Mundt6902aa82008-09-21 17:14:42 +09001677 nofpu [SH] Disable hardware FPU at boot time.
1678
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001679 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001680 register save and restore. The kernel will only save
1681 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001682
Suresh Siddha0c752a92009-05-22 12:17:45 -07001683 noxsave [BUGS=X86] Disables x86 extended register state save
1684 and restore using xsave. The kernel will fallback to
1685 enabling legacy floating-point and sse state.
1686
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001687 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1688 wfi(ARM) instruction doesn't work correctly and not to
1689 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001690
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001691 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001692 instruction doesn't work correctly and not to
1693 use it.
1694
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001695 no_file_caps Tells the kernel not to honor file capabilities. The
1696 only way then for a file to be executed with privilege
1697 is to be setuid root or executed by root.
1698
Linus Torvalds1da177e2005-04-16 15:20:36 -07001699 nohalt [IA-64] Tells the kernel not to use the power saving
1700 function PAL_HALT_LIGHT when idle. This increases
1701 power-consumption. On the positive side, it reduces
1702 interrupt wake-up latency, which may improve performance
1703 in certain environments such as networked servers or
1704 real-time systems.
1705
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001706 nohz= [KNL] Boottime enable/disable dynamic ticks
1707 Valid arguments: on, off
1708 Default: on
1709
Paul Mundteeee7852009-04-02 12:31:16 +09001710 noiotrap [SH] Disables trapped I/O port accesses.
1711
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001712 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001713 disable unhandled interrupt sources.
1714
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301715 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001716 broken timer IRQ sources.
1717
Linus Torvalds1da177e2005-04-16 15:20:36 -07001718 noisapnp [ISAPNP] Disables ISA PnP code.
1719
1720 noinitrd [RAM] Tells the kernel not to load any configured
1721 initial RAM disk.
1722
Weidong Han03ea8152009-04-17 16:42:15 +08001723 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1724 remapping.
1725
Linus Torvalds1da177e2005-04-16 15:20:36 -07001726 nointroute [IA-64]
1727
Tony Luck0aa366f2007-07-20 11:22:30 -07001728 nojitter [IA64] Disables jitter checking for ITC timers.
1729
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001730 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001732 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001733
Linus Torvalds1da177e2005-04-16 15:20:36 -07001734 noltlbs [PPC] Do not use large page/tlb entries for kernel
1735 lowmem mapping on PPC40x.
1736
Horms312f1f02006-02-22 09:57:55 +09001737 nomca [IA-64] Disable machine check abort handling
1738
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001739 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001740
Andres Salomon83d73842007-10-12 23:04:06 +02001741 nomfgpt [X86-32] Disable Multi-Function General Purpose
1742 Timer usage (for AMD Geode machines).
1743
Jiri Kosina016ddd92010-01-18 17:05:40 +01001744 nopat [X86] Disable PAT (page attribute table extension of
1745 pagetables) support.
1746
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001747 norandmaps Don't use address space randomization. Equivalent to
1748 echo 0 > /proc/sys/kernel/randomize_va_space
1749
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001750 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001751
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001752 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001753 with UP alternatives
1754
Linus Torvalds1da177e2005-04-16 15:20:36 -07001755 noresidual [PPC] Don't use residual data on PReP machines.
1756
Randy Dunlapa9913042005-10-23 12:57:11 -07001757 noresume [SWSUSP] Disables resume and restores original swap
1758 space.
1759
Linus Torvalds1da177e2005-04-16 15:20:36 -07001760 no-scroll [VGA] Disables scrollback.
1761 This is required for the Braillex ib80-piezo Braille
1762 reader made by F.H. Papenmeier (Germany).
1763
1764 nosbagart [IA-64]
1765
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001766 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001767
Len Brown61ec7562007-08-16 03:34:22 -04001768 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1769 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001770
Dave Jones97842212007-07-15 23:41:05 -07001771 nosoftlockup [KNL] Disable the soft-lockup detector.
1772
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001773 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001774 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001775
Linus Torvalds1da177e2005-04-16 15:20:36 -07001776 nosync [HW,M68K] Disables sync negotiation for all devices.
1777
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001778 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001779
1780 nousb [USB] Disable the USB subsystem
1781
1782 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001783
Weidong Han2b2fd872009-04-17 16:42:12 +08001784 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1785
Fenghua Yua6c75b862008-03-14 13:57:08 -07001786 nptcg= [IA64] Override max number of concurrent global TLB
1787 purges which is reported from either PAL_VM_SUMMARY or
1788 SAL PALO.
1789
Yinghai Lu2b633e32010-02-10 01:20:37 -08001790 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1791 could support. nr_cpus=n : n >= 1 limits the kernel to
1792 supporting 'n' processors. Later in runtime you can not
1793 use hotplug cpu feature to put more cpu back to online.
1794 just like you compile the kernel NR_CPUS=n
1795
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001796 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1797
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001798 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1799 one of ['zone', 'node', 'default'] can be specified
1800 This can be set from sysctl after boot.
1801 See Documentation/sysctl/vm.txt for details.
1802
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001803 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1804 See Documentation/debugging-via-ohci1394.txt for more
1805 info.
1806
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001807 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1808 Rather than timing out after 20 ms if an EC
1809 command is not properly ACKed, override the length
1810 of the timeout. We have interrupts disabled while
1811 waiting for the ACK, so if this is set too high
1812 interrupts *may* be lost!
1813
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001814 omap_mux= [OMAP] Override bootloader pin multiplexing.
1815 Format: <mux_mode0.mode_name=value>...
1816 For example, to override I2C bus2:
1817 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1818
Linus Torvalds1da177e2005-04-16 15:20:36 -07001819 opl3= [HW,OSS]
1820 Format: <io>
1821
Linus Torvalds1da177e2005-04-16 15:20:36 -07001822 oprofile.timer= [HW]
1823 Use timer interrupt instead of performance counters
1824
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001825 oprofile.cpu_type= Force an oprofile cpu type
1826 This might be useful if you have an older oprofile
1827 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001828 Format: { arch_perfmon }
1829 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001830 perfmon on Intel CPUs instead of the
1831 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001832
Linus Torvalds1da177e2005-04-16 15:20:36 -07001833 osst= [HW,SCSI] SCSI Tape Driver
1834 Format: <buffer_size>,<write_threshold>
1835 See also Documentation/scsi/st.txt.
1836
1837 panic= [KNL] Kernel behaviour on panic
1838 Format: <timeout>
1839
1840 parkbd.port= [HW] Parallel port number the keyboard adapter is
1841 connected to, default is 0.
1842 Format: <parport#>
1843 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1844 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001845 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001846
Randy Dunlapa9913042005-10-23 12:57:11 -07001847 parport= [HW,PPT] Specify parallel ports. 0 disables.
1848 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1849 Use 'auto' to force the driver to use any
1850 IRQ/DMA settings detected (the default is to
1851 ignore detected IRQ/DMA settings because of
1852 possible conflicts). You can specify the base
1853 address, IRQ, and DMA settings; IRQ and DMA
1854 should be numbers, or 'auto' (for using detected
1855 settings on that particular port), or 'nofifo'
1856 (to avoid using a FIFO even if it is detected).
1857 Parallel ports are assigned in the order they
1858 are specified on the command line, starting
1859 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001860
Randy Dunlapa9913042005-10-23 12:57:11 -07001861 parport_init_mode= [HW,PPT]
1862 Configure VIA parallel port to operate in
1863 a specific mode. This is necessary on Pegasos
1864 computer where firmware has no options for setting
1865 up parallel port mode and sets it to spp.
1866 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001867 Format: [spp|ps2|epp|ecp|ecpepp]
1868
Randy Dunlapa9913042005-10-23 12:57:11 -07001869 pas2= [HW,OSS] Format:
1870 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1871
Linus Torvalds1da177e2005-04-16 15:20:36 -07001872 pas16= [HW,SCSI]
1873 See header of drivers/scsi/pas16.c.
1874
Andrew Mortondd287792006-03-23 03:00:57 -08001875 pause_on_oops=
1876 Halt all CPUs after the first oops has been printed for
1877 the specified number of seconds. This is to be used if
1878 your oopses keep scrolling off the screen.
1879
Linus Torvalds1da177e2005-04-16 15:20:36 -07001880 pcbit= [HW,ISDN]
1881
1882 pcd. [PARIDE]
1883 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001884 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001885
Randy Dunlapa9913042005-10-23 12:57:11 -07001886 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001887 earlydump [X86] dump PCI config space before the kernel
1888 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001889 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001890 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001891 the hardware directly. Use this if your machine
1892 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001893 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001894 hardware access methods are allowed. Use this
1895 if you experience crashes upon bootup and you
1896 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001897 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001898 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001899 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001900 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001901 noaer [PCIE] If the PCIEAER kernel config parameter is
1902 enabled, this kernel boot option can be used to
1903 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001904 nodomains [PCI] Disable support for multiple PCI
1905 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301906 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001907 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001908 check_enable_amd_mmconf [X86] check for and enable
1909 properly configured MMIO access to PCI
1910 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001911 nomsi [MSI] If the PCI_MSI kernel config parameter is
1912 enabled, this kernel boot option can be used to
1913 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001914 noioapicquirk [APIC] Disable all boot interrupt quirks.
1915 Safety option to keep boot IRQs enabled. This
1916 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001917 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1918 primary IO-APIC for bridges that cannot disable
1919 boot IRQs. This fixes a source of spurious IRQs
1920 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001921 noioapicreroute [APIC] Disable workaround that uses the
1922 boot IRQ equivalent of an IRQ that connects to
1923 a chipset where boot IRQs cannot be disabled.
1924 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001925 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001926 routing table. These calls are known to be buggy
1927 on several machines and they hang the machine
1928 when used, but on other computers it's the only
1929 way to get the interrupt routing table. Try
1930 this option if the kernel is unable to allocate
1931 IRQs or discover secondary PCI buses on your
1932 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001933 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001934 Use with caution as certain devices share
1935 address decoders between ROMs and other
1936 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001937 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001938 expansion ROMs that do not already have
1939 BIOS assigned address ranges.
Andi Kleenc0115602008-08-22 09:53:39 +02001940 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001941 assigned automatically to PCI devices. You can
1942 make the kernel exclude IRQs of your ISA cards
1943 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001944 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001945 of the PIRQ table (normally generated
1946 by the BIOS) if it is outside the
1947 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001948 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001949 useful if the kernel is unable to find your
1950 secondary buses and you want to tell it
1951 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001952 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001953 numbers ourselves, overriding
1954 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001955 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001956 in the BIOS $PIR table. This is needed on
1957 some systems with broken BIOSes, notably
1958 some HP Pavilion N5400 and Omnibook XE3
1959 notebooks. This will have no effect if ACPI
1960 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001961 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001962 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07001963 use_crs [X86] Use PCI host bridge window information
1964 from ACPI. On BIOSes from 2008 or later, this
1965 is enabled by default. If you need to use this,
1966 please report a bug.
1967 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1968 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07001969 routeirq Do IRQ routing for all PCI devices.
1970 This is normally done in pci_enable_device(),
1971 so this option is a temporary workaround
1972 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001973 skip_isa_align [X86] do not align io start addr, so can
1974 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001975 firmware [ARM] Do not re-enumerate the bus but instead
1976 just use the configuration from the
1977 bootloader. This is currently used on
1978 IXP2000 systems where the bus has to be
1979 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001980 noearly [X86] Don't do any early type 1 scanning.
1981 This might help on some broken boards which
1982 machine check when some devices' config space
1983 is read. But various workarounds are disabled
1984 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001985 bfsort Sort PCI devices into breadth-first order.
1986 This sorting is done to get a device
1987 order compatible with older (<= 2.4) kernels.
1988 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001989 cbiosize=nn[KMG] The fixed amount of bus space which is
1990 reserved for the CardBus bridge's IO window.
1991 The default value is 256 bytes.
1992 cbmemsize=nn[KMG] The fixed amount of bus space which is
1993 reserved for the CardBus bridge's memory
1994 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09001995 resource_alignment=
1996 Format:
1997 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1998 Specifies alignment and device to reassign
1999 aligned memory resources.
2000 If <order of align> is not specified,
2001 PAGE_SIZE is used as alignment.
2002 PCI-PCI bridge can be specified, if resource
2003 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002004 ecrc= Enable/disable PCIe ECRC (transaction layer
2005 end-to-end CRC checking).
2006 bios: Use BIOS/firmware settings. This is the
2007 the default.
2008 off: Turn ECRC off
2009 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002010
Chuck Ebberte5665a42008-09-24 20:40:34 -04002011 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2012 Management.
2013 off Disable ASPM.
2014 force Enable ASPM even on devices that claim not to support it.
2015 WARNING: Forcing ASPM on may cause system lockups.
2016
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002017 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2018 off Do not use native PCIe PME signaling.
2019 force Use native PCIe PME signaling even if the BIOS refuses
2020 to allow the kernel to control the relevant PCIe config
2021 registers.
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002022 nomsi Do not use MSI for native PCIe PME signaling (this makes
2023 all PCIe root ports use INTx for everything).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002024
Linus Torvalds1da177e2005-04-16 15:20:36 -07002025 pcmv= [HW,PCMCIA] BadgePAD 4
2026
2027 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002028 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002029
2030 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2031 boot time.
2032 Format: { 0 | 1 }
2033 See arch/parisc/kernel/pdc_chassis.c
2034
Tejun Heof58dc012009-08-14 15:00:50 +09002035 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002036 Currently supported values are "embed" and "page".
2037 Archs may support subset or none of the selections.
2038 See comments in mm/percpu.c for details on each
2039 allocator. This parameter is primarily for debugging
2040 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002041
Linus Torvalds1da177e2005-04-16 15:20:36 -07002042 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002043 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002044
2045 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002046 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047
2048 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002049 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002050
2051 plip= [PPT,NET] Parallel port network link
2052 Format: { parport<nr> | timid | 0 }
2053 See also Documentation/parport.txt.
2054
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002055 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2056 Override pmtimer IOPort with a hex value.
2057 e.g. pmtmr=0x508
2058
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002059 pnp.debug [PNP]
2060 Enable PNP debug messages. This depends on the
2061 CONFIG_PNP_DEBUG_MESSAGES option.
2062
Linus Torvalds1da177e2005-04-16 15:20:36 -07002063 pnpacpi= [ACPI]
2064 { off }
2065
2066 pnpbios= [ISAPNP]
2067 { on | off | curr | res | no-curr | no-res }
2068
2069 pnp_reserve_irq=
2070 [ISAPNP] Exclude IRQs for the autoconfiguration
2071
2072 pnp_reserve_dma=
2073 [ISAPNP] Exclude DMAs for the autoconfiguration
2074
2075 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002076 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002077
2078 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002079 [ISAPNP] Exclude memory regions for the
2080 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002081 Ranges are in pairs (memory base and size).
2082
Randy Dunlap4af94f32009-04-17 18:30:28 -07002083 ports= [IP_VS_FTP] IPVS ftp helper module
2084 Default is 21.
2085 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2086 may be specified.
2087 Format: <port>,<port>....
2088
Ingo Molnar45807a12007-07-15 23:40:10 -07002089 print-fatal-signals=
2090 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002091
2092 If enabled, warn about various signal handling
2093 related application anomalies: too many signals,
2094 too many POSIX.1 timers, fatal signals causing a
2095 coredump - etc.
2096
2097 If you hit the warning due to signal overflow,
2098 you might want to try "ulimit -i unlimited".
2099
Ingo Molnar45807a12007-07-15 23:40:10 -07002100 default: off.
2101
Randy Dunlape84845c2007-07-15 23:40:25 -07002102 printk.time= Show timing data prefixed to each printk message line
2103 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2104
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002105 processor.max_cstate= [HW,ACPI]
2106 Limit processor to maximum C-state
2107 max_cstate=9 overrides any DMI blacklist limit.
2108
2109 processor.nocst [HW,ACPI]
2110 Ignore the _CST method to determine C-states,
2111 instead using the legacy FADT method
2112
Linus Torvalds1da177e2005-04-16 15:20:36 -07002113 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002114 Format: [schedule,]<number>
2115 Param: "schedule" - profile schedule points.
2116 Param: <number> - step/bucket size as a power of 2 for
2117 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002118 Param: "sleep" - profile D-state sleeping (millisecs).
2119 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002120 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002121
Linus Torvalds1da177e2005-04-16 15:20:36 -07002122 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2123 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002124 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002125
Randy Dunlapa9913042005-10-23 12:57:11 -07002126 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2127 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002128 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2129 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002130 psmouse.resetafter= [HW,MOUSE]
2131 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002132 (0 = never).
2133 psmouse.resolution=
2134 [HW,MOUSE] Set desired mouse resolution, in dpi.
2135 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002136 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002137 0 = disabled, 1 = enabled (default).
2138
2139 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
Randy Dunlapa9913042005-10-23 12:57:11 -07002140 Format:
2141 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002142
2143 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002144 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002145
Kay Sieversdc8c8582007-08-15 12:25:38 +02002146 pty.legacy_count=
2147 [KNL] Number of legacy pty's. Overwrites compiled-in
2148 default number.
2149
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002150 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002151
Linus Torvalds1da177e2005-04-16 15:20:36 -07002152 r128= [HW,DRM]
2153
2154 raid= [HW,RAID]
2155 See Documentation/md.txt.
2156
Randy Dunlapa9913042005-10-23 12:57:11 -07002157 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002158 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002159
Linus Torvalds1da177e2005-04-16 15:20:36 -07002160 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002161 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002162
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002163 rcupdate.blimit= [KNL,BOOT]
2164 Set maximum number of finished RCU callbacks to process
2165 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002166
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002167 rcupdate.qhimark= [KNL,BOOT]
2168 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002169 RCU callbacks over which batch limiting is disabled.
2170
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002171 rcupdate.qlowmark= [KNL,BOOT]
2172 Set threshold of queued RCU callbacks below which
2173 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002174
Olof Johanssonffdfc402005-09-06 15:17:19 -07002175 rdinit= [KNL]
2176 Format: <full_path>
2177 Run specified binary instead of /init from the ramdisk,
2178 used for early userspace startup. See initrd.
2179
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002180 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002181 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002182 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002183
Paul Jackson46b6d942008-07-04 10:00:09 -07002184 relax_domain_level=
2185 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002186 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002187
Linus Torvalds1da177e2005-04-16 15:20:36 -07002188 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2189
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002190 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002191 Format: nn[KMG]
2192 Reserves a hole at the top of the kernel virtual
2193 address space.
2194
Vivek Goyal7e962872006-09-27 01:50:44 -07002195 reset_devices [KNL] Force drivers to reset the underlying device
2196 during initialization.
2197
Randy Dunlapa9913042005-10-23 12:57:11 -07002198 resume= [SWSUSP]
2199 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002200
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002201 resume_offset= [SWSUSP]
2202 Specify the offset from the beginning of the partition
2203 given by "resume=" at which the swap header is located,
2204 in <PAGE_SIZE> units (needed only for swap files).
2205 See Documentation/power/swsusp-and-swap-files.txt
2206
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002207 retain_initrd [RAM] Keep initrd memory after extraction
2208
Linus Torvalds1da177e2005-04-16 15:20:36 -07002209 rhash_entries= [KNL,NET]
2210 Set number of hash buckets for route cache
2211
2212 riscom8= [HW,SERIAL]
2213 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2214
2215 ro [KNL] Mount root device read-only on boot
2216
2217 root= [KNL] Root filesystem
2218
2219 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2220 mount the root filesystem
2221
2222 rootflags= [KNL] Set root filesystem mount option string
2223
2224 rootfstype= [KNL] Set root filesystem type
2225
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002226 rootwait [KNL] Wait (indefinitely) for root device to show up.
2227 Useful for devices that are detected asynchronously
2228 (e.g. USB and MMC devices).
2229
Linus Torvalds1da177e2005-04-16 15:20:36 -07002230 rw [KNL] Mount root device read-write on boot
2231
2232 S [KNL] Run init in single mode
2233
2234 sa1100ir [NET]
2235 See drivers/net/irda/sa1100_ir.c.
2236
Linus Torvalds1da177e2005-04-16 15:20:36 -07002237 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002238
Mike Travisf6630112009-11-17 18:22:15 -06002239 sched_debug [KNL] Enables verbose scheduler debug messages.
2240
Linus Torvalds1da177e2005-04-16 15:20:36 -07002241 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2242 Format: <io>[,<timeout>[,<isapnp>]]
2243
2244 scsi_debug_*= [SCSI]
2245 See drivers/scsi/scsi_debug.c.
2246
2247 scsi_default_dev_flags=
2248 [SCSI] SCSI default device flags
2249 Format: <integer>
2250
2251 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2252 Format: <vendor>:<model>:<flags>
2253 (flags are integer value)
2254
Randy Dunlap6af66322007-11-14 16:52:25 -08002255 scsi_logging_level= [SCSI] a bit mask of logging levels
2256 See drivers/scsi/scsi_logging.h for bits. Also
2257 settable via sysctl at dev.scsi.logging_level
2258 (/proc/sys/dev/scsi/logging_level).
2259 There is also a nice 'scsi_logging_level' script in the
2260 S390-tools package, available for download at
2261 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
Linus Torvalds1da177e2005-04-16 15:20:36 -07002262
Matthew Wilcox3e082a92006-09-28 15:19:20 -06002263 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2264 discovered. async scans them in kernel threads,
2265 allowing boot to proceed. none ignores them, expecting
2266 user space to do the scan.
2267
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002268 security= [SECURITY] Choose a security module to enable at boot.
2269 If this boot parameter is not specified, only the first
2270 security module asking for security registration will be
2271 loaded. An invalid security module name will be treated
2272 as if no module has been chosen.
2273
2274 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002275 Format: { "0" | "1" }
2276 See security/selinux/Kconfig help text.
2277 0 -- disable.
2278 1 -- enable.
2279 Default value is set via kernel config option.
2280 If enabled at boot time, /selinux/disable can be used
2281 later to disable prior to initial policy load.
2282
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002283 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002284
Linus Torvalds1da177e2005-04-16 15:20:36 -07002285 shapers= [NET]
2286 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002287
Yinghai Lub05f78f2008-08-22 01:32:50 -07002288 show_msr= [x86] show boot-time MSR settings
2289 Format: { <integer> }
2290 Show boot-time (BIOS-initialized) MSR settings.
2291 The parameter means the number of CPUs to show,
2292 for example 1 means boot CPU only.
2293
Linus Torvalds1da177e2005-04-16 15:20:36 -07002294 sim710= [SCSI,HW]
2295 See header of drivers/scsi/sim710.c.
2296
2297 simeth= [IA-64]
2298 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002299
Linus Torvalds1da177e2005-04-16 15:20:36 -07002300 slram= [HW,MTD]
2301
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002302 slub_debug[=options[,slabs]] [MM, SLUB]
2303 Enabling slub_debug allows one to determine the
2304 culprit if slab objects become corrupted. Enabling
2305 slub_debug can create guard zones around objects and
2306 may poison objects when not in use. Also tracks the
2307 last alloc / free. For more information see
2308 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002309
2310 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002311 Determines the maximum allowed order for slabs.
2312 A high setting may cause OOMs due to memory
2313 fragmentation. For more information see
2314 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002315
2316 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002317 The minimum number of objects per slab. SLUB will
2318 increase the slab order up to slub_max_order to
2319 generate a sufficiently large slab able to contain
2320 the number of objects indicated. The higher the number
2321 of objects the smaller the overhead of tracking slabs
2322 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002323 For more information see Documentation/vm/slub.txt.
2324
2325 slub_min_order= [MM, SLUB]
2326 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002327 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002328 For more information see Documentation/vm/slub.txt.
2329
2330 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002331 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002332 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002333 allocs to different slabs. Debug options disable
2334 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002335 For more information see Documentation/vm/slub.txt.
2336
Linus Torvalds1da177e2005-04-16 15:20:36 -07002337 smart2= [HW]
2338 Format: <io1>[,<io2>[,...,<io8>]]
2339
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002340 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002341 attempt to substitute SMP alternatives once at boot.
2342
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002343 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2344 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2345 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2346 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2347 smsc-ircc2.ircc_irq= [HW] IRQ line
2348 smsc-ircc2.ircc_dma= [HW] DMA channel
2349 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2350 0: Toshiba Satellite 1800 (GP data pin select)
2351 1: Fast pin select (default)
2352 2: ATC IRMode
2353
Linus Torvalds1da177e2005-04-16 15:20:36 -07002354 snd-ad1816a= [HW,ALSA]
2355
2356 snd-ad1848= [HW,ALSA]
2357
2358 snd-ali5451= [HW,ALSA]
2359
2360 snd-als100= [HW,ALSA]
2361
2362 snd-als4000= [HW,ALSA]
2363
2364 snd-azt2320= [HW,ALSA]
2365
2366 snd-cmi8330= [HW,ALSA]
2367
2368 snd-cmipci= [HW,ALSA]
2369
2370 snd-cs4231= [HW,ALSA]
2371
2372 snd-cs4232= [HW,ALSA]
2373
2374 snd-cs4236= [HW,ALSA]
2375
2376 snd-cs4281= [HW,ALSA]
2377
2378 snd-cs46xx= [HW,ALSA]
2379
2380 snd-dt019x= [HW,ALSA]
2381
2382 snd-dummy= [HW,ALSA]
2383
2384 snd-emu10k1= [HW,ALSA]
2385
2386 snd-ens1370= [HW,ALSA]
2387
2388 snd-ens1371= [HW,ALSA]
2389
2390 snd-es968= [HW,ALSA]
2391
2392 snd-es1688= [HW,ALSA]
2393
2394 snd-es18xx= [HW,ALSA]
2395
2396 snd-es1938= [HW,ALSA]
2397
2398 snd-es1968= [HW,ALSA]
2399
2400 snd-fm801= [HW,ALSA]
2401
2402 snd-gusclassic= [HW,ALSA]
2403
2404 snd-gusextreme= [HW,ALSA]
2405
2406 snd-gusmax= [HW,ALSA]
2407
2408 snd-hdsp= [HW,ALSA]
2409
2410 snd-ice1712= [HW,ALSA]
2411
2412 snd-intel8x0= [HW,ALSA]
2413
2414 snd-interwave= [HW,ALSA]
2415
2416 snd-interwave-stb=
2417 [HW,ALSA]
2418
2419 snd-korg1212= [HW,ALSA]
2420
2421 snd-maestro3= [HW,ALSA]
2422
2423 snd-mpu401= [HW,ALSA]
2424
2425 snd-mtpav= [HW,ALSA]
2426
2427 snd-nm256= [HW,ALSA]
2428
2429 snd-opl3sa2= [HW,ALSA]
2430
2431 snd-opti92x-ad1848=
2432 [HW,ALSA]
2433
2434 snd-opti92x-cs4231=
2435 [HW,ALSA]
2436
2437 snd-opti93x= [HW,ALSA]
2438
2439 snd-pmac= [HW,ALSA]
2440
2441 snd-rme32= [HW,ALSA]
2442
2443 snd-rme96= [HW,ALSA]
2444
2445 snd-rme9652= [HW,ALSA]
2446
2447 snd-sb8= [HW,ALSA]
2448
2449 snd-sb16= [HW,ALSA]
2450
2451 snd-sbawe= [HW,ALSA]
2452
2453 snd-serial= [HW,ALSA]
2454
2455 snd-sgalaxy= [HW,ALSA]
2456
2457 snd-sonicvibes= [HW,ALSA]
2458
2459 snd-sun-amd7930=
2460 [HW,ALSA]
2461
2462 snd-sun-cs4231= [HW,ALSA]
2463
2464 snd-trident= [HW,ALSA]
2465
2466 snd-usb-audio= [HW,ALSA,USB]
2467
2468 snd-via82xx= [HW,ALSA]
2469
2470 snd-virmidi= [HW,ALSA]
2471
2472 snd-wavefront= [HW,ALSA]
2473
2474 snd-ymfpci= [HW,ALSA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002475
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002476 softlockup_panic=
2477 [KNL] Should the soft-lockup detector generate panics.
2478
Linus Torvalds1da177e2005-04-16 15:20:36 -07002479 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2480 See Documentation/sonypi.txt
2481
2482 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002483 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002484
2485 spia_io_base= [HW,MTD]
2486 spia_fio_base=
2487 spia_pedr=
2488 spia_peddr=
2489
2490 sscape= [HW,OSS]
2491 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
Randy Dunlapa9913042005-10-23 12:57:11 -07002492
Linus Torvalds1da177e2005-04-16 15:20:36 -07002493 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2494 See Documentation/scsi/st.txt.
2495
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002496 stacktrace [FTRACE]
2497 Enabled the stack tracer on boot up.
2498
Linus Torvalds1da177e2005-04-16 15:20:36 -07002499 sti= [PARISC,HW]
2500 Format: <num>
2501 Set the STI (builtin display/keyboard on the HP-PARISC
2502 machines) console (graphic card) which should be used
2503 as the initial boot-console.
2504 See also comment in drivers/video/console/sticore.c.
2505
2506 sti_font= [HW]
2507 See comment in drivers/video/console/sticore.c.
2508
2509 stifb= [HW]
2510 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2511
Trond Myklebustcbf11072009-08-09 15:06:19 -04002512 sunrpc.min_resvport=
2513 sunrpc.max_resvport=
2514 [NFS,SUNRPC]
2515 SunRPC servers often require that client requests
2516 originate from a privileged port (i.e. a port in the
2517 range 0 < portnr < 1024).
2518 An administrator who wishes to reserve some of these
2519 ports for other uses may adjust the range that the
2520 kernel's sunrpc client considers to be privileged
2521 using these two parameters to set the minimum and
2522 maximum port values.
2523
Greg Banks42a7fc42007-03-06 01:42:23 -08002524 sunrpc.pool_mode=
2525 [NFS]
2526 Control how the NFS server code allocates CPUs to
2527 service thread pools. Depending on how many NICs
2528 you have and where their interrupts are bound, this
2529 option will affect which CPUs will do NFS serving.
2530 Note: this parameter cannot be changed while the
2531 NFS server is running.
2532
2533 auto the server chooses an appropriate mode
2534 automatically using heuristics
2535 global a single global pool contains all CPUs
2536 percpu one pool for each CPU
2537 pernode one pool for each NUMA node (equivalent
2538 to global on non-NUMA machines)
2539
Trond Myklebustcbf11072009-08-09 15:06:19 -04002540 sunrpc.tcp_slot_table_entries=
2541 sunrpc.udp_slot_table_entries=
2542 [NFS,SUNRPC]
2543 Sets the upper limit on the number of simultaneous
2544 RPC calls that can be sent from the client to a
2545 server. Increasing these values may allow you to
2546 improve throughput, but will also increase the
2547 amount of memory reserved for use by the client.
2548
Linus Torvalds1da177e2005-04-16 15:20:36 -07002549 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002550
Linus Torvalds1da177e2005-04-16 15:20:36 -07002551 switches= [HW,M68k]
2552
2553 sym53c416= [HW,SCSI]
2554 See header of drivers/scsi/sym53c416.c.
2555
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002556 sysrq_always_enabled
2557 [KNL]
2558 Ignore sysrq setting - this boot parameter will
2559 neutralize any effect of /proc/sys/kernel/sysrq.
2560 Useful for debugging.
2561
Linus Torvalds1da177e2005-04-16 15:20:36 -07002562 t128= [HW,SCSI]
2563 See header of drivers/scsi/t128.c.
2564
2565 tdfx= [HW,DRM]
2566
David Brownell77437fd2008-07-23 21:28:33 -07002567 test_suspend= [SUSPEND]
2568 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2569 standby suspend) as the system sleep state to briefly
2570 enter during system startup. The system is woken from
2571 this state using a wakeup-capable RTC alarm.
2572
Linus Torvalds1da177e2005-04-16 15:20:36 -07002573 thash_entries= [KNL,NET]
2574 Set number of hash buckets for TCP connection
2575
Len Brownf8707ec2007-08-12 00:12:54 -04002576 thermal.act= [HW,ACPI]
2577 -1: disable all active trip points in all thermal zones
2578 <degrees C>: override all lowest active trip points
2579
Len Brownc52a7412007-08-14 15:49:32 -04002580 thermal.crt= [HW,ACPI]
2581 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002582 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002583
Len Brownf5487142007-08-12 00:12:44 -04002584 thermal.nocrt= [HW,ACPI]
2585 Set to disable actions on ACPI thermal zone
2586 critical and hot trip points.
2587
Len Brown72b33ef2007-08-12 00:12:17 -04002588 thermal.off= [HW,ACPI]
2589 1: disable ACPI thermal control
2590
Len Browna70cdc52007-08-12 00:12:35 -04002591 thermal.psv= [HW,ACPI]
2592 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002593 <degrees C>: override all passive trip points to this
2594 value
Len Browna70cdc52007-08-12 00:12:35 -04002595
Len Brown730ff342007-08-12 00:12:26 -04002596 thermal.tzp= [HW,ACPI]
2597 Specify global default ACPI thermal zone polling rate
2598 <deci-seconds>: poll all this frequency
2599 0: no polling (default)
2600
Linus Torvalds1da177e2005-04-16 15:20:36 -07002601 tmscsim= [HW,SCSI]
2602 See comment before function dc390_setup() in
2603 drivers/scsi/tmscsim.c.
2604
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002605 topology= [S390]
2606 Format: {off | on}
2607 Specify if the kernel should make use of the cpu
2608 topology informations if the hardware supports these.
2609 The scheduler will make use of these informations and
2610 e.g. base its process migration decisions on it.
2611 Default is off.
2612
Linus Torvalds1da177e2005-04-16 15:20:36 -07002613 tp720= [HW,PS2]
2614
Li Zefan9d612be2009-06-24 17:33:15 +08002615 trace_buf_size=nn[KMG]
2616 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002617
Li Zefan020e5f82009-07-01 10:47:05 +08002618 trace_event=[event-list]
2619 [FTRACE] Set and start specified trace events in order
2620 to facilitate early boot debugging.
2621 See also Documentation/trace/events.txt
2622
Linus Torvalds1da177e2005-04-16 15:20:36 -07002623 trix= [HW,OSS] MediaTrix AudioTrix Pro
Randy Dunlapa9913042005-10-23 12:57:11 -07002624 Format:
2625 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2626
Alok Kataria395628e2008-10-24 17:22:01 -07002627 tsc= Disable clocksource-must-verify flag for TSC.
2628 Format: <string>
2629 [x86] reliable: mark tsc clocksource as reliable, this
2630 disables clocksource verification at runtime.
2631 Used to enable high-resolution timer mode on older
2632 hardware, and in virtualized environment.
2633
Randy Dunlapa9913042005-10-23 12:57:11 -07002634 turbografx.map[2|3]= [HW,JOY]
2635 TurboGraFX parallel port interface
2636 Format:
2637 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002638 See also Documentation/input/joystick-parport.txt
2639
2640 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2641 See header of drivers/scsi/u14-34f.c.
2642
2643 uart401= [HW,OSS]
2644 Format: <io>,<irq>
2645
2646 uart6850= [HW,OSS]
2647 Format: <io>,<irq>
2648
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002649 uhash_entries= [KNL,NET]
2650 Set number of hash buckets for UDP/UDP-Lite connections
2651
Alan Stern5f8364b2006-12-05 16:29:55 -05002652 uhci-hcd.ignore_oc=
2653 [USB] Ignore overcurrent events (default N).
2654 Some badly-designed motherboards generate lots of
2655 bogus events, for ports that aren't wired to
2656 anything. Set this parameter to avoid log spamming.
2657 Note that genuine overcurrent events won't be
2658 reported either.
2659
Simon Arlotte3a61b02008-07-19 23:32:54 +01002660 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302661 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002662 Set unknown_nmi_panic=1 early on boot.
2663
Alan Sternb5e795f2007-02-20 15:00:53 -05002664 usbcore.autosuspend=
2665 [USB] The autosuspend time delay (in seconds) used
2666 for newly-detected USB devices (default 2). This
2667 is the time required before an idle device will be
2668 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002669 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002670
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002671 usbcore.usbfs_snoop=
2672 [USB] Set to log all usbfs traffic (default 0 = off).
2673
2674 usbcore.blinkenlights=
2675 [USB] Set to cycle leds on hubs (default 0 = off).
2676
2677 usbcore.old_scheme_first=
2678 [USB] Start with the old device initialization
2679 scheme (default 0 = off).
2680
2681 usbcore.use_both_schemes=
2682 [USB] Try the other device initialization scheme
2683 if the first one fails (default 1 = enabled).
2684
2685 usbcore.initial_descriptor_timeout=
2686 [USB] Specifies timeout for the initial 64-byte
2687 USB_REQ_GET_DESCRIPTOR request in milliseconds
2688 (default 5000 = 5.0 seconds).
2689
Linus Torvalds1da177e2005-04-16 15:20:36 -07002690 usbhid.mousepoll=
2691 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002692
Alan Sternd4f373e2008-11-10 14:07:45 -05002693 usb-storage.delay_use=
2694 [UMS] The delay in seconds before a new device is
2695 scanned for Logical Units (default 5).
2696
2697 usb-storage.quirks=
2698 [UMS] A list of quirks entries to supplement or
2699 override the built-in unusual_devs list. List
2700 entries are separated by commas. Each entry has
2701 the form VID:PID:Flags where VID and PID are Vendor
2702 and Product ID values (4-digit hex numbers) and
2703 Flags is a set of characters, each corresponding
2704 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002705 a = SANE_SENSE (collect more than 18 bytes
2706 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002707 b = BAD_SENSE (don't collect more than 18
2708 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002709 c = FIX_CAPACITY (decrease the reported
2710 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002711 h = CAPACITY_HEURISTICS (decrease the
2712 reported device capacity by one
2713 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002714 i = IGNORE_DEVICE (don't bind to this
2715 device);
2716 l = NOT_LOCKABLE (don't try to lock and
2717 unlock ejectable media);
2718 m = MAX_SECTORS_64 (don't transfer more
2719 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002720 o = CAPACITY_OK (accept the capacity
2721 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002722 r = IGNORE_RESIDUE (the device reports
2723 bogus residue values);
2724 s = SINGLE_LUN (the device has only one
2725 Logical Unit);
2726 w = NO_WP_DETECT (don't test whether the
2727 medium is write-protected).
2728 Example: quirks=0419:aaf5:rl,0421:0433:rc
2729
Ian Campbell14315592010-02-17 10:38:10 +00002730 userpte=
2731 [X86] Flags controlling user PTE allocations.
2732
2733 nohigh = do not allocate PTE pages in
2734 HIGHMEM regardless of setting
2735 of CONFIG_HIGHPTE.
2736
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302737 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002738 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002739 vdso=1: enable VDSO (default)
2740 vdso=0: disable VDSO mapping
2741
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302742 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002743 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2744 vdso32=1: enable 32-bit VDSO (default)
2745 vdso32=0: disable 32-bit VDSO mapping
2746
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002747 vector= [IA-64,SMP]
2748 vector=percpu: enable percpu vector domain
2749
Linus Torvalds1da177e2005-04-16 15:20:36 -07002750 video= [FB] Frame buffer configuration
2751 See Documentation/fb/modedb.txt.
2752
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002753 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002754 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002755 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002756 Use vga=ask for menu.
2757 This is actually a boot loader parameter; the value is
2758 passed to the kernel using a special protocol.
2759
Randy Dunlapa9913042005-10-23 12:57:11 -07002760 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002761 size of <nn>. This can be used to increase the
2762 minimum size (128MB on x86). It can also be used to
2763 decrease the size and leave more room for directly
2764 mapped kernel RAM.
2765
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002766 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2767 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002768
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002769 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2770 Format: <command>
2771
2772 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2773 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002774
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002775 vt.cur_default= [VT] Default cursor shape.
2776 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2777 the parameters of the <Esc>[?A;B;Cc escape sequence;
2778 see VGA-softcursor.txt. Default: 2 = underline.
2779
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002780 vt.default_blu= [VT]
2781 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2782 Change the default blue palette of the console.
2783 This is a 16-member array composed of values
2784 ranging from 0-255.
2785
2786 vt.default_grn= [VT]
2787 Format: <green0>,<green1>,<green2>,...,<green15>
2788 Change the default green palette of the console.
2789 This is a 16-member array composed of values
2790 ranging from 0-255.
2791
2792 vt.default_red= [VT]
2793 Format: <red0>,<red1>,<red2>,...,<red15>
2794 Change the default red palette of the console.
2795 This is a 16-member array composed of values
2796 ranging from 0-255.
2797
2798 vt.default_utf8=
2799 [VT]
2800 Format=<0|1>
2801 Set system-wide default UTF-8 mode for all tty's.
2802 Default is 1, i.e. UTF-8 mode is enabled for all
2803 newly opened terminals.
2804
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002805 vt.global_cursor_default=
2806 [VT]
2807 Format=<-1|0|1>
2808 Set system-wide default for whether a cursor
2809 is shown on new VTs. Default is -1,
2810 i.e. cursors will be created by default unless
2811 overridden by individual drivers. 0 will hide
2812 cursors, 1 will display them.
2813
Linus Torvalds1da177e2005-04-16 15:20:36 -07002814 waveartist= [HW,OSS]
2815 Format: <io>,<irq>,<dma>,<dma2>
Randy Dunlapa9913042005-10-23 12:57:11 -07002816
Linus Torvalds1da177e2005-04-16 15:20:36 -07002817 wd33c93= [HW,SCSI]
2818 See header of drivers/scsi/wd33c93.c.
2819
2820 wd7000= [HW,SCSI]
2821 See header of drivers/scsi/wd7000.c.
2822
2823 wdt= [WDT] Watchdog
Gabriel C8dfe9c22007-08-10 13:01:00 -07002824 See Documentation/watchdog/wdt.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002825
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002826 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2827 default x2apic cluster mode on platforms
2828 supporting x2apic.
2829
Jacob Panbb24c472009-09-02 07:37:17 -07002830 x86_mrst_timer= [X86-32,APBT]
2831 Choose timer option for x86 Moorestown MID platform.
2832 Two valid options are apbt timer only and lapic timer
2833 plus one apbt timer for broadcast timer.
2834 x86_mrst_timer=apbt_only | lapic_and_apbt
2835
Linus Torvalds1da177e2005-04-16 15:20:36 -07002836 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2837 xd_geo= See header of drivers/block/xd.c.
2838
2839 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002840 Format:
2841 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002842
Randy Dunlapa9913042005-10-23 12:57:11 -07002843______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002844
2845TODO:
2846
2847 Add documentation for ALSA options.
2848 Add more DRM drivers.