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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.
Linus Torvalds1da177e2005-04-16 15:20:36 -070057 ISAPNP ISA PnP code is enabled.
58 ISDN Appropriate ISDN support is enabled.
59 JOY Appropriate joystick support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020060 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070061 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070062 LP Printer support is enabled.
63 LOOP Loopback device support is enabled.
64 M68k M68k architecture is enabled.
65 These options have more detailed description inside of
66 Documentation/m68k/kernel-options.txt.
67 MCA MCA bus support is enabled.
68 MDA MDA console support is enabled.
69 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070070 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070071 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070072 NET Appropriate network support is enabled.
73 NUMA NUMA support is enabled.
john stultz734efb42006-06-26 00:25:05 -070074 GENERIC_TIME The generic timeofday code is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070075 NFS Appropriate NFS support is enabled.
76 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070077 PV_OPS A paravirtualized kernel is enabled.
78 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070079 PARISC The PA-RISC architecture is enabled.
80 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070081 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070082 PCMCIA The PCMCIA subsystem is enabled.
83 PNP Plug & Play support is enabled.
84 PPC PowerPC architecture is enabled.
85 PPT Parallel port support is enabled.
86 PS2 Appropriate PS/2 support is enabled.
87 RAM RAM disk support is enabled.
88 S390 S390 architecture is enabled.
89 SCSI Appropriate SCSI support is enabled.
90 A lot of drivers has their options described inside of
91 Documentation/scsi/.
James Morris20510f22007-10-16 23:31:32 -070092 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070093 SELINUX SELinux support is enabled.
94 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +090095 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 SMP The kernel is an SMP kernel.
97 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -070098 SWSUSP Software suspend (hibernation) is enabled.
99 SUSPEND System suspend states are enabled.
Steven Rostedtf38f1d22008-12-16 23:06:40 -0500100 FTRACE Function tracing enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500102 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 USB USB support is enabled.
104 USBHID USB Human Interface Device support is enabled.
105 V4L Video For Linux support is enabled.
106 VGA The VGA console has been enabled.
107 VT Virtual terminal support is enabled.
108 WDT Watchdog support is enabled.
109 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700110 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 X86-64 X86-64 architecture is enabled.
112 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700113 Documentation/x86/x86_64/boot-options.txt .
Andi Kleenc0115602008-08-22 09:53:39 +0200114 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115
116In addition, the following text indicates that the option:
117
118 BUGS= Relates to possible processor bugs on the said processor.
119 KNL Is a kernel start-up parameter.
120 BOOT Is a boot loader parameter.
121
122Parameters denoted with BOOT are actually interpreted by the boot
123loader, and have no meaning to the kernel directly.
124Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500125need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126
Karsten Weiss55588702007-02-13 13:26:21 +0100127There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700128See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100129
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
131a trailing = on the name of any parameter states that that parameter will
132be entered as an environment variable, whereas its absence indicates that
133it will appear as a kernel argument readable via /proc/cmdline by programs
134running once the system is up.
135
jens m. noedler9c4751f2006-09-29 02:00:27 -0700136The number of kernel parameters is not limited, but the length of the
137complete command line (parameters including spaces etc.) is limited to
138a fixed number of characters. This limit depends on the architecture
139and is between 256 and 4096 characters. It is defined in the file
140./include/asm/setup.h as COMMAND_LINE_SIZE.
141
142
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530143 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800144 Advanced Configuration and Power Interface
Randy Dunlapaf23f572009-02-22 17:05:22 -0800145 Format: { force | off | ht | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146 force -- enable ACPI if default was off
147 off -- disable ACPI if default was on
148 noirq -- do not use ACPI for IRQ routing
149 ht -- run only enough ACPI to enable Hyper Threading
Randy Dunlapa9913042005-10-23 12:57:11 -0700150 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800152 rsdt -- prefer RSDT over (default) XSDT
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153
Randy Dunlap53471122008-03-12 18:10:51 -0400154 See also Documentation/power/pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155
Len Browna1fdcc02007-03-11 03:26:14 -0400156 acpi_apic_instance= [ACPI, IOAPIC]
157 Format: <int>
158 2: use 2nd APIC table, if available
159 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400160 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400161
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200162 acpi_backlight= [HW,ACPI]
163 acpi_backlight=vendor
164 acpi_backlight=video
165 If set to vendor, prefer vendor specific driver
166 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
167 of the ACPI video.ko driver.
168
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700169 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
170 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700172 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
173 debug output. Bits in debug_layer correspond to a
174 _COMPONENT in an ACPI source file, e.g.,
175 #define _COMPONENT ACPI_PCI_COMPONENT
176 Bits in debug_level correspond to a level in
177 ACPI_DEBUG_PRINT statements, e.g.,
178 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600179 The debug_level mask defaults to "info". See
180 Documentation/acpi/debug.txt for more information about
181 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600183 Enable processor driver info messages:
184 acpi.debug_layer=0x20000000
185 Enable PCI/PCI interrupt routing info messages:
186 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700187 Enable AML "Debug" output, i.e., stores to the Debug
188 object while interpreting AML:
189 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700190 Enable all messages related to ACPI hardware:
191 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200192
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700193 Some values produce so much output that the system is
194 unusable. The "log_buf_len" parameter may be useful
195 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800196
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700197 acpi_display_output= [HW,ACPI]
198 acpi_display_output=vendor
199 acpi_display_output=video
200 See above.
201
Alex Chiang0406ad32010-01-20 00:06:30 -0700202 acpi_early_pdc_eval [HW,ACPI] Evaluate processor _PDC methods
203 early. Needed on some platforms to properly
204 initialize the EC.
205
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700206 acpi_irq_balance [HW,ACPI]
207 ACPI will balance active IRQs
208 default in APIC mode
209
210 acpi_irq_nobalance [HW,ACPI]
211 ACPI will not move active IRQs (default)
212 default in PIC mode
213
214 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
215 Format: <irq>,<irq>...
216
217 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
218 use by PCI
219 Format: <irq>,<irq>...
220
221 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
222
223 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
224 Format: To spoof as Windows 98: ="Microsoft Windows"
225
226 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
227 acpi_osi="string1" # add string1 -- only one string
228 acpi_osi="!string2" # remove built-in string2
229 acpi_osi= # disable all strings
230
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530231 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700232 Override the pmtimer bug detection: force the kernel
233 to assume that this machine's pmtimer latches its value
234 and always returns good values.
235
Randy Dunlap4af94f32009-04-17 18:30:28 -0700236 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
237 Format: { level | edge | high | low }
238
239 acpi_serialize [HW,ACPI] force serialization of AML methods
240
241 acpi_skip_timer_override [HW,ACPI]
242 Recognize and ignore IRQ0/pin2 Interrupt Override.
243 For broken nForce2 BIOS resulting in XT-PIC timer.
244
245 acpi_sleep= [HW,ACPI] Sleep options
246 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800247 old_ordering, s4_nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700248 See Documentation/power/video.txt for information on
249 s3_bios and s3_mode.
250 s3_beep is for debugging; it makes the PC's speaker beep
251 as soon as the kernel's real-mode entry point is called.
252 s4_nohwsig prevents ACPI hardware signature from being
253 used during resume from hibernation.
254 old_ordering causes the ACPI 1.0 ordering of the _PTS
255 control method, with respect to putting devices into
256 low power states, to be enforced (the ACPI 2.0 ordering
257 of _PTS is used by default).
258 s4_nonvs prevents the kernel from saving/restoring the
259 ACPI NVS memory during hibernation.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800260 sci_force_enable causes the kernel to set SCI_EN directly
261 on resume from S1/S3 (which is against the ACPI spec,
262 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700263
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
267
Luca Tettamanti7e905602009-03-30 00:01:27 +0200268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
283
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284 ad1848= [HW,OSS]
285 Format: <io>,<irq>,<dma>,<dma2>,<type>
286
Randy Dunlap4af94f32009-04-17 18:30:28 -0700287 add_efi_memmap [EFI; X86] Include EFI memory map in
288 kernel's map of available physical RAM.
289
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290 advansys= [HW,SCSI]
291 See header of drivers/scsi/advansys.c.
292
293 advwdt= [HW,WDT] Advantech WDT
294 Format: <iostart>,<iostop>
295
296 aedsp16= [HW,OSS] Audio Excel DSP 16
297 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
298 See also header of sound/oss/aedsp16.c.
Randy Dunlapa9913042005-10-23 12:57:11 -0700299
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700300 agp= [AGP]
301 { off | try_unsupported }
302 off: disable AGP support
303 try_unsupported: try to drive unsupported chipsets
304 (may crash computer or cause data corruption)
305
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306 aha152x= [HW,SCSI]
307 See Documentation/scsi/aha152x.txt.
308
309 aha1542= [HW,SCSI]
310 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
311
312 aic7xxx= [HW,SCSI]
313 See Documentation/scsi/aic7xxx.txt.
314
315 aic79xx= [HW,SCSI]
316 See Documentation/scsi/aic79xx.txt.
317
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200318 amd_iommu= [HW,X86-84]
319 Pass parameters to the AMD IOMMU driver in the system.
320 Possible values are:
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200321 isolate - enable device isolation (each device, as far
322 as possible, will get its own protection
Joerg Roedel3ce1f932008-11-17 15:09:20 +0100323 domain) [default]
Joerg Roedele5e1f602008-11-17 15:07:17 +0100324 share - put every device behind one IOMMU into the
325 same protection domain
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
329 is a lot of faster
330
Linus Torvalds1da177e2005-04-16 15:20:36 -0700331 amijoy.map= [HW,JOY] Amiga joystick support
332 Map of devices attached to JOY0DAT and JOY1DAT
333 Format: <a>,<b>
334 See also Documentation/kernel/input/joystick.txt
335
336 analog.map= [HW,JOY] Analog joystick and gamepad support
337 Specifies type or capabilities of an analog joystick
338 connected to one of 16 gameports
339 Format: <type1>,<type2>,..<type16>
340
Randy Dunlapa9913042005-10-23 12:57:11 -0700341 apc= [HW,SPARC]
342 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343 Format: noidle
344 Disable APC CPU standby support. SPARCstation-Fox does
345 not play well with APC CPU idle - disable it if you have
346 APC and your system crashes randomly.
347
Randy Dunlapca1eda22009-05-06 16:02:58 -0700348 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700349 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700350 Format: { quiet (default) | verbose | debug }
351 Change the amount of debugging information output
352 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700353
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400354 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
355 Limit apic dumping. The parameter defines the maximal
356 number of local apics being dumped. Also it is possible
357 to set it to "all" by meaning -- no limit here.
358 Format: { 1 (default) | 2 | ... | all }.
359 The parameter valid if only apic=debug or
360 apic=verbose is specified.
361 Example: apic=debug show_lapic=all
362
Linus Torvalds1da177e2005-04-16 15:20:36 -0700363 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700364 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
367 Format: <io>,<irq>,<nodeID>
368
369 ataflop= [HW,M68k]
370
371 atarimouse= [HW,MOUSE] Atari Mouse
372
373 atascsi= [HW,SCSI] Atari SCSI
374
375 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
376 EzKey and similar keyboards
377
378 atkbd.reset= [HW] Reset keyboard during initialization
379
Randy Dunlapa9913042005-10-23 12:57:11 -0700380 atkbd.set= [HW] Select keyboard code set
381 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382
383 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
384 keyboards
385
386 atkbd.softraw= [HW] Choose between synthetic and real raw mode
387 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700388
389 atkbd.softrepeat= [HW]
390 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391
392 autotest [IA64]
393
Linus Torvalds1da177e2005-04-16 15:20:36 -0700394 baycom_epp= [HW,AX25]
395 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700396
Linus Torvalds1da177e2005-04-16 15:20:36 -0700397 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
398 Format: <io>,<mode>
399 See header of drivers/net/hamradio/baycom_par.c.
400
Randy Dunlapa9913042005-10-23 12:57:11 -0700401 baycom_ser_fdx= [HW,AX25]
402 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403 Format: <io>,<irq>,<mode>[,<baud>]
404 See header of drivers/net/hamradio/baycom_ser_fdx.c.
405
Randy Dunlapa9913042005-10-23 12:57:11 -0700406 baycom_ser_hdx= [HW,AX25]
407 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 Format: <io>,<irq>,<mode>
409 See header of drivers/net/hamradio/baycom_ser_hdx.c.
410
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700411 boot_delay= Milliseconds to delay each printk during boot.
412 Values larger than 10 seconds (10000) are changed to
413 no delay (0).
414 Format: integer
415
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700416 bootmem_debug [KNL] Enable bootmem allocator debug messages.
417
Linus Torvalds1da177e2005-04-16 15:20:36 -0700418 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700419 bttv.radio= Most important insmod options are available as
420 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700421 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
422 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
423
424 BusLogic= [HW,SCSI]
425 See drivers/scsi/BusLogic.c, comment before function
426 BusLogic_ParseDriverOptions().
427
428 c101= [NET] Moxa C101 synchronous serial card
429
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700430 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431 Sometimes CPU hardware bugs make them report the cache
432 size incorrectly. The kernel will attempt work arounds
433 to fix known problems, but for some CPUs it is not
434 possible to determine what the correct size should be.
435 This option provides an override for these situations.
436
James Morris20510f22007-10-16 23:31:32 -0700437 capability.disable=
438 [SECURITY] Disable capabilities. This would normally
439 be used only if an alternative security model is to be
440 configured. Potentially dangerous and should only be
441 used if you are entirely sure of the consequences.
442
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100443 ccw_timeout_log [S390]
444 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445
Paul Menage8bab8dd2008-04-04 14:29:57 -0700446 cgroup_disable= [KNL] Disable a particular controller
447 Format: {name of the controller(s) to disable}
448 {Currently supported controllers - "memory"}
449
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450 checkreqprot [SELINUX] Set initial checkreqprot flag value.
451 Format: { "0" | "1" }
452 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700453 0 -- check protection applied by kernel (includes
454 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700455 1 -- check protection requested by application.
456 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700457 Value can be changed at runtime via
458 /selinux/checkreqprot.
459
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100460 cio_ignore= [S390]
461 See Documentation/s390/CommonIO for details.
462
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700463 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700464 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200465 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700466 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200467 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700468 Format: { pit | tsc | cyclone | pmtmr }
469
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700470 clocksource= [GENERIC_TIME] Override the default clocksource
471 Format: <string>
472 Override the default clocksource and use the clocksource
473 with the name specified.
474 Some clocksource names to choose from, depending on
475 the platform:
476 [all] jiffies (this is the base, fallback clocksource)
477 [ACPI] acpi_pm
478 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
479 pxa_timer,timer3,32k_counter,timer0_1
480 [AVR32] avr32
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700481 [X86-32] pit,hpet,tsc,vmi-timer;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700482 scx200_hrt on Geode; cyclone on IBM x440
483 [MIPS] MIPS
484 [PARISC] cr16
485 [S390] tod
486 [SH] SuperH
487 [SPARC64] tick
488 [X86-64] hpet,tsc
489
Andi Kleenac72e782008-01-30 13:33:21 +0100490 clearcpuid=BITNUM [X86]
491 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800492 arch/x86/include/asm/cpufeature.h for the valid bit
493 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100494 stable over kernel options, but the vendor specific
495 ones should be.
496 Also note that user programs calling CPUID directly
497 or using the feature without checking anything
498 will still see it. This just prevents it from
499 being used by the kernel or shown in /proc/cpuinfo.
500 Also note the kernel might malfunction if you disable
501 some critical bits.
502
Robert Jennings14f966e2009-04-15 05:55:32 +0000503 cmo_free_hint= [PPC] Format: { yes | no }
504 Specify whether pages are marked as being inactive
505 when they are freed. This is used in CMO environments
506 to determine OS memory pressure for page stealing by
507 a hypervisor.
508 Default: yes
509
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530510 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100511 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100512 Range: 0 - 8192
513 Default: 64
514
Linus Torvalds1da177e2005-04-16 15:20:36 -0700515 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700516 Format:
517 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518
519 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
520 Format: <io>[,<irq>]
521
Randy Dunlapa9913042005-10-23 12:57:11 -0700522 com90xx= [HW,NET]
523 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700524 Format: <io>[,<irq>[,<memstart>]]
525
526 condev= [HW,S390] console device
527 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700528
Linus Torvalds1da177e2005-04-16 15:20:36 -0700529 console= [KNL] Output console device and options.
530
531 tty<n> Use the virtual console device <n>.
532
533 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800534 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700535 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800536 the form "bbbbpnf", where "bbbb" is the baud rate,
537 "p" is parity ("n", "o", or "e"), "n" is number of
538 bits, and "f" is flow control ("r" for RTS or
539 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700540
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800541 See Documentation/serial-console.txt for more
542 information. See
543 Documentation/networking/netconsole.txt for an
544 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700546 uart[8250],io,<addr>[,options]
547 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700548 Start an early, polled-mode console on the 8250/16550
549 UART at the specified I/O port or MMIO address,
550 switching to the matching ttyS device later. The
551 options are the same as for ttyS, above.
552
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700553 If the device connected to the port is not a TTY but a braille
554 device, prepend "brl," before the device type, for instance
555 console=brl,ttyS0
556 For now, only VisioBraille is supported.
557
Daniel Mackf324edc2009-06-16 15:33:52 -0700558 consoleblank= [KNL] The console blank (screen saver) timeout in
559 seconds. Defaults to 10*60 = 10mins. A value of 0
560 disables the blank timer.
561
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800562 coredump_filter=
563 [KNL] Change the default value for
564 /proc/<pid>/coredump_filter.
565 See also Documentation/filesystems/proc.txt.
566
Linus Torvalds1da177e2005-04-16 15:20:36 -0700567 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700568 Format:
569 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700570
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700571 crashkernel=nn[KMG]@ss[KMG]
572 [KNL] Reserve a chunk of physical memory to
573 hold a kernel to switch to with kexec on panic.
574
Bernhard Wallefb391592007-10-18 23:41:02 -0700575 crashkernel=range1:size1[,range2:size2,...][@offset]
576 [KNL] Same as above, but depends on the memory
577 in the running system. The syntax of range is
578 start-[end] where start and end are both
579 a memory unit (amount[KMG]). See also
580 Documentation/kdump/kdump.txt for a example.
581
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582 cs89x0_dma= [HW,NET]
583 Format: <dma>
584
585 cs89x0_media= [HW,NET]
586 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700587
Randy Dunlapa9913042005-10-23 12:57:11 -0700588 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589 See header of drivers/s390/block/dasd_devmap.c.
590
591 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
592 (one device per port)
593 Format: <port#>,<type>
594 See also Documentation/input/joystick-parport.txt
595
596 debug [KNL] Enable kernel debugging (events log level).
597
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700598 debug_locks_verbose=
599 [KNL] verbose self-tests
600 Format=<0|1>
601 Print debugging info while doing the locking API
602 self-tests.
603 We default to 0 (no extra messages), setting it to
604 1 will print _a lot_ more information - normally
605 only useful to kernel developers.
606
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700607 debug_objects [KNL] Enable object debugging
608
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500609 no_debug_objects
610 [KNL] Disable object debugging
611
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200612 debugpat [X86] Enable PAT debugging
613
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200614 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615 Format: <area>[,<node>]
616 See also Documentation/networking/decnet.txt.
617
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700618 default_hugepagesz=
619 [same as hugepagesz=] The size of the default
620 HugeTLB page size. This is the size represented by
621 the legacy /proc/ hugepages APIs, used for SHM, and
622 default size when mounting hugetlbfs filesystems.
623 Defaults to the default architecture's huge page size
624 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700625
Linus Torvalds1da177e2005-04-16 15:20:36 -0700626 dhash_entries= [KNL]
627 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700628
Linus Torvalds1da177e2005-04-16 15:20:36 -0700629 digi= [HW,SERIAL]
630 IO parameters + enable/disable command.
631
632 digiepca= [HW,SERIAL]
633 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000634 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700635
Yinghai Lu95ffa242008-04-29 03:52:33 -0700636 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700637 The kernel tries to adjust MTRR layout from continuous
638 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700639 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700640
Yinghai Lu093af8d2008-01-30 13:33:32 +0100641 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100642 By default the kernel will trim any uncacheable
643 memory out of your available memory pool based on
644 MTRR settings. This parameter disables that behavior,
645 possibly causing your machine to run very slowly.
646
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530647 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700648 Disable PIN 1 of APIC timer
649 Can be useful to work around chipset bugs.
650
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651 dmasound= [HW,OSS] Sound subsystem buffers
652
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700653 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
654 this option disables the debugging code at boot.
655
656 dma_debug_entries=<number>
657 This option allows to tune the number of preallocated
658 entries for DMA-API debugging code. One entry is
659 required per DMA-API allocation. Use this if the
660 DMA-API debugging code disables itself because the
661 architectural default is too low.
662
Joerg Roedel1745de52009-05-22 21:49:51 +0200663 dma_debug_driver=<driver_name>
664 With this option the DMA-API debugging driver
665 filter feature can be enabled at boot time. Just
666 pass the driver to filter for as the parameter.
667 The filter can be disabled or changed to another
668 driver later using sysfs.
669
Linus Torvalds1da177e2005-04-16 15:20:36 -0700670 dscc4.setup= [NET]
671
672 dtc3181e= [HW,SCSI]
673
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700674 dynamic_printk Enables pr_debug()/dev_dbg() calls if
675 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
676 These can also be switched on/off via
677 <debugfs>/dynamic_printk/modules
678
679 earlycon= [KNL] Output early console device and options.
680 uart[8250],io,<addr>[,options]
681 uart[8250],mmio,<addr>[,options]
682 Start an early, polled-mode console on the 8250/16550
683 UART at the specified I/O port or MMIO address.
684 The options are the same as for ttyS, above.
685
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530686 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 earlyprintk=vga
688 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500689 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500690 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700691
Randy Dunlapa9913042005-10-23 12:57:11 -0700692 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693 takes over.
694
Yinghai Lu5c059172008-07-24 17:29:40 -0700695 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700696
697 Currently only ttyS0 and ttyS1 are supported.
698
699 Interaction with the standard serial driver is not
700 very good.
701
702 The VGA output is eventually overwritten by the real
703 console.
704
705 eata= [HW,SCSI]
706
Linus Torvalds1da177e2005-04-16 15:20:36 -0700707 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700708 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700709
Linus Torvalds1da177e2005-04-16 15:20:36 -0700710 eisa_irq_edge= [PARISC,HW]
711 See header of drivers/parisc/eisa.c.
712
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700713 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700715 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716
717 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800718 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700719 See Documentation/block/as-iosched.txt and
720 Documentation/block/deadline-iosched.txt for details.
721
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530722 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700723 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800724 image elf header. Generally kexec loader will
725 pass this option to capture kernel.
726 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700728 enable_mtrr_cleanup [X86]
729 The kernel tries to adjust MTRR layout from continuous
730 to discrete, to make X server driver able to add WB
731 entry later. This parameter enables that.
732
Randy Dunlapca1eda22009-05-06 16:02:58 -0700733 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700734 Enable PIN 1 of APIC timer
735 Can be useful to work around chipset bugs
736 (in particular on some ATI chipsets).
737 The kernel tries to set a reasonable default.
738
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739 enforcing [SELINUX] Set initial enforcing status.
740 Format: {"0" | "1"}
741 See security/selinux/Kconfig help text.
742 0 -- permissive (log only, no denials).
743 1 -- enforcing (deny and log).
744 Default value is 0.
745 Value can be changed at runtime via /selinux/enforce.
746
Linus Torvalds1da177e2005-04-16 15:20:36 -0700747 ether= [HW,NET] Ethernet cards parameters
748 This option is obsoleted by the "netdev=" option, which
749 has equivalent usage. See its documentation for details.
750
751 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
752 Format: <io>[,<irq>]
753
Akinobu Mitade1ba092006-12-08 02:39:42 -0800754 failslab=
755 fail_page_alloc=
756 fail_make_request=[KNL]
757 General fault injection mechanism.
758 Format: <interval>,<probability>,<space>,<times>
759 See also /Documentation/fault-injection/.
760
Linus Torvalds1da177e2005-04-16 15:20:36 -0700761 fd_mcs= [HW,SCSI]
762 See header of drivers/scsi/fd_mcs.c.
763
764 fdomain= [HW,SCSI]
765 See header of drivers/scsi/fdomain.c.
766
767 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000768 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700769
Alex Chiangf13ae302008-05-08 14:03:23 -0600770 force_pal_cache_flush
771 [IA-64] Avoid check_sal_cache_flush which may hang on
772 buggy SAL_CACHE_FLUSH implementations. Using this
773 parameter will force ia64_sal_cache_flush to call
774 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
775
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100776 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400777 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100778 as early as possible in order to facilitate early
779 boot debugging.
780
781 ftrace_dump_on_oops
Steven Rostedt2af15d62009-05-28 13:37:24 -0400782 [FTRACE] will dump the trace buffers on oops.
783
784 ftrace_filter=[function-list]
785 [FTRACE] Limit the functions traced by the function
786 tracer at boot up. function-list is a comma separated
787 list of functions. This list can be changed at run
788 time by the set_ftrace_filter file in the debugfs
789 tracing directory.
790
791 ftrace_notrace=[function-list]
792 [FTRACE] Do not trace the functions specified in
793 function-list. This list can be changed at run time
794 by the set_ftrace_notrace file in the debugfs
795 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100796
Stefan Assmann369bc182009-10-12 22:17:21 +0200797 ftrace_graph_filter=[function-list]
798 [FTRACE] Limit the top level callers functions traced
799 by the function graph tracer at boot up.
800 function-list is a comma separated list of functions
801 that can be changed at run time by the
802 set_graph_function file in the debugfs tracing directory.
803
Linus Torvalds1da177e2005-04-16 15:20:36 -0700804 gamecon.map[2|3]=
805 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
806 support via parallel port (up to 5 devices per port)
807 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
808 See also Documentation/input/joystick-parport.txt
809
810 gamma= [HW,DRM]
811
Yinghai Luaaf23042008-01-30 13:33:09 +0100812 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
813 Format: off | on
814 default: on
815
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700816 gcov_persist= [GCOV] When non-zero (default), profiling data for
817 kernel modules is saved and remains accessible via
818 debugfs, even when the module is unloaded/reloaded.
819 When zero, profiling data is discarded and associated
820 debugfs files are removed at module unload time.
821
Linus Torvalds1da177e2005-04-16 15:20:36 -0700822 gdth= [HW,SCSI]
823 See header of drivers/scsi/gdth.c.
824
825 gpt [EFI] Forces disk with valid GPT signature but
826 invalid Protective MBR to be treated as GPT.
827
Linus Torvalds1da177e2005-04-16 15:20:36 -0700828 gvp11= [HW,SCSI]
829
830 hashdist= [KNL,NUMA] Large hashes allocated during boot
831 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700832 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700833 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700834
835 hcl= [IA-64] SGI's Hardware Graph compatibility layer
836
837 hd= [EIDE] (E)IDE hard drive subsystem geometry
838 Format: <cyl>,<head>,<sect>
839
Linus Torvalds1da177e2005-04-16 15:20:36 -0700840 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
841 size of <nn>. This works even on boxes that have no
842 highmem otherwise. This also works to reduce highmem
843 size on bigger boxes.
844
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800845 highres= [KNL] Enable/disable high resolution timer mode.
846 Valid parameters: "on", "off"
847 Default: "on"
848
Linus Torvalds1da177e2005-04-16 15:20:36 -0700849 hisax= [HW,ISDN]
850 See Documentation/isdn/README.HiSax.
851
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700852 hlt [BUGS=ARM,SH]
853
854 hpet= [X86-32,HPET] option to control HPET usage
855 Format: { enable (default) | disable | force |
856 verbose }
857 disable: disable HPET and use PIT instead
858 force: allow force enabled of undocumented chips (ICH4,
859 VIA, nVidia)
860 verbose: show contents of HPET registers during setup
861
Andi Kleenb4718e62008-07-23 21:27:51 -0700862 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
863 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700864 On x86-64 and powerpc, this option can be specified
865 multiple times interleaved with hugepages= to reserve
866 huge pages of different sizes. Valid pages sizes on
867 x86-64 are 2M (when the CPU supports "pse") and 1G
868 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700869 Note that 1GB pages can only be allocated at boot time
870 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900871
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100872 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
873 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100874 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
875 If specified, z/VM IUCV HVC accepts connections
876 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100877
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700878 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700879 or register an additional I2C bus that is not
880 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700881 Format:
882 <bus_id>,<clkrate>
883
Jiri Kosina36d95732008-10-06 02:51:09 -0400884 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700885 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200886 i8042.dumbkbd [HW] Pretend that controller can only read data from
887 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700888 (Don't attempt to blink the leds)
889 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500890 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400891 i8042.noloop [HW] Disable the AUX Loopback command while probing
892 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700893 i8042.nomux [HW] Don't check presence of an active multiplexing
894 controller
895 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
896 controllers
897 i8042.panicblink=
898 [HW] Frequency with which keyboard LEDs should blink
899 when kernel panics (default is 0.5 sec)
900 i8042.reset [HW] Reset the controller during init and cleanup
901 i8042.unlock [HW] Unlock (ignore) the keylock
902
903 i810= [HW,DRM]
904
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700905 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
906 indicates that the driver is running on unsupported
907 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700908 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
909 does not match list of supported models.
910 i8k.power_status
911 [HW] Report power status in /proc/i8k
912 (disabled by default)
913 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
914 capability is set.
915
916 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
917 See Documentation/mca.txt.
918
919 icn= [HW,ISDN]
920 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
921
David Fries0af80c02009-02-25 20:28:21 +0100922 ide-core.nodma= [HW] (E)IDE subsystem
923 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200924 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
925 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100926 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700927
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700928 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
929 Claim all unknown PCI IDE storage controllers.
930
Andi Kleenf039b752007-05-02 19:27:12 +0200931 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800932 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
933 Poll forces a polling idle loop that can slightly
934 improve the performance of waking up a idle CPU, but
935 will use a lot of power and make the system run hot.
936 Not recommended.
937 idle=mwait: On systems which support MONITOR/MWAIT but
938 the kernel chose to not use it because it doesn't save
939 as much power as a normal idle loop, use the
940 MONITOR/MWAIT idle loop anyways. Performance should be
941 the same as idle=poll.
942 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800943 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800944 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700945
Ingo Molnar792908222006-12-06 20:40:51 -0800946 ignore_loglevel [KNL]
947 Ignore loglevel setting - this will print /all/
948 kernel messages to the console. Useful for debugging.
949
Linus Torvalds1da177e2005-04-16 15:20:36 -0700950 ihash_entries= [KNL]
951 Set number of hash buckets for inode cache.
952
Mimi Zohar3323eec92009-02-04 09:06:58 -0500953 ima_audit= [IMA]
954 Format: { "0" | "1" }
955 0 -- integrity auditing messages. (Default)
956 1 -- enable informational integrity auditing messages.
957
958 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700959 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -0500960 default: "sha1"
961
Eric Paris5789ba32009-05-21 15:47:06 -0400962 ima_tcb [IMA]
963 Load a policy which meets the needs of the Trusted
964 Computing Base. This means IMA will measure all
965 programs exec'd, files mmap'd for exec, and all files
966 opened for read by uid=0.
967
Linus Torvalds1da177e2005-04-16 15:20:36 -0700968 in2000= [HW,SCSI]
969 See header of drivers/scsi/in2000.c.
970
971 init= [KNL]
972 Format: <full_path>
973 Run specified binary instead of /sbin/init as init
974 process.
975
976 initcall_debug [KNL] Trace initcalls as they are executed. Useful
977 for working out where the kernel is dying during
978 startup.
979
980 initrd= [BOOT] Specify the location of the initial ramdisk
981
982 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
983 Format: <irq>
984
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700985 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800986 on
987 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700988 off
989 Disable intel iommu driver.
990 igfx_off [Default Off]
991 By default, gfx is mapped as normal device. If a gfx
992 device has a dedicated DMAR unit, the DMAR unit is
993 bypassed by not enabling DMAR with this option. In
994 this case, gfx device will use physical address for
995 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700996 forcedac [x86_64]
997 With this option iommu will not optimize to look
998 for io virtual address below 32 bit forcing dual
999 address cycle on pci bus for cards supporting greater
1000 than 32 bit addressing. The default is to look
1001 for translation below 32 bit and if not available
1002 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001003 strict [Default Off]
1004 With this option on every unmap_single operation will
1005 result in a hardware IOTLB flush operation as opposed
1006 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001007
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001008 inttest= [IA64]
1009
1010 iomem= Disable strict checking of access to MMIO memory
1011 strict regions from userspace.
1012 relaxed
1013
1014 iommu= [x86]
1015 off
1016 force
1017 noforce
1018 biomerge
1019 panic
1020 nopanic
1021 merge
1022 nomerge
1023 forcesac
1024 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001025 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001026
1027 io7= [HW] IO7 for Marvel based alpha systems
1028 See comment before marvel_specify_io7 in
1029 arch/alpha/kernel/core_marvel.c.
1030
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301031 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001032 0x80
1033 Standard port 0x80 based delay
1034 0xed
1035 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001036 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001037 Simple two microseconds delay
1038 none
1039 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001040
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001042 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043
1044 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001045 See comment before ip2_setup() in
1046 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001047
1048 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1049 See header of drivers/scsi/ips.c.
1050
Alan Cox200803d2005-06-28 20:45:18 -07001051 irqfixup [HW]
1052 When an interrupt is not handled search all handlers
1053 for it. Intended to get systems with badly broken
1054 firmware running.
1055
1056 irqpoll [HW]
1057 When an interrupt is not handled search all handlers
1058 for it. Also check all handlers each timer
1059 interrupt. Intended to get systems with badly broken
1060 firmware running.
1061
Linus Torvalds1da177e2005-04-16 15:20:36 -07001062 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001063 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001064
1065 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001066 Format:
1067 <cpu number>,...,<cpu number>
1068 or
Li Zefanb225d442008-11-06 12:53:39 -08001069 <cpu number>-<cpu number>
1070 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001071 or a mixture
1072 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001073
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074 This option can be used to specify one or more CPUs
1075 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001076 algorithms. You can move a process onto or off an
1077 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078 <cpu number> begins at 0 and the maximum value is
1079 "number of CPUs in system - 1".
1080
1081 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001082 alternative -- manually setting the CPU mask of all
1083 tasks in the system -- can cause problems and
1084 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001085
Randy Dunlapa9913042005-10-23 12:57:11 -07001086 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001087
1088 js= [HW,JOY] Analog joystick
1089 See Documentation/input/joystick.txt.
1090
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001091 keepinitrd [HW,ARM]
1092
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301093 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001094 specifies the amount of memory usable by the kernel
1095 for non-movable allocations. The requested amount is
1096 spread evenly throughout all nodes in the system. The
1097 remaining memory in each node is used for Movable
1098 pages. In the event, a node is too small to have both
1099 kernelcore and Movable pages, kernelcore pages will
1100 take priority and other nodes will have a larger number
1101 of kernelcore pages. The Movable zone is used for the
1102 allocation of pages that may be reclaimed or moved
1103 by the page migration subsystem. This means that
1104 HugeTLB pages may not be allocated from this zone.
1105 Note that allocations like PTEs-from-HighMem still
1106 use the HighMem zone if it exists, and the Normal
1107 zone if it does not.
1108
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001109 kgdboc= [HW] kgdb over consoles.
1110 Requires a tty driver that supports console polling.
Matt LaPlante19f59462009-04-27 15:06:31 +02001111 (only serial supported for now)
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001112 Format: <serial_device>[,baud]
1113
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001114 kmac= [MIPS] korina ethernet MAC address.
1115 Configure the RouterBoard 532 series on-chip
1116 Ethernet adapter MAC address.
1117
Catalin Marinas04f70332009-06-11 13:22:39 +01001118 kmemleak= [KNL] Boot-time kmemleak enable/disable
1119 Valid arguments: on, off
1120 Default: on
1121
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301122 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001123 in oops dumps.
1124
Andre Przywarafef07aa2009-07-10 14:20:35 +02001125 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1126 Default is 0 (don't ignore, but inject #GP)
1127
1128 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1129 Default is 1 (enabled)
1130
1131 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1132 Default is 0 (off)
1133
1134 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1135 for all guests.
1136 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1137
1138 kvm-intel.bypass_guest_pf=
1139 [KVM,Intel] Disables bypassing of guest page faults
1140 on Intel chips. Default is 1 (enabled)
1141
1142 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1143 (virtualized MMU) support on capable Intel chips.
1144 Default is 1 (enabled)
1145
1146 kvm-intel.emulate_invalid_guest_state=
1147 [KVM,Intel] Enable emulation of invalid guest states
1148 Default is 0 (disabled)
1149
1150 kvm-intel.flexpriority=
1151 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1152 Default is 1 (enabled)
1153
1154 kvm-intel.unrestricted_guest=
1155 [KVM,Intel] Disable unrestricted guest feature
1156 (virtualized real and unpaged mode) on capable
1157 Intel chips. Default is 1 (enabled)
1158
1159 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1160 feature (tagged TLBs) on capable Intel chips.
1161 Default is 1 (enabled)
1162
Linus Torvalds1da177e2005-04-16 15:20:36 -07001163 l2cr= [PPC]
1164
Robert Brosea78bfbf2008-03-29 07:20:23 +11001165 l3cr= [PPC]
1166
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001167 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001168 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001169
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301170 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001171 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001172
FD Camifcb71f62008-01-06 19:08:56 +01001173 libata.dma= [LIBATA] DMA control
1174 libata.dma=0 Disable all PATA and SATA DMA
1175 libata.dma=1 PATA and SATA Disk DMA only
1176 libata.dma=2 ATAPI (CDROM) DMA only
1177 libata.dma=4 Compact Flash DMA only
1178 Combinations also work, so libata.dma=3 enables DMA
1179 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001180
1181 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1182 libata.ignore_hpa=0 keep BIOS limits (default)
1183 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001184
Dave Jones78e70c22007-09-27 11:50:13 -04001185 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1186 when set.
1187 Format: <int>
1188
Tejun Heo33267322008-02-13 09:15:09 +09001189 libata.force= [LIBATA] Force configurations. The format is comma
1190 separated list of "[ID:]VAL" where ID is
1191 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1192 matching port, link or device. Basically, it matches
1193 the ATA ID string printed on console by libata. If
1194 the whole ID part is omitted, the last PORT and DEVICE
1195 values are used. If ID hasn't been specified yet, the
1196 configuration applies to all ports, links and devices.
1197
1198 If only DEVICE is omitted, the parameter applies to
1199 the port and all links and devices behind it. DEVICE
1200 number of 0 either selects the first device or the
1201 first fan-out link behind PMP device. It does not
1202 select the host link. DEVICE number of 15 selects the
1203 host link and device attached to it.
1204
1205 The VAL specifies the configuration to force. As long
1206 as there's no ambiguity shortcut notation is allowed.
1207 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1208 The following configurations can be forced.
1209
1210 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1211 Any ID with matching PORT is used.
1212
1213 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1214
1215 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1216 udma[/][16,25,33,44,66,100,133] notation is also
1217 allowed.
1218
1219 * [no]ncq: Turn on or off NCQ.
1220
Tejun Heo05944bd2008-08-13 20:19:09 +09001221 * nohrst, nosrst, norst: suppress hard, soft
1222 and both resets.
1223
Tejun Heo33267322008-02-13 09:15:09 +09001224 If there are multiple matching configurations changing
1225 the same attribute, the last one is used.
1226
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001227 lmb=debug [KNL] Enable lmb debug messages.
1228
Linus Torvalds1da177e2005-04-16 15:20:36 -07001229 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001230 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001231
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001232 lockd.nlm_grace_period=P [NFS] Assign grace period.
1233 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001234
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001235 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1236 Format: <integer>
1237
1238 lockd.nlm_timeout=T [NFS] Assign timeout value.
1239 Format: <integer>
1240
1241 lockd.nlm_udpport=M [NFS] Assign UDP port.
1242 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001243
1244 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1245 Format: <irq>
1246
1247 loglevel= All Kernel Messages with a loglevel smaller than the
1248 console loglevel will be printed to the console. It can
1249 also be changed with klogd or other programs. The
1250 loglevels are defined as follows:
1251
1252 0 (KERN_EMERG) system is unusable
1253 1 (KERN_ALERT) action must be taken immediately
1254 2 (KERN_CRIT) critical conditions
1255 3 (KERN_ERR) error conditions
1256 4 (KERN_WARNING) warning conditions
1257 5 (KERN_NOTICE) normal but significant condition
1258 6 (KERN_INFO) informational
1259 7 (KERN_DEBUG) debug-level messages
1260
1261 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001262 Format: { n | nk | nM }
1263 n must be a power of two. The default size
1264 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265
Randy Dunlapaccaa242007-10-16 01:29:37 -07001266 logo.nologo [FB] Disables display of the built-in Linux logo.
1267 This may be used to provide more screen space for
1268 kernel log messages and is useful when debugging
1269 kernel boot problems.
1270
Linus Torvalds1da177e2005-04-16 15:20:36 -07001271 lp=0 [LP] Specify parallel ports to use, e.g,
1272 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1273 lp=reset first parallel port). 'lp=0' disables the
1274 lp=auto printer driver. 'lp=reset' (which can be
1275 specified in addition to the ports) causes
1276 attached printers to be reset. Using
1277 lp=port1,port2,... specifies the parallel ports
1278 to associate lp devices with, starting with
1279 lp0. A port specification may be 'none' to skip
1280 that lp device, or a parport name such as
1281 'parport0'. Specifying 'lp=auto' instead of a
1282 port specification list means that device IDs
1283 from each port should be examined, to see if
1284 an IEEE 1284-compliant printer is attached; if
1285 so, the driver will manage that printer.
1286 See also header of drivers/char/lp.c.
1287
1288 lpj=n [KNL]
1289 Sets loops_per_jiffy to given constant, thus avoiding
1290 time-consuming boot-time autodetection (up to 250 ms per
1291 CPU). 0 enables autodetection (default). To determine
1292 the correct value for your kernel, boot with normal
1293 autodetection and see what value is printed. Note that
1294 on SMP systems the preset will be applied to all CPUs,
1295 which is likely to cause problems if your CPUs need
1296 significantly divergent settings. An incorrect value
1297 will cause delays in the kernel to be wrong, leading to
1298 unpredictable I/O errors and other breakage. Although
1299 unlikely, in the extreme case this might damage your
1300 hardware.
1301
1302 ltpc= [NET]
1303 Format: <io>,<irq>,<dma>
1304
Randy Dunlapa9913042005-10-23 12:57:11 -07001305 mac5380= [HW,SCSI] Format:
1306 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001307
Randy Dunlapa9913042005-10-23 12:57:11 -07001308 machvec= [IA64] Force the use of a particular machine-vector
1309 (machvec) in a generic kernel.
1310 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001311
Wu Zhangjin3209e702009-07-02 23:27:12 +08001312 machtype= [Loongson] Share the same kernel image file between different
1313 yeeloong laptop.
1314 Example: machtype=lemote-yeeloong-2f-7inch
1315
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001316 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1317 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001318
1319 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001320 should make use of. maxcpus=n : n >= 0 limits the
1321 kernel to using 'n' processors. n=0 is a special case,
1322 it is equivalent to "nosmp", which also disables
1323 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001325 max_loop= [LOOP] Maximum number of loopback devices that can
1326 be mounted
1327 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001328
Randy Dunlapa9913042005-10-23 12:57:11 -07001329 max_luns= [SCSI] Maximum number of LUNs to probe.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330 Should be between 1 and 2^32-1.
1331
1332 max_report_luns=
Randy Dunlapa9913042005-10-23 12:57:11 -07001333 [SCSI] Maximum number of LUNs received.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001334 Should be between 1 and 16384.
1335
Linus Torvalds1da177e2005-04-16 15:20:36 -07001336 mcatest= [IA-64]
1337
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001338 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001339
Uwe Hermann71cced62008-10-20 09:32:21 -07001340 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001341
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342 md= [HW] RAID subsystems devices and level
1343 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001344
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345 mdacon= [MDA]
1346 Format: <first>,<last>
1347 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001348
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1350 Amount of memory to be used when the kernel is not able
1351 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001352 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353 address space collisions. Without memmap= PCI devices
1354 could be placed at addresses belonging to unused RAM.
1355
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001356 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001357 memory.
1358
Paul Mundt6902aa82008-09-21 17:14:42 +09001359 memchunk=nn[KMG]
1360 [KNL,SH] Allow user to override the default size for
1361 per-device physically contiguous DMA buffers.
1362
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301363 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001364 E820 memory map, as specified by the user.
1365 Such memmap=exactmap lines can be constructed based on
1366 BIOS output or other requirements. See the memmap=nn@ss
1367 option description.
1368
1369 memmap=nn[KMG]@ss[KMG]
1370 [KNL] Force usage of a specific region of memory
1371 Region of memory to be used, from ss to ss+nn.
1372
1373 memmap=nn[KMG]#ss[KMG]
1374 [KNL,ACPI] Mark specific memory as ACPI data.
1375 Region of memory to be used, from ss to ss+nn.
1376
1377 memmap=nn[KMG]$ss[KMG]
1378 [KNL,ACPI] Mark specific memory as reserved.
1379 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001380 Example: Exclude memory from 0x18690000-0x1869ffff
1381 memmap=64K$0x18690000
1382 or
1383 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001384
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001385 memory_corruption_check=0/1 [X86]
1386 Some BIOSes seem to corrupt the first 64k of
1387 memory when doing things like suspend/resume.
1388 Setting this option will scan the memory
1389 looking for corruption. Enabling this will
1390 both detect corruption and prevent the kernel
1391 from using the memory being corrupted.
1392 However, its intended as a diagnostic tool; if
1393 repeatable BIOS-originated corruption always
1394 affects the same memory, you can use memmap=
1395 to prevent the kernel from using that memory.
1396
1397 memory_corruption_check_size=size [X86]
1398 By default it checks for corruption in the low
1399 64k, making this memory unavailable for normal
1400 use. Use this parameter to scan for
1401 corruption in more or less memory.
1402
1403 memory_corruption_check_period=seconds [X86]
1404 By default it checks for corruption every 60
1405 seconds. Use this parameter to check at some
1406 other rate. 0 disables periodic checking.
1407
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001408 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001409 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001410 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001411 Specifies the number of memtest passes to be
1412 performed. Each pass selects another test
1413 pattern from a given set of patterns. Memtest
1414 fills the memory with this pattern, validates
1415 memory contents and reserves bad memory
1416 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001417
Linus Torvalds1da177e2005-04-16 15:20:36 -07001418 meye.*= [HW] Set MotionEye Camera parameters
1419 See Documentation/video4linux/meye.txt.
1420
Andres Salomon8f368812007-10-12 23:04:06 +02001421 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1422 Multi-Function General Purpose Timers on AMD Geode
1423 platforms.
1424
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001425 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1426 the BIOS has incorrectly applied a workaround. TinyBIOS
1427 version 0.98 is known to be affected, 0.99 fixes the
1428 problem by letting the user disable the workaround.
1429
Linus Torvalds1da177e2005-04-16 15:20:36 -07001430 mga= [HW,DRM]
1431
Randy Dunlap1c207f92008-11-19 15:36:16 -08001432 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1433 physical address is ignored.
1434
Michel Pollet39f45d72009-05-20 11:10:31 +01001435 mini2440= [ARM,HW,KNL]
1436 Format:[0..2][b][c][t]
1437 Default: "0tb"
1438 MINI2440 configuration specification:
1439 0 - The attached screen is the 3.5" TFT
1440 1 - The attached screen is the 7" TFT
1441 2 - The VGA Shield is attached (1024x768)
1442 Leaving out the screen size parameter will not load
1443 the TFT driver, and the framebuffer will be left
1444 unconfigured.
1445 b - Enable backlight. The TFT backlight pin will be
1446 linked to the kernel VESA blanking code and a GPIO
1447 LED. This parameter is not necessary when using the
1448 VGA shield.
1449 c - Enable the s3c camera interface.
1450 t - Reserved for enabling touchscreen support. The
1451 touchscreen support is not enabled in the mainstream
1452 kernel as of 2.6.30, a preliminary port can be found
1453 in the "bleeding edge" mini2440 support kernel at
1454 http://repo.or.cz/w/linux-2.6/mini2440.git
1455
Mel Gorman6b74ab92008-07-23 21:26:49 -07001456 mminit_loglevel=
1457 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1458 parameter allows control of the logging verbosity for
1459 the additional memory initialisation checks. A value
1460 of 0 disables mminit logging and a level of 4 will
1461 log everything. Information is printed at KERN_DEBUG
1462 so loglevel=8 may also need to be specified.
1463
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464 mousedev.tap_time=
1465 [MOUSE] Maximum time between finger touching and
1466 leaving touchpad surface for touch to be considered
1467 a tap and be reported as a left button click (for
1468 touchpads working in absolute mode only).
1469 Format: <msecs>
1470 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1471 reporting absolute coordinates, such as tablets
1472 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1473 reporting absolute coordinates, such as tablets
1474
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301475 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001476 is similar to kernelcore except it specifies the
1477 amount of memory used for migratable allocations.
1478 If both kernelcore and movablecore is specified,
1479 then kernelcore will be at *least* the specified
1480 value but may be more. If movablecore on its own
1481 is specified, the administrator must be careful
1482 that the amount of memory usable for all allocations
1483 is not too small.
1484
Linus Torvalds1da177e2005-04-16 15:20:36 -07001485 mpu401= [HW,OSS]
1486 Format: <io>,<irq>
1487
1488 MTD_Partition= [MTD]
1489 Format: <name>,<region-number>,<size>,<offset>
1490
Randy Dunlapa9913042005-10-23 12:57:11 -07001491 MTD_Region= [MTD] Format:
1492 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001493
1494 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001495 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001496
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001497 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1498
1499 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1500
1501 boundary - index of last SLC block on Flex-OneNAND.
1502 The remaining blocks are configured as MLC blocks.
1503 lock - Configure if Flex-OneNAND boundary should be locked.
1504 Once locked, the boundary cannot be changed.
1505 1 indicates lock status, 0 indicates unlock status.
1506
Ben Dooks9db829f2008-07-03 11:24:29 +01001507 mtdset= [ARM]
1508 ARM/S3C2412 JIVE boot control
1509
1510 See arch/arm/mach-s3c2412/mach-jive.c
1511
Linus Torvalds1da177e2005-04-16 15:20:36 -07001512 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001513 [HW] Make the MicroTouch USB driver use raw coordinates
1514 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001516 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001517 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001518 that could hold holes aka. UC entries.
1519
1520 mtrr_gran_size=nn[KMG] [X86]
1521 Used for mtrr cleanup. It is granularity of mtrr block.
1522 Default is 1.
1523 Large value could prevent small alignment from
1524 using up MTRRs.
1525
1526 mtrr_spare_reg_nr=n [X86]
1527 Format: <integer>
1528 Range: 0,7 : spare reg number
1529 Default : 1
1530 Used for mtrr cleanup. It is spare mtrr entries number.
1531 Set to 2 or more if your graphical card needs more.
1532
Linus Torvalds1da177e2005-04-16 15:20:36 -07001533 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1534
1535 NCR_D700= [HW,SCSI]
1536 See header of drivers/scsi/NCR_D700.c.
1537
1538 ncr5380= [HW,SCSI]
1539
1540 ncr53c400= [HW,SCSI]
1541
1542 ncr53c400a= [HW,SCSI]
1543
1544 ncr53c406a= [HW,SCSI]
1545
1546 ncr53c8xx= [HW,SCSI]
1547
1548 netdev= [NET] Network devices parameters
1549 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1550 Note that mem_start is often overloaded to mean
1551 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001552 This usage is only documented in each driver source
1553 file if at all.
1554
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001555 nf_conntrack.acct=
1556 [NETFILTER] Enable connection tracking flow accounting
1557 0 to disable accounting
1558 1 to enable accounting
1559 Default value depends on CONFIG_NF_CT_ACCT that is
1560 going to be removed in 2.6.29.
1561
Linus Torvalds1da177e2005-04-16 15:20:36 -07001562 nfsaddrs= [NFS]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001563 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001564
1565 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001566 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001567
Trond Myklebusta72b4422006-01-03 09:55:41 +01001568 nfs.callback_tcpport=
1569 [NFS] set the TCP port on which the NFSv4 callback
1570 channel should listen.
1571
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001572 nfs.cache_getent=
1573 [NFS] sets the pathname to the program which is used
1574 to update the NFS client cache entries.
1575
1576 nfs.cache_getent_timeout=
1577 [NFS] sets the timeout after which an attempt to
1578 update a cache entry is deemed to have failed.
1579
Trond Myklebust58df0952006-01-03 09:55:57 +01001580 nfs.idmap_cache_timeout=
1581 [NFS] set the maximum lifetime for idmapper cache
1582 entries.
1583
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001584 nfs.enable_ino64=
1585 [NFS] enable 64-bit inode numbers.
1586 If zero, the NFS client will fake up a 32-bit inode
1587 number for the readdir() and stat() syscalls instead
1588 of returning the full 64-bit number.
1589 The default is to return 64-bit inode numbers.
1590
Paul Mundt1e1030d2009-09-01 17:38:32 +09001591 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001592 when a NMI is triggered.
1593 Format: [state][,regs][,debounce][,die]
1594
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301595 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001596 Format: [panic,][num]
1597 Valid num: 0,1,2
1598 0 - turn nmi_watchdog off
1599 1 - use the IO-APIC timer for the NMI watchdog
1600 2 - use the local APIC for the NMI watchdog using
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001601 a performance counter. Note: This will use one
1602 performance counter and the local APIC's performance
1603 vector.
1604 When panic is specified, panic when an NMI watchdog
1605 timeout occurs.
1606 This is useful when you use a panic=... timeout and
1607 need the box quickly up again.
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001608 Instead of 1 and 2 it is possible to use the following
1609 symbolic names: lapic and ioapic
1610 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
Linus Torvalds1da177e2005-04-16 15:20:36 -07001611
Anton Vorontsovbff38772009-07-08 11:10:56 -07001612 netpoll.carrier_timeout=
1613 [NET] Specifies amount of time (in seconds) that
1614 netpoll should wait for a carrier. By default netpoll
1615 waits 4 seconds.
1616
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001617 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001618 emulation library even if a 387 maths coprocessor
1619 is present.
1620
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001621 no_console_suspend
1622 [HW] Never suspend the console
1623 Disable suspending of consoles during suspend and
1624 hibernate operations. Once disabled, debugging
1625 messages can reach various consoles while the rest
1626 of the system is being put to sleep (ie, while
1627 debugging driver suspend/resume hooks). This may
1628 not work reliably with all consoles, but is known
1629 to work with serial and VGA consoles.
1630
Christoph Lameterc1aee212007-05-31 00:40:47 -07001631 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1632 caches in the slab allocator. Saves per-node memory,
1633 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001634
Randy Dunlapa9913042005-10-23 12:57:11 -07001635 noalign [KNL,ARM]
1636
Linus Torvalds1da177e2005-04-16 15:20:36 -07001637 noapic [SMP,APIC] Tells the kernel to not make use of any
1638 IOAPICs that may be present in the system.
1639
Linus Torvalds1da177e2005-04-16 15:20:36 -07001640 nobats [PPC] Do not use BATs for mapping kernel lowmem
1641 on "Classic" PPC cores.
1642
1643 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001644
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001645 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1646
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001647 nodelayacct [KNL] Disable per-task delay accounting
1648
Linus Torvalds1da177e2005-04-16 15:20:36 -07001649 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1650
Paul Mundt6902aa82008-09-21 17:14:42 +09001651 nodsp [SH] Disable hardware DSP at boot time.
1652
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301653 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001654
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655 noexec [IA-64]
1656
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301657 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001658 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001659 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001660 noexec=off: disable non-executable mappings
1661
1662 noexec32 [X86-64]
1663 This affects only 32-bit executables.
1664 noexec32=on: enable non-executable mappings (default)
1665 read doesn't imply executable mappings
1666 noexec32=off: disable non-executable mappings
1667 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001668
Paul Mundt6902aa82008-09-21 17:14:42 +09001669 nofpu [SH] Disable hardware FPU at boot time.
1670
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001671 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001672 register save and restore. The kernel will only save
1673 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001674
Suresh Siddha0c752a92009-05-22 12:17:45 -07001675 noxsave [BUGS=X86] Disables x86 extended register state save
1676 and restore using xsave. The kernel will fallback to
1677 enabling legacy floating-point and sse state.
1678
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001679 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1680 wfi(ARM) instruction doesn't work correctly and not to
1681 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001682
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001683 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001684 instruction doesn't work correctly and not to
1685 use it.
1686
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001687 no_file_caps Tells the kernel not to honor file capabilities. The
1688 only way then for a file to be executed with privilege
1689 is to be setuid root or executed by root.
1690
Linus Torvalds1da177e2005-04-16 15:20:36 -07001691 nohalt [IA-64] Tells the kernel not to use the power saving
1692 function PAL_HALT_LIGHT when idle. This increases
1693 power-consumption. On the positive side, it reduces
1694 interrupt wake-up latency, which may improve performance
1695 in certain environments such as networked servers or
1696 real-time systems.
1697
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001698 nohz= [KNL] Boottime enable/disable dynamic ticks
1699 Valid arguments: on, off
1700 Default: on
1701
Paul Mundteeee7852009-04-02 12:31:16 +09001702 noiotrap [SH] Disables trapped I/O port accesses.
1703
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001704 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001705 disable unhandled interrupt sources.
1706
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301707 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001708 broken timer IRQ sources.
1709
Linus Torvalds1da177e2005-04-16 15:20:36 -07001710 noisapnp [ISAPNP] Disables ISA PnP code.
1711
1712 noinitrd [RAM] Tells the kernel not to load any configured
1713 initial RAM disk.
1714
Weidong Han03ea8152009-04-17 16:42:15 +08001715 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1716 remapping.
1717
Linus Torvalds1da177e2005-04-16 15:20:36 -07001718 nointroute [IA-64]
1719
Tony Luck0aa366f2007-07-20 11:22:30 -07001720 nojitter [IA64] Disables jitter checking for ITC timers.
1721
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001722 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001723
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001724 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001725
Linus Torvalds1da177e2005-04-16 15:20:36 -07001726 noltlbs [PPC] Do not use large page/tlb entries for kernel
1727 lowmem mapping on PPC40x.
1728
Horms312f1f02006-02-22 09:57:55 +09001729 nomca [IA-64] Disable machine check abort handling
1730
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001731 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001732
Andres Salomon83d73842007-10-12 23:04:06 +02001733 nomfgpt [X86-32] Disable Multi-Function General Purpose
1734 Timer usage (for AMD Geode machines).
1735
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001736 norandmaps Don't use address space randomization. Equivalent to
1737 echo 0 > /proc/sys/kernel/randomize_va_space
1738
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001739 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001740
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001741 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001742 with UP alternatives
1743
Linus Torvalds1da177e2005-04-16 15:20:36 -07001744 noresidual [PPC] Don't use residual data on PReP machines.
1745
Randy Dunlapa9913042005-10-23 12:57:11 -07001746 noresume [SWSUSP] Disables resume and restores original swap
1747 space.
1748
Linus Torvalds1da177e2005-04-16 15:20:36 -07001749 no-scroll [VGA] Disables scrollback.
1750 This is required for the Braillex ib80-piezo Braille
1751 reader made by F.H. Papenmeier (Germany).
1752
1753 nosbagart [IA-64]
1754
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001755 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001756
Len Brown61ec7562007-08-16 03:34:22 -04001757 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1758 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001759
Dave Jones97842212007-07-15 23:41:05 -07001760 nosoftlockup [KNL] Disable the soft-lockup detector.
1761
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001762 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001763 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001764
Linus Torvalds1da177e2005-04-16 15:20:36 -07001765 nosync [HW,M68K] Disables sync negotiation for all devices.
1766
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001767 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001768
1769 nousb [USB] Disable the USB subsystem
1770
1771 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001772
Weidong Han2b2fd872009-04-17 16:42:12 +08001773 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1774
Fenghua Yua6c75b862008-03-14 13:57:08 -07001775 nptcg= [IA64] Override max number of concurrent global TLB
1776 purges which is reported from either PAL_VM_SUMMARY or
1777 SAL PALO.
1778
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001779 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1780
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001781 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1782 one of ['zone', 'node', 'default'] can be specified
1783 This can be set from sysctl after boot.
1784 See Documentation/sysctl/vm.txt for details.
1785
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001786 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1787 See Documentation/debugging-via-ohci1394.txt for more
1788 info.
1789
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001790 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1791 Rather than timing out after 20 ms if an EC
1792 command is not properly ACKed, override the length
1793 of the timeout. We have interrupts disabled while
1794 waiting for the ACK, so if this is set too high
1795 interrupts *may* be lost!
1796
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001797 omap_mux= [OMAP] Override bootloader pin multiplexing.
1798 Format: <mux_mode0.mode_name=value>...
1799 For example, to override I2C bus2:
1800 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1801
Linus Torvalds1da177e2005-04-16 15:20:36 -07001802 opl3= [HW,OSS]
1803 Format: <io>
1804
Linus Torvalds1da177e2005-04-16 15:20:36 -07001805 oprofile.timer= [HW]
1806 Use timer interrupt instead of performance counters
1807
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001808 oprofile.cpu_type= Force an oprofile cpu type
1809 This might be useful if you have an older oprofile
1810 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001811 Format: { arch_perfmon }
1812 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001813 perfmon on Intel CPUs instead of the
1814 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001815
Linus Torvalds1da177e2005-04-16 15:20:36 -07001816 osst= [HW,SCSI] SCSI Tape Driver
1817 Format: <buffer_size>,<write_threshold>
1818 See also Documentation/scsi/st.txt.
1819
1820 panic= [KNL] Kernel behaviour on panic
1821 Format: <timeout>
1822
1823 parkbd.port= [HW] Parallel port number the keyboard adapter is
1824 connected to, default is 0.
1825 Format: <parport#>
1826 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1827 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001828 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001829
Randy Dunlapa9913042005-10-23 12:57:11 -07001830 parport= [HW,PPT] Specify parallel ports. 0 disables.
1831 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1832 Use 'auto' to force the driver to use any
1833 IRQ/DMA settings detected (the default is to
1834 ignore detected IRQ/DMA settings because of
1835 possible conflicts). You can specify the base
1836 address, IRQ, and DMA settings; IRQ and DMA
1837 should be numbers, or 'auto' (for using detected
1838 settings on that particular port), or 'nofifo'
1839 (to avoid using a FIFO even if it is detected).
1840 Parallel ports are assigned in the order they
1841 are specified on the command line, starting
1842 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001843
Randy Dunlapa9913042005-10-23 12:57:11 -07001844 parport_init_mode= [HW,PPT]
1845 Configure VIA parallel port to operate in
1846 a specific mode. This is necessary on Pegasos
1847 computer where firmware has no options for setting
1848 up parallel port mode and sets it to spp.
1849 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001850 Format: [spp|ps2|epp|ecp|ecpepp]
1851
Randy Dunlapa9913042005-10-23 12:57:11 -07001852 pas2= [HW,OSS] Format:
1853 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1854
Linus Torvalds1da177e2005-04-16 15:20:36 -07001855 pas16= [HW,SCSI]
1856 See header of drivers/scsi/pas16.c.
1857
Andrew Mortondd287792006-03-23 03:00:57 -08001858 pause_on_oops=
1859 Halt all CPUs after the first oops has been printed for
1860 the specified number of seconds. This is to be used if
1861 your oopses keep scrolling off the screen.
1862
Linus Torvalds1da177e2005-04-16 15:20:36 -07001863 pcbit= [HW,ISDN]
1864
1865 pcd. [PARIDE]
1866 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001867 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868
Randy Dunlapa9913042005-10-23 12:57:11 -07001869 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001870 earlydump [X86] dump PCI config space before the kernel
1871 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001872 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001873 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001874 the hardware directly. Use this if your machine
1875 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001876 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001877 hardware access methods are allowed. Use this
1878 if you experience crashes upon bootup and you
1879 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001880 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001881 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001882 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001883 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001884 noaer [PCIE] If the PCIEAER kernel config parameter is
1885 enabled, this kernel boot option can be used to
1886 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001887 nodomains [PCI] Disable support for multiple PCI
1888 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301889 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001890 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001891 check_enable_amd_mmconf [X86] check for and enable
1892 properly configured MMIO access to PCI
1893 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001894 nomsi [MSI] If the PCI_MSI kernel config parameter is
1895 enabled, this kernel boot option can be used to
1896 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001897 noioapicquirk [APIC] Disable all boot interrupt quirks.
1898 Safety option to keep boot IRQs enabled. This
1899 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001900 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1901 primary IO-APIC for bridges that cannot disable
1902 boot IRQs. This fixes a source of spurious IRQs
1903 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001904 noioapicreroute [APIC] Disable workaround that uses the
1905 boot IRQ equivalent of an IRQ that connects to
1906 a chipset where boot IRQs cannot be disabled.
1907 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001908 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001909 routing table. These calls are known to be buggy
1910 on several machines and they hang the machine
1911 when used, but on other computers it's the only
1912 way to get the interrupt routing table. Try
1913 this option if the kernel is unable to allocate
1914 IRQs or discover secondary PCI buses on your
1915 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001916 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001917 Use with caution as certain devices share
1918 address decoders between ROMs and other
1919 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001920 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001921 expansion ROMs that do not already have
1922 BIOS assigned address ranges.
Andi Kleenc0115602008-08-22 09:53:39 +02001923 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001924 assigned automatically to PCI devices. You can
1925 make the kernel exclude IRQs of your ISA cards
1926 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001927 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001928 of the PIRQ table (normally generated
1929 by the BIOS) if it is outside the
1930 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001931 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001932 useful if the kernel is unable to find your
1933 secondary buses and you want to tell it
1934 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001935 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001936 numbers ourselves, overriding
1937 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001938 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001939 in the BIOS $PIR table. This is needed on
1940 some systems with broken BIOSes, notably
1941 some HP Pavilion N5400 and Omnibook XE3
1942 notebooks. This will have no effect if ACPI
1943 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001944 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001945 or for PCI scanning.
Linus Torvalds236e9462009-06-24 16:23:03 -07001946 use_crs [X86] Use _CRS for PCI resource
Gary Hade62f420f2007-10-03 15:56:51 -07001947 allocation.
Randy Dunlapa9913042005-10-23 12:57:11 -07001948 routeirq Do IRQ routing for all PCI devices.
1949 This is normally done in pci_enable_device(),
1950 so this option is a temporary workaround
1951 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001952 skip_isa_align [X86] do not align io start addr, so can
1953 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001954 firmware [ARM] Do not re-enumerate the bus but instead
1955 just use the configuration from the
1956 bootloader. This is currently used on
1957 IXP2000 systems where the bus has to be
1958 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001959 noearly [X86] Don't do any early type 1 scanning.
1960 This might help on some broken boards which
1961 machine check when some devices' config space
1962 is read. But various workarounds are disabled
1963 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001964 bfsort Sort PCI devices into breadth-first order.
1965 This sorting is done to get a device
1966 order compatible with older (<= 2.4) kernels.
1967 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001968 cbiosize=nn[KMG] The fixed amount of bus space which is
1969 reserved for the CardBus bridge's IO window.
1970 The default value is 256 bytes.
1971 cbmemsize=nn[KMG] The fixed amount of bus space which is
1972 reserved for the CardBus bridge's memory
1973 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09001974 resource_alignment=
1975 Format:
1976 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1977 Specifies alignment and device to reassign
1978 aligned memory resources.
1979 If <order of align> is not specified,
1980 PAGE_SIZE is used as alignment.
1981 PCI-PCI bridge can be specified, if resource
1982 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06001983 ecrc= Enable/disable PCIe ECRC (transaction layer
1984 end-to-end CRC checking).
1985 bios: Use BIOS/firmware settings. This is the
1986 the default.
1987 off: Turn ECRC off
1988 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001989
Chuck Ebberte5665a42008-09-24 20:40:34 -04001990 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1991 Management.
1992 off Disable ASPM.
1993 force Enable ASPM even on devices that claim not to support it.
1994 WARNING: Forcing ASPM on may cause system lockups.
1995
Linus Torvalds1da177e2005-04-16 15:20:36 -07001996 pcmv= [HW,PCMCIA] BadgePAD 4
1997
1998 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001999 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000
2001 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2002 boot time.
2003 Format: { 0 | 1 }
2004 See arch/parisc/kernel/pdc_chassis.c
2005
Tejun Heof58dc012009-08-14 15:00:50 +09002006 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002007 Currently supported values are "embed" and "page".
2008 Archs may support subset or none of the selections.
2009 See comments in mm/percpu.c for details on each
2010 allocator. This parameter is primarily for debugging
2011 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002012
Linus Torvalds1da177e2005-04-16 15:20:36 -07002013 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002014 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002015
2016 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002017 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002018
2019 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002020 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002021
2022 plip= [PPT,NET] Parallel port network link
2023 Format: { parport<nr> | timid | 0 }
2024 See also Documentation/parport.txt.
2025
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002026 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2027 Override pmtimer IOPort with a hex value.
2028 e.g. pmtmr=0x508
2029
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002030 pnp.debug [PNP]
2031 Enable PNP debug messages. This depends on the
2032 CONFIG_PNP_DEBUG_MESSAGES option.
2033
Linus Torvalds1da177e2005-04-16 15:20:36 -07002034 pnpacpi= [ACPI]
2035 { off }
2036
2037 pnpbios= [ISAPNP]
2038 { on | off | curr | res | no-curr | no-res }
2039
2040 pnp_reserve_irq=
2041 [ISAPNP] Exclude IRQs for the autoconfiguration
2042
2043 pnp_reserve_dma=
2044 [ISAPNP] Exclude DMAs for the autoconfiguration
2045
2046 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002047 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002048
2049 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002050 [ISAPNP] Exclude memory regions for the
2051 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002052 Ranges are in pairs (memory base and size).
2053
Randy Dunlap4af94f32009-04-17 18:30:28 -07002054 ports= [IP_VS_FTP] IPVS ftp helper module
2055 Default is 21.
2056 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2057 may be specified.
2058 Format: <port>,<port>....
2059
Ingo Molnar45807a12007-07-15 23:40:10 -07002060 print-fatal-signals=
2061 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002062
2063 If enabled, warn about various signal handling
2064 related application anomalies: too many signals,
2065 too many POSIX.1 timers, fatal signals causing a
2066 coredump - etc.
2067
2068 If you hit the warning due to signal overflow,
2069 you might want to try "ulimit -i unlimited".
2070
Ingo Molnar45807a12007-07-15 23:40:10 -07002071 default: off.
2072
Randy Dunlape84845c2007-07-15 23:40:25 -07002073 printk.time= Show timing data prefixed to each printk message line
2074 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2075
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002076 processor.max_cstate= [HW,ACPI]
2077 Limit processor to maximum C-state
2078 max_cstate=9 overrides any DMI blacklist limit.
2079
2080 processor.nocst [HW,ACPI]
2081 Ignore the _CST method to determine C-states,
2082 instead using the legacy FADT method
2083
Linus Torvalds1da177e2005-04-16 15:20:36 -07002084 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002085 Format: [schedule,]<number>
2086 Param: "schedule" - profile schedule points.
2087 Param: <number> - step/bucket size as a power of 2 for
2088 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002089 Param: "sleep" - profile D-state sleeping (millisecs).
2090 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002091 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002092
Linus Torvalds1da177e2005-04-16 15:20:36 -07002093 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2094 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002095 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002096
Randy Dunlapa9913042005-10-23 12:57:11 -07002097 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2098 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002099 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2100 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002101 psmouse.resetafter= [HW,MOUSE]
2102 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002103 (0 = never).
2104 psmouse.resolution=
2105 [HW,MOUSE] Set desired mouse resolution, in dpi.
2106 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002107 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002108 0 = disabled, 1 = enabled (default).
2109
2110 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
Randy Dunlapa9913042005-10-23 12:57:11 -07002111 Format:
2112 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002113
2114 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002115 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002116
Kay Sieversdc8c8582007-08-15 12:25:38 +02002117 pty.legacy_count=
2118 [KNL] Number of legacy pty's. Overwrites compiled-in
2119 default number.
2120
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002121 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002122
Linus Torvalds1da177e2005-04-16 15:20:36 -07002123 r128= [HW,DRM]
2124
2125 raid= [HW,RAID]
2126 See Documentation/md.txt.
2127
Randy Dunlapa9913042005-10-23 12:57:11 -07002128 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002129 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002130
Linus Torvalds1da177e2005-04-16 15:20:36 -07002131 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002132 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002133
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002134 rcupdate.blimit= [KNL,BOOT]
2135 Set maximum number of finished RCU callbacks to process
2136 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002137
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002138 rcupdate.qhimark= [KNL,BOOT]
2139 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002140 RCU callbacks over which batch limiting is disabled.
2141
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002142 rcupdate.qlowmark= [KNL,BOOT]
2143 Set threshold of queued RCU callbacks below which
2144 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002145
Olof Johanssonffdfc402005-09-06 15:17:19 -07002146 rdinit= [KNL]
2147 Format: <full_path>
2148 Run specified binary instead of /init from the ramdisk,
2149 used for early userspace startup. See initrd.
2150
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002151 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002152 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002153 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002154
Paul Jackson46b6d942008-07-04 10:00:09 -07002155 relax_domain_level=
2156 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002157 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002158
Linus Torvalds1da177e2005-04-16 15:20:36 -07002159 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2160
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002161 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002162 Format: nn[KMG]
2163 Reserves a hole at the top of the kernel virtual
2164 address space.
2165
Vivek Goyal7e962872006-09-27 01:50:44 -07002166 reset_devices [KNL] Force drivers to reset the underlying device
2167 during initialization.
2168
Randy Dunlapa9913042005-10-23 12:57:11 -07002169 resume= [SWSUSP]
2170 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002171
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002172 resume_offset= [SWSUSP]
2173 Specify the offset from the beginning of the partition
2174 given by "resume=" at which the swap header is located,
2175 in <PAGE_SIZE> units (needed only for swap files).
2176 See Documentation/power/swsusp-and-swap-files.txt
2177
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002178 retain_initrd [RAM] Keep initrd memory after extraction
2179
Linus Torvalds1da177e2005-04-16 15:20:36 -07002180 rhash_entries= [KNL,NET]
2181 Set number of hash buckets for route cache
2182
2183 riscom8= [HW,SERIAL]
2184 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2185
2186 ro [KNL] Mount root device read-only on boot
2187
2188 root= [KNL] Root filesystem
2189
2190 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2191 mount the root filesystem
2192
2193 rootflags= [KNL] Set root filesystem mount option string
2194
2195 rootfstype= [KNL] Set root filesystem type
2196
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002197 rootwait [KNL] Wait (indefinitely) for root device to show up.
2198 Useful for devices that are detected asynchronously
2199 (e.g. USB and MMC devices).
2200
Linus Torvalds1da177e2005-04-16 15:20:36 -07002201 rw [KNL] Mount root device read-write on boot
2202
2203 S [KNL] Run init in single mode
2204
2205 sa1100ir [NET]
2206 See drivers/net/irda/sa1100_ir.c.
2207
Linus Torvalds1da177e2005-04-16 15:20:36 -07002208 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002209
Mike Travisf6630112009-11-17 18:22:15 -06002210 sched_debug [KNL] Enables verbose scheduler debug messages.
2211
Linus Torvalds1da177e2005-04-16 15:20:36 -07002212 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2213 Format: <io>[,<timeout>[,<isapnp>]]
2214
2215 scsi_debug_*= [SCSI]
2216 See drivers/scsi/scsi_debug.c.
2217
2218 scsi_default_dev_flags=
2219 [SCSI] SCSI default device flags
2220 Format: <integer>
2221
2222 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2223 Format: <vendor>:<model>:<flags>
2224 (flags are integer value)
2225
Randy Dunlap6af66322007-11-14 16:52:25 -08002226 scsi_logging_level= [SCSI] a bit mask of logging levels
2227 See drivers/scsi/scsi_logging.h for bits. Also
2228 settable via sysctl at dev.scsi.logging_level
2229 (/proc/sys/dev/scsi/logging_level).
2230 There is also a nice 'scsi_logging_level' script in the
2231 S390-tools package, available for download at
2232 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
Linus Torvalds1da177e2005-04-16 15:20:36 -07002233
Matthew Wilcox3e082a92006-09-28 15:19:20 -06002234 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2235 discovered. async scans them in kernel threads,
2236 allowing boot to proceed. none ignores them, expecting
2237 user space to do the scan.
2238
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002239 security= [SECURITY] Choose a security module to enable at boot.
2240 If this boot parameter is not specified, only the first
2241 security module asking for security registration will be
2242 loaded. An invalid security module name will be treated
2243 as if no module has been chosen.
2244
2245 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002246 Format: { "0" | "1" }
2247 See security/selinux/Kconfig help text.
2248 0 -- disable.
2249 1 -- enable.
2250 Default value is set via kernel config option.
2251 If enabled at boot time, /selinux/disable can be used
2252 later to disable prior to initial policy load.
2253
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002254 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002255
Linus Torvalds1da177e2005-04-16 15:20:36 -07002256 shapers= [NET]
2257 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002258
Yinghai Lub05f78f2008-08-22 01:32:50 -07002259 show_msr= [x86] show boot-time MSR settings
2260 Format: { <integer> }
2261 Show boot-time (BIOS-initialized) MSR settings.
2262 The parameter means the number of CPUs to show,
2263 for example 1 means boot CPU only.
2264
Linus Torvalds1da177e2005-04-16 15:20:36 -07002265 sim710= [SCSI,HW]
2266 See header of drivers/scsi/sim710.c.
2267
2268 simeth= [IA-64]
2269 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002270
Linus Torvalds1da177e2005-04-16 15:20:36 -07002271 slram= [HW,MTD]
2272
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002273 slub_debug[=options[,slabs]] [MM, SLUB]
2274 Enabling slub_debug allows one to determine the
2275 culprit if slab objects become corrupted. Enabling
2276 slub_debug can create guard zones around objects and
2277 may poison objects when not in use. Also tracks the
2278 last alloc / free. For more information see
2279 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002280
2281 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002282 Determines the maximum allowed order for slabs.
2283 A high setting may cause OOMs due to memory
2284 fragmentation. For more information see
2285 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002286
2287 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002288 The minimum number of objects per slab. SLUB will
2289 increase the slab order up to slub_max_order to
2290 generate a sufficiently large slab able to contain
2291 the number of objects indicated. The higher the number
2292 of objects the smaller the overhead of tracking slabs
2293 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002294 For more information see Documentation/vm/slub.txt.
2295
2296 slub_min_order= [MM, SLUB]
2297 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002298 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002299 For more information see Documentation/vm/slub.txt.
2300
2301 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002302 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002303 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002304 allocs to different slabs. Debug options disable
2305 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002306 For more information see Documentation/vm/slub.txt.
2307
Linus Torvalds1da177e2005-04-16 15:20:36 -07002308 smart2= [HW]
2309 Format: <io1>[,<io2>[,...,<io8>]]
2310
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002311 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002312 attempt to substitute SMP alternatives once at boot.
2313
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002314 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2315 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2316 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2317 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2318 smsc-ircc2.ircc_irq= [HW] IRQ line
2319 smsc-ircc2.ircc_dma= [HW] DMA channel
2320 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2321 0: Toshiba Satellite 1800 (GP data pin select)
2322 1: Fast pin select (default)
2323 2: ATC IRMode
2324
Linus Torvalds1da177e2005-04-16 15:20:36 -07002325 snd-ad1816a= [HW,ALSA]
2326
2327 snd-ad1848= [HW,ALSA]
2328
2329 snd-ali5451= [HW,ALSA]
2330
2331 snd-als100= [HW,ALSA]
2332
2333 snd-als4000= [HW,ALSA]
2334
2335 snd-azt2320= [HW,ALSA]
2336
2337 snd-cmi8330= [HW,ALSA]
2338
2339 snd-cmipci= [HW,ALSA]
2340
2341 snd-cs4231= [HW,ALSA]
2342
2343 snd-cs4232= [HW,ALSA]
2344
2345 snd-cs4236= [HW,ALSA]
2346
2347 snd-cs4281= [HW,ALSA]
2348
2349 snd-cs46xx= [HW,ALSA]
2350
2351 snd-dt019x= [HW,ALSA]
2352
2353 snd-dummy= [HW,ALSA]
2354
2355 snd-emu10k1= [HW,ALSA]
2356
2357 snd-ens1370= [HW,ALSA]
2358
2359 snd-ens1371= [HW,ALSA]
2360
2361 snd-es968= [HW,ALSA]
2362
2363 snd-es1688= [HW,ALSA]
2364
2365 snd-es18xx= [HW,ALSA]
2366
2367 snd-es1938= [HW,ALSA]
2368
2369 snd-es1968= [HW,ALSA]
2370
2371 snd-fm801= [HW,ALSA]
2372
2373 snd-gusclassic= [HW,ALSA]
2374
2375 snd-gusextreme= [HW,ALSA]
2376
2377 snd-gusmax= [HW,ALSA]
2378
2379 snd-hdsp= [HW,ALSA]
2380
2381 snd-ice1712= [HW,ALSA]
2382
2383 snd-intel8x0= [HW,ALSA]
2384
2385 snd-interwave= [HW,ALSA]
2386
2387 snd-interwave-stb=
2388 [HW,ALSA]
2389
2390 snd-korg1212= [HW,ALSA]
2391
2392 snd-maestro3= [HW,ALSA]
2393
2394 snd-mpu401= [HW,ALSA]
2395
2396 snd-mtpav= [HW,ALSA]
2397
2398 snd-nm256= [HW,ALSA]
2399
2400 snd-opl3sa2= [HW,ALSA]
2401
2402 snd-opti92x-ad1848=
2403 [HW,ALSA]
2404
2405 snd-opti92x-cs4231=
2406 [HW,ALSA]
2407
2408 snd-opti93x= [HW,ALSA]
2409
2410 snd-pmac= [HW,ALSA]
2411
2412 snd-rme32= [HW,ALSA]
2413
2414 snd-rme96= [HW,ALSA]
2415
2416 snd-rme9652= [HW,ALSA]
2417
2418 snd-sb8= [HW,ALSA]
2419
2420 snd-sb16= [HW,ALSA]
2421
2422 snd-sbawe= [HW,ALSA]
2423
2424 snd-serial= [HW,ALSA]
2425
2426 snd-sgalaxy= [HW,ALSA]
2427
2428 snd-sonicvibes= [HW,ALSA]
2429
2430 snd-sun-amd7930=
2431 [HW,ALSA]
2432
2433 snd-sun-cs4231= [HW,ALSA]
2434
2435 snd-trident= [HW,ALSA]
2436
2437 snd-usb-audio= [HW,ALSA,USB]
2438
2439 snd-via82xx= [HW,ALSA]
2440
2441 snd-virmidi= [HW,ALSA]
2442
2443 snd-wavefront= [HW,ALSA]
2444
2445 snd-ymfpci= [HW,ALSA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002446
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002447 softlockup_panic=
2448 [KNL] Should the soft-lockup detector generate panics.
2449
Linus Torvalds1da177e2005-04-16 15:20:36 -07002450 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2451 See Documentation/sonypi.txt
2452
2453 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002454 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002455
2456 spia_io_base= [HW,MTD]
2457 spia_fio_base=
2458 spia_pedr=
2459 spia_peddr=
2460
2461 sscape= [HW,OSS]
2462 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
Randy Dunlapa9913042005-10-23 12:57:11 -07002463
Linus Torvalds1da177e2005-04-16 15:20:36 -07002464 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2465 See Documentation/scsi/st.txt.
2466
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002467 stacktrace [FTRACE]
2468 Enabled the stack tracer on boot up.
2469
Linus Torvalds1da177e2005-04-16 15:20:36 -07002470 sti= [PARISC,HW]
2471 Format: <num>
2472 Set the STI (builtin display/keyboard on the HP-PARISC
2473 machines) console (graphic card) which should be used
2474 as the initial boot-console.
2475 See also comment in drivers/video/console/sticore.c.
2476
2477 sti_font= [HW]
2478 See comment in drivers/video/console/sticore.c.
2479
2480 stifb= [HW]
2481 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2482
Trond Myklebustcbf11072009-08-09 15:06:19 -04002483 sunrpc.min_resvport=
2484 sunrpc.max_resvport=
2485 [NFS,SUNRPC]
2486 SunRPC servers often require that client requests
2487 originate from a privileged port (i.e. a port in the
2488 range 0 < portnr < 1024).
2489 An administrator who wishes to reserve some of these
2490 ports for other uses may adjust the range that the
2491 kernel's sunrpc client considers to be privileged
2492 using these two parameters to set the minimum and
2493 maximum port values.
2494
Greg Banks42a7fc42007-03-06 01:42:23 -08002495 sunrpc.pool_mode=
2496 [NFS]
2497 Control how the NFS server code allocates CPUs to
2498 service thread pools. Depending on how many NICs
2499 you have and where their interrupts are bound, this
2500 option will affect which CPUs will do NFS serving.
2501 Note: this parameter cannot be changed while the
2502 NFS server is running.
2503
2504 auto the server chooses an appropriate mode
2505 automatically using heuristics
2506 global a single global pool contains all CPUs
2507 percpu one pool for each CPU
2508 pernode one pool for each NUMA node (equivalent
2509 to global on non-NUMA machines)
2510
Trond Myklebustcbf11072009-08-09 15:06:19 -04002511 sunrpc.tcp_slot_table_entries=
2512 sunrpc.udp_slot_table_entries=
2513 [NFS,SUNRPC]
2514 Sets the upper limit on the number of simultaneous
2515 RPC calls that can be sent from the client to a
2516 server. Increasing these values may allow you to
2517 improve throughput, but will also increase the
2518 amount of memory reserved for use by the client.
2519
Linus Torvalds1da177e2005-04-16 15:20:36 -07002520 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002521
Linus Torvalds1da177e2005-04-16 15:20:36 -07002522 switches= [HW,M68k]
2523
2524 sym53c416= [HW,SCSI]
2525 See header of drivers/scsi/sym53c416.c.
2526
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002527 sysrq_always_enabled
2528 [KNL]
2529 Ignore sysrq setting - this boot parameter will
2530 neutralize any effect of /proc/sys/kernel/sysrq.
2531 Useful for debugging.
2532
Linus Torvalds1da177e2005-04-16 15:20:36 -07002533 t128= [HW,SCSI]
2534 See header of drivers/scsi/t128.c.
2535
2536 tdfx= [HW,DRM]
2537
David Brownell77437fd2008-07-23 21:28:33 -07002538 test_suspend= [SUSPEND]
2539 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2540 standby suspend) as the system sleep state to briefly
2541 enter during system startup. The system is woken from
2542 this state using a wakeup-capable RTC alarm.
2543
Linus Torvalds1da177e2005-04-16 15:20:36 -07002544 thash_entries= [KNL,NET]
2545 Set number of hash buckets for TCP connection
2546
Len Brownf8707ec2007-08-12 00:12:54 -04002547 thermal.act= [HW,ACPI]
2548 -1: disable all active trip points in all thermal zones
2549 <degrees C>: override all lowest active trip points
2550
Len Brownc52a7412007-08-14 15:49:32 -04002551 thermal.crt= [HW,ACPI]
2552 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002553 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002554
Len Brownf5487142007-08-12 00:12:44 -04002555 thermal.nocrt= [HW,ACPI]
2556 Set to disable actions on ACPI thermal zone
2557 critical and hot trip points.
2558
Len Brown72b33ef2007-08-12 00:12:17 -04002559 thermal.off= [HW,ACPI]
2560 1: disable ACPI thermal control
2561
Len Browna70cdc52007-08-12 00:12:35 -04002562 thermal.psv= [HW,ACPI]
2563 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002564 <degrees C>: override all passive trip points to this
2565 value
Len Browna70cdc52007-08-12 00:12:35 -04002566
Len Brown730ff342007-08-12 00:12:26 -04002567 thermal.tzp= [HW,ACPI]
2568 Specify global default ACPI thermal zone polling rate
2569 <deci-seconds>: poll all this frequency
2570 0: no polling (default)
2571
Linus Torvalds1da177e2005-04-16 15:20:36 -07002572 tmscsim= [HW,SCSI]
2573 See comment before function dc390_setup() in
2574 drivers/scsi/tmscsim.c.
2575
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002576 topology= [S390]
2577 Format: {off | on}
2578 Specify if the kernel should make use of the cpu
2579 topology informations if the hardware supports these.
2580 The scheduler will make use of these informations and
2581 e.g. base its process migration decisions on it.
2582 Default is off.
2583
Linus Torvalds1da177e2005-04-16 15:20:36 -07002584 tp720= [HW,PS2]
2585
Li Zefan9d612be2009-06-24 17:33:15 +08002586 trace_buf_size=nn[KMG]
2587 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002588
Li Zefan020e5f82009-07-01 10:47:05 +08002589 trace_event=[event-list]
2590 [FTRACE] Set and start specified trace events in order
2591 to facilitate early boot debugging.
2592 See also Documentation/trace/events.txt
2593
Linus Torvalds1da177e2005-04-16 15:20:36 -07002594 trix= [HW,OSS] MediaTrix AudioTrix Pro
Randy Dunlapa9913042005-10-23 12:57:11 -07002595 Format:
2596 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2597
Alok Kataria395628e2008-10-24 17:22:01 -07002598 tsc= Disable clocksource-must-verify flag for TSC.
2599 Format: <string>
2600 [x86] reliable: mark tsc clocksource as reliable, this
2601 disables clocksource verification at runtime.
2602 Used to enable high-resolution timer mode on older
2603 hardware, and in virtualized environment.
2604
Randy Dunlapa9913042005-10-23 12:57:11 -07002605 turbografx.map[2|3]= [HW,JOY]
2606 TurboGraFX parallel port interface
2607 Format:
2608 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002609 See also Documentation/input/joystick-parport.txt
2610
2611 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2612 See header of drivers/scsi/u14-34f.c.
2613
2614 uart401= [HW,OSS]
2615 Format: <io>,<irq>
2616
2617 uart6850= [HW,OSS]
2618 Format: <io>,<irq>
2619
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002620 uhash_entries= [KNL,NET]
2621 Set number of hash buckets for UDP/UDP-Lite connections
2622
Alan Stern5f8364b2006-12-05 16:29:55 -05002623 uhci-hcd.ignore_oc=
2624 [USB] Ignore overcurrent events (default N).
2625 Some badly-designed motherboards generate lots of
2626 bogus events, for ports that aren't wired to
2627 anything. Set this parameter to avoid log spamming.
2628 Note that genuine overcurrent events won't be
2629 reported either.
2630
Simon Arlotte3a61b02008-07-19 23:32:54 +01002631 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302632 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002633 Set unknown_nmi_panic=1 early on boot.
2634
Alan Sternb5e795f2007-02-20 15:00:53 -05002635 usbcore.autosuspend=
2636 [USB] The autosuspend time delay (in seconds) used
2637 for newly-detected USB devices (default 2). This
2638 is the time required before an idle device will be
2639 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002640 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002641
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002642 usbcore.usbfs_snoop=
2643 [USB] Set to log all usbfs traffic (default 0 = off).
2644
2645 usbcore.blinkenlights=
2646 [USB] Set to cycle leds on hubs (default 0 = off).
2647
2648 usbcore.old_scheme_first=
2649 [USB] Start with the old device initialization
2650 scheme (default 0 = off).
2651
2652 usbcore.use_both_schemes=
2653 [USB] Try the other device initialization scheme
2654 if the first one fails (default 1 = enabled).
2655
2656 usbcore.initial_descriptor_timeout=
2657 [USB] Specifies timeout for the initial 64-byte
2658 USB_REQ_GET_DESCRIPTOR request in milliseconds
2659 (default 5000 = 5.0 seconds).
2660
Linus Torvalds1da177e2005-04-16 15:20:36 -07002661 usbhid.mousepoll=
2662 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002663
Alan Sternd4f373e2008-11-10 14:07:45 -05002664 usb-storage.delay_use=
2665 [UMS] The delay in seconds before a new device is
2666 scanned for Logical Units (default 5).
2667
2668 usb-storage.quirks=
2669 [UMS] A list of quirks entries to supplement or
2670 override the built-in unusual_devs list. List
2671 entries are separated by commas. Each entry has
2672 the form VID:PID:Flags where VID and PID are Vendor
2673 and Product ID values (4-digit hex numbers) and
2674 Flags is a set of characters, each corresponding
2675 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002676 a = SANE_SENSE (collect more than 18 bytes
2677 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002678 b = BAD_SENSE (don't collect more than 18
2679 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002680 c = FIX_CAPACITY (decrease the reported
2681 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002682 h = CAPACITY_HEURISTICS (decrease the
2683 reported device capacity by one
2684 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002685 i = IGNORE_DEVICE (don't bind to this
2686 device);
2687 l = NOT_LOCKABLE (don't try to lock and
2688 unlock ejectable media);
2689 m = MAX_SECTORS_64 (don't transfer more
2690 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002691 o = CAPACITY_OK (accept the capacity
2692 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002693 r = IGNORE_RESIDUE (the device reports
2694 bogus residue values);
2695 s = SINGLE_LUN (the device has only one
2696 Logical Unit);
2697 w = NO_WP_DETECT (don't test whether the
2698 medium is write-protected).
2699 Example: quirks=0419:aaf5:rl,0421:0433:rc
2700
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302701 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002702 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002703 vdso=1: enable VDSO (default)
2704 vdso=0: disable VDSO mapping
2705
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302706 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002707 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2708 vdso32=1: enable 32-bit VDSO (default)
2709 vdso32=0: disable 32-bit VDSO mapping
2710
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002711 vector= [IA-64,SMP]
2712 vector=percpu: enable percpu vector domain
2713
Linus Torvalds1da177e2005-04-16 15:20:36 -07002714 video= [FB] Frame buffer configuration
2715 See Documentation/fb/modedb.txt.
2716
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002717 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002718 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002719 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002720 Use vga=ask for menu.
2721 This is actually a boot loader parameter; the value is
2722 passed to the kernel using a special protocol.
2723
Randy Dunlapa9913042005-10-23 12:57:11 -07002724 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002725 size of <nn>. This can be used to increase the
2726 minimum size (128MB on x86). It can also be used to
2727 decrease the size and leave more room for directly
2728 mapped kernel RAM.
2729
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002730 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2731 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002732
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002733 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2734 Format: <command>
2735
2736 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2737 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002738
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002739 vt.cur_default= [VT] Default cursor shape.
2740 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2741 the parameters of the <Esc>[?A;B;Cc escape sequence;
2742 see VGA-softcursor.txt. Default: 2 = underline.
2743
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002744 vt.default_blu= [VT]
2745 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2746 Change the default blue palette of the console.
2747 This is a 16-member array composed of values
2748 ranging from 0-255.
2749
2750 vt.default_grn= [VT]
2751 Format: <green0>,<green1>,<green2>,...,<green15>
2752 Change the default green palette of the console.
2753 This is a 16-member array composed of values
2754 ranging from 0-255.
2755
2756 vt.default_red= [VT]
2757 Format: <red0>,<red1>,<red2>,...,<red15>
2758 Change the default red palette of the console.
2759 This is a 16-member array composed of values
2760 ranging from 0-255.
2761
2762 vt.default_utf8=
2763 [VT]
2764 Format=<0|1>
2765 Set system-wide default UTF-8 mode for all tty's.
2766 Default is 1, i.e. UTF-8 mode is enabled for all
2767 newly opened terminals.
2768
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002769 vt.global_cursor_default=
2770 [VT]
2771 Format=<-1|0|1>
2772 Set system-wide default for whether a cursor
2773 is shown on new VTs. Default is -1,
2774 i.e. cursors will be created by default unless
2775 overridden by individual drivers. 0 will hide
2776 cursors, 1 will display them.
2777
Linus Torvalds1da177e2005-04-16 15:20:36 -07002778 waveartist= [HW,OSS]
2779 Format: <io>,<irq>,<dma>,<dma2>
Randy Dunlapa9913042005-10-23 12:57:11 -07002780
Linus Torvalds1da177e2005-04-16 15:20:36 -07002781 wd33c93= [HW,SCSI]
2782 See header of drivers/scsi/wd33c93.c.
2783
2784 wd7000= [HW,SCSI]
2785 See header of drivers/scsi/wd7000.c.
2786
2787 wdt= [WDT] Watchdog
Gabriel C8dfe9c22007-08-10 13:01:00 -07002788 See Documentation/watchdog/wdt.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002789
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002790 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2791 default x2apic cluster mode on platforms
2792 supporting x2apic.
2793
Linus Torvalds1da177e2005-04-16 15:20:36 -07002794 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2795 xd_geo= See header of drivers/block/xd.c.
2796
2797 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002798 Format:
2799 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002800
Randy Dunlapa9913042005-10-23 12:57:11 -07002801______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002802
2803TODO:
2804
2805 Add documentation for ALSA options.
2806 Add more DRM drivers.