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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
Russell Kingd944d542010-02-20 16:13:29 +0000318 alignment= [KNL,ARM]
319 Allow the default userspace alignment fault handler
320 behaviour to be specified. Bit 0 enables warnings,
321 bit 1 enables fixups, and bit 2 sends a segfault.
322
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200323 amd_iommu= [HW,X86-84]
324 Pass parameters to the AMD IOMMU driver in the system.
325 Possible values are:
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200326 isolate - enable device isolation (each device, as far
327 as possible, will get its own protection
Joerg Roedel3ce1f932008-11-17 15:09:20 +0100328 domain) [default]
Joerg Roedele5e1f602008-11-17 15:07:17 +0100329 share - put every device behind one IOMMU into the
330 same protection domain
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900331 fullflush - enable flushing of IO/TLB entries when
332 they are unmapped. Otherwise they are
333 flushed before they will be reused, which
334 is a lot of faster
335
Linus Torvalds1da177e2005-04-16 15:20:36 -0700336 amijoy.map= [HW,JOY] Amiga joystick support
337 Map of devices attached to JOY0DAT and JOY1DAT
338 Format: <a>,<b>
339 See also Documentation/kernel/input/joystick.txt
340
341 analog.map= [HW,JOY] Analog joystick and gamepad support
342 Specifies type or capabilities of an analog joystick
343 connected to one of 16 gameports
344 Format: <type1>,<type2>,..<type16>
345
Randy Dunlapa9913042005-10-23 12:57:11 -0700346 apc= [HW,SPARC]
347 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348 Format: noidle
349 Disable APC CPU standby support. SPARCstation-Fox does
350 not play well with APC CPU idle - disable it if you have
351 APC and your system crashes randomly.
352
Randy Dunlapca1eda22009-05-06 16:02:58 -0700353 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700354 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700355 Format: { quiet (default) | verbose | debug }
356 Change the amount of debugging information output
357 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700358
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400359 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
360 Limit apic dumping. The parameter defines the maximal
361 number of local apics being dumped. Also it is possible
362 to set it to "all" by meaning -- no limit here.
363 Format: { 1 (default) | 2 | ... | all }.
364 The parameter valid if only apic=debug or
365 apic=verbose is specified.
366 Example: apic=debug show_lapic=all
367
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700369 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370
Linus Torvalds1da177e2005-04-16 15:20:36 -0700371 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
372 Format: <io>,<irq>,<nodeID>
373
374 ataflop= [HW,M68k]
375
376 atarimouse= [HW,MOUSE] Atari Mouse
377
378 atascsi= [HW,SCSI] Atari SCSI
379
380 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
381 EzKey and similar keyboards
382
383 atkbd.reset= [HW] Reset keyboard during initialization
384
Randy Dunlapa9913042005-10-23 12:57:11 -0700385 atkbd.set= [HW] Select keyboard code set
386 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387
388 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
389 keyboards
390
391 atkbd.softraw= [HW] Choose between synthetic and real raw mode
392 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700393
394 atkbd.softrepeat= [HW]
395 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700396
397 autotest [IA64]
398
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399 baycom_epp= [HW,AX25]
400 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700401
Linus Torvalds1da177e2005-04-16 15:20:36 -0700402 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
403 Format: <io>,<mode>
404 See header of drivers/net/hamradio/baycom_par.c.
405
Randy Dunlapa9913042005-10-23 12:57:11 -0700406 baycom_ser_fdx= [HW,AX25]
407 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 Format: <io>,<irq>,<mode>[,<baud>]
409 See header of drivers/net/hamradio/baycom_ser_fdx.c.
410
Randy Dunlapa9913042005-10-23 12:57:11 -0700411 baycom_ser_hdx= [HW,AX25]
412 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413 Format: <io>,<irq>,<mode>
414 See header of drivers/net/hamradio/baycom_ser_hdx.c.
415
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700416 boot_delay= Milliseconds to delay each printk during boot.
417 Values larger than 10 seconds (10000) are changed to
418 no delay (0).
419 Format: integer
420
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700421 bootmem_debug [KNL] Enable bootmem allocator debug messages.
422
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700424 bttv.radio= Most important insmod options are available as
425 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
427 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
428
429 BusLogic= [HW,SCSI]
430 See drivers/scsi/BusLogic.c, comment before function
431 BusLogic_ParseDriverOptions().
432
433 c101= [NET] Moxa C101 synchronous serial card
434
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700435 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700436 Sometimes CPU hardware bugs make them report the cache
437 size incorrectly. The kernel will attempt work arounds
438 to fix known problems, but for some CPUs it is not
439 possible to determine what the correct size should be.
440 This option provides an override for these situations.
441
James Morris20510f22007-10-16 23:31:32 -0700442 capability.disable=
443 [SECURITY] Disable capabilities. This would normally
444 be used only if an alternative security model is to be
445 configured. Potentially dangerous and should only be
446 used if you are entirely sure of the consequences.
447
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100448 ccw_timeout_log [S390]
449 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450
Paul Menage8bab8dd2008-04-04 14:29:57 -0700451 cgroup_disable= [KNL] Disable a particular controller
452 Format: {name of the controller(s) to disable}
453 {Currently supported controllers - "memory"}
454
Linus Torvalds1da177e2005-04-16 15:20:36 -0700455 checkreqprot [SELINUX] Set initial checkreqprot flag value.
456 Format: { "0" | "1" }
457 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700458 0 -- check protection applied by kernel (includes
459 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700460 1 -- check protection requested by application.
461 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700462 Value can be changed at runtime via
463 /selinux/checkreqprot.
464
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100465 cio_ignore= [S390]
466 See Documentation/s390/CommonIO for details.
467
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700468 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700469 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200470 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700471 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200472 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700473 Format: { pit | tsc | cyclone | pmtmr }
474
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700475 clocksource= [GENERIC_TIME] Override the default clocksource
476 Format: <string>
477 Override the default clocksource and use the clocksource
478 with the name specified.
479 Some clocksource names to choose from, depending on
480 the platform:
481 [all] jiffies (this is the base, fallback clocksource)
482 [ACPI] acpi_pm
483 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
484 pxa_timer,timer3,32k_counter,timer0_1
485 [AVR32] avr32
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700486 [X86-32] pit,hpet,tsc,vmi-timer;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700487 scx200_hrt on Geode; cyclone on IBM x440
488 [MIPS] MIPS
489 [PARISC] cr16
490 [S390] tod
491 [SH] SuperH
492 [SPARC64] tick
493 [X86-64] hpet,tsc
494
Andi Kleenac72e782008-01-30 13:33:21 +0100495 clearcpuid=BITNUM [X86]
496 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800497 arch/x86/include/asm/cpufeature.h for the valid bit
498 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100499 stable over kernel options, but the vendor specific
500 ones should be.
501 Also note that user programs calling CPUID directly
502 or using the feature without checking anything
503 will still see it. This just prevents it from
504 being used by the kernel or shown in /proc/cpuinfo.
505 Also note the kernel might malfunction if you disable
506 some critical bits.
507
Robert Jennings14f966e2009-04-15 05:55:32 +0000508 cmo_free_hint= [PPC] Format: { yes | no }
509 Specify whether pages are marked as being inactive
510 when they are freed. This is used in CMO environments
511 to determine OS memory pressure for page stealing by
512 a hypervisor.
513 Default: yes
514
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530515 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100516 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100517 Range: 0 - 8192
518 Default: 64
519
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700521 Format:
522 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700523
524 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
525 Format: <io>[,<irq>]
526
Randy Dunlapa9913042005-10-23 12:57:11 -0700527 com90xx= [HW,NET]
528 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700529 Format: <io>[,<irq>[,<memstart>]]
530
531 condev= [HW,S390] console device
532 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700533
Linus Torvalds1da177e2005-04-16 15:20:36 -0700534 console= [KNL] Output console device and options.
535
536 tty<n> Use the virtual console device <n>.
537
538 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800539 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700540 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800541 the form "bbbbpnf", where "bbbb" is the baud rate,
542 "p" is parity ("n", "o", or "e"), "n" is number of
543 bits, and "f" is flow control ("r" for RTS or
544 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800546 See Documentation/serial-console.txt for more
547 information. See
548 Documentation/networking/netconsole.txt for an
549 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700551 uart[8250],io,<addr>[,options]
552 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 Start an early, polled-mode console on the 8250/16550
554 UART at the specified I/O port or MMIO address,
555 switching to the matching ttyS device later. The
556 options are the same as for ttyS, above.
557
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700558 If the device connected to the port is not a TTY but a braille
559 device, prepend "brl," before the device type, for instance
560 console=brl,ttyS0
561 For now, only VisioBraille is supported.
562
Daniel Mackf324edc2009-06-16 15:33:52 -0700563 consoleblank= [KNL] The console blank (screen saver) timeout in
564 seconds. Defaults to 10*60 = 10mins. A value of 0
565 disables the blank timer.
566
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800567 coredump_filter=
568 [KNL] Change the default value for
569 /proc/<pid>/coredump_filter.
570 See also Documentation/filesystems/proc.txt.
571
Linus Torvalds1da177e2005-04-16 15:20:36 -0700572 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700573 Format:
574 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700575
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700576 crashkernel=nn[KMG]@ss[KMG]
577 [KNL] Reserve a chunk of physical memory to
578 hold a kernel to switch to with kexec on panic.
579
Bernhard Wallefb391592007-10-18 23:41:02 -0700580 crashkernel=range1:size1[,range2:size2,...][@offset]
581 [KNL] Same as above, but depends on the memory
582 in the running system. The syntax of range is
583 start-[end] where start and end are both
584 a memory unit (amount[KMG]). See also
585 Documentation/kdump/kdump.txt for a example.
586
Linus Torvalds1da177e2005-04-16 15:20:36 -0700587 cs89x0_dma= [HW,NET]
588 Format: <dma>
589
590 cs89x0_media= [HW,NET]
591 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700592
Randy Dunlapa9913042005-10-23 12:57:11 -0700593 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700594 See header of drivers/s390/block/dasd_devmap.c.
595
596 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
597 (one device per port)
598 Format: <port#>,<type>
599 See also Documentation/input/joystick-parport.txt
600
601 debug [KNL] Enable kernel debugging (events log level).
602
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700603 debug_locks_verbose=
604 [KNL] verbose self-tests
605 Format=<0|1>
606 Print debugging info while doing the locking API
607 self-tests.
608 We default to 0 (no extra messages), setting it to
609 1 will print _a lot_ more information - normally
610 only useful to kernel developers.
611
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700612 debug_objects [KNL] Enable object debugging
613
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500614 no_debug_objects
615 [KNL] Disable object debugging
616
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200617 debugpat [X86] Enable PAT debugging
618
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200619 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700620 Format: <area>[,<node>]
621 See also Documentation/networking/decnet.txt.
622
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700623 default_hugepagesz=
624 [same as hugepagesz=] The size of the default
625 HugeTLB page size. This is the size represented by
626 the legacy /proc/ hugepages APIs, used for SHM, and
627 default size when mounting hugetlbfs filesystems.
628 Defaults to the default architecture's huge page size
629 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700630
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 dhash_entries= [KNL]
632 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700633
Linus Torvalds1da177e2005-04-16 15:20:36 -0700634 digi= [HW,SERIAL]
635 IO parameters + enable/disable command.
636
637 digiepca= [HW,SERIAL]
638 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000639 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700640
Yinghai Lu95ffa242008-04-29 03:52:33 -0700641 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700642 The kernel tries to adjust MTRR layout from continuous
643 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700644 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700645
Yinghai Lu093af8d2008-01-30 13:33:32 +0100646 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100647 By default the kernel will trim any uncacheable
648 memory out of your available memory pool based on
649 MTRR settings. This parameter disables that behavior,
650 possibly causing your machine to run very slowly.
651
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530652 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700653 Disable PIN 1 of APIC timer
654 Can be useful to work around chipset bugs.
655
Linus Torvalds1da177e2005-04-16 15:20:36 -0700656 dmasound= [HW,OSS] Sound subsystem buffers
657
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700658 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
659 this option disables the debugging code at boot.
660
661 dma_debug_entries=<number>
662 This option allows to tune the number of preallocated
663 entries for DMA-API debugging code. One entry is
664 required per DMA-API allocation. Use this if the
665 DMA-API debugging code disables itself because the
666 architectural default is too low.
667
Joerg Roedel1745de52009-05-22 21:49:51 +0200668 dma_debug_driver=<driver_name>
669 With this option the DMA-API debugging driver
670 filter feature can be enabled at boot time. Just
671 pass the driver to filter for as the parameter.
672 The filter can be disabled or changed to another
673 driver later using sysfs.
674
Linus Torvalds1da177e2005-04-16 15:20:36 -0700675 dscc4.setup= [NET]
676
677 dtc3181e= [HW,SCSI]
678
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700679 dynamic_printk Enables pr_debug()/dev_dbg() calls if
680 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
681 These can also be switched on/off via
682 <debugfs>/dynamic_printk/modules
683
684 earlycon= [KNL] Output early console device and options.
685 uart[8250],io,<addr>[,options]
686 uart[8250],mmio,<addr>[,options]
687 Start an early, polled-mode console on the 8250/16550
688 UART at the specified I/O port or MMIO address.
689 The options are the same as for ttyS, above.
690
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530691 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692 earlyprintk=vga
693 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500694 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500695 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700696
Randy Dunlapa9913042005-10-23 12:57:11 -0700697 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698 takes over.
699
Yinghai Lu5c059172008-07-24 17:29:40 -0700700 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700701
702 Currently only ttyS0 and ttyS1 are supported.
703
704 Interaction with the standard serial driver is not
705 very good.
706
707 The VGA output is eventually overwritten by the real
708 console.
709
710 eata= [HW,SCSI]
711
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700713 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715 eisa_irq_edge= [PARISC,HW]
716 See header of drivers/parisc/eisa.c.
717
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700718 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700719 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700720 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700721
722 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800723 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700724 See Documentation/block/as-iosched.txt and
725 Documentation/block/deadline-iosched.txt for details.
726
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530727 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700728 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800729 image elf header. Generally kexec loader will
730 pass this option to capture kernel.
731 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700732
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700733 enable_mtrr_cleanup [X86]
734 The kernel tries to adjust MTRR layout from continuous
735 to discrete, to make X server driver able to add WB
736 entry later. This parameter enables that.
737
Randy Dunlapca1eda22009-05-06 16:02:58 -0700738 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700739 Enable PIN 1 of APIC timer
740 Can be useful to work around chipset bugs
741 (in particular on some ATI chipsets).
742 The kernel tries to set a reasonable default.
743
Linus Torvalds1da177e2005-04-16 15:20:36 -0700744 enforcing [SELINUX] Set initial enforcing status.
745 Format: {"0" | "1"}
746 See security/selinux/Kconfig help text.
747 0 -- permissive (log only, no denials).
748 1 -- enforcing (deny and log).
749 Default value is 0.
750 Value can be changed at runtime via /selinux/enforce.
751
Linus Torvalds1da177e2005-04-16 15:20:36 -0700752 ether= [HW,NET] Ethernet cards parameters
753 This option is obsoleted by the "netdev=" option, which
754 has equivalent usage. See its documentation for details.
755
756 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
757 Format: <io>[,<irq>]
758
Akinobu Mitade1ba092006-12-08 02:39:42 -0800759 failslab=
760 fail_page_alloc=
761 fail_make_request=[KNL]
762 General fault injection mechanism.
763 Format: <interval>,<probability>,<space>,<times>
764 See also /Documentation/fault-injection/.
765
Linus Torvalds1da177e2005-04-16 15:20:36 -0700766 fd_mcs= [HW,SCSI]
767 See header of drivers/scsi/fd_mcs.c.
768
769 fdomain= [HW,SCSI]
770 See header of drivers/scsi/fdomain.c.
771
772 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000773 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700774
Alex Chiangf13ae302008-05-08 14:03:23 -0600775 force_pal_cache_flush
776 [IA-64] Avoid check_sal_cache_flush which may hang on
777 buggy SAL_CACHE_FLUSH implementations. Using this
778 parameter will force ia64_sal_cache_flush to call
779 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
780
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100781 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400782 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100783 as early as possible in order to facilitate early
784 boot debugging.
785
786 ftrace_dump_on_oops
Steven Rostedt2af15d62009-05-28 13:37:24 -0400787 [FTRACE] will dump the trace buffers on oops.
788
789 ftrace_filter=[function-list]
790 [FTRACE] Limit the functions traced by the function
791 tracer at boot up. function-list is a comma separated
792 list of functions. This list can be changed at run
793 time by the set_ftrace_filter file in the debugfs
794 tracing directory.
795
796 ftrace_notrace=[function-list]
797 [FTRACE] Do not trace the functions specified in
798 function-list. This list can be changed at run time
799 by the set_ftrace_notrace file in the debugfs
800 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100801
Stefan Assmann369bc182009-10-12 22:17:21 +0200802 ftrace_graph_filter=[function-list]
803 [FTRACE] Limit the top level callers functions traced
804 by the function graph tracer at boot up.
805 function-list is a comma separated list of functions
806 that can be changed at run time by the
807 set_graph_function file in the debugfs tracing directory.
808
Linus Torvalds1da177e2005-04-16 15:20:36 -0700809 gamecon.map[2|3]=
810 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
811 support via parallel port (up to 5 devices per port)
812 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
813 See also Documentation/input/joystick-parport.txt
814
815 gamma= [HW,DRM]
816
Yinghai Luaaf23042008-01-30 13:33:09 +0100817 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
818 Format: off | on
819 default: on
820
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700821 gcov_persist= [GCOV] When non-zero (default), profiling data for
822 kernel modules is saved and remains accessible via
823 debugfs, even when the module is unloaded/reloaded.
824 When zero, profiling data is discarded and associated
825 debugfs files are removed at module unload time.
826
Linus Torvalds1da177e2005-04-16 15:20:36 -0700827 gdth= [HW,SCSI]
828 See header of drivers/scsi/gdth.c.
829
830 gpt [EFI] Forces disk with valid GPT signature but
831 invalid Protective MBR to be treated as GPT.
832
Linus Torvalds1da177e2005-04-16 15:20:36 -0700833 gvp11= [HW,SCSI]
834
835 hashdist= [KNL,NUMA] Large hashes allocated during boot
836 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700837 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700838 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700839
840 hcl= [IA-64] SGI's Hardware Graph compatibility layer
841
842 hd= [EIDE] (E)IDE hard drive subsystem geometry
843 Format: <cyl>,<head>,<sect>
844
Linus Torvalds1da177e2005-04-16 15:20:36 -0700845 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
846 size of <nn>. This works even on boxes that have no
847 highmem otherwise. This also works to reduce highmem
848 size on bigger boxes.
849
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800850 highres= [KNL] Enable/disable high resolution timer mode.
851 Valid parameters: "on", "off"
852 Default: "on"
853
Linus Torvalds1da177e2005-04-16 15:20:36 -0700854 hisax= [HW,ISDN]
855 See Documentation/isdn/README.HiSax.
856
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700857 hlt [BUGS=ARM,SH]
858
859 hpet= [X86-32,HPET] option to control HPET usage
860 Format: { enable (default) | disable | force |
861 verbose }
862 disable: disable HPET and use PIT instead
863 force: allow force enabled of undocumented chips (ICH4,
864 VIA, nVidia)
865 verbose: show contents of HPET registers during setup
866
Andi Kleenb4718e62008-07-23 21:27:51 -0700867 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
868 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700869 On x86-64 and powerpc, this option can be specified
870 multiple times interleaved with hugepages= to reserve
871 huge pages of different sizes. Valid pages sizes on
872 x86-64 are 2M (when the CPU supports "pse") and 1G
873 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700874 Note that 1GB pages can only be allocated at boot time
875 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900876
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100877 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
878 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100879 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
880 If specified, z/VM IUCV HVC accepts connections
881 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100882
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700883 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700884 or register an additional I2C bus that is not
885 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700886 Format:
887 <bus_id>,<clkrate>
888
Jiri Kosina36d95732008-10-06 02:51:09 -0400889 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200891 i8042.dumbkbd [HW] Pretend that controller can only read data from
892 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700893 (Don't attempt to blink the leds)
894 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500895 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400896 i8042.noloop [HW] Disable the AUX Loopback command while probing
897 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700898 i8042.nomux [HW] Don't check presence of an active multiplexing
899 controller
900 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
901 controllers
902 i8042.panicblink=
903 [HW] Frequency with which keyboard LEDs should blink
904 when kernel panics (default is 0.5 sec)
905 i8042.reset [HW] Reset the controller during init and cleanup
906 i8042.unlock [HW] Unlock (ignore) the keylock
907
908 i810= [HW,DRM]
909
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700910 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
911 indicates that the driver is running on unsupported
912 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700913 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
914 does not match list of supported models.
915 i8k.power_status
916 [HW] Report power status in /proc/i8k
917 (disabled by default)
918 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
919 capability is set.
920
921 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
922 See Documentation/mca.txt.
923
924 icn= [HW,ISDN]
925 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
926
David Fries0af80c02009-02-25 20:28:21 +0100927 ide-core.nodma= [HW] (E)IDE subsystem
928 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200929 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
930 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100931 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700932
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700933 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
934 Claim all unknown PCI IDE storage controllers.
935
Andi Kleenf039b752007-05-02 19:27:12 +0200936 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800937 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
938 Poll forces a polling idle loop that can slightly
939 improve the performance of waking up a idle CPU, but
940 will use a lot of power and make the system run hot.
941 Not recommended.
942 idle=mwait: On systems which support MONITOR/MWAIT but
943 the kernel chose to not use it because it doesn't save
944 as much power as a normal idle loop, use the
945 MONITOR/MWAIT idle loop anyways. Performance should be
946 the same as idle=poll.
947 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800948 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800949 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700950
Ingo Molnar792908222006-12-06 20:40:51 -0800951 ignore_loglevel [KNL]
952 Ignore loglevel setting - this will print /all/
953 kernel messages to the console. Useful for debugging.
954
Linus Torvalds1da177e2005-04-16 15:20:36 -0700955 ihash_entries= [KNL]
956 Set number of hash buckets for inode cache.
957
Mimi Zohar3323eec92009-02-04 09:06:58 -0500958 ima_audit= [IMA]
959 Format: { "0" | "1" }
960 0 -- integrity auditing messages. (Default)
961 1 -- enable informational integrity auditing messages.
962
963 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700964 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -0500965 default: "sha1"
966
Eric Paris5789ba32009-05-21 15:47:06 -0400967 ima_tcb [IMA]
968 Load a policy which meets the needs of the Trusted
969 Computing Base. This means IMA will measure all
970 programs exec'd, files mmap'd for exec, and all files
971 opened for read by uid=0.
972
Linus Torvalds1da177e2005-04-16 15:20:36 -0700973 in2000= [HW,SCSI]
974 See header of drivers/scsi/in2000.c.
975
976 init= [KNL]
977 Format: <full_path>
978 Run specified binary instead of /sbin/init as init
979 process.
980
981 initcall_debug [KNL] Trace initcalls as they are executed. Useful
982 for working out where the kernel is dying during
983 startup.
984
985 initrd= [BOOT] Specify the location of the initial ramdisk
986
987 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
988 Format: <irq>
989
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700990 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800991 on
992 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700993 off
994 Disable intel iommu driver.
995 igfx_off [Default Off]
996 By default, gfx is mapped as normal device. If a gfx
997 device has a dedicated DMAR unit, the DMAR unit is
998 bypassed by not enabling DMAR with this option. In
999 this case, gfx device will use physical address for
1000 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001001 forcedac [x86_64]
1002 With this option iommu will not optimize to look
1003 for io virtual address below 32 bit forcing dual
1004 address cycle on pci bus for cards supporting greater
1005 than 32 bit addressing. The default is to look
1006 for translation below 32 bit and if not available
1007 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001008 strict [Default Off]
1009 With this option on every unmap_single operation will
1010 result in a hardware IOTLB flush operation as opposed
1011 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001012
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001013 inttest= [IA64]
1014
1015 iomem= Disable strict checking of access to MMIO memory
1016 strict regions from userspace.
1017 relaxed
1018
1019 iommu= [x86]
1020 off
1021 force
1022 noforce
1023 biomerge
1024 panic
1025 nopanic
1026 merge
1027 nomerge
1028 forcesac
1029 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001030 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001031
1032 io7= [HW] IO7 for Marvel based alpha systems
1033 See comment before marvel_specify_io7 in
1034 arch/alpha/kernel/core_marvel.c.
1035
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301036 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001037 0x80
1038 Standard port 0x80 based delay
1039 0xed
1040 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001041 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001042 Simple two microseconds delay
1043 none
1044 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001045
Linus Torvalds1da177e2005-04-16 15:20:36 -07001046 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001047 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001048
1049 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001050 See comment before ip2_setup() in
1051 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052
1053 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1054 See header of drivers/scsi/ips.c.
1055
Alan Cox200803d2005-06-28 20:45:18 -07001056 irqfixup [HW]
1057 When an interrupt is not handled search all handlers
1058 for it. Intended to get systems with badly broken
1059 firmware running.
1060
1061 irqpoll [HW]
1062 When an interrupt is not handled search all handlers
1063 for it. Also check all handlers each timer
1064 interrupt. Intended to get systems with badly broken
1065 firmware running.
1066
Linus Torvalds1da177e2005-04-16 15:20:36 -07001067 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001068 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001069
1070 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001071 Format:
1072 <cpu number>,...,<cpu number>
1073 or
Li Zefanb225d442008-11-06 12:53:39 -08001074 <cpu number>-<cpu number>
1075 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001076 or a mixture
1077 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001078
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079 This option can be used to specify one or more CPUs
1080 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001081 algorithms. You can move a process onto or off an
1082 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083 <cpu number> begins at 0 and the maximum value is
1084 "number of CPUs in system - 1".
1085
1086 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001087 alternative -- manually setting the CPU mask of all
1088 tasks in the system -- can cause problems and
1089 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001090
Randy Dunlapa9913042005-10-23 12:57:11 -07001091 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001092
1093 js= [HW,JOY] Analog joystick
1094 See Documentation/input/joystick.txt.
1095
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001096 keepinitrd [HW,ARM]
1097
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301098 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001099 specifies the amount of memory usable by the kernel
1100 for non-movable allocations. The requested amount is
1101 spread evenly throughout all nodes in the system. The
1102 remaining memory in each node is used for Movable
1103 pages. In the event, a node is too small to have both
1104 kernelcore and Movable pages, kernelcore pages will
1105 take priority and other nodes will have a larger number
1106 of kernelcore pages. The Movable zone is used for the
1107 allocation of pages that may be reclaimed or moved
1108 by the page migration subsystem. This means that
1109 HugeTLB pages may not be allocated from this zone.
1110 Note that allocations like PTEs-from-HighMem still
1111 use the HighMem zone if it exists, and the Normal
1112 zone if it does not.
1113
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001114 kgdboc= [HW] kgdb over consoles.
1115 Requires a tty driver that supports console polling.
Matt LaPlante19f59462009-04-27 15:06:31 +02001116 (only serial supported for now)
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001117 Format: <serial_device>[,baud]
1118
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001119 kmac= [MIPS] korina ethernet MAC address.
1120 Configure the RouterBoard 532 series on-chip
1121 Ethernet adapter MAC address.
1122
Catalin Marinas04f70332009-06-11 13:22:39 +01001123 kmemleak= [KNL] Boot-time kmemleak enable/disable
1124 Valid arguments: on, off
1125 Default: on
1126
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301127 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001128 in oops dumps.
1129
Andre Przywarafef07aa2009-07-10 14:20:35 +02001130 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1131 Default is 0 (don't ignore, but inject #GP)
1132
1133 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1134 Default is 1 (enabled)
1135
1136 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1137 Default is 0 (off)
1138
1139 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1140 for all guests.
1141 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1142
1143 kvm-intel.bypass_guest_pf=
1144 [KVM,Intel] Disables bypassing of guest page faults
1145 on Intel chips. Default is 1 (enabled)
1146
1147 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1148 (virtualized MMU) support on capable Intel chips.
1149 Default is 1 (enabled)
1150
1151 kvm-intel.emulate_invalid_guest_state=
1152 [KVM,Intel] Enable emulation of invalid guest states
1153 Default is 0 (disabled)
1154
1155 kvm-intel.flexpriority=
1156 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1157 Default is 1 (enabled)
1158
1159 kvm-intel.unrestricted_guest=
1160 [KVM,Intel] Disable unrestricted guest feature
1161 (virtualized real and unpaged mode) on capable
1162 Intel chips. Default is 1 (enabled)
1163
1164 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1165 feature (tagged TLBs) on capable Intel chips.
1166 Default is 1 (enabled)
1167
Linus Torvalds1da177e2005-04-16 15:20:36 -07001168 l2cr= [PPC]
1169
Robert Brosea78bfbf2008-03-29 07:20:23 +11001170 l3cr= [PPC]
1171
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001172 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001173 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001174
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301175 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001176 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001177
FD Camifcb71f62008-01-06 19:08:56 +01001178 libata.dma= [LIBATA] DMA control
1179 libata.dma=0 Disable all PATA and SATA DMA
1180 libata.dma=1 PATA and SATA Disk DMA only
1181 libata.dma=2 ATAPI (CDROM) DMA only
1182 libata.dma=4 Compact Flash DMA only
1183 Combinations also work, so libata.dma=3 enables DMA
1184 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001185
1186 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1187 libata.ignore_hpa=0 keep BIOS limits (default)
1188 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001189
Dave Jones78e70c22007-09-27 11:50:13 -04001190 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1191 when set.
1192 Format: <int>
1193
Tejun Heo33267322008-02-13 09:15:09 +09001194 libata.force= [LIBATA] Force configurations. The format is comma
1195 separated list of "[ID:]VAL" where ID is
1196 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1197 matching port, link or device. Basically, it matches
1198 the ATA ID string printed on console by libata. If
1199 the whole ID part is omitted, the last PORT and DEVICE
1200 values are used. If ID hasn't been specified yet, the
1201 configuration applies to all ports, links and devices.
1202
1203 If only DEVICE is omitted, the parameter applies to
1204 the port and all links and devices behind it. DEVICE
1205 number of 0 either selects the first device or the
1206 first fan-out link behind PMP device. It does not
1207 select the host link. DEVICE number of 15 selects the
1208 host link and device attached to it.
1209
1210 The VAL specifies the configuration to force. As long
1211 as there's no ambiguity shortcut notation is allowed.
1212 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1213 The following configurations can be forced.
1214
1215 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1216 Any ID with matching PORT is used.
1217
1218 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1219
1220 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1221 udma[/][16,25,33,44,66,100,133] notation is also
1222 allowed.
1223
1224 * [no]ncq: Turn on or off NCQ.
1225
Tejun Heo05944bd2008-08-13 20:19:09 +09001226 * nohrst, nosrst, norst: suppress hard, soft
1227 and both resets.
1228
Tejun Heo33267322008-02-13 09:15:09 +09001229 If there are multiple matching configurations changing
1230 the same attribute, the last one is used.
1231
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001232 lmb=debug [KNL] Enable lmb debug messages.
1233
Linus Torvalds1da177e2005-04-16 15:20:36 -07001234 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001235 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001236
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001237 lockd.nlm_grace_period=P [NFS] Assign grace period.
1238 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001239
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001240 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1241 Format: <integer>
1242
1243 lockd.nlm_timeout=T [NFS] Assign timeout value.
1244 Format: <integer>
1245
1246 lockd.nlm_udpport=M [NFS] Assign UDP port.
1247 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001248
1249 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1250 Format: <irq>
1251
1252 loglevel= All Kernel Messages with a loglevel smaller than the
1253 console loglevel will be printed to the console. It can
1254 also be changed with klogd or other programs. The
1255 loglevels are defined as follows:
1256
1257 0 (KERN_EMERG) system is unusable
1258 1 (KERN_ALERT) action must be taken immediately
1259 2 (KERN_CRIT) critical conditions
1260 3 (KERN_ERR) error conditions
1261 4 (KERN_WARNING) warning conditions
1262 5 (KERN_NOTICE) normal but significant condition
1263 6 (KERN_INFO) informational
1264 7 (KERN_DEBUG) debug-level messages
1265
1266 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001267 Format: { n | nk | nM }
1268 n must be a power of two. The default size
1269 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001270
Randy Dunlapaccaa242007-10-16 01:29:37 -07001271 logo.nologo [FB] Disables display of the built-in Linux logo.
1272 This may be used to provide more screen space for
1273 kernel log messages and is useful when debugging
1274 kernel boot problems.
1275
Linus Torvalds1da177e2005-04-16 15:20:36 -07001276 lp=0 [LP] Specify parallel ports to use, e.g,
1277 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1278 lp=reset first parallel port). 'lp=0' disables the
1279 lp=auto printer driver. 'lp=reset' (which can be
1280 specified in addition to the ports) causes
1281 attached printers to be reset. Using
1282 lp=port1,port2,... specifies the parallel ports
1283 to associate lp devices with, starting with
1284 lp0. A port specification may be 'none' to skip
1285 that lp device, or a parport name such as
1286 'parport0'. Specifying 'lp=auto' instead of a
1287 port specification list means that device IDs
1288 from each port should be examined, to see if
1289 an IEEE 1284-compliant printer is attached; if
1290 so, the driver will manage that printer.
1291 See also header of drivers/char/lp.c.
1292
1293 lpj=n [KNL]
1294 Sets loops_per_jiffy to given constant, thus avoiding
1295 time-consuming boot-time autodetection (up to 250 ms per
1296 CPU). 0 enables autodetection (default). To determine
1297 the correct value for your kernel, boot with normal
1298 autodetection and see what value is printed. Note that
1299 on SMP systems the preset will be applied to all CPUs,
1300 which is likely to cause problems if your CPUs need
1301 significantly divergent settings. An incorrect value
1302 will cause delays in the kernel to be wrong, leading to
1303 unpredictable I/O errors and other breakage. Although
1304 unlikely, in the extreme case this might damage your
1305 hardware.
1306
1307 ltpc= [NET]
1308 Format: <io>,<irq>,<dma>
1309
Randy Dunlapa9913042005-10-23 12:57:11 -07001310 mac5380= [HW,SCSI] Format:
1311 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001312
Randy Dunlapa9913042005-10-23 12:57:11 -07001313 machvec= [IA64] Force the use of a particular machine-vector
1314 (machvec) in a generic kernel.
1315 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001316
Wu Zhangjin3209e702009-07-02 23:27:12 +08001317 machtype= [Loongson] Share the same kernel image file between different
1318 yeeloong laptop.
1319 Example: machtype=lemote-yeeloong-2f-7inch
1320
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001321 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1322 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001323
1324 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001325 should make use of. maxcpus=n : n >= 0 limits the
1326 kernel to using 'n' processors. n=0 is a special case,
1327 it is equivalent to "nosmp", which also disables
1328 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001329
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001330 max_loop= [LOOP] Maximum number of loopback devices that can
1331 be mounted
1332 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001333
Randy Dunlapa9913042005-10-23 12:57:11 -07001334 max_luns= [SCSI] Maximum number of LUNs to probe.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001335 Should be between 1 and 2^32-1.
1336
1337 max_report_luns=
Randy Dunlapa9913042005-10-23 12:57:11 -07001338 [SCSI] Maximum number of LUNs received.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001339 Should be between 1 and 16384.
1340
Linus Torvalds1da177e2005-04-16 15:20:36 -07001341 mcatest= [IA-64]
1342
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001343 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344
Uwe Hermann71cced62008-10-20 09:32:21 -07001345 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001346
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347 md= [HW] RAID subsystems devices and level
1348 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001349
Linus Torvalds1da177e2005-04-16 15:20:36 -07001350 mdacon= [MDA]
1351 Format: <first>,<last>
1352 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001353
Linus Torvalds1da177e2005-04-16 15:20:36 -07001354 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1355 Amount of memory to be used when the kernel is not able
1356 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001357 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001358 address space collisions. Without memmap= PCI devices
1359 could be placed at addresses belonging to unused RAM.
1360
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001361 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001362 memory.
1363
Paul Mundt6902aa82008-09-21 17:14:42 +09001364 memchunk=nn[KMG]
1365 [KNL,SH] Allow user to override the default size for
1366 per-device physically contiguous DMA buffers.
1367
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301368 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001369 E820 memory map, as specified by the user.
1370 Such memmap=exactmap lines can be constructed based on
1371 BIOS output or other requirements. See the memmap=nn@ss
1372 option description.
1373
1374 memmap=nn[KMG]@ss[KMG]
1375 [KNL] Force usage of a specific region of memory
1376 Region of memory to be used, from ss to ss+nn.
1377
1378 memmap=nn[KMG]#ss[KMG]
1379 [KNL,ACPI] Mark specific memory as ACPI data.
1380 Region of memory to be used, from ss to ss+nn.
1381
1382 memmap=nn[KMG]$ss[KMG]
1383 [KNL,ACPI] Mark specific memory as reserved.
1384 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001385 Example: Exclude memory from 0x18690000-0x1869ffff
1386 memmap=64K$0x18690000
1387 or
1388 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001389
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001390 memory_corruption_check=0/1 [X86]
1391 Some BIOSes seem to corrupt the first 64k of
1392 memory when doing things like suspend/resume.
1393 Setting this option will scan the memory
1394 looking for corruption. Enabling this will
1395 both detect corruption and prevent the kernel
1396 from using the memory being corrupted.
1397 However, its intended as a diagnostic tool; if
1398 repeatable BIOS-originated corruption always
1399 affects the same memory, you can use memmap=
1400 to prevent the kernel from using that memory.
1401
1402 memory_corruption_check_size=size [X86]
1403 By default it checks for corruption in the low
1404 64k, making this memory unavailable for normal
1405 use. Use this parameter to scan for
1406 corruption in more or less memory.
1407
1408 memory_corruption_check_period=seconds [X86]
1409 By default it checks for corruption every 60
1410 seconds. Use this parameter to check at some
1411 other rate. 0 disables periodic checking.
1412
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001413 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001414 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001415 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001416 Specifies the number of memtest passes to be
1417 performed. Each pass selects another test
1418 pattern from a given set of patterns. Memtest
1419 fills the memory with this pattern, validates
1420 memory contents and reserves bad memory
1421 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001422
Linus Torvalds1da177e2005-04-16 15:20:36 -07001423 meye.*= [HW] Set MotionEye Camera parameters
1424 See Documentation/video4linux/meye.txt.
1425
Andres Salomon8f368812007-10-12 23:04:06 +02001426 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1427 Multi-Function General Purpose Timers on AMD Geode
1428 platforms.
1429
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001430 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1431 the BIOS has incorrectly applied a workaround. TinyBIOS
1432 version 0.98 is known to be affected, 0.99 fixes the
1433 problem by letting the user disable the workaround.
1434
Linus Torvalds1da177e2005-04-16 15:20:36 -07001435 mga= [HW,DRM]
1436
Randy Dunlap1c207f92008-11-19 15:36:16 -08001437 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1438 physical address is ignored.
1439
Michel Pollet39f45d72009-05-20 11:10:31 +01001440 mini2440= [ARM,HW,KNL]
1441 Format:[0..2][b][c][t]
1442 Default: "0tb"
1443 MINI2440 configuration specification:
1444 0 - The attached screen is the 3.5" TFT
1445 1 - The attached screen is the 7" TFT
1446 2 - The VGA Shield is attached (1024x768)
1447 Leaving out the screen size parameter will not load
1448 the TFT driver, and the framebuffer will be left
1449 unconfigured.
1450 b - Enable backlight. The TFT backlight pin will be
1451 linked to the kernel VESA blanking code and a GPIO
1452 LED. This parameter is not necessary when using the
1453 VGA shield.
1454 c - Enable the s3c camera interface.
1455 t - Reserved for enabling touchscreen support. The
1456 touchscreen support is not enabled in the mainstream
1457 kernel as of 2.6.30, a preliminary port can be found
1458 in the "bleeding edge" mini2440 support kernel at
1459 http://repo.or.cz/w/linux-2.6/mini2440.git
1460
Mel Gorman6b74ab92008-07-23 21:26:49 -07001461 mminit_loglevel=
1462 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1463 parameter allows control of the logging verbosity for
1464 the additional memory initialisation checks. A value
1465 of 0 disables mminit logging and a level of 4 will
1466 log everything. Information is printed at KERN_DEBUG
1467 so loglevel=8 may also need to be specified.
1468
Linus Torvalds1da177e2005-04-16 15:20:36 -07001469 mousedev.tap_time=
1470 [MOUSE] Maximum time between finger touching and
1471 leaving touchpad surface for touch to be considered
1472 a tap and be reported as a left button click (for
1473 touchpads working in absolute mode only).
1474 Format: <msecs>
1475 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1476 reporting absolute coordinates, such as tablets
1477 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1478 reporting absolute coordinates, such as tablets
1479
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301480 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001481 is similar to kernelcore except it specifies the
1482 amount of memory used for migratable allocations.
1483 If both kernelcore and movablecore is specified,
1484 then kernelcore will be at *least* the specified
1485 value but may be more. If movablecore on its own
1486 is specified, the administrator must be careful
1487 that the amount of memory usable for all allocations
1488 is not too small.
1489
Linus Torvalds1da177e2005-04-16 15:20:36 -07001490 mpu401= [HW,OSS]
1491 Format: <io>,<irq>
1492
1493 MTD_Partition= [MTD]
1494 Format: <name>,<region-number>,<size>,<offset>
1495
Randy Dunlapa9913042005-10-23 12:57:11 -07001496 MTD_Region= [MTD] Format:
1497 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001498
1499 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001500 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001501
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001502 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1503
1504 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1505
1506 boundary - index of last SLC block on Flex-OneNAND.
1507 The remaining blocks are configured as MLC blocks.
1508 lock - Configure if Flex-OneNAND boundary should be locked.
1509 Once locked, the boundary cannot be changed.
1510 1 indicates lock status, 0 indicates unlock status.
1511
Ben Dooks9db829f2008-07-03 11:24:29 +01001512 mtdset= [ARM]
1513 ARM/S3C2412 JIVE boot control
1514
1515 See arch/arm/mach-s3c2412/mach-jive.c
1516
Linus Torvalds1da177e2005-04-16 15:20:36 -07001517 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001518 [HW] Make the MicroTouch USB driver use raw coordinates
1519 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001521 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001522 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001523 that could hold holes aka. UC entries.
1524
1525 mtrr_gran_size=nn[KMG] [X86]
1526 Used for mtrr cleanup. It is granularity of mtrr block.
1527 Default is 1.
1528 Large value could prevent small alignment from
1529 using up MTRRs.
1530
1531 mtrr_spare_reg_nr=n [X86]
1532 Format: <integer>
1533 Range: 0,7 : spare reg number
1534 Default : 1
1535 Used for mtrr cleanup. It is spare mtrr entries number.
1536 Set to 2 or more if your graphical card needs more.
1537
Linus Torvalds1da177e2005-04-16 15:20:36 -07001538 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1539
1540 NCR_D700= [HW,SCSI]
1541 See header of drivers/scsi/NCR_D700.c.
1542
1543 ncr5380= [HW,SCSI]
1544
1545 ncr53c400= [HW,SCSI]
1546
1547 ncr53c400a= [HW,SCSI]
1548
1549 ncr53c406a= [HW,SCSI]
1550
1551 ncr53c8xx= [HW,SCSI]
1552
1553 netdev= [NET] Network devices parameters
1554 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1555 Note that mem_start is often overloaded to mean
1556 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001557 This usage is only documented in each driver source
1558 file if at all.
1559
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001560 nf_conntrack.acct=
1561 [NETFILTER] Enable connection tracking flow accounting
1562 0 to disable accounting
1563 1 to enable accounting
1564 Default value depends on CONFIG_NF_CT_ACCT that is
1565 going to be removed in 2.6.29.
1566
Linus Torvalds1da177e2005-04-16 15:20:36 -07001567 nfsaddrs= [NFS]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001568 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001569
1570 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001571 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001572
Trond Myklebusta72b4422006-01-03 09:55:41 +01001573 nfs.callback_tcpport=
1574 [NFS] set the TCP port on which the NFSv4 callback
1575 channel should listen.
1576
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001577 nfs.cache_getent=
1578 [NFS] sets the pathname to the program which is used
1579 to update the NFS client cache entries.
1580
1581 nfs.cache_getent_timeout=
1582 [NFS] sets the timeout after which an attempt to
1583 update a cache entry is deemed to have failed.
1584
Trond Myklebust58df0952006-01-03 09:55:57 +01001585 nfs.idmap_cache_timeout=
1586 [NFS] set the maximum lifetime for idmapper cache
1587 entries.
1588
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001589 nfs.enable_ino64=
1590 [NFS] enable 64-bit inode numbers.
1591 If zero, the NFS client will fake up a 32-bit inode
1592 number for the readdir() and stat() syscalls instead
1593 of returning the full 64-bit number.
1594 The default is to return 64-bit inode numbers.
1595
Paul Mundt1e1030d2009-09-01 17:38:32 +09001596 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001597 when a NMI is triggered.
1598 Format: [state][,regs][,debounce][,die]
1599
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301600 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001601 Format: [panic,][num]
1602 Valid num: 0,1,2
1603 0 - turn nmi_watchdog off
1604 1 - use the IO-APIC timer for the NMI watchdog
1605 2 - use the local APIC for the NMI watchdog using
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001606 a performance counter. Note: This will use one
1607 performance counter and the local APIC's performance
1608 vector.
1609 When panic is specified, panic when an NMI watchdog
1610 timeout occurs.
1611 This is useful when you use a panic=... timeout and
1612 need the box quickly up again.
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001613 Instead of 1 and 2 it is possible to use the following
1614 symbolic names: lapic and ioapic
1615 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
Linus Torvalds1da177e2005-04-16 15:20:36 -07001616
Anton Vorontsovbff38772009-07-08 11:10:56 -07001617 netpoll.carrier_timeout=
1618 [NET] Specifies amount of time (in seconds) that
1619 netpoll should wait for a carrier. By default netpoll
1620 waits 4 seconds.
1621
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001622 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001623 emulation library even if a 387 maths coprocessor
1624 is present.
1625
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001626 no_console_suspend
1627 [HW] Never suspend the console
1628 Disable suspending of consoles during suspend and
1629 hibernate operations. Once disabled, debugging
1630 messages can reach various consoles while the rest
1631 of the system is being put to sleep (ie, while
1632 debugging driver suspend/resume hooks). This may
1633 not work reliably with all consoles, but is known
1634 to work with serial and VGA consoles.
1635
Christoph Lameterc1aee212007-05-31 00:40:47 -07001636 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1637 caches in the slab allocator. Saves per-node memory,
1638 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001639
Randy Dunlapa9913042005-10-23 12:57:11 -07001640 noalign [KNL,ARM]
1641
Linus Torvalds1da177e2005-04-16 15:20:36 -07001642 noapic [SMP,APIC] Tells the kernel to not make use of any
1643 IOAPICs that may be present in the system.
1644
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 nobats [PPC] Do not use BATs for mapping kernel lowmem
1646 on "Classic" PPC cores.
1647
1648 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001649
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001650 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1651
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001652 nodelayacct [KNL] Disable per-task delay accounting
1653
Linus Torvalds1da177e2005-04-16 15:20:36 -07001654 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1655
Paul Mundt6902aa82008-09-21 17:14:42 +09001656 nodsp [SH] Disable hardware DSP at boot time.
1657
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301658 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001659
Linus Torvalds1da177e2005-04-16 15:20:36 -07001660 noexec [IA-64]
1661
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301662 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001663 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001664 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001665 noexec=off: disable non-executable mappings
1666
1667 noexec32 [X86-64]
1668 This affects only 32-bit executables.
1669 noexec32=on: enable non-executable mappings (default)
1670 read doesn't imply executable mappings
1671 noexec32=off: disable non-executable mappings
1672 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001673
Paul Mundt6902aa82008-09-21 17:14:42 +09001674 nofpu [SH] Disable hardware FPU at boot time.
1675
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001676 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001677 register save and restore. The kernel will only save
1678 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001679
Suresh Siddha0c752a92009-05-22 12:17:45 -07001680 noxsave [BUGS=X86] Disables x86 extended register state save
1681 and restore using xsave. The kernel will fallback to
1682 enabling legacy floating-point and sse state.
1683
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001684 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1685 wfi(ARM) instruction doesn't work correctly and not to
1686 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001687
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001688 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001689 instruction doesn't work correctly and not to
1690 use it.
1691
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001692 no_file_caps Tells the kernel not to honor file capabilities. The
1693 only way then for a file to be executed with privilege
1694 is to be setuid root or executed by root.
1695
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696 nohalt [IA-64] Tells the kernel not to use the power saving
1697 function PAL_HALT_LIGHT when idle. This increases
1698 power-consumption. On the positive side, it reduces
1699 interrupt wake-up latency, which may improve performance
1700 in certain environments such as networked servers or
1701 real-time systems.
1702
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001703 nohz= [KNL] Boottime enable/disable dynamic ticks
1704 Valid arguments: on, off
1705 Default: on
1706
Paul Mundteeee7852009-04-02 12:31:16 +09001707 noiotrap [SH] Disables trapped I/O port accesses.
1708
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001709 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001710 disable unhandled interrupt sources.
1711
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301712 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001713 broken timer IRQ sources.
1714
Linus Torvalds1da177e2005-04-16 15:20:36 -07001715 noisapnp [ISAPNP] Disables ISA PnP code.
1716
1717 noinitrd [RAM] Tells the kernel not to load any configured
1718 initial RAM disk.
1719
Weidong Han03ea8152009-04-17 16:42:15 +08001720 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1721 remapping.
1722
Linus Torvalds1da177e2005-04-16 15:20:36 -07001723 nointroute [IA-64]
1724
Tony Luck0aa366f2007-07-20 11:22:30 -07001725 nojitter [IA64] Disables jitter checking for ITC timers.
1726
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001727 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001728
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001729 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001730
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731 noltlbs [PPC] Do not use large page/tlb entries for kernel
1732 lowmem mapping on PPC40x.
1733
Horms312f1f02006-02-22 09:57:55 +09001734 nomca [IA-64] Disable machine check abort handling
1735
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001736 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001737
Andres Salomon83d73842007-10-12 23:04:06 +02001738 nomfgpt [X86-32] Disable Multi-Function General Purpose
1739 Timer usage (for AMD Geode machines).
1740
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001741 norandmaps Don't use address space randomization. Equivalent to
1742 echo 0 > /proc/sys/kernel/randomize_va_space
1743
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001744 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001745
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001746 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001747 with UP alternatives
1748
Linus Torvalds1da177e2005-04-16 15:20:36 -07001749 noresidual [PPC] Don't use residual data on PReP machines.
1750
Randy Dunlapa9913042005-10-23 12:57:11 -07001751 noresume [SWSUSP] Disables resume and restores original swap
1752 space.
1753
Linus Torvalds1da177e2005-04-16 15:20:36 -07001754 no-scroll [VGA] Disables scrollback.
1755 This is required for the Braillex ib80-piezo Braille
1756 reader made by F.H. Papenmeier (Germany).
1757
1758 nosbagart [IA-64]
1759
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001760 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001761
Len Brown61ec7562007-08-16 03:34:22 -04001762 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1763 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001764
Dave Jones97842212007-07-15 23:41:05 -07001765 nosoftlockup [KNL] Disable the soft-lockup detector.
1766
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001767 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001768 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001769
Linus Torvalds1da177e2005-04-16 15:20:36 -07001770 nosync [HW,M68K] Disables sync negotiation for all devices.
1771
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001772 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001773
1774 nousb [USB] Disable the USB subsystem
1775
1776 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001777
Weidong Han2b2fd872009-04-17 16:42:12 +08001778 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1779
Fenghua Yua6c75b862008-03-14 13:57:08 -07001780 nptcg= [IA64] Override max number of concurrent global TLB
1781 purges which is reported from either PAL_VM_SUMMARY or
1782 SAL PALO.
1783
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001784 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1785
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001786 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1787 one of ['zone', 'node', 'default'] can be specified
1788 This can be set from sysctl after boot.
1789 See Documentation/sysctl/vm.txt for details.
1790
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001791 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1792 See Documentation/debugging-via-ohci1394.txt for more
1793 info.
1794
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001795 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1796 Rather than timing out after 20 ms if an EC
1797 command is not properly ACKed, override the length
1798 of the timeout. We have interrupts disabled while
1799 waiting for the ACK, so if this is set too high
1800 interrupts *may* be lost!
1801
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001802 omap_mux= [OMAP] Override bootloader pin multiplexing.
1803 Format: <mux_mode0.mode_name=value>...
1804 For example, to override I2C bus2:
1805 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1806
Linus Torvalds1da177e2005-04-16 15:20:36 -07001807 opl3= [HW,OSS]
1808 Format: <io>
1809
Linus Torvalds1da177e2005-04-16 15:20:36 -07001810 oprofile.timer= [HW]
1811 Use timer interrupt instead of performance counters
1812
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001813 oprofile.cpu_type= Force an oprofile cpu type
1814 This might be useful if you have an older oprofile
1815 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001816 Format: { arch_perfmon }
1817 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001818 perfmon on Intel CPUs instead of the
1819 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001820
Linus Torvalds1da177e2005-04-16 15:20:36 -07001821 osst= [HW,SCSI] SCSI Tape Driver
1822 Format: <buffer_size>,<write_threshold>
1823 See also Documentation/scsi/st.txt.
1824
1825 panic= [KNL] Kernel behaviour on panic
1826 Format: <timeout>
1827
1828 parkbd.port= [HW] Parallel port number the keyboard adapter is
1829 connected to, default is 0.
1830 Format: <parport#>
1831 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1832 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001833 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001834
Randy Dunlapa9913042005-10-23 12:57:11 -07001835 parport= [HW,PPT] Specify parallel ports. 0 disables.
1836 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1837 Use 'auto' to force the driver to use any
1838 IRQ/DMA settings detected (the default is to
1839 ignore detected IRQ/DMA settings because of
1840 possible conflicts). You can specify the base
1841 address, IRQ, and DMA settings; IRQ and DMA
1842 should be numbers, or 'auto' (for using detected
1843 settings on that particular port), or 'nofifo'
1844 (to avoid using a FIFO even if it is detected).
1845 Parallel ports are assigned in the order they
1846 are specified on the command line, starting
1847 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001848
Randy Dunlapa9913042005-10-23 12:57:11 -07001849 parport_init_mode= [HW,PPT]
1850 Configure VIA parallel port to operate in
1851 a specific mode. This is necessary on Pegasos
1852 computer where firmware has no options for setting
1853 up parallel port mode and sets it to spp.
1854 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001855 Format: [spp|ps2|epp|ecp|ecpepp]
1856
Randy Dunlapa9913042005-10-23 12:57:11 -07001857 pas2= [HW,OSS] Format:
1858 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1859
Linus Torvalds1da177e2005-04-16 15:20:36 -07001860 pas16= [HW,SCSI]
1861 See header of drivers/scsi/pas16.c.
1862
Andrew Mortondd287792006-03-23 03:00:57 -08001863 pause_on_oops=
1864 Halt all CPUs after the first oops has been printed for
1865 the specified number of seconds. This is to be used if
1866 your oopses keep scrolling off the screen.
1867
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868 pcbit= [HW,ISDN]
1869
1870 pcd. [PARIDE]
1871 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001872 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001873
Randy Dunlapa9913042005-10-23 12:57:11 -07001874 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001875 earlydump [X86] dump PCI config space before the kernel
1876 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001877 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001878 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001879 the hardware directly. Use this if your machine
1880 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001881 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001882 hardware access methods are allowed. Use this
1883 if you experience crashes upon bootup and you
1884 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001885 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001886 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001887 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001888 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001889 noaer [PCIE] If the PCIEAER kernel config parameter is
1890 enabled, this kernel boot option can be used to
1891 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001892 nodomains [PCI] Disable support for multiple PCI
1893 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301894 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001895 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001896 check_enable_amd_mmconf [X86] check for and enable
1897 properly configured MMIO access to PCI
1898 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001899 nomsi [MSI] If the PCI_MSI kernel config parameter is
1900 enabled, this kernel boot option can be used to
1901 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001902 noioapicquirk [APIC] Disable all boot interrupt quirks.
1903 Safety option to keep boot IRQs enabled. This
1904 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001905 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1906 primary IO-APIC for bridges that cannot disable
1907 boot IRQs. This fixes a source of spurious IRQs
1908 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001909 noioapicreroute [APIC] Disable workaround that uses the
1910 boot IRQ equivalent of an IRQ that connects to
1911 a chipset where boot IRQs cannot be disabled.
1912 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001913 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001914 routing table. These calls are known to be buggy
1915 on several machines and they hang the machine
1916 when used, but on other computers it's the only
1917 way to get the interrupt routing table. Try
1918 this option if the kernel is unable to allocate
1919 IRQs or discover secondary PCI buses on your
1920 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001921 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001922 Use with caution as certain devices share
1923 address decoders between ROMs and other
1924 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001925 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001926 expansion ROMs that do not already have
1927 BIOS assigned address ranges.
Andi Kleenc0115602008-08-22 09:53:39 +02001928 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001929 assigned automatically to PCI devices. You can
1930 make the kernel exclude IRQs of your ISA cards
1931 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001932 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001933 of the PIRQ table (normally generated
1934 by the BIOS) if it is outside the
1935 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001936 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001937 useful if the kernel is unable to find your
1938 secondary buses and you want to tell it
1939 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001940 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001941 numbers ourselves, overriding
1942 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001943 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001944 in the BIOS $PIR table. This is needed on
1945 some systems with broken BIOSes, notably
1946 some HP Pavilion N5400 and Omnibook XE3
1947 notebooks. This will have no effect if ACPI
1948 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001949 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001950 or for PCI scanning.
Linus Torvalds236e9462009-06-24 16:23:03 -07001951 use_crs [X86] Use _CRS for PCI resource
Gary Hade62f420f2007-10-03 15:56:51 -07001952 allocation.
Randy Dunlapa9913042005-10-23 12:57:11 -07001953 routeirq Do IRQ routing for all PCI devices.
1954 This is normally done in pci_enable_device(),
1955 so this option is a temporary workaround
1956 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001957 skip_isa_align [X86] do not align io start addr, so can
1958 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001959 firmware [ARM] Do not re-enumerate the bus but instead
1960 just use the configuration from the
1961 bootloader. This is currently used on
1962 IXP2000 systems where the bus has to be
1963 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001964 noearly [X86] Don't do any early type 1 scanning.
1965 This might help on some broken boards which
1966 machine check when some devices' config space
1967 is read. But various workarounds are disabled
1968 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001969 bfsort Sort PCI devices into breadth-first order.
1970 This sorting is done to get a device
1971 order compatible with older (<= 2.4) kernels.
1972 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001973 cbiosize=nn[KMG] The fixed amount of bus space which is
1974 reserved for the CardBus bridge's IO window.
1975 The default value is 256 bytes.
1976 cbmemsize=nn[KMG] The fixed amount of bus space which is
1977 reserved for the CardBus bridge's memory
1978 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09001979 resource_alignment=
1980 Format:
1981 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1982 Specifies alignment and device to reassign
1983 aligned memory resources.
1984 If <order of align> is not specified,
1985 PAGE_SIZE is used as alignment.
1986 PCI-PCI bridge can be specified, if resource
1987 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06001988 ecrc= Enable/disable PCIe ECRC (transaction layer
1989 end-to-end CRC checking).
1990 bios: Use BIOS/firmware settings. This is the
1991 the default.
1992 off: Turn ECRC off
1993 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001994
Chuck Ebberte5665a42008-09-24 20:40:34 -04001995 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1996 Management.
1997 off Disable ASPM.
1998 force Enable ASPM even on devices that claim not to support it.
1999 WARNING: Forcing ASPM on may cause system lockups.
2000
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002001 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2002 off Do not use native PCIe PME signaling.
2003 force Use native PCIe PME signaling even if the BIOS refuses
2004 to allow the kernel to control the relevant PCIe config
2005 registers.
2006
Linus Torvalds1da177e2005-04-16 15:20:36 -07002007 pcmv= [HW,PCMCIA] BadgePAD 4
2008
2009 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002010 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002011
2012 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2013 boot time.
2014 Format: { 0 | 1 }
2015 See arch/parisc/kernel/pdc_chassis.c
2016
Tejun Heof58dc012009-08-14 15:00:50 +09002017 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002018 Currently supported values are "embed" and "page".
2019 Archs may support subset or none of the selections.
2020 See comments in mm/percpu.c for details on each
2021 allocator. This parameter is primarily for debugging
2022 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002023
Linus Torvalds1da177e2005-04-16 15:20:36 -07002024 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002025 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002026
2027 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002028 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002029
2030 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002031 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002032
2033 plip= [PPT,NET] Parallel port network link
2034 Format: { parport<nr> | timid | 0 }
2035 See also Documentation/parport.txt.
2036
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002037 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2038 Override pmtimer IOPort with a hex value.
2039 e.g. pmtmr=0x508
2040
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002041 pnp.debug [PNP]
2042 Enable PNP debug messages. This depends on the
2043 CONFIG_PNP_DEBUG_MESSAGES option.
2044
Linus Torvalds1da177e2005-04-16 15:20:36 -07002045 pnpacpi= [ACPI]
2046 { off }
2047
2048 pnpbios= [ISAPNP]
2049 { on | off | curr | res | no-curr | no-res }
2050
2051 pnp_reserve_irq=
2052 [ISAPNP] Exclude IRQs for the autoconfiguration
2053
2054 pnp_reserve_dma=
2055 [ISAPNP] Exclude DMAs for the autoconfiguration
2056
2057 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002058 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002059
2060 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002061 [ISAPNP] Exclude memory regions for the
2062 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002063 Ranges are in pairs (memory base and size).
2064
Randy Dunlap4af94f32009-04-17 18:30:28 -07002065 ports= [IP_VS_FTP] IPVS ftp helper module
2066 Default is 21.
2067 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2068 may be specified.
2069 Format: <port>,<port>....
2070
Ingo Molnar45807a12007-07-15 23:40:10 -07002071 print-fatal-signals=
2072 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002073
2074 If enabled, warn about various signal handling
2075 related application anomalies: too many signals,
2076 too many POSIX.1 timers, fatal signals causing a
2077 coredump - etc.
2078
2079 If you hit the warning due to signal overflow,
2080 you might want to try "ulimit -i unlimited".
2081
Ingo Molnar45807a12007-07-15 23:40:10 -07002082 default: off.
2083
Randy Dunlape84845c2007-07-15 23:40:25 -07002084 printk.time= Show timing data prefixed to each printk message line
2085 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2086
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002087 processor.max_cstate= [HW,ACPI]
2088 Limit processor to maximum C-state
2089 max_cstate=9 overrides any DMI blacklist limit.
2090
2091 processor.nocst [HW,ACPI]
2092 Ignore the _CST method to determine C-states,
2093 instead using the legacy FADT method
2094
Linus Torvalds1da177e2005-04-16 15:20:36 -07002095 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002096 Format: [schedule,]<number>
2097 Param: "schedule" - profile schedule points.
2098 Param: <number> - step/bucket size as a power of 2 for
2099 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002100 Param: "sleep" - profile D-state sleeping (millisecs).
2101 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002102 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002103
Linus Torvalds1da177e2005-04-16 15:20:36 -07002104 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2105 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002106 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002107
Randy Dunlapa9913042005-10-23 12:57:11 -07002108 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2109 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002110 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2111 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002112 psmouse.resetafter= [HW,MOUSE]
2113 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002114 (0 = never).
2115 psmouse.resolution=
2116 [HW,MOUSE] Set desired mouse resolution, in dpi.
2117 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002118 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002119 0 = disabled, 1 = enabled (default).
2120
2121 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
Randy Dunlapa9913042005-10-23 12:57:11 -07002122 Format:
2123 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002124
2125 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002126 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002127
Kay Sieversdc8c8582007-08-15 12:25:38 +02002128 pty.legacy_count=
2129 [KNL] Number of legacy pty's. Overwrites compiled-in
2130 default number.
2131
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002132 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002133
Linus Torvalds1da177e2005-04-16 15:20:36 -07002134 r128= [HW,DRM]
2135
2136 raid= [HW,RAID]
2137 See Documentation/md.txt.
2138
Randy Dunlapa9913042005-10-23 12:57:11 -07002139 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002140 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002141
Linus Torvalds1da177e2005-04-16 15:20:36 -07002142 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002143 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002144
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002145 rcupdate.blimit= [KNL,BOOT]
2146 Set maximum number of finished RCU callbacks to process
2147 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002148
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002149 rcupdate.qhimark= [KNL,BOOT]
2150 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002151 RCU callbacks over which batch limiting is disabled.
2152
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002153 rcupdate.qlowmark= [KNL,BOOT]
2154 Set threshold of queued RCU callbacks below which
2155 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002156
Olof Johanssonffdfc402005-09-06 15:17:19 -07002157 rdinit= [KNL]
2158 Format: <full_path>
2159 Run specified binary instead of /init from the ramdisk,
2160 used for early userspace startup. See initrd.
2161
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002162 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002163 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002164 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002165
Paul Jackson46b6d942008-07-04 10:00:09 -07002166 relax_domain_level=
2167 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002168 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002169
Linus Torvalds1da177e2005-04-16 15:20:36 -07002170 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2171
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002172 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002173 Format: nn[KMG]
2174 Reserves a hole at the top of the kernel virtual
2175 address space.
2176
Vivek Goyal7e962872006-09-27 01:50:44 -07002177 reset_devices [KNL] Force drivers to reset the underlying device
2178 during initialization.
2179
Randy Dunlapa9913042005-10-23 12:57:11 -07002180 resume= [SWSUSP]
2181 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002182
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002183 resume_offset= [SWSUSP]
2184 Specify the offset from the beginning of the partition
2185 given by "resume=" at which the swap header is located,
2186 in <PAGE_SIZE> units (needed only for swap files).
2187 See Documentation/power/swsusp-and-swap-files.txt
2188
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002189 retain_initrd [RAM] Keep initrd memory after extraction
2190
Linus Torvalds1da177e2005-04-16 15:20:36 -07002191 rhash_entries= [KNL,NET]
2192 Set number of hash buckets for route cache
2193
2194 riscom8= [HW,SERIAL]
2195 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2196
2197 ro [KNL] Mount root device read-only on boot
2198
2199 root= [KNL] Root filesystem
2200
2201 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2202 mount the root filesystem
2203
2204 rootflags= [KNL] Set root filesystem mount option string
2205
2206 rootfstype= [KNL] Set root filesystem type
2207
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002208 rootwait [KNL] Wait (indefinitely) for root device to show up.
2209 Useful for devices that are detected asynchronously
2210 (e.g. USB and MMC devices).
2211
Linus Torvalds1da177e2005-04-16 15:20:36 -07002212 rw [KNL] Mount root device read-write on boot
2213
2214 S [KNL] Run init in single mode
2215
2216 sa1100ir [NET]
2217 See drivers/net/irda/sa1100_ir.c.
2218
Linus Torvalds1da177e2005-04-16 15:20:36 -07002219 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002220
Mike Travisf6630112009-11-17 18:22:15 -06002221 sched_debug [KNL] Enables verbose scheduler debug messages.
2222
Linus Torvalds1da177e2005-04-16 15:20:36 -07002223 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2224 Format: <io>[,<timeout>[,<isapnp>]]
2225
2226 scsi_debug_*= [SCSI]
2227 See drivers/scsi/scsi_debug.c.
2228
2229 scsi_default_dev_flags=
2230 [SCSI] SCSI default device flags
2231 Format: <integer>
2232
2233 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2234 Format: <vendor>:<model>:<flags>
2235 (flags are integer value)
2236
Randy Dunlap6af66322007-11-14 16:52:25 -08002237 scsi_logging_level= [SCSI] a bit mask of logging levels
2238 See drivers/scsi/scsi_logging.h for bits. Also
2239 settable via sysctl at dev.scsi.logging_level
2240 (/proc/sys/dev/scsi/logging_level).
2241 There is also a nice 'scsi_logging_level' script in the
2242 S390-tools package, available for download at
2243 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
Linus Torvalds1da177e2005-04-16 15:20:36 -07002244
Matthew Wilcox3e082a92006-09-28 15:19:20 -06002245 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2246 discovered. async scans them in kernel threads,
2247 allowing boot to proceed. none ignores them, expecting
2248 user space to do the scan.
2249
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002250 security= [SECURITY] Choose a security module to enable at boot.
2251 If this boot parameter is not specified, only the first
2252 security module asking for security registration will be
2253 loaded. An invalid security module name will be treated
2254 as if no module has been chosen.
2255
2256 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002257 Format: { "0" | "1" }
2258 See security/selinux/Kconfig help text.
2259 0 -- disable.
2260 1 -- enable.
2261 Default value is set via kernel config option.
2262 If enabled at boot time, /selinux/disable can be used
2263 later to disable prior to initial policy load.
2264
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002265 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002266
Linus Torvalds1da177e2005-04-16 15:20:36 -07002267 shapers= [NET]
2268 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002269
Yinghai Lub05f78f2008-08-22 01:32:50 -07002270 show_msr= [x86] show boot-time MSR settings
2271 Format: { <integer> }
2272 Show boot-time (BIOS-initialized) MSR settings.
2273 The parameter means the number of CPUs to show,
2274 for example 1 means boot CPU only.
2275
Linus Torvalds1da177e2005-04-16 15:20:36 -07002276 sim710= [SCSI,HW]
2277 See header of drivers/scsi/sim710.c.
2278
2279 simeth= [IA-64]
2280 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002281
Linus Torvalds1da177e2005-04-16 15:20:36 -07002282 slram= [HW,MTD]
2283
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002284 slub_debug[=options[,slabs]] [MM, SLUB]
2285 Enabling slub_debug allows one to determine the
2286 culprit if slab objects become corrupted. Enabling
2287 slub_debug can create guard zones around objects and
2288 may poison objects when not in use. Also tracks the
2289 last alloc / free. For more information see
2290 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002291
2292 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002293 Determines the maximum allowed order for slabs.
2294 A high setting may cause OOMs due to memory
2295 fragmentation. For more information see
2296 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002297
2298 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002299 The minimum number of objects per slab. SLUB will
2300 increase the slab order up to slub_max_order to
2301 generate a sufficiently large slab able to contain
2302 the number of objects indicated. The higher the number
2303 of objects the smaller the overhead of tracking slabs
2304 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002305 For more information see Documentation/vm/slub.txt.
2306
2307 slub_min_order= [MM, SLUB]
2308 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002309 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002310 For more information see Documentation/vm/slub.txt.
2311
2312 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002313 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002314 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002315 allocs to different slabs. Debug options disable
2316 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002317 For more information see Documentation/vm/slub.txt.
2318
Linus Torvalds1da177e2005-04-16 15:20:36 -07002319 smart2= [HW]
2320 Format: <io1>[,<io2>[,...,<io8>]]
2321
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002322 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002323 attempt to substitute SMP alternatives once at boot.
2324
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002325 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2326 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2327 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2328 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2329 smsc-ircc2.ircc_irq= [HW] IRQ line
2330 smsc-ircc2.ircc_dma= [HW] DMA channel
2331 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2332 0: Toshiba Satellite 1800 (GP data pin select)
2333 1: Fast pin select (default)
2334 2: ATC IRMode
2335
Linus Torvalds1da177e2005-04-16 15:20:36 -07002336 snd-ad1816a= [HW,ALSA]
2337
2338 snd-ad1848= [HW,ALSA]
2339
2340 snd-ali5451= [HW,ALSA]
2341
2342 snd-als100= [HW,ALSA]
2343
2344 snd-als4000= [HW,ALSA]
2345
2346 snd-azt2320= [HW,ALSA]
2347
2348 snd-cmi8330= [HW,ALSA]
2349
2350 snd-cmipci= [HW,ALSA]
2351
2352 snd-cs4231= [HW,ALSA]
2353
2354 snd-cs4232= [HW,ALSA]
2355
2356 snd-cs4236= [HW,ALSA]
2357
2358 snd-cs4281= [HW,ALSA]
2359
2360 snd-cs46xx= [HW,ALSA]
2361
2362 snd-dt019x= [HW,ALSA]
2363
2364 snd-dummy= [HW,ALSA]
2365
2366 snd-emu10k1= [HW,ALSA]
2367
2368 snd-ens1370= [HW,ALSA]
2369
2370 snd-ens1371= [HW,ALSA]
2371
2372 snd-es968= [HW,ALSA]
2373
2374 snd-es1688= [HW,ALSA]
2375
2376 snd-es18xx= [HW,ALSA]
2377
2378 snd-es1938= [HW,ALSA]
2379
2380 snd-es1968= [HW,ALSA]
2381
2382 snd-fm801= [HW,ALSA]
2383
2384 snd-gusclassic= [HW,ALSA]
2385
2386 snd-gusextreme= [HW,ALSA]
2387
2388 snd-gusmax= [HW,ALSA]
2389
2390 snd-hdsp= [HW,ALSA]
2391
2392 snd-ice1712= [HW,ALSA]
2393
2394 snd-intel8x0= [HW,ALSA]
2395
2396 snd-interwave= [HW,ALSA]
2397
2398 snd-interwave-stb=
2399 [HW,ALSA]
2400
2401 snd-korg1212= [HW,ALSA]
2402
2403 snd-maestro3= [HW,ALSA]
2404
2405 snd-mpu401= [HW,ALSA]
2406
2407 snd-mtpav= [HW,ALSA]
2408
2409 snd-nm256= [HW,ALSA]
2410
2411 snd-opl3sa2= [HW,ALSA]
2412
2413 snd-opti92x-ad1848=
2414 [HW,ALSA]
2415
2416 snd-opti92x-cs4231=
2417 [HW,ALSA]
2418
2419 snd-opti93x= [HW,ALSA]
2420
2421 snd-pmac= [HW,ALSA]
2422
2423 snd-rme32= [HW,ALSA]
2424
2425 snd-rme96= [HW,ALSA]
2426
2427 snd-rme9652= [HW,ALSA]
2428
2429 snd-sb8= [HW,ALSA]
2430
2431 snd-sb16= [HW,ALSA]
2432
2433 snd-sbawe= [HW,ALSA]
2434
2435 snd-serial= [HW,ALSA]
2436
2437 snd-sgalaxy= [HW,ALSA]
2438
2439 snd-sonicvibes= [HW,ALSA]
2440
2441 snd-sun-amd7930=
2442 [HW,ALSA]
2443
2444 snd-sun-cs4231= [HW,ALSA]
2445
2446 snd-trident= [HW,ALSA]
2447
2448 snd-usb-audio= [HW,ALSA,USB]
2449
2450 snd-via82xx= [HW,ALSA]
2451
2452 snd-virmidi= [HW,ALSA]
2453
2454 snd-wavefront= [HW,ALSA]
2455
2456 snd-ymfpci= [HW,ALSA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002457
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002458 softlockup_panic=
2459 [KNL] Should the soft-lockup detector generate panics.
2460
Linus Torvalds1da177e2005-04-16 15:20:36 -07002461 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2462 See Documentation/sonypi.txt
2463
2464 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002465 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002466
2467 spia_io_base= [HW,MTD]
2468 spia_fio_base=
2469 spia_pedr=
2470 spia_peddr=
2471
2472 sscape= [HW,OSS]
2473 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
Randy Dunlapa9913042005-10-23 12:57:11 -07002474
Linus Torvalds1da177e2005-04-16 15:20:36 -07002475 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2476 See Documentation/scsi/st.txt.
2477
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002478 stacktrace [FTRACE]
2479 Enabled the stack tracer on boot up.
2480
Linus Torvalds1da177e2005-04-16 15:20:36 -07002481 sti= [PARISC,HW]
2482 Format: <num>
2483 Set the STI (builtin display/keyboard on the HP-PARISC
2484 machines) console (graphic card) which should be used
2485 as the initial boot-console.
2486 See also comment in drivers/video/console/sticore.c.
2487
2488 sti_font= [HW]
2489 See comment in drivers/video/console/sticore.c.
2490
2491 stifb= [HW]
2492 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2493
Trond Myklebustcbf11072009-08-09 15:06:19 -04002494 sunrpc.min_resvport=
2495 sunrpc.max_resvport=
2496 [NFS,SUNRPC]
2497 SunRPC servers often require that client requests
2498 originate from a privileged port (i.e. a port in the
2499 range 0 < portnr < 1024).
2500 An administrator who wishes to reserve some of these
2501 ports for other uses may adjust the range that the
2502 kernel's sunrpc client considers to be privileged
2503 using these two parameters to set the minimum and
2504 maximum port values.
2505
Greg Banks42a7fc42007-03-06 01:42:23 -08002506 sunrpc.pool_mode=
2507 [NFS]
2508 Control how the NFS server code allocates CPUs to
2509 service thread pools. Depending on how many NICs
2510 you have and where their interrupts are bound, this
2511 option will affect which CPUs will do NFS serving.
2512 Note: this parameter cannot be changed while the
2513 NFS server is running.
2514
2515 auto the server chooses an appropriate mode
2516 automatically using heuristics
2517 global a single global pool contains all CPUs
2518 percpu one pool for each CPU
2519 pernode one pool for each NUMA node (equivalent
2520 to global on non-NUMA machines)
2521
Trond Myklebustcbf11072009-08-09 15:06:19 -04002522 sunrpc.tcp_slot_table_entries=
2523 sunrpc.udp_slot_table_entries=
2524 [NFS,SUNRPC]
2525 Sets the upper limit on the number of simultaneous
2526 RPC calls that can be sent from the client to a
2527 server. Increasing these values may allow you to
2528 improve throughput, but will also increase the
2529 amount of memory reserved for use by the client.
2530
Linus Torvalds1da177e2005-04-16 15:20:36 -07002531 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002532
Linus Torvalds1da177e2005-04-16 15:20:36 -07002533 switches= [HW,M68k]
2534
2535 sym53c416= [HW,SCSI]
2536 See header of drivers/scsi/sym53c416.c.
2537
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002538 sysrq_always_enabled
2539 [KNL]
2540 Ignore sysrq setting - this boot parameter will
2541 neutralize any effect of /proc/sys/kernel/sysrq.
2542 Useful for debugging.
2543
Linus Torvalds1da177e2005-04-16 15:20:36 -07002544 t128= [HW,SCSI]
2545 See header of drivers/scsi/t128.c.
2546
2547 tdfx= [HW,DRM]
2548
David Brownell77437fd2008-07-23 21:28:33 -07002549 test_suspend= [SUSPEND]
2550 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2551 standby suspend) as the system sleep state to briefly
2552 enter during system startup. The system is woken from
2553 this state using a wakeup-capable RTC alarm.
2554
Linus Torvalds1da177e2005-04-16 15:20:36 -07002555 thash_entries= [KNL,NET]
2556 Set number of hash buckets for TCP connection
2557
Len Brownf8707ec2007-08-12 00:12:54 -04002558 thermal.act= [HW,ACPI]
2559 -1: disable all active trip points in all thermal zones
2560 <degrees C>: override all lowest active trip points
2561
Len Brownc52a7412007-08-14 15:49:32 -04002562 thermal.crt= [HW,ACPI]
2563 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002564 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002565
Len Brownf5487142007-08-12 00:12:44 -04002566 thermal.nocrt= [HW,ACPI]
2567 Set to disable actions on ACPI thermal zone
2568 critical and hot trip points.
2569
Len Brown72b33ef2007-08-12 00:12:17 -04002570 thermal.off= [HW,ACPI]
2571 1: disable ACPI thermal control
2572
Len Browna70cdc52007-08-12 00:12:35 -04002573 thermal.psv= [HW,ACPI]
2574 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002575 <degrees C>: override all passive trip points to this
2576 value
Len Browna70cdc52007-08-12 00:12:35 -04002577
Len Brown730ff342007-08-12 00:12:26 -04002578 thermal.tzp= [HW,ACPI]
2579 Specify global default ACPI thermal zone polling rate
2580 <deci-seconds>: poll all this frequency
2581 0: no polling (default)
2582
Linus Torvalds1da177e2005-04-16 15:20:36 -07002583 tmscsim= [HW,SCSI]
2584 See comment before function dc390_setup() in
2585 drivers/scsi/tmscsim.c.
2586
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002587 topology= [S390]
2588 Format: {off | on}
2589 Specify if the kernel should make use of the cpu
2590 topology informations if the hardware supports these.
2591 The scheduler will make use of these informations and
2592 e.g. base its process migration decisions on it.
2593 Default is off.
2594
Linus Torvalds1da177e2005-04-16 15:20:36 -07002595 tp720= [HW,PS2]
2596
Li Zefan9d612be2009-06-24 17:33:15 +08002597 trace_buf_size=nn[KMG]
2598 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002599
Li Zefan020e5f82009-07-01 10:47:05 +08002600 trace_event=[event-list]
2601 [FTRACE] Set and start specified trace events in order
2602 to facilitate early boot debugging.
2603 See also Documentation/trace/events.txt
2604
Linus Torvalds1da177e2005-04-16 15:20:36 -07002605 trix= [HW,OSS] MediaTrix AudioTrix Pro
Randy Dunlapa9913042005-10-23 12:57:11 -07002606 Format:
2607 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2608
Alok Kataria395628e2008-10-24 17:22:01 -07002609 tsc= Disable clocksource-must-verify flag for TSC.
2610 Format: <string>
2611 [x86] reliable: mark tsc clocksource as reliable, this
2612 disables clocksource verification at runtime.
2613 Used to enable high-resolution timer mode on older
2614 hardware, and in virtualized environment.
2615
Randy Dunlapa9913042005-10-23 12:57:11 -07002616 turbografx.map[2|3]= [HW,JOY]
2617 TurboGraFX parallel port interface
2618 Format:
2619 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002620 See also Documentation/input/joystick-parport.txt
2621
2622 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2623 See header of drivers/scsi/u14-34f.c.
2624
2625 uart401= [HW,OSS]
2626 Format: <io>,<irq>
2627
2628 uart6850= [HW,OSS]
2629 Format: <io>,<irq>
2630
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002631 uhash_entries= [KNL,NET]
2632 Set number of hash buckets for UDP/UDP-Lite connections
2633
Alan Stern5f8364b2006-12-05 16:29:55 -05002634 uhci-hcd.ignore_oc=
2635 [USB] Ignore overcurrent events (default N).
2636 Some badly-designed motherboards generate lots of
2637 bogus events, for ports that aren't wired to
2638 anything. Set this parameter to avoid log spamming.
2639 Note that genuine overcurrent events won't be
2640 reported either.
2641
Simon Arlotte3a61b02008-07-19 23:32:54 +01002642 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302643 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002644 Set unknown_nmi_panic=1 early on boot.
2645
Alan Sternb5e795f2007-02-20 15:00:53 -05002646 usbcore.autosuspend=
2647 [USB] The autosuspend time delay (in seconds) used
2648 for newly-detected USB devices (default 2). This
2649 is the time required before an idle device will be
2650 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002651 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002652
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002653 usbcore.usbfs_snoop=
2654 [USB] Set to log all usbfs traffic (default 0 = off).
2655
2656 usbcore.blinkenlights=
2657 [USB] Set to cycle leds on hubs (default 0 = off).
2658
2659 usbcore.old_scheme_first=
2660 [USB] Start with the old device initialization
2661 scheme (default 0 = off).
2662
2663 usbcore.use_both_schemes=
2664 [USB] Try the other device initialization scheme
2665 if the first one fails (default 1 = enabled).
2666
2667 usbcore.initial_descriptor_timeout=
2668 [USB] Specifies timeout for the initial 64-byte
2669 USB_REQ_GET_DESCRIPTOR request in milliseconds
2670 (default 5000 = 5.0 seconds).
2671
Linus Torvalds1da177e2005-04-16 15:20:36 -07002672 usbhid.mousepoll=
2673 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002674
Alan Sternd4f373e2008-11-10 14:07:45 -05002675 usb-storage.delay_use=
2676 [UMS] The delay in seconds before a new device is
2677 scanned for Logical Units (default 5).
2678
2679 usb-storage.quirks=
2680 [UMS] A list of quirks entries to supplement or
2681 override the built-in unusual_devs list. List
2682 entries are separated by commas. Each entry has
2683 the form VID:PID:Flags where VID and PID are Vendor
2684 and Product ID values (4-digit hex numbers) and
2685 Flags is a set of characters, each corresponding
2686 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002687 a = SANE_SENSE (collect more than 18 bytes
2688 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002689 b = BAD_SENSE (don't collect more than 18
2690 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002691 c = FIX_CAPACITY (decrease the reported
2692 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002693 h = CAPACITY_HEURISTICS (decrease the
2694 reported device capacity by one
2695 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002696 i = IGNORE_DEVICE (don't bind to this
2697 device);
2698 l = NOT_LOCKABLE (don't try to lock and
2699 unlock ejectable media);
2700 m = MAX_SECTORS_64 (don't transfer more
2701 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002702 o = CAPACITY_OK (accept the capacity
2703 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002704 r = IGNORE_RESIDUE (the device reports
2705 bogus residue values);
2706 s = SINGLE_LUN (the device has only one
2707 Logical Unit);
2708 w = NO_WP_DETECT (don't test whether the
2709 medium is write-protected).
2710 Example: quirks=0419:aaf5:rl,0421:0433:rc
2711
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302712 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002713 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002714 vdso=1: enable VDSO (default)
2715 vdso=0: disable VDSO mapping
2716
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302717 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002718 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2719 vdso32=1: enable 32-bit VDSO (default)
2720 vdso32=0: disable 32-bit VDSO mapping
2721
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002722 vector= [IA-64,SMP]
2723 vector=percpu: enable percpu vector domain
2724
Linus Torvalds1da177e2005-04-16 15:20:36 -07002725 video= [FB] Frame buffer configuration
2726 See Documentation/fb/modedb.txt.
2727
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002728 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002729 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002730 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002731 Use vga=ask for menu.
2732 This is actually a boot loader parameter; the value is
2733 passed to the kernel using a special protocol.
2734
Randy Dunlapa9913042005-10-23 12:57:11 -07002735 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002736 size of <nn>. This can be used to increase the
2737 minimum size (128MB on x86). It can also be used to
2738 decrease the size and leave more room for directly
2739 mapped kernel RAM.
2740
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002741 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2742 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002743
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002744 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2745 Format: <command>
2746
2747 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2748 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002749
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002750 vt.cur_default= [VT] Default cursor shape.
2751 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2752 the parameters of the <Esc>[?A;B;Cc escape sequence;
2753 see VGA-softcursor.txt. Default: 2 = underline.
2754
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002755 vt.default_blu= [VT]
2756 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2757 Change the default blue palette of the console.
2758 This is a 16-member array composed of values
2759 ranging from 0-255.
2760
2761 vt.default_grn= [VT]
2762 Format: <green0>,<green1>,<green2>,...,<green15>
2763 Change the default green palette of the console.
2764 This is a 16-member array composed of values
2765 ranging from 0-255.
2766
2767 vt.default_red= [VT]
2768 Format: <red0>,<red1>,<red2>,...,<red15>
2769 Change the default red palette of the console.
2770 This is a 16-member array composed of values
2771 ranging from 0-255.
2772
2773 vt.default_utf8=
2774 [VT]
2775 Format=<0|1>
2776 Set system-wide default UTF-8 mode for all tty's.
2777 Default is 1, i.e. UTF-8 mode is enabled for all
2778 newly opened terminals.
2779
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002780 vt.global_cursor_default=
2781 [VT]
2782 Format=<-1|0|1>
2783 Set system-wide default for whether a cursor
2784 is shown on new VTs. Default is -1,
2785 i.e. cursors will be created by default unless
2786 overridden by individual drivers. 0 will hide
2787 cursors, 1 will display them.
2788
Linus Torvalds1da177e2005-04-16 15:20:36 -07002789 waveartist= [HW,OSS]
2790 Format: <io>,<irq>,<dma>,<dma2>
Randy Dunlapa9913042005-10-23 12:57:11 -07002791
Linus Torvalds1da177e2005-04-16 15:20:36 -07002792 wd33c93= [HW,SCSI]
2793 See header of drivers/scsi/wd33c93.c.
2794
2795 wd7000= [HW,SCSI]
2796 See header of drivers/scsi/wd7000.c.
2797
2798 wdt= [WDT] Watchdog
Gabriel C8dfe9c22007-08-10 13:01:00 -07002799 See Documentation/watchdog/wdt.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002800
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002801 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2802 default x2apic cluster mode on platforms
2803 supporting x2apic.
2804
Linus Torvalds1da177e2005-04-16 15:20:36 -07002805 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2806 xd_geo= See header of drivers/block/xd.c.
2807
2808 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002809 Format:
2810 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002811
Randy Dunlapa9913042005-10-23 12:57:11 -07002812______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002813
2814TODO:
2815
2816 Add documentation for ALSA options.
2817 Add more DRM drivers.