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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
202 acpi_irq_balance [HW,ACPI]
203 ACPI will balance active IRQs
204 default in APIC mode
205
206 acpi_irq_nobalance [HW,ACPI]
207 ACPI will not move active IRQs (default)
208 default in PIC mode
209
210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
211 Format: <irq>,<irq>...
212
213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
214 use by PCI
215 Format: <irq>,<irq>...
216
217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
218
219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
220 Format: To spoof as Windows 98: ="Microsoft Windows"
221
222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
223 acpi_osi="string1" # add string1 -- only one string
224 acpi_osi="!string2" # remove built-in string2
225 acpi_osi= # disable all strings
226
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530227 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700228 Override the pmtimer bug detection: force the kernel
229 to assume that this machine's pmtimer latches its value
230 and always returns good values.
231
Randy Dunlap4af94f32009-04-17 18:30:28 -0700232 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
233 Format: { level | edge | high | low }
234
235 acpi_serialize [HW,ACPI] force serialization of AML methods
236
237 acpi_skip_timer_override [HW,ACPI]
238 Recognize and ignore IRQ0/pin2 Interrupt Override.
239 For broken nForce2 BIOS resulting in XT-PIC timer.
240
241 acpi_sleep= [HW,ACPI] Sleep options
242 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
243 old_ordering, s4_nonvs }
244 See Documentation/power/video.txt for information on
245 s3_bios and s3_mode.
246 s3_beep is for debugging; it makes the PC's speaker beep
247 as soon as the kernel's real-mode entry point is called.
248 s4_nohwsig prevents ACPI hardware signature from being
249 used during resume from hibernation.
250 old_ordering causes the ACPI 1.0 ordering of the _PTS
251 control method, with respect to putting devices into
252 low power states, to be enforced (the ACPI 2.0 ordering
253 of _PTS is used by default).
254 s4_nonvs prevents the kernel from saving/restoring the
255 ACPI NVS memory during hibernation.
256
257 acpi_use_timer_override [HW,ACPI]
258 Use timer override. For some broken Nvidia NF5 boards
259 that require a timer override, but don't have HPET
260
Luca Tettamanti7e905602009-03-30 00:01:27 +0200261 acpi_enforce_resources= [ACPI]
262 { strict | lax | no }
263 Check for resource conflicts between native drivers
264 and ACPI OperationRegions (SystemIO and SystemMemory
265 only). IO ports and memory declared in ACPI might be
266 used by the ACPI subsystem in arbitrary AML code and
267 can interfere with legacy drivers.
268 strict (default): access to resources claimed by ACPI
269 is denied; legacy drivers trying to access reserved
270 resources will fail to bind to device using them.
271 lax: access to resources claimed by ACPI is allowed;
272 legacy drivers trying to access reserved resources
273 will bind successfully but a warning message is logged.
274 no: ACPI OperationRegions are not marked as reserved,
275 no further checks are performed.
276
Linus Torvalds1da177e2005-04-16 15:20:36 -0700277 ad1848= [HW,OSS]
278 Format: <io>,<irq>,<dma>,<dma2>,<type>
279
Randy Dunlap4af94f32009-04-17 18:30:28 -0700280 add_efi_memmap [EFI; X86] Include EFI memory map in
281 kernel's map of available physical RAM.
282
Linus Torvalds1da177e2005-04-16 15:20:36 -0700283 advansys= [HW,SCSI]
284 See header of drivers/scsi/advansys.c.
285
286 advwdt= [HW,WDT] Advantech WDT
287 Format: <iostart>,<iostop>
288
289 aedsp16= [HW,OSS] Audio Excel DSP 16
290 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
291 See also header of sound/oss/aedsp16.c.
Randy Dunlapa9913042005-10-23 12:57:11 -0700292
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700293 agp= [AGP]
294 { off | try_unsupported }
295 off: disable AGP support
296 try_unsupported: try to drive unsupported chipsets
297 (may crash computer or cause data corruption)
298
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299 aha152x= [HW,SCSI]
300 See Documentation/scsi/aha152x.txt.
301
302 aha1542= [HW,SCSI]
303 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
304
305 aic7xxx= [HW,SCSI]
306 See Documentation/scsi/aic7xxx.txt.
307
308 aic79xx= [HW,SCSI]
309 See Documentation/scsi/aic79xx.txt.
310
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200311 amd_iommu= [HW,X86-84]
312 Pass parameters to the AMD IOMMU driver in the system.
313 Possible values are:
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200314 isolate - enable device isolation (each device, as far
315 as possible, will get its own protection
Joerg Roedel3ce1f932008-11-17 15:09:20 +0100316 domain) [default]
Joerg Roedele5e1f602008-11-17 15:07:17 +0100317 share - put every device behind one IOMMU into the
318 same protection domain
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900319 fullflush - enable flushing of IO/TLB entries when
320 they are unmapped. Otherwise they are
321 flushed before they will be reused, which
322 is a lot of faster
323
Linus Torvalds1da177e2005-04-16 15:20:36 -0700324 amijoy.map= [HW,JOY] Amiga joystick support
325 Map of devices attached to JOY0DAT and JOY1DAT
326 Format: <a>,<b>
327 See also Documentation/kernel/input/joystick.txt
328
329 analog.map= [HW,JOY] Analog joystick and gamepad support
330 Specifies type or capabilities of an analog joystick
331 connected to one of 16 gameports
332 Format: <type1>,<type2>,..<type16>
333
Randy Dunlapa9913042005-10-23 12:57:11 -0700334 apc= [HW,SPARC]
335 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700336 Format: noidle
337 Disable APC CPU standby support. SPARCstation-Fox does
338 not play well with APC CPU idle - disable it if you have
339 APC and your system crashes randomly.
340
Randy Dunlapca1eda22009-05-06 16:02:58 -0700341 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700342 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343 Format: { quiet (default) | verbose | debug }
344 Change the amount of debugging information output
345 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700346
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400347 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
348 Limit apic dumping. The parameter defines the maximal
349 number of local apics being dumped. Also it is possible
350 to set it to "all" by meaning -- no limit here.
351 Format: { 1 (default) | 2 | ... | all }.
352 The parameter valid if only apic=debug or
353 apic=verbose is specified.
354 Example: apic=debug show_lapic=all
355
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700357 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358
Linus Torvalds1da177e2005-04-16 15:20:36 -0700359 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
360 Format: <io>,<irq>,<nodeID>
361
362 ataflop= [HW,M68k]
363
364 atarimouse= [HW,MOUSE] Atari Mouse
365
366 atascsi= [HW,SCSI] Atari SCSI
367
368 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
369 EzKey and similar keyboards
370
371 atkbd.reset= [HW] Reset keyboard during initialization
372
Randy Dunlapa9913042005-10-23 12:57:11 -0700373 atkbd.set= [HW] Select keyboard code set
374 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375
376 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
377 keyboards
378
379 atkbd.softraw= [HW] Choose between synthetic and real raw mode
380 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700381
382 atkbd.softrepeat= [HW]
383 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384
385 autotest [IA64]
386
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387 baycom_epp= [HW,AX25]
388 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700389
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
391 Format: <io>,<mode>
392 See header of drivers/net/hamradio/baycom_par.c.
393
Randy Dunlapa9913042005-10-23 12:57:11 -0700394 baycom_ser_fdx= [HW,AX25]
395 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700396 Format: <io>,<irq>,<mode>[,<baud>]
397 See header of drivers/net/hamradio/baycom_ser_fdx.c.
398
Randy Dunlapa9913042005-10-23 12:57:11 -0700399 baycom_ser_hdx= [HW,AX25]
400 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401 Format: <io>,<irq>,<mode>
402 See header of drivers/net/hamradio/baycom_ser_hdx.c.
403
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700404 boot_delay= Milliseconds to delay each printk during boot.
405 Values larger than 10 seconds (10000) are changed to
406 no delay (0).
407 Format: integer
408
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700409 bootmem_debug [KNL] Enable bootmem allocator debug messages.
410
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700412 bttv.radio= Most important insmod options are available as
413 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700414 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
415 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
416
417 BusLogic= [HW,SCSI]
418 See drivers/scsi/BusLogic.c, comment before function
419 BusLogic_ParseDriverOptions().
420
421 c101= [NET] Moxa C101 synchronous serial card
422
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700423 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700424 Sometimes CPU hardware bugs make them report the cache
425 size incorrectly. The kernel will attempt work arounds
426 to fix known problems, but for some CPUs it is not
427 possible to determine what the correct size should be.
428 This option provides an override for these situations.
429
James Morris20510f22007-10-16 23:31:32 -0700430 capability.disable=
431 [SECURITY] Disable capabilities. This would normally
432 be used only if an alternative security model is to be
433 configured. Potentially dangerous and should only be
434 used if you are entirely sure of the consequences.
435
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100436 ccw_timeout_log [S390]
437 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700438
Paul Menage8bab8dd2008-04-04 14:29:57 -0700439 cgroup_disable= [KNL] Disable a particular controller
440 Format: {name of the controller(s) to disable}
441 {Currently supported controllers - "memory"}
442
Linus Torvalds1da177e2005-04-16 15:20:36 -0700443 checkreqprot [SELINUX] Set initial checkreqprot flag value.
444 Format: { "0" | "1" }
445 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700446 0 -- check protection applied by kernel (includes
447 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700448 1 -- check protection requested by application.
449 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700450 Value can be changed at runtime via
451 /selinux/checkreqprot.
452
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100453 cio_ignore= [S390]
454 See Documentation/s390/CommonIO for details.
455
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700456 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700457 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200458 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700459 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200460 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700461 Format: { pit | tsc | cyclone | pmtmr }
462
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700463 clocksource= [GENERIC_TIME] Override the default clocksource
464 Format: <string>
465 Override the default clocksource and use the clocksource
466 with the name specified.
467 Some clocksource names to choose from, depending on
468 the platform:
469 [all] jiffies (this is the base, fallback clocksource)
470 [ACPI] acpi_pm
471 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
472 pxa_timer,timer3,32k_counter,timer0_1
473 [AVR32] avr32
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700474 [X86-32] pit,hpet,tsc,vmi-timer;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700475 scx200_hrt on Geode; cyclone on IBM x440
476 [MIPS] MIPS
477 [PARISC] cr16
478 [S390] tod
479 [SH] SuperH
480 [SPARC64] tick
481 [X86-64] hpet,tsc
482
Andi Kleenac72e782008-01-30 13:33:21 +0100483 clearcpuid=BITNUM [X86]
484 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800485 arch/x86/include/asm/cpufeature.h for the valid bit
486 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100487 stable over kernel options, but the vendor specific
488 ones should be.
489 Also note that user programs calling CPUID directly
490 or using the feature without checking anything
491 will still see it. This just prevents it from
492 being used by the kernel or shown in /proc/cpuinfo.
493 Also note the kernel might malfunction if you disable
494 some critical bits.
495
Robert Jennings14f966e2009-04-15 05:55:32 +0000496 cmo_free_hint= [PPC] Format: { yes | no }
497 Specify whether pages are marked as being inactive
498 when they are freed. This is used in CMO environments
499 to determine OS memory pressure for page stealing by
500 a hypervisor.
501 Default: yes
502
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530503 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100504 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100505 Range: 0 - 8192
506 Default: 64
507
Linus Torvalds1da177e2005-04-16 15:20:36 -0700508 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700509 Format:
510 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511
512 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
513 Format: <io>[,<irq>]
514
Randy Dunlapa9913042005-10-23 12:57:11 -0700515 com90xx= [HW,NET]
516 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700517 Format: <io>[,<irq>[,<memstart>]]
518
519 condev= [HW,S390] console device
520 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700521
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 console= [KNL] Output console device and options.
523
524 tty<n> Use the virtual console device <n>.
525
526 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800527 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700528 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800529 the form "bbbbpnf", where "bbbb" is the baud rate,
530 "p" is parity ("n", "o", or "e"), "n" is number of
531 bits, and "f" is flow control ("r" for RTS or
532 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800534 See Documentation/serial-console.txt for more
535 information. See
536 Documentation/networking/netconsole.txt for an
537 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700538
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700539 uart[8250],io,<addr>[,options]
540 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541 Start an early, polled-mode console on the 8250/16550
542 UART at the specified I/O port or MMIO address,
543 switching to the matching ttyS device later. The
544 options are the same as for ttyS, above.
545
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700546 If the device connected to the port is not a TTY but a braille
547 device, prepend "brl," before the device type, for instance
548 console=brl,ttyS0
549 For now, only VisioBraille is supported.
550
Daniel Mackf324edc2009-06-16 15:33:52 -0700551 consoleblank= [KNL] The console blank (screen saver) timeout in
552 seconds. Defaults to 10*60 = 10mins. A value of 0
553 disables the blank timer.
554
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800555 coredump_filter=
556 [KNL] Change the default value for
557 /proc/<pid>/coredump_filter.
558 See also Documentation/filesystems/proc.txt.
559
Linus Torvalds1da177e2005-04-16 15:20:36 -0700560 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700561 Format:
562 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700563
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700564 crashkernel=nn[KMG]@ss[KMG]
565 [KNL] Reserve a chunk of physical memory to
566 hold a kernel to switch to with kexec on panic.
567
Bernhard Wallefb391592007-10-18 23:41:02 -0700568 crashkernel=range1:size1[,range2:size2,...][@offset]
569 [KNL] Same as above, but depends on the memory
570 in the running system. The syntax of range is
571 start-[end] where start and end are both
572 a memory unit (amount[KMG]). See also
573 Documentation/kdump/kdump.txt for a example.
574
Linus Torvalds1da177e2005-04-16 15:20:36 -0700575 cs89x0_dma= [HW,NET]
576 Format: <dma>
577
578 cs89x0_media= [HW,NET]
579 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700580
Randy Dunlapa9913042005-10-23 12:57:11 -0700581 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582 See header of drivers/s390/block/dasd_devmap.c.
583
584 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
585 (one device per port)
586 Format: <port#>,<type>
587 See also Documentation/input/joystick-parport.txt
588
589 debug [KNL] Enable kernel debugging (events log level).
590
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700591 debug_locks_verbose=
592 [KNL] verbose self-tests
593 Format=<0|1>
594 Print debugging info while doing the locking API
595 self-tests.
596 We default to 0 (no extra messages), setting it to
597 1 will print _a lot_ more information - normally
598 only useful to kernel developers.
599
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700600 debug_objects [KNL] Enable object debugging
601
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500602 no_debug_objects
603 [KNL] Disable object debugging
604
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200605 debugpat [X86] Enable PAT debugging
606
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200607 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700608 Format: <area>[,<node>]
609 See also Documentation/networking/decnet.txt.
610
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700611 default_hugepagesz=
612 [same as hugepagesz=] The size of the default
613 HugeTLB page size. This is the size represented by
614 the legacy /proc/ hugepages APIs, used for SHM, and
615 default size when mounting hugetlbfs filesystems.
616 Defaults to the default architecture's huge page size
617 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700618
Linus Torvalds1da177e2005-04-16 15:20:36 -0700619 dhash_entries= [KNL]
620 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700621
Linus Torvalds1da177e2005-04-16 15:20:36 -0700622 digi= [HW,SERIAL]
623 IO parameters + enable/disable command.
624
625 digiepca= [HW,SERIAL]
626 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000627 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628
Yinghai Lu95ffa242008-04-29 03:52:33 -0700629 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700630 The kernel tries to adjust MTRR layout from continuous
631 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700632 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700633
Yinghai Lu093af8d2008-01-30 13:33:32 +0100634 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100635 By default the kernel will trim any uncacheable
636 memory out of your available memory pool based on
637 MTRR settings. This parameter disables that behavior,
638 possibly causing your machine to run very slowly.
639
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530640 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700641 Disable PIN 1 of APIC timer
642 Can be useful to work around chipset bugs.
643
Linus Torvalds1da177e2005-04-16 15:20:36 -0700644 dmasound= [HW,OSS] Sound subsystem buffers
645
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700646 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
647 this option disables the debugging code at boot.
648
649 dma_debug_entries=<number>
650 This option allows to tune the number of preallocated
651 entries for DMA-API debugging code. One entry is
652 required per DMA-API allocation. Use this if the
653 DMA-API debugging code disables itself because the
654 architectural default is too low.
655
Joerg Roedel1745de52009-05-22 21:49:51 +0200656 dma_debug_driver=<driver_name>
657 With this option the DMA-API debugging driver
658 filter feature can be enabled at boot time. Just
659 pass the driver to filter for as the parameter.
660 The filter can be disabled or changed to another
661 driver later using sysfs.
662
Linus Torvalds1da177e2005-04-16 15:20:36 -0700663 dscc4.setup= [NET]
664
665 dtc3181e= [HW,SCSI]
666
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700667 dynamic_printk Enables pr_debug()/dev_dbg() calls if
668 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
669 These can also be switched on/off via
670 <debugfs>/dynamic_printk/modules
671
672 earlycon= [KNL] Output early console device and options.
673 uart[8250],io,<addr>[,options]
674 uart[8250],mmio,<addr>[,options]
675 Start an early, polled-mode console on the 8250/16550
676 UART at the specified I/O port or MMIO address.
677 The options are the same as for ttyS, above.
678
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530679 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 earlyprintk=vga
681 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500682 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500683 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700684
Randy Dunlapa9913042005-10-23 12:57:11 -0700685 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700686 takes over.
687
Yinghai Lu5c059172008-07-24 17:29:40 -0700688 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700689
690 Currently only ttyS0 and ttyS1 are supported.
691
692 Interaction with the standard serial driver is not
693 very good.
694
695 The VGA output is eventually overwritten by the real
696 console.
697
698 eata= [HW,SCSI]
699
Linus Torvalds1da177e2005-04-16 15:20:36 -0700700 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700701 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700702
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703 eisa_irq_edge= [PARISC,HW]
704 See header of drivers/parisc/eisa.c.
705
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700706 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700707 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700708 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700709
710 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800711 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700712 See Documentation/block/as-iosched.txt and
713 Documentation/block/deadline-iosched.txt for details.
714
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530715 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700716 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800717 image elf header. Generally kexec loader will
718 pass this option to capture kernel.
719 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700721 enable_mtrr_cleanup [X86]
722 The kernel tries to adjust MTRR layout from continuous
723 to discrete, to make X server driver able to add WB
724 entry later. This parameter enables that.
725
Randy Dunlapca1eda22009-05-06 16:02:58 -0700726 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700727 Enable PIN 1 of APIC timer
728 Can be useful to work around chipset bugs
729 (in particular on some ATI chipsets).
730 The kernel tries to set a reasonable default.
731
Linus Torvalds1da177e2005-04-16 15:20:36 -0700732 enforcing [SELINUX] Set initial enforcing status.
733 Format: {"0" | "1"}
734 See security/selinux/Kconfig help text.
735 0 -- permissive (log only, no denials).
736 1 -- enforcing (deny and log).
737 Default value is 0.
738 Value can be changed at runtime via /selinux/enforce.
739
Linus Torvalds1da177e2005-04-16 15:20:36 -0700740 ether= [HW,NET] Ethernet cards parameters
741 This option is obsoleted by the "netdev=" option, which
742 has equivalent usage. See its documentation for details.
743
744 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
745 Format: <io>[,<irq>]
746
Akinobu Mitade1ba092006-12-08 02:39:42 -0800747 failslab=
748 fail_page_alloc=
749 fail_make_request=[KNL]
750 General fault injection mechanism.
751 Format: <interval>,<probability>,<space>,<times>
752 See also /Documentation/fault-injection/.
753
Linus Torvalds1da177e2005-04-16 15:20:36 -0700754 fd_mcs= [HW,SCSI]
755 See header of drivers/scsi/fd_mcs.c.
756
757 fdomain= [HW,SCSI]
758 See header of drivers/scsi/fdomain.c.
759
760 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000761 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700762
Alex Chiangf13ae302008-05-08 14:03:23 -0600763 force_pal_cache_flush
764 [IA-64] Avoid check_sal_cache_flush which may hang on
765 buggy SAL_CACHE_FLUSH implementations. Using this
766 parameter will force ia64_sal_cache_flush to call
767 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
768
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100769 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400770 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100771 as early as possible in order to facilitate early
772 boot debugging.
773
774 ftrace_dump_on_oops
Steven Rostedt2af15d62009-05-28 13:37:24 -0400775 [FTRACE] will dump the trace buffers on oops.
776
777 ftrace_filter=[function-list]
778 [FTRACE] Limit the functions traced by the function
779 tracer at boot up. function-list is a comma separated
780 list of functions. This list can be changed at run
781 time by the set_ftrace_filter file in the debugfs
782 tracing directory.
783
784 ftrace_notrace=[function-list]
785 [FTRACE] Do not trace the functions specified in
786 function-list. This list can be changed at run time
787 by the set_ftrace_notrace file in the debugfs
788 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100789
Stefan Assmann369bc182009-10-12 22:17:21 +0200790 ftrace_graph_filter=[function-list]
791 [FTRACE] Limit the top level callers functions traced
792 by the function graph tracer at boot up.
793 function-list is a comma separated list of functions
794 that can be changed at run time by the
795 set_graph_function file in the debugfs tracing directory.
796
Linus Torvalds1da177e2005-04-16 15:20:36 -0700797 gamecon.map[2|3]=
798 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
799 support via parallel port (up to 5 devices per port)
800 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
801 See also Documentation/input/joystick-parport.txt
802
803 gamma= [HW,DRM]
804
Yinghai Luaaf23042008-01-30 13:33:09 +0100805 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
806 Format: off | on
807 default: on
808
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700809 gcov_persist= [GCOV] When non-zero (default), profiling data for
810 kernel modules is saved and remains accessible via
811 debugfs, even when the module is unloaded/reloaded.
812 When zero, profiling data is discarded and associated
813 debugfs files are removed at module unload time.
814
Linus Torvalds1da177e2005-04-16 15:20:36 -0700815 gdth= [HW,SCSI]
816 See header of drivers/scsi/gdth.c.
817
818 gpt [EFI] Forces disk with valid GPT signature but
819 invalid Protective MBR to be treated as GPT.
820
Linus Torvalds1da177e2005-04-16 15:20:36 -0700821 gvp11= [HW,SCSI]
822
823 hashdist= [KNL,NUMA] Large hashes allocated during boot
824 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700825 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700826 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700827
828 hcl= [IA-64] SGI's Hardware Graph compatibility layer
829
830 hd= [EIDE] (E)IDE hard drive subsystem geometry
831 Format: <cyl>,<head>,<sect>
832
Linus Torvalds1da177e2005-04-16 15:20:36 -0700833 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
834 size of <nn>. This works even on boxes that have no
835 highmem otherwise. This also works to reduce highmem
836 size on bigger boxes.
837
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800838 highres= [KNL] Enable/disable high resolution timer mode.
839 Valid parameters: "on", "off"
840 Default: "on"
841
Linus Torvalds1da177e2005-04-16 15:20:36 -0700842 hisax= [HW,ISDN]
843 See Documentation/isdn/README.HiSax.
844
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700845 hlt [BUGS=ARM,SH]
846
847 hpet= [X86-32,HPET] option to control HPET usage
848 Format: { enable (default) | disable | force |
849 verbose }
850 disable: disable HPET and use PIT instead
851 force: allow force enabled of undocumented chips (ICH4,
852 VIA, nVidia)
853 verbose: show contents of HPET registers during setup
854
Andi Kleenb4718e62008-07-23 21:27:51 -0700855 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
856 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700857 On x86-64 and powerpc, this option can be specified
858 multiple times interleaved with hugepages= to reserve
859 huge pages of different sizes. Valid pages sizes on
860 x86-64 are 2M (when the CPU supports "pse") and 1G
861 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700862 Note that 1GB pages can only be allocated at boot time
863 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900864
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100865 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
866 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100867 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
868 If specified, z/VM IUCV HVC accepts connections
869 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100870
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700871 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700872 or register an additional I2C bus that is not
873 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700874 Format:
875 <bus_id>,<clkrate>
876
Jiri Kosina36d95732008-10-06 02:51:09 -0400877 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700878 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200879 i8042.dumbkbd [HW] Pretend that controller can only read data from
880 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700881 (Don't attempt to blink the leds)
882 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500883 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400884 i8042.noloop [HW] Disable the AUX Loopback command while probing
885 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700886 i8042.nomux [HW] Don't check presence of an active multiplexing
887 controller
888 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
889 controllers
890 i8042.panicblink=
891 [HW] Frequency with which keyboard LEDs should blink
892 when kernel panics (default is 0.5 sec)
893 i8042.reset [HW] Reset the controller during init and cleanup
894 i8042.unlock [HW] Unlock (ignore) the keylock
895
896 i810= [HW,DRM]
897
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700898 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
899 indicates that the driver is running on unsupported
900 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
902 does not match list of supported models.
903 i8k.power_status
904 [HW] Report power status in /proc/i8k
905 (disabled by default)
906 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
907 capability is set.
908
909 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
910 See Documentation/mca.txt.
911
912 icn= [HW,ISDN]
913 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
914
David Fries0af80c02009-02-25 20:28:21 +0100915 ide-core.nodma= [HW] (E)IDE subsystem
916 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200917 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
918 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100919 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700920
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700921 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
922 Claim all unknown PCI IDE storage controllers.
923
Andi Kleenf039b752007-05-02 19:27:12 +0200924 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800925 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
926 Poll forces a polling idle loop that can slightly
927 improve the performance of waking up a idle CPU, but
928 will use a lot of power and make the system run hot.
929 Not recommended.
930 idle=mwait: On systems which support MONITOR/MWAIT but
931 the kernel chose to not use it because it doesn't save
932 as much power as a normal idle loop, use the
933 MONITOR/MWAIT idle loop anyways. Performance should be
934 the same as idle=poll.
935 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800936 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800937 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700938
Ingo Molnar792908222006-12-06 20:40:51 -0800939 ignore_loglevel [KNL]
940 Ignore loglevel setting - this will print /all/
941 kernel messages to the console. Useful for debugging.
942
Linus Torvalds1da177e2005-04-16 15:20:36 -0700943 ihash_entries= [KNL]
944 Set number of hash buckets for inode cache.
945
Mimi Zohar3323eec2009-02-04 09:06:58 -0500946 ima_audit= [IMA]
947 Format: { "0" | "1" }
948 0 -- integrity auditing messages. (Default)
949 1 -- enable informational integrity auditing messages.
950
951 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700952 Format: { "sha1" | "md5" }
Mimi Zohar3323eec2009-02-04 09:06:58 -0500953 default: "sha1"
954
Eric Paris5789ba32009-05-21 15:47:06 -0400955 ima_tcb [IMA]
956 Load a policy which meets the needs of the Trusted
957 Computing Base. This means IMA will measure all
958 programs exec'd, files mmap'd for exec, and all files
959 opened for read by uid=0.
960
Linus Torvalds1da177e2005-04-16 15:20:36 -0700961 in2000= [HW,SCSI]
962 See header of drivers/scsi/in2000.c.
963
964 init= [KNL]
965 Format: <full_path>
966 Run specified binary instead of /sbin/init as init
967 process.
968
969 initcall_debug [KNL] Trace initcalls as they are executed. Useful
970 for working out where the kernel is dying during
971 startup.
972
973 initrd= [BOOT] Specify the location of the initial ramdisk
974
975 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
976 Format: <irq>
977
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700978 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800979 on
980 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700981 off
982 Disable intel iommu driver.
983 igfx_off [Default Off]
984 By default, gfx is mapped as normal device. If a gfx
985 device has a dedicated DMAR unit, the DMAR unit is
986 bypassed by not enabling DMAR with this option. In
987 this case, gfx device will use physical address for
988 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700989 forcedac [x86_64]
990 With this option iommu will not optimize to look
991 for io virtual address below 32 bit forcing dual
992 address cycle on pci bus for cards supporting greater
993 than 32 bit addressing. The default is to look
994 for translation below 32 bit and if not available
995 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -0800996 strict [Default Off]
997 With this option on every unmap_single operation will
998 result in a hardware IOTLB flush operation as opposed
999 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001000
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001001 inttest= [IA64]
1002
1003 iomem= Disable strict checking of access to MMIO memory
1004 strict regions from userspace.
1005 relaxed
1006
1007 iommu= [x86]
1008 off
1009 force
1010 noforce
1011 biomerge
1012 panic
1013 nopanic
1014 merge
1015 nomerge
1016 forcesac
1017 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001018 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001019
1020 io7= [HW] IO7 for Marvel based alpha systems
1021 See comment before marvel_specify_io7 in
1022 arch/alpha/kernel/core_marvel.c.
1023
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301024 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001025 0x80
1026 Standard port 0x80 based delay
1027 0xed
1028 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001029 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001030 Simple two microseconds delay
1031 none
1032 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001033
Linus Torvalds1da177e2005-04-16 15:20:36 -07001034 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001035 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036
1037 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001038 See comment before ip2_setup() in
1039 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001040
1041 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1042 See header of drivers/scsi/ips.c.
1043
Alan Cox200803d2005-06-28 20:45:18 -07001044 irqfixup [HW]
1045 When an interrupt is not handled search all handlers
1046 for it. Intended to get systems with badly broken
1047 firmware running.
1048
1049 irqpoll [HW]
1050 When an interrupt is not handled search all handlers
1051 for it. Also check all handlers each timer
1052 interrupt. Intended to get systems with badly broken
1053 firmware running.
1054
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001056 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001057
1058 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001059 Format:
1060 <cpu number>,...,<cpu number>
1061 or
Li Zefanb225d442008-11-06 12:53:39 -08001062 <cpu number>-<cpu number>
1063 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001064 or a mixture
1065 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001066
Linus Torvalds1da177e2005-04-16 15:20:36 -07001067 This option can be used to specify one or more CPUs
1068 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001069 algorithms. You can move a process onto or off an
1070 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071 <cpu number> begins at 0 and the maximum value is
1072 "number of CPUs in system - 1".
1073
1074 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001075 alternative -- manually setting the CPU mask of all
1076 tasks in the system -- can cause problems and
1077 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078
Randy Dunlapa9913042005-10-23 12:57:11 -07001079 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001080
1081 js= [HW,JOY] Analog joystick
1082 See Documentation/input/joystick.txt.
1083
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001084 keepinitrd [HW,ARM]
1085
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301086 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001087 specifies the amount of memory usable by the kernel
1088 for non-movable allocations. The requested amount is
1089 spread evenly throughout all nodes in the system. The
1090 remaining memory in each node is used for Movable
1091 pages. In the event, a node is too small to have both
1092 kernelcore and Movable pages, kernelcore pages will
1093 take priority and other nodes will have a larger number
1094 of kernelcore pages. The Movable zone is used for the
1095 allocation of pages that may be reclaimed or moved
1096 by the page migration subsystem. This means that
1097 HugeTLB pages may not be allocated from this zone.
1098 Note that allocations like PTEs-from-HighMem still
1099 use the HighMem zone if it exists, and the Normal
1100 zone if it does not.
1101
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001102 kgdboc= [HW] kgdb over consoles.
1103 Requires a tty driver that supports console polling.
Matt LaPlante19f59462009-04-27 15:06:31 +02001104 (only serial supported for now)
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001105 Format: <serial_device>[,baud]
1106
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001107 kmac= [MIPS] korina ethernet MAC address.
1108 Configure the RouterBoard 532 series on-chip
1109 Ethernet adapter MAC address.
1110
Catalin Marinas04f70332009-06-11 13:22:39 +01001111 kmemleak= [KNL] Boot-time kmemleak enable/disable
1112 Valid arguments: on, off
1113 Default: on
1114
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301115 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001116 in oops dumps.
1117
Andre Przywarafef07aa2009-07-10 14:20:35 +02001118 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1119 Default is 0 (don't ignore, but inject #GP)
1120
1121 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1122 Default is 1 (enabled)
1123
1124 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1125 Default is 0 (off)
1126
1127 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1128 for all guests.
1129 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1130
1131 kvm-intel.bypass_guest_pf=
1132 [KVM,Intel] Disables bypassing of guest page faults
1133 on Intel chips. Default is 1 (enabled)
1134
1135 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1136 (virtualized MMU) support on capable Intel chips.
1137 Default is 1 (enabled)
1138
1139 kvm-intel.emulate_invalid_guest_state=
1140 [KVM,Intel] Enable emulation of invalid guest states
1141 Default is 0 (disabled)
1142
1143 kvm-intel.flexpriority=
1144 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1145 Default is 1 (enabled)
1146
1147 kvm-intel.unrestricted_guest=
1148 [KVM,Intel] Disable unrestricted guest feature
1149 (virtualized real and unpaged mode) on capable
1150 Intel chips. Default is 1 (enabled)
1151
1152 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1153 feature (tagged TLBs) on capable Intel chips.
1154 Default is 1 (enabled)
1155
Linus Torvalds1da177e2005-04-16 15:20:36 -07001156 l2cr= [PPC]
1157
Robert Brosea78bfbf2008-03-29 07:20:23 +11001158 l3cr= [PPC]
1159
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001160 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001161 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001162
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301163 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001164 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001165
FD Camifcb71f62008-01-06 19:08:56 +01001166 libata.dma= [LIBATA] DMA control
1167 libata.dma=0 Disable all PATA and SATA DMA
1168 libata.dma=1 PATA and SATA Disk DMA only
1169 libata.dma=2 ATAPI (CDROM) DMA only
1170 libata.dma=4 Compact Flash DMA only
1171 Combinations also work, so libata.dma=3 enables DMA
1172 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001173
1174 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1175 libata.ignore_hpa=0 keep BIOS limits (default)
1176 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001177
Dave Jones78e70c22007-09-27 11:50:13 -04001178 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1179 when set.
1180 Format: <int>
1181
Tejun Heo33267322008-02-13 09:15:09 +09001182 libata.force= [LIBATA] Force configurations. The format is comma
1183 separated list of "[ID:]VAL" where ID is
1184 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1185 matching port, link or device. Basically, it matches
1186 the ATA ID string printed on console by libata. If
1187 the whole ID part is omitted, the last PORT and DEVICE
1188 values are used. If ID hasn't been specified yet, the
1189 configuration applies to all ports, links and devices.
1190
1191 If only DEVICE is omitted, the parameter applies to
1192 the port and all links and devices behind it. DEVICE
1193 number of 0 either selects the first device or the
1194 first fan-out link behind PMP device. It does not
1195 select the host link. DEVICE number of 15 selects the
1196 host link and device attached to it.
1197
1198 The VAL specifies the configuration to force. As long
1199 as there's no ambiguity shortcut notation is allowed.
1200 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1201 The following configurations can be forced.
1202
1203 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1204 Any ID with matching PORT is used.
1205
1206 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1207
1208 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1209 udma[/][16,25,33,44,66,100,133] notation is also
1210 allowed.
1211
1212 * [no]ncq: Turn on or off NCQ.
1213
Tejun Heo05944bd2008-08-13 20:19:09 +09001214 * nohrst, nosrst, norst: suppress hard, soft
1215 and both resets.
1216
Tejun Heo33267322008-02-13 09:15:09 +09001217 If there are multiple matching configurations changing
1218 the same attribute, the last one is used.
1219
Randy Dunlap7c4be252009-01-06 14:42:44 -08001220 lmb=debug [KNL] Enable lmb debug messages.
1221
Linus Torvalds1da177e2005-04-16 15:20:36 -07001222 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001223 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001224
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001225 lockd.nlm_grace_period=P [NFS] Assign grace period.
1226 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001227
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001228 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1229 Format: <integer>
1230
1231 lockd.nlm_timeout=T [NFS] Assign timeout value.
1232 Format: <integer>
1233
1234 lockd.nlm_udpport=M [NFS] Assign UDP port.
1235 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001236
1237 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1238 Format: <irq>
1239
1240 loglevel= All Kernel Messages with a loglevel smaller than the
1241 console loglevel will be printed to the console. It can
1242 also be changed with klogd or other programs. The
1243 loglevels are defined as follows:
1244
1245 0 (KERN_EMERG) system is unusable
1246 1 (KERN_ALERT) action must be taken immediately
1247 2 (KERN_CRIT) critical conditions
1248 3 (KERN_ERR) error conditions
1249 4 (KERN_WARNING) warning conditions
1250 5 (KERN_NOTICE) normal but significant condition
1251 6 (KERN_INFO) informational
1252 7 (KERN_DEBUG) debug-level messages
1253
1254 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001255 Format: { n | nk | nM }
1256 n must be a power of two. The default size
1257 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001258
Randy Dunlapaccaa242007-10-16 01:29:37 -07001259 logo.nologo [FB] Disables display of the built-in Linux logo.
1260 This may be used to provide more screen space for
1261 kernel log messages and is useful when debugging
1262 kernel boot problems.
1263
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264 lp=0 [LP] Specify parallel ports to use, e.g,
1265 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1266 lp=reset first parallel port). 'lp=0' disables the
1267 lp=auto printer driver. 'lp=reset' (which can be
1268 specified in addition to the ports) causes
1269 attached printers to be reset. Using
1270 lp=port1,port2,... specifies the parallel ports
1271 to associate lp devices with, starting with
1272 lp0. A port specification may be 'none' to skip
1273 that lp device, or a parport name such as
1274 'parport0'. Specifying 'lp=auto' instead of a
1275 port specification list means that device IDs
1276 from each port should be examined, to see if
1277 an IEEE 1284-compliant printer is attached; if
1278 so, the driver will manage that printer.
1279 See also header of drivers/char/lp.c.
1280
1281 lpj=n [KNL]
1282 Sets loops_per_jiffy to given constant, thus avoiding
1283 time-consuming boot-time autodetection (up to 250 ms per
1284 CPU). 0 enables autodetection (default). To determine
1285 the correct value for your kernel, boot with normal
1286 autodetection and see what value is printed. Note that
1287 on SMP systems the preset will be applied to all CPUs,
1288 which is likely to cause problems if your CPUs need
1289 significantly divergent settings. An incorrect value
1290 will cause delays in the kernel to be wrong, leading to
1291 unpredictable I/O errors and other breakage. Although
1292 unlikely, in the extreme case this might damage your
1293 hardware.
1294
1295 ltpc= [NET]
1296 Format: <io>,<irq>,<dma>
1297
Randy Dunlapa9913042005-10-23 12:57:11 -07001298 mac5380= [HW,SCSI] Format:
1299 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001300
Randy Dunlapa9913042005-10-23 12:57:11 -07001301 machvec= [IA64] Force the use of a particular machine-vector
1302 (machvec) in a generic kernel.
1303 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001304
Wu Zhangjin3209e702009-07-02 23:27:12 +08001305 machtype= [Loongson] Share the same kernel image file between different
1306 yeeloong laptop.
1307 Example: machtype=lemote-yeeloong-2f-7inch
1308
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001309 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1310 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001311
1312 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001313 should make use of. maxcpus=n : n >= 0 limits the
1314 kernel to using 'n' processors. n=0 is a special case,
1315 it is equivalent to "nosmp", which also disables
1316 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001317
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001318 max_loop= [LOOP] Maximum number of loopback devices that can
1319 be mounted
1320 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001321
Randy Dunlapa9913042005-10-23 12:57:11 -07001322 max_luns= [SCSI] Maximum number of LUNs to probe.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001323 Should be between 1 and 2^32-1.
1324
1325 max_report_luns=
Randy Dunlapa9913042005-10-23 12:57:11 -07001326 [SCSI] Maximum number of LUNs received.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001327 Should be between 1 and 16384.
1328
Linus Torvalds1da177e2005-04-16 15:20:36 -07001329 mcatest= [IA-64]
1330
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001331 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332
Uwe Hermann71cced62008-10-20 09:32:21 -07001333 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001334
Linus Torvalds1da177e2005-04-16 15:20:36 -07001335 md= [HW] RAID subsystems devices and level
1336 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001337
Linus Torvalds1da177e2005-04-16 15:20:36 -07001338 mdacon= [MDA]
1339 Format: <first>,<last>
1340 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001341
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1343 Amount of memory to be used when the kernel is not able
1344 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001345 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001346 address space collisions. Without memmap= PCI devices
1347 could be placed at addresses belonging to unused RAM.
1348
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001349 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001350 memory.
1351
Paul Mundt6902aa82008-09-21 17:14:42 +09001352 memchunk=nn[KMG]
1353 [KNL,SH] Allow user to override the default size for
1354 per-device physically contiguous DMA buffers.
1355
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301356 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001357 E820 memory map, as specified by the user.
1358 Such memmap=exactmap lines can be constructed based on
1359 BIOS output or other requirements. See the memmap=nn@ss
1360 option description.
1361
1362 memmap=nn[KMG]@ss[KMG]
1363 [KNL] Force usage of a specific region of memory
1364 Region of memory to be used, from ss to ss+nn.
1365
1366 memmap=nn[KMG]#ss[KMG]
1367 [KNL,ACPI] Mark specific memory as ACPI data.
1368 Region of memory to be used, from ss to ss+nn.
1369
1370 memmap=nn[KMG]$ss[KMG]
1371 [KNL,ACPI] Mark specific memory as reserved.
1372 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001373 Example: Exclude memory from 0x18690000-0x1869ffff
1374 memmap=64K$0x18690000
1375 or
1376 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001377
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001378 memory_corruption_check=0/1 [X86]
1379 Some BIOSes seem to corrupt the first 64k of
1380 memory when doing things like suspend/resume.
1381 Setting this option will scan the memory
1382 looking for corruption. Enabling this will
1383 both detect corruption and prevent the kernel
1384 from using the memory being corrupted.
1385 However, its intended as a diagnostic tool; if
1386 repeatable BIOS-originated corruption always
1387 affects the same memory, you can use memmap=
1388 to prevent the kernel from using that memory.
1389
1390 memory_corruption_check_size=size [X86]
1391 By default it checks for corruption in the low
1392 64k, making this memory unavailable for normal
1393 use. Use this parameter to scan for
1394 corruption in more or less memory.
1395
1396 memory_corruption_check_period=seconds [X86]
1397 By default it checks for corruption every 60
1398 seconds. Use this parameter to check at some
1399 other rate. 0 disables periodic checking.
1400
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001401 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001402 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001403 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001404 Specifies the number of memtest passes to be
1405 performed. Each pass selects another test
1406 pattern from a given set of patterns. Memtest
1407 fills the memory with this pattern, validates
1408 memory contents and reserves bad memory
1409 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001410
Linus Torvalds1da177e2005-04-16 15:20:36 -07001411 meye.*= [HW] Set MotionEye Camera parameters
1412 See Documentation/video4linux/meye.txt.
1413
Andres Salomon8f368812007-10-12 23:04:06 +02001414 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1415 Multi-Function General Purpose Timers on AMD Geode
1416 platforms.
1417
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001418 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1419 the BIOS has incorrectly applied a workaround. TinyBIOS
1420 version 0.98 is known to be affected, 0.99 fixes the
1421 problem by letting the user disable the workaround.
1422
Linus Torvalds1da177e2005-04-16 15:20:36 -07001423 mga= [HW,DRM]
1424
Randy Dunlap1c207f92008-11-19 15:36:16 -08001425 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1426 physical address is ignored.
1427
Michel Pollet39f45d72009-05-20 11:10:31 +01001428 mini2440= [ARM,HW,KNL]
1429 Format:[0..2][b][c][t]
1430 Default: "0tb"
1431 MINI2440 configuration specification:
1432 0 - The attached screen is the 3.5" TFT
1433 1 - The attached screen is the 7" TFT
1434 2 - The VGA Shield is attached (1024x768)
1435 Leaving out the screen size parameter will not load
1436 the TFT driver, and the framebuffer will be left
1437 unconfigured.
1438 b - Enable backlight. The TFT backlight pin will be
1439 linked to the kernel VESA blanking code and a GPIO
1440 LED. This parameter is not necessary when using the
1441 VGA shield.
1442 c - Enable the s3c camera interface.
1443 t - Reserved for enabling touchscreen support. The
1444 touchscreen support is not enabled in the mainstream
1445 kernel as of 2.6.30, a preliminary port can be found
1446 in the "bleeding edge" mini2440 support kernel at
1447 http://repo.or.cz/w/linux-2.6/mini2440.git
1448
Mel Gorman6b74ab92008-07-23 21:26:49 -07001449 mminit_loglevel=
1450 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1451 parameter allows control of the logging verbosity for
1452 the additional memory initialisation checks. A value
1453 of 0 disables mminit logging and a level of 4 will
1454 log everything. Information is printed at KERN_DEBUG
1455 so loglevel=8 may also need to be specified.
1456
Linus Torvalds1da177e2005-04-16 15:20:36 -07001457 mousedev.tap_time=
1458 [MOUSE] Maximum time between finger touching and
1459 leaving touchpad surface for touch to be considered
1460 a tap and be reported as a left button click (for
1461 touchpads working in absolute mode only).
1462 Format: <msecs>
1463 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1464 reporting absolute coordinates, such as tablets
1465 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1466 reporting absolute coordinates, such as tablets
1467
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301468 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001469 is similar to kernelcore except it specifies the
1470 amount of memory used for migratable allocations.
1471 If both kernelcore and movablecore is specified,
1472 then kernelcore will be at *least* the specified
1473 value but may be more. If movablecore on its own
1474 is specified, the administrator must be careful
1475 that the amount of memory usable for all allocations
1476 is not too small.
1477
Linus Torvalds1da177e2005-04-16 15:20:36 -07001478 mpu401= [HW,OSS]
1479 Format: <io>,<irq>
1480
1481 MTD_Partition= [MTD]
1482 Format: <name>,<region-number>,<size>,<offset>
1483
Randy Dunlapa9913042005-10-23 12:57:11 -07001484 MTD_Region= [MTD] Format:
1485 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001486
1487 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001488 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001490 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1491
1492 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1493
1494 boundary - index of last SLC block on Flex-OneNAND.
1495 The remaining blocks are configured as MLC blocks.
1496 lock - Configure if Flex-OneNAND boundary should be locked.
1497 Once locked, the boundary cannot be changed.
1498 1 indicates lock status, 0 indicates unlock status.
1499
Ben Dooks9db829f2008-07-03 11:24:29 +01001500 mtdset= [ARM]
1501 ARM/S3C2412 JIVE boot control
1502
1503 See arch/arm/mach-s3c2412/mach-jive.c
1504
Linus Torvalds1da177e2005-04-16 15:20:36 -07001505 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001506 [HW] Make the MicroTouch USB driver use raw coordinates
1507 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001508
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001509 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001510 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001511 that could hold holes aka. UC entries.
1512
1513 mtrr_gran_size=nn[KMG] [X86]
1514 Used for mtrr cleanup. It is granularity of mtrr block.
1515 Default is 1.
1516 Large value could prevent small alignment from
1517 using up MTRRs.
1518
1519 mtrr_spare_reg_nr=n [X86]
1520 Format: <integer>
1521 Range: 0,7 : spare reg number
1522 Default : 1
1523 Used for mtrr cleanup. It is spare mtrr entries number.
1524 Set to 2 or more if your graphical card needs more.
1525
Linus Torvalds1da177e2005-04-16 15:20:36 -07001526 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1527
1528 NCR_D700= [HW,SCSI]
1529 See header of drivers/scsi/NCR_D700.c.
1530
1531 ncr5380= [HW,SCSI]
1532
1533 ncr53c400= [HW,SCSI]
1534
1535 ncr53c400a= [HW,SCSI]
1536
1537 ncr53c406a= [HW,SCSI]
1538
1539 ncr53c8xx= [HW,SCSI]
1540
1541 netdev= [NET] Network devices parameters
1542 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1543 Note that mem_start is often overloaded to mean
1544 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001545 This usage is only documented in each driver source
1546 file if at all.
1547
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001548 nf_conntrack.acct=
1549 [NETFILTER] Enable connection tracking flow accounting
1550 0 to disable accounting
1551 1 to enable accounting
1552 Default value depends on CONFIG_NF_CT_ACCT that is
1553 going to be removed in 2.6.29.
1554
Linus Torvalds1da177e2005-04-16 15:20:36 -07001555 nfsaddrs= [NFS]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001556 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001557
1558 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001559 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560
Trond Myklebusta72b4422006-01-03 09:55:41 +01001561 nfs.callback_tcpport=
1562 [NFS] set the TCP port on which the NFSv4 callback
1563 channel should listen.
1564
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001565 nfs.cache_getent=
1566 [NFS] sets the pathname to the program which is used
1567 to update the NFS client cache entries.
1568
1569 nfs.cache_getent_timeout=
1570 [NFS] sets the timeout after which an attempt to
1571 update a cache entry is deemed to have failed.
1572
Trond Myklebust58df0952006-01-03 09:55:57 +01001573 nfs.idmap_cache_timeout=
1574 [NFS] set the maximum lifetime for idmapper cache
1575 entries.
1576
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001577 nfs.enable_ino64=
1578 [NFS] enable 64-bit inode numbers.
1579 If zero, the NFS client will fake up a 32-bit inode
1580 number for the readdir() and stat() syscalls instead
1581 of returning the full 64-bit number.
1582 The default is to return 64-bit inode numbers.
1583
Paul Mundt1e1030d2009-09-01 17:38:32 +09001584 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001585 when a NMI is triggered.
1586 Format: [state][,regs][,debounce][,die]
1587
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301588 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001589 Format: [panic,][num]
1590 Valid num: 0,1,2
1591 0 - turn nmi_watchdog off
1592 1 - use the IO-APIC timer for the NMI watchdog
1593 2 - use the local APIC for the NMI watchdog using
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001594 a performance counter. Note: This will use one
1595 performance counter and the local APIC's performance
1596 vector.
1597 When panic is specified, panic when an NMI watchdog
1598 timeout occurs.
1599 This is useful when you use a panic=... timeout and
1600 need the box quickly up again.
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001601 Instead of 1 and 2 it is possible to use the following
1602 symbolic names: lapic and ioapic
1603 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
Linus Torvalds1da177e2005-04-16 15:20:36 -07001604
Anton Vorontsovbff38772009-07-08 11:10:56 -07001605 netpoll.carrier_timeout=
1606 [NET] Specifies amount of time (in seconds) that
1607 netpoll should wait for a carrier. By default netpoll
1608 waits 4 seconds.
1609
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001610 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001611 emulation library even if a 387 maths coprocessor
1612 is present.
1613
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001614 no_console_suspend
1615 [HW] Never suspend the console
1616 Disable suspending of consoles during suspend and
1617 hibernate operations. Once disabled, debugging
1618 messages can reach various consoles while the rest
1619 of the system is being put to sleep (ie, while
1620 debugging driver suspend/resume hooks). This may
1621 not work reliably with all consoles, but is known
1622 to work with serial and VGA consoles.
1623
Christoph Lameterc1aee212007-05-31 00:40:47 -07001624 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1625 caches in the slab allocator. Saves per-node memory,
1626 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001627
Randy Dunlapa9913042005-10-23 12:57:11 -07001628 noalign [KNL,ARM]
1629
Linus Torvalds1da177e2005-04-16 15:20:36 -07001630 noapic [SMP,APIC] Tells the kernel to not make use of any
1631 IOAPICs that may be present in the system.
1632
Linus Torvalds1da177e2005-04-16 15:20:36 -07001633 nobats [PPC] Do not use BATs for mapping kernel lowmem
1634 on "Classic" PPC cores.
1635
1636 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001637
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001638 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1639
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001640 nodelayacct [KNL] Disable per-task delay accounting
1641
Linus Torvalds1da177e2005-04-16 15:20:36 -07001642 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1643
Paul Mundt6902aa82008-09-21 17:14:42 +09001644 nodsp [SH] Disable hardware DSP at boot time.
1645
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301646 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001647
Linus Torvalds1da177e2005-04-16 15:20:36 -07001648 noexec [IA-64]
1649
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301650 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001651 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001652 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001653 noexec=off: disable non-executable mappings
1654
1655 noexec32 [X86-64]
1656 This affects only 32-bit executables.
1657 noexec32=on: enable non-executable mappings (default)
1658 read doesn't imply executable mappings
1659 noexec32=off: disable non-executable mappings
1660 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001661
Paul Mundt6902aa82008-09-21 17:14:42 +09001662 nofpu [SH] Disable hardware FPU at boot time.
1663
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001664 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001665 register save and restore. The kernel will only save
1666 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001667
Suresh Siddha0c752a92009-05-22 12:17:45 -07001668 noxsave [BUGS=X86] Disables x86 extended register state save
1669 and restore using xsave. The kernel will fallback to
1670 enabling legacy floating-point and sse state.
1671
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001672 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1673 wfi(ARM) instruction doesn't work correctly and not to
1674 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001675
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001676 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001677 instruction doesn't work correctly and not to
1678 use it.
1679
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001680 no_file_caps Tells the kernel not to honor file capabilities. The
1681 only way then for a file to be executed with privilege
1682 is to be setuid root or executed by root.
1683
Linus Torvalds1da177e2005-04-16 15:20:36 -07001684 nohalt [IA-64] Tells the kernel not to use the power saving
1685 function PAL_HALT_LIGHT when idle. This increases
1686 power-consumption. On the positive side, it reduces
1687 interrupt wake-up latency, which may improve performance
1688 in certain environments such as networked servers or
1689 real-time systems.
1690
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001691 nohz= [KNL] Boottime enable/disable dynamic ticks
1692 Valid arguments: on, off
1693 Default: on
1694
Paul Mundteeee7852009-04-02 12:31:16 +09001695 noiotrap [SH] Disables trapped I/O port accesses.
1696
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001697 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001698 disable unhandled interrupt sources.
1699
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301700 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001701 broken timer IRQ sources.
1702
Linus Torvalds1da177e2005-04-16 15:20:36 -07001703 noisapnp [ISAPNP] Disables ISA PnP code.
1704
1705 noinitrd [RAM] Tells the kernel not to load any configured
1706 initial RAM disk.
1707
Weidong Han03ea8152009-04-17 16:42:15 +08001708 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1709 remapping.
1710
Linus Torvalds1da177e2005-04-16 15:20:36 -07001711 nointroute [IA-64]
1712
Tony Luck0aa366f2007-07-20 11:22:30 -07001713 nojitter [IA64] Disables jitter checking for ITC timers.
1714
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001715 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001716
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001717 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001718
Linus Torvalds1da177e2005-04-16 15:20:36 -07001719 noltlbs [PPC] Do not use large page/tlb entries for kernel
1720 lowmem mapping on PPC40x.
1721
Horms312f1f02006-02-22 09:57:55 +09001722 nomca [IA-64] Disable machine check abort handling
1723
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001724 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001725
Andres Salomon83d73842007-10-12 23:04:06 +02001726 nomfgpt [X86-32] Disable Multi-Function General Purpose
1727 Timer usage (for AMD Geode machines).
1728
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001729 norandmaps Don't use address space randomization. Equivalent to
1730 echo 0 > /proc/sys/kernel/randomize_va_space
1731
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001732 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001733
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001734 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001735 with UP alternatives
1736
Linus Torvalds1da177e2005-04-16 15:20:36 -07001737 noresidual [PPC] Don't use residual data on PReP machines.
1738
Randy Dunlapa9913042005-10-23 12:57:11 -07001739 noresume [SWSUSP] Disables resume and restores original swap
1740 space.
1741
Linus Torvalds1da177e2005-04-16 15:20:36 -07001742 no-scroll [VGA] Disables scrollback.
1743 This is required for the Braillex ib80-piezo Braille
1744 reader made by F.H. Papenmeier (Germany).
1745
1746 nosbagart [IA-64]
1747
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001748 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001749
Len Brown61ec7562007-08-16 03:34:22 -04001750 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1751 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001752
Dave Jones97842212007-07-15 23:41:05 -07001753 nosoftlockup [KNL] Disable the soft-lockup detector.
1754
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001755 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001756 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001757
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758 nosync [HW,M68K] Disables sync negotiation for all devices.
1759
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001760 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001761
1762 nousb [USB] Disable the USB subsystem
1763
1764 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001765
Weidong Han2b2fd872009-04-17 16:42:12 +08001766 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1767
Fenghua Yua6c75b862008-03-14 13:57:08 -07001768 nptcg= [IA64] Override max number of concurrent global TLB
1769 purges which is reported from either PAL_VM_SUMMARY or
1770 SAL PALO.
1771
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001772 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1773
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001774 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1775 one of ['zone', 'node', 'default'] can be specified
1776 This can be set from sysctl after boot.
1777 See Documentation/sysctl/vm.txt for details.
1778
Randy Dunlap7c4be252009-01-06 14:42:44 -08001779 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1780 See Documentation/debugging-via-ohci1394.txt for more
1781 info.
1782
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001783 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1784 Rather than timing out after 20 ms if an EC
1785 command is not properly ACKed, override the length
1786 of the timeout. We have interrupts disabled while
1787 waiting for the ACK, so if this is set too high
1788 interrupts *may* be lost!
1789
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001790 omap_mux= [OMAP] Override bootloader pin multiplexing.
1791 Format: <mux_mode0.mode_name=value>...
1792 For example, to override I2C bus2:
1793 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1794
Linus Torvalds1da177e2005-04-16 15:20:36 -07001795 opl3= [HW,OSS]
1796 Format: <io>
1797
Linus Torvalds1da177e2005-04-16 15:20:36 -07001798 oprofile.timer= [HW]
1799 Use timer interrupt instead of performance counters
1800
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001801 oprofile.cpu_type= Force an oprofile cpu type
1802 This might be useful if you have an older oprofile
1803 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001804 Format: { arch_perfmon }
1805 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001806 perfmon on Intel CPUs instead of the
1807 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001808
Linus Torvalds1da177e2005-04-16 15:20:36 -07001809 osst= [HW,SCSI] SCSI Tape Driver
1810 Format: <buffer_size>,<write_threshold>
1811 See also Documentation/scsi/st.txt.
1812
1813 panic= [KNL] Kernel behaviour on panic
1814 Format: <timeout>
1815
1816 parkbd.port= [HW] Parallel port number the keyboard adapter is
1817 connected to, default is 0.
1818 Format: <parport#>
1819 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1820 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001821 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001822
Randy Dunlapa9913042005-10-23 12:57:11 -07001823 parport= [HW,PPT] Specify parallel ports. 0 disables.
1824 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1825 Use 'auto' to force the driver to use any
1826 IRQ/DMA settings detected (the default is to
1827 ignore detected IRQ/DMA settings because of
1828 possible conflicts). You can specify the base
1829 address, IRQ, and DMA settings; IRQ and DMA
1830 should be numbers, or 'auto' (for using detected
1831 settings on that particular port), or 'nofifo'
1832 (to avoid using a FIFO even if it is detected).
1833 Parallel ports are assigned in the order they
1834 are specified on the command line, starting
1835 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001836
Randy Dunlapa9913042005-10-23 12:57:11 -07001837 parport_init_mode= [HW,PPT]
1838 Configure VIA parallel port to operate in
1839 a specific mode. This is necessary on Pegasos
1840 computer where firmware has no options for setting
1841 up parallel port mode and sets it to spp.
1842 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001843 Format: [spp|ps2|epp|ecp|ecpepp]
1844
Randy Dunlapa9913042005-10-23 12:57:11 -07001845 pas2= [HW,OSS] Format:
1846 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1847
Linus Torvalds1da177e2005-04-16 15:20:36 -07001848 pas16= [HW,SCSI]
1849 See header of drivers/scsi/pas16.c.
1850
Andrew Mortondd287792006-03-23 03:00:57 -08001851 pause_on_oops=
1852 Halt all CPUs after the first oops has been printed for
1853 the specified number of seconds. This is to be used if
1854 your oopses keep scrolling off the screen.
1855
Linus Torvalds1da177e2005-04-16 15:20:36 -07001856 pcbit= [HW,ISDN]
1857
1858 pcd. [PARIDE]
1859 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001860 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001861
Randy Dunlapa9913042005-10-23 12:57:11 -07001862 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001863 earlydump [X86] dump PCI config space before the kernel
1864 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001865 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001866 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001867 the hardware directly. Use this if your machine
1868 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001869 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001870 hardware access methods are allowed. Use this
1871 if you experience crashes upon bootup and you
1872 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001873 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001874 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001875 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001876 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001877 noaer [PCIE] If the PCIEAER kernel config parameter is
1878 enabled, this kernel boot option can be used to
1879 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001880 nodomains [PCI] Disable support for multiple PCI
1881 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301882 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001883 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001884 check_enable_amd_mmconf [X86] check for and enable
1885 properly configured MMIO access to PCI
1886 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001887 nomsi [MSI] If the PCI_MSI kernel config parameter is
1888 enabled, this kernel boot option can be used to
1889 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001890 noioapicquirk [APIC] Disable all boot interrupt quirks.
1891 Safety option to keep boot IRQs enabled. This
1892 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001893 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1894 primary IO-APIC for bridges that cannot disable
1895 boot IRQs. This fixes a source of spurious IRQs
1896 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001897 noioapicreroute [APIC] Disable workaround that uses the
1898 boot IRQ equivalent of an IRQ that connects to
1899 a chipset where boot IRQs cannot be disabled.
1900 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001901 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001902 routing table. These calls are known to be buggy
1903 on several machines and they hang the machine
1904 when used, but on other computers it's the only
1905 way to get the interrupt routing table. Try
1906 this option if the kernel is unable to allocate
1907 IRQs or discover secondary PCI buses on your
1908 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001909 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001910 Use with caution as certain devices share
1911 address decoders between ROMs and other
1912 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001913 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001914 expansion ROMs that do not already have
1915 BIOS assigned address ranges.
Andi Kleenc0115602008-08-22 09:53:39 +02001916 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001917 assigned automatically to PCI devices. You can
1918 make the kernel exclude IRQs of your ISA cards
1919 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001920 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001921 of the PIRQ table (normally generated
1922 by the BIOS) if it is outside the
1923 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001924 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001925 useful if the kernel is unable to find your
1926 secondary buses and you want to tell it
1927 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001928 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001929 numbers ourselves, overriding
1930 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001931 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001932 in the BIOS $PIR table. This is needed on
1933 some systems with broken BIOSes, notably
1934 some HP Pavilion N5400 and Omnibook XE3
1935 notebooks. This will have no effect if ACPI
1936 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001937 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001938 or for PCI scanning.
Linus Torvalds236e9462009-06-24 16:23:03 -07001939 use_crs [X86] Use _CRS for PCI resource
Gary Hade62f420f2007-10-03 15:56:51 -07001940 allocation.
Randy Dunlapa9913042005-10-23 12:57:11 -07001941 routeirq Do IRQ routing for all PCI devices.
1942 This is normally done in pci_enable_device(),
1943 so this option is a temporary workaround
1944 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001945 skip_isa_align [X86] do not align io start addr, so can
1946 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001947 firmware [ARM] Do not re-enumerate the bus but instead
1948 just use the configuration from the
1949 bootloader. This is currently used on
1950 IXP2000 systems where the bus has to be
1951 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001952 noearly [X86] Don't do any early type 1 scanning.
1953 This might help on some broken boards which
1954 machine check when some devices' config space
1955 is read. But various workarounds are disabled
1956 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001957 bfsort Sort PCI devices into breadth-first order.
1958 This sorting is done to get a device
1959 order compatible with older (<= 2.4) kernels.
1960 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001961 cbiosize=nn[KMG] The fixed amount of bus space which is
1962 reserved for the CardBus bridge's IO window.
1963 The default value is 256 bytes.
1964 cbmemsize=nn[KMG] The fixed amount of bus space which is
1965 reserved for the CardBus bridge's memory
1966 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09001967 resource_alignment=
1968 Format:
1969 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1970 Specifies alignment and device to reassign
1971 aligned memory resources.
1972 If <order of align> is not specified,
1973 PAGE_SIZE is used as alignment.
1974 PCI-PCI bridge can be specified, if resource
1975 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06001976 ecrc= Enable/disable PCIe ECRC (transaction layer
1977 end-to-end CRC checking).
1978 bios: Use BIOS/firmware settings. This is the
1979 the default.
1980 off: Turn ECRC off
1981 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001982
Chuck Ebberte5665a42008-09-24 20:40:34 -04001983 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1984 Management.
1985 off Disable ASPM.
1986 force Enable ASPM even on devices that claim not to support it.
1987 WARNING: Forcing ASPM on may cause system lockups.
1988
Linus Torvalds1da177e2005-04-16 15:20:36 -07001989 pcmv= [HW,PCMCIA] BadgePAD 4
1990
1991 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001992 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001993
1994 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1995 boot time.
1996 Format: { 0 | 1 }
1997 See arch/parisc/kernel/pdc_chassis.c
1998
Tejun Heof58dc012009-08-14 15:00:50 +09001999 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002000 Currently supported values are "embed" and "page".
2001 Archs may support subset or none of the selections.
2002 See comments in mm/percpu.c for details on each
2003 allocator. This parameter is primarily for debugging
2004 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002005
Linus Torvalds1da177e2005-04-16 15:20:36 -07002006 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002007 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002008
2009 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002010 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002011
2012 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002013 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002014
2015 plip= [PPT,NET] Parallel port network link
2016 Format: { parport<nr> | timid | 0 }
2017 See also Documentation/parport.txt.
2018
Thomas Gleixnerde32a2432008-07-12 05:33:30 +02002019 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2020 Override pmtimer IOPort with a hex value.
2021 e.g. pmtmr=0x508
2022
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002023 pnp.debug [PNP]
2024 Enable PNP debug messages. This depends on the
2025 CONFIG_PNP_DEBUG_MESSAGES option.
2026
Linus Torvalds1da177e2005-04-16 15:20:36 -07002027 pnpacpi= [ACPI]
2028 { off }
2029
2030 pnpbios= [ISAPNP]
2031 { on | off | curr | res | no-curr | no-res }
2032
2033 pnp_reserve_irq=
2034 [ISAPNP] Exclude IRQs for the autoconfiguration
2035
2036 pnp_reserve_dma=
2037 [ISAPNP] Exclude DMAs for the autoconfiguration
2038
2039 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002040 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041
2042 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002043 [ISAPNP] Exclude memory regions for the
2044 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002045 Ranges are in pairs (memory base and size).
2046
Randy Dunlap4af94f32009-04-17 18:30:28 -07002047 ports= [IP_VS_FTP] IPVS ftp helper module
2048 Default is 21.
2049 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2050 may be specified.
2051 Format: <port>,<port>....
2052
Ingo Molnar45807a12007-07-15 23:40:10 -07002053 print-fatal-signals=
2054 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002055
2056 If enabled, warn about various signal handling
2057 related application anomalies: too many signals,
2058 too many POSIX.1 timers, fatal signals causing a
2059 coredump - etc.
2060
2061 If you hit the warning due to signal overflow,
2062 you might want to try "ulimit -i unlimited".
2063
Ingo Molnar45807a12007-07-15 23:40:10 -07002064 default: off.
2065
Randy Dunlape84845c2007-07-15 23:40:25 -07002066 printk.time= Show timing data prefixed to each printk message line
2067 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2068
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002069 processor.max_cstate= [HW,ACPI]
2070 Limit processor to maximum C-state
2071 max_cstate=9 overrides any DMI blacklist limit.
2072
2073 processor.nocst [HW,ACPI]
2074 Ignore the _CST method to determine C-states,
2075 instead using the legacy FADT method
2076
Linus Torvalds1da177e2005-04-16 15:20:36 -07002077 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002078 Format: [schedule,]<number>
2079 Param: "schedule" - profile schedule points.
2080 Param: <number> - step/bucket size as a power of 2 for
2081 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002082 Param: "sleep" - profile D-state sleeping (millisecs).
2083 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002084 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002085
Linus Torvalds1da177e2005-04-16 15:20:36 -07002086 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2087 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002088 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002089
Randy Dunlapa9913042005-10-23 12:57:11 -07002090 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2091 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002092 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2093 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002094 psmouse.resetafter= [HW,MOUSE]
2095 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002096 (0 = never).
2097 psmouse.resolution=
2098 [HW,MOUSE] Set desired mouse resolution, in dpi.
2099 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002100 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002101 0 = disabled, 1 = enabled (default).
2102
2103 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
Randy Dunlapa9913042005-10-23 12:57:11 -07002104 Format:
2105 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002106
2107 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002108 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002109
Kay Sieversdc8c8582007-08-15 12:25:38 +02002110 pty.legacy_count=
2111 [KNL] Number of legacy pty's. Overwrites compiled-in
2112 default number.
2113
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002114 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002115
Linus Torvalds1da177e2005-04-16 15:20:36 -07002116 r128= [HW,DRM]
2117
2118 raid= [HW,RAID]
2119 See Documentation/md.txt.
2120
Randy Dunlapa9913042005-10-23 12:57:11 -07002121 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002122 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002123
Linus Torvalds1da177e2005-04-16 15:20:36 -07002124 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002125 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002126
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002127 rcupdate.blimit= [KNL,BOOT]
2128 Set maximum number of finished RCU callbacks to process
2129 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002130
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002131 rcupdate.qhimark= [KNL,BOOT]
2132 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002133 RCU callbacks over which batch limiting is disabled.
2134
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002135 rcupdate.qlowmark= [KNL,BOOT]
2136 Set threshold of queued RCU callbacks below which
2137 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002138
Olof Johanssonffdfc402005-09-06 15:17:19 -07002139 rdinit= [KNL]
2140 Format: <full_path>
2141 Run specified binary instead of /init from the ramdisk,
2142 used for early userspace startup. See initrd.
2143
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002144 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002145 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002146 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002147
Paul Jackson46b6d942008-07-04 10:00:09 -07002148 relax_domain_level=
2149 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002150 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002151
Linus Torvalds1da177e2005-04-16 15:20:36 -07002152 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2153
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002154 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07002155 Format: nn[KMG]
2156 Reserves a hole at the top of the kernel virtual
2157 address space.
2158
Vivek Goyal7e962872006-09-27 01:50:44 -07002159 reset_devices [KNL] Force drivers to reset the underlying device
2160 during initialization.
2161
Randy Dunlapa9913042005-10-23 12:57:11 -07002162 resume= [SWSUSP]
2163 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002164
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002165 resume_offset= [SWSUSP]
2166 Specify the offset from the beginning of the partition
2167 given by "resume=" at which the swap header is located,
2168 in <PAGE_SIZE> units (needed only for swap files).
2169 See Documentation/power/swsusp-and-swap-files.txt
2170
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002171 retain_initrd [RAM] Keep initrd memory after extraction
2172
Linus Torvalds1da177e2005-04-16 15:20:36 -07002173 rhash_entries= [KNL,NET]
2174 Set number of hash buckets for route cache
2175
2176 riscom8= [HW,SERIAL]
2177 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2178
2179 ro [KNL] Mount root device read-only on boot
2180
2181 root= [KNL] Root filesystem
2182
2183 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2184 mount the root filesystem
2185
2186 rootflags= [KNL] Set root filesystem mount option string
2187
2188 rootfstype= [KNL] Set root filesystem type
2189
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002190 rootwait [KNL] Wait (indefinitely) for root device to show up.
2191 Useful for devices that are detected asynchronously
2192 (e.g. USB and MMC devices).
2193
Linus Torvalds1da177e2005-04-16 15:20:36 -07002194 rw [KNL] Mount root device read-write on boot
2195
2196 S [KNL] Run init in single mode
2197
2198 sa1100ir [NET]
2199 See drivers/net/irda/sa1100_ir.c.
2200
Linus Torvalds1da177e2005-04-16 15:20:36 -07002201 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002202
Mike Travisf6630112009-11-17 18:22:15 -06002203 sched_debug [KNL] Enables verbose scheduler debug messages.
2204
Linus Torvalds1da177e2005-04-16 15:20:36 -07002205 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2206 Format: <io>[,<timeout>[,<isapnp>]]
2207
2208 scsi_debug_*= [SCSI]
2209 See drivers/scsi/scsi_debug.c.
2210
2211 scsi_default_dev_flags=
2212 [SCSI] SCSI default device flags
2213 Format: <integer>
2214
2215 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2216 Format: <vendor>:<model>:<flags>
2217 (flags are integer value)
2218
Randy Dunlap6af66322007-11-14 16:52:25 -08002219 scsi_logging_level= [SCSI] a bit mask of logging levels
2220 See drivers/scsi/scsi_logging.h for bits. Also
2221 settable via sysctl at dev.scsi.logging_level
2222 (/proc/sys/dev/scsi/logging_level).
2223 There is also a nice 'scsi_logging_level' script in the
2224 S390-tools package, available for download at
2225 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
Linus Torvalds1da177e2005-04-16 15:20:36 -07002226
Matthew Wilcox3e082a92006-09-28 15:19:20 -06002227 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2228 discovered. async scans them in kernel threads,
2229 allowing boot to proceed. none ignores them, expecting
2230 user space to do the scan.
2231
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002232 security= [SECURITY] Choose a security module to enable at boot.
2233 If this boot parameter is not specified, only the first
2234 security module asking for security registration will be
2235 loaded. An invalid security module name will be treated
2236 as if no module has been chosen.
2237
2238 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002239 Format: { "0" | "1" }
2240 See security/selinux/Kconfig help text.
2241 0 -- disable.
2242 1 -- enable.
2243 Default value is set via kernel config option.
2244 If enabled at boot time, /selinux/disable can be used
2245 later to disable prior to initial policy load.
2246
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002247 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002248
Linus Torvalds1da177e2005-04-16 15:20:36 -07002249 shapers= [NET]
2250 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002251
Yinghai Lub05f78f2008-08-22 01:32:50 -07002252 show_msr= [x86] show boot-time MSR settings
2253 Format: { <integer> }
2254 Show boot-time (BIOS-initialized) MSR settings.
2255 The parameter means the number of CPUs to show,
2256 for example 1 means boot CPU only.
2257
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258 sim710= [SCSI,HW]
2259 See header of drivers/scsi/sim710.c.
2260
2261 simeth= [IA-64]
2262 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002263
Linus Torvalds1da177e2005-04-16 15:20:36 -07002264 slram= [HW,MTD]
2265
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002266 slub_debug[=options[,slabs]] [MM, SLUB]
2267 Enabling slub_debug allows one to determine the
2268 culprit if slab objects become corrupted. Enabling
2269 slub_debug can create guard zones around objects and
2270 may poison objects when not in use. Also tracks the
2271 last alloc / free. For more information see
2272 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002273
2274 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002275 Determines the maximum allowed order for slabs.
2276 A high setting may cause OOMs due to memory
2277 fragmentation. For more information see
2278 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002279
2280 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002281 The minimum number of objects per slab. SLUB will
2282 increase the slab order up to slub_max_order to
2283 generate a sufficiently large slab able to contain
2284 the number of objects indicated. The higher the number
2285 of objects the smaller the overhead of tracking slabs
2286 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002287 For more information see Documentation/vm/slub.txt.
2288
2289 slub_min_order= [MM, SLUB]
2290 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002291 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002292 For more information see Documentation/vm/slub.txt.
2293
2294 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002295 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002296 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002297 allocs to different slabs. Debug options disable
2298 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002299 For more information see Documentation/vm/slub.txt.
2300
Linus Torvalds1da177e2005-04-16 15:20:36 -07002301 smart2= [HW]
2302 Format: <io1>[,<io2>[,...,<io8>]]
2303
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002304 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002305 attempt to substitute SMP alternatives once at boot.
2306
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002307 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2308 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2309 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2310 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2311 smsc-ircc2.ircc_irq= [HW] IRQ line
2312 smsc-ircc2.ircc_dma= [HW] DMA channel
2313 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2314 0: Toshiba Satellite 1800 (GP data pin select)
2315 1: Fast pin select (default)
2316 2: ATC IRMode
2317
Linus Torvalds1da177e2005-04-16 15:20:36 -07002318 snd-ad1816a= [HW,ALSA]
2319
2320 snd-ad1848= [HW,ALSA]
2321
2322 snd-ali5451= [HW,ALSA]
2323
2324 snd-als100= [HW,ALSA]
2325
2326 snd-als4000= [HW,ALSA]
2327
2328 snd-azt2320= [HW,ALSA]
2329
2330 snd-cmi8330= [HW,ALSA]
2331
2332 snd-cmipci= [HW,ALSA]
2333
2334 snd-cs4231= [HW,ALSA]
2335
2336 snd-cs4232= [HW,ALSA]
2337
2338 snd-cs4236= [HW,ALSA]
2339
2340 snd-cs4281= [HW,ALSA]
2341
2342 snd-cs46xx= [HW,ALSA]
2343
2344 snd-dt019x= [HW,ALSA]
2345
2346 snd-dummy= [HW,ALSA]
2347
2348 snd-emu10k1= [HW,ALSA]
2349
2350 snd-ens1370= [HW,ALSA]
2351
2352 snd-ens1371= [HW,ALSA]
2353
2354 snd-es968= [HW,ALSA]
2355
2356 snd-es1688= [HW,ALSA]
2357
2358 snd-es18xx= [HW,ALSA]
2359
2360 snd-es1938= [HW,ALSA]
2361
2362 snd-es1968= [HW,ALSA]
2363
2364 snd-fm801= [HW,ALSA]
2365
2366 snd-gusclassic= [HW,ALSA]
2367
2368 snd-gusextreme= [HW,ALSA]
2369
2370 snd-gusmax= [HW,ALSA]
2371
2372 snd-hdsp= [HW,ALSA]
2373
2374 snd-ice1712= [HW,ALSA]
2375
2376 snd-intel8x0= [HW,ALSA]
2377
2378 snd-interwave= [HW,ALSA]
2379
2380 snd-interwave-stb=
2381 [HW,ALSA]
2382
2383 snd-korg1212= [HW,ALSA]
2384
2385 snd-maestro3= [HW,ALSA]
2386
2387 snd-mpu401= [HW,ALSA]
2388
2389 snd-mtpav= [HW,ALSA]
2390
2391 snd-nm256= [HW,ALSA]
2392
2393 snd-opl3sa2= [HW,ALSA]
2394
2395 snd-opti92x-ad1848=
2396 [HW,ALSA]
2397
2398 snd-opti92x-cs4231=
2399 [HW,ALSA]
2400
2401 snd-opti93x= [HW,ALSA]
2402
2403 snd-pmac= [HW,ALSA]
2404
2405 snd-rme32= [HW,ALSA]
2406
2407 snd-rme96= [HW,ALSA]
2408
2409 snd-rme9652= [HW,ALSA]
2410
2411 snd-sb8= [HW,ALSA]
2412
2413 snd-sb16= [HW,ALSA]
2414
2415 snd-sbawe= [HW,ALSA]
2416
2417 snd-serial= [HW,ALSA]
2418
2419 snd-sgalaxy= [HW,ALSA]
2420
2421 snd-sonicvibes= [HW,ALSA]
2422
2423 snd-sun-amd7930=
2424 [HW,ALSA]
2425
2426 snd-sun-cs4231= [HW,ALSA]
2427
2428 snd-trident= [HW,ALSA]
2429
2430 snd-usb-audio= [HW,ALSA,USB]
2431
2432 snd-via82xx= [HW,ALSA]
2433
2434 snd-virmidi= [HW,ALSA]
2435
2436 snd-wavefront= [HW,ALSA]
2437
2438 snd-ymfpci= [HW,ALSA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002439
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002440 softlockup_panic=
2441 [KNL] Should the soft-lockup detector generate panics.
2442
Linus Torvalds1da177e2005-04-16 15:20:36 -07002443 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2444 See Documentation/sonypi.txt
2445
2446 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002447 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002448
2449 spia_io_base= [HW,MTD]
2450 spia_fio_base=
2451 spia_pedr=
2452 spia_peddr=
2453
2454 sscape= [HW,OSS]
2455 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
Randy Dunlapa9913042005-10-23 12:57:11 -07002456
Linus Torvalds1da177e2005-04-16 15:20:36 -07002457 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2458 See Documentation/scsi/st.txt.
2459
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002460 stacktrace [FTRACE]
2461 Enabled the stack tracer on boot up.
2462
Linus Torvalds1da177e2005-04-16 15:20:36 -07002463 sti= [PARISC,HW]
2464 Format: <num>
2465 Set the STI (builtin display/keyboard on the HP-PARISC
2466 machines) console (graphic card) which should be used
2467 as the initial boot-console.
2468 See also comment in drivers/video/console/sticore.c.
2469
2470 sti_font= [HW]
2471 See comment in drivers/video/console/sticore.c.
2472
2473 stifb= [HW]
2474 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2475
Trond Myklebustcbf11072009-08-09 15:06:19 -04002476 sunrpc.min_resvport=
2477 sunrpc.max_resvport=
2478 [NFS,SUNRPC]
2479 SunRPC servers often require that client requests
2480 originate from a privileged port (i.e. a port in the
2481 range 0 < portnr < 1024).
2482 An administrator who wishes to reserve some of these
2483 ports for other uses may adjust the range that the
2484 kernel's sunrpc client considers to be privileged
2485 using these two parameters to set the minimum and
2486 maximum port values.
2487
Greg Banks42a7fc42007-03-06 01:42:23 -08002488 sunrpc.pool_mode=
2489 [NFS]
2490 Control how the NFS server code allocates CPUs to
2491 service thread pools. Depending on how many NICs
2492 you have and where their interrupts are bound, this
2493 option will affect which CPUs will do NFS serving.
2494 Note: this parameter cannot be changed while the
2495 NFS server is running.
2496
2497 auto the server chooses an appropriate mode
2498 automatically using heuristics
2499 global a single global pool contains all CPUs
2500 percpu one pool for each CPU
2501 pernode one pool for each NUMA node (equivalent
2502 to global on non-NUMA machines)
2503
Trond Myklebustcbf11072009-08-09 15:06:19 -04002504 sunrpc.tcp_slot_table_entries=
2505 sunrpc.udp_slot_table_entries=
2506 [NFS,SUNRPC]
2507 Sets the upper limit on the number of simultaneous
2508 RPC calls that can be sent from the client to a
2509 server. Increasing these values may allow you to
2510 improve throughput, but will also increase the
2511 amount of memory reserved for use by the client.
2512
Linus Torvalds1da177e2005-04-16 15:20:36 -07002513 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002514
Linus Torvalds1da177e2005-04-16 15:20:36 -07002515 switches= [HW,M68k]
2516
2517 sym53c416= [HW,SCSI]
2518 See header of drivers/scsi/sym53c416.c.
2519
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002520 sysrq_always_enabled
2521 [KNL]
2522 Ignore sysrq setting - this boot parameter will
2523 neutralize any effect of /proc/sys/kernel/sysrq.
2524 Useful for debugging.
2525
Linus Torvalds1da177e2005-04-16 15:20:36 -07002526 t128= [HW,SCSI]
2527 See header of drivers/scsi/t128.c.
2528
2529 tdfx= [HW,DRM]
2530
David Brownell77437fd2008-07-23 21:28:33 -07002531 test_suspend= [SUSPEND]
2532 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2533 standby suspend) as the system sleep state to briefly
2534 enter during system startup. The system is woken from
2535 this state using a wakeup-capable RTC alarm.
2536
Linus Torvalds1da177e2005-04-16 15:20:36 -07002537 thash_entries= [KNL,NET]
2538 Set number of hash buckets for TCP connection
2539
Len Brownf8707ec2007-08-12 00:12:54 -04002540 thermal.act= [HW,ACPI]
2541 -1: disable all active trip points in all thermal zones
2542 <degrees C>: override all lowest active trip points
2543
Len Brownc52a7412007-08-14 15:49:32 -04002544 thermal.crt= [HW,ACPI]
2545 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002546 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002547
Len Brownf5487142007-08-12 00:12:44 -04002548 thermal.nocrt= [HW,ACPI]
2549 Set to disable actions on ACPI thermal zone
2550 critical and hot trip points.
2551
Len Brown72b33ef2007-08-12 00:12:17 -04002552 thermal.off= [HW,ACPI]
2553 1: disable ACPI thermal control
2554
Len Browna70cdc52007-08-12 00:12:35 -04002555 thermal.psv= [HW,ACPI]
2556 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002557 <degrees C>: override all passive trip points to this
2558 value
Len Browna70cdc52007-08-12 00:12:35 -04002559
Len Brown730ff342007-08-12 00:12:26 -04002560 thermal.tzp= [HW,ACPI]
2561 Specify global default ACPI thermal zone polling rate
2562 <deci-seconds>: poll all this frequency
2563 0: no polling (default)
2564
Linus Torvalds1da177e2005-04-16 15:20:36 -07002565 tmscsim= [HW,SCSI]
2566 See comment before function dc390_setup() in
2567 drivers/scsi/tmscsim.c.
2568
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002569 topology= [S390]
2570 Format: {off | on}
2571 Specify if the kernel should make use of the cpu
2572 topology informations if the hardware supports these.
2573 The scheduler will make use of these informations and
2574 e.g. base its process migration decisions on it.
2575 Default is off.
2576
Linus Torvalds1da177e2005-04-16 15:20:36 -07002577 tp720= [HW,PS2]
2578
Li Zefan9d612be2009-06-24 17:33:15 +08002579 trace_buf_size=nn[KMG]
2580 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002581
Li Zefan020e5f82009-07-01 10:47:05 +08002582 trace_event=[event-list]
2583 [FTRACE] Set and start specified trace events in order
2584 to facilitate early boot debugging.
2585 See also Documentation/trace/events.txt
2586
Linus Torvalds1da177e2005-04-16 15:20:36 -07002587 trix= [HW,OSS] MediaTrix AudioTrix Pro
Randy Dunlapa9913042005-10-23 12:57:11 -07002588 Format:
2589 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2590
Alok Kataria395628e2008-10-24 17:22:01 -07002591 tsc= Disable clocksource-must-verify flag for TSC.
2592 Format: <string>
2593 [x86] reliable: mark tsc clocksource as reliable, this
2594 disables clocksource verification at runtime.
2595 Used to enable high-resolution timer mode on older
2596 hardware, and in virtualized environment.
2597
Randy Dunlapa9913042005-10-23 12:57:11 -07002598 turbografx.map[2|3]= [HW,JOY]
2599 TurboGraFX parallel port interface
2600 Format:
2601 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002602 See also Documentation/input/joystick-parport.txt
2603
2604 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2605 See header of drivers/scsi/u14-34f.c.
2606
2607 uart401= [HW,OSS]
2608 Format: <io>,<irq>
2609
2610 uart6850= [HW,OSS]
2611 Format: <io>,<irq>
2612
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002613 uhash_entries= [KNL,NET]
2614 Set number of hash buckets for UDP/UDP-Lite connections
2615
Alan Stern5f8364b2006-12-05 16:29:55 -05002616 uhci-hcd.ignore_oc=
2617 [USB] Ignore overcurrent events (default N).
2618 Some badly-designed motherboards generate lots of
2619 bogus events, for ports that aren't wired to
2620 anything. Set this parameter to avoid log spamming.
2621 Note that genuine overcurrent events won't be
2622 reported either.
2623
Simon Arlotte3a61b02008-07-19 23:32:54 +01002624 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302625 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002626 Set unknown_nmi_panic=1 early on boot.
2627
Alan Sternb5e795f2007-02-20 15:00:53 -05002628 usbcore.autosuspend=
2629 [USB] The autosuspend time delay (in seconds) used
2630 for newly-detected USB devices (default 2). This
2631 is the time required before an idle device will be
2632 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002633 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002634
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002635 usbcore.usbfs_snoop=
2636 [USB] Set to log all usbfs traffic (default 0 = off).
2637
2638 usbcore.blinkenlights=
2639 [USB] Set to cycle leds on hubs (default 0 = off).
2640
2641 usbcore.old_scheme_first=
2642 [USB] Start with the old device initialization
2643 scheme (default 0 = off).
2644
2645 usbcore.use_both_schemes=
2646 [USB] Try the other device initialization scheme
2647 if the first one fails (default 1 = enabled).
2648
2649 usbcore.initial_descriptor_timeout=
2650 [USB] Specifies timeout for the initial 64-byte
2651 USB_REQ_GET_DESCRIPTOR request in milliseconds
2652 (default 5000 = 5.0 seconds).
2653
Linus Torvalds1da177e2005-04-16 15:20:36 -07002654 usbhid.mousepoll=
2655 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002656
Alan Sternd4f373e2008-11-10 14:07:45 -05002657 usb-storage.delay_use=
2658 [UMS] The delay in seconds before a new device is
2659 scanned for Logical Units (default 5).
2660
2661 usb-storage.quirks=
2662 [UMS] A list of quirks entries to supplement or
2663 override the built-in unusual_devs list. List
2664 entries are separated by commas. Each entry has
2665 the form VID:PID:Flags where VID and PID are Vendor
2666 and Product ID values (4-digit hex numbers) and
2667 Flags is a set of characters, each corresponding
2668 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002669 a = SANE_SENSE (collect more than 18 bytes
2670 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002671 b = BAD_SENSE (don't collect more than 18
2672 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002673 c = FIX_CAPACITY (decrease the reported
2674 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002675 h = CAPACITY_HEURISTICS (decrease the
2676 reported device capacity by one
2677 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002678 i = IGNORE_DEVICE (don't bind to this
2679 device);
2680 l = NOT_LOCKABLE (don't try to lock and
2681 unlock ejectable media);
2682 m = MAX_SECTORS_64 (don't transfer more
2683 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002684 o = CAPACITY_OK (accept the capacity
2685 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002686 r = IGNORE_RESIDUE (the device reports
2687 bogus residue values);
2688 s = SINGLE_LUN (the device has only one
2689 Logical Unit);
2690 w = NO_WP_DETECT (don't test whether the
2691 medium is write-protected).
2692 Example: quirks=0419:aaf5:rl,0421:0433:rc
2693
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302694 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002695 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002696 vdso=1: enable VDSO (default)
2697 vdso=0: disable VDSO mapping
2698
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302699 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002700 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2701 vdso32=1: enable 32-bit VDSO (default)
2702 vdso32=0: disable 32-bit VDSO mapping
2703
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002704 vector= [IA-64,SMP]
2705 vector=percpu: enable percpu vector domain
2706
Linus Torvalds1da177e2005-04-16 15:20:36 -07002707 video= [FB] Frame buffer configuration
2708 See Documentation/fb/modedb.txt.
2709
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002710 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002711 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002712 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002713 Use vga=ask for menu.
2714 This is actually a boot loader parameter; the value is
2715 passed to the kernel using a special protocol.
2716
Randy Dunlapa9913042005-10-23 12:57:11 -07002717 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002718 size of <nn>. This can be used to increase the
2719 minimum size (128MB on x86). It can also be used to
2720 decrease the size and leave more room for directly
2721 mapped kernel RAM.
2722
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002723 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2724 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002725
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002726 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2727 Format: <command>
2728
2729 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2730 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002731
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002732 vt.cur_default= [VT] Default cursor shape.
2733 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2734 the parameters of the <Esc>[?A;B;Cc escape sequence;
2735 see VGA-softcursor.txt. Default: 2 = underline.
2736
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002737 vt.default_blu= [VT]
2738 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2739 Change the default blue palette of the console.
2740 This is a 16-member array composed of values
2741 ranging from 0-255.
2742
2743 vt.default_grn= [VT]
2744 Format: <green0>,<green1>,<green2>,...,<green15>
2745 Change the default green palette of the console.
2746 This is a 16-member array composed of values
2747 ranging from 0-255.
2748
2749 vt.default_red= [VT]
2750 Format: <red0>,<red1>,<red2>,...,<red15>
2751 Change the default red palette of the console.
2752 This is a 16-member array composed of values
2753 ranging from 0-255.
2754
2755 vt.default_utf8=
2756 [VT]
2757 Format=<0|1>
2758 Set system-wide default UTF-8 mode for all tty's.
2759 Default is 1, i.e. UTF-8 mode is enabled for all
2760 newly opened terminals.
2761
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002762 vt.global_cursor_default=
2763 [VT]
2764 Format=<-1|0|1>
2765 Set system-wide default for whether a cursor
2766 is shown on new VTs. Default is -1,
2767 i.e. cursors will be created by default unless
2768 overridden by individual drivers. 0 will hide
2769 cursors, 1 will display them.
2770
Linus Torvalds1da177e2005-04-16 15:20:36 -07002771 waveartist= [HW,OSS]
2772 Format: <io>,<irq>,<dma>,<dma2>
Randy Dunlapa9913042005-10-23 12:57:11 -07002773
Linus Torvalds1da177e2005-04-16 15:20:36 -07002774 wd33c93= [HW,SCSI]
2775 See header of drivers/scsi/wd33c93.c.
2776
2777 wd7000= [HW,SCSI]
2778 See header of drivers/scsi/wd7000.c.
2779
2780 wdt= [WDT] Watchdog
Gabriel C8dfe9c22007-08-10 13:01:00 -07002781 See Documentation/watchdog/wdt.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002782
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002783 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2784 default x2apic cluster mode on platforms
2785 supporting x2apic.
2786
Linus Torvalds1da177e2005-04-16 15:20:36 -07002787 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2788 xd_geo= See header of drivers/block/xd.c.
2789
2790 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002791 Format:
2792 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002793
Randy Dunlapa9913042005-10-23 12:57:11 -07002794______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002795
2796TODO:
2797
2798 Add documentation for ALSA options.
2799 Add more DRM drivers.