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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,
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800243 old_ordering, s4_nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700244 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.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800256 sci_force_enable causes the kernel to set SCI_EN directly
257 on resume from S1/S3 (which is against the ACPI spec,
258 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700259
260 acpi_use_timer_override [HW,ACPI]
261 Use timer override. For some broken Nvidia NF5 boards
262 that require a timer override, but don't have HPET
263
Luca Tettamanti7e905602009-03-30 00:01:27 +0200264 acpi_enforce_resources= [ACPI]
265 { strict | lax | no }
266 Check for resource conflicts between native drivers
267 and ACPI OperationRegions (SystemIO and SystemMemory
268 only). IO ports and memory declared in ACPI might be
269 used by the ACPI subsystem in arbitrary AML code and
270 can interfere with legacy drivers.
271 strict (default): access to resources claimed by ACPI
272 is denied; legacy drivers trying to access reserved
273 resources will fail to bind to device using them.
274 lax: access to resources claimed by ACPI is allowed;
275 legacy drivers trying to access reserved resources
276 will bind successfully but a warning message is logged.
277 no: ACPI OperationRegions are not marked as reserved,
278 no further checks are performed.
279
Linus Torvalds1da177e2005-04-16 15:20:36 -0700280 ad1848= [HW,OSS]
281 Format: <io>,<irq>,<dma>,<dma2>,<type>
282
Randy Dunlap4af94f32009-04-17 18:30:28 -0700283 add_efi_memmap [EFI; X86] Include EFI memory map in
284 kernel's map of available physical RAM.
285
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286 advansys= [HW,SCSI]
287 See header of drivers/scsi/advansys.c.
288
289 advwdt= [HW,WDT] Advantech WDT
290 Format: <iostart>,<iostop>
291
292 aedsp16= [HW,OSS] Audio Excel DSP 16
293 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
294 See also header of sound/oss/aedsp16.c.
Randy Dunlapa9913042005-10-23 12:57:11 -0700295
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700296 agp= [AGP]
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
301
Linus Torvalds1da177e2005-04-16 15:20:36 -0700302 aha152x= [HW,SCSI]
303 See Documentation/scsi/aha152x.txt.
304
305 aha1542= [HW,SCSI]
306 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
307
308 aic7xxx= [HW,SCSI]
309 See Documentation/scsi/aic7xxx.txt.
310
311 aic79xx= [HW,SCSI]
312 See Documentation/scsi/aic79xx.txt.
313
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200314 amd_iommu= [HW,X86-84]
315 Pass parameters to the AMD IOMMU driver in the system.
316 Possible values are:
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200317 isolate - enable device isolation (each device, as far
318 as possible, will get its own protection
Joerg Roedel3ce1f932008-11-17 15:09:20 +0100319 domain) [default]
Joerg Roedele5e1f602008-11-17 15:07:17 +0100320 share - put every device behind one IOMMU into the
321 same protection domain
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900322 fullflush - enable flushing of IO/TLB entries when
323 they are unmapped. Otherwise they are
324 flushed before they will be reused, which
325 is a lot of faster
326
Linus Torvalds1da177e2005-04-16 15:20:36 -0700327 amijoy.map= [HW,JOY] Amiga joystick support
328 Map of devices attached to JOY0DAT and JOY1DAT
329 Format: <a>,<b>
330 See also Documentation/kernel/input/joystick.txt
331
332 analog.map= [HW,JOY] Analog joystick and gamepad support
333 Specifies type or capabilities of an analog joystick
334 connected to one of 16 gameports
335 Format: <type1>,<type2>,..<type16>
336
Randy Dunlapa9913042005-10-23 12:57:11 -0700337 apc= [HW,SPARC]
338 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700339 Format: noidle
340 Disable APC CPU standby support. SPARCstation-Fox does
341 not play well with APC CPU idle - disable it if you have
342 APC and your system crashes randomly.
343
Randy Dunlapca1eda22009-05-06 16:02:58 -0700344 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700345 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700346 Format: { quiet (default) | verbose | debug }
347 Change the amount of debugging information output
348 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700349
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400350 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
351 Limit apic dumping. The parameter defines the maximal
352 number of local apics being dumped. Also it is possible
353 to set it to "all" by meaning -- no limit here.
354 Format: { 1 (default) | 2 | ... | all }.
355 The parameter valid if only apic=debug or
356 apic=verbose is specified.
357 Example: apic=debug show_lapic=all
358
Linus Torvalds1da177e2005-04-16 15:20:36 -0700359 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700360 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700361
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
363 Format: <io>,<irq>,<nodeID>
364
365 ataflop= [HW,M68k]
366
367 atarimouse= [HW,MOUSE] Atari Mouse
368
369 atascsi= [HW,SCSI] Atari SCSI
370
371 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
372 EzKey and similar keyboards
373
374 atkbd.reset= [HW] Reset keyboard during initialization
375
Randy Dunlapa9913042005-10-23 12:57:11 -0700376 atkbd.set= [HW] Select keyboard code set
377 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378
379 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
380 keyboards
381
382 atkbd.softraw= [HW] Choose between synthetic and real raw mode
383 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700384
385 atkbd.softrepeat= [HW]
386 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387
388 autotest [IA64]
389
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390 baycom_epp= [HW,AX25]
391 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700392
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
394 Format: <io>,<mode>
395 See header of drivers/net/hamradio/baycom_par.c.
396
Randy Dunlapa9913042005-10-23 12:57:11 -0700397 baycom_ser_fdx= [HW,AX25]
398 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399 Format: <io>,<irq>,<mode>[,<baud>]
400 See header of drivers/net/hamradio/baycom_ser_fdx.c.
401
Randy Dunlapa9913042005-10-23 12:57:11 -0700402 baycom_ser_hdx= [HW,AX25]
403 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700404 Format: <io>,<irq>,<mode>
405 See header of drivers/net/hamradio/baycom_ser_hdx.c.
406
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700407 boot_delay= Milliseconds to delay each printk during boot.
408 Values larger than 10 seconds (10000) are changed to
409 no delay (0).
410 Format: integer
411
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700412 bootmem_debug [KNL] Enable bootmem allocator debug messages.
413
Linus Torvalds1da177e2005-04-16 15:20:36 -0700414 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700415 bttv.radio= Most important insmod options are available as
416 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700417 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
418 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
419
420 BusLogic= [HW,SCSI]
421 See drivers/scsi/BusLogic.c, comment before function
422 BusLogic_ParseDriverOptions().
423
424 c101= [NET] Moxa C101 synchronous serial card
425
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700426 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700427 Sometimes CPU hardware bugs make them report the cache
428 size incorrectly. The kernel will attempt work arounds
429 to fix known problems, but for some CPUs it is not
430 possible to determine what the correct size should be.
431 This option provides an override for these situations.
432
James Morris20510f22007-10-16 23:31:32 -0700433 capability.disable=
434 [SECURITY] Disable capabilities. This would normally
435 be used only if an alternative security model is to be
436 configured. Potentially dangerous and should only be
437 used if you are entirely sure of the consequences.
438
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100439 ccw_timeout_log [S390]
440 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700441
Paul Menage8bab8dd2008-04-04 14:29:57 -0700442 cgroup_disable= [KNL] Disable a particular controller
443 Format: {name of the controller(s) to disable}
444 {Currently supported controllers - "memory"}
445
Linus Torvalds1da177e2005-04-16 15:20:36 -0700446 checkreqprot [SELINUX] Set initial checkreqprot flag value.
447 Format: { "0" | "1" }
448 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700449 0 -- check protection applied by kernel (includes
450 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700451 1 -- check protection requested by application.
452 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700453 Value can be changed at runtime via
454 /selinux/checkreqprot.
455
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100456 cio_ignore= [S390]
457 See Documentation/s390/CommonIO for details.
458
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700459 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700460 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200461 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700462 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200463 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700464 Format: { pit | tsc | cyclone | pmtmr }
465
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700466 clocksource= [GENERIC_TIME] Override the default clocksource
467 Format: <string>
468 Override the default clocksource and use the clocksource
469 with the name specified.
470 Some clocksource names to choose from, depending on
471 the platform:
472 [all] jiffies (this is the base, fallback clocksource)
473 [ACPI] acpi_pm
474 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
475 pxa_timer,timer3,32k_counter,timer0_1
476 [AVR32] avr32
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700477 [X86-32] pit,hpet,tsc,vmi-timer;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700478 scx200_hrt on Geode; cyclone on IBM x440
479 [MIPS] MIPS
480 [PARISC] cr16
481 [S390] tod
482 [SH] SuperH
483 [SPARC64] tick
484 [X86-64] hpet,tsc
485
Andi Kleenac72e782008-01-30 13:33:21 +0100486 clearcpuid=BITNUM [X86]
487 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800488 arch/x86/include/asm/cpufeature.h for the valid bit
489 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100490 stable over kernel options, but the vendor specific
491 ones should be.
492 Also note that user programs calling CPUID directly
493 or using the feature without checking anything
494 will still see it. This just prevents it from
495 being used by the kernel or shown in /proc/cpuinfo.
496 Also note the kernel might malfunction if you disable
497 some critical bits.
498
Robert Jennings14f966e2009-04-15 05:55:32 +0000499 cmo_free_hint= [PPC] Format: { yes | no }
500 Specify whether pages are marked as being inactive
501 when they are freed. This is used in CMO environments
502 to determine OS memory pressure for page stealing by
503 a hypervisor.
504 Default: yes
505
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530506 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100507 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100508 Range: 0 - 8192
509 Default: 64
510
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700512 Format:
513 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700514
515 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
516 Format: <io>[,<irq>]
517
Randy Dunlapa9913042005-10-23 12:57:11 -0700518 com90xx= [HW,NET]
519 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520 Format: <io>[,<irq>[,<memstart>]]
521
522 condev= [HW,S390] console device
523 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700524
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 console= [KNL] Output console device and options.
526
527 tty<n> Use the virtual console device <n>.
528
529 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800530 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700531 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800532 the form "bbbbpnf", where "bbbb" is the baud rate,
533 "p" is parity ("n", "o", or "e"), "n" is number of
534 bits, and "f" is flow control ("r" for RTS or
535 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800537 See Documentation/serial-console.txt for more
538 information. See
539 Documentation/networking/netconsole.txt for an
540 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700542 uart[8250],io,<addr>[,options]
543 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544 Start an early, polled-mode console on the 8250/16550
545 UART at the specified I/O port or MMIO address,
546 switching to the matching ttyS device later. The
547 options are the same as for ttyS, above.
548
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700549 If the device connected to the port is not a TTY but a braille
550 device, prepend "brl," before the device type, for instance
551 console=brl,ttyS0
552 For now, only VisioBraille is supported.
553
Daniel Mackf324edc2009-06-16 15:33:52 -0700554 consoleblank= [KNL] The console blank (screen saver) timeout in
555 seconds. Defaults to 10*60 = 10mins. A value of 0
556 disables the blank timer.
557
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800558 coredump_filter=
559 [KNL] Change the default value for
560 /proc/<pid>/coredump_filter.
561 See also Documentation/filesystems/proc.txt.
562
Linus Torvalds1da177e2005-04-16 15:20:36 -0700563 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700564 Format:
565 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700567 crashkernel=nn[KMG]@ss[KMG]
568 [KNL] Reserve a chunk of physical memory to
569 hold a kernel to switch to with kexec on panic.
570
Bernhard Wallefb391592007-10-18 23:41:02 -0700571 crashkernel=range1:size1[,range2:size2,...][@offset]
572 [KNL] Same as above, but depends on the memory
573 in the running system. The syntax of range is
574 start-[end] where start and end are both
575 a memory unit (amount[KMG]). See also
576 Documentation/kdump/kdump.txt for a example.
577
Linus Torvalds1da177e2005-04-16 15:20:36 -0700578 cs89x0_dma= [HW,NET]
579 Format: <dma>
580
581 cs89x0_media= [HW,NET]
582 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700583
Randy Dunlapa9913042005-10-23 12:57:11 -0700584 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700585 See header of drivers/s390/block/dasd_devmap.c.
586
587 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
588 (one device per port)
589 Format: <port#>,<type>
590 See also Documentation/input/joystick-parport.txt
591
592 debug [KNL] Enable kernel debugging (events log level).
593
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700594 debug_locks_verbose=
595 [KNL] verbose self-tests
596 Format=<0|1>
597 Print debugging info while doing the locking API
598 self-tests.
599 We default to 0 (no extra messages), setting it to
600 1 will print _a lot_ more information - normally
601 only useful to kernel developers.
602
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700603 debug_objects [KNL] Enable object debugging
604
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500605 no_debug_objects
606 [KNL] Disable object debugging
607
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200608 debugpat [X86] Enable PAT debugging
609
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200610 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700611 Format: <area>[,<node>]
612 See also Documentation/networking/decnet.txt.
613
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700614 default_hugepagesz=
615 [same as hugepagesz=] The size of the default
616 HugeTLB page size. This is the size represented by
617 the legacy /proc/ hugepages APIs, used for SHM, and
618 default size when mounting hugetlbfs filesystems.
619 Defaults to the default architecture's huge page size
620 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700621
Linus Torvalds1da177e2005-04-16 15:20:36 -0700622 dhash_entries= [KNL]
623 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700624
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625 digi= [HW,SERIAL]
626 IO parameters + enable/disable command.
627
628 digiepca= [HW,SERIAL]
629 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000630 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631
Yinghai Lu95ffa242008-04-29 03:52:33 -0700632 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700633 The kernel tries to adjust MTRR layout from continuous
634 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700635 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700636
Yinghai Lu093af8d2008-01-30 13:33:32 +0100637 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100638 By default the kernel will trim any uncacheable
639 memory out of your available memory pool based on
640 MTRR settings. This parameter disables that behavior,
641 possibly causing your machine to run very slowly.
642
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530643 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700644 Disable PIN 1 of APIC timer
645 Can be useful to work around chipset bugs.
646
Linus Torvalds1da177e2005-04-16 15:20:36 -0700647 dmasound= [HW,OSS] Sound subsystem buffers
648
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700649 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
650 this option disables the debugging code at boot.
651
652 dma_debug_entries=<number>
653 This option allows to tune the number of preallocated
654 entries for DMA-API debugging code. One entry is
655 required per DMA-API allocation. Use this if the
656 DMA-API debugging code disables itself because the
657 architectural default is too low.
658
Joerg Roedel1745de52009-05-22 21:49:51 +0200659 dma_debug_driver=<driver_name>
660 With this option the DMA-API debugging driver
661 filter feature can be enabled at boot time. Just
662 pass the driver to filter for as the parameter.
663 The filter can be disabled or changed to another
664 driver later using sysfs.
665
Linus Torvalds1da177e2005-04-16 15:20:36 -0700666 dscc4.setup= [NET]
667
668 dtc3181e= [HW,SCSI]
669
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700670 dynamic_printk Enables pr_debug()/dev_dbg() calls if
671 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
672 These can also be switched on/off via
673 <debugfs>/dynamic_printk/modules
674
675 earlycon= [KNL] Output early console device and options.
676 uart[8250],io,<addr>[,options]
677 uart[8250],mmio,<addr>[,options]
678 Start an early, polled-mode console on the 8250/16550
679 UART at the specified I/O port or MMIO address.
680 The options are the same as for ttyS, above.
681
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530682 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683 earlyprintk=vga
684 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500685 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500686 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687
Randy Dunlapa9913042005-10-23 12:57:11 -0700688 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700689 takes over.
690
Yinghai Lu5c059172008-07-24 17:29:40 -0700691 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692
693 Currently only ttyS0 and ttyS1 are supported.
694
695 Interaction with the standard serial driver is not
696 very good.
697
698 The VGA output is eventually overwritten by the real
699 console.
700
701 eata= [HW,SCSI]
702
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700704 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700705
Linus Torvalds1da177e2005-04-16 15:20:36 -0700706 eisa_irq_edge= [PARISC,HW]
707 See header of drivers/parisc/eisa.c.
708
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700709 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700710 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700711 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712
713 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800714 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700715 See Documentation/block/as-iosched.txt and
716 Documentation/block/deadline-iosched.txt for details.
717
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530718 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700719 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800720 image elf header. Generally kexec loader will
721 pass this option to capture kernel.
722 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700723
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700724 enable_mtrr_cleanup [X86]
725 The kernel tries to adjust MTRR layout from continuous
726 to discrete, to make X server driver able to add WB
727 entry later. This parameter enables that.
728
Randy Dunlapca1eda22009-05-06 16:02:58 -0700729 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700730 Enable PIN 1 of APIC timer
731 Can be useful to work around chipset bugs
732 (in particular on some ATI chipsets).
733 The kernel tries to set a reasonable default.
734
Linus Torvalds1da177e2005-04-16 15:20:36 -0700735 enforcing [SELINUX] Set initial enforcing status.
736 Format: {"0" | "1"}
737 See security/selinux/Kconfig help text.
738 0 -- permissive (log only, no denials).
739 1 -- enforcing (deny and log).
740 Default value is 0.
741 Value can be changed at runtime via /selinux/enforce.
742
Linus Torvalds1da177e2005-04-16 15:20:36 -0700743 ether= [HW,NET] Ethernet cards parameters
744 This option is obsoleted by the "netdev=" option, which
745 has equivalent usage. See its documentation for details.
746
747 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
748 Format: <io>[,<irq>]
749
Akinobu Mitade1ba092006-12-08 02:39:42 -0800750 failslab=
751 fail_page_alloc=
752 fail_make_request=[KNL]
753 General fault injection mechanism.
754 Format: <interval>,<probability>,<space>,<times>
755 See also /Documentation/fault-injection/.
756
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757 fd_mcs= [HW,SCSI]
758 See header of drivers/scsi/fd_mcs.c.
759
760 fdomain= [HW,SCSI]
761 See header of drivers/scsi/fdomain.c.
762
763 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000764 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700765
Alex Chiangf13ae302008-05-08 14:03:23 -0600766 force_pal_cache_flush
767 [IA-64] Avoid check_sal_cache_flush which may hang on
768 buggy SAL_CACHE_FLUSH implementations. Using this
769 parameter will force ia64_sal_cache_flush to call
770 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
771
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100772 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400773 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100774 as early as possible in order to facilitate early
775 boot debugging.
776
777 ftrace_dump_on_oops
Steven Rostedt2af15d62009-05-28 13:37:24 -0400778 [FTRACE] will dump the trace buffers on oops.
779
780 ftrace_filter=[function-list]
781 [FTRACE] Limit the functions traced by the function
782 tracer at boot up. function-list is a comma separated
783 list of functions. This list can be changed at run
784 time by the set_ftrace_filter file in the debugfs
785 tracing directory.
786
787 ftrace_notrace=[function-list]
788 [FTRACE] Do not trace the functions specified in
789 function-list. This list can be changed at run time
790 by the set_ftrace_notrace file in the debugfs
791 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100792
Stefan Assmann369bc182009-10-12 22:17:21 +0200793 ftrace_graph_filter=[function-list]
794 [FTRACE] Limit the top level callers functions traced
795 by the function graph tracer at boot up.
796 function-list is a comma separated list of functions
797 that can be changed at run time by the
798 set_graph_function file in the debugfs tracing directory.
799
Linus Torvalds1da177e2005-04-16 15:20:36 -0700800 gamecon.map[2|3]=
801 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
802 support via parallel port (up to 5 devices per port)
803 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
804 See also Documentation/input/joystick-parport.txt
805
806 gamma= [HW,DRM]
807
Yinghai Luaaf23042008-01-30 13:33:09 +0100808 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
809 Format: off | on
810 default: on
811
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700812 gcov_persist= [GCOV] When non-zero (default), profiling data for
813 kernel modules is saved and remains accessible via
814 debugfs, even when the module is unloaded/reloaded.
815 When zero, profiling data is discarded and associated
816 debugfs files are removed at module unload time.
817
Linus Torvalds1da177e2005-04-16 15:20:36 -0700818 gdth= [HW,SCSI]
819 See header of drivers/scsi/gdth.c.
820
821 gpt [EFI] Forces disk with valid GPT signature but
822 invalid Protective MBR to be treated as GPT.
823
Linus Torvalds1da177e2005-04-16 15:20:36 -0700824 gvp11= [HW,SCSI]
825
826 hashdist= [KNL,NUMA] Large hashes allocated during boot
827 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700828 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700829 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830
831 hcl= [IA-64] SGI's Hardware Graph compatibility layer
832
833 hd= [EIDE] (E)IDE hard drive subsystem geometry
834 Format: <cyl>,<head>,<sect>
835
Linus Torvalds1da177e2005-04-16 15:20:36 -0700836 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
837 size of <nn>. This works even on boxes that have no
838 highmem otherwise. This also works to reduce highmem
839 size on bigger boxes.
840
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800841 highres= [KNL] Enable/disable high resolution timer mode.
842 Valid parameters: "on", "off"
843 Default: "on"
844
Linus Torvalds1da177e2005-04-16 15:20:36 -0700845 hisax= [HW,ISDN]
846 See Documentation/isdn/README.HiSax.
847
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700848 hlt [BUGS=ARM,SH]
849
850 hpet= [X86-32,HPET] option to control HPET usage
851 Format: { enable (default) | disable | force |
852 verbose }
853 disable: disable HPET and use PIT instead
854 force: allow force enabled of undocumented chips (ICH4,
855 VIA, nVidia)
856 verbose: show contents of HPET registers during setup
857
Andi Kleenb4718e62008-07-23 21:27:51 -0700858 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
859 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700860 On x86-64 and powerpc, this option can be specified
861 multiple times interleaved with hugepages= to reserve
862 huge pages of different sizes. Valid pages sizes on
863 x86-64 are 2M (when the CPU supports "pse") and 1G
864 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700865 Note that 1GB pages can only be allocated at boot time
866 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900867
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100868 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
869 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100870 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
871 If specified, z/VM IUCV HVC accepts connections
872 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100873
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700874 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700875 or register an additional I2C bus that is not
876 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700877 Format:
878 <bus_id>,<clkrate>
879
Jiri Kosina36d95732008-10-06 02:51:09 -0400880 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700881 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200882 i8042.dumbkbd [HW] Pretend that controller can only read data from
883 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700884 (Don't attempt to blink the leds)
885 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500886 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400887 i8042.noloop [HW] Disable the AUX Loopback command while probing
888 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700889 i8042.nomux [HW] Don't check presence of an active multiplexing
890 controller
891 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
892 controllers
893 i8042.panicblink=
894 [HW] Frequency with which keyboard LEDs should blink
895 when kernel panics (default is 0.5 sec)
896 i8042.reset [HW] Reset the controller during init and cleanup
897 i8042.unlock [HW] Unlock (ignore) the keylock
898
899 i810= [HW,DRM]
900
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700901 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
902 indicates that the driver is running on unsupported
903 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
905 does not match list of supported models.
906 i8k.power_status
907 [HW] Report power status in /proc/i8k
908 (disabled by default)
909 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
910 capability is set.
911
912 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
913 See Documentation/mca.txt.
914
915 icn= [HW,ISDN]
916 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
917
David Fries0af80c02009-02-25 20:28:21 +0100918 ide-core.nodma= [HW] (E)IDE subsystem
919 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200920 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
921 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100922 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700923
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700924 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
925 Claim all unknown PCI IDE storage controllers.
926
Andi Kleenf039b752007-05-02 19:27:12 +0200927 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800928 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
929 Poll forces a polling idle loop that can slightly
930 improve the performance of waking up a idle CPU, but
931 will use a lot of power and make the system run hot.
932 Not recommended.
933 idle=mwait: On systems which support MONITOR/MWAIT but
934 the kernel chose to not use it because it doesn't save
935 as much power as a normal idle loop, use the
936 MONITOR/MWAIT idle loop anyways. Performance should be
937 the same as idle=poll.
938 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800939 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800940 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700941
Ingo Molnar792908222006-12-06 20:40:51 -0800942 ignore_loglevel [KNL]
943 Ignore loglevel setting - this will print /all/
944 kernel messages to the console. Useful for debugging.
945
Linus Torvalds1da177e2005-04-16 15:20:36 -0700946 ihash_entries= [KNL]
947 Set number of hash buckets for inode cache.
948
Mimi Zohar3323eec2009-02-04 09:06:58 -0500949 ima_audit= [IMA]
950 Format: { "0" | "1" }
951 0 -- integrity auditing messages. (Default)
952 1 -- enable informational integrity auditing messages.
953
954 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700955 Format: { "sha1" | "md5" }
Mimi Zohar3323eec2009-02-04 09:06:58 -0500956 default: "sha1"
957
Eric Paris5789ba32009-05-21 15:47:06 -0400958 ima_tcb [IMA]
959 Load a policy which meets the needs of the Trusted
960 Computing Base. This means IMA will measure all
961 programs exec'd, files mmap'd for exec, and all files
962 opened for read by uid=0.
963
Linus Torvalds1da177e2005-04-16 15:20:36 -0700964 in2000= [HW,SCSI]
965 See header of drivers/scsi/in2000.c.
966
967 init= [KNL]
968 Format: <full_path>
969 Run specified binary instead of /sbin/init as init
970 process.
971
972 initcall_debug [KNL] Trace initcalls as they are executed. Useful
973 for working out where the kernel is dying during
974 startup.
975
976 initrd= [BOOT] Specify the location of the initial ramdisk
977
978 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
979 Format: <irq>
980
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700981 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800982 on
983 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700984 off
985 Disable intel iommu driver.
986 igfx_off [Default Off]
987 By default, gfx is mapped as normal device. If a gfx
988 device has a dedicated DMAR unit, the DMAR unit is
989 bypassed by not enabling DMAR with this option. In
990 this case, gfx device will use physical address for
991 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700992 forcedac [x86_64]
993 With this option iommu will not optimize to look
994 for io virtual address below 32 bit forcing dual
995 address cycle on pci bus for cards supporting greater
996 than 32 bit addressing. The default is to look
997 for translation below 32 bit and if not available
998 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -0800999 strict [Default Off]
1000 With this option on every unmap_single operation will
1001 result in a hardware IOTLB flush operation as opposed
1002 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001003
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001004 inttest= [IA64]
1005
1006 iomem= Disable strict checking of access to MMIO memory
1007 strict regions from userspace.
1008 relaxed
1009
1010 iommu= [x86]
1011 off
1012 force
1013 noforce
1014 biomerge
1015 panic
1016 nopanic
1017 merge
1018 nomerge
1019 forcesac
1020 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001021 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001022
1023 io7= [HW] IO7 for Marvel based alpha systems
1024 See comment before marvel_specify_io7 in
1025 arch/alpha/kernel/core_marvel.c.
1026
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301027 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001028 0x80
1029 Standard port 0x80 based delay
1030 0xed
1031 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001032 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001033 Simple two microseconds delay
1034 none
1035 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001036
Linus Torvalds1da177e2005-04-16 15:20:36 -07001037 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001038 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001039
1040 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001041 See comment before ip2_setup() in
1042 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043
1044 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1045 See header of drivers/scsi/ips.c.
1046
Alan Cox200803d2005-06-28 20:45:18 -07001047 irqfixup [HW]
1048 When an interrupt is not handled search all handlers
1049 for it. Intended to get systems with badly broken
1050 firmware running.
1051
1052 irqpoll [HW]
1053 When an interrupt is not handled search all handlers
1054 for it. Also check all handlers each timer
1055 interrupt. Intended to get systems with badly broken
1056 firmware running.
1057
Linus Torvalds1da177e2005-04-16 15:20:36 -07001058 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001059 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001060
1061 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001062 Format:
1063 <cpu number>,...,<cpu number>
1064 or
Li Zefanb225d442008-11-06 12:53:39 -08001065 <cpu number>-<cpu number>
1066 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001067 or a mixture
1068 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001069
Linus Torvalds1da177e2005-04-16 15:20:36 -07001070 This option can be used to specify one or more CPUs
1071 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001072 algorithms. You can move a process onto or off an
1073 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074 <cpu number> begins at 0 and the maximum value is
1075 "number of CPUs in system - 1".
1076
1077 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001078 alternative -- manually setting the CPU mask of all
1079 tasks in the system -- can cause problems and
1080 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001081
Randy Dunlapa9913042005-10-23 12:57:11 -07001082 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083
1084 js= [HW,JOY] Analog joystick
1085 See Documentation/input/joystick.txt.
1086
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001087 keepinitrd [HW,ARM]
1088
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301089 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001090 specifies the amount of memory usable by the kernel
1091 for non-movable allocations. The requested amount is
1092 spread evenly throughout all nodes in the system. The
1093 remaining memory in each node is used for Movable
1094 pages. In the event, a node is too small to have both
1095 kernelcore and Movable pages, kernelcore pages will
1096 take priority and other nodes will have a larger number
1097 of kernelcore pages. The Movable zone is used for the
1098 allocation of pages that may be reclaimed or moved
1099 by the page migration subsystem. This means that
1100 HugeTLB pages may not be allocated from this zone.
1101 Note that allocations like PTEs-from-HighMem still
1102 use the HighMem zone if it exists, and the Normal
1103 zone if it does not.
1104
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001105 kgdboc= [HW] kgdb over consoles.
1106 Requires a tty driver that supports console polling.
Matt LaPlante19f59462009-04-27 15:06:31 +02001107 (only serial supported for now)
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001108 Format: <serial_device>[,baud]
1109
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001110 kmac= [MIPS] korina ethernet MAC address.
1111 Configure the RouterBoard 532 series on-chip
1112 Ethernet adapter MAC address.
1113
Catalin Marinas04f70332009-06-11 13:22:39 +01001114 kmemleak= [KNL] Boot-time kmemleak enable/disable
1115 Valid arguments: on, off
1116 Default: on
1117
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301118 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001119 in oops dumps.
1120
Andre Przywarafef07aa2009-07-10 14:20:35 +02001121 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1122 Default is 0 (don't ignore, but inject #GP)
1123
1124 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1125 Default is 1 (enabled)
1126
1127 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1128 Default is 0 (off)
1129
1130 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1131 for all guests.
1132 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1133
1134 kvm-intel.bypass_guest_pf=
1135 [KVM,Intel] Disables bypassing of guest page faults
1136 on Intel chips. Default is 1 (enabled)
1137
1138 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1139 (virtualized MMU) support on capable Intel chips.
1140 Default is 1 (enabled)
1141
1142 kvm-intel.emulate_invalid_guest_state=
1143 [KVM,Intel] Enable emulation of invalid guest states
1144 Default is 0 (disabled)
1145
1146 kvm-intel.flexpriority=
1147 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1148 Default is 1 (enabled)
1149
1150 kvm-intel.unrestricted_guest=
1151 [KVM,Intel] Disable unrestricted guest feature
1152 (virtualized real and unpaged mode) on capable
1153 Intel chips. Default is 1 (enabled)
1154
1155 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1156 feature (tagged TLBs) on capable Intel chips.
1157 Default is 1 (enabled)
1158
Linus Torvalds1da177e2005-04-16 15:20:36 -07001159 l2cr= [PPC]
1160
Robert Brosea78bfbf2008-03-29 07:20:23 +11001161 l3cr= [PPC]
1162
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001163 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001164 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001165
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301166 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001167 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001168
FD Camifcb71f62008-01-06 19:08:56 +01001169 libata.dma= [LIBATA] DMA control
1170 libata.dma=0 Disable all PATA and SATA DMA
1171 libata.dma=1 PATA and SATA Disk DMA only
1172 libata.dma=2 ATAPI (CDROM) DMA only
1173 libata.dma=4 Compact Flash DMA only
1174 Combinations also work, so libata.dma=3 enables DMA
1175 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001176
1177 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1178 libata.ignore_hpa=0 keep BIOS limits (default)
1179 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001180
Dave Jones78e70c22007-09-27 11:50:13 -04001181 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1182 when set.
1183 Format: <int>
1184
Tejun Heo33267322008-02-13 09:15:09 +09001185 libata.force= [LIBATA] Force configurations. The format is comma
1186 separated list of "[ID:]VAL" where ID is
1187 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1188 matching port, link or device. Basically, it matches
1189 the ATA ID string printed on console by libata. If
1190 the whole ID part is omitted, the last PORT and DEVICE
1191 values are used. If ID hasn't been specified yet, the
1192 configuration applies to all ports, links and devices.
1193
1194 If only DEVICE is omitted, the parameter applies to
1195 the port and all links and devices behind it. DEVICE
1196 number of 0 either selects the first device or the
1197 first fan-out link behind PMP device. It does not
1198 select the host link. DEVICE number of 15 selects the
1199 host link and device attached to it.
1200
1201 The VAL specifies the configuration to force. As long
1202 as there's no ambiguity shortcut notation is allowed.
1203 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1204 The following configurations can be forced.
1205
1206 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1207 Any ID with matching PORT is used.
1208
1209 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1210
1211 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1212 udma[/][16,25,33,44,66,100,133] notation is also
1213 allowed.
1214
1215 * [no]ncq: Turn on or off NCQ.
1216
Tejun Heo05944bd2008-08-13 20:19:09 +09001217 * nohrst, nosrst, norst: suppress hard, soft
1218 and both resets.
1219
Tejun Heo33267322008-02-13 09:15:09 +09001220 If there are multiple matching configurations changing
1221 the same attribute, the last one is used.
1222
Randy Dunlap7c4be252009-01-06 14:42:44 -08001223 lmb=debug [KNL] Enable lmb debug messages.
1224
Linus Torvalds1da177e2005-04-16 15:20:36 -07001225 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001226 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001227
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001228 lockd.nlm_grace_period=P [NFS] Assign grace period.
1229 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001230
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001231 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1232 Format: <integer>
1233
1234 lockd.nlm_timeout=T [NFS] Assign timeout value.
1235 Format: <integer>
1236
1237 lockd.nlm_udpport=M [NFS] Assign UDP port.
1238 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001239
1240 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1241 Format: <irq>
1242
1243 loglevel= All Kernel Messages with a loglevel smaller than the
1244 console loglevel will be printed to the console. It can
1245 also be changed with klogd or other programs. The
1246 loglevels are defined as follows:
1247
1248 0 (KERN_EMERG) system is unusable
1249 1 (KERN_ALERT) action must be taken immediately
1250 2 (KERN_CRIT) critical conditions
1251 3 (KERN_ERR) error conditions
1252 4 (KERN_WARNING) warning conditions
1253 5 (KERN_NOTICE) normal but significant condition
1254 6 (KERN_INFO) informational
1255 7 (KERN_DEBUG) debug-level messages
1256
1257 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001258 Format: { n | nk | nM }
1259 n must be a power of two. The default size
1260 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001261
Randy Dunlapaccaa242007-10-16 01:29:37 -07001262 logo.nologo [FB] Disables display of the built-in Linux logo.
1263 This may be used to provide more screen space for
1264 kernel log messages and is useful when debugging
1265 kernel boot problems.
1266
Linus Torvalds1da177e2005-04-16 15:20:36 -07001267 lp=0 [LP] Specify parallel ports to use, e.g,
1268 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1269 lp=reset first parallel port). 'lp=0' disables the
1270 lp=auto printer driver. 'lp=reset' (which can be
1271 specified in addition to the ports) causes
1272 attached printers to be reset. Using
1273 lp=port1,port2,... specifies the parallel ports
1274 to associate lp devices with, starting with
1275 lp0. A port specification may be 'none' to skip
1276 that lp device, or a parport name such as
1277 'parport0'. Specifying 'lp=auto' instead of a
1278 port specification list means that device IDs
1279 from each port should be examined, to see if
1280 an IEEE 1284-compliant printer is attached; if
1281 so, the driver will manage that printer.
1282 See also header of drivers/char/lp.c.
1283
1284 lpj=n [KNL]
1285 Sets loops_per_jiffy to given constant, thus avoiding
1286 time-consuming boot-time autodetection (up to 250 ms per
1287 CPU). 0 enables autodetection (default). To determine
1288 the correct value for your kernel, boot with normal
1289 autodetection and see what value is printed. Note that
1290 on SMP systems the preset will be applied to all CPUs,
1291 which is likely to cause problems if your CPUs need
1292 significantly divergent settings. An incorrect value
1293 will cause delays in the kernel to be wrong, leading to
1294 unpredictable I/O errors and other breakage. Although
1295 unlikely, in the extreme case this might damage your
1296 hardware.
1297
1298 ltpc= [NET]
1299 Format: <io>,<irq>,<dma>
1300
Randy Dunlapa9913042005-10-23 12:57:11 -07001301 mac5380= [HW,SCSI] Format:
1302 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001303
Randy Dunlapa9913042005-10-23 12:57:11 -07001304 machvec= [IA64] Force the use of a particular machine-vector
1305 (machvec) in a generic kernel.
1306 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001307
Wu Zhangjin3209e702009-07-02 23:27:12 +08001308 machtype= [Loongson] Share the same kernel image file between different
1309 yeeloong laptop.
1310 Example: machtype=lemote-yeeloong-2f-7inch
1311
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001312 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1313 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001314
1315 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001316 should make use of. maxcpus=n : n >= 0 limits the
1317 kernel to using 'n' processors. n=0 is a special case,
1318 it is equivalent to "nosmp", which also disables
1319 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001320
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001321 max_loop= [LOOP] Maximum number of loopback devices that can
1322 be mounted
1323 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001324
Randy Dunlapa9913042005-10-23 12:57:11 -07001325 max_luns= [SCSI] Maximum number of LUNs to probe.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001326 Should be between 1 and 2^32-1.
1327
1328 max_report_luns=
Randy Dunlapa9913042005-10-23 12:57:11 -07001329 [SCSI] Maximum number of LUNs received.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330 Should be between 1 and 16384.
1331
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332 mcatest= [IA-64]
1333
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001334 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001335
Uwe Hermann71cced62008-10-20 09:32:21 -07001336 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001337
Linus Torvalds1da177e2005-04-16 15:20:36 -07001338 md= [HW] RAID subsystems devices and level
1339 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001340
Linus Torvalds1da177e2005-04-16 15:20:36 -07001341 mdacon= [MDA]
1342 Format: <first>,<last>
1343 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001344
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1346 Amount of memory to be used when the kernel is not able
1347 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001348 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349 address space collisions. Without memmap= PCI devices
1350 could be placed at addresses belonging to unused RAM.
1351
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001352 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353 memory.
1354
Paul Mundt6902aa82008-09-21 17:14:42 +09001355 memchunk=nn[KMG]
1356 [KNL,SH] Allow user to override the default size for
1357 per-device physically contiguous DMA buffers.
1358
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301359 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360 E820 memory map, as specified by the user.
1361 Such memmap=exactmap lines can be constructed based on
1362 BIOS output or other requirements. See the memmap=nn@ss
1363 option description.
1364
1365 memmap=nn[KMG]@ss[KMG]
1366 [KNL] Force usage of a specific region of memory
1367 Region of memory to be used, from ss to ss+nn.
1368
1369 memmap=nn[KMG]#ss[KMG]
1370 [KNL,ACPI] Mark specific memory as ACPI data.
1371 Region of memory to be used, from ss to ss+nn.
1372
1373 memmap=nn[KMG]$ss[KMG]
1374 [KNL,ACPI] Mark specific memory as reserved.
1375 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001376 Example: Exclude memory from 0x18690000-0x1869ffff
1377 memmap=64K$0x18690000
1378 or
1379 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001380
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001381 memory_corruption_check=0/1 [X86]
1382 Some BIOSes seem to corrupt the first 64k of
1383 memory when doing things like suspend/resume.
1384 Setting this option will scan the memory
1385 looking for corruption. Enabling this will
1386 both detect corruption and prevent the kernel
1387 from using the memory being corrupted.
1388 However, its intended as a diagnostic tool; if
1389 repeatable BIOS-originated corruption always
1390 affects the same memory, you can use memmap=
1391 to prevent the kernel from using that memory.
1392
1393 memory_corruption_check_size=size [X86]
1394 By default it checks for corruption in the low
1395 64k, making this memory unavailable for normal
1396 use. Use this parameter to scan for
1397 corruption in more or less memory.
1398
1399 memory_corruption_check_period=seconds [X86]
1400 By default it checks for corruption every 60
1401 seconds. Use this parameter to check at some
1402 other rate. 0 disables periodic checking.
1403
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001404 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001405 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001406 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001407 Specifies the number of memtest passes to be
1408 performed. Each pass selects another test
1409 pattern from a given set of patterns. Memtest
1410 fills the memory with this pattern, validates
1411 memory contents and reserves bad memory
1412 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001413
Linus Torvalds1da177e2005-04-16 15:20:36 -07001414 meye.*= [HW] Set MotionEye Camera parameters
1415 See Documentation/video4linux/meye.txt.
1416
Andres Salomon8f368812007-10-12 23:04:06 +02001417 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1418 Multi-Function General Purpose Timers on AMD Geode
1419 platforms.
1420
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001421 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1422 the BIOS has incorrectly applied a workaround. TinyBIOS
1423 version 0.98 is known to be affected, 0.99 fixes the
1424 problem by letting the user disable the workaround.
1425
Linus Torvalds1da177e2005-04-16 15:20:36 -07001426 mga= [HW,DRM]
1427
Randy Dunlap1c207f952008-11-19 15:36:16 -08001428 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1429 physical address is ignored.
1430
Michel Pollet39f45d72009-05-20 11:10:31 +01001431 mini2440= [ARM,HW,KNL]
1432 Format:[0..2][b][c][t]
1433 Default: "0tb"
1434 MINI2440 configuration specification:
1435 0 - The attached screen is the 3.5" TFT
1436 1 - The attached screen is the 7" TFT
1437 2 - The VGA Shield is attached (1024x768)
1438 Leaving out the screen size parameter will not load
1439 the TFT driver, and the framebuffer will be left
1440 unconfigured.
1441 b - Enable backlight. The TFT backlight pin will be
1442 linked to the kernel VESA blanking code and a GPIO
1443 LED. This parameter is not necessary when using the
1444 VGA shield.
1445 c - Enable the s3c camera interface.
1446 t - Reserved for enabling touchscreen support. The
1447 touchscreen support is not enabled in the mainstream
1448 kernel as of 2.6.30, a preliminary port can be found
1449 in the "bleeding edge" mini2440 support kernel at
1450 http://repo.or.cz/w/linux-2.6/mini2440.git
1451
Mel Gorman6b74ab92008-07-23 21:26:49 -07001452 mminit_loglevel=
1453 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1454 parameter allows control of the logging verbosity for
1455 the additional memory initialisation checks. A value
1456 of 0 disables mminit logging and a level of 4 will
1457 log everything. Information is printed at KERN_DEBUG
1458 so loglevel=8 may also need to be specified.
1459
Linus Torvalds1da177e2005-04-16 15:20:36 -07001460 mousedev.tap_time=
1461 [MOUSE] Maximum time between finger touching and
1462 leaving touchpad surface for touch to be considered
1463 a tap and be reported as a left button click (for
1464 touchpads working in absolute mode only).
1465 Format: <msecs>
1466 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1467 reporting absolute coordinates, such as tablets
1468 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1469 reporting absolute coordinates, such as tablets
1470
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301471 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001472 is similar to kernelcore except it specifies the
1473 amount of memory used for migratable allocations.
1474 If both kernelcore and movablecore is specified,
1475 then kernelcore will be at *least* the specified
1476 value but may be more. If movablecore on its own
1477 is specified, the administrator must be careful
1478 that the amount of memory usable for all allocations
1479 is not too small.
1480
Linus Torvalds1da177e2005-04-16 15:20:36 -07001481 mpu401= [HW,OSS]
1482 Format: <io>,<irq>
1483
1484 MTD_Partition= [MTD]
1485 Format: <name>,<region-number>,<size>,<offset>
1486
Randy Dunlapa9913042005-10-23 12:57:11 -07001487 MTD_Region= [MTD] Format:
1488 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489
1490 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001491 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001492
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001493 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1494
1495 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1496
1497 boundary - index of last SLC block on Flex-OneNAND.
1498 The remaining blocks are configured as MLC blocks.
1499 lock - Configure if Flex-OneNAND boundary should be locked.
1500 Once locked, the boundary cannot be changed.
1501 1 indicates lock status, 0 indicates unlock status.
1502
Ben Dooks9db829f2008-07-03 11:24:29 +01001503 mtdset= [ARM]
1504 ARM/S3C2412 JIVE boot control
1505
1506 See arch/arm/mach-s3c2412/mach-jive.c
1507
Linus Torvalds1da177e2005-04-16 15:20:36 -07001508 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001509 [HW] Make the MicroTouch USB driver use raw coordinates
1510 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001511
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001512 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001513 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001514 that could hold holes aka. UC entries.
1515
1516 mtrr_gran_size=nn[KMG] [X86]
1517 Used for mtrr cleanup. It is granularity of mtrr block.
1518 Default is 1.
1519 Large value could prevent small alignment from
1520 using up MTRRs.
1521
1522 mtrr_spare_reg_nr=n [X86]
1523 Format: <integer>
1524 Range: 0,7 : spare reg number
1525 Default : 1
1526 Used for mtrr cleanup. It is spare mtrr entries number.
1527 Set to 2 or more if your graphical card needs more.
1528
Linus Torvalds1da177e2005-04-16 15:20:36 -07001529 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1530
1531 NCR_D700= [HW,SCSI]
1532 See header of drivers/scsi/NCR_D700.c.
1533
1534 ncr5380= [HW,SCSI]
1535
1536 ncr53c400= [HW,SCSI]
1537
1538 ncr53c400a= [HW,SCSI]
1539
1540 ncr53c406a= [HW,SCSI]
1541
1542 ncr53c8xx= [HW,SCSI]
1543
1544 netdev= [NET] Network devices parameters
1545 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1546 Note that mem_start is often overloaded to mean
1547 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001548 This usage is only documented in each driver source
1549 file if at all.
1550
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001551 nf_conntrack.acct=
1552 [NETFILTER] Enable connection tracking flow accounting
1553 0 to disable accounting
1554 1 to enable accounting
1555 Default value depends on CONFIG_NF_CT_ACCT that is
1556 going to be removed in 2.6.29.
1557
Linus Torvalds1da177e2005-04-16 15:20:36 -07001558 nfsaddrs= [NFS]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001559 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560
1561 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001562 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001563
Trond Myklebusta72b4422006-01-03 09:55:41 +01001564 nfs.callback_tcpport=
1565 [NFS] set the TCP port on which the NFSv4 callback
1566 channel should listen.
1567
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001568 nfs.cache_getent=
1569 [NFS] sets the pathname to the program which is used
1570 to update the NFS client cache entries.
1571
1572 nfs.cache_getent_timeout=
1573 [NFS] sets the timeout after which an attempt to
1574 update a cache entry is deemed to have failed.
1575
Trond Myklebust58df0952006-01-03 09:55:57 +01001576 nfs.idmap_cache_timeout=
1577 [NFS] set the maximum lifetime for idmapper cache
1578 entries.
1579
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001580 nfs.enable_ino64=
1581 [NFS] enable 64-bit inode numbers.
1582 If zero, the NFS client will fake up a 32-bit inode
1583 number for the readdir() and stat() syscalls instead
1584 of returning the full 64-bit number.
1585 The default is to return 64-bit inode numbers.
1586
Paul Mundt1e1030d2009-09-01 17:38:32 +09001587 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001588 when a NMI is triggered.
1589 Format: [state][,regs][,debounce][,die]
1590
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301591 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001592 Format: [panic,][num]
1593 Valid num: 0,1,2
1594 0 - turn nmi_watchdog off
1595 1 - use the IO-APIC timer for the NMI watchdog
1596 2 - use the local APIC for the NMI watchdog using
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001597 a performance counter. Note: This will use one
1598 performance counter and the local APIC's performance
1599 vector.
1600 When panic is specified, panic when an NMI watchdog
1601 timeout occurs.
1602 This is useful when you use a panic=... timeout and
1603 need the box quickly up again.
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001604 Instead of 1 and 2 it is possible to use the following
1605 symbolic names: lapic and ioapic
1606 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
Linus Torvalds1da177e2005-04-16 15:20:36 -07001607
Anton Vorontsovbff38772009-07-08 11:10:56 -07001608 netpoll.carrier_timeout=
1609 [NET] Specifies amount of time (in seconds) that
1610 netpoll should wait for a carrier. By default netpoll
1611 waits 4 seconds.
1612
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001613 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001614 emulation library even if a 387 maths coprocessor
1615 is present.
1616
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001617 no_console_suspend
1618 [HW] Never suspend the console
1619 Disable suspending of consoles during suspend and
1620 hibernate operations. Once disabled, debugging
1621 messages can reach various consoles while the rest
1622 of the system is being put to sleep (ie, while
1623 debugging driver suspend/resume hooks). This may
1624 not work reliably with all consoles, but is known
1625 to work with serial and VGA consoles.
1626
Christoph Lameterc1aee212007-05-31 00:40:47 -07001627 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1628 caches in the slab allocator. Saves per-node memory,
1629 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001630
Randy Dunlapa9913042005-10-23 12:57:11 -07001631 noalign [KNL,ARM]
1632
Linus Torvalds1da177e2005-04-16 15:20:36 -07001633 noapic [SMP,APIC] Tells the kernel to not make use of any
1634 IOAPICs that may be present in the system.
1635
Linus Torvalds1da177e2005-04-16 15:20:36 -07001636 nobats [PPC] Do not use BATs for mapping kernel lowmem
1637 on "Classic" PPC cores.
1638
1639 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001640
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001641 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1642
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001643 nodelayacct [KNL] Disable per-task delay accounting
1644
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1646
Paul Mundt6902aa82008-09-21 17:14:42 +09001647 nodsp [SH] Disable hardware DSP at boot time.
1648
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301649 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001650
Linus Torvalds1da177e2005-04-16 15:20:36 -07001651 noexec [IA-64]
1652
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301653 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001654 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001656 noexec=off: disable non-executable mappings
1657
1658 noexec32 [X86-64]
1659 This affects only 32-bit executables.
1660 noexec32=on: enable non-executable mappings (default)
1661 read doesn't imply executable mappings
1662 noexec32=off: disable non-executable mappings
1663 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001664
Paul Mundt6902aa82008-09-21 17:14:42 +09001665 nofpu [SH] Disable hardware FPU at boot time.
1666
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001667 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001668 register save and restore. The kernel will only save
1669 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001670
Suresh Siddha0c752a92009-05-22 12:17:45 -07001671 noxsave [BUGS=X86] Disables x86 extended register state save
1672 and restore using xsave. The kernel will fallback to
1673 enabling legacy floating-point and sse state.
1674
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001675 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1676 wfi(ARM) instruction doesn't work correctly and not to
1677 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001678
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001679 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001680 instruction doesn't work correctly and not to
1681 use it.
1682
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001683 no_file_caps Tells the kernel not to honor file capabilities. The
1684 only way then for a file to be executed with privilege
1685 is to be setuid root or executed by root.
1686
Linus Torvalds1da177e2005-04-16 15:20:36 -07001687 nohalt [IA-64] Tells the kernel not to use the power saving
1688 function PAL_HALT_LIGHT when idle. This increases
1689 power-consumption. On the positive side, it reduces
1690 interrupt wake-up latency, which may improve performance
1691 in certain environments such as networked servers or
1692 real-time systems.
1693
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001694 nohz= [KNL] Boottime enable/disable dynamic ticks
1695 Valid arguments: on, off
1696 Default: on
1697
Paul Mundteeee7852009-04-02 12:31:16 +09001698 noiotrap [SH] Disables trapped I/O port accesses.
1699
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001700 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001701 disable unhandled interrupt sources.
1702
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301703 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001704 broken timer IRQ sources.
1705
Linus Torvalds1da177e2005-04-16 15:20:36 -07001706 noisapnp [ISAPNP] Disables ISA PnP code.
1707
1708 noinitrd [RAM] Tells the kernel not to load any configured
1709 initial RAM disk.
1710
Weidong Han03ea8152009-04-17 16:42:15 +08001711 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1712 remapping.
1713
Linus Torvalds1da177e2005-04-16 15:20:36 -07001714 nointroute [IA-64]
1715
Tony Luck0aa366f2007-07-20 11:22:30 -07001716 nojitter [IA64] Disables jitter checking for ITC timers.
1717
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001718 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001719
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001720 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001721
Linus Torvalds1da177e2005-04-16 15:20:36 -07001722 noltlbs [PPC] Do not use large page/tlb entries for kernel
1723 lowmem mapping on PPC40x.
1724
Horms312f1f02006-02-22 09:57:55 +09001725 nomca [IA-64] Disable machine check abort handling
1726
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001727 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001728
Andres Salomon83d73842007-10-12 23:04:06 +02001729 nomfgpt [X86-32] Disable Multi-Function General Purpose
1730 Timer usage (for AMD Geode machines).
1731
Jiri Kosina016ddd92010-01-18 17:05:40 +01001732 nopat [X86] Disable PAT (page attribute table extension of
1733 pagetables) support.
1734
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001735 norandmaps Don't use address space randomization. Equivalent to
1736 echo 0 > /proc/sys/kernel/randomize_va_space
1737
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001738 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001739
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001740 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001741 with UP alternatives
1742
Linus Torvalds1da177e2005-04-16 15:20:36 -07001743 noresidual [PPC] Don't use residual data on PReP machines.
1744
Randy Dunlapa9913042005-10-23 12:57:11 -07001745 noresume [SWSUSP] Disables resume and restores original swap
1746 space.
1747
Linus Torvalds1da177e2005-04-16 15:20:36 -07001748 no-scroll [VGA] Disables scrollback.
1749 This is required for the Braillex ib80-piezo Braille
1750 reader made by F.H. Papenmeier (Germany).
1751
1752 nosbagart [IA-64]
1753
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001754 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001755
Len Brown61ec7562007-08-16 03:34:22 -04001756 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1757 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758
Dave Jones97842212007-07-15 23:41:05 -07001759 nosoftlockup [KNL] Disable the soft-lockup detector.
1760
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001761 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001762 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001763
Linus Torvalds1da177e2005-04-16 15:20:36 -07001764 nosync [HW,M68K] Disables sync negotiation for all devices.
1765
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001766 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001767
1768 nousb [USB] Disable the USB subsystem
1769
1770 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001771
Weidong Han2b2fd872009-04-17 16:42:12 +08001772 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1773
Fenghua Yua6c75b862008-03-14 13:57:08 -07001774 nptcg= [IA64] Override max number of concurrent global TLB
1775 purges which is reported from either PAL_VM_SUMMARY or
1776 SAL PALO.
1777
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001778 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1779
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001780 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1781 one of ['zone', 'node', 'default'] can be specified
1782 This can be set from sysctl after boot.
1783 See Documentation/sysctl/vm.txt for details.
1784
Randy Dunlap7c4be252009-01-06 14:42:44 -08001785 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1786 See Documentation/debugging-via-ohci1394.txt for more
1787 info.
1788
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001789 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1790 Rather than timing out after 20 ms if an EC
1791 command is not properly ACKed, override the length
1792 of the timeout. We have interrupts disabled while
1793 waiting for the ACK, so if this is set too high
1794 interrupts *may* be lost!
1795
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001796 omap_mux= [OMAP] Override bootloader pin multiplexing.
1797 Format: <mux_mode0.mode_name=value>...
1798 For example, to override I2C bus2:
1799 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1800
Linus Torvalds1da177e2005-04-16 15:20:36 -07001801 opl3= [HW,OSS]
1802 Format: <io>
1803
Linus Torvalds1da177e2005-04-16 15:20:36 -07001804 oprofile.timer= [HW]
1805 Use timer interrupt instead of performance counters
1806
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001807 oprofile.cpu_type= Force an oprofile cpu type
1808 This might be useful if you have an older oprofile
1809 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001810 Format: { arch_perfmon }
1811 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001812 perfmon on Intel CPUs instead of the
1813 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001814
Linus Torvalds1da177e2005-04-16 15:20:36 -07001815 osst= [HW,SCSI] SCSI Tape Driver
1816 Format: <buffer_size>,<write_threshold>
1817 See also Documentation/scsi/st.txt.
1818
1819 panic= [KNL] Kernel behaviour on panic
1820 Format: <timeout>
1821
1822 parkbd.port= [HW] Parallel port number the keyboard adapter is
1823 connected to, default is 0.
1824 Format: <parport#>
1825 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1826 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001827 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828
Randy Dunlapa9913042005-10-23 12:57:11 -07001829 parport= [HW,PPT] Specify parallel ports. 0 disables.
1830 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1831 Use 'auto' to force the driver to use any
1832 IRQ/DMA settings detected (the default is to
1833 ignore detected IRQ/DMA settings because of
1834 possible conflicts). You can specify the base
1835 address, IRQ, and DMA settings; IRQ and DMA
1836 should be numbers, or 'auto' (for using detected
1837 settings on that particular port), or 'nofifo'
1838 (to avoid using a FIFO even if it is detected).
1839 Parallel ports are assigned in the order they
1840 are specified on the command line, starting
1841 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001842
Randy Dunlapa9913042005-10-23 12:57:11 -07001843 parport_init_mode= [HW,PPT]
1844 Configure VIA parallel port to operate in
1845 a specific mode. This is necessary on Pegasos
1846 computer where firmware has no options for setting
1847 up parallel port mode and sets it to spp.
1848 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849 Format: [spp|ps2|epp|ecp|ecpepp]
1850
Randy Dunlapa9913042005-10-23 12:57:11 -07001851 pas2= [HW,OSS] Format:
1852 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1853
Linus Torvalds1da177e2005-04-16 15:20:36 -07001854 pas16= [HW,SCSI]
1855 See header of drivers/scsi/pas16.c.
1856
Andrew Mortondd287792006-03-23 03:00:57 -08001857 pause_on_oops=
1858 Halt all CPUs after the first oops has been printed for
1859 the specified number of seconds. This is to be used if
1860 your oopses keep scrolling off the screen.
1861
Linus Torvalds1da177e2005-04-16 15:20:36 -07001862 pcbit= [HW,ISDN]
1863
1864 pcd. [PARIDE]
1865 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001866 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001867
Randy Dunlapa9913042005-10-23 12:57:11 -07001868 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001869 earlydump [X86] dump PCI config space before the kernel
1870 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001871 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001872 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001873 the hardware directly. Use this if your machine
1874 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001875 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001876 hardware access methods are allowed. Use this
1877 if you experience crashes upon bootup and you
1878 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001879 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001880 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001881 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001882 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001883 noaer [PCIE] If the PCIEAER kernel config parameter is
1884 enabled, this kernel boot option can be used to
1885 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001886 nodomains [PCI] Disable support for multiple PCI
1887 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301888 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001889 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001890 check_enable_amd_mmconf [X86] check for and enable
1891 properly configured MMIO access to PCI
1892 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001893 nomsi [MSI] If the PCI_MSI kernel config parameter is
1894 enabled, this kernel boot option can be used to
1895 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001896 noioapicquirk [APIC] Disable all boot interrupt quirks.
1897 Safety option to keep boot IRQs enabled. This
1898 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001899 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1900 primary IO-APIC for bridges that cannot disable
1901 boot IRQs. This fixes a source of spurious IRQs
1902 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001903 noioapicreroute [APIC] Disable workaround that uses the
1904 boot IRQ equivalent of an IRQ that connects to
1905 a chipset where boot IRQs cannot be disabled.
1906 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001907 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001908 routing table. These calls are known to be buggy
1909 on several machines and they hang the machine
1910 when used, but on other computers it's the only
1911 way to get the interrupt routing table. Try
1912 this option if the kernel is unable to allocate
1913 IRQs or discover secondary PCI buses on your
1914 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001915 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001916 Use with caution as certain devices share
1917 address decoders between ROMs and other
1918 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001919 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001920 expansion ROMs that do not already have
1921 BIOS assigned address ranges.
Andi Kleenc0115602008-08-22 09:53:39 +02001922 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001923 assigned automatically to PCI devices. You can
1924 make the kernel exclude IRQs of your ISA cards
1925 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001926 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001927 of the PIRQ table (normally generated
1928 by the BIOS) if it is outside the
1929 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001930 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001931 useful if the kernel is unable to find your
1932 secondary buses and you want to tell it
1933 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001934 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001935 numbers ourselves, overriding
1936 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001937 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001938 in the BIOS $PIR table. This is needed on
1939 some systems with broken BIOSes, notably
1940 some HP Pavilion N5400 and Omnibook XE3
1941 notebooks. This will have no effect if ACPI
1942 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001943 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001944 or for PCI scanning.
Linus Torvalds236e9462009-06-24 16:23:03 -07001945 use_crs [X86] Use _CRS for PCI resource
Gary Hade62f420f2007-10-03 15:56:51 -07001946 allocation.
Randy Dunlapa9913042005-10-23 12:57:11 -07001947 routeirq Do IRQ routing for all PCI devices.
1948 This is normally done in pci_enable_device(),
1949 so this option is a temporary workaround
1950 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001951 skip_isa_align [X86] do not align io start addr, so can
1952 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001953 firmware [ARM] Do not re-enumerate the bus but instead
1954 just use the configuration from the
1955 bootloader. This is currently used on
1956 IXP2000 systems where the bus has to be
1957 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001958 noearly [X86] Don't do any early type 1 scanning.
1959 This might help on some broken boards which
1960 machine check when some devices' config space
1961 is read. But various workarounds are disabled
1962 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001963 bfsort Sort PCI devices into breadth-first order.
1964 This sorting is done to get a device
1965 order compatible with older (<= 2.4) kernels.
1966 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001967 cbiosize=nn[KMG] The fixed amount of bus space which is
1968 reserved for the CardBus bridge's IO window.
1969 The default value is 256 bytes.
1970 cbmemsize=nn[KMG] The fixed amount of bus space which is
1971 reserved for the CardBus bridge's memory
1972 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09001973 resource_alignment=
1974 Format:
1975 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1976 Specifies alignment and device to reassign
1977 aligned memory resources.
1978 If <order of align> is not specified,
1979 PAGE_SIZE is used as alignment.
1980 PCI-PCI bridge can be specified, if resource
1981 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06001982 ecrc= Enable/disable PCIe ECRC (transaction layer
1983 end-to-end CRC checking).
1984 bios: Use BIOS/firmware settings. This is the
1985 the default.
1986 off: Turn ECRC off
1987 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001988
Chuck Ebberte5665a42008-09-24 20:40:34 -04001989 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1990 Management.
1991 off Disable ASPM.
1992 force Enable ASPM even on devices that claim not to support it.
1993 WARNING: Forcing ASPM on may cause system lockups.
1994
Linus Torvalds1da177e2005-04-16 15:20:36 -07001995 pcmv= [HW,PCMCIA] BadgePAD 4
1996
1997 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001998 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001999
2000 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2001 boot time.
2002 Format: { 0 | 1 }
2003 See arch/parisc/kernel/pdc_chassis.c
2004
Tejun Heof58dc012009-08-14 15:00:50 +09002005 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002006 Currently supported values are "embed" and "page".
2007 Archs may support subset or none of the selections.
2008 See comments in mm/percpu.c for details on each
2009 allocator. This parameter is primarily for debugging
2010 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002011
Linus Torvalds1da177e2005-04-16 15:20:36 -07002012 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002013 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002014
2015 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002016 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002017
2018 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002019 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002020
2021 plip= [PPT,NET] Parallel port network link
2022 Format: { parport<nr> | timid | 0 }
2023 See also Documentation/parport.txt.
2024
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002025 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2026 Override pmtimer IOPort with a hex value.
2027 e.g. pmtmr=0x508
2028
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002029 pnp.debug [PNP]
2030 Enable PNP debug messages. This depends on the
2031 CONFIG_PNP_DEBUG_MESSAGES option.
2032
Linus Torvalds1da177e2005-04-16 15:20:36 -07002033 pnpacpi= [ACPI]
2034 { off }
2035
2036 pnpbios= [ISAPNP]
2037 { on | off | curr | res | no-curr | no-res }
2038
2039 pnp_reserve_irq=
2040 [ISAPNP] Exclude IRQs for the autoconfiguration
2041
2042 pnp_reserve_dma=
2043 [ISAPNP] Exclude DMAs for the autoconfiguration
2044
2045 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002046 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047
2048 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002049 [ISAPNP] Exclude memory regions for the
2050 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002051 Ranges are in pairs (memory base and size).
2052
Randy Dunlap4af94f32009-04-17 18:30:28 -07002053 ports= [IP_VS_FTP] IPVS ftp helper module
2054 Default is 21.
2055 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2056 may be specified.
2057 Format: <port>,<port>....
2058
Ingo Molnar45807a12007-07-15 23:40:10 -07002059 print-fatal-signals=
2060 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002061
2062 If enabled, warn about various signal handling
2063 related application anomalies: too many signals,
2064 too many POSIX.1 timers, fatal signals causing a
2065 coredump - etc.
2066
2067 If you hit the warning due to signal overflow,
2068 you might want to try "ulimit -i unlimited".
2069
Ingo Molnar45807a12007-07-15 23:40:10 -07002070 default: off.
2071
Randy Dunlape84845c2007-07-15 23:40:25 -07002072 printk.time= Show timing data prefixed to each printk message line
2073 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2074
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002075 processor.max_cstate= [HW,ACPI]
2076 Limit processor to maximum C-state
2077 max_cstate=9 overrides any DMI blacklist limit.
2078
2079 processor.nocst [HW,ACPI]
2080 Ignore the _CST method to determine C-states,
2081 instead using the legacy FADT method
2082
Linus Torvalds1da177e2005-04-16 15:20:36 -07002083 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002084 Format: [schedule,]<number>
2085 Param: "schedule" - profile schedule points.
2086 Param: <number> - step/bucket size as a power of 2 for
2087 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002088 Param: "sleep" - profile D-state sleeping (millisecs).
2089 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002090 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002091
Linus Torvalds1da177e2005-04-16 15:20:36 -07002092 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2093 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002094 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002095
Randy Dunlapa9913042005-10-23 12:57:11 -07002096 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2097 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002098 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2099 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002100 psmouse.resetafter= [HW,MOUSE]
2101 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002102 (0 = never).
2103 psmouse.resolution=
2104 [HW,MOUSE] Set desired mouse resolution, in dpi.
2105 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002106 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002107 0 = disabled, 1 = enabled (default).
2108
2109 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
Randy Dunlapa9913042005-10-23 12:57:11 -07002110 Format:
2111 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002112
2113 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002114 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002115
Kay Sieversdc8c8582007-08-15 12:25:38 +02002116 pty.legacy_count=
2117 [KNL] Number of legacy pty's. Overwrites compiled-in
2118 default number.
2119
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002120 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002121
Linus Torvalds1da177e2005-04-16 15:20:36 -07002122 r128= [HW,DRM]
2123
2124 raid= [HW,RAID]
2125 See Documentation/md.txt.
2126
Randy Dunlapa9913042005-10-23 12:57:11 -07002127 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002128 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002129
Linus Torvalds1da177e2005-04-16 15:20:36 -07002130 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002131 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002132
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002133 rcupdate.blimit= [KNL,BOOT]
2134 Set maximum number of finished RCU callbacks to process
2135 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002136
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002137 rcupdate.qhimark= [KNL,BOOT]
2138 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002139 RCU callbacks over which batch limiting is disabled.
2140
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002141 rcupdate.qlowmark= [KNL,BOOT]
2142 Set threshold of queued RCU callbacks below which
2143 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002144
Olof Johanssonffdfc402005-09-06 15:17:19 -07002145 rdinit= [KNL]
2146 Format: <full_path>
2147 Run specified binary instead of /init from the ramdisk,
2148 used for early userspace startup. See initrd.
2149
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002150 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002152 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002153
Paul Jackson46b6d942008-07-04 10:00:09 -07002154 relax_domain_level=
2155 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002156 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002157
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2159
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002160 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07002161 Format: nn[KMG]
2162 Reserves a hole at the top of the kernel virtual
2163 address space.
2164
Vivek Goyal7e962872006-09-27 01:50:44 -07002165 reset_devices [KNL] Force drivers to reset the underlying device
2166 during initialization.
2167
Randy Dunlapa9913042005-10-23 12:57:11 -07002168 resume= [SWSUSP]
2169 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002170
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002171 resume_offset= [SWSUSP]
2172 Specify the offset from the beginning of the partition
2173 given by "resume=" at which the swap header is located,
2174 in <PAGE_SIZE> units (needed only for swap files).
2175 See Documentation/power/swsusp-and-swap-files.txt
2176
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002177 retain_initrd [RAM] Keep initrd memory after extraction
2178
Linus Torvalds1da177e2005-04-16 15:20:36 -07002179 rhash_entries= [KNL,NET]
2180 Set number of hash buckets for route cache
2181
2182 riscom8= [HW,SERIAL]
2183 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2184
2185 ro [KNL] Mount root device read-only on boot
2186
2187 root= [KNL] Root filesystem
2188
2189 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2190 mount the root filesystem
2191
2192 rootflags= [KNL] Set root filesystem mount option string
2193
2194 rootfstype= [KNL] Set root filesystem type
2195
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002196 rootwait [KNL] Wait (indefinitely) for root device to show up.
2197 Useful for devices that are detected asynchronously
2198 (e.g. USB and MMC devices).
2199
Linus Torvalds1da177e2005-04-16 15:20:36 -07002200 rw [KNL] Mount root device read-write on boot
2201
2202 S [KNL] Run init in single mode
2203
2204 sa1100ir [NET]
2205 See drivers/net/irda/sa1100_ir.c.
2206
Linus Torvalds1da177e2005-04-16 15:20:36 -07002207 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002208
Mike Travisf6630112009-11-17 18:22:15 -06002209 sched_debug [KNL] Enables verbose scheduler debug messages.
2210
Linus Torvalds1da177e2005-04-16 15:20:36 -07002211 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2212 Format: <io>[,<timeout>[,<isapnp>]]
2213
2214 scsi_debug_*= [SCSI]
2215 See drivers/scsi/scsi_debug.c.
2216
2217 scsi_default_dev_flags=
2218 [SCSI] SCSI default device flags
2219 Format: <integer>
2220
2221 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2222 Format: <vendor>:<model>:<flags>
2223 (flags are integer value)
2224
Randy Dunlap6af66322007-11-14 16:52:25 -08002225 scsi_logging_level= [SCSI] a bit mask of logging levels
2226 See drivers/scsi/scsi_logging.h for bits. Also
2227 settable via sysctl at dev.scsi.logging_level
2228 (/proc/sys/dev/scsi/logging_level).
2229 There is also a nice 'scsi_logging_level' script in the
2230 S390-tools package, available for download at
2231 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
Linus Torvalds1da177e2005-04-16 15:20:36 -07002232
Matthew Wilcox3e082a92006-09-28 15:19:20 -06002233 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2234 discovered. async scans them in kernel threads,
2235 allowing boot to proceed. none ignores them, expecting
2236 user space to do the scan.
2237
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002238 security= [SECURITY] Choose a security module to enable at boot.
2239 If this boot parameter is not specified, only the first
2240 security module asking for security registration will be
2241 loaded. An invalid security module name will be treated
2242 as if no module has been chosen.
2243
2244 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002245 Format: { "0" | "1" }
2246 See security/selinux/Kconfig help text.
2247 0 -- disable.
2248 1 -- enable.
2249 Default value is set via kernel config option.
2250 If enabled at boot time, /selinux/disable can be used
2251 later to disable prior to initial policy load.
2252
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002253 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002254
Linus Torvalds1da177e2005-04-16 15:20:36 -07002255 shapers= [NET]
2256 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002257
Yinghai Lub05f78f2008-08-22 01:32:50 -07002258 show_msr= [x86] show boot-time MSR settings
2259 Format: { <integer> }
2260 Show boot-time (BIOS-initialized) MSR settings.
2261 The parameter means the number of CPUs to show,
2262 for example 1 means boot CPU only.
2263
Linus Torvalds1da177e2005-04-16 15:20:36 -07002264 sim710= [SCSI,HW]
2265 See header of drivers/scsi/sim710.c.
2266
2267 simeth= [IA-64]
2268 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002269
Linus Torvalds1da177e2005-04-16 15:20:36 -07002270 slram= [HW,MTD]
2271
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002272 slub_debug[=options[,slabs]] [MM, SLUB]
2273 Enabling slub_debug allows one to determine the
2274 culprit if slab objects become corrupted. Enabling
2275 slub_debug can create guard zones around objects and
2276 may poison objects when not in use. Also tracks the
2277 last alloc / free. For more information see
2278 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002279
2280 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002281 Determines the maximum allowed order for slabs.
2282 A high setting may cause OOMs due to memory
2283 fragmentation. For more information see
2284 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002285
2286 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002287 The minimum number of objects per slab. SLUB will
2288 increase the slab order up to slub_max_order to
2289 generate a sufficiently large slab able to contain
2290 the number of objects indicated. The higher the number
2291 of objects the smaller the overhead of tracking slabs
2292 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002293 For more information see Documentation/vm/slub.txt.
2294
2295 slub_min_order= [MM, SLUB]
2296 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002297 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002298 For more information see Documentation/vm/slub.txt.
2299
2300 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002301 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002302 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002303 allocs to different slabs. Debug options disable
2304 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002305 For more information see Documentation/vm/slub.txt.
2306
Linus Torvalds1da177e2005-04-16 15:20:36 -07002307 smart2= [HW]
2308 Format: <io1>[,<io2>[,...,<io8>]]
2309
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002310 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002311 attempt to substitute SMP alternatives once at boot.
2312
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002313 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2314 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2315 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2316 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2317 smsc-ircc2.ircc_irq= [HW] IRQ line
2318 smsc-ircc2.ircc_dma= [HW] DMA channel
2319 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2320 0: Toshiba Satellite 1800 (GP data pin select)
2321 1: Fast pin select (default)
2322 2: ATC IRMode
2323
Linus Torvalds1da177e2005-04-16 15:20:36 -07002324 snd-ad1816a= [HW,ALSA]
2325
2326 snd-ad1848= [HW,ALSA]
2327
2328 snd-ali5451= [HW,ALSA]
2329
2330 snd-als100= [HW,ALSA]
2331
2332 snd-als4000= [HW,ALSA]
2333
2334 snd-azt2320= [HW,ALSA]
2335
2336 snd-cmi8330= [HW,ALSA]
2337
2338 snd-cmipci= [HW,ALSA]
2339
2340 snd-cs4231= [HW,ALSA]
2341
2342 snd-cs4232= [HW,ALSA]
2343
2344 snd-cs4236= [HW,ALSA]
2345
2346 snd-cs4281= [HW,ALSA]
2347
2348 snd-cs46xx= [HW,ALSA]
2349
2350 snd-dt019x= [HW,ALSA]
2351
2352 snd-dummy= [HW,ALSA]
2353
2354 snd-emu10k1= [HW,ALSA]
2355
2356 snd-ens1370= [HW,ALSA]
2357
2358 snd-ens1371= [HW,ALSA]
2359
2360 snd-es968= [HW,ALSA]
2361
2362 snd-es1688= [HW,ALSA]
2363
2364 snd-es18xx= [HW,ALSA]
2365
2366 snd-es1938= [HW,ALSA]
2367
2368 snd-es1968= [HW,ALSA]
2369
2370 snd-fm801= [HW,ALSA]
2371
2372 snd-gusclassic= [HW,ALSA]
2373
2374 snd-gusextreme= [HW,ALSA]
2375
2376 snd-gusmax= [HW,ALSA]
2377
2378 snd-hdsp= [HW,ALSA]
2379
2380 snd-ice1712= [HW,ALSA]
2381
2382 snd-intel8x0= [HW,ALSA]
2383
2384 snd-interwave= [HW,ALSA]
2385
2386 snd-interwave-stb=
2387 [HW,ALSA]
2388
2389 snd-korg1212= [HW,ALSA]
2390
2391 snd-maestro3= [HW,ALSA]
2392
2393 snd-mpu401= [HW,ALSA]
2394
2395 snd-mtpav= [HW,ALSA]
2396
2397 snd-nm256= [HW,ALSA]
2398
2399 snd-opl3sa2= [HW,ALSA]
2400
2401 snd-opti92x-ad1848=
2402 [HW,ALSA]
2403
2404 snd-opti92x-cs4231=
2405 [HW,ALSA]
2406
2407 snd-opti93x= [HW,ALSA]
2408
2409 snd-pmac= [HW,ALSA]
2410
2411 snd-rme32= [HW,ALSA]
2412
2413 snd-rme96= [HW,ALSA]
2414
2415 snd-rme9652= [HW,ALSA]
2416
2417 snd-sb8= [HW,ALSA]
2418
2419 snd-sb16= [HW,ALSA]
2420
2421 snd-sbawe= [HW,ALSA]
2422
2423 snd-serial= [HW,ALSA]
2424
2425 snd-sgalaxy= [HW,ALSA]
2426
2427 snd-sonicvibes= [HW,ALSA]
2428
2429 snd-sun-amd7930=
2430 [HW,ALSA]
2431
2432 snd-sun-cs4231= [HW,ALSA]
2433
2434 snd-trident= [HW,ALSA]
2435
2436 snd-usb-audio= [HW,ALSA,USB]
2437
2438 snd-via82xx= [HW,ALSA]
2439
2440 snd-virmidi= [HW,ALSA]
2441
2442 snd-wavefront= [HW,ALSA]
2443
2444 snd-ymfpci= [HW,ALSA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002445
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002446 softlockup_panic=
2447 [KNL] Should the soft-lockup detector generate panics.
2448
Linus Torvalds1da177e2005-04-16 15:20:36 -07002449 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2450 See Documentation/sonypi.txt
2451
2452 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002453 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002454
2455 spia_io_base= [HW,MTD]
2456 spia_fio_base=
2457 spia_pedr=
2458 spia_peddr=
2459
2460 sscape= [HW,OSS]
2461 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
Randy Dunlapa9913042005-10-23 12:57:11 -07002462
Linus Torvalds1da177e2005-04-16 15:20:36 -07002463 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2464 See Documentation/scsi/st.txt.
2465
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002466 stacktrace [FTRACE]
2467 Enabled the stack tracer on boot up.
2468
Linus Torvalds1da177e2005-04-16 15:20:36 -07002469 sti= [PARISC,HW]
2470 Format: <num>
2471 Set the STI (builtin display/keyboard on the HP-PARISC
2472 machines) console (graphic card) which should be used
2473 as the initial boot-console.
2474 See also comment in drivers/video/console/sticore.c.
2475
2476 sti_font= [HW]
2477 See comment in drivers/video/console/sticore.c.
2478
2479 stifb= [HW]
2480 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2481
Trond Myklebustcbf11072009-08-09 15:06:19 -04002482 sunrpc.min_resvport=
2483 sunrpc.max_resvport=
2484 [NFS,SUNRPC]
2485 SunRPC servers often require that client requests
2486 originate from a privileged port (i.e. a port in the
2487 range 0 < portnr < 1024).
2488 An administrator who wishes to reserve some of these
2489 ports for other uses may adjust the range that the
2490 kernel's sunrpc client considers to be privileged
2491 using these two parameters to set the minimum and
2492 maximum port values.
2493
Greg Banks42a7fc42007-03-06 01:42:23 -08002494 sunrpc.pool_mode=
2495 [NFS]
2496 Control how the NFS server code allocates CPUs to
2497 service thread pools. Depending on how many NICs
2498 you have and where their interrupts are bound, this
2499 option will affect which CPUs will do NFS serving.
2500 Note: this parameter cannot be changed while the
2501 NFS server is running.
2502
2503 auto the server chooses an appropriate mode
2504 automatically using heuristics
2505 global a single global pool contains all CPUs
2506 percpu one pool for each CPU
2507 pernode one pool for each NUMA node (equivalent
2508 to global on non-NUMA machines)
2509
Trond Myklebustcbf11072009-08-09 15:06:19 -04002510 sunrpc.tcp_slot_table_entries=
2511 sunrpc.udp_slot_table_entries=
2512 [NFS,SUNRPC]
2513 Sets the upper limit on the number of simultaneous
2514 RPC calls that can be sent from the client to a
2515 server. Increasing these values may allow you to
2516 improve throughput, but will also increase the
2517 amount of memory reserved for use by the client.
2518
Linus Torvalds1da177e2005-04-16 15:20:36 -07002519 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002520
Linus Torvalds1da177e2005-04-16 15:20:36 -07002521 switches= [HW,M68k]
2522
2523 sym53c416= [HW,SCSI]
2524 See header of drivers/scsi/sym53c416.c.
2525
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002526 sysrq_always_enabled
2527 [KNL]
2528 Ignore sysrq setting - this boot parameter will
2529 neutralize any effect of /proc/sys/kernel/sysrq.
2530 Useful for debugging.
2531
Linus Torvalds1da177e2005-04-16 15:20:36 -07002532 t128= [HW,SCSI]
2533 See header of drivers/scsi/t128.c.
2534
2535 tdfx= [HW,DRM]
2536
David Brownell77437fd2008-07-23 21:28:33 -07002537 test_suspend= [SUSPEND]
2538 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2539 standby suspend) as the system sleep state to briefly
2540 enter during system startup. The system is woken from
2541 this state using a wakeup-capable RTC alarm.
2542
Linus Torvalds1da177e2005-04-16 15:20:36 -07002543 thash_entries= [KNL,NET]
2544 Set number of hash buckets for TCP connection
2545
Len Brownf8707ec2007-08-12 00:12:54 -04002546 thermal.act= [HW,ACPI]
2547 -1: disable all active trip points in all thermal zones
2548 <degrees C>: override all lowest active trip points
2549
Len Brownc52a7412007-08-14 15:49:32 -04002550 thermal.crt= [HW,ACPI]
2551 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002552 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002553
Len Brownf5487142007-08-12 00:12:44 -04002554 thermal.nocrt= [HW,ACPI]
2555 Set to disable actions on ACPI thermal zone
2556 critical and hot trip points.
2557
Len Brown72b33ef2007-08-12 00:12:17 -04002558 thermal.off= [HW,ACPI]
2559 1: disable ACPI thermal control
2560
Len Browna70cdc52007-08-12 00:12:35 -04002561 thermal.psv= [HW,ACPI]
2562 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002563 <degrees C>: override all passive trip points to this
2564 value
Len Browna70cdc52007-08-12 00:12:35 -04002565
Len Brown730ff342007-08-12 00:12:26 -04002566 thermal.tzp= [HW,ACPI]
2567 Specify global default ACPI thermal zone polling rate
2568 <deci-seconds>: poll all this frequency
2569 0: no polling (default)
2570
Linus Torvalds1da177e2005-04-16 15:20:36 -07002571 tmscsim= [HW,SCSI]
2572 See comment before function dc390_setup() in
2573 drivers/scsi/tmscsim.c.
2574
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002575 topology= [S390]
2576 Format: {off | on}
2577 Specify if the kernel should make use of the cpu
2578 topology informations if the hardware supports these.
2579 The scheduler will make use of these informations and
2580 e.g. base its process migration decisions on it.
2581 Default is off.
2582
Linus Torvalds1da177e2005-04-16 15:20:36 -07002583 tp720= [HW,PS2]
2584
Li Zefan9d612be2009-06-24 17:33:15 +08002585 trace_buf_size=nn[KMG]
2586 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002587
Li Zefan020e5f82009-07-01 10:47:05 +08002588 trace_event=[event-list]
2589 [FTRACE] Set and start specified trace events in order
2590 to facilitate early boot debugging.
2591 See also Documentation/trace/events.txt
2592
Linus Torvalds1da177e2005-04-16 15:20:36 -07002593 trix= [HW,OSS] MediaTrix AudioTrix Pro
Randy Dunlapa9913042005-10-23 12:57:11 -07002594 Format:
2595 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2596
Alok Kataria395628e2008-10-24 17:22:01 -07002597 tsc= Disable clocksource-must-verify flag for TSC.
2598 Format: <string>
2599 [x86] reliable: mark tsc clocksource as reliable, this
2600 disables clocksource verification at runtime.
2601 Used to enable high-resolution timer mode on older
2602 hardware, and in virtualized environment.
2603
Randy Dunlapa9913042005-10-23 12:57:11 -07002604 turbografx.map[2|3]= [HW,JOY]
2605 TurboGraFX parallel port interface
2606 Format:
2607 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002608 See also Documentation/input/joystick-parport.txt
2609
2610 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2611 See header of drivers/scsi/u14-34f.c.
2612
2613 uart401= [HW,OSS]
2614 Format: <io>,<irq>
2615
2616 uart6850= [HW,OSS]
2617 Format: <io>,<irq>
2618
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002619 uhash_entries= [KNL,NET]
2620 Set number of hash buckets for UDP/UDP-Lite connections
2621
Alan Stern5f8364b2006-12-05 16:29:55 -05002622 uhci-hcd.ignore_oc=
2623 [USB] Ignore overcurrent events (default N).
2624 Some badly-designed motherboards generate lots of
2625 bogus events, for ports that aren't wired to
2626 anything. Set this parameter to avoid log spamming.
2627 Note that genuine overcurrent events won't be
2628 reported either.
2629
Simon Arlotte3a61b02008-07-19 23:32:54 +01002630 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302631 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002632 Set unknown_nmi_panic=1 early on boot.
2633
Alan Sternb5e795f2007-02-20 15:00:53 -05002634 usbcore.autosuspend=
2635 [USB] The autosuspend time delay (in seconds) used
2636 for newly-detected USB devices (default 2). This
2637 is the time required before an idle device will be
2638 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002639 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002640
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002641 usbcore.usbfs_snoop=
2642 [USB] Set to log all usbfs traffic (default 0 = off).
2643
2644 usbcore.blinkenlights=
2645 [USB] Set to cycle leds on hubs (default 0 = off).
2646
2647 usbcore.old_scheme_first=
2648 [USB] Start with the old device initialization
2649 scheme (default 0 = off).
2650
2651 usbcore.use_both_schemes=
2652 [USB] Try the other device initialization scheme
2653 if the first one fails (default 1 = enabled).
2654
2655 usbcore.initial_descriptor_timeout=
2656 [USB] Specifies timeout for the initial 64-byte
2657 USB_REQ_GET_DESCRIPTOR request in milliseconds
2658 (default 5000 = 5.0 seconds).
2659
Linus Torvalds1da177e2005-04-16 15:20:36 -07002660 usbhid.mousepoll=
2661 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002662
Alan Sternd4f373e2008-11-10 14:07:45 -05002663 usb-storage.delay_use=
2664 [UMS] The delay in seconds before a new device is
2665 scanned for Logical Units (default 5).
2666
2667 usb-storage.quirks=
2668 [UMS] A list of quirks entries to supplement or
2669 override the built-in unusual_devs list. List
2670 entries are separated by commas. Each entry has
2671 the form VID:PID:Flags where VID and PID are Vendor
2672 and Product ID values (4-digit hex numbers) and
2673 Flags is a set of characters, each corresponding
2674 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002675 a = SANE_SENSE (collect more than 18 bytes
2676 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002677 b = BAD_SENSE (don't collect more than 18
2678 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002679 c = FIX_CAPACITY (decrease the reported
2680 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002681 h = CAPACITY_HEURISTICS (decrease the
2682 reported device capacity by one
2683 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002684 i = IGNORE_DEVICE (don't bind to this
2685 device);
2686 l = NOT_LOCKABLE (don't try to lock and
2687 unlock ejectable media);
2688 m = MAX_SECTORS_64 (don't transfer more
2689 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002690 o = CAPACITY_OK (accept the capacity
2691 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002692 r = IGNORE_RESIDUE (the device reports
2693 bogus residue values);
2694 s = SINGLE_LUN (the device has only one
2695 Logical Unit);
2696 w = NO_WP_DETECT (don't test whether the
2697 medium is write-protected).
2698 Example: quirks=0419:aaf5:rl,0421:0433:rc
2699
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302700 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002701 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002702 vdso=1: enable VDSO (default)
2703 vdso=0: disable VDSO mapping
2704
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302705 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002706 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2707 vdso32=1: enable 32-bit VDSO (default)
2708 vdso32=0: disable 32-bit VDSO mapping
2709
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002710 vector= [IA-64,SMP]
2711 vector=percpu: enable percpu vector domain
2712
Linus Torvalds1da177e2005-04-16 15:20:36 -07002713 video= [FB] Frame buffer configuration
2714 See Documentation/fb/modedb.txt.
2715
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002716 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002717 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002718 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002719 Use vga=ask for menu.
2720 This is actually a boot loader parameter; the value is
2721 passed to the kernel using a special protocol.
2722
Randy Dunlapa9913042005-10-23 12:57:11 -07002723 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002724 size of <nn>. This can be used to increase the
2725 minimum size (128MB on x86). It can also be used to
2726 decrease the size and leave more room for directly
2727 mapped kernel RAM.
2728
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002729 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2730 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002731
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002732 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2733 Format: <command>
2734
2735 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2736 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002737
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002738 vt.cur_default= [VT] Default cursor shape.
2739 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2740 the parameters of the <Esc>[?A;B;Cc escape sequence;
2741 see VGA-softcursor.txt. Default: 2 = underline.
2742
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002743 vt.default_blu= [VT]
2744 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2745 Change the default blue palette of the console.
2746 This is a 16-member array composed of values
2747 ranging from 0-255.
2748
2749 vt.default_grn= [VT]
2750 Format: <green0>,<green1>,<green2>,...,<green15>
2751 Change the default green palette of the console.
2752 This is a 16-member array composed of values
2753 ranging from 0-255.
2754
2755 vt.default_red= [VT]
2756 Format: <red0>,<red1>,<red2>,...,<red15>
2757 Change the default red palette of the console.
2758 This is a 16-member array composed of values
2759 ranging from 0-255.
2760
2761 vt.default_utf8=
2762 [VT]
2763 Format=<0|1>
2764 Set system-wide default UTF-8 mode for all tty's.
2765 Default is 1, i.e. UTF-8 mode is enabled for all
2766 newly opened terminals.
2767
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002768 vt.global_cursor_default=
2769 [VT]
2770 Format=<-1|0|1>
2771 Set system-wide default for whether a cursor
2772 is shown on new VTs. Default is -1,
2773 i.e. cursors will be created by default unless
2774 overridden by individual drivers. 0 will hide
2775 cursors, 1 will display them.
2776
Linus Torvalds1da177e2005-04-16 15:20:36 -07002777 waveartist= [HW,OSS]
2778 Format: <io>,<irq>,<dma>,<dma2>
Randy Dunlapa9913042005-10-23 12:57:11 -07002779
Linus Torvalds1da177e2005-04-16 15:20:36 -07002780 wd33c93= [HW,SCSI]
2781 See header of drivers/scsi/wd33c93.c.
2782
2783 wd7000= [HW,SCSI]
2784 See header of drivers/scsi/wd7000.c.
2785
2786 wdt= [WDT] Watchdog
Gabriel C8dfe9c22007-08-10 13:01:00 -07002787 See Documentation/watchdog/wdt.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002788
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002789 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2790 default x2apic cluster mode on platforms
2791 supporting x2apic.
2792
Linus Torvalds1da177e2005-04-16 15:20:36 -07002793 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2794 xd_geo= See header of drivers/block/xd.c.
2795
2796 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002797 Format:
2798 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002799
Randy Dunlapa9913042005-10-23 12:57:11 -07002800______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002801
2802TODO:
2803
2804 Add documentation for ALSA options.
2805 Add more DRM drivers.