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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.
Linus Torvalds1da177e2005-04-16 15:20:36 -070046 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
47 EFI EFI Partitioning (GPT) is enabled
48 EIDE EIDE/ATAPI support is enabled.
Thomas Renningera648ec02010-08-06 16:11:02 +020049 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070051 FB The frame buffer device is enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070052 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070054 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050055 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070056 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070057 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080058 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050062 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020063 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070064 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070073 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070074 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070075 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070079 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070081 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070083 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -070092 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -070094 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070095 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -070096 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +090098 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
Steven Rostedtf38f1d22008-12-16 23:06:40 -0500103 FTRACE Function tracing enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300104 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500106 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700114 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700117 Documentation/x86/x86_64/boot-options.txt .
Andi Kleenc0115602008-08-22 09:53:39 +0200118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100119 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120
121In addition, the following text indicates that the option:
122
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
126
127Parameters denoted with BOOT are actually interpreted by the boot
128loader, and have no meaning to the kernel directly.
129Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500130need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131
Karsten Weiss55588702007-02-13 13:26:21 +0100132There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700133See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100134
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136a trailing = on the name of any parameter states that that parameter will
137be entered as an environment variable, whereas its absence indicates that
138it will appear as a kernel argument readable via /proc/cmdline by programs
139running once the system is up.
140
jens m. noedler9c4751f2006-09-29 02:00:27 -0700141The number of kernel parameters is not limited, but the length of the
142complete command line (parameters including spaces etc.) is limited to
143a fixed number of characters. This limit depends on the architecture
144and is between 256 and 4096 characters. It is defined in the file
145./include/asm/setup.h as COMMAND_LINE_SIZE.
146
147
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530148 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800149 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500150 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151 force -- enable ACPI if default was off
152 off -- disable ACPI if default was on
153 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700154 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800156 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800157 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158
Randy Dunlap53471122008-03-12 18:10:51 -0400159 See also Documentation/power/pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160
Len Browna1fdcc02007-03-11 03:26:14 -0400161 acpi_apic_instance= [ACPI, IOAPIC]
162 Format: <int>
163 2: use 2nd APIC table, if available
164 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400165 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400166
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200167 acpi_backlight= [HW,ACPI]
168 acpi_backlight=vendor
169 acpi_backlight=video
170 If set to vendor, prefer vendor specific driver
171 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
172 of the ACPI video.ko driver.
173
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700174 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
175 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700177 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
178 debug output. Bits in debug_layer correspond to a
179 _COMPONENT in an ACPI source file, e.g.,
180 #define _COMPONENT ACPI_PCI_COMPONENT
181 Bits in debug_level correspond to a level in
182 ACPI_DEBUG_PRINT statements, e.g.,
183 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600184 The debug_level mask defaults to "info". See
185 Documentation/acpi/debug.txt for more information about
186 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600188 Enable processor driver info messages:
189 acpi.debug_layer=0x20000000
190 Enable PCI/PCI interrupt routing info messages:
191 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700192 Enable AML "Debug" output, i.e., stores to the Debug
193 object while interpreting AML:
194 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700195 Enable all messages related to ACPI hardware:
196 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200197
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700198 Some values produce so much output that the system is
199 unusable. The "log_buf_len" parameter may be useful
200 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800201
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700202 acpi_display_output= [HW,ACPI]
203 acpi_display_output=vendor
204 acpi_display_output=video
205 See above.
206
207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
209 default in APIC mode
210
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
213 default in PIC mode
214
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
217
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219 use by PCI
220 Format: <irq>,<irq>...
221
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
226
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
231
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530232 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
236
Randy Dunlap4af94f32009-04-17 18:30:28 -0700237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
239
240 acpi_serialize [HW,ACPI] force serialization of AML methods
241
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
245
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800248 old_ordering, s4_nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700249 See Documentation/power/video.txt for information on
250 s3_bios and s3_mode.
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200259 nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700264
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
268
Luca Tettamanti7e905602009-03-30 00:01:27 +0200269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
284
Randy Dunlap4af94f32009-04-17 18:30:28 -0700285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
287
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700288 agp= [AGP]
289 { off | try_unsupported }
290 off: disable AGP support
291 try_unsupported: try to drive unsupported chipsets
292 (may crash computer or cause data corruption)
293
Randy Dunlapbcfde332010-06-07 17:10:38 -0700294 ALSA [HW,ALSA]
295 See Documentation/sound/alsa/alsa-parameters.txt
296
Russell Kingd944d542010-02-20 16:13:29 +0000297 alignment= [KNL,ARM]
298 Allow the default userspace alignment fault handler
299 behaviour to be specified. Bit 0 enables warnings,
300 bit 1 enables fixups, and bit 2 sends a segfault.
301
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
304 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
308 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200309 off - do not initialize any AMD IOMMU found in
310 the system
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900311
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312 amijoy.map= [HW,JOY] Amiga joystick support
313 Map of devices attached to JOY0DAT and JOY1DAT
314 Format: <a>,<b>
315 See also Documentation/kernel/input/joystick.txt
316
317 analog.map= [HW,JOY] Analog joystick and gamepad support
318 Specifies type or capabilities of an analog joystick
319 connected to one of 16 gameports
320 Format: <type1>,<type2>,..<type16>
321
Randy Dunlapa9913042005-10-23 12:57:11 -0700322 apc= [HW,SPARC]
323 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700324 Format: noidle
325 Disable APC CPU standby support. SPARCstation-Fox does
326 not play well with APC CPU idle - disable it if you have
327 APC and your system crashes randomly.
328
Randy Dunlapca1eda22009-05-06 16:02:58 -0700329 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700330 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700331 Format: { quiet (default) | verbose | debug }
332 Change the amount of debugging information output
333 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700334
Brian Haleyb0f83b22010-02-04 13:36:50 -0800335 autoconf= [IPV6]
336 See Documentation/networking/ipv6.txt.
337
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400338 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
339 Limit apic dumping. The parameter defines the maximal
340 number of local apics being dumped. Also it is possible
341 to set it to "all" by meaning -- no limit here.
342 Format: { 1 (default) | 2 | ... | all }.
343 The parameter valid if only apic=debug or
344 apic=verbose is specified.
345 Example: apic=debug show_lapic=all
346
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700348 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349
Linus Torvalds1da177e2005-04-16 15:20:36 -0700350 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
351 Format: <io>,<irq>,<nodeID>
352
353 ataflop= [HW,M68k]
354
355 atarimouse= [HW,MOUSE] Atari Mouse
356
Linus Torvalds1da177e2005-04-16 15:20:36 -0700357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358 EzKey and similar keyboards
359
360 atkbd.reset= [HW] Reset keyboard during initialization
361
Randy Dunlapa9913042005-10-23 12:57:11 -0700362 atkbd.set= [HW] Select keyboard code set
363 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364
365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
366 keyboards
367
368 atkbd.softraw= [HW] Choose between synthetic and real raw mode
369 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700370
371 atkbd.softrepeat= [HW]
372 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700373
374 autotest [IA64]
375
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 baycom_epp= [HW,AX25]
377 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700378
Linus Torvalds1da177e2005-04-16 15:20:36 -0700379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
380 Format: <io>,<mode>
381 See header of drivers/net/hamradio/baycom_par.c.
382
Randy Dunlapa9913042005-10-23 12:57:11 -0700383 baycom_ser_fdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700385 Format: <io>,<irq>,<mode>[,<baud>]
386 See header of drivers/net/hamradio/baycom_ser_fdx.c.
387
Randy Dunlapa9913042005-10-23 12:57:11 -0700388 baycom_ser_hdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390 Format: <io>,<irq>,<mode>
391 See header of drivers/net/hamradio/baycom_ser_hdx.c.
392
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700393 boot_delay= Milliseconds to delay each printk during boot.
394 Values larger than 10 seconds (10000) are changed to
395 no delay (0).
396 Format: integer
397
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700398 bootmem_debug [KNL] Enable bootmem allocator debug messages.
399
Linus Torvalds1da177e2005-04-16 15:20:36 -0700400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700401 bttv.radio= Most important insmod options are available as
402 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
405
Linus Torvalds1da177e2005-04-16 15:20:36 -0700406 c101= [NET] Moxa C101 synchronous serial card
407
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700408 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409 Sometimes CPU hardware bugs make them report the cache
410 size incorrectly. The kernel will attempt work arounds
411 to fix known problems, but for some CPUs it is not
412 possible to determine what the correct size should be.
413 This option provides an override for these situations.
414
James Morris20510f22007-10-16 23:31:32 -0700415 capability.disable=
416 [SECURITY] Disable capabilities. This would normally
417 be used only if an alternative security model is to be
418 configured. Potentially dangerous and should only be
419 used if you are entirely sure of the consequences.
420
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100421 ccw_timeout_log [S390]
422 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423
Paul Menage8bab8dd2008-04-04 14:29:57 -0700424 cgroup_disable= [KNL] Disable a particular controller
425 Format: {name of the controller(s) to disable}
426 {Currently supported controllers - "memory"}
427
Linus Torvalds1da177e2005-04-16 15:20:36 -0700428 checkreqprot [SELINUX] Set initial checkreqprot flag value.
429 Format: { "0" | "1" }
430 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700431 0 -- check protection applied by kernel (includes
432 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700433 1 -- check protection requested by application.
434 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700435 Value can be changed at runtime via
436 /selinux/checkreqprot.
437
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100438 cio_ignore= [S390]
439 See Documentation/s390/CommonIO for details.
440
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700441 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700442 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200443 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700444 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200445 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700446 Format: { pit | tsc | cyclone | pmtmr }
447
John Stultz592913e2010-07-13 17:56:20 -0700448 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700449 Format: <string>
450 Override the default clocksource and use the clocksource
451 with the name specified.
452 Some clocksource names to choose from, depending on
453 the platform:
454 [all] jiffies (this is the base, fallback clocksource)
455 [ACPI] acpi_pm
456 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
457 pxa_timer,timer3,32k_counter,timer0_1
458 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700459 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700460 scx200_hrt on Geode; cyclone on IBM x440
461 [MIPS] MIPS
462 [PARISC] cr16
463 [S390] tod
464 [SH] SuperH
465 [SPARC64] tick
466 [X86-64] hpet,tsc
467
Andi Kleenac72e782008-01-30 13:33:21 +0100468 clearcpuid=BITNUM [X86]
469 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800470 arch/x86/include/asm/cpufeature.h for the valid bit
471 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100472 stable over kernel options, but the vendor specific
473 ones should be.
474 Also note that user programs calling CPUID directly
475 or using the feature without checking anything
476 will still see it. This just prevents it from
477 being used by the kernel or shown in /proc/cpuinfo.
478 Also note the kernel might malfunction if you disable
479 some critical bits.
480
Robert Jennings14f966e2009-04-15 05:55:32 +0000481 cmo_free_hint= [PPC] Format: { yes | no }
482 Specify whether pages are marked as being inactive
483 when they are freed. This is used in CMO environments
484 to determine OS memory pressure for page stealing by
485 a hypervisor.
486 Default: yes
487
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530488 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100489 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100490 Range: 0 - 8192
491 Default: 64
492
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700494 Format:
495 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700496
497 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
498 Format: <io>[,<irq>]
499
Randy Dunlapa9913042005-10-23 12:57:11 -0700500 com90xx= [HW,NET]
501 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700502 Format: <io>[,<irq>[,<memstart>]]
503
504 condev= [HW,S390] console device
505 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700506
Linus Torvalds1da177e2005-04-16 15:20:36 -0700507 console= [KNL] Output console device and options.
508
509 tty<n> Use the virtual console device <n>.
510
511 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800512 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800514 the form "bbbbpnf", where "bbbb" is the baud rate,
515 "p" is parity ("n", "o", or "e"), "n" is number of
516 bits, and "f" is flow control ("r" for RTS or
517 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800519 See Documentation/serial-console.txt for more
520 information. See
521 Documentation/networking/netconsole.txt for an
522 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700523
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700524 uart[8250],io,<addr>[,options]
525 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700526 Start an early, polled-mode console on the 8250/16550
527 UART at the specified I/O port or MMIO address,
528 switching to the matching ttyS device later. The
529 options are the same as for ttyS, above.
530
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700531 If the device connected to the port is not a TTY but a braille
532 device, prepend "brl," before the device type, for instance
533 console=brl,ttyS0
534 For now, only VisioBraille is supported.
535
Daniel Mackf324edc2009-06-16 15:33:52 -0700536 consoleblank= [KNL] The console blank (screen saver) timeout in
537 seconds. Defaults to 10*60 = 10mins. A value of 0
538 disables the blank timer.
539
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800540 coredump_filter=
541 [KNL] Change the default value for
542 /proc/<pid>/coredump_filter.
543 See also Documentation/filesystems/proc.txt.
544
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700546 Format:
547 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700548
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700549 crashkernel=nn[KMG]@ss[KMG]
550 [KNL] Reserve a chunk of physical memory to
551 hold a kernel to switch to with kexec on panic.
552
Bernhard Wallefb391592007-10-18 23:41:02 -0700553 crashkernel=range1:size1[,range2:size2,...][@offset]
554 [KNL] Same as above, but depends on the memory
555 in the running system. The syntax of range is
556 start-[end] where start and end are both
557 a memory unit (amount[KMG]). See also
558 Documentation/kdump/kdump.txt for a example.
559
Linus Torvalds1da177e2005-04-16 15:20:36 -0700560 cs89x0_dma= [HW,NET]
561 Format: <dma>
562
563 cs89x0_media= [HW,NET]
564 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700565
Randy Dunlapa9913042005-10-23 12:57:11 -0700566 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700567 See header of drivers/s390/block/dasd_devmap.c.
568
569 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
570 (one device per port)
571 Format: <port#>,<type>
572 See also Documentation/input/joystick-parport.txt
573
Thomas Renningera648ec02010-08-06 16:11:02 +0200574 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
575 time. See Documentation/dynamic-debug-howto.txt for
576 details.
577
Linus Torvalds1da177e2005-04-16 15:20:36 -0700578 debug [KNL] Enable kernel debugging (events log level).
579
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700580 debug_locks_verbose=
581 [KNL] verbose self-tests
582 Format=<0|1>
583 Print debugging info while doing the locking API
584 self-tests.
585 We default to 0 (no extra messages), setting it to
586 1 will print _a lot_ more information - normally
587 only useful to kernel developers.
588
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700589 debug_objects [KNL] Enable object debugging
590
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500591 no_debug_objects
592 [KNL] Disable object debugging
593
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200594 debugpat [X86] Enable PAT debugging
595
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200596 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700597 Format: <area>[,<node>]
598 See also Documentation/networking/decnet.txt.
599
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700600 default_hugepagesz=
601 [same as hugepagesz=] The size of the default
602 HugeTLB page size. This is the size represented by
603 the legacy /proc/ hugepages APIs, used for SHM, and
604 default size when mounting hugetlbfs filesystems.
605 Defaults to the default architecture's huge page size
606 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700607
Linus Torvalds1da177e2005-04-16 15:20:36 -0700608 dhash_entries= [KNL]
609 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700610
Linus Torvalds1da177e2005-04-16 15:20:36 -0700611 digi= [HW,SERIAL]
612 IO parameters + enable/disable command.
613
614 digiepca= [HW,SERIAL]
615 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000616 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700617
Brian Haleyb0f83b22010-02-04 13:36:50 -0800618 disable= [IPV6]
619 See Documentation/networking/ipv6.txt.
620
621 disable_ipv6= [IPV6]
622 See Documentation/networking/ipv6.txt.
623
Yinghai Lu95ffa242008-04-29 03:52:33 -0700624 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700625 The kernel tries to adjust MTRR layout from continuous
626 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700627 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700628
Yinghai Lu093af8d2008-01-30 13:33:32 +0100629 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100630 By default the kernel will trim any uncacheable
631 memory out of your available memory pool based on
632 MTRR settings. This parameter disables that behavior,
633 possibly causing your machine to run very slowly.
634
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530635 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700636 Disable PIN 1 of APIC timer
637 Can be useful to work around chipset bugs.
638
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700639 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
640 this option disables the debugging code at boot.
641
642 dma_debug_entries=<number>
643 This option allows to tune the number of preallocated
644 entries for DMA-API debugging code. One entry is
645 required per DMA-API allocation. Use this if the
646 DMA-API debugging code disables itself because the
647 architectural default is too low.
648
Joerg Roedel1745de52009-05-22 21:49:51 +0200649 dma_debug_driver=<driver_name>
650 With this option the DMA-API debugging driver
651 filter feature can be enabled at boot time. Just
652 pass the driver to filter for as the parameter.
653 The filter can be disabled or changed to another
654 driver later using sysfs.
655
Linus Torvalds1da177e2005-04-16 15:20:36 -0700656 dscc4.setup= [NET]
657
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700658 dynamic_printk Enables pr_debug()/dev_dbg() calls if
659 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
660 These can also be switched on/off via
661 <debugfs>/dynamic_printk/modules
662
663 earlycon= [KNL] Output early console device and options.
664 uart[8250],io,<addr>[,options]
665 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700666 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700667 Start an early, polled-mode console on the 8250/16550
668 UART at the specified I/O port or MMIO address.
Samium Gromoff1917ac72010-07-20 15:26:51 -0700669 MMIO inter-register address stride is either 8bit (mmio)
670 or 32bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700671 The options are the same as for ttyS, above.
672
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530673 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674 earlyprintk=vga
675 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500676 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500677 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678
Randy Dunlapa9913042005-10-23 12:57:11 -0700679 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 takes over.
681
Yinghai Lu5c059172008-07-24 17:29:40 -0700682 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683
684 Currently only ttyS0 and ttyS1 are supported.
685
686 Interaction with the standard serial driver is not
687 very good.
688
689 The VGA output is eventually overwritten by the real
690 console.
691
Jason Wessel97311912010-05-20 21:04:30 -0500692 ekgdboc= [X86,KGDB] Allow early kernel console debugging
693 ekgdboc=kbd
694
695 This is desgined to be used in conjunction with
696 the boot argument: earlyprintk=vga
697
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700699 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700700
Linus Torvalds1da177e2005-04-16 15:20:36 -0700701 eisa_irq_edge= [PARISC,HW]
702 See header of drivers/parisc/eisa.c.
703
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700704 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700705 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700706 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700707
708 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800709 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700710 See Documentation/block/as-iosched.txt and
711 Documentation/block/deadline-iosched.txt for details.
712
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530713 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700714 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800715 image elf header. Generally kexec loader will
716 pass this option to capture kernel.
717 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700718
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700719 enable_mtrr_cleanup [X86]
720 The kernel tries to adjust MTRR layout from continuous
721 to discrete, to make X server driver able to add WB
722 entry later. This parameter enables that.
723
Randy Dunlapca1eda22009-05-06 16:02:58 -0700724 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700725 Enable PIN 1 of APIC timer
726 Can be useful to work around chipset bugs
727 (in particular on some ATI chipsets).
728 The kernel tries to set a reasonable default.
729
Linus Torvalds1da177e2005-04-16 15:20:36 -0700730 enforcing [SELINUX] Set initial enforcing status.
731 Format: {"0" | "1"}
732 See security/selinux/Kconfig help text.
733 0 -- permissive (log only, no denials).
734 1 -- enforcing (deny and log).
735 Default value is 0.
736 Value can be changed at runtime via /selinux/enforce.
737
Huang Yinga08f82d2010-05-18 14:35:21 +0800738 erst_disable [ACPI]
739 Disable Error Record Serialization Table (ERST)
740 support.
741
Linus Torvalds1da177e2005-04-16 15:20:36 -0700742 ether= [HW,NET] Ethernet cards parameters
743 This option is obsoleted by the "netdev=" option, which
744 has equivalent usage. See its documentation for details.
745
Akinobu Mitade1ba092006-12-08 02:39:42 -0800746 failslab=
747 fail_page_alloc=
748 fail_make_request=[KNL]
749 General fault injection mechanism.
750 Format: <interval>,<probability>,<space>,<times>
751 See also /Documentation/fault-injection/.
752
Linus Torvalds1da177e2005-04-16 15:20:36 -0700753 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000754 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700755
Alex Chiangf13ae302008-05-08 14:03:23 -0600756 force_pal_cache_flush
757 [IA-64] Avoid check_sal_cache_flush which may hang on
758 buggy SAL_CACHE_FLUSH implementations. Using this
759 parameter will force ia64_sal_cache_flush to call
760 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
761
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100762 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400763 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100764 as early as possible in order to facilitate early
765 boot debugging.
766
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200767 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400768 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200769 If no parameter is passed, ftrace will dump
770 buffers of all CPUs, but if you pass orig_cpu, it will
771 dump only the buffer of the CPU that triggered the
772 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400773
774 ftrace_filter=[function-list]
775 [FTRACE] Limit the functions traced by the function
776 tracer at boot up. function-list is a comma separated
777 list of functions. This list can be changed at run
778 time by the set_ftrace_filter file in the debugfs
779 tracing directory.
780
781 ftrace_notrace=[function-list]
782 [FTRACE] Do not trace the functions specified in
783 function-list. This list can be changed at run time
784 by the set_ftrace_notrace file in the debugfs
785 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100786
Stefan Assmann369bc182009-10-12 22:17:21 +0200787 ftrace_graph_filter=[function-list]
788 [FTRACE] Limit the top level callers functions traced
789 by the function graph tracer at boot up.
790 function-list is a comma separated list of functions
791 that can be changed at run time by the
792 set_graph_function file in the debugfs tracing directory.
793
Linus Torvalds1da177e2005-04-16 15:20:36 -0700794 gamecon.map[2|3]=
795 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
796 support via parallel port (up to 5 devices per port)
797 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
798 See also Documentation/input/joystick-parport.txt
799
800 gamma= [HW,DRM]
801
Yinghai Luaaf23042008-01-30 13:33:09 +0100802 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
803 Format: off | on
804 default: on
805
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700806 gcov_persist= [GCOV] When non-zero (default), profiling data for
807 kernel modules is saved and remains accessible via
808 debugfs, even when the module is unloaded/reloaded.
809 When zero, profiling data is discarded and associated
810 debugfs files are removed at module unload time.
811
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812 gpt [EFI] Forces disk with valid GPT signature but
813 invalid Protective MBR to be treated as GPT.
814
Linus Torvalds1da177e2005-04-16 15:20:36 -0700815 hashdist= [KNL,NUMA] Large hashes allocated during boot
816 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700817 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700818 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700819
820 hcl= [IA-64] SGI's Hardware Graph compatibility layer
821
822 hd= [EIDE] (E)IDE hard drive subsystem geometry
823 Format: <cyl>,<head>,<sect>
824
Huang Yingea8c0712010-05-18 14:35:15 +0800825 hest_disable [ACPI]
826 Disable Hardware Error Source Table (HEST) support;
827 corresponding firmware-first mode error processing
828 logic will be disabled.
829
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
831 size of <nn>. This works even on boxes that have no
832 highmem otherwise. This also works to reduce highmem
833 size on bigger boxes.
834
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800835 highres= [KNL] Enable/disable high resolution timer mode.
836 Valid parameters: "on", "off"
837 Default: "on"
838
Linus Torvalds1da177e2005-04-16 15:20:36 -0700839 hisax= [HW,ISDN]
840 See Documentation/isdn/README.HiSax.
841
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700842 hlt [BUGS=ARM,SH]
843
844 hpet= [X86-32,HPET] option to control HPET usage
845 Format: { enable (default) | disable | force |
846 verbose }
847 disable: disable HPET and use PIT instead
848 force: allow force enabled of undocumented chips (ICH4,
849 VIA, nVidia)
850 verbose: show contents of HPET registers during setup
851
Andi Kleenb4718e62008-07-23 21:27:51 -0700852 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
853 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700854 On x86-64 and powerpc, this option can be specified
855 multiple times interleaved with hugepages= to reserve
856 huge pages of different sizes. Valid pages sizes on
857 x86-64 are 2M (when the CPU supports "pse") and 1G
858 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700859 Note that 1GB pages can only be allocated at boot time
860 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900861
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100862 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
863 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100864 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
865 If specified, z/VM IUCV HVC accepts connections
866 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100867
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700868 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700869 or register an additional I2C bus that is not
870 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700871 Format:
872 <bus_id>,<clkrate>
873
Jiri Kosina36d95732008-10-06 02:51:09 -0400874 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200876 i8042.dumbkbd [HW] Pretend that controller can only read data from
877 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700878 (Don't attempt to blink the leds)
879 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500880 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400881 i8042.noloop [HW] Disable the AUX Loopback command while probing
882 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700883 i8042.nomux [HW] Don't check presence of an active multiplexing
884 controller
885 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
886 controllers
Linus Torvalds1da177e2005-04-16 15:20:36 -0700887 i8042.reset [HW] Reset the controller during init and cleanup
888 i8042.unlock [HW] Unlock (ignore) the keylock
889
890 i810= [HW,DRM]
891
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700892 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
893 indicates that the driver is running on unsupported
894 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700895 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
896 does not match list of supported models.
897 i8k.power_status
898 [HW] Report power status in /proc/i8k
899 (disabled by default)
900 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
901 capability is set.
902
Linus Torvalds1da177e2005-04-16 15:20:36 -0700903 icn= [HW,ISDN]
904 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
905
David Fries0af80c02009-02-25 20:28:21 +0100906 ide-core.nodma= [HW] (E)IDE subsystem
907 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200908 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
909 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100910 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700911
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700912 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
913 Claim all unknown PCI IDE storage controllers.
914
Andi Kleenf039b752007-05-02 19:27:12 +0200915 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800916 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
917 Poll forces a polling idle loop that can slightly
918 improve the performance of waking up a idle CPU, but
919 will use a lot of power and make the system run hot.
920 Not recommended.
921 idle=mwait: On systems which support MONITOR/MWAIT but
922 the kernel chose to not use it because it doesn't save
923 as much power as a normal idle loop, use the
924 MONITOR/MWAIT idle loop anyways. Performance should be
925 the same as idle=poll.
926 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800927 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800928 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700929
Ingo Molnar792908222006-12-06 20:40:51 -0800930 ignore_loglevel [KNL]
931 Ignore loglevel setting - this will print /all/
932 kernel messages to the console. Useful for debugging.
933
Linus Torvalds1da177e2005-04-16 15:20:36 -0700934 ihash_entries= [KNL]
935 Set number of hash buckets for inode cache.
936
Mimi Zohar3323eec92009-02-04 09:06:58 -0500937 ima_audit= [IMA]
938 Format: { "0" | "1" }
939 0 -- integrity auditing messages. (Default)
940 1 -- enable informational integrity auditing messages.
941
942 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700943 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -0500944 default: "sha1"
945
Eric Paris5789ba32009-05-21 15:47:06 -0400946 ima_tcb [IMA]
947 Load a policy which meets the needs of the Trusted
948 Computing Base. This means IMA will measure all
949 programs exec'd, files mmap'd for exec, and all files
950 opened for read by uid=0.
951
Linus Torvalds1da177e2005-04-16 15:20:36 -0700952 init= [KNL]
953 Format: <full_path>
954 Run specified binary instead of /sbin/init as init
955 process.
956
957 initcall_debug [KNL] Trace initcalls as they are executed. Useful
958 for working out where the kernel is dying during
959 startup.
960
961 initrd= [BOOT] Specify the location of the initial ramdisk
962
963 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
964 Format: <irq>
965
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700966 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800967 on
968 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700969 off
970 Disable intel iommu driver.
971 igfx_off [Default Off]
972 By default, gfx is mapped as normal device. If a gfx
973 device has a dedicated DMAR unit, the DMAR unit is
974 bypassed by not enabling DMAR with this option. In
975 this case, gfx device will use physical address for
976 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700977 forcedac [x86_64]
978 With this option iommu will not optimize to look
979 for io virtual address below 32 bit forcing dual
980 address cycle on pci bus for cards supporting greater
981 than 32 bit addressing. The default is to look
982 for translation below 32 bit and if not available
983 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -0800984 strict [Default Off]
985 With this option on every unmap_single operation will
986 result in a hardware IOTLB flush operation as opposed
987 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700988
Chris Wrightd1423d52010-07-20 11:06:49 -0700989 intremap= [X86-64, Intel-IOMMU]
990 Format: { on (default) | off | nosid }
991 on enable Interrupt Remapping (default)
992 off disable Interrupt Remapping
993 nosid disable Source ID checking
994
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700995 inttest= [IA64]
996
997 iomem= Disable strict checking of access to MMIO memory
998 strict regions from userspace.
999 relaxed
1000
1001 iommu= [x86]
1002 off
1003 force
1004 noforce
1005 biomerge
1006 panic
1007 nopanic
1008 merge
1009 nomerge
1010 forcesac
1011 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001012 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001013
1014 io7= [HW] IO7 for Marvel based alpha systems
1015 See comment before marvel_specify_io7 in
1016 arch/alpha/kernel/core_marvel.c.
1017
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301018 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001019 0x80
1020 Standard port 0x80 based delay
1021 0xed
1022 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001023 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001024 Simple two microseconds delay
1025 none
1026 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001027
Linus Torvalds1da177e2005-04-16 15:20:36 -07001028 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001029 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030
1031 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001032 See comment before ip2_setup() in
1033 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001034
Alan Cox200803d2005-06-28 20:45:18 -07001035 irqfixup [HW]
1036 When an interrupt is not handled search all handlers
1037 for it. Intended to get systems with badly broken
1038 firmware running.
1039
1040 irqpoll [HW]
1041 When an interrupt is not handled search all handlers
1042 for it. Also check all handlers each timer
1043 interrupt. Intended to get systems with badly broken
1044 firmware running.
1045
Linus Torvalds1da177e2005-04-16 15:20:36 -07001046 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001047 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001048
1049 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001050 Format:
1051 <cpu number>,...,<cpu number>
1052 or
Li Zefanb225d442008-11-06 12:53:39 -08001053 <cpu number>-<cpu number>
1054 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001055 or a mixture
1056 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001057
Linus Torvalds1da177e2005-04-16 15:20:36 -07001058 This option can be used to specify one or more CPUs
1059 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001060 algorithms. You can move a process onto or off an
1061 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001062 <cpu number> begins at 0 and the maximum value is
1063 "number of CPUs in system - 1".
1064
1065 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001066 alternative -- manually setting the CPU mask of all
1067 tasks in the system -- can cause problems and
1068 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001069
Randy Dunlapa9913042005-10-23 12:57:11 -07001070 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001071
1072 js= [HW,JOY] Analog joystick
1073 See Documentation/input/joystick.txt.
1074
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001075 keepinitrd [HW,ARM]
1076
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301077 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001078 specifies the amount of memory usable by the kernel
1079 for non-movable allocations. The requested amount is
1080 spread evenly throughout all nodes in the system. The
1081 remaining memory in each node is used for Movable
1082 pages. In the event, a node is too small to have both
1083 kernelcore and Movable pages, kernelcore pages will
1084 take priority and other nodes will have a larger number
1085 of kernelcore pages. The Movable zone is used for the
1086 allocation of pages that may be reclaimed or moved
1087 by the page migration subsystem. This means that
1088 HugeTLB pages may not be allocated from this zone.
1089 Note that allocations like PTEs-from-HighMem still
1090 use the HighMem zone if it exists, and the Normal
1091 zone if it does not.
1092
Jason Wessel4fe1da42010-05-20 21:04:31 -05001093 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1094 Format: <Controller#>[,poll interval]
1095 The controller # is the number of the ehci usb debug
1096 port as it is probed via PCI. The poll interval is
1097 optional and is the number seconds in between
1098 each poll cycle to the debug port in case you need
1099 the functionality for interrupting the kernel with
1100 gdb or control-c on the dbgp connection. When
1101 not using this parameter you use sysrq-g to break into
1102 the kernel debugger.
1103
Jason Wessel84c08fd2010-05-20 21:04:24 -05001104 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001105 Requires a tty driver that supports console polling,
1106 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001107 Serial only format: <serial_device>[,baud]
1108 keyboard only format: kbd
1109 keyboard and serial format: kbd,<serial_device>[,baud]
1110 Optional Kernel mode setting:
1111 kms, kbd format: kms,kbd
1112 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001113
Jason Wessel84c08fd2010-05-20 21:04:24 -05001114 kgdbwait [KGDB] Stop kernel execution and enter the
1115 kernel debugger at the earliest opportunity.
1116
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001117 kmac= [MIPS] korina ethernet MAC address.
1118 Configure the RouterBoard 532 series on-chip
1119 Ethernet adapter MAC address.
1120
Catalin Marinas04f70332009-06-11 13:22:39 +01001121 kmemleak= [KNL] Boot-time kmemleak enable/disable
1122 Valid arguments: on, off
1123 Default: on
1124
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301125 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001126 in oops dumps.
1127
Andre Przywarafef07aa2009-07-10 14:20:35 +02001128 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1129 Default is 0 (don't ignore, but inject #GP)
1130
1131 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1132 Default is 1 (enabled)
1133
Xiao Guangronga182d872010-09-20 22:17:48 +08001134 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1135 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001136 Default is 0 (off)
1137
Andre Przywarafef07aa2009-07-10 14:20:35 +02001138 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001139 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001140
1141 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1142 for all guests.
1143 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1144
1145 kvm-intel.bypass_guest_pf=
1146 [KVM,Intel] Disables bypassing of guest page faults
1147 on Intel chips. Default is 1 (enabled)
1148
1149 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1150 (virtualized MMU) support on capable Intel chips.
1151 Default is 1 (enabled)
1152
1153 kvm-intel.emulate_invalid_guest_state=
1154 [KVM,Intel] Enable emulation of invalid guest states
1155 Default is 0 (disabled)
1156
1157 kvm-intel.flexpriority=
1158 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1159 Default is 1 (enabled)
1160
1161 kvm-intel.unrestricted_guest=
1162 [KVM,Intel] Disable unrestricted guest feature
1163 (virtualized real and unpaged mode) on capable
1164 Intel chips. Default is 1 (enabled)
1165
1166 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1167 feature (tagged TLBs) on capable Intel chips.
1168 Default is 1 (enabled)
1169
Linus Torvalds1da177e2005-04-16 15:20:36 -07001170 l2cr= [PPC]
1171
Robert Brosea78bfbf2008-03-29 07:20:23 +11001172 l3cr= [PPC]
1173
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001174 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001175 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001176
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301177 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001178 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001179
FD Camifcb71f62008-01-06 19:08:56 +01001180 libata.dma= [LIBATA] DMA control
1181 libata.dma=0 Disable all PATA and SATA DMA
1182 libata.dma=1 PATA and SATA Disk DMA only
1183 libata.dma=2 ATAPI (CDROM) DMA only
1184 libata.dma=4 Compact Flash DMA only
1185 Combinations also work, so libata.dma=3 enables DMA
1186 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001187
1188 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1189 libata.ignore_hpa=0 keep BIOS limits (default)
1190 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001191
Dave Jones78e70c22007-09-27 11:50:13 -04001192 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1193 when set.
1194 Format: <int>
1195
Tejun Heo33267322008-02-13 09:15:09 +09001196 libata.force= [LIBATA] Force configurations. The format is comma
1197 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001198 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001199 matching port, link or device. Basically, it matches
1200 the ATA ID string printed on console by libata. If
1201 the whole ID part is omitted, the last PORT and DEVICE
1202 values are used. If ID hasn't been specified yet, the
1203 configuration applies to all ports, links and devices.
1204
1205 If only DEVICE is omitted, the parameter applies to
1206 the port and all links and devices behind it. DEVICE
1207 number of 0 either selects the first device or the
1208 first fan-out link behind PMP device. It does not
1209 select the host link. DEVICE number of 15 selects the
1210 host link and device attached to it.
1211
1212 The VAL specifies the configuration to force. As long
1213 as there's no ambiguity shortcut notation is allowed.
1214 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1215 The following configurations can be forced.
1216
1217 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1218 Any ID with matching PORT is used.
1219
1220 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1221
1222 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1223 udma[/][16,25,33,44,66,100,133] notation is also
1224 allowed.
1225
1226 * [no]ncq: Turn on or off NCQ.
1227
Tejun Heo05944bd2008-08-13 20:19:09 +09001228 * nohrst, nosrst, norst: suppress hard, soft
1229 and both resets.
1230
Tejun Heo43c9c592010-05-23 12:59:11 +02001231 * dump_id: dump IDENTIFY data.
1232
Tejun Heo33267322008-02-13 09:15:09 +09001233 If there are multiple matching configurations changing
1234 the same attribute, the last one is used.
1235
Yinghai Lu95f72d12010-07-12 14:36:09 +10001236 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001237
Linus Torvalds1da177e2005-04-16 15:20:36 -07001238 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001239 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001240
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001241 lockd.nlm_grace_period=P [NFS] Assign grace period.
1242 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001243
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001244 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1245 Format: <integer>
1246
1247 lockd.nlm_timeout=T [NFS] Assign timeout value.
1248 Format: <integer>
1249
1250 lockd.nlm_udpport=M [NFS] Assign UDP port.
1251 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001252
1253 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1254 Format: <irq>
1255
1256 loglevel= All Kernel Messages with a loglevel smaller than the
1257 console loglevel will be printed to the console. It can
1258 also be changed with klogd or other programs. The
1259 loglevels are defined as follows:
1260
1261 0 (KERN_EMERG) system is unusable
1262 1 (KERN_ALERT) action must be taken immediately
1263 2 (KERN_CRIT) critical conditions
1264 3 (KERN_ERR) error conditions
1265 4 (KERN_WARNING) warning conditions
1266 5 (KERN_NOTICE) normal but significant condition
1267 6 (KERN_INFO) informational
1268 7 (KERN_DEBUG) debug-level messages
1269
1270 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001271 Format: { n | nk | nM }
1272 n must be a power of two. The default size
1273 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001274
Randy Dunlapaccaa242007-10-16 01:29:37 -07001275 logo.nologo [FB] Disables display of the built-in Linux logo.
1276 This may be used to provide more screen space for
1277 kernel log messages and is useful when debugging
1278 kernel boot problems.
1279
Linus Torvalds1da177e2005-04-16 15:20:36 -07001280 lp=0 [LP] Specify parallel ports to use, e.g,
1281 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1282 lp=reset first parallel port). 'lp=0' disables the
1283 lp=auto printer driver. 'lp=reset' (which can be
1284 specified in addition to the ports) causes
1285 attached printers to be reset. Using
1286 lp=port1,port2,... specifies the parallel ports
1287 to associate lp devices with, starting with
1288 lp0. A port specification may be 'none' to skip
1289 that lp device, or a parport name such as
1290 'parport0'. Specifying 'lp=auto' instead of a
1291 port specification list means that device IDs
1292 from each port should be examined, to see if
1293 an IEEE 1284-compliant printer is attached; if
1294 so, the driver will manage that printer.
1295 See also header of drivers/char/lp.c.
1296
1297 lpj=n [KNL]
1298 Sets loops_per_jiffy to given constant, thus avoiding
1299 time-consuming boot-time autodetection (up to 250 ms per
1300 CPU). 0 enables autodetection (default). To determine
1301 the correct value for your kernel, boot with normal
1302 autodetection and see what value is printed. Note that
1303 on SMP systems the preset will be applied to all CPUs,
1304 which is likely to cause problems if your CPUs need
1305 significantly divergent settings. An incorrect value
1306 will cause delays in the kernel to be wrong, leading to
1307 unpredictable I/O errors and other breakage. Although
1308 unlikely, in the extreme case this might damage your
1309 hardware.
1310
1311 ltpc= [NET]
1312 Format: <io>,<irq>,<dma>
1313
Randy Dunlapa9913042005-10-23 12:57:11 -07001314 machvec= [IA64] Force the use of a particular machine-vector
1315 (machvec) in a generic kernel.
1316 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001317
Wu Zhangjin3209e702009-07-02 23:27:12 +08001318 machtype= [Loongson] Share the same kernel image file between different
1319 yeeloong laptop.
1320 Example: machtype=lemote-yeeloong-2f-7inch
1321
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001322 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1323 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324
1325 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001326 should make use of. maxcpus=n : n >= 0 limits the
1327 kernel to using 'n' processors. n=0 is a special case,
1328 it is equivalent to "nosmp", which also disables
1329 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001331 max_loop= [LOOP] Maximum number of loopback devices that can
1332 be mounted
1333 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001334
Linus Torvalds1da177e2005-04-16 15:20:36 -07001335 mcatest= [IA-64]
1336
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001337 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001338
Uwe Hermann71cced62008-10-20 09:32:21 -07001339 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001340
Linus Torvalds1da177e2005-04-16 15:20:36 -07001341 md= [HW] RAID subsystems devices and level
1342 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001343
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344 mdacon= [MDA]
1345 Format: <first>,<last>
1346 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001347
Linus Torvalds1da177e2005-04-16 15:20:36 -07001348 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1349 Amount of memory to be used when the kernel is not able
1350 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001351 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001352 address space collisions. Without memmap= PCI devices
1353 could be placed at addresses belonging to unused RAM.
1354
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001355 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001356 memory.
1357
Paul Mundt6902aa82008-09-21 17:14:42 +09001358 memchunk=nn[KMG]
1359 [KNL,SH] Allow user to override the default size for
1360 per-device physically contiguous DMA buffers.
1361
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301362 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001363 E820 memory map, as specified by the user.
1364 Such memmap=exactmap lines can be constructed based on
1365 BIOS output or other requirements. See the memmap=nn@ss
1366 option description.
1367
1368 memmap=nn[KMG]@ss[KMG]
1369 [KNL] Force usage of a specific region of memory
1370 Region of memory to be used, from ss to ss+nn.
1371
1372 memmap=nn[KMG]#ss[KMG]
1373 [KNL,ACPI] Mark specific memory as ACPI data.
1374 Region of memory to be used, from ss to ss+nn.
1375
1376 memmap=nn[KMG]$ss[KMG]
1377 [KNL,ACPI] Mark specific memory as reserved.
1378 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001379 Example: Exclude memory from 0x18690000-0x1869ffff
1380 memmap=64K$0x18690000
1381 or
1382 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001383
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001384 memory_corruption_check=0/1 [X86]
1385 Some BIOSes seem to corrupt the first 64k of
1386 memory when doing things like suspend/resume.
1387 Setting this option will scan the memory
1388 looking for corruption. Enabling this will
1389 both detect corruption and prevent the kernel
1390 from using the memory being corrupted.
1391 However, its intended as a diagnostic tool; if
1392 repeatable BIOS-originated corruption always
1393 affects the same memory, you can use memmap=
1394 to prevent the kernel from using that memory.
1395
1396 memory_corruption_check_size=size [X86]
1397 By default it checks for corruption in the low
1398 64k, making this memory unavailable for normal
1399 use. Use this parameter to scan for
1400 corruption in more or less memory.
1401
1402 memory_corruption_check_period=seconds [X86]
1403 By default it checks for corruption every 60
1404 seconds. Use this parameter to check at some
1405 other rate. 0 disables periodic checking.
1406
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001407 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001408 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001409 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001410 Specifies the number of memtest passes to be
1411 performed. Each pass selects another test
1412 pattern from a given set of patterns. Memtest
1413 fills the memory with this pattern, validates
1414 memory contents and reserves bad memory
1415 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001416
Linus Torvalds1da177e2005-04-16 15:20:36 -07001417 meye.*= [HW] Set MotionEye Camera parameters
1418 See Documentation/video4linux/meye.txt.
1419
Andres Salomon8f368812007-10-12 23:04:06 +02001420 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1421 Multi-Function General Purpose Timers on AMD Geode
1422 platforms.
1423
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001424 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1425 the BIOS has incorrectly applied a workaround. TinyBIOS
1426 version 0.98 is known to be affected, 0.99 fixes the
1427 problem by letting the user disable the workaround.
1428
Linus Torvalds1da177e2005-04-16 15:20:36 -07001429 mga= [HW,DRM]
1430
Randy Dunlap1c207f92008-11-19 15:36:16 -08001431 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1432 physical address is ignored.
1433
Michel Pollet39f45d72009-05-20 11:10:31 +01001434 mini2440= [ARM,HW,KNL]
1435 Format:[0..2][b][c][t]
1436 Default: "0tb"
1437 MINI2440 configuration specification:
1438 0 - The attached screen is the 3.5" TFT
1439 1 - The attached screen is the 7" TFT
1440 2 - The VGA Shield is attached (1024x768)
1441 Leaving out the screen size parameter will not load
1442 the TFT driver, and the framebuffer will be left
1443 unconfigured.
1444 b - Enable backlight. The TFT backlight pin will be
1445 linked to the kernel VESA blanking code and a GPIO
1446 LED. This parameter is not necessary when using the
1447 VGA shield.
1448 c - Enable the s3c camera interface.
1449 t - Reserved for enabling touchscreen support. The
1450 touchscreen support is not enabled in the mainstream
1451 kernel as of 2.6.30, a preliminary port can be found
1452 in the "bleeding edge" mini2440 support kernel at
1453 http://repo.or.cz/w/linux-2.6/mini2440.git
1454
Mel Gorman6b74ab92008-07-23 21:26:49 -07001455 mminit_loglevel=
1456 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1457 parameter allows control of the logging verbosity for
1458 the additional memory initialisation checks. A value
1459 of 0 disables mminit logging and a level of 4 will
1460 log everything. Information is printed at KERN_DEBUG
1461 so loglevel=8 may also need to be specified.
1462
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463 mousedev.tap_time=
1464 [MOUSE] Maximum time between finger touching and
1465 leaving touchpad surface for touch to be considered
1466 a tap and be reported as a left button click (for
1467 touchpads working in absolute mode only).
1468 Format: <msecs>
1469 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1470 reporting absolute coordinates, such as tablets
1471 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1472 reporting absolute coordinates, such as tablets
1473
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301474 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001475 is similar to kernelcore except it specifies the
1476 amount of memory used for migratable allocations.
1477 If both kernelcore and movablecore is specified,
1478 then kernelcore will be at *least* the specified
1479 value but may be more. If movablecore on its own
1480 is specified, the administrator must be careful
1481 that the amount of memory usable for all allocations
1482 is not too small.
1483
Linus Torvalds1da177e2005-04-16 15:20:36 -07001484 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
Linus Torvalds1da177e2005-04-16 15:20:36 -07001531 netdev= [NET] Network devices parameters
1532 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1533 Note that mem_start is often overloaded to mean
1534 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001535 This usage is only documented in each driver source
1536 file if at all.
1537
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001538 nf_conntrack.acct=
1539 [NETFILTER] Enable connection tracking flow accounting
1540 0 to disable accounting
1541 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001542 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001543
Chuck Lever306a0752010-09-17 10:54:37 -04001544 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001545 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001546
1547 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001548 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001549
Chuck Lever306a0752010-09-17 10:54:37 -04001550 nfsrootdebug [NFS] enable nfsroot debugging messages.
1551 See Documentation/filesystems/nfs/nfsroot.txt.
1552
Trond Myklebusta72b4422006-01-03 09:55:41 +01001553 nfs.callback_tcpport=
1554 [NFS] set the TCP port on which the NFSv4 callback
1555 channel should listen.
1556
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001557 nfs.cache_getent=
1558 [NFS] sets the pathname to the program which is used
1559 to update the NFS client cache entries.
1560
1561 nfs.cache_getent_timeout=
1562 [NFS] sets the timeout after which an attempt to
1563 update a cache entry is deemed to have failed.
1564
Trond Myklebust58df0952006-01-03 09:55:57 +01001565 nfs.idmap_cache_timeout=
1566 [NFS] set the maximum lifetime for idmapper cache
1567 entries.
1568
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001569 nfs.enable_ino64=
1570 [NFS] enable 64-bit inode numbers.
1571 If zero, the NFS client will fake up a 32-bit inode
1572 number for the readdir() and stat() syscalls instead
1573 of returning the full 64-bit number.
1574 The default is to return 64-bit inode numbers.
1575
Paul Mundt1e1030d2009-09-01 17:38:32 +09001576 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001577 when a NMI is triggered.
1578 Format: [state][,regs][,debounce][,die]
1579
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301580 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001581 Format: [panic,][num]
1582 Valid num: 0,1,2
1583 0 - turn nmi_watchdog off
1584 1 - use the IO-APIC timer for the NMI watchdog
1585 2 - use the local APIC for the NMI watchdog using
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001586 a performance counter. Note: This will use one
1587 performance counter and the local APIC's performance
1588 vector.
1589 When panic is specified, panic when an NMI watchdog
1590 timeout occurs.
1591 This is useful when you use a panic=... timeout and
1592 need the box quickly up again.
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001593 Instead of 1 and 2 it is possible to use the following
1594 symbolic names: lapic and ioapic
1595 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
Linus Torvalds1da177e2005-04-16 15:20:36 -07001596
Anton Vorontsovbff38772009-07-08 11:10:56 -07001597 netpoll.carrier_timeout=
1598 [NET] Specifies amount of time (in seconds) that
1599 netpoll should wait for a carrier. By default netpoll
1600 waits 4 seconds.
1601
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001602 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001603 emulation library even if a 387 maths coprocessor
1604 is present.
1605
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001606 no_console_suspend
1607 [HW] Never suspend the console
1608 Disable suspending of consoles during suspend and
1609 hibernate operations. Once disabled, debugging
1610 messages can reach various consoles while the rest
1611 of the system is being put to sleep (ie, while
1612 debugging driver suspend/resume hooks). This may
1613 not work reliably with all consoles, but is known
1614 to work with serial and VGA consoles.
1615
Christoph Lameterc1aee212007-05-31 00:40:47 -07001616 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1617 caches in the slab allocator. Saves per-node memory,
1618 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001619
Randy Dunlapa9913042005-10-23 12:57:11 -07001620 noalign [KNL,ARM]
1621
Linus Torvalds1da177e2005-04-16 15:20:36 -07001622 noapic [SMP,APIC] Tells the kernel to not make use of any
1623 IOAPICs that may be present in the system.
1624
Linus Torvalds1da177e2005-04-16 15:20:36 -07001625 nobats [PPC] Do not use BATs for mapping kernel lowmem
1626 on "Classic" PPC cores.
1627
1628 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001629
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001630 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1631
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001632 nodelayacct [KNL] Disable per-task delay accounting
1633
Linus Torvalds1da177e2005-04-16 15:20:36 -07001634 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1635
Paul Mundt6902aa82008-09-21 17:14:42 +09001636 nodsp [SH] Disable hardware DSP at boot time.
1637
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301638 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001639
Linus Torvalds1da177e2005-04-16 15:20:36 -07001640 noexec [IA-64]
1641
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301642 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001643 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001644 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001645 noexec=off: disable non-executable mappings
1646
1647 noexec32 [X86-64]
1648 This affects only 32-bit executables.
1649 noexec32=on: enable non-executable mappings (default)
1650 read doesn't imply executable mappings
1651 noexec32=off: disable non-executable mappings
1652 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001653
Paul Mundt6902aa82008-09-21 17:14:42 +09001654 nofpu [SH] Disable hardware FPU at boot time.
1655
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001656 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001657 register save and restore. The kernel will only save
1658 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001659
Suresh Siddha0c752a92009-05-22 12:17:45 -07001660 noxsave [BUGS=X86] Disables x86 extended register state save
1661 and restore using xsave. The kernel will fallback to
1662 enabling legacy floating-point and sse state.
1663
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001664 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1665 wfi(ARM) instruction doesn't work correctly and not to
1666 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001667
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001668 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001669 instruction doesn't work correctly and not to
1670 use it.
1671
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001672 no_file_caps Tells the kernel not to honor file capabilities. The
1673 only way then for a file to be executed with privilege
1674 is to be setuid root or executed by root.
1675
Linus Torvalds1da177e2005-04-16 15:20:36 -07001676 nohalt [IA-64] Tells the kernel not to use the power saving
1677 function PAL_HALT_LIGHT when idle. This increases
1678 power-consumption. On the positive side, it reduces
1679 interrupt wake-up latency, which may improve performance
1680 in certain environments such as networked servers or
1681 real-time systems.
1682
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001683 nohz= [KNL] Boottime enable/disable dynamic ticks
1684 Valid arguments: on, off
1685 Default: on
1686
Paul Mundteeee7852009-04-02 12:31:16 +09001687 noiotrap [SH] Disables trapped I/O port accesses.
1688
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001689 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001690 disable unhandled interrupt sources.
1691
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301692 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001693 broken timer IRQ sources.
1694
Linus Torvalds1da177e2005-04-16 15:20:36 -07001695 noisapnp [ISAPNP] Disables ISA PnP code.
1696
1697 noinitrd [RAM] Tells the kernel not to load any configured
1698 initial RAM disk.
1699
Weidong Han03ea8152009-04-17 16:42:15 +08001700 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1701 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07001702 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08001703
Linus Torvalds1da177e2005-04-16 15:20:36 -07001704 nointroute [IA-64]
1705
Tony Luck0aa366f2007-07-20 11:22:30 -07001706 nojitter [IA64] Disables jitter checking for ITC timers.
1707
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02001708 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1709
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001710 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001711
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001712 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001713
Linus Torvalds1da177e2005-04-16 15:20:36 -07001714 noltlbs [PPC] Do not use large page/tlb entries for kernel
1715 lowmem mapping on PPC40x.
1716
Horms312f1f02006-02-22 09:57:55 +09001717 nomca [IA-64] Disable machine check abort handling
1718
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001719 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001720
Andres Salomon83d73842007-10-12 23:04:06 +02001721 nomfgpt [X86-32] Disable Multi-Function General Purpose
1722 Timer usage (for AMD Geode machines).
1723
Jiri Kosina016ddd92010-01-18 17:05:40 +01001724 nopat [X86] Disable PAT (page attribute table extension of
1725 pagetables) support.
1726
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001727 norandmaps Don't use address space randomization. Equivalent to
1728 echo 0 > /proc/sys/kernel/randomize_va_space
1729
Jiri Kosinabbff2162010-08-11 18:34:09 +02001730 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001731
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001732 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001733 with UP alternatives
1734
Linus Torvalds1da177e2005-04-16 15:20:36 -07001735 noresidual [PPC] Don't use residual data on PReP machines.
1736
Randy Dunlapa9913042005-10-23 12:57:11 -07001737 noresume [SWSUSP] Disables resume and restores original swap
1738 space.
1739
Linus Torvalds1da177e2005-04-16 15:20:36 -07001740 no-scroll [VGA] Disables scrollback.
1741 This is required for the Braillex ib80-piezo Braille
1742 reader made by F.H. Papenmeier (Germany).
1743
1744 nosbagart [IA-64]
1745
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001746 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001747
Len Brown61ec7562007-08-16 03:34:22 -04001748 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1749 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001750
Dave Jones97842212007-07-15 23:41:05 -07001751 nosoftlockup [KNL] Disable the soft-lockup detector.
1752
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001753 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001754 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001755
Linus Torvalds1da177e2005-04-16 15:20:36 -07001756 nosync [HW,M68K] Disables sync negotiation for all devices.
1757
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001758 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001759
1760 nousb [USB] Disable the USB subsystem
1761
Don Zickus58687ac2010-05-07 17:11:44 -04001762 nowatchdog [KNL] Disable the lockup detector.
1763
Linus Torvalds1da177e2005-04-16 15:20:36 -07001764 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001765
Weidong Han2b2fd872009-04-17 16:42:12 +08001766 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1767
Fenghua Yua6c75b862008-03-14 13:57:08 -07001768 nptcg= [IA64] Override max number of concurrent global TLB
1769 purges which is reported from either PAL_VM_SUMMARY or
1770 SAL PALO.
1771
Yinghai Lu2b633e32010-02-10 01:20:37 -08001772 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1773 could support. nr_cpus=n : n >= 1 limits the kernel to
1774 supporting 'n' processors. Later in runtime you can not
1775 use hotplug cpu feature to put more cpu back to online.
1776 just like you compile the kernel NR_CPUS=n
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 Dunlap7c4be2532009-01-06 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 oprofile.timer= [HW]
1802 Use timer interrupt instead of performance counters
1803
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001804 oprofile.cpu_type= Force an oprofile cpu type
1805 This might be useful if you have an older oprofile
1806 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001807 Format: { arch_perfmon }
1808 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001809 perfmon on Intel CPUs instead of the
1810 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001811
Randy Dunlapbcfde332010-06-07 17:10:38 -07001812 OSS [HW,OSS]
1813 See Documentation/sound/oss/oss-parameters.txt
1814
Linus Torvalds1da177e2005-04-16 15:20:36 -07001815 panic= [KNL] Kernel behaviour on panic
1816 Format: <timeout>
1817
1818 parkbd.port= [HW] Parallel port number the keyboard adapter is
1819 connected to, default is 0.
1820 Format: <parport#>
1821 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1822 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001823 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001824
Randy Dunlapa9913042005-10-23 12:57:11 -07001825 parport= [HW,PPT] Specify parallel ports. 0 disables.
1826 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1827 Use 'auto' to force the driver to use any
1828 IRQ/DMA settings detected (the default is to
1829 ignore detected IRQ/DMA settings because of
1830 possible conflicts). You can specify the base
1831 address, IRQ, and DMA settings; IRQ and DMA
1832 should be numbers, or 'auto' (for using detected
1833 settings on that particular port), or 'nofifo'
1834 (to avoid using a FIFO even if it is detected).
1835 Parallel ports are assigned in the order they
1836 are specified on the command line, starting
1837 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001838
Randy Dunlapa9913042005-10-23 12:57:11 -07001839 parport_init_mode= [HW,PPT]
1840 Configure VIA parallel port to operate in
1841 a specific mode. This is necessary on Pegasos
1842 computer where firmware has no options for setting
1843 up parallel port mode and sets it to spp.
1844 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845 Format: [spp|ps2|epp|ecp|ecpepp]
1846
Andrew Mortondd287792006-03-23 03:00:57 -08001847 pause_on_oops=
1848 Halt all CPUs after the first oops has been printed for
1849 the specified number of seconds. This is to be used if
1850 your oopses keep scrolling off the screen.
1851
Linus Torvalds1da177e2005-04-16 15:20:36 -07001852 pcbit= [HW,ISDN]
1853
1854 pcd. [PARIDE]
1855 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001856 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001857
Randy Dunlapa9913042005-10-23 12:57:11 -07001858 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001859 earlydump [X86] dump PCI config space before the kernel
1860 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001861 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001862 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001863 the hardware directly. Use this if your machine
1864 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001865 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001866 hardware access methods are allowed. Use this
1867 if you experience crashes upon bootup and you
1868 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001869 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001870 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001871 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001872 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001873 noaer [PCIE] If the PCIEAER kernel config parameter is
1874 enabled, this kernel boot option can be used to
1875 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001876 nodomains [PCI] Disable support for multiple PCI
1877 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301878 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001879 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001880 check_enable_amd_mmconf [X86] check for and enable
1881 properly configured MMIO access to PCI
1882 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001883 nomsi [MSI] If the PCI_MSI kernel config parameter is
1884 enabled, this kernel boot option can be used to
1885 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001886 noioapicquirk [APIC] Disable all boot interrupt quirks.
1887 Safety option to keep boot IRQs enabled. This
1888 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001889 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1890 primary IO-APIC for bridges that cannot disable
1891 boot IRQs. This fixes a source of spurious IRQs
1892 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001893 noioapicreroute [APIC] Disable workaround that uses the
1894 boot IRQ equivalent of an IRQ that connects to
1895 a chipset where boot IRQs cannot be disabled.
1896 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001897 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001898 routing table. These calls are known to be buggy
1899 on several machines and they hang the machine
1900 when used, but on other computers it's the only
1901 way to get the interrupt routing table. Try
1902 this option if the kernel is unable to allocate
1903 IRQs or discover secondary PCI buses on your
1904 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001905 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001906 Use with caution as certain devices share
1907 address decoders between ROMs and other
1908 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001909 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001910 expansion ROMs that do not already have
1911 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07001912 nobar [X86] Do not assign address space to the
1913 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001914 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001915 assigned automatically to PCI devices. You can
1916 make the kernel exclude IRQs of your ISA cards
1917 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001918 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001919 of the PIRQ table (normally generated
1920 by the BIOS) if it is outside the
1921 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001922 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001923 useful if the kernel is unable to find your
1924 secondary buses and you want to tell it
1925 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001926 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001927 numbers ourselves, overriding
1928 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001929 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001930 in the BIOS $PIR table. This is needed on
1931 some systems with broken BIOSes, notably
1932 some HP Pavilion N5400 and Omnibook XE3
1933 notebooks. This will have no effect if ACPI
1934 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001935 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001936 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07001937 use_crs [X86] Use PCI host bridge window information
1938 from ACPI. On BIOSes from 2008 or later, this
1939 is enabled by default. If you need to use this,
1940 please report a bug.
1941 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1942 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07001943 routeirq Do IRQ routing for all PCI devices.
1944 This is normally done in pci_enable_device(),
1945 so this option is a temporary workaround
1946 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001947 skip_isa_align [X86] do not align io start addr, so can
1948 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001949 firmware [ARM] Do not re-enumerate the bus but instead
1950 just use the configuration from the
1951 bootloader. This is currently used on
1952 IXP2000 systems where the bus has to be
1953 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001954 noearly [X86] Don't do any early type 1 scanning.
1955 This might help on some broken boards which
1956 machine check when some devices' config space
1957 is read. But various workarounds are disabled
1958 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001959 bfsort Sort PCI devices into breadth-first order.
1960 This sorting is done to get a device
1961 order compatible with older (<= 2.4) kernels.
1962 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001963 cbiosize=nn[KMG] The fixed amount of bus space which is
1964 reserved for the CardBus bridge's IO window.
1965 The default value is 256 bytes.
1966 cbmemsize=nn[KMG] The fixed amount of bus space which is
1967 reserved for the CardBus bridge's memory
1968 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09001969 resource_alignment=
1970 Format:
1971 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1972 Specifies alignment and device to reassign
1973 aligned memory resources.
1974 If <order of align> is not specified,
1975 PAGE_SIZE is used as alignment.
1976 PCI-PCI bridge can be specified, if resource
1977 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06001978 ecrc= Enable/disable PCIe ECRC (transaction layer
1979 end-to-end CRC checking).
1980 bios: Use BIOS/firmware settings. This is the
1981 the default.
1982 off: Turn ECRC off
1983 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001984
Chuck Ebberte5665a42008-09-24 20:40:34 -04001985 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1986 Management.
1987 off Disable ASPM.
1988 force Enable ASPM even on devices that claim not to support it.
1989 WARNING: Forcing ASPM on may cause system lockups.
1990
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02001991 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02001992 auto Ask the BIOS whether or not to use native PCIe services
1993 associated with PCIe ports (PME, hot-plug, AER). Use
1994 them only if that is allowed by the BIOS.
1995 native Use native PCIe services associated with PCIe ports
1996 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02001997 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1998 ports driver.
1999
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002000 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002001 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002002 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002003
Linus Torvalds1da177e2005-04-16 15:20:36 -07002004 pcmv= [HW,PCMCIA] BadgePAD 4
2005
2006 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002007 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002008
2009 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2010 boot time.
2011 Format: { 0 | 1 }
2012 See arch/parisc/kernel/pdc_chassis.c
2013
Tejun Heof58dc012009-08-14 15:00:50 +09002014 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002015 Currently supported values are "embed" and "page".
2016 Archs may support subset or none of the selections.
2017 See comments in mm/percpu.c for details on each
2018 allocator. This parameter is primarily for debugging
2019 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002020
Linus Torvalds1da177e2005-04-16 15:20:36 -07002021 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002022 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002023
2024 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002025 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002026
2027 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002028 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002029
2030 plip= [PPT,NET] Parallel port network link
2031 Format: { parport<nr> | timid | 0 }
2032 See also Documentation/parport.txt.
2033
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002034 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2035 Override pmtimer IOPort with a hex value.
2036 e.g. pmtmr=0x508
2037
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002038 pnp.debug [PNP]
2039 Enable PNP debug messages. This depends on the
2040 CONFIG_PNP_DEBUG_MESSAGES option.
2041
Linus Torvalds1da177e2005-04-16 15:20:36 -07002042 pnpacpi= [ACPI]
2043 { off }
2044
2045 pnpbios= [ISAPNP]
2046 { on | off | curr | res | no-curr | no-res }
2047
2048 pnp_reserve_irq=
2049 [ISAPNP] Exclude IRQs for the autoconfiguration
2050
2051 pnp_reserve_dma=
2052 [ISAPNP] Exclude DMAs for the autoconfiguration
2053
2054 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002055 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002056
2057 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002058 [ISAPNP] Exclude memory regions for the
2059 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002060 Ranges are in pairs (memory base and size).
2061
Randy Dunlap4af94f32009-04-17 18:30:28 -07002062 ports= [IP_VS_FTP] IPVS ftp helper module
2063 Default is 21.
2064 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2065 may be specified.
2066 Format: <port>,<port>....
2067
Ingo Molnar45807a12007-07-15 23:40:10 -07002068 print-fatal-signals=
2069 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002070
2071 If enabled, warn about various signal handling
2072 related application anomalies: too many signals,
2073 too many POSIX.1 timers, fatal signals causing a
2074 coredump - etc.
2075
2076 If you hit the warning due to signal overflow,
2077 you might want to try "ulimit -i unlimited".
2078
Ingo Molnar45807a12007-07-15 23:40:10 -07002079 default: off.
2080
Randy Dunlape84845c2007-07-15 23:40:25 -07002081 printk.time= Show timing data prefixed to each printk message line
2082 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2083
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002084 processor.max_cstate= [HW,ACPI]
2085 Limit processor to maximum C-state
2086 max_cstate=9 overrides any DMI blacklist limit.
2087
2088 processor.nocst [HW,ACPI]
2089 Ignore the _CST method to determine C-states,
2090 instead using the legacy FADT method
2091
Linus Torvalds1da177e2005-04-16 15:20:36 -07002092 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002093 Format: [schedule,]<number>
2094 Param: "schedule" - profile schedule points.
2095 Param: <number> - step/bucket size as a power of 2 for
2096 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002097 Param: "sleep" - profile D-state sleeping (millisecs).
2098 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002099 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002100
Linus Torvalds1da177e2005-04-16 15:20:36 -07002101 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2102 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002103 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002104
Randy Dunlapa9913042005-10-23 12:57:11 -07002105 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2106 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002107 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2108 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002109 psmouse.resetafter= [HW,MOUSE]
2110 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002111 (0 = never).
2112 psmouse.resolution=
2113 [HW,MOUSE] Set desired mouse resolution, in dpi.
2114 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002115 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002116 0 = disabled, 1 = enabled (default).
2117
Linus Torvalds1da177e2005-04-16 15:20:36 -07002118 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002119 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002120
Kay Sieversdc8c8582007-08-15 12:25:38 +02002121 pty.legacy_count=
2122 [KNL] Number of legacy pty's. Overwrites compiled-in
2123 default number.
2124
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002125 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002126
Linus Torvalds1da177e2005-04-16 15:20:36 -07002127 r128= [HW,DRM]
2128
2129 raid= [HW,RAID]
2130 See Documentation/md.txt.
2131
Randy Dunlapa9913042005-10-23 12:57:11 -07002132 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002133 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002134
Linus Torvalds1da177e2005-04-16 15:20:36 -07002135 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002136 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002137
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002138 rcupdate.blimit= [KNL,BOOT]
2139 Set maximum number of finished RCU callbacks to process
2140 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002141
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002142 rcupdate.qhimark= [KNL,BOOT]
2143 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002144 RCU callbacks over which batch limiting is disabled.
2145
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002146 rcupdate.qlowmark= [KNL,BOOT]
2147 Set threshold of queued RCU callbacks below which
2148 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002149
Olof Johanssonffdfc402005-09-06 15:17:19 -07002150 rdinit= [KNL]
2151 Format: <full_path>
2152 Run specified binary instead of /init from the ramdisk,
2153 used for early userspace startup. See initrd.
2154
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002155 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002156 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002157 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158
Paul Jackson46b6d942008-07-04 10:00:09 -07002159 relax_domain_level=
2160 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002161 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002162
Linus Torvalds1da177e2005-04-16 15:20:36 -07002163 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2164
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002165 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002166 Format: nn[KMG]
2167 Reserves a hole at the top of the kernel virtual
2168 address space.
2169
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002170 reservelow= [X86]
2171 Format: nn[K]
2172 Set the amount of memory to reserve for BIOS at
2173 the bottom of the address space.
2174
Vivek Goyal7e962872006-09-27 01:50:44 -07002175 reset_devices [KNL] Force drivers to reset the underlying device
2176 during initialization.
2177
Bjorn Helgaase7f85672010-10-26 15:41:33 -06002178 resource_alloc_from_bottom
2179 Allocate new resources from the beginning of available
2180 space, not the end. If you need to use this, please
2181 report a bug.
2182
Randy Dunlapa9913042005-10-23 12:57:11 -07002183 resume= [SWSUSP]
2184 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002185
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002186 resume_offset= [SWSUSP]
2187 Specify the offset from the beginning of the partition
2188 given by "resume=" at which the swap header is located,
2189 in <PAGE_SIZE> units (needed only for swap files).
2190 See Documentation/power/swsusp-and-swap-files.txt
2191
Bojan Smojverf996fc92010-09-09 23:06:23 +02002192 hibernate= [HIBERNATION]
2193 noresume Don't check if there's a hibernation image
2194 present during boot.
2195 nocompress Don't compress/decompress hibernation images.
2196
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002197 retain_initrd [RAM] Keep initrd memory after extraction
2198
Linus Torvalds1da177e2005-04-16 15:20:36 -07002199 rhash_entries= [KNL,NET]
2200 Set number of hash buckets for route cache
2201
2202 riscom8= [HW,SERIAL]
2203 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2204
2205 ro [KNL] Mount root device read-only on boot
2206
2207 root= [KNL] Root filesystem
2208
2209 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2210 mount the root filesystem
2211
2212 rootflags= [KNL] Set root filesystem mount option string
2213
2214 rootfstype= [KNL] Set root filesystem type
2215
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002216 rootwait [KNL] Wait (indefinitely) for root device to show up.
2217 Useful for devices that are detected asynchronously
2218 (e.g. USB and MMC devices).
2219
Linus Torvalds1da177e2005-04-16 15:20:36 -07002220 rw [KNL] Mount root device read-write on boot
2221
2222 S [KNL] Run init in single mode
2223
2224 sa1100ir [NET]
2225 See drivers/net/irda/sa1100_ir.c.
2226
Linus Torvalds1da177e2005-04-16 15:20:36 -07002227 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002228
Mike Travisf6630112009-11-17 18:22:15 -06002229 sched_debug [KNL] Enables verbose scheduler debug messages.
2230
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002231 security= [SECURITY] Choose a security module to enable at boot.
2232 If this boot parameter is not specified, only the first
2233 security module asking for security registration will be
2234 loaded. An invalid security module name will be treated
2235 as if no module has been chosen.
2236
2237 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002238 Format: { "0" | "1" }
2239 See security/selinux/Kconfig help text.
2240 0 -- disable.
2241 1 -- enable.
2242 Default value is set via kernel config option.
2243 If enabled at boot time, /selinux/disable can be used
2244 later to disable prior to initial policy load.
2245
John Johansenc1c124e2010-07-29 14:48:09 -07002246 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2247 Format: { "0" | "1" }
2248 See security/apparmor/Kconfig help text
2249 0 -- disable.
2250 1 -- enable.
2251 Default value is set via kernel config option.
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 simeth= [IA-64]
2265 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002266
Linus Torvalds1da177e2005-04-16 15:20:36 -07002267 slram= [HW,MTD]
2268
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002269 slub_debug[=options[,slabs]] [MM, SLUB]
2270 Enabling slub_debug allows one to determine the
2271 culprit if slab objects become corrupted. Enabling
2272 slub_debug can create guard zones around objects and
2273 may poison objects when not in use. Also tracks the
2274 last alloc / free. For more information see
2275 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002276
2277 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002278 Determines the maximum allowed order for slabs.
2279 A high setting may cause OOMs due to memory
2280 fragmentation. For more information see
2281 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002282
2283 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002284 The minimum number of objects per slab. SLUB will
2285 increase the slab order up to slub_max_order to
2286 generate a sufficiently large slab able to contain
2287 the number of objects indicated. The higher the number
2288 of objects the smaller the overhead of tracking slabs
2289 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002290 For more information see Documentation/vm/slub.txt.
2291
2292 slub_min_order= [MM, SLUB]
2293 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002294 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002295 For more information see Documentation/vm/slub.txt.
2296
2297 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002298 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002299 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002300 allocs to different slabs. Debug options disable
2301 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002302 For more information see Documentation/vm/slub.txt.
2303
Linus Torvalds1da177e2005-04-16 15:20:36 -07002304 smart2= [HW]
2305 Format: <io1>[,<io2>[,...,<io8>]]
2306
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002307 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002308 attempt to substitute SMP alternatives once at boot.
2309
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002310 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2311 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2312 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2313 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2314 smsc-ircc2.ircc_irq= [HW] IRQ line
2315 smsc-ircc2.ircc_dma= [HW] DMA channel
2316 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2317 0: Toshiba Satellite 1800 (GP data pin select)
2318 1: Fast pin select (default)
2319 2: ATC IRMode
2320
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002321 softlockup_panic=
2322 [KNL] Should the soft-lockup detector generate panics.
2323
Linus Torvalds1da177e2005-04-16 15:20:36 -07002324 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2325 See Documentation/sonypi.txt
2326
2327 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002328 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002329
2330 spia_io_base= [HW,MTD]
2331 spia_fio_base=
2332 spia_pedr=
2333 spia_peddr=
2334
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002335 stacktrace [FTRACE]
2336 Enabled the stack tracer on boot up.
2337
Linus Torvalds1da177e2005-04-16 15:20:36 -07002338 sti= [PARISC,HW]
2339 Format: <num>
2340 Set the STI (builtin display/keyboard on the HP-PARISC
2341 machines) console (graphic card) which should be used
2342 as the initial boot-console.
2343 See also comment in drivers/video/console/sticore.c.
2344
2345 sti_font= [HW]
2346 See comment in drivers/video/console/sticore.c.
2347
2348 stifb= [HW]
2349 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2350
Trond Myklebustcbf11072009-08-09 15:06:19 -04002351 sunrpc.min_resvport=
2352 sunrpc.max_resvport=
2353 [NFS,SUNRPC]
2354 SunRPC servers often require that client requests
2355 originate from a privileged port (i.e. a port in the
2356 range 0 < portnr < 1024).
2357 An administrator who wishes to reserve some of these
2358 ports for other uses may adjust the range that the
2359 kernel's sunrpc client considers to be privileged
2360 using these two parameters to set the minimum and
2361 maximum port values.
2362
Greg Banks42a7fc42007-03-06 01:42:23 -08002363 sunrpc.pool_mode=
2364 [NFS]
2365 Control how the NFS server code allocates CPUs to
2366 service thread pools. Depending on how many NICs
2367 you have and where their interrupts are bound, this
2368 option will affect which CPUs will do NFS serving.
2369 Note: this parameter cannot be changed while the
2370 NFS server is running.
2371
2372 auto the server chooses an appropriate mode
2373 automatically using heuristics
2374 global a single global pool contains all CPUs
2375 percpu one pool for each CPU
2376 pernode one pool for each NUMA node (equivalent
2377 to global on non-NUMA machines)
2378
Trond Myklebustcbf11072009-08-09 15:06:19 -04002379 sunrpc.tcp_slot_table_entries=
2380 sunrpc.udp_slot_table_entries=
2381 [NFS,SUNRPC]
2382 Sets the upper limit on the number of simultaneous
2383 RPC calls that can be sent from the client to a
2384 server. Increasing these values may allow you to
2385 improve throughput, but will also increase the
2386 amount of memory reserved for use by the client.
2387
Linus Torvalds1da177e2005-04-16 15:20:36 -07002388 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002389
Linus Torvalds1da177e2005-04-16 15:20:36 -07002390 switches= [HW,M68k]
2391
Andi Kleene52eec12010-09-08 16:54:17 +02002392 sysfs.deprecated=0|1 [KNL]
2393 Enable/disable old style sysfs layout for old udev
2394 on older distributions. When this option is enabled
2395 very new udev will not work anymore. When this option
2396 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2397 in older udev will not work anymore.
2398 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2399 the kernel configuration.
2400
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002401 sysrq_always_enabled
2402 [KNL]
2403 Ignore sysrq setting - this boot parameter will
2404 neutralize any effect of /proc/sys/kernel/sysrq.
2405 Useful for debugging.
2406
Linus Torvalds1da177e2005-04-16 15:20:36 -07002407 tdfx= [HW,DRM]
2408
David Brownell77437fd2008-07-23 21:28:33 -07002409 test_suspend= [SUSPEND]
2410 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2411 standby suspend) as the system sleep state to briefly
2412 enter during system startup. The system is woken from
2413 this state using a wakeup-capable RTC alarm.
2414
Linus Torvalds1da177e2005-04-16 15:20:36 -07002415 thash_entries= [KNL,NET]
2416 Set number of hash buckets for TCP connection
2417
Len Brownf8707ec2007-08-12 00:12:54 -04002418 thermal.act= [HW,ACPI]
2419 -1: disable all active trip points in all thermal zones
2420 <degrees C>: override all lowest active trip points
2421
Len Brownc52a7412007-08-14 15:49:32 -04002422 thermal.crt= [HW,ACPI]
2423 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002424 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002425
Len Brownf5487142007-08-12 00:12:44 -04002426 thermal.nocrt= [HW,ACPI]
2427 Set to disable actions on ACPI thermal zone
2428 critical and hot trip points.
2429
Len Brown72b33ef2007-08-12 00:12:17 -04002430 thermal.off= [HW,ACPI]
2431 1: disable ACPI thermal control
2432
Len Browna70cdc52007-08-12 00:12:35 -04002433 thermal.psv= [HW,ACPI]
2434 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002435 <degrees C>: override all passive trip points to this
2436 value
Len Browna70cdc52007-08-12 00:12:35 -04002437
Len Brown730ff342007-08-12 00:12:26 -04002438 thermal.tzp= [HW,ACPI]
2439 Specify global default ACPI thermal zone polling rate
2440 <deci-seconds>: poll all this frequency
2441 0: no polling (default)
2442
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002443 topology= [S390]
2444 Format: {off | on}
2445 Specify if the kernel should make use of the cpu
2446 topology informations if the hardware supports these.
2447 The scheduler will make use of these informations and
2448 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02002449 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002450
Linus Torvalds1da177e2005-04-16 15:20:36 -07002451 tp720= [HW,PS2]
2452
Rajiv Andrade225a9be2010-03-25 00:55:32 -03002453 tpm_suspend_pcr=[HW,TPM]
2454 Format: integer pcr id
2455 Specify that at suspend time, the tpm driver
2456 should extend the specified pcr with zeros,
2457 as a workaround for some chips which fail to
2458 flush the last written pcr on TPM_SaveState.
2459 This will guarantee that all the other pcrs
2460 are saved.
2461
Li Zefan9d612be2009-06-24 17:33:15 +08002462 trace_buf_size=nn[KMG]
2463 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002464
Li Zefan020e5f82009-07-01 10:47:05 +08002465 trace_event=[event-list]
2466 [FTRACE] Set and start specified trace events in order
2467 to facilitate early boot debugging.
2468 See also Documentation/trace/events.txt
2469
Alok Kataria395628e2008-10-24 17:22:01 -07002470 tsc= Disable clocksource-must-verify flag for TSC.
2471 Format: <string>
2472 [x86] reliable: mark tsc clocksource as reliable, this
2473 disables clocksource verification at runtime.
2474 Used to enable high-resolution timer mode on older
2475 hardware, and in virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07002476 [x86] noirqtime: Do not use TSC to do irq accounting.
2477 Used to run time disable IRQ_TIME_ACCOUNTING on any
2478 platforms where RDTSC is slow and this accounting
2479 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07002480
Randy Dunlapa9913042005-10-23 12:57:11 -07002481 turbografx.map[2|3]= [HW,JOY]
2482 TurboGraFX parallel port interface
2483 Format:
2484 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002485 See also Documentation/input/joystick-parport.txt
2486
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002487 uhash_entries= [KNL,NET]
2488 Set number of hash buckets for UDP/UDP-Lite connections
2489
Alan Stern5f8364b2006-12-05 16:29:55 -05002490 uhci-hcd.ignore_oc=
2491 [USB] Ignore overcurrent events (default N).
2492 Some badly-designed motherboards generate lots of
2493 bogus events, for ports that aren't wired to
2494 anything. Set this parameter to avoid log spamming.
2495 Note that genuine overcurrent events won't be
2496 reported either.
2497
Simon Arlotte3a61b02008-07-19 23:32:54 +01002498 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302499 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002500 Set unknown_nmi_panic=1 early on boot.
2501
Alan Sternb5e795f2007-02-20 15:00:53 -05002502 usbcore.autosuspend=
2503 [USB] The autosuspend time delay (in seconds) used
2504 for newly-detected USB devices (default 2). This
2505 is the time required before an idle device will be
2506 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002507 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002508
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002509 usbcore.usbfs_snoop=
2510 [USB] Set to log all usbfs traffic (default 0 = off).
2511
2512 usbcore.blinkenlights=
2513 [USB] Set to cycle leds on hubs (default 0 = off).
2514
2515 usbcore.old_scheme_first=
2516 [USB] Start with the old device initialization
2517 scheme (default 0 = off).
2518
2519 usbcore.use_both_schemes=
2520 [USB] Try the other device initialization scheme
2521 if the first one fails (default 1 = enabled).
2522
2523 usbcore.initial_descriptor_timeout=
2524 [USB] Specifies timeout for the initial 64-byte
2525 USB_REQ_GET_DESCRIPTOR request in milliseconds
2526 (default 5000 = 5.0 seconds).
2527
Linus Torvalds1da177e2005-04-16 15:20:36 -07002528 usbhid.mousepoll=
2529 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002530
Alan Sternd4f373e2008-11-10 14:07:45 -05002531 usb-storage.delay_use=
2532 [UMS] The delay in seconds before a new device is
2533 scanned for Logical Units (default 5).
2534
2535 usb-storage.quirks=
2536 [UMS] A list of quirks entries to supplement or
2537 override the built-in unusual_devs list. List
2538 entries are separated by commas. Each entry has
2539 the form VID:PID:Flags where VID and PID are Vendor
2540 and Product ID values (4-digit hex numbers) and
2541 Flags is a set of characters, each corresponding
2542 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002543 a = SANE_SENSE (collect more than 18 bytes
2544 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002545 b = BAD_SENSE (don't collect more than 18
2546 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002547 c = FIX_CAPACITY (decrease the reported
2548 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002549 h = CAPACITY_HEURISTICS (decrease the
2550 reported device capacity by one
2551 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002552 i = IGNORE_DEVICE (don't bind to this
2553 device);
2554 l = NOT_LOCKABLE (don't try to lock and
2555 unlock ejectable media);
2556 m = MAX_SECTORS_64 (don't transfer more
2557 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002558 o = CAPACITY_OK (accept the capacity
2559 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002560 r = IGNORE_RESIDUE (the device reports
2561 bogus residue values);
2562 s = SINGLE_LUN (the device has only one
2563 Logical Unit);
2564 w = NO_WP_DETECT (don't test whether the
2565 medium is write-protected).
2566 Example: quirks=0419:aaf5:rl,0421:0433:rc
2567
Ian Campbell14315592010-02-17 10:38:10 +00002568 userpte=
2569 [X86] Flags controlling user PTE allocations.
2570
2571 nohigh = do not allocate PTE pages in
2572 HIGHMEM regardless of setting
2573 of CONFIG_HIGHPTE.
2574
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302575 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002576 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002577 vdso=1: enable VDSO (default)
2578 vdso=0: disable VDSO mapping
2579
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302580 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002581 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2582 vdso32=1: enable 32-bit VDSO (default)
2583 vdso32=0: disable 32-bit VDSO mapping
2584
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002585 vector= [IA-64,SMP]
2586 vector=percpu: enable percpu vector domain
2587
Linus Torvalds1da177e2005-04-16 15:20:36 -07002588 video= [FB] Frame buffer configuration
2589 See Documentation/fb/modedb.txt.
2590
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002591 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002592 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002593 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002594 Use vga=ask for menu.
2595 This is actually a boot loader parameter; the value is
2596 passed to the kernel using a special protocol.
2597
Randy Dunlapa9913042005-10-23 12:57:11 -07002598 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002599 size of <nn>. This can be used to increase the
2600 minimum size (128MB on x86). It can also be used to
2601 decrease the size and leave more room for directly
2602 mapped kernel RAM.
2603
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002604 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2605 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002606
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002607 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2608 Format: <command>
2609
2610 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2611 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002612
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002613 vt.cur_default= [VT] Default cursor shape.
2614 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2615 the parameters of the <Esc>[?A;B;Cc escape sequence;
2616 see VGA-softcursor.txt. Default: 2 = underline.
2617
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002618 vt.default_blu= [VT]
2619 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2620 Change the default blue palette of the console.
2621 This is a 16-member array composed of values
2622 ranging from 0-255.
2623
2624 vt.default_grn= [VT]
2625 Format: <green0>,<green1>,<green2>,...,<green15>
2626 Change the default green palette of the console.
2627 This is a 16-member array composed of values
2628 ranging from 0-255.
2629
2630 vt.default_red= [VT]
2631 Format: <red0>,<red1>,<red2>,...,<red15>
2632 Change the default red palette of the console.
2633 This is a 16-member array composed of values
2634 ranging from 0-255.
2635
2636 vt.default_utf8=
2637 [VT]
2638 Format=<0|1>
2639 Set system-wide default UTF-8 mode for all tty's.
2640 Default is 1, i.e. UTF-8 mode is enabled for all
2641 newly opened terminals.
2642
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002643 vt.global_cursor_default=
2644 [VT]
2645 Format=<-1|0|1>
2646 Set system-wide default for whether a cursor
2647 is shown on new VTs. Default is -1,
2648 i.e. cursors will be created by default unless
2649 overridden by individual drivers. 0 will hide
2650 cursors, 1 will display them.
2651
Randy Dunlap4724ba572010-05-03 11:42:52 -07002652 watchdog timers [HW,WDT] For information on watchdog timers,
2653 see Documentation/watchdog/watchdog-parameters.txt
2654 or other driver-specific files in the
2655 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002656
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002657 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2658 default x2apic cluster mode on platforms
2659 supporting x2apic.
2660
Jacob Panbb24c472009-09-02 07:37:17 -07002661 x86_mrst_timer= [X86-32,APBT]
2662 Choose timer option for x86 Moorestown MID platform.
2663 Two valid options are apbt timer only and lapic timer
2664 plus one apbt timer for broadcast timer.
2665 x86_mrst_timer=apbt_only | lapic_and_apbt
2666
Linus Torvalds1da177e2005-04-16 15:20:36 -07002667 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2668 xd_geo= See header of drivers/block/xd.c.
2669
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002670 xen_emul_unplug= [HW,X86,XEN]
2671 Unplug Xen emulated devices
2672 Format: [unplug0,][unplug1]
2673 ide-disks -- unplug primary master IDE devices
2674 aux-ide-disks -- unplug non-primary-master IDE devices
2675 nics -- unplug network devices
2676 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01002677 unnecessary -- unplugging emulated devices is
2678 unnecessary even if the host did not respond to
2679 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01002680 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002681
Linus Torvalds1da177e2005-04-16 15:20:36 -07002682 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002683 Format:
2684 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002685
Randy Dunlapa9913042005-10-23 12:57:11 -07002686______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002687
2688TODO:
2689
Linus Torvalds1da177e2005-04-16 15:20:36 -07002690 Add more DRM drivers.