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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.
Alan Cox9cfe2682011-01-25 14:18:38 +000046 DRM Direct Rendering Management support is enabled.
47 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070048 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49 EFI EFI Partitioning (GPT) is enabled
50 EIDE EIDE/ATAPI support is enabled.
51 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_irq_balance [HW,ACPI]
203 ACPI will balance active IRQs
204 default in APIC mode
205
206 acpi_irq_nobalance [HW,ACPI]
207 ACPI will not move active IRQs (default)
208 default in PIC mode
209
210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
211 Format: <irq>,<irq>...
212
213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
214 use by PCI
215 Format: <irq>,<irq>...
216
217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
218
219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
220 Format: To spoof as Windows 98: ="Microsoft Windows"
221
222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
223 acpi_osi="string1" # add string1 -- only one string
224 acpi_osi="!string2" # remove built-in string2
225 acpi_osi= # disable all strings
226
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530227 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700228 Override the pmtimer bug detection: force the kernel
229 to assume that this machine's pmtimer latches its value
230 and always returns good values.
231
Randy Dunlap4af94f32009-04-17 18:30:28 -0700232 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
233 Format: { level | edge | high | low }
234
235 acpi_serialize [HW,ACPI] force serialization of AML methods
236
237 acpi_skip_timer_override [HW,ACPI]
238 Recognize and ignore IRQ0/pin2 Interrupt Override.
239 For broken nForce2 BIOS resulting in XT-PIC timer.
240
241 acpi_sleep= [HW,ACPI] Sleep options
242 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800243 old_ordering, s4_nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700244 See Documentation/power/video.txt for information on
245 s3_bios and s3_mode.
246 s3_beep is for debugging; it makes the PC's speaker beep
247 as soon as the kernel's real-mode entry point is called.
248 s4_nohwsig prevents ACPI hardware signature from being
249 used during resume from hibernation.
250 old_ordering causes the ACPI 1.0 ordering of the _PTS
251 control method, with respect to putting devices into
252 low power states, to be enforced (the ACPI 2.0 ordering
253 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200254 nonvs prevents the kernel from saving/restoring the
255 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800256 sci_force_enable causes the kernel to set SCI_EN directly
257 on resume from S1/S3 (which is against the ACPI spec,
258 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700259
260 acpi_use_timer_override [HW,ACPI]
261 Use timer override. For some broken Nvidia NF5 boards
262 that require a timer override, but don't have HPET
263
Luca Tettamanti7e905602009-03-30 00:01:27 +0200264 acpi_enforce_resources= [ACPI]
265 { strict | lax | no }
266 Check for resource conflicts between native drivers
267 and ACPI OperationRegions (SystemIO and SystemMemory
268 only). IO ports and memory declared in ACPI might be
269 used by the ACPI subsystem in arbitrary AML code and
270 can interfere with legacy drivers.
271 strict (default): access to resources claimed by ACPI
272 is denied; legacy drivers trying to access reserved
273 resources will fail to bind to device using them.
274 lax: access to resources claimed by ACPI is allowed;
275 legacy drivers trying to access reserved resources
276 will bind successfully but a warning message is logged.
277 no: ACPI OperationRegions are not marked as reserved,
278 no further checks are performed.
279
Randy Dunlap4af94f32009-04-17 18:30:28 -0700280 add_efi_memmap [EFI; X86] Include EFI memory map in
281 kernel's map of available physical RAM.
282
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700283 agp= [AGP]
284 { off | try_unsupported }
285 off: disable AGP support
286 try_unsupported: try to drive unsupported chipsets
287 (may crash computer or cause data corruption)
288
Randy Dunlapbcfde332010-06-07 17:10:38 -0700289 ALSA [HW,ALSA]
290 See Documentation/sound/alsa/alsa-parameters.txt
291
Russell Kingd944d542010-02-20 16:13:29 +0000292 alignment= [KNL,ARM]
293 Allow the default userspace alignment fault handler
294 behaviour to be specified. Bit 0 enables warnings,
295 bit 1 enables fixups, and bit 2 sends a segfault.
296
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200297 amd_iommu= [HW,X86-84]
298 Pass parameters to the AMD IOMMU driver in the system.
299 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900300 fullflush - enable flushing of IO/TLB entries when
301 they are unmapped. Otherwise they are
302 flushed before they will be reused, which
303 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200304 off - do not initialize any AMD IOMMU found in
305 the system
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900306
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307 amijoy.map= [HW,JOY] Amiga joystick support
308 Map of devices attached to JOY0DAT and JOY1DAT
309 Format: <a>,<b>
310 See also Documentation/kernel/input/joystick.txt
311
312 analog.map= [HW,JOY] Analog joystick and gamepad support
313 Specifies type or capabilities of an analog joystick
314 connected to one of 16 gameports
315 Format: <type1>,<type2>,..<type16>
316
Randy Dunlapa9913042005-10-23 12:57:11 -0700317 apc= [HW,SPARC]
318 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700319 Format: noidle
320 Disable APC CPU standby support. SPARCstation-Fox does
321 not play well with APC CPU idle - disable it if you have
322 APC and your system crashes randomly.
323
Randy Dunlapca1eda22009-05-06 16:02:58 -0700324 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700325 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700326 Format: { quiet (default) | verbose | debug }
327 Change the amount of debugging information output
328 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700329
Brian Haleyb0f83b22010-02-04 13:36:50 -0800330 autoconf= [IPV6]
331 See Documentation/networking/ipv6.txt.
332
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400333 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
334 Limit apic dumping. The parameter defines the maximal
335 number of local apics being dumped. Also it is possible
336 to set it to "all" by meaning -- no limit here.
337 Format: { 1 (default) | 2 | ... | all }.
338 The parameter valid if only apic=debug or
339 apic=verbose is specified.
340 Example: apic=debug show_lapic=all
341
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700343 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
346 Format: <io>,<irq>,<nodeID>
347
348 ataflop= [HW,M68k]
349
350 atarimouse= [HW,MOUSE] Atari Mouse
351
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
353 EzKey and similar keyboards
354
355 atkbd.reset= [HW] Reset keyboard during initialization
356
Randy Dunlapa9913042005-10-23 12:57:11 -0700357 atkbd.set= [HW] Select keyboard code set
358 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700359
360 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
361 keyboards
362
363 atkbd.softraw= [HW] Choose between synthetic and real raw mode
364 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700365
366 atkbd.softrepeat= [HW]
367 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368
369 autotest [IA64]
370
Linus Torvalds1da177e2005-04-16 15:20:36 -0700371 baycom_epp= [HW,AX25]
372 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700373
Linus Torvalds1da177e2005-04-16 15:20:36 -0700374 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
375 Format: <io>,<mode>
376 See header of drivers/net/hamradio/baycom_par.c.
377
Randy Dunlapa9913042005-10-23 12:57:11 -0700378 baycom_ser_fdx= [HW,AX25]
379 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700380 Format: <io>,<irq>,<mode>[,<baud>]
381 See header of drivers/net/hamradio/baycom_ser_fdx.c.
382
Randy Dunlapa9913042005-10-23 12:57:11 -0700383 baycom_ser_hdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700385 Format: <io>,<irq>,<mode>
386 See header of drivers/net/hamradio/baycom_ser_hdx.c.
387
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700388 boot_delay= Milliseconds to delay each printk during boot.
389 Values larger than 10 seconds (10000) are changed to
390 no delay (0).
391 Format: integer
392
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700393 bootmem_debug [KNL] Enable bootmem allocator debug messages.
394
Linus Torvalds1da177e2005-04-16 15:20:36 -0700395 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700396 bttv.radio= Most important insmod options are available as
397 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700398 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
399 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
400
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000401 bulk_remove=off [PPC] This parameter disables the use of the pSeries
402 firmware feature for flushing multiple hpte entries
403 at a time.
404
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405 c101= [NET] Moxa C101 synchronous serial card
406
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700407 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 Sometimes CPU hardware bugs make them report the cache
409 size incorrectly. The kernel will attempt work arounds
410 to fix known problems, but for some CPUs it is not
411 possible to determine what the correct size should be.
412 This option provides an override for these situations.
413
James Morris20510f22007-10-16 23:31:32 -0700414 capability.disable=
415 [SECURITY] Disable capabilities. This would normally
416 be used only if an alternative security model is to be
417 configured. Potentially dangerous and should only be
418 used if you are entirely sure of the consequences.
419
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100420 ccw_timeout_log [S390]
421 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422
Paul Menage8bab8dd2008-04-04 14:29:57 -0700423 cgroup_disable= [KNL] Disable a particular controller
424 Format: {name of the controller(s) to disable}
425 {Currently supported controllers - "memory"}
426
Linus Torvalds1da177e2005-04-16 15:20:36 -0700427 checkreqprot [SELINUX] Set initial checkreqprot flag value.
428 Format: { "0" | "1" }
429 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700430 0 -- check protection applied by kernel (includes
431 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432 1 -- check protection requested by application.
433 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700434 Value can be changed at runtime via
435 /selinux/checkreqprot.
436
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100437 cio_ignore= [S390]
438 See Documentation/s390/CommonIO for details.
439
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700440 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700441 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200442 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700443 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200444 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 Format: { pit | tsc | cyclone | pmtmr }
446
John Stultz592913e2010-07-13 17:56:20 -0700447 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700448 Format: <string>
449 Override the default clocksource and use the clocksource
450 with the name specified.
451 Some clocksource names to choose from, depending on
452 the platform:
453 [all] jiffies (this is the base, fallback clocksource)
454 [ACPI] acpi_pm
455 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
456 pxa_timer,timer3,32k_counter,timer0_1
457 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700458 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700459 scx200_hrt on Geode; cyclone on IBM x440
460 [MIPS] MIPS
461 [PARISC] cr16
462 [S390] tod
463 [SH] SuperH
464 [SPARC64] tick
465 [X86-64] hpet,tsc
466
Andi Kleenac72e782008-01-30 13:33:21 +0100467 clearcpuid=BITNUM [X86]
468 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800469 arch/x86/include/asm/cpufeature.h for the valid bit
470 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100471 stable over kernel options, but the vendor specific
472 ones should be.
473 Also note that user programs calling CPUID directly
474 or using the feature without checking anything
475 will still see it. This just prevents it from
476 being used by the kernel or shown in /proc/cpuinfo.
477 Also note the kernel might malfunction if you disable
478 some critical bits.
479
Robert Jennings14f966e2009-04-15 05:55:32 +0000480 cmo_free_hint= [PPC] Format: { yes | no }
481 Specify whether pages are marked as being inactive
482 when they are freed. This is used in CMO environments
483 to determine OS memory pressure for page stealing by
484 a hypervisor.
485 Default: yes
486
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530487 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100488 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100489 Range: 0 - 8192
490 Default: 64
491
Linus Torvalds1da177e2005-04-16 15:20:36 -0700492 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700493 Format:
494 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700495
496 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
497 Format: <io>[,<irq>]
498
Randy Dunlapa9913042005-10-23 12:57:11 -0700499 com90xx= [HW,NET]
500 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700501 Format: <io>[,<irq>[,<memstart>]]
502
503 condev= [HW,S390] console device
504 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700505
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506 console= [KNL] Output console device and options.
507
508 tty<n> Use the virtual console device <n>.
509
510 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800511 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800513 the form "bbbbpnf", where "bbbb" is the baud rate,
514 "p" is parity ("n", "o", or "e"), "n" is number of
515 bits, and "f" is flow control ("r" for RTS or
516 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700517
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800518 See Documentation/serial-console.txt for more
519 information. See
520 Documentation/networking/netconsole.txt for an
521 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700523 uart[8250],io,<addr>[,options]
524 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 Start an early, polled-mode console on the 8250/16550
526 UART at the specified I/O port or MMIO address,
527 switching to the matching ttyS device later. The
528 options are the same as for ttyS, above.
529
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700530 If the device connected to the port is not a TTY but a braille
531 device, prepend "brl," before the device type, for instance
532 console=brl,ttyS0
533 For now, only VisioBraille is supported.
534
Daniel Mackf324edc2009-06-16 15:33:52 -0700535 consoleblank= [KNL] The console blank (screen saver) timeout in
536 seconds. Defaults to 10*60 = 10mins. A value of 0
537 disables the blank timer.
538
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800539 coredump_filter=
540 [KNL] Change the default value for
541 /proc/<pid>/coredump_filter.
542 See also Documentation/filesystems/proc.txt.
543
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700545 Format:
546 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700548 crashkernel=nn[KMG]@ss[KMG]
549 [KNL] Reserve a chunk of physical memory to
550 hold a kernel to switch to with kexec on panic.
551
Bernhard Wallefb391592007-10-18 23:41:02 -0700552 crashkernel=range1:size1[,range2:size2,...][@offset]
553 [KNL] Same as above, but depends on the memory
554 in the running system. The syntax of range is
555 start-[end] where start and end are both
556 a memory unit (amount[KMG]). See also
557 Documentation/kdump/kdump.txt for a example.
558
Linus Torvalds1da177e2005-04-16 15:20:36 -0700559 cs89x0_dma= [HW,NET]
560 Format: <dma>
561
562 cs89x0_media= [HW,NET]
563 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700564
Randy Dunlapa9913042005-10-23 12:57:11 -0700565 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566 See header of drivers/s390/block/dasd_devmap.c.
567
568 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
569 (one device per port)
570 Format: <port#>,<type>
571 See also Documentation/input/joystick-parport.txt
572
Thomas Renningera648ec02010-08-06 16:11:02 +0200573 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
574 time. See Documentation/dynamic-debug-howto.txt for
575 details.
576
Linus Torvalds1da177e2005-04-16 15:20:36 -0700577 debug [KNL] Enable kernel debugging (events log level).
578
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700579 debug_locks_verbose=
580 [KNL] verbose self-tests
581 Format=<0|1>
582 Print debugging info while doing the locking API
583 self-tests.
584 We default to 0 (no extra messages), setting it to
585 1 will print _a lot_ more information - normally
586 only useful to kernel developers.
587
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700588 debug_objects [KNL] Enable object debugging
589
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500590 no_debug_objects
591 [KNL] Disable object debugging
592
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200593 debugpat [X86] Enable PAT debugging
594
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200595 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700596 Format: <area>[,<node>]
597 See also Documentation/networking/decnet.txt.
598
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700599 default_hugepagesz=
600 [same as hugepagesz=] The size of the default
601 HugeTLB page size. This is the size represented by
602 the legacy /proc/ hugepages APIs, used for SHM, and
603 default size when mounting hugetlbfs filesystems.
604 Defaults to the default architecture's huge page size
605 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700606
Linus Torvalds1da177e2005-04-16 15:20:36 -0700607 dhash_entries= [KNL]
608 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700609
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610 digi= [HW,SERIAL]
611 IO parameters + enable/disable command.
612
613 digiepca= [HW,SERIAL]
614 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000615 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616
Brian Haleyb0f83b22010-02-04 13:36:50 -0800617 disable= [IPV6]
618 See Documentation/networking/ipv6.txt.
619
620 disable_ipv6= [IPV6]
621 See Documentation/networking/ipv6.txt.
622
Yinghai Lu95ffa242008-04-29 03:52:33 -0700623 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700624 The kernel tries to adjust MTRR layout from continuous
625 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700626 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700627
Yinghai Lu093af8d2008-01-30 13:33:32 +0100628 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100629 By default the kernel will trim any uncacheable
630 memory out of your available memory pool based on
631 MTRR settings. This parameter disables that behavior,
632 possibly causing your machine to run very slowly.
633
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530634 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700635 Disable PIN 1 of APIC timer
636 Can be useful to work around chipset bugs.
637
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700638 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
639 this option disables the debugging code at boot.
640
641 dma_debug_entries=<number>
642 This option allows to tune the number of preallocated
643 entries for DMA-API debugging code. One entry is
644 required per DMA-API allocation. Use this if the
645 DMA-API debugging code disables itself because the
646 architectural default is too low.
647
Joerg Roedel1745de52009-05-22 21:49:51 +0200648 dma_debug_driver=<driver_name>
649 With this option the DMA-API debugging driver
650 filter feature can be enabled at boot time. Just
651 pass the driver to filter for as the parameter.
652 The filter can be disabled or changed to another
653 driver later using sysfs.
654
Linus Torvalds1da177e2005-04-16 15:20:36 -0700655 dscc4.setup= [NET]
656
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700657 earlycon= [KNL] Output early console device and options.
658 uart[8250],io,<addr>[,options]
659 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700660 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700661 Start an early, polled-mode console on the 8250/16550
662 UART at the specified I/O port or MMIO address.
Samium Gromoff1917ac72010-07-20 15:26:51 -0700663 MMIO inter-register address stride is either 8bit (mmio)
664 or 32bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700665 The options are the same as for ttyS, above.
666
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530667 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700668 earlyprintk=vga
669 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500670 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500671 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700672
Randy Dunlapa9913042005-10-23 12:57:11 -0700673 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674 takes over.
675
Yinghai Lu5c059172008-07-24 17:29:40 -0700676 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700677
678 Currently only ttyS0 and ttyS1 are supported.
679
680 Interaction with the standard serial driver is not
681 very good.
682
683 The VGA output is eventually overwritten by the real
684 console.
685
Jason Wessel97311912010-05-20 21:04:30 -0500686 ekgdboc= [X86,KGDB] Allow early kernel console debugging
687 ekgdboc=kbd
688
689 This is desgined to be used in conjunction with
690 the boot argument: earlyprintk=vga
691
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700693 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694
Linus Torvalds1da177e2005-04-16 15:20:36 -0700695 eisa_irq_edge= [PARISC,HW]
696 See header of drivers/parisc/eisa.c.
697
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700698 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700699 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700700 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700701
702 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +0100703 Format: {"cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700704 See Documentation/block/as-iosched.txt and
705 Documentation/block/deadline-iosched.txt for details.
706
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530707 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700708 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800709 image elf header. Generally kexec loader will
710 pass this option to capture kernel.
711 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700713 enable_mtrr_cleanup [X86]
714 The kernel tries to adjust MTRR layout from continuous
715 to discrete, to make X server driver able to add WB
716 entry later. This parameter enables that.
717
Randy Dunlapca1eda22009-05-06 16:02:58 -0700718 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700719 Enable PIN 1 of APIC timer
720 Can be useful to work around chipset bugs
721 (in particular on some ATI chipsets).
722 The kernel tries to set a reasonable default.
723
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724 enforcing [SELINUX] Set initial enforcing status.
725 Format: {"0" | "1"}
726 See security/selinux/Kconfig help text.
727 0 -- permissive (log only, no denials).
728 1 -- enforcing (deny and log).
729 Default value is 0.
730 Value can be changed at runtime via /selinux/enforce.
731
Huang Yinga08f82d2010-05-18 14:35:21 +0800732 erst_disable [ACPI]
733 Disable Error Record Serialization Table (ERST)
734 support.
735
Linus Torvalds1da177e2005-04-16 15:20:36 -0700736 ether= [HW,NET] Ethernet cards parameters
737 This option is obsoleted by the "netdev=" option, which
738 has equivalent usage. See its documentation for details.
739
Akinobu Mitade1ba092006-12-08 02:39:42 -0800740 failslab=
741 fail_page_alloc=
742 fail_make_request=[KNL]
743 General fault injection mechanism.
744 Format: <interval>,<probability>,<space>,<times>
745 See also /Documentation/fault-injection/.
746
Linus Torvalds1da177e2005-04-16 15:20:36 -0700747 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000748 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700749
Alex Chiangf13ae302008-05-08 14:03:23 -0600750 force_pal_cache_flush
751 [IA-64] Avoid check_sal_cache_flush which may hang on
752 buggy SAL_CACHE_FLUSH implementations. Using this
753 parameter will force ia64_sal_cache_flush to call
754 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
755
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100756 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400757 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100758 as early as possible in order to facilitate early
759 boot debugging.
760
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200761 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400762 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200763 If no parameter is passed, ftrace will dump
764 buffers of all CPUs, but if you pass orig_cpu, it will
765 dump only the buffer of the CPU that triggered the
766 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400767
768 ftrace_filter=[function-list]
769 [FTRACE] Limit the functions traced by the function
770 tracer at boot up. function-list is a comma separated
771 list of functions. This list can be changed at run
772 time by the set_ftrace_filter file in the debugfs
773 tracing directory.
774
775 ftrace_notrace=[function-list]
776 [FTRACE] Do not trace the functions specified in
777 function-list. This list can be changed at run time
778 by the set_ftrace_notrace file in the debugfs
779 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100780
Stefan Assmann369bc182009-10-12 22:17:21 +0200781 ftrace_graph_filter=[function-list]
782 [FTRACE] Limit the top level callers functions traced
783 by the function graph tracer at boot up.
784 function-list is a comma separated list of functions
785 that can be changed at run time by the
786 set_graph_function file in the debugfs tracing directory.
787
Linus Torvalds1da177e2005-04-16 15:20:36 -0700788 gamecon.map[2|3]=
789 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
790 support via parallel port (up to 5 devices per port)
791 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
792 See also Documentation/input/joystick-parport.txt
793
794 gamma= [HW,DRM]
795
Yinghai Luaaf23042008-01-30 13:33:09 +0100796 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
797 Format: off | on
798 default: on
799
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700800 gcov_persist= [GCOV] When non-zero (default), profiling data for
801 kernel modules is saved and remains accessible via
802 debugfs, even when the module is unloaded/reloaded.
803 When zero, profiling data is discarded and associated
804 debugfs files are removed at module unload time.
805
Linus Torvalds1da177e2005-04-16 15:20:36 -0700806 gpt [EFI] Forces disk with valid GPT signature but
807 invalid Protective MBR to be treated as GPT.
808
Linus Torvalds1da177e2005-04-16 15:20:36 -0700809 hashdist= [KNL,NUMA] Large hashes allocated during boot
810 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700811 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700812 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700813
814 hcl= [IA-64] SGI's Hardware Graph compatibility layer
815
816 hd= [EIDE] (E)IDE hard drive subsystem geometry
817 Format: <cyl>,<head>,<sect>
818
Huang Yingea8c0712010-05-18 14:35:15 +0800819 hest_disable [ACPI]
820 Disable Hardware Error Source Table (HEST) support;
821 corresponding firmware-first mode error processing
822 logic will be disabled.
823
Linus Torvalds1da177e2005-04-16 15:20:36 -0700824 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
825 size of <nn>. This works even on boxes that have no
826 highmem otherwise. This also works to reduce highmem
827 size on bigger boxes.
828
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800829 highres= [KNL] Enable/disable high resolution timer mode.
830 Valid parameters: "on", "off"
831 Default: "on"
832
Linus Torvalds1da177e2005-04-16 15:20:36 -0700833 hisax= [HW,ISDN]
834 See Documentation/isdn/README.HiSax.
835
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700836 hlt [BUGS=ARM,SH]
837
838 hpet= [X86-32,HPET] option to control HPET usage
839 Format: { enable (default) | disable | force |
840 verbose }
841 disable: disable HPET and use PIT instead
842 force: allow force enabled of undocumented chips (ICH4,
843 VIA, nVidia)
844 verbose: show contents of HPET registers during setup
845
Andi Kleenb4718e62008-07-23 21:27:51 -0700846 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
847 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700848 On x86-64 and powerpc, this option can be specified
849 multiple times interleaved with hugepages= to reserve
850 huge pages of different sizes. Valid pages sizes on
851 x86-64 are 2M (when the CPU supports "pse") and 1G
852 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700853 Note that 1GB pages can only be allocated at boot time
854 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900855
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100856 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
857 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100858 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
859 If specified, z/VM IUCV HVC accepts connections
860 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100861
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700862 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700863 or register an additional I2C bus that is not
864 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700865 Format:
866 <bus_id>,<clkrate>
867
Jiri Kosina36d95732008-10-06 02:51:09 -0400868 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700869 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200870 i8042.dumbkbd [HW] Pretend that controller can only read data from
871 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700872 (Don't attempt to blink the leds)
873 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500874 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400875 i8042.noloop [HW] Disable the AUX Loopback command while probing
876 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700877 i8042.nomux [HW] Don't check presence of an active multiplexing
878 controller
879 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
880 controllers
Jiri Kosinaf8313ef2011-01-08 01:37:26 -0800881 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
Linus Torvalds1da177e2005-04-16 15:20:36 -0700882 i8042.reset [HW] Reset the controller during init and cleanup
883 i8042.unlock [HW] Unlock (ignore) the keylock
884
885 i810= [HW,DRM]
886
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700887 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
888 indicates that the driver is running on unsupported
889 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
891 does not match list of supported models.
892 i8k.power_status
893 [HW] Report power status in /proc/i8k
894 (disabled by default)
895 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
896 capability is set.
897
Linus Torvalds1da177e2005-04-16 15:20:36 -0700898 icn= [HW,ISDN]
899 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
900
David Fries0af80c02009-02-25 20:28:21 +0100901 ide-core.nodma= [HW] (E)IDE subsystem
902 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200903 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
904 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100905 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700906
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700907 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
908 Claim all unknown PCI IDE storage controllers.
909
Andi Kleenf039b752007-05-02 19:27:12 +0200910 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800911 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
912 Poll forces a polling idle loop that can slightly
913 improve the performance of waking up a idle CPU, but
914 will use a lot of power and make the system run hot.
915 Not recommended.
916 idle=mwait: On systems which support MONITOR/MWAIT but
917 the kernel chose to not use it because it doesn't save
918 as much power as a normal idle loop, use the
919 MONITOR/MWAIT idle loop anyways. Performance should be
920 the same as idle=poll.
921 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800922 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800923 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700924
Ingo Molnar792908222006-12-06 20:40:51 -0800925 ignore_loglevel [KNL]
926 Ignore loglevel setting - this will print /all/
927 kernel messages to the console. Useful for debugging.
928
Linus Torvalds1da177e2005-04-16 15:20:36 -0700929 ihash_entries= [KNL]
930 Set number of hash buckets for inode cache.
931
Mimi Zohar3323eec92009-02-04 09:06:58 -0500932 ima_audit= [IMA]
933 Format: { "0" | "1" }
934 0 -- integrity auditing messages. (Default)
935 1 -- enable informational integrity auditing messages.
936
937 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700938 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -0500939 default: "sha1"
940
Eric Paris5789ba32009-05-21 15:47:06 -0400941 ima_tcb [IMA]
942 Load a policy which meets the needs of the Trusted
943 Computing Base. This means IMA will measure all
944 programs exec'd, files mmap'd for exec, and all files
945 opened for read by uid=0.
946
Linus Torvalds1da177e2005-04-16 15:20:36 -0700947 init= [KNL]
948 Format: <full_path>
949 Run specified binary instead of /sbin/init as init
950 process.
951
952 initcall_debug [KNL] Trace initcalls as they are executed. Useful
953 for working out where the kernel is dying during
954 startup.
955
956 initrd= [BOOT] Specify the location of the initial ramdisk
957
958 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
959 Format: <irq>
960
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700961 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800962 on
963 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700964 off
965 Disable intel iommu driver.
966 igfx_off [Default Off]
967 By default, gfx is mapped as normal device. If a gfx
968 device has a dedicated DMAR unit, the DMAR unit is
969 bypassed by not enabling DMAR with this option. In
970 this case, gfx device will use physical address for
971 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700972 forcedac [x86_64]
973 With this option iommu will not optimize to look
974 for io virtual address below 32 bit forcing dual
975 address cycle on pci bus for cards supporting greater
976 than 32 bit addressing. The default is to look
977 for translation below 32 bit and if not available
978 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -0800979 strict [Default Off]
980 With this option on every unmap_single operation will
981 result in a hardware IOTLB flush operation as opposed
982 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700983
Chris Wrightd1423d52010-07-20 11:06:49 -0700984 intremap= [X86-64, Intel-IOMMU]
985 Format: { on (default) | off | nosid }
986 on enable Interrupt Remapping (default)
987 off disable Interrupt Remapping
988 nosid disable Source ID checking
989
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700990 inttest= [IA64]
991
992 iomem= Disable strict checking of access to MMIO memory
993 strict regions from userspace.
994 relaxed
995
996 iommu= [x86]
997 off
998 force
999 noforce
1000 biomerge
1001 panic
1002 nopanic
1003 merge
1004 nomerge
1005 forcesac
1006 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001007 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001008
1009 io7= [HW] IO7 for Marvel based alpha systems
1010 See comment before marvel_specify_io7 in
1011 arch/alpha/kernel/core_marvel.c.
1012
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301013 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001014 0x80
1015 Standard port 0x80 based delay
1016 0xed
1017 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001018 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001019 Simple two microseconds delay
1020 none
1021 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001022
Linus Torvalds1da177e2005-04-16 15:20:36 -07001023 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001024 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001025
1026 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001027 See comment before ip2_setup() in
1028 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001029
Alan Cox200803d2005-06-28 20:45:18 -07001030 irqfixup [HW]
1031 When an interrupt is not handled search all handlers
1032 for it. Intended to get systems with badly broken
1033 firmware running.
1034
1035 irqpoll [HW]
1036 When an interrupt is not handled search all handlers
1037 for it. Also check all handlers each timer
1038 interrupt. Intended to get systems with badly broken
1039 firmware running.
1040
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001042 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043
1044 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001045 Format:
1046 <cpu number>,...,<cpu number>
1047 or
Li Zefanb225d442008-11-06 12:53:39 -08001048 <cpu number>-<cpu number>
1049 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001050 or a mixture
1051 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001052
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053 This option can be used to specify one or more CPUs
1054 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001055 algorithms. You can move a process onto or off an
1056 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001057 <cpu number> begins at 0 and the maximum value is
1058 "number of CPUs in system - 1".
1059
1060 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001061 alternative -- manually setting the CPU mask of all
1062 tasks in the system -- can cause problems and
1063 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001064
Randy Dunlapa9913042005-10-23 12:57:11 -07001065 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066
1067 js= [HW,JOY] Analog joystick
1068 See Documentation/input/joystick.txt.
1069
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001070 keepinitrd [HW,ARM]
1071
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301072 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001073 specifies the amount of memory usable by the kernel
1074 for non-movable allocations. The requested amount is
1075 spread evenly throughout all nodes in the system. The
1076 remaining memory in each node is used for Movable
1077 pages. In the event, a node is too small to have both
1078 kernelcore and Movable pages, kernelcore pages will
1079 take priority and other nodes will have a larger number
1080 of kernelcore pages. The Movable zone is used for the
1081 allocation of pages that may be reclaimed or moved
1082 by the page migration subsystem. This means that
1083 HugeTLB pages may not be allocated from this zone.
1084 Note that allocations like PTEs-from-HighMem still
1085 use the HighMem zone if it exists, and the Normal
1086 zone if it does not.
1087
Jason Wessel4fe1da42010-05-20 21:04:31 -05001088 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1089 Format: <Controller#>[,poll interval]
1090 The controller # is the number of the ehci usb debug
1091 port as it is probed via PCI. The poll interval is
1092 optional and is the number seconds in between
1093 each poll cycle to the debug port in case you need
1094 the functionality for interrupting the kernel with
1095 gdb or control-c on the dbgp connection. When
1096 not using this parameter you use sysrq-g to break into
1097 the kernel debugger.
1098
Jason Wessel84c08fd2010-05-20 21:04:24 -05001099 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001100 Requires a tty driver that supports console polling,
1101 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001102 Serial only format: <serial_device>[,baud]
1103 keyboard only format: kbd
1104 keyboard and serial format: kbd,<serial_device>[,baud]
1105 Optional Kernel mode setting:
1106 kms, kbd format: kms,kbd
1107 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001108
Jason Wessel84c08fd2010-05-20 21:04:24 -05001109 kgdbwait [KGDB] Stop kernel execution and enter the
1110 kernel debugger at the earliest opportunity.
1111
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001112 kmac= [MIPS] korina ethernet MAC address.
1113 Configure the RouterBoard 532 series on-chip
1114 Ethernet adapter MAC address.
1115
Catalin Marinas04f70332009-06-11 13:22:39 +01001116 kmemleak= [KNL] Boot-time kmemleak enable/disable
1117 Valid arguments: on, off
1118 Default: on
1119
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301120 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001121 in oops dumps.
1122
Andre Przywarafef07aa2009-07-10 14:20:35 +02001123 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1124 Default is 0 (don't ignore, but inject #GP)
1125
1126 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1127 Default is 1 (enabled)
1128
Xiao Guangronga182d872010-09-20 22:17:48 +08001129 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1130 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001131 Default is 0 (off)
1132
Andre Przywarafef07aa2009-07-10 14:20:35 +02001133 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001134 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001135
1136 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1137 for all guests.
1138 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1139
1140 kvm-intel.bypass_guest_pf=
1141 [KVM,Intel] Disables bypassing of guest page faults
1142 on Intel chips. Default is 1 (enabled)
1143
1144 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1145 (virtualized MMU) support on capable Intel chips.
1146 Default is 1 (enabled)
1147
1148 kvm-intel.emulate_invalid_guest_state=
1149 [KVM,Intel] Enable emulation of invalid guest states
1150 Default is 0 (disabled)
1151
1152 kvm-intel.flexpriority=
1153 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1154 Default is 1 (enabled)
1155
1156 kvm-intel.unrestricted_guest=
1157 [KVM,Intel] Disable unrestricted guest feature
1158 (virtualized real and unpaged mode) on capable
1159 Intel chips. Default is 1 (enabled)
1160
1161 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1162 feature (tagged TLBs) on capable Intel chips.
1163 Default is 1 (enabled)
1164
Linus Torvalds1da177e2005-04-16 15:20:36 -07001165 l2cr= [PPC]
1166
Robert Brosea78bfbf2008-03-29 07:20:23 +11001167 l3cr= [PPC]
1168
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001169 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001170 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001171
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301172 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001173 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001174
FD Camifcb71f62008-01-06 19:08:56 +01001175 libata.dma= [LIBATA] DMA control
1176 libata.dma=0 Disable all PATA and SATA DMA
1177 libata.dma=1 PATA and SATA Disk DMA only
1178 libata.dma=2 ATAPI (CDROM) DMA only
1179 libata.dma=4 Compact Flash DMA only
1180 Combinations also work, so libata.dma=3 enables DMA
1181 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001182
1183 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1184 libata.ignore_hpa=0 keep BIOS limits (default)
1185 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001186
Dave Jones78e70c22007-09-27 11:50:13 -04001187 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1188 when set.
1189 Format: <int>
1190
Tejun Heo33267322008-02-13 09:15:09 +09001191 libata.force= [LIBATA] Force configurations. The format is comma
1192 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001193 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001194 matching port, link or device. Basically, it matches
1195 the ATA ID string printed on console by libata. If
1196 the whole ID part is omitted, the last PORT and DEVICE
1197 values are used. If ID hasn't been specified yet, the
1198 configuration applies to all ports, links and devices.
1199
1200 If only DEVICE is omitted, the parameter applies to
1201 the port and all links and devices behind it. DEVICE
1202 number of 0 either selects the first device or the
1203 first fan-out link behind PMP device. It does not
1204 select the host link. DEVICE number of 15 selects the
1205 host link and device attached to it.
1206
1207 The VAL specifies the configuration to force. As long
1208 as there's no ambiguity shortcut notation is allowed.
1209 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1210 The following configurations can be forced.
1211
1212 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1213 Any ID with matching PORT is used.
1214
1215 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1216
1217 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1218 udma[/][16,25,33,44,66,100,133] notation is also
1219 allowed.
1220
1221 * [no]ncq: Turn on or off NCQ.
1222
Tejun Heo05944bd2008-08-13 20:19:09 +09001223 * nohrst, nosrst, norst: suppress hard, soft
1224 and both resets.
1225
Tejun Heo43c9c592010-05-23 12:59:11 +02001226 * dump_id: dump IDENTIFY data.
1227
Tejun Heo33267322008-02-13 09:15:09 +09001228 If there are multiple matching configurations changing
1229 the same attribute, the last one is used.
1230
Yinghai Lu95f72d12010-07-12 14:36:09 +10001231 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001232
Linus Torvalds1da177e2005-04-16 15:20:36 -07001233 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001234 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001235
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001236 lockd.nlm_grace_period=P [NFS] Assign grace period.
1237 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001238
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001239 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1240 Format: <integer>
1241
1242 lockd.nlm_timeout=T [NFS] Assign timeout value.
1243 Format: <integer>
1244
1245 lockd.nlm_udpport=M [NFS] Assign UDP port.
1246 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001247
1248 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1249 Format: <irq>
1250
1251 loglevel= All Kernel Messages with a loglevel smaller than the
1252 console loglevel will be printed to the console. It can
1253 also be changed with klogd or other programs. The
1254 loglevels are defined as follows:
1255
1256 0 (KERN_EMERG) system is unusable
1257 1 (KERN_ALERT) action must be taken immediately
1258 2 (KERN_CRIT) critical conditions
1259 3 (KERN_ERR) error conditions
1260 4 (KERN_WARNING) warning conditions
1261 5 (KERN_NOTICE) normal but significant condition
1262 6 (KERN_INFO) informational
1263 7 (KERN_DEBUG) debug-level messages
1264
1265 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001266 Format: { n | nk | nM }
1267 n must be a power of two. The default size
1268 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001269
Randy Dunlapaccaa242007-10-16 01:29:37 -07001270 logo.nologo [FB] Disables display of the built-in Linux logo.
1271 This may be used to provide more screen space for
1272 kernel log messages and is useful when debugging
1273 kernel boot problems.
1274
Linus Torvalds1da177e2005-04-16 15:20:36 -07001275 lp=0 [LP] Specify parallel ports to use, e.g,
1276 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1277 lp=reset first parallel port). 'lp=0' disables the
1278 lp=auto printer driver. 'lp=reset' (which can be
1279 specified in addition to the ports) causes
1280 attached printers to be reset. Using
1281 lp=port1,port2,... specifies the parallel ports
1282 to associate lp devices with, starting with
1283 lp0. A port specification may be 'none' to skip
1284 that lp device, or a parport name such as
1285 'parport0'. Specifying 'lp=auto' instead of a
1286 port specification list means that device IDs
1287 from each port should be examined, to see if
1288 an IEEE 1284-compliant printer is attached; if
1289 so, the driver will manage that printer.
1290 See also header of drivers/char/lp.c.
1291
1292 lpj=n [KNL]
1293 Sets loops_per_jiffy to given constant, thus avoiding
1294 time-consuming boot-time autodetection (up to 250 ms per
1295 CPU). 0 enables autodetection (default). To determine
1296 the correct value for your kernel, boot with normal
1297 autodetection and see what value is printed. Note that
1298 on SMP systems the preset will be applied to all CPUs,
1299 which is likely to cause problems if your CPUs need
1300 significantly divergent settings. An incorrect value
1301 will cause delays in the kernel to be wrong, leading to
1302 unpredictable I/O errors and other breakage. Although
1303 unlikely, in the extreme case this might damage your
1304 hardware.
1305
1306 ltpc= [NET]
1307 Format: <io>,<irq>,<dma>
1308
Randy Dunlapa9913042005-10-23 12:57:11 -07001309 machvec= [IA64] Force the use of a particular machine-vector
1310 (machvec) in a generic kernel.
1311 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001312
Wu Zhangjin3209e702009-07-02 23:27:12 +08001313 machtype= [Loongson] Share the same kernel image file between different
1314 yeeloong laptop.
1315 Example: machtype=lemote-yeeloong-2f-7inch
1316
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001317 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1318 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319
1320 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001321 should make use of. maxcpus=n : n >= 0 limits the
1322 kernel to using 'n' processors. n=0 is a special case,
1323 it is equivalent to "nosmp", which also disables
1324 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001325
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001326 max_loop= [LOOP] Maximum number of loopback devices that can
1327 be mounted
1328 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001329
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330 mcatest= [IA-64]
1331
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001332 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001333
Uwe Hermann71cced62008-10-20 09:32:21 -07001334 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001335
Linus Torvalds1da177e2005-04-16 15:20:36 -07001336 md= [HW] RAID subsystems devices and level
1337 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001338
Linus Torvalds1da177e2005-04-16 15:20:36 -07001339 mdacon= [MDA]
1340 Format: <first>,<last>
1341 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001342
Linus Torvalds1da177e2005-04-16 15:20:36 -07001343 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1344 Amount of memory to be used when the kernel is not able
1345 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001346 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347 address space collisions. Without memmap= PCI devices
1348 could be placed at addresses belonging to unused RAM.
1349
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001350 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351 memory.
1352
Paul Mundt6902aa82008-09-21 17:14:42 +09001353 memchunk=nn[KMG]
1354 [KNL,SH] Allow user to override the default size for
1355 per-device physically contiguous DMA buffers.
1356
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301357 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001358 E820 memory map, as specified by the user.
1359 Such memmap=exactmap lines can be constructed based on
1360 BIOS output or other requirements. See the memmap=nn@ss
1361 option description.
1362
1363 memmap=nn[KMG]@ss[KMG]
1364 [KNL] Force usage of a specific region of memory
1365 Region of memory to be used, from ss to ss+nn.
1366
1367 memmap=nn[KMG]#ss[KMG]
1368 [KNL,ACPI] Mark specific memory as ACPI data.
1369 Region of memory to be used, from ss to ss+nn.
1370
1371 memmap=nn[KMG]$ss[KMG]
1372 [KNL,ACPI] Mark specific memory as reserved.
1373 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001374 Example: Exclude memory from 0x18690000-0x1869ffff
1375 memmap=64K$0x18690000
1376 or
1377 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001378
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001379 memory_corruption_check=0/1 [X86]
1380 Some BIOSes seem to corrupt the first 64k of
1381 memory when doing things like suspend/resume.
1382 Setting this option will scan the memory
1383 looking for corruption. Enabling this will
1384 both detect corruption and prevent the kernel
1385 from using the memory being corrupted.
1386 However, its intended as a diagnostic tool; if
1387 repeatable BIOS-originated corruption always
1388 affects the same memory, you can use memmap=
1389 to prevent the kernel from using that memory.
1390
1391 memory_corruption_check_size=size [X86]
1392 By default it checks for corruption in the low
1393 64k, making this memory unavailable for normal
1394 use. Use this parameter to scan for
1395 corruption in more or less memory.
1396
1397 memory_corruption_check_period=seconds [X86]
1398 By default it checks for corruption every 60
1399 seconds. Use this parameter to check at some
1400 other rate. 0 disables periodic checking.
1401
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001402 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001403 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001404 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001405 Specifies the number of memtest passes to be
1406 performed. Each pass selects another test
1407 pattern from a given set of patterns. Memtest
1408 fills the memory with this pattern, validates
1409 memory contents and reserves bad memory
1410 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001411
Linus Torvalds1da177e2005-04-16 15:20:36 -07001412 meye.*= [HW] Set MotionEye Camera parameters
1413 See Documentation/video4linux/meye.txt.
1414
Andres Salomon8f368812007-10-12 23:04:06 +02001415 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1416 Multi-Function General Purpose Timers on AMD Geode
1417 platforms.
1418
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001419 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1420 the BIOS has incorrectly applied a workaround. TinyBIOS
1421 version 0.98 is known to be affected, 0.99 fixes the
1422 problem by letting the user disable the workaround.
1423
Linus Torvalds1da177e2005-04-16 15:20:36 -07001424 mga= [HW,DRM]
1425
Randy Dunlap1c207f92008-11-19 15:36:16 -08001426 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1427 physical address is ignored.
1428
Michel Pollet39f45d72009-05-20 11:10:31 +01001429 mini2440= [ARM,HW,KNL]
1430 Format:[0..2][b][c][t]
1431 Default: "0tb"
1432 MINI2440 configuration specification:
1433 0 - The attached screen is the 3.5" TFT
1434 1 - The attached screen is the 7" TFT
1435 2 - The VGA Shield is attached (1024x768)
1436 Leaving out the screen size parameter will not load
1437 the TFT driver, and the framebuffer will be left
1438 unconfigured.
1439 b - Enable backlight. The TFT backlight pin will be
1440 linked to the kernel VESA blanking code and a GPIO
1441 LED. This parameter is not necessary when using the
1442 VGA shield.
1443 c - Enable the s3c camera interface.
1444 t - Reserved for enabling touchscreen support. The
1445 touchscreen support is not enabled in the mainstream
1446 kernel as of 2.6.30, a preliminary port can be found
1447 in the "bleeding edge" mini2440 support kernel at
1448 http://repo.or.cz/w/linux-2.6/mini2440.git
1449
Mel Gorman6b74ab92008-07-23 21:26:49 -07001450 mminit_loglevel=
1451 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1452 parameter allows control of the logging verbosity for
1453 the additional memory initialisation checks. A value
1454 of 0 disables mminit logging and a level of 4 will
1455 log everything. Information is printed at KERN_DEBUG
1456 so loglevel=8 may also need to be specified.
1457
Linus Torvalds1da177e2005-04-16 15:20:36 -07001458 mousedev.tap_time=
1459 [MOUSE] Maximum time between finger touching and
1460 leaving touchpad surface for touch to be considered
1461 a tap and be reported as a left button click (for
1462 touchpads working in absolute mode only).
1463 Format: <msecs>
1464 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1465 reporting absolute coordinates, such as tablets
1466 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1467 reporting absolute coordinates, such as tablets
1468
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301469 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001470 is similar to kernelcore except it specifies the
1471 amount of memory used for migratable allocations.
1472 If both kernelcore and movablecore is specified,
1473 then kernelcore will be at *least* the specified
1474 value but may be more. If movablecore on its own
1475 is specified, the administrator must be careful
1476 that the amount of memory usable for all allocations
1477 is not too small.
1478
Linus Torvalds1da177e2005-04-16 15:20:36 -07001479 MTD_Partition= [MTD]
1480 Format: <name>,<region-number>,<size>,<offset>
1481
Randy Dunlapa9913042005-10-23 12:57:11 -07001482 MTD_Region= [MTD] Format:
1483 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001484
1485 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001486 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001487
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001488 multitce=off [PPC] This parameter disables the use of the pSeries
1489 firmware feature for updating multiple TCE entries
1490 at a time.
1491
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001492 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1493
1494 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1495
1496 boundary - index of last SLC block on Flex-OneNAND.
1497 The remaining blocks are configured as MLC blocks.
1498 lock - Configure if Flex-OneNAND boundary should be locked.
1499 Once locked, the boundary cannot be changed.
1500 1 indicates lock status, 0 indicates unlock status.
1501
Ben Dooks9db829f2008-07-03 11:24:29 +01001502 mtdset= [ARM]
1503 ARM/S3C2412 JIVE boot control
1504
1505 See arch/arm/mach-s3c2412/mach-jive.c
1506
Linus Torvalds1da177e2005-04-16 15:20:36 -07001507 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001508 [HW] Make the MicroTouch USB driver use raw coordinates
1509 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001510
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001511 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001512 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001513 that could hold holes aka. UC entries.
1514
1515 mtrr_gran_size=nn[KMG] [X86]
1516 Used for mtrr cleanup. It is granularity of mtrr block.
1517 Default is 1.
1518 Large value could prevent small alignment from
1519 using up MTRRs.
1520
1521 mtrr_spare_reg_nr=n [X86]
1522 Format: <integer>
1523 Range: 0,7 : spare reg number
1524 Default : 1
1525 Used for mtrr cleanup. It is spare mtrr entries number.
1526 Set to 2 or more if your graphical card needs more.
1527
Linus Torvalds1da177e2005-04-16 15:20:36 -07001528 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1529
Linus Torvalds1da177e2005-04-16 15:20:36 -07001530 netdev= [NET] Network devices parameters
1531 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1532 Note that mem_start is often overloaded to mean
1533 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001534 This usage is only documented in each driver source
1535 file if at all.
1536
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001537 nf_conntrack.acct=
1538 [NETFILTER] Enable connection tracking flow accounting
1539 0 to disable accounting
1540 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001541 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001542
Chuck Lever306a0752010-09-17 10:54:37 -04001543 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001544 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001545
1546 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001547 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001548
Chuck Lever306a0752010-09-17 10:54:37 -04001549 nfsrootdebug [NFS] enable nfsroot debugging messages.
1550 See Documentation/filesystems/nfs/nfsroot.txt.
1551
Trond Myklebusta72b4422006-01-03 09:55:41 +01001552 nfs.callback_tcpport=
1553 [NFS] set the TCP port on which the NFSv4 callback
1554 channel should listen.
1555
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001556 nfs.cache_getent=
1557 [NFS] sets the pathname to the program which is used
1558 to update the NFS client cache entries.
1559
1560 nfs.cache_getent_timeout=
1561 [NFS] sets the timeout after which an attempt to
1562 update a cache entry is deemed to have failed.
1563
Trond Myklebust58df0952006-01-03 09:55:57 +01001564 nfs.idmap_cache_timeout=
1565 [NFS] set the maximum lifetime for idmapper cache
1566 entries.
1567
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001568 nfs.enable_ino64=
1569 [NFS] enable 64-bit inode numbers.
1570 If zero, the NFS client will fake up a 32-bit inode
1571 number for the readdir() and stat() syscalls instead
1572 of returning the full 64-bit number.
1573 The default is to return 64-bit inode numbers.
1574
Paul Mundt1e1030d2009-09-01 17:38:32 +09001575 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001576 when a NMI is triggered.
1577 Format: [state][,regs][,debounce][,die]
1578
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301579 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001580 Format: [panic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05001581 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001582 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001583 When panic is specified, panic when an NMI watchdog
1584 timeout occurs.
1585 This is useful when you use a panic=... timeout and
1586 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001587
Anton Vorontsovbff38772009-07-08 11:10:56 -07001588 netpoll.carrier_timeout=
1589 [NET] Specifies amount of time (in seconds) that
1590 netpoll should wait for a carrier. By default netpoll
1591 waits 4 seconds.
1592
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001593 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001594 emulation library even if a 387 maths coprocessor
1595 is present.
1596
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001597 no_console_suspend
1598 [HW] Never suspend the console
1599 Disable suspending of consoles during suspend and
1600 hibernate operations. Once disabled, debugging
1601 messages can reach various consoles while the rest
1602 of the system is being put to sleep (ie, while
1603 debugging driver suspend/resume hooks). This may
1604 not work reliably with all consoles, but is known
1605 to work with serial and VGA consoles.
1606
Christoph Lameterc1aee212007-05-31 00:40:47 -07001607 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1608 caches in the slab allocator. Saves per-node memory,
1609 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001610
Randy Dunlapa9913042005-10-23 12:57:11 -07001611 noalign [KNL,ARM]
1612
Linus Torvalds1da177e2005-04-16 15:20:36 -07001613 noapic [SMP,APIC] Tells the kernel to not make use of any
1614 IOAPICs that may be present in the system.
1615
Mike Galbraith5091faa2010-11-30 14:18:03 +01001616 noautogroup Disable scheduler automatic task group creation.
1617
Linus Torvalds1da177e2005-04-16 15:20:36 -07001618 nobats [PPC] Do not use BATs for mapping kernel lowmem
1619 on "Classic" PPC cores.
1620
1621 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001622
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001623 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1624
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001625 nodelayacct [KNL] Disable per-task delay accounting
1626
Linus Torvalds1da177e2005-04-16 15:20:36 -07001627 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1628
Paul Mundt6902aa82008-09-21 17:14:42 +09001629 nodsp [SH] Disable hardware DSP at boot time.
1630
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301631 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001632
Linus Torvalds1da177e2005-04-16 15:20:36 -07001633 noexec [IA-64]
1634
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301635 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001636 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001637 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001638 noexec=off: disable non-executable mappings
1639
1640 noexec32 [X86-64]
1641 This affects only 32-bit executables.
1642 noexec32=on: enable non-executable mappings (default)
1643 read doesn't imply executable mappings
1644 noexec32=off: disable non-executable mappings
1645 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001646
Paul Mundt6902aa82008-09-21 17:14:42 +09001647 nofpu [SH] Disable hardware FPU at boot time.
1648
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001649 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001650 register save and restore. The kernel will only save
1651 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001652
Suresh Siddha0c752a92009-05-22 12:17:45 -07001653 noxsave [BUGS=X86] Disables x86 extended register state save
1654 and restore using xsave. The kernel will fallback to
1655 enabling legacy floating-point and sse state.
1656
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001657 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1658 wfi(ARM) instruction doesn't work correctly and not to
1659 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001660
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001661 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001662 instruction doesn't work correctly and not to
1663 use it.
1664
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001665 no_file_caps Tells the kernel not to honor file capabilities. The
1666 only way then for a file to be executed with privilege
1667 is to be setuid root or executed by root.
1668
Linus Torvalds1da177e2005-04-16 15:20:36 -07001669 nohalt [IA-64] Tells the kernel not to use the power saving
1670 function PAL_HALT_LIGHT when idle. This increases
1671 power-consumption. On the positive side, it reduces
1672 interrupt wake-up latency, which may improve performance
1673 in certain environments such as networked servers or
1674 real-time systems.
1675
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001676 nohz= [KNL] Boottime enable/disable dynamic ticks
1677 Valid arguments: on, off
1678 Default: on
1679
Paul Mundteeee7852009-04-02 12:31:16 +09001680 noiotrap [SH] Disables trapped I/O port accesses.
1681
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001682 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001683 disable unhandled interrupt sources.
1684
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301685 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001686 broken timer IRQ sources.
1687
Linus Torvalds1da177e2005-04-16 15:20:36 -07001688 noisapnp [ISAPNP] Disables ISA PnP code.
1689
1690 noinitrd [RAM] Tells the kernel not to load any configured
1691 initial RAM disk.
1692
Weidong Han03ea8152009-04-17 16:42:15 +08001693 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1694 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07001695 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08001696
Linus Torvalds1da177e2005-04-16 15:20:36 -07001697 nointroute [IA-64]
1698
Tony Luck0aa366f2007-07-20 11:22:30 -07001699 nojitter [IA64] Disables jitter checking for ITC timers.
1700
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02001701 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1702
Gleb Natapovfd10cde2010-10-14 11:22:51 +02001703 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1704 fault handling.
1705
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001706 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001707
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001708 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001709
Linus Torvalds1da177e2005-04-16 15:20:36 -07001710 noltlbs [PPC] Do not use large page/tlb entries for kernel
1711 lowmem mapping on PPC40x.
1712
Horms312f1f02006-02-22 09:57:55 +09001713 nomca [IA-64] Disable machine check abort handling
1714
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001715 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001716
Andres Salomon83d73842007-10-12 23:04:06 +02001717 nomfgpt [X86-32] Disable Multi-Function General Purpose
1718 Timer usage (for AMD Geode machines).
1719
Jiri Kosina016ddd92010-01-18 17:05:40 +01001720 nopat [X86] Disable PAT (page attribute table extension of
1721 pagetables) support.
1722
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001723 norandmaps Don't use address space randomization. Equivalent to
1724 echo 0 > /proc/sys/kernel/randomize_va_space
1725
Jiri Kosinabbff2162010-08-11 18:34:09 +02001726 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001727
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001728 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001729 with UP alternatives
1730
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731 noresidual [PPC] Don't use residual data on PReP machines.
1732
Randy Dunlapa9913042005-10-23 12:57:11 -07001733 noresume [SWSUSP] Disables resume and restores original swap
1734 space.
1735
Linus Torvalds1da177e2005-04-16 15:20:36 -07001736 no-scroll [VGA] Disables scrollback.
1737 This is required for the Braillex ib80-piezo Braille
1738 reader made by F.H. Papenmeier (Germany).
1739
1740 nosbagart [IA-64]
1741
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001742 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001743
Len Brown61ec7562007-08-16 03:34:22 -04001744 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1745 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001746
Dave Jones97842212007-07-15 23:41:05 -07001747 nosoftlockup [KNL] Disable the soft-lockup detector.
1748
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001749 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001750 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001751
Linus Torvalds1da177e2005-04-16 15:20:36 -07001752 nosync [HW,M68K] Disables sync negotiation for all devices.
1753
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001754 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001755
1756 nousb [USB] Disable the USB subsystem
1757
Ben Hutchings55142372011-01-02 23:02:42 +00001758 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04001759
Linus Torvalds1da177e2005-04-16 15:20:36 -07001760 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001761
Weidong Han2b2fd872009-04-17 16:42:12 +08001762 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1763
Fenghua Yua6c75b862008-03-14 13:57:08 -07001764 nptcg= [IA64] Override max number of concurrent global TLB
1765 purges which is reported from either PAL_VM_SUMMARY or
1766 SAL PALO.
1767
Yinghai Lu2b633e32010-02-10 01:20:37 -08001768 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1769 could support. nr_cpus=n : n >= 1 limits the kernel to
1770 supporting 'n' processors. Later in runtime you can not
1771 use hotplug cpu feature to put more cpu back to online.
1772 just like you compile the kernel NR_CPUS=n
1773
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001774 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1775
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001776 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1777 one of ['zone', 'node', 'default'] can be specified
1778 This can be set from sysctl after boot.
1779 See Documentation/sysctl/vm.txt for details.
1780
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001781 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1782 See Documentation/debugging-via-ohci1394.txt for more
1783 info.
1784
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001785 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1786 Rather than timing out after 20 ms if an EC
1787 command is not properly ACKed, override the length
1788 of the timeout. We have interrupts disabled while
1789 waiting for the ACK, so if this is set too high
1790 interrupts *may* be lost!
1791
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001792 omap_mux= [OMAP] Override bootloader pin multiplexing.
1793 Format: <mux_mode0.mode_name=value>...
1794 For example, to override I2C bus2:
1795 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1796
Linus Torvalds1da177e2005-04-16 15:20:36 -07001797 oprofile.timer= [HW]
1798 Use timer interrupt instead of performance counters
1799
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001800 oprofile.cpu_type= Force an oprofile cpu type
1801 This might be useful if you have an older oprofile
1802 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001803 Format: { arch_perfmon }
1804 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001805 perfmon on Intel CPUs instead of the
1806 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001807
Randy Dunlapbcfde332010-06-07 17:10:38 -07001808 OSS [HW,OSS]
1809 See Documentation/sound/oss/oss-parameters.txt
1810
Linus Torvalds1da177e2005-04-16 15:20:36 -07001811 panic= [KNL] Kernel behaviour on panic
1812 Format: <timeout>
1813
1814 parkbd.port= [HW] Parallel port number the keyboard adapter is
1815 connected to, default is 0.
1816 Format: <parport#>
1817 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1818 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001819 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001820
Randy Dunlapa9913042005-10-23 12:57:11 -07001821 parport= [HW,PPT] Specify parallel ports. 0 disables.
1822 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1823 Use 'auto' to force the driver to use any
1824 IRQ/DMA settings detected (the default is to
1825 ignore detected IRQ/DMA settings because of
1826 possible conflicts). You can specify the base
1827 address, IRQ, and DMA settings; IRQ and DMA
1828 should be numbers, or 'auto' (for using detected
1829 settings on that particular port), or 'nofifo'
1830 (to avoid using a FIFO even if it is detected).
1831 Parallel ports are assigned in the order they
1832 are specified on the command line, starting
1833 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001834
Randy Dunlapa9913042005-10-23 12:57:11 -07001835 parport_init_mode= [HW,PPT]
1836 Configure VIA parallel port to operate in
1837 a specific mode. This is necessary on Pegasos
1838 computer where firmware has no options for setting
1839 up parallel port mode and sets it to spp.
1840 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001841 Format: [spp|ps2|epp|ecp|ecpepp]
1842
Andrew Mortondd287792006-03-23 03:00:57 -08001843 pause_on_oops=
1844 Halt all CPUs after the first oops has been printed for
1845 the specified number of seconds. This is to be used if
1846 your oopses keep scrolling off the screen.
1847
Linus Torvalds1da177e2005-04-16 15:20:36 -07001848 pcbit= [HW,ISDN]
1849
1850 pcd. [PARIDE]
1851 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001852 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001853
Randy Dunlapa9913042005-10-23 12:57:11 -07001854 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001855 earlydump [X86] dump PCI config space before the kernel
1856 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001857 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001858 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001859 the hardware directly. Use this if your machine
1860 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001861 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001862 hardware access methods are allowed. Use this
1863 if you experience crashes upon bootup and you
1864 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001865 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001866 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001867 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001868 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001869 noaer [PCIE] If the PCIEAER kernel config parameter is
1870 enabled, this kernel boot option can be used to
1871 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001872 nodomains [PCI] Disable support for multiple PCI
1873 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301874 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001875 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001876 check_enable_amd_mmconf [X86] check for and enable
1877 properly configured MMIO access to PCI
1878 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001879 nomsi [MSI] If the PCI_MSI kernel config parameter is
1880 enabled, this kernel boot option can be used to
1881 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001882 noioapicquirk [APIC] Disable all boot interrupt quirks.
1883 Safety option to keep boot IRQs enabled. This
1884 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001885 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1886 primary IO-APIC for bridges that cannot disable
1887 boot IRQs. This fixes a source of spurious IRQs
1888 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001889 noioapicreroute [APIC] Disable workaround that uses the
1890 boot IRQ equivalent of an IRQ that connects to
1891 a chipset where boot IRQs cannot be disabled.
1892 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001893 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001894 routing table. These calls are known to be buggy
1895 on several machines and they hang the machine
1896 when used, but on other computers it's the only
1897 way to get the interrupt routing table. Try
1898 this option if the kernel is unable to allocate
1899 IRQs or discover secondary PCI buses on your
1900 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001901 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001902 Use with caution as certain devices share
1903 address decoders between ROMs and other
1904 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001905 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001906 expansion ROMs that do not already have
1907 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07001908 nobar [X86] Do not assign address space to the
1909 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001910 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001911 assigned automatically to PCI devices. You can
1912 make the kernel exclude IRQs of your ISA cards
1913 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001914 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001915 of the PIRQ table (normally generated
1916 by the BIOS) if it is outside the
1917 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001918 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001919 useful if the kernel is unable to find your
1920 secondary buses and you want to tell it
1921 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001922 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001923 numbers ourselves, overriding
1924 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001925 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001926 in the BIOS $PIR table. This is needed on
1927 some systems with broken BIOSes, notably
1928 some HP Pavilion N5400 and Omnibook XE3
1929 notebooks. This will have no effect if ACPI
1930 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001931 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001932 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07001933 use_crs [X86] Use PCI host bridge window information
1934 from ACPI. On BIOSes from 2008 or later, this
1935 is enabled by default. If you need to use this,
1936 please report a bug.
1937 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1938 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07001939 routeirq Do IRQ routing for all PCI devices.
1940 This is normally done in pci_enable_device(),
1941 so this option is a temporary workaround
1942 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001943 skip_isa_align [X86] do not align io start addr, so can
1944 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001945 firmware [ARM] Do not re-enumerate the bus but instead
1946 just use the configuration from the
1947 bootloader. This is currently used on
1948 IXP2000 systems where the bus has to be
1949 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001950 noearly [X86] Don't do any early type 1 scanning.
1951 This might help on some broken boards which
1952 machine check when some devices' config space
1953 is read. But various workarounds are disabled
1954 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001955 bfsort Sort PCI devices into breadth-first order.
1956 This sorting is done to get a device
1957 order compatible with older (<= 2.4) kernels.
1958 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001959 cbiosize=nn[KMG] The fixed amount of bus space which is
1960 reserved for the CardBus bridge's IO window.
1961 The default value is 256 bytes.
1962 cbmemsize=nn[KMG] The fixed amount of bus space which is
1963 reserved for the CardBus bridge's memory
1964 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09001965 resource_alignment=
1966 Format:
1967 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1968 Specifies alignment and device to reassign
1969 aligned memory resources.
1970 If <order of align> is not specified,
1971 PAGE_SIZE is used as alignment.
1972 PCI-PCI bridge can be specified, if resource
1973 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06001974 ecrc= Enable/disable PCIe ECRC (transaction layer
1975 end-to-end CRC checking).
1976 bios: Use BIOS/firmware settings. This is the
1977 the default.
1978 off: Turn ECRC off
1979 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001980
Chuck Ebberte5665a42008-09-24 20:40:34 -04001981 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1982 Management.
1983 off Disable ASPM.
1984 force Enable ASPM even on devices that claim not to support it.
1985 WARNING: Forcing ASPM on may cause system lockups.
1986
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02001987 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02001988 auto Ask the BIOS whether or not to use native PCIe services
1989 associated with PCIe ports (PME, hot-plug, AER). Use
1990 them only if that is allowed by the BIOS.
1991 native Use native PCIe services associated with PCIe ports
1992 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02001993 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1994 ports driver.
1995
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01001996 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01001997 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02001998 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01001999
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000 pcmv= [HW,PCMCIA] BadgePAD 4
2001
2002 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002003 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002004
2005 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2006 boot time.
2007 Format: { 0 | 1 }
2008 See arch/parisc/kernel/pdc_chassis.c
2009
Tejun Heof58dc012009-08-14 15:00:50 +09002010 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002011 Currently supported values are "embed" and "page".
2012 Archs may support subset or none of the selections.
2013 See comments in mm/percpu.c for details on each
2014 allocator. This parameter is primarily for debugging
2015 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002016
Linus Torvalds1da177e2005-04-16 15:20:36 -07002017 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002018 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002019
2020 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002021 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002022
2023 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002024 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002025
2026 plip= [PPT,NET] Parallel port network link
2027 Format: { parport<nr> | timid | 0 }
2028 See also Documentation/parport.txt.
2029
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002030 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2031 Override pmtimer IOPort with a hex value.
2032 e.g. pmtmr=0x508
2033
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002034 pnp.debug [PNP]
2035 Enable PNP debug messages. This depends on the
2036 CONFIG_PNP_DEBUG_MESSAGES option.
2037
Linus Torvalds1da177e2005-04-16 15:20:36 -07002038 pnpacpi= [ACPI]
2039 { off }
2040
2041 pnpbios= [ISAPNP]
2042 { on | off | curr | res | no-curr | no-res }
2043
2044 pnp_reserve_irq=
2045 [ISAPNP] Exclude IRQs for the autoconfiguration
2046
2047 pnp_reserve_dma=
2048 [ISAPNP] Exclude DMAs for the autoconfiguration
2049
2050 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002051 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002052
2053 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002054 [ISAPNP] Exclude memory regions for the
2055 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002056 Ranges are in pairs (memory base and size).
2057
Randy Dunlap4af94f32009-04-17 18:30:28 -07002058 ports= [IP_VS_FTP] IPVS ftp helper module
2059 Default is 21.
2060 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2061 may be specified.
2062 Format: <port>,<port>....
2063
Ingo Molnar45807a12007-07-15 23:40:10 -07002064 print-fatal-signals=
2065 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002066
2067 If enabled, warn about various signal handling
2068 related application anomalies: too many signals,
2069 too many POSIX.1 timers, fatal signals causing a
2070 coredump - etc.
2071
2072 If you hit the warning due to signal overflow,
2073 you might want to try "ulimit -i unlimited".
2074
Ingo Molnar45807a12007-07-15 23:40:10 -07002075 default: off.
2076
Randy Dunlape84845c2007-07-15 23:40:25 -07002077 printk.time= Show timing data prefixed to each printk message line
2078 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2079
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002080 processor.max_cstate= [HW,ACPI]
2081 Limit processor to maximum C-state
2082 max_cstate=9 overrides any DMI blacklist limit.
2083
2084 processor.nocst [HW,ACPI]
2085 Ignore the _CST method to determine C-states,
2086 instead using the legacy FADT method
2087
Linus Torvalds1da177e2005-04-16 15:20:36 -07002088 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002089 Format: [schedule,]<number>
2090 Param: "schedule" - profile schedule points.
2091 Param: <number> - step/bucket size as a power of 2 for
2092 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002093 Param: "sleep" - profile D-state sleeping (millisecs).
2094 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002095 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002096
Linus Torvalds1da177e2005-04-16 15:20:36 -07002097 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2098 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002099 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002100
Randy Dunlapa9913042005-10-23 12:57:11 -07002101 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2102 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002103 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2104 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002105 psmouse.resetafter= [HW,MOUSE]
2106 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002107 (0 = never).
2108 psmouse.resolution=
2109 [HW,MOUSE] Set desired mouse resolution, in dpi.
2110 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002111 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002112 0 = disabled, 1 = enabled (default).
2113
Linus Torvalds1da177e2005-04-16 15:20:36 -07002114 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002115 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002116
Kay Sieversdc8c8582007-08-15 12:25:38 +02002117 pty.legacy_count=
2118 [KNL] Number of legacy pty's. Overwrites compiled-in
2119 default number.
2120
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002121 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002122
Linus Torvalds1da177e2005-04-16 15:20:36 -07002123 r128= [HW,DRM]
2124
2125 raid= [HW,RAID]
2126 See Documentation/md.txt.
2127
Randy Dunlapa9913042005-10-23 12:57:11 -07002128 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002129 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002130
Linus Torvalds1da177e2005-04-16 15:20:36 -07002131 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002132 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002133
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002134 rcupdate.blimit= [KNL,BOOT]
2135 Set maximum number of finished RCU callbacks to process
2136 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002137
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002138 rcupdate.qhimark= [KNL,BOOT]
2139 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002140 RCU callbacks over which batch limiting is disabled.
2141
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002142 rcupdate.qlowmark= [KNL,BOOT]
2143 Set threshold of queued RCU callbacks below which
2144 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002145
Olof Johanssonffdfc402005-09-06 15:17:19 -07002146 rdinit= [KNL]
2147 Format: <full_path>
2148 Run specified binary instead of /init from the ramdisk,
2149 used for early userspace startup. See initrd.
2150
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002151 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002152 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002153 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002154
Paul Jackson46b6d942008-07-04 10:00:09 -07002155 relax_domain_level=
2156 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002157 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002158
Linus Torvalds1da177e2005-04-16 15:20:36 -07002159 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2160
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002161 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002162 Format: nn[KMG]
2163 Reserves a hole at the top of the kernel virtual
2164 address space.
2165
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002166 reservelow= [X86]
2167 Format: nn[K]
2168 Set the amount of memory to reserve for BIOS at
2169 the bottom of the address space.
2170
Vivek Goyal7e962872006-09-27 01:50:44 -07002171 reset_devices [KNL] Force drivers to reset the underlying device
2172 during initialization.
2173
Randy Dunlapa9913042005-10-23 12:57:11 -07002174 resume= [SWSUSP]
2175 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002176
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002177 resume_offset= [SWSUSP]
2178 Specify the offset from the beginning of the partition
2179 given by "resume=" at which the swap header is located,
2180 in <PAGE_SIZE> units (needed only for swap files).
2181 See Documentation/power/swsusp-and-swap-files.txt
2182
Bojan Smojverf996fc92010-09-09 23:06:23 +02002183 hibernate= [HIBERNATION]
2184 noresume Don't check if there's a hibernation image
2185 present during boot.
2186 nocompress Don't compress/decompress hibernation images.
2187
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002188 retain_initrd [RAM] Keep initrd memory after extraction
2189
Linus Torvalds1da177e2005-04-16 15:20:36 -07002190 rhash_entries= [KNL,NET]
2191 Set number of hash buckets for route cache
2192
2193 riscom8= [HW,SERIAL]
2194 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2195
2196 ro [KNL] Mount root device read-only on boot
2197
2198 root= [KNL] Root filesystem
2199
2200 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2201 mount the root filesystem
2202
2203 rootflags= [KNL] Set root filesystem mount option string
2204
2205 rootfstype= [KNL] Set root filesystem type
2206
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002207 rootwait [KNL] Wait (indefinitely) for root device to show up.
2208 Useful for devices that are detected asynchronously
2209 (e.g. USB and MMC devices).
2210
Linus Torvalds1da177e2005-04-16 15:20:36 -07002211 rw [KNL] Mount root device read-write on boot
2212
2213 S [KNL] Run init in single mode
2214
2215 sa1100ir [NET]
2216 See drivers/net/irda/sa1100_ir.c.
2217
Linus Torvalds1da177e2005-04-16 15:20:36 -07002218 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002219
Mike Travisf6630112009-11-17 18:22:15 -06002220 sched_debug [KNL] Enables verbose scheduler debug messages.
2221
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002222 security= [SECURITY] Choose a security module to enable at boot.
2223 If this boot parameter is not specified, only the first
2224 security module asking for security registration will be
2225 loaded. An invalid security module name will be treated
2226 as if no module has been chosen.
2227
2228 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002229 Format: { "0" | "1" }
2230 See security/selinux/Kconfig help text.
2231 0 -- disable.
2232 1 -- enable.
2233 Default value is set via kernel config option.
2234 If enabled at boot time, /selinux/disable can be used
2235 later to disable prior to initial policy load.
2236
John Johansenc1c124e2010-07-29 14:48:09 -07002237 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2238 Format: { "0" | "1" }
2239 See security/apparmor/Kconfig help text
2240 0 -- disable.
2241 1 -- enable.
2242 Default value is set via kernel config option.
2243
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002244 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002245
Linus Torvalds1da177e2005-04-16 15:20:36 -07002246 shapers= [NET]
2247 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002248
Yinghai Lub05f78f2008-08-22 01:32:50 -07002249 show_msr= [x86] show boot-time MSR settings
2250 Format: { <integer> }
2251 Show boot-time (BIOS-initialized) MSR settings.
2252 The parameter means the number of CPUs to show,
2253 for example 1 means boot CPU only.
2254
Linus Torvalds1da177e2005-04-16 15:20:36 -07002255 simeth= [IA-64]
2256 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002257
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258 slram= [HW,MTD]
2259
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002260 slub_debug[=options[,slabs]] [MM, SLUB]
2261 Enabling slub_debug allows one to determine the
2262 culprit if slab objects become corrupted. Enabling
2263 slub_debug can create guard zones around objects and
2264 may poison objects when not in use. Also tracks the
2265 last alloc / free. For more information see
2266 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002267
2268 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002269 Determines the maximum allowed order for slabs.
2270 A high setting may cause OOMs due to memory
2271 fragmentation. For more information see
2272 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002273
2274 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002275 The minimum number of objects per slab. SLUB will
2276 increase the slab order up to slub_max_order to
2277 generate a sufficiently large slab able to contain
2278 the number of objects indicated. The higher the number
2279 of objects the smaller the overhead of tracking slabs
2280 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002281 For more information see Documentation/vm/slub.txt.
2282
2283 slub_min_order= [MM, SLUB]
2284 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002285 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002286 For more information see Documentation/vm/slub.txt.
2287
2288 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002289 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002290 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002291 allocs to different slabs. Debug options disable
2292 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002293 For more information see Documentation/vm/slub.txt.
2294
Linus Torvalds1da177e2005-04-16 15:20:36 -07002295 smart2= [HW]
2296 Format: <io1>[,<io2>[,...,<io8>]]
2297
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002298 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002299 attempt to substitute SMP alternatives once at boot.
2300
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002301 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2302 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2303 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2304 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2305 smsc-ircc2.ircc_irq= [HW] IRQ line
2306 smsc-ircc2.ircc_dma= [HW] DMA channel
2307 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2308 0: Toshiba Satellite 1800 (GP data pin select)
2309 1: Fast pin select (default)
2310 2: ATC IRMode
2311
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002312 softlockup_panic=
2313 [KNL] Should the soft-lockup detector generate panics.
2314
Linus Torvalds1da177e2005-04-16 15:20:36 -07002315 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2316 See Documentation/sonypi.txt
2317
2318 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002319 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002320
2321 spia_io_base= [HW,MTD]
2322 spia_fio_base=
2323 spia_pedr=
2324 spia_peddr=
2325
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002326 stacktrace [FTRACE]
2327 Enabled the stack tracer on boot up.
2328
Linus Torvalds1da177e2005-04-16 15:20:36 -07002329 sti= [PARISC,HW]
2330 Format: <num>
2331 Set the STI (builtin display/keyboard on the HP-PARISC
2332 machines) console (graphic card) which should be used
2333 as the initial boot-console.
2334 See also comment in drivers/video/console/sticore.c.
2335
2336 sti_font= [HW]
2337 See comment in drivers/video/console/sticore.c.
2338
2339 stifb= [HW]
2340 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2341
Trond Myklebustcbf11072009-08-09 15:06:19 -04002342 sunrpc.min_resvport=
2343 sunrpc.max_resvport=
2344 [NFS,SUNRPC]
2345 SunRPC servers often require that client requests
2346 originate from a privileged port (i.e. a port in the
2347 range 0 < portnr < 1024).
2348 An administrator who wishes to reserve some of these
2349 ports for other uses may adjust the range that the
2350 kernel's sunrpc client considers to be privileged
2351 using these two parameters to set the minimum and
2352 maximum port values.
2353
Greg Banks42a7fc42007-03-06 01:42:23 -08002354 sunrpc.pool_mode=
2355 [NFS]
2356 Control how the NFS server code allocates CPUs to
2357 service thread pools. Depending on how many NICs
2358 you have and where their interrupts are bound, this
2359 option will affect which CPUs will do NFS serving.
2360 Note: this parameter cannot be changed while the
2361 NFS server is running.
2362
2363 auto the server chooses an appropriate mode
2364 automatically using heuristics
2365 global a single global pool contains all CPUs
2366 percpu one pool for each CPU
2367 pernode one pool for each NUMA node (equivalent
2368 to global on non-NUMA machines)
2369
Trond Myklebustcbf11072009-08-09 15:06:19 -04002370 sunrpc.tcp_slot_table_entries=
2371 sunrpc.udp_slot_table_entries=
2372 [NFS,SUNRPC]
2373 Sets the upper limit on the number of simultaneous
2374 RPC calls that can be sent from the client to a
2375 server. Increasing these values may allow you to
2376 improve throughput, but will also increase the
2377 amount of memory reserved for use by the client.
2378
Michal Hockoa42c3902010-11-24 12:57:08 -08002379 swapaccount[=0|1]
2380 [KNL] Enable accounting of swap in memory resource
2381 controller if no parameter or 1 is given or disable
2382 it if 0 is given (See Documentation/cgroups/memory.txt)
2383
Linus Torvalds1da177e2005-04-16 15:20:36 -07002384 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002385
Linus Torvalds1da177e2005-04-16 15:20:36 -07002386 switches= [HW,M68k]
2387
Andi Kleene52eec12010-09-08 16:54:17 +02002388 sysfs.deprecated=0|1 [KNL]
2389 Enable/disable old style sysfs layout for old udev
2390 on older distributions. When this option is enabled
2391 very new udev will not work anymore. When this option
2392 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2393 in older udev will not work anymore.
2394 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2395 the kernel configuration.
2396
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002397 sysrq_always_enabled
2398 [KNL]
2399 Ignore sysrq setting - this boot parameter will
2400 neutralize any effect of /proc/sys/kernel/sysrq.
2401 Useful for debugging.
2402
Linus Torvalds1da177e2005-04-16 15:20:36 -07002403 tdfx= [HW,DRM]
2404
David Brownell77437fd2008-07-23 21:28:33 -07002405 test_suspend= [SUSPEND]
2406 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2407 standby suspend) as the system sleep state to briefly
2408 enter during system startup. The system is woken from
2409 this state using a wakeup-capable RTC alarm.
2410
Linus Torvalds1da177e2005-04-16 15:20:36 -07002411 thash_entries= [KNL,NET]
2412 Set number of hash buckets for TCP connection
2413
Len Brownf8707ec2007-08-12 00:12:54 -04002414 thermal.act= [HW,ACPI]
2415 -1: disable all active trip points in all thermal zones
2416 <degrees C>: override all lowest active trip points
2417
Len Brownc52a7412007-08-14 15:49:32 -04002418 thermal.crt= [HW,ACPI]
2419 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002420 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002421
Len Brownf5487142007-08-12 00:12:44 -04002422 thermal.nocrt= [HW,ACPI]
2423 Set to disable actions on ACPI thermal zone
2424 critical and hot trip points.
2425
Len Brown72b33ef2007-08-12 00:12:17 -04002426 thermal.off= [HW,ACPI]
2427 1: disable ACPI thermal control
2428
Len Browna70cdc52007-08-12 00:12:35 -04002429 thermal.psv= [HW,ACPI]
2430 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002431 <degrees C>: override all passive trip points to this
2432 value
Len Browna70cdc52007-08-12 00:12:35 -04002433
Len Brown730ff342007-08-12 00:12:26 -04002434 thermal.tzp= [HW,ACPI]
2435 Specify global default ACPI thermal zone polling rate
2436 <deci-seconds>: poll all this frequency
2437 0: no polling (default)
2438
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002439 topology= [S390]
2440 Format: {off | on}
2441 Specify if the kernel should make use of the cpu
2442 topology informations if the hardware supports these.
2443 The scheduler will make use of these informations and
2444 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02002445 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002446
Linus Torvalds1da177e2005-04-16 15:20:36 -07002447 tp720= [HW,PS2]
2448
Rajiv Andrade225a9be2010-03-25 00:55:32 -03002449 tpm_suspend_pcr=[HW,TPM]
2450 Format: integer pcr id
2451 Specify that at suspend time, the tpm driver
2452 should extend the specified pcr with zeros,
2453 as a workaround for some chips which fail to
2454 flush the last written pcr on TPM_SaveState.
2455 This will guarantee that all the other pcrs
2456 are saved.
2457
Li Zefan9d612be2009-06-24 17:33:15 +08002458 trace_buf_size=nn[KMG]
2459 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002460
Li Zefan020e5f82009-07-01 10:47:05 +08002461 trace_event=[event-list]
2462 [FTRACE] Set and start specified trace events in order
2463 to facilitate early boot debugging.
2464 See also Documentation/trace/events.txt
2465
john stultzd3b8f882009-08-17 16:40:47 -07002466 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07002467 Format: <string>
2468 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07002469 disables clocksource verification at runtime, as well
2470 as the stability checks done at bootup. Used to enable
2471 high-resolution timer mode on older hardware, and in
2472 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07002473 [x86] noirqtime: Do not use TSC to do irq accounting.
2474 Used to run time disable IRQ_TIME_ACCOUNTING on any
2475 platforms where RDTSC is slow and this accounting
2476 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07002477
Randy Dunlapa9913042005-10-23 12:57:11 -07002478 turbografx.map[2|3]= [HW,JOY]
2479 TurboGraFX parallel port interface
2480 Format:
2481 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002482 See also Documentation/input/joystick-parport.txt
2483
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002484 uhash_entries= [KNL,NET]
2485 Set number of hash buckets for UDP/UDP-Lite connections
2486
Alan Stern5f8364b2006-12-05 16:29:55 -05002487 uhci-hcd.ignore_oc=
2488 [USB] Ignore overcurrent events (default N).
2489 Some badly-designed motherboards generate lots of
2490 bogus events, for ports that aren't wired to
2491 anything. Set this parameter to avoid log spamming.
2492 Note that genuine overcurrent events won't be
2493 reported either.
2494
Simon Arlotte3a61b02008-07-19 23:32:54 +01002495 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302496 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002497 Set unknown_nmi_panic=1 early on boot.
2498
Alan Sternb5e795f2007-02-20 15:00:53 -05002499 usbcore.autosuspend=
2500 [USB] The autosuspend time delay (in seconds) used
2501 for newly-detected USB devices (default 2). This
2502 is the time required before an idle device will be
2503 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002504 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002505
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002506 usbcore.usbfs_snoop=
2507 [USB] Set to log all usbfs traffic (default 0 = off).
2508
2509 usbcore.blinkenlights=
2510 [USB] Set to cycle leds on hubs (default 0 = off).
2511
2512 usbcore.old_scheme_first=
2513 [USB] Start with the old device initialization
2514 scheme (default 0 = off).
2515
2516 usbcore.use_both_schemes=
2517 [USB] Try the other device initialization scheme
2518 if the first one fails (default 1 = enabled).
2519
2520 usbcore.initial_descriptor_timeout=
2521 [USB] Specifies timeout for the initial 64-byte
2522 USB_REQ_GET_DESCRIPTOR request in milliseconds
2523 (default 5000 = 5.0 seconds).
2524
Linus Torvalds1da177e2005-04-16 15:20:36 -07002525 usbhid.mousepoll=
2526 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002527
Alan Sternd4f373e2008-11-10 14:07:45 -05002528 usb-storage.delay_use=
2529 [UMS] The delay in seconds before a new device is
2530 scanned for Logical Units (default 5).
2531
2532 usb-storage.quirks=
2533 [UMS] A list of quirks entries to supplement or
2534 override the built-in unusual_devs list. List
2535 entries are separated by commas. Each entry has
2536 the form VID:PID:Flags where VID and PID are Vendor
2537 and Product ID values (4-digit hex numbers) and
2538 Flags is a set of characters, each corresponding
2539 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002540 a = SANE_SENSE (collect more than 18 bytes
2541 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002542 b = BAD_SENSE (don't collect more than 18
2543 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002544 c = FIX_CAPACITY (decrease the reported
2545 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002546 h = CAPACITY_HEURISTICS (decrease the
2547 reported device capacity by one
2548 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002549 i = IGNORE_DEVICE (don't bind to this
2550 device);
2551 l = NOT_LOCKABLE (don't try to lock and
2552 unlock ejectable media);
2553 m = MAX_SECTORS_64 (don't transfer more
2554 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002555 o = CAPACITY_OK (accept the capacity
2556 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002557 r = IGNORE_RESIDUE (the device reports
2558 bogus residue values);
2559 s = SINGLE_LUN (the device has only one
2560 Logical Unit);
2561 w = NO_WP_DETECT (don't test whether the
2562 medium is write-protected).
2563 Example: quirks=0419:aaf5:rl,0421:0433:rc
2564
Ian Campbell14315592010-02-17 10:38:10 +00002565 userpte=
2566 [X86] Flags controlling user PTE allocations.
2567
2568 nohigh = do not allocate PTE pages in
2569 HIGHMEM regardless of setting
2570 of CONFIG_HIGHPTE.
2571
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302572 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002573 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002574 vdso=1: enable VDSO (default)
2575 vdso=0: disable VDSO mapping
2576
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302577 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002578 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2579 vdso32=1: enable 32-bit VDSO (default)
2580 vdso32=0: disable 32-bit VDSO mapping
2581
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002582 vector= [IA-64,SMP]
2583 vector=percpu: enable percpu vector domain
2584
Linus Torvalds1da177e2005-04-16 15:20:36 -07002585 video= [FB] Frame buffer configuration
2586 See Documentation/fb/modedb.txt.
2587
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002588 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002589 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002590 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002591 Use vga=ask for menu.
2592 This is actually a boot loader parameter; the value is
2593 passed to the kernel using a special protocol.
2594
Randy Dunlapa9913042005-10-23 12:57:11 -07002595 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002596 size of <nn>. This can be used to increase the
2597 minimum size (128MB on x86). It can also be used to
2598 decrease the size and leave more room for directly
2599 mapped kernel RAM.
2600
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002601 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2602 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002603
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002604 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2605 Format: <command>
2606
2607 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2608 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002609
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002610 vt.cur_default= [VT] Default cursor shape.
2611 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2612 the parameters of the <Esc>[?A;B;Cc escape sequence;
2613 see VGA-softcursor.txt. Default: 2 = underline.
2614
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002615 vt.default_blu= [VT]
2616 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2617 Change the default blue palette of the console.
2618 This is a 16-member array composed of values
2619 ranging from 0-255.
2620
2621 vt.default_grn= [VT]
2622 Format: <green0>,<green1>,<green2>,...,<green15>
2623 Change the default green palette of the console.
2624 This is a 16-member array composed of values
2625 ranging from 0-255.
2626
2627 vt.default_red= [VT]
2628 Format: <red0>,<red1>,<red2>,...,<red15>
2629 Change the default red palette of the console.
2630 This is a 16-member array composed of values
2631 ranging from 0-255.
2632
2633 vt.default_utf8=
2634 [VT]
2635 Format=<0|1>
2636 Set system-wide default UTF-8 mode for all tty's.
2637 Default is 1, i.e. UTF-8 mode is enabled for all
2638 newly opened terminals.
2639
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002640 vt.global_cursor_default=
2641 [VT]
2642 Format=<-1|0|1>
2643 Set system-wide default for whether a cursor
2644 is shown on new VTs. Default is -1,
2645 i.e. cursors will be created by default unless
2646 overridden by individual drivers. 0 will hide
2647 cursors, 1 will display them.
2648
Randy Dunlap4724ba572010-05-03 11:42:52 -07002649 watchdog timers [HW,WDT] For information on watchdog timers,
2650 see Documentation/watchdog/watchdog-parameters.txt
2651 or other driver-specific files in the
2652 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002653
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002654 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2655 default x2apic cluster mode on platforms
2656 supporting x2apic.
2657
Jacob Panbb24c472009-09-02 07:37:17 -07002658 x86_mrst_timer= [X86-32,APBT]
2659 Choose timer option for x86 Moorestown MID platform.
2660 Two valid options are apbt timer only and lapic timer
2661 plus one apbt timer for broadcast timer.
2662 x86_mrst_timer=apbt_only | lapic_and_apbt
2663
Linus Torvalds1da177e2005-04-16 15:20:36 -07002664 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2665 xd_geo= See header of drivers/block/xd.c.
2666
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002667 xen_emul_unplug= [HW,X86,XEN]
2668 Unplug Xen emulated devices
2669 Format: [unplug0,][unplug1]
2670 ide-disks -- unplug primary master IDE devices
2671 aux-ide-disks -- unplug non-primary-master IDE devices
2672 nics -- unplug network devices
2673 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01002674 unnecessary -- unplugging emulated devices is
2675 unnecessary even if the host did not respond to
2676 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01002677 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002678
Linus Torvalds1da177e2005-04-16 15:20:36 -07002679 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002680 Format:
2681 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002682
Randy Dunlapa9913042005-10-23 12:57:11 -07002683______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002684
2685TODO:
2686
Linus Torvalds1da177e2005-04-16 15:20:36 -07002687 Add more DRM drivers.