blob: d18a9e12152a701bb2729afdb65288ad6da2fccf [file] [log] [blame]
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
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800147Finally, the [KMG] suffix is commonly described after a number of kernel
148parameter values. These 'K', 'M', and 'G' letters represent the _binary_
149multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
150bytes respectively. Such letter suffixes can also be entirely omitted.
151
jens m. noedler9c4751f2006-09-29 02:00:27 -0700152
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530153 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800154 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500155 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 force -- enable ACPI if default was off
157 off -- disable ACPI if default was on
158 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700159 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800161 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800162 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163
Randy Dunlap53471122008-03-12 18:10:51 -0400164 See also Documentation/power/pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165
Len Browna1fdcc02007-03-11 03:26:14 -0400166 acpi_apic_instance= [ACPI, IOAPIC]
167 Format: <int>
168 2: use 2nd APIC table, if available
169 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400170 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400171
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200172 acpi_backlight= [HW,ACPI]
173 acpi_backlight=vendor
174 acpi_backlight=video
175 If set to vendor, prefer vendor specific driver
176 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
177 of the ACPI video.ko driver.
178
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700179 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
180 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700182 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
183 debug output. Bits in debug_layer correspond to a
184 _COMPONENT in an ACPI source file, e.g.,
185 #define _COMPONENT ACPI_PCI_COMPONENT
186 Bits in debug_level correspond to a level in
187 ACPI_DEBUG_PRINT statements, e.g.,
188 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600189 The debug_level mask defaults to "info". See
190 Documentation/acpi/debug.txt for more information about
191 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600193 Enable processor driver info messages:
194 acpi.debug_layer=0x20000000
195 Enable PCI/PCI interrupt routing info messages:
196 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700197 Enable AML "Debug" output, i.e., stores to the Debug
198 object while interpreting AML:
199 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700200 Enable all messages related to ACPI hardware:
201 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200202
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700203 Some values produce so much output that the system is
204 unusable. The "log_buf_len" parameter may be useful
205 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800206
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
209 default in APIC mode
210
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
213 default in PIC mode
214
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
217
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219 use by PCI
220 Format: <irq>,<irq>...
221
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
226
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
231
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530232 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
236
Randy Dunlap4af94f32009-04-17 18:30:28 -0700237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
239
240 acpi_serialize [HW,ACPI] force serialization of AML methods
241
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
245
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800248 old_ordering, s4_nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700249 See Documentation/power/video.txt for information on
250 s3_bios and s3_mode.
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200259 nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700264
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
268
Luca Tettamanti7e905602009-03-30 00:01:27 +0200269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
284
Randy Dunlap4af94f32009-04-17 18:30:28 -0700285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
287
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700288 agp= [AGP]
289 { off | try_unsupported }
290 off: disable AGP support
291 try_unsupported: try to drive unsupported chipsets
292 (may crash computer or cause data corruption)
293
Randy Dunlapbcfde332010-06-07 17:10:38 -0700294 ALSA [HW,ALSA]
295 See Documentation/sound/alsa/alsa-parameters.txt
296
Russell Kingd944d542010-02-20 16:13:29 +0000297 alignment= [KNL,ARM]
298 Allow the default userspace alignment fault handler
299 behaviour to be specified. Bit 0 enables warnings,
300 bit 1 enables fixups, and bit 2 sends a segfault.
301
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
304 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
308 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200309 off - do not initialize any AMD IOMMU found in
310 the system
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900311
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312 amijoy.map= [HW,JOY] Amiga joystick support
313 Map of devices attached to JOY0DAT and JOY1DAT
314 Format: <a>,<b>
315 See also Documentation/kernel/input/joystick.txt
316
317 analog.map= [HW,JOY] Analog joystick and gamepad support
318 Specifies type or capabilities of an analog joystick
319 connected to one of 16 gameports
320 Format: <type1>,<type2>,..<type16>
321
Randy Dunlapa9913042005-10-23 12:57:11 -0700322 apc= [HW,SPARC]
323 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700324 Format: noidle
325 Disable APC CPU standby support. SPARCstation-Fox does
326 not play well with APC CPU idle - disable it if you have
327 APC and your system crashes randomly.
328
Randy Dunlapca1eda22009-05-06 16:02:58 -0700329 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700330 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700331 Format: { quiet (default) | verbose | debug }
332 Change the amount of debugging information output
333 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700334
Brian Haleyb0f83b22010-02-04 13:36:50 -0800335 autoconf= [IPV6]
336 See Documentation/networking/ipv6.txt.
337
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400338 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
339 Limit apic dumping. The parameter defines the maximal
340 number of local apics being dumped. Also it is possible
341 to set it to "all" by meaning -- no limit here.
342 Format: { 1 (default) | 2 | ... | all }.
343 The parameter valid if only apic=debug or
344 apic=verbose is specified.
345 Example: apic=debug show_lapic=all
346
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700348 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349
Linus Torvalds1da177e2005-04-16 15:20:36 -0700350 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
351 Format: <io>,<irq>,<nodeID>
352
353 ataflop= [HW,M68k]
354
355 atarimouse= [HW,MOUSE] Atari Mouse
356
Linus Torvalds1da177e2005-04-16 15:20:36 -0700357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358 EzKey and similar keyboards
359
360 atkbd.reset= [HW] Reset keyboard during initialization
361
Randy Dunlapa9913042005-10-23 12:57:11 -0700362 atkbd.set= [HW] Select keyboard code set
363 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364
365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
366 keyboards
367
368 atkbd.softraw= [HW] Choose between synthetic and real raw mode
369 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700370
371 atkbd.softrepeat= [HW]
372 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700373
374 autotest [IA64]
375
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 baycom_epp= [HW,AX25]
377 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700378
Linus Torvalds1da177e2005-04-16 15:20:36 -0700379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
380 Format: <io>,<mode>
381 See header of drivers/net/hamradio/baycom_par.c.
382
Randy Dunlapa9913042005-10-23 12:57:11 -0700383 baycom_ser_fdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700385 Format: <io>,<irq>,<mode>[,<baud>]
386 See header of drivers/net/hamradio/baycom_ser_fdx.c.
387
Randy Dunlapa9913042005-10-23 12:57:11 -0700388 baycom_ser_hdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390 Format: <io>,<irq>,<mode>
391 See header of drivers/net/hamradio/baycom_ser_hdx.c.
392
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700393 boot_delay= Milliseconds to delay each printk during boot.
394 Values larger than 10 seconds (10000) are changed to
395 no delay (0).
396 Format: integer
397
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700398 bootmem_debug [KNL] Enable bootmem allocator debug messages.
399
Linus Torvalds1da177e2005-04-16 15:20:36 -0700400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700401 bttv.radio= Most important insmod options are available as
402 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
405
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000406 bulk_remove=off [PPC] This parameter disables the use of the pSeries
407 firmware feature for flushing multiple hpte entries
408 at a time.
409
Linus Torvalds1da177e2005-04-16 15:20:36 -0700410 c101= [NET] Moxa C101 synchronous serial card
411
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700412 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413 Sometimes CPU hardware bugs make them report the cache
414 size incorrectly. The kernel will attempt work arounds
415 to fix known problems, but for some CPUs it is not
416 possible to determine what the correct size should be.
417 This option provides an override for these situations.
418
James Morris20510f22007-10-16 23:31:32 -0700419 capability.disable=
420 [SECURITY] Disable capabilities. This would normally
421 be used only if an alternative security model is to be
422 configured. Potentially dangerous and should only be
423 used if you are entirely sure of the consequences.
424
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100425 ccw_timeout_log [S390]
426 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700427
Paul Menage8bab8dd2008-04-04 14:29:57 -0700428 cgroup_disable= [KNL] Disable a particular controller
429 Format: {name of the controller(s) to disable}
430 {Currently supported controllers - "memory"}
431
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432 checkreqprot [SELINUX] Set initial checkreqprot flag value.
433 Format: { "0" | "1" }
434 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700435 0 -- check protection applied by kernel (includes
436 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700437 1 -- check protection requested by application.
438 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700439 Value can be changed at runtime via
440 /selinux/checkreqprot.
441
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100442 cio_ignore= [S390]
443 See Documentation/s390/CommonIO for details.
444
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700445 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700446 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200447 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700448 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200449 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450 Format: { pit | tsc | cyclone | pmtmr }
451
John Stultz592913e2010-07-13 17:56:20 -0700452 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700453 Format: <string>
454 Override the default clocksource and use the clocksource
455 with the name specified.
456 Some clocksource names to choose from, depending on
457 the platform:
458 [all] jiffies (this is the base, fallback clocksource)
459 [ACPI] acpi_pm
460 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
461 pxa_timer,timer3,32k_counter,timer0_1
462 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700463 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700464 scx200_hrt on Geode; cyclone on IBM x440
465 [MIPS] MIPS
466 [PARISC] cr16
467 [S390] tod
468 [SH] SuperH
469 [SPARC64] tick
470 [X86-64] hpet,tsc
471
Andi Kleenac72e782008-01-30 13:33:21 +0100472 clearcpuid=BITNUM [X86]
473 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800474 arch/x86/include/asm/cpufeature.h for the valid bit
475 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100476 stable over kernel options, but the vendor specific
477 ones should be.
478 Also note that user programs calling CPUID directly
479 or using the feature without checking anything
480 will still see it. This just prevents it from
481 being used by the kernel or shown in /proc/cpuinfo.
482 Also note the kernel might malfunction if you disable
483 some critical bits.
484
Robert Jennings14f966e2009-04-15 05:55:32 +0000485 cmo_free_hint= [PPC] Format: { yes | no }
486 Specify whether pages are marked as being inactive
487 when they are freed. This is used in CMO environments
488 to determine OS memory pressure for page stealing by
489 a hypervisor.
490 Default: yes
491
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530492 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100493 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100494 Range: 0 - 8192
495 Default: 64
496
Linus Torvalds1da177e2005-04-16 15:20:36 -0700497 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700498 Format:
499 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500
501 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
502 Format: <io>[,<irq>]
503
Randy Dunlapa9913042005-10-23 12:57:11 -0700504 com90xx= [HW,NET]
505 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506 Format: <io>[,<irq>[,<memstart>]]
507
508 condev= [HW,S390] console device
509 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700510
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511 console= [KNL] Output console device and options.
512
513 tty<n> Use the virtual console device <n>.
514
515 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800516 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700517 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800518 the form "bbbbpnf", where "bbbb" is the baud rate,
519 "p" is parity ("n", "o", or "e"), "n" is number of
520 bits, and "f" is flow control ("r" for RTS or
521 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800523 See Documentation/serial-console.txt for more
524 information. See
525 Documentation/networking/netconsole.txt for an
526 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700527
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700528 uart[8250],io,<addr>[,options]
529 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530 Start an early, polled-mode console on the 8250/16550
531 UART at the specified I/O port or MMIO address,
532 switching to the matching ttyS device later. The
533 options are the same as for ttyS, above.
534
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700535 If the device connected to the port is not a TTY but a braille
536 device, prepend "brl," before the device type, for instance
537 console=brl,ttyS0
538 For now, only VisioBraille is supported.
539
Daniel Mackf324edc2009-06-16 15:33:52 -0700540 consoleblank= [KNL] The console blank (screen saver) timeout in
541 seconds. Defaults to 10*60 = 10mins. A value of 0
542 disables the blank timer.
543
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800544 coredump_filter=
545 [KNL] Change the default value for
546 /proc/<pid>/coredump_filter.
547 See also Documentation/filesystems/proc.txt.
548
Linus Torvalds1da177e2005-04-16 15:20:36 -0700549 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700550 Format:
551 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700552
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800553 crashkernel=size[KMG][@offset[KMG]]
554 [KNL] Using kexec, Linux can switch to a 'crash kernel'
555 upon panic. This parameter reserves the physical
556 memory region [offset, offset + size] for that kernel
557 image. If '@offset' is omitted, then a suitable offset
558 is selected automatically. Check
559 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700560
Bernhard Wallefb391592007-10-18 23:41:02 -0700561 crashkernel=range1:size1[,range2:size2,...][@offset]
562 [KNL] Same as above, but depends on the memory
563 in the running system. The syntax of range is
564 start-[end] where start and end are both
565 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800566 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700567
Linus Torvalds1da177e2005-04-16 15:20:36 -0700568 cs89x0_dma= [HW,NET]
569 Format: <dma>
570
571 cs89x0_media= [HW,NET]
572 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700573
Randy Dunlapa9913042005-10-23 12:57:11 -0700574 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700575 See header of drivers/s390/block/dasd_devmap.c.
576
577 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
578 (one device per port)
579 Format: <port#>,<type>
580 See also Documentation/input/joystick-parport.txt
581
Thomas Renningera648ec02010-08-06 16:11:02 +0200582 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
583 time. See Documentation/dynamic-debug-howto.txt for
584 details.
585
Linus Torvalds1da177e2005-04-16 15:20:36 -0700586 debug [KNL] Enable kernel debugging (events log level).
587
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700588 debug_locks_verbose=
589 [KNL] verbose self-tests
590 Format=<0|1>
591 Print debugging info while doing the locking API
592 self-tests.
593 We default to 0 (no extra messages), setting it to
594 1 will print _a lot_ more information - normally
595 only useful to kernel developers.
596
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700597 debug_objects [KNL] Enable object debugging
598
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500599 no_debug_objects
600 [KNL] Disable object debugging
601
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200602 debugpat [X86] Enable PAT debugging
603
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200604 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700605 Format: <area>[,<node>]
606 See also Documentation/networking/decnet.txt.
607
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700608 default_hugepagesz=
609 [same as hugepagesz=] The size of the default
610 HugeTLB page size. This is the size represented by
611 the legacy /proc/ hugepages APIs, used for SHM, and
612 default size when mounting hugetlbfs filesystems.
613 Defaults to the default architecture's huge page size
614 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700615
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616 dhash_entries= [KNL]
617 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700618
Linus Torvalds1da177e2005-04-16 15:20:36 -0700619 digi= [HW,SERIAL]
620 IO parameters + enable/disable command.
621
622 digiepca= [HW,SERIAL]
623 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000624 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625
Brian Haleyb0f83b22010-02-04 13:36:50 -0800626 disable= [IPV6]
627 See Documentation/networking/ipv6.txt.
628
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000629 disable_ddw [PPC/PSERIES]
630 Disable Dynamic DMA Window support. Use this if
631 to workaround buggy firmware.
632
Brian Haleyb0f83b22010-02-04 13:36:50 -0800633 disable_ipv6= [IPV6]
634 See Documentation/networking/ipv6.txt.
635
Yinghai Lu95ffa242008-04-29 03:52:33 -0700636 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700637 The kernel tries to adjust MTRR layout from continuous
638 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700639 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700640
Yinghai Lu093af8d2008-01-30 13:33:32 +0100641 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100642 By default the kernel will trim any uncacheable
643 memory out of your available memory pool based on
644 MTRR settings. This parameter disables that behavior,
645 possibly causing your machine to run very slowly.
646
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530647 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700648 Disable PIN 1 of APIC timer
649 Can be useful to work around chipset bugs.
650
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700651 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
652 this option disables the debugging code at boot.
653
654 dma_debug_entries=<number>
655 This option allows to tune the number of preallocated
656 entries for DMA-API debugging code. One entry is
657 required per DMA-API allocation. Use this if the
658 DMA-API debugging code disables itself because the
659 architectural default is too low.
660
Joerg Roedel1745de52009-05-22 21:49:51 +0200661 dma_debug_driver=<driver_name>
662 With this option the DMA-API debugging driver
663 filter feature can be enabled at boot time. Just
664 pass the driver to filter for as the parameter.
665 The filter can be disabled or changed to another
666 driver later using sysfs.
667
Linus Torvalds1da177e2005-04-16 15:20:36 -0700668 dscc4.setup= [NET]
669
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700670 earlycon= [KNL] Output early console device and options.
671 uart[8250],io,<addr>[,options]
672 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700673 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700674 Start an early, polled-mode console on the 8250/16550
675 UART at the specified I/O port or MMIO address.
Samium Gromoff1917ac72010-07-20 15:26:51 -0700676 MMIO inter-register address stride is either 8bit (mmio)
677 or 32bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700678 The options are the same as for ttyS, above.
679
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530680 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700681 earlyprintk=vga
682 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500683 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500684 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700685
Randy Dunlapa9913042005-10-23 12:57:11 -0700686 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 takes over.
688
Yinghai Lu5c059172008-07-24 17:29:40 -0700689 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700690
691 Currently only ttyS0 and ttyS1 are supported.
692
693 Interaction with the standard serial driver is not
694 very good.
695
696 The VGA output is eventually overwritten by the real
697 console.
698
Jason Wessel97311912010-05-20 21:04:30 -0500699 ekgdboc= [X86,KGDB] Allow early kernel console debugging
700 ekgdboc=kbd
701
702 This is desgined to be used in conjunction with
703 the boot argument: earlyprintk=vga
704
Linus Torvalds1da177e2005-04-16 15:20:36 -0700705 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700706 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700707
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708 eisa_irq_edge= [PARISC,HW]
709 See header of drivers/parisc/eisa.c.
710
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700711 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700713 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714
715 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +0100716 Format: {"cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700717 See Documentation/block/as-iosched.txt and
718 Documentation/block/deadline-iosched.txt for details.
719
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530720 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700721 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800722 image elf header. Generally kexec loader will
723 pass this option to capture kernel.
724 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700726 enable_mtrr_cleanup [X86]
727 The kernel tries to adjust MTRR layout from continuous
728 to discrete, to make X server driver able to add WB
729 entry later. This parameter enables that.
730
Randy Dunlapca1eda22009-05-06 16:02:58 -0700731 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700732 Enable PIN 1 of APIC timer
733 Can be useful to work around chipset bugs
734 (in particular on some ATI chipsets).
735 The kernel tries to set a reasonable default.
736
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737 enforcing [SELINUX] Set initial enforcing status.
738 Format: {"0" | "1"}
739 See security/selinux/Kconfig help text.
740 0 -- permissive (log only, no denials).
741 1 -- enforcing (deny and log).
742 Default value is 0.
743 Value can be changed at runtime via /selinux/enforce.
744
Huang Yinga08f82d2010-05-18 14:35:21 +0800745 erst_disable [ACPI]
746 Disable Error Record Serialization Table (ERST)
747 support.
748
Linus Torvalds1da177e2005-04-16 15:20:36 -0700749 ether= [HW,NET] Ethernet cards parameters
750 This option is obsoleted by the "netdev=" option, which
751 has equivalent usage. See its documentation for details.
752
Akinobu Mitade1ba092006-12-08 02:39:42 -0800753 failslab=
754 fail_page_alloc=
755 fail_make_request=[KNL]
756 General fault injection mechanism.
757 Format: <interval>,<probability>,<space>,<times>
758 See also /Documentation/fault-injection/.
759
Linus Torvalds1da177e2005-04-16 15:20:36 -0700760 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000761 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700762
Alex Chiangf13ae302008-05-08 14:03:23 -0600763 force_pal_cache_flush
764 [IA-64] Avoid check_sal_cache_flush which may hang on
765 buggy SAL_CACHE_FLUSH implementations. Using this
766 parameter will force ia64_sal_cache_flush to call
767 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
768
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100769 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400770 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100771 as early as possible in order to facilitate early
772 boot debugging.
773
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200774 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400775 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200776 If no parameter is passed, ftrace will dump
777 buffers of all CPUs, but if you pass orig_cpu, it will
778 dump only the buffer of the CPU that triggered the
779 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400780
781 ftrace_filter=[function-list]
782 [FTRACE] Limit the functions traced by the function
783 tracer at boot up. function-list is a comma separated
784 list of functions. This list can be changed at run
785 time by the set_ftrace_filter file in the debugfs
786 tracing directory.
787
788 ftrace_notrace=[function-list]
789 [FTRACE] Do not trace the functions specified in
790 function-list. This list can be changed at run time
791 by the set_ftrace_notrace file in the debugfs
792 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100793
Stefan Assmann369bc182009-10-12 22:17:21 +0200794 ftrace_graph_filter=[function-list]
795 [FTRACE] Limit the top level callers functions traced
796 by the function graph tracer at boot up.
797 function-list is a comma separated list of functions
798 that can be changed at run time by the
799 set_graph_function file in the debugfs tracing directory.
800
Linus Torvalds1da177e2005-04-16 15:20:36 -0700801 gamecon.map[2|3]=
802 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
803 support via parallel port (up to 5 devices per port)
804 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
805 See also Documentation/input/joystick-parport.txt
806
807 gamma= [HW,DRM]
808
Yinghai Luaaf23042008-01-30 13:33:09 +0100809 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
810 Format: off | on
811 default: on
812
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700813 gcov_persist= [GCOV] When non-zero (default), profiling data for
814 kernel modules is saved and remains accessible via
815 debugfs, even when the module is unloaded/reloaded.
816 When zero, profiling data is discarded and associated
817 debugfs files are removed at module unload time.
818
Linus Torvalds1da177e2005-04-16 15:20:36 -0700819 gpt [EFI] Forces disk with valid GPT signature but
820 invalid Protective MBR to be treated as GPT.
821
Linus Torvalds1da177e2005-04-16 15:20:36 -0700822 hashdist= [KNL,NUMA] Large hashes allocated during boot
823 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700824 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700825 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700826
827 hcl= [IA-64] SGI's Hardware Graph compatibility layer
828
829 hd= [EIDE] (E)IDE hard drive subsystem geometry
830 Format: <cyl>,<head>,<sect>
831
Huang Yingea8c0712010-05-18 14:35:15 +0800832 hest_disable [ACPI]
833 Disable Hardware Error Source Table (HEST) support;
834 corresponding firmware-first mode error processing
835 logic will be disabled.
836
Linus Torvalds1da177e2005-04-16 15:20:36 -0700837 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
838 size of <nn>. This works even on boxes that have no
839 highmem otherwise. This also works to reduce highmem
840 size on bigger boxes.
841
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800842 highres= [KNL] Enable/disable high resolution timer mode.
843 Valid parameters: "on", "off"
844 Default: "on"
845
Linus Torvalds1da177e2005-04-16 15:20:36 -0700846 hisax= [HW,ISDN]
847 See Documentation/isdn/README.HiSax.
848
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700849 hlt [BUGS=ARM,SH]
850
851 hpet= [X86-32,HPET] option to control HPET usage
852 Format: { enable (default) | disable | force |
853 verbose }
854 disable: disable HPET and use PIT instead
855 force: allow force enabled of undocumented chips (ICH4,
856 VIA, nVidia)
857 verbose: show contents of HPET registers during setup
858
Andi Kleenb4718e62008-07-23 21:27:51 -0700859 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
860 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700861 On x86-64 and powerpc, this option can be specified
862 multiple times interleaved with hugepages= to reserve
863 huge pages of different sizes. Valid pages sizes on
864 x86-64 are 2M (when the CPU supports "pse") and 1G
865 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700866 Note that 1GB pages can only be allocated at boot time
867 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900868
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100869 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
870 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100871 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
872 If specified, z/VM IUCV HVC accepts connections
873 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100874
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700875 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700876 or register an additional I2C bus that is not
877 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700878 Format:
879 <bus_id>,<clkrate>
880
Jiri Kosina36d95732008-10-06 02:51:09 -0400881 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700882 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200883 i8042.dumbkbd [HW] Pretend that controller can only read data from
884 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700885 (Don't attempt to blink the leds)
886 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500887 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400888 i8042.noloop [HW] Disable the AUX Loopback command while probing
889 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 i8042.nomux [HW] Don't check presence of an active multiplexing
891 controller
892 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
893 controllers
Jiri Kosinaf8313ef2011-01-08 01:37:26 -0800894 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
Linus Torvalds1da177e2005-04-16 15:20:36 -0700895 i8042.reset [HW] Reset the controller during init and cleanup
896 i8042.unlock [HW] Unlock (ignore) the keylock
897
898 i810= [HW,DRM]
899
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700900 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
901 indicates that the driver is running on unsupported
902 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700903 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
904 does not match list of supported models.
905 i8k.power_status
906 [HW] Report power status in /proc/i8k
907 (disabled by default)
908 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
909 capability is set.
910
Linus Torvalds1da177e2005-04-16 15:20:36 -0700911 icn= [HW,ISDN]
912 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
913
David Fries0af80c02009-02-25 20:28:21 +0100914 ide-core.nodma= [HW] (E)IDE subsystem
915 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200916 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
917 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100918 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700919
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700920 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
921 Claim all unknown PCI IDE storage controllers.
922
Andi Kleenf039b752007-05-02 19:27:12 +0200923 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800924 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
925 Poll forces a polling idle loop that can slightly
926 improve the performance of waking up a idle CPU, but
927 will use a lot of power and make the system run hot.
928 Not recommended.
929 idle=mwait: On systems which support MONITOR/MWAIT but
930 the kernel chose to not use it because it doesn't save
931 as much power as a normal idle loop, use the
932 MONITOR/MWAIT idle loop anyways. Performance should be
933 the same as idle=poll.
934 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800935 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800936 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700937
Ingo Molnar792908222006-12-06 20:40:51 -0800938 ignore_loglevel [KNL]
939 Ignore loglevel setting - this will print /all/
940 kernel messages to the console. Useful for debugging.
941
Linus Torvalds1da177e2005-04-16 15:20:36 -0700942 ihash_entries= [KNL]
943 Set number of hash buckets for inode cache.
944
Mimi Zohar3323eec92009-02-04 09:06:58 -0500945 ima_audit= [IMA]
946 Format: { "0" | "1" }
947 0 -- integrity auditing messages. (Default)
948 1 -- enable informational integrity auditing messages.
949
950 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700951 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -0500952 default: "sha1"
953
Eric Paris5789ba32009-05-21 15:47:06 -0400954 ima_tcb [IMA]
955 Load a policy which meets the needs of the Trusted
956 Computing Base. This means IMA will measure all
957 programs exec'd, files mmap'd for exec, and all files
958 opened for read by uid=0.
959
Linus Torvalds1da177e2005-04-16 15:20:36 -0700960 init= [KNL]
961 Format: <full_path>
962 Run specified binary instead of /sbin/init as init
963 process.
964
965 initcall_debug [KNL] Trace initcalls as they are executed. Useful
966 for working out where the kernel is dying during
967 startup.
968
969 initrd= [BOOT] Specify the location of the initial ramdisk
970
971 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
972 Format: <irq>
973
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700974 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800975 on
976 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700977 off
978 Disable intel iommu driver.
979 igfx_off [Default Off]
980 By default, gfx is mapped as normal device. If a gfx
981 device has a dedicated DMAR unit, the DMAR unit is
982 bypassed by not enabling DMAR with this option. In
983 this case, gfx device will use physical address for
984 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700985 forcedac [x86_64]
986 With this option iommu will not optimize to look
987 for io virtual address below 32 bit forcing dual
988 address cycle on pci bus for cards supporting greater
989 than 32 bit addressing. The default is to look
990 for translation below 32 bit and if not available
991 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -0800992 strict [Default Off]
993 With this option on every unmap_single operation will
994 result in a hardware IOTLB flush operation as opposed
995 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700996
Chris Wrightd1423d52010-07-20 11:06:49 -0700997 intremap= [X86-64, Intel-IOMMU]
998 Format: { on (default) | off | nosid }
999 on enable Interrupt Remapping (default)
1000 off disable Interrupt Remapping
1001 nosid disable Source ID checking
1002
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001003 inttest= [IA64]
1004
1005 iomem= Disable strict checking of access to MMIO memory
1006 strict regions from userspace.
1007 relaxed
1008
1009 iommu= [x86]
1010 off
1011 force
1012 noforce
1013 biomerge
1014 panic
1015 nopanic
1016 merge
1017 nomerge
1018 forcesac
1019 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001020 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001021
1022 io7= [HW] IO7 for Marvel based alpha systems
1023 See comment before marvel_specify_io7 in
1024 arch/alpha/kernel/core_marvel.c.
1025
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301026 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001027 0x80
1028 Standard port 0x80 based delay
1029 0xed
1030 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001031 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001032 Simple two microseconds delay
1033 none
1034 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001035
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001037 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038
1039 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001040 See comment before ip2_setup() in
1041 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001042
Alan Cox200803d2005-06-28 20:45:18 -07001043 irqfixup [HW]
1044 When an interrupt is not handled search all handlers
1045 for it. Intended to get systems with badly broken
1046 firmware running.
1047
1048 irqpoll [HW]
1049 When an interrupt is not handled search all handlers
1050 for it. Also check all handlers each timer
1051 interrupt. Intended to get systems with badly broken
1052 firmware running.
1053
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001055 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001056
1057 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001058 Format:
1059 <cpu number>,...,<cpu number>
1060 or
Li Zefanb225d442008-11-06 12:53:39 -08001061 <cpu number>-<cpu number>
1062 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001063 or a mixture
1064 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001065
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066 This option can be used to specify one or more CPUs
1067 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001068 algorithms. You can move a process onto or off an
1069 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001070 <cpu number> begins at 0 and the maximum value is
1071 "number of CPUs in system - 1".
1072
1073 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001074 alternative -- manually setting the CPU mask of all
1075 tasks in the system -- can cause problems and
1076 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077
Randy Dunlapa9913042005-10-23 12:57:11 -07001078 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079
1080 js= [HW,JOY] Analog joystick
1081 See Documentation/input/joystick.txt.
1082
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001083 keepinitrd [HW,ARM]
1084
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301085 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001086 specifies the amount of memory usable by the kernel
1087 for non-movable allocations. The requested amount is
1088 spread evenly throughout all nodes in the system. The
1089 remaining memory in each node is used for Movable
1090 pages. In the event, a node is too small to have both
1091 kernelcore and Movable pages, kernelcore pages will
1092 take priority and other nodes will have a larger number
1093 of kernelcore pages. The Movable zone is used for the
1094 allocation of pages that may be reclaimed or moved
1095 by the page migration subsystem. This means that
1096 HugeTLB pages may not be allocated from this zone.
1097 Note that allocations like PTEs-from-HighMem still
1098 use the HighMem zone if it exists, and the Normal
1099 zone if it does not.
1100
Jason Wessel4fe1da42010-05-20 21:04:31 -05001101 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1102 Format: <Controller#>[,poll interval]
1103 The controller # is the number of the ehci usb debug
1104 port as it is probed via PCI. The poll interval is
1105 optional and is the number seconds in between
1106 each poll cycle to the debug port in case you need
1107 the functionality for interrupting the kernel with
1108 gdb or control-c on the dbgp connection. When
1109 not using this parameter you use sysrq-g to break into
1110 the kernel debugger.
1111
Jason Wessel84c08fd2010-05-20 21:04:24 -05001112 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001113 Requires a tty driver that supports console polling,
1114 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001115 Serial only format: <serial_device>[,baud]
1116 keyboard only format: kbd
1117 keyboard and serial format: kbd,<serial_device>[,baud]
1118 Optional Kernel mode setting:
1119 kms, kbd format: kms,kbd
1120 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001121
Jason Wessel84c08fd2010-05-20 21:04:24 -05001122 kgdbwait [KGDB] Stop kernel execution and enter the
1123 kernel debugger at the earliest opportunity.
1124
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001125 kmac= [MIPS] korina ethernet MAC address.
1126 Configure the RouterBoard 532 series on-chip
1127 Ethernet adapter MAC address.
1128
Catalin Marinas04f70332009-06-11 13:22:39 +01001129 kmemleak= [KNL] Boot-time kmemleak enable/disable
1130 Valid arguments: on, off
1131 Default: on
1132
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301133 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001134 in oops dumps.
1135
Andre Przywarafef07aa2009-07-10 14:20:35 +02001136 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1137 Default is 0 (don't ignore, but inject #GP)
1138
1139 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1140 Default is 1 (enabled)
1141
Xiao Guangronga182d872010-09-20 22:17:48 +08001142 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1143 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001144 Default is 0 (off)
1145
Andre Przywarafef07aa2009-07-10 14:20:35 +02001146 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001147 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001148
1149 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1150 for all guests.
1151 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1152
1153 kvm-intel.bypass_guest_pf=
1154 [KVM,Intel] Disables bypassing of guest page faults
1155 on Intel chips. Default is 1 (enabled)
1156
1157 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1158 (virtualized MMU) support on capable Intel chips.
1159 Default is 1 (enabled)
1160
1161 kvm-intel.emulate_invalid_guest_state=
1162 [KVM,Intel] Enable emulation of invalid guest states
1163 Default is 0 (disabled)
1164
1165 kvm-intel.flexpriority=
1166 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1167 Default is 1 (enabled)
1168
1169 kvm-intel.unrestricted_guest=
1170 [KVM,Intel] Disable unrestricted guest feature
1171 (virtualized real and unpaged mode) on capable
1172 Intel chips. Default is 1 (enabled)
1173
1174 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1175 feature (tagged TLBs) on capable Intel chips.
1176 Default is 1 (enabled)
1177
Linus Torvalds1da177e2005-04-16 15:20:36 -07001178 l2cr= [PPC]
1179
Robert Brosea78bfbf2008-03-29 07:20:23 +11001180 l3cr= [PPC]
1181
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001182 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001183 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001184
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301185 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001186 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001187
FD Camifcb71f62008-01-06 19:08:56 +01001188 libata.dma= [LIBATA] DMA control
1189 libata.dma=0 Disable all PATA and SATA DMA
1190 libata.dma=1 PATA and SATA Disk DMA only
1191 libata.dma=2 ATAPI (CDROM) DMA only
1192 libata.dma=4 Compact Flash DMA only
1193 Combinations also work, so libata.dma=3 enables DMA
1194 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001195
1196 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1197 libata.ignore_hpa=0 keep BIOS limits (default)
1198 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001199
Dave Jones78e70c22007-09-27 11:50:13 -04001200 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1201 when set.
1202 Format: <int>
1203
Tejun Heo33267322008-02-13 09:15:09 +09001204 libata.force= [LIBATA] Force configurations. The format is comma
1205 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001206 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001207 matching port, link or device. Basically, it matches
1208 the ATA ID string printed on console by libata. If
1209 the whole ID part is omitted, the last PORT and DEVICE
1210 values are used. If ID hasn't been specified yet, the
1211 configuration applies to all ports, links and devices.
1212
1213 If only DEVICE is omitted, the parameter applies to
1214 the port and all links and devices behind it. DEVICE
1215 number of 0 either selects the first device or the
1216 first fan-out link behind PMP device. It does not
1217 select the host link. DEVICE number of 15 selects the
1218 host link and device attached to it.
1219
1220 The VAL specifies the configuration to force. As long
1221 as there's no ambiguity shortcut notation is allowed.
1222 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1223 The following configurations can be forced.
1224
1225 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1226 Any ID with matching PORT is used.
1227
1228 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1229
1230 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1231 udma[/][16,25,33,44,66,100,133] notation is also
1232 allowed.
1233
1234 * [no]ncq: Turn on or off NCQ.
1235
Tejun Heo05944bd2008-08-13 20:19:09 +09001236 * nohrst, nosrst, norst: suppress hard, soft
1237 and both resets.
1238
Tejun Heo43c9c592010-05-23 12:59:11 +02001239 * dump_id: dump IDENTIFY data.
1240
Tejun Heo33267322008-02-13 09:15:09 +09001241 If there are multiple matching configurations changing
1242 the same attribute, the last one is used.
1243
Yinghai Lu95f72d12010-07-12 14:36:09 +10001244 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001245
Linus Torvalds1da177e2005-04-16 15:20:36 -07001246 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001247 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001248
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001249 lockd.nlm_grace_period=P [NFS] Assign grace period.
1250 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001251
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001252 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1253 Format: <integer>
1254
1255 lockd.nlm_timeout=T [NFS] Assign timeout value.
1256 Format: <integer>
1257
1258 lockd.nlm_udpport=M [NFS] Assign UDP port.
1259 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001260
1261 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1262 Format: <irq>
1263
1264 loglevel= All Kernel Messages with a loglevel smaller than the
1265 console loglevel will be printed to the console. It can
1266 also be changed with klogd or other programs. The
1267 loglevels are defined as follows:
1268
1269 0 (KERN_EMERG) system is unusable
1270 1 (KERN_ALERT) action must be taken immediately
1271 2 (KERN_CRIT) critical conditions
1272 3 (KERN_ERR) error conditions
1273 4 (KERN_WARNING) warning conditions
1274 5 (KERN_NOTICE) normal but significant condition
1275 6 (KERN_INFO) informational
1276 7 (KERN_DEBUG) debug-level messages
1277
Randy Dunlapc756d082011-02-20 20:08:35 -08001278 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1279 in bytes. n must be a power of two. The default
1280 size is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001281
Randy Dunlapaccaa242007-10-16 01:29:37 -07001282 logo.nologo [FB] Disables display of the built-in Linux logo.
1283 This may be used to provide more screen space for
1284 kernel log messages and is useful when debugging
1285 kernel boot problems.
1286
Linus Torvalds1da177e2005-04-16 15:20:36 -07001287 lp=0 [LP] Specify parallel ports to use, e.g,
1288 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1289 lp=reset first parallel port). 'lp=0' disables the
1290 lp=auto printer driver. 'lp=reset' (which can be
1291 specified in addition to the ports) causes
1292 attached printers to be reset. Using
1293 lp=port1,port2,... specifies the parallel ports
1294 to associate lp devices with, starting with
1295 lp0. A port specification may be 'none' to skip
1296 that lp device, or a parport name such as
1297 'parport0'. Specifying 'lp=auto' instead of a
1298 port specification list means that device IDs
1299 from each port should be examined, to see if
1300 an IEEE 1284-compliant printer is attached; if
1301 so, the driver will manage that printer.
1302 See also header of drivers/char/lp.c.
1303
1304 lpj=n [KNL]
1305 Sets loops_per_jiffy to given constant, thus avoiding
1306 time-consuming boot-time autodetection (up to 250 ms per
1307 CPU). 0 enables autodetection (default). To determine
1308 the correct value for your kernel, boot with normal
1309 autodetection and see what value is printed. Note that
1310 on SMP systems the preset will be applied to all CPUs,
1311 which is likely to cause problems if your CPUs need
1312 significantly divergent settings. An incorrect value
1313 will cause delays in the kernel to be wrong, leading to
1314 unpredictable I/O errors and other breakage. Although
1315 unlikely, in the extreme case this might damage your
1316 hardware.
1317
1318 ltpc= [NET]
1319 Format: <io>,<irq>,<dma>
1320
Randy Dunlapa9913042005-10-23 12:57:11 -07001321 machvec= [IA64] Force the use of a particular machine-vector
1322 (machvec) in a generic kernel.
1323 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324
Wu Zhangjin3209e702009-07-02 23:27:12 +08001325 machtype= [Loongson] Share the same kernel image file between different
1326 yeeloong laptop.
1327 Example: machtype=lemote-yeeloong-2f-7inch
1328
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001329 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1330 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001331
1332 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001333 should make use of. maxcpus=n : n >= 0 limits the
1334 kernel to using 'n' processors. n=0 is a special case,
1335 it is equivalent to "nosmp", which also disables
1336 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001337
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001338 max_loop= [LOOP] Maximum number of loopback devices that can
1339 be mounted
1340 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001341
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342 mcatest= [IA-64]
1343
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001344 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345
Uwe Hermann71cced62008-10-20 09:32:21 -07001346 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001347
Linus Torvalds1da177e2005-04-16 15:20:36 -07001348 md= [HW] RAID subsystems devices and level
1349 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001350
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351 mdacon= [MDA]
1352 Format: <first>,<last>
1353 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001354
Linus Torvalds1da177e2005-04-16 15:20:36 -07001355 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1356 Amount of memory to be used when the kernel is not able
1357 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001358 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001359 address space collisions. Without memmap= PCI devices
1360 could be placed at addresses belonging to unused RAM.
1361
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001362 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001363 memory.
1364
Paul Mundt6902aa82008-09-21 17:14:42 +09001365 memchunk=nn[KMG]
1366 [KNL,SH] Allow user to override the default size for
1367 per-device physically contiguous DMA buffers.
1368
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301369 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001370 E820 memory map, as specified by the user.
1371 Such memmap=exactmap lines can be constructed based on
1372 BIOS output or other requirements. See the memmap=nn@ss
1373 option description.
1374
1375 memmap=nn[KMG]@ss[KMG]
1376 [KNL] Force usage of a specific region of memory
1377 Region of memory to be used, from ss to ss+nn.
1378
1379 memmap=nn[KMG]#ss[KMG]
1380 [KNL,ACPI] Mark specific memory as ACPI data.
1381 Region of memory to be used, from ss to ss+nn.
1382
1383 memmap=nn[KMG]$ss[KMG]
1384 [KNL,ACPI] Mark specific memory as reserved.
1385 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001386 Example: Exclude memory from 0x18690000-0x1869ffff
1387 memmap=64K$0x18690000
1388 or
1389 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001390
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001391 memory_corruption_check=0/1 [X86]
1392 Some BIOSes seem to corrupt the first 64k of
1393 memory when doing things like suspend/resume.
1394 Setting this option will scan the memory
1395 looking for corruption. Enabling this will
1396 both detect corruption and prevent the kernel
1397 from using the memory being corrupted.
1398 However, its intended as a diagnostic tool; if
1399 repeatable BIOS-originated corruption always
1400 affects the same memory, you can use memmap=
1401 to prevent the kernel from using that memory.
1402
1403 memory_corruption_check_size=size [X86]
1404 By default it checks for corruption in the low
1405 64k, making this memory unavailable for normal
1406 use. Use this parameter to scan for
1407 corruption in more or less memory.
1408
1409 memory_corruption_check_period=seconds [X86]
1410 By default it checks for corruption every 60
1411 seconds. Use this parameter to check at some
1412 other rate. 0 disables periodic checking.
1413
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001414 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001415 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001416 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001417 Specifies the number of memtest passes to be
1418 performed. Each pass selects another test
1419 pattern from a given set of patterns. Memtest
1420 fills the memory with this pattern, validates
1421 memory contents and reserves bad memory
1422 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001423
Linus Torvalds1da177e2005-04-16 15:20:36 -07001424 meye.*= [HW] Set MotionEye Camera parameters
1425 See Documentation/video4linux/meye.txt.
1426
Andres Salomon8f368812007-10-12 23:04:06 +02001427 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1428 Multi-Function General Purpose Timers on AMD Geode
1429 platforms.
1430
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001431 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1432 the BIOS has incorrectly applied a workaround. TinyBIOS
1433 version 0.98 is known to be affected, 0.99 fixes the
1434 problem by letting the user disable the workaround.
1435
Linus Torvalds1da177e2005-04-16 15:20:36 -07001436 mga= [HW,DRM]
1437
Randy Dunlap1c207f92008-11-19 15:36:16 -08001438 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1439 physical address is ignored.
1440
Michel Pollet39f45d72009-05-20 11:10:31 +01001441 mini2440= [ARM,HW,KNL]
1442 Format:[0..2][b][c][t]
1443 Default: "0tb"
1444 MINI2440 configuration specification:
1445 0 - The attached screen is the 3.5" TFT
1446 1 - The attached screen is the 7" TFT
1447 2 - The VGA Shield is attached (1024x768)
1448 Leaving out the screen size parameter will not load
1449 the TFT driver, and the framebuffer will be left
1450 unconfigured.
1451 b - Enable backlight. The TFT backlight pin will be
1452 linked to the kernel VESA blanking code and a GPIO
1453 LED. This parameter is not necessary when using the
1454 VGA shield.
1455 c - Enable the s3c camera interface.
1456 t - Reserved for enabling touchscreen support. The
1457 touchscreen support is not enabled in the mainstream
1458 kernel as of 2.6.30, a preliminary port can be found
1459 in the "bleeding edge" mini2440 support kernel at
1460 http://repo.or.cz/w/linux-2.6/mini2440.git
1461
Mel Gorman6b74ab92008-07-23 21:26:49 -07001462 mminit_loglevel=
1463 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1464 parameter allows control of the logging verbosity for
1465 the additional memory initialisation checks. A value
1466 of 0 disables mminit logging and a level of 4 will
1467 log everything. Information is printed at KERN_DEBUG
1468 so loglevel=8 may also need to be specified.
1469
Linus Torvalds1da177e2005-04-16 15:20:36 -07001470 mousedev.tap_time=
1471 [MOUSE] Maximum time between finger touching and
1472 leaving touchpad surface for touch to be considered
1473 a tap and be reported as a left button click (for
1474 touchpads working in absolute mode only).
1475 Format: <msecs>
1476 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1477 reporting absolute coordinates, such as tablets
1478 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1479 reporting absolute coordinates, such as tablets
1480
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301481 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001482 is similar to kernelcore except it specifies the
1483 amount of memory used for migratable allocations.
1484 If both kernelcore and movablecore is specified,
1485 then kernelcore will be at *least* the specified
1486 value but may be more. If movablecore on its own
1487 is specified, the administrator must be careful
1488 that the amount of memory usable for all allocations
1489 is not too small.
1490
Linus Torvalds1da177e2005-04-16 15:20:36 -07001491 MTD_Partition= [MTD]
1492 Format: <name>,<region-number>,<size>,<offset>
1493
Randy Dunlapa9913042005-10-23 12:57:11 -07001494 MTD_Region= [MTD] Format:
1495 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001496
1497 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001498 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001499
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001500 multitce=off [PPC] This parameter disables the use of the pSeries
1501 firmware feature for updating multiple TCE entries
1502 at a time.
1503
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001504 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1505
1506 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1507
1508 boundary - index of last SLC block on Flex-OneNAND.
1509 The remaining blocks are configured as MLC blocks.
1510 lock - Configure if Flex-OneNAND boundary should be locked.
1511 Once locked, the boundary cannot be changed.
1512 1 indicates lock status, 0 indicates unlock status.
1513
Ben Dooks9db829f2008-07-03 11:24:29 +01001514 mtdset= [ARM]
1515 ARM/S3C2412 JIVE boot control
1516
1517 See arch/arm/mach-s3c2412/mach-jive.c
1518
Linus Torvalds1da177e2005-04-16 15:20:36 -07001519 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001520 [HW] Make the MicroTouch USB driver use raw coordinates
1521 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001522
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001523 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001524 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001525 that could hold holes aka. UC entries.
1526
1527 mtrr_gran_size=nn[KMG] [X86]
1528 Used for mtrr cleanup. It is granularity of mtrr block.
1529 Default is 1.
1530 Large value could prevent small alignment from
1531 using up MTRRs.
1532
1533 mtrr_spare_reg_nr=n [X86]
1534 Format: <integer>
1535 Range: 0,7 : spare reg number
1536 Default : 1
1537 Used for mtrr cleanup. It is spare mtrr entries number.
1538 Set to 2 or more if your graphical card needs more.
1539
Linus Torvalds1da177e2005-04-16 15:20:36 -07001540 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1541
Linus Torvalds1da177e2005-04-16 15:20:36 -07001542 netdev= [NET] Network devices parameters
1543 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1544 Note that mem_start is often overloaded to mean
1545 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001546 This usage is only documented in each driver source
1547 file if at all.
1548
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001549 nf_conntrack.acct=
1550 [NETFILTER] Enable connection tracking flow accounting
1551 0 to disable accounting
1552 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001553 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001554
Chuck Lever306a0752010-09-17 10:54:37 -04001555 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001556 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001557
1558 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001559 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560
Chuck Lever306a0752010-09-17 10:54:37 -04001561 nfsrootdebug [NFS] enable nfsroot debugging messages.
1562 See Documentation/filesystems/nfs/nfsroot.txt.
1563
Trond Myklebusta72b4422006-01-03 09:55:41 +01001564 nfs.callback_tcpport=
1565 [NFS] set the TCP port on which the NFSv4 callback
1566 channel should listen.
1567
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001568 nfs.cache_getent=
1569 [NFS] sets the pathname to the program which is used
1570 to update the NFS client cache entries.
1571
1572 nfs.cache_getent_timeout=
1573 [NFS] sets the timeout after which an attempt to
1574 update a cache entry is deemed to have failed.
1575
Trond Myklebust58df0952006-01-03 09:55:57 +01001576 nfs.idmap_cache_timeout=
1577 [NFS] set the maximum lifetime for idmapper cache
1578 entries.
1579
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001580 nfs.enable_ino64=
1581 [NFS] enable 64-bit inode numbers.
1582 If zero, the NFS client will fake up a 32-bit inode
1583 number for the readdir() and stat() syscalls instead
1584 of returning the full 64-bit number.
1585 The default is to return 64-bit inode numbers.
1586
Trond Myklebustb064eca22011-02-22 15:44:32 -08001587 nfs.nfs4_disable_idmapping=
1588 [NFSv4] When set, this option disables the NFSv4
1589 idmapper on the client, but only if the mount
1590 is using the 'sec=sys' security flavour. This may
1591 make migration from legacy NFSv2/v3 systems easier
1592 provided that the server has the appropriate support.
1593 The default is to always enable NFSv4 idmapping.
1594
Paul Mundt1e1030d2009-09-01 17:38:32 +09001595 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001596 when a NMI is triggered.
1597 Format: [state][,regs][,debounce][,die]
1598
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301599 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001600 Format: [panic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05001601 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001602 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001603 When panic is specified, panic when an NMI watchdog
1604 timeout occurs.
1605 This is useful when you use a panic=... timeout and
1606 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001607
Anton Vorontsovbff38772009-07-08 11:10:56 -07001608 netpoll.carrier_timeout=
1609 [NET] Specifies amount of time (in seconds) that
1610 netpoll should wait for a carrier. By default netpoll
1611 waits 4 seconds.
1612
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001613 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001614 emulation library even if a 387 maths coprocessor
1615 is present.
1616
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001617 no_console_suspend
1618 [HW] Never suspend the console
1619 Disable suspending of consoles during suspend and
1620 hibernate operations. Once disabled, debugging
1621 messages can reach various consoles while the rest
1622 of the system is being put to sleep (ie, while
1623 debugging driver suspend/resume hooks). This may
1624 not work reliably with all consoles, but is known
1625 to work with serial and VGA consoles.
1626
Christoph Lameterc1aee212007-05-31 00:40:47 -07001627 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1628 caches in the slab allocator. Saves per-node memory,
1629 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001630
Randy Dunlapa9913042005-10-23 12:57:11 -07001631 noalign [KNL,ARM]
1632
Linus Torvalds1da177e2005-04-16 15:20:36 -07001633 noapic [SMP,APIC] Tells the kernel to not make use of any
1634 IOAPICs that may be present in the system.
1635
Mike Galbraith5091faa2010-11-30 14:18:03 +01001636 noautogroup Disable scheduler automatic task group creation.
1637
Linus Torvalds1da177e2005-04-16 15:20:36 -07001638 nobats [PPC] Do not use BATs for mapping kernel lowmem
1639 on "Classic" PPC cores.
1640
1641 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001642
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001643 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1644
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001645 nodelayacct [KNL] Disable per-task delay accounting
1646
Linus Torvalds1da177e2005-04-16 15:20:36 -07001647 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1648
Paul Mundt6902aa82008-09-21 17:14:42 +09001649 nodsp [SH] Disable hardware DSP at boot time.
1650
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301651 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001652
Linus Torvalds1da177e2005-04-16 15:20:36 -07001653 noexec [IA-64]
1654
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301655 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001656 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001657 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001658 noexec=off: disable non-executable mappings
1659
1660 noexec32 [X86-64]
1661 This affects only 32-bit executables.
1662 noexec32=on: enable non-executable mappings (default)
1663 read doesn't imply executable mappings
1664 noexec32=off: disable non-executable mappings
1665 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001666
Paul Mundt6902aa82008-09-21 17:14:42 +09001667 nofpu [SH] Disable hardware FPU at boot time.
1668
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001669 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001670 register save and restore. The kernel will only save
1671 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001672
Suresh Siddha0c752a92009-05-22 12:17:45 -07001673 noxsave [BUGS=X86] Disables x86 extended register state save
1674 and restore using xsave. The kernel will fallback to
1675 enabling legacy floating-point and sse state.
1676
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001677 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1678 wfi(ARM) instruction doesn't work correctly and not to
1679 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001680
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001681 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001682 instruction doesn't work correctly and not to
1683 use it.
1684
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001685 no_file_caps Tells the kernel not to honor file capabilities. The
1686 only way then for a file to be executed with privilege
1687 is to be setuid root or executed by root.
1688
Linus Torvalds1da177e2005-04-16 15:20:36 -07001689 nohalt [IA-64] Tells the kernel not to use the power saving
1690 function PAL_HALT_LIGHT when idle. This increases
1691 power-consumption. On the positive side, it reduces
1692 interrupt wake-up latency, which may improve performance
1693 in certain environments such as networked servers or
1694 real-time systems.
1695
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001696 nohz= [KNL] Boottime enable/disable dynamic ticks
1697 Valid arguments: on, off
1698 Default: on
1699
Paul Mundteeee7852009-04-02 12:31:16 +09001700 noiotrap [SH] Disables trapped I/O port accesses.
1701
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001702 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001703 disable unhandled interrupt sources.
1704
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301705 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001706 broken timer IRQ sources.
1707
Linus Torvalds1da177e2005-04-16 15:20:36 -07001708 noisapnp [ISAPNP] Disables ISA PnP code.
1709
1710 noinitrd [RAM] Tells the kernel not to load any configured
1711 initial RAM disk.
1712
Weidong Han03ea8152009-04-17 16:42:15 +08001713 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1714 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07001715 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08001716
Linus Torvalds1da177e2005-04-16 15:20:36 -07001717 nointroute [IA-64]
1718
Tony Luck0aa366f2007-07-20 11:22:30 -07001719 nojitter [IA64] Disables jitter checking for ITC timers.
1720
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02001721 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1722
Gleb Natapovfd10cde2010-10-14 11:22:51 +02001723 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1724 fault handling.
1725
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001726 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001727
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001728 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001729
Linus Torvalds1da177e2005-04-16 15:20:36 -07001730 noltlbs [PPC] Do not use large page/tlb entries for kernel
1731 lowmem mapping on PPC40x.
1732
Horms312f1f02006-02-22 09:57:55 +09001733 nomca [IA-64] Disable machine check abort handling
1734
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001735 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001736
Andres Salomon83d73842007-10-12 23:04:06 +02001737 nomfgpt [X86-32] Disable Multi-Function General Purpose
1738 Timer usage (for AMD Geode machines).
1739
Jiri Kosina016ddd92010-01-18 17:05:40 +01001740 nopat [X86] Disable PAT (page attribute table extension of
1741 pagetables) support.
1742
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001743 norandmaps Don't use address space randomization. Equivalent to
1744 echo 0 > /proc/sys/kernel/randomize_va_space
1745
Jiri Kosinabbff2162010-08-11 18:34:09 +02001746 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001747
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001748 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001749 with UP alternatives
1750
Linus Torvalds1da177e2005-04-16 15:20:36 -07001751 noresidual [PPC] Don't use residual data on PReP machines.
1752
Randy Dunlapa9913042005-10-23 12:57:11 -07001753 noresume [SWSUSP] Disables resume and restores original swap
1754 space.
1755
Linus Torvalds1da177e2005-04-16 15:20:36 -07001756 no-scroll [VGA] Disables scrollback.
1757 This is required for the Braillex ib80-piezo Braille
1758 reader made by F.H. Papenmeier (Germany).
1759
1760 nosbagart [IA-64]
1761
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001762 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001763
Len Brown61ec7562007-08-16 03:34:22 -04001764 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1765 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001766
Dave Jones97842212007-07-15 23:41:05 -07001767 nosoftlockup [KNL] Disable the soft-lockup detector.
1768
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001769 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001770 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001771
Linus Torvalds1da177e2005-04-16 15:20:36 -07001772 nosync [HW,M68K] Disables sync negotiation for all devices.
1773
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001774 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001775
1776 nousb [USB] Disable the USB subsystem
1777
Ben Hutchings55142372011-01-02 23:02:42 +00001778 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04001779
Linus Torvalds1da177e2005-04-16 15:20:36 -07001780 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001781
Weidong Han2b2fd872009-04-17 16:42:12 +08001782 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1783
Fenghua Yua6c75b862008-03-14 13:57:08 -07001784 nptcg= [IA64] Override max number of concurrent global TLB
1785 purges which is reported from either PAL_VM_SUMMARY or
1786 SAL PALO.
1787
Yinghai Lu2b633e32010-02-10 01:20:37 -08001788 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1789 could support. nr_cpus=n : n >= 1 limits the kernel to
1790 supporting 'n' processors. Later in runtime you can not
1791 use hotplug cpu feature to put more cpu back to online.
1792 just like you compile the kernel NR_CPUS=n
1793
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001794 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1795
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001796 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1797 one of ['zone', 'node', 'default'] can be specified
1798 This can be set from sysctl after boot.
1799 See Documentation/sysctl/vm.txt for details.
1800
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001801 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1802 See Documentation/debugging-via-ohci1394.txt for more
1803 info.
1804
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001805 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1806 Rather than timing out after 20 ms if an EC
1807 command is not properly ACKed, override the length
1808 of the timeout. We have interrupts disabled while
1809 waiting for the ACK, so if this is set too high
1810 interrupts *may* be lost!
1811
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001812 omap_mux= [OMAP] Override bootloader pin multiplexing.
1813 Format: <mux_mode0.mode_name=value>...
1814 For example, to override I2C bus2:
1815 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1816
Linus Torvalds1da177e2005-04-16 15:20:36 -07001817 oprofile.timer= [HW]
1818 Use timer interrupt instead of performance counters
1819
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001820 oprofile.cpu_type= Force an oprofile cpu type
1821 This might be useful if you have an older oprofile
1822 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001823 Format: { arch_perfmon }
1824 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001825 perfmon on Intel CPUs instead of the
1826 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001827
Randy Dunlapbcfde332010-06-07 17:10:38 -07001828 OSS [HW,OSS]
1829 See Documentation/sound/oss/oss-parameters.txt
1830
Linus Torvalds1da177e2005-04-16 15:20:36 -07001831 panic= [KNL] Kernel behaviour on panic
1832 Format: <timeout>
1833
1834 parkbd.port= [HW] Parallel port number the keyboard adapter is
1835 connected to, default is 0.
1836 Format: <parport#>
1837 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1838 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001839 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001840
Randy Dunlapa9913042005-10-23 12:57:11 -07001841 parport= [HW,PPT] Specify parallel ports. 0 disables.
1842 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1843 Use 'auto' to force the driver to use any
1844 IRQ/DMA settings detected (the default is to
1845 ignore detected IRQ/DMA settings because of
1846 possible conflicts). You can specify the base
1847 address, IRQ, and DMA settings; IRQ and DMA
1848 should be numbers, or 'auto' (for using detected
1849 settings on that particular port), or 'nofifo'
1850 (to avoid using a FIFO even if it is detected).
1851 Parallel ports are assigned in the order they
1852 are specified on the command line, starting
1853 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001854
Randy Dunlapa9913042005-10-23 12:57:11 -07001855 parport_init_mode= [HW,PPT]
1856 Configure VIA parallel port to operate in
1857 a specific mode. This is necessary on Pegasos
1858 computer where firmware has no options for setting
1859 up parallel port mode and sets it to spp.
1860 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001861 Format: [spp|ps2|epp|ecp|ecpepp]
1862
Andrew Mortondd287792006-03-23 03:00:57 -08001863 pause_on_oops=
1864 Halt all CPUs after the first oops has been printed for
1865 the specified number of seconds. This is to be used if
1866 your oopses keep scrolling off the screen.
1867
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868 pcbit= [HW,ISDN]
1869
1870 pcd. [PARIDE]
1871 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001872 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001873
Randy Dunlapa9913042005-10-23 12:57:11 -07001874 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001875 earlydump [X86] dump PCI config space before the kernel
1876 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001877 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001878 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001879 the hardware directly. Use this if your machine
1880 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001881 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001882 hardware access methods are allowed. Use this
1883 if you experience crashes upon bootup and you
1884 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001885 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001886 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001887 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001888 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001889 noaer [PCIE] If the PCIEAER kernel config parameter is
1890 enabled, this kernel boot option can be used to
1891 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001892 nodomains [PCI] Disable support for multiple PCI
1893 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301894 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001895 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001896 check_enable_amd_mmconf [X86] check for and enable
1897 properly configured MMIO access to PCI
1898 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001899 nomsi [MSI] If the PCI_MSI kernel config parameter is
1900 enabled, this kernel boot option can be used to
1901 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001902 noioapicquirk [APIC] Disable all boot interrupt quirks.
1903 Safety option to keep boot IRQs enabled. This
1904 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001905 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1906 primary IO-APIC for bridges that cannot disable
1907 boot IRQs. This fixes a source of spurious IRQs
1908 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001909 noioapicreroute [APIC] Disable workaround that uses the
1910 boot IRQ equivalent of an IRQ that connects to
1911 a chipset where boot IRQs cannot be disabled.
1912 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001913 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001914 routing table. These calls are known to be buggy
1915 on several machines and they hang the machine
1916 when used, but on other computers it's the only
1917 way to get the interrupt routing table. Try
1918 this option if the kernel is unable to allocate
1919 IRQs or discover secondary PCI buses on your
1920 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001921 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001922 Use with caution as certain devices share
1923 address decoders between ROMs and other
1924 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001925 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001926 expansion ROMs that do not already have
1927 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07001928 nobar [X86] Do not assign address space to the
1929 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001930 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001931 assigned automatically to PCI devices. You can
1932 make the kernel exclude IRQs of your ISA cards
1933 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001934 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001935 of the PIRQ table (normally generated
1936 by the BIOS) if it is outside the
1937 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001938 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001939 useful if the kernel is unable to find your
1940 secondary buses and you want to tell it
1941 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001942 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001943 numbers ourselves, overriding
1944 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001945 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001946 in the BIOS $PIR table. This is needed on
1947 some systems with broken BIOSes, notably
1948 some HP Pavilion N5400 and Omnibook XE3
1949 notebooks. This will have no effect if ACPI
1950 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001951 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001952 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07001953 use_crs [X86] Use PCI host bridge window information
1954 from ACPI. On BIOSes from 2008 or later, this
1955 is enabled by default. If you need to use this,
1956 please report a bug.
1957 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1958 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07001959 routeirq Do IRQ routing for all PCI devices.
1960 This is normally done in pci_enable_device(),
1961 so this option is a temporary workaround
1962 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001963 skip_isa_align [X86] do not align io start addr, so can
1964 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001965 firmware [ARM] Do not re-enumerate the bus but instead
1966 just use the configuration from the
1967 bootloader. This is currently used on
1968 IXP2000 systems where the bus has to be
1969 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001970 noearly [X86] Don't do any early type 1 scanning.
1971 This might help on some broken boards which
1972 machine check when some devices' config space
1973 is read. But various workarounds are disabled
1974 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001975 bfsort Sort PCI devices into breadth-first order.
1976 This sorting is done to get a device
1977 order compatible with older (<= 2.4) kernels.
1978 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001979 cbiosize=nn[KMG] The fixed amount of bus space which is
1980 reserved for the CardBus bridge's IO window.
1981 The default value is 256 bytes.
1982 cbmemsize=nn[KMG] The fixed amount of bus space which is
1983 reserved for the CardBus bridge's memory
1984 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09001985 resource_alignment=
1986 Format:
1987 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1988 Specifies alignment and device to reassign
1989 aligned memory resources.
1990 If <order of align> is not specified,
1991 PAGE_SIZE is used as alignment.
1992 PCI-PCI bridge can be specified, if resource
1993 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06001994 ecrc= Enable/disable PCIe ECRC (transaction layer
1995 end-to-end CRC checking).
1996 bios: Use BIOS/firmware settings. This is the
1997 the default.
1998 off: Turn ECRC off
1999 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002000
Chuck Ebberte5665a42008-09-24 20:40:34 -04002001 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2002 Management.
2003 off Disable ASPM.
2004 force Enable ASPM even on devices that claim not to support it.
2005 WARNING: Forcing ASPM on may cause system lockups.
2006
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002007 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002008 auto Ask the BIOS whether or not to use native PCIe services
2009 associated with PCIe ports (PME, hot-plug, AER). Use
2010 them only if that is allowed by the BIOS.
2011 native Use native PCIe services associated with PCIe ports
2012 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002013 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2014 ports driver.
2015
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002016 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002017 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002018 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002019
Linus Torvalds1da177e2005-04-16 15:20:36 -07002020 pcmv= [HW,PCMCIA] BadgePAD 4
2021
2022 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002023 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002024
2025 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2026 boot time.
2027 Format: { 0 | 1 }
2028 See arch/parisc/kernel/pdc_chassis.c
2029
Tejun Heof58dc012009-08-14 15:00:50 +09002030 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002031 Currently supported values are "embed" and "page".
2032 Archs may support subset or none of the selections.
2033 See comments in mm/percpu.c for details on each
2034 allocator. This parameter is primarily for debugging
2035 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002036
Linus Torvalds1da177e2005-04-16 15:20:36 -07002037 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002038 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002039
2040 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002041 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002042
2043 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002044 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002045
2046 plip= [PPT,NET] Parallel port network link
2047 Format: { parport<nr> | timid | 0 }
2048 See also Documentation/parport.txt.
2049
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002050 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2051 Override pmtimer IOPort with a hex value.
2052 e.g. pmtmr=0x508
2053
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002054 pnp.debug [PNP]
2055 Enable PNP debug messages. This depends on the
2056 CONFIG_PNP_DEBUG_MESSAGES option.
2057
Linus Torvalds1da177e2005-04-16 15:20:36 -07002058 pnpacpi= [ACPI]
2059 { off }
2060
2061 pnpbios= [ISAPNP]
2062 { on | off | curr | res | no-curr | no-res }
2063
2064 pnp_reserve_irq=
2065 [ISAPNP] Exclude IRQs for the autoconfiguration
2066
2067 pnp_reserve_dma=
2068 [ISAPNP] Exclude DMAs for the autoconfiguration
2069
2070 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002071 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002072
2073 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002074 [ISAPNP] Exclude memory regions for the
2075 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002076 Ranges are in pairs (memory base and size).
2077
Randy Dunlap4af94f32009-04-17 18:30:28 -07002078 ports= [IP_VS_FTP] IPVS ftp helper module
2079 Default is 21.
2080 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2081 may be specified.
2082 Format: <port>,<port>....
2083
Ingo Molnar45807a12007-07-15 23:40:10 -07002084 print-fatal-signals=
2085 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002086
2087 If enabled, warn about various signal handling
2088 related application anomalies: too many signals,
2089 too many POSIX.1 timers, fatal signals causing a
2090 coredump - etc.
2091
2092 If you hit the warning due to signal overflow,
2093 you might want to try "ulimit -i unlimited".
2094
Ingo Molnar45807a12007-07-15 23:40:10 -07002095 default: off.
2096
Randy Dunlape84845c2007-07-15 23:40:25 -07002097 printk.time= Show timing data prefixed to each printk message line
2098 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2099
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002100 processor.max_cstate= [HW,ACPI]
2101 Limit processor to maximum C-state
2102 max_cstate=9 overrides any DMI blacklist limit.
2103
2104 processor.nocst [HW,ACPI]
2105 Ignore the _CST method to determine C-states,
2106 instead using the legacy FADT method
2107
Linus Torvalds1da177e2005-04-16 15:20:36 -07002108 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002109 Format: [schedule,]<number>
2110 Param: "schedule" - profile schedule points.
2111 Param: <number> - step/bucket size as a power of 2 for
2112 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002113 Param: "sleep" - profile D-state sleeping (millisecs).
2114 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002115 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002116
Linus Torvalds1da177e2005-04-16 15:20:36 -07002117 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2118 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002119 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002120
Randy Dunlapa9913042005-10-23 12:57:11 -07002121 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2122 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002123 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2124 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002125 psmouse.resetafter= [HW,MOUSE]
2126 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002127 (0 = never).
2128 psmouse.resolution=
2129 [HW,MOUSE] Set desired mouse resolution, in dpi.
2130 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002131 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002132 0 = disabled, 1 = enabled (default).
2133
Linus Torvalds1da177e2005-04-16 15:20:36 -07002134 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002135 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002136
Kay Sieversdc8c8582007-08-15 12:25:38 +02002137 pty.legacy_count=
2138 [KNL] Number of legacy pty's. Overwrites compiled-in
2139 default number.
2140
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002141 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002142
Linus Torvalds1da177e2005-04-16 15:20:36 -07002143 r128= [HW,DRM]
2144
2145 raid= [HW,RAID]
2146 See Documentation/md.txt.
2147
Randy Dunlapa9913042005-10-23 12:57:11 -07002148 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002149 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002150
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002152 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002153
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002154 rcupdate.blimit= [KNL,BOOT]
2155 Set maximum number of finished RCU callbacks to process
2156 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002157
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002158 rcupdate.qhimark= [KNL,BOOT]
2159 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002160 RCU callbacks over which batch limiting is disabled.
2161
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002162 rcupdate.qlowmark= [KNL,BOOT]
2163 Set threshold of queued RCU callbacks below which
2164 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002165
Olof Johanssonffdfc402005-09-06 15:17:19 -07002166 rdinit= [KNL]
2167 Format: <full_path>
2168 Run specified binary instead of /init from the ramdisk,
2169 used for early userspace startup. See initrd.
2170
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002171 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002172 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002173 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002174
Paul Jackson46b6d942008-07-04 10:00:09 -07002175 relax_domain_level=
2176 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002177 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002178
Linus Torvalds1da177e2005-04-16 15:20:36 -07002179 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2180
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002181 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002182 Format: nn[KMG]
2183 Reserves a hole at the top of the kernel virtual
2184 address space.
2185
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002186 reservelow= [X86]
2187 Format: nn[K]
2188 Set the amount of memory to reserve for BIOS at
2189 the bottom of the address space.
2190
Vivek Goyal7e962872006-09-27 01:50:44 -07002191 reset_devices [KNL] Force drivers to reset the underlying device
2192 during initialization.
2193
Randy Dunlapa9913042005-10-23 12:57:11 -07002194 resume= [SWSUSP]
2195 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002196
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002197 resume_offset= [SWSUSP]
2198 Specify the offset from the beginning of the partition
2199 given by "resume=" at which the swap header is located,
2200 in <PAGE_SIZE> units (needed only for swap files).
2201 See Documentation/power/swsusp-and-swap-files.txt
2202
Bojan Smojverf996fc92010-09-09 23:06:23 +02002203 hibernate= [HIBERNATION]
2204 noresume Don't check if there's a hibernation image
2205 present during boot.
2206 nocompress Don't compress/decompress hibernation images.
2207
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002208 retain_initrd [RAM] Keep initrd memory after extraction
2209
Linus Torvalds1da177e2005-04-16 15:20:36 -07002210 rhash_entries= [KNL,NET]
2211 Set number of hash buckets for route cache
2212
2213 riscom8= [HW,SERIAL]
2214 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2215
2216 ro [KNL] Mount root device read-only on boot
2217
2218 root= [KNL] Root filesystem
2219
2220 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2221 mount the root filesystem
2222
2223 rootflags= [KNL] Set root filesystem mount option string
2224
2225 rootfstype= [KNL] Set root filesystem type
2226
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002227 rootwait [KNL] Wait (indefinitely) for root device to show up.
2228 Useful for devices that are detected asynchronously
2229 (e.g. USB and MMC devices).
2230
Linus Torvalds1da177e2005-04-16 15:20:36 -07002231 rw [KNL] Mount root device read-write on boot
2232
2233 S [KNL] Run init in single mode
2234
2235 sa1100ir [NET]
2236 See drivers/net/irda/sa1100_ir.c.
2237
Linus Torvalds1da177e2005-04-16 15:20:36 -07002238 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002239
Mike Travisf6630112009-11-17 18:22:15 -06002240 sched_debug [KNL] Enables verbose scheduler debug messages.
2241
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002242 security= [SECURITY] Choose a security module to enable at boot.
2243 If this boot parameter is not specified, only the first
2244 security module asking for security registration will be
2245 loaded. An invalid security module name will be treated
2246 as if no module has been chosen.
2247
2248 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002249 Format: { "0" | "1" }
2250 See security/selinux/Kconfig help text.
2251 0 -- disable.
2252 1 -- enable.
2253 Default value is set via kernel config option.
2254 If enabled at boot time, /selinux/disable can be used
2255 later to disable prior to initial policy load.
2256
John Johansenc1c124e2010-07-29 14:48:09 -07002257 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2258 Format: { "0" | "1" }
2259 See security/apparmor/Kconfig help text
2260 0 -- disable.
2261 1 -- enable.
2262 Default value is set via kernel config option.
2263
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002264 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002265
Linus Torvalds1da177e2005-04-16 15:20:36 -07002266 shapers= [NET]
2267 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002268
Yinghai Lub05f78f2008-08-22 01:32:50 -07002269 show_msr= [x86] show boot-time MSR settings
2270 Format: { <integer> }
2271 Show boot-time (BIOS-initialized) MSR settings.
2272 The parameter means the number of CPUs to show,
2273 for example 1 means boot CPU only.
2274
Linus Torvalds1da177e2005-04-16 15:20:36 -07002275 simeth= [IA-64]
2276 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002277
Linus Torvalds1da177e2005-04-16 15:20:36 -07002278 slram= [HW,MTD]
2279
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002280 slub_debug[=options[,slabs]] [MM, SLUB]
2281 Enabling slub_debug allows one to determine the
2282 culprit if slab objects become corrupted. Enabling
2283 slub_debug can create guard zones around objects and
2284 may poison objects when not in use. Also tracks the
2285 last alloc / free. For more information see
2286 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002287
2288 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002289 Determines the maximum allowed order for slabs.
2290 A high setting may cause OOMs due to memory
2291 fragmentation. For more information see
2292 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002293
2294 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002295 The minimum number of objects per slab. SLUB will
2296 increase the slab order up to slub_max_order to
2297 generate a sufficiently large slab able to contain
2298 the number of objects indicated. The higher the number
2299 of objects the smaller the overhead of tracking slabs
2300 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002301 For more information see Documentation/vm/slub.txt.
2302
2303 slub_min_order= [MM, SLUB]
2304 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002305 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002306 For more information see Documentation/vm/slub.txt.
2307
2308 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002309 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002310 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002311 allocs to different slabs. Debug options disable
2312 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002313 For more information see Documentation/vm/slub.txt.
2314
Linus Torvalds1da177e2005-04-16 15:20:36 -07002315 smart2= [HW]
2316 Format: <io1>[,<io2>[,...,<io8>]]
2317
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002318 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002319 attempt to substitute SMP alternatives once at boot.
2320
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002321 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2322 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2323 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2324 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2325 smsc-ircc2.ircc_irq= [HW] IRQ line
2326 smsc-ircc2.ircc_dma= [HW] DMA channel
2327 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2328 0: Toshiba Satellite 1800 (GP data pin select)
2329 1: Fast pin select (default)
2330 2: ATC IRMode
2331
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002332 softlockup_panic=
2333 [KNL] Should the soft-lockup detector generate panics.
2334
Linus Torvalds1da177e2005-04-16 15:20:36 -07002335 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2336 See Documentation/sonypi.txt
2337
2338 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002339 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002340
2341 spia_io_base= [HW,MTD]
2342 spia_fio_base=
2343 spia_pedr=
2344 spia_peddr=
2345
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002346 stacktrace [FTRACE]
2347 Enabled the stack tracer on boot up.
2348
Linus Torvalds1da177e2005-04-16 15:20:36 -07002349 sti= [PARISC,HW]
2350 Format: <num>
2351 Set the STI (builtin display/keyboard on the HP-PARISC
2352 machines) console (graphic card) which should be used
2353 as the initial boot-console.
2354 See also comment in drivers/video/console/sticore.c.
2355
2356 sti_font= [HW]
2357 See comment in drivers/video/console/sticore.c.
2358
2359 stifb= [HW]
2360 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2361
Trond Myklebustcbf11072009-08-09 15:06:19 -04002362 sunrpc.min_resvport=
2363 sunrpc.max_resvport=
2364 [NFS,SUNRPC]
2365 SunRPC servers often require that client requests
2366 originate from a privileged port (i.e. a port in the
2367 range 0 < portnr < 1024).
2368 An administrator who wishes to reserve some of these
2369 ports for other uses may adjust the range that the
2370 kernel's sunrpc client considers to be privileged
2371 using these two parameters to set the minimum and
2372 maximum port values.
2373
Greg Banks42a7fc42007-03-06 01:42:23 -08002374 sunrpc.pool_mode=
2375 [NFS]
2376 Control how the NFS server code allocates CPUs to
2377 service thread pools. Depending on how many NICs
2378 you have and where their interrupts are bound, this
2379 option will affect which CPUs will do NFS serving.
2380 Note: this parameter cannot be changed while the
2381 NFS server is running.
2382
2383 auto the server chooses an appropriate mode
2384 automatically using heuristics
2385 global a single global pool contains all CPUs
2386 percpu one pool for each CPU
2387 pernode one pool for each NUMA node (equivalent
2388 to global on non-NUMA machines)
2389
Trond Myklebustcbf11072009-08-09 15:06:19 -04002390 sunrpc.tcp_slot_table_entries=
2391 sunrpc.udp_slot_table_entries=
2392 [NFS,SUNRPC]
2393 Sets the upper limit on the number of simultaneous
2394 RPC calls that can be sent from the client to a
2395 server. Increasing these values may allow you to
2396 improve throughput, but will also increase the
2397 amount of memory reserved for use by the client.
2398
Michal Hockoa42c3902010-11-24 12:57:08 -08002399 swapaccount[=0|1]
2400 [KNL] Enable accounting of swap in memory resource
2401 controller if no parameter or 1 is given or disable
2402 it if 0 is given (See Documentation/cgroups/memory.txt)
2403
Linus Torvalds1da177e2005-04-16 15:20:36 -07002404 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002405
Linus Torvalds1da177e2005-04-16 15:20:36 -07002406 switches= [HW,M68k]
2407
Andi Kleene52eec12010-09-08 16:54:17 +02002408 sysfs.deprecated=0|1 [KNL]
2409 Enable/disable old style sysfs layout for old udev
2410 on older distributions. When this option is enabled
2411 very new udev will not work anymore. When this option
2412 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2413 in older udev will not work anymore.
2414 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2415 the kernel configuration.
2416
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002417 sysrq_always_enabled
2418 [KNL]
2419 Ignore sysrq setting - this boot parameter will
2420 neutralize any effect of /proc/sys/kernel/sysrq.
2421 Useful for debugging.
2422
Linus Torvalds1da177e2005-04-16 15:20:36 -07002423 tdfx= [HW,DRM]
2424
David Brownell77437fd2008-07-23 21:28:33 -07002425 test_suspend= [SUSPEND]
2426 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2427 standby suspend) as the system sleep state to briefly
2428 enter during system startup. The system is woken from
2429 this state using a wakeup-capable RTC alarm.
2430
Linus Torvalds1da177e2005-04-16 15:20:36 -07002431 thash_entries= [KNL,NET]
2432 Set number of hash buckets for TCP connection
2433
Len Brownf8707ec2007-08-12 00:12:54 -04002434 thermal.act= [HW,ACPI]
2435 -1: disable all active trip points in all thermal zones
2436 <degrees C>: override all lowest active trip points
2437
Len Brownc52a7412007-08-14 15:49:32 -04002438 thermal.crt= [HW,ACPI]
2439 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002440 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002441
Len Brownf5487142007-08-12 00:12:44 -04002442 thermal.nocrt= [HW,ACPI]
2443 Set to disable actions on ACPI thermal zone
2444 critical and hot trip points.
2445
Len Brown72b33ef2007-08-12 00:12:17 -04002446 thermal.off= [HW,ACPI]
2447 1: disable ACPI thermal control
2448
Len Browna70cdc52007-08-12 00:12:35 -04002449 thermal.psv= [HW,ACPI]
2450 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002451 <degrees C>: override all passive trip points to this
2452 value
Len Browna70cdc52007-08-12 00:12:35 -04002453
Len Brown730ff342007-08-12 00:12:26 -04002454 thermal.tzp= [HW,ACPI]
2455 Specify global default ACPI thermal zone polling rate
2456 <deci-seconds>: poll all this frequency
2457 0: no polling (default)
2458
Thomas Gleixner8d32a302011-02-23 23:52:23 +00002459 threadirqs [KNL]
2460 Force threading of all interrupt handlers except those
2461 marked explicitely IRQF_NO_THREAD.
2462
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002463 topology= [S390]
2464 Format: {off | on}
2465 Specify if the kernel should make use of the cpu
2466 topology informations if the hardware supports these.
2467 The scheduler will make use of these informations and
2468 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02002469 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002470
Linus Torvalds1da177e2005-04-16 15:20:36 -07002471 tp720= [HW,PS2]
2472
Rajiv Andrade225a9be2010-03-25 00:55:32 -03002473 tpm_suspend_pcr=[HW,TPM]
2474 Format: integer pcr id
2475 Specify that at suspend time, the tpm driver
2476 should extend the specified pcr with zeros,
2477 as a workaround for some chips which fail to
2478 flush the last written pcr on TPM_SaveState.
2479 This will guarantee that all the other pcrs
2480 are saved.
2481
Li Zefan9d612be2009-06-24 17:33:15 +08002482 trace_buf_size=nn[KMG]
2483 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002484
Li Zefan020e5f82009-07-01 10:47:05 +08002485 trace_event=[event-list]
2486 [FTRACE] Set and start specified trace events in order
2487 to facilitate early boot debugging.
2488 See also Documentation/trace/events.txt
2489
john stultzd3b8f882009-08-17 16:40:47 -07002490 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07002491 Format: <string>
2492 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07002493 disables clocksource verification at runtime, as well
2494 as the stability checks done at bootup. Used to enable
2495 high-resolution timer mode on older hardware, and in
2496 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07002497 [x86] noirqtime: Do not use TSC to do irq accounting.
2498 Used to run time disable IRQ_TIME_ACCOUNTING on any
2499 platforms where RDTSC is slow and this accounting
2500 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07002501
Randy Dunlapa9913042005-10-23 12:57:11 -07002502 turbografx.map[2|3]= [HW,JOY]
2503 TurboGraFX parallel port interface
2504 Format:
2505 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002506 See also Documentation/input/joystick-parport.txt
2507
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002508 uhash_entries= [KNL,NET]
2509 Set number of hash buckets for UDP/UDP-Lite connections
2510
Alan Stern5f8364b2006-12-05 16:29:55 -05002511 uhci-hcd.ignore_oc=
2512 [USB] Ignore overcurrent events (default N).
2513 Some badly-designed motherboards generate lots of
2514 bogus events, for ports that aren't wired to
2515 anything. Set this parameter to avoid log spamming.
2516 Note that genuine overcurrent events won't be
2517 reported either.
2518
Simon Arlotte3a61b02008-07-19 23:32:54 +01002519 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302520 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002521 Set unknown_nmi_panic=1 early on boot.
2522
Alan Sternb5e795f2007-02-20 15:00:53 -05002523 usbcore.autosuspend=
2524 [USB] The autosuspend time delay (in seconds) used
2525 for newly-detected USB devices (default 2). This
2526 is the time required before an idle device will be
2527 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002528 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002529
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002530 usbcore.usbfs_snoop=
2531 [USB] Set to log all usbfs traffic (default 0 = off).
2532
2533 usbcore.blinkenlights=
2534 [USB] Set to cycle leds on hubs (default 0 = off).
2535
2536 usbcore.old_scheme_first=
2537 [USB] Start with the old device initialization
2538 scheme (default 0 = off).
2539
2540 usbcore.use_both_schemes=
2541 [USB] Try the other device initialization scheme
2542 if the first one fails (default 1 = enabled).
2543
2544 usbcore.initial_descriptor_timeout=
2545 [USB] Specifies timeout for the initial 64-byte
2546 USB_REQ_GET_DESCRIPTOR request in milliseconds
2547 (default 5000 = 5.0 seconds).
2548
Linus Torvalds1da177e2005-04-16 15:20:36 -07002549 usbhid.mousepoll=
2550 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002551
Alan Sternd4f373e2008-11-10 14:07:45 -05002552 usb-storage.delay_use=
2553 [UMS] The delay in seconds before a new device is
2554 scanned for Logical Units (default 5).
2555
2556 usb-storage.quirks=
2557 [UMS] A list of quirks entries to supplement or
2558 override the built-in unusual_devs list. List
2559 entries are separated by commas. Each entry has
2560 the form VID:PID:Flags where VID and PID are Vendor
2561 and Product ID values (4-digit hex numbers) and
2562 Flags is a set of characters, each corresponding
2563 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002564 a = SANE_SENSE (collect more than 18 bytes
2565 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002566 b = BAD_SENSE (don't collect more than 18
2567 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002568 c = FIX_CAPACITY (decrease the reported
2569 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002570 h = CAPACITY_HEURISTICS (decrease the
2571 reported device capacity by one
2572 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002573 i = IGNORE_DEVICE (don't bind to this
2574 device);
2575 l = NOT_LOCKABLE (don't try to lock and
2576 unlock ejectable media);
2577 m = MAX_SECTORS_64 (don't transfer more
2578 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002579 o = CAPACITY_OK (accept the capacity
2580 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002581 r = IGNORE_RESIDUE (the device reports
2582 bogus residue values);
2583 s = SINGLE_LUN (the device has only one
2584 Logical Unit);
2585 w = NO_WP_DETECT (don't test whether the
2586 medium is write-protected).
2587 Example: quirks=0419:aaf5:rl,0421:0433:rc
2588
Ian Campbell14315592010-02-17 10:38:10 +00002589 userpte=
2590 [X86] Flags controlling user PTE allocations.
2591
2592 nohigh = do not allocate PTE pages in
2593 HIGHMEM regardless of setting
2594 of CONFIG_HIGHPTE.
2595
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302596 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002597 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002598 vdso=1: enable VDSO (default)
2599 vdso=0: disable VDSO mapping
2600
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302601 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002602 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2603 vdso32=1: enable 32-bit VDSO (default)
2604 vdso32=0: disable 32-bit VDSO mapping
2605
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002606 vector= [IA-64,SMP]
2607 vector=percpu: enable percpu vector domain
2608
Linus Torvalds1da177e2005-04-16 15:20:36 -07002609 video= [FB] Frame buffer configuration
2610 See Documentation/fb/modedb.txt.
2611
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002612 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002613 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002614 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002615 Use vga=ask for menu.
2616 This is actually a boot loader parameter; the value is
2617 passed to the kernel using a special protocol.
2618
Randy Dunlapa9913042005-10-23 12:57:11 -07002619 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002620 size of <nn>. This can be used to increase the
2621 minimum size (128MB on x86). It can also be used to
2622 decrease the size and leave more room for directly
2623 mapped kernel RAM.
2624
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002625 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2626 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002627
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002628 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2629 Format: <command>
2630
2631 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2632 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002633
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002634 vt.cur_default= [VT] Default cursor shape.
2635 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2636 the parameters of the <Esc>[?A;B;Cc escape sequence;
2637 see VGA-softcursor.txt. Default: 2 = underline.
2638
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002639 vt.default_blu= [VT]
2640 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2641 Change the default blue palette of the console.
2642 This is a 16-member array composed of values
2643 ranging from 0-255.
2644
2645 vt.default_grn= [VT]
2646 Format: <green0>,<green1>,<green2>,...,<green15>
2647 Change the default green palette of the console.
2648 This is a 16-member array composed of values
2649 ranging from 0-255.
2650
2651 vt.default_red= [VT]
2652 Format: <red0>,<red1>,<red2>,...,<red15>
2653 Change the default red palette of the console.
2654 This is a 16-member array composed of values
2655 ranging from 0-255.
2656
2657 vt.default_utf8=
2658 [VT]
2659 Format=<0|1>
2660 Set system-wide default UTF-8 mode for all tty's.
2661 Default is 1, i.e. UTF-8 mode is enabled for all
2662 newly opened terminals.
2663
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002664 vt.global_cursor_default=
2665 [VT]
2666 Format=<-1|0|1>
2667 Set system-wide default for whether a cursor
2668 is shown on new VTs. Default is -1,
2669 i.e. cursors will be created by default unless
2670 overridden by individual drivers. 0 will hide
2671 cursors, 1 will display them.
2672
Randy Dunlap4724ba572010-05-03 11:42:52 -07002673 watchdog timers [HW,WDT] For information on watchdog timers,
2674 see Documentation/watchdog/watchdog-parameters.txt
2675 or other driver-specific files in the
2676 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002677
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002678 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2679 default x2apic cluster mode on platforms
2680 supporting x2apic.
2681
Jacob Panbb24c472009-09-02 07:37:17 -07002682 x86_mrst_timer= [X86-32,APBT]
2683 Choose timer option for x86 Moorestown MID platform.
2684 Two valid options are apbt timer only and lapic timer
2685 plus one apbt timer for broadcast timer.
2686 x86_mrst_timer=apbt_only | lapic_and_apbt
2687
Linus Torvalds1da177e2005-04-16 15:20:36 -07002688 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2689 xd_geo= See header of drivers/block/xd.c.
2690
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002691 xen_emul_unplug= [HW,X86,XEN]
2692 Unplug Xen emulated devices
2693 Format: [unplug0,][unplug1]
2694 ide-disks -- unplug primary master IDE devices
2695 aux-ide-disks -- unplug non-primary-master IDE devices
2696 nics -- unplug network devices
2697 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01002698 unnecessary -- unplugging emulated devices is
2699 unnecessary even if the host did not respond to
2700 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01002701 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002702
Linus Torvalds1da177e2005-04-16 15:20:36 -07002703 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002704 Format:
2705 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002706
Randy Dunlapa9913042005-10-23 12:57:11 -07002707______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002708
2709TODO:
2710
Linus Torvalds1da177e2005-04-16 15:20:36 -07002711 Add more DRM drivers.