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Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -07003
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
Randy Dunlapca1eda22009-05-06 16:02:58 -070020Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22can also be entered as
23 log-buf-len=1M print_fatal_signals=1
24
25
Stefan Richtera901ebb2006-04-01 01:43:18 +020026This document may not be entirely up to date and comprehensive. The command
27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28module. Loadable modules, after being loaded into the running kernel, also
29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30parameters may be changed at runtime by the command
31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32
Stefan Richter6585fa82006-04-01 01:44:30 +020033The parameters listed below are only valid if certain kernel build options were
34enabled and if respective hardware is present. The text in square brackets at
35the beginning of each description states the restrictions within which a
36parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070037
38 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100039 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070040 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020043 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070044 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080045 BLACKFIN Blackfin architecture is enabled.
Randy Dunlapa9913042005-10-23 12:57:11 -070046 DRM Direct Rendering Management support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070047 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070051 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070052 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050054 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070056 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080057 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050061 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020062 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070063 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070064 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070072 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070073 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 NET Appropriate network support is enabled.
75 NUMA NUMA support is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070078 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070082 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -070091 A lot of drivers have their options described inside
92 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -070093 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070094 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -070095 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +090097 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070098 SMP The kernel is an SMP kernel.
99 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700100 SWSUSP Software suspend (hibernation) is enabled.
101 SUSPEND System suspend states are enabled.
Steven Rostedtf38f1d22008-12-16 23:06:40 -0500102 FTRACE Function tracing enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300103 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500105 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 USB USB support is enabled.
107 USBHID USB Human Interface Device support is enabled.
108 V4L Video For Linux support is enabled.
109 VGA The VGA console has been enabled.
110 VT Virtual terminal support is enabled.
111 WDT Watchdog support is enabled.
112 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700113 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 X86-64 X86-64 architecture is enabled.
115 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700116 Documentation/x86/x86_64/boot-options.txt .
Andi Kleenc0115602008-08-22 09:53:39 +0200117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100118 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119
120In addition, the following text indicates that the option:
121
122 BUGS= Relates to possible processor bugs on the said processor.
123 KNL Is a kernel start-up parameter.
124 BOOT Is a boot loader parameter.
125
126Parameters denoted with BOOT are actually interpreted by the boot
127loader, and have no meaning to the kernel directly.
128Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500129need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130
Karsten Weiss55588702007-02-13 13:26:21 +0100131There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700132See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100133
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
135a trailing = on the name of any parameter states that that parameter will
136be entered as an environment variable, whereas its absence indicates that
137it will appear as a kernel argument readable via /proc/cmdline by programs
138running once the system is up.
139
jens m. noedler9c4751f2006-09-29 02:00:27 -0700140The number of kernel parameters is not limited, but the length of the
141complete command line (parameters including spaces etc.) is limited to
142a fixed number of characters. This limit depends on the architecture
143and is between 256 and 4096 characters. It is defined in the file
144./include/asm/setup.h as COMMAND_LINE_SIZE.
145
146
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530147 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800148 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500149 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150 force -- enable ACPI if default was off
151 off -- disable ACPI if default was on
152 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700153 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800155 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800156 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157
Randy Dunlap53471122008-03-12 18:10:51 -0400158 See also Documentation/power/pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159
Len Browna1fdcc02007-03-11 03:26:14 -0400160 acpi_apic_instance= [ACPI, IOAPIC]
161 Format: <int>
162 2: use 2nd APIC table, if available
163 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400164 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400165
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200166 acpi_backlight= [HW,ACPI]
167 acpi_backlight=vendor
168 acpi_backlight=video
169 If set to vendor, prefer vendor specific driver
170 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
171 of the ACPI video.ko driver.
172
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700173 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
174 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700176 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
177 debug output. Bits in debug_layer correspond to a
178 _COMPONENT in an ACPI source file, e.g.,
179 #define _COMPONENT ACPI_PCI_COMPONENT
180 Bits in debug_level correspond to a level in
181 ACPI_DEBUG_PRINT statements, e.g.,
182 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600183 The debug_level mask defaults to "info". See
184 Documentation/acpi/debug.txt for more information about
185 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600187 Enable processor driver info messages:
188 acpi.debug_layer=0x20000000
189 Enable PCI/PCI interrupt routing info messages:
190 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700191 Enable AML "Debug" output, i.e., stores to the Debug
192 object while interpreting AML:
193 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700194 Enable all messages related to ACPI hardware:
195 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200196
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700197 Some values produce so much output that the system is
198 unusable. The "log_buf_len" parameter may be useful
199 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800200
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700201 acpi_display_output= [HW,ACPI]
202 acpi_display_output=vendor
203 acpi_display_output=video
204 See above.
205
206 acpi_irq_balance [HW,ACPI]
207 ACPI will balance active IRQs
208 default in APIC mode
209
210 acpi_irq_nobalance [HW,ACPI]
211 ACPI will not move active IRQs (default)
212 default in PIC mode
213
214 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
215 Format: <irq>,<irq>...
216
217 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
218 use by PCI
219 Format: <irq>,<irq>...
220
221 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
222
223 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
224 Format: To spoof as Windows 98: ="Microsoft Windows"
225
226 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
227 acpi_osi="string1" # add string1 -- only one string
228 acpi_osi="!string2" # remove built-in string2
229 acpi_osi= # disable all strings
230
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530231 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700232 Override the pmtimer bug detection: force the kernel
233 to assume that this machine's pmtimer latches its value
234 and always returns good values.
235
Randy Dunlap4af94f32009-04-17 18:30:28 -0700236 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
237 Format: { level | edge | high | low }
238
239 acpi_serialize [HW,ACPI] force serialization of AML methods
240
241 acpi_skip_timer_override [HW,ACPI]
242 Recognize and ignore IRQ0/pin2 Interrupt Override.
243 For broken nForce2 BIOS resulting in XT-PIC timer.
244
245 acpi_sleep= [HW,ACPI] Sleep options
246 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800247 old_ordering, s4_nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700248 See Documentation/power/video.txt for information on
249 s3_bios and s3_mode.
250 s3_beep is for debugging; it makes the PC's speaker beep
251 as soon as the kernel's real-mode entry point is called.
252 s4_nohwsig prevents ACPI hardware signature from being
253 used during resume from hibernation.
254 old_ordering causes the ACPI 1.0 ordering of the _PTS
255 control method, with respect to putting devices into
256 low power states, to be enforced (the ACPI 2.0 ordering
257 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200258 nonvs prevents the kernel from saving/restoring the
259 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800260 sci_force_enable causes the kernel to set SCI_EN directly
261 on resume from S1/S3 (which is against the ACPI spec,
262 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700263
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
267
Luca Tettamanti7e905602009-03-30 00:01:27 +0200268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
283
Randy Dunlap4af94f32009-04-17 18:30:28 -0700284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
286
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700287 agp= [AGP]
288 { off | try_unsupported }
289 off: disable AGP support
290 try_unsupported: try to drive unsupported chipsets
291 (may crash computer or cause data corruption)
292
Randy Dunlapbcfde332010-06-07 17:10:38 -0700293 ALSA [HW,ALSA]
294 See Documentation/sound/alsa/alsa-parameters.txt
295
Russell Kingd944d542010-02-20 16:13:29 +0000296 alignment= [KNL,ARM]
297 Allow the default userspace alignment fault handler
298 behaviour to be specified. Bit 0 enables warnings,
299 bit 1 enables fixups, and bit 2 sends a segfault.
300
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200301 amd_iommu= [HW,X86-84]
302 Pass parameters to the AMD IOMMU driver in the system.
303 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900304 fullflush - enable flushing of IO/TLB entries when
305 they are unmapped. Otherwise they are
306 flushed before they will be reused, which
307 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200308 off - do not initialize any AMD IOMMU found in
309 the system
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900310
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311 amijoy.map= [HW,JOY] Amiga joystick support
312 Map of devices attached to JOY0DAT and JOY1DAT
313 Format: <a>,<b>
314 See also Documentation/kernel/input/joystick.txt
315
316 analog.map= [HW,JOY] Analog joystick and gamepad support
317 Specifies type or capabilities of an analog joystick
318 connected to one of 16 gameports
319 Format: <type1>,<type2>,..<type16>
320
Randy Dunlapa9913042005-10-23 12:57:11 -0700321 apc= [HW,SPARC]
322 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700323 Format: noidle
324 Disable APC CPU standby support. SPARCstation-Fox does
325 not play well with APC CPU idle - disable it if you have
326 APC and your system crashes randomly.
327
Randy Dunlapca1eda22009-05-06 16:02:58 -0700328 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700329 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330 Format: { quiet (default) | verbose | debug }
331 Change the amount of debugging information output
332 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700333
Brian Haleyb0f83b22010-02-04 13:36:50 -0800334 autoconf= [IPV6]
335 See Documentation/networking/ipv6.txt.
336
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400337 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
338 Limit apic dumping. The parameter defines the maximal
339 number of local apics being dumped. Also it is possible
340 to set it to "all" by meaning -- no limit here.
341 Format: { 1 (default) | 2 | ... | all }.
342 The parameter valid if only apic=debug or
343 apic=verbose is specified.
344 Example: apic=debug show_lapic=all
345
Linus Torvalds1da177e2005-04-16 15:20:36 -0700346 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700347 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
350 Format: <io>,<irq>,<nodeID>
351
352 ataflop= [HW,M68k]
353
354 atarimouse= [HW,MOUSE] Atari Mouse
355
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
357 EzKey and similar keyboards
358
359 atkbd.reset= [HW] Reset keyboard during initialization
360
Randy Dunlapa9913042005-10-23 12:57:11 -0700361 atkbd.set= [HW] Select keyboard code set
362 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700363
364 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
365 keyboards
366
367 atkbd.softraw= [HW] Choose between synthetic and real raw mode
368 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700369
370 atkbd.softrepeat= [HW]
371 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700372
373 autotest [IA64]
374
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375 baycom_epp= [HW,AX25]
376 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700377
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
379 Format: <io>,<mode>
380 See header of drivers/net/hamradio/baycom_par.c.
381
Randy Dunlapa9913042005-10-23 12:57:11 -0700382 baycom_ser_fdx= [HW,AX25]
383 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384 Format: <io>,<irq>,<mode>[,<baud>]
385 See header of drivers/net/hamradio/baycom_ser_fdx.c.
386
Randy Dunlapa9913042005-10-23 12:57:11 -0700387 baycom_ser_hdx= [HW,AX25]
388 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700389 Format: <io>,<irq>,<mode>
390 See header of drivers/net/hamradio/baycom_ser_hdx.c.
391
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700392 boot_delay= Milliseconds to delay each printk during boot.
393 Values larger than 10 seconds (10000) are changed to
394 no delay (0).
395 Format: integer
396
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700397 bootmem_debug [KNL] Enable bootmem allocator debug messages.
398
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700400 bttv.radio= Most important insmod options are available as
401 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700402 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
403 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
404
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405 c101= [NET] Moxa C101 synchronous serial card
406
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700407 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 Sometimes CPU hardware bugs make them report the cache
409 size incorrectly. The kernel will attempt work arounds
410 to fix known problems, but for some CPUs it is not
411 possible to determine what the correct size should be.
412 This option provides an override for these situations.
413
James Morris20510f22007-10-16 23:31:32 -0700414 capability.disable=
415 [SECURITY] Disable capabilities. This would normally
416 be used only if an alternative security model is to be
417 configured. Potentially dangerous and should only be
418 used if you are entirely sure of the consequences.
419
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100420 ccw_timeout_log [S390]
421 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422
Paul Menage8bab8dd2008-04-04 14:29:57 -0700423 cgroup_disable= [KNL] Disable a particular controller
424 Format: {name of the controller(s) to disable}
425 {Currently supported controllers - "memory"}
426
Linus Torvalds1da177e2005-04-16 15:20:36 -0700427 checkreqprot [SELINUX] Set initial checkreqprot flag value.
428 Format: { "0" | "1" }
429 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700430 0 -- check protection applied by kernel (includes
431 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432 1 -- check protection requested by application.
433 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700434 Value can be changed at runtime via
435 /selinux/checkreqprot.
436
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100437 cio_ignore= [S390]
438 See Documentation/s390/CommonIO for details.
439
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700440 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700441 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200442 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700443 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200444 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 Format: { pit | tsc | cyclone | pmtmr }
446
John Stultz592913e2010-07-13 17:56:20 -0700447 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700448 Format: <string>
449 Override the default clocksource and use the clocksource
450 with the name specified.
451 Some clocksource names to choose from, depending on
452 the platform:
453 [all] jiffies (this is the base, fallback clocksource)
454 [ACPI] acpi_pm
455 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
456 pxa_timer,timer3,32k_counter,timer0_1
457 [AVR32] avr32
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700458 [X86-32] pit,hpet,tsc,vmi-timer;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700459 scx200_hrt on Geode; cyclone on IBM x440
460 [MIPS] MIPS
461 [PARISC] cr16
462 [S390] tod
463 [SH] SuperH
464 [SPARC64] tick
465 [X86-64] hpet,tsc
466
Andi Kleenac72e782008-01-30 13:33:21 +0100467 clearcpuid=BITNUM [X86]
468 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800469 arch/x86/include/asm/cpufeature.h for the valid bit
470 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100471 stable over kernel options, but the vendor specific
472 ones should be.
473 Also note that user programs calling CPUID directly
474 or using the feature without checking anything
475 will still see it. This just prevents it from
476 being used by the kernel or shown in /proc/cpuinfo.
477 Also note the kernel might malfunction if you disable
478 some critical bits.
479
Robert Jennings14f966e2009-04-15 05:55:32 +0000480 cmo_free_hint= [PPC] Format: { yes | no }
481 Specify whether pages are marked as being inactive
482 when they are freed. This is used in CMO environments
483 to determine OS memory pressure for page stealing by
484 a hypervisor.
485 Default: yes
486
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530487 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100488 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100489 Range: 0 - 8192
490 Default: 64
491
Linus Torvalds1da177e2005-04-16 15:20:36 -0700492 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700493 Format:
494 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700495
496 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
497 Format: <io>[,<irq>]
498
Randy Dunlapa9913042005-10-23 12:57:11 -0700499 com90xx= [HW,NET]
500 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700501 Format: <io>[,<irq>[,<memstart>]]
502
503 condev= [HW,S390] console device
504 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700505
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506 console= [KNL] Output console device and options.
507
508 tty<n> Use the virtual console device <n>.
509
510 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800511 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800513 the form "bbbbpnf", where "bbbb" is the baud rate,
514 "p" is parity ("n", "o", or "e"), "n" is number of
515 bits, and "f" is flow control ("r" for RTS or
516 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700517
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800518 See Documentation/serial-console.txt for more
519 information. See
520 Documentation/networking/netconsole.txt for an
521 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700523 uart[8250],io,<addr>[,options]
524 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 Start an early, polled-mode console on the 8250/16550
526 UART at the specified I/O port or MMIO address,
527 switching to the matching ttyS device later. The
528 options are the same as for ttyS, above.
529
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700530 If the device connected to the port is not a TTY but a braille
531 device, prepend "brl," before the device type, for instance
532 console=brl,ttyS0
533 For now, only VisioBraille is supported.
534
Daniel Mackf324edc2009-06-16 15:33:52 -0700535 consoleblank= [KNL] The console blank (screen saver) timeout in
536 seconds. Defaults to 10*60 = 10mins. A value of 0
537 disables the blank timer.
538
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800539 coredump_filter=
540 [KNL] Change the default value for
541 /proc/<pid>/coredump_filter.
542 See also Documentation/filesystems/proc.txt.
543
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700545 Format:
546 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700548 crashkernel=nn[KMG]@ss[KMG]
549 [KNL] Reserve a chunk of physical memory to
550 hold a kernel to switch to with kexec on panic.
551
Bernhard Wallefb391592007-10-18 23:41:02 -0700552 crashkernel=range1:size1[,range2:size2,...][@offset]
553 [KNL] Same as above, but depends on the memory
554 in the running system. The syntax of range is
555 start-[end] where start and end are both
556 a memory unit (amount[KMG]). See also
557 Documentation/kdump/kdump.txt for a example.
558
Linus Torvalds1da177e2005-04-16 15:20:36 -0700559 cs89x0_dma= [HW,NET]
560 Format: <dma>
561
562 cs89x0_media= [HW,NET]
563 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700564
Randy Dunlapa9913042005-10-23 12:57:11 -0700565 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566 See header of drivers/s390/block/dasd_devmap.c.
567
568 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
569 (one device per port)
570 Format: <port#>,<type>
571 See also Documentation/input/joystick-parport.txt
572
573 debug [KNL] Enable kernel debugging (events log level).
574
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700575 debug_locks_verbose=
576 [KNL] verbose self-tests
577 Format=<0|1>
578 Print debugging info while doing the locking API
579 self-tests.
580 We default to 0 (no extra messages), setting it to
581 1 will print _a lot_ more information - normally
582 only useful to kernel developers.
583
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700584 debug_objects [KNL] Enable object debugging
585
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500586 no_debug_objects
587 [KNL] Disable object debugging
588
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200589 debugpat [X86] Enable PAT debugging
590
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200591 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700592 Format: <area>[,<node>]
593 See also Documentation/networking/decnet.txt.
594
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700595 default_hugepagesz=
596 [same as hugepagesz=] The size of the default
597 HugeTLB page size. This is the size represented by
598 the legacy /proc/ hugepages APIs, used for SHM, and
599 default size when mounting hugetlbfs filesystems.
600 Defaults to the default architecture's huge page size
601 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700602
Linus Torvalds1da177e2005-04-16 15:20:36 -0700603 dhash_entries= [KNL]
604 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700605
Linus Torvalds1da177e2005-04-16 15:20:36 -0700606 digi= [HW,SERIAL]
607 IO parameters + enable/disable command.
608
609 digiepca= [HW,SERIAL]
610 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000611 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700612
Brian Haleyb0f83b22010-02-04 13:36:50 -0800613 disable= [IPV6]
614 See Documentation/networking/ipv6.txt.
615
616 disable_ipv6= [IPV6]
617 See Documentation/networking/ipv6.txt.
618
Yinghai Lu95ffa242008-04-29 03:52:33 -0700619 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700620 The kernel tries to adjust MTRR layout from continuous
621 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700622 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700623
Yinghai Lu093af8d2008-01-30 13:33:32 +0100624 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100625 By default the kernel will trim any uncacheable
626 memory out of your available memory pool based on
627 MTRR settings. This parameter disables that behavior,
628 possibly causing your machine to run very slowly.
629
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530630 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700631 Disable PIN 1 of APIC timer
632 Can be useful to work around chipset bugs.
633
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700634 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
635 this option disables the debugging code at boot.
636
637 dma_debug_entries=<number>
638 This option allows to tune the number of preallocated
639 entries for DMA-API debugging code. One entry is
640 required per DMA-API allocation. Use this if the
641 DMA-API debugging code disables itself because the
642 architectural default is too low.
643
Joerg Roedel1745de52009-05-22 21:49:51 +0200644 dma_debug_driver=<driver_name>
645 With this option the DMA-API debugging driver
646 filter feature can be enabled at boot time. Just
647 pass the driver to filter for as the parameter.
648 The filter can be disabled or changed to another
649 driver later using sysfs.
650
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651 dscc4.setup= [NET]
652
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700653 dynamic_printk Enables pr_debug()/dev_dbg() calls if
654 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
655 These can also be switched on/off via
656 <debugfs>/dynamic_printk/modules
657
658 earlycon= [KNL] Output early console device and options.
659 uart[8250],io,<addr>[,options]
660 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700661 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700662 Start an early, polled-mode console on the 8250/16550
663 UART at the specified I/O port or MMIO address.
Samium Gromoff1917ac72010-07-20 15:26:51 -0700664 MMIO inter-register address stride is either 8bit (mmio)
665 or 32bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700666 The options are the same as for ttyS, above.
667
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530668 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700669 earlyprintk=vga
670 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500671 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500672 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700673
Randy Dunlapa9913042005-10-23 12:57:11 -0700674 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700675 takes over.
676
Yinghai Lu5c059172008-07-24 17:29:40 -0700677 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678
679 Currently only ttyS0 and ttyS1 are supported.
680
681 Interaction with the standard serial driver is not
682 very good.
683
684 The VGA output is eventually overwritten by the real
685 console.
686
Jason Wessel97311912010-05-20 21:04:30 -0500687 ekgdboc= [X86,KGDB] Allow early kernel console debugging
688 ekgdboc=kbd
689
690 This is desgined to be used in conjunction with
691 the boot argument: earlyprintk=vga
692
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700694 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700695
Linus Torvalds1da177e2005-04-16 15:20:36 -0700696 eisa_irq_edge= [PARISC,HW]
697 See header of drivers/parisc/eisa.c.
698
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700699 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700700 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700701 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700702
703 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800704 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700705 See Documentation/block/as-iosched.txt and
706 Documentation/block/deadline-iosched.txt for details.
707
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530708 elfcorehdr= [IA64,PPC,SH,X86]
Randy Dunlapa9913042005-10-23 12:57:11 -0700709 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800710 image elf header. Generally kexec loader will
711 pass this option to capture kernel.
712 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700713
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700714 enable_mtrr_cleanup [X86]
715 The kernel tries to adjust MTRR layout from continuous
716 to discrete, to make X server driver able to add WB
717 entry later. This parameter enables that.
718
Randy Dunlapca1eda22009-05-06 16:02:58 -0700719 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700720 Enable PIN 1 of APIC timer
721 Can be useful to work around chipset bugs
722 (in particular on some ATI chipsets).
723 The kernel tries to set a reasonable default.
724
Linus Torvalds1da177e2005-04-16 15:20:36 -0700725 enforcing [SELINUX] Set initial enforcing status.
726 Format: {"0" | "1"}
727 See security/selinux/Kconfig help text.
728 0 -- permissive (log only, no denials).
729 1 -- enforcing (deny and log).
730 Default value is 0.
731 Value can be changed at runtime via /selinux/enforce.
732
Huang Yinga08f82d2010-05-18 14:35:21 +0800733 erst_disable [ACPI]
734 Disable Error Record Serialization Table (ERST)
735 support.
736
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737 ether= [HW,NET] Ethernet cards parameters
738 This option is obsoleted by the "netdev=" option, which
739 has equivalent usage. See its documentation for details.
740
Akinobu Mitade1ba092006-12-08 02:39:42 -0800741 failslab=
742 fail_page_alloc=
743 fail_make_request=[KNL]
744 General fault injection mechanism.
745 Format: <interval>,<probability>,<space>,<times>
746 See also /Documentation/fault-injection/.
747
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000749 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700750
Alex Chiangf13ae302008-05-08 14:03:23 -0600751 force_pal_cache_flush
752 [IA-64] Avoid check_sal_cache_flush which may hang on
753 buggy SAL_CACHE_FLUSH implementations. Using this
754 parameter will force ia64_sal_cache_flush to call
755 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
756
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100757 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400758 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100759 as early as possible in order to facilitate early
760 boot debugging.
761
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200762 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400763 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200764 If no parameter is passed, ftrace will dump
765 buffers of all CPUs, but if you pass orig_cpu, it will
766 dump only the buffer of the CPU that triggered the
767 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400768
769 ftrace_filter=[function-list]
770 [FTRACE] Limit the functions traced by the function
771 tracer at boot up. function-list is a comma separated
772 list of functions. This list can be changed at run
773 time by the set_ftrace_filter file in the debugfs
774 tracing directory.
775
776 ftrace_notrace=[function-list]
777 [FTRACE] Do not trace the functions specified in
778 function-list. This list can be changed at run time
779 by the set_ftrace_notrace file in the debugfs
780 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100781
Stefan Assmann369bc182009-10-12 22:17:21 +0200782 ftrace_graph_filter=[function-list]
783 [FTRACE] Limit the top level callers functions traced
784 by the function graph tracer at boot up.
785 function-list is a comma separated list of functions
786 that can be changed at run time by the
787 set_graph_function file in the debugfs tracing directory.
788
Linus Torvalds1da177e2005-04-16 15:20:36 -0700789 gamecon.map[2|3]=
790 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
791 support via parallel port (up to 5 devices per port)
792 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
793 See also Documentation/input/joystick-parport.txt
794
795 gamma= [HW,DRM]
796
Yinghai Luaaf23042008-01-30 13:33:09 +0100797 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
798 Format: off | on
799 default: on
800
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700801 gcov_persist= [GCOV] When non-zero (default), profiling data for
802 kernel modules is saved and remains accessible via
803 debugfs, even when the module is unloaded/reloaded.
804 When zero, profiling data is discarded and associated
805 debugfs files are removed at module unload time.
806
Linus Torvalds1da177e2005-04-16 15:20:36 -0700807 gpt [EFI] Forces disk with valid GPT signature but
808 invalid Protective MBR to be treated as GPT.
809
Linus Torvalds1da177e2005-04-16 15:20:36 -0700810 hashdist= [KNL,NUMA] Large hashes allocated during boot
811 are distributed across NUMA nodes. Defaults on
Hugh Dickins429aa0f2009-05-06 16:02:51 -0700812 for 64bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700813 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700814
815 hcl= [IA-64] SGI's Hardware Graph compatibility layer
816
817 hd= [EIDE] (E)IDE hard drive subsystem geometry
818 Format: <cyl>,<head>,<sect>
819
Huang Yingea8c0712010-05-18 14:35:15 +0800820 hest_disable [ACPI]
821 Disable Hardware Error Source Table (HEST) support;
822 corresponding firmware-first mode error processing
823 logic will be disabled.
824
Linus Torvalds1da177e2005-04-16 15:20:36 -0700825 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
826 size of <nn>. This works even on boxes that have no
827 highmem otherwise. This also works to reduce highmem
828 size on bigger boxes.
829
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800830 highres= [KNL] Enable/disable high resolution timer mode.
831 Valid parameters: "on", "off"
832 Default: "on"
833
Linus Torvalds1da177e2005-04-16 15:20:36 -0700834 hisax= [HW,ISDN]
835 See Documentation/isdn/README.HiSax.
836
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700837 hlt [BUGS=ARM,SH]
838
839 hpet= [X86-32,HPET] option to control HPET usage
840 Format: { enable (default) | disable | force |
841 verbose }
842 disable: disable HPET and use PIT instead
843 force: allow force enabled of undocumented chips (ICH4,
844 VIA, nVidia)
845 verbose: show contents of HPET registers during setup
846
Andi Kleenb4718e62008-07-23 21:27:51 -0700847 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
848 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700849 On x86-64 and powerpc, this option can be specified
850 multiple times interleaved with hugepages= to reserve
851 huge pages of different sizes. Valid pages sizes on
852 x86-64 are 2M (when the CPU supports "pse") and 1G
853 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700854 Note that 1GB pages can only be allocated at boot time
855 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900856
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100857 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
858 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100859 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
860 If specified, z/VM IUCV HVC accepts connections
861 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100862
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700863 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700864 or register an additional I2C bus that is not
865 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700866 Format:
867 <bus_id>,<clkrate>
868
Jiri Kosina36d95732008-10-06 02:51:09 -0400869 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700870 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200871 i8042.dumbkbd [HW] Pretend that controller can only read data from
872 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700873 (Don't attempt to blink the leds)
874 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500875 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400876 i8042.noloop [HW] Disable the AUX Loopback command while probing
877 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700878 i8042.nomux [HW] Don't check presence of an active multiplexing
879 controller
880 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
881 controllers
Linus Torvalds1da177e2005-04-16 15:20:36 -0700882 i8042.reset [HW] Reset the controller during init and cleanup
883 i8042.unlock [HW] Unlock (ignore) the keylock
884
885 i810= [HW,DRM]
886
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700887 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
888 indicates that the driver is running on unsupported
889 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
891 does not match list of supported models.
892 i8k.power_status
893 [HW] Report power status in /proc/i8k
894 (disabled by default)
895 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
896 capability is set.
897
Linus Torvalds1da177e2005-04-16 15:20:36 -0700898 icn= [HW,ISDN]
899 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
900
David Fries0af80c02009-02-25 20:28:21 +0100901 ide-core.nodma= [HW] (E)IDE subsystem
902 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200903 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
904 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100905 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700906
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700907 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
908 Claim all unknown PCI IDE storage controllers.
909
Andi Kleenf039b752007-05-02 19:27:12 +0200910 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800911 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
912 Poll forces a polling idle loop that can slightly
913 improve the performance of waking up a idle CPU, but
914 will use a lot of power and make the system run hot.
915 Not recommended.
916 idle=mwait: On systems which support MONITOR/MWAIT but
917 the kernel chose to not use it because it doesn't save
918 as much power as a normal idle loop, use the
919 MONITOR/MWAIT idle loop anyways. Performance should be
920 the same as idle=poll.
921 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800922 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800923 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700924
Ingo Molnar792908222006-12-06 20:40:51 -0800925 ignore_loglevel [KNL]
926 Ignore loglevel setting - this will print /all/
927 kernel messages to the console. Useful for debugging.
928
Linus Torvalds1da177e2005-04-16 15:20:36 -0700929 ihash_entries= [KNL]
930 Set number of hash buckets for inode cache.
931
Mimi Zohar3323eec2009-02-04 09:06:58 -0500932 ima_audit= [IMA]
933 Format: { "0" | "1" }
934 0 -- integrity auditing messages. (Default)
935 1 -- enable informational integrity auditing messages.
936
937 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -0700938 Format: { "sha1" | "md5" }
Mimi Zohar3323eec2009-02-04 09:06:58 -0500939 default: "sha1"
940
Eric Paris5789ba32009-05-21 15:47:06 -0400941 ima_tcb [IMA]
942 Load a policy which meets the needs of the Trusted
943 Computing Base. This means IMA will measure all
944 programs exec'd, files mmap'd for exec, and all files
945 opened for read by uid=0.
946
Linus Torvalds1da177e2005-04-16 15:20:36 -0700947 init= [KNL]
948 Format: <full_path>
949 Run specified binary instead of /sbin/init as init
950 process.
951
952 initcall_debug [KNL] Trace initcalls as they are executed. Useful
953 for working out where the kernel is dying during
954 startup.
955
956 initrd= [BOOT] Specify the location of the initial ramdisk
957
958 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
959 Format: <irq>
960
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700961 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -0800962 on
963 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700964 off
965 Disable intel iommu driver.
966 igfx_off [Default Off]
967 By default, gfx is mapped as normal device. If a gfx
968 device has a dedicated DMAR unit, the DMAR unit is
969 bypassed by not enabling DMAR with this option. In
970 this case, gfx device will use physical address for
971 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700972 forcedac [x86_64]
973 With this option iommu will not optimize to look
974 for io virtual address below 32 bit forcing dual
975 address cycle on pci bus for cards supporting greater
976 than 32 bit addressing. The default is to look
977 for translation below 32 bit and if not available
978 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -0800979 strict [Default Off]
980 With this option on every unmap_single operation will
981 result in a hardware IOTLB flush operation as opposed
982 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700983
Chris Wrightd1423d52010-07-20 11:06:49 -0700984 intremap= [X86-64, Intel-IOMMU]
985 Format: { on (default) | off | nosid }
986 on enable Interrupt Remapping (default)
987 off disable Interrupt Remapping
988 nosid disable Source ID checking
989
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700990 inttest= [IA64]
991
992 iomem= Disable strict checking of access to MMIO memory
993 strict regions from userspace.
994 relaxed
995
996 iommu= [x86]
997 off
998 force
999 noforce
1000 biomerge
1001 panic
1002 nopanic
1003 merge
1004 nomerge
1005 forcesac
1006 soft
Fenghua Yu4ed0d3e2009-04-24 17:30:20 -07001007 pt [x86, IA64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001008
1009 io7= [HW] IO7 for Marvel based alpha systems
1010 See comment before marvel_specify_io7 in
1011 arch/alpha/kernel/core_marvel.c.
1012
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301013 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001014 0x80
1015 Standard port 0x80 based delay
1016 0xed
1017 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001018 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001019 Simple two microseconds delay
1020 none
1021 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001022
Linus Torvalds1da177e2005-04-16 15:20:36 -07001023 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001024 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001025
1026 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001027 See comment before ip2_setup() in
1028 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001029
Alan Cox200803d2005-06-28 20:45:18 -07001030 irqfixup [HW]
1031 When an interrupt is not handled search all handlers
1032 for it. Intended to get systems with badly broken
1033 firmware running.
1034
1035 irqpoll [HW]
1036 When an interrupt is not handled search all handlers
1037 for it. Also check all handlers each timer
1038 interrupt. Intended to get systems with badly broken
1039 firmware running.
1040
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001042 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043
1044 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001045 Format:
1046 <cpu number>,...,<cpu number>
1047 or
Li Zefanb225d442008-11-06 12:53:39 -08001048 <cpu number>-<cpu number>
1049 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001050 or a mixture
1051 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001052
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053 This option can be used to specify one or more CPUs
1054 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001055 algorithms. You can move a process onto or off an
1056 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001057 <cpu number> begins at 0 and the maximum value is
1058 "number of CPUs in system - 1".
1059
1060 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001061 alternative -- manually setting the CPU mask of all
1062 tasks in the system -- can cause problems and
1063 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001064
Randy Dunlapa9913042005-10-23 12:57:11 -07001065 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066
1067 js= [HW,JOY] Analog joystick
1068 See Documentation/input/joystick.txt.
1069
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001070 keepinitrd [HW,ARM]
1071
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301072 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001073 specifies the amount of memory usable by the kernel
1074 for non-movable allocations. The requested amount is
1075 spread evenly throughout all nodes in the system. The
1076 remaining memory in each node is used for Movable
1077 pages. In the event, a node is too small to have both
1078 kernelcore and Movable pages, kernelcore pages will
1079 take priority and other nodes will have a larger number
1080 of kernelcore pages. The Movable zone is used for the
1081 allocation of pages that may be reclaimed or moved
1082 by the page migration subsystem. This means that
1083 HugeTLB pages may not be allocated from this zone.
1084 Note that allocations like PTEs-from-HighMem still
1085 use the HighMem zone if it exists, and the Normal
1086 zone if it does not.
1087
Jason Wessel4fe1da42010-05-20 21:04:31 -05001088 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1089 Format: <Controller#>[,poll interval]
1090 The controller # is the number of the ehci usb debug
1091 port as it is probed via PCI. The poll interval is
1092 optional and is the number seconds in between
1093 each poll cycle to the debug port in case you need
1094 the functionality for interrupting the kernel with
1095 gdb or control-c on the dbgp connection. When
1096 not using this parameter you use sysrq-g to break into
1097 the kernel debugger.
1098
Jason Wessel84c08fd2010-05-20 21:04:24 -05001099 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001100 Requires a tty driver that supports console polling,
1101 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001102 Serial only format: <serial_device>[,baud]
1103 keyboard only format: kbd
1104 keyboard and serial format: kbd,<serial_device>[,baud]
1105 Optional Kernel mode setting:
1106 kms, kbd format: kms,kbd
1107 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001108
Jason Wessel84c08fd2010-05-20 21:04:24 -05001109 kgdbwait [KGDB] Stop kernel execution and enter the
1110 kernel debugger at the earliest opportunity.
1111
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001112 kmac= [MIPS] korina ethernet MAC address.
1113 Configure the RouterBoard 532 series on-chip
1114 Ethernet adapter MAC address.
1115
Catalin Marinas04f70332009-06-11 13:22:39 +01001116 kmemleak= [KNL] Boot-time kmemleak enable/disable
1117 Valid arguments: on, off
1118 Default: on
1119
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301120 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001121 in oops dumps.
1122
Andre Przywarafef07aa2009-07-10 14:20:35 +02001123 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1124 Default is 0 (don't ignore, but inject #GP)
1125
1126 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1127 Default is 1 (enabled)
1128
1129 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1130 Default is 0 (off)
1131
1132 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1133 for all guests.
1134 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1135
1136 kvm-intel.bypass_guest_pf=
1137 [KVM,Intel] Disables bypassing of guest page faults
1138 on Intel chips. Default is 1 (enabled)
1139
1140 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1141 (virtualized MMU) support on capable Intel chips.
1142 Default is 1 (enabled)
1143
1144 kvm-intel.emulate_invalid_guest_state=
1145 [KVM,Intel] Enable emulation of invalid guest states
1146 Default is 0 (disabled)
1147
1148 kvm-intel.flexpriority=
1149 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1150 Default is 1 (enabled)
1151
1152 kvm-intel.unrestricted_guest=
1153 [KVM,Intel] Disable unrestricted guest feature
1154 (virtualized real and unpaged mode) on capable
1155 Intel chips. Default is 1 (enabled)
1156
1157 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1158 feature (tagged TLBs) on capable Intel chips.
1159 Default is 1 (enabled)
1160
Linus Torvalds1da177e2005-04-16 15:20:36 -07001161 l2cr= [PPC]
1162
Robert Brosea78bfbf2008-03-29 07:20:23 +11001163 l3cr= [PPC]
1164
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001165 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001166 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001167
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301168 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001169 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001170
FD Camifcb71f62008-01-06 19:08:56 +01001171 libata.dma= [LIBATA] DMA control
1172 libata.dma=0 Disable all PATA and SATA DMA
1173 libata.dma=1 PATA and SATA Disk DMA only
1174 libata.dma=2 ATAPI (CDROM) DMA only
1175 libata.dma=4 Compact Flash DMA only
1176 Combinations also work, so libata.dma=3 enables DMA
1177 for disks and CDROMs, but not CFs.
Michael Prokop20308872009-08-06 00:14:10 +02001178
1179 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1180 libata.ignore_hpa=0 keep BIOS limits (default)
1181 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001182
Dave Jones78e70c22007-09-27 11:50:13 -04001183 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1184 when set.
1185 Format: <int>
1186
Tejun Heo33267322008-02-13 09:15:09 +09001187 libata.force= [LIBATA] Force configurations. The format is comma
1188 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f3092010-04-21 12:17:12 +02001189 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001190 matching port, link or device. Basically, it matches
1191 the ATA ID string printed on console by libata. If
1192 the whole ID part is omitted, the last PORT and DEVICE
1193 values are used. If ID hasn't been specified yet, the
1194 configuration applies to all ports, links and devices.
1195
1196 If only DEVICE is omitted, the parameter applies to
1197 the port and all links and devices behind it. DEVICE
1198 number of 0 either selects the first device or the
1199 first fan-out link behind PMP device. It does not
1200 select the host link. DEVICE number of 15 selects the
1201 host link and device attached to it.
1202
1203 The VAL specifies the configuration to force. As long
1204 as there's no ambiguity shortcut notation is allowed.
1205 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1206 The following configurations can be forced.
1207
1208 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1209 Any ID with matching PORT is used.
1210
1211 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1212
1213 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1214 udma[/][16,25,33,44,66,100,133] notation is also
1215 allowed.
1216
1217 * [no]ncq: Turn on or off NCQ.
1218
Tejun Heo05944bd2008-08-13 20:19:09 +09001219 * nohrst, nosrst, norst: suppress hard, soft
1220 and both resets.
1221
Tejun Heo43c9c592010-05-23 12:59:11 +02001222 * dump_id: dump IDENTIFY data.
1223
Tejun Heo33267322008-02-13 09:15:09 +09001224 If there are multiple matching configurations changing
1225 the same attribute, the last one is used.
1226
Yinghai Lu95f72d12010-07-12 14:36:09 +10001227 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001228
Linus Torvalds1da177e2005-04-16 15:20:36 -07001229 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001230 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001231
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001232 lockd.nlm_grace_period=P [NFS] Assign grace period.
1233 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001234
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001235 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1236 Format: <integer>
1237
1238 lockd.nlm_timeout=T [NFS] Assign timeout value.
1239 Format: <integer>
1240
1241 lockd.nlm_udpport=M [NFS] Assign UDP port.
1242 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001243
1244 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1245 Format: <irq>
1246
1247 loglevel= All Kernel Messages with a loglevel smaller than the
1248 console loglevel will be printed to the console. It can
1249 also be changed with klogd or other programs. The
1250 loglevels are defined as follows:
1251
1252 0 (KERN_EMERG) system is unusable
1253 1 (KERN_ALERT) action must be taken immediately
1254 2 (KERN_CRIT) critical conditions
1255 3 (KERN_ERR) error conditions
1256 4 (KERN_WARNING) warning conditions
1257 5 (KERN_NOTICE) normal but significant condition
1258 6 (KERN_INFO) informational
1259 7 (KERN_DEBUG) debug-level messages
1260
1261 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001262 Format: { n | nk | nM }
1263 n must be a power of two. The default size
1264 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265
Randy Dunlapaccaa242007-10-16 01:29:37 -07001266 logo.nologo [FB] Disables display of the built-in Linux logo.
1267 This may be used to provide more screen space for
1268 kernel log messages and is useful when debugging
1269 kernel boot problems.
1270
Linus Torvalds1da177e2005-04-16 15:20:36 -07001271 lp=0 [LP] Specify parallel ports to use, e.g,
1272 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1273 lp=reset first parallel port). 'lp=0' disables the
1274 lp=auto printer driver. 'lp=reset' (which can be
1275 specified in addition to the ports) causes
1276 attached printers to be reset. Using
1277 lp=port1,port2,... specifies the parallel ports
1278 to associate lp devices with, starting with
1279 lp0. A port specification may be 'none' to skip
1280 that lp device, or a parport name such as
1281 'parport0'. Specifying 'lp=auto' instead of a
1282 port specification list means that device IDs
1283 from each port should be examined, to see if
1284 an IEEE 1284-compliant printer is attached; if
1285 so, the driver will manage that printer.
1286 See also header of drivers/char/lp.c.
1287
1288 lpj=n [KNL]
1289 Sets loops_per_jiffy to given constant, thus avoiding
1290 time-consuming boot-time autodetection (up to 250 ms per
1291 CPU). 0 enables autodetection (default). To determine
1292 the correct value for your kernel, boot with normal
1293 autodetection and see what value is printed. Note that
1294 on SMP systems the preset will be applied to all CPUs,
1295 which is likely to cause problems if your CPUs need
1296 significantly divergent settings. An incorrect value
1297 will cause delays in the kernel to be wrong, leading to
1298 unpredictable I/O errors and other breakage. Although
1299 unlikely, in the extreme case this might damage your
1300 hardware.
1301
1302 ltpc= [NET]
1303 Format: <io>,<irq>,<dma>
1304
Randy Dunlapa9913042005-10-23 12:57:11 -07001305 machvec= [IA64] Force the use of a particular machine-vector
1306 (machvec) in a generic kernel.
1307 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001308
Wu Zhangjin3209e702009-07-02 23:27:12 +08001309 machtype= [Loongson] Share the same kernel image file between different
1310 yeeloong laptop.
1311 Example: machtype=lemote-yeeloong-2f-7inch
1312
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001313 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1314 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001315
1316 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001317 should make use of. maxcpus=n : n >= 0 limits the
1318 kernel to using 'n' processors. n=0 is a special case,
1319 it is equivalent to "nosmp", which also disables
1320 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001321
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001322 max_loop= [LOOP] Maximum number of loopback devices that can
1323 be mounted
1324 Format: <1-256>
Bob Picco2b2c3752005-06-29 18:00:00 -07001325
Linus Torvalds1da177e2005-04-16 15:20:36 -07001326 mcatest= [IA-64]
1327
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001328 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001329
Uwe Hermann71cced62008-10-20 09:32:21 -07001330 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001331
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332 md= [HW] RAID subsystems devices and level
1333 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001334
Linus Torvalds1da177e2005-04-16 15:20:36 -07001335 mdacon= [MDA]
1336 Format: <first>,<last>
1337 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001338
Linus Torvalds1da177e2005-04-16 15:20:36 -07001339 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1340 Amount of memory to be used when the kernel is not able
1341 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001342 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001343 address space collisions. Without memmap= PCI devices
1344 could be placed at addresses belonging to unused RAM.
1345
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001346 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347 memory.
1348
Paul Mundt6902aa82008-09-21 17:14:42 +09001349 memchunk=nn[KMG]
1350 [KNL,SH] Allow user to override the default size for
1351 per-device physically contiguous DMA buffers.
1352
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301353 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001354 E820 memory map, as specified by the user.
1355 Such memmap=exactmap lines can be constructed based on
1356 BIOS output or other requirements. See the memmap=nn@ss
1357 option description.
1358
1359 memmap=nn[KMG]@ss[KMG]
1360 [KNL] Force usage of a specific region of memory
1361 Region of memory to be used, from ss to ss+nn.
1362
1363 memmap=nn[KMG]#ss[KMG]
1364 [KNL,ACPI] Mark specific memory as ACPI data.
1365 Region of memory to be used, from ss to ss+nn.
1366
1367 memmap=nn[KMG]$ss[KMG]
1368 [KNL,ACPI] Mark specific memory as reserved.
1369 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001370 Example: Exclude memory from 0x18690000-0x1869ffff
1371 memmap=64K$0x18690000
1372 or
1373 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001374
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001375 memory_corruption_check=0/1 [X86]
1376 Some BIOSes seem to corrupt the first 64k of
1377 memory when doing things like suspend/resume.
1378 Setting this option will scan the memory
1379 looking for corruption. Enabling this will
1380 both detect corruption and prevent the kernel
1381 from using the memory being corrupted.
1382 However, its intended as a diagnostic tool; if
1383 repeatable BIOS-originated corruption always
1384 affects the same memory, you can use memmap=
1385 to prevent the kernel from using that memory.
1386
1387 memory_corruption_check_size=size [X86]
1388 By default it checks for corruption in the low
1389 64k, making this memory unavailable for normal
1390 use. Use this parameter to scan for
1391 corruption in more or less memory.
1392
1393 memory_corruption_check_period=seconds [X86]
1394 By default it checks for corruption every 60
1395 seconds. Use this parameter to check at some
1396 other rate. 0 disables periodic checking.
1397
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001398 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001399 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001400 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001401 Specifies the number of memtest passes to be
1402 performed. Each pass selects another test
1403 pattern from a given set of patterns. Memtest
1404 fills the memory with this pattern, validates
1405 memory contents and reserves bad memory
1406 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001407
Linus Torvalds1da177e2005-04-16 15:20:36 -07001408 meye.*= [HW] Set MotionEye Camera parameters
1409 See Documentation/video4linux/meye.txt.
1410
Andres Salomon8f368812007-10-12 23:04:06 +02001411 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1412 Multi-Function General Purpose Timers on AMD Geode
1413 platforms.
1414
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001415 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1416 the BIOS has incorrectly applied a workaround. TinyBIOS
1417 version 0.98 is known to be affected, 0.99 fixes the
1418 problem by letting the user disable the workaround.
1419
Linus Torvalds1da177e2005-04-16 15:20:36 -07001420 mga= [HW,DRM]
1421
Randy Dunlap1c207f92008-11-19 15:36:16 -08001422 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1423 physical address is ignored.
1424
Michel Pollet39f45d72009-05-20 11:10:31 +01001425 mini2440= [ARM,HW,KNL]
1426 Format:[0..2][b][c][t]
1427 Default: "0tb"
1428 MINI2440 configuration specification:
1429 0 - The attached screen is the 3.5" TFT
1430 1 - The attached screen is the 7" TFT
1431 2 - The VGA Shield is attached (1024x768)
1432 Leaving out the screen size parameter will not load
1433 the TFT driver, and the framebuffer will be left
1434 unconfigured.
1435 b - Enable backlight. The TFT backlight pin will be
1436 linked to the kernel VESA blanking code and a GPIO
1437 LED. This parameter is not necessary when using the
1438 VGA shield.
1439 c - Enable the s3c camera interface.
1440 t - Reserved for enabling touchscreen support. The
1441 touchscreen support is not enabled in the mainstream
1442 kernel as of 2.6.30, a preliminary port can be found
1443 in the "bleeding edge" mini2440 support kernel at
1444 http://repo.or.cz/w/linux-2.6/mini2440.git
1445
Mel Gorman6b74ab92008-07-23 21:26:49 -07001446 mminit_loglevel=
1447 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1448 parameter allows control of the logging verbosity for
1449 the additional memory initialisation checks. A value
1450 of 0 disables mminit logging and a level of 4 will
1451 log everything. Information is printed at KERN_DEBUG
1452 so loglevel=8 may also need to be specified.
1453
Linus Torvalds1da177e2005-04-16 15:20:36 -07001454 mousedev.tap_time=
1455 [MOUSE] Maximum time between finger touching and
1456 leaving touchpad surface for touch to be considered
1457 a tap and be reported as a left button click (for
1458 touchpads working in absolute mode only).
1459 Format: <msecs>
1460 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1461 reporting absolute coordinates, such as tablets
1462 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1463 reporting absolute coordinates, such as tablets
1464
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301465 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001466 is similar to kernelcore except it specifies the
1467 amount of memory used for migratable allocations.
1468 If both kernelcore and movablecore is specified,
1469 then kernelcore will be at *least* the specified
1470 value but may be more. If movablecore on its own
1471 is specified, the administrator must be careful
1472 that the amount of memory usable for all allocations
1473 is not too small.
1474
Linus Torvalds1da177e2005-04-16 15:20:36 -07001475 MTD_Partition= [MTD]
1476 Format: <name>,<region-number>,<size>,<offset>
1477
Randy Dunlapa9913042005-10-23 12:57:11 -07001478 MTD_Region= [MTD] Format:
1479 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001480
1481 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001482 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001483
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001484 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1485
1486 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1487
1488 boundary - index of last SLC block on Flex-OneNAND.
1489 The remaining blocks are configured as MLC blocks.
1490 lock - Configure if Flex-OneNAND boundary should be locked.
1491 Once locked, the boundary cannot be changed.
1492 1 indicates lock status, 0 indicates unlock status.
1493
Ben Dooks9db829f2008-07-03 11:24:29 +01001494 mtdset= [ARM]
1495 ARM/S3C2412 JIVE boot control
1496
1497 See arch/arm/mach-s3c2412/mach-jive.c
1498
Linus Torvalds1da177e2005-04-16 15:20:36 -07001499 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001500 [HW] Make the MicroTouch USB driver use raw coordinates
1501 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001502
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001503 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001504 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001505 that could hold holes aka. UC entries.
1506
1507 mtrr_gran_size=nn[KMG] [X86]
1508 Used for mtrr cleanup. It is granularity of mtrr block.
1509 Default is 1.
1510 Large value could prevent small alignment from
1511 using up MTRRs.
1512
1513 mtrr_spare_reg_nr=n [X86]
1514 Format: <integer>
1515 Range: 0,7 : spare reg number
1516 Default : 1
1517 Used for mtrr cleanup. It is spare mtrr entries number.
1518 Set to 2 or more if your graphical card needs more.
1519
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1521
Linus Torvalds1da177e2005-04-16 15:20:36 -07001522 netdev= [NET] Network devices parameters
1523 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1524 Note that mem_start is often overloaded to mean
1525 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001526 This usage is only documented in each driver source
1527 file if at all.
1528
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001529 nf_conntrack.acct=
1530 [NETFILTER] Enable connection tracking flow accounting
1531 0 to disable accounting
1532 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001533 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001534
Linus Torvalds1da177e2005-04-16 15:20:36 -07001535 nfsaddrs= [NFS]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001536 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001537
1538 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001539 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001540
Trond Myklebusta72b4422006-01-03 09:55:41 +01001541 nfs.callback_tcpport=
1542 [NFS] set the TCP port on which the NFSv4 callback
1543 channel should listen.
1544
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001545 nfs.cache_getent=
1546 [NFS] sets the pathname to the program which is used
1547 to update the NFS client cache entries.
1548
1549 nfs.cache_getent_timeout=
1550 [NFS] sets the timeout after which an attempt to
1551 update a cache entry is deemed to have failed.
1552
Trond Myklebust58df0952006-01-03 09:55:57 +01001553 nfs.idmap_cache_timeout=
1554 [NFS] set the maximum lifetime for idmapper cache
1555 entries.
1556
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001557 nfs.enable_ino64=
1558 [NFS] enable 64-bit inode numbers.
1559 If zero, the NFS client will fake up a 32-bit inode
1560 number for the readdir() and stat() syscalls instead
1561 of returning the full 64-bit number.
1562 The default is to return 64-bit inode numbers.
1563
Paul Mundt1e1030d2009-09-01 17:38:32 +09001564 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001565 when a NMI is triggered.
1566 Format: [state][,regs][,debounce][,die]
1567
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301568 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001569 Format: [panic,][num]
1570 Valid num: 0,1,2
1571 0 - turn nmi_watchdog off
1572 1 - use the IO-APIC timer for the NMI watchdog
1573 2 - use the local APIC for the NMI watchdog using
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001574 a performance counter. Note: This will use one
1575 performance counter and the local APIC's performance
1576 vector.
1577 When panic is specified, panic when an NMI watchdog
1578 timeout occurs.
1579 This is useful when you use a panic=... timeout and
1580 need the box quickly up again.
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001581 Instead of 1 and 2 it is possible to use the following
1582 symbolic names: lapic and ioapic
1583 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
Linus Torvalds1da177e2005-04-16 15:20:36 -07001584
Anton Vorontsovbff38772009-07-08 11:10:56 -07001585 netpoll.carrier_timeout=
1586 [NET] Specifies amount of time (in seconds) that
1587 netpoll should wait for a carrier. By default netpoll
1588 waits 4 seconds.
1589
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001590 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001591 emulation library even if a 387 maths coprocessor
1592 is present.
1593
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001594 no_console_suspend
1595 [HW] Never suspend the console
1596 Disable suspending of consoles during suspend and
1597 hibernate operations. Once disabled, debugging
1598 messages can reach various consoles while the rest
1599 of the system is being put to sleep (ie, while
1600 debugging driver suspend/resume hooks). This may
1601 not work reliably with all consoles, but is known
1602 to work with serial and VGA consoles.
1603
Christoph Lameterc1aee212007-05-31 00:40:47 -07001604 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1605 caches in the slab allocator. Saves per-node memory,
1606 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001607
Randy Dunlapa9913042005-10-23 12:57:11 -07001608 noalign [KNL,ARM]
1609
Linus Torvalds1da177e2005-04-16 15:20:36 -07001610 noapic [SMP,APIC] Tells the kernel to not make use of any
1611 IOAPICs that may be present in the system.
1612
Linus Torvalds1da177e2005-04-16 15:20:36 -07001613 nobats [PPC] Do not use BATs for mapping kernel lowmem
1614 on "Classic" PPC cores.
1615
1616 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001617
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001618 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1619
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001620 nodelayacct [KNL] Disable per-task delay accounting
1621
Linus Torvalds1da177e2005-04-16 15:20:36 -07001622 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1623
Paul Mundt6902aa82008-09-21 17:14:42 +09001624 nodsp [SH] Disable hardware DSP at boot time.
1625
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301626 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001627
Linus Torvalds1da177e2005-04-16 15:20:36 -07001628 noexec [IA-64]
1629
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301630 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001631 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001632 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001633 noexec=off: disable non-executable mappings
1634
1635 noexec32 [X86-64]
1636 This affects only 32-bit executables.
1637 noexec32=on: enable non-executable mappings (default)
1638 read doesn't imply executable mappings
1639 noexec32=off: disable non-executable mappings
1640 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001641
Paul Mundt6902aa82008-09-21 17:14:42 +09001642 nofpu [SH] Disable hardware FPU at boot time.
1643
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001644 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001645 register save and restore. The kernel will only save
1646 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001647
Suresh Siddha0c752a92009-05-22 12:17:45 -07001648 noxsave [BUGS=X86] Disables x86 extended register state save
1649 and restore using xsave. The kernel will fallback to
1650 enabling legacy floating-point and sse state.
1651
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001652 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1653 wfi(ARM) instruction doesn't work correctly and not to
1654 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001655
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001656 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001657 instruction doesn't work correctly and not to
1658 use it.
1659
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001660 no_file_caps Tells the kernel not to honor file capabilities. The
1661 only way then for a file to be executed with privilege
1662 is to be setuid root or executed by root.
1663
Linus Torvalds1da177e2005-04-16 15:20:36 -07001664 nohalt [IA-64] Tells the kernel not to use the power saving
1665 function PAL_HALT_LIGHT when idle. This increases
1666 power-consumption. On the positive side, it reduces
1667 interrupt wake-up latency, which may improve performance
1668 in certain environments such as networked servers or
1669 real-time systems.
1670
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001671 nohz= [KNL] Boottime enable/disable dynamic ticks
1672 Valid arguments: on, off
1673 Default: on
1674
Paul Mundteeee7852009-04-02 12:31:16 +09001675 noiotrap [SH] Disables trapped I/O port accesses.
1676
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001677 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001678 disable unhandled interrupt sources.
1679
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301680 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001681 broken timer IRQ sources.
1682
Linus Torvalds1da177e2005-04-16 15:20:36 -07001683 noisapnp [ISAPNP] Disables ISA PnP code.
1684
1685 noinitrd [RAM] Tells the kernel not to load any configured
1686 initial RAM disk.
1687
Weidong Han03ea8152009-04-17 16:42:15 +08001688 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1689 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07001690 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08001691
Linus Torvalds1da177e2005-04-16 15:20:36 -07001692 nointroute [IA-64]
1693
Tony Luck0aa366f2007-07-20 11:22:30 -07001694 nojitter [IA64] Disables jitter checking for ITC timers.
1695
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001696 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001697
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001698 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001699
Linus Torvalds1da177e2005-04-16 15:20:36 -07001700 noltlbs [PPC] Do not use large page/tlb entries for kernel
1701 lowmem mapping on PPC40x.
1702
Horms312f1f02006-02-22 09:57:55 +09001703 nomca [IA-64] Disable machine check abort handling
1704
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001705 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001706
Andres Salomon83d73842007-10-12 23:04:06 +02001707 nomfgpt [X86-32] Disable Multi-Function General Purpose
1708 Timer usage (for AMD Geode machines).
1709
Jiri Kosina016ddd92010-01-18 17:05:40 +01001710 nopat [X86] Disable PAT (page attribute table extension of
1711 pagetables) support.
1712
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001713 norandmaps Don't use address space randomization. Equivalent to
1714 echo 0 > /proc/sys/kernel/randomize_va_space
1715
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001716 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001717
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001718 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001719 with UP alternatives
1720
Linus Torvalds1da177e2005-04-16 15:20:36 -07001721 noresidual [PPC] Don't use residual data on PReP machines.
1722
Randy Dunlapa9913042005-10-23 12:57:11 -07001723 noresume [SWSUSP] Disables resume and restores original swap
1724 space.
1725
Linus Torvalds1da177e2005-04-16 15:20:36 -07001726 no-scroll [VGA] Disables scrollback.
1727 This is required for the Braillex ib80-piezo Braille
1728 reader made by F.H. Papenmeier (Germany).
1729
1730 nosbagart [IA-64]
1731
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001732 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001733
Len Brown61ec7562007-08-16 03:34:22 -04001734 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1735 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001736
Dave Jones97842212007-07-15 23:41:05 -07001737 nosoftlockup [KNL] Disable the soft-lockup detector.
1738
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001739 noswapaccount [KNL] Disable accounting of swap in memory resource
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01001740 controller. (See Documentation/cgroups/memory.txt)
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001741
Linus Torvalds1da177e2005-04-16 15:20:36 -07001742 nosync [HW,M68K] Disables sync negotiation for all devices.
1743
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001744 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001745
1746 nousb [USB] Disable the USB subsystem
1747
Don Zickus58687ac2010-05-07 17:11:44 -04001748 nowatchdog [KNL] Disable the lockup detector.
1749
Linus Torvalds1da177e2005-04-16 15:20:36 -07001750 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001751
Weidong Han2b2fd872009-04-17 16:42:12 +08001752 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1753
Fenghua Yua6c75b862008-03-14 13:57:08 -07001754 nptcg= [IA64] Override max number of concurrent global TLB
1755 purges which is reported from either PAL_VM_SUMMARY or
1756 SAL PALO.
1757
Yinghai Lu2b633e32010-02-10 01:20:37 -08001758 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1759 could support. nr_cpus=n : n >= 1 limits the kernel to
1760 supporting 'n' processors. Later in runtime you can not
1761 use hotplug cpu feature to put more cpu back to online.
1762 just like you compile the kernel NR_CPUS=n
1763
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001764 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1765
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001766 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1767 one of ['zone', 'node', 'default'] can be specified
1768 This can be set from sysctl after boot.
1769 See Documentation/sysctl/vm.txt for details.
1770
Randy Dunlap7c4be252009-01-06 14:42:44 -08001771 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1772 See Documentation/debugging-via-ohci1394.txt for more
1773 info.
1774
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001775 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1776 Rather than timing out after 20 ms if an EC
1777 command is not properly ACKed, override the length
1778 of the timeout. We have interrupts disabled while
1779 waiting for the ACK, so if this is set too high
1780 interrupts *may* be lost!
1781
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001782 omap_mux= [OMAP] Override bootloader pin multiplexing.
1783 Format: <mux_mode0.mode_name=value>...
1784 For example, to override I2C bus2:
1785 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1786
Linus Torvalds1da177e2005-04-16 15:20:36 -07001787 oprofile.timer= [HW]
1788 Use timer interrupt instead of performance counters
1789
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001790 oprofile.cpu_type= Force an oprofile cpu type
1791 This might be useful if you have an older oprofile
1792 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001793 Format: { arch_perfmon }
1794 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001795 perfmon on Intel CPUs instead of the
1796 CPU specific event set.
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001797
Randy Dunlapbcfde332010-06-07 17:10:38 -07001798 OSS [HW,OSS]
1799 See Documentation/sound/oss/oss-parameters.txt
1800
Linus Torvalds1da177e2005-04-16 15:20:36 -07001801 panic= [KNL] Kernel behaviour on panic
1802 Format: <timeout>
1803
1804 parkbd.port= [HW] Parallel port number the keyboard adapter is
1805 connected to, default is 0.
1806 Format: <parport#>
1807 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1808 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001809 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001810
Randy Dunlapa9913042005-10-23 12:57:11 -07001811 parport= [HW,PPT] Specify parallel ports. 0 disables.
1812 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1813 Use 'auto' to force the driver to use any
1814 IRQ/DMA settings detected (the default is to
1815 ignore detected IRQ/DMA settings because of
1816 possible conflicts). You can specify the base
1817 address, IRQ, and DMA settings; IRQ and DMA
1818 should be numbers, or 'auto' (for using detected
1819 settings on that particular port), or 'nofifo'
1820 (to avoid using a FIFO even if it is detected).
1821 Parallel ports are assigned in the order they
1822 are specified on the command line, starting
1823 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001824
Randy Dunlapa9913042005-10-23 12:57:11 -07001825 parport_init_mode= [HW,PPT]
1826 Configure VIA parallel port to operate in
1827 a specific mode. This is necessary on Pegasos
1828 computer where firmware has no options for setting
1829 up parallel port mode and sets it to spp.
1830 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001831 Format: [spp|ps2|epp|ecp|ecpepp]
1832
Andrew Mortondd287792006-03-23 03:00:57 -08001833 pause_on_oops=
1834 Halt all CPUs after the first oops has been printed for
1835 the specified number of seconds. This is to be used if
1836 your oopses keep scrolling off the screen.
1837
Linus Torvalds1da177e2005-04-16 15:20:36 -07001838 pcbit= [HW,ISDN]
1839
1840 pcd. [PARIDE]
1841 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001842 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001843
Randy Dunlapa9913042005-10-23 12:57:11 -07001844 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001845 earlydump [X86] dump PCI config space before the kernel
1846 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001847 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001848 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001849 the hardware directly. Use this if your machine
1850 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001851 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001852 hardware access methods are allowed. Use this
1853 if you experience crashes upon bootup and you
1854 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001855 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001856 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001857 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001858 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001859 noaer [PCIE] If the PCIEAER kernel config parameter is
1860 enabled, this kernel boot option can be used to
1861 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001862 nodomains [PCI] Disable support for multiple PCI
1863 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301864 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001865 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02001866 check_enable_amd_mmconf [X86] check for and enable
1867 properly configured MMIO access to PCI
1868 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001869 nomsi [MSI] If the PCI_MSI kernel config parameter is
1870 enabled, this kernel boot option can be used to
1871 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001872 noioapicquirk [APIC] Disable all boot interrupt quirks.
1873 Safety option to keep boot IRQs enabled. This
1874 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001875 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1876 primary IO-APIC for bridges that cannot disable
1877 boot IRQs. This fixes a source of spurious IRQs
1878 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001879 noioapicreroute [APIC] Disable workaround that uses the
1880 boot IRQ equivalent of an IRQ that connects to
1881 a chipset where boot IRQs cannot be disabled.
1882 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001883 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001884 routing table. These calls are known to be buggy
1885 on several machines and they hang the machine
1886 when used, but on other computers it's the only
1887 way to get the interrupt routing table. Try
1888 this option if the kernel is unable to allocate
1889 IRQs or discover secondary PCI buses on your
1890 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001891 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001892 Use with caution as certain devices share
1893 address decoders between ROMs and other
1894 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001895 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001896 expansion ROMs that do not already have
1897 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07001898 nobar [X86] Do not assign address space to the
1899 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001900 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001901 assigned automatically to PCI devices. You can
1902 make the kernel exclude IRQs of your ISA cards
1903 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001904 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001905 of the PIRQ table (normally generated
1906 by the BIOS) if it is outside the
1907 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001908 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001909 useful if the kernel is unable to find your
1910 secondary buses and you want to tell it
1911 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001912 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001913 numbers ourselves, overriding
1914 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001915 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001916 in the BIOS $PIR table. This is needed on
1917 some systems with broken BIOSes, notably
1918 some HP Pavilion N5400 and Omnibook XE3
1919 notebooks. This will have no effect if ACPI
1920 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001921 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001922 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07001923 use_crs [X86] Use PCI host bridge window information
1924 from ACPI. On BIOSes from 2008 or later, this
1925 is enabled by default. If you need to use this,
1926 please report a bug.
1927 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1928 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07001929 routeirq Do IRQ routing for all PCI devices.
1930 This is normally done in pci_enable_device(),
1931 so this option is a temporary workaround
1932 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001933 skip_isa_align [X86] do not align io start addr, so can
1934 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001935 firmware [ARM] Do not re-enumerate the bus but instead
1936 just use the configuration from the
1937 bootloader. This is currently used on
1938 IXP2000 systems where the bus has to be
1939 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001940 noearly [X86] Don't do any early type 1 scanning.
1941 This might help on some broken boards which
1942 machine check when some devices' config space
1943 is read. But various workarounds are disabled
1944 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001945 bfsort Sort PCI devices into breadth-first order.
1946 This sorting is done to get a device
1947 order compatible with older (<= 2.4) kernels.
1948 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001949 cbiosize=nn[KMG] The fixed amount of bus space which is
1950 reserved for the CardBus bridge's IO window.
1951 The default value is 256 bytes.
1952 cbmemsize=nn[KMG] The fixed amount of bus space which is
1953 reserved for the CardBus bridge's memory
1954 window. The default value is 64 megabytes.
Yuji Shimada32a9a682009-03-16 17:13:39 +09001955 resource_alignment=
1956 Format:
1957 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1958 Specifies alignment and device to reassign
1959 aligned memory resources.
1960 If <order of align> is not specified,
1961 PAGE_SIZE is used as alignment.
1962 PCI-PCI bridge can be specified, if resource
1963 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06001964 ecrc= Enable/disable PCIe ECRC (transaction layer
1965 end-to-end CRC checking).
1966 bios: Use BIOS/firmware settings. This is the
1967 the default.
1968 off: Turn ECRC off
1969 on: Turn ECRC on.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001970
Chuck Ebberte5665a42008-09-24 20:40:34 -04001971 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1972 Management.
1973 off Disable ASPM.
1974 force Enable ASPM even on devices that claim not to support it.
1975 WARNING: Forcing ASPM on may cause system lockups.
1976
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02001977 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02001978 auto Ask the BIOS whether or not to use native PCIe services
1979 associated with PCIe ports (PME, hot-plug, AER). Use
1980 them only if that is allowed by the BIOS.
1981 native Use native PCIe services associated with PCIe ports
1982 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02001983 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1984 ports driver.
1985
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01001986 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01001987 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02001988 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01001989
Linus Torvalds1da177e2005-04-16 15:20:36 -07001990 pcmv= [HW,PCMCIA] BadgePAD 4
1991
1992 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001993 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001994
1995 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1996 boot time.
1997 Format: { 0 | 1 }
1998 See arch/parisc/kernel/pdc_chassis.c
1999
Tejun Heof58dc012009-08-14 15:00:50 +09002000 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002001 Currently supported values are "embed" and "page".
2002 Archs may support subset or none of the selections.
2003 See comments in mm/percpu.c for details on each
2004 allocator. This parameter is primarily for debugging
2005 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002006
Linus Torvalds1da177e2005-04-16 15:20:36 -07002007 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002008 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002009
2010 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002011 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002012
2013 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002014 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002015
2016 plip= [PPT,NET] Parallel port network link
2017 Format: { parport<nr> | timid | 0 }
2018 See also Documentation/parport.txt.
2019
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002020 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2021 Override pmtimer IOPort with a hex value.
2022 e.g. pmtmr=0x508
2023
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002024 pnp.debug [PNP]
2025 Enable PNP debug messages. This depends on the
2026 CONFIG_PNP_DEBUG_MESSAGES option.
2027
Linus Torvalds1da177e2005-04-16 15:20:36 -07002028 pnpacpi= [ACPI]
2029 { off }
2030
2031 pnpbios= [ISAPNP]
2032 { on | off | curr | res | no-curr | no-res }
2033
2034 pnp_reserve_irq=
2035 [ISAPNP] Exclude IRQs for the autoconfiguration
2036
2037 pnp_reserve_dma=
2038 [ISAPNP] Exclude DMAs for the autoconfiguration
2039
2040 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002041 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002042
2043 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002044 [ISAPNP] Exclude memory regions for the
2045 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002046 Ranges are in pairs (memory base and size).
2047
Randy Dunlap4af94f32009-04-17 18:30:28 -07002048 ports= [IP_VS_FTP] IPVS ftp helper module
2049 Default is 21.
2050 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2051 may be specified.
2052 Format: <port>,<port>....
2053
Ingo Molnar45807a12007-07-15 23:40:10 -07002054 print-fatal-signals=
2055 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002056
2057 If enabled, warn about various signal handling
2058 related application anomalies: too many signals,
2059 too many POSIX.1 timers, fatal signals causing a
2060 coredump - etc.
2061
2062 If you hit the warning due to signal overflow,
2063 you might want to try "ulimit -i unlimited".
2064
Ingo Molnar45807a12007-07-15 23:40:10 -07002065 default: off.
2066
Randy Dunlape84845c2007-07-15 23:40:25 -07002067 printk.time= Show timing data prefixed to each printk message line
2068 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2069
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002070 processor.max_cstate= [HW,ACPI]
2071 Limit processor to maximum C-state
2072 max_cstate=9 overrides any DMI blacklist limit.
2073
2074 processor.nocst [HW,ACPI]
2075 Ignore the _CST method to determine C-states,
2076 instead using the legacy FADT method
2077
Linus Torvalds1da177e2005-04-16 15:20:36 -07002078 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002079 Format: [schedule,]<number>
2080 Param: "schedule" - profile schedule points.
2081 Param: <number> - step/bucket size as a power of 2 for
2082 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002083 Param: "sleep" - profile D-state sleeping (millisecs).
2084 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002085 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002086
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2088 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002089 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002090
Randy Dunlapa9913042005-10-23 12:57:11 -07002091 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2092 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002093 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2094 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002095 psmouse.resetafter= [HW,MOUSE]
2096 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002097 (0 = never).
2098 psmouse.resolution=
2099 [HW,MOUSE] Set desired mouse resolution, in dpi.
2100 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002101 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002102 0 = disabled, 1 = enabled (default).
2103
Linus Torvalds1da177e2005-04-16 15:20:36 -07002104 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002105 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002106
Kay Sieversdc8c8582007-08-15 12:25:38 +02002107 pty.legacy_count=
2108 [KNL] Number of legacy pty's. Overwrites compiled-in
2109 default number.
2110
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002111 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002112
Linus Torvalds1da177e2005-04-16 15:20:36 -07002113 r128= [HW,DRM]
2114
2115 raid= [HW,RAID]
2116 See Documentation/md.txt.
2117
Randy Dunlapa9913042005-10-23 12:57:11 -07002118 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002119 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002120
Linus Torvalds1da177e2005-04-16 15:20:36 -07002121 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002122 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002123
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002124 rcupdate.blimit= [KNL,BOOT]
2125 Set maximum number of finished RCU callbacks to process
2126 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002127
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002128 rcupdate.qhimark= [KNL,BOOT]
2129 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002130 RCU callbacks over which batch limiting is disabled.
2131
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002132 rcupdate.qlowmark= [KNL,BOOT]
2133 Set threshold of queued RCU callbacks below which
2134 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002135
Olof Johanssonffdfc402005-09-06 15:17:19 -07002136 rdinit= [KNL]
2137 Format: <full_path>
2138 Run specified binary instead of /init from the ramdisk,
2139 used for early userspace startup. See initrd.
2140
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002141 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002142 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002143 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002144
Paul Jackson46b6d942008-07-04 10:00:09 -07002145 relax_domain_level=
2146 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002147 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002148
Linus Torvalds1da177e2005-04-16 15:20:36 -07002149 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2150
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002151 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002152 Format: nn[KMG]
2153 Reserves a hole at the top of the kernel virtual
2154 address space.
2155
Vivek Goyal7e962872006-09-27 01:50:44 -07002156 reset_devices [KNL] Force drivers to reset the underlying device
2157 during initialization.
2158
Randy Dunlapa9913042005-10-23 12:57:11 -07002159 resume= [SWSUSP]
2160 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002161
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002162 resume_offset= [SWSUSP]
2163 Specify the offset from the beginning of the partition
2164 given by "resume=" at which the swap header is located,
2165 in <PAGE_SIZE> units (needed only for swap files).
2166 See Documentation/power/swsusp-and-swap-files.txt
2167
Michael Neuling0a7b35c2007-02-10 01:44:33 -08002168 retain_initrd [RAM] Keep initrd memory after extraction
2169
Linus Torvalds1da177e2005-04-16 15:20:36 -07002170 rhash_entries= [KNL,NET]
2171 Set number of hash buckets for route cache
2172
2173 riscom8= [HW,SERIAL]
2174 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2175
2176 ro [KNL] Mount root device read-only on boot
2177
2178 root= [KNL] Root filesystem
2179
2180 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2181 mount the root filesystem
2182
2183 rootflags= [KNL] Set root filesystem mount option string
2184
2185 rootfstype= [KNL] Set root filesystem type
2186
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002187 rootwait [KNL] Wait (indefinitely) for root device to show up.
2188 Useful for devices that are detected asynchronously
2189 (e.g. USB and MMC devices).
2190
Linus Torvalds1da177e2005-04-16 15:20:36 -07002191 rw [KNL] Mount root device read-write on boot
2192
2193 S [KNL] Run init in single mode
2194
2195 sa1100ir [NET]
2196 See drivers/net/irda/sa1100_ir.c.
2197
Linus Torvalds1da177e2005-04-16 15:20:36 -07002198 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002199
Mike Travisf6630112009-11-17 18:22:15 -06002200 sched_debug [KNL] Enables verbose scheduler debug messages.
2201
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002202 security= [SECURITY] Choose a security module to enable at boot.
2203 If this boot parameter is not specified, only the first
2204 security module asking for security registration will be
2205 loaded. An invalid security module name will be treated
2206 as if no module has been chosen.
2207
2208 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002209 Format: { "0" | "1" }
2210 See security/selinux/Kconfig help text.
2211 0 -- disable.
2212 1 -- enable.
2213 Default value is set via kernel config option.
2214 If enabled at boot time, /selinux/disable can be used
2215 later to disable prior to initial policy load.
2216
John Johansenc1c124e2010-07-29 14:48:09 -07002217 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2218 Format: { "0" | "1" }
2219 See security/apparmor/Kconfig help text
2220 0 -- disable.
2221 1 -- enable.
2222 Default value is set via kernel config option.
2223
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002224 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002225
Linus Torvalds1da177e2005-04-16 15:20:36 -07002226 shapers= [NET]
2227 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002228
Yinghai Lub05f78f2008-08-22 01:32:50 -07002229 show_msr= [x86] show boot-time MSR settings
2230 Format: { <integer> }
2231 Show boot-time (BIOS-initialized) MSR settings.
2232 The parameter means the number of CPUs to show,
2233 for example 1 means boot CPU only.
2234
Linus Torvalds1da177e2005-04-16 15:20:36 -07002235 simeth= [IA-64]
2236 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002237
Linus Torvalds1da177e2005-04-16 15:20:36 -07002238 slram= [HW,MTD]
2239
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002240 slub_debug[=options[,slabs]] [MM, SLUB]
2241 Enabling slub_debug allows one to determine the
2242 culprit if slab objects become corrupted. Enabling
2243 slub_debug can create guard zones around objects and
2244 may poison objects when not in use. Also tracks the
2245 last alloc / free. For more information see
2246 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002247
2248 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002249 Determines the maximum allowed order for slabs.
2250 A high setting may cause OOMs due to memory
2251 fragmentation. For more information see
2252 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002253
2254 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002255 The minimum number of objects per slab. SLUB will
2256 increase the slab order up to slub_max_order to
2257 generate a sufficiently large slab able to contain
2258 the number of objects indicated. The higher the number
2259 of objects the smaller the overhead of tracking slabs
2260 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002261 For more information see Documentation/vm/slub.txt.
2262
2263 slub_min_order= [MM, SLUB]
2264 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002265 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002266 For more information see Documentation/vm/slub.txt.
2267
2268 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002269 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002270 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002271 allocs to different slabs. Debug options disable
2272 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002273 For more information see Documentation/vm/slub.txt.
2274
Linus Torvalds1da177e2005-04-16 15:20:36 -07002275 smart2= [HW]
2276 Format: <io1>[,<io2>[,...,<io8>]]
2277
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002278 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002279 attempt to substitute SMP alternatives once at boot.
2280
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002281 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2282 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2283 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2284 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2285 smsc-ircc2.ircc_irq= [HW] IRQ line
2286 smsc-ircc2.ircc_dma= [HW] DMA channel
2287 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2288 0: Toshiba Satellite 1800 (GP data pin select)
2289 1: Fast pin select (default)
2290 2: ATC IRMode
2291
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002292 softlockup_panic=
2293 [KNL] Should the soft-lockup detector generate panics.
2294
Linus Torvalds1da177e2005-04-16 15:20:36 -07002295 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2296 See Documentation/sonypi.txt
2297
2298 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002299 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002300
2301 spia_io_base= [HW,MTD]
2302 spia_fio_base=
2303 spia_pedr=
2304 spia_peddr=
2305
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002306 stacktrace [FTRACE]
2307 Enabled the stack tracer on boot up.
2308
Linus Torvalds1da177e2005-04-16 15:20:36 -07002309 sti= [PARISC,HW]
2310 Format: <num>
2311 Set the STI (builtin display/keyboard on the HP-PARISC
2312 machines) console (graphic card) which should be used
2313 as the initial boot-console.
2314 See also comment in drivers/video/console/sticore.c.
2315
2316 sti_font= [HW]
2317 See comment in drivers/video/console/sticore.c.
2318
2319 stifb= [HW]
2320 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2321
Trond Myklebustcbf11072009-08-09 15:06:19 -04002322 sunrpc.min_resvport=
2323 sunrpc.max_resvport=
2324 [NFS,SUNRPC]
2325 SunRPC servers often require that client requests
2326 originate from a privileged port (i.e. a port in the
2327 range 0 < portnr < 1024).
2328 An administrator who wishes to reserve some of these
2329 ports for other uses may adjust the range that the
2330 kernel's sunrpc client considers to be privileged
2331 using these two parameters to set the minimum and
2332 maximum port values.
2333
Greg Banks42a7fc42007-03-06 01:42:23 -08002334 sunrpc.pool_mode=
2335 [NFS]
2336 Control how the NFS server code allocates CPUs to
2337 service thread pools. Depending on how many NICs
2338 you have and where their interrupts are bound, this
2339 option will affect which CPUs will do NFS serving.
2340 Note: this parameter cannot be changed while the
2341 NFS server is running.
2342
2343 auto the server chooses an appropriate mode
2344 automatically using heuristics
2345 global a single global pool contains all CPUs
2346 percpu one pool for each CPU
2347 pernode one pool for each NUMA node (equivalent
2348 to global on non-NUMA machines)
2349
Trond Myklebustcbf11072009-08-09 15:06:19 -04002350 sunrpc.tcp_slot_table_entries=
2351 sunrpc.udp_slot_table_entries=
2352 [NFS,SUNRPC]
2353 Sets the upper limit on the number of simultaneous
2354 RPC calls that can be sent from the client to a
2355 server. Increasing these values may allow you to
2356 improve throughput, but will also increase the
2357 amount of memory reserved for use by the client.
2358
Linus Torvalds1da177e2005-04-16 15:20:36 -07002359 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002360
Linus Torvalds1da177e2005-04-16 15:20:36 -07002361 switches= [HW,M68k]
2362
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002363 sysrq_always_enabled
2364 [KNL]
2365 Ignore sysrq setting - this boot parameter will
2366 neutralize any effect of /proc/sys/kernel/sysrq.
2367 Useful for debugging.
2368
Linus Torvalds1da177e2005-04-16 15:20:36 -07002369 tdfx= [HW,DRM]
2370
David Brownell77437fd2008-07-23 21:28:33 -07002371 test_suspend= [SUSPEND]
2372 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2373 standby suspend) as the system sleep state to briefly
2374 enter during system startup. The system is woken from
2375 this state using a wakeup-capable RTC alarm.
2376
Linus Torvalds1da177e2005-04-16 15:20:36 -07002377 thash_entries= [KNL,NET]
2378 Set number of hash buckets for TCP connection
2379
Len Brownf8707ec2007-08-12 00:12:54 -04002380 thermal.act= [HW,ACPI]
2381 -1: disable all active trip points in all thermal zones
2382 <degrees C>: override all lowest active trip points
2383
Len Brownc52a7412007-08-14 15:49:32 -04002384 thermal.crt= [HW,ACPI]
2385 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002386 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002387
Len Brownf5487142007-08-12 00:12:44 -04002388 thermal.nocrt= [HW,ACPI]
2389 Set to disable actions on ACPI thermal zone
2390 critical and hot trip points.
2391
Len Brown72b33ef2007-08-12 00:12:17 -04002392 thermal.off= [HW,ACPI]
2393 1: disable ACPI thermal control
2394
Len Browna70cdc52007-08-12 00:12:35 -04002395 thermal.psv= [HW,ACPI]
2396 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002397 <degrees C>: override all passive trip points to this
2398 value
Len Browna70cdc52007-08-12 00:12:35 -04002399
Len Brown730ff342007-08-12 00:12:26 -04002400 thermal.tzp= [HW,ACPI]
2401 Specify global default ACPI thermal zone polling rate
2402 <deci-seconds>: poll all this frequency
2403 0: no polling (default)
2404
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002405 topology= [S390]
2406 Format: {off | on}
2407 Specify if the kernel should make use of the cpu
2408 topology informations if the hardware supports these.
2409 The scheduler will make use of these informations and
2410 e.g. base its process migration decisions on it.
2411 Default is off.
2412
Linus Torvalds1da177e2005-04-16 15:20:36 -07002413 tp720= [HW,PS2]
2414
Rajiv Andrade225a9be2010-03-25 00:55:32 -03002415 tpm_suspend_pcr=[HW,TPM]
2416 Format: integer pcr id
2417 Specify that at suspend time, the tpm driver
2418 should extend the specified pcr with zeros,
2419 as a workaround for some chips which fail to
2420 flush the last written pcr on TPM_SaveState.
2421 This will guarantee that all the other pcrs
2422 are saved.
2423
Li Zefan9d612be2009-06-24 17:33:15 +08002424 trace_buf_size=nn[KMG]
2425 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002426
Li Zefan020e5f82009-07-01 10:47:05 +08002427 trace_event=[event-list]
2428 [FTRACE] Set and start specified trace events in order
2429 to facilitate early boot debugging.
2430 See also Documentation/trace/events.txt
2431
Alok Kataria395628e2008-10-24 17:22:01 -07002432 tsc= Disable clocksource-must-verify flag for TSC.
2433 Format: <string>
2434 [x86] reliable: mark tsc clocksource as reliable, this
2435 disables clocksource verification at runtime.
2436 Used to enable high-resolution timer mode on older
2437 hardware, and in virtualized environment.
2438
Randy Dunlapa9913042005-10-23 12:57:11 -07002439 turbografx.map[2|3]= [HW,JOY]
2440 TurboGraFX parallel port interface
2441 Format:
2442 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002443 See also Documentation/input/joystick-parport.txt
2444
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002445 uhash_entries= [KNL,NET]
2446 Set number of hash buckets for UDP/UDP-Lite connections
2447
Alan Stern5f8364b2006-12-05 16:29:55 -05002448 uhci-hcd.ignore_oc=
2449 [USB] Ignore overcurrent events (default N).
2450 Some badly-designed motherboards generate lots of
2451 bogus events, for ports that aren't wired to
2452 anything. Set this parameter to avoid log spamming.
2453 Note that genuine overcurrent events won't be
2454 reported either.
2455
Simon Arlotte3a61b02008-07-19 23:32:54 +01002456 unknown_nmi_panic
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302457 [X86]
Simon Arlotte3a61b02008-07-19 23:32:54 +01002458 Set unknown_nmi_panic=1 early on boot.
2459
Alan Sternb5e795f2007-02-20 15:00:53 -05002460 usbcore.autosuspend=
2461 [USB] The autosuspend time delay (in seconds) used
2462 for newly-detected USB devices (default 2). This
2463 is the time required before an idle device will be
2464 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002465 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002466
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002467 usbcore.usbfs_snoop=
2468 [USB] Set to log all usbfs traffic (default 0 = off).
2469
2470 usbcore.blinkenlights=
2471 [USB] Set to cycle leds on hubs (default 0 = off).
2472
2473 usbcore.old_scheme_first=
2474 [USB] Start with the old device initialization
2475 scheme (default 0 = off).
2476
2477 usbcore.use_both_schemes=
2478 [USB] Try the other device initialization scheme
2479 if the first one fails (default 1 = enabled).
2480
2481 usbcore.initial_descriptor_timeout=
2482 [USB] Specifies timeout for the initial 64-byte
2483 USB_REQ_GET_DESCRIPTOR request in milliseconds
2484 (default 5000 = 5.0 seconds).
2485
Linus Torvalds1da177e2005-04-16 15:20:36 -07002486 usbhid.mousepoll=
2487 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002488
Alan Sternd4f373e2008-11-10 14:07:45 -05002489 usb-storage.delay_use=
2490 [UMS] The delay in seconds before a new device is
2491 scanned for Logical Units (default 5).
2492
2493 usb-storage.quirks=
2494 [UMS] A list of quirks entries to supplement or
2495 override the built-in unusual_devs list. List
2496 entries are separated by commas. Each entry has
2497 the form VID:PID:Flags where VID and PID are Vendor
2498 and Product ID values (4-digit hex numbers) and
2499 Flags is a set of characters, each corresponding
2500 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002501 a = SANE_SENSE (collect more than 18 bytes
2502 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002503 b = BAD_SENSE (don't collect more than 18
2504 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002505 c = FIX_CAPACITY (decrease the reported
2506 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002507 h = CAPACITY_HEURISTICS (decrease the
2508 reported device capacity by one
2509 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002510 i = IGNORE_DEVICE (don't bind to this
2511 device);
2512 l = NOT_LOCKABLE (don't try to lock and
2513 unlock ejectable media);
2514 m = MAX_SECTORS_64 (don't transfer more
2515 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002516 o = CAPACITY_OK (accept the capacity
2517 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002518 r = IGNORE_RESIDUE (the device reports
2519 bogus residue values);
2520 s = SINGLE_LUN (the device has only one
2521 Logical Unit);
2522 w = NO_WP_DETECT (don't test whether the
2523 medium is write-protected).
2524 Example: quirks=0419:aaf5:rl,0421:0433:rc
2525
Ian Campbell14315592010-02-17 10:38:10 +00002526 userpte=
2527 [X86] Flags controlling user PTE allocations.
2528
2529 nohigh = do not allocate PTE pages in
2530 HIGHMEM regardless of setting
2531 of CONFIG_HIGHPTE.
2532
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302533 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf5272007-05-02 19:27:12 +02002534 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002535 vdso=1: enable VDSO (default)
2536 vdso=0: disable VDSO mapping
2537
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302538 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002539 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2540 vdso32=1: enable 32-bit VDSO (default)
2541 vdso32=0: disable 32-bit VDSO mapping
2542
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002543 vector= [IA-64,SMP]
2544 vector=percpu: enable percpu vector domain
2545
Linus Torvalds1da177e2005-04-16 15:20:36 -07002546 video= [FB] Frame buffer configuration
2547 See Documentation/fb/modedb.txt.
2548
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002549 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002550 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002551 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002552 Use vga=ask for menu.
2553 This is actually a boot loader parameter; the value is
2554 passed to the kernel using a special protocol.
2555
Randy Dunlapa9913042005-10-23 12:57:11 -07002556 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002557 size of <nn>. This can be used to increase the
2558 minimum size (128MB on x86). It can also be used to
2559 decrease the size and leave more room for directly
2560 mapped kernel RAM.
2561
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002562 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2563 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002564
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002565 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2566 Format: <command>
2567
2568 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2569 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002570
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002571 vt.cur_default= [VT] Default cursor shape.
2572 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2573 the parameters of the <Esc>[?A;B;Cc escape sequence;
2574 see VGA-softcursor.txt. Default: 2 = underline.
2575
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002576 vt.default_blu= [VT]
2577 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2578 Change the default blue palette of the console.
2579 This is a 16-member array composed of values
2580 ranging from 0-255.
2581
2582 vt.default_grn= [VT]
2583 Format: <green0>,<green1>,<green2>,...,<green15>
2584 Change the default green palette of the console.
2585 This is a 16-member array composed of values
2586 ranging from 0-255.
2587
2588 vt.default_red= [VT]
2589 Format: <red0>,<red1>,<red2>,...,<red15>
2590 Change the default red palette of the console.
2591 This is a 16-member array composed of values
2592 ranging from 0-255.
2593
2594 vt.default_utf8=
2595 [VT]
2596 Format=<0|1>
2597 Set system-wide default UTF-8 mode for all tty's.
2598 Default is 1, i.e. UTF-8 mode is enabled for all
2599 newly opened terminals.
2600
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002601 vt.global_cursor_default=
2602 [VT]
2603 Format=<-1|0|1>
2604 Set system-wide default for whether a cursor
2605 is shown on new VTs. Default is -1,
2606 i.e. cursors will be created by default unless
2607 overridden by individual drivers. 0 will hide
2608 cursors, 1 will display them.
2609
Randy Dunlap4724ba52010-05-03 11:42:52 -07002610 watchdog timers [HW,WDT] For information on watchdog timers,
2611 see Documentation/watchdog/watchdog-parameters.txt
2612 or other driver-specific files in the
2613 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002614
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002615 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2616 default x2apic cluster mode on platforms
2617 supporting x2apic.
2618
Jacob Panbb24c472009-09-02 07:37:17 -07002619 x86_mrst_timer= [X86-32,APBT]
2620 Choose timer option for x86 Moorestown MID platform.
2621 Two valid options are apbt timer only and lapic timer
2622 plus one apbt timer for broadcast timer.
2623 x86_mrst_timer=apbt_only | lapic_and_apbt
2624
Linus Torvalds1da177e2005-04-16 15:20:36 -07002625 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2626 xd_geo= See header of drivers/block/xd.c.
2627
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002628 xen_emul_unplug= [HW,X86,XEN]
2629 Unplug Xen emulated devices
2630 Format: [unplug0,][unplug1]
2631 ide-disks -- unplug primary master IDE devices
2632 aux-ide-disks -- unplug non-primary-master IDE devices
2633 nics -- unplug network devices
2634 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01002635 unnecessary -- unplugging emulated devices is
2636 unnecessary even if the host did not respond to
2637 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01002638 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002639
Linus Torvalds1da177e2005-04-16 15:20:36 -07002640 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002641 Format:
2642 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002643
Randy Dunlapa9913042005-10-23 12:57:11 -07002644______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002645
2646TODO:
2647
Linus Torvalds1da177e2005-04-16 15:20:36 -07002648 Add more DRM drivers.