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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.
Randy Dunlap16290242011-08-13 12:34:52 -070043 ARM ARM architecture is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020044 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070045 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080046 BLACKFIN Blackfin architecture is enabled.
Alan Cox9cfe2682011-01-25 14:18:38 +000047 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070049 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
Mimi Zohar7102ebc2011-05-12 18:33:20 -040052 EVM Extended Verification Module
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 FB The frame buffer device is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070054 FTRACE Function tracing enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070055 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070056 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070057 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050058 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070060 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080061 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070062 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050065 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020066 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070067 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MCA MCA bus support is enabled.
74 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070075 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070076 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070077 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070078 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070079 NET Appropriate network support is enabled.
80 NUMA NUMA support is enabled.
81 NFS Appropriate NFS support is enabled.
82 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070083 PV_OPS A paravirtualized kernel is enabled.
84 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 PARISC The PA-RISC architecture is enabled.
86 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070087 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070088 PCMCIA The PCMCIA subsystem is enabled.
89 PNP Plug & Play support is enabled.
90 PPC PowerPC architecture is enabled.
91 PPT Parallel port support is enabled.
92 PS2 Appropriate PS/2 support is enabled.
93 RAM RAM disk support is enabled.
94 S390 S390 architecture is enabled.
95 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -070096 A lot of drivers have their options described inside
97 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -070098 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -0700100 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900102 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 SMP The kernel is an SMP kernel.
104 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700105 SWSUSP Software suspend (hibernation) is enabled.
106 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300107 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500109 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110 USB USB support is enabled.
111 USBHID USB Human Interface Device support is enabled.
112 V4L Video For Linux support is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700117 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700120 Documentation/x86/x86_64/boot-options.txt .
Randy Dunlap16290242011-08-13 12:34:52 -0700121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100122 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123
124In addition, the following text indicates that the option:
125
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
129
130Parameters denoted with BOOT are actually interpreted by the boot
131loader, and have no meaning to the kernel directly.
132Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500133need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134
Karsten Weiss55588702007-02-13 13:26:21 +0100135There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700136See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100137
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139a trailing = on the name of any parameter states that that parameter will
140be entered as an environment variable, whereas its absence indicates that
141it will appear as a kernel argument readable via /proc/cmdline by programs
142running once the system is up.
143
jens m. noedler9c4751f2006-09-29 02:00:27 -0700144The number of kernel parameters is not limited, but the length of the
145complete command line (parameters including spaces etc.) is limited to
146a fixed number of characters. This limit depends on the architecture
147and is between 256 and 4096 characters. It is defined in the file
148./include/asm/setup.h as COMMAND_LINE_SIZE.
149
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800150Finally, the [KMG] suffix is commonly described after a number of kernel
151parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153bytes respectively. Such letter suffixes can also be entirely omitted.
154
jens m. noedler9c4751f2006-09-29 02:00:27 -0700155
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530156 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800157 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500158 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700162 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800164 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800165 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166
Paul Bolle395cf962011-08-15 02:02:26 +0200167 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168
Takao Indoh4996c022011-07-14 18:05:21 -0400169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
173
Len Browna1fdcc02007-03-11 03:26:14 -0400174 acpi_apic_instance= [ACPI, IOAPIC]
175 Format: <int>
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400178 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400179
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
182 acpi_backlight=video
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
186
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200210
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800214
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
217 default in APIC mode
218
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
221 default in PIC mode
222
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
225
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
227 use by PCI
228 Format: <irq>,<irq>...
229
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
231
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
234
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
239
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530240 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
244
Randy Dunlap4af94f32009-04-17 18:30:28 -0700245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
247
248 acpi_serialize [HW,ACPI] force serialization of AML methods
249
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
253
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200256 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700257 See Documentation/power/video.txt for information on
258 s3_bios and s3_mode.
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700272
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
276
Luca Tettamanti7e905602009-03-30 00:01:27 +0200277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
292
Randy Dunlap4af94f32009-04-17 18:30:28 -0700293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
295
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700296 agp= [AGP]
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
301
Randy Dunlapbcfde332010-06-07 17:10:38 -0700302 ALSA [HW,ALSA]
303 See Documentation/sound/alsa/alsa-parameters.txt
304
Russell Kingd944d542010-02-20 16:13:29 +0000305 alignment= [KNL,ARM]
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
309
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
317
Borislav Petkov8360ee22011-11-21 12:10:19 +0100318 32: only for 32-bit processes
319 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
322
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100323 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200324 Pass parameters to the AMD IOMMU driver in the system.
325 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
329 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200330 off - do not initialize any AMD IOMMU found in
331 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900337
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338 amijoy.map= [HW,JOY] Amiga joystick support
339 Map of devices attached to JOY0DAT and JOY1DAT
340 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200341 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342
343 analog.map= [HW,JOY] Analog joystick and gamepad support
344 Specifies type or capabilities of an analog joystick
345 connected to one of 16 gameports
346 Format: <type1>,<type2>,..<type16>
347
Randy Dunlapa9913042005-10-23 12:57:11 -0700348 apc= [HW,SPARC]
349 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700350 Format: noidle
351 Disable APC CPU standby support. SPARCstation-Fox does
352 not play well with APC CPU idle - disable it if you have
353 APC and your system crashes randomly.
354
Randy Dunlapca1eda22009-05-06 16:02:58 -0700355 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700356 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700357 Format: { quiet (default) | verbose | debug }
358 Change the amount of debugging information output
359 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700360
Brian Haleyb0f83b22010-02-04 13:36:50 -0800361 autoconf= [IPV6]
362 See Documentation/networking/ipv6.txt.
363
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400364 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
365 Limit apic dumping. The parameter defines the maximal
366 number of local apics being dumped. Also it is possible
367 to set it to "all" by meaning -- no limit here.
368 Format: { 1 (default) | 2 | ... | all }.
369 The parameter valid if only apic=debug or
370 apic=verbose is specified.
371 Example: apic=debug show_lapic=all
372
Linus Torvalds1da177e2005-04-16 15:20:36 -0700373 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700374 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
377 Format: <io>,<irq>,<nodeID>
378
379 ataflop= [HW,M68k]
380
381 atarimouse= [HW,MOUSE] Atari Mouse
382
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
384 EzKey and similar keyboards
385
386 atkbd.reset= [HW] Reset keyboard during initialization
387
Randy Dunlapa9913042005-10-23 12:57:11 -0700388 atkbd.set= [HW] Select keyboard code set
389 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390
391 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
392 keyboards
393
394 atkbd.softraw= [HW] Choose between synthetic and real raw mode
395 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700396
397 atkbd.softrepeat= [HW]
398 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399
Randy Dunlap16290242011-08-13 12:34:52 -0700400 autotest [IA-64]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401
Linus Torvalds1da177e2005-04-16 15:20:36 -0700402 baycom_epp= [HW,AX25]
403 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700404
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
406 Format: <io>,<mode>
407 See header of drivers/net/hamradio/baycom_par.c.
408
Randy Dunlapa9913042005-10-23 12:57:11 -0700409 baycom_ser_fdx= [HW,AX25]
410 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411 Format: <io>,<irq>,<mode>[,<baud>]
412 See header of drivers/net/hamradio/baycom_ser_fdx.c.
413
Randy Dunlapa9913042005-10-23 12:57:11 -0700414 baycom_ser_hdx= [HW,AX25]
415 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416 Format: <io>,<irq>,<mode>
417 See header of drivers/net/hamradio/baycom_ser_hdx.c.
418
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700419 boot_delay= Milliseconds to delay each printk during boot.
420 Values larger than 10 seconds (10000) are changed to
421 no delay (0).
422 Format: integer
423
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700424 bootmem_debug [KNL] Enable bootmem allocator debug messages.
425
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700427 bttv.radio= Most important insmod options are available as
428 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200430 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000432 bulk_remove=off [PPC] This parameter disables the use of the pSeries
433 firmware feature for flushing multiple hpte entries
434 at a time.
435
Linus Torvalds1da177e2005-04-16 15:20:36 -0700436 c101= [NET] Moxa C101 synchronous serial card
437
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700438 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439 Sometimes CPU hardware bugs make them report the cache
440 size incorrectly. The kernel will attempt work arounds
441 to fix known problems, but for some CPUs it is not
442 possible to determine what the correct size should be.
443 This option provides an override for these situations.
444
James Morris20510f22007-10-16 23:31:32 -0700445 capability.disable=
446 [SECURITY] Disable capabilities. This would normally
447 be used only if an alternative security model is to be
448 configured. Potentially dangerous and should only be
449 used if you are entirely sure of the consequences.
450
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100451 ccw_timeout_log [S390]
452 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700453
Paul Menage8bab8dd2008-04-04 14:29:57 -0700454 cgroup_disable= [KNL] Disable a particular controller
455 Format: {name of the controller(s) to disable}
456 {Currently supported controllers - "memory"}
457
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458 checkreqprot [SELINUX] Set initial checkreqprot flag value.
459 Format: { "0" | "1" }
460 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700461 0 -- check protection applied by kernel (includes
462 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463 1 -- check protection requested by application.
464 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700465 Value can be changed at runtime via
466 /selinux/checkreqprot.
467
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100468 cio_ignore= [S390]
469 See Documentation/s390/CommonIO for details.
470
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700471 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700472 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200473 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700474 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200475 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700476 Format: { pit | tsc | cyclone | pmtmr }
477
John Stultz592913e2010-07-13 17:56:20 -0700478 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700479 Format: <string>
480 Override the default clocksource and use the clocksource
481 with the name specified.
482 Some clocksource names to choose from, depending on
483 the platform:
484 [all] jiffies (this is the base, fallback clocksource)
485 [ACPI] acpi_pm
486 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
487 pxa_timer,timer3,32k_counter,timer0_1
488 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700489 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700490 scx200_hrt on Geode; cyclone on IBM x440
491 [MIPS] MIPS
492 [PARISC] cr16
493 [S390] tod
494 [SH] SuperH
495 [SPARC64] tick
496 [X86-64] hpet,tsc
497
Andi Kleenac72e782008-01-30 13:33:21 +0100498 clearcpuid=BITNUM [X86]
499 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800500 arch/x86/include/asm/cpufeature.h for the valid bit
501 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100502 stable over kernel options, but the vendor specific
503 ones should be.
504 Also note that user programs calling CPUID directly
505 or using the feature without checking anything
506 will still see it. This just prevents it from
507 being used by the kernel or shown in /proc/cpuinfo.
508 Also note the kernel might malfunction if you disable
509 some critical bits.
510
Robert Jennings14f966e2009-04-15 05:55:32 +0000511 cmo_free_hint= [PPC] Format: { yes | no }
512 Specify whether pages are marked as being inactive
513 when they are freed. This is used in CMO environments
514 to determine OS memory pressure for page stealing by
515 a hypervisor.
516 Default: yes
517
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530518 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100519 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100520 Range: 0 - 8192
521 Default: 64
522
Linus Torvalds1da177e2005-04-16 15:20:36 -0700523 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700524 Format:
525 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700526
527 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
528 Format: <io>[,<irq>]
529
Randy Dunlapa9913042005-10-23 12:57:11 -0700530 com90xx= [HW,NET]
531 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532 Format: <io>[,<irq>[,<memstart>]]
533
534 condev= [HW,S390] console device
535 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700536
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537 console= [KNL] Output console device and options.
538
539 tty<n> Use the virtual console device <n>.
540
541 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800542 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700543 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800544 the form "bbbbpnf", where "bbbb" is the baud rate,
545 "p" is parity ("n", "o", or "e"), "n" is number of
546 bits, and "f" is flow control ("r" for RTS or
547 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700548
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800549 See Documentation/serial-console.txt for more
550 information. See
551 Documentation/networking/netconsole.txt for an
552 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700554 uart[8250],io,<addr>[,options]
555 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700556 Start an early, polled-mode console on the 8250/16550
557 UART at the specified I/O port or MMIO address,
558 switching to the matching ttyS device later. The
559 options are the same as for ttyS, above.
560
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700561 If the device connected to the port is not a TTY but a braille
562 device, prepend "brl," before the device type, for instance
563 console=brl,ttyS0
564 For now, only VisioBraille is supported.
565
Daniel Mackf324edc2009-06-16 15:33:52 -0700566 consoleblank= [KNL] The console blank (screen saver) timeout in
567 seconds. Defaults to 10*60 = 10mins. A value of 0
568 disables the blank timer.
569
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800570 coredump_filter=
571 [KNL] Change the default value for
572 /proc/<pid>/coredump_filter.
573 See also Documentation/filesystems/proc.txt.
574
Len Brown62027ae2011-04-01 18:13:10 -0400575 cpuidle.off=1 [CPU_IDLE]
576 disable the cpuidle sub-system
577
Linus Torvalds1da177e2005-04-16 15:20:36 -0700578 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700579 Format:
580 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700581
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800582 crashkernel=size[KMG][@offset[KMG]]
583 [KNL] Using kexec, Linux can switch to a 'crash kernel'
584 upon panic. This parameter reserves the physical
585 memory region [offset, offset + size] for that kernel
586 image. If '@offset' is omitted, then a suitable offset
587 is selected automatically. Check
588 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700589
Bernhard Wallefb391592007-10-18 23:41:02 -0700590 crashkernel=range1:size1[,range2:size2,...][@offset]
591 [KNL] Same as above, but depends on the memory
592 in the running system. The syntax of range is
593 start-[end] where start and end are both
594 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800595 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700596
Linus Torvalds1da177e2005-04-16 15:20:36 -0700597 cs89x0_dma= [HW,NET]
598 Format: <dma>
599
600 cs89x0_media= [HW,NET]
601 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700602
Randy Dunlapa9913042005-10-23 12:57:11 -0700603 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700604 See header of drivers/s390/block/dasd_devmap.c.
605
606 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
607 (one device per port)
608 Format: <port#>,<type>
609 See also Documentation/input/joystick-parport.txt
610
Thomas Renningera648ec02010-08-06 16:11:02 +0200611 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
612 time. See Documentation/dynamic-debug-howto.txt for
613 details.
614
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615 debug [KNL] Enable kernel debugging (events log level).
616
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700617 debug_locks_verbose=
618 [KNL] verbose self-tests
619 Format=<0|1>
620 Print debugging info while doing the locking API
621 self-tests.
622 We default to 0 (no extra messages), setting it to
623 1 will print _a lot_ more information - normally
624 only useful to kernel developers.
625
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700626 debug_objects [KNL] Enable object debugging
627
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500628 no_debug_objects
629 [KNL] Disable object debugging
630
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800631 debug_guardpage_minorder=
632 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
633 parameter allows control of the order of pages that will
634 be intentionally kept free (and hence protected) by the
635 buddy allocator. Bigger value increase the probability
636 of catching random memory corruption, but reduce the
637 amount of memory for normal system use. The maximum
638 possible value is MAX_ORDER/2. Setting this parameter
639 to 1 or 2 should be enough to identify most random
640 memory corruption problems caused by bugs in kernel or
641 driver code when a CPU writes to (or reads from) a
642 random memory location. Note that there exists a class
643 of memory corruptions problems caused by buggy H/W or
644 F/W or by drivers badly programing DMA (basically when
645 memory is written at bus level and the CPU MMU is
646 bypassed) which are not detectable by
647 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
648 tracking down these problems.
649
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200650 debugpat [X86] Enable PAT debugging
651
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200652 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700653 Format: <area>[,<node>]
654 See also Documentation/networking/decnet.txt.
655
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700656 default_hugepagesz=
657 [same as hugepagesz=] The size of the default
658 HugeTLB page size. This is the size represented by
659 the legacy /proc/ hugepages APIs, used for SHM, and
660 default size when mounting hugetlbfs filesystems.
661 Defaults to the default architecture's huge page size
662 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700663
Linus Torvalds1da177e2005-04-16 15:20:36 -0700664 dhash_entries= [KNL]
665 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700666
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667 digi= [HW,SERIAL]
668 IO parameters + enable/disable command.
669
670 digiepca= [HW,SERIAL]
671 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000672 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700673
Brian Haleyb0f83b22010-02-04 13:36:50 -0800674 disable= [IPV6]
675 See Documentation/networking/ipv6.txt.
676
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000677 disable_ddw [PPC/PSERIES]
678 Disable Dynamic DMA Window support. Use this if
679 to workaround buggy firmware.
680
Brian Haleyb0f83b22010-02-04 13:36:50 -0800681 disable_ipv6= [IPV6]
682 See Documentation/networking/ipv6.txt.
683
Yinghai Lu95ffa242008-04-29 03:52:33 -0700684 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700685 The kernel tries to adjust MTRR layout from continuous
686 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700687 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700688
Yinghai Lu093af8d2008-01-30 13:33:32 +0100689 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100690 By default the kernel will trim any uncacheable
691 memory out of your available memory pool based on
692 MTRR settings. This parameter disables that behavior,
693 possibly causing your machine to run very slowly.
694
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530695 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700696 Disable PIN 1 of APIC timer
697 Can be useful to work around chipset bugs.
698
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700699 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
700 this option disables the debugging code at boot.
701
702 dma_debug_entries=<number>
703 This option allows to tune the number of preallocated
704 entries for DMA-API debugging code. One entry is
705 required per DMA-API allocation. Use this if the
706 DMA-API debugging code disables itself because the
707 architectural default is too low.
708
Joerg Roedel1745de52009-05-22 21:49:51 +0200709 dma_debug_driver=<driver_name>
710 With this option the DMA-API debugging driver
711 filter feature can be enabled at boot time. Just
712 pass the driver to filter for as the parameter.
713 The filter can be disabled or changed to another
714 driver later using sysfs.
715
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716 dscc4.setup= [NET]
717
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700718 earlycon= [KNL] Output early console device and options.
719 uart[8250],io,<addr>[,options]
720 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700721 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700722 Start an early, polled-mode console on the 8250/16550
723 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700724 MMIO inter-register address stride is either 8-bit
725 (mmio) or 32-bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700726 The options are the same as for ttyS, above.
727
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530728 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700729 earlyprintk=vga
730 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500731 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500732 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700733
Randy Dunlapa9913042005-10-23 12:57:11 -0700734 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700735 takes over.
736
Yinghai Lu5c059172008-07-24 17:29:40 -0700737 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700738
739 Currently only ttyS0 and ttyS1 are supported.
740
741 Interaction with the standard serial driver is not
742 very good.
743
744 The VGA output is eventually overwritten by the real
745 console.
746
Jason Wessel97311912010-05-20 21:04:30 -0500747 ekgdboc= [X86,KGDB] Allow early kernel console debugging
748 ekgdboc=kbd
749
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300750 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -0500751 the boot argument: earlyprintk=vga
752
Linus Torvalds1da177e2005-04-16 15:20:36 -0700753 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700754 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700755
Linus Torvalds1da177e2005-04-16 15:20:36 -0700756 eisa_irq_edge= [PARISC,HW]
757 See header of drivers/parisc/eisa.c.
758
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700759 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700760 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700761 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700762
763 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +0100764 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +0200765 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -0700766 Documentation/block/deadline-iosched.txt for details.
767
Michael Holzheud3bf37952011-10-30 15:16:37 +0100768 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -0700769 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +0100770 image elf header and optionally the size. Generally
771 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -0800772 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700774 enable_mtrr_cleanup [X86]
775 The kernel tries to adjust MTRR layout from continuous
776 to discrete, to make X server driver able to add WB
777 entry later. This parameter enables that.
778
Randy Dunlapca1eda22009-05-06 16:02:58 -0700779 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700780 Enable PIN 1 of APIC timer
781 Can be useful to work around chipset bugs
782 (in particular on some ATI chipsets).
783 The kernel tries to set a reasonable default.
784
Linus Torvalds1da177e2005-04-16 15:20:36 -0700785 enforcing [SELINUX] Set initial enforcing status.
786 Format: {"0" | "1"}
787 See security/selinux/Kconfig help text.
788 0 -- permissive (log only, no denials).
789 1 -- enforcing (deny and log).
790 Default value is 0.
791 Value can be changed at runtime via /selinux/enforce.
792
Huang Yinga08f82d2010-05-18 14:35:21 +0800793 erst_disable [ACPI]
794 Disable Error Record Serialization Table (ERST)
795 support.
796
Linus Torvalds1da177e2005-04-16 15:20:36 -0700797 ether= [HW,NET] Ethernet cards parameters
798 This option is obsoleted by the "netdev=" option, which
799 has equivalent usage. See its documentation for details.
800
Mimi Zohar7102ebc2011-05-12 18:33:20 -0400801 evm= [EVM]
802 Format: { "fix" }
803 Permit 'security.evm' to be updated regardless of
804 current integrity status.
805
Akinobu Mitade1ba092006-12-08 02:39:42 -0800806 failslab=
807 fail_page_alloc=
808 fail_make_request=[KNL]
809 General fault injection mechanism.
810 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +0200811 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -0800812
Linus Torvalds1da177e2005-04-16 15:20:36 -0700813 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000814 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700815
Alex Chiangf13ae302008-05-08 14:03:23 -0600816 force_pal_cache_flush
817 [IA-64] Avoid check_sal_cache_flush which may hang on
818 buggy SAL_CACHE_FLUSH implementations. Using this
819 parameter will force ia64_sal_cache_flush to call
820 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
821
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100822 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400823 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100824 as early as possible in order to facilitate early
825 boot debugging.
826
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200827 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400828 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200829 If no parameter is passed, ftrace will dump
830 buffers of all CPUs, but if you pass orig_cpu, it will
831 dump only the buffer of the CPU that triggered the
832 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400833
834 ftrace_filter=[function-list]
835 [FTRACE] Limit the functions traced by the function
836 tracer at boot up. function-list is a comma separated
837 list of functions. This list can be changed at run
838 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -0700839 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400840
841 ftrace_notrace=[function-list]
842 [FTRACE] Do not trace the functions specified in
843 function-list. This list can be changed at run time
844 by the set_ftrace_notrace file in the debugfs
845 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100846
Stefan Assmann369bc182009-10-12 22:17:21 +0200847 ftrace_graph_filter=[function-list]
848 [FTRACE] Limit the top level callers functions traced
849 by the function graph tracer at boot up.
850 function-list is a comma separated list of functions
851 that can be changed at run time by the
852 set_graph_function file in the debugfs tracing directory.
853
Linus Torvalds1da177e2005-04-16 15:20:36 -0700854 gamecon.map[2|3]=
855 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
856 support via parallel port (up to 5 devices per port)
857 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
858 See also Documentation/input/joystick-parport.txt
859
860 gamma= [HW,DRM]
861
Yinghai Luaaf23042008-01-30 13:33:09 +0100862 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
863 Format: off | on
864 default: on
865
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700866 gcov_persist= [GCOV] When non-zero (default), profiling data for
867 kernel modules is saved and remains accessible via
868 debugfs, even when the module is unloaded/reloaded.
869 When zero, profiling data is discarded and associated
870 debugfs files are removed at module unload time.
871
Linus Torvalds1da177e2005-04-16 15:20:36 -0700872 gpt [EFI] Forces disk with valid GPT signature but
873 invalid Protective MBR to be treated as GPT.
874
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875 hashdist= [KNL,NUMA] Large hashes allocated during boot
876 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -0700877 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700878 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700879
880 hcl= [IA-64] SGI's Hardware Graph compatibility layer
881
882 hd= [EIDE] (E)IDE hard drive subsystem geometry
883 Format: <cyl>,<head>,<sect>
884
Huang Yingea8c0712010-05-18 14:35:15 +0800885 hest_disable [ACPI]
886 Disable Hardware Error Source Table (HEST) support;
887 corresponding firmware-first mode error processing
888 logic will be disabled.
889
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
891 size of <nn>. This works even on boxes that have no
892 highmem otherwise. This also works to reduce highmem
893 size on bigger boxes.
894
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800895 highres= [KNL] Enable/disable high resolution timer mode.
896 Valid parameters: "on", "off"
897 Default: "on"
898
Linus Torvalds1da177e2005-04-16 15:20:36 -0700899 hisax= [HW,ISDN]
900 See Documentation/isdn/README.HiSax.
901
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700902 hlt [BUGS=ARM,SH]
903
904 hpet= [X86-32,HPET] option to control HPET usage
905 Format: { enable (default) | disable | force |
906 verbose }
907 disable: disable HPET and use PIT instead
908 force: allow force enabled of undocumented chips (ICH4,
909 VIA, nVidia)
910 verbose: show contents of HPET registers during setup
911
Andi Kleenb4718e62008-07-23 21:27:51 -0700912 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
913 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700914 On x86-64 and powerpc, this option can be specified
915 multiple times interleaved with hugepages= to reserve
916 huge pages of different sizes. Valid pages sizes on
917 x86-64 are 2M (when the CPU supports "pse") and 1G
918 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700919 Note that 1GB pages can only be allocated at boot time
920 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900921
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100922 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
923 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100924 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
925 If specified, z/VM IUCV HVC accepts connections
926 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100927
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -0700928 keep_bootcon [KNL]
929 Do not unregister boot console at start. This is only
930 useful for debugging when something happens in the window
931 between unregistering the boot console and initializing
932 the real console.
933
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700934 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700935 or register an additional I2C bus that is not
936 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700937 Format:
938 <bus_id>,<clkrate>
939
Jiri Kosina36d95732008-10-06 02:51:09 -0400940 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700941 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200942 i8042.dumbkbd [HW] Pretend that controller can only read data from
943 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700944 (Don't attempt to blink the leds)
945 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500946 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400947 i8042.noloop [HW] Disable the AUX Loopback command while probing
948 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700949 i8042.nomux [HW] Don't check presence of an active multiplexing
950 controller
951 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
952 controllers
Jiri Kosinaf8313ef2011-01-08 01:37:26 -0800953 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
Linus Torvalds1da177e2005-04-16 15:20:36 -0700954 i8042.reset [HW] Reset the controller during init and cleanup
955 i8042.unlock [HW] Unlock (ignore) the keylock
956
957 i810= [HW,DRM]
958
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700959 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
960 indicates that the driver is running on unsupported
961 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700962 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
963 does not match list of supported models.
964 i8k.power_status
965 [HW] Report power status in /proc/i8k
966 (disabled by default)
967 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
968 capability is set.
969
Linus Torvalds1da177e2005-04-16 15:20:36 -0700970 icn= [HW,ISDN]
971 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
972
David Fries0af80c02009-02-25 20:28:21 +0100973 ide-core.nodma= [HW] (E)IDE subsystem
974 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +0200975 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
976 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +0100977 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700978
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700979 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
980 Claim all unknown PCI IDE storage controllers.
981
Andi Kleenf039b752007-05-02 19:27:12 +0200982 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800983 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
984 Poll forces a polling idle loop that can slightly
985 improve the performance of waking up a idle CPU, but
986 will use a lot of power and make the system run hot.
987 Not recommended.
988 idle=mwait: On systems which support MONITOR/MWAIT but
989 the kernel chose to not use it because it doesn't save
990 as much power as a normal idle loop, use the
991 MONITOR/MWAIT idle loop anyways. Performance should be
992 the same as idle=poll.
993 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800994 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800995 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700996
Ingo Molnar792908222006-12-06 20:40:51 -0800997 ignore_loglevel [KNL]
998 Ignore loglevel setting - this will print /all/
999 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001000 We also add it as printk module parameter, so users
1001 could change it dynamically, usually by
1002 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001003
Linus Torvalds1da177e2005-04-16 15:20:36 -07001004 ihash_entries= [KNL]
1005 Set number of hash buckets for inode cache.
1006
Mimi Zohar3323eec92009-02-04 09:06:58 -05001007 ima_audit= [IMA]
1008 Format: { "0" | "1" }
1009 0 -- integrity auditing messages. (Default)
1010 1 -- enable informational integrity auditing messages.
1011
1012 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -07001013 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001014 default: "sha1"
1015
Eric Paris5789ba32009-05-21 15:47:06 -04001016 ima_tcb [IMA]
1017 Load a policy which meets the needs of the Trusted
1018 Computing Base. This means IMA will measure all
1019 programs exec'd, files mmap'd for exec, and all files
1020 opened for read by uid=0.
1021
Linus Torvalds1da177e2005-04-16 15:20:36 -07001022 init= [KNL]
1023 Format: <full_path>
1024 Run specified binary instead of /sbin/init as init
1025 process.
1026
1027 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1028 for working out where the kernel is dying during
1029 startup.
1030
1031 initrd= [BOOT] Specify the location of the initial ramdisk
1032
1033 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1034 Format: <irq>
1035
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001036 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001037 on
1038 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001039 off
1040 Disable intel iommu driver.
1041 igfx_off [Default Off]
1042 By default, gfx is mapped as normal device. If a gfx
1043 device has a dedicated DMAR unit, the DMAR unit is
1044 bypassed by not enabling DMAR with this option. In
1045 this case, gfx device will use physical address for
1046 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001047 forcedac [x86_64]
1048 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001049 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001050 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001051 than 32-bit addressing. The default is to look
1052 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001053 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001054 strict [Default Off]
1055 With this option on every unmap_single operation will
1056 result in a hardware IOTLB flush operation as opposed
1057 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001058 sp_off [Default Off]
1059 By default, super page will be supported if Intel IOMMU
1060 has the capability. With this option, super page will
1061 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001062
1063 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1064 0 disables intel_idle and fall back on acpi_idle.
1065 1 to 6 specify maximum depth of C-state.
1066
Chris Wrightd1423d52010-07-20 11:06:49 -07001067 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001068 on enable Interrupt Remapping (default)
1069 off disable Interrupt Remapping
1070 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001071 no_x2apic_optout
1072 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001073
Randy Dunlap16290242011-08-13 12:34:52 -07001074 inttest= [IA-64]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001075
1076 iomem= Disable strict checking of access to MMIO memory
1077 strict regions from userspace.
1078 relaxed
1079
1080 iommu= [x86]
1081 off
1082 force
1083 noforce
1084 biomerge
1085 panic
1086 nopanic
1087 merge
1088 nomerge
1089 forcesac
1090 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001091 pt [x86, IA-64]
1092 group_mf [x86, IA-64]
1093
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001094
1095 io7= [HW] IO7 for Marvel based alpha systems
1096 See comment before marvel_specify_io7 in
1097 arch/alpha/kernel/core_marvel.c.
1098
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301099 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001100 0x80
1101 Standard port 0x80 based delay
1102 0xed
1103 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001104 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001105 Simple two microseconds delay
1106 none
1107 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001108
Linus Torvalds1da177e2005-04-16 15:20:36 -07001109 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001110 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111
1112 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001113 See comment before ip2_setup() in
1114 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001115
Alan Cox200803d2005-06-28 20:45:18 -07001116 irqfixup [HW]
1117 When an interrupt is not handled search all handlers
1118 for it. Intended to get systems with badly broken
1119 firmware running.
1120
1121 irqpoll [HW]
1122 When an interrupt is not handled search all handlers
1123 for it. Also check all handlers each timer
1124 interrupt. Intended to get systems with badly broken
1125 firmware running.
1126
Linus Torvalds1da177e2005-04-16 15:20:36 -07001127 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001128 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001129
1130 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001131 Format:
1132 <cpu number>,...,<cpu number>
1133 or
Li Zefanb225d442008-11-06 12:53:39 -08001134 <cpu number>-<cpu number>
1135 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001136 or a mixture
1137 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001138
Linus Torvalds1da177e2005-04-16 15:20:36 -07001139 This option can be used to specify one or more CPUs
1140 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001141 algorithms. You can move a process onto or off an
1142 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001143 <cpu number> begins at 0 and the maximum value is
1144 "number of CPUs in system - 1".
1145
1146 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001147 alternative -- manually setting the CPU mask of all
1148 tasks in the system -- can cause problems and
1149 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001150
Randy Dunlapa9913042005-10-23 12:57:11 -07001151 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001152
1153 js= [HW,JOY] Analog joystick
1154 See Documentation/input/joystick.txt.
1155
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001156 keepinitrd [HW,ARM]
1157
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301158 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001159 specifies the amount of memory usable by the kernel
1160 for non-movable allocations. The requested amount is
1161 spread evenly throughout all nodes in the system. The
1162 remaining memory in each node is used for Movable
1163 pages. In the event, a node is too small to have both
1164 kernelcore and Movable pages, kernelcore pages will
1165 take priority and other nodes will have a larger number
1166 of kernelcore pages. The Movable zone is used for the
1167 allocation of pages that may be reclaimed or moved
1168 by the page migration subsystem. This means that
1169 HugeTLB pages may not be allocated from this zone.
1170 Note that allocations like PTEs-from-HighMem still
1171 use the HighMem zone if it exists, and the Normal
1172 zone if it does not.
1173
Jason Wessel4fe1da42010-05-20 21:04:31 -05001174 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1175 Format: <Controller#>[,poll interval]
1176 The controller # is the number of the ehci usb debug
1177 port as it is probed via PCI. The poll interval is
1178 optional and is the number seconds in between
1179 each poll cycle to the debug port in case you need
1180 the functionality for interrupting the kernel with
1181 gdb or control-c on the dbgp connection. When
1182 not using this parameter you use sysrq-g to break into
1183 the kernel debugger.
1184
Jason Wessel84c08fd2010-05-20 21:04:24 -05001185 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001186 Requires a tty driver that supports console polling,
1187 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001188 Serial only format: <serial_device>[,baud]
1189 keyboard only format: kbd
1190 keyboard and serial format: kbd,<serial_device>[,baud]
1191 Optional Kernel mode setting:
1192 kms, kbd format: kms,kbd
1193 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001194
Jason Wessel84c08fd2010-05-20 21:04:24 -05001195 kgdbwait [KGDB] Stop kernel execution and enter the
1196 kernel debugger at the earliest opportunity.
1197
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001198 kmac= [MIPS] korina ethernet MAC address.
1199 Configure the RouterBoard 532 series on-chip
1200 Ethernet adapter MAC address.
1201
Catalin Marinas04f70332009-06-11 13:22:39 +01001202 kmemleak= [KNL] Boot-time kmemleak enable/disable
1203 Valid arguments: on, off
1204 Default: on
1205
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301206 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001207 in oops dumps.
1208
Andre Przywarafef07aa2009-07-10 14:20:35 +02001209 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1210 Default is 0 (don't ignore, but inject #GP)
1211
Xiao Guangronga182d872010-09-20 22:17:48 +08001212 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1213 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001214 Default is 0 (off)
1215
Andre Przywarafef07aa2009-07-10 14:20:35 +02001216 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001217 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001218
1219 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1220 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001221 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001222
Andre Przywarafef07aa2009-07-10 14:20:35 +02001223 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1224 (virtualized MMU) support on capable Intel chips.
1225 Default is 1 (enabled)
1226
1227 kvm-intel.emulate_invalid_guest_state=
1228 [KVM,Intel] Enable emulation of invalid guest states
1229 Default is 0 (disabled)
1230
1231 kvm-intel.flexpriority=
1232 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1233 Default is 1 (enabled)
1234
Sasha Levine1a72ae2011-08-09 14:28:35 +03001235 kvm-intel.nested=
1236 [KVM,Intel] Enable VMX nesting (nVMX).
1237 Default is 0 (disabled)
1238
Andre Przywarafef07aa2009-07-10 14:20:35 +02001239 kvm-intel.unrestricted_guest=
1240 [KVM,Intel] Disable unrestricted guest feature
1241 (virtualized real and unpaged mode) on capable
1242 Intel chips. Default is 1 (enabled)
1243
1244 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1245 feature (tagged TLBs) on capable Intel chips.
1246 Default is 1 (enabled)
1247
Linus Torvalds1da177e2005-04-16 15:20:36 -07001248 l2cr= [PPC]
1249
Robert Brosea78bfbf2008-03-29 07:20:23 +11001250 l3cr= [PPC]
1251
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001252 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001253 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001254
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301255 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001256 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001257
FD Camifcb71f62008-01-06 19:08:56 +01001258 libata.dma= [LIBATA] DMA control
1259 libata.dma=0 Disable all PATA and SATA DMA
1260 libata.dma=1 PATA and SATA Disk DMA only
1261 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001262 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001263 Combinations also work, so libata.dma=3 enables DMA
1264 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001265
Michael Prokop20308872009-08-06 00:14:10 +02001266 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1267 libata.ignore_hpa=0 keep BIOS limits (default)
1268 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001269
Dave Jones78e70c22007-09-27 11:50:13 -04001270 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1271 when set.
1272 Format: <int>
1273
Tejun Heo33267322008-02-13 09:15:09 +09001274 libata.force= [LIBATA] Force configurations. The format is comma
1275 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001276 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001277 matching port, link or device. Basically, it matches
1278 the ATA ID string printed on console by libata. If
1279 the whole ID part is omitted, the last PORT and DEVICE
1280 values are used. If ID hasn't been specified yet, the
1281 configuration applies to all ports, links and devices.
1282
1283 If only DEVICE is omitted, the parameter applies to
1284 the port and all links and devices behind it. DEVICE
1285 number of 0 either selects the first device or the
1286 first fan-out link behind PMP device. It does not
1287 select the host link. DEVICE number of 15 selects the
1288 host link and device attached to it.
1289
1290 The VAL specifies the configuration to force. As long
1291 as there's no ambiguity shortcut notation is allowed.
1292 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1293 The following configurations can be forced.
1294
1295 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1296 Any ID with matching PORT is used.
1297
1298 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1299
1300 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1301 udma[/][16,25,33,44,66,100,133] notation is also
1302 allowed.
1303
1304 * [no]ncq: Turn on or off NCQ.
1305
Tejun Heo05944bd2008-08-13 20:19:09 +09001306 * nohrst, nosrst, norst: suppress hard, soft
1307 and both resets.
1308
Tejun Heo43c9c592010-05-23 12:59:11 +02001309 * dump_id: dump IDENTIFY data.
1310
Tejun Heo33267322008-02-13 09:15:09 +09001311 If there are multiple matching configurations changing
1312 the same attribute, the last one is used.
1313
Yinghai Lu95f72d12010-07-12 14:36:09 +10001314 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001315
Linus Torvalds1da177e2005-04-16 15:20:36 -07001316 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001317 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001318
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001319 lockd.nlm_grace_period=P [NFS] Assign grace period.
1320 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001321
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001322 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1323 Format: <integer>
1324
1325 lockd.nlm_timeout=T [NFS] Assign timeout value.
1326 Format: <integer>
1327
1328 lockd.nlm_udpport=M [NFS] Assign UDP port.
1329 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330
1331 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1332 Format: <irq>
1333
1334 loglevel= All Kernel Messages with a loglevel smaller than the
1335 console loglevel will be printed to the console. It can
1336 also be changed with klogd or other programs. The
1337 loglevels are defined as follows:
1338
1339 0 (KERN_EMERG) system is unusable
1340 1 (KERN_ALERT) action must be taken immediately
1341 2 (KERN_CRIT) critical conditions
1342 3 (KERN_ERR) error conditions
1343 4 (KERN_WARNING) warning conditions
1344 5 (KERN_NOTICE) normal but significant condition
1345 6 (KERN_INFO) informational
1346 7 (KERN_DEBUG) debug-level messages
1347
Randy Dunlapc756d082011-02-20 20:08:35 -08001348 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1349 in bytes. n must be a power of two. The default
1350 size is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351
Randy Dunlapaccaa242007-10-16 01:29:37 -07001352 logo.nologo [FB] Disables display of the built-in Linux logo.
1353 This may be used to provide more screen space for
1354 kernel log messages and is useful when debugging
1355 kernel boot problems.
1356
Linus Torvalds1da177e2005-04-16 15:20:36 -07001357 lp=0 [LP] Specify parallel ports to use, e.g,
1358 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1359 lp=reset first parallel port). 'lp=0' disables the
1360 lp=auto printer driver. 'lp=reset' (which can be
1361 specified in addition to the ports) causes
1362 attached printers to be reset. Using
1363 lp=port1,port2,... specifies the parallel ports
1364 to associate lp devices with, starting with
1365 lp0. A port specification may be 'none' to skip
1366 that lp device, or a parport name such as
1367 'parport0'. Specifying 'lp=auto' instead of a
1368 port specification list means that device IDs
1369 from each port should be examined, to see if
1370 an IEEE 1284-compliant printer is attached; if
1371 so, the driver will manage that printer.
1372 See also header of drivers/char/lp.c.
1373
1374 lpj=n [KNL]
1375 Sets loops_per_jiffy to given constant, thus avoiding
1376 time-consuming boot-time autodetection (up to 250 ms per
1377 CPU). 0 enables autodetection (default). To determine
1378 the correct value for your kernel, boot with normal
1379 autodetection and see what value is printed. Note that
1380 on SMP systems the preset will be applied to all CPUs,
1381 which is likely to cause problems if your CPUs need
1382 significantly divergent settings. An incorrect value
1383 will cause delays in the kernel to be wrong, leading to
1384 unpredictable I/O errors and other breakage. Although
1385 unlikely, in the extreme case this might damage your
1386 hardware.
1387
1388 ltpc= [NET]
1389 Format: <io>,<irq>,<dma>
1390
Randy Dunlap16290242011-08-13 12:34:52 -07001391 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001392 (machvec) in a generic kernel.
1393 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001394
Wu Zhangjin3209e702009-07-02 23:27:12 +08001395 machtype= [Loongson] Share the same kernel image file between different
1396 yeeloong laptop.
1397 Example: machtype=lemote-yeeloong-2f-7inch
1398
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001399 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1400 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001401
1402 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001403 should make use of. maxcpus=n : n >= 0 limits the
1404 kernel to using 'n' processors. n=0 is a special case,
1405 it is equivalent to "nosmp", which also disables
1406 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407
Kay Sieversd134b002011-07-31 22:08:04 +02001408 max_loop= [LOOP] The number of loop block devices that get
1409 (loop.max_loop) unconditionally pre-created at init time. The default
1410 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1411 of statically allocating a predefined number, loop
1412 devices can be requested on-demand with the
1413 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001414
Linus Torvalds1da177e2005-04-16 15:20:36 -07001415 mcatest= [IA-64]
1416
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001417 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001418
Uwe Hermann71cced62008-10-20 09:32:21 -07001419 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001420
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421 md= [HW] RAID subsystems devices and level
1422 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001423
Linus Torvalds1da177e2005-04-16 15:20:36 -07001424 mdacon= [MDA]
1425 Format: <first>,<last>
1426 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001427
Linus Torvalds1da177e2005-04-16 15:20:36 -07001428 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1429 Amount of memory to be used when the kernel is not able
1430 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001431 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001432 address space collisions. Without memmap= PCI devices
1433 could be placed at addresses belonging to unused RAM.
1434
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001435 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001436 memory.
1437
Paul Mundt6902aa82008-09-21 17:14:42 +09001438 memchunk=nn[KMG]
1439 [KNL,SH] Allow user to override the default size for
1440 per-device physically contiguous DMA buffers.
1441
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301442 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001443 E820 memory map, as specified by the user.
1444 Such memmap=exactmap lines can be constructed based on
1445 BIOS output or other requirements. See the memmap=nn@ss
1446 option description.
1447
1448 memmap=nn[KMG]@ss[KMG]
1449 [KNL] Force usage of a specific region of memory
1450 Region of memory to be used, from ss to ss+nn.
1451
1452 memmap=nn[KMG]#ss[KMG]
1453 [KNL,ACPI] Mark specific memory as ACPI data.
1454 Region of memory to be used, from ss to ss+nn.
1455
1456 memmap=nn[KMG]$ss[KMG]
1457 [KNL,ACPI] Mark specific memory as reserved.
1458 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001459 Example: Exclude memory from 0x18690000-0x1869ffff
1460 memmap=64K$0x18690000
1461 or
1462 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001464 memory_corruption_check=0/1 [X86]
1465 Some BIOSes seem to corrupt the first 64k of
1466 memory when doing things like suspend/resume.
1467 Setting this option will scan the memory
1468 looking for corruption. Enabling this will
1469 both detect corruption and prevent the kernel
1470 from using the memory being corrupted.
1471 However, its intended as a diagnostic tool; if
1472 repeatable BIOS-originated corruption always
1473 affects the same memory, you can use memmap=
1474 to prevent the kernel from using that memory.
1475
1476 memory_corruption_check_size=size [X86]
1477 By default it checks for corruption in the low
1478 64k, making this memory unavailable for normal
1479 use. Use this parameter to scan for
1480 corruption in more or less memory.
1481
1482 memory_corruption_check_period=seconds [X86]
1483 By default it checks for corruption every 60
1484 seconds. Use this parameter to check at some
1485 other rate. 0 disables periodic checking.
1486
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001487 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001488 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001489 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001490 Specifies the number of memtest passes to be
1491 performed. Each pass selects another test
1492 pattern from a given set of patterns. Memtest
1493 fills the memory with this pattern, validates
1494 memory contents and reserves bad memory
1495 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001496
Linus Torvalds1da177e2005-04-16 15:20:36 -07001497 meye.*= [HW] Set MotionEye Camera parameters
1498 See Documentation/video4linux/meye.txt.
1499
Andres Salomon8f368812007-10-12 23:04:06 +02001500 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1501 Multi-Function General Purpose Timers on AMD Geode
1502 platforms.
1503
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001504 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1505 the BIOS has incorrectly applied a workaround. TinyBIOS
1506 version 0.98 is known to be affected, 0.99 fixes the
1507 problem by letting the user disable the workaround.
1508
Linus Torvalds1da177e2005-04-16 15:20:36 -07001509 mga= [HW,DRM]
1510
Randy Dunlap1c207f92008-11-19 15:36:16 -08001511 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1512 physical address is ignored.
1513
Michel Pollet39f45d72009-05-20 11:10:31 +01001514 mini2440= [ARM,HW,KNL]
1515 Format:[0..2][b][c][t]
1516 Default: "0tb"
1517 MINI2440 configuration specification:
1518 0 - The attached screen is the 3.5" TFT
1519 1 - The attached screen is the 7" TFT
1520 2 - The VGA Shield is attached (1024x768)
1521 Leaving out the screen size parameter will not load
1522 the TFT driver, and the framebuffer will be left
1523 unconfigured.
1524 b - Enable backlight. The TFT backlight pin will be
1525 linked to the kernel VESA blanking code and a GPIO
1526 LED. This parameter is not necessary when using the
1527 VGA shield.
1528 c - Enable the s3c camera interface.
1529 t - Reserved for enabling touchscreen support. The
1530 touchscreen support is not enabled in the mainstream
1531 kernel as of 2.6.30, a preliminary port can be found
1532 in the "bleeding edge" mini2440 support kernel at
1533 http://repo.or.cz/w/linux-2.6/mini2440.git
1534
Mel Gorman6b74ab92008-07-23 21:26:49 -07001535 mminit_loglevel=
1536 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1537 parameter allows control of the logging verbosity for
1538 the additional memory initialisation checks. A value
1539 of 0 disables mminit logging and a level of 4 will
1540 log everything. Information is printed at KERN_DEBUG
1541 so loglevel=8 may also need to be specified.
1542
Linus Torvalds1da177e2005-04-16 15:20:36 -07001543 mousedev.tap_time=
1544 [MOUSE] Maximum time between finger touching and
1545 leaving touchpad surface for touch to be considered
1546 a tap and be reported as a left button click (for
1547 touchpads working in absolute mode only).
1548 Format: <msecs>
1549 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1550 reporting absolute coordinates, such as tablets
1551 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1552 reporting absolute coordinates, such as tablets
1553
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301554 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001555 is similar to kernelcore except it specifies the
1556 amount of memory used for migratable allocations.
1557 If both kernelcore and movablecore is specified,
1558 then kernelcore will be at *least* the specified
1559 value but may be more. If movablecore on its own
1560 is specified, the administrator must be careful
1561 that the amount of memory usable for all allocations
1562 is not too small.
1563
Linus Torvalds1da177e2005-04-16 15:20:36 -07001564 MTD_Partition= [MTD]
1565 Format: <name>,<region-number>,<size>,<offset>
1566
Randy Dunlapa9913042005-10-23 12:57:11 -07001567 MTD_Region= [MTD] Format:
1568 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001569
1570 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001571 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001572
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001573 multitce=off [PPC] This parameter disables the use of the pSeries
1574 firmware feature for updating multiple TCE entries
1575 at a time.
1576
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001577 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1578
1579 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1580
1581 boundary - index of last SLC block on Flex-OneNAND.
1582 The remaining blocks are configured as MLC blocks.
1583 lock - Configure if Flex-OneNAND boundary should be locked.
1584 Once locked, the boundary cannot be changed.
1585 1 indicates lock status, 0 indicates unlock status.
1586
Ben Dooks9db829f2008-07-03 11:24:29 +01001587 mtdset= [ARM]
1588 ARM/S3C2412 JIVE boot control
1589
1590 See arch/arm/mach-s3c2412/mach-jive.c
1591
Linus Torvalds1da177e2005-04-16 15:20:36 -07001592 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001593 [HW] Make the MicroTouch USB driver use raw coordinates
1594 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001596 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001597 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001598 that could hold holes aka. UC entries.
1599
1600 mtrr_gran_size=nn[KMG] [X86]
1601 Used for mtrr cleanup. It is granularity of mtrr block.
1602 Default is 1.
1603 Large value could prevent small alignment from
1604 using up MTRRs.
1605
1606 mtrr_spare_reg_nr=n [X86]
1607 Format: <integer>
1608 Range: 0,7 : spare reg number
1609 Default : 1
1610 Used for mtrr cleanup. It is spare mtrr entries number.
1611 Set to 2 or more if your graphical card needs more.
1612
Linus Torvalds1da177e2005-04-16 15:20:36 -07001613 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1614
Linus Torvalds1da177e2005-04-16 15:20:36 -07001615 netdev= [NET] Network devices parameters
1616 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1617 Note that mem_start is often overloaded to mean
1618 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001619 This usage is only documented in each driver source
1620 file if at all.
1621
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001622 nf_conntrack.acct=
1623 [NETFILTER] Enable connection tracking flow accounting
1624 0 to disable accounting
1625 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001626 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001627
Chuck Lever306a0752010-09-17 10:54:37 -04001628 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001629 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001630
1631 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001632 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001633
Chuck Lever306a0752010-09-17 10:54:37 -04001634 nfsrootdebug [NFS] enable nfsroot debugging messages.
1635 See Documentation/filesystems/nfs/nfsroot.txt.
1636
Trond Myklebusta72b4422006-01-03 09:55:41 +01001637 nfs.callback_tcpport=
1638 [NFS] set the TCP port on which the NFSv4 callback
1639 channel should listen.
1640
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001641 nfs.cache_getent=
1642 [NFS] sets the pathname to the program which is used
1643 to update the NFS client cache entries.
1644
1645 nfs.cache_getent_timeout=
1646 [NFS] sets the timeout after which an attempt to
1647 update a cache entry is deemed to have failed.
1648
Trond Myklebust58df0952006-01-03 09:55:57 +01001649 nfs.idmap_cache_timeout=
1650 [NFS] set the maximum lifetime for idmapper cache
1651 entries.
1652
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001653 nfs.enable_ino64=
1654 [NFS] enable 64-bit inode numbers.
1655 If zero, the NFS client will fake up a 32-bit inode
1656 number for the readdir() and stat() syscalls instead
1657 of returning the full 64-bit number.
1658 The default is to return 64-bit inode numbers.
1659
Trond Myklebustb064eca22011-02-22 15:44:32 -08001660 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05001661 [NFSv4] When set to the default of '1', this option
1662 ensures that both the RPC level authentication
1663 scheme and the NFS level operations agree to use
1664 numeric uids/gids if the mount is using the
1665 'sec=sys' security flavour. In effect it is
1666 disabling idmapping, which can make migration from
1667 legacy NFSv2/v3 systems to NFSv4 easier.
1668 Servers that do not support this mode of operation
1669 will be autodetected by the client, and it will fall
1670 back to using the idmapper.
1671 To turn off this behaviour, set the value to '0'.
Trond Myklebustb064eca22011-02-22 15:44:32 -08001672
Paul Mundt1e1030d2009-09-01 17:38:32 +09001673 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001674 when a NMI is triggered.
1675 Format: [state][,regs][,debounce][,die]
1676
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301677 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07001678 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05001679 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001680 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001681 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07001682 timeout occurs (or 'nopanic' to override the opposite
1683 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001684 This is useful when you use a panic=... timeout and
1685 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001686
Anton Vorontsovbff38772009-07-08 11:10:56 -07001687 netpoll.carrier_timeout=
1688 [NET] Specifies amount of time (in seconds) that
1689 netpoll should wait for a carrier. By default netpoll
1690 waits 4 seconds.
1691
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001692 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001693 emulation library even if a 387 maths coprocessor
1694 is present.
1695
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001696 no_console_suspend
1697 [HW] Never suspend the console
1698 Disable suspending of consoles during suspend and
1699 hibernate operations. Once disabled, debugging
1700 messages can reach various consoles while the rest
1701 of the system is being put to sleep (ie, while
1702 debugging driver suspend/resume hooks). This may
1703 not work reliably with all consoles, but is known
1704 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07001705 To facilitate more flexible debugging, we also add
1706 console_suspend, a printk module parameter to control
1707 it. Users could use console_suspend (usually
1708 /sys/module/printk/parameters/console_suspend) to
1709 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001710
Christoph Lameterc1aee212007-05-31 00:40:47 -07001711 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1712 caches in the slab allocator. Saves per-node memory,
1713 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001714
Randy Dunlapa9913042005-10-23 12:57:11 -07001715 noalign [KNL,ARM]
1716
Linus Torvalds1da177e2005-04-16 15:20:36 -07001717 noapic [SMP,APIC] Tells the kernel to not make use of any
1718 IOAPICs that may be present in the system.
1719
Mike Galbraith5091faa2010-11-30 14:18:03 +01001720 noautogroup Disable scheduler automatic task group creation.
1721
Linus Torvalds1da177e2005-04-16 15:20:36 -07001722 nobats [PPC] Do not use BATs for mapping kernel lowmem
1723 on "Classic" PPC cores.
1724
1725 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001726
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001727 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1728
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001729 nodelayacct [KNL] Disable per-task delay accounting
1730
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1732
Paul Mundt6902aa82008-09-21 17:14:42 +09001733 nodsp [SH] Disable hardware DSP at boot time.
1734
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301735 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001736
Linus Torvalds1da177e2005-04-16 15:20:36 -07001737 noexec [IA-64]
1738
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301739 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001740 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001741 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001742 noexec=off: disable non-executable mappings
1743
Fenghua Yude5397a2011-05-11 16:51:05 -07001744 nosmep [X86]
1745 Disable SMEP (Supervisor Mode Execution Protection)
1746 even if it is supported by processor.
1747
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001748 noexec32 [X86-64]
1749 This affects only 32-bit executables.
1750 noexec32=on: enable non-executable mappings (default)
1751 read doesn't imply executable mappings
1752 noexec32=off: disable non-executable mappings
1753 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001754
Paul Mundt6902aa82008-09-21 17:14:42 +09001755 nofpu [SH] Disable hardware FPU at boot time.
1756
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001757 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001758 register save and restore. The kernel will only save
1759 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001760
Suresh Siddha0c752a92009-05-22 12:17:45 -07001761 noxsave [BUGS=X86] Disables x86 extended register state save
1762 and restore using xsave. The kernel will fallback to
1763 enabling legacy floating-point and sse state.
1764
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001765 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1766 wfi(ARM) instruction doesn't work correctly and not to
1767 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001768
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001769 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001770 instruction doesn't work correctly and not to
1771 use it.
1772
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001773 no_file_caps Tells the kernel not to honor file capabilities. The
1774 only way then for a file to be executed with privilege
1775 is to be setuid root or executed by root.
1776
Linus Torvalds1da177e2005-04-16 15:20:36 -07001777 nohalt [IA-64] Tells the kernel not to use the power saving
1778 function PAL_HALT_LIGHT when idle. This increases
1779 power-consumption. On the positive side, it reduces
1780 interrupt wake-up latency, which may improve performance
1781 in certain environments such as networked servers or
1782 real-time systems.
1783
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001784 nohz= [KNL] Boottime enable/disable dynamic ticks
1785 Valid arguments: on, off
1786 Default: on
1787
Paul Mundteeee7852009-04-02 12:31:16 +09001788 noiotrap [SH] Disables trapped I/O port accesses.
1789
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001790 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001791 disable unhandled interrupt sources.
1792
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301793 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001794 broken timer IRQ sources.
1795
Linus Torvalds1da177e2005-04-16 15:20:36 -07001796 noisapnp [ISAPNP] Disables ISA PnP code.
1797
1798 noinitrd [RAM] Tells the kernel not to load any configured
1799 initial RAM disk.
1800
Weidong Han03ea8152009-04-17 16:42:15 +08001801 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1802 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07001803 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08001804
Linus Torvalds1da177e2005-04-16 15:20:36 -07001805 nointroute [IA-64]
1806
Randy Dunlap16290242011-08-13 12:34:52 -07001807 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07001808
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02001809 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1810
Gleb Natapovfd10cde2010-10-14 11:22:51 +02001811 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1812 fault handling.
1813
Glauber Costad910f5c2011-07-11 15:28:19 -04001814 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1815 steal time is computed, but won't influence scheduler
1816 behaviour
1817
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001818 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001819
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001820 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001821
Linus Torvalds1da177e2005-04-16 15:20:36 -07001822 noltlbs [PPC] Do not use large page/tlb entries for kernel
1823 lowmem mapping on PPC40x.
1824
Horms312f1f02006-02-22 09:57:55 +09001825 nomca [IA-64] Disable machine check abort handling
1826
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001827 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001828
Andres Salomon83d73842007-10-12 23:04:06 +02001829 nomfgpt [X86-32] Disable Multi-Function General Purpose
1830 Timer usage (for AMD Geode machines).
1831
Don Zickusbda62632011-10-13 15:14:27 -04001832 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1833 shutdown the other cpus. Instead use the REBOOT_VECTOR
1834 irq.
1835
Jiri Kosina016ddd92010-01-18 17:05:40 +01001836 nopat [X86] Disable PAT (page attribute table extension of
1837 pagetables) support.
1838
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001839 norandmaps Don't use address space randomization. Equivalent to
1840 echo 0 > /proc/sys/kernel/randomize_va_space
1841
Jiri Kosinabbff2162010-08-11 18:34:09 +02001842 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001843
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001844 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001845 with UP alternatives
1846
Linus Torvalds1da177e2005-04-16 15:20:36 -07001847 noresidual [PPC] Don't use residual data on PReP machines.
1848
H. Peter Anvin49d859d2011-07-31 14:02:19 -07001849 nordrand [X86] Disable the direct use of the RDRAND
1850 instruction even if it is supported by the
1851 processor. RDRAND is still available to user
1852 space applications.
1853
Randy Dunlapa9913042005-10-23 12:57:11 -07001854 noresume [SWSUSP] Disables resume and restores original swap
1855 space.
1856
Linus Torvalds1da177e2005-04-16 15:20:36 -07001857 no-scroll [VGA] Disables scrollback.
1858 This is required for the Braillex ib80-piezo Braille
1859 reader made by F.H. Papenmeier (Germany).
1860
1861 nosbagart [IA-64]
1862
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001863 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001864
Len Brown61ec7562007-08-16 03:34:22 -04001865 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1866 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001867
Dave Jones97842212007-07-15 23:41:05 -07001868 nosoftlockup [KNL] Disable the soft-lockup detector.
1869
Linus Torvalds1da177e2005-04-16 15:20:36 -07001870 nosync [HW,M68K] Disables sync negotiation for all devices.
1871
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001872 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001873
1874 nousb [USB] Disable the USB subsystem
1875
Ben Hutchings55142372011-01-02 23:02:42 +00001876 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04001877
Linus Torvalds1da177e2005-04-16 15:20:36 -07001878 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001879
Weidong Han2b2fd872009-04-17 16:42:12 +08001880 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1881
Randy Dunlap16290242011-08-13 12:34:52 -07001882 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07001883 purges which is reported from either PAL_VM_SUMMARY or
1884 SAL PALO.
1885
Yinghai Lu2b633e32010-02-10 01:20:37 -08001886 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1887 could support. nr_cpus=n : n >= 1 limits the kernel to
1888 supporting 'n' processors. Later in runtime you can not
1889 use hotplug cpu feature to put more cpu back to online.
1890 just like you compile the kernel NR_CPUS=n
1891
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001892 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1893
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001894 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1895 one of ['zone', 'node', 'default'] can be specified
1896 This can be set from sysctl after boot.
1897 See Documentation/sysctl/vm.txt for details.
1898
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001899 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1900 See Documentation/debugging-via-ohci1394.txt for more
1901 info.
1902
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001903 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1904 Rather than timing out after 20 ms if an EC
1905 command is not properly ACKed, override the length
1906 of the timeout. We have interrupts disabled while
1907 waiting for the ACK, so if this is set too high
1908 interrupts *may* be lost!
1909
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001910 omap_mux= [OMAP] Override bootloader pin multiplexing.
1911 Format: <mux_mode0.mode_name=value>...
1912 For example, to override I2C bus2:
1913 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1914
Linus Torvalds1da177e2005-04-16 15:20:36 -07001915 oprofile.timer= [HW]
1916 Use timer interrupt instead of performance counters
1917
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001918 oprofile.cpu_type= Force an oprofile cpu type
1919 This might be useful if you have an older oprofile
1920 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001921 Format: { arch_perfmon }
1922 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001923 perfmon on Intel CPUs instead of the
1924 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02001925 timer: [X86] Force use of architectural NMI
1926 timer mode (see also oprofile.timer
1927 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01001928 [s390] Force legacy basic mode sampling
1929 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02001930
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07001931 oops=panic Always panic on oopses. Default is to just kill the
1932 process, but there is a small probability of
1933 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07001934 This will also cause panics on machine check exceptions.
1935 Useful together with panic=30 to trigger a reboot.
1936
Randy Dunlapbcfde332010-06-07 17:10:38 -07001937 OSS [HW,OSS]
1938 See Documentation/sound/oss/oss-parameters.txt
1939
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07001940 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07001941 timeout > 0: seconds before rebooting
1942 timeout = 0: wait forever
1943 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07001944 Format: <timeout>
1945
1946 parkbd.port= [HW] Parallel port number the keyboard adapter is
1947 connected to, default is 0.
1948 Format: <parport#>
1949 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1950 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001951 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001952
Randy Dunlapa9913042005-10-23 12:57:11 -07001953 parport= [HW,PPT] Specify parallel ports. 0 disables.
1954 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1955 Use 'auto' to force the driver to use any
1956 IRQ/DMA settings detected (the default is to
1957 ignore detected IRQ/DMA settings because of
1958 possible conflicts). You can specify the base
1959 address, IRQ, and DMA settings; IRQ and DMA
1960 should be numbers, or 'auto' (for using detected
1961 settings on that particular port), or 'nofifo'
1962 (to avoid using a FIFO even if it is detected).
1963 Parallel ports are assigned in the order they
1964 are specified on the command line, starting
1965 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001966
Randy Dunlapa9913042005-10-23 12:57:11 -07001967 parport_init_mode= [HW,PPT]
1968 Configure VIA parallel port to operate in
1969 a specific mode. This is necessary on Pegasos
1970 computer where firmware has no options for setting
1971 up parallel port mode and sets it to spp.
1972 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001973 Format: [spp|ps2|epp|ecp|ecpepp]
1974
Andrew Mortondd287792006-03-23 03:00:57 -08001975 pause_on_oops=
1976 Halt all CPUs after the first oops has been printed for
1977 the specified number of seconds. This is to be used if
1978 your oopses keep scrolling off the screen.
1979
Linus Torvalds1da177e2005-04-16 15:20:36 -07001980 pcbit= [HW,ISDN]
1981
1982 pcd. [PARIDE]
1983 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001984 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001985
Randy Dunlapa9913042005-10-23 12:57:11 -07001986 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07001987 earlydump [X86] dump PCI config space before the kernel
1988 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02001989 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001990 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001991 the hardware directly. Use this if your machine
1992 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001993 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001994 hardware access methods are allowed. Use this
1995 if you experience crashes upon bootup and you
1996 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001997 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001998 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001999 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002000 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002001 noaer [PCIE] If the PCIEAER kernel config parameter is
2002 enabled, this kernel boot option can be used to
2003 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002004 nodomains [PCI] Disable support for multiple PCI
2005 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302006 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002007 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002008 check_enable_amd_mmconf [X86] check for and enable
2009 properly configured MMIO access to PCI
2010 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002011 nomsi [MSI] If the PCI_MSI kernel config parameter is
2012 enabled, this kernel boot option can be used to
2013 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002014 noioapicquirk [APIC] Disable all boot interrupt quirks.
2015 Safety option to keep boot IRQs enabled. This
2016 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002017 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2018 primary IO-APIC for bridges that cannot disable
2019 boot IRQs. This fixes a source of spurious IRQs
2020 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002021 noioapicreroute [APIC] Disable workaround that uses the
2022 boot IRQ equivalent of an IRQ that connects to
2023 a chipset where boot IRQs cannot be disabled.
2024 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002025 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002026 routing table. These calls are known to be buggy
2027 on several machines and they hang the machine
2028 when used, but on other computers it's the only
2029 way to get the interrupt routing table. Try
2030 this option if the kernel is unable to allocate
2031 IRQs or discover secondary PCI buses on your
2032 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002033 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002034 Use with caution as certain devices share
2035 address decoders between ROMs and other
2036 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002037 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002038 expansion ROMs that do not already have
2039 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002040 nobar [X86] Do not assign address space to the
2041 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002042 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002043 assigned automatically to PCI devices. You can
2044 make the kernel exclude IRQs of your ISA cards
2045 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002046 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002047 of the PIRQ table (normally generated
2048 by the BIOS) if it is outside the
2049 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002050 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002051 useful if the kernel is unable to find your
2052 secondary buses and you want to tell it
2053 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002054 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002055 numbers ourselves, overriding
2056 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002057 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002058 in the BIOS $PIR table. This is needed on
2059 some systems with broken BIOSes, notably
2060 some HP Pavilion N5400 and Omnibook XE3
2061 notebooks. This will have no effect if ACPI
2062 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002063 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002064 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002065 use_crs [X86] Use PCI host bridge window information
2066 from ACPI. On BIOSes from 2008 or later, this
2067 is enabled by default. If you need to use this,
2068 please report a bug.
2069 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2070 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002071 routeirq Do IRQ routing for all PCI devices.
2072 This is normally done in pci_enable_device(),
2073 so this option is a temporary workaround
2074 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002075 skip_isa_align [X86] do not align io start addr, so can
2076 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002077 firmware [ARM] Do not re-enumerate the bus but instead
2078 just use the configuration from the
2079 bootloader. This is currently used on
2080 IXP2000 systems where the bus has to be
2081 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002082 noearly [X86] Don't do any early type 1 scanning.
2083 This might help on some broken boards which
2084 machine check when some devices' config space
2085 is read. But various workarounds are disabled
2086 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002087 bfsort Sort PCI devices into breadth-first order.
2088 This sorting is done to get a device
2089 order compatible with older (<= 2.4) kernels.
2090 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002091 cbiosize=nn[KMG] The fixed amount of bus space which is
2092 reserved for the CardBus bridge's IO window.
2093 The default value is 256 bytes.
2094 cbmemsize=nn[KMG] The fixed amount of bus space which is
2095 reserved for the CardBus bridge's memory
2096 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002097 resource_alignment=
2098 Format:
2099 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2100 Specifies alignment and device to reassign
2101 aligned memory resources.
2102 If <order of align> is not specified,
2103 PAGE_SIZE is used as alignment.
2104 PCI-PCI bridge can be specified, if resource
2105 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002106 ecrc= Enable/disable PCIe ECRC (transaction layer
2107 end-to-end CRC checking).
2108 bios: Use BIOS/firmware settings. This is the
2109 the default.
2110 off: Turn ECRC off
2111 on: Turn ECRC on.
Ram Paif483d392011-07-07 11:19:10 -07002112 realloc reallocate PCI resources if allocations done by BIOS
2113 are erroneous.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002114
Chuck Ebberte5665a42008-09-24 20:40:34 -04002115 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2116 Management.
2117 off Disable ASPM.
2118 force Enable ASPM even on devices that claim not to support it.
2119 WARNING: Forcing ASPM on may cause system lockups.
2120
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002121 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002122 auto Ask the BIOS whether or not to use native PCIe services
2123 associated with PCIe ports (PME, hot-plug, AER). Use
2124 them only if that is allowed by the BIOS.
2125 native Use native PCIe services associated with PCIe ports
2126 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002127 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2128 ports driver.
2129
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002130 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002131 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002132 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002133
Linus Torvalds1da177e2005-04-16 15:20:36 -07002134 pcmv= [HW,PCMCIA] BadgePAD 4
2135
2136 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002137 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002138
2139 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2140 boot time.
2141 Format: { 0 | 1 }
2142 See arch/parisc/kernel/pdc_chassis.c
2143
Tejun Heof58dc012009-08-14 15:00:50 +09002144 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002145 Currently supported values are "embed" and "page".
2146 Archs may support subset or none of the selections.
2147 See comments in mm/percpu.c for details on each
2148 allocator. This parameter is primarily for debugging
2149 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002150
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002152 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002153
2154 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002155 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002156
2157 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002158 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002159
2160 plip= [PPT,NET] Parallel port network link
2161 Format: { parport<nr> | timid | 0 }
2162 See also Documentation/parport.txt.
2163
Randy Dunlap16290242011-08-13 12:34:52 -07002164 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002165 Override pmtimer IOPort with a hex value.
2166 e.g. pmtmr=0x508
2167
Bjorn Helgaas96242112011-08-11 12:14:05 -06002168 pnp.debug=1 [PNP]
2169 Enable PNP debug messages (depends on the
2170 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2171 via /sys/module/pnp/parameters/debug. We always show
2172 current resource usage; turning this on also shows
2173 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002174
Linus Torvalds1da177e2005-04-16 15:20:36 -07002175 pnpacpi= [ACPI]
2176 { off }
2177
2178 pnpbios= [ISAPNP]
2179 { on | off | curr | res | no-curr | no-res }
2180
2181 pnp_reserve_irq=
2182 [ISAPNP] Exclude IRQs for the autoconfiguration
2183
2184 pnp_reserve_dma=
2185 [ISAPNP] Exclude DMAs for the autoconfiguration
2186
2187 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002188 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002189
2190 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002191 [ISAPNP] Exclude memory regions for the
2192 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002193 Ranges are in pairs (memory base and size).
2194
Randy Dunlap4af94f32009-04-17 18:30:28 -07002195 ports= [IP_VS_FTP] IPVS ftp helper module
2196 Default is 21.
2197 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2198 may be specified.
2199 Format: <port>,<port>....
2200
Ingo Molnar45807a12007-07-15 23:40:10 -07002201 print-fatal-signals=
2202 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002203
2204 If enabled, warn about various signal handling
2205 related application anomalies: too many signals,
2206 too many POSIX.1 timers, fatal signals causing a
2207 coredump - etc.
2208
2209 If you hit the warning due to signal overflow,
2210 you might want to try "ulimit -i unlimited".
2211
Ingo Molnar45807a12007-07-15 23:40:10 -07002212 default: off.
2213
Matthew Garrettc22ab332012-03-05 14:59:10 -08002214 printk.always_kmsg_dump=
2215 Trigger kmsg_dump for cases other than kernel oops or
2216 panics
2217 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2218 default: disabled
2219
Randy Dunlape84845c2007-07-15 23:40:25 -07002220 printk.time= Show timing data prefixed to each printk message line
2221 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2222
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002223 processor.max_cstate= [HW,ACPI]
2224 Limit processor to maximum C-state
2225 max_cstate=9 overrides any DMI blacklist limit.
2226
2227 processor.nocst [HW,ACPI]
2228 Ignore the _CST method to determine C-states,
2229 instead using the legacy FADT method
2230
Linus Torvalds1da177e2005-04-16 15:20:36 -07002231 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002232 Format: [schedule,]<number>
2233 Param: "schedule" - profile schedule points.
2234 Param: <number> - step/bucket size as a power of 2 for
2235 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002236 Param: "sleep" - profile D-state sleeping (millisecs).
2237 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002238 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002239
Linus Torvalds1da177e2005-04-16 15:20:36 -07002240 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2241 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002242 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002243
Randy Dunlapa9913042005-10-23 12:57:11 -07002244 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2245 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002246 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2247 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002248 psmouse.resetafter= [HW,MOUSE]
2249 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002250 (0 = never).
2251 psmouse.resolution=
2252 [HW,MOUSE] Set desired mouse resolution, in dpi.
2253 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002254 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002255 0 = disabled, 1 = enabled (default).
2256
Matthew Garrettdee28e72011-07-21 16:57:55 -04002257 pstore.backend= Specify the name of the pstore backend to use
2258
Linus Torvalds1da177e2005-04-16 15:20:36 -07002259 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002260 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002261
Kay Sieversdc8c8582007-08-15 12:25:38 +02002262 pty.legacy_count=
2263 [KNL] Number of legacy pty's. Overwrites compiled-in
2264 default number.
2265
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002266 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002267
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268 r128= [HW,DRM]
2269
2270 raid= [HW,RAID]
2271 See Documentation/md.txt.
2272
Randy Dunlapa9913042005-10-23 12:57:11 -07002273 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002274 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002275
Linus Torvalds1da177e2005-04-16 15:20:36 -07002276 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002277 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002278
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002279 rcupdate.blimit= [KNL,BOOT]
2280 Set maximum number of finished RCU callbacks to process
2281 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002282
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002283 rcupdate.qhimark= [KNL,BOOT]
2284 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002285 RCU callbacks over which batch limiting is disabled.
2286
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002287 rcupdate.qlowmark= [KNL,BOOT]
2288 Set threshold of queued RCU callbacks below which
2289 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002290
Olof Johanssonffdfc402005-09-06 15:17:19 -07002291 rdinit= [KNL]
2292 Format: <full_path>
2293 Run specified binary instead of /init from the ramdisk,
2294 used for early userspace startup. See initrd.
2295
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002296 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002297 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002298 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002299
Paul Jackson46b6d942008-07-04 10:00:09 -07002300 relax_domain_level=
2301 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002302 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002303
Linus Torvalds1da177e2005-04-16 15:20:36 -07002304 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2305
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002306 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002307 Format: nn[KMG]
2308 Reserves a hole at the top of the kernel virtual
2309 address space.
2310
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002311 reservelow= [X86]
2312 Format: nn[K]
2313 Set the amount of memory to reserve for BIOS at
2314 the bottom of the address space.
2315
Vivek Goyal7e962872006-09-27 01:50:44 -07002316 reset_devices [KNL] Force drivers to reset the underlying device
2317 during initialization.
2318
Randy Dunlapa9913042005-10-23 12:57:11 -07002319 resume= [SWSUSP]
2320 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07002321
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002322 resume_offset= [SWSUSP]
2323 Specify the offset from the beginning of the partition
2324 given by "resume=" at which the swap header is located,
2325 in <PAGE_SIZE> units (needed only for swap files).
2326 See Documentation/power/swsusp-and-swap-files.txt
2327
Barry Songf126f732011-10-10 23:38:41 +02002328 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2329 read the resume files
2330
Barry Song6f8d7022011-10-06 20:34:46 +02002331 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2332 Useful for devices that are detected asynchronously
2333 (e.g. USB and MMC devices).
2334
Bojan Smojverf996fc92010-09-09 23:06:23 +02002335 hibernate= [HIBERNATION]
2336 noresume Don't check if there's a hibernation image
2337 present during boot.
2338 nocompress Don't compress/decompress hibernation images.
2339
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002340 retain_initrd [RAM] Keep initrd memory after extraction
2341
Linus Torvalds1da177e2005-04-16 15:20:36 -07002342 rhash_entries= [KNL,NET]
2343 Set number of hash buckets for route cache
2344
2345 riscom8= [HW,SERIAL]
2346 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2347
2348 ro [KNL] Mount root device read-only on boot
2349
2350 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07002351 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002352
2353 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2354 mount the root filesystem
2355
2356 rootflags= [KNL] Set root filesystem mount option string
2357
2358 rootfstype= [KNL] Set root filesystem type
2359
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002360 rootwait [KNL] Wait (indefinitely) for root device to show up.
2361 Useful for devices that are detected asynchronously
2362 (e.g. USB and MMC devices).
2363
Linus Torvalds1da177e2005-04-16 15:20:36 -07002364 rw [KNL] Mount root device read-write on boot
2365
2366 S [KNL] Run init in single mode
2367
2368 sa1100ir [NET]
2369 See drivers/net/irda/sa1100_ir.c.
2370
Linus Torvalds1da177e2005-04-16 15:20:36 -07002371 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002372
Mike Travisf6630112009-11-17 18:22:15 -06002373 sched_debug [KNL] Enables verbose scheduler debug messages.
2374
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002375 security= [SECURITY] Choose a security module to enable at boot.
2376 If this boot parameter is not specified, only the first
2377 security module asking for security registration will be
2378 loaded. An invalid security module name will be treated
2379 as if no module has been chosen.
2380
2381 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002382 Format: { "0" | "1" }
2383 See security/selinux/Kconfig help text.
2384 0 -- disable.
2385 1 -- enable.
2386 Default value is set via kernel config option.
2387 If enabled at boot time, /selinux/disable can be used
2388 later to disable prior to initial policy load.
2389
John Johansenc1c124e2010-07-29 14:48:09 -07002390 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2391 Format: { "0" | "1" }
2392 See security/apparmor/Kconfig help text
2393 0 -- disable.
2394 1 -- enable.
2395 Default value is set via kernel config option.
2396
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002397 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002398
Linus Torvalds1da177e2005-04-16 15:20:36 -07002399 shapers= [NET]
2400 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002401
Yinghai Lub05f78f2008-08-22 01:32:50 -07002402 show_msr= [x86] show boot-time MSR settings
2403 Format: { <integer> }
2404 Show boot-time (BIOS-initialized) MSR settings.
2405 The parameter means the number of CPUs to show,
2406 for example 1 means boot CPU only.
2407
Linus Torvalds1da177e2005-04-16 15:20:36 -07002408 simeth= [IA-64]
2409 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002410
Linus Torvalds1da177e2005-04-16 15:20:36 -07002411 slram= [HW,MTD]
2412
David Rientjes3df1ccc2011-10-18 22:09:28 -07002413 slab_max_order= [MM, SLAB]
2414 Determines the maximum allowed order for slabs.
2415 A high setting may cause OOMs due to memory
2416 fragmentation. Defaults to 1 for systems with
2417 more than 32MB of RAM, 0 otherwise.
2418
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002419 slub_debug[=options[,slabs]] [MM, SLUB]
2420 Enabling slub_debug allows one to determine the
2421 culprit if slab objects become corrupted. Enabling
2422 slub_debug can create guard zones around objects and
2423 may poison objects when not in use. Also tracks the
2424 last alloc / free. For more information see
2425 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002426
2427 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002428 Determines the maximum allowed order for slabs.
2429 A high setting may cause OOMs due to memory
2430 fragmentation. For more information see
2431 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002432
2433 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002434 The minimum number of objects per slab. SLUB will
2435 increase the slab order up to slub_max_order to
2436 generate a sufficiently large slab able to contain
2437 the number of objects indicated. The higher the number
2438 of objects the smaller the overhead of tracking slabs
2439 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002440 For more information see Documentation/vm/slub.txt.
2441
2442 slub_min_order= [MM, SLUB]
2443 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002444 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002445 For more information see Documentation/vm/slub.txt.
2446
2447 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002448 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002449 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002450 allocs to different slabs. Debug options disable
2451 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002452 For more information see Documentation/vm/slub.txt.
2453
Linus Torvalds1da177e2005-04-16 15:20:36 -07002454 smart2= [HW]
2455 Format: <io1>[,<io2>[,...,<io8>]]
2456
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002457 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002458 attempt to substitute SMP alternatives once at boot.
2459
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002460 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2461 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2462 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2463 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2464 smsc-ircc2.ircc_irq= [HW] IRQ line
2465 smsc-ircc2.ircc_dma= [HW] DMA channel
2466 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2467 0: Toshiba Satellite 1800 (GP data pin select)
2468 1: Fast pin select (default)
2469 2: ATC IRMode
2470
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002471 softlockup_panic=
2472 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002473 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002474
Linus Torvalds1da177e2005-04-16 15:20:36 -07002475 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02002476 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07002477
2478 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002479 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002480
2481 spia_io_base= [HW,MTD]
2482 spia_fio_base=
2483 spia_pedr=
2484 spia_peddr=
2485
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002486 stacktrace [FTRACE]
2487 Enabled the stack tracer on boot up.
2488
Steven Rostedt762e1202011-12-19 22:01:00 -05002489 stacktrace_filter=[function-list]
2490 [FTRACE] Limit the functions that the stack tracer
2491 will trace at boot up. function-list is a comma separated
2492 list of functions. This list can be changed at run
2493 time by the stack_trace_filter file in the debugfs
2494 tracing directory. Note, this enables stack tracing
2495 and the stacktrace above is not needed.
2496
Linus Torvalds1da177e2005-04-16 15:20:36 -07002497 sti= [PARISC,HW]
2498 Format: <num>
2499 Set the STI (builtin display/keyboard on the HP-PARISC
2500 machines) console (graphic card) which should be used
2501 as the initial boot-console.
2502 See also comment in drivers/video/console/sticore.c.
2503
2504 sti_font= [HW]
2505 See comment in drivers/video/console/sticore.c.
2506
2507 stifb= [HW]
2508 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2509
Trond Myklebustcbf11072009-08-09 15:06:19 -04002510 sunrpc.min_resvport=
2511 sunrpc.max_resvport=
2512 [NFS,SUNRPC]
2513 SunRPC servers often require that client requests
2514 originate from a privileged port (i.e. a port in the
2515 range 0 < portnr < 1024).
2516 An administrator who wishes to reserve some of these
2517 ports for other uses may adjust the range that the
2518 kernel's sunrpc client considers to be privileged
2519 using these two parameters to set the minimum and
2520 maximum port values.
2521
Greg Banks42a7fc42007-03-06 01:42:23 -08002522 sunrpc.pool_mode=
2523 [NFS]
2524 Control how the NFS server code allocates CPUs to
2525 service thread pools. Depending on how many NICs
2526 you have and where their interrupts are bound, this
2527 option will affect which CPUs will do NFS serving.
2528 Note: this parameter cannot be changed while the
2529 NFS server is running.
2530
2531 auto the server chooses an appropriate mode
2532 automatically using heuristics
2533 global a single global pool contains all CPUs
2534 percpu one pool for each CPU
2535 pernode one pool for each NUMA node (equivalent
2536 to global on non-NUMA machines)
2537
Trond Myklebustcbf11072009-08-09 15:06:19 -04002538 sunrpc.tcp_slot_table_entries=
2539 sunrpc.udp_slot_table_entries=
2540 [NFS,SUNRPC]
2541 Sets the upper limit on the number of simultaneous
2542 RPC calls that can be sent from the client to a
2543 server. Increasing these values may allow you to
2544 improve throughput, but will also increase the
2545 amount of memory reserved for use by the client.
2546
Michal Hockoa42c3902010-11-24 12:57:08 -08002547 swapaccount[=0|1]
2548 [KNL] Enable accounting of swap in memory resource
2549 controller if no parameter or 1 is given or disable
2550 it if 0 is given (See Documentation/cgroups/memory.txt)
2551
Linus Torvalds1da177e2005-04-16 15:20:36 -07002552 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002553
Linus Torvalds1da177e2005-04-16 15:20:36 -07002554 switches= [HW,M68k]
2555
Andi Kleene52eec12010-09-08 16:54:17 +02002556 sysfs.deprecated=0|1 [KNL]
2557 Enable/disable old style sysfs layout for old udev
2558 on older distributions. When this option is enabled
2559 very new udev will not work anymore. When this option
2560 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2561 in older udev will not work anymore.
2562 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2563 the kernel configuration.
2564
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002565 sysrq_always_enabled
2566 [KNL]
2567 Ignore sysrq setting - this boot parameter will
2568 neutralize any effect of /proc/sys/kernel/sysrq.
2569 Useful for debugging.
2570
Linus Torvalds1da177e2005-04-16 15:20:36 -07002571 tdfx= [HW,DRM]
2572
David Brownell77437fd2008-07-23 21:28:33 -07002573 test_suspend= [SUSPEND]
2574 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2575 standby suspend) as the system sleep state to briefly
2576 enter during system startup. The system is woken from
2577 this state using a wakeup-capable RTC alarm.
2578
Linus Torvalds1da177e2005-04-16 15:20:36 -07002579 thash_entries= [KNL,NET]
2580 Set number of hash buckets for TCP connection
2581
Len Brownf8707ec2007-08-12 00:12:54 -04002582 thermal.act= [HW,ACPI]
2583 -1: disable all active trip points in all thermal zones
2584 <degrees C>: override all lowest active trip points
2585
Len Brownc52a7412007-08-14 15:49:32 -04002586 thermal.crt= [HW,ACPI]
2587 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002588 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002589
Len Brownf5487142007-08-12 00:12:44 -04002590 thermal.nocrt= [HW,ACPI]
2591 Set to disable actions on ACPI thermal zone
2592 critical and hot trip points.
2593
Len Brown72b33ef2007-08-12 00:12:17 -04002594 thermal.off= [HW,ACPI]
2595 1: disable ACPI thermal control
2596
Len Browna70cdc52007-08-12 00:12:35 -04002597 thermal.psv= [HW,ACPI]
2598 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002599 <degrees C>: override all passive trip points to this
2600 value
Len Browna70cdc52007-08-12 00:12:35 -04002601
Len Brown730ff342007-08-12 00:12:26 -04002602 thermal.tzp= [HW,ACPI]
2603 Specify global default ACPI thermal zone polling rate
2604 <deci-seconds>: poll all this frequency
2605 0: no polling (default)
2606
Thomas Gleixner8d32a302011-02-23 23:52:23 +00002607 threadirqs [KNL]
2608 Force threading of all interrupt handlers except those
2609 marked explicitely IRQF_NO_THREAD.
2610
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002611 topology= [S390]
2612 Format: {off | on}
2613 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07002614 topology information if the hardware supports this.
2615 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002616 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02002617 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002618
Linus Torvalds1da177e2005-04-16 15:20:36 -07002619 tp720= [HW,PS2]
2620
Rajiv Andrade225a9be2010-03-25 00:55:32 -03002621 tpm_suspend_pcr=[HW,TPM]
2622 Format: integer pcr id
2623 Specify that at suspend time, the tpm driver
2624 should extend the specified pcr with zeros,
2625 as a workaround for some chips which fail to
2626 flush the last written pcr on TPM_SaveState.
2627 This will guarantee that all the other pcrs
2628 are saved.
2629
Li Zefan9d612be2009-06-24 17:33:15 +08002630 trace_buf_size=nn[KMG]
2631 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002632
Li Zefan020e5f82009-07-01 10:47:05 +08002633 trace_event=[event-list]
2634 [FTRACE] Set and start specified trace events in order
2635 to facilitate early boot debugging.
2636 See also Documentation/trace/events.txt
2637
john stultzd3b8f882009-08-17 16:40:47 -07002638 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07002639 Format: <string>
2640 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07002641 disables clocksource verification at runtime, as well
2642 as the stability checks done at bootup. Used to enable
2643 high-resolution timer mode on older hardware, and in
2644 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07002645 [x86] noirqtime: Do not use TSC to do irq accounting.
2646 Used to run time disable IRQ_TIME_ACCOUNTING on any
2647 platforms where RDTSC is slow and this accounting
2648 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07002649
Randy Dunlapa9913042005-10-23 12:57:11 -07002650 turbografx.map[2|3]= [HW,JOY]
2651 TurboGraFX parallel port interface
2652 Format:
2653 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002654 See also Documentation/input/joystick-parport.txt
2655
Christian Kujaub6935f82011-05-31 15:22:05 +00002656 udbg-immortal [PPC] When debugging early kernel crashes that
2657 happen after console_init() and before a proper
2658 console driver takes over, this boot options might
2659 help "seeing" what's going on.
2660
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002661 uhash_entries= [KNL,NET]
2662 Set number of hash buckets for UDP/UDP-Lite connections
2663
Alan Stern5f8364b2006-12-05 16:29:55 -05002664 uhci-hcd.ignore_oc=
2665 [USB] Ignore overcurrent events (default N).
2666 Some badly-designed motherboards generate lots of
2667 bogus events, for ports that aren't wired to
2668 anything. Set this parameter to avoid log spamming.
2669 Note that genuine overcurrent events won't be
2670 reported either.
2671
Simon Arlotte3a61b02008-07-19 23:32:54 +01002672 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002673 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01002674
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02002675 usbcore.authorized_default=
2676 [USB] Default USB device authorization:
2677 (default -1 = authorized except for wireless USB,
2678 0 = not authorized, 1 = authorized)
2679
Alan Sternb5e795f2007-02-20 15:00:53 -05002680 usbcore.autosuspend=
2681 [USB] The autosuspend time delay (in seconds) used
2682 for newly-detected USB devices (default 2). This
2683 is the time required before an idle device will be
2684 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002685 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002686
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002687 usbcore.usbfs_snoop=
2688 [USB] Set to log all usbfs traffic (default 0 = off).
2689
2690 usbcore.blinkenlights=
2691 [USB] Set to cycle leds on hubs (default 0 = off).
2692
2693 usbcore.old_scheme_first=
2694 [USB] Start with the old device initialization
2695 scheme (default 0 = off).
2696
Alan Stern3f5eb8d2011-11-17 16:41:35 -05002697 usbcore.usbfs_memory_mb=
2698 [USB] Memory limit (in MB) for buffers allocated by
2699 usbfs (default = 16, 0 = max = 2047).
2700
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002701 usbcore.use_both_schemes=
2702 [USB] Try the other device initialization scheme
2703 if the first one fails (default 1 = enabled).
2704
2705 usbcore.initial_descriptor_timeout=
2706 [USB] Specifies timeout for the initial 64-byte
2707 USB_REQ_GET_DESCRIPTOR request in milliseconds
2708 (default 5000 = 5.0 seconds).
2709
Linus Torvalds1da177e2005-04-16 15:20:36 -07002710 usbhid.mousepoll=
2711 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002712
Alan Sternd4f373e2008-11-10 14:07:45 -05002713 usb-storage.delay_use=
2714 [UMS] The delay in seconds before a new device is
2715 scanned for Logical Units (default 5).
2716
2717 usb-storage.quirks=
2718 [UMS] A list of quirks entries to supplement or
2719 override the built-in unusual_devs list. List
2720 entries are separated by commas. Each entry has
2721 the form VID:PID:Flags where VID and PID are Vendor
2722 and Product ID values (4-digit hex numbers) and
2723 Flags is a set of characters, each corresponding
2724 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002725 a = SANE_SENSE (collect more than 18 bytes
2726 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002727 b = BAD_SENSE (don't collect more than 18
2728 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002729 c = FIX_CAPACITY (decrease the reported
2730 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01002731 d = NO_READ_DISC_INFO (don't use
2732 READ_DISC_INFO command);
2733 e = NO_READ_CAPACITY_16 (don't use
2734 READ_CAPACITY_16 command);
Alan Sternc838ea42008-12-15 10:40:06 -05002735 h = CAPACITY_HEURISTICS (decrease the
2736 reported device capacity by one
2737 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002738 i = IGNORE_DEVICE (don't bind to this
2739 device);
2740 l = NOT_LOCKABLE (don't try to lock and
2741 unlock ejectable media);
2742 m = MAX_SECTORS_64 (don't transfer more
2743 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04002744 n = INITIAL_READ10 (force a retry of the
2745 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05002746 o = CAPACITY_OK (accept the capacity
2747 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002748 r = IGNORE_RESIDUE (the device reports
2749 bogus residue values);
2750 s = SINGLE_LUN (the device has only one
2751 Logical Unit);
2752 w = NO_WP_DETECT (don't test whether the
2753 medium is write-protected).
2754 Example: quirks=0419:aaf5:rl,0421:0433:rc
2755
Stephen Boydac1667d2011-08-13 12:34:50 -07002756 user_debug= [KNL,ARM]
2757 Format: <int>
2758 See arch/arm/Kconfig.debug help text.
2759 1 - undefined instruction events
2760 2 - system calls
2761 4 - invalid data aborts
2762 8 - SIGSEGV faults
2763 16 - SIGBUS faults
2764 Example: user_debug=31
2765
Ian Campbell14315592010-02-17 10:38:10 +00002766 userpte=
2767 [X86] Flags controlling user PTE allocations.
2768
2769 nohigh = do not allocate PTE pages in
2770 HIGHMEM regardless of setting
2771 of CONFIG_HIGHPTE.
2772
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302773 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002774 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002775 vdso=1: enable VDSO (default)
2776 vdso=0: disable VDSO mapping
2777
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302778 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002779 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2780 vdso32=1: enable 32-bit VDSO (default)
2781 vdso32=0: disable 32-bit VDSO mapping
2782
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002783 vector= [IA-64,SMP]
2784 vector=percpu: enable percpu vector domain
2785
Linus Torvalds1da177e2005-04-16 15:20:36 -07002786 video= [FB] Frame buffer configuration
2787 See Documentation/fb/modedb.txt.
2788
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002789 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002790 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002791 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002792 Use vga=ask for menu.
2793 This is actually a boot loader parameter; the value is
2794 passed to the kernel using a special protocol.
2795
Randy Dunlapa9913042005-10-23 12:57:11 -07002796 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002797 size of <nn>. This can be used to increase the
2798 minimum size (128MB on x86). It can also be used to
2799 decrease the size and leave more room for directly
2800 mapped kernel RAM.
2801
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002802 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2803 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002804
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002805 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2806 Format: <command>
2807
2808 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2809 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002810
Andy Lutomirski3ae36652011-08-10 11:15:32 -04002811 vsyscall= [X86-64]
2812 Controls the behavior of vsyscalls (i.e. calls to
2813 fixed addresses of 0xffffffffff600x00 from legacy
2814 code). Most statically-linked binaries and older
2815 versions of glibc use these calls. Because these
2816 functions are at fixed addresses, they make nice
2817 targets for exploits that can control RIP.
2818
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08002819 emulate [default] Vsyscalls turn into traps and are
2820 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04002821
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08002822 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04002823 This is a little bit faster than trapping
2824 and makes a few dynamic recompilers work
2825 better than they would in emulation mode.
2826 It also makes exploits much easier to write.
2827
2828 none Vsyscalls don't work at all. This makes
2829 them quite hard to use for exploits but
2830 might break your system.
2831
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08002832 vt.cur_default= [VT] Default cursor shape.
2833 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2834 the parameters of the <Esc>[?A;B;Cc escape sequence;
2835 see VGA-softcursor.txt. Default: 2 = underline.
2836
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002837 vt.default_blu= [VT]
2838 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2839 Change the default blue palette of the console.
2840 This is a 16-member array composed of values
2841 ranging from 0-255.
2842
2843 vt.default_grn= [VT]
2844 Format: <green0>,<green1>,<green2>,...,<green15>
2845 Change the default green palette of the console.
2846 This is a 16-member array composed of values
2847 ranging from 0-255.
2848
2849 vt.default_red= [VT]
2850 Format: <red0>,<red1>,<red2>,...,<red15>
2851 Change the default red palette of the console.
2852 This is a 16-member array composed of values
2853 ranging from 0-255.
2854
2855 vt.default_utf8=
2856 [VT]
2857 Format=<0|1>
2858 Set system-wide default UTF-8 mode for all tty's.
2859 Default is 1, i.e. UTF-8 mode is enabled for all
2860 newly opened terminals.
2861
Matthew Garrettf6c06b62009-11-13 15:14:11 -05002862 vt.global_cursor_default=
2863 [VT]
2864 Format=<-1|0|1>
2865 Set system-wide default for whether a cursor
2866 is shown on new VTs. Default is -1,
2867 i.e. cursors will be created by default unless
2868 overridden by individual drivers. 0 will hide
2869 cursors, 1 will display them.
2870
Randy Dunlap4724ba572010-05-03 11:42:52 -07002871 watchdog timers [HW,WDT] For information on watchdog timers,
2872 see Documentation/watchdog/watchdog-parameters.txt
2873 or other driver-specific files in the
2874 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002875
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002876 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2877 default x2apic cluster mode on platforms
2878 supporting x2apic.
2879
Jacob Panbb24c472009-09-02 07:37:17 -07002880 x86_mrst_timer= [X86-32,APBT]
2881 Choose timer option for x86 Moorestown MID platform.
2882 Two valid options are apbt timer only and lapic timer
2883 plus one apbt timer for broadcast timer.
2884 x86_mrst_timer=apbt_only | lapic_and_apbt
2885
Linus Torvalds1da177e2005-04-16 15:20:36 -07002886 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2887 xd_geo= See header of drivers/block/xd.c.
2888
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002889 xen_emul_unplug= [HW,X86,XEN]
2890 Unplug Xen emulated devices
2891 Format: [unplug0,][unplug1]
2892 ide-disks -- unplug primary master IDE devices
2893 aux-ide-disks -- unplug non-primary-master IDE devices
2894 nics -- unplug network devices
2895 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01002896 unnecessary -- unplugging emulated devices is
2897 unnecessary even if the host did not respond to
2898 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01002899 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01002900
Linus Torvalds1da177e2005-04-16 15:20:36 -07002901 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002902 Format:
2903 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002904
Randy Dunlapa9913042005-10-23 12:57:11 -07002905______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002906
2907TODO:
2908
Linus Torvalds1da177e2005-04-16 15:20:36 -07002909 Add more DRM drivers.