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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.
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070074 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070075 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070076 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070077 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070078 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070082 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070086 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -070095 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -070097 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070098 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -070099 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900101 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300106 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500108 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
Pawel Moll81a054c2012-05-09 18:30:16 +0100112 VMMIO Driver for memory mapped virtio devices is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 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
Shuah Khanc099cf12012-05-24 15:58:25 -0600338 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
343
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
346 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200347 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
353
Randy Dunlapa9913042005-10-23 12:57:11 -0700354 apc= [HW,SPARC]
355 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356 Format: noidle
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
360
Randy Dunlapca1eda22009-05-06 16:02:58 -0700361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700362 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700366
Brian Haleyb0f83b22010-02-04 13:36:50 -0800367 autoconf= [IPV6]
368 See Documentation/networking/ipv6.txt.
369
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
378
Linus Torvalds1da177e2005-04-16 15:20:36 -0700379 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700380 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
384
385 ataflop= [HW,M68k]
386
387 atarimouse= [HW,MOUSE] Atari Mouse
388
Linus Torvalds1da177e2005-04-16 15:20:36 -0700389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
391
392 atkbd.reset= [HW] Reset keyboard during initialization
393
Randy Dunlapa9913042005-10-23 12:57:11 -0700394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700396
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
398 keyboards
399
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700402
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405
Linus Torvalds1da177e2005-04-16 15:20:36 -0700406 baycom_epp= [HW,AX25]
407 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700408
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
410 Format: <io>,<mode>
411 See header of drivers/net/hamradio/baycom_par.c.
412
Randy Dunlapa9913042005-10-23 12:57:11 -0700413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
417
Randy Dunlapa9913042005-10-23 12:57:11 -0700418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
422
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
425 no delay (0).
426 Format: integer
427
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
429
Linus Torvalds1da177e2005-04-16 15:20:36 -0700430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700431 bttv.radio= Most important insmod options are available as
432 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200434 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
438 at a time.
439
Linus Torvalds1da177e2005-04-16 15:20:36 -0700440 c101= [NET] Moxa C101 synchronous serial card
441
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
448
James Morris20510f22007-10-16 23:31:32 -0700449 capability.disable=
450 [SECURITY] Disable capabilities. This would normally
451 be used only if an alternative security model is to be
452 configured. Potentially dangerous and should only be
453 used if you are entirely sure of the consequences.
454
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100455 ccw_timeout_log [S390]
456 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700457
Paul Menage8bab8dd2008-04-04 14:29:57 -0700458 cgroup_disable= [KNL] Disable a particular controller
459 Format: {name of the controller(s) to disable}
460 {Currently supported controllers - "memory"}
461
Linus Torvalds1da177e2005-04-16 15:20:36 -0700462 checkreqprot [SELINUX] Set initial checkreqprot flag value.
463 Format: { "0" | "1" }
464 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700465 0 -- check protection applied by kernel (includes
466 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700467 1 -- check protection requested by application.
468 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700469 Value can be changed at runtime via
470 /selinux/checkreqprot.
471
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100472 cio_ignore= [S390]
473 See Documentation/s390/CommonIO for details.
474
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700475 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700476 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200477 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700478 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200479 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 Format: { pit | tsc | cyclone | pmtmr }
481
John Stultz592913e2010-07-13 17:56:20 -0700482 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700483 Format: <string>
484 Override the default clocksource and use the clocksource
485 with the name specified.
486 Some clocksource names to choose from, depending on
487 the platform:
488 [all] jiffies (this is the base, fallback clocksource)
489 [ACPI] acpi_pm
490 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
491 pxa_timer,timer3,32k_counter,timer0_1
492 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700493 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700494 scx200_hrt on Geode; cyclone on IBM x440
495 [MIPS] MIPS
496 [PARISC] cr16
497 [S390] tod
498 [SH] SuperH
499 [SPARC64] tick
500 [X86-64] hpet,tsc
501
Andi Kleenac72e782008-01-30 13:33:21 +0100502 clearcpuid=BITNUM [X86]
503 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800504 arch/x86/include/asm/cpufeature.h for the valid bit
505 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100506 stable over kernel options, but the vendor specific
507 ones should be.
508 Also note that user programs calling CPUID directly
509 or using the feature without checking anything
510 will still see it. This just prevents it from
511 being used by the kernel or shown in /proc/cpuinfo.
512 Also note the kernel might malfunction if you disable
513 some critical bits.
514
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100515 cma=nn[MG] [ARM,KNL]
516 Sets the size of kernel global memory area for contiguous
517 memory allocations. For more information, see
518 include/linux/dma-contiguous.h
519
Robert Jennings14f966e2009-04-15 05:55:32 +0000520 cmo_free_hint= [PPC] Format: { yes | no }
521 Specify whether pages are marked as being inactive
522 when they are freed. This is used in CMO environments
523 to determine OS memory pressure for page stealing by
524 a hypervisor.
525 Default: yes
526
Marek Szyprowskic7909502011-12-29 13:09:51 +0100527 coherent_pool=nn[KMG] [ARM,KNL]
528 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200529 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100530
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530531 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100532 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100533 Range: 0 - 8192
534 Default: 64
535
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700537 Format:
538 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700539
540 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
541 Format: <io>[,<irq>]
542
Randy Dunlapa9913042005-10-23 12:57:11 -0700543 com90xx= [HW,NET]
544 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545 Format: <io>[,<irq>[,<memstart>]]
546
547 condev= [HW,S390] console device
548 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700549
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 console= [KNL] Output console device and options.
551
552 tty<n> Use the virtual console device <n>.
553
554 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800555 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700556 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800557 the form "bbbbpnf", where "bbbb" is the baud rate,
558 "p" is parity ("n", "o", or "e"), "n" is number of
559 bits, and "f" is flow control ("r" for RTS or
560 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700561
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800562 See Documentation/serial-console.txt for more
563 information. See
564 Documentation/networking/netconsole.txt for an
565 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700567 uart[8250],io,<addr>[,options]
568 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700569 Start an early, polled-mode console on the 8250/16550
570 UART at the specified I/O port or MMIO address,
571 switching to the matching ttyS device later. The
572 options are the same as for ttyS, above.
573
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700574 If the device connected to the port is not a TTY but a braille
575 device, prepend "brl," before the device type, for instance
576 console=brl,ttyS0
577 For now, only VisioBraille is supported.
578
Daniel Mackf324edc2009-06-16 15:33:52 -0700579 consoleblank= [KNL] The console blank (screen saver) timeout in
580 seconds. Defaults to 10*60 = 10mins. A value of 0
581 disables the blank timer.
582
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800583 coredump_filter=
584 [KNL] Change the default value for
585 /proc/<pid>/coredump_filter.
586 See also Documentation/filesystems/proc.txt.
587
Len Brown62027ae2011-04-01 18:13:10 -0400588 cpuidle.off=1 [CPU_IDLE]
589 disable the cpuidle sub-system
590
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700592 Format:
593 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700594
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800595 crashkernel=size[KMG][@offset[KMG]]
596 [KNL] Using kexec, Linux can switch to a 'crash kernel'
597 upon panic. This parameter reserves the physical
598 memory region [offset, offset + size] for that kernel
599 image. If '@offset' is omitted, then a suitable offset
600 is selected automatically. Check
601 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700602
Bernhard Wallefb391592007-10-18 23:41:02 -0700603 crashkernel=range1:size1[,range2:size2,...][@offset]
604 [KNL] Same as above, but depends on the memory
605 in the running system. The syntax of range is
606 start-[end] where start and end are both
607 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800608 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700609
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610 cs89x0_dma= [HW,NET]
611 Format: <dma>
612
613 cs89x0_media= [HW,NET]
614 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700615
Randy Dunlapa9913042005-10-23 12:57:11 -0700616 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700617 See header of drivers/s390/block/dasd_devmap.c.
618
619 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
620 (one device per port)
621 Format: <port#>,<type>
622 See also Documentation/input/joystick-parport.txt
623
Thomas Renningera648ec02010-08-06 16:11:02 +0200624 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
625 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600626 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200627
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628 debug [KNL] Enable kernel debugging (events log level).
629
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700630 debug_locks_verbose=
631 [KNL] verbose self-tests
632 Format=<0|1>
633 Print debugging info while doing the locking API
634 self-tests.
635 We default to 0 (no extra messages), setting it to
636 1 will print _a lot_ more information - normally
637 only useful to kernel developers.
638
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700639 debug_objects [KNL] Enable object debugging
640
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500641 no_debug_objects
642 [KNL] Disable object debugging
643
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800644 debug_guardpage_minorder=
645 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
646 parameter allows control of the order of pages that will
647 be intentionally kept free (and hence protected) by the
648 buddy allocator. Bigger value increase the probability
649 of catching random memory corruption, but reduce the
650 amount of memory for normal system use. The maximum
651 possible value is MAX_ORDER/2. Setting this parameter
652 to 1 or 2 should be enough to identify most random
653 memory corruption problems caused by bugs in kernel or
654 driver code when a CPU writes to (or reads from) a
655 random memory location. Note that there exists a class
656 of memory corruptions problems caused by buggy H/W or
657 F/W or by drivers badly programing DMA (basically when
658 memory is written at bus level and the CPU MMU is
659 bypassed) which are not detectable by
660 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
661 tracking down these problems.
662
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200663 debugpat [X86] Enable PAT debugging
664
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200665 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700666 Format: <area>[,<node>]
667 See also Documentation/networking/decnet.txt.
668
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700669 default_hugepagesz=
670 [same as hugepagesz=] The size of the default
671 HugeTLB page size. This is the size represented by
672 the legacy /proc/ hugepages APIs, used for SHM, and
673 default size when mounting hugetlbfs filesystems.
674 Defaults to the default architecture's huge page size
675 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700676
Linus Torvalds1da177e2005-04-16 15:20:36 -0700677 dhash_entries= [KNL]
678 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700679
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 digi= [HW,SERIAL]
681 IO parameters + enable/disable command.
682
683 digiepca= [HW,SERIAL]
684 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000685 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700686
Brian Haleyb0f83b22010-02-04 13:36:50 -0800687 disable= [IPV6]
688 See Documentation/networking/ipv6.txt.
689
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000690 disable_ddw [PPC/PSERIES]
691 Disable Dynamic DMA Window support. Use this if
692 to workaround buggy firmware.
693
Brian Haleyb0f83b22010-02-04 13:36:50 -0800694 disable_ipv6= [IPV6]
695 See Documentation/networking/ipv6.txt.
696
Yinghai Lu95ffa242008-04-29 03:52:33 -0700697 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700698 The kernel tries to adjust MTRR layout from continuous
699 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700700 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700701
Yinghai Lu093af8d2008-01-30 13:33:32 +0100702 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100703 By default the kernel will trim any uncacheable
704 memory out of your available memory pool based on
705 MTRR settings. This parameter disables that behavior,
706 possibly causing your machine to run very slowly.
707
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530708 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700709 Disable PIN 1 of APIC timer
710 Can be useful to work around chipset bugs.
711
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700712 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
713 this option disables the debugging code at boot.
714
715 dma_debug_entries=<number>
716 This option allows to tune the number of preallocated
717 entries for DMA-API debugging code. One entry is
718 required per DMA-API allocation. Use this if the
719 DMA-API debugging code disables itself because the
720 architectural default is too low.
721
Joerg Roedel1745de52009-05-22 21:49:51 +0200722 dma_debug_driver=<driver_name>
723 With this option the DMA-API debugging driver
724 filter feature can be enabled at boot time. Just
725 pass the driver to filter for as the parameter.
726 The filter can be disabled or changed to another
727 driver later using sysfs.
728
Carsten Emdeda0df922012-03-18 22:37:33 +0100729 drm_kms_helper.edid_firmware=[<connector>:]<file>
730 Broken monitors, graphic adapters and KVMs may
731 send no or incorrect EDID data sets. This parameter
732 allows to specify an EDID data set in the
733 /lib/firmware directory that is used instead.
734 Generic built-in EDID data sets are used, if one of
735 edid/1024x768.bin, edid/1280x1024.bin,
736 edid/1680x1050.bin, or edid/1920x1080.bin is given
737 and no file with the same name exists. Details and
738 instructions how to build your own EDID data are
739 available in Documentation/EDID/HOWTO.txt. An EDID
740 data set will only be used for a particular connector,
741 if its name and a colon are prepended to the EDID
742 name.
743
Linus Torvalds1da177e2005-04-16 15:20:36 -0700744 dscc4.setup= [NET]
745
Jim Cromie29e36c92012-04-27 14:30:41 -0600746 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
747 module.dyndbg[="val"]
748 Enable debug messages at boot time. See
749 Documentation/dynamic-debug-howto.txt for details.
750
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700751 earlycon= [KNL] Output early console device and options.
752 uart[8250],io,<addr>[,options]
753 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700754 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700755 Start an early, polled-mode console on the 8250/16550
756 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700757 MMIO inter-register address stride is either 8-bit
758 (mmio) or 32-bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700759 The options are the same as for ttyS, above.
760
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530761 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700762 earlyprintk=vga
763 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500764 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500765 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700766
Randy Dunlapa9913042005-10-23 12:57:11 -0700767 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768 takes over.
769
Yinghai Lu5c059172008-07-24 17:29:40 -0700770 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700771
772 Currently only ttyS0 and ttyS1 are supported.
773
774 Interaction with the standard serial driver is not
775 very good.
776
777 The VGA output is eventually overwritten by the real
778 console.
779
Jason Wessel97311912010-05-20 21:04:30 -0500780 ekgdboc= [X86,KGDB] Allow early kernel console debugging
781 ekgdboc=kbd
782
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300783 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -0500784 the boot argument: earlyprintk=vga
785
Linus Torvalds1da177e2005-04-16 15:20:36 -0700786 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700787 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700788
Linus Torvalds1da177e2005-04-16 15:20:36 -0700789 eisa_irq_edge= [PARISC,HW]
790 See header of drivers/parisc/eisa.c.
791
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700792 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700793 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700794 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700795
796 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +0100797 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +0200798 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -0700799 Documentation/block/deadline-iosched.txt for details.
800
Michael Holzheud3bf37952011-10-30 15:16:37 +0100801 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -0700802 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +0100803 image elf header and optionally the size. Generally
804 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -0800805 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700806
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700807 enable_mtrr_cleanup [X86]
808 The kernel tries to adjust MTRR layout from continuous
809 to discrete, to make X server driver able to add WB
810 entry later. This parameter enables that.
811
Randy Dunlapca1eda22009-05-06 16:02:58 -0700812 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700813 Enable PIN 1 of APIC timer
814 Can be useful to work around chipset bugs
815 (in particular on some ATI chipsets).
816 The kernel tries to set a reasonable default.
817
Linus Torvalds1da177e2005-04-16 15:20:36 -0700818 enforcing [SELINUX] Set initial enforcing status.
819 Format: {"0" | "1"}
820 See security/selinux/Kconfig help text.
821 0 -- permissive (log only, no denials).
822 1 -- enforcing (deny and log).
823 Default value is 0.
824 Value can be changed at runtime via /selinux/enforce.
825
Huang Yinga08f82d2010-05-18 14:35:21 +0800826 erst_disable [ACPI]
827 Disable Error Record Serialization Table (ERST)
828 support.
829
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 ether= [HW,NET] Ethernet cards parameters
831 This option is obsoleted by the "netdev=" option, which
832 has equivalent usage. See its documentation for details.
833
Mimi Zohar7102ebc2011-05-12 18:33:20 -0400834 evm= [EVM]
835 Format: { "fix" }
836 Permit 'security.evm' to be updated regardless of
837 current integrity status.
838
Akinobu Mitade1ba092006-12-08 02:39:42 -0800839 failslab=
840 fail_page_alloc=
841 fail_make_request=[KNL]
842 General fault injection mechanism.
843 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +0200844 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -0800845
Linus Torvalds1da177e2005-04-16 15:20:36 -0700846 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000847 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700848
Alex Chiangf13ae302008-05-08 14:03:23 -0600849 force_pal_cache_flush
850 [IA-64] Avoid check_sal_cache_flush which may hang on
851 buggy SAL_CACHE_FLUSH implementations. Using this
852 parameter will force ia64_sal_cache_flush to call
853 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
854
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100855 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400856 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100857 as early as possible in order to facilitate early
858 boot debugging.
859
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200860 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400861 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200862 If no parameter is passed, ftrace will dump
863 buffers of all CPUs, but if you pass orig_cpu, it will
864 dump only the buffer of the CPU that triggered the
865 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400866
867 ftrace_filter=[function-list]
868 [FTRACE] Limit the functions traced by the function
869 tracer at boot up. function-list is a comma separated
870 list of functions. This list can be changed at run
871 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -0700872 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400873
874 ftrace_notrace=[function-list]
875 [FTRACE] Do not trace the functions specified in
876 function-list. This list can be changed at run time
877 by the set_ftrace_notrace file in the debugfs
878 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100879
Stefan Assmann369bc182009-10-12 22:17:21 +0200880 ftrace_graph_filter=[function-list]
881 [FTRACE] Limit the top level callers functions traced
882 by the function graph tracer at boot up.
883 function-list is a comma separated list of functions
884 that can be changed at run time by the
885 set_graph_function file in the debugfs tracing directory.
886
Linus Torvalds1da177e2005-04-16 15:20:36 -0700887 gamecon.map[2|3]=
888 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
889 support via parallel port (up to 5 devices per port)
890 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
891 See also Documentation/input/joystick-parport.txt
892
893 gamma= [HW,DRM]
894
Yinghai Luaaf23042008-01-30 13:33:09 +0100895 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
896 Format: off | on
897 default: on
898
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700899 gcov_persist= [GCOV] When non-zero (default), profiling data for
900 kernel modules is saved and remains accessible via
901 debugfs, even when the module is unloaded/reloaded.
902 When zero, profiling data is discarded and associated
903 debugfs files are removed at module unload time.
904
Linus Torvalds1da177e2005-04-16 15:20:36 -0700905 gpt [EFI] Forces disk with valid GPT signature but
906 invalid Protective MBR to be treated as GPT.
907
Linus Torvalds1da177e2005-04-16 15:20:36 -0700908 hashdist= [KNL,NUMA] Large hashes allocated during boot
909 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -0700910 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700911 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700912
913 hcl= [IA-64] SGI's Hardware Graph compatibility layer
914
915 hd= [EIDE] (E)IDE hard drive subsystem geometry
916 Format: <cyl>,<head>,<sect>
917
Huang Yingea8c0712010-05-18 14:35:15 +0800918 hest_disable [ACPI]
919 Disable Hardware Error Source Table (HEST) support;
920 corresponding firmware-first mode error processing
921 logic will be disabled.
922
Linus Torvalds1da177e2005-04-16 15:20:36 -0700923 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
924 size of <nn>. This works even on boxes that have no
925 highmem otherwise. This also works to reduce highmem
926 size on bigger boxes.
927
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800928 highres= [KNL] Enable/disable high resolution timer mode.
929 Valid parameters: "on", "off"
930 Default: "on"
931
Linus Torvalds1da177e2005-04-16 15:20:36 -0700932 hisax= [HW,ISDN]
933 See Documentation/isdn/README.HiSax.
934
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700935 hlt [BUGS=ARM,SH]
936
937 hpet= [X86-32,HPET] option to control HPET usage
938 Format: { enable (default) | disable | force |
939 verbose }
940 disable: disable HPET and use PIT instead
941 force: allow force enabled of undocumented chips (ICH4,
942 VIA, nVidia)
943 verbose: show contents of HPET registers during setup
944
Andi Kleenb4718e62008-07-23 21:27:51 -0700945 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
946 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700947 On x86-64 and powerpc, this option can be specified
948 multiple times interleaved with hugepages= to reserve
949 huge pages of different sizes. Valid pages sizes on
950 x86-64 are 2M (when the CPU supports "pse") and 1G
951 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700952 Note that 1GB pages can only be allocated at boot time
953 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900954
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100955 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
956 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100957 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
958 If specified, z/VM IUCV HVC accepts connections
959 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100960
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -0700961 keep_bootcon [KNL]
962 Do not unregister boot console at start. This is only
963 useful for debugging when something happens in the window
964 between unregistering the boot console and initializing
965 the real console.
966
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700967 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700968 or register an additional I2C bus that is not
969 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700970 Format:
971 <bus_id>,<clkrate>
972
Jiri Kosina36d95732008-10-06 02:51:09 -0400973 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200975 i8042.dumbkbd [HW] Pretend that controller can only read data from
976 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977 (Don't attempt to blink the leds)
978 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500979 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400980 i8042.noloop [HW] Disable the AUX Loopback command while probing
981 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700982 i8042.nomux [HW] Don't check presence of an active multiplexing
983 controller
984 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
985 controllers
Masanari Iida24775d62012-02-15 00:26:42 +0900986 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -0700987 i8042.reset [HW] Reset the controller during init and cleanup
988 i8042.unlock [HW] Unlock (ignore) the keylock
989
990 i810= [HW,DRM]
991
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700992 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
993 indicates that the driver is running on unsupported
994 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700995 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
996 does not match list of supported models.
997 i8k.power_status
998 [HW] Report power status in /proc/i8k
999 (disabled by default)
1000 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1001 capability is set.
1002
Carsten Emde4dca20e2012-03-15 15:56:26 +01001003 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001004 [DRM] Invert the sense of the variable that is used to
1005 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001006 brightness value of 0 indicates backlight switched off,
1007 and the maximum of the brightness value sets the backlight
1008 to maximum brightness. If this parameter is set to 0
1009 (default) and the machine requires it, or this parameter
1010 is set to 1, a brightness value of 0 sets the backlight
1011 to maximum brightness, and the maximum of the brightness
1012 value switches the backlight off.
1013 -1 -- never invert brightness
1014 0 -- machine default
1015 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001016
Linus Torvalds1da177e2005-04-16 15:20:36 -07001017 icn= [HW,ISDN]
1018 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1019
David Fries0af80c02009-02-25 20:28:21 +01001020 ide-core.nodma= [HW] (E)IDE subsystem
1021 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001022 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1023 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001024 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001025
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001026 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1027 Claim all unknown PCI IDE storage controllers.
1028
Andi Kleenf039b752007-05-02 19:27:12 +02001029 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001030 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1031 Poll forces a polling idle loop that can slightly
1032 improve the performance of waking up a idle CPU, but
1033 will use a lot of power and make the system run hot.
1034 Not recommended.
1035 idle=mwait: On systems which support MONITOR/MWAIT but
1036 the kernel chose to not use it because it doesn't save
1037 as much power as a normal idle loop, use the
1038 MONITOR/MWAIT idle loop anyways. Performance should be
1039 the same as idle=poll.
1040 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001041 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001042 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001043
Ingo Molnar792908222006-12-06 20:40:51 -08001044 ignore_loglevel [KNL]
1045 Ignore loglevel setting - this will print /all/
1046 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001047 We also add it as printk module parameter, so users
1048 could change it dynamically, usually by
1049 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001050
Linus Torvalds1da177e2005-04-16 15:20:36 -07001051 ihash_entries= [KNL]
1052 Set number of hash buckets for inode cache.
1053
Mimi Zohar3323eec92009-02-04 09:06:58 -05001054 ima_audit= [IMA]
1055 Format: { "0" | "1" }
1056 0 -- integrity auditing messages. (Default)
1057 1 -- enable informational integrity auditing messages.
1058
1059 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -07001060 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001061 default: "sha1"
1062
Eric Paris5789ba32009-05-21 15:47:06 -04001063 ima_tcb [IMA]
1064 Load a policy which meets the needs of the Trusted
1065 Computing Base. This means IMA will measure all
1066 programs exec'd, files mmap'd for exec, and all files
1067 opened for read by uid=0.
1068
Linus Torvalds1da177e2005-04-16 15:20:36 -07001069 init= [KNL]
1070 Format: <full_path>
1071 Run specified binary instead of /sbin/init as init
1072 process.
1073
1074 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1075 for working out where the kernel is dying during
1076 startup.
1077
1078 initrd= [BOOT] Specify the location of the initial ramdisk
1079
1080 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1081 Format: <irq>
1082
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001083 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001084 on
1085 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001086 off
1087 Disable intel iommu driver.
1088 igfx_off [Default Off]
1089 By default, gfx is mapped as normal device. If a gfx
1090 device has a dedicated DMAR unit, the DMAR unit is
1091 bypassed by not enabling DMAR with this option. In
1092 this case, gfx device will use physical address for
1093 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001094 forcedac [x86_64]
1095 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001096 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001097 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001098 than 32-bit addressing. The default is to look
1099 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001100 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001101 strict [Default Off]
1102 With this option on every unmap_single operation will
1103 result in a hardware IOTLB flush operation as opposed
1104 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001105 sp_off [Default Off]
1106 By default, super page will be supported if Intel IOMMU
1107 has the capability. With this option, super page will
1108 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001109
1110 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1111 0 disables intel_idle and fall back on acpi_idle.
1112 1 to 6 specify maximum depth of C-state.
1113
Chris Wrightd1423d52010-07-20 11:06:49 -07001114 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001115 on enable Interrupt Remapping (default)
1116 off disable Interrupt Remapping
1117 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001118 no_x2apic_optout
1119 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001120
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001121 iomem= Disable strict checking of access to MMIO memory
1122 strict regions from userspace.
1123 relaxed
1124
1125 iommu= [x86]
1126 off
1127 force
1128 noforce
1129 biomerge
1130 panic
1131 nopanic
1132 merge
1133 nomerge
1134 forcesac
1135 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001136 pt [x86, IA-64]
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001137
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001138
1139 io7= [HW] IO7 for Marvel based alpha systems
1140 See comment before marvel_specify_io7 in
1141 arch/alpha/kernel/core_marvel.c.
1142
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301143 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001144 0x80
1145 Standard port 0x80 based delay
1146 0xed
1147 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001148 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001149 Simple two microseconds delay
1150 none
1151 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001152
Linus Torvalds1da177e2005-04-16 15:20:36 -07001153 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001154 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001155
1156 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001157 See comment before ip2_setup() in
1158 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001159
Alan Cox200803d2005-06-28 20:45:18 -07001160 irqfixup [HW]
1161 When an interrupt is not handled search all handlers
1162 for it. Intended to get systems with badly broken
1163 firmware running.
1164
1165 irqpoll [HW]
1166 When an interrupt is not handled search all handlers
1167 for it. Also check all handlers each timer
1168 interrupt. Intended to get systems with badly broken
1169 firmware running.
1170
Linus Torvalds1da177e2005-04-16 15:20:36 -07001171 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001172 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001173
1174 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001175 Format:
1176 <cpu number>,...,<cpu number>
1177 or
Li Zefanb225d442008-11-06 12:53:39 -08001178 <cpu number>-<cpu number>
1179 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001180 or a mixture
1181 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001182
Linus Torvalds1da177e2005-04-16 15:20:36 -07001183 This option can be used to specify one or more CPUs
1184 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001185 algorithms. You can move a process onto or off an
1186 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001187 <cpu number> begins at 0 and the maximum value is
1188 "number of CPUs in system - 1".
1189
1190 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001191 alternative -- manually setting the CPU mask of all
1192 tasks in the system -- can cause problems and
1193 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001194
Randy Dunlapa9913042005-10-23 12:57:11 -07001195 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001196
1197 js= [HW,JOY] Analog joystick
1198 See Documentation/input/joystick.txt.
1199
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001200 keepinitrd [HW,ARM]
1201
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301202 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001203 specifies the amount of memory usable by the kernel
1204 for non-movable allocations. The requested amount is
1205 spread evenly throughout all nodes in the system. The
1206 remaining memory in each node is used for Movable
1207 pages. In the event, a node is too small to have both
1208 kernelcore and Movable pages, kernelcore pages will
1209 take priority and other nodes will have a larger number
1210 of kernelcore pages. The Movable zone is used for the
1211 allocation of pages that may be reclaimed or moved
1212 by the page migration subsystem. This means that
1213 HugeTLB pages may not be allocated from this zone.
1214 Note that allocations like PTEs-from-HighMem still
1215 use the HighMem zone if it exists, and the Normal
1216 zone if it does not.
1217
Jason Wessel4fe1da42010-05-20 21:04:31 -05001218 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1219 Format: <Controller#>[,poll interval]
1220 The controller # is the number of the ehci usb debug
1221 port as it is probed via PCI. The poll interval is
1222 optional and is the number seconds in between
1223 each poll cycle to the debug port in case you need
1224 the functionality for interrupting the kernel with
1225 gdb or control-c on the dbgp connection. When
1226 not using this parameter you use sysrq-g to break into
1227 the kernel debugger.
1228
Jason Wessel84c08fd2010-05-20 21:04:24 -05001229 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001230 Requires a tty driver that supports console polling,
1231 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001232 Serial only format: <serial_device>[,baud]
1233 keyboard only format: kbd
1234 keyboard and serial format: kbd,<serial_device>[,baud]
1235 Optional Kernel mode setting:
1236 kms, kbd format: kms,kbd
1237 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001238
Jason Wessel84c08fd2010-05-20 21:04:24 -05001239 kgdbwait [KGDB] Stop kernel execution and enter the
1240 kernel debugger at the earliest opportunity.
1241
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001242 kmac= [MIPS] korina ethernet MAC address.
1243 Configure the RouterBoard 532 series on-chip
1244 Ethernet adapter MAC address.
1245
Catalin Marinas04f70332009-06-11 13:22:39 +01001246 kmemleak= [KNL] Boot-time kmemleak enable/disable
1247 Valid arguments: on, off
1248 Default: on
1249
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301250 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001251 in oops dumps.
1252
Andre Przywarafef07aa2009-07-10 14:20:35 +02001253 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1254 Default is 0 (don't ignore, but inject #GP)
1255
Xiao Guangronga182d872010-09-20 22:17:48 +08001256 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1257 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001258 Default is 0 (off)
1259
Andre Przywarafef07aa2009-07-10 14:20:35 +02001260 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001261 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001262
1263 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1264 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001265 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001266
Andre Przywarafef07aa2009-07-10 14:20:35 +02001267 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1268 (virtualized MMU) support on capable Intel chips.
1269 Default is 1 (enabled)
1270
1271 kvm-intel.emulate_invalid_guest_state=
1272 [KVM,Intel] Enable emulation of invalid guest states
1273 Default is 0 (disabled)
1274
1275 kvm-intel.flexpriority=
1276 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1277 Default is 1 (enabled)
1278
Sasha Levine1a72ae2011-08-09 14:28:35 +03001279 kvm-intel.nested=
1280 [KVM,Intel] Enable VMX nesting (nVMX).
1281 Default is 0 (disabled)
1282
Andre Przywarafef07aa2009-07-10 14:20:35 +02001283 kvm-intel.unrestricted_guest=
1284 [KVM,Intel] Disable unrestricted guest feature
1285 (virtualized real and unpaged mode) on capable
1286 Intel chips. Default is 1 (enabled)
1287
1288 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1289 feature (tagged TLBs) on capable Intel chips.
1290 Default is 1 (enabled)
1291
Linus Torvalds1da177e2005-04-16 15:20:36 -07001292 l2cr= [PPC]
1293
Robert Brosea78bfbf2008-03-29 07:20:23 +11001294 l3cr= [PPC]
1295
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001296 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001297 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001298
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301299 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001300 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001301
FD Camifcb71f62008-01-06 19:08:56 +01001302 libata.dma= [LIBATA] DMA control
1303 libata.dma=0 Disable all PATA and SATA DMA
1304 libata.dma=1 PATA and SATA Disk DMA only
1305 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001306 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001307 Combinations also work, so libata.dma=3 enables DMA
1308 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001309
Michael Prokop20308872009-08-06 00:14:10 +02001310 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1311 libata.ignore_hpa=0 keep BIOS limits (default)
1312 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001313
Dave Jones78e70c22007-09-27 11:50:13 -04001314 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1315 when set.
1316 Format: <int>
1317
Tejun Heo33267322008-02-13 09:15:09 +09001318 libata.force= [LIBATA] Force configurations. The format is comma
1319 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001320 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001321 matching port, link or device. Basically, it matches
1322 the ATA ID string printed on console by libata. If
1323 the whole ID part is omitted, the last PORT and DEVICE
1324 values are used. If ID hasn't been specified yet, the
1325 configuration applies to all ports, links and devices.
1326
1327 If only DEVICE is omitted, the parameter applies to
1328 the port and all links and devices behind it. DEVICE
1329 number of 0 either selects the first device or the
1330 first fan-out link behind PMP device. It does not
1331 select the host link. DEVICE number of 15 selects the
1332 host link and device attached to it.
1333
1334 The VAL specifies the configuration to force. As long
1335 as there's no ambiguity shortcut notation is allowed.
1336 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1337 The following configurations can be forced.
1338
1339 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1340 Any ID with matching PORT is used.
1341
1342 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1343
1344 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1345 udma[/][16,25,33,44,66,100,133] notation is also
1346 allowed.
1347
1348 * [no]ncq: Turn on or off NCQ.
1349
Tejun Heo05944bd2008-08-13 20:19:09 +09001350 * nohrst, nosrst, norst: suppress hard, soft
1351 and both resets.
1352
Tejun Heo43c9c592010-05-23 12:59:11 +02001353 * dump_id: dump IDENTIFY data.
1354
Tejun Heo33267322008-02-13 09:15:09 +09001355 If there are multiple matching configurations changing
1356 the same attribute, the last one is used.
1357
Yinghai Lu95f72d12010-07-12 14:36:09 +10001358 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001359
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001361 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001362
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001363 lockd.nlm_grace_period=P [NFS] Assign grace period.
1364 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001365
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001366 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1367 Format: <integer>
1368
1369 lockd.nlm_timeout=T [NFS] Assign timeout value.
1370 Format: <integer>
1371
1372 lockd.nlm_udpport=M [NFS] Assign UDP port.
1373 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001374
1375 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1376 Format: <irq>
1377
1378 loglevel= All Kernel Messages with a loglevel smaller than the
1379 console loglevel will be printed to the console. It can
1380 also be changed with klogd or other programs. The
1381 loglevels are defined as follows:
1382
1383 0 (KERN_EMERG) system is unusable
1384 1 (KERN_ALERT) action must be taken immediately
1385 2 (KERN_CRIT) critical conditions
1386 3 (KERN_ERR) error conditions
1387 4 (KERN_WARNING) warning conditions
1388 5 (KERN_NOTICE) normal but significant condition
1389 6 (KERN_INFO) informational
1390 7 (KERN_DEBUG) debug-level messages
1391
Randy Dunlapc756d082011-02-20 20:08:35 -08001392 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1393 in bytes. n must be a power of two. The default
1394 size is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001395
Randy Dunlapaccaa242007-10-16 01:29:37 -07001396 logo.nologo [FB] Disables display of the built-in Linux logo.
1397 This may be used to provide more screen space for
1398 kernel log messages and is useful when debugging
1399 kernel boot problems.
1400
Linus Torvalds1da177e2005-04-16 15:20:36 -07001401 lp=0 [LP] Specify parallel ports to use, e.g,
1402 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1403 lp=reset first parallel port). 'lp=0' disables the
1404 lp=auto printer driver. 'lp=reset' (which can be
1405 specified in addition to the ports) causes
1406 attached printers to be reset. Using
1407 lp=port1,port2,... specifies the parallel ports
1408 to associate lp devices with, starting with
1409 lp0. A port specification may be 'none' to skip
1410 that lp device, or a parport name such as
1411 'parport0'. Specifying 'lp=auto' instead of a
1412 port specification list means that device IDs
1413 from each port should be examined, to see if
1414 an IEEE 1284-compliant printer is attached; if
1415 so, the driver will manage that printer.
1416 See also header of drivers/char/lp.c.
1417
1418 lpj=n [KNL]
1419 Sets loops_per_jiffy to given constant, thus avoiding
1420 time-consuming boot-time autodetection (up to 250 ms per
1421 CPU). 0 enables autodetection (default). To determine
1422 the correct value for your kernel, boot with normal
1423 autodetection and see what value is printed. Note that
1424 on SMP systems the preset will be applied to all CPUs,
1425 which is likely to cause problems if your CPUs need
1426 significantly divergent settings. An incorrect value
1427 will cause delays in the kernel to be wrong, leading to
1428 unpredictable I/O errors and other breakage. Although
1429 unlikely, in the extreme case this might damage your
1430 hardware.
1431
1432 ltpc= [NET]
1433 Format: <io>,<irq>,<dma>
1434
Randy Dunlap16290242011-08-13 12:34:52 -07001435 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001436 (machvec) in a generic kernel.
1437 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001438
Wu Zhangjin3209e702009-07-02 23:27:12 +08001439 machtype= [Loongson] Share the same kernel image file between different
1440 yeeloong laptop.
1441 Example: machtype=lemote-yeeloong-2f-7inch
1442
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001443 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1444 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001445
1446 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001447 should make use of. maxcpus=n : n >= 0 limits the
1448 kernel to using 'n' processors. n=0 is a special case,
1449 it is equivalent to "nosmp", which also disables
1450 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001451
Kay Sieversd134b002011-07-31 22:08:04 +02001452 max_loop= [LOOP] The number of loop block devices that get
1453 (loop.max_loop) unconditionally pre-created at init time. The default
1454 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1455 of statically allocating a predefined number, loop
1456 devices can be requested on-demand with the
1457 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001458
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001459 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001460
Uwe Hermann71cced62008-10-20 09:32:21 -07001461 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001462
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463 md= [HW] RAID subsystems devices and level
1464 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001465
Linus Torvalds1da177e2005-04-16 15:20:36 -07001466 mdacon= [MDA]
1467 Format: <first>,<last>
1468 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001469
Linus Torvalds1da177e2005-04-16 15:20:36 -07001470 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1471 Amount of memory to be used when the kernel is not able
1472 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001473 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001474 address space collisions. Without memmap= PCI devices
1475 could be placed at addresses belonging to unused RAM.
1476
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001477 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001478 memory.
1479
Paul Mundt6902aa82008-09-21 17:14:42 +09001480 memchunk=nn[KMG]
1481 [KNL,SH] Allow user to override the default size for
1482 per-device physically contiguous DMA buffers.
1483
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301484 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001485 E820 memory map, as specified by the user.
1486 Such memmap=exactmap lines can be constructed based on
1487 BIOS output or other requirements. See the memmap=nn@ss
1488 option description.
1489
1490 memmap=nn[KMG]@ss[KMG]
1491 [KNL] Force usage of a specific region of memory
1492 Region of memory to be used, from ss to ss+nn.
1493
1494 memmap=nn[KMG]#ss[KMG]
1495 [KNL,ACPI] Mark specific memory as ACPI data.
1496 Region of memory to be used, from ss to ss+nn.
1497
1498 memmap=nn[KMG]$ss[KMG]
1499 [KNL,ACPI] Mark specific memory as reserved.
1500 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001501 Example: Exclude memory from 0x18690000-0x1869ffff
1502 memmap=64K$0x18690000
1503 or
1504 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001505
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001506 memory_corruption_check=0/1 [X86]
1507 Some BIOSes seem to corrupt the first 64k of
1508 memory when doing things like suspend/resume.
1509 Setting this option will scan the memory
1510 looking for corruption. Enabling this will
1511 both detect corruption and prevent the kernel
1512 from using the memory being corrupted.
1513 However, its intended as a diagnostic tool; if
1514 repeatable BIOS-originated corruption always
1515 affects the same memory, you can use memmap=
1516 to prevent the kernel from using that memory.
1517
1518 memory_corruption_check_size=size [X86]
1519 By default it checks for corruption in the low
1520 64k, making this memory unavailable for normal
1521 use. Use this parameter to scan for
1522 corruption in more or less memory.
1523
1524 memory_corruption_check_period=seconds [X86]
1525 By default it checks for corruption every 60
1526 seconds. Use this parameter to check at some
1527 other rate. 0 disables periodic checking.
1528
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001529 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001530 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001531 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001532 Specifies the number of memtest passes to be
1533 performed. Each pass selects another test
1534 pattern from a given set of patterns. Memtest
1535 fills the memory with this pattern, validates
1536 memory contents and reserves bad memory
1537 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001538
Linus Torvalds1da177e2005-04-16 15:20:36 -07001539 meye.*= [HW] Set MotionEye Camera parameters
1540 See Documentation/video4linux/meye.txt.
1541
Andres Salomon8f368812007-10-12 23:04:06 +02001542 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1543 Multi-Function General Purpose Timers on AMD Geode
1544 platforms.
1545
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001546 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1547 the BIOS has incorrectly applied a workaround. TinyBIOS
1548 version 0.98 is known to be affected, 0.99 fixes the
1549 problem by letting the user disable the workaround.
1550
Linus Torvalds1da177e2005-04-16 15:20:36 -07001551 mga= [HW,DRM]
1552
Randy Dunlap1c207f92008-11-19 15:36:16 -08001553 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1554 physical address is ignored.
1555
Michel Pollet39f45d72009-05-20 11:10:31 +01001556 mini2440= [ARM,HW,KNL]
1557 Format:[0..2][b][c][t]
1558 Default: "0tb"
1559 MINI2440 configuration specification:
1560 0 - The attached screen is the 3.5" TFT
1561 1 - The attached screen is the 7" TFT
1562 2 - The VGA Shield is attached (1024x768)
1563 Leaving out the screen size parameter will not load
1564 the TFT driver, and the framebuffer will be left
1565 unconfigured.
1566 b - Enable backlight. The TFT backlight pin will be
1567 linked to the kernel VESA blanking code and a GPIO
1568 LED. This parameter is not necessary when using the
1569 VGA shield.
1570 c - Enable the s3c camera interface.
1571 t - Reserved for enabling touchscreen support. The
1572 touchscreen support is not enabled in the mainstream
1573 kernel as of 2.6.30, a preliminary port can be found
1574 in the "bleeding edge" mini2440 support kernel at
1575 http://repo.or.cz/w/linux-2.6/mini2440.git
1576
Mel Gorman6b74ab92008-07-23 21:26:49 -07001577 mminit_loglevel=
1578 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1579 parameter allows control of the logging verbosity for
1580 the additional memory initialisation checks. A value
1581 of 0 disables mminit logging and a level of 4 will
1582 log everything. Information is printed at KERN_DEBUG
1583 so loglevel=8 may also need to be specified.
1584
Linus Torvalds1da177e2005-04-16 15:20:36 -07001585 mousedev.tap_time=
1586 [MOUSE] Maximum time between finger touching and
1587 leaving touchpad surface for touch to be considered
1588 a tap and be reported as a left button click (for
1589 touchpads working in absolute mode only).
1590 Format: <msecs>
1591 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1592 reporting absolute coordinates, such as tablets
1593 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1594 reporting absolute coordinates, such as tablets
1595
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301596 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001597 is similar to kernelcore except it specifies the
1598 amount of memory used for migratable allocations.
1599 If both kernelcore and movablecore is specified,
1600 then kernelcore will be at *least* the specified
1601 value but may be more. If movablecore on its own
1602 is specified, the administrator must be careful
1603 that the amount of memory usable for all allocations
1604 is not too small.
1605
Linus Torvalds1da177e2005-04-16 15:20:36 -07001606 MTD_Partition= [MTD]
1607 Format: <name>,<region-number>,<size>,<offset>
1608
Randy Dunlapa9913042005-10-23 12:57:11 -07001609 MTD_Region= [MTD] Format:
1610 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001611
1612 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001613 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001614
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001615 multitce=off [PPC] This parameter disables the use of the pSeries
1616 firmware feature for updating multiple TCE entries
1617 at a time.
1618
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001619 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1620
1621 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1622
1623 boundary - index of last SLC block on Flex-OneNAND.
1624 The remaining blocks are configured as MLC blocks.
1625 lock - Configure if Flex-OneNAND boundary should be locked.
1626 Once locked, the boundary cannot be changed.
1627 1 indicates lock status, 0 indicates unlock status.
1628
Ben Dooks9db829f2008-07-03 11:24:29 +01001629 mtdset= [ARM]
1630 ARM/S3C2412 JIVE boot control
1631
1632 See arch/arm/mach-s3c2412/mach-jive.c
1633
Linus Torvalds1da177e2005-04-16 15:20:36 -07001634 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001635 [HW] Make the MicroTouch USB driver use raw coordinates
1636 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001637
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001638 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001639 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001640 that could hold holes aka. UC entries.
1641
1642 mtrr_gran_size=nn[KMG] [X86]
1643 Used for mtrr cleanup. It is granularity of mtrr block.
1644 Default is 1.
1645 Large value could prevent small alignment from
1646 using up MTRRs.
1647
1648 mtrr_spare_reg_nr=n [X86]
1649 Format: <integer>
1650 Range: 0,7 : spare reg number
1651 Default : 1
1652 Used for mtrr cleanup. It is spare mtrr entries number.
1653 Set to 2 or more if your graphical card needs more.
1654
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1656
Linus Torvalds1da177e2005-04-16 15:20:36 -07001657 netdev= [NET] Network devices parameters
1658 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1659 Note that mem_start is often overloaded to mean
1660 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001661 This usage is only documented in each driver source
1662 file if at all.
1663
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001664 nf_conntrack.acct=
1665 [NETFILTER] Enable connection tracking flow accounting
1666 0 to disable accounting
1667 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001668 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001669
Chuck Lever306a0752010-09-17 10:54:37 -04001670 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001671 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001672
1673 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001674 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001675
Chuck Lever306a0752010-09-17 10:54:37 -04001676 nfsrootdebug [NFS] enable nfsroot debugging messages.
1677 See Documentation/filesystems/nfs/nfsroot.txt.
1678
Trond Myklebusta72b4422006-01-03 09:55:41 +01001679 nfs.callback_tcpport=
1680 [NFS] set the TCP port on which the NFSv4 callback
1681 channel should listen.
1682
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001683 nfs.cache_getent=
1684 [NFS] sets the pathname to the program which is used
1685 to update the NFS client cache entries.
1686
1687 nfs.cache_getent_timeout=
1688 [NFS] sets the timeout after which an attempt to
1689 update a cache entry is deemed to have failed.
1690
Trond Myklebust58df0952006-01-03 09:55:57 +01001691 nfs.idmap_cache_timeout=
1692 [NFS] set the maximum lifetime for idmapper cache
1693 entries.
1694
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001695 nfs.enable_ino64=
1696 [NFS] enable 64-bit inode numbers.
1697 If zero, the NFS client will fake up a 32-bit inode
1698 number for the readdir() and stat() syscalls instead
1699 of returning the full 64-bit number.
1700 The default is to return 64-bit inode numbers.
1701
Trond Myklebustef159e92012-02-06 19:50:40 -05001702 nfs.max_session_slots=
1703 [NFSv4.1] Sets the maximum number of session slots
1704 the client will attempt to negotiate with the server.
1705 This limits the number of simultaneous RPC requests
1706 that the client can send to the NFSv4.1 server.
1707 Note that there is little point in setting this
1708 value higher than the max_tcp_slot_table_limit.
1709
Trond Myklebustb064eca22011-02-22 15:44:32 -08001710 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05001711 [NFSv4] When set to the default of '1', this option
1712 ensures that both the RPC level authentication
1713 scheme and the NFS level operations agree to use
1714 numeric uids/gids if the mount is using the
1715 'sec=sys' security flavour. In effect it is
1716 disabling idmapping, which can make migration from
1717 legacy NFSv2/v3 systems to NFSv4 easier.
1718 Servers that do not support this mode of operation
1719 will be autodetected by the client, and it will fall
1720 back to using the idmapper.
1721 To turn off this behaviour, set the value to '0'.
Trond Myklebustb064eca22011-02-22 15:44:32 -08001722
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05001723 nfs.send_implementation_id =
1724 [NFSv4.1] Send client implementation identification
1725 information in exchange_id requests.
1726 If zero, no implementation identification information
1727 will be sent.
1728 The default is to send the implementation identification
1729 information.
1730
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04001731 nfsd.nfs4_disable_idmapping=
1732 [NFSv4] When set to the default of '1', the NFSv4
1733 server will return only numeric uids and gids to
1734 clients using auth_sys, and will accept numeric uids
1735 and gids from such clients. This is intended to ease
1736 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05001737
Sachin Bhamare18d98f62012-03-19 20:47:58 -07001738 objlayoutdriver.osd_login_prog=
1739 [NFS] [OBJLAYOUT] sets the pathname to the program which
1740 is used to automatically discover and login into new
1741 osd-targets. Please see:
1742 Documentation/filesystems/pnfs.txt for more explanations
1743
Paul Mundt1e1030d2009-09-01 17:38:32 +09001744 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001745 when a NMI is triggered.
1746 Format: [state][,regs][,debounce][,die]
1747
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301748 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07001749 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05001750 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001751 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001752 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07001753 timeout occurs (or 'nopanic' to override the opposite
1754 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001755 This is useful when you use a panic=... timeout and
1756 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001757
Anton Vorontsovbff38772009-07-08 11:10:56 -07001758 netpoll.carrier_timeout=
1759 [NET] Specifies amount of time (in seconds) that
1760 netpoll should wait for a carrier. By default netpoll
1761 waits 4 seconds.
1762
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001763 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001764 emulation library even if a 387 maths coprocessor
1765 is present.
1766
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001767 no_console_suspend
1768 [HW] Never suspend the console
1769 Disable suspending of consoles during suspend and
1770 hibernate operations. Once disabled, debugging
1771 messages can reach various consoles while the rest
1772 of the system is being put to sleep (ie, while
1773 debugging driver suspend/resume hooks). This may
1774 not work reliably with all consoles, but is known
1775 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07001776 To facilitate more flexible debugging, we also add
1777 console_suspend, a printk module parameter to control
1778 it. Users could use console_suspend (usually
1779 /sys/module/printk/parameters/console_suspend) to
1780 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001781
Christoph Lameterc1aee212007-05-31 00:40:47 -07001782 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1783 caches in the slab allocator. Saves per-node memory,
1784 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001785
Randy Dunlapa9913042005-10-23 12:57:11 -07001786 noalign [KNL,ARM]
1787
Linus Torvalds1da177e2005-04-16 15:20:36 -07001788 noapic [SMP,APIC] Tells the kernel to not make use of any
1789 IOAPICs that may be present in the system.
1790
Mike Galbraith5091faa2010-11-30 14:18:03 +01001791 noautogroup Disable scheduler automatic task group creation.
1792
Linus Torvalds1da177e2005-04-16 15:20:36 -07001793 nobats [PPC] Do not use BATs for mapping kernel lowmem
1794 on "Classic" PPC cores.
1795
1796 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001797
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001798 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1799
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001800 nodelayacct [KNL] Disable per-task delay accounting
1801
Linus Torvalds1da177e2005-04-16 15:20:36 -07001802 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1803
Paul Mundt6902aa82008-09-21 17:14:42 +09001804 nodsp [SH] Disable hardware DSP at boot time.
1805
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301806 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001807
Linus Torvalds1da177e2005-04-16 15:20:36 -07001808 noexec [IA-64]
1809
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301810 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001811 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001812 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001813 noexec=off: disable non-executable mappings
1814
Fenghua Yude5397a2011-05-11 16:51:05 -07001815 nosmep [X86]
1816 Disable SMEP (Supervisor Mode Execution Protection)
1817 even if it is supported by processor.
1818
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001819 noexec32 [X86-64]
1820 This affects only 32-bit executables.
1821 noexec32=on: enable non-executable mappings (default)
1822 read doesn't imply executable mappings
1823 noexec32=off: disable non-executable mappings
1824 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001825
Paul Mundt6902aa82008-09-21 17:14:42 +09001826 nofpu [SH] Disable hardware FPU at boot time.
1827
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001828 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001829 register save and restore. The kernel will only save
1830 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001831
Suresh Siddha0c752a92009-05-22 12:17:45 -07001832 noxsave [BUGS=X86] Disables x86 extended register state save
1833 and restore using xsave. The kernel will fallback to
1834 enabling legacy floating-point and sse state.
1835
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001836 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1837 wfi(ARM) instruction doesn't work correctly and not to
1838 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001839
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001840 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001841 instruction doesn't work correctly and not to
1842 use it.
1843
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001844 no_file_caps Tells the kernel not to honor file capabilities. The
1845 only way then for a file to be executed with privilege
1846 is to be setuid root or executed by root.
1847
Linus Torvalds1da177e2005-04-16 15:20:36 -07001848 nohalt [IA-64] Tells the kernel not to use the power saving
1849 function PAL_HALT_LIGHT when idle. This increases
1850 power-consumption. On the positive side, it reduces
1851 interrupt wake-up latency, which may improve performance
1852 in certain environments such as networked servers or
1853 real-time systems.
1854
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001855 nohz= [KNL] Boottime enable/disable dynamic ticks
1856 Valid arguments: on, off
1857 Default: on
1858
Paul Mundteeee7852009-04-02 12:31:16 +09001859 noiotrap [SH] Disables trapped I/O port accesses.
1860
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001861 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001862 disable unhandled interrupt sources.
1863
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301864 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001865 broken timer IRQ sources.
1866
Linus Torvalds1da177e2005-04-16 15:20:36 -07001867 noisapnp [ISAPNP] Disables ISA PnP code.
1868
1869 noinitrd [RAM] Tells the kernel not to load any configured
1870 initial RAM disk.
1871
Weidong Han03ea8152009-04-17 16:42:15 +08001872 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1873 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07001874 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08001875
Linus Torvalds1da177e2005-04-16 15:20:36 -07001876 nointroute [IA-64]
1877
Randy Dunlap16290242011-08-13 12:34:52 -07001878 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07001879
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02001880 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1881
Gleb Natapovfd10cde2010-10-14 11:22:51 +02001882 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1883 fault handling.
1884
Glauber Costad910f5c2011-07-11 15:28:19 -04001885 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1886 steal time is computed, but won't influence scheduler
1887 behaviour
1888
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001889 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001890
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001891 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001892
Linus Torvalds1da177e2005-04-16 15:20:36 -07001893 noltlbs [PPC] Do not use large page/tlb entries for kernel
1894 lowmem mapping on PPC40x.
1895
Horms312f1f02006-02-22 09:57:55 +09001896 nomca [IA-64] Disable machine check abort handling
1897
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001898 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001899
Andres Salomon83d73842007-10-12 23:04:06 +02001900 nomfgpt [X86-32] Disable Multi-Function General Purpose
1901 Timer usage (for AMD Geode machines).
1902
Don Zickusbda62632011-10-13 15:14:27 -04001903 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1904 shutdown the other cpus. Instead use the REBOOT_VECTOR
1905 irq.
1906
Dave Young02608be2012-02-01 10:33:14 +08001907 nomodule Disable module load
1908
Jiri Kosina016ddd92010-01-18 17:05:40 +01001909 nopat [X86] Disable PAT (page attribute table extension of
1910 pagetables) support.
1911
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001912 norandmaps Don't use address space randomization. Equivalent to
1913 echo 0 > /proc/sys/kernel/randomize_va_space
1914
Jiri Kosinabbff2162010-08-11 18:34:09 +02001915 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001916
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001917 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001918 with UP alternatives
1919
Linus Torvalds1da177e2005-04-16 15:20:36 -07001920 noresidual [PPC] Don't use residual data on PReP machines.
1921
H. Peter Anvin49d859d2011-07-31 14:02:19 -07001922 nordrand [X86] Disable the direct use of the RDRAND
1923 instruction even if it is supported by the
1924 processor. RDRAND is still available to user
1925 space applications.
1926
Randy Dunlapa9913042005-10-23 12:57:11 -07001927 noresume [SWSUSP] Disables resume and restores original swap
1928 space.
1929
Linus Torvalds1da177e2005-04-16 15:20:36 -07001930 no-scroll [VGA] Disables scrollback.
1931 This is required for the Braillex ib80-piezo Braille
1932 reader made by F.H. Papenmeier (Germany).
1933
1934 nosbagart [IA-64]
1935
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001936 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001937
Len Brown61ec7562007-08-16 03:34:22 -04001938 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1939 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001940
Dave Jones97842212007-07-15 23:41:05 -07001941 nosoftlockup [KNL] Disable the soft-lockup detector.
1942
Linus Torvalds1da177e2005-04-16 15:20:36 -07001943 nosync [HW,M68K] Disables sync negotiation for all devices.
1944
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001945 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001946
1947 nousb [USB] Disable the USB subsystem
1948
Ben Hutchings55142372011-01-02 23:02:42 +00001949 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04001950
Linus Torvalds1da177e2005-04-16 15:20:36 -07001951 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001952
Weidong Han2b2fd872009-04-17 16:42:12 +08001953 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1954
Randy Dunlap16290242011-08-13 12:34:52 -07001955 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07001956 purges which is reported from either PAL_VM_SUMMARY or
1957 SAL PALO.
1958
Yinghai Lu2b633e32010-02-10 01:20:37 -08001959 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1960 could support. nr_cpus=n : n >= 1 limits the kernel to
1961 supporting 'n' processors. Later in runtime you can not
1962 use hotplug cpu feature to put more cpu back to online.
1963 just like you compile the kernel NR_CPUS=n
1964
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001965 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1966
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001967 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1968 one of ['zone', 'node', 'default'] can be specified
1969 This can be set from sysctl after boot.
1970 See Documentation/sysctl/vm.txt for details.
1971
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001972 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1973 See Documentation/debugging-via-ohci1394.txt for more
1974 info.
1975
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001976 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1977 Rather than timing out after 20 ms if an EC
1978 command is not properly ACKed, override the length
1979 of the timeout. We have interrupts disabled while
1980 waiting for the ACK, so if this is set too high
1981 interrupts *may* be lost!
1982
Tony Lindgren15ac7af2009-12-11 16:16:32 -08001983 omap_mux= [OMAP] Override bootloader pin multiplexing.
1984 Format: <mux_mode0.mode_name=value>...
1985 For example, to override I2C bus2:
1986 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1987
Linus Torvalds1da177e2005-04-16 15:20:36 -07001988 oprofile.timer= [HW]
1989 Use timer interrupt instead of performance counters
1990
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001991 oprofile.cpu_type= Force an oprofile cpu type
1992 This might be useful if you have an older oprofile
1993 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02001994 Format: { arch_perfmon }
1995 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02001996 perfmon on Intel CPUs instead of the
1997 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02001998 timer: [X86] Force use of architectural NMI
1999 timer mode (see also oprofile.timer
2000 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002001 [s390] Force legacy basic mode sampling
2002 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002003
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002004 oops=panic Always panic on oopses. Default is to just kill the
2005 process, but there is a small probability of
2006 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002007 This will also cause panics on machine check exceptions.
2008 Useful together with panic=30 to trigger a reboot.
2009
Randy Dunlapbcfde332010-06-07 17:10:38 -07002010 OSS [HW,OSS]
2011 See Documentation/sound/oss/oss-parameters.txt
2012
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002013 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002014 timeout > 0: seconds before rebooting
2015 timeout = 0: wait forever
2016 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002017 Format: <timeout>
2018
2019 parkbd.port= [HW] Parallel port number the keyboard adapter is
2020 connected to, default is 0.
2021 Format: <parport#>
2022 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2023 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002024 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002025
Randy Dunlapa9913042005-10-23 12:57:11 -07002026 parport= [HW,PPT] Specify parallel ports. 0 disables.
2027 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2028 Use 'auto' to force the driver to use any
2029 IRQ/DMA settings detected (the default is to
2030 ignore detected IRQ/DMA settings because of
2031 possible conflicts). You can specify the base
2032 address, IRQ, and DMA settings; IRQ and DMA
2033 should be numbers, or 'auto' (for using detected
2034 settings on that particular port), or 'nofifo'
2035 (to avoid using a FIFO even if it is detected).
2036 Parallel ports are assigned in the order they
2037 are specified on the command line, starting
2038 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002039
Randy Dunlapa9913042005-10-23 12:57:11 -07002040 parport_init_mode= [HW,PPT]
2041 Configure VIA parallel port to operate in
2042 a specific mode. This is necessary on Pegasos
2043 computer where firmware has no options for setting
2044 up parallel port mode and sets it to spp.
2045 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002046 Format: [spp|ps2|epp|ecp|ecpepp]
2047
Andrew Mortondd287792006-03-23 03:00:57 -08002048 pause_on_oops=
2049 Halt all CPUs after the first oops has been printed for
2050 the specified number of seconds. This is to be used if
2051 your oopses keep scrolling off the screen.
2052
Linus Torvalds1da177e2005-04-16 15:20:36 -07002053 pcbit= [HW,ISDN]
2054
2055 pcd. [PARIDE]
2056 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002057 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002058
Randy Dunlapa9913042005-10-23 12:57:11 -07002059 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002060 earlydump [X86] dump PCI config space before the kernel
2061 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002062 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002063 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002064 the hardware directly. Use this if your machine
2065 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002066 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002067 hardware access methods are allowed. Use this
2068 if you experience crashes upon bootup and you
2069 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002070 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002071 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002072 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002073 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002074 noaer [PCIE] If the PCIEAER kernel config parameter is
2075 enabled, this kernel boot option can be used to
2076 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002077 nodomains [PCI] Disable support for multiple PCI
2078 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302079 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002080 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002081 check_enable_amd_mmconf [X86] check for and enable
2082 properly configured MMIO access to PCI
2083 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002084 nomsi [MSI] If the PCI_MSI kernel config parameter is
2085 enabled, this kernel boot option can be used to
2086 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002087 noioapicquirk [APIC] Disable all boot interrupt quirks.
2088 Safety option to keep boot IRQs enabled. This
2089 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002090 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2091 primary IO-APIC for bridges that cannot disable
2092 boot IRQs. This fixes a source of spurious IRQs
2093 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002094 noioapicreroute [APIC] Disable workaround that uses the
2095 boot IRQ equivalent of an IRQ that connects to
2096 a chipset where boot IRQs cannot be disabled.
2097 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002098 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002099 routing table. These calls are known to be buggy
2100 on several machines and they hang the machine
2101 when used, but on other computers it's the only
2102 way to get the interrupt routing table. Try
2103 this option if the kernel is unable to allocate
2104 IRQs or discover secondary PCI buses on your
2105 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002106 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002107 Use with caution as certain devices share
2108 address decoders between ROMs and other
2109 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002110 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002111 expansion ROMs that do not already have
2112 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002113 nobar [X86] Do not assign address space to the
2114 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002115 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002116 assigned automatically to PCI devices. You can
2117 make the kernel exclude IRQs of your ISA cards
2118 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002119 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002120 of the PIRQ table (normally generated
2121 by the BIOS) if it is outside the
2122 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002123 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002124 useful if the kernel is unable to find your
2125 secondary buses and you want to tell it
2126 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002127 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002128 numbers ourselves, overriding
2129 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002130 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002131 in the BIOS $PIR table. This is needed on
2132 some systems with broken BIOSes, notably
2133 some HP Pavilion N5400 and Omnibook XE3
2134 notebooks. This will have no effect if ACPI
2135 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002136 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002137 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002138 use_crs [X86] Use PCI host bridge window information
2139 from ACPI. On BIOSes from 2008 or later, this
2140 is enabled by default. If you need to use this,
2141 please report a bug.
2142 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2143 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002144 routeirq Do IRQ routing for all PCI devices.
2145 This is normally done in pci_enable_device(),
2146 so this option is a temporary workaround
2147 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002148 skip_isa_align [X86] do not align io start addr, so can
2149 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002150 firmware [ARM] Do not re-enumerate the bus but instead
2151 just use the configuration from the
2152 bootloader. This is currently used on
2153 IXP2000 systems where the bus has to be
2154 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002155 noearly [X86] Don't do any early type 1 scanning.
2156 This might help on some broken boards which
2157 machine check when some devices' config space
2158 is read. But various workarounds are disabled
2159 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002160 bfsort Sort PCI devices into breadth-first order.
2161 This sorting is done to get a device
2162 order compatible with older (<= 2.4) kernels.
2163 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002164 cbiosize=nn[KMG] The fixed amount of bus space which is
2165 reserved for the CardBus bridge's IO window.
2166 The default value is 256 bytes.
2167 cbmemsize=nn[KMG] The fixed amount of bus space which is
2168 reserved for the CardBus bridge's memory
2169 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002170 resource_alignment=
2171 Format:
2172 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2173 Specifies alignment and device to reassign
2174 aligned memory resources.
2175 If <order of align> is not specified,
2176 PAGE_SIZE is used as alignment.
2177 PCI-PCI bridge can be specified, if resource
2178 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002179 ecrc= Enable/disable PCIe ECRC (transaction layer
2180 end-to-end CRC checking).
2181 bios: Use BIOS/firmware settings. This is the
2182 the default.
2183 off: Turn ECRC off
2184 on: Turn ECRC on.
Yinghai Lub55438f2012-02-23 19:23:30 -08002185 realloc= Enable/disable reallocating PCI bridge resources
2186 if allocations done by BIOS are too small to
2187 accommodate resources required by all child
2188 devices.
2189 off: Turn realloc off
2190 on: Turn realloc on
2191 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002192 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002193 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2194 only look for one device below a PCIe downstream
2195 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002196
Chuck Ebberte5665a42008-09-24 20:40:34 -04002197 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2198 Management.
2199 off Disable ASPM.
2200 force Enable ASPM even on devices that claim not to support it.
2201 WARNING: Forcing ASPM on may cause system lockups.
2202
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002203 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2204 nomsi Do not use MSI for PCI Express Native Hotplug (this
2205 makes all PCIe ports use INTx for hotplug services).
2206
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002207 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002208 auto Ask the BIOS whether or not to use native PCIe services
2209 associated with PCIe ports (PME, hot-plug, AER). Use
2210 them only if that is allowed by the BIOS.
2211 native Use native PCIe services associated with PCIe ports
2212 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002213 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2214 ports driver.
2215
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002216 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002217 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002218 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002219
Linus Torvalds1da177e2005-04-16 15:20:36 -07002220 pcmv= [HW,PCMCIA] BadgePAD 4
2221
2222 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002223 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002224
2225 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2226 boot time.
2227 Format: { 0 | 1 }
2228 See arch/parisc/kernel/pdc_chassis.c
2229
Tejun Heof58dc012009-08-14 15:00:50 +09002230 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002231 Currently supported values are "embed" and "page".
2232 Archs may support subset or none of the selections.
2233 See comments in mm/percpu.c for details on each
2234 allocator. This parameter is primarily for debugging
2235 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002236
Linus Torvalds1da177e2005-04-16 15:20:36 -07002237 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002238 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002239
2240 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002241 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002242
2243 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002244 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002245
2246 plip= [PPT,NET] Parallel port network link
2247 Format: { parport<nr> | timid | 0 }
2248 See also Documentation/parport.txt.
2249
Randy Dunlap16290242011-08-13 12:34:52 -07002250 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002251 Override pmtimer IOPort with a hex value.
2252 e.g. pmtmr=0x508
2253
Bjorn Helgaas96242112011-08-11 12:14:05 -06002254 pnp.debug=1 [PNP]
2255 Enable PNP debug messages (depends on the
2256 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2257 via /sys/module/pnp/parameters/debug. We always show
2258 current resource usage; turning this on also shows
2259 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002260
Linus Torvalds1da177e2005-04-16 15:20:36 -07002261 pnpacpi= [ACPI]
2262 { off }
2263
2264 pnpbios= [ISAPNP]
2265 { on | off | curr | res | no-curr | no-res }
2266
2267 pnp_reserve_irq=
2268 [ISAPNP] Exclude IRQs for the autoconfiguration
2269
2270 pnp_reserve_dma=
2271 [ISAPNP] Exclude DMAs for the autoconfiguration
2272
2273 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002274 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002275
2276 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002277 [ISAPNP] Exclude memory regions for the
2278 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002279 Ranges are in pairs (memory base and size).
2280
Randy Dunlap4af94f32009-04-17 18:30:28 -07002281 ports= [IP_VS_FTP] IPVS ftp helper module
2282 Default is 21.
2283 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2284 may be specified.
2285 Format: <port>,<port>....
2286
Ingo Molnar45807a12007-07-15 23:40:10 -07002287 print-fatal-signals=
2288 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002289
2290 If enabled, warn about various signal handling
2291 related application anomalies: too many signals,
2292 too many POSIX.1 timers, fatal signals causing a
2293 coredump - etc.
2294
2295 If you hit the warning due to signal overflow,
2296 you might want to try "ulimit -i unlimited".
2297
Ingo Molnar45807a12007-07-15 23:40:10 -07002298 default: off.
2299
Matthew Garrettc22ab332012-03-05 14:59:10 -08002300 printk.always_kmsg_dump=
2301 Trigger kmsg_dump for cases other than kernel oops or
2302 panics
2303 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2304 default: disabled
2305
Randy Dunlape84845c2007-07-15 23:40:25 -07002306 printk.time= Show timing data prefixed to each printk message line
2307 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2308
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002309 processor.max_cstate= [HW,ACPI]
2310 Limit processor to maximum C-state
2311 max_cstate=9 overrides any DMI blacklist limit.
2312
2313 processor.nocst [HW,ACPI]
2314 Ignore the _CST method to determine C-states,
2315 instead using the legacy FADT method
2316
Linus Torvalds1da177e2005-04-16 15:20:36 -07002317 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002318 Format: [schedule,]<number>
2319 Param: "schedule" - profile schedule points.
2320 Param: <number> - step/bucket size as a power of 2 for
2321 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002322 Param: "sleep" - profile D-state sleeping (millisecs).
2323 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002324 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002325
Linus Torvalds1da177e2005-04-16 15:20:36 -07002326 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2327 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002328 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002329
Randy Dunlapa9913042005-10-23 12:57:11 -07002330 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2331 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002332 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2333 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002334 psmouse.resetafter= [HW,MOUSE]
2335 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002336 (0 = never).
2337 psmouse.resolution=
2338 [HW,MOUSE] Set desired mouse resolution, in dpi.
2339 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002340 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002341 0 = disabled, 1 = enabled (default).
2342
Matthew Garrettdee28e72011-07-21 16:57:55 -04002343 pstore.backend= Specify the name of the pstore backend to use
2344
Linus Torvalds1da177e2005-04-16 15:20:36 -07002345 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002346 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002347
Kay Sieversdc8c8582007-08-15 12:25:38 +02002348 pty.legacy_count=
2349 [KNL] Number of legacy pty's. Overwrites compiled-in
2350 default number.
2351
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002352 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002353
Linus Torvalds1da177e2005-04-16 15:20:36 -07002354 r128= [HW,DRM]
2355
2356 raid= [HW,RAID]
2357 See Documentation/md.txt.
2358
Randy Dunlapa9913042005-10-23 12:57:11 -07002359 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002360 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002361
Linus Torvalds1da177e2005-04-16 15:20:36 -07002362 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002363 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002364
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002365 rcutree.blimit= [KNL,BOOT]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002366 Set maximum number of finished RCU callbacks to process
2367 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002368
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07002369 rcutree.fanout_leaf= [KNL,BOOT]
2370 Increase the number of CPUs assigned to each
2371 leaf rcu_node structure. Useful for very large
2372 systems.
2373
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002374 rcutree.qhimark= [KNL,BOOT]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002375 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002376 RCU callbacks over which batch limiting is disabled.
2377
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002378 rcutree.qlowmark= [KNL,BOOT]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002379 Set threshold of queued RCU callbacks below which
2380 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002381
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002382 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2383 Suppress RCU CPU stall warning messages.
2384
2385 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2386 Set timeout for RCU CPU stall warning messages.
2387
2388 rcutorture.fqs_duration= [KNL,BOOT]
2389 Set duration of force_quiescent_state bursts.
2390
2391 rcutorture.fqs_holdoff= [KNL,BOOT]
2392 Set holdoff time within force_quiescent_state bursts.
2393
2394 rcutorture.fqs_stutter= [KNL,BOOT]
2395 Set wait time between force_quiescent_state bursts.
2396
2397 rcutorture.irqreader= [KNL,BOOT]
2398 Test RCU readers from irq handlers.
2399
2400 rcutorture.n_barrier_cbs= [KNL,BOOT]
2401 Set callbacks/threads for rcu_barrier() testing.
2402
2403 rcutorture.nfakewriters= [KNL,BOOT]
2404 Set number of concurrent RCU writers. These just
2405 stress RCU, they don't participate in the actual
2406 test, hence the "fake".
2407
2408 rcutorture.nreaders= [KNL,BOOT]
2409 Set number of RCU readers.
2410
2411 rcutorture.onoff_holdoff= [KNL,BOOT]
2412 Set time (s) after boot for CPU-hotplug testing.
2413
2414 rcutorture.onoff_interval= [KNL,BOOT]
2415 Set time (s) between CPU-hotplug operations, or
2416 zero to disable CPU-hotplug testing.
2417
2418 rcutorture.shuffle_interval= [KNL,BOOT]
2419 Set task-shuffle interval (s). Shuffling tasks
2420 allows some CPUs to go into dyntick-idle mode
2421 during the rcutorture test.
2422
2423 rcutorture.shutdown_secs= [KNL,BOOT]
2424 Set time (s) after boot system shutdown. This
2425 is useful for hands-off automated testing.
2426
2427 rcutorture.stall_cpu= [KNL,BOOT]
2428 Duration of CPU stall (s) to test RCU CPU stall
2429 warnings, zero to disable.
2430
2431 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2432 Time to wait (s) after boot before inducing stall.
2433
2434 rcutorture.stat_interval= [KNL,BOOT]
2435 Time (s) between statistics printk()s.
2436
2437 rcutorture.stutter= [KNL,BOOT]
2438 Time (s) to stutter testing, for example, specifying
2439 five seconds causes the test to run for five seconds,
2440 wait for five seconds, and so on. This tests RCU's
2441 ability to transition abruptly to and from idle.
2442
2443 rcutorture.test_boost= [KNL,BOOT]
2444 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2445 "Maybe" means test if the RCU implementation
2446 under test support RCU priority boosting.
2447
2448 rcutorture.test_boost_duration= [KNL,BOOT]
2449 Duration (s) of each individual boost test.
2450
2451 rcutorture.test_boost_interval= [KNL,BOOT]
2452 Interval (s) between each boost test.
2453
2454 rcutorture.test_no_idle_hz= [KNL,BOOT]
2455 Test RCU's dyntick-idle handling. See also the
2456 rcutorture.shuffle_interval parameter.
2457
2458 rcutorture.torture_type= [KNL,BOOT]
2459 Specify the RCU implementation to test.
2460
2461 rcutorture.verbose= [KNL,BOOT]
2462 Enable additional printk() statements.
2463
Olof Johanssonffdfc402005-09-06 15:17:19 -07002464 rdinit= [KNL]
2465 Format: <full_path>
2466 Run specified binary instead of /init from the ramdisk,
2467 used for early userspace startup. See initrd.
2468
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002469 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002470 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002471 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002472
Paul Jackson46b6d942008-07-04 10:00:09 -07002473 relax_domain_level=
2474 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002475 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002476
Linus Torvalds1da177e2005-04-16 15:20:36 -07002477 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2478
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002479 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002480 Format: nn[KMG]
2481 Reserves a hole at the top of the kernel virtual
2482 address space.
2483
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002484 reservelow= [X86]
2485 Format: nn[K]
2486 Set the amount of memory to reserve for BIOS at
2487 the bottom of the address space.
2488
Vivek Goyal7e962872006-09-27 01:50:44 -07002489 reset_devices [KNL] Force drivers to reset the underlying device
2490 during initialization.
2491
Randy Dunlapa9913042005-10-23 12:57:11 -07002492 resume= [SWSUSP]
2493 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02002494 Format:
2495 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002496
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002497 resume_offset= [SWSUSP]
2498 Specify the offset from the beginning of the partition
2499 given by "resume=" at which the swap header is located,
2500 in <PAGE_SIZE> units (needed only for swap files).
2501 See Documentation/power/swsusp-and-swap-files.txt
2502
Barry Songf126f732011-10-10 23:38:41 +02002503 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2504 read the resume files
2505
Barry Song6f8d7022011-10-06 20:34:46 +02002506 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2507 Useful for devices that are detected asynchronously
2508 (e.g. USB and MMC devices).
2509
Bojan Smojverf996fc92010-09-09 23:06:23 +02002510 hibernate= [HIBERNATION]
2511 noresume Don't check if there's a hibernation image
2512 present during boot.
2513 nocompress Don't compress/decompress hibernation images.
2514
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002515 retain_initrd [RAM] Keep initrd memory after extraction
2516
Linus Torvalds1da177e2005-04-16 15:20:36 -07002517 rhash_entries= [KNL,NET]
2518 Set number of hash buckets for route cache
2519
2520 riscom8= [HW,SERIAL]
2521 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2522
2523 ro [KNL] Mount root device read-only on boot
2524
2525 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07002526 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002527
2528 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2529 mount the root filesystem
2530
2531 rootflags= [KNL] Set root filesystem mount option string
2532
2533 rootfstype= [KNL] Set root filesystem type
2534
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002535 rootwait [KNL] Wait (indefinitely) for root device to show up.
2536 Useful for devices that are detected asynchronously
2537 (e.g. USB and MMC devices).
2538
Linus Torvalds1da177e2005-04-16 15:20:36 -07002539 rw [KNL] Mount root device read-write on boot
2540
2541 S [KNL] Run init in single mode
2542
2543 sa1100ir [NET]
2544 See drivers/net/irda/sa1100_ir.c.
2545
Linus Torvalds1da177e2005-04-16 15:20:36 -07002546 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002547
Mike Travisf6630112009-11-17 18:22:15 -06002548 sched_debug [KNL] Enables verbose scheduler debug messages.
2549
Mike Galbraith5307c952012-05-08 12:20:58 +02002550 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2551 xtime_lock contention on larger systems, and/or RCU lock
2552 contention on all systems with CONFIG_MAXSMP set.
2553 Format: { "0" | "1" }
2554 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2555 1 -- enable.
2556 Note: increases power consumption, thus should only be
2557 enabled if running jitter sensitive (HPC/RT) workloads.
2558
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002559 security= [SECURITY] Choose a security module to enable at boot.
2560 If this boot parameter is not specified, only the first
2561 security module asking for security registration will be
2562 loaded. An invalid security module name will be treated
2563 as if no module has been chosen.
2564
2565 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002566 Format: { "0" | "1" }
2567 See security/selinux/Kconfig help text.
2568 0 -- disable.
2569 1 -- enable.
2570 Default value is set via kernel config option.
2571 If enabled at boot time, /selinux/disable can be used
2572 later to disable prior to initial policy load.
2573
John Johansenc1c124e2010-07-29 14:48:09 -07002574 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2575 Format: { "0" | "1" }
2576 See security/apparmor/Kconfig help text
2577 0 -- disable.
2578 1 -- enable.
2579 Default value is set via kernel config option.
2580
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002581 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002582
Linus Torvalds1da177e2005-04-16 15:20:36 -07002583 shapers= [NET]
2584 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002585
Yinghai Lub05f78f2008-08-22 01:32:50 -07002586 show_msr= [x86] show boot-time MSR settings
2587 Format: { <integer> }
2588 Show boot-time (BIOS-initialized) MSR settings.
2589 The parameter means the number of CPUs to show,
2590 for example 1 means boot CPU only.
2591
Linus Torvalds1da177e2005-04-16 15:20:36 -07002592 simeth= [IA-64]
2593 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002594
Linus Torvalds1da177e2005-04-16 15:20:36 -07002595 slram= [HW,MTD]
2596
David Rientjes3df1ccc2011-10-18 22:09:28 -07002597 slab_max_order= [MM, SLAB]
2598 Determines the maximum allowed order for slabs.
2599 A high setting may cause OOMs due to memory
2600 fragmentation. Defaults to 1 for systems with
2601 more than 32MB of RAM, 0 otherwise.
2602
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002603 slub_debug[=options[,slabs]] [MM, SLUB]
2604 Enabling slub_debug allows one to determine the
2605 culprit if slab objects become corrupted. Enabling
2606 slub_debug can create guard zones around objects and
2607 may poison objects when not in use. Also tracks the
2608 last alloc / free. For more information see
2609 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002610
2611 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002612 Determines the maximum allowed order for slabs.
2613 A high setting may cause OOMs due to memory
2614 fragmentation. For more information see
2615 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002616
2617 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002618 The minimum number of objects per slab. SLUB will
2619 increase the slab order up to slub_max_order to
2620 generate a sufficiently large slab able to contain
2621 the number of objects indicated. The higher the number
2622 of objects the smaller the overhead of tracking slabs
2623 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002624 For more information see Documentation/vm/slub.txt.
2625
2626 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09002627 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002628 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002629 For more information see Documentation/vm/slub.txt.
2630
2631 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002632 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002633 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002634 allocs to different slabs. Debug options disable
2635 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002636 For more information see Documentation/vm/slub.txt.
2637
Linus Torvalds1da177e2005-04-16 15:20:36 -07002638 smart2= [HW]
2639 Format: <io1>[,<io2>[,...,<io8>]]
2640
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002641 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002642 attempt to substitute SMP alternatives once at boot.
2643
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002644 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2645 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2646 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2647 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2648 smsc-ircc2.ircc_irq= [HW] IRQ line
2649 smsc-ircc2.ircc_dma= [HW] DMA channel
2650 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2651 0: Toshiba Satellite 1800 (GP data pin select)
2652 1: Fast pin select (default)
2653 2: ATC IRMode
2654
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002655 softlockup_panic=
2656 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002657 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002658
Linus Torvalds1da177e2005-04-16 15:20:36 -07002659 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02002660 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07002661
2662 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002663 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002664
2665 spia_io_base= [HW,MTD]
2666 spia_fio_base=
2667 spia_pedr=
2668 spia_peddr=
2669
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002670 stacktrace [FTRACE]
2671 Enabled the stack tracer on boot up.
2672
Steven Rostedt762e1202011-12-19 22:01:00 -05002673 stacktrace_filter=[function-list]
2674 [FTRACE] Limit the functions that the stack tracer
2675 will trace at boot up. function-list is a comma separated
2676 list of functions. This list can be changed at run
2677 time by the stack_trace_filter file in the debugfs
2678 tracing directory. Note, this enables stack tracing
2679 and the stacktrace above is not needed.
2680
Linus Torvalds1da177e2005-04-16 15:20:36 -07002681 sti= [PARISC,HW]
2682 Format: <num>
2683 Set the STI (builtin display/keyboard on the HP-PARISC
2684 machines) console (graphic card) which should be used
2685 as the initial boot-console.
2686 See also comment in drivers/video/console/sticore.c.
2687
2688 sti_font= [HW]
2689 See comment in drivers/video/console/sticore.c.
2690
2691 stifb= [HW]
2692 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2693
Trond Myklebustcbf11072009-08-09 15:06:19 -04002694 sunrpc.min_resvport=
2695 sunrpc.max_resvport=
2696 [NFS,SUNRPC]
2697 SunRPC servers often require that client requests
2698 originate from a privileged port (i.e. a port in the
2699 range 0 < portnr < 1024).
2700 An administrator who wishes to reserve some of these
2701 ports for other uses may adjust the range that the
2702 kernel's sunrpc client considers to be privileged
2703 using these two parameters to set the minimum and
2704 maximum port values.
2705
Greg Banks42a7fc42007-03-06 01:42:23 -08002706 sunrpc.pool_mode=
2707 [NFS]
2708 Control how the NFS server code allocates CPUs to
2709 service thread pools. Depending on how many NICs
2710 you have and where their interrupts are bound, this
2711 option will affect which CPUs will do NFS serving.
2712 Note: this parameter cannot be changed while the
2713 NFS server is running.
2714
2715 auto the server chooses an appropriate mode
2716 automatically using heuristics
2717 global a single global pool contains all CPUs
2718 percpu one pool for each CPU
2719 pernode one pool for each NUMA node (equivalent
2720 to global on non-NUMA machines)
2721
Trond Myklebustcbf11072009-08-09 15:06:19 -04002722 sunrpc.tcp_slot_table_entries=
2723 sunrpc.udp_slot_table_entries=
2724 [NFS,SUNRPC]
2725 Sets the upper limit on the number of simultaneous
2726 RPC calls that can be sent from the client to a
2727 server. Increasing these values may allow you to
2728 improve throughput, but will also increase the
2729 amount of memory reserved for use by the client.
2730
Michal Hockoa42c3902010-11-24 12:57:08 -08002731 swapaccount[=0|1]
2732 [KNL] Enable accounting of swap in memory resource
2733 controller if no parameter or 1 is given or disable
2734 it if 0 is given (See Documentation/cgroups/memory.txt)
2735
Linus Torvalds1da177e2005-04-16 15:20:36 -07002736 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002737
Linus Torvalds1da177e2005-04-16 15:20:36 -07002738 switches= [HW,M68k]
2739
Andi Kleene52eec12010-09-08 16:54:17 +02002740 sysfs.deprecated=0|1 [KNL]
2741 Enable/disable old style sysfs layout for old udev
2742 on older distributions. When this option is enabled
2743 very new udev will not work anymore. When this option
2744 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2745 in older udev will not work anymore.
2746 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2747 the kernel configuration.
2748
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002749 sysrq_always_enabled
2750 [KNL]
2751 Ignore sysrq setting - this boot parameter will
2752 neutralize any effect of /proc/sys/kernel/sysrq.
2753 Useful for debugging.
2754
Linus Torvalds1da177e2005-04-16 15:20:36 -07002755 tdfx= [HW,DRM]
2756
David Brownell77437fd2008-07-23 21:28:33 -07002757 test_suspend= [SUSPEND]
2758 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2759 standby suspend) as the system sleep state to briefly
2760 enter during system startup. The system is woken from
2761 this state using a wakeup-capable RTC alarm.
2762
Linus Torvalds1da177e2005-04-16 15:20:36 -07002763 thash_entries= [KNL,NET]
2764 Set number of hash buckets for TCP connection
2765
Len Brownf8707ec2007-08-12 00:12:54 -04002766 thermal.act= [HW,ACPI]
2767 -1: disable all active trip points in all thermal zones
2768 <degrees C>: override all lowest active trip points
2769
Len Brownc52a7412007-08-14 15:49:32 -04002770 thermal.crt= [HW,ACPI]
2771 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002772 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002773
Len Brownf5487142007-08-12 00:12:44 -04002774 thermal.nocrt= [HW,ACPI]
2775 Set to disable actions on ACPI thermal zone
2776 critical and hot trip points.
2777
Len Brown72b33ef2007-08-12 00:12:17 -04002778 thermal.off= [HW,ACPI]
2779 1: disable ACPI thermal control
2780
Len Browna70cdc52007-08-12 00:12:35 -04002781 thermal.psv= [HW,ACPI]
2782 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002783 <degrees C>: override all passive trip points to this
2784 value
Len Browna70cdc52007-08-12 00:12:35 -04002785
Len Brown730ff342007-08-12 00:12:26 -04002786 thermal.tzp= [HW,ACPI]
2787 Specify global default ACPI thermal zone polling rate
2788 <deci-seconds>: poll all this frequency
2789 0: no polling (default)
2790
Thomas Gleixner8d32a302011-02-23 23:52:23 +00002791 threadirqs [KNL]
2792 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09002793 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00002794
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002795 topology= [S390]
2796 Format: {off | on}
2797 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07002798 topology information if the hardware supports this.
2799 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002800 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02002801 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002802
Linus Torvalds1da177e2005-04-16 15:20:36 -07002803 tp720= [HW,PS2]
2804
Rajiv Andrade225a9be2010-03-25 00:55:32 -03002805 tpm_suspend_pcr=[HW,TPM]
2806 Format: integer pcr id
2807 Specify that at suspend time, the tpm driver
2808 should extend the specified pcr with zeros,
2809 as a workaround for some chips which fail to
2810 flush the last written pcr on TPM_SaveState.
2811 This will guarantee that all the other pcrs
2812 are saved.
2813
Li Zefan9d612be2009-06-24 17:33:15 +08002814 trace_buf_size=nn[KMG]
2815 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002816
Li Zefan020e5f82009-07-01 10:47:05 +08002817 trace_event=[event-list]
2818 [FTRACE] Set and start specified trace events in order
2819 to facilitate early boot debugging.
2820 See also Documentation/trace/events.txt
2821
Jiri Kosinafcf4d822012-03-21 16:34:02 -07002822 transparent_hugepage=
2823 [KNL]
2824 Format: [always|madvise|never]
2825 Can be used to control the default behavior of the system
2826 with respect to transparent hugepages.
2827 See Documentation/vm/transhuge.txt for more details.
2828
john stultzd3b8f882009-08-17 16:40:47 -07002829 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07002830 Format: <string>
2831 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07002832 disables clocksource verification at runtime, as well
2833 as the stability checks done at bootup. Used to enable
2834 high-resolution timer mode on older hardware, and in
2835 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07002836 [x86] noirqtime: Do not use TSC to do irq accounting.
2837 Used to run time disable IRQ_TIME_ACCOUNTING on any
2838 platforms where RDTSC is slow and this accounting
2839 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07002840
Randy Dunlapa9913042005-10-23 12:57:11 -07002841 turbografx.map[2|3]= [HW,JOY]
2842 TurboGraFX parallel port interface
2843 Format:
2844 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002845 See also Documentation/input/joystick-parport.txt
2846
Christian Kujaub6935f82011-05-31 15:22:05 +00002847 udbg-immortal [PPC] When debugging early kernel crashes that
2848 happen after console_init() and before a proper
2849 console driver takes over, this boot options might
2850 help "seeing" what's going on.
2851
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002852 uhash_entries= [KNL,NET]
2853 Set number of hash buckets for UDP/UDP-Lite connections
2854
Alan Stern5f8364b2006-12-05 16:29:55 -05002855 uhci-hcd.ignore_oc=
2856 [USB] Ignore overcurrent events (default N).
2857 Some badly-designed motherboards generate lots of
2858 bogus events, for ports that aren't wired to
2859 anything. Set this parameter to avoid log spamming.
2860 Note that genuine overcurrent events won't be
2861 reported either.
2862
Simon Arlotte3a61b02008-07-19 23:32:54 +01002863 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002864 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01002865
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02002866 usbcore.authorized_default=
2867 [USB] Default USB device authorization:
2868 (default -1 = authorized except for wireless USB,
2869 0 = not authorized, 1 = authorized)
2870
Alan Sternb5e795f2007-02-20 15:00:53 -05002871 usbcore.autosuspend=
2872 [USB] The autosuspend time delay (in seconds) used
2873 for newly-detected USB devices (default 2). This
2874 is the time required before an idle device will be
2875 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002876 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002877
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002878 usbcore.usbfs_snoop=
2879 [USB] Set to log all usbfs traffic (default 0 = off).
2880
2881 usbcore.blinkenlights=
2882 [USB] Set to cycle leds on hubs (default 0 = off).
2883
2884 usbcore.old_scheme_first=
2885 [USB] Start with the old device initialization
2886 scheme (default 0 = off).
2887
Alan Stern3f5eb8d2011-11-17 16:41:35 -05002888 usbcore.usbfs_memory_mb=
2889 [USB] Memory limit (in MB) for buffers allocated by
2890 usbfs (default = 16, 0 = max = 2047).
2891
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002892 usbcore.use_both_schemes=
2893 [USB] Try the other device initialization scheme
2894 if the first one fails (default 1 = enabled).
2895
2896 usbcore.initial_descriptor_timeout=
2897 [USB] Specifies timeout for the initial 64-byte
2898 USB_REQ_GET_DESCRIPTOR request in milliseconds
2899 (default 5000 = 5.0 seconds).
2900
Linus Torvalds1da177e2005-04-16 15:20:36 -07002901 usbhid.mousepoll=
2902 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002903
Alan Sternd4f373e2008-11-10 14:07:45 -05002904 usb-storage.delay_use=
2905 [UMS] The delay in seconds before a new device is
2906 scanned for Logical Units (default 5).
2907
2908 usb-storage.quirks=
2909 [UMS] A list of quirks entries to supplement or
2910 override the built-in unusual_devs list. List
2911 entries are separated by commas. Each entry has
2912 the form VID:PID:Flags where VID and PID are Vendor
2913 and Product ID values (4-digit hex numbers) and
2914 Flags is a set of characters, each corresponding
2915 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002916 a = SANE_SENSE (collect more than 18 bytes
2917 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002918 b = BAD_SENSE (don't collect more than 18
2919 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002920 c = FIX_CAPACITY (decrease the reported
2921 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01002922 d = NO_READ_DISC_INFO (don't use
2923 READ_DISC_INFO command);
2924 e = NO_READ_CAPACITY_16 (don't use
2925 READ_CAPACITY_16 command);
Alan Sternc838ea42008-12-15 10:40:06 -05002926 h = CAPACITY_HEURISTICS (decrease the
2927 reported device capacity by one
2928 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002929 i = IGNORE_DEVICE (don't bind to this
2930 device);
2931 l = NOT_LOCKABLE (don't try to lock and
2932 unlock ejectable media);
2933 m = MAX_SECTORS_64 (don't transfer more
2934 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04002935 n = INITIAL_READ10 (force a retry of the
2936 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05002937 o = CAPACITY_OK (accept the capacity
2938 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04002939 p = WRITE_CACHE (the device cache is ON
2940 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05002941 r = IGNORE_RESIDUE (the device reports
2942 bogus residue values);
2943 s = SINGLE_LUN (the device has only one
2944 Logical Unit);
2945 w = NO_WP_DETECT (don't test whether the
2946 medium is write-protected).
2947 Example: quirks=0419:aaf5:rl,0421:0433:rc
2948
Stephen Boydac1667d2011-08-13 12:34:50 -07002949 user_debug= [KNL,ARM]
2950 Format: <int>
2951 See arch/arm/Kconfig.debug help text.
2952 1 - undefined instruction events
2953 2 - system calls
2954 4 - invalid data aborts
2955 8 - SIGSEGV faults
2956 16 - SIGBUS faults
2957 Example: user_debug=31
2958
Ian Campbell14315592010-02-17 10:38:10 +00002959 userpte=
2960 [X86] Flags controlling user PTE allocations.
2961
2962 nohigh = do not allocate PTE pages in
2963 HIGHMEM regardless of setting
2964 of CONFIG_HIGHPTE.
2965
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302966 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002967 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002968 vdso=1: enable VDSO (default)
2969 vdso=0: disable VDSO mapping
2970
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302971 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01002972 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2973 vdso32=1: enable 32-bit VDSO (default)
2974 vdso32=0: disable 32-bit VDSO mapping
2975
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002976 vector= [IA-64,SMP]
2977 vector=percpu: enable percpu vector domain
2978
Linus Torvalds1da177e2005-04-16 15:20:36 -07002979 video= [FB] Frame buffer configuration
2980 See Documentation/fb/modedb.txt.
2981
Pawel Moll81a054c2012-05-09 18:30:16 +01002982 virtio_mmio.device=
2983 [VMMIO] Memory mapped virtio (platform) device.
2984
2985 <size>@<baseaddr>:<irq>[:<id>]
2986 where:
2987 <size> := size (can use standard suffixes
2988 like K, M and G)
2989 <baseaddr> := physical base address
2990 <irq> := interrupt number (as passed to
2991 request_irq())
2992 <id> := (optional) platform device id
2993 example:
2994 virtio_mmio.device=1K@0x100b0000:48:7
2995
2996 Can be used multiple times for multiple devices.
2997
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002998 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05002999 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003000 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003001 Use vga=ask for menu.
3002 This is actually a boot loader parameter; the value is
3003 passed to the kernel using a special protocol.
3004
Randy Dunlapa9913042005-10-23 12:57:11 -07003005 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003006 size of <nn>. This can be used to increase the
3007 minimum size (128MB on x86). It can also be used to
3008 decrease the size and leave more room for directly
3009 mapped kernel RAM.
3010
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003011 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3012 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003013
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003014 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3015 Format: <command>
3016
3017 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3018 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003019
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003020 vsyscall= [X86-64]
3021 Controls the behavior of vsyscalls (i.e. calls to
3022 fixed addresses of 0xffffffffff600x00 from legacy
3023 code). Most statically-linked binaries and older
3024 versions of glibc use these calls. Because these
3025 functions are at fixed addresses, they make nice
3026 targets for exploits that can control RIP.
3027
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003028 emulate [default] Vsyscalls turn into traps and are
3029 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003030
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003031 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003032 This is a little bit faster than trapping
3033 and makes a few dynamic recompilers work
3034 better than they would in emulation mode.
3035 It also makes exploits much easier to write.
3036
3037 none Vsyscalls don't work at all. This makes
3038 them quite hard to use for exploits but
3039 might break your system.
3040
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08003041 vt.cur_default= [VT] Default cursor shape.
3042 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3043 the parameters of the <Esc>[?A;B;Cc escape sequence;
3044 see VGA-softcursor.txt. Default: 2 = underline.
3045
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003046 vt.default_blu= [VT]
3047 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3048 Change the default blue palette of the console.
3049 This is a 16-member array composed of values
3050 ranging from 0-255.
3051
3052 vt.default_grn= [VT]
3053 Format: <green0>,<green1>,<green2>,...,<green15>
3054 Change the default green palette of the console.
3055 This is a 16-member array composed of values
3056 ranging from 0-255.
3057
3058 vt.default_red= [VT]
3059 Format: <red0>,<red1>,<red2>,...,<red15>
3060 Change the default red palette of the console.
3061 This is a 16-member array composed of values
3062 ranging from 0-255.
3063
3064 vt.default_utf8=
3065 [VT]
3066 Format=<0|1>
3067 Set system-wide default UTF-8 mode for all tty's.
3068 Default is 1, i.e. UTF-8 mode is enabled for all
3069 newly opened terminals.
3070
Matthew Garrettf6c06b62009-11-13 15:14:11 -05003071 vt.global_cursor_default=
3072 [VT]
3073 Format=<-1|0|1>
3074 Set system-wide default for whether a cursor
3075 is shown on new VTs. Default is -1,
3076 i.e. cursors will be created by default unless
3077 overridden by individual drivers. 0 will hide
3078 cursors, 1 will display them.
3079
Randy Dunlap4724ba572010-05-03 11:42:52 -07003080 watchdog timers [HW,WDT] For information on watchdog timers,
3081 see Documentation/watchdog/watchdog-parameters.txt
3082 or other driver-specific files in the
3083 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003084
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003085 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3086 default x2apic cluster mode on platforms
3087 supporting x2apic.
3088
Jacob Panbb24c472009-09-02 07:37:17 -07003089 x86_mrst_timer= [X86-32,APBT]
3090 Choose timer option for x86 Moorestown MID platform.
3091 Two valid options are apbt timer only and lapic timer
3092 plus one apbt timer for broadcast timer.
3093 x86_mrst_timer=apbt_only | lapic_and_apbt
3094
Linus Torvalds1da177e2005-04-16 15:20:36 -07003095 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3096 xd_geo= See header of drivers/block/xd.c.
3097
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003098 xen_emul_unplug= [HW,X86,XEN]
3099 Unplug Xen emulated devices
3100 Format: [unplug0,][unplug1]
3101 ide-disks -- unplug primary master IDE devices
3102 aux-ide-disks -- unplug non-primary-master IDE devices
3103 nics -- unplug network devices
3104 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01003105 unnecessary -- unplugging emulated devices is
3106 unnecessary even if the host did not respond to
3107 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01003108 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003109
Linus Torvalds1da177e2005-04-16 15:20:36 -07003110 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07003111 Format:
3112 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003113
Randy Dunlapa9913042005-10-23 12:57:11 -07003114______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07003115
3116TODO:
3117
Linus Torvalds1da177e2005-04-16 15:20:36 -07003118 Add more DRM drivers.