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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.
Olof Johansson1e435252013-04-27 14:10:18 -070047 CLK Common clock infrastructure is enabled.
Robert Tivy5c71d612013-03-28 18:41:46 -070048 CMA Contiguous Memory Area support is enabled.
Alan Cox9cfe2682011-01-25 14:18:38 +000049 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070051 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
Mimi Zohar7102ebc2011-05-12 18:33:20 -040054 EVM Extended Verification Module
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 FB The frame buffer device is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070056 FTRACE Function tracing enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070057 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050060 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070062 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080063 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070064 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050067 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020068 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070069 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070070 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -070075 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070076 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070078 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070079 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070084 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070086 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070088 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070089 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -070097 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -070099 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -0700101 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900103 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300108 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500110 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
Pawel Moll81a054c2012-05-09 18:30:16 +0100114 VMMIO Driver for memory mapped virtio devices is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700119 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700122 Documentation/x86/x86_64/boot-options.txt .
Randy Dunlap16290242011-08-13 12:34:52 -0700123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100124 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125
126In addition, the following text indicates that the option:
127
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
131
132Parameters denoted with BOOT are actually interpreted by the boot
133loader, and have no meaning to the kernel directly.
134Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500135need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136
Karsten Weiss55588702007-02-13 13:26:21 +0100137There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700138See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100139
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141a trailing = on the name of any parameter states that that parameter will
142be entered as an environment variable, whereas its absence indicates that
143it will appear as a kernel argument readable via /proc/cmdline by programs
144running once the system is up.
145
jens m. noedler9c4751f2006-09-29 02:00:27 -0700146The number of kernel parameters is not limited, but the length of the
147complete command line (parameters including spaces etc.) is limited to
148a fixed number of characters. This limit depends on the architecture
149and is between 256 and 4096 characters. It is defined in the file
150./include/asm/setup.h as COMMAND_LINE_SIZE.
151
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800152Finally, the [KMG] suffix is commonly described after a number of kernel
153parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155bytes respectively. Such letter suffixes can also be entirely omitted.
156
jens m. noedler9c4751f2006-09-29 02:00:27 -0700157
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530158 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800159 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500160 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700164 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800166 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800167 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168
Paul Bolle395cf962011-08-15 02:02:26 +0200169 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170
Takao Indoh4996c022011-07-14 18:05:21 -0400171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
175
Len Browna1fdcc02007-03-11 03:26:14 -0400176 acpi_apic_instance= [ACPI, IOAPIC]
177 Format: <int>
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400180 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400181
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
184 acpi_backlight=video
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
188
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200212
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800216
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
219 default in APIC mode
220
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
223 default in PIC mode
224
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
227
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
229 use by PCI
230 Format: <irq>,<irq>...
231
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
233
234 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
236
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800238 acpi_osi="string1" # add string1
239 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800240 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800241 acpi_osi=! # disable all built-in OS vendor
242 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700243 acpi_osi= # disable all strings
244
Lv Zheng5dc17982013-07-22 16:08:25 +0800245 'acpi_osi=!' can be used in combination with single or
246 multiple 'acpi_osi="string1"' to support specific OS
247 vendor string(s). Note that such command can only
248 affect the default state of the OS vendor strings, thus
249 it cannot affect the default state of the feature group
250 strings and the current state of the OS vendor strings,
251 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800252 is meaningless. This command is useful when one do not
253 care about the state of the feature group strings which
254 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800255 Examples:
256 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258 can make '_OSI("Windows 2000")' TRUE.
259
260 'acpi_osi=' cannot be used in combination with other
261 'acpi_osi=' command lines, the _OSI method will not
262 exist in the ACPI namespace. NOTE that such command can
263 only affect the _OSI support state, thus specifying it
264 multiple times through kernel command line is also
265 meaningless.
266 Examples:
267 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
268 FALSE.
269
Lv Zheng741d8122013-07-22 16:08:36 +0800270 'acpi_osi=!*' can be used in combination with single or
271 multiple 'acpi_osi="string1"' to support specific
272 string(s). Note that such command can affect the
273 current state of both the OS vendor strings and the
274 feature group strings, thus specifying it multiple times
275 through kernel command line is meaningful. But it may
276 still not able to affect the final state of a string if
277 there are quirks related to this string. This command
278 is useful when one want to control the state of the
279 feature group strings to debug BIOS issues related to
280 the OSPM features.
281 Examples:
282 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283 '_OSI("Module Device")' FALSE.
284 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285 '_OSI("Module Device")' TRUE.
286 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
287 equivalent to
288 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
289 and
290 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291 they all will make '_OSI("Windows 2000")' TRUE.
292
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530293 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700294 Override the pmtimer bug detection: force the kernel
295 to assume that this machine's pmtimer latches its value
296 and always returns good values.
297
Randy Dunlap4af94f32009-04-17 18:30:28 -0700298 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
299 Format: { level | edge | high | low }
300
301 acpi_serialize [HW,ACPI] force serialization of AML methods
302
303 acpi_skip_timer_override [HW,ACPI]
304 Recognize and ignore IRQ0/pin2 Interrupt Override.
305 For broken nForce2 BIOS resulting in XT-PIC timer.
306
307 acpi_sleep= [HW,ACPI] Sleep options
308 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200309 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700310 See Documentation/power/video.txt for information on
311 s3_bios and s3_mode.
312 s3_beep is for debugging; it makes the PC's speaker beep
313 as soon as the kernel's real-mode entry point is called.
314 s4_nohwsig prevents ACPI hardware signature from being
315 used during resume from hibernation.
316 old_ordering causes the ACPI 1.0 ordering of the _PTS
317 control method, with respect to putting devices into
318 low power states, to be enforced (the ACPI 2.0 ordering
319 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200320 nonvs prevents the kernel from saving/restoring the
321 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800322 sci_force_enable causes the kernel to set SCI_EN directly
323 on resume from S1/S3 (which is against the ACPI spec,
324 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700325
326 acpi_use_timer_override [HW,ACPI]
327 Use timer override. For some broken Nvidia NF5 boards
328 that require a timer override, but don't have HPET
329
Luca Tettamanti7e905602009-03-30 00:01:27 +0200330 acpi_enforce_resources= [ACPI]
331 { strict | lax | no }
332 Check for resource conflicts between native drivers
333 and ACPI OperationRegions (SystemIO and SystemMemory
334 only). IO ports and memory declared in ACPI might be
335 used by the ACPI subsystem in arbitrary AML code and
336 can interfere with legacy drivers.
337 strict (default): access to resources claimed by ACPI
338 is denied; legacy drivers trying to access reserved
339 resources will fail to bind to device using them.
340 lax: access to resources claimed by ACPI is allowed;
341 legacy drivers trying to access reserved resources
342 will bind successfully but a warning message is logged.
343 no: ACPI OperationRegions are not marked as reserved,
344 no further checks are performed.
345
Randy Dunlap4af94f32009-04-17 18:30:28 -0700346 add_efi_memmap [EFI; X86] Include EFI memory map in
347 kernel's map of available physical RAM.
348
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700349 agp= [AGP]
350 { off | try_unsupported }
351 off: disable AGP support
352 try_unsupported: try to drive unsupported chipsets
353 (may crash computer or cause data corruption)
354
Randy Dunlapbcfde332010-06-07 17:10:38 -0700355 ALSA [HW,ALSA]
356 See Documentation/sound/alsa/alsa-parameters.txt
357
Russell Kingd944d542010-02-20 16:13:29 +0000358 alignment= [KNL,ARM]
359 Allow the default userspace alignment fault handler
360 behaviour to be specified. Bit 0 enables warnings,
361 bit 1 enables fixups, and bit 2 sends a segfault.
362
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200363 align_va_addr= [X86-64]
364 Align virtual addresses by clearing slice [14:12] when
365 allocating a VMA at process creation time. This option
366 gives you up to 3% performance improvement on AMD F15h
367 machines (where it is enabled by default) for a
368 CPU-intensive style benchmark, and it can vary highly in
369 a microbenchmark depending on workload and compiler.
370
Borislav Petkov8360ee22011-11-21 12:10:19 +0100371 32: only for 32-bit processes
372 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200373 on: enable for both 32- and 64-bit processes
374 off: disable for both 32- and 64-bit processes
375
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500376 alloc_snapshot [FTRACE]
377 Allocate the ftrace snapshot buffer on boot up when the
378 main buffer is allocated. This is handy if debugging
379 and you need to use tracing_snapshot() on boot up, and
380 do not want to use tracing_snapshot_alloc() as it needs
381 to be done where GFP_KERNEL allocations are allowed.
382
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100383 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200384 Pass parameters to the AMD IOMMU driver in the system.
385 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900386 fullflush - enable flushing of IO/TLB entries when
387 they are unmapped. Otherwise they are
388 flushed before they will be reused, which
389 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200390 off - do not initialize any AMD IOMMU found in
391 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100392 force_isolation - Force device isolation for all
393 devices. The IOMMU driver is not
394 allowed anymore to lift isolation
395 requirements as needed. This option
396 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900397
Shuah Khanc099cf12012-05-24 15:58:25 -0600398 amd_iommu_dump= [HW,X86-64]
399 Enable AMD IOMMU driver option to dump the ACPI table
400 for AMD IOMMU. With this option enabled, AMD IOMMU
401 driver will print ACPI tables for AMD IOMMU during
402 IOMMU initialization.
403
Linus Torvalds1da177e2005-04-16 15:20:36 -0700404 amijoy.map= [HW,JOY] Amiga joystick support
405 Map of devices attached to JOY0DAT and JOY1DAT
406 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200407 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408
409 analog.map= [HW,JOY] Analog joystick and gamepad support
410 Specifies type or capabilities of an analog joystick
411 connected to one of 16 gameports
412 Format: <type1>,<type2>,..<type16>
413
Randy Dunlapa9913042005-10-23 12:57:11 -0700414 apc= [HW,SPARC]
415 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416 Format: noidle
417 Disable APC CPU standby support. SPARCstation-Fox does
418 not play well with APC CPU idle - disable it if you have
419 APC and your system crashes randomly.
420
Randy Dunlapca1eda22009-05-06 16:02:58 -0700421 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700422 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423 Format: { quiet (default) | verbose | debug }
424 Change the amount of debugging information output
425 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700426
Brian Haleyb0f83b22010-02-04 13:36:50 -0800427 autoconf= [IPV6]
428 See Documentation/networking/ipv6.txt.
429
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400430 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
431 Limit apic dumping. The parameter defines the maximal
432 number of local apics being dumped. Also it is possible
433 to set it to "all" by meaning -- no limit here.
434 Format: { 1 (default) | 2 | ... | all }.
435 The parameter valid if only apic=debug or
436 apic=verbose is specified.
437 Example: apic=debug show_lapic=all
438
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700440 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700441
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443 Format: <io>,<irq>,<nodeID>
444
445 ataflop= [HW,M68k]
446
447 atarimouse= [HW,MOUSE] Atari Mouse
448
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
450 EzKey and similar keyboards
451
452 atkbd.reset= [HW] Reset keyboard during initialization
453
Randy Dunlapa9913042005-10-23 12:57:11 -0700454 atkbd.set= [HW] Select keyboard code set
455 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456
457 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
458 keyboards
459
460 atkbd.softraw= [HW] Choose between synthetic and real raw mode
461 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700462
463 atkbd.softrepeat= [HW]
464 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700465
Linus Torvalds1da177e2005-04-16 15:20:36 -0700466 baycom_epp= [HW,AX25]
467 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700468
Linus Torvalds1da177e2005-04-16 15:20:36 -0700469 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
470 Format: <io>,<mode>
471 See header of drivers/net/hamradio/baycom_par.c.
472
Randy Dunlapa9913042005-10-23 12:57:11 -0700473 baycom_ser_fdx= [HW,AX25]
474 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475 Format: <io>,<irq>,<mode>[,<baud>]
476 See header of drivers/net/hamradio/baycom_ser_fdx.c.
477
Randy Dunlapa9913042005-10-23 12:57:11 -0700478 baycom_ser_hdx= [HW,AX25]
479 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 Format: <io>,<irq>,<mode>
481 See header of drivers/net/hamradio/baycom_ser_hdx.c.
482
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700483 boot_delay= Milliseconds to delay each printk during boot.
484 Values larger than 10 seconds (10000) are changed to
485 no delay (0).
486 Format: integer
487
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700488 bootmem_debug [KNL] Enable bootmem allocator debug messages.
489
Linus Torvalds1da177e2005-04-16 15:20:36 -0700490 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700491 bttv.radio= Most important insmod options are available as
492 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200494 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700495
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000496 bulk_remove=off [PPC] This parameter disables the use of the pSeries
497 firmware feature for flushing multiple hpte entries
498 at a time.
499
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500 c101= [NET] Moxa C101 synchronous serial card
501
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700502 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700503 Sometimes CPU hardware bugs make them report the cache
504 size incorrectly. The kernel will attempt work arounds
505 to fix known problems, but for some CPUs it is not
506 possible to determine what the correct size should be.
507 This option provides an override for these situations.
508
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100509 ccw_timeout_log [S390]
510 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511
Paul Menage8bab8dd2008-04-04 14:29:57 -0700512 cgroup_disable= [KNL] Disable a particular controller
513 Format: {name of the controller(s) to disable}
514 {Currently supported controllers - "memory"}
515
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 checkreqprot [SELINUX] Set initial checkreqprot flag value.
517 Format: { "0" | "1" }
518 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700519 0 -- check protection applied by kernel (includes
520 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700521 1 -- check protection requested by application.
522 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700523 Value can be changed at runtime via
524 /selinux/checkreqprot.
525
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100526 cio_ignore= [S390]
527 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700528 clk_ignore_unused
529 [CLK]
530 Keep all clocks already enabled by bootloader on,
531 even if no driver has claimed them. This is useful
532 for debug and development, but should not be
533 needed on a platform with proper driver support.
534 For more information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100535
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700536 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700537 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200538 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700539 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200540 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541 Format: { pit | tsc | cyclone | pmtmr }
542
John Stultz592913e2010-07-13 17:56:20 -0700543 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700544 Format: <string>
545 Override the default clocksource and use the clocksource
546 with the name specified.
547 Some clocksource names to choose from, depending on
548 the platform:
549 [all] jiffies (this is the base, fallback clocksource)
550 [ACPI] acpi_pm
551 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
552 pxa_timer,timer3,32k_counter,timer0_1
553 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700554 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700555 scx200_hrt on Geode; cyclone on IBM x440
556 [MIPS] MIPS
557 [PARISC] cr16
558 [S390] tod
559 [SH] SuperH
560 [SPARC64] tick
561 [X86-64] hpet,tsc
562
Andi Kleenac72e782008-01-30 13:33:21 +0100563 clearcpuid=BITNUM [X86]
564 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800565 arch/x86/include/asm/cpufeature.h for the valid bit
566 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100567 stable over kernel options, but the vendor specific
568 ones should be.
569 Also note that user programs calling CPUID directly
570 or using the feature without checking anything
571 will still see it. This just prevents it from
572 being used by the kernel or shown in /proc/cpuinfo.
573 Also note the kernel might malfunction if you disable
574 some critical bits.
575
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100576 cma=nn[MG] [ARM,KNL]
577 Sets the size of kernel global memory area for contiguous
578 memory allocations. For more information, see
579 include/linux/dma-contiguous.h
580
Robert Jennings14f966e2009-04-15 05:55:32 +0000581 cmo_free_hint= [PPC] Format: { yes | no }
582 Specify whether pages are marked as being inactive
583 when they are freed. This is used in CMO environments
584 to determine OS memory pressure for page stealing by
585 a hypervisor.
586 Default: yes
587
Marek Szyprowskic7909502011-12-29 13:09:51 +0100588 coherent_pool=nn[KMG] [ARM,KNL]
589 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200590 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100591
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530592 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100593 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100594 Range: 0 - 8192
595 Default: 64
596
Linus Torvalds1da177e2005-04-16 15:20:36 -0700597 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700598 Format:
599 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700600
601 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
602 Format: <io>[,<irq>]
603
Randy Dunlapa9913042005-10-23 12:57:11 -0700604 com90xx= [HW,NET]
605 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700606 Format: <io>[,<irq>[,<memstart>]]
607
608 condev= [HW,S390] console device
609 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700610
Linus Torvalds1da177e2005-04-16 15:20:36 -0700611 console= [KNL] Output console device and options.
612
613 tty<n> Use the virtual console device <n>.
614
615 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800616 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700617 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800618 the form "bbbbpnf", where "bbbb" is the baud rate,
619 "p" is parity ("n", "o", or "e"), "n" is number of
620 bits, and "f" is flow control ("r" for RTS or
621 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700622
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800623 See Documentation/serial-console.txt for more
624 information. See
625 Documentation/networking/netconsole.txt for an
626 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700628 uart[8250],io,<addr>[,options]
629 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630 Start an early, polled-mode console on the 8250/16550
631 UART at the specified I/O port or MMIO address,
632 switching to the matching ttyS device later. The
633 options are the same as for ttyS, above.
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500634 hvc<n> Use the hypervisor console device <n>. This is for
635 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700637 If the device connected to the port is not a TTY but a braille
638 device, prepend "brl," before the device type, for instance
639 console=brl,ttyS0
640 For now, only VisioBraille is supported.
641
Daniel Mackf324edc2009-06-16 15:33:52 -0700642 consoleblank= [KNL] The console blank (screen saver) timeout in
643 seconds. Defaults to 10*60 = 10mins. A value of 0
644 disables the blank timer.
645
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800646 coredump_filter=
647 [KNL] Change the default value for
648 /proc/<pid>/coredump_filter.
649 See also Documentation/filesystems/proc.txt.
650
Len Brown62027ae2011-04-01 18:13:10 -0400651 cpuidle.off=1 [CPU_IDLE]
652 disable the cpuidle sub-system
653
Linus Torvalds1da177e2005-04-16 15:20:36 -0700654 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700655 Format:
656 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700657
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800658 crashkernel=size[KMG][@offset[KMG]]
659 [KNL] Using kexec, Linux can switch to a 'crash kernel'
660 upon panic. This parameter reserves the physical
661 memory region [offset, offset + size] for that kernel
662 image. If '@offset' is omitted, then a suitable offset
663 is selected automatically. Check
664 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700665
Bernhard Wallefb391592007-10-18 23:41:02 -0700666 crashkernel=range1:size1[,range2:size2,...][@offset]
667 [KNL] Same as above, but depends on the memory
668 in the running system. The syntax of range is
669 start-[end] where start and end are both
670 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800671 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700672
Yinghai Luadbc7422013-04-15 22:23:48 -0700673 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700674 [KNL, x86_64] range could be above 4G. Allow kernel
675 to allocate physical memory region from top, so could
676 be above 4G if system have more than 4G ram installed.
677 Otherwise memory region will be allocated below 4G, if
678 available.
679 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700680 crashkernel=size[KMG],low
681 [KNL, x86_64] range under 4G. When crashkernel=X,high
682 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700683 above 4G, that cause second kernel crash on system
684 that require some amount of low memory, e.g. swiotlb
685 requires at least 64M+32K low memory. Kernel would
686 try to allocate 72M below 4G automatically.
687 This one let user to specify own low range under 4G
688 for second kernel instead.
689 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700690 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700691 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700692
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693 cs89x0_dma= [HW,NET]
694 Format: <dma>
695
696 cs89x0_media= [HW,NET]
697 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700698
Randy Dunlapa9913042005-10-23 12:57:11 -0700699 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700700 See header of drivers/s390/block/dasd_devmap.c.
701
702 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
703 (one device per port)
704 Format: <port#>,<type>
705 See also Documentation/input/joystick-parport.txt
706
Thomas Renningera648ec02010-08-06 16:11:02 +0200707 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
708 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600709 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200710
Linus Torvalds1da177e2005-04-16 15:20:36 -0700711 debug [KNL] Enable kernel debugging (events log level).
712
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700713 debug_locks_verbose=
714 [KNL] verbose self-tests
715 Format=<0|1>
716 Print debugging info while doing the locking API
717 self-tests.
718 We default to 0 (no extra messages), setting it to
719 1 will print _a lot_ more information - normally
720 only useful to kernel developers.
721
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700722 debug_objects [KNL] Enable object debugging
723
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500724 no_debug_objects
725 [KNL] Disable object debugging
726
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800727 debug_guardpage_minorder=
728 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
729 parameter allows control of the order of pages that will
730 be intentionally kept free (and hence protected) by the
731 buddy allocator. Bigger value increase the probability
732 of catching random memory corruption, but reduce the
733 amount of memory for normal system use. The maximum
734 possible value is MAX_ORDER/2. Setting this parameter
735 to 1 or 2 should be enough to identify most random
736 memory corruption problems caused by bugs in kernel or
737 driver code when a CPU writes to (or reads from) a
738 random memory location. Note that there exists a class
739 of memory corruptions problems caused by buggy H/W or
740 F/W or by drivers badly programing DMA (basically when
741 memory is written at bus level and the CPU MMU is
742 bypassed) which are not detectable by
743 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
744 tracking down these problems.
745
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200746 debugpat [X86] Enable PAT debugging
747
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200748 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700749 Format: <area>[,<node>]
750 See also Documentation/networking/decnet.txt.
751
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700752 default_hugepagesz=
753 [same as hugepagesz=] The size of the default
754 HugeTLB page size. This is the size represented by
755 the legacy /proc/ hugepages APIs, used for SHM, and
756 default size when mounting hugetlbfs filesystems.
757 Defaults to the default architecture's huge page size
758 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700759
Linus Torvalds1da177e2005-04-16 15:20:36 -0700760 dhash_entries= [KNL]
761 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700762
Linus Torvalds1da177e2005-04-16 15:20:36 -0700763 digi= [HW,SERIAL]
764 IO parameters + enable/disable command.
765
766 digiepca= [HW,SERIAL]
767 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000768 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700769
Brian Haleyb0f83b22010-02-04 13:36:50 -0800770 disable= [IPV6]
771 See Documentation/networking/ipv6.txt.
772
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000773 disable_ddw [PPC/PSERIES]
774 Disable Dynamic DMA Window support. Use this if
775 to workaround buggy firmware.
776
Brian Haleyb0f83b22010-02-04 13:36:50 -0800777 disable_ipv6= [IPV6]
778 See Documentation/networking/ipv6.txt.
779
Yinghai Lu95ffa242008-04-29 03:52:33 -0700780 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700781 The kernel tries to adjust MTRR layout from continuous
782 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700783 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700784
Yinghai Lu093af8d2008-01-30 13:33:32 +0100785 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100786 By default the kernel will trim any uncacheable
787 memory out of your available memory pool based on
788 MTRR settings. This parameter disables that behavior,
789 possibly causing your machine to run very slowly.
790
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530791 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700792 Disable PIN 1 of APIC timer
793 Can be useful to work around chipset bugs.
794
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700795 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
796 this option disables the debugging code at boot.
797
798 dma_debug_entries=<number>
799 This option allows to tune the number of preallocated
800 entries for DMA-API debugging code. One entry is
801 required per DMA-API allocation. Use this if the
802 DMA-API debugging code disables itself because the
803 architectural default is too low.
804
Joerg Roedel1745de52009-05-22 21:49:51 +0200805 dma_debug_driver=<driver_name>
806 With this option the DMA-API debugging driver
807 filter feature can be enabled at boot time. Just
808 pass the driver to filter for as the parameter.
809 The filter can be disabled or changed to another
810 driver later using sysfs.
811
Carsten Emdeda0df922012-03-18 22:37:33 +0100812 drm_kms_helper.edid_firmware=[<connector>:]<file>
813 Broken monitors, graphic adapters and KVMs may
814 send no or incorrect EDID data sets. This parameter
815 allows to specify an EDID data set in the
816 /lib/firmware directory that is used instead.
817 Generic built-in EDID data sets are used, if one of
818 edid/1024x768.bin, edid/1280x1024.bin,
819 edid/1680x1050.bin, or edid/1920x1080.bin is given
820 and no file with the same name exists. Details and
821 instructions how to build your own EDID data are
822 available in Documentation/EDID/HOWTO.txt. An EDID
823 data set will only be used for a particular connector,
824 if its name and a colon are prepended to the EDID
825 name.
826
Linus Torvalds1da177e2005-04-16 15:20:36 -0700827 dscc4.setup= [NET]
828
Jim Cromie29e36c92012-04-27 14:30:41 -0600829 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
830 module.dyndbg[="val"]
831 Enable debug messages at boot time. See
832 Documentation/dynamic-debug-howto.txt for details.
833
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700834 earlycon= [KNL] Output early console device and options.
835 uart[8250],io,<addr>[,options]
836 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700837 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700838 Start an early, polled-mode console on the 8250/16550
839 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700840 MMIO inter-register address stride is either 8-bit
841 (mmio) or 32-bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700842 The options are the same as for ttyS, above.
843
Dave Hansen147ea092013-04-10 14:03:38 -0700844 earlyprintk= [X86,SH,BLACKFIN,ARM]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700845 earlyprintk=vga
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500846 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700847 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -0700848 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500849 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500850 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700851
Dave Hansen147ea092013-04-10 14:03:38 -0700852 earlyprintk is useful when the kernel crashes before
853 the normal console is initialized. It is not enabled by
854 default because it has some cosmetic problems.
855
Randy Dunlapa9913042005-10-23 12:57:11 -0700856 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700857 takes over.
858
Yinghai Lu5c059172008-07-24 17:29:40 -0700859 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700860
Dave Hansen147ea092013-04-10 14:03:38 -0700861 Currently only ttyS0 and ttyS1 may be specified by
862 name. Other I/O ports may be explicitly specified
863 on some architectures (x86 and arm at least) by
864 replacing ttySn with an I/O port address, like this:
865 earlyprintk=serial,0x1008,115200
866 You can find the port for a given device in
867 /proc/tty/driver/serial:
868 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -0700869
870 Interaction with the standard serial driver is not
871 very good.
872
873 The VGA output is eventually overwritten by the real
874 console.
875
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500876 The xen output can only be used by Xen PV guests.
877
Jason Wessel97311912010-05-20 21:04:30 -0500878 ekgdboc= [X86,KGDB] Allow early kernel console debugging
879 ekgdboc=kbd
880
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300881 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -0500882 the boot argument: earlyprintk=vga
883
Linus Torvalds1da177e2005-04-16 15:20:36 -0700884 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700885 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700886
Richard Weinberger8c58bf32013-04-17 01:00:53 +0200887 efi_no_storage_paranoia [EFI; X86]
888 Using this parameter you can use more than 50% of
889 your efi variable storage. Use this parameter only if
890 you are really sure that your UEFI does sane gc and
891 fulfills the spec otherwise your board may brick.
892
Linus Torvalds1da177e2005-04-16 15:20:36 -0700893 eisa_irq_edge= [PARISC,HW]
894 See header of drivers/parisc/eisa.c.
895
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700896 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700898 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700899
900 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +0100901 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +0200902 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -0700903 Documentation/block/deadline-iosched.txt for details.
904
Michael Holzheud3bf37952011-10-30 15:16:37 +0100905 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -0700906 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +0100907 image elf header and optionally the size. Generally
908 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -0800909 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700910
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700911 enable_mtrr_cleanup [X86]
912 The kernel tries to adjust MTRR layout from continuous
913 to discrete, to make X server driver able to add WB
914 entry later. This parameter enables that.
915
Randy Dunlapca1eda22009-05-06 16:02:58 -0700916 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700917 Enable PIN 1 of APIC timer
918 Can be useful to work around chipset bugs
919 (in particular on some ATI chipsets).
920 The kernel tries to set a reasonable default.
921
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922 enforcing [SELINUX] Set initial enforcing status.
923 Format: {"0" | "1"}
924 See security/selinux/Kconfig help text.
925 0 -- permissive (log only, no denials).
926 1 -- enforcing (deny and log).
927 Default value is 0.
928 Value can be changed at runtime via /selinux/enforce.
929
Huang Yinga08f82d2010-05-18 14:35:21 +0800930 erst_disable [ACPI]
931 Disable Error Record Serialization Table (ERST)
932 support.
933
Linus Torvalds1da177e2005-04-16 15:20:36 -0700934 ether= [HW,NET] Ethernet cards parameters
935 This option is obsoleted by the "netdev=" option, which
936 has equivalent usage. See its documentation for details.
937
Mimi Zohar7102ebc2011-05-12 18:33:20 -0400938 evm= [EVM]
939 Format: { "fix" }
940 Permit 'security.evm' to be updated regardless of
941 current integrity status.
942
Akinobu Mitade1ba092006-12-08 02:39:42 -0800943 failslab=
944 fail_page_alloc=
945 fail_make_request=[KNL]
946 General fault injection mechanism.
947 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +0200948 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -0800949
Linus Torvalds1da177e2005-04-16 15:20:36 -0700950 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000951 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700952
Alex Chiangf13ae302008-05-08 14:03:23 -0600953 force_pal_cache_flush
954 [IA-64] Avoid check_sal_cache_flush which may hang on
955 buggy SAL_CACHE_FLUSH implementations. Using this
956 parameter will force ia64_sal_cache_flush to call
957 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
958
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100959 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400960 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100961 as early as possible in order to facilitate early
962 boot debugging.
963
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200964 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400965 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200966 If no parameter is passed, ftrace will dump
967 buffers of all CPUs, but if you pass orig_cpu, it will
968 dump only the buffer of the CPU that triggered the
969 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400970
971 ftrace_filter=[function-list]
972 [FTRACE] Limit the functions traced by the function
973 tracer at boot up. function-list is a comma separated
974 list of functions. This list can be changed at run
975 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -0700976 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400977
978 ftrace_notrace=[function-list]
979 [FTRACE] Do not trace the functions specified in
980 function-list. This list can be changed at run time
981 by the set_ftrace_notrace file in the debugfs
982 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100983
Stefan Assmann369bc182009-10-12 22:17:21 +0200984 ftrace_graph_filter=[function-list]
985 [FTRACE] Limit the top level callers functions traced
986 by the function graph tracer at boot up.
987 function-list is a comma separated list of functions
988 that can be changed at run time by the
989 set_graph_function file in the debugfs tracing directory.
990
Linus Torvalds1da177e2005-04-16 15:20:36 -0700991 gamecon.map[2|3]=
992 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
993 support via parallel port (up to 5 devices per port)
994 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
995 See also Documentation/input/joystick-parport.txt
996
997 gamma= [HW,DRM]
998
Yinghai Luaaf23042008-01-30 13:33:09 +0100999 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1000 Format: off | on
1001 default: on
1002
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001003 gcov_persist= [GCOV] When non-zero (default), profiling data for
1004 kernel modules is saved and remains accessible via
1005 debugfs, even when the module is unloaded/reloaded.
1006 When zero, profiling data is discarded and associated
1007 debugfs files are removed at module unload time.
1008
Linus Torvalds1da177e2005-04-16 15:20:36 -07001009 gpt [EFI] Forces disk with valid GPT signature but
1010 invalid Protective MBR to be treated as GPT.
1011
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001012 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1013 the "Enable 0" bit of the configuration register.
1014 Format: 0 | 1
1015 Default: 0
1016 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1017 the "Enable 0" bit of the configuration register.
1018 Format: 0 | 1
1019 Default: 0
1020 grcan.select= [HW] Select which physical interface to use.
1021 Format: 0 | 1
1022 Default: 0
1023 grcan.txsize= [HW] Sets the size of the tx buffer.
1024 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1025 Default: 1024
1026 grcan.rxsize= [HW] Sets the size of the rx buffer.
1027 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1028 Default: 1024
1029
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030 hashdist= [KNL,NUMA] Large hashes allocated during boot
1031 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001032 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001033 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001034
1035 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1036
1037 hd= [EIDE] (E)IDE hard drive subsystem geometry
1038 Format: <cyl>,<head>,<sect>
1039
Huang Yingea8c0712010-05-18 14:35:15 +08001040 hest_disable [ACPI]
1041 Disable Hardware Error Source Table (HEST) support;
1042 corresponding firmware-first mode error processing
1043 logic will be disabled.
1044
Linus Torvalds1da177e2005-04-16 15:20:36 -07001045 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1046 size of <nn>. This works even on boxes that have no
1047 highmem otherwise. This also works to reduce highmem
1048 size on bigger boxes.
1049
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001050 highres= [KNL] Enable/disable high resolution timer mode.
1051 Valid parameters: "on", "off"
1052 Default: "on"
1053
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054 hisax= [HW,ISDN]
1055 See Documentation/isdn/README.HiSax.
1056
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001057 hlt [BUGS=ARM,SH]
1058
1059 hpet= [X86-32,HPET] option to control HPET usage
1060 Format: { enable (default) | disable | force |
1061 verbose }
1062 disable: disable HPET and use PIT instead
1063 force: allow force enabled of undocumented chips (ICH4,
1064 VIA, nVidia)
1065 verbose: show contents of HPET registers during setup
1066
Andi Kleenb4718e62008-07-23 21:27:51 -07001067 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1068 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001069 On x86-64 and powerpc, this option can be specified
1070 multiple times interleaved with hugepages= to reserve
1071 huge pages of different sizes. Valid pages sizes on
1072 x86-64 are 2M (when the CPU supports "pse") and 1G
1073 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -07001074 Note that 1GB pages can only be allocated at boot time
1075 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +09001076
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001077 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1078 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001079 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1080 If specified, z/VM IUCV HVC accepts connections
1081 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001082
James Hoganfdabf522012-10-09 11:00:27 +01001083 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1084 hardware thread id mappings.
1085 Format: <cpu>:<hwthread>
1086
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001087 keep_bootcon [KNL]
1088 Do not unregister boot console at start. This is only
1089 useful for debugging when something happens in the window
1090 between unregistering the boot console and initializing
1091 the real console.
1092
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001093 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001094 or register an additional I2C bus that is not
1095 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001096 Format:
1097 <bus_id>,<clkrate>
1098
Jiri Kosina36d95732008-10-06 02:51:09 -04001099 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001100 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001101 i8042.dumbkbd [HW] Pretend that controller can only read data from
1102 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103 (Don't attempt to blink the leds)
1104 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001105 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001106 i8042.noloop [HW] Disable the AUX Loopback command while probing
1107 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001108 i8042.nomux [HW] Don't check presence of an active multiplexing
1109 controller
1110 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1111 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001112 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001113 i8042.reset [HW] Reset the controller during init and cleanup
1114 i8042.unlock [HW] Unlock (ignore) the keylock
1115
1116 i810= [HW,DRM]
1117
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001118 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1119 indicates that the driver is running on unsupported
1120 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1122 does not match list of supported models.
1123 i8k.power_status
1124 [HW] Report power status in /proc/i8k
1125 (disabled by default)
1126 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1127 capability is set.
1128
Carsten Emde4dca20e2012-03-15 15:56:26 +01001129 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001130 [DRM] Invert the sense of the variable that is used to
1131 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001132 brightness value of 0 indicates backlight switched off,
1133 and the maximum of the brightness value sets the backlight
1134 to maximum brightness. If this parameter is set to 0
1135 (default) and the machine requires it, or this parameter
1136 is set to 1, a brightness value of 0 sets the backlight
1137 to maximum brightness, and the maximum of the brightness
1138 value switches the backlight off.
1139 -1 -- never invert brightness
1140 0 -- machine default
1141 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001142
Linus Torvalds1da177e2005-04-16 15:20:36 -07001143 icn= [HW,ISDN]
1144 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1145
David Fries0af80c02009-02-25 20:28:21 +01001146 ide-core.nodma= [HW] (E)IDE subsystem
1147 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001148 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1149 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001150 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001151
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001152 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1153 Claim all unknown PCI IDE storage controllers.
1154
Andi Kleenf039b752007-05-02 19:27:12 +02001155 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001156 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001157 Poll forces a polling idle loop that can slightly
1158 improve the performance of waking up a idle CPU, but
1159 will use a lot of power and make the system run hot.
1160 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001161 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001162 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001163 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001164
Ingo Molnar792908222006-12-06 20:40:51 -08001165 ignore_loglevel [KNL]
1166 Ignore loglevel setting - this will print /all/
1167 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001168 We also add it as printk module parameter, so users
1169 could change it dynamically, usually by
1170 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001171
Linus Torvalds1da177e2005-04-16 15:20:36 -07001172 ihash_entries= [KNL]
1173 Set number of hash buckets for inode cache.
1174
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001175 ima_appraise= [IMA] appraise integrity measurements
1176 Format: { "off" | "enforce" | "fix" }
1177 default: "enforce"
1178
Mimi Zohar07f6a792011-03-09 22:25:48 -05001179 ima_appraise_tcb [IMA]
1180 The builtin appraise policy appraises all files
1181 owned by uid=0.
1182
Mimi Zohar3323eec92009-02-04 09:06:58 -05001183 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -07001184 Format: { "sha1" | "md5" }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001185 default: "sha1"
1186
Eric Paris5789ba32009-05-21 15:47:06 -04001187 ima_tcb [IMA]
1188 Load a policy which meets the needs of the Trusted
1189 Computing Base. This means IMA will measure all
1190 programs exec'd, files mmap'd for exec, and all files
1191 opened for read by uid=0.
1192
Linus Torvalds1da177e2005-04-16 15:20:36 -07001193 init= [KNL]
1194 Format: <full_path>
1195 Run specified binary instead of /sbin/init as init
1196 process.
1197
1198 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1199 for working out where the kernel is dying during
1200 startup.
1201
1202 initrd= [BOOT] Specify the location of the initial ramdisk
1203
1204 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1205 Format: <irq>
1206
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001207 int_pln_enable [x86] Enable power limit notification interrupt
1208
Mimi Zohard726d8d2013-03-18 14:48:02 -04001209 integrity_audit=[IMA]
1210 Format: { "0" | "1" }
1211 0 -- basic integrity auditing messages. (Default)
1212 1 -- additional integrity auditing messages.
1213
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001214 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001215 on
1216 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001217 off
1218 Disable intel iommu driver.
1219 igfx_off [Default Off]
1220 By default, gfx is mapped as normal device. If a gfx
1221 device has a dedicated DMAR unit, the DMAR unit is
1222 bypassed by not enabling DMAR with this option. In
1223 this case, gfx device will use physical address for
1224 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001225 forcedac [x86_64]
1226 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001227 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001228 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001229 than 32-bit addressing. The default is to look
1230 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001231 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001232 strict [Default Off]
1233 With this option on every unmap_single operation will
1234 result in a hardware IOTLB flush operation as opposed
1235 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001236 sp_off [Default Off]
1237 By default, super page will be supported if Intel IOMMU
1238 has the capability. With this option, super page will
1239 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001240
1241 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1242 0 disables intel_idle and fall back on acpi_idle.
1243 1 to 6 specify maximum depth of C-state.
1244
Dirk Brandewie6be26492013-02-15 22:55:10 +01001245 intel_pstate= [X86]
1246 disable
1247 Do not enable intel_pstate as the default
1248 scaling driver for the supported processors
1249
Chris Wrightd1423d52010-07-20 11:06:49 -07001250 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001251 on enable Interrupt Remapping (default)
1252 off disable Interrupt Remapping
1253 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001254 no_x2apic_optout
1255 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001256
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001257 iomem= Disable strict checking of access to MMIO memory
1258 strict regions from userspace.
1259 relaxed
1260
1261 iommu= [x86]
1262 off
1263 force
1264 noforce
1265 biomerge
1266 panic
1267 nopanic
1268 merge
1269 nomerge
1270 forcesac
1271 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001272 pt [x86, IA-64]
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001273
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001274
1275 io7= [HW] IO7 for Marvel based alpha systems
1276 See comment before marvel_specify_io7 in
1277 arch/alpha/kernel/core_marvel.c.
1278
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301279 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001280 0x80
1281 Standard port 0x80 based delay
1282 0xed
1283 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001284 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001285 Simple two microseconds delay
1286 none
1287 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001288
Linus Torvalds1da177e2005-04-16 15:20:36 -07001289 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001290 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001291
1292 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001293 See comment before ip2_setup() in
1294 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001295
Alan Cox200803d2005-06-28 20:45:18 -07001296 irqfixup [HW]
1297 When an interrupt is not handled search all handlers
1298 for it. Intended to get systems with badly broken
1299 firmware running.
1300
1301 irqpoll [HW]
1302 When an interrupt is not handled search all handlers
1303 for it. Also check all handlers each timer
1304 interrupt. Intended to get systems with badly broken
1305 firmware running.
1306
Linus Torvalds1da177e2005-04-16 15:20:36 -07001307 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001308 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001309
1310 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001311 Format:
1312 <cpu number>,...,<cpu number>
1313 or
Li Zefanb225d442008-11-06 12:53:39 -08001314 <cpu number>-<cpu number>
1315 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001316 or a mixture
1317 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001318
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319 This option can be used to specify one or more CPUs
1320 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001321 algorithms. You can move a process onto or off an
1322 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001323 <cpu number> begins at 0 and the maximum value is
1324 "number of CPUs in system - 1".
1325
1326 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001327 alternative -- manually setting the CPU mask of all
1328 tasks in the system -- can cause problems and
1329 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330
Randy Dunlapa9913042005-10-23 12:57:11 -07001331 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001333 ivrs_ioapic [HW,X86_64]
1334 Provide an override to the IOAPIC-ID<->DEVICE-ID
1335 mapping provided in the IVRS ACPI table. For
1336 example, to map IOAPIC-ID decimal 10 to
1337 PCI device 00:14.0 write the parameter as:
1338 ivrs_ioapic[10]=00:14.0
1339
1340 ivrs_hpet [HW,X86_64]
1341 Provide an override to the HPET-ID<->DEVICE-ID
1342 mapping provided in the IVRS ACPI table. For
1343 example, to map HPET-ID decimal 0 to
1344 PCI device 00:14.0 write the parameter as:
1345 ivrs_hpet[0]=00:14.0
1346
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347 js= [HW,JOY] Analog joystick
1348 See Documentation/input/joystick.txt.
1349
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001350 keepinitrd [HW,ARM]
1351
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301352 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001353 specifies the amount of memory usable by the kernel
1354 for non-movable allocations. The requested amount is
1355 spread evenly throughout all nodes in the system. The
1356 remaining memory in each node is used for Movable
1357 pages. In the event, a node is too small to have both
1358 kernelcore and Movable pages, kernelcore pages will
1359 take priority and other nodes will have a larger number
1360 of kernelcore pages. The Movable zone is used for the
1361 allocation of pages that may be reclaimed or moved
1362 by the page migration subsystem. This means that
1363 HugeTLB pages may not be allocated from this zone.
1364 Note that allocations like PTEs-from-HighMem still
1365 use the HighMem zone if it exists, and the Normal
1366 zone if it does not.
1367
Jason Wessel4fe1da42010-05-20 21:04:31 -05001368 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1369 Format: <Controller#>[,poll interval]
1370 The controller # is the number of the ehci usb debug
1371 port as it is probed via PCI. The poll interval is
1372 optional and is the number seconds in between
1373 each poll cycle to the debug port in case you need
1374 the functionality for interrupting the kernel with
1375 gdb or control-c on the dbgp connection. When
1376 not using this parameter you use sysrq-g to break into
1377 the kernel debugger.
1378
Jason Wessel84c08fd2010-05-20 21:04:24 -05001379 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001380 Requires a tty driver that supports console polling,
1381 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001382 Serial only format: <serial_device>[,baud]
1383 keyboard only format: kbd
1384 keyboard and serial format: kbd,<serial_device>[,baud]
1385 Optional Kernel mode setting:
1386 kms, kbd format: kms,kbd
1387 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001388
Jason Wessel84c08fd2010-05-20 21:04:24 -05001389 kgdbwait [KGDB] Stop kernel execution and enter the
1390 kernel debugger at the earliest opportunity.
1391
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001392 kmac= [MIPS] korina ethernet MAC address.
1393 Configure the RouterBoard 532 series on-chip
1394 Ethernet adapter MAC address.
1395
Catalin Marinas04f70332009-06-11 13:22:39 +01001396 kmemleak= [KNL] Boot-time kmemleak enable/disable
1397 Valid arguments: on, off
1398 Default: on
1399
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301400 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001401 in oops dumps.
1402
Andre Przywarafef07aa2009-07-10 14:20:35 +02001403 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1404 Default is 0 (don't ignore, but inject #GP)
1405
Xiao Guangronga182d872010-09-20 22:17:48 +08001406 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1407 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001408 Default is 0 (off)
1409
Andre Przywarafef07aa2009-07-10 14:20:35 +02001410 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001411 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001412
1413 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1414 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001415 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001416
Andre Przywarafef07aa2009-07-10 14:20:35 +02001417 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1418 (virtualized MMU) support on capable Intel chips.
1419 Default is 1 (enabled)
1420
1421 kvm-intel.emulate_invalid_guest_state=
1422 [KVM,Intel] Enable emulation of invalid guest states
1423 Default is 0 (disabled)
1424
1425 kvm-intel.flexpriority=
1426 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1427 Default is 1 (enabled)
1428
Sasha Levine1a72ae2011-08-09 14:28:35 +03001429 kvm-intel.nested=
1430 [KVM,Intel] Enable VMX nesting (nVMX).
1431 Default is 0 (disabled)
1432
Andre Przywarafef07aa2009-07-10 14:20:35 +02001433 kvm-intel.unrestricted_guest=
1434 [KVM,Intel] Disable unrestricted guest feature
1435 (virtualized real and unpaged mode) on capable
1436 Intel chips. Default is 1 (enabled)
1437
1438 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1439 feature (tagged TLBs) on capable Intel chips.
1440 Default is 1 (enabled)
1441
Linus Torvalds1da177e2005-04-16 15:20:36 -07001442 l2cr= [PPC]
1443
Robert Brosea78bfbf2008-03-29 07:20:23 +11001444 l3cr= [PPC]
1445
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001446 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001447 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001448
Suresh Siddha279f1462012-10-22 14:37:58 -07001449 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1450 value for LAPIC timer one-shot implementation. Default
1451 back to the programmable timer unit in the LAPIC.
1452
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301453 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001454 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001455
FD Camifcb71f62008-01-06 19:08:56 +01001456 libata.dma= [LIBATA] DMA control
1457 libata.dma=0 Disable all PATA and SATA DMA
1458 libata.dma=1 PATA and SATA Disk DMA only
1459 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001460 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001461 Combinations also work, so libata.dma=3 enables DMA
1462 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001463
Michael Prokop20308872009-08-06 00:14:10 +02001464 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1465 libata.ignore_hpa=0 keep BIOS limits (default)
1466 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001467
Dave Jones78e70c22007-09-27 11:50:13 -04001468 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1469 when set.
1470 Format: <int>
1471
Tejun Heo33267322008-02-13 09:15:09 +09001472 libata.force= [LIBATA] Force configurations. The format is comma
1473 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001474 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001475 matching port, link or device. Basically, it matches
1476 the ATA ID string printed on console by libata. If
1477 the whole ID part is omitted, the last PORT and DEVICE
1478 values are used. If ID hasn't been specified yet, the
1479 configuration applies to all ports, links and devices.
1480
1481 If only DEVICE is omitted, the parameter applies to
1482 the port and all links and devices behind it. DEVICE
1483 number of 0 either selects the first device or the
1484 first fan-out link behind PMP device. It does not
1485 select the host link. DEVICE number of 15 selects the
1486 host link and device attached to it.
1487
1488 The VAL specifies the configuration to force. As long
1489 as there's no ambiguity shortcut notation is allowed.
1490 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1491 The following configurations can be forced.
1492
1493 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1494 Any ID with matching PORT is used.
1495
1496 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1497
1498 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1499 udma[/][16,25,33,44,66,100,133] notation is also
1500 allowed.
1501
1502 * [no]ncq: Turn on or off NCQ.
1503
Tejun Heo05944bd2008-08-13 20:19:09 +09001504 * nohrst, nosrst, norst: suppress hard, soft
1505 and both resets.
1506
Dan Williamsca6d43b2012-06-21 23:41:41 -07001507 * rstonce: only attempt one reset during
1508 hot-unplug link recovery
1509
Tejun Heo43c9c592010-05-23 12:59:11 +02001510 * dump_id: dump IDENTIFY data.
1511
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001512 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1513
Tejun Heo33267322008-02-13 09:15:09 +09001514 If there are multiple matching configurations changing
1515 the same attribute, the last one is used.
1516
Yinghai Lu95f72d12010-07-12 14:36:09 +10001517 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001518
Linus Torvalds1da177e2005-04-16 15:20:36 -07001519 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001520 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001521
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001522 lockd.nlm_grace_period=P [NFS] Assign grace period.
1523 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001525 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1526 Format: <integer>
1527
1528 lockd.nlm_timeout=T [NFS] Assign timeout value.
1529 Format: <integer>
1530
1531 lockd.nlm_udpport=M [NFS] Assign UDP port.
1532 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001533
1534 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1535 Format: <irq>
1536
1537 loglevel= All Kernel Messages with a loglevel smaller than the
1538 console loglevel will be printed to the console. It can
1539 also be changed with klogd or other programs. The
1540 loglevels are defined as follows:
1541
1542 0 (KERN_EMERG) system is unusable
1543 1 (KERN_ALERT) action must be taken immediately
1544 2 (KERN_CRIT) critical conditions
1545 3 (KERN_ERR) error conditions
1546 4 (KERN_WARNING) warning conditions
1547 5 (KERN_NOTICE) normal but significant condition
1548 6 (KERN_INFO) informational
1549 7 (KERN_DEBUG) debug-level messages
1550
Randy Dunlapc756d082011-02-20 20:08:35 -08001551 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1552 in bytes. n must be a power of two. The default
1553 size is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001554
Randy Dunlapaccaa242007-10-16 01:29:37 -07001555 logo.nologo [FB] Disables display of the built-in Linux logo.
1556 This may be used to provide more screen space for
1557 kernel log messages and is useful when debugging
1558 kernel boot problems.
1559
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560 lp=0 [LP] Specify parallel ports to use, e.g,
1561 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1562 lp=reset first parallel port). 'lp=0' disables the
1563 lp=auto printer driver. 'lp=reset' (which can be
1564 specified in addition to the ports) causes
1565 attached printers to be reset. Using
1566 lp=port1,port2,... specifies the parallel ports
1567 to associate lp devices with, starting with
1568 lp0. A port specification may be 'none' to skip
1569 that lp device, or a parport name such as
1570 'parport0'. Specifying 'lp=auto' instead of a
1571 port specification list means that device IDs
1572 from each port should be examined, to see if
1573 an IEEE 1284-compliant printer is attached; if
1574 so, the driver will manage that printer.
1575 See also header of drivers/char/lp.c.
1576
1577 lpj=n [KNL]
1578 Sets loops_per_jiffy to given constant, thus avoiding
1579 time-consuming boot-time autodetection (up to 250 ms per
1580 CPU). 0 enables autodetection (default). To determine
1581 the correct value for your kernel, boot with normal
1582 autodetection and see what value is printed. Note that
1583 on SMP systems the preset will be applied to all CPUs,
1584 which is likely to cause problems if your CPUs need
1585 significantly divergent settings. An incorrect value
1586 will cause delays in the kernel to be wrong, leading to
1587 unpredictable I/O errors and other breakage. Although
1588 unlikely, in the extreme case this might damage your
1589 hardware.
1590
1591 ltpc= [NET]
1592 Format: <io>,<irq>,<dma>
1593
Randy Dunlap16290242011-08-13 12:34:52 -07001594 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001595 (machvec) in a generic kernel.
1596 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001597
Wu Zhangjin3209e702009-07-02 23:27:12 +08001598 machtype= [Loongson] Share the same kernel image file between different
1599 yeeloong laptop.
1600 Example: machtype=lemote-yeeloong-2f-7inch
1601
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001602 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1603 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001604
1605 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001606 should make use of. maxcpus=n : n >= 0 limits the
1607 kernel to using 'n' processors. n=0 is a special case,
1608 it is equivalent to "nosmp", which also disables
1609 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001610
Kay Sieversd134b002011-07-31 22:08:04 +02001611 max_loop= [LOOP] The number of loop block devices that get
1612 (loop.max_loop) unconditionally pre-created at init time. The default
1613 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1614 of statically allocating a predefined number, loop
1615 devices can be requested on-demand with the
1616 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001617
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001618 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001619
Uwe Hermann71cced62008-10-20 09:32:21 -07001620 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001621
Linus Torvalds1da177e2005-04-16 15:20:36 -07001622 md= [HW] RAID subsystems devices and level
1623 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001624
Linus Torvalds1da177e2005-04-16 15:20:36 -07001625 mdacon= [MDA]
1626 Format: <first>,<last>
1627 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001628
Linus Torvalds1da177e2005-04-16 15:20:36 -07001629 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1630 Amount of memory to be used when the kernel is not able
1631 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08001632 [X86] Work as limiting max address. Use together
1633 with memmap= to avoid physical address space collisions.
1634 Without memmap= PCI devices could be placed at addresses
1635 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001636
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001637 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001638 memory.
1639
Paul Mundt6902aa82008-09-21 17:14:42 +09001640 memchunk=nn[KMG]
1641 [KNL,SH] Allow user to override the default size for
1642 per-device physically contiguous DMA buffers.
1643
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301644 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 E820 memory map, as specified by the user.
1646 Such memmap=exactmap lines can be constructed based on
1647 BIOS output or other requirements. See the memmap=nn@ss
1648 option description.
1649
1650 memmap=nn[KMG]@ss[KMG]
1651 [KNL] Force usage of a specific region of memory
1652 Region of memory to be used, from ss to ss+nn.
1653
1654 memmap=nn[KMG]#ss[KMG]
1655 [KNL,ACPI] Mark specific memory as ACPI data.
1656 Region of memory to be used, from ss to ss+nn.
1657
1658 memmap=nn[KMG]$ss[KMG]
1659 [KNL,ACPI] Mark specific memory as reserved.
1660 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001661 Example: Exclude memory from 0x18690000-0x1869ffff
1662 memmap=64K$0x18690000
1663 or
1664 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001665
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001666 memory_corruption_check=0/1 [X86]
1667 Some BIOSes seem to corrupt the first 64k of
1668 memory when doing things like suspend/resume.
1669 Setting this option will scan the memory
1670 looking for corruption. Enabling this will
1671 both detect corruption and prevent the kernel
1672 from using the memory being corrupted.
1673 However, its intended as a diagnostic tool; if
1674 repeatable BIOS-originated corruption always
1675 affects the same memory, you can use memmap=
1676 to prevent the kernel from using that memory.
1677
1678 memory_corruption_check_size=size [X86]
1679 By default it checks for corruption in the low
1680 64k, making this memory unavailable for normal
1681 use. Use this parameter to scan for
1682 corruption in more or less memory.
1683
1684 memory_corruption_check_period=seconds [X86]
1685 By default it checks for corruption every 60
1686 seconds. Use this parameter to check at some
1687 other rate. 0 disables periodic checking.
1688
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001689 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001690 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001691 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001692 Specifies the number of memtest passes to be
1693 performed. Each pass selects another test
1694 pattern from a given set of patterns. Memtest
1695 fills the memory with this pattern, validates
1696 memory contents and reserves bad memory
1697 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001698
Linus Torvalds1da177e2005-04-16 15:20:36 -07001699 meye.*= [HW] Set MotionEye Camera parameters
1700 See Documentation/video4linux/meye.txt.
1701
Andres Salomon8f368812007-10-12 23:04:06 +02001702 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1703 Multi-Function General Purpose Timers on AMD Geode
1704 platforms.
1705
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001706 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1707 the BIOS has incorrectly applied a workaround. TinyBIOS
1708 version 0.98 is known to be affected, 0.99 fixes the
1709 problem by letting the user disable the workaround.
1710
Linus Torvalds1da177e2005-04-16 15:20:36 -07001711 mga= [HW,DRM]
1712
Randy Dunlap1c207f92008-11-19 15:36:16 -08001713 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1714 physical address is ignored.
1715
Michel Pollet39f45d72009-05-20 11:10:31 +01001716 mini2440= [ARM,HW,KNL]
1717 Format:[0..2][b][c][t]
1718 Default: "0tb"
1719 MINI2440 configuration specification:
1720 0 - The attached screen is the 3.5" TFT
1721 1 - The attached screen is the 7" TFT
1722 2 - The VGA Shield is attached (1024x768)
1723 Leaving out the screen size parameter will not load
1724 the TFT driver, and the framebuffer will be left
1725 unconfigured.
1726 b - Enable backlight. The TFT backlight pin will be
1727 linked to the kernel VESA blanking code and a GPIO
1728 LED. This parameter is not necessary when using the
1729 VGA shield.
1730 c - Enable the s3c camera interface.
1731 t - Reserved for enabling touchscreen support. The
1732 touchscreen support is not enabled in the mainstream
1733 kernel as of 2.6.30, a preliminary port can be found
1734 in the "bleeding edge" mini2440 support kernel at
1735 http://repo.or.cz/w/linux-2.6/mini2440.git
1736
Mel Gorman6b74ab92008-07-23 21:26:49 -07001737 mminit_loglevel=
1738 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1739 parameter allows control of the logging verbosity for
1740 the additional memory initialisation checks. A value
1741 of 0 disables mminit logging and a level of 4 will
1742 log everything. Information is printed at KERN_DEBUG
1743 so loglevel=8 may also need to be specified.
1744
Rusty Russell106a4ee2012-09-26 10:09:40 +01001745 module.sig_enforce
1746 [KNL] When CONFIG_MODULE_SIG is set, this means that
1747 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01001748 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01001749 is always true, so this option does nothing.
1750
Linus Torvalds1da177e2005-04-16 15:20:36 -07001751 mousedev.tap_time=
1752 [MOUSE] Maximum time between finger touching and
1753 leaving touchpad surface for touch to be considered
1754 a tap and be reported as a left button click (for
1755 touchpads working in absolute mode only).
1756 Format: <msecs>
1757 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1758 reporting absolute coordinates, such as tablets
1759 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1760 reporting absolute coordinates, such as tablets
1761
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301762 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001763 is similar to kernelcore except it specifies the
1764 amount of memory used for migratable allocations.
1765 If both kernelcore and movablecore is specified,
1766 then kernelcore will be at *least* the specified
1767 value but may be more. If movablecore on its own
1768 is specified, the administrator must be careful
1769 that the amount of memory usable for all allocations
1770 is not too small.
1771
Linus Torvalds1da177e2005-04-16 15:20:36 -07001772 MTD_Partition= [MTD]
1773 Format: <name>,<region-number>,<size>,<offset>
1774
Randy Dunlapa9913042005-10-23 12:57:11 -07001775 MTD_Region= [MTD] Format:
1776 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001777
1778 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001779 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001780
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001781 multitce=off [PPC] This parameter disables the use of the pSeries
1782 firmware feature for updating multiple TCE entries
1783 at a time.
1784
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001785 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1786
1787 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1788
1789 boundary - index of last SLC block on Flex-OneNAND.
1790 The remaining blocks are configured as MLC blocks.
1791 lock - Configure if Flex-OneNAND boundary should be locked.
1792 Once locked, the boundary cannot be changed.
1793 1 indicates lock status, 0 indicates unlock status.
1794
Ben Dooks9db829f2008-07-03 11:24:29 +01001795 mtdset= [ARM]
1796 ARM/S3C2412 JIVE boot control
1797
1798 See arch/arm/mach-s3c2412/mach-jive.c
1799
Linus Torvalds1da177e2005-04-16 15:20:36 -07001800 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001801 [HW] Make the MicroTouch USB driver use raw coordinates
1802 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001803
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001804 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001805 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001806 that could hold holes aka. UC entries.
1807
1808 mtrr_gran_size=nn[KMG] [X86]
1809 Used for mtrr cleanup. It is granularity of mtrr block.
1810 Default is 1.
1811 Large value could prevent small alignment from
1812 using up MTRRs.
1813
1814 mtrr_spare_reg_nr=n [X86]
1815 Format: <integer>
1816 Range: 0,7 : spare reg number
1817 Default : 1
1818 Used for mtrr cleanup. It is spare mtrr entries number.
1819 Set to 2 or more if your graphical card needs more.
1820
Linus Torvalds1da177e2005-04-16 15:20:36 -07001821 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1822
Linus Torvalds1da177e2005-04-16 15:20:36 -07001823 netdev= [NET] Network devices parameters
1824 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1825 Note that mem_start is often overloaded to mean
1826 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001827 This usage is only documented in each driver source
1828 file if at all.
1829
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001830 nf_conntrack.acct=
1831 [NETFILTER] Enable connection tracking flow accounting
1832 0 to disable accounting
1833 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001834 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001835
Chuck Lever306a0752010-09-17 10:54:37 -04001836 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001837 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001838
1839 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001840 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001841
Chuck Lever306a0752010-09-17 10:54:37 -04001842 nfsrootdebug [NFS] enable nfsroot debugging messages.
1843 See Documentation/filesystems/nfs/nfsroot.txt.
1844
Trond Myklebusta72b4422006-01-03 09:55:41 +01001845 nfs.callback_tcpport=
1846 [NFS] set the TCP port on which the NFSv4 callback
1847 channel should listen.
1848
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001849 nfs.cache_getent=
1850 [NFS] sets the pathname to the program which is used
1851 to update the NFS client cache entries.
1852
1853 nfs.cache_getent_timeout=
1854 [NFS] sets the timeout after which an attempt to
1855 update a cache entry is deemed to have failed.
1856
Trond Myklebust58df0952006-01-03 09:55:57 +01001857 nfs.idmap_cache_timeout=
1858 [NFS] set the maximum lifetime for idmapper cache
1859 entries.
1860
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001861 nfs.enable_ino64=
1862 [NFS] enable 64-bit inode numbers.
1863 If zero, the NFS client will fake up a 32-bit inode
1864 number for the readdir() and stat() syscalls instead
1865 of returning the full 64-bit number.
1866 The default is to return 64-bit inode numbers.
1867
Trond Myklebustef159e92012-02-06 19:50:40 -05001868 nfs.max_session_slots=
1869 [NFSv4.1] Sets the maximum number of session slots
1870 the client will attempt to negotiate with the server.
1871 This limits the number of simultaneous RPC requests
1872 that the client can send to the NFSv4.1 server.
1873 Note that there is little point in setting this
1874 value higher than the max_tcp_slot_table_limit.
1875
Trond Myklebustb064eca22011-02-22 15:44:32 -08001876 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05001877 [NFSv4] When set to the default of '1', this option
1878 ensures that both the RPC level authentication
1879 scheme and the NFS level operations agree to use
1880 numeric uids/gids if the mount is using the
1881 'sec=sys' security flavour. In effect it is
1882 disabling idmapping, which can make migration from
1883 legacy NFSv2/v3 systems to NFSv4 easier.
1884 Servers that do not support this mode of operation
1885 will be autodetected by the client, and it will fall
1886 back to using the idmapper.
1887 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04001888 nfs.nfs4_unique_id=
1889 [NFS4] Specify an additional fixed unique ident-
1890 ification string that NFSv4 clients can insert into
1891 their nfs_client_id4 string. This is typically a
1892 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08001893
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05001894 nfs.send_implementation_id =
1895 [NFSv4.1] Send client implementation identification
1896 information in exchange_id requests.
1897 If zero, no implementation identification information
1898 will be sent.
1899 The default is to send the implementation identification
1900 information.
1901
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04001902 nfsd.nfs4_disable_idmapping=
1903 [NFSv4] When set to the default of '1', the NFSv4
1904 server will return only numeric uids and gids to
1905 clients using auth_sys, and will accept numeric uids
1906 and gids from such clients. This is intended to ease
1907 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05001908
Sachin Bhamare18d98f62012-03-19 20:47:58 -07001909 objlayoutdriver.osd_login_prog=
1910 [NFS] [OBJLAYOUT] sets the pathname to the program which
1911 is used to automatically discover and login into new
1912 osd-targets. Please see:
1913 Documentation/filesystems/pnfs.txt for more explanations
1914
Paul Mundt1e1030d2009-09-01 17:38:32 +09001915 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001916 when a NMI is triggered.
1917 Format: [state][,regs][,debounce][,die]
1918
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301919 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07001920 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05001921 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001922 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001923 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07001924 timeout occurs (or 'nopanic' to override the opposite
1925 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001926 This is useful when you use a panic=... timeout and
1927 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001928
Anton Vorontsovbff38772009-07-08 11:10:56 -07001929 netpoll.carrier_timeout=
1930 [NET] Specifies amount of time (in seconds) that
1931 netpoll should wait for a carrier. By default netpoll
1932 waits 4 seconds.
1933
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001934 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001935 emulation library even if a 387 maths coprocessor
1936 is present.
1937
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001938 no_console_suspend
1939 [HW] Never suspend the console
1940 Disable suspending of consoles during suspend and
1941 hibernate operations. Once disabled, debugging
1942 messages can reach various consoles while the rest
1943 of the system is being put to sleep (ie, while
1944 debugging driver suspend/resume hooks). This may
1945 not work reliably with all consoles, but is known
1946 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07001947 To facilitate more flexible debugging, we also add
1948 console_suspend, a printk module parameter to control
1949 it. Users could use console_suspend (usually
1950 /sys/module/printk/parameters/console_suspend) to
1951 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001952
Christoph Lameterc1aee212007-05-31 00:40:47 -07001953 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1954 caches in the slab allocator. Saves per-node memory,
1955 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001956
Randy Dunlapa9913042005-10-23 12:57:11 -07001957 noalign [KNL,ARM]
1958
Linus Torvalds1da177e2005-04-16 15:20:36 -07001959 noapic [SMP,APIC] Tells the kernel to not make use of any
1960 IOAPICs that may be present in the system.
1961
Mike Galbraith5091faa2010-11-30 14:18:03 +01001962 noautogroup Disable scheduler automatic task group creation.
1963
Linus Torvalds1da177e2005-04-16 15:20:36 -07001964 nobats [PPC] Do not use BATs for mapping kernel lowmem
1965 on "Classic" PPC cores.
1966
1967 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001968
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001969 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1970
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001971 nodelayacct [KNL] Disable per-task delay accounting
1972
Linus Torvalds1da177e2005-04-16 15:20:36 -07001973 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1974
Paul Mundt6902aa82008-09-21 17:14:42 +09001975 nodsp [SH] Disable hardware DSP at boot time.
1976
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301977 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001978
Linus Torvalds1da177e2005-04-16 15:20:36 -07001979 noexec [IA-64]
1980
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301981 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001982 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001983 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001984 noexec=off: disable non-executable mappings
1985
H. Peter Anvin52b61792012-09-21 12:43:13 -07001986 nosmap [X86]
1987 Disable SMAP (Supervisor Mode Access Prevention)
1988 even if it is supported by processor.
1989
Fenghua Yude5397a2011-05-11 16:51:05 -07001990 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07001991 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07001992 even if it is supported by processor.
1993
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001994 noexec32 [X86-64]
1995 This affects only 32-bit executables.
1996 noexec32=on: enable non-executable mappings (default)
1997 read doesn't imply executable mappings
1998 noexec32=off: disable non-executable mappings
1999 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000
Paul Mundt6902aa82008-09-21 17:14:42 +09002001 nofpu [SH] Disable hardware FPU at boot time.
2002
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002003 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002004 register save and restore. The kernel will only save
2005 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002006
Suresh Siddha0c752a92009-05-22 12:17:45 -07002007 noxsave [BUGS=X86] Disables x86 extended register state save
2008 and restore using xsave. The kernel will fallback to
2009 enabling legacy floating-point and sse state.
2010
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002011 eagerfpu= [X86]
Suresh Siddhae0022982012-09-10 10:32:32 -07002012 on enable eager fpu restore
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002013 off disable eager fpu restore
Suresh Siddhae0022982012-09-10 10:32:32 -07002014 auto selects the default scheme, which automatically
2015 enables eagerfpu restore for xsaveopt.
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002016
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002017 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2018 wfi(ARM) instruction doesn't work correctly and not to
2019 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002020
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002021 no_file_caps Tells the kernel not to honor file capabilities. The
2022 only way then for a file to be executed with privilege
2023 is to be setuid root or executed by root.
2024
Linus Torvalds1da177e2005-04-16 15:20:36 -07002025 nohalt [IA-64] Tells the kernel not to use the power saving
2026 function PAL_HALT_LIGHT when idle. This increases
2027 power-consumption. On the positive side, it reduces
2028 interrupt wake-up latency, which may improve performance
2029 in certain environments such as networked servers or
2030 real-time systems.
2031
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002032 nohz= [KNL] Boottime enable/disable dynamic ticks
2033 Valid arguments: on, off
2034 Default: on
2035
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002036 nohz_full= [KNL,BOOT]
2037 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002038 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002039 whenever possible. The boot CPU will be forced outside
2040 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002041 The CPUs in this range must also be included in the
2042 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002043
Paul Mundteeee7852009-04-02 12:31:16 +09002044 noiotrap [SH] Disables trapped I/O port accesses.
2045
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002046 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047 disable unhandled interrupt sources.
2048
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302049 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002050 broken timer IRQ sources.
2051
Linus Torvalds1da177e2005-04-16 15:20:36 -07002052 noisapnp [ISAPNP] Disables ISA PnP code.
2053
2054 noinitrd [RAM] Tells the kernel not to load any configured
2055 initial RAM disk.
2056
Weidong Han03ea8152009-04-17 16:42:15 +08002057 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2058 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002059 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002060
Linus Torvalds1da177e2005-04-16 15:20:36 -07002061 nointroute [IA-64]
2062
Randy Dunlap16290242011-08-13 12:34:52 -07002063 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002064
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002065 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2066
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002067 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2068 fault handling.
2069
Glauber Costad910f5c2011-07-11 15:28:19 -04002070 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2071 steal time is computed, but won't influence scheduler
2072 behaviour
2073
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002074 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002075
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002076 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002077
Linus Torvalds1da177e2005-04-16 15:20:36 -07002078 noltlbs [PPC] Do not use large page/tlb entries for kernel
2079 lowmem mapping on PPC40x.
2080
Horms312f1f02006-02-22 09:57:55 +09002081 nomca [IA-64] Disable machine check abort handling
2082
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002083 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002084
Andres Salomon83d73842007-10-12 23:04:06 +02002085 nomfgpt [X86-32] Disable Multi-Function General Purpose
2086 Timer usage (for AMD Geode machines).
2087
Don Zickusbda62632011-10-13 15:14:27 -04002088 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2089 shutdown the other cpus. Instead use the REBOOT_VECTOR
2090 irq.
2091
Dave Young02608be2012-02-01 10:33:14 +08002092 nomodule Disable module load
2093
Jiri Kosina016ddd92010-01-18 17:05:40 +01002094 nopat [X86] Disable PAT (page attribute table extension of
2095 pagetables) support.
2096
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002097 norandmaps Don't use address space randomization. Equivalent to
2098 echo 0 > /proc/sys/kernel/randomize_va_space
2099
Jiri Kosinabbff2162010-08-11 18:34:09 +02002100 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002101
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002102 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002103 with UP alternatives
2104
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002105 nordrand [X86] Disable the direct use of the RDRAND
2106 instruction even if it is supported by the
2107 processor. RDRAND is still available to user
2108 space applications.
2109
Randy Dunlapa9913042005-10-23 12:57:11 -07002110 noresume [SWSUSP] Disables resume and restores original swap
2111 space.
2112
Linus Torvalds1da177e2005-04-16 15:20:36 -07002113 no-scroll [VGA] Disables scrollback.
2114 This is required for the Braillex ib80-piezo Braille
2115 reader made by F.H. Papenmeier (Germany).
2116
2117 nosbagart [IA-64]
2118
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002119 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002120
Len Brown61ec7562007-08-16 03:34:22 -04002121 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2122 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002123
Dave Jones97842212007-07-15 23:41:05 -07002124 nosoftlockup [KNL] Disable the soft-lockup detector.
2125
Linus Torvalds1da177e2005-04-16 15:20:36 -07002126 nosync [HW,M68K] Disables sync negotiation for all devices.
2127
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002128 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002129
2130 nousb [USB] Disable the USB subsystem
2131
Ben Hutchings55142372011-01-02 23:02:42 +00002132 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04002133
Linus Torvalds1da177e2005-04-16 15:20:36 -07002134 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002135
Weidong Han2b2fd872009-04-17 16:42:12 +08002136 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2137
Fenghua Yuf78cff42012-11-13 11:32:38 -08002138 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2139 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2140 Some features depend on CPU0. Known dependencies are:
2141 1. Resume from suspend/hibernate depends on CPU0.
2142 Suspend/hibernate will fail if CPU0 is offline and you
2143 need to online CPU0 before suspend/hibernate.
2144 2. PIC interrupts also depend on CPU0. CPU0 can't be
2145 removed if a PIC interrupt is detected.
2146 It's said poweroff/reboot may depend on CPU0 on some
2147 machines although I haven't seen such issues so far
2148 after CPU0 is offline on a few tested machines.
2149 If the dependencies are under your control, you can
2150 turn on cpu0_hotplug.
2151
Randy Dunlap16290242011-08-13 12:34:52 -07002152 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002153 purges which is reported from either PAL_VM_SUMMARY or
2154 SAL PALO.
2155
Yinghai Lu2b633e32010-02-10 01:20:37 -08002156 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2157 could support. nr_cpus=n : n >= 1 limits the kernel to
2158 supporting 'n' processors. Later in runtime you can not
2159 use hotplug cpu feature to put more cpu back to online.
2160 just like you compile the kernel NR_CPUS=n
2161
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002162 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2163
Mel Gorman1a687c22012-11-22 11:16:36 +00002164 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2165 Allowed values are enable and disable
2166
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002167 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2168 one of ['zone', 'node', 'default'] can be specified
2169 This can be set from sysctl after boot.
2170 See Documentation/sysctl/vm.txt for details.
2171
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002172 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2173 See Documentation/debugging-via-ohci1394.txt for more
2174 info.
2175
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002176 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2177 Rather than timing out after 20 ms if an EC
2178 command is not properly ACKed, override the length
2179 of the timeout. We have interrupts disabled while
2180 waiting for the ACK, so if this is set too high
2181 interrupts *may* be lost!
2182
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002183 omap_mux= [OMAP] Override bootloader pin multiplexing.
2184 Format: <mux_mode0.mode_name=value>...
2185 For example, to override I2C bus2:
2186 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2187
Linus Torvalds1da177e2005-04-16 15:20:36 -07002188 oprofile.timer= [HW]
2189 Use timer interrupt instead of performance counters
2190
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002191 oprofile.cpu_type= Force an oprofile cpu type
2192 This might be useful if you have an older oprofile
2193 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002194 Format: { arch_perfmon }
2195 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002196 perfmon on Intel CPUs instead of the
2197 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002198 timer: [X86] Force use of architectural NMI
2199 timer mode (see also oprofile.timer
2200 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002201 [s390] Force legacy basic mode sampling
2202 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002203
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002204 oops=panic Always panic on oopses. Default is to just kill the
2205 process, but there is a small probability of
2206 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002207 This will also cause panics on machine check exceptions.
2208 Useful together with panic=30 to trigger a reboot.
2209
Randy Dunlapbcfde332010-06-07 17:10:38 -07002210 OSS [HW,OSS]
2211 See Documentation/sound/oss/oss-parameters.txt
2212
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002213 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002214 timeout > 0: seconds before rebooting
2215 timeout = 0: wait forever
2216 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002217 Format: <timeout>
2218
2219 parkbd.port= [HW] Parallel port number the keyboard adapter is
2220 connected to, default is 0.
2221 Format: <parport#>
2222 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2223 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002224 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002225
Randy Dunlapa9913042005-10-23 12:57:11 -07002226 parport= [HW,PPT] Specify parallel ports. 0 disables.
2227 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2228 Use 'auto' to force the driver to use any
2229 IRQ/DMA settings detected (the default is to
2230 ignore detected IRQ/DMA settings because of
2231 possible conflicts). You can specify the base
2232 address, IRQ, and DMA settings; IRQ and DMA
2233 should be numbers, or 'auto' (for using detected
2234 settings on that particular port), or 'nofifo'
2235 (to avoid using a FIFO even if it is detected).
2236 Parallel ports are assigned in the order they
2237 are specified on the command line, starting
2238 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002239
Randy Dunlapa9913042005-10-23 12:57:11 -07002240 parport_init_mode= [HW,PPT]
2241 Configure VIA parallel port to operate in
2242 a specific mode. This is necessary on Pegasos
2243 computer where firmware has no options for setting
2244 up parallel port mode and sets it to spp.
2245 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002246 Format: [spp|ps2|epp|ecp|ecpepp]
2247
Andrew Mortondd287792006-03-23 03:00:57 -08002248 pause_on_oops=
2249 Halt all CPUs after the first oops has been printed for
2250 the specified number of seconds. This is to be used if
2251 your oopses keep scrolling off the screen.
2252
Linus Torvalds1da177e2005-04-16 15:20:36 -07002253 pcbit= [HW,ISDN]
2254
2255 pcd. [PARIDE]
2256 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002257 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258
Randy Dunlapa9913042005-10-23 12:57:11 -07002259 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002260 earlydump [X86] dump PCI config space before the kernel
2261 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002262 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002263 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002264 the hardware directly. Use this if your machine
2265 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002266 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002267 hardware access methods are allowed. Use this
2268 if you experience crashes upon bootup and you
2269 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002270 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002271 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002272 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002273 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002274 noaer [PCIE] If the PCIEAER kernel config parameter is
2275 enabled, this kernel boot option can be used to
2276 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002277 nodomains [PCI] Disable support for multiple PCI
2278 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302279 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002280 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002281 check_enable_amd_mmconf [X86] check for and enable
2282 properly configured MMIO access to PCI
2283 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002284 nomsi [MSI] If the PCI_MSI kernel config parameter is
2285 enabled, this kernel boot option can be used to
2286 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002287 noioapicquirk [APIC] Disable all boot interrupt quirks.
2288 Safety option to keep boot IRQs enabled. This
2289 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002290 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2291 primary IO-APIC for bridges that cannot disable
2292 boot IRQs. This fixes a source of spurious IRQs
2293 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002294 noioapicreroute [APIC] Disable workaround that uses the
2295 boot IRQ equivalent of an IRQ that connects to
2296 a chipset where boot IRQs cannot be disabled.
2297 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002298 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002299 routing table. These calls are known to be buggy
2300 on several machines and they hang the machine
2301 when used, but on other computers it's the only
2302 way to get the interrupt routing table. Try
2303 this option if the kernel is unable to allocate
2304 IRQs or discover secondary PCI buses on your
2305 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002306 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002307 Use with caution as certain devices share
2308 address decoders between ROMs and other
2309 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002310 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002311 expansion ROMs that do not already have
2312 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002313 nobar [X86] Do not assign address space to the
2314 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002315 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002316 assigned automatically to PCI devices. You can
2317 make the kernel exclude IRQs of your ISA cards
2318 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002319 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002320 of the PIRQ table (normally generated
2321 by the BIOS) if it is outside the
2322 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002323 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002324 useful if the kernel is unable to find your
2325 secondary buses and you want to tell it
2326 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002327 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002328 numbers ourselves, overriding
2329 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002330 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002331 in the BIOS $PIR table. This is needed on
2332 some systems with broken BIOSes, notably
2333 some HP Pavilion N5400 and Omnibook XE3
2334 notebooks. This will have no effect if ACPI
2335 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002336 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002337 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002338 use_crs [X86] Use PCI host bridge window information
2339 from ACPI. On BIOSes from 2008 or later, this
2340 is enabled by default. If you need to use this,
2341 please report a bug.
2342 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2343 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002344 routeirq Do IRQ routing for all PCI devices.
2345 This is normally done in pci_enable_device(),
2346 so this option is a temporary workaround
2347 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002348 skip_isa_align [X86] do not align io start addr, so can
2349 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002350 firmware [ARM] Do not re-enumerate the bus but instead
2351 just use the configuration from the
2352 bootloader. This is currently used on
2353 IXP2000 systems where the bus has to be
2354 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002355 noearly [X86] Don't do any early type 1 scanning.
2356 This might help on some broken boards which
2357 machine check when some devices' config space
2358 is read. But various workarounds are disabled
2359 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002360 bfsort Sort PCI devices into breadth-first order.
2361 This sorting is done to get a device
2362 order compatible with older (<= 2.4) kernels.
2363 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002364 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2365 tuning and use the BIOS-configured MPS defaults.
2366 pcie_bus_safe Set every device's MPS to the largest value
2367 supported by all devices below the root complex.
2368 pcie_bus_perf Set device MPS to the largest allowable MPS
2369 based on its parent bus. Also set MRRS (Max
2370 Read Request Size) to the largest supported
2371 value (no larger than the MPS that the device
2372 or bus can support) for best performance.
2373 pcie_bus_peer2peer Set every device's MPS to 128B, which
2374 every device is guaranteed to support. This
2375 configuration allows peer-to-peer DMA between
2376 any pair of devices, possibly at the cost of
2377 reduced performance. This also guarantees
2378 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002379 cbiosize=nn[KMG] The fixed amount of bus space which is
2380 reserved for the CardBus bridge's IO window.
2381 The default value is 256 bytes.
2382 cbmemsize=nn[KMG] The fixed amount of bus space which is
2383 reserved for the CardBus bridge's memory
2384 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002385 resource_alignment=
2386 Format:
2387 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2388 Specifies alignment and device to reassign
2389 aligned memory resources.
2390 If <order of align> is not specified,
2391 PAGE_SIZE is used as alignment.
2392 PCI-PCI bridge can be specified, if resource
2393 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002394 ecrc= Enable/disable PCIe ECRC (transaction layer
2395 end-to-end CRC checking).
2396 bios: Use BIOS/firmware settings. This is the
2397 the default.
2398 off: Turn ECRC off
2399 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002400 hpiosize=nn[KMG] The fixed amount of bus space which is
2401 reserved for hotplug bridge's IO window.
2402 Default size is 256 bytes.
2403 hpmemsize=nn[KMG] The fixed amount of bus space which is
2404 reserved for hotplug bridge's memory window.
2405 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002406 realloc= Enable/disable reallocating PCI bridge resources
2407 if allocations done by BIOS are too small to
2408 accommodate resources required by all child
2409 devices.
2410 off: Turn realloc off
2411 on: Turn realloc on
2412 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002413 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002414 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2415 only look for one device below a PCIe downstream
2416 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002417
Chuck Ebberte5665a42008-09-24 20:40:34 -04002418 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2419 Management.
2420 off Disable ASPM.
2421 force Enable ASPM even on devices that claim not to support it.
2422 WARNING: Forcing ASPM on may cause system lockups.
2423
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002424 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2425 nomsi Do not use MSI for PCI Express Native Hotplug (this
2426 makes all PCIe ports use INTx for hotplug services).
2427
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002428 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002429 auto Ask the BIOS whether or not to use native PCIe services
2430 associated with PCIe ports (PME, hot-plug, AER). Use
2431 them only if that is allowed by the BIOS.
2432 native Use native PCIe services associated with PCIe ports
2433 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002434 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2435 ports driver.
2436
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002437 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002438 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002439 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002440
Linus Torvalds1da177e2005-04-16 15:20:36 -07002441 pcmv= [HW,PCMCIA] BadgePAD 4
2442
2443 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002444 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002445
2446 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2447 boot time.
2448 Format: { 0 | 1 }
2449 See arch/parisc/kernel/pdc_chassis.c
2450
Tejun Heof58dc012009-08-14 15:00:50 +09002451 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002452 Currently supported values are "embed" and "page".
2453 Archs may support subset or none of the selections.
2454 See comments in mm/percpu.c for details on each
2455 allocator. This parameter is primarily for debugging
2456 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002457
Linus Torvalds1da177e2005-04-16 15:20:36 -07002458 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002459 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002460
2461 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002462 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002463
2464 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002465 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002466
2467 plip= [PPT,NET] Parallel port network link
2468 Format: { parport<nr> | timid | 0 }
2469 See also Documentation/parport.txt.
2470
Randy Dunlap16290242011-08-13 12:34:52 -07002471 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002472 Override pmtimer IOPort with a hex value.
2473 e.g. pmtmr=0x508
2474
Bjorn Helgaas96242112011-08-11 12:14:05 -06002475 pnp.debug=1 [PNP]
2476 Enable PNP debug messages (depends on the
2477 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2478 via /sys/module/pnp/parameters/debug. We always show
2479 current resource usage; turning this on also shows
2480 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002481
Linus Torvalds1da177e2005-04-16 15:20:36 -07002482 pnpacpi= [ACPI]
2483 { off }
2484
2485 pnpbios= [ISAPNP]
2486 { on | off | curr | res | no-curr | no-res }
2487
2488 pnp_reserve_irq=
2489 [ISAPNP] Exclude IRQs for the autoconfiguration
2490
2491 pnp_reserve_dma=
2492 [ISAPNP] Exclude DMAs for the autoconfiguration
2493
2494 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002495 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002496
2497 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002498 [ISAPNP] Exclude memory regions for the
2499 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002500 Ranges are in pairs (memory base and size).
2501
Randy Dunlap4af94f32009-04-17 18:30:28 -07002502 ports= [IP_VS_FTP] IPVS ftp helper module
2503 Default is 21.
2504 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2505 may be specified.
2506 Format: <port>,<port>....
2507
Ingo Molnar45807a12007-07-15 23:40:10 -07002508 print-fatal-signals=
2509 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002510
2511 If enabled, warn about various signal handling
2512 related application anomalies: too many signals,
2513 too many POSIX.1 timers, fatal signals causing a
2514 coredump - etc.
2515
2516 If you hit the warning due to signal overflow,
2517 you might want to try "ulimit -i unlimited".
2518
Ingo Molnar45807a12007-07-15 23:40:10 -07002519 default: off.
2520
Matthew Garrettc22ab332012-03-05 14:59:10 -08002521 printk.always_kmsg_dump=
2522 Trigger kmsg_dump for cases other than kernel oops or
2523 panics
2524 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2525 default: disabled
2526
Randy Dunlape84845c2007-07-15 23:40:25 -07002527 printk.time= Show timing data prefixed to each printk message line
2528 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2529
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002530 processor.max_cstate= [HW,ACPI]
2531 Limit processor to maximum C-state
2532 max_cstate=9 overrides any DMI blacklist limit.
2533
2534 processor.nocst [HW,ACPI]
2535 Ignore the _CST method to determine C-states,
2536 instead using the legacy FADT method
2537
Linus Torvalds1da177e2005-04-16 15:20:36 -07002538 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002539 Format: [schedule,]<number>
2540 Param: "schedule" - profile schedule points.
2541 Param: <number> - step/bucket size as a power of 2 for
2542 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002543 Param: "sleep" - profile D-state sleeping (millisecs).
2544 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002545 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002546
Linus Torvalds1da177e2005-04-16 15:20:36 -07002547 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2548 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002549 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002550
Randy Dunlapa9913042005-10-23 12:57:11 -07002551 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2552 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002553 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2554 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002555 psmouse.resetafter= [HW,MOUSE]
2556 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002557 (0 = never).
2558 psmouse.resolution=
2559 [HW,MOUSE] Set desired mouse resolution, in dpi.
2560 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002561 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002562 0 = disabled, 1 = enabled (default).
2563
Matthew Garrettdee28e72011-07-21 16:57:55 -04002564 pstore.backend= Specify the name of the pstore backend to use
2565
Linus Torvalds1da177e2005-04-16 15:20:36 -07002566 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002567 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002568
Kay Sieversdc8c8582007-08-15 12:25:38 +02002569 pty.legacy_count=
2570 [KNL] Number of legacy pty's. Overwrites compiled-in
2571 default number.
2572
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002573 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002574
Linus Torvalds1da177e2005-04-16 15:20:36 -07002575 r128= [HW,DRM]
2576
2577 raid= [HW,RAID]
2578 See Documentation/md.txt.
2579
Randy Dunlapa9913042005-10-23 12:57:11 -07002580 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002581 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002582
Linus Torvalds1da177e2005-04-16 15:20:36 -07002583 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002584 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002585
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002586 rcu_nocbs= [KNL,BOOT]
2587 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2588 the specified list of CPUs to be no-callback CPUs.
2589 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08002590 be offloaded to "rcuox/N" kthreads created for
2591 that purpose, where "x" is "b" for RCU-bh, "p"
2592 for RCU-preempt, and "s" for RCU-sched, and "N"
2593 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002594 offloaded CPUs, which can be useful for HPC and
Paul E. McKenneya4889852012-12-03 08:16:28 -08002595
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002596 real-time workloads. It can also improve energy
2597 efficiency for asymmetric multiprocessors.
2598
Paul Gortmaker1b0048a2012-12-20 13:19:22 -08002599 rcu_nocb_poll [KNL,BOOT]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002600 Rather than requiring that offloaded CPUs
2601 (specified by rcu_nocbs= above) explicitly
2602 awaken the corresponding "rcuoN" kthreads,
2603 make these kthreads poll for callbacks.
2604 This improves the real-time response for the
2605 offloaded CPUs by relieving them of the need to
2606 wake up the corresponding kthread, but degrades
2607 energy efficiency by requiring that the kthreads
2608 periodically wake up to do the polling.
2609
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002610 rcutree.blimit= [KNL,BOOT]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002611 Set maximum number of finished RCU callbacks to process
2612 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002613
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07002614 rcutree.fanout_leaf= [KNL,BOOT]
2615 Increase the number of CPUs assigned to each
2616 leaf rcu_node structure. Useful for very large
2617 systems.
2618
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002619 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2620 Set delay from grace-period initialization to
2621 first attempt to force quiescent states.
2622 Units are jiffies, minimum value is zero,
2623 and maximum value is HZ.
2624
2625 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2626 Set delay between subsequent attempts to force
2627 quiescent states. Units are jiffies, minimum
2628 value is one, and maximum value is HZ.
2629
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002630 rcutree.qhimark= [KNL,BOOT]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002631 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002632 RCU callbacks over which batch limiting is disabled.
2633
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002634 rcutree.qlowmark= [KNL,BOOT]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002635 Set threshold of queued RCU callbacks below which
2636 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002637
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002638 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2639 Suppress RCU CPU stall warning messages.
2640
2641 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2642 Set timeout for RCU CPU stall warning messages.
2643
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002644 rcutree.rcu_idle_gp_delay= [KNL,BOOT]
2645 Set wakeup interval for idle CPUs that have
2646 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002647
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002648 rcutree.rcu_idle_lazy_gp_delay= [KNL,BOOT]
2649 Set wakeup interval for idle CPUs that have
2650 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2651 Lazy RCU callbacks are those which RCU can
2652 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002653
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002654 rcutorture.fqs_duration= [KNL,BOOT]
2655 Set duration of force_quiescent_state bursts.
2656
2657 rcutorture.fqs_holdoff= [KNL,BOOT]
2658 Set holdoff time within force_quiescent_state bursts.
2659
2660 rcutorture.fqs_stutter= [KNL,BOOT]
2661 Set wait time between force_quiescent_state bursts.
2662
2663 rcutorture.irqreader= [KNL,BOOT]
2664 Test RCU readers from irq handlers.
2665
2666 rcutorture.n_barrier_cbs= [KNL,BOOT]
2667 Set callbacks/threads for rcu_barrier() testing.
2668
2669 rcutorture.nfakewriters= [KNL,BOOT]
2670 Set number of concurrent RCU writers. These just
2671 stress RCU, they don't participate in the actual
2672 test, hence the "fake".
2673
2674 rcutorture.nreaders= [KNL,BOOT]
2675 Set number of RCU readers.
2676
2677 rcutorture.onoff_holdoff= [KNL,BOOT]
2678 Set time (s) after boot for CPU-hotplug testing.
2679
2680 rcutorture.onoff_interval= [KNL,BOOT]
2681 Set time (s) between CPU-hotplug operations, or
2682 zero to disable CPU-hotplug testing.
2683
2684 rcutorture.shuffle_interval= [KNL,BOOT]
2685 Set task-shuffle interval (s). Shuffling tasks
2686 allows some CPUs to go into dyntick-idle mode
2687 during the rcutorture test.
2688
2689 rcutorture.shutdown_secs= [KNL,BOOT]
2690 Set time (s) after boot system shutdown. This
2691 is useful for hands-off automated testing.
2692
2693 rcutorture.stall_cpu= [KNL,BOOT]
2694 Duration of CPU stall (s) to test RCU CPU stall
2695 warnings, zero to disable.
2696
2697 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2698 Time to wait (s) after boot before inducing stall.
2699
2700 rcutorture.stat_interval= [KNL,BOOT]
2701 Time (s) between statistics printk()s.
2702
2703 rcutorture.stutter= [KNL,BOOT]
2704 Time (s) to stutter testing, for example, specifying
2705 five seconds causes the test to run for five seconds,
2706 wait for five seconds, and so on. This tests RCU's
2707 ability to transition abruptly to and from idle.
2708
2709 rcutorture.test_boost= [KNL,BOOT]
2710 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2711 "Maybe" means test if the RCU implementation
2712 under test support RCU priority boosting.
2713
2714 rcutorture.test_boost_duration= [KNL,BOOT]
2715 Duration (s) of each individual boost test.
2716
2717 rcutorture.test_boost_interval= [KNL,BOOT]
2718 Interval (s) between each boost test.
2719
2720 rcutorture.test_no_idle_hz= [KNL,BOOT]
2721 Test RCU's dyntick-idle handling. See also the
2722 rcutorture.shuffle_interval parameter.
2723
2724 rcutorture.torture_type= [KNL,BOOT]
2725 Specify the RCU implementation to test.
2726
2727 rcutorture.verbose= [KNL,BOOT]
2728 Enable additional printk() statements.
2729
Olof Johanssonffdfc402005-09-06 15:17:19 -07002730 rdinit= [KNL]
2731 Format: <full_path>
2732 Run specified binary instead of /init from the ramdisk,
2733 used for early userspace startup. See initrd.
2734
Robin Holt1b3a5d02013-07-08 16:01:42 -07002735 reboot= [KNL]
2736 Format (x86 or x86_64):
2737 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2738 [[,]s[mp]#### \
2739 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2740 [[,]f[orce]
2741 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2742 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2743 reboot_force is either force or not specified,
2744 reboot_cpu is s[mp]#### with #### being the processor
2745 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002746
Paul Jackson46b6d942008-07-04 10:00:09 -07002747 relax_domain_level=
2748 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002749 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002750
Linus Torvalds1da177e2005-04-16 15:20:36 -07002751 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2752
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002753 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002754 Format: nn[KMG]
2755 Reserves a hole at the top of the kernel virtual
2756 address space.
2757
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002758 reservelow= [X86]
2759 Format: nn[K]
2760 Set the amount of memory to reserve for BIOS at
2761 the bottom of the address space.
2762
Vivek Goyal7e962872006-09-27 01:50:44 -07002763 reset_devices [KNL] Force drivers to reset the underlying device
2764 during initialization.
2765
Randy Dunlapa9913042005-10-23 12:57:11 -07002766 resume= [SWSUSP]
2767 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02002768 Format:
2769 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002770
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002771 resume_offset= [SWSUSP]
2772 Specify the offset from the beginning of the partition
2773 given by "resume=" at which the swap header is located,
2774 in <PAGE_SIZE> units (needed only for swap files).
2775 See Documentation/power/swsusp-and-swap-files.txt
2776
Barry Songf126f732011-10-10 23:38:41 +02002777 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2778 read the resume files
2779
Barry Song6f8d7022011-10-06 20:34:46 +02002780 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2781 Useful for devices that are detected asynchronously
2782 (e.g. USB and MMC devices).
2783
Bojan Smojverf996fc92010-09-09 23:06:23 +02002784 hibernate= [HIBERNATION]
2785 noresume Don't check if there's a hibernation image
2786 present during boot.
2787 nocompress Don't compress/decompress hibernation images.
2788
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002789 retain_initrd [RAM] Keep initrd memory after extraction
2790
Linus Torvalds1da177e2005-04-16 15:20:36 -07002791 rhash_entries= [KNL,NET]
2792 Set number of hash buckets for route cache
2793
2794 riscom8= [HW,SERIAL]
2795 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2796
2797 ro [KNL] Mount root device read-only on boot
2798
2799 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07002800 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002801
2802 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2803 mount the root filesystem
2804
2805 rootflags= [KNL] Set root filesystem mount option string
2806
2807 rootfstype= [KNL] Set root filesystem type
2808
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002809 rootwait [KNL] Wait (indefinitely) for root device to show up.
2810 Useful for devices that are detected asynchronously
2811 (e.g. USB and MMC devices).
2812
Robert Tivy5c71d612013-03-28 18:41:46 -07002813 rproc_mem=nn[KMG][@address]
2814 [KNL,ARM,CMA] Remoteproc physical memory block.
2815 Memory area to be used by remote processor image,
2816 managed by CMA.
2817
Linus Torvalds1da177e2005-04-16 15:20:36 -07002818 rw [KNL] Mount root device read-write on boot
2819
2820 S [KNL] Run init in single mode
2821
2822 sa1100ir [NET]
2823 See drivers/net/irda/sa1100_ir.c.
2824
Linus Torvalds1da177e2005-04-16 15:20:36 -07002825 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002826
Mike Travisf6630112009-11-17 18:22:15 -06002827 sched_debug [KNL] Enables verbose scheduler debug messages.
2828
Mike Galbraith5307c952012-05-08 12:20:58 +02002829 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2830 xtime_lock contention on larger systems, and/or RCU lock
2831 contention on all systems with CONFIG_MAXSMP set.
2832 Format: { "0" | "1" }
2833 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2834 1 -- enable.
2835 Note: increases power consumption, thus should only be
2836 enabled if running jitter sensitive (HPC/RT) workloads.
2837
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002838 security= [SECURITY] Choose a security module to enable at boot.
2839 If this boot parameter is not specified, only the first
2840 security module asking for security registration will be
2841 loaded. An invalid security module name will be treated
2842 as if no module has been chosen.
2843
2844 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002845 Format: { "0" | "1" }
2846 See security/selinux/Kconfig help text.
2847 0 -- disable.
2848 1 -- enable.
2849 Default value is set via kernel config option.
2850 If enabled at boot time, /selinux/disable can be used
2851 later to disable prior to initial policy load.
2852
John Johansenc1c124e2010-07-29 14:48:09 -07002853 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2854 Format: { "0" | "1" }
2855 See security/apparmor/Kconfig help text
2856 0 -- disable.
2857 1 -- enable.
2858 Default value is set via kernel config option.
2859
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002860 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002861
Linus Torvalds1da177e2005-04-16 15:20:36 -07002862 shapers= [NET]
2863 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002864
Yinghai Lub05f78f2008-08-22 01:32:50 -07002865 show_msr= [x86] show boot-time MSR settings
2866 Format: { <integer> }
2867 Show boot-time (BIOS-initialized) MSR settings.
2868 The parameter means the number of CPUs to show,
2869 for example 1 means boot CPU only.
2870
Linus Torvalds1da177e2005-04-16 15:20:36 -07002871 simeth= [IA-64]
2872 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002873
Linus Torvalds1da177e2005-04-16 15:20:36 -07002874 slram= [HW,MTD]
2875
David Rientjes3df1ccc2011-10-18 22:09:28 -07002876 slab_max_order= [MM, SLAB]
2877 Determines the maximum allowed order for slabs.
2878 A high setting may cause OOMs due to memory
2879 fragmentation. Defaults to 1 for systems with
2880 more than 32MB of RAM, 0 otherwise.
2881
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002882 slub_debug[=options[,slabs]] [MM, SLUB]
2883 Enabling slub_debug allows one to determine the
2884 culprit if slab objects become corrupted. Enabling
2885 slub_debug can create guard zones around objects and
2886 may poison objects when not in use. Also tracks the
2887 last alloc / free. For more information see
2888 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002889
2890 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002891 Determines the maximum allowed order for slabs.
2892 A high setting may cause OOMs due to memory
2893 fragmentation. For more information see
2894 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002895
2896 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002897 The minimum number of objects per slab. SLUB will
2898 increase the slab order up to slub_max_order to
2899 generate a sufficiently large slab able to contain
2900 the number of objects indicated. The higher the number
2901 of objects the smaller the overhead of tracking slabs
2902 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002903 For more information see Documentation/vm/slub.txt.
2904
2905 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09002906 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002907 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002908 For more information see Documentation/vm/slub.txt.
2909
2910 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002911 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002912 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002913 allocs to different slabs. Debug options disable
2914 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002915 For more information see Documentation/vm/slub.txt.
2916
Linus Torvalds1da177e2005-04-16 15:20:36 -07002917 smart2= [HW]
2918 Format: <io1>[,<io2>[,...,<io8>]]
2919
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002920 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2921 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2922 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2923 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2924 smsc-ircc2.ircc_irq= [HW] IRQ line
2925 smsc-ircc2.ircc_dma= [HW] DMA channel
2926 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2927 0: Toshiba Satellite 1800 (GP data pin select)
2928 1: Fast pin select (default)
2929 2: ATC IRMode
2930
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002931 softlockup_panic=
2932 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002933 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002934
Linus Torvalds1da177e2005-04-16 15:20:36 -07002935 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02002936 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07002937
2938 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002939 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002940
2941 spia_io_base= [HW,MTD]
2942 spia_fio_base=
2943 spia_pedr=
2944 spia_peddr=
2945
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002946 stacktrace [FTRACE]
2947 Enabled the stack tracer on boot up.
2948
Steven Rostedt762e1202011-12-19 22:01:00 -05002949 stacktrace_filter=[function-list]
2950 [FTRACE] Limit the functions that the stack tracer
2951 will trace at boot up. function-list is a comma separated
2952 list of functions. This list can be changed at run
2953 time by the stack_trace_filter file in the debugfs
2954 tracing directory. Note, this enables stack tracing
2955 and the stacktrace above is not needed.
2956
Linus Torvalds1da177e2005-04-16 15:20:36 -07002957 sti= [PARISC,HW]
2958 Format: <num>
2959 Set the STI (builtin display/keyboard on the HP-PARISC
2960 machines) console (graphic card) which should be used
2961 as the initial boot-console.
2962 See also comment in drivers/video/console/sticore.c.
2963
2964 sti_font= [HW]
2965 See comment in drivers/video/console/sticore.c.
2966
2967 stifb= [HW]
2968 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2969
Trond Myklebustcbf11072009-08-09 15:06:19 -04002970 sunrpc.min_resvport=
2971 sunrpc.max_resvport=
2972 [NFS,SUNRPC]
2973 SunRPC servers often require that client requests
2974 originate from a privileged port (i.e. a port in the
2975 range 0 < portnr < 1024).
2976 An administrator who wishes to reserve some of these
2977 ports for other uses may adjust the range that the
2978 kernel's sunrpc client considers to be privileged
2979 using these two parameters to set the minimum and
2980 maximum port values.
2981
Greg Banks42a7fc42007-03-06 01:42:23 -08002982 sunrpc.pool_mode=
2983 [NFS]
2984 Control how the NFS server code allocates CPUs to
2985 service thread pools. Depending on how many NICs
2986 you have and where their interrupts are bound, this
2987 option will affect which CPUs will do NFS serving.
2988 Note: this parameter cannot be changed while the
2989 NFS server is running.
2990
2991 auto the server chooses an appropriate mode
2992 automatically using heuristics
2993 global a single global pool contains all CPUs
2994 percpu one pool for each CPU
2995 pernode one pool for each NUMA node (equivalent
2996 to global on non-NUMA machines)
2997
Trond Myklebustcbf11072009-08-09 15:06:19 -04002998 sunrpc.tcp_slot_table_entries=
2999 sunrpc.udp_slot_table_entries=
3000 [NFS,SUNRPC]
3001 Sets the upper limit on the number of simultaneous
3002 RPC calls that can be sent from the client to a
3003 server. Increasing these values may allow you to
3004 improve throughput, but will also increase the
3005 amount of memory reserved for use by the client.
3006
Michal Hocko07555ac2013-08-22 16:35:46 -07003007 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003008 [KNL] Enable accounting of swap in memory resource
3009 controller if no parameter or 1 is given or disable
3010 it if 0 is given (See Documentation/cgroups/memory.txt)
3011
Linus Torvalds1da177e2005-04-16 15:20:36 -07003012 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07003013
Linus Torvalds1da177e2005-04-16 15:20:36 -07003014 switches= [HW,M68k]
3015
Andi Kleene52eec12010-09-08 16:54:17 +02003016 sysfs.deprecated=0|1 [KNL]
3017 Enable/disable old style sysfs layout for old udev
3018 on older distributions. When this option is enabled
3019 very new udev will not work anymore. When this option
3020 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3021 in older udev will not work anymore.
3022 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3023 the kernel configuration.
3024
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003025 sysrq_always_enabled
3026 [KNL]
3027 Ignore sysrq setting - this boot parameter will
3028 neutralize any effect of /proc/sys/kernel/sysrq.
3029 Useful for debugging.
3030
Linus Torvalds1da177e2005-04-16 15:20:36 -07003031 tdfx= [HW,DRM]
3032
David Brownell77437fd2008-07-23 21:28:33 -07003033 test_suspend= [SUSPEND]
3034 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3035 standby suspend) as the system sleep state to briefly
3036 enter during system startup. The system is woken from
3037 this state using a wakeup-capable RTC alarm.
3038
Linus Torvalds1da177e2005-04-16 15:20:36 -07003039 thash_entries= [KNL,NET]
3040 Set number of hash buckets for TCP connection
3041
Len Brownf8707ec2007-08-12 00:12:54 -04003042 thermal.act= [HW,ACPI]
3043 -1: disable all active trip points in all thermal zones
3044 <degrees C>: override all lowest active trip points
3045
Len Brownc52a7412007-08-14 15:49:32 -04003046 thermal.crt= [HW,ACPI]
3047 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003048 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003049
Len Brownf5487142007-08-12 00:12:44 -04003050 thermal.nocrt= [HW,ACPI]
3051 Set to disable actions on ACPI thermal zone
3052 critical and hot trip points.
3053
Len Brown72b33ef2007-08-12 00:12:17 -04003054 thermal.off= [HW,ACPI]
3055 1: disable ACPI thermal control
3056
Len Browna70cdc52007-08-12 00:12:35 -04003057 thermal.psv= [HW,ACPI]
3058 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003059 <degrees C>: override all passive trip points to this
3060 value
Len Browna70cdc52007-08-12 00:12:35 -04003061
Len Brown730ff342007-08-12 00:12:26 -04003062 thermal.tzp= [HW,ACPI]
3063 Specify global default ACPI thermal zone polling rate
3064 <deci-seconds>: poll all this frequency
3065 0: no polling (default)
3066
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003067 threadirqs [KNL]
3068 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003069 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003070
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003071 tmem [KNL,XEN]
3072 Enable the Transcendent memory driver if built-in.
3073
3074 tmem.cleancache=0|1 [KNL, XEN]
3075 Default is on (1). Disable the usage of the cleancache
3076 API to send anonymous pages to the hypervisor.
3077
3078 tmem.frontswap=0|1 [KNL, XEN]
3079 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003080 API to send swap pages to the hypervisor. If disabled
3081 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003082
3083 tmem.selfballooning=0|1 [KNL, XEN]
3084 Default is on (1). Disable the driving of swap pages
3085 to the hypervisor.
3086
3087 tmem.selfshrinking=0|1 [KNL, XEN]
3088 Default is on (1). Partial swapoff that immediately
3089 transfers pages from Xen hypervisor back to the
3090 kernel based on different criteria.
3091
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003092 topology= [S390]
3093 Format: {off | on}
3094 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003095 topology information if the hardware supports this.
3096 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003097 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003098 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003099
Linus Torvalds1da177e2005-04-16 15:20:36 -07003100 tp720= [HW,PS2]
3101
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003102 tpm_suspend_pcr=[HW,TPM]
3103 Format: integer pcr id
3104 Specify that at suspend time, the tpm driver
3105 should extend the specified pcr with zeros,
3106 as a workaround for some chips which fail to
3107 flush the last written pcr on TPM_SaveState.
3108 This will guarantee that all the other pcrs
3109 are saved.
3110
Li Zefan9d612be2009-06-24 17:33:15 +08003111 trace_buf_size=nn[KMG]
3112 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003113
Li Zefan020e5f82009-07-01 10:47:05 +08003114 trace_event=[event-list]
3115 [FTRACE] Set and start specified trace events in order
3116 to facilitate early boot debugging.
3117 See also Documentation/trace/events.txt
3118
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003119 trace_options=[option-list]
3120 [FTRACE] Enable or disable tracer options at boot.
3121 The option-list is a comma delimited list of options
3122 that can be enabled or disabled just as if you were
3123 to echo the option name into
3124
3125 /sys/kernel/debug/tracing/trace_options
3126
3127 For example, to enable stacktrace option (to dump the
3128 stack trace of each event), add to the command line:
3129
3130 trace_options=stacktrace
3131
3132 See also Documentation/trace/ftrace.txt "trace options"
3133 section.
3134
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003135 traceoff_on_warning
3136 [FTRACE] enable this option to disable tracing when a
3137 warning is hit. This turns off "tracing_on". Tracing can
3138 be enabled again by echoing '1' into the "tracing_on"
3139 file located in /sys/kernel/debug/tracing/
3140
3141 This option is useful, as it disables the trace before
3142 the WARNING dump is called, which prevents the trace to
3143 be filled with content caused by the warning output.
3144
3145 This option can also be set at run time via the sysctl
3146 option: kernel/traceoff_on_warning
3147
Jiri Kosinafcf4d822012-03-21 16:34:02 -07003148 transparent_hugepage=
3149 [KNL]
3150 Format: [always|madvise|never]
3151 Can be used to control the default behavior of the system
3152 with respect to transparent hugepages.
3153 See Documentation/vm/transhuge.txt for more details.
3154
john stultzd3b8f882009-08-17 16:40:47 -07003155 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003156 Format: <string>
3157 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003158 disables clocksource verification at runtime, as well
3159 as the stability checks done at bootup. Used to enable
3160 high-resolution timer mode on older hardware, and in
3161 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003162 [x86] noirqtime: Do not use TSC to do irq accounting.
3163 Used to run time disable IRQ_TIME_ACCOUNTING on any
3164 platforms where RDTSC is slow and this accounting
3165 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003166
Randy Dunlapa9913042005-10-23 12:57:11 -07003167 turbografx.map[2|3]= [HW,JOY]
3168 TurboGraFX parallel port interface
3169 Format:
3170 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003171 See also Documentation/input/joystick-parport.txt
3172
Christian Kujaub6935f82011-05-31 15:22:05 +00003173 udbg-immortal [PPC] When debugging early kernel crashes that
3174 happen after console_init() and before a proper
3175 console driver takes over, this boot options might
3176 help "seeing" what's going on.
3177
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003178 uhash_entries= [KNL,NET]
3179 Set number of hash buckets for UDP/UDP-Lite connections
3180
Alan Stern5f8364b2006-12-05 16:29:55 -05003181 uhci-hcd.ignore_oc=
3182 [USB] Ignore overcurrent events (default N).
3183 Some badly-designed motherboards generate lots of
3184 bogus events, for ports that aren't wired to
3185 anything. Set this parameter to avoid log spamming.
3186 Note that genuine overcurrent events won't be
3187 reported either.
3188
Simon Arlotte3a61b02008-07-19 23:32:54 +01003189 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003190 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003191
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003192 usbcore.authorized_default=
3193 [USB] Default USB device authorization:
3194 (default -1 = authorized except for wireless USB,
3195 0 = not authorized, 1 = authorized)
3196
Alan Sternb5e795f2007-02-20 15:00:53 -05003197 usbcore.autosuspend=
3198 [USB] The autosuspend time delay (in seconds) used
3199 for newly-detected USB devices (default 2). This
3200 is the time required before an idle device will be
3201 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003202 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003203
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003204 usbcore.usbfs_snoop=
3205 [USB] Set to log all usbfs traffic (default 0 = off).
3206
3207 usbcore.blinkenlights=
3208 [USB] Set to cycle leds on hubs (default 0 = off).
3209
3210 usbcore.old_scheme_first=
3211 [USB] Start with the old device initialization
3212 scheme (default 0 = off).
3213
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003214 usbcore.usbfs_memory_mb=
3215 [USB] Memory limit (in MB) for buffers allocated by
3216 usbfs (default = 16, 0 = max = 2047).
3217
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003218 usbcore.use_both_schemes=
3219 [USB] Try the other device initialization scheme
3220 if the first one fails (default 1 = enabled).
3221
3222 usbcore.initial_descriptor_timeout=
3223 [USB] Specifies timeout for the initial 64-byte
3224 USB_REQ_GET_DESCRIPTOR request in milliseconds
3225 (default 5000 = 5.0 seconds).
3226
Linus Torvalds1da177e2005-04-16 15:20:36 -07003227 usbhid.mousepoll=
3228 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003229
Alan Sternd4f373e2008-11-10 14:07:45 -05003230 usb-storage.delay_use=
3231 [UMS] The delay in seconds before a new device is
3232 scanned for Logical Units (default 5).
3233
3234 usb-storage.quirks=
3235 [UMS] A list of quirks entries to supplement or
3236 override the built-in unusual_devs list. List
3237 entries are separated by commas. Each entry has
3238 the form VID:PID:Flags where VID and PID are Vendor
3239 and Product ID values (4-digit hex numbers) and
3240 Flags is a set of characters, each corresponding
3241 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003242 a = SANE_SENSE (collect more than 18 bytes
3243 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003244 b = BAD_SENSE (don't collect more than 18
3245 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003246 c = FIX_CAPACITY (decrease the reported
3247 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003248 d = NO_READ_DISC_INFO (don't use
3249 READ_DISC_INFO command);
3250 e = NO_READ_CAPACITY_16 (don't use
3251 READ_CAPACITY_16 command);
Alan Sternc838ea42008-12-15 10:40:06 -05003252 h = CAPACITY_HEURISTICS (decrease the
3253 reported device capacity by one
3254 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003255 i = IGNORE_DEVICE (don't bind to this
3256 device);
3257 l = NOT_LOCKABLE (don't try to lock and
3258 unlock ejectable media);
3259 m = MAX_SECTORS_64 (don't transfer more
3260 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003261 n = INITIAL_READ10 (force a retry of the
3262 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003263 o = CAPACITY_OK (accept the capacity
3264 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003265 p = WRITE_CACHE (the device cache is ON
3266 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003267 r = IGNORE_RESIDUE (the device reports
3268 bogus residue values);
3269 s = SINGLE_LUN (the device has only one
3270 Logical Unit);
3271 w = NO_WP_DETECT (don't test whether the
3272 medium is write-protected).
3273 Example: quirks=0419:aaf5:rl,0421:0433:rc
3274
Stephen Boydac1667d2011-08-13 12:34:50 -07003275 user_debug= [KNL,ARM]
3276 Format: <int>
3277 See arch/arm/Kconfig.debug help text.
3278 1 - undefined instruction events
3279 2 - system calls
3280 4 - invalid data aborts
3281 8 - SIGSEGV faults
3282 16 - SIGBUS faults
3283 Example: user_debug=31
3284
Ian Campbell14315592010-02-17 10:38:10 +00003285 userpte=
3286 [X86] Flags controlling user PTE allocations.
3287
3288 nohigh = do not allocate PTE pages in
3289 HIGHMEM regardless of setting
3290 of CONFIG_HIGHPTE.
3291
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303292 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02003293 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07003294 vdso=1: enable VDSO (default)
3295 vdso=0: disable VDSO mapping
3296
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303297 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01003298 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3299 vdso32=1: enable 32-bit VDSO (default)
3300 vdso32=0: disable 32-bit VDSO mapping
3301
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003302 vector= [IA-64,SMP]
3303 vector=percpu: enable percpu vector domain
3304
Linus Torvalds1da177e2005-04-16 15:20:36 -07003305 video= [FB] Frame buffer configuration
3306 See Documentation/fb/modedb.txt.
3307
Aaron Lu3afe6da2013-06-20 15:08:55 +08003308 video.brightness_switch_enabled= [0,1]
3309 If set to 1, on receiving an ACPI notify event
3310 generated by hotkey, video driver will adjust brightness
3311 level and then send out the event to user space through
3312 the allocated input device; If set to 0, video driver
3313 will only send out the event without touching backlight
3314 brightness level.
3315 default: 1
3316
Pawel Moll81a054c2012-05-09 18:30:16 +01003317 virtio_mmio.device=
3318 [VMMIO] Memory mapped virtio (platform) device.
3319
3320 <size>@<baseaddr>:<irq>[:<id>]
3321 where:
3322 <size> := size (can use standard suffixes
3323 like K, M and G)
3324 <baseaddr> := physical base address
3325 <irq> := interrupt number (as passed to
3326 request_irq())
3327 <id> := (optional) platform device id
3328 example:
3329 virtio_mmio.device=1K@0x100b0000:48:7
3330
3331 Can be used multiple times for multiple devices.
3332
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003333 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003334 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003335 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003336 Use vga=ask for menu.
3337 This is actually a boot loader parameter; the value is
3338 passed to the kernel using a special protocol.
3339
Randy Dunlapa9913042005-10-23 12:57:11 -07003340 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003341 size of <nn>. This can be used to increase the
3342 minimum size (128MB on x86). It can also be used to
3343 decrease the size and leave more room for directly
3344 mapped kernel RAM.
3345
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003346 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3347 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003348
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003349 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3350 Format: <command>
3351
3352 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3353 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003354
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003355 vsyscall= [X86-64]
3356 Controls the behavior of vsyscalls (i.e. calls to
3357 fixed addresses of 0xffffffffff600x00 from legacy
3358 code). Most statically-linked binaries and older
3359 versions of glibc use these calls. Because these
3360 functions are at fixed addresses, they make nice
3361 targets for exploits that can control RIP.
3362
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003363 emulate [default] Vsyscalls turn into traps and are
3364 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003365
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003366 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003367 This is a little bit faster than trapping
3368 and makes a few dynamic recompilers work
3369 better than they would in emulation mode.
3370 It also makes exploits much easier to write.
3371
3372 none Vsyscalls don't work at all. This makes
3373 them quite hard to use for exploits but
3374 might break your system.
3375
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003376 vt.color= [VT] Default text color.
3377 Format: 0xYX, X = foreground, Y = background.
3378 Default: 0x07 = light gray on black.
3379
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08003380 vt.cur_default= [VT] Default cursor shape.
3381 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3382 the parameters of the <Esc>[?A;B;Cc escape sequence;
3383 see VGA-softcursor.txt. Default: 2 = underline.
3384
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003385 vt.default_blu= [VT]
3386 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3387 Change the default blue palette of the console.
3388 This is a 16-member array composed of values
3389 ranging from 0-255.
3390
3391 vt.default_grn= [VT]
3392 Format: <green0>,<green1>,<green2>,...,<green15>
3393 Change the default green palette of the console.
3394 This is a 16-member array composed of values
3395 ranging from 0-255.
3396
3397 vt.default_red= [VT]
3398 Format: <red0>,<red1>,<red2>,...,<red15>
3399 Change the default red palette of the console.
3400 This is a 16-member array composed of values
3401 ranging from 0-255.
3402
3403 vt.default_utf8=
3404 [VT]
3405 Format=<0|1>
3406 Set system-wide default UTF-8 mode for all tty's.
3407 Default is 1, i.e. UTF-8 mode is enabled for all
3408 newly opened terminals.
3409
Matthew Garrettf6c06b62009-11-13 15:14:11 -05003410 vt.global_cursor_default=
3411 [VT]
3412 Format=<-1|0|1>
3413 Set system-wide default for whether a cursor
3414 is shown on new VTs. Default is -1,
3415 i.e. cursors will be created by default unless
3416 overridden by individual drivers. 0 will hide
3417 cursors, 1 will display them.
3418
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003419 vt.italic= [VT] Default color for italic text; 0-15.
3420 Default: 2 = green.
3421
3422 vt.underline= [VT] Default color for underlined text; 0-15.
3423 Default: 3 = cyan.
3424
Randy Dunlap4724ba572010-05-03 11:42:52 -07003425 watchdog timers [HW,WDT] For information on watchdog timers,
3426 see Documentation/watchdog/watchdog-parameters.txt
3427 or other driver-specific files in the
3428 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003429
Tejun Heod55262c2013-04-01 11:23:38 -07003430 workqueue.disable_numa
3431 By default, all work items queued to unbound
3432 workqueues are affine to the NUMA nodes they're
3433 issued on, which results in better behavior in
3434 general. If NUMA affinity needs to be disabled for
3435 whatever reason, this option can be used. Note
3436 that this also can be controlled per-workqueue for
3437 workqueues visible under /sys/bus/workqueue/.
3438
Viresh Kumarcee22a12013-04-08 16:45:40 +05303439 workqueue.power_efficient
3440 Per-cpu workqueues are generally preferred because
3441 they show better performance thanks to cache
3442 locality; unfortunately, per-cpu workqueues tend to
3443 be more power hungry than unbound workqueues.
3444
3445 Enabling this makes the per-cpu workqueues which
3446 were observed to contribute significantly to power
3447 consumption unbound, leading to measurably lower
3448 power usage at the cost of small performance
3449 overhead.
3450
3451 The default value of this parameter is determined by
3452 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3453
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003454 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3455 default x2apic cluster mode on platforms
3456 supporting x2apic.
3457
Jacob Panbb24c472009-09-02 07:37:17 -07003458 x86_mrst_timer= [X86-32,APBT]
3459 Choose timer option for x86 Moorestown MID platform.
3460 Two valid options are apbt timer only and lapic timer
3461 plus one apbt timer for broadcast timer.
3462 x86_mrst_timer=apbt_only | lapic_and_apbt
3463
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003464 xen_emul_unplug= [HW,X86,XEN]
3465 Unplug Xen emulated devices
3466 Format: [unplug0,][unplug1]
3467 ide-disks -- unplug primary master IDE devices
3468 aux-ide-disks -- unplug non-primary-master IDE devices
3469 nics -- unplug network devices
3470 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01003471 unnecessary -- unplugging emulated devices is
3472 unnecessary even if the host did not respond to
3473 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01003474 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003475
Linus Torvalds1da177e2005-04-16 15:20:36 -07003476 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07003477 Format:
3478 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003479
Randy Dunlapa9913042005-10-23 12:57:11 -07003480______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07003481
3482TODO:
3483
Linus Torvalds1da177e2005-04-16 15:20:36 -07003484 Add more DRM drivers.