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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
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800232 acpi_no_auto_serialize [HW,ACPI]
233 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800234 AML control methods that contain the opcodes to create
235 named objects will be marked as "Serialized" by the
236 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800237 This feature is enabled by default.
238 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800239
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700240 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
241
Lv Zheng4dde5072014-02-11 11:01:52 +0800242 acpica_no_return_repair [HW, ACPI]
243 Disable AML predefined validation mechanism
244 This mechanism can repair the evaluation result to make
245 the return objects more ACPI specification compliant.
246 This option is useful for developers to identify the
247 root cause of an AML interpreter issue when the issue
248 has something to do with the repair mechanism.
249
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700250 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
251 Format: To spoof as Windows 98: ="Microsoft Windows"
252
253 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800254 acpi_osi="string1" # add string1
255 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800256 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800257 acpi_osi=! # disable all built-in OS vendor
258 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700259 acpi_osi= # disable all strings
260
Lv Zheng5dc17982013-07-22 16:08:25 +0800261 'acpi_osi=!' can be used in combination with single or
262 multiple 'acpi_osi="string1"' to support specific OS
263 vendor string(s). Note that such command can only
264 affect the default state of the OS vendor strings, thus
265 it cannot affect the default state of the feature group
266 strings and the current state of the OS vendor strings,
267 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800268 is meaningless. This command is useful when one do not
269 care about the state of the feature group strings which
270 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800271 Examples:
272 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
273 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
274 can make '_OSI("Windows 2000")' TRUE.
275
276 'acpi_osi=' cannot be used in combination with other
277 'acpi_osi=' command lines, the _OSI method will not
278 exist in the ACPI namespace. NOTE that such command can
279 only affect the _OSI support state, thus specifying it
280 multiple times through kernel command line is also
281 meaningless.
282 Examples:
283 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
284 FALSE.
285
Lv Zheng741d8122013-07-22 16:08:36 +0800286 'acpi_osi=!*' can be used in combination with single or
287 multiple 'acpi_osi="string1"' to support specific
288 string(s). Note that such command can affect the
289 current state of both the OS vendor strings and the
290 feature group strings, thus specifying it multiple times
291 through kernel command line is meaningful. But it may
292 still not able to affect the final state of a string if
293 there are quirks related to this string. This command
294 is useful when one want to control the state of the
295 feature group strings to debug BIOS issues related to
296 the OSPM features.
297 Examples:
298 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
299 '_OSI("Module Device")' FALSE.
300 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
301 '_OSI("Module Device")' TRUE.
302 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
303 equivalent to
304 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
305 and
306 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
307 they all will make '_OSI("Windows 2000")' TRUE.
308
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530309 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700310 Override the pmtimer bug detection: force the kernel
311 to assume that this machine's pmtimer latches its value
312 and always returns good values.
313
Randy Dunlap4af94f32009-04-17 18:30:28 -0700314 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
315 Format: { level | edge | high | low }
316
Randy Dunlap4af94f32009-04-17 18:30:28 -0700317 acpi_skip_timer_override [HW,ACPI]
318 Recognize and ignore IRQ0/pin2 Interrupt Override.
319 For broken nForce2 BIOS resulting in XT-PIC timer.
320
321 acpi_sleep= [HW,ACPI] Sleep options
322 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200323 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700324 See Documentation/power/video.txt for information on
325 s3_bios and s3_mode.
326 s3_beep is for debugging; it makes the PC's speaker beep
327 as soon as the kernel's real-mode entry point is called.
328 s4_nohwsig prevents ACPI hardware signature from being
329 used during resume from hibernation.
330 old_ordering causes the ACPI 1.0 ordering of the _PTS
331 control method, with respect to putting devices into
332 low power states, to be enforced (the ACPI 2.0 ordering
333 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200334 nonvs prevents the kernel from saving/restoring the
335 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800336 sci_force_enable causes the kernel to set SCI_EN directly
337 on resume from S1/S3 (which is against the ACPI spec,
338 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700339
340 acpi_use_timer_override [HW,ACPI]
341 Use timer override. For some broken Nvidia NF5 boards
342 that require a timer override, but don't have HPET
343
Luca Tettamanti7e905602009-03-30 00:01:27 +0200344 acpi_enforce_resources= [ACPI]
345 { strict | lax | no }
346 Check for resource conflicts between native drivers
347 and ACPI OperationRegions (SystemIO and SystemMemory
348 only). IO ports and memory declared in ACPI might be
349 used by the ACPI subsystem in arbitrary AML code and
350 can interfere with legacy drivers.
351 strict (default): access to resources claimed by ACPI
352 is denied; legacy drivers trying to access reserved
353 resources will fail to bind to device using them.
354 lax: access to resources claimed by ACPI is allowed;
355 legacy drivers trying to access reserved resources
356 will bind successfully but a warning message is logged.
357 no: ACPI OperationRegions are not marked as reserved,
358 no further checks are performed.
359
Prarit Bhargava00159a22014-01-14 14:21:13 -0500360 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
361 kernels.
362
Randy Dunlap4af94f32009-04-17 18:30:28 -0700363 add_efi_memmap [EFI; X86] Include EFI memory map in
364 kernel's map of available physical RAM.
365
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700366 agp= [AGP]
367 { off | try_unsupported }
368 off: disable AGP support
369 try_unsupported: try to drive unsupported chipsets
370 (may crash computer or cause data corruption)
371
Randy Dunlapbcfde332010-06-07 17:10:38 -0700372 ALSA [HW,ALSA]
373 See Documentation/sound/alsa/alsa-parameters.txt
374
Russell Kingd944d542010-02-20 16:13:29 +0000375 alignment= [KNL,ARM]
376 Allow the default userspace alignment fault handler
377 behaviour to be specified. Bit 0 enables warnings,
378 bit 1 enables fixups, and bit 2 sends a segfault.
379
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200380 align_va_addr= [X86-64]
381 Align virtual addresses by clearing slice [14:12] when
382 allocating a VMA at process creation time. This option
383 gives you up to 3% performance improvement on AMD F15h
384 machines (where it is enabled by default) for a
385 CPU-intensive style benchmark, and it can vary highly in
386 a microbenchmark depending on workload and compiler.
387
Borislav Petkov8360ee22011-11-21 12:10:19 +0100388 32: only for 32-bit processes
389 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200390 on: enable for both 32- and 64-bit processes
391 off: disable for both 32- and 64-bit processes
392
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500393 alloc_snapshot [FTRACE]
394 Allocate the ftrace snapshot buffer on boot up when the
395 main buffer is allocated. This is handy if debugging
396 and you need to use tracing_snapshot() on boot up, and
397 do not want to use tracing_snapshot_alloc() as it needs
398 to be done where GFP_KERNEL allocations are allowed.
399
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100400 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200401 Pass parameters to the AMD IOMMU driver in the system.
402 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900403 fullflush - enable flushing of IO/TLB entries when
404 they are unmapped. Otherwise they are
405 flushed before they will be reused, which
406 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200407 off - do not initialize any AMD IOMMU found in
408 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100409 force_isolation - Force device isolation for all
410 devices. The IOMMU driver is not
411 allowed anymore to lift isolation
412 requirements as needed. This option
413 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900414
Shuah Khanc099cf12012-05-24 15:58:25 -0600415 amd_iommu_dump= [HW,X86-64]
416 Enable AMD IOMMU driver option to dump the ACPI table
417 for AMD IOMMU. With this option enabled, AMD IOMMU
418 driver will print ACPI tables for AMD IOMMU during
419 IOMMU initialization.
420
Linus Torvalds1da177e2005-04-16 15:20:36 -0700421 amijoy.map= [HW,JOY] Amiga joystick support
422 Map of devices attached to JOY0DAT and JOY1DAT
423 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200424 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700425
426 analog.map= [HW,JOY] Analog joystick and gamepad support
427 Specifies type or capabilities of an analog joystick
428 connected to one of 16 gameports
429 Format: <type1>,<type2>,..<type16>
430
Randy Dunlapa9913042005-10-23 12:57:11 -0700431 apc= [HW,SPARC]
432 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700433 Format: noidle
434 Disable APC CPU standby support. SPARCstation-Fox does
435 not play well with APC CPU idle - disable it if you have
436 APC and your system crashes randomly.
437
Randy Dunlapca1eda22009-05-06 16:02:58 -0700438 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700439 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700440 Format: { quiet (default) | verbose | debug }
441 Change the amount of debugging information output
442 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700443
Brian Haleyb0f83b22010-02-04 13:36:50 -0800444 autoconf= [IPV6]
445 See Documentation/networking/ipv6.txt.
446
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400447 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
448 Limit apic dumping. The parameter defines the maximal
449 number of local apics being dumped. Also it is possible
450 to set it to "all" by meaning -- no limit here.
451 Format: { 1 (default) | 2 | ... | all }.
452 The parameter valid if only apic=debug or
453 apic=verbose is specified.
454 Example: apic=debug show_lapic=all
455
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700457 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458
Linus Torvalds1da177e2005-04-16 15:20:36 -0700459 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
460 Format: <io>,<irq>,<nodeID>
461
462 ataflop= [HW,M68k]
463
464 atarimouse= [HW,MOUSE] Atari Mouse
465
Linus Torvalds1da177e2005-04-16 15:20:36 -0700466 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
467 EzKey and similar keyboards
468
469 atkbd.reset= [HW] Reset keyboard during initialization
470
Randy Dunlapa9913042005-10-23 12:57:11 -0700471 atkbd.set= [HW] Select keyboard code set
472 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700473
474 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
475 keyboards
476
477 atkbd.softraw= [HW] Choose between synthetic and real raw mode
478 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700479
480 atkbd.softrepeat= [HW]
481 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700482
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400483 audit= [KNL] Enable the audit sub-system
484 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500485 0 - kernel audit is disabled and can not be enabled
486 until the next reboot
487 unset - kernel audit is initialized but disabled and
488 will be fully enabled by the userspace auditd.
489 1 - kernel audit is initialized and partially enabled,
490 storing at most audit_backlog_limit messages in
491 RAM until it is fully enabled by the userspace
492 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400493 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400494
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400495 audit_backlog_limit= [KNL] Set the audit queue size limit.
496 Format: <int> (must be >=0)
497 Default: 64
498
Linus Torvalds1da177e2005-04-16 15:20:36 -0700499 baycom_epp= [HW,AX25]
500 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700501
Linus Torvalds1da177e2005-04-16 15:20:36 -0700502 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
503 Format: <io>,<mode>
504 See header of drivers/net/hamradio/baycom_par.c.
505
Randy Dunlapa9913042005-10-23 12:57:11 -0700506 baycom_ser_fdx= [HW,AX25]
507 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700508 Format: <io>,<irq>,<mode>[,<baud>]
509 See header of drivers/net/hamradio/baycom_ser_fdx.c.
510
Randy Dunlapa9913042005-10-23 12:57:11 -0700511 baycom_ser_hdx= [HW,AX25]
512 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513 Format: <io>,<irq>,<mode>
514 See header of drivers/net/hamradio/baycom_ser_hdx.c.
515
Paul Gortmaker080506a2013-09-30 13:45:19 -0700516 blkdevparts= Manual partition parsing of block device(s) for
517 embedded devices based on command line input.
518 See Documentation/block/cmdline-partition.txt
519
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700520 boot_delay= Milliseconds to delay each printk during boot.
521 Values larger than 10 seconds (10000) are changed to
522 no delay (0).
523 Format: integer
524
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700525 bootmem_debug [KNL] Enable bootmem allocator debug messages.
526
Linus Torvalds1da177e2005-04-16 15:20:36 -0700527 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700528 bttv.radio= Most important insmod options are available as
529 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200531 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700532
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000533 bulk_remove=off [PPC] This parameter disables the use of the pSeries
534 firmware feature for flushing multiple hpte entries
535 at a time.
536
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537 c101= [NET] Moxa C101 synchronous serial card
538
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700539 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700540 Sometimes CPU hardware bugs make them report the cache
541 size incorrectly. The kernel will attempt work arounds
542 to fix known problems, but for some CPUs it is not
543 possible to determine what the correct size should be.
544 This option provides an override for these situations.
545
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100546 ccw_timeout_log [S390]
547 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700548
Paul Menage8bab8dd2008-04-04 14:29:57 -0700549 cgroup_disable= [KNL] Disable a particular controller
550 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800551 The effects of cgroup_disable=foo are:
552 - foo isn't auto-mounted if you mount all cgroups in
553 a single hierarchy
554 - foo isn't visible as an individually mountable
555 subsystem
556 {Currently only "memory" controller deal with this and
557 cut the overhead, others just disable the usage. So
558 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700559
Linus Torvalds1da177e2005-04-16 15:20:36 -0700560 checkreqprot [SELINUX] Set initial checkreqprot flag value.
561 Format: { "0" | "1" }
562 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700563 0 -- check protection applied by kernel (includes
564 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700565 1 -- check protection requested by application.
566 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700567 Value can be changed at runtime via
568 /selinux/checkreqprot.
569
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100570 cio_ignore= [S390]
571 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700572 clk_ignore_unused
573 [CLK]
574 Keep all clocks already enabled by bootloader on,
575 even if no driver has claimed them. This is useful
576 for debug and development, but should not be
577 needed on a platform with proper driver support.
578 For more information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100579
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700580 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700581 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200582 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700583 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200584 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700585 Format: { pit | tsc | cyclone | pmtmr }
586
John Stultz592913e2010-07-13 17:56:20 -0700587 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700588 Format: <string>
589 Override the default clocksource and use the clocksource
590 with the name specified.
591 Some clocksource names to choose from, depending on
592 the platform:
593 [all] jiffies (this is the base, fallback clocksource)
594 [ACPI] acpi_pm
595 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
596 pxa_timer,timer3,32k_counter,timer0_1
597 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700598 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700599 scx200_hrt on Geode; cyclone on IBM x440
600 [MIPS] MIPS
601 [PARISC] cr16
602 [S390] tod
603 [SH] SuperH
604 [SPARC64] tick
605 [X86-64] hpet,tsc
606
Andi Kleenac72e782008-01-30 13:33:21 +0100607 clearcpuid=BITNUM [X86]
608 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800609 arch/x86/include/asm/cpufeature.h for the valid bit
610 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100611 stable over kernel options, but the vendor specific
612 ones should be.
613 Also note that user programs calling CPUID directly
614 or using the feature without checking anything
615 will still see it. This just prevents it from
616 being used by the kernel or shown in /proc/cpuinfo.
617 Also note the kernel might malfunction if you disable
618 some critical bits.
619
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100620 cma=nn[MG] [ARM,KNL]
621 Sets the size of kernel global memory area for contiguous
622 memory allocations. For more information, see
623 include/linux/dma-contiguous.h
624
Robert Jennings14f966e2009-04-15 05:55:32 +0000625 cmo_free_hint= [PPC] Format: { yes | no }
626 Specify whether pages are marked as being inactive
627 when they are freed. This is used in CMO environments
628 to determine OS memory pressure for page stealing by
629 a hypervisor.
630 Default: yes
631
Marek Szyprowskic7909502011-12-29 13:09:51 +0100632 coherent_pool=nn[KMG] [ARM,KNL]
633 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200634 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100635
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530636 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100637 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100638 Range: 0 - 8192
639 Default: 64
640
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700642 Format:
643 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700644
645 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
646 Format: <io>[,<irq>]
647
Randy Dunlapa9913042005-10-23 12:57:11 -0700648 com90xx= [HW,NET]
649 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700650 Format: <io>[,<irq>[,<memstart>]]
651
652 condev= [HW,S390] console device
653 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700654
Linus Torvalds1da177e2005-04-16 15:20:36 -0700655 console= [KNL] Output console device and options.
656
657 tty<n> Use the virtual console device <n>.
658
659 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800660 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700661 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800662 the form "bbbbpnf", where "bbbb" is the baud rate,
663 "p" is parity ("n", "o", or "e"), "n" is number of
664 bits, and "f" is flow control ("r" for RTS or
665 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700666
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800667 See Documentation/serial-console.txt for more
668 information. See
669 Documentation/networking/netconsole.txt for an
670 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700671
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700672 uart[8250],io,<addr>[,options]
673 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674 Start an early, polled-mode console on the 8250/16550
675 UART at the specified I/O port or MMIO address,
676 switching to the matching ttyS device later. The
677 options are the same as for ttyS, above.
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500678 hvc<n> Use the hypervisor console device <n>. This is for
679 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700681 If the device connected to the port is not a TTY but a braille
682 device, prepend "brl," before the device type, for instance
683 console=brl,ttyS0
684 For now, only VisioBraille is supported.
685
Daniel Mackf324edc2009-06-16 15:33:52 -0700686 consoleblank= [KNL] The console blank (screen saver) timeout in
687 seconds. Defaults to 10*60 = 10mins. A value of 0
688 disables the blank timer.
689
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800690 coredump_filter=
691 [KNL] Change the default value for
692 /proc/<pid>/coredump_filter.
693 See also Documentation/filesystems/proc.txt.
694
Len Brown62027ae2011-04-01 18:13:10 -0400695 cpuidle.off=1 [CPU_IDLE]
696 disable the cpuidle sub-system
697
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700699 Format:
700 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700701
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800702 crashkernel=size[KMG][@offset[KMG]]
703 [KNL] Using kexec, Linux can switch to a 'crash kernel'
704 upon panic. This parameter reserves the physical
705 memory region [offset, offset + size] for that kernel
706 image. If '@offset' is omitted, then a suitable offset
707 is selected automatically. Check
708 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700709
Bernhard Wallefb391592007-10-18 23:41:02 -0700710 crashkernel=range1:size1[,range2:size2,...][@offset]
711 [KNL] Same as above, but depends on the memory
712 in the running system. The syntax of range is
713 start-[end] where start and end are both
714 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800715 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700716
Yinghai Luadbc7422013-04-15 22:23:48 -0700717 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700718 [KNL, x86_64] range could be above 4G. Allow kernel
719 to allocate physical memory region from top, so could
720 be above 4G if system have more than 4G ram installed.
721 Otherwise memory region will be allocated below 4G, if
722 available.
723 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700724 crashkernel=size[KMG],low
725 [KNL, x86_64] range under 4G. When crashkernel=X,high
726 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700727 above 4G, that cause second kernel crash on system
728 that require some amount of low memory, e.g. swiotlb
729 requires at least 64M+32K low memory. Kernel would
730 try to allocate 72M below 4G automatically.
731 This one let user to specify own low range under 4G
732 for second kernel instead.
733 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700734 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700735 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700736
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737 cs89x0_dma= [HW,NET]
738 Format: <dma>
739
740 cs89x0_media= [HW,NET]
741 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700742
Randy Dunlapa9913042005-10-23 12:57:11 -0700743 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700744 See header of drivers/s390/block/dasd_devmap.c.
745
746 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
747 (one device per port)
748 Format: <port#>,<type>
749 See also Documentation/input/joystick-parport.txt
750
Thomas Renningera648ec02010-08-06 16:11:02 +0200751 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
752 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600753 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200754
Linus Torvalds1da177e2005-04-16 15:20:36 -0700755 debug [KNL] Enable kernel debugging (events log level).
756
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700757 debug_locks_verbose=
758 [KNL] verbose self-tests
759 Format=<0|1>
760 Print debugging info while doing the locking API
761 self-tests.
762 We default to 0 (no extra messages), setting it to
763 1 will print _a lot_ more information - normally
764 only useful to kernel developers.
765
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700766 debug_objects [KNL] Enable object debugging
767
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500768 no_debug_objects
769 [KNL] Disable object debugging
770
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800771 debug_guardpage_minorder=
772 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
773 parameter allows control of the order of pages that will
774 be intentionally kept free (and hence protected) by the
775 buddy allocator. Bigger value increase the probability
776 of catching random memory corruption, but reduce the
777 amount of memory for normal system use. The maximum
778 possible value is MAX_ORDER/2. Setting this parameter
779 to 1 or 2 should be enough to identify most random
780 memory corruption problems caused by bugs in kernel or
781 driver code when a CPU writes to (or reads from) a
782 random memory location. Note that there exists a class
783 of memory corruptions problems caused by buggy H/W or
784 F/W or by drivers badly programing DMA (basically when
785 memory is written at bus level and the CPU MMU is
786 bypassed) which are not detectable by
787 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
788 tracking down these problems.
789
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200790 debugpat [X86] Enable PAT debugging
791
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200792 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700793 Format: <area>[,<node>]
794 See also Documentation/networking/decnet.txt.
795
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700796 default_hugepagesz=
797 [same as hugepagesz=] The size of the default
798 HugeTLB page size. This is the size represented by
799 the legacy /proc/ hugepages APIs, used for SHM, and
800 default size when mounting hugetlbfs filesystems.
801 Defaults to the default architecture's huge page size
802 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700803
Linus Torvalds1da177e2005-04-16 15:20:36 -0700804 dhash_entries= [KNL]
805 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700806
Linus Torvalds1da177e2005-04-16 15:20:36 -0700807 digi= [HW,SERIAL]
808 IO parameters + enable/disable command.
809
810 digiepca= [HW,SERIAL]
811 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000812 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700813
Brian Haleyb0f83b22010-02-04 13:36:50 -0800814 disable= [IPV6]
815 See Documentation/networking/ipv6.txt.
816
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900817 disable_cpu_apicid= [X86,APIC,SMP]
818 Format: <int>
819 The number of initial APIC ID for the
820 corresponding CPU to be disabled at boot,
821 mostly used for the kdump 2nd kernel to
822 disable BSP to wake up multiple CPUs without
823 causing system reset or hang due to sending
824 INIT from AP to BSP.
825
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000826 disable_ddw [PPC/PSERIES]
827 Disable Dynamic DMA Window support. Use this if
828 to workaround buggy firmware.
829
Brian Haleyb0f83b22010-02-04 13:36:50 -0800830 disable_ipv6= [IPV6]
831 See Documentation/networking/ipv6.txt.
832
Yinghai Lu95ffa242008-04-29 03:52:33 -0700833 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700834 The kernel tries to adjust MTRR layout from continuous
835 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700836 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700837
Yinghai Lu093af8d2008-01-30 13:33:32 +0100838 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100839 By default the kernel will trim any uncacheable
840 memory out of your available memory pool based on
841 MTRR settings. This parameter disables that behavior,
842 possibly causing your machine to run very slowly.
843
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530844 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700845 Disable PIN 1 of APIC timer
846 Can be useful to work around chipset bugs.
847
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700848 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
849 this option disables the debugging code at boot.
850
851 dma_debug_entries=<number>
852 This option allows to tune the number of preallocated
853 entries for DMA-API debugging code. One entry is
854 required per DMA-API allocation. Use this if the
855 DMA-API debugging code disables itself because the
856 architectural default is too low.
857
Joerg Roedel1745de52009-05-22 21:49:51 +0200858 dma_debug_driver=<driver_name>
859 With this option the DMA-API debugging driver
860 filter feature can be enabled at boot time. Just
861 pass the driver to filter for as the parameter.
862 The filter can be disabled or changed to another
863 driver later using sysfs.
864
Carsten Emdeda0df922012-03-18 22:37:33 +0100865 drm_kms_helper.edid_firmware=[<connector>:]<file>
866 Broken monitors, graphic adapters and KVMs may
867 send no or incorrect EDID data sets. This parameter
868 allows to specify an EDID data set in the
869 /lib/firmware directory that is used instead.
870 Generic built-in EDID data sets are used, if one of
871 edid/1024x768.bin, edid/1280x1024.bin,
872 edid/1680x1050.bin, or edid/1920x1080.bin is given
873 and no file with the same name exists. Details and
874 instructions how to build your own EDID data are
875 available in Documentation/EDID/HOWTO.txt. An EDID
876 data set will only be used for a particular connector,
877 if its name and a colon are prepended to the EDID
878 name.
879
Linus Torvalds1da177e2005-04-16 15:20:36 -0700880 dscc4.setup= [NET]
881
Jim Cromie29e36c92012-04-27 14:30:41 -0600882 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
883 module.dyndbg[="val"]
884 Enable debug messages at boot time. See
885 Documentation/dynamic-debug-howto.txt for details.
886
Mark Salter56aeeba2014-04-07 15:39:53 -0700887 early_ioremap_debug [KNL]
888 Enable debug messages in early_ioremap support. This
889 is useful for tracking down temporary early mappings
890 which are not unmapped.
891
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700892 earlycon= [KNL] Output early console device and options.
893 uart[8250],io,<addr>[,options]
894 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700895 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700896 Start an early, polled-mode console on the 8250/16550
897 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700898 MMIO inter-register address stride is either 8-bit
899 (mmio) or 32-bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700900 The options are the same as for ttyS, above.
901
Dave Hansen147ea092013-04-10 14:03:38 -0700902 earlyprintk= [X86,SH,BLACKFIN,ARM]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700903 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +0100904 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500905 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700906 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -0700907 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500908 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500909 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700910
Dave Hansen147ea092013-04-10 14:03:38 -0700911 earlyprintk is useful when the kernel crashes before
912 the normal console is initialized. It is not enabled by
913 default because it has some cosmetic problems.
914
Randy Dunlapa9913042005-10-23 12:57:11 -0700915 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700916 takes over.
917
Matt Fleming72548e82013-10-04 09:36:56 +0100918 Only one of vga, efi, serial, or usb debug port can
919 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700920
Dave Hansen147ea092013-04-10 14:03:38 -0700921 Currently only ttyS0 and ttyS1 may be specified by
922 name. Other I/O ports may be explicitly specified
923 on some architectures (x86 and arm at least) by
924 replacing ttySn with an I/O port address, like this:
925 earlyprintk=serial,0x1008,115200
926 You can find the port for a given device in
927 /proc/tty/driver/serial:
928 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -0700929
930 Interaction with the standard serial driver is not
931 very good.
932
Matt Fleming72548e82013-10-04 09:36:56 +0100933 The VGA and EFI output is eventually overwritten by
934 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700935
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500936 The xen output can only be used by Xen PV guests.
937
Chen, Gongc700f012013-12-06 01:17:08 -0500938 edac_report= [HW,EDAC] Control how to report EDAC event
939 Format: {"on" | "off" | "force"}
940 on: enable EDAC to report H/W event. May be overridden
941 by other higher priority error reporting module.
942 off: disable H/W event reporting through EDAC.
943 force: enforce the use of EDAC to report H/W event.
944 default: on.
945
Jason Wessel97311912010-05-20 21:04:30 -0500946 ekgdboc= [X86,KGDB] Allow early kernel console debugging
947 ekgdboc=kbd
948
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300949 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -0500950 the boot argument: earlyprintk=vga
951
Linus Torvalds1da177e2005-04-16 15:20:36 -0700952 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700953 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700954
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +0100955 efi= [EFI]
956 Format: { "old_map" }
957 old_map [X86-64]: switch to the old ioremap-based EFI
958 runtime services mapping. 32-bit still uses this one by
959 default.
960
Richard Weinberger8c58bf32013-04-17 01:00:53 +0200961 efi_no_storage_paranoia [EFI; X86]
962 Using this parameter you can use more than 50% of
963 your efi variable storage. Use this parameter only if
964 you are really sure that your UEFI does sane gc and
965 fulfills the spec otherwise your board may brick.
966
Linus Torvalds1da177e2005-04-16 15:20:36 -0700967 eisa_irq_edge= [PARISC,HW]
968 See header of drivers/parisc/eisa.c.
969
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700970 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700971 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700972 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700973
974 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +0100975 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +0200976 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -0700977 Documentation/block/deadline-iosched.txt for details.
978
Michael Holzheud3bf37952011-10-30 15:16:37 +0100979 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -0700980 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +0100981 image elf header and optionally the size. Generally
982 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -0800983 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700984
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700985 enable_mtrr_cleanup [X86]
986 The kernel tries to adjust MTRR layout from continuous
987 to discrete, to make X server driver able to add WB
988 entry later. This parameter enables that.
989
Randy Dunlapca1eda22009-05-06 16:02:58 -0700990 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700991 Enable PIN 1 of APIC timer
992 Can be useful to work around chipset bugs
993 (in particular on some ATI chipsets).
994 The kernel tries to set a reasonable default.
995
Linus Torvalds1da177e2005-04-16 15:20:36 -0700996 enforcing [SELINUX] Set initial enforcing status.
997 Format: {"0" | "1"}
998 See security/selinux/Kconfig help text.
999 0 -- permissive (log only, no denials).
1000 1 -- enforcing (deny and log).
1001 Default value is 0.
1002 Value can be changed at runtime via /selinux/enforce.
1003
Huang Yinga08f82d2010-05-18 14:35:21 +08001004 erst_disable [ACPI]
1005 Disable Error Record Serialization Table (ERST)
1006 support.
1007
Linus Torvalds1da177e2005-04-16 15:20:36 -07001008 ether= [HW,NET] Ethernet cards parameters
1009 This option is obsoleted by the "netdev=" option, which
1010 has equivalent usage. See its documentation for details.
1011
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001012 evm= [EVM]
1013 Format: { "fix" }
1014 Permit 'security.evm' to be updated regardless of
1015 current integrity status.
1016
Akinobu Mitade1ba092006-12-08 02:39:42 -08001017 failslab=
1018 fail_page_alloc=
1019 fail_make_request=[KNL]
1020 General fault injection mechanism.
1021 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001022 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001023
Linus Torvalds1da177e2005-04-16 15:20:36 -07001024 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001025 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001026
Alex Chiangf13ae302008-05-08 14:03:23 -06001027 force_pal_cache_flush
1028 [IA-64] Avoid check_sal_cache_flush which may hang on
1029 buggy SAL_CACHE_FLUSH implementations. Using this
1030 parameter will force ia64_sal_cache_flush to call
1031 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1032
Chris Bainbridge69f23662014-03-07 18:40:42 +07001033 forcepae [X86-32]
1034 Forcefully enable Physical Address Extension (PAE).
1035 Many Pentium M systems disable PAE but may have a
1036 functionally usable PAE implementation.
1037 Warning: use of this parameter will taint the kernel
1038 and may cause unknown problems.
1039
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001040 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001041 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001042 as early as possible in order to facilitate early
1043 boot debugging.
1044
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001045 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001046 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001047 If no parameter is passed, ftrace will dump
1048 buffers of all CPUs, but if you pass orig_cpu, it will
1049 dump only the buffer of the CPU that triggered the
1050 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001051
1052 ftrace_filter=[function-list]
1053 [FTRACE] Limit the functions traced by the function
1054 tracer at boot up. function-list is a comma separated
1055 list of functions. This list can be changed at run
1056 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001057 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001058
1059 ftrace_notrace=[function-list]
1060 [FTRACE] Do not trace the functions specified in
1061 function-list. This list can be changed at run time
1062 by the set_ftrace_notrace file in the debugfs
1063 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001064
Stefan Assmann369bc182009-10-12 22:17:21 +02001065 ftrace_graph_filter=[function-list]
1066 [FTRACE] Limit the top level callers functions traced
1067 by the function graph tracer at boot up.
1068 function-list is a comma separated list of functions
1069 that can be changed at run time by the
1070 set_graph_function file in the debugfs tracing directory.
1071
Linus Torvalds1da177e2005-04-16 15:20:36 -07001072 gamecon.map[2|3]=
1073 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1074 support via parallel port (up to 5 devices per port)
1075 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1076 See also Documentation/input/joystick-parport.txt
1077
1078 gamma= [HW,DRM]
1079
Yinghai Luaaf23042008-01-30 13:33:09 +01001080 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1081 Format: off | on
1082 default: on
1083
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001084 gcov_persist= [GCOV] When non-zero (default), profiling data for
1085 kernel modules is saved and remains accessible via
1086 debugfs, even when the module is unloaded/reloaded.
1087 When zero, profiling data is discarded and associated
1088 debugfs files are removed at module unload time.
1089
Linus Torvalds1da177e2005-04-16 15:20:36 -07001090 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001091 invalid Protective MBR to be treated as GPT. If the
1092 primary GPT is corrupted, it enables the backup/alternate
1093 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001094
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001095 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1096 the "Enable 0" bit of the configuration register.
1097 Format: 0 | 1
1098 Default: 0
1099 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1100 the "Enable 0" bit of the configuration register.
1101 Format: 0 | 1
1102 Default: 0
1103 grcan.select= [HW] Select which physical interface to use.
1104 Format: 0 | 1
1105 Default: 0
1106 grcan.txsize= [HW] Sets the size of the tx buffer.
1107 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1108 Default: 1024
1109 grcan.rxsize= [HW] Sets the size of the rx buffer.
1110 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1111 Default: 1024
1112
Linus Torvalds1da177e2005-04-16 15:20:36 -07001113 hashdist= [KNL,NUMA] Large hashes allocated during boot
1114 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001115 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001116 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001117
1118 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1119
1120 hd= [EIDE] (E)IDE hard drive subsystem geometry
1121 Format: <cyl>,<head>,<sect>
1122
Huang Yingea8c0712010-05-18 14:35:15 +08001123 hest_disable [ACPI]
1124 Disable Hardware Error Source Table (HEST) support;
1125 corresponding firmware-first mode error processing
1126 logic will be disabled.
1127
Linus Torvalds1da177e2005-04-16 15:20:36 -07001128 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1129 size of <nn>. This works even on boxes that have no
1130 highmem otherwise. This also works to reduce highmem
1131 size on bigger boxes.
1132
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001133 highres= [KNL] Enable/disable high resolution timer mode.
1134 Valid parameters: "on", "off"
1135 Default: "on"
1136
Linus Torvalds1da177e2005-04-16 15:20:36 -07001137 hisax= [HW,ISDN]
1138 See Documentation/isdn/README.HiSax.
1139
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001140 hlt [BUGS=ARM,SH]
1141
1142 hpet= [X86-32,HPET] option to control HPET usage
1143 Format: { enable (default) | disable | force |
1144 verbose }
1145 disable: disable HPET and use PIT instead
1146 force: allow force enabled of undocumented chips (ICH4,
1147 VIA, nVidia)
1148 verbose: show contents of HPET registers during setup
1149
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001150 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1151 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1152
Andi Kleenb4718e62008-07-23 21:27:51 -07001153 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1154 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001155 On x86-64 and powerpc, this option can be specified
1156 multiple times interleaved with hugepages= to reserve
1157 huge pages of different sizes. Valid pages sizes on
1158 x86-64 are 2M (when the CPU supports "pse") and 1G
1159 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -07001160 Note that 1GB pages can only be allocated at boot time
1161 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +09001162
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001163 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1164 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001165 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1166 If specified, z/VM IUCV HVC accepts connections
1167 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001168
James Hoganfdabf522012-10-09 11:00:27 +01001169 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1170 hardware thread id mappings.
1171 Format: <cpu>:<hwthread>
1172
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001173 keep_bootcon [KNL]
1174 Do not unregister boot console at start. This is only
1175 useful for debugging when something happens in the window
1176 between unregistering the boot console and initializing
1177 the real console.
1178
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001179 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001180 or register an additional I2C bus that is not
1181 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001182 Format:
1183 <bus_id>,<clkrate>
1184
Jiri Kosina36d95732008-10-06 02:51:09 -04001185 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001186 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001187 i8042.dumbkbd [HW] Pretend that controller can only read data from
1188 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001189 (Don't attempt to blink the leds)
1190 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001191 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001192 i8042.noloop [HW] Disable the AUX Loopback command while probing
1193 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001194 i8042.nomux [HW] Don't check presence of an active multiplexing
1195 controller
1196 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1197 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001198 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001199 i8042.reset [HW] Reset the controller during init and cleanup
1200 i8042.unlock [HW] Unlock (ignore) the keylock
1201
1202 i810= [HW,DRM]
1203
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001204 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1205 indicates that the driver is running on unsupported
1206 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001207 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1208 does not match list of supported models.
1209 i8k.power_status
1210 [HW] Report power status in /proc/i8k
1211 (disabled by default)
1212 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1213 capability is set.
1214
Carsten Emde4dca20e2012-03-15 15:56:26 +01001215 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001216 [DRM] Invert the sense of the variable that is used to
1217 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001218 brightness value of 0 indicates backlight switched off,
1219 and the maximum of the brightness value sets the backlight
1220 to maximum brightness. If this parameter is set to 0
1221 (default) and the machine requires it, or this parameter
1222 is set to 1, a brightness value of 0 sets the backlight
1223 to maximum brightness, and the maximum of the brightness
1224 value switches the backlight off.
1225 -1 -- never invert brightness
1226 0 -- machine default
1227 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001228
Linus Torvalds1da177e2005-04-16 15:20:36 -07001229 icn= [HW,ISDN]
1230 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1231
David Fries0af80c02009-02-25 20:28:21 +01001232 ide-core.nodma= [HW] (E)IDE subsystem
1233 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001234 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1235 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001236 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001237
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001238 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1239 Claim all unknown PCI IDE storage controllers.
1240
Andi Kleenf039b752007-05-02 19:27:12 +02001241 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001242 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001243 Poll forces a polling idle loop that can slightly
1244 improve the performance of waking up a idle CPU, but
1245 will use a lot of power and make the system run hot.
1246 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001247 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001248 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001249 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001250
Ingo Molnar792908222006-12-06 20:40:51 -08001251 ignore_loglevel [KNL]
1252 Ignore loglevel setting - this will print /all/
1253 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001254 We also add it as printk module parameter, so users
1255 could change it dynamically, usually by
1256 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001257
Linus Torvalds1da177e2005-04-16 15:20:36 -07001258 ihash_entries= [KNL]
1259 Set number of hash buckets for inode cache.
1260
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001261 ima_appraise= [IMA] appraise integrity measurements
1262 Format: { "off" | "enforce" | "fix" }
1263 default: "enforce"
1264
Mimi Zohar07f6a792011-03-09 22:25:48 -05001265 ima_appraise_tcb [IMA]
1266 The builtin appraise policy appraises all files
1267 owned by uid=0.
1268
Mimi Zohar3323eec92009-02-04 09:06:58 -05001269 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001270 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1271 | sha512 | ... }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001272 default: "sha1"
1273
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001274 The list of supported hash algorithms is defined
1275 in crypto/hash_info.h.
1276
Eric Paris5789ba32009-05-21 15:47:06 -04001277 ima_tcb [IMA]
1278 Load a policy which meets the needs of the Trusted
1279 Computing Base. This means IMA will measure all
1280 programs exec'd, files mmap'd for exec, and all files
1281 opened for read by uid=0.
1282
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001283 ima_template= [IMA]
1284 Select one of defined IMA measurements template formats.
1285 Formats: { "ima" | "ima-ng" }
1286 Default: "ima-ng"
1287
Linus Torvalds1da177e2005-04-16 15:20:36 -07001288 init= [KNL]
1289 Format: <full_path>
1290 Run specified binary instead of /sbin/init as init
1291 process.
1292
1293 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1294 for working out where the kernel is dying during
1295 startup.
1296
1297 initrd= [BOOT] Specify the location of the initial ramdisk
1298
1299 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1300 Format: <irq>
1301
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001302 int_pln_enable [x86] Enable power limit notification interrupt
1303
Mimi Zohard726d8d2013-03-18 14:48:02 -04001304 integrity_audit=[IMA]
1305 Format: { "0" | "1" }
1306 0 -- basic integrity auditing messages. (Default)
1307 1 -- additional integrity auditing messages.
1308
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001309 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001310 on
1311 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001312 off
1313 Disable intel iommu driver.
1314 igfx_off [Default Off]
1315 By default, gfx is mapped as normal device. If a gfx
1316 device has a dedicated DMAR unit, the DMAR unit is
1317 bypassed by not enabling DMAR with this option. In
1318 this case, gfx device will use physical address for
1319 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001320 forcedac [x86_64]
1321 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001322 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001323 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001324 than 32-bit addressing. The default is to look
1325 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001326 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001327 strict [Default Off]
1328 With this option on every unmap_single operation will
1329 result in a hardware IOTLB flush operation as opposed
1330 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001331 sp_off [Default Off]
1332 By default, super page will be supported if Intel IOMMU
1333 has the capability. With this option, super page will
1334 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001335
1336 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1337 0 disables intel_idle and fall back on acpi_idle.
1338 1 to 6 specify maximum depth of C-state.
1339
Dirk Brandewie6be26492013-02-15 22:55:10 +01001340 intel_pstate= [X86]
1341 disable
1342 Do not enable intel_pstate as the default
1343 scaling driver for the supported processors
1344
Chris Wrightd1423d52010-07-20 11:06:49 -07001345 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001346 on enable Interrupt Remapping (default)
1347 off disable Interrupt Remapping
1348 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001349 no_x2apic_optout
1350 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001351
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001352 iomem= Disable strict checking of access to MMIO memory
1353 strict regions from userspace.
1354 relaxed
1355
1356 iommu= [x86]
1357 off
1358 force
1359 noforce
1360 biomerge
1361 panic
1362 nopanic
1363 merge
1364 nomerge
1365 forcesac
1366 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001367 pt [x86, IA-64]
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001368
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001369
1370 io7= [HW] IO7 for Marvel based alpha systems
1371 See comment before marvel_specify_io7 in
1372 arch/alpha/kernel/core_marvel.c.
1373
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301374 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001375 0x80
1376 Standard port 0x80 based delay
1377 0xed
1378 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001379 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001380 Simple two microseconds delay
1381 none
1382 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001383
Linus Torvalds1da177e2005-04-16 15:20:36 -07001384 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001385 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001386
1387 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001388 See comment before ip2_setup() in
1389 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001390
Alan Cox200803d2005-06-28 20:45:18 -07001391 irqfixup [HW]
1392 When an interrupt is not handled search all handlers
1393 for it. Intended to get systems with badly broken
1394 firmware running.
1395
1396 irqpoll [HW]
1397 When an interrupt is not handled search all handlers
1398 for it. Also check all handlers each timer
1399 interrupt. Intended to get systems with badly broken
1400 firmware running.
1401
Linus Torvalds1da177e2005-04-16 15:20:36 -07001402 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001403 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001404
1405 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001406 Format:
1407 <cpu number>,...,<cpu number>
1408 or
Li Zefanb225d442008-11-06 12:53:39 -08001409 <cpu number>-<cpu number>
1410 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001411 or a mixture
1412 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001413
Linus Torvalds1da177e2005-04-16 15:20:36 -07001414 This option can be used to specify one or more CPUs
1415 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001416 algorithms. You can move a process onto or off an
1417 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001418 <cpu number> begins at 0 and the maximum value is
1419 "number of CPUs in system - 1".
1420
1421 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001422 alternative -- manually setting the CPU mask of all
1423 tasks in the system -- can cause problems and
1424 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001425
Randy Dunlapa9913042005-10-23 12:57:11 -07001426 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001427
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001428 ivrs_ioapic [HW,X86_64]
1429 Provide an override to the IOAPIC-ID<->DEVICE-ID
1430 mapping provided in the IVRS ACPI table. For
1431 example, to map IOAPIC-ID decimal 10 to
1432 PCI device 00:14.0 write the parameter as:
1433 ivrs_ioapic[10]=00:14.0
1434
1435 ivrs_hpet [HW,X86_64]
1436 Provide an override to the HPET-ID<->DEVICE-ID
1437 mapping provided in the IVRS ACPI table. For
1438 example, to map HPET-ID decimal 0 to
1439 PCI device 00:14.0 write the parameter as:
1440 ivrs_hpet[0]=00:14.0
1441
Linus Torvalds1da177e2005-04-16 15:20:36 -07001442 js= [HW,JOY] Analog joystick
1443 See Documentation/input/joystick.txt.
1444
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001445 keepinitrd [HW,ARM]
1446
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301447 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001448 specifies the amount of memory usable by the kernel
1449 for non-movable allocations. The requested amount is
1450 spread evenly throughout all nodes in the system. The
1451 remaining memory in each node is used for Movable
1452 pages. In the event, a node is too small to have both
1453 kernelcore and Movable pages, kernelcore pages will
1454 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001455 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001456 allocation of pages that may be reclaimed or moved
1457 by the page migration subsystem. This means that
1458 HugeTLB pages may not be allocated from this zone.
1459 Note that allocations like PTEs-from-HighMem still
1460 use the HighMem zone if it exists, and the Normal
1461 zone if it does not.
1462
Jason Wessel4fe1da42010-05-20 21:04:31 -05001463 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1464 Format: <Controller#>[,poll interval]
1465 The controller # is the number of the ehci usb debug
1466 port as it is probed via PCI. The poll interval is
1467 optional and is the number seconds in between
1468 each poll cycle to the debug port in case you need
1469 the functionality for interrupting the kernel with
1470 gdb or control-c on the dbgp connection. When
1471 not using this parameter you use sysrq-g to break into
1472 the kernel debugger.
1473
Jason Wessel84c08fd2010-05-20 21:04:24 -05001474 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001475 Requires a tty driver that supports console polling,
1476 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001477 Serial only format: <serial_device>[,baud]
1478 keyboard only format: kbd
1479 keyboard and serial format: kbd,<serial_device>[,baud]
1480 Optional Kernel mode setting:
1481 kms, kbd format: kms,kbd
1482 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001483
Jason Wessel84c08fd2010-05-20 21:04:24 -05001484 kgdbwait [KGDB] Stop kernel execution and enter the
1485 kernel debugger at the earliest opportunity.
1486
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001487 kmac= [MIPS] korina ethernet MAC address.
1488 Configure the RouterBoard 532 series on-chip
1489 Ethernet adapter MAC address.
1490
Catalin Marinas04f70332009-06-11 13:22:39 +01001491 kmemleak= [KNL] Boot-time kmemleak enable/disable
1492 Valid arguments: on, off
1493 Default: on
1494
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001495 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1496 Valid arguments: 0, 1, 2
1497 kmemcheck=0 (disabled)
1498 kmemcheck=1 (enabled)
1499 kmemcheck=2 (one-shot mode)
1500 Default: 2 (one-shot mode)
1501
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301502 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001503 in oops dumps.
1504
Andre Przywarafef07aa2009-07-10 14:20:35 +02001505 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1506 Default is 0 (don't ignore, but inject #GP)
1507
Xiao Guangronga182d872010-09-20 22:17:48 +08001508 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1509 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001510 Default is 0 (off)
1511
Andre Przywarafef07aa2009-07-10 14:20:35 +02001512 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001513 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001514
1515 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1516 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001517 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001518
Andre Przywarafef07aa2009-07-10 14:20:35 +02001519 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1520 (virtualized MMU) support on capable Intel chips.
1521 Default is 1 (enabled)
1522
1523 kvm-intel.emulate_invalid_guest_state=
1524 [KVM,Intel] Enable emulation of invalid guest states
1525 Default is 0 (disabled)
1526
1527 kvm-intel.flexpriority=
1528 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1529 Default is 1 (enabled)
1530
Sasha Levine1a72ae2011-08-09 14:28:35 +03001531 kvm-intel.nested=
1532 [KVM,Intel] Enable VMX nesting (nVMX).
1533 Default is 0 (disabled)
1534
Andre Przywarafef07aa2009-07-10 14:20:35 +02001535 kvm-intel.unrestricted_guest=
1536 [KVM,Intel] Disable unrestricted guest feature
1537 (virtualized real and unpaged mode) on capable
1538 Intel chips. Default is 1 (enabled)
1539
1540 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1541 feature (tagged TLBs) on capable Intel chips.
1542 Default is 1 (enabled)
1543
Linus Torvalds1da177e2005-04-16 15:20:36 -07001544 l2cr= [PPC]
1545
Robert Brosea78bfbf2008-03-29 07:20:23 +11001546 l3cr= [PPC]
1547
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001548 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001549 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001550
Suresh Siddha279f1462012-10-22 14:37:58 -07001551 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1552 value for LAPIC timer one-shot implementation. Default
1553 back to the programmable timer unit in the LAPIC.
1554
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301555 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001556 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001557
FD Camifcb71f62008-01-06 19:08:56 +01001558 libata.dma= [LIBATA] DMA control
1559 libata.dma=0 Disable all PATA and SATA DMA
1560 libata.dma=1 PATA and SATA Disk DMA only
1561 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001562 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001563 Combinations also work, so libata.dma=3 enables DMA
1564 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001565
Michael Prokop20308872009-08-06 00:14:10 +02001566 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1567 libata.ignore_hpa=0 keep BIOS limits (default)
1568 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001569
Dave Jones78e70c22007-09-27 11:50:13 -04001570 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1571 when set.
1572 Format: <int>
1573
Tejun Heo33267322008-02-13 09:15:09 +09001574 libata.force= [LIBATA] Force configurations. The format is comma
1575 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001576 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001577 matching port, link or device. Basically, it matches
1578 the ATA ID string printed on console by libata. If
1579 the whole ID part is omitted, the last PORT and DEVICE
1580 values are used. If ID hasn't been specified yet, the
1581 configuration applies to all ports, links and devices.
1582
1583 If only DEVICE is omitted, the parameter applies to
1584 the port and all links and devices behind it. DEVICE
1585 number of 0 either selects the first device or the
1586 first fan-out link behind PMP device. It does not
1587 select the host link. DEVICE number of 15 selects the
1588 host link and device attached to it.
1589
1590 The VAL specifies the configuration to force. As long
1591 as there's no ambiguity shortcut notation is allowed.
1592 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1593 The following configurations can be forced.
1594
1595 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1596 Any ID with matching PORT is used.
1597
1598 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1599
1600 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1601 udma[/][16,25,33,44,66,100,133] notation is also
1602 allowed.
1603
1604 * [no]ncq: Turn on or off NCQ.
1605
Tejun Heo05944bd2008-08-13 20:19:09 +09001606 * nohrst, nosrst, norst: suppress hard, soft
1607 and both resets.
1608
Dan Williamsca6d43b2012-06-21 23:41:41 -07001609 * rstonce: only attempt one reset during
1610 hot-unplug link recovery
1611
Tejun Heo43c9c592010-05-23 12:59:11 +02001612 * dump_id: dump IDENTIFY data.
1613
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001614 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1615
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001616 * disable: Disable this device.
1617
Tejun Heo33267322008-02-13 09:15:09 +09001618 If there are multiple matching configurations changing
1619 the same attribute, the last one is used.
1620
Yinghai Lu95f72d12010-07-12 14:36:09 +10001621 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001622
Linus Torvalds1da177e2005-04-16 15:20:36 -07001623 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001624 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001625
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001626 lockd.nlm_grace_period=P [NFS] Assign grace period.
1627 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001628
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001629 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1630 Format: <integer>
1631
1632 lockd.nlm_timeout=T [NFS] Assign timeout value.
1633 Format: <integer>
1634
1635 lockd.nlm_udpport=M [NFS] Assign UDP port.
1636 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001637
1638 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1639 Format: <irq>
1640
1641 loglevel= All Kernel Messages with a loglevel smaller than the
1642 console loglevel will be printed to the console. It can
1643 also be changed with klogd or other programs. The
1644 loglevels are defined as follows:
1645
1646 0 (KERN_EMERG) system is unusable
1647 1 (KERN_ALERT) action must be taken immediately
1648 2 (KERN_CRIT) critical conditions
1649 3 (KERN_ERR) error conditions
1650 4 (KERN_WARNING) warning conditions
1651 5 (KERN_NOTICE) normal but significant condition
1652 6 (KERN_INFO) informational
1653 7 (KERN_DEBUG) debug-level messages
1654
Randy Dunlapc756d082011-02-20 20:08:35 -08001655 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1656 in bytes. n must be a power of two. The default
1657 size is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001658
Randy Dunlapaccaa242007-10-16 01:29:37 -07001659 logo.nologo [FB] Disables display of the built-in Linux logo.
1660 This may be used to provide more screen space for
1661 kernel log messages and is useful when debugging
1662 kernel boot problems.
1663
Linus Torvalds1da177e2005-04-16 15:20:36 -07001664 lp=0 [LP] Specify parallel ports to use, e.g,
1665 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1666 lp=reset first parallel port). 'lp=0' disables the
1667 lp=auto printer driver. 'lp=reset' (which can be
1668 specified in addition to the ports) causes
1669 attached printers to be reset. Using
1670 lp=port1,port2,... specifies the parallel ports
1671 to associate lp devices with, starting with
1672 lp0. A port specification may be 'none' to skip
1673 that lp device, or a parport name such as
1674 'parport0'. Specifying 'lp=auto' instead of a
1675 port specification list means that device IDs
1676 from each port should be examined, to see if
1677 an IEEE 1284-compliant printer is attached; if
1678 so, the driver will manage that printer.
1679 See also header of drivers/char/lp.c.
1680
1681 lpj=n [KNL]
1682 Sets loops_per_jiffy to given constant, thus avoiding
1683 time-consuming boot-time autodetection (up to 250 ms per
1684 CPU). 0 enables autodetection (default). To determine
1685 the correct value for your kernel, boot with normal
1686 autodetection and see what value is printed. Note that
1687 on SMP systems the preset will be applied to all CPUs,
1688 which is likely to cause problems if your CPUs need
1689 significantly divergent settings. An incorrect value
1690 will cause delays in the kernel to be wrong, leading to
1691 unpredictable I/O errors and other breakage. Although
1692 unlikely, in the extreme case this might damage your
1693 hardware.
1694
1695 ltpc= [NET]
1696 Format: <io>,<irq>,<dma>
1697
Randy Dunlap16290242011-08-13 12:34:52 -07001698 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001699 (machvec) in a generic kernel.
1700 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001701
Wu Zhangjin3209e702009-07-02 23:27:12 +08001702 machtype= [Loongson] Share the same kernel image file between different
1703 yeeloong laptop.
1704 Example: machtype=lemote-yeeloong-2f-7inch
1705
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001706 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1707 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001708
1709 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001710 should make use of. maxcpus=n : n >= 0 limits the
1711 kernel to using 'n' processors. n=0 is a special case,
1712 it is equivalent to "nosmp", which also disables
1713 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001714
Kay Sieversd134b002011-07-31 22:08:04 +02001715 max_loop= [LOOP] The number of loop block devices that get
1716 (loop.max_loop) unconditionally pre-created at init time. The default
1717 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1718 of statically allocating a predefined number, loop
1719 devices can be requested on-demand with the
1720 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001721
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001722 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001723
Uwe Hermann71cced62008-10-20 09:32:21 -07001724 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001725
Linus Torvalds1da177e2005-04-16 15:20:36 -07001726 md= [HW] RAID subsystems devices and level
1727 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001728
Linus Torvalds1da177e2005-04-16 15:20:36 -07001729 mdacon= [MDA]
1730 Format: <first>,<last>
1731 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001732
Linus Torvalds1da177e2005-04-16 15:20:36 -07001733 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1734 Amount of memory to be used when the kernel is not able
1735 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08001736 [X86] Work as limiting max address. Use together
1737 with memmap= to avoid physical address space collisions.
1738 Without memmap= PCI devices could be placed at addresses
1739 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001740
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001741 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001742 memory.
1743
Paul Mundt6902aa82008-09-21 17:14:42 +09001744 memchunk=nn[KMG]
1745 [KNL,SH] Allow user to override the default size for
1746 per-device physically contiguous DMA buffers.
1747
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301748 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001749 E820 memory map, as specified by the user.
1750 Such memmap=exactmap lines can be constructed based on
1751 BIOS output or other requirements. See the memmap=nn@ss
1752 option description.
1753
1754 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08001755 [KNL] Force usage of a specific region of memory.
1756 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001757
1758 memmap=nn[KMG]#ss[KMG]
1759 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08001760 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001761
1762 memmap=nn[KMG]$ss[KMG]
1763 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08001764 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001765 Example: Exclude memory from 0x18690000-0x1869ffff
1766 memmap=64K$0x18690000
1767 or
1768 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001769
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001770 memory_corruption_check=0/1 [X86]
1771 Some BIOSes seem to corrupt the first 64k of
1772 memory when doing things like suspend/resume.
1773 Setting this option will scan the memory
1774 looking for corruption. Enabling this will
1775 both detect corruption and prevent the kernel
1776 from using the memory being corrupted.
1777 However, its intended as a diagnostic tool; if
1778 repeatable BIOS-originated corruption always
1779 affects the same memory, you can use memmap=
1780 to prevent the kernel from using that memory.
1781
1782 memory_corruption_check_size=size [X86]
1783 By default it checks for corruption in the low
1784 64k, making this memory unavailable for normal
1785 use. Use this parameter to scan for
1786 corruption in more or less memory.
1787
1788 memory_corruption_check_period=seconds [X86]
1789 By default it checks for corruption every 60
1790 seconds. Use this parameter to check at some
1791 other rate. 0 disables periodic checking.
1792
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001793 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001794 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001795 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001796 Specifies the number of memtest passes to be
1797 performed. Each pass selects another test
1798 pattern from a given set of patterns. Memtest
1799 fills the memory with this pattern, validates
1800 memory contents and reserves bad memory
1801 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001802
Linus Torvalds1da177e2005-04-16 15:20:36 -07001803 meye.*= [HW] Set MotionEye Camera parameters
1804 See Documentation/video4linux/meye.txt.
1805
Andres Salomon8f368812007-10-12 23:04:06 +02001806 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1807 Multi-Function General Purpose Timers on AMD Geode
1808 platforms.
1809
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001810 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1811 the BIOS has incorrectly applied a workaround. TinyBIOS
1812 version 0.98 is known to be affected, 0.99 fixes the
1813 problem by letting the user disable the workaround.
1814
Linus Torvalds1da177e2005-04-16 15:20:36 -07001815 mga= [HW,DRM]
1816
Randy Dunlap1c207f92008-11-19 15:36:16 -08001817 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1818 physical address is ignored.
1819
Michel Pollet39f45d72009-05-20 11:10:31 +01001820 mini2440= [ARM,HW,KNL]
1821 Format:[0..2][b][c][t]
1822 Default: "0tb"
1823 MINI2440 configuration specification:
1824 0 - The attached screen is the 3.5" TFT
1825 1 - The attached screen is the 7" TFT
1826 2 - The VGA Shield is attached (1024x768)
1827 Leaving out the screen size parameter will not load
1828 the TFT driver, and the framebuffer will be left
1829 unconfigured.
1830 b - Enable backlight. The TFT backlight pin will be
1831 linked to the kernel VESA blanking code and a GPIO
1832 LED. This parameter is not necessary when using the
1833 VGA shield.
1834 c - Enable the s3c camera interface.
1835 t - Reserved for enabling touchscreen support. The
1836 touchscreen support is not enabled in the mainstream
1837 kernel as of 2.6.30, a preliminary port can be found
1838 in the "bleeding edge" mini2440 support kernel at
1839 http://repo.or.cz/w/linux-2.6/mini2440.git
1840
Mel Gorman6b74ab92008-07-23 21:26:49 -07001841 mminit_loglevel=
1842 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1843 parameter allows control of the logging verbosity for
1844 the additional memory initialisation checks. A value
1845 of 0 disables mminit logging and a level of 4 will
1846 log everything. Information is printed at KERN_DEBUG
1847 so loglevel=8 may also need to be specified.
1848
Rusty Russell106a4ee2012-09-26 10:09:40 +01001849 module.sig_enforce
1850 [KNL] When CONFIG_MODULE_SIG is set, this means that
1851 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01001852 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01001853 is always true, so this option does nothing.
1854
Linus Torvalds1da177e2005-04-16 15:20:36 -07001855 mousedev.tap_time=
1856 [MOUSE] Maximum time between finger touching and
1857 leaving touchpad surface for touch to be considered
1858 a tap and be reported as a left button click (for
1859 touchpads working in absolute mode only).
1860 Format: <msecs>
1861 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1862 reporting absolute coordinates, such as tablets
1863 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1864 reporting absolute coordinates, such as tablets
1865
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301866 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001867 is similar to kernelcore except it specifies the
1868 amount of memory used for migratable allocations.
1869 If both kernelcore and movablecore is specified,
1870 then kernelcore will be at *least* the specified
1871 value but may be more. If movablecore on its own
1872 is specified, the administrator must be careful
1873 that the amount of memory usable for all allocations
1874 is not too small.
1875
Tang Chenc5320922013-11-12 15:08:10 -08001876 movable_node [KNL,X86] Boot-time switch to enable the effects
1877 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1878
Linus Torvalds1da177e2005-04-16 15:20:36 -07001879 MTD_Partition= [MTD]
1880 Format: <name>,<region-number>,<size>,<offset>
1881
Randy Dunlapa9913042005-10-23 12:57:11 -07001882 MTD_Region= [MTD] Format:
1883 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001884
1885 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001886 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001887
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001888 multitce=off [PPC] This parameter disables the use of the pSeries
1889 firmware feature for updating multiple TCE entries
1890 at a time.
1891
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001892 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1893
1894 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1895
1896 boundary - index of last SLC block on Flex-OneNAND.
1897 The remaining blocks are configured as MLC blocks.
1898 lock - Configure if Flex-OneNAND boundary should be locked.
1899 Once locked, the boundary cannot be changed.
1900 1 indicates lock status, 0 indicates unlock status.
1901
Ben Dooks9db829f2008-07-03 11:24:29 +01001902 mtdset= [ARM]
1903 ARM/S3C2412 JIVE boot control
1904
1905 See arch/arm/mach-s3c2412/mach-jive.c
1906
Linus Torvalds1da177e2005-04-16 15:20:36 -07001907 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001908 [HW] Make the MicroTouch USB driver use raw coordinates
1909 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001910
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001911 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001912 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001913 that could hold holes aka. UC entries.
1914
1915 mtrr_gran_size=nn[KMG] [X86]
1916 Used for mtrr cleanup. It is granularity of mtrr block.
1917 Default is 1.
1918 Large value could prevent small alignment from
1919 using up MTRRs.
1920
1921 mtrr_spare_reg_nr=n [X86]
1922 Format: <integer>
1923 Range: 0,7 : spare reg number
1924 Default : 1
1925 Used for mtrr cleanup. It is spare mtrr entries number.
1926 Set to 2 or more if your graphical card needs more.
1927
Linus Torvalds1da177e2005-04-16 15:20:36 -07001928 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1929
Linus Torvalds1da177e2005-04-16 15:20:36 -07001930 netdev= [NET] Network devices parameters
1931 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1932 Note that mem_start is often overloaded to mean
1933 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001934 This usage is only documented in each driver source
1935 file if at all.
1936
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001937 nf_conntrack.acct=
1938 [NETFILTER] Enable connection tracking flow accounting
1939 0 to disable accounting
1940 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001941 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001942
Chuck Lever306a0752010-09-17 10:54:37 -04001943 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001944 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001945
1946 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001947 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001948
Chuck Lever306a0752010-09-17 10:54:37 -04001949 nfsrootdebug [NFS] enable nfsroot debugging messages.
1950 See Documentation/filesystems/nfs/nfsroot.txt.
1951
Trond Myklebusta72b4422006-01-03 09:55:41 +01001952 nfs.callback_tcpport=
1953 [NFS] set the TCP port on which the NFSv4 callback
1954 channel should listen.
1955
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001956 nfs.cache_getent=
1957 [NFS] sets the pathname to the program which is used
1958 to update the NFS client cache entries.
1959
1960 nfs.cache_getent_timeout=
1961 [NFS] sets the timeout after which an attempt to
1962 update a cache entry is deemed to have failed.
1963
Trond Myklebust58df0952006-01-03 09:55:57 +01001964 nfs.idmap_cache_timeout=
1965 [NFS] set the maximum lifetime for idmapper cache
1966 entries.
1967
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001968 nfs.enable_ino64=
1969 [NFS] enable 64-bit inode numbers.
1970 If zero, the NFS client will fake up a 32-bit inode
1971 number for the readdir() and stat() syscalls instead
1972 of returning the full 64-bit number.
1973 The default is to return 64-bit inode numbers.
1974
Trond Myklebustef159e92012-02-06 19:50:40 -05001975 nfs.max_session_slots=
1976 [NFSv4.1] Sets the maximum number of session slots
1977 the client will attempt to negotiate with the server.
1978 This limits the number of simultaneous RPC requests
1979 that the client can send to the NFSv4.1 server.
1980 Note that there is little point in setting this
1981 value higher than the max_tcp_slot_table_limit.
1982
Trond Myklebustb064eca22011-02-22 15:44:32 -08001983 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05001984 [NFSv4] When set to the default of '1', this option
1985 ensures that both the RPC level authentication
1986 scheme and the NFS level operations agree to use
1987 numeric uids/gids if the mount is using the
1988 'sec=sys' security flavour. In effect it is
1989 disabling idmapping, which can make migration from
1990 legacy NFSv2/v3 systems to NFSv4 easier.
1991 Servers that do not support this mode of operation
1992 will be autodetected by the client, and it will fall
1993 back to using the idmapper.
1994 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04001995 nfs.nfs4_unique_id=
1996 [NFS4] Specify an additional fixed unique ident-
1997 ification string that NFSv4 clients can insert into
1998 their nfs_client_id4 string. This is typically a
1999 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002000
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002001 nfs.send_implementation_id =
2002 [NFSv4.1] Send client implementation identification
2003 information in exchange_id requests.
2004 If zero, no implementation identification information
2005 will be sent.
2006 The default is to send the implementation identification
2007 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002008
2009 nfs.recover_lost_locks =
2010 [NFSv4] Attempt to recover locks that were lost due
2011 to a lease timeout on the server. Please note that
2012 doing this risks data corruption, since there are
2013 no guarantees that the file will remain unchanged
2014 after the locks are lost.
2015 If you want to enable the kernel legacy behaviour of
2016 attempting to recover these locks, then set this
2017 parameter to '1'.
2018 The default parameter value of '0' causes the kernel
2019 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002020
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002021 nfsd.nfs4_disable_idmapping=
2022 [NFSv4] When set to the default of '1', the NFSv4
2023 server will return only numeric uids and gids to
2024 clients using auth_sys, and will accept numeric uids
2025 and gids from such clients. This is intended to ease
2026 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002027
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002028 objlayoutdriver.osd_login_prog=
2029 [NFS] [OBJLAYOUT] sets the pathname to the program which
2030 is used to automatically discover and login into new
2031 osd-targets. Please see:
2032 Documentation/filesystems/pnfs.txt for more explanations
2033
Paul Mundt1e1030d2009-09-01 17:38:32 +09002034 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002035 when a NMI is triggered.
2036 Format: [state][,regs][,debounce][,die]
2037
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302038 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002039 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05002040 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03002041 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002042 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002043 timeout occurs (or 'nopanic' to override the opposite
2044 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002045 This is useful when you use a panic=... timeout and
2046 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047
Anton Vorontsovbff38772009-07-08 11:10:56 -07002048 netpoll.carrier_timeout=
2049 [NET] Specifies amount of time (in seconds) that
2050 netpoll should wait for a carrier. By default netpoll
2051 waits 4 seconds.
2052
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002053 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002054 emulation library even if a 387 maths coprocessor
2055 is present.
2056
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002057 no_console_suspend
2058 [HW] Never suspend the console
2059 Disable suspending of consoles during suspend and
2060 hibernate operations. Once disabled, debugging
2061 messages can reach various consoles while the rest
2062 of the system is being put to sleep (ie, while
2063 debugging driver suspend/resume hooks). This may
2064 not work reliably with all consoles, but is known
2065 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002066 To facilitate more flexible debugging, we also add
2067 console_suspend, a printk module parameter to control
2068 it. Users could use console_suspend (usually
2069 /sys/module/printk/parameters/console_suspend) to
2070 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002071
Christoph Lameterc1aee212007-05-31 00:40:47 -07002072 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2073 caches in the slab allocator. Saves per-node memory,
2074 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002075
Randy Dunlapa9913042005-10-23 12:57:11 -07002076 noalign [KNL,ARM]
2077
Linus Torvalds1da177e2005-04-16 15:20:36 -07002078 noapic [SMP,APIC] Tells the kernel to not make use of any
2079 IOAPICs that may be present in the system.
2080
Kees Cook8ab38202013-10-10 17:18:14 -07002081 nokaslr [X86]
Kees Cooke2b32e62014-02-25 16:59:17 -08002082 Disable kernel and module base offset ASLR (Address
2083 Space Layout Randomization) if built into the kernel.
Kees Cook8ab38202013-10-10 17:18:14 -07002084
Mike Galbraith5091faa2010-11-30 14:18:03 +01002085 noautogroup Disable scheduler automatic task group creation.
2086
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087 nobats [PPC] Do not use BATs for mapping kernel lowmem
2088 on "Classic" PPC cores.
2089
2090 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002091
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002092 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2093
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002094 nodelayacct [KNL] Disable per-task delay accounting
2095
Linus Torvalds1da177e2005-04-16 15:20:36 -07002096 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2097
Paul Mundt6902aa82008-09-21 17:14:42 +09002098 nodsp [SH] Disable hardware DSP at boot time.
2099
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302100 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002101
Linus Torvalds1da177e2005-04-16 15:20:36 -07002102 noexec [IA-64]
2103
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302104 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002105 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002106 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002107 noexec=off: disable non-executable mappings
2108
H. Peter Anvin52b61792012-09-21 12:43:13 -07002109 nosmap [X86]
2110 Disable SMAP (Supervisor Mode Access Prevention)
2111 even if it is supported by processor.
2112
Fenghua Yude5397a2011-05-11 16:51:05 -07002113 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002114 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002115 even if it is supported by processor.
2116
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002117 noexec32 [X86-64]
2118 This affects only 32-bit executables.
2119 noexec32=on: enable non-executable mappings (default)
2120 read doesn't imply executable mappings
2121 noexec32=off: disable non-executable mappings
2122 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002123
Paul Mundt6902aa82008-09-21 17:14:42 +09002124 nofpu [SH] Disable hardware FPU at boot time.
2125
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002126 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002127 register save and restore. The kernel will only save
2128 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002129
Suresh Siddha0c752a92009-05-22 12:17:45 -07002130 noxsave [BUGS=X86] Disables x86 extended register state save
2131 and restore using xsave. The kernel will fallback to
2132 enabling legacy floating-point and sse state.
2133
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002134 eagerfpu= [X86]
Suresh Siddhae0022982012-09-10 10:32:32 -07002135 on enable eager fpu restore
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002136 off disable eager fpu restore
Suresh Siddhae0022982012-09-10 10:32:32 -07002137 auto selects the default scheme, which automatically
2138 enables eagerfpu restore for xsaveopt.
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002139
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002140 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2141 wfi(ARM) instruction doesn't work correctly and not to
2142 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002143
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002144 no_file_caps Tells the kernel not to honor file capabilities. The
2145 only way then for a file to be executed with privilege
2146 is to be setuid root or executed by root.
2147
Linus Torvalds1da177e2005-04-16 15:20:36 -07002148 nohalt [IA-64] Tells the kernel not to use the power saving
2149 function PAL_HALT_LIGHT when idle. This increases
2150 power-consumption. On the positive side, it reduces
2151 interrupt wake-up latency, which may improve performance
2152 in certain environments such as networked servers or
2153 real-time systems.
2154
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002155 nohz= [KNL] Boottime enable/disable dynamic ticks
2156 Valid arguments: on, off
2157 Default: on
2158
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002159 nohz_full= [KNL,BOOT]
2160 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002161 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002162 whenever possible. The boot CPU will be forced outside
2163 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002164 The CPUs in this range must also be included in the
2165 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002166
Paul Mundteeee7852009-04-02 12:31:16 +09002167 noiotrap [SH] Disables trapped I/O port accesses.
2168
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002169 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002170 disable unhandled interrupt sources.
2171
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302172 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002173 broken timer IRQ sources.
2174
Linus Torvalds1da177e2005-04-16 15:20:36 -07002175 noisapnp [ISAPNP] Disables ISA PnP code.
2176
2177 noinitrd [RAM] Tells the kernel not to load any configured
2178 initial RAM disk.
2179
Weidong Han03ea8152009-04-17 16:42:15 +08002180 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2181 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002182 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002183
Linus Torvalds1da177e2005-04-16 15:20:36 -07002184 nointroute [IA-64]
2185
Randy Dunlap16290242011-08-13 12:34:52 -07002186 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002187
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002188 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2189
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002190 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2191 fault handling.
2192
Glauber Costad910f5c2011-07-11 15:28:19 -04002193 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2194 steal time is computed, but won't influence scheduler
2195 behaviour
2196
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002197 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002198
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002199 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002200
Linus Torvalds1da177e2005-04-16 15:20:36 -07002201 noltlbs [PPC] Do not use large page/tlb entries for kernel
2202 lowmem mapping on PPC40x.
2203
Horms312f1f02006-02-22 09:57:55 +09002204 nomca [IA-64] Disable machine check abort handling
2205
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002206 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002207
Andres Salomon83d73842007-10-12 23:04:06 +02002208 nomfgpt [X86-32] Disable Multi-Function General Purpose
2209 Timer usage (for AMD Geode machines).
2210
Don Zickusbda62632011-10-13 15:14:27 -04002211 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2212 shutdown the other cpus. Instead use the REBOOT_VECTOR
2213 irq.
2214
Dave Young02608be2012-02-01 10:33:14 +08002215 nomodule Disable module load
2216
Jiri Kosina016ddd92010-01-18 17:05:40 +01002217 nopat [X86] Disable PAT (page attribute table extension of
2218 pagetables) support.
2219
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002220 norandmaps Don't use address space randomization. Equivalent to
2221 echo 0 > /proc/sys/kernel/randomize_va_space
2222
Jiri Kosinabbff2162010-08-11 18:34:09 +02002223 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002224
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002225 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002226 with UP alternatives
2227
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002228 nordrand [X86] Disable the direct use of the RDRAND
2229 instruction even if it is supported by the
2230 processor. RDRAND is still available to user
2231 space applications.
2232
Randy Dunlapa9913042005-10-23 12:57:11 -07002233 noresume [SWSUSP] Disables resume and restores original swap
2234 space.
2235
Linus Torvalds1da177e2005-04-16 15:20:36 -07002236 no-scroll [VGA] Disables scrollback.
2237 This is required for the Braillex ib80-piezo Braille
2238 reader made by F.H. Papenmeier (Germany).
2239
2240 nosbagart [IA-64]
2241
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002242 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002243
Len Brown61ec7562007-08-16 03:34:22 -04002244 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2245 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002246
Dave Jones97842212007-07-15 23:41:05 -07002247 nosoftlockup [KNL] Disable the soft-lockup detector.
2248
Linus Torvalds1da177e2005-04-16 15:20:36 -07002249 nosync [HW,M68K] Disables sync negotiation for all devices.
2250
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002251 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002252
2253 nousb [USB] Disable the USB subsystem
2254
Ben Hutchings55142372011-01-02 23:02:42 +00002255 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04002256
Linus Torvalds1da177e2005-04-16 15:20:36 -07002257 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002258
Weidong Han2b2fd872009-04-17 16:42:12 +08002259 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2260
Fenghua Yuf78cff42012-11-13 11:32:38 -08002261 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2262 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2263 Some features depend on CPU0. Known dependencies are:
2264 1. Resume from suspend/hibernate depends on CPU0.
2265 Suspend/hibernate will fail if CPU0 is offline and you
2266 need to online CPU0 before suspend/hibernate.
2267 2. PIC interrupts also depend on CPU0. CPU0 can't be
2268 removed if a PIC interrupt is detected.
2269 It's said poweroff/reboot may depend on CPU0 on some
2270 machines although I haven't seen such issues so far
2271 after CPU0 is offline on a few tested machines.
2272 If the dependencies are under your control, you can
2273 turn on cpu0_hotplug.
2274
Randy Dunlap16290242011-08-13 12:34:52 -07002275 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002276 purges which is reported from either PAL_VM_SUMMARY or
2277 SAL PALO.
2278
Yinghai Lu2b633e32010-02-10 01:20:37 -08002279 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2280 could support. nr_cpus=n : n >= 1 limits the kernel to
2281 supporting 'n' processors. Later in runtime you can not
2282 use hotplug cpu feature to put more cpu back to online.
2283 just like you compile the kernel NR_CPUS=n
2284
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002285 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2286
Mel Gorman1a687c22012-11-22 11:16:36 +00002287 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2288 Allowed values are enable and disable
2289
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002290 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2291 one of ['zone', 'node', 'default'] can be specified
2292 This can be set from sysctl after boot.
2293 See Documentation/sysctl/vm.txt for details.
2294
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002295 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2296 See Documentation/debugging-via-ohci1394.txt for more
2297 info.
2298
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002299 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2300 Rather than timing out after 20 ms if an EC
2301 command is not properly ACKed, override the length
2302 of the timeout. We have interrupts disabled while
2303 waiting for the ACK, so if this is set too high
2304 interrupts *may* be lost!
2305
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002306 omap_mux= [OMAP] Override bootloader pin multiplexing.
2307 Format: <mux_mode0.mode_name=value>...
2308 For example, to override I2C bus2:
2309 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2310
Linus Torvalds1da177e2005-04-16 15:20:36 -07002311 oprofile.timer= [HW]
2312 Use timer interrupt instead of performance counters
2313
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002314 oprofile.cpu_type= Force an oprofile cpu type
2315 This might be useful if you have an older oprofile
2316 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002317 Format: { arch_perfmon }
2318 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002319 perfmon on Intel CPUs instead of the
2320 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002321 timer: [X86] Force use of architectural NMI
2322 timer mode (see also oprofile.timer
2323 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002324 [s390] Force legacy basic mode sampling
2325 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002326
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002327 oops=panic Always panic on oopses. Default is to just kill the
2328 process, but there is a small probability of
2329 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002330 This will also cause panics on machine check exceptions.
2331 Useful together with panic=30 to trigger a reboot.
2332
Randy Dunlapbcfde332010-06-07 17:10:38 -07002333 OSS [HW,OSS]
2334 See Documentation/sound/oss/oss-parameters.txt
2335
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002336 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002337 timeout > 0: seconds before rebooting
2338 timeout = 0: wait forever
2339 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002340 Format: <timeout>
2341
2342 parkbd.port= [HW] Parallel port number the keyboard adapter is
2343 connected to, default is 0.
2344 Format: <parport#>
2345 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2346 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002347 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002348
Randy Dunlapa9913042005-10-23 12:57:11 -07002349 parport= [HW,PPT] Specify parallel ports. 0 disables.
2350 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2351 Use 'auto' to force the driver to use any
2352 IRQ/DMA settings detected (the default is to
2353 ignore detected IRQ/DMA settings because of
2354 possible conflicts). You can specify the base
2355 address, IRQ, and DMA settings; IRQ and DMA
2356 should be numbers, or 'auto' (for using detected
2357 settings on that particular port), or 'nofifo'
2358 (to avoid using a FIFO even if it is detected).
2359 Parallel ports are assigned in the order they
2360 are specified on the command line, starting
2361 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002362
Randy Dunlapa9913042005-10-23 12:57:11 -07002363 parport_init_mode= [HW,PPT]
2364 Configure VIA parallel port to operate in
2365 a specific mode. This is necessary on Pegasos
2366 computer where firmware has no options for setting
2367 up parallel port mode and sets it to spp.
2368 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002369 Format: [spp|ps2|epp|ecp|ecpepp]
2370
Andrew Mortondd287792006-03-23 03:00:57 -08002371 pause_on_oops=
2372 Halt all CPUs after the first oops has been printed for
2373 the specified number of seconds. This is to be used if
2374 your oopses keep scrolling off the screen.
2375
Linus Torvalds1da177e2005-04-16 15:20:36 -07002376 pcbit= [HW,ISDN]
2377
2378 pcd. [PARIDE]
2379 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002380 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002381
Randy Dunlapa9913042005-10-23 12:57:11 -07002382 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002383 earlydump [X86] dump PCI config space before the kernel
2384 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002385 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002386 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002387 the hardware directly. Use this if your machine
2388 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002389 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002390 hardware access methods are allowed. Use this
2391 if you experience crashes upon bootup and you
2392 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002393 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002394 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002395 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002396 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002397 noaer [PCIE] If the PCIEAER kernel config parameter is
2398 enabled, this kernel boot option can be used to
2399 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002400 nodomains [PCI] Disable support for multiple PCI
2401 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302402 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002403 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002404 check_enable_amd_mmconf [X86] check for and enable
2405 properly configured MMIO access to PCI
2406 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002407 nomsi [MSI] If the PCI_MSI kernel config parameter is
2408 enabled, this kernel boot option can be used to
2409 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002410 noioapicquirk [APIC] Disable all boot interrupt quirks.
2411 Safety option to keep boot IRQs enabled. This
2412 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002413 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2414 primary IO-APIC for bridges that cannot disable
2415 boot IRQs. This fixes a source of spurious IRQs
2416 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002417 noioapicreroute [APIC] Disable workaround that uses the
2418 boot IRQ equivalent of an IRQ that connects to
2419 a chipset where boot IRQs cannot be disabled.
2420 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002421 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002422 routing table. These calls are known to be buggy
2423 on several machines and they hang the machine
2424 when used, but on other computers it's the only
2425 way to get the interrupt routing table. Try
2426 this option if the kernel is unable to allocate
2427 IRQs or discover secondary PCI buses on your
2428 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002429 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002430 Use with caution as certain devices share
2431 address decoders between ROMs and other
2432 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002433 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002434 expansion ROMs that do not already have
2435 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002436 nobar [X86] Do not assign address space to the
2437 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002438 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002439 assigned automatically to PCI devices. You can
2440 make the kernel exclude IRQs of your ISA cards
2441 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002442 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002443 of the PIRQ table (normally generated
2444 by the BIOS) if it is outside the
2445 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002446 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002447 useful if the kernel is unable to find your
2448 secondary buses and you want to tell it
2449 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002450 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002451 numbers ourselves, overriding
2452 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002453 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002454 in the BIOS $PIR table. This is needed on
2455 some systems with broken BIOSes, notably
2456 some HP Pavilion N5400 and Omnibook XE3
2457 notebooks. This will have no effect if ACPI
2458 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002459 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002460 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002461 use_crs [X86] Use PCI host bridge window information
2462 from ACPI. On BIOSes from 2008 or later, this
2463 is enabled by default. If you need to use this,
2464 please report a bug.
2465 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2466 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002467 routeirq Do IRQ routing for all PCI devices.
2468 This is normally done in pci_enable_device(),
2469 so this option is a temporary workaround
2470 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002471 skip_isa_align [X86] do not align io start addr, so can
2472 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002473 firmware [ARM] Do not re-enumerate the bus but instead
2474 just use the configuration from the
2475 bootloader. This is currently used on
2476 IXP2000 systems where the bus has to be
2477 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002478 noearly [X86] Don't do any early type 1 scanning.
2479 This might help on some broken boards which
2480 machine check when some devices' config space
2481 is read. But various workarounds are disabled
2482 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002483 bfsort Sort PCI devices into breadth-first order.
2484 This sorting is done to get a device
2485 order compatible with older (<= 2.4) kernels.
2486 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002487 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2488 tuning and use the BIOS-configured MPS defaults.
2489 pcie_bus_safe Set every device's MPS to the largest value
2490 supported by all devices below the root complex.
2491 pcie_bus_perf Set device MPS to the largest allowable MPS
2492 based on its parent bus. Also set MRRS (Max
2493 Read Request Size) to the largest supported
2494 value (no larger than the MPS that the device
2495 or bus can support) for best performance.
2496 pcie_bus_peer2peer Set every device's MPS to 128B, which
2497 every device is guaranteed to support. This
2498 configuration allows peer-to-peer DMA between
2499 any pair of devices, possibly at the cost of
2500 reduced performance. This also guarantees
2501 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002502 cbiosize=nn[KMG] The fixed amount of bus space which is
2503 reserved for the CardBus bridge's IO window.
2504 The default value is 256 bytes.
2505 cbmemsize=nn[KMG] The fixed amount of bus space which is
2506 reserved for the CardBus bridge's memory
2507 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002508 resource_alignment=
2509 Format:
2510 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2511 Specifies alignment and device to reassign
2512 aligned memory resources.
2513 If <order of align> is not specified,
2514 PAGE_SIZE is used as alignment.
2515 PCI-PCI bridge can be specified, if resource
2516 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002517 ecrc= Enable/disable PCIe ECRC (transaction layer
2518 end-to-end CRC checking).
2519 bios: Use BIOS/firmware settings. This is the
2520 the default.
2521 off: Turn ECRC off
2522 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002523 hpiosize=nn[KMG] The fixed amount of bus space which is
2524 reserved for hotplug bridge's IO window.
2525 Default size is 256 bytes.
2526 hpmemsize=nn[KMG] The fixed amount of bus space which is
2527 reserved for hotplug bridge's memory window.
2528 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002529 realloc= Enable/disable reallocating PCI bridge resources
2530 if allocations done by BIOS are too small to
2531 accommodate resources required by all child
2532 devices.
2533 off: Turn realloc off
2534 on: Turn realloc on
2535 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002536 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002537 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2538 only look for one device below a PCIe downstream
2539 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002540
Chuck Ebberte5665a42008-09-24 20:40:34 -04002541 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2542 Management.
2543 off Disable ASPM.
2544 force Enable ASPM even on devices that claim not to support it.
2545 WARNING: Forcing ASPM on may cause system lockups.
2546
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002547 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2548 nomsi Do not use MSI for PCI Express Native Hotplug (this
2549 makes all PCIe ports use INTx for hotplug services).
2550
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002551 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002552 auto Ask the BIOS whether or not to use native PCIe services
2553 associated with PCIe ports (PME, hot-plug, AER). Use
2554 them only if that is allowed by the BIOS.
2555 native Use native PCIe services associated with PCIe ports
2556 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002557 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2558 ports driver.
2559
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002560 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002561 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002562 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002563
Linus Torvalds1da177e2005-04-16 15:20:36 -07002564 pcmv= [HW,PCMCIA] BadgePAD 4
2565
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302566 pd_ignore_unused
2567 [PM]
2568 Keep all power-domains already enabled by bootloader on,
2569 even if no driver has claimed them. This is useful
2570 for debug and development, but should not be
2571 needed on a platform with proper driver support.
2572
Linus Torvalds1da177e2005-04-16 15:20:36 -07002573 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002574 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002575
2576 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2577 boot time.
2578 Format: { 0 | 1 }
2579 See arch/parisc/kernel/pdc_chassis.c
2580
Tejun Heof58dc012009-08-14 15:00:50 +09002581 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002582 Currently supported values are "embed" and "page".
2583 Archs may support subset or none of the selections.
2584 See comments in mm/percpu.c for details on each
2585 allocator. This parameter is primarily for debugging
2586 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002587
Linus Torvalds1da177e2005-04-16 15:20:36 -07002588 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002589 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002590
2591 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002592 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002593
2594 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002595 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002596
2597 plip= [PPT,NET] Parallel port network link
2598 Format: { parport<nr> | timid | 0 }
2599 See also Documentation/parport.txt.
2600
Randy Dunlap16290242011-08-13 12:34:52 -07002601 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002602 Override pmtimer IOPort with a hex value.
2603 e.g. pmtmr=0x508
2604
Bjorn Helgaas96242112011-08-11 12:14:05 -06002605 pnp.debug=1 [PNP]
2606 Enable PNP debug messages (depends on the
2607 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2608 via /sys/module/pnp/parameters/debug. We always show
2609 current resource usage; turning this on also shows
2610 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002611
Linus Torvalds1da177e2005-04-16 15:20:36 -07002612 pnpacpi= [ACPI]
2613 { off }
2614
2615 pnpbios= [ISAPNP]
2616 { on | off | curr | res | no-curr | no-res }
2617
2618 pnp_reserve_irq=
2619 [ISAPNP] Exclude IRQs for the autoconfiguration
2620
2621 pnp_reserve_dma=
2622 [ISAPNP] Exclude DMAs for the autoconfiguration
2623
2624 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002625 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002626
2627 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002628 [ISAPNP] Exclude memory regions for the
2629 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002630 Ranges are in pairs (memory base and size).
2631
Randy Dunlap4af94f32009-04-17 18:30:28 -07002632 ports= [IP_VS_FTP] IPVS ftp helper module
2633 Default is 21.
2634 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2635 may be specified.
2636 Format: <port>,<port>....
2637
Ingo Molnar45807a12007-07-15 23:40:10 -07002638 print-fatal-signals=
2639 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002640
2641 If enabled, warn about various signal handling
2642 related application anomalies: too many signals,
2643 too many POSIX.1 timers, fatal signals causing a
2644 coredump - etc.
2645
2646 If you hit the warning due to signal overflow,
2647 you might want to try "ulimit -i unlimited".
2648
Ingo Molnar45807a12007-07-15 23:40:10 -07002649 default: off.
2650
Matthew Garrettc22ab332012-03-05 14:59:10 -08002651 printk.always_kmsg_dump=
2652 Trigger kmsg_dump for cases other than kernel oops or
2653 panics
2654 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2655 default: disabled
2656
Randy Dunlape84845c2007-07-15 23:40:25 -07002657 printk.time= Show timing data prefixed to each printk message line
2658 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2659
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002660 processor.max_cstate= [HW,ACPI]
2661 Limit processor to maximum C-state
2662 max_cstate=9 overrides any DMI blacklist limit.
2663
2664 processor.nocst [HW,ACPI]
2665 Ignore the _CST method to determine C-states,
2666 instead using the legacy FADT method
2667
Linus Torvalds1da177e2005-04-16 15:20:36 -07002668 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002669 Format: [schedule,]<number>
2670 Param: "schedule" - profile schedule points.
2671 Param: <number> - step/bucket size as a power of 2 for
2672 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002673 Param: "sleep" - profile D-state sleeping (millisecs).
2674 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002675 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002676
Linus Torvalds1da177e2005-04-16 15:20:36 -07002677 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2678 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002679 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002680
Randy Dunlapa9913042005-10-23 12:57:11 -07002681 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2682 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002683 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2684 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002685 psmouse.resetafter= [HW,MOUSE]
2686 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002687 (0 = never).
2688 psmouse.resolution=
2689 [HW,MOUSE] Set desired mouse resolution, in dpi.
2690 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002691 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002692 0 = disabled, 1 = enabled (default).
2693
Matthew Garrettdee28e72011-07-21 16:57:55 -04002694 pstore.backend= Specify the name of the pstore backend to use
2695
Linus Torvalds1da177e2005-04-16 15:20:36 -07002696 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002697 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002698
Kay Sieversdc8c8582007-08-15 12:25:38 +02002699 pty.legacy_count=
2700 [KNL] Number of legacy pty's. Overwrites compiled-in
2701 default number.
2702
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002703 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002704
Linus Torvalds1da177e2005-04-16 15:20:36 -07002705 r128= [HW,DRM]
2706
2707 raid= [HW,RAID]
2708 See Documentation/md.txt.
2709
Randy Dunlapa9913042005-10-23 12:57:11 -07002710 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002711 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002712
Linus Torvalds1da177e2005-04-16 15:20:36 -07002713 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002714 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002715
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002716 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002717 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2718 the specified list of CPUs to be no-callback CPUs.
2719 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08002720 be offloaded to "rcuox/N" kthreads created for
2721 that purpose, where "x" is "b" for RCU-bh, "p"
2722 for RCU-preempt, and "s" for RCU-sched, and "N"
2723 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002724 offloaded CPUs, which can be useful for HPC and
2725 real-time workloads. It can also improve energy
2726 efficiency for asymmetric multiprocessors.
2727
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002728 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002729 Rather than requiring that offloaded CPUs
2730 (specified by rcu_nocbs= above) explicitly
2731 awaken the corresponding "rcuoN" kthreads,
2732 make these kthreads poll for callbacks.
2733 This improves the real-time response for the
2734 offloaded CPUs by relieving them of the need to
2735 wake up the corresponding kthread, but degrades
2736 energy efficiency by requiring that the kthreads
2737 periodically wake up to do the polling.
2738
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002739 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002740 Set maximum number of finished RCU callbacks to
2741 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002742
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002743 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07002744 Increase the number of CPUs assigned to each
2745 leaf rcu_node structure. Useful for very large
2746 systems.
2747
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002748 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002749 Set delay from grace-period initialization to
2750 first attempt to force quiescent states.
2751 Units are jiffies, minimum value is zero,
2752 and maximum value is HZ.
2753
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002754 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002755 Set delay between subsequent attempts to force
2756 quiescent states. Units are jiffies, minimum
2757 value is one, and maximum value is HZ.
2758
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002759 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002760 Set threshold of queued RCU callbacks beyond which
2761 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002762
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002763 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002764 Set threshold of queued RCU callbacks below which
2765 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002766
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002767 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002768 Set wakeup interval for idle CPUs that have
2769 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002770
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002771 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002772 Set wakeup interval for idle CPUs that have
2773 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2774 Lazy RCU callbacks are those which RCU can
2775 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002776
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002777 rcutorture.fqs_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002778 Set duration of force_quiescent_state bursts.
2779
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002780 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002781 Set holdoff time within force_quiescent_state bursts.
2782
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002783 rcutorture.fqs_stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002784 Set wait time between force_quiescent_state bursts.
2785
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002786 rcutorture.gp_exp= [KNL]
2787 Use expedited update-side primitives.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002788
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002789 rcutorture.gp_normal= [KNL]
2790 Use normal (non-expedited) update-side primitives.
2791 If both gp_exp and gp_normal are set, do both.
2792 If neither gp_exp nor gp_normal are set, still
2793 do both.
2794
2795 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002796 Set callbacks/threads for rcu_barrier() testing.
2797
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002798 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002799 Set number of concurrent RCU writers. These just
2800 stress RCU, they don't participate in the actual
2801 test, hence the "fake".
2802
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002803 rcutorture.nreaders= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002804 Set number of RCU readers.
2805
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002806 rcutorture.object_debug= [KNL]
2807 Enable debug-object double-call_rcu() testing.
2808
2809 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002810 Set time (s) after boot for CPU-hotplug testing.
2811
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002812 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002813 Set time (s) between CPU-hotplug operations, or
2814 zero to disable CPU-hotplug testing.
2815
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002816 rcutorture.rcutorture_runnable= [BOOT]
2817 Start rcutorture running at boot time.
2818
2819 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002820 Set task-shuffle interval (s). Shuffling tasks
2821 allows some CPUs to go into dyntick-idle mode
2822 during the rcutorture test.
2823
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002824 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002825 Set time (s) after boot system shutdown. This
2826 is useful for hands-off automated testing.
2827
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002828 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002829 Duration of CPU stall (s) to test RCU CPU stall
2830 warnings, zero to disable.
2831
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002832 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002833 Time to wait (s) after boot before inducing stall.
2834
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002835 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002836 Time (s) between statistics printk()s.
2837
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002838 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002839 Time (s) to stutter testing, for example, specifying
2840 five seconds causes the test to run for five seconds,
2841 wait for five seconds, and so on. This tests RCU's
2842 ability to transition abruptly to and from idle.
2843
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002844 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002845 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2846 "Maybe" means test if the RCU implementation
2847 under test support RCU priority boosting.
2848
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002849 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002850 Duration (s) of each individual boost test.
2851
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002852 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002853 Interval (s) between each boost test.
2854
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002855 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002856 Test RCU's dyntick-idle handling. See also the
2857 rcutorture.shuffle_interval parameter.
2858
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002859 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002860 Specify the RCU implementation to test.
2861
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002862 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002863 Enable additional printk() statements.
2864
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002865 rcupdate.rcu_expedited= [KNL]
2866 Use expedited grace-period primitives, for
2867 example, synchronize_rcu_expedited() instead
2868 of synchronize_rcu(). This reduces latency,
2869 but can increase CPU utilization, degrade
2870 real-time latency, and degrade energy efficiency.
2871
2872 rcupdate.rcu_cpu_stall_suppress= [KNL]
2873 Suppress RCU CPU stall warning messages.
2874
2875 rcupdate.rcu_cpu_stall_timeout= [KNL]
2876 Set timeout for RCU CPU stall warning messages.
2877
Olof Johanssonffdfc402005-09-06 15:17:19 -07002878 rdinit= [KNL]
2879 Format: <full_path>
2880 Run specified binary instead of /init from the ramdisk,
2881 used for early userspace startup. See initrd.
2882
Robin Holt1b3a5d02013-07-08 16:01:42 -07002883 reboot= [KNL]
2884 Format (x86 or x86_64):
2885 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2886 [[,]s[mp]#### \
2887 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2888 [[,]f[orce]
2889 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2890 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2891 reboot_force is either force or not specified,
2892 reboot_cpu is s[mp]#### with #### being the processor
2893 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002894
Paul Jackson46b6d942008-07-04 10:00:09 -07002895 relax_domain_level=
2896 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002897 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002898
Linus Torvalds1da177e2005-04-16 15:20:36 -07002899 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2900
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002901 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002902 Format: nn[KMG]
2903 Reserves a hole at the top of the kernel virtual
2904 address space.
2905
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002906 reservelow= [X86]
2907 Format: nn[K]
2908 Set the amount of memory to reserve for BIOS at
2909 the bottom of the address space.
2910
Vivek Goyal7e962872006-09-27 01:50:44 -07002911 reset_devices [KNL] Force drivers to reset the underlying device
2912 during initialization.
2913
Randy Dunlapa9913042005-10-23 12:57:11 -07002914 resume= [SWSUSP]
2915 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02002916 Format:
2917 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002918
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002919 resume_offset= [SWSUSP]
2920 Specify the offset from the beginning of the partition
2921 given by "resume=" at which the swap header is located,
2922 in <PAGE_SIZE> units (needed only for swap files).
2923 See Documentation/power/swsusp-and-swap-files.txt
2924
Barry Songf126f732011-10-10 23:38:41 +02002925 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2926 read the resume files
2927
Barry Song6f8d7022011-10-06 20:34:46 +02002928 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2929 Useful for devices that are detected asynchronously
2930 (e.g. USB and MMC devices).
2931
Bojan Smojverf996fc92010-09-09 23:06:23 +02002932 hibernate= [HIBERNATION]
2933 noresume Don't check if there's a hibernation image
2934 present during boot.
2935 nocompress Don't compress/decompress hibernation images.
2936
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002937 retain_initrd [RAM] Keep initrd memory after extraction
2938
Linus Torvalds1da177e2005-04-16 15:20:36 -07002939 rhash_entries= [KNL,NET]
2940 Set number of hash buckets for route cache
2941
2942 riscom8= [HW,SERIAL]
2943 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2944
2945 ro [KNL] Mount root device read-only on boot
2946
2947 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07002948 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002949
2950 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2951 mount the root filesystem
2952
2953 rootflags= [KNL] Set root filesystem mount option string
2954
2955 rootfstype= [KNL] Set root filesystem type
2956
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002957 rootwait [KNL] Wait (indefinitely) for root device to show up.
2958 Useful for devices that are detected asynchronously
2959 (e.g. USB and MMC devices).
2960
Robert Tivy5c71d612013-03-28 18:41:46 -07002961 rproc_mem=nn[KMG][@address]
2962 [KNL,ARM,CMA] Remoteproc physical memory block.
2963 Memory area to be used by remote processor image,
2964 managed by CMA.
2965
Linus Torvalds1da177e2005-04-16 15:20:36 -07002966 rw [KNL] Mount root device read-write on boot
2967
2968 S [KNL] Run init in single mode
2969
2970 sa1100ir [NET]
2971 See drivers/net/irda/sa1100_ir.c.
2972
Linus Torvalds1da177e2005-04-16 15:20:36 -07002973 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002974
Mike Travisf6630112009-11-17 18:22:15 -06002975 sched_debug [KNL] Enables verbose scheduler debug messages.
2976
Mike Galbraith5307c952012-05-08 12:20:58 +02002977 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2978 xtime_lock contention on larger systems, and/or RCU lock
2979 contention on all systems with CONFIG_MAXSMP set.
2980 Format: { "0" | "1" }
2981 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2982 1 -- enable.
2983 Note: increases power consumption, thus should only be
2984 enabled if running jitter sensitive (HPC/RT) workloads.
2985
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002986 security= [SECURITY] Choose a security module to enable at boot.
2987 If this boot parameter is not specified, only the first
2988 security module asking for security registration will be
2989 loaded. An invalid security module name will be treated
2990 as if no module has been chosen.
2991
2992 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002993 Format: { "0" | "1" }
2994 See security/selinux/Kconfig help text.
2995 0 -- disable.
2996 1 -- enable.
2997 Default value is set via kernel config option.
2998 If enabled at boot time, /selinux/disable can be used
2999 later to disable prior to initial policy load.
3000
John Johansenc1c124e2010-07-29 14:48:09 -07003001 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3002 Format: { "0" | "1" }
3003 See security/apparmor/Kconfig help text
3004 0 -- disable.
3005 1 -- enable.
3006 Default value is set via kernel config option.
3007
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003008 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003009
Linus Torvalds1da177e2005-04-16 15:20:36 -07003010 shapers= [NET]
3011 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003012
Yinghai Lub05f78f2008-08-22 01:32:50 -07003013 show_msr= [x86] show boot-time MSR settings
3014 Format: { <integer> }
3015 Show boot-time (BIOS-initialized) MSR settings.
3016 The parameter means the number of CPUs to show,
3017 for example 1 means boot CPU only.
3018
Linus Torvalds1da177e2005-04-16 15:20:36 -07003019 simeth= [IA-64]
3020 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003021
Linus Torvalds1da177e2005-04-16 15:20:36 -07003022 slram= [HW,MTD]
3023
David Rientjes3df1ccc2011-10-18 22:09:28 -07003024 slab_max_order= [MM, SLAB]
3025 Determines the maximum allowed order for slabs.
3026 A high setting may cause OOMs due to memory
3027 fragmentation. Defaults to 1 for systems with
3028 more than 32MB of RAM, 0 otherwise.
3029
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003030 slub_debug[=options[,slabs]] [MM, SLUB]
3031 Enabling slub_debug allows one to determine the
3032 culprit if slab objects become corrupted. Enabling
3033 slub_debug can create guard zones around objects and
3034 may poison objects when not in use. Also tracks the
3035 last alloc / free. For more information see
3036 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003037
3038 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003039 Determines the maximum allowed order for slabs.
3040 A high setting may cause OOMs due to memory
3041 fragmentation. For more information see
3042 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003043
3044 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003045 The minimum number of objects per slab. SLUB will
3046 increase the slab order up to slub_max_order to
3047 generate a sufficiently large slab able to contain
3048 the number of objects indicated. The higher the number
3049 of objects the smaller the overhead of tracking slabs
3050 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003051 For more information see Documentation/vm/slub.txt.
3052
3053 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003054 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003055 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003056 For more information see Documentation/vm/slub.txt.
3057
3058 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003059 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07003060 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003061 allocs to different slabs. Debug options disable
3062 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003063 For more information see Documentation/vm/slub.txt.
3064
Linus Torvalds1da177e2005-04-16 15:20:36 -07003065 smart2= [HW]
3066 Format: <io1>[,<io2>[,...,<io8>]]
3067
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003068 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3069 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3070 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3071 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3072 smsc-ircc2.ircc_irq= [HW] IRQ line
3073 smsc-ircc2.ircc_dma= [HW] DMA channel
3074 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3075 0: Toshiba Satellite 1800 (GP data pin select)
3076 1: Fast pin select (default)
3077 2: ATC IRMode
3078
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003079 softlockup_panic=
3080 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003081 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003082
Linus Torvalds1da177e2005-04-16 15:20:36 -07003083 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003084 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003085
3086 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003087 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003088
3089 spia_io_base= [HW,MTD]
3090 spia_fio_base=
3091 spia_pedr=
3092 spia_peddr=
3093
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003094 stacktrace [FTRACE]
3095 Enabled the stack tracer on boot up.
3096
Steven Rostedt762e1202011-12-19 22:01:00 -05003097 stacktrace_filter=[function-list]
3098 [FTRACE] Limit the functions that the stack tracer
3099 will trace at boot up. function-list is a comma separated
3100 list of functions. This list can be changed at run
3101 time by the stack_trace_filter file in the debugfs
3102 tracing directory. Note, this enables stack tracing
3103 and the stacktrace above is not needed.
3104
Linus Torvalds1da177e2005-04-16 15:20:36 -07003105 sti= [PARISC,HW]
3106 Format: <num>
3107 Set the STI (builtin display/keyboard on the HP-PARISC
3108 machines) console (graphic card) which should be used
3109 as the initial boot-console.
3110 See also comment in drivers/video/console/sticore.c.
3111
3112 sti_font= [HW]
3113 See comment in drivers/video/console/sticore.c.
3114
3115 stifb= [HW]
3116 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3117
Trond Myklebustcbf11072009-08-09 15:06:19 -04003118 sunrpc.min_resvport=
3119 sunrpc.max_resvport=
3120 [NFS,SUNRPC]
3121 SunRPC servers often require that client requests
3122 originate from a privileged port (i.e. a port in the
3123 range 0 < portnr < 1024).
3124 An administrator who wishes to reserve some of these
3125 ports for other uses may adjust the range that the
3126 kernel's sunrpc client considers to be privileged
3127 using these two parameters to set the minimum and
3128 maximum port values.
3129
Greg Banks42a7fc42007-03-06 01:42:23 -08003130 sunrpc.pool_mode=
3131 [NFS]
3132 Control how the NFS server code allocates CPUs to
3133 service thread pools. Depending on how many NICs
3134 you have and where their interrupts are bound, this
3135 option will affect which CPUs will do NFS serving.
3136 Note: this parameter cannot be changed while the
3137 NFS server is running.
3138
3139 auto the server chooses an appropriate mode
3140 automatically using heuristics
3141 global a single global pool contains all CPUs
3142 percpu one pool for each CPU
3143 pernode one pool for each NUMA node (equivalent
3144 to global on non-NUMA machines)
3145
Trond Myklebustcbf11072009-08-09 15:06:19 -04003146 sunrpc.tcp_slot_table_entries=
3147 sunrpc.udp_slot_table_entries=
3148 [NFS,SUNRPC]
3149 Sets the upper limit on the number of simultaneous
3150 RPC calls that can be sent from the client to a
3151 server. Increasing these values may allow you to
3152 improve throughput, but will also increase the
3153 amount of memory reserved for use by the client.
3154
Michal Hocko07555ac2013-08-22 16:35:46 -07003155 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003156 [KNL] Enable accounting of swap in memory resource
3157 controller if no parameter or 1 is given or disable
3158 it if 0 is given (See Documentation/cgroups/memory.txt)
3159
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003160 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3161 Format: { <int> | force }
3162 <int> -- Number of I/O TLB slabs
3163 force -- force using of bounce buffers even if they
3164 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003165
Linus Torvalds1da177e2005-04-16 15:20:36 -07003166 switches= [HW,M68k]
3167
Andi Kleene52eec12010-09-08 16:54:17 +02003168 sysfs.deprecated=0|1 [KNL]
3169 Enable/disable old style sysfs layout for old udev
3170 on older distributions. When this option is enabled
3171 very new udev will not work anymore. When this option
3172 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3173 in older udev will not work anymore.
3174 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3175 the kernel configuration.
3176
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003177 sysrq_always_enabled
3178 [KNL]
3179 Ignore sysrq setting - this boot parameter will
3180 neutralize any effect of /proc/sys/kernel/sysrq.
3181 Useful for debugging.
3182
Linus Torvalds1da177e2005-04-16 15:20:36 -07003183 tdfx= [HW,DRM]
3184
David Brownell77437fd2008-07-23 21:28:33 -07003185 test_suspend= [SUSPEND]
3186 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3187 standby suspend) as the system sleep state to briefly
3188 enter during system startup. The system is woken from
3189 this state using a wakeup-capable RTC alarm.
3190
Linus Torvalds1da177e2005-04-16 15:20:36 -07003191 thash_entries= [KNL,NET]
3192 Set number of hash buckets for TCP connection
3193
Len Brownf8707ec2007-08-12 00:12:54 -04003194 thermal.act= [HW,ACPI]
3195 -1: disable all active trip points in all thermal zones
3196 <degrees C>: override all lowest active trip points
3197
Len Brownc52a7412007-08-14 15:49:32 -04003198 thermal.crt= [HW,ACPI]
3199 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003200 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003201
Len Brownf5487142007-08-12 00:12:44 -04003202 thermal.nocrt= [HW,ACPI]
3203 Set to disable actions on ACPI thermal zone
3204 critical and hot trip points.
3205
Len Brown72b33ef2007-08-12 00:12:17 -04003206 thermal.off= [HW,ACPI]
3207 1: disable ACPI thermal control
3208
Len Browna70cdc52007-08-12 00:12:35 -04003209 thermal.psv= [HW,ACPI]
3210 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003211 <degrees C>: override all passive trip points to this
3212 value
Len Browna70cdc52007-08-12 00:12:35 -04003213
Len Brown730ff342007-08-12 00:12:26 -04003214 thermal.tzp= [HW,ACPI]
3215 Specify global default ACPI thermal zone polling rate
3216 <deci-seconds>: poll all this frequency
3217 0: no polling (default)
3218
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003219 threadirqs [KNL]
3220 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003221 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003222
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003223 tmem [KNL,XEN]
3224 Enable the Transcendent memory driver if built-in.
3225
3226 tmem.cleancache=0|1 [KNL, XEN]
3227 Default is on (1). Disable the usage of the cleancache
3228 API to send anonymous pages to the hypervisor.
3229
3230 tmem.frontswap=0|1 [KNL, XEN]
3231 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003232 API to send swap pages to the hypervisor. If disabled
3233 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003234
3235 tmem.selfballooning=0|1 [KNL, XEN]
3236 Default is on (1). Disable the driving of swap pages
3237 to the hypervisor.
3238
3239 tmem.selfshrinking=0|1 [KNL, XEN]
3240 Default is on (1). Partial swapoff that immediately
3241 transfers pages from Xen hypervisor back to the
3242 kernel based on different criteria.
3243
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003244 topology= [S390]
3245 Format: {off | on}
3246 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003247 topology information if the hardware supports this.
3248 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003249 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003250 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003251
Linus Torvalds1da177e2005-04-16 15:20:36 -07003252 tp720= [HW,PS2]
3253
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003254 tpm_suspend_pcr=[HW,TPM]
3255 Format: integer pcr id
3256 Specify that at suspend time, the tpm driver
3257 should extend the specified pcr with zeros,
3258 as a workaround for some chips which fail to
3259 flush the last written pcr on TPM_SaveState.
3260 This will guarantee that all the other pcrs
3261 are saved.
3262
Li Zefan9d612be2009-06-24 17:33:15 +08003263 trace_buf_size=nn[KMG]
3264 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003265
Li Zefan020e5f82009-07-01 10:47:05 +08003266 trace_event=[event-list]
3267 [FTRACE] Set and start specified trace events in order
3268 to facilitate early boot debugging.
3269 See also Documentation/trace/events.txt
3270
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003271 trace_options=[option-list]
3272 [FTRACE] Enable or disable tracer options at boot.
3273 The option-list is a comma delimited list of options
3274 that can be enabled or disabled just as if you were
3275 to echo the option name into
3276
3277 /sys/kernel/debug/tracing/trace_options
3278
3279 For example, to enable stacktrace option (to dump the
3280 stack trace of each event), add to the command line:
3281
3282 trace_options=stacktrace
3283
3284 See also Documentation/trace/ftrace.txt "trace options"
3285 section.
3286
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003287 traceoff_on_warning
3288 [FTRACE] enable this option to disable tracing when a
3289 warning is hit. This turns off "tracing_on". Tracing can
3290 be enabled again by echoing '1' into the "tracing_on"
3291 file located in /sys/kernel/debug/tracing/
3292
3293 This option is useful, as it disables the trace before
3294 the WARNING dump is called, which prevents the trace to
3295 be filled with content caused by the warning output.
3296
3297 This option can also be set at run time via the sysctl
3298 option: kernel/traceoff_on_warning
3299
Jiri Kosinafcf4d822012-03-21 16:34:02 -07003300 transparent_hugepage=
3301 [KNL]
3302 Format: [always|madvise|never]
3303 Can be used to control the default behavior of the system
3304 with respect to transparent hugepages.
3305 See Documentation/vm/transhuge.txt for more details.
3306
john stultzd3b8f882009-08-17 16:40:47 -07003307 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003308 Format: <string>
3309 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003310 disables clocksource verification at runtime, as well
3311 as the stability checks done at bootup. Used to enable
3312 high-resolution timer mode on older hardware, and in
3313 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003314 [x86] noirqtime: Do not use TSC to do irq accounting.
3315 Used to run time disable IRQ_TIME_ACCOUNTING on any
3316 platforms where RDTSC is slow and this accounting
3317 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003318
Randy Dunlapa9913042005-10-23 12:57:11 -07003319 turbografx.map[2|3]= [HW,JOY]
3320 TurboGraFX parallel port interface
3321 Format:
3322 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003323 See also Documentation/input/joystick-parport.txt
3324
Christian Kujaub6935f82011-05-31 15:22:05 +00003325 udbg-immortal [PPC] When debugging early kernel crashes that
3326 happen after console_init() and before a proper
3327 console driver takes over, this boot options might
3328 help "seeing" what's going on.
3329
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003330 uhash_entries= [KNL,NET]
3331 Set number of hash buckets for UDP/UDP-Lite connections
3332
Alan Stern5f8364b2006-12-05 16:29:55 -05003333 uhci-hcd.ignore_oc=
3334 [USB] Ignore overcurrent events (default N).
3335 Some badly-designed motherboards generate lots of
3336 bogus events, for ports that aren't wired to
3337 anything. Set this parameter to avoid log spamming.
3338 Note that genuine overcurrent events won't be
3339 reported either.
3340
Simon Arlotte3a61b02008-07-19 23:32:54 +01003341 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003342 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003343
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003344 usbcore.authorized_default=
3345 [USB] Default USB device authorization:
3346 (default -1 = authorized except for wireless USB,
3347 0 = not authorized, 1 = authorized)
3348
Alan Sternb5e795f2007-02-20 15:00:53 -05003349 usbcore.autosuspend=
3350 [USB] The autosuspend time delay (in seconds) used
3351 for newly-detected USB devices (default 2). This
3352 is the time required before an idle device will be
3353 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003354 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003355
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003356 usbcore.usbfs_snoop=
3357 [USB] Set to log all usbfs traffic (default 0 = off).
3358
3359 usbcore.blinkenlights=
3360 [USB] Set to cycle leds on hubs (default 0 = off).
3361
3362 usbcore.old_scheme_first=
3363 [USB] Start with the old device initialization
3364 scheme (default 0 = off).
3365
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003366 usbcore.usbfs_memory_mb=
3367 [USB] Memory limit (in MB) for buffers allocated by
3368 usbfs (default = 16, 0 = max = 2047).
3369
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003370 usbcore.use_both_schemes=
3371 [USB] Try the other device initialization scheme
3372 if the first one fails (default 1 = enabled).
3373
3374 usbcore.initial_descriptor_timeout=
3375 [USB] Specifies timeout for the initial 64-byte
3376 USB_REQ_GET_DESCRIPTOR request in milliseconds
3377 (default 5000 = 5.0 seconds).
3378
Linus Torvalds1da177e2005-04-16 15:20:36 -07003379 usbhid.mousepoll=
3380 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003381
Alan Sternd4f373e2008-11-10 14:07:45 -05003382 usb-storage.delay_use=
3383 [UMS] The delay in seconds before a new device is
3384 scanned for Logical Units (default 5).
3385
3386 usb-storage.quirks=
3387 [UMS] A list of quirks entries to supplement or
3388 override the built-in unusual_devs list. List
3389 entries are separated by commas. Each entry has
3390 the form VID:PID:Flags where VID and PID are Vendor
3391 and Product ID values (4-digit hex numbers) and
3392 Flags is a set of characters, each corresponding
3393 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003394 a = SANE_SENSE (collect more than 18 bytes
3395 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003396 b = BAD_SENSE (don't collect more than 18
3397 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003398 c = FIX_CAPACITY (decrease the reported
3399 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003400 d = NO_READ_DISC_INFO (don't use
3401 READ_DISC_INFO command);
3402 e = NO_READ_CAPACITY_16 (don't use
3403 READ_CAPACITY_16 command);
Alan Sternc838ea42008-12-15 10:40:06 -05003404 h = CAPACITY_HEURISTICS (decrease the
3405 reported device capacity by one
3406 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003407 i = IGNORE_DEVICE (don't bind to this
3408 device);
3409 l = NOT_LOCKABLE (don't try to lock and
3410 unlock ejectable media);
3411 m = MAX_SECTORS_64 (don't transfer more
3412 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003413 n = INITIAL_READ10 (force a retry of the
3414 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003415 o = CAPACITY_OK (accept the capacity
3416 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003417 p = WRITE_CACHE (the device cache is ON
3418 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003419 r = IGNORE_RESIDUE (the device reports
3420 bogus residue values);
3421 s = SINGLE_LUN (the device has only one
3422 Logical Unit);
3423 w = NO_WP_DETECT (don't test whether the
3424 medium is write-protected).
3425 Example: quirks=0419:aaf5:rl,0421:0433:rc
3426
Stephen Boydac1667d2011-08-13 12:34:50 -07003427 user_debug= [KNL,ARM]
3428 Format: <int>
3429 See arch/arm/Kconfig.debug help text.
3430 1 - undefined instruction events
3431 2 - system calls
3432 4 - invalid data aborts
3433 8 - SIGSEGV faults
3434 16 - SIGBUS faults
3435 Example: user_debug=31
3436
Ian Campbell14315592010-02-17 10:38:10 +00003437 userpte=
3438 [X86] Flags controlling user PTE allocations.
3439
3440 nohigh = do not allocate PTE pages in
3441 HIGHMEM regardless of setting
3442 of CONFIG_HIGHPTE.
3443
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303444 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003445 On X86_32, this is an alias for vdso32=. Otherwise:
3446
3447 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07003448 vdso=0: disable VDSO mapping
3449
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003450 vdso32= [X86] Control the 32-bit vDSO
3451 vdso32=1: enable 32-bit VDSO
3452 vdso32=0 or vdso32=2: disable 32-bit VDSO
3453
3454 See the help text for CONFIG_COMPAT_VDSO for more
3455 details. If CONFIG_COMPAT_VDSO is set, the default is
3456 vdso32=0; otherwise, the default is vdso32=1.
3457
3458 For compatibility with older kernels, vdso32=2 is an
3459 alias for vdso32=0.
3460
3461 Try vdso32=0 if you encounter an error that says:
3462 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01003463
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003464 vector= [IA-64,SMP]
3465 vector=percpu: enable percpu vector domain
3466
Linus Torvalds1da177e2005-04-16 15:20:36 -07003467 video= [FB] Frame buffer configuration
3468 See Documentation/fb/modedb.txt.
3469
Aaron Lu3afe6da2013-06-20 15:08:55 +08003470 video.brightness_switch_enabled= [0,1]
3471 If set to 1, on receiving an ACPI notify event
3472 generated by hotkey, video driver will adjust brightness
3473 level and then send out the event to user space through
3474 the allocated input device; If set to 0, video driver
3475 will only send out the event without touching backlight
3476 brightness level.
3477 default: 1
3478
Pawel Moll81a054c2012-05-09 18:30:16 +01003479 virtio_mmio.device=
3480 [VMMIO] Memory mapped virtio (platform) device.
3481
3482 <size>@<baseaddr>:<irq>[:<id>]
3483 where:
3484 <size> := size (can use standard suffixes
3485 like K, M and G)
3486 <baseaddr> := physical base address
3487 <irq> := interrupt number (as passed to
3488 request_irq())
3489 <id> := (optional) platform device id
3490 example:
3491 virtio_mmio.device=1K@0x100b0000:48:7
3492
3493 Can be used multiple times for multiple devices.
3494
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003495 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003496 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003497 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003498 Use vga=ask for menu.
3499 This is actually a boot loader parameter; the value is
3500 passed to the kernel using a special protocol.
3501
Randy Dunlapa9913042005-10-23 12:57:11 -07003502 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003503 size of <nn>. This can be used to increase the
3504 minimum size (128MB on x86). It can also be used to
3505 decrease the size and leave more room for directly
3506 mapped kernel RAM.
3507
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003508 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3509 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003510
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003511 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3512 Format: <command>
3513
3514 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3515 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003516
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003517 vsyscall= [X86-64]
3518 Controls the behavior of vsyscalls (i.e. calls to
3519 fixed addresses of 0xffffffffff600x00 from legacy
3520 code). Most statically-linked binaries and older
3521 versions of glibc use these calls. Because these
3522 functions are at fixed addresses, they make nice
3523 targets for exploits that can control RIP.
3524
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003525 emulate [default] Vsyscalls turn into traps and are
3526 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003527
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003528 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003529 This is a little bit faster than trapping
3530 and makes a few dynamic recompilers work
3531 better than they would in emulation mode.
3532 It also makes exploits much easier to write.
3533
3534 none Vsyscalls don't work at all. This makes
3535 them quite hard to use for exploits but
3536 might break your system.
3537
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003538 vt.color= [VT] Default text color.
3539 Format: 0xYX, X = foreground, Y = background.
3540 Default: 0x07 = light gray on black.
3541
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08003542 vt.cur_default= [VT] Default cursor shape.
3543 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3544 the parameters of the <Esc>[?A;B;Cc escape sequence;
3545 see VGA-softcursor.txt. Default: 2 = underline.
3546
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003547 vt.default_blu= [VT]
3548 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3549 Change the default blue palette of the console.
3550 This is a 16-member array composed of values
3551 ranging from 0-255.
3552
3553 vt.default_grn= [VT]
3554 Format: <green0>,<green1>,<green2>,...,<green15>
3555 Change the default green palette of the console.
3556 This is a 16-member array composed of values
3557 ranging from 0-255.
3558
3559 vt.default_red= [VT]
3560 Format: <red0>,<red1>,<red2>,...,<red15>
3561 Change the default red palette of the console.
3562 This is a 16-member array composed of values
3563 ranging from 0-255.
3564
3565 vt.default_utf8=
3566 [VT]
3567 Format=<0|1>
3568 Set system-wide default UTF-8 mode for all tty's.
3569 Default is 1, i.e. UTF-8 mode is enabled for all
3570 newly opened terminals.
3571
Matthew Garrettf6c06b62009-11-13 15:14:11 -05003572 vt.global_cursor_default=
3573 [VT]
3574 Format=<-1|0|1>
3575 Set system-wide default for whether a cursor
3576 is shown on new VTs. Default is -1,
3577 i.e. cursors will be created by default unless
3578 overridden by individual drivers. 0 will hide
3579 cursors, 1 will display them.
3580
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003581 vt.italic= [VT] Default color for italic text; 0-15.
3582 Default: 2 = green.
3583
3584 vt.underline= [VT] Default color for underlined text; 0-15.
3585 Default: 3 = cyan.
3586
Randy Dunlap4724ba572010-05-03 11:42:52 -07003587 watchdog timers [HW,WDT] For information on watchdog timers,
3588 see Documentation/watchdog/watchdog-parameters.txt
3589 or other driver-specific files in the
3590 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003591
Tejun Heod55262c2013-04-01 11:23:38 -07003592 workqueue.disable_numa
3593 By default, all work items queued to unbound
3594 workqueues are affine to the NUMA nodes they're
3595 issued on, which results in better behavior in
3596 general. If NUMA affinity needs to be disabled for
3597 whatever reason, this option can be used. Note
3598 that this also can be controlled per-workqueue for
3599 workqueues visible under /sys/bus/workqueue/.
3600
Viresh Kumarcee22a12013-04-08 16:45:40 +05303601 workqueue.power_efficient
3602 Per-cpu workqueues are generally preferred because
3603 they show better performance thanks to cache
3604 locality; unfortunately, per-cpu workqueues tend to
3605 be more power hungry than unbound workqueues.
3606
3607 Enabling this makes the per-cpu workqueues which
3608 were observed to contribute significantly to power
3609 consumption unbound, leading to measurably lower
3610 power usage at the cost of small performance
3611 overhead.
3612
3613 The default value of this parameter is determined by
3614 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3615
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003616 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3617 default x2apic cluster mode on platforms
3618 supporting x2apic.
3619
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003620 x86_intel_mid_timer= [X86-32,APBT]
3621 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07003622 Two valid options are apbt timer only and lapic timer
3623 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003624 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07003625
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003626 xen_emul_unplug= [HW,X86,XEN]
3627 Unplug Xen emulated devices
3628 Format: [unplug0,][unplug1]
3629 ide-disks -- unplug primary master IDE devices
3630 aux-ide-disks -- unplug non-primary-master IDE devices
3631 nics -- unplug network devices
3632 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01003633 unnecessary -- unplugging emulated devices is
3634 unnecessary even if the host did not respond to
3635 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01003636 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003637
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04003638 xen_nopvspin [X86,XEN]
3639 Disables the ticketlock slowpath using Xen PV
3640 optimizations.
3641
Linus Torvalds1da177e2005-04-16 15:20:36 -07003642 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07003643 Format:
3644 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003645
Randy Dunlapa9913042005-10-23 12:57:11 -07003646______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07003647
3648TODO:
3649
Linus Torvalds1da177e2005-04-16 15:20:36 -07003650 Add more DRM drivers.