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Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -07003
Rusty Russell5888bcc2014-05-14 10:33:45 +09304The following is a consolidated list of the kernel parameters as
5implemented by the __setup(), core_param() and module_param() macros
6and sorted into English Dictionary order (defined as ignoring all
7punctuation and sorting digits before letters in a case insensitive
8manner), and with descriptions where known.
Linus Torvalds1da177e2005-04-16 15:20:36 -07009
Rusty Russell5888bcc2014-05-14 10:33:45 +093010The kernel parses parameters from the kernel command line up to "--";
11if it doesn't recognize a parameter and it doesn't contain a '.', the
12parameter gets passed to init: parameters with '=' go into init's
13environment, others are passed as command line arguments to init.
14Everything after "--" is passed as an argument to init.
Linus Torvalds1da177e2005-04-16 15:20:36 -070015
Rusty Russell5888bcc2014-05-14 10:33:45 +093016Module parameters can be specified in two ways: via the kernel command
17line with a module name prefix, or via modprobe, e.g.:
Linus Torvalds1da177e2005-04-16 15:20:36 -070018
Rusty Russell5888bcc2014-05-14 10:33:45 +093019 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
Linus Torvalds1da177e2005-04-16 15:20:36 -070021
Rusty Russell5888bcc2014-05-14 10:33:45 +093022Parameters for modules which are built into the kernel need to be
23specified on the kernel command line. modprobe looks through the
24kernel command line (/proc/cmdline) and collects module parameters
25when it loads a module, so the kernel command line can be used for
26loadable modules too.
Linus Torvalds1da177e2005-04-16 15:20:36 -070027
Randy Dunlapca1eda22009-05-06 16:02:58 -070028Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30can also be entered as
31 log-buf-len=1M print_fatal_signals=1
32
Rusty Russell5888bcc2014-05-14 10:33:45 +093033Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
Randy Dunlapca1eda22009-05-06 16:02:58 -070035
Stefan Richtera901ebb2006-04-01 01:43:18 +020036This document may not be entirely up to date and comprehensive. The command
37"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38module. Loadable modules, after being loaded into the running kernel, also
39reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40parameters may be changed at runtime by the command
41"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
42
Stefan Richter6585fa82006-04-01 01:44:30 +020043The parameters listed below are only valid if certain kernel build options were
44enabled and if respective hardware is present. The text in square brackets at
45the beginning of each description states the restrictions within which a
46parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070047
48 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100049 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070050 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070053 ARM ARM architecture is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020054 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080056 BLACKFIN Blackfin architecture is enabled.
Olof Johansson1e435252013-04-27 14:10:18 -070057 CLK Common clock infrastructure is enabled.
Robert Tivy5c71d612013-03-28 18:41:46 -070058 CMA Contiguous Memory Area support is enabled.
Alan Cox9cfe2682011-01-25 14:18:38 +000059 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
Mimi Zohar7102ebc2011-05-12 18:33:20 -040064 EVM Extended Verification Module
Linus Torvalds1da177e2005-04-16 15:20:36 -070065 FB The frame buffer device is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070066 FTRACE Function tracing enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070067 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070069 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050070 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070071 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070072 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080073 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050077 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020078 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070079 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070086 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070088 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070089 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070090 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070094 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070098 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -0700107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -0700109 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -0700111 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900113 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300118 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500120 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
Pawel Moll81a054c2012-05-09 18:30:16 +0100124 VMMIO Driver for memory mapped virtio devices is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700129 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700132 Documentation/x86/x86_64/boot-options.txt .
Randy Dunlap16290242011-08-13 12:34:52 -0700133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100134 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135
136In addition, the following text indicates that the option:
137
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
141
142Parameters denoted with BOOT are actually interpreted by the boot
143loader, and have no meaning to the kernel directly.
144Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500145need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146
Karsten Weiss55588702007-02-13 13:26:21 +0100147There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700148See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100149
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151a trailing = on the name of any parameter states that that parameter will
152be entered as an environment variable, whereas its absence indicates that
153it will appear as a kernel argument readable via /proc/cmdline by programs
154running once the system is up.
155
jens m. noedler9c4751f2006-09-29 02:00:27 -0700156The number of kernel parameters is not limited, but the length of the
157complete command line (parameters including spaces etc.) is limited to
158a fixed number of characters. This limit depends on the architecture
159and is between 256 and 4096 characters. It is defined in the file
160./include/asm/setup.h as COMMAND_LINE_SIZE.
161
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800162Finally, the [KMG] suffix is commonly described after a number of kernel
163parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165bytes respectively. Such letter suffixes can also be entirely omitted.
166
jens m. noedler9c4751f2006-09-29 02:00:27 -0700167
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530168 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800169 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500170 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700174 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800176 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800177 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178
Paul Bolle395cf962011-08-15 02:02:26 +0200179 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180
Takao Indoh4996c022011-07-14 18:05:21 -0400181 acpi_rsdp= [ACPI,EFI,KEXEC]
182 Pass the RSDP address to the kernel, mostly used
183 on machines running EFI runtime service to boot the
184 second kernel for kdump.
185
Len Browna1fdcc02007-03-11 03:26:14 -0400186 acpi_apic_instance= [ACPI, IOAPIC]
187 Format: <int>
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400190 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400191
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
194 acpi_backlight=video
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
198
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700199 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
200 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700202 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203 debug output. Bits in debug_layer correspond to a
204 _COMPONENT in an ACPI source file, e.g.,
205 #define _COMPONENT ACPI_PCI_COMPONENT
206 Bits in debug_level correspond to a level in
207 ACPI_DEBUG_PRINT statements, e.g.,
208 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600209 The debug_level mask defaults to "info". See
210 Documentation/acpi/debug.txt for more information about
211 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600213 Enable processor driver info messages:
214 acpi.debug_layer=0x20000000
215 Enable PCI/PCI interrupt routing info messages:
216 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700217 Enable AML "Debug" output, i.e., stores to the Debug
218 object while interpreting AML:
219 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700220 Enable all messages related to ACPI hardware:
221 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200222
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700223 Some values produce so much output that the system is
224 unusable. The "log_buf_len" parameter may be useful
225 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800226
Lv Zheng4fc0a7e2014-05-31 08:15:02 +0800227 acpi_force_table_verification [HW,ACPI]
228 Enable table checksum verification during early stage.
229 By default, this is disabled due to x86 early mapping
230 size limitation.
231
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700232 acpi_irq_balance [HW,ACPI]
233 ACPI will balance active IRQs
234 default in APIC mode
235
236 acpi_irq_nobalance [HW,ACPI]
237 ACPI will not move active IRQs (default)
238 default in PIC mode
239
240 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241 Format: <irq>,<irq>...
242
243 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
244 use by PCI
245 Format: <irq>,<irq>...
246
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800247 acpi_no_auto_serialize [HW,ACPI]
248 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800249 AML control methods that contain the opcodes to create
250 named objects will be marked as "Serialized" by the
251 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800252 This feature is enabled by default.
253 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800254
Lv Zhenga94e88c2014-04-04 12:39:11 +0800255 acpi_no_static_ssdt [HW,ACPI]
256 Disable installation of static SSDTs at early boot time
257 By default, SSDTs contained in the RSDT/XSDT will be
258 installed automatically and they will appear under
259 /sys/firmware/acpi/tables.
260 This option turns off this feature.
261 Note that specifying this option does not affect
262 dynamic table installation which will install SSDT
263 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700264
Lv Zheng4dde5072014-02-11 11:01:52 +0800265 acpica_no_return_repair [HW, ACPI]
266 Disable AML predefined validation mechanism
267 This mechanism can repair the evaluation result to make
268 the return objects more ACPI specification compliant.
269 This option is useful for developers to identify the
270 root cause of an AML interpreter issue when the issue
271 has something to do with the repair mechanism.
272
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700273 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
274 Format: To spoof as Windows 98: ="Microsoft Windows"
275
276 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800277 acpi_osi="string1" # add string1
278 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800279 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800280 acpi_osi=! # disable all built-in OS vendor
281 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700282 acpi_osi= # disable all strings
283
Lv Zheng5dc17982013-07-22 16:08:25 +0800284 'acpi_osi=!' can be used in combination with single or
285 multiple 'acpi_osi="string1"' to support specific OS
286 vendor string(s). Note that such command can only
287 affect the default state of the OS vendor strings, thus
288 it cannot affect the default state of the feature group
289 strings and the current state of the OS vendor strings,
290 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800291 is meaningless. This command is useful when one do not
292 care about the state of the feature group strings which
293 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800294 Examples:
295 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297 can make '_OSI("Windows 2000")' TRUE.
298
299 'acpi_osi=' cannot be used in combination with other
300 'acpi_osi=' command lines, the _OSI method will not
301 exist in the ACPI namespace. NOTE that such command can
302 only affect the _OSI support state, thus specifying it
303 multiple times through kernel command line is also
304 meaningless.
305 Examples:
306 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
307 FALSE.
308
Lv Zheng741d8122013-07-22 16:08:36 +0800309 'acpi_osi=!*' can be used in combination with single or
310 multiple 'acpi_osi="string1"' to support specific
311 string(s). Note that such command can affect the
312 current state of both the OS vendor strings and the
313 feature group strings, thus specifying it multiple times
314 through kernel command line is meaningful. But it may
315 still not able to affect the final state of a string if
316 there are quirks related to this string. This command
317 is useful when one want to control the state of the
318 feature group strings to debug BIOS issues related to
319 the OSPM features.
320 Examples:
321 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322 '_OSI("Module Device")' FALSE.
323 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324 '_OSI("Module Device")' TRUE.
325 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
326 equivalent to
327 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
328 and
329 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330 they all will make '_OSI("Windows 2000")' TRUE.
331
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530332 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700333 Override the pmtimer bug detection: force the kernel
334 to assume that this machine's pmtimer latches its value
335 and always returns good values.
336
Randy Dunlap4af94f32009-04-17 18:30:28 -0700337 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
338 Format: { level | edge | high | low }
339
Randy Dunlap4af94f32009-04-17 18:30:28 -0700340 acpi_skip_timer_override [HW,ACPI]
341 Recognize and ignore IRQ0/pin2 Interrupt Override.
342 For broken nForce2 BIOS resulting in XT-PIC timer.
343
344 acpi_sleep= [HW,ACPI] Sleep options
345 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200346 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700347 See Documentation/power/video.txt for information on
348 s3_bios and s3_mode.
349 s3_beep is for debugging; it makes the PC's speaker beep
350 as soon as the kernel's real-mode entry point is called.
351 s4_nohwsig prevents ACPI hardware signature from being
352 used during resume from hibernation.
353 old_ordering causes the ACPI 1.0 ordering of the _PTS
354 control method, with respect to putting devices into
355 low power states, to be enforced (the ACPI 2.0 ordering
356 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200357 nonvs prevents the kernel from saving/restoring the
358 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800359 sci_force_enable causes the kernel to set SCI_EN directly
360 on resume from S1/S3 (which is against the ACPI spec,
361 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700362
363 acpi_use_timer_override [HW,ACPI]
364 Use timer override. For some broken Nvidia NF5 boards
365 that require a timer override, but don't have HPET
366
Luca Tettamanti7e905602009-03-30 00:01:27 +0200367 acpi_enforce_resources= [ACPI]
368 { strict | lax | no }
369 Check for resource conflicts between native drivers
370 and ACPI OperationRegions (SystemIO and SystemMemory
371 only). IO ports and memory declared in ACPI might be
372 used by the ACPI subsystem in arbitrary AML code and
373 can interfere with legacy drivers.
374 strict (default): access to resources claimed by ACPI
375 is denied; legacy drivers trying to access reserved
376 resources will fail to bind to device using them.
377 lax: access to resources claimed by ACPI is allowed;
378 legacy drivers trying to access reserved resources
379 will bind successfully but a warning message is logged.
380 no: ACPI OperationRegions are not marked as reserved,
381 no further checks are performed.
382
Prarit Bhargava00159a22014-01-14 14:21:13 -0500383 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
384 kernels.
385
Randy Dunlap4af94f32009-04-17 18:30:28 -0700386 add_efi_memmap [EFI; X86] Include EFI memory map in
387 kernel's map of available physical RAM.
388
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700389 agp= [AGP]
390 { off | try_unsupported }
391 off: disable AGP support
392 try_unsupported: try to drive unsupported chipsets
393 (may crash computer or cause data corruption)
394
Randy Dunlapbcfde332010-06-07 17:10:38 -0700395 ALSA [HW,ALSA]
396 See Documentation/sound/alsa/alsa-parameters.txt
397
Russell Kingd944d542010-02-20 16:13:29 +0000398 alignment= [KNL,ARM]
399 Allow the default userspace alignment fault handler
400 behaviour to be specified. Bit 0 enables warnings,
401 bit 1 enables fixups, and bit 2 sends a segfault.
402
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200403 align_va_addr= [X86-64]
404 Align virtual addresses by clearing slice [14:12] when
405 allocating a VMA at process creation time. This option
406 gives you up to 3% performance improvement on AMD F15h
407 machines (where it is enabled by default) for a
408 CPU-intensive style benchmark, and it can vary highly in
409 a microbenchmark depending on workload and compiler.
410
Borislav Petkov8360ee22011-11-21 12:10:19 +0100411 32: only for 32-bit processes
412 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200413 on: enable for both 32- and 64-bit processes
414 off: disable for both 32- and 64-bit processes
415
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500416 alloc_snapshot [FTRACE]
417 Allocate the ftrace snapshot buffer on boot up when the
418 main buffer is allocated. This is handy if debugging
419 and you need to use tracing_snapshot() on boot up, and
420 do not want to use tracing_snapshot_alloc() as it needs
421 to be done where GFP_KERNEL allocations are allowed.
422
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100423 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200424 Pass parameters to the AMD IOMMU driver in the system.
425 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900426 fullflush - enable flushing of IO/TLB entries when
427 they are unmapped. Otherwise they are
428 flushed before they will be reused, which
429 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200430 off - do not initialize any AMD IOMMU found in
431 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100432 force_isolation - Force device isolation for all
433 devices. The IOMMU driver is not
434 allowed anymore to lift isolation
435 requirements as needed. This option
436 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900437
Shuah Khanc099cf12012-05-24 15:58:25 -0600438 amd_iommu_dump= [HW,X86-64]
439 Enable AMD IOMMU driver option to dump the ACPI table
440 for AMD IOMMU. With this option enabled, AMD IOMMU
441 driver will print ACPI tables for AMD IOMMU during
442 IOMMU initialization.
443
Linus Torvalds1da177e2005-04-16 15:20:36 -0700444 amijoy.map= [HW,JOY] Amiga joystick support
445 Map of devices attached to JOY0DAT and JOY1DAT
446 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200447 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700448
449 analog.map= [HW,JOY] Analog joystick and gamepad support
450 Specifies type or capabilities of an analog joystick
451 connected to one of 16 gameports
452 Format: <type1>,<type2>,..<type16>
453
Randy Dunlapa9913042005-10-23 12:57:11 -0700454 apc= [HW,SPARC]
455 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456 Format: noidle
457 Disable APC CPU standby support. SPARCstation-Fox does
458 not play well with APC CPU idle - disable it if you have
459 APC and your system crashes randomly.
460
Randy Dunlapca1eda22009-05-06 16:02:58 -0700461 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700462 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463 Format: { quiet (default) | verbose | debug }
464 Change the amount of debugging information output
465 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700466
Brian Haleyb0f83b22010-02-04 13:36:50 -0800467 autoconf= [IPV6]
468 See Documentation/networking/ipv6.txt.
469
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400470 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
471 Limit apic dumping. The parameter defines the maximal
472 number of local apics being dumped. Also it is possible
473 to set it to "all" by meaning -- no limit here.
474 Format: { 1 (default) | 2 | ... | all }.
475 The parameter valid if only apic=debug or
476 apic=verbose is specified.
477 Example: apic=debug show_lapic=all
478
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700480 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700481
Linus Torvalds1da177e2005-04-16 15:20:36 -0700482 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483 Format: <io>,<irq>,<nodeID>
484
485 ataflop= [HW,M68k]
486
487 atarimouse= [HW,MOUSE] Atari Mouse
488
Linus Torvalds1da177e2005-04-16 15:20:36 -0700489 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
490 EzKey and similar keyboards
491
492 atkbd.reset= [HW] Reset keyboard during initialization
493
Randy Dunlapa9913042005-10-23 12:57:11 -0700494 atkbd.set= [HW] Select keyboard code set
495 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700496
497 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
498 keyboards
499
500 atkbd.softraw= [HW] Choose between synthetic and real raw mode
501 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700502
503 atkbd.softrepeat= [HW]
504 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700505
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400506 audit= [KNL] Enable the audit sub-system
507 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500508 0 - kernel audit is disabled and can not be enabled
509 until the next reboot
510 unset - kernel audit is initialized but disabled and
511 will be fully enabled by the userspace auditd.
512 1 - kernel audit is initialized and partially enabled,
513 storing at most audit_backlog_limit messages in
514 RAM until it is fully enabled by the userspace
515 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400516 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400517
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400518 audit_backlog_limit= [KNL] Set the audit queue size limit.
519 Format: <int> (must be >=0)
520 Default: 64
521
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 baycom_epp= [HW,AX25]
523 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700524
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
526 Format: <io>,<mode>
527 See header of drivers/net/hamradio/baycom_par.c.
528
Randy Dunlapa9913042005-10-23 12:57:11 -0700529 baycom_ser_fdx= [HW,AX25]
530 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700531 Format: <io>,<irq>,<mode>[,<baud>]
532 See header of drivers/net/hamradio/baycom_ser_fdx.c.
533
Randy Dunlapa9913042005-10-23 12:57:11 -0700534 baycom_ser_hdx= [HW,AX25]
535 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536 Format: <io>,<irq>,<mode>
537 See header of drivers/net/hamradio/baycom_ser_hdx.c.
538
Paul Gortmaker080506a2013-09-30 13:45:19 -0700539 blkdevparts= Manual partition parsing of block device(s) for
540 embedded devices based on command line input.
541 See Documentation/block/cmdline-partition.txt
542
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700543 boot_delay= Milliseconds to delay each printk during boot.
544 Values larger than 10 seconds (10000) are changed to
545 no delay (0).
546 Format: integer
547
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700548 bootmem_debug [KNL] Enable bootmem allocator debug messages.
549
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700551 bttv.radio= Most important insmod options are available as
552 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200554 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000556 bulk_remove=off [PPC] This parameter disables the use of the pSeries
557 firmware feature for flushing multiple hpte entries
558 at a time.
559
Linus Torvalds1da177e2005-04-16 15:20:36 -0700560 c101= [NET] Moxa C101 synchronous serial card
561
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700562 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700563 Sometimes CPU hardware bugs make them report the cache
564 size incorrectly. The kernel will attempt work arounds
565 to fix known problems, but for some CPUs it is not
566 possible to determine what the correct size should be.
567 This option provides an override for these situations.
568
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300569 ca_keys= [KEYS] This parameter identifies a specific key(s) on
570 the system trusted keyring to be used for certificate
571 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300572 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300573
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700574 cca= [MIPS] Override the kernel pages' cache coherency
575 algorithm. Accepted values range from 0 to 7
576 inclusive. See arch/mips/include/asm/pgtable-bits.h
577 for platform specific values (SB1, Loongson3 and
578 others).
579
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100580 ccw_timeout_log [S390]
581 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582
Paul Menage8bab8dd2008-04-04 14:29:57 -0700583 cgroup_disable= [KNL] Disable a particular controller
584 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800585 The effects of cgroup_disable=foo are:
586 - foo isn't auto-mounted if you mount all cgroups in
587 a single hierarchy
588 - foo isn't visible as an individually mountable
589 subsystem
590 {Currently only "memory" controller deal with this and
591 cut the overhead, others just disable the usage. So
592 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700593
Linus Torvalds1da177e2005-04-16 15:20:36 -0700594 checkreqprot [SELINUX] Set initial checkreqprot flag value.
595 Format: { "0" | "1" }
596 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700597 0 -- check protection applied by kernel (includes
598 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599 1 -- check protection requested by application.
600 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700601 Value can be changed at runtime via
602 /selinux/checkreqprot.
603
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100604 cio_ignore= [S390]
605 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700606 clk_ignore_unused
607 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700608 Prevents the clock framework from automatically gating
609 clocks that have not been explicitly enabled by a Linux
610 device driver but are enabled in hardware at reset or
611 by the bootloader/firmware. Note that this does not
612 force such clocks to be always-on nor does it reserve
613 those clocks in any way. This parameter is useful for
614 debug and development, but should not be needed on a
615 platform with proper driver support. For more
616 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100617
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700618 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700619 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200620 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700621 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200622 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700623 Format: { pit | tsc | cyclone | pmtmr }
624
John Stultz592913e2010-07-13 17:56:20 -0700625 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700626 Format: <string>
627 Override the default clocksource and use the clocksource
628 with the name specified.
629 Some clocksource names to choose from, depending on
630 the platform:
631 [all] jiffies (this is the base, fallback clocksource)
632 [ACPI] acpi_pm
633 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
634 pxa_timer,timer3,32k_counter,timer0_1
635 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700636 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700637 scx200_hrt on Geode; cyclone on IBM x440
638 [MIPS] MIPS
639 [PARISC] cr16
640 [S390] tod
641 [SH] SuperH
642 [SPARC64] tick
643 [X86-64] hpet,tsc
644
Andi Kleenac72e782008-01-30 13:33:21 +0100645 clearcpuid=BITNUM [X86]
646 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800647 arch/x86/include/asm/cpufeature.h for the valid bit
648 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100649 stable over kernel options, but the vendor specific
650 ones should be.
651 Also note that user programs calling CPUID directly
652 or using the feature without checking anything
653 will still see it. This just prevents it from
654 being used by the kernel or shown in /proc/cpuinfo.
655 Also note the kernel might malfunction if you disable
656 some critical bits.
657
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700658 cma=nn[MG]@[start[MG][-end[MG]]]
659 [ARM,X86,KNL]
660 Sets the size of kernel global memory area for
661 contiguous memory allocations and optionally the
662 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700663 memory allocations. A value of 0 disables CMA
664 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100665 include/linux/dma-contiguous.h
666
Robert Jennings14f966e2009-04-15 05:55:32 +0000667 cmo_free_hint= [PPC] Format: { yes | no }
668 Specify whether pages are marked as being inactive
669 when they are freed. This is used in CMO environments
670 to determine OS memory pressure for page stealing by
671 a hypervisor.
672 Default: yes
673
Marek Szyprowskic7909502011-12-29 13:09:51 +0100674 coherent_pool=nn[KMG] [ARM,KNL]
675 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200676 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100677
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530678 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100679 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100680 Range: 0 - 8192
681 Default: 64
682
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700684 Format:
685 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700686
687 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
688 Format: <io>[,<irq>]
689
Randy Dunlapa9913042005-10-23 12:57:11 -0700690 com90xx= [HW,NET]
691 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692 Format: <io>[,<irq>[,<memstart>]]
693
694 condev= [HW,S390] console device
695 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700696
Linus Torvalds1da177e2005-04-16 15:20:36 -0700697 console= [KNL] Output console device and options.
698
699 tty<n> Use the virtual console device <n>.
700
701 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800702 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800704 the form "bbbbpnf", where "bbbb" is the baud rate,
705 "p" is parity ("n", "o", or "e"), "n" is number of
706 bits, and "f" is flow control ("r" for RTS or
707 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800709 See Documentation/serial-console.txt for more
710 information. See
711 Documentation/networking/netconsole.txt for an
712 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700713
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700714 uart[8250],io,<addr>[,options]
715 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716 Start an early, polled-mode console on the 8250/16550
717 UART at the specified I/O port or MMIO address,
718 switching to the matching ttyS device later. The
719 options are the same as for ttyS, above.
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500720 hvc<n> Use the hypervisor console device <n>. This is for
721 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700723 If the device connected to the port is not a TTY but a braille
724 device, prepend "brl," before the device type, for instance
725 console=brl,ttyS0
726 For now, only VisioBraille is supported.
727
Daniel Mackf324edc2009-06-16 15:33:52 -0700728 consoleblank= [KNL] The console blank (screen saver) timeout in
729 seconds. Defaults to 10*60 = 10mins. A value of 0
730 disables the blank timer.
731
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800732 coredump_filter=
733 [KNL] Change the default value for
734 /proc/<pid>/coredump_filter.
735 See also Documentation/filesystems/proc.txt.
736
Len Brown62027ae2011-04-01 18:13:10 -0400737 cpuidle.off=1 [CPU_IDLE]
738 disable the cpuidle sub-system
739
Linus Torvalds1da177e2005-04-16 15:20:36 -0700740 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700741 Format:
742 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700743
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800744 crashkernel=size[KMG][@offset[KMG]]
745 [KNL] Using kexec, Linux can switch to a 'crash kernel'
746 upon panic. This parameter reserves the physical
747 memory region [offset, offset + size] for that kernel
748 image. If '@offset' is omitted, then a suitable offset
749 is selected automatically. Check
750 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700751
Bernhard Wallefb391592007-10-18 23:41:02 -0700752 crashkernel=range1:size1[,range2:size2,...][@offset]
753 [KNL] Same as above, but depends on the memory
754 in the running system. The syntax of range is
755 start-[end] where start and end are both
756 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800757 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700758
Yinghai Luadbc7422013-04-15 22:23:48 -0700759 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700760 [KNL, x86_64] range could be above 4G. Allow kernel
761 to allocate physical memory region from top, so could
762 be above 4G if system have more than 4G ram installed.
763 Otherwise memory region will be allocated below 4G, if
764 available.
765 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700766 crashkernel=size[KMG],low
767 [KNL, x86_64] range under 4G. When crashkernel=X,high
768 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700769 above 4G, that cause second kernel crash on system
770 that require some amount of low memory, e.g. swiotlb
771 requires at least 64M+32K low memory. Kernel would
772 try to allocate 72M below 4G automatically.
773 This one let user to specify own low range under 4G
774 for second kernel instead.
775 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700776 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700777 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700778
Linus Torvalds1da177e2005-04-16 15:20:36 -0700779 cs89x0_dma= [HW,NET]
780 Format: <dma>
781
782 cs89x0_media= [HW,NET]
783 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700784
Randy Dunlapa9913042005-10-23 12:57:11 -0700785 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700786 See header of drivers/s390/block/dasd_devmap.c.
787
788 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
789 (one device per port)
790 Format: <port#>,<type>
791 See also Documentation/input/joystick-parport.txt
792
Thomas Renningera648ec02010-08-06 16:11:02 +0200793 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
794 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600795 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200796
Linus Torvalds1da177e2005-04-16 15:20:36 -0700797 debug [KNL] Enable kernel debugging (events log level).
798
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700799 debug_locks_verbose=
800 [KNL] verbose self-tests
801 Format=<0|1>
802 Print debugging info while doing the locking API
803 self-tests.
804 We default to 0 (no extra messages), setting it to
805 1 will print _a lot_ more information - normally
806 only useful to kernel developers.
807
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700808 debug_objects [KNL] Enable object debugging
809
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500810 no_debug_objects
811 [KNL] Disable object debugging
812
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800813 debug_guardpage_minorder=
814 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
815 parameter allows control of the order of pages that will
816 be intentionally kept free (and hence protected) by the
817 buddy allocator. Bigger value increase the probability
818 of catching random memory corruption, but reduce the
819 amount of memory for normal system use. The maximum
820 possible value is MAX_ORDER/2. Setting this parameter
821 to 1 or 2 should be enough to identify most random
822 memory corruption problems caused by bugs in kernel or
823 driver code when a CPU writes to (or reads from) a
824 random memory location. Note that there exists a class
825 of memory corruptions problems caused by buggy H/W or
826 F/W or by drivers badly programing DMA (basically when
827 memory is written at bus level and the CPU MMU is
828 bypassed) which are not detectable by
829 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
830 tracking down these problems.
831
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200832 debugpat [X86] Enable PAT debugging
833
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200834 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700835 Format: <area>[,<node>]
836 See also Documentation/networking/decnet.txt.
837
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700838 default_hugepagesz=
839 [same as hugepagesz=] The size of the default
840 HugeTLB page size. This is the size represented by
841 the legacy /proc/ hugepages APIs, used for SHM, and
842 default size when mounting hugetlbfs filesystems.
843 Defaults to the default architecture's huge page size
844 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700845
Linus Torvalds1da177e2005-04-16 15:20:36 -0700846 dhash_entries= [KNL]
847 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700848
Brian Haleyb0f83b22010-02-04 13:36:50 -0800849 disable= [IPV6]
850 See Documentation/networking/ipv6.txt.
851
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900852 disable_cpu_apicid= [X86,APIC,SMP]
853 Format: <int>
854 The number of initial APIC ID for the
855 corresponding CPU to be disabled at boot,
856 mostly used for the kdump 2nd kernel to
857 disable BSP to wake up multiple CPUs without
858 causing system reset or hang due to sending
859 INIT from AP to BSP.
860
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000861 disable_ddw [PPC/PSERIES]
862 Disable Dynamic DMA Window support. Use this if
863 to workaround buggy firmware.
864
Brian Haleyb0f83b22010-02-04 13:36:50 -0800865 disable_ipv6= [IPV6]
866 See Documentation/networking/ipv6.txt.
867
Yinghai Lu95ffa242008-04-29 03:52:33 -0700868 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700869 The kernel tries to adjust MTRR layout from continuous
870 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700871 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700872
Yinghai Lu093af8d2008-01-30 13:33:32 +0100873 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100874 By default the kernel will trim any uncacheable
875 memory out of your available memory pool based on
876 MTRR settings. This parameter disables that behavior,
877 possibly causing your machine to run very slowly.
878
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530879 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700880 Disable PIN 1 of APIC timer
881 Can be useful to work around chipset bugs.
882
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700883 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
884 this option disables the debugging code at boot.
885
886 dma_debug_entries=<number>
887 This option allows to tune the number of preallocated
888 entries for DMA-API debugging code. One entry is
889 required per DMA-API allocation. Use this if the
890 DMA-API debugging code disables itself because the
891 architectural default is too low.
892
Joerg Roedel1745de52009-05-22 21:49:51 +0200893 dma_debug_driver=<driver_name>
894 With this option the DMA-API debugging driver
895 filter feature can be enabled at boot time. Just
896 pass the driver to filter for as the parameter.
897 The filter can be disabled or changed to another
898 driver later using sysfs.
899
Carsten Emdeda0df922012-03-18 22:37:33 +0100900 drm_kms_helper.edid_firmware=[<connector>:]<file>
901 Broken monitors, graphic adapters and KVMs may
902 send no or incorrect EDID data sets. This parameter
903 allows to specify an EDID data set in the
904 /lib/firmware directory that is used instead.
905 Generic built-in EDID data sets are used, if one of
906 edid/1024x768.bin, edid/1280x1024.bin,
907 edid/1680x1050.bin, or edid/1920x1080.bin is given
908 and no file with the same name exists. Details and
909 instructions how to build your own EDID data are
910 available in Documentation/EDID/HOWTO.txt. An EDID
911 data set will only be used for a particular connector,
912 if its name and a colon are prepended to the EDID
913 name.
914
Linus Torvalds1da177e2005-04-16 15:20:36 -0700915 dscc4.setup= [NET]
916
Jim Cromie29e36c92012-04-27 14:30:41 -0600917 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
918 module.dyndbg[="val"]
919 Enable debug messages at boot time. See
920 Documentation/dynamic-debug-howto.txt for details.
921
Mark Salter56aeeba2014-04-07 15:39:53 -0700922 early_ioremap_debug [KNL]
923 Enable debug messages in early_ioremap support. This
924 is useful for tracking down temporary early mappings
925 which are not unmapped.
926
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700927 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500928
Michal Simek6fa62fc2014-09-10 12:43:02 +0200929 cdns,<addr>
930 Start an early, polled-mode console on a cadence serial
931 port at the specified address. The cadence serial port
932 must already be setup and configured. Options are not
933 yet supported.
934
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700935 uart[8250],io,<addr>[,options]
936 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700937 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700938 Start an early, polled-mode console on the 8250/16550
939 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700940 MMIO inter-register address stride is either 8-bit
941 (mmio) or 32-bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700942 The options are the same as for ttyS, above.
943
Rob Herring0d3c6732014-04-18 17:19:57 -0500944 pl011,<addr>
945 Start an early, polled-mode console on a pl011 serial
946 port at the specified address. The pl011 serial port
947 must already be setup and configured. Options are not
948 yet supported.
949
Stephen Boyd0efe7292014-09-15 17:22:51 -0700950 msm_serial,<addr>
951 Start an early, polled-mode console on an msm serial
952 port at the specified address. The serial port
953 must already be setup and configured. Options are not
954 yet supported.
955
956 msm_serial_dm,<addr>
957 Start an early, polled-mode console on an msm serial
958 dm port at the specified address. The serial port
959 must already be setup and configured. Options are not
960 yet supported.
961
Rob Herringd50d7262014-04-18 17:19:58 -0500962 smh Use ARM semihosting calls for early console.
963
Finn Thain7913ad12014-04-12 23:48:56 +1000964 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700965 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +0100966 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500967 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700968 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -0700969 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500970 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500971 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700972
Dave Hansen147ea092013-04-10 14:03:38 -0700973 earlyprintk is useful when the kernel crashes before
974 the normal console is initialized. It is not enabled by
975 default because it has some cosmetic problems.
976
Randy Dunlapa9913042005-10-23 12:57:11 -0700977 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700978 takes over.
979
Matt Fleming72548e82013-10-04 09:36:56 +0100980 Only one of vga, efi, serial, or usb debug port can
981 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700982
Dave Hansen147ea092013-04-10 14:03:38 -0700983 Currently only ttyS0 and ttyS1 may be specified by
984 name. Other I/O ports may be explicitly specified
985 on some architectures (x86 and arm at least) by
986 replacing ttySn with an I/O port address, like this:
987 earlyprintk=serial,0x1008,115200
988 You can find the port for a given device in
989 /proc/tty/driver/serial:
990 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -0700991
992 Interaction with the standard serial driver is not
993 very good.
994
Matt Fleming72548e82013-10-04 09:36:56 +0100995 The VGA and EFI output is eventually overwritten by
996 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500998 The xen output can only be used by Xen PV guests.
999
Chen, Gongc700f012013-12-06 01:17:08 -05001000 edac_report= [HW,EDAC] Control how to report EDAC event
1001 Format: {"on" | "off" | "force"}
1002 on: enable EDAC to report H/W event. May be overridden
1003 by other higher priority error reporting module.
1004 off: disable H/W event reporting through EDAC.
1005 force: enforce the use of EDAC to report H/W event.
1006 default: on.
1007
Jason Wessel97311912010-05-20 21:04:30 -05001008 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1009 ekgdboc=kbd
1010
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001011 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001012 the boot argument: earlyprintk=vga
1013
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001015 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001016
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001017 efi= [EFI]
1018 Format: { "old_map" }
1019 old_map [X86-64]: switch to the old ioremap-based EFI
1020 runtime services mapping. 32-bit still uses this one by
1021 default.
1022
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001023 efi_no_storage_paranoia [EFI; X86]
1024 Using this parameter you can use more than 50% of
1025 your efi variable storage. Use this parameter only if
1026 you are really sure that your UEFI does sane gc and
1027 fulfills the spec otherwise your board may brick.
1028
Linus Torvalds1da177e2005-04-16 15:20:36 -07001029 eisa_irq_edge= [PARISC,HW]
1030 See header of drivers/parisc/eisa.c.
1031
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001032 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001034 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035
1036 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001037 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001038 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001039 Documentation/block/deadline-iosched.txt for details.
1040
Michael Holzheud3bf37952011-10-30 15:16:37 +01001041 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001042 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001043 image elf header and optionally the size. Generally
1044 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001045 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001046
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001047 enable_mtrr_cleanup [X86]
1048 The kernel tries to adjust MTRR layout from continuous
1049 to discrete, to make X server driver able to add WB
1050 entry later. This parameter enables that.
1051
Randy Dunlapca1eda22009-05-06 16:02:58 -07001052 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001053 Enable PIN 1 of APIC timer
1054 Can be useful to work around chipset bugs
1055 (in particular on some ATI chipsets).
1056 The kernel tries to set a reasonable default.
1057
Linus Torvalds1da177e2005-04-16 15:20:36 -07001058 enforcing [SELINUX] Set initial enforcing status.
1059 Format: {"0" | "1"}
1060 See security/selinux/Kconfig help text.
1061 0 -- permissive (log only, no denials).
1062 1 -- enforcing (deny and log).
1063 Default value is 0.
1064 Value can be changed at runtime via /selinux/enforce.
1065
Huang Yinga08f82d2010-05-18 14:35:21 +08001066 erst_disable [ACPI]
1067 Disable Error Record Serialization Table (ERST)
1068 support.
1069
Linus Torvalds1da177e2005-04-16 15:20:36 -07001070 ether= [HW,NET] Ethernet cards parameters
1071 This option is obsoleted by the "netdev=" option, which
1072 has equivalent usage. See its documentation for details.
1073
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001074 evm= [EVM]
1075 Format: { "fix" }
1076 Permit 'security.evm' to be updated regardless of
1077 current integrity status.
1078
Akinobu Mitade1ba092006-12-08 02:39:42 -08001079 failslab=
1080 fail_page_alloc=
1081 fail_make_request=[KNL]
1082 General fault injection mechanism.
1083 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001084 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001085
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001087 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001088
Alex Chiangf13ae302008-05-08 14:03:23 -06001089 force_pal_cache_flush
1090 [IA-64] Avoid check_sal_cache_flush which may hang on
1091 buggy SAL_CACHE_FLUSH implementations. Using this
1092 parameter will force ia64_sal_cache_flush to call
1093 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1094
Chris Bainbridge69f23662014-03-07 18:40:42 +07001095 forcepae [X86-32]
1096 Forcefully enable Physical Address Extension (PAE).
1097 Many Pentium M systems disable PAE but may have a
1098 functionally usable PAE implementation.
1099 Warning: use of this parameter will taint the kernel
1100 and may cause unknown problems.
1101
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001102 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001103 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001104 as early as possible in order to facilitate early
1105 boot debugging.
1106
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001107 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001108 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001109 If no parameter is passed, ftrace will dump
1110 buffers of all CPUs, but if you pass orig_cpu, it will
1111 dump only the buffer of the CPU that triggered the
1112 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001113
1114 ftrace_filter=[function-list]
1115 [FTRACE] Limit the functions traced by the function
1116 tracer at boot up. function-list is a comma separated
1117 list of functions. This list can be changed at run
1118 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001119 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001120
1121 ftrace_notrace=[function-list]
1122 [FTRACE] Do not trace the functions specified in
1123 function-list. This list can be changed at run time
1124 by the set_ftrace_notrace file in the debugfs
1125 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001126
Stefan Assmann369bc182009-10-12 22:17:21 +02001127 ftrace_graph_filter=[function-list]
1128 [FTRACE] Limit the top level callers functions traced
1129 by the function graph tracer at boot up.
1130 function-list is a comma separated list of functions
1131 that can be changed at run time by the
1132 set_graph_function file in the debugfs tracing directory.
1133
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001134 ftrace_graph_notrace=[function-list]
1135 [FTRACE] Do not trace from the functions specified in
1136 function-list. This list is a comma separated list of
1137 functions that can be changed at run time by the
1138 set_graph_notrace file in the debugfs tracing directory.
1139
Linus Torvalds1da177e2005-04-16 15:20:36 -07001140 gamecon.map[2|3]=
1141 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1142 support via parallel port (up to 5 devices per port)
1143 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1144 See also Documentation/input/joystick-parport.txt
1145
1146 gamma= [HW,DRM]
1147
Yinghai Luaaf23042008-01-30 13:33:09 +01001148 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1149 Format: off | on
1150 default: on
1151
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001152 gcov_persist= [GCOV] When non-zero (default), profiling data for
1153 kernel modules is saved and remains accessible via
1154 debugfs, even when the module is unloaded/reloaded.
1155 When zero, profiling data is discarded and associated
1156 debugfs files are removed at module unload time.
1157
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001159 invalid Protective MBR to be treated as GPT. If the
1160 primary GPT is corrupted, it enables the backup/alternate
1161 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001162
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001163 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1164 the "Enable 0" bit of the configuration register.
1165 Format: 0 | 1
1166 Default: 0
1167 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1168 the "Enable 0" bit of the configuration register.
1169 Format: 0 | 1
1170 Default: 0
1171 grcan.select= [HW] Select which physical interface to use.
1172 Format: 0 | 1
1173 Default: 0
1174 grcan.txsize= [HW] Sets the size of the tx buffer.
1175 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1176 Default: 1024
1177 grcan.rxsize= [HW] Sets the size of the rx buffer.
1178 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1179 Default: 1024
1180
Linus Torvalds1da177e2005-04-16 15:20:36 -07001181 hashdist= [KNL,NUMA] Large hashes allocated during boot
1182 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001183 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001184 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185
1186 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1187
1188 hd= [EIDE] (E)IDE hard drive subsystem geometry
1189 Format: <cyl>,<head>,<sect>
1190
Huang Yingea8c0712010-05-18 14:35:15 +08001191 hest_disable [ACPI]
1192 Disable Hardware Error Source Table (HEST) support;
1193 corresponding firmware-first mode error processing
1194 logic will be disabled.
1195
Linus Torvalds1da177e2005-04-16 15:20:36 -07001196 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1197 size of <nn>. This works even on boxes that have no
1198 highmem otherwise. This also works to reduce highmem
1199 size on bigger boxes.
1200
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001201 highres= [KNL] Enable/disable high resolution timer mode.
1202 Valid parameters: "on", "off"
1203 Default: "on"
1204
Linus Torvalds1da177e2005-04-16 15:20:36 -07001205 hisax= [HW,ISDN]
1206 See Documentation/isdn/README.HiSax.
1207
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001208 hlt [BUGS=ARM,SH]
1209
1210 hpet= [X86-32,HPET] option to control HPET usage
1211 Format: { enable (default) | disable | force |
1212 verbose }
1213 disable: disable HPET and use PIT instead
1214 force: allow force enabled of undocumented chips (ICH4,
1215 VIA, nVidia)
1216 verbose: show contents of HPET registers during setup
1217
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001218 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1219 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1220
Andi Kleenb4718e62008-07-23 21:27:51 -07001221 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1222 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001223 On x86-64 and powerpc, this option can be specified
1224 multiple times interleaved with hugepages= to reserve
1225 huge pages of different sizes. Valid pages sizes on
1226 x86-64 are 2M (when the CPU supports "pse") and 1G
1227 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -07001228 Note that 1GB pages can only be allocated at boot time
1229 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +09001230
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001231 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1232 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001233 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1234 If specified, z/VM IUCV HVC accepts connections
1235 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001236
James Hoganfdabf522012-10-09 11:00:27 +01001237 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1238 hardware thread id mappings.
1239 Format: <cpu>:<hwthread>
1240
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001241 keep_bootcon [KNL]
1242 Do not unregister boot console at start. This is only
1243 useful for debugging when something happens in the window
1244 between unregistering the boot console and initializing
1245 the real console.
1246
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001247 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001248 or register an additional I2C bus that is not
1249 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001250 Format:
1251 <bus_id>,<clkrate>
1252
Jiri Kosina36d95732008-10-06 02:51:09 -04001253 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001254 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001255 i8042.dumbkbd [HW] Pretend that controller can only read data from
1256 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001257 (Don't attempt to blink the leds)
1258 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001259 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001260 i8042.noloop [HW] Disable the AUX Loopback command while probing
1261 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001262 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhov68da1662014-10-10 12:19:03 -07001263 controller. Default: true.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1265 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001266 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001267 i8042.reset [HW] Reset the controller during init and cleanup
1268 i8042.unlock [HW] Unlock (ignore) the keylock
1269
1270 i810= [HW,DRM]
1271
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001272 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1273 indicates that the driver is running on unsupported
1274 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001275 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1276 does not match list of supported models.
1277 i8k.power_status
1278 [HW] Report power status in /proc/i8k
1279 (disabled by default)
1280 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1281 capability is set.
1282
Carsten Emde4dca20e2012-03-15 15:56:26 +01001283 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001284 [DRM] Invert the sense of the variable that is used to
1285 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001286 brightness value of 0 indicates backlight switched off,
1287 and the maximum of the brightness value sets the backlight
1288 to maximum brightness. If this parameter is set to 0
1289 (default) and the machine requires it, or this parameter
1290 is set to 1, a brightness value of 0 sets the backlight
1291 to maximum brightness, and the maximum of the brightness
1292 value switches the backlight off.
1293 -1 -- never invert brightness
1294 0 -- machine default
1295 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001296
Linus Torvalds1da177e2005-04-16 15:20:36 -07001297 icn= [HW,ISDN]
1298 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1299
David Fries0af80c02009-02-25 20:28:21 +01001300 ide-core.nodma= [HW] (E)IDE subsystem
1301 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001302 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1303 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001304 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001305
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001306 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1307 Claim all unknown PCI IDE storage controllers.
1308
Andi Kleenf039b752007-05-02 19:27:12 +02001309 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001310 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001311 Poll forces a polling idle loop that can slightly
1312 improve the performance of waking up a idle CPU, but
1313 will use a lot of power and make the system run hot.
1314 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001315 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001316 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001317 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001318
Ingo Molnar792908222006-12-06 20:40:51 -08001319 ignore_loglevel [KNL]
1320 Ignore loglevel setting - this will print /all/
1321 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001322 We also add it as printk module parameter, so users
1323 could change it dynamically, usually by
1324 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001325
Linus Torvalds1da177e2005-04-16 15:20:36 -07001326 ihash_entries= [KNL]
1327 Set number of hash buckets for inode cache.
1328
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001329 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001330 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001331 default: "enforce"
1332
Mimi Zohar07f6a792011-03-09 22:25:48 -05001333 ima_appraise_tcb [IMA]
1334 The builtin appraise policy appraises all files
1335 owned by uid=0.
1336
Mimi Zohar3323eec92009-02-04 09:06:58 -05001337 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001338 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1339 | sha512 | ... }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001340 default: "sha1"
1341
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001342 The list of supported hash algorithms is defined
1343 in crypto/hash_info.h.
1344
Eric Paris5789ba32009-05-21 15:47:06 -04001345 ima_tcb [IMA]
1346 Load a policy which meets the needs of the Trusted
1347 Computing Base. This means IMA will measure all
1348 programs exec'd, files mmap'd for exec, and all files
1349 opened for read by uid=0.
1350
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001351 ima_template= [IMA]
1352 Select one of defined IMA measurements template formats.
1353 Formats: { "ima" | "ima-ng" }
1354 Default: "ima-ng"
1355
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001356 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1357 Format: <min_file_size>
1358 Set the minimal file size for using asynchronous hash.
1359 If left unspecified, ahash usage is disabled.
1360
1361 ahash performance varies for different data sizes on
1362 different crypto accelerators. This option can be used
1363 to achieve the best performance for a particular HW.
1364
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001365 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1366 Format: <bufsize>
1367 Set hashing buffer size. Default: 4k.
1368
1369 ahash performance varies for different chunk sizes on
1370 different crypto accelerators. This option can be used
1371 to achieve best performance for particular HW.
1372
Linus Torvalds1da177e2005-04-16 15:20:36 -07001373 init= [KNL]
1374 Format: <full_path>
1375 Run specified binary instead of /sbin/init as init
1376 process.
1377
1378 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1379 for working out where the kernel is dying during
1380 startup.
1381
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001382 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1383 initcall functions. Useful for debugging built-in
1384 modules and initcalls.
1385
Linus Torvalds1da177e2005-04-16 15:20:36 -07001386 initrd= [BOOT] Specify the location of the initial ramdisk
1387
1388 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1389 Format: <irq>
1390
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001391 int_pln_enable [x86] Enable power limit notification interrupt
1392
Mimi Zohard726d8d2013-03-18 14:48:02 -04001393 integrity_audit=[IMA]
1394 Format: { "0" | "1" }
1395 0 -- basic integrity auditing messages. (Default)
1396 1 -- additional integrity auditing messages.
1397
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001398 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001399 on
1400 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001401 off
1402 Disable intel iommu driver.
1403 igfx_off [Default Off]
1404 By default, gfx is mapped as normal device. If a gfx
1405 device has a dedicated DMAR unit, the DMAR unit is
1406 bypassed by not enabling DMAR with this option. In
1407 this case, gfx device will use physical address for
1408 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001409 forcedac [x86_64]
1410 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001411 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001412 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001413 than 32-bit addressing. The default is to look
1414 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001415 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001416 strict [Default Off]
1417 With this option on every unmap_single operation will
1418 result in a hardware IOTLB flush operation as opposed
1419 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001420 sp_off [Default Off]
1421 By default, super page will be supported if Intel IOMMU
1422 has the capability. With this option, super page will
1423 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001424
1425 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1426 0 disables intel_idle and fall back on acpi_idle.
1427 1 to 6 specify maximum depth of C-state.
1428
Dirk Brandewie6be26492013-02-15 22:55:10 +01001429 intel_pstate= [X86]
1430 disable
1431 Do not enable intel_pstate as the default
1432 scaling driver for the supported processors
1433
Chris Wrightd1423d52010-07-20 11:06:49 -07001434 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001435 on enable Interrupt Remapping (default)
1436 off disable Interrupt Remapping
1437 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001438 no_x2apic_optout
1439 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001440
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001441 iomem= Disable strict checking of access to MMIO memory
1442 strict regions from userspace.
1443 relaxed
1444
1445 iommu= [x86]
1446 off
1447 force
1448 noforce
1449 biomerge
1450 panic
1451 nopanic
1452 merge
1453 nomerge
1454 forcesac
1455 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001456 pt [x86, IA-64]
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001457
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001458
1459 io7= [HW] IO7 for Marvel based alpha systems
1460 See comment before marvel_specify_io7 in
1461 arch/alpha/kernel/core_marvel.c.
1462
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301463 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001464 0x80
1465 Standard port 0x80 based delay
1466 0xed
1467 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001468 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001469 Simple two microseconds delay
1470 none
1471 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001472
Linus Torvalds1da177e2005-04-16 15:20:36 -07001473 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001474 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001475
Alan Cox200803d2005-06-28 20:45:18 -07001476 irqfixup [HW]
1477 When an interrupt is not handled search all handlers
1478 for it. Intended to get systems with badly broken
1479 firmware running.
1480
1481 irqpoll [HW]
1482 When an interrupt is not handled search all handlers
1483 for it. Also check all handlers each timer
1484 interrupt. Intended to get systems with badly broken
1485 firmware running.
1486
Linus Torvalds1da177e2005-04-16 15:20:36 -07001487 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001488 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489
1490 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001491 Format:
1492 <cpu number>,...,<cpu number>
1493 or
Li Zefanb225d442008-11-06 12:53:39 -08001494 <cpu number>-<cpu number>
1495 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001496 or a mixture
1497 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001498
Linus Torvalds1da177e2005-04-16 15:20:36 -07001499 This option can be used to specify one or more CPUs
1500 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001501 algorithms. You can move a process onto or off an
1502 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503 <cpu number> begins at 0 and the maximum value is
1504 "number of CPUs in system - 1".
1505
1506 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001507 alternative -- manually setting the CPU mask of all
1508 tasks in the system -- can cause problems and
1509 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001510
Randy Dunlapa9913042005-10-23 12:57:11 -07001511 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001512
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001513 ivrs_ioapic [HW,X86_64]
1514 Provide an override to the IOAPIC-ID<->DEVICE-ID
1515 mapping provided in the IVRS ACPI table. For
1516 example, to map IOAPIC-ID decimal 10 to
1517 PCI device 00:14.0 write the parameter as:
1518 ivrs_ioapic[10]=00:14.0
1519
1520 ivrs_hpet [HW,X86_64]
1521 Provide an override to the HPET-ID<->DEVICE-ID
1522 mapping provided in the IVRS ACPI table. For
1523 example, to map HPET-ID decimal 0 to
1524 PCI device 00:14.0 write the parameter as:
1525 ivrs_hpet[0]=00:14.0
1526
Linus Torvalds1da177e2005-04-16 15:20:36 -07001527 js= [HW,JOY] Analog joystick
1528 See Documentation/input/joystick.txt.
1529
Kees Cook24f2e022014-06-13 13:30:36 -07001530 kaslr/nokaslr [X86]
1531 Enable/disable kernel and module base offset ASLR
1532 (Address Space Layout Randomization) if built into
1533 the kernel. When CONFIG_HIBERNATION is selected,
1534 kASLR is disabled by default. When kASLR is enabled,
1535 hibernation will be disabled.
1536
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001537 keepinitrd [HW,ARM]
1538
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301539 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001540 specifies the amount of memory usable by the kernel
1541 for non-movable allocations. The requested amount is
1542 spread evenly throughout all nodes in the system. The
1543 remaining memory in each node is used for Movable
1544 pages. In the event, a node is too small to have both
1545 kernelcore and Movable pages, kernelcore pages will
1546 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001547 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001548 allocation of pages that may be reclaimed or moved
1549 by the page migration subsystem. This means that
1550 HugeTLB pages may not be allocated from this zone.
1551 Note that allocations like PTEs-from-HighMem still
1552 use the HighMem zone if it exists, and the Normal
1553 zone if it does not.
1554
Jason Wessel4fe1da42010-05-20 21:04:31 -05001555 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1556 Format: <Controller#>[,poll interval]
1557 The controller # is the number of the ehci usb debug
1558 port as it is probed via PCI. The poll interval is
1559 optional and is the number seconds in between
1560 each poll cycle to the debug port in case you need
1561 the functionality for interrupting the kernel with
1562 gdb or control-c on the dbgp connection. When
1563 not using this parameter you use sysrq-g to break into
1564 the kernel debugger.
1565
Jason Wessel84c08fd2010-05-20 21:04:24 -05001566 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001567 Requires a tty driver that supports console polling,
1568 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001569 Serial only format: <serial_device>[,baud]
1570 keyboard only format: kbd
1571 keyboard and serial format: kbd,<serial_device>[,baud]
1572 Optional Kernel mode setting:
1573 kms, kbd format: kms,kbd
1574 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001575
Jason Wessel84c08fd2010-05-20 21:04:24 -05001576 kgdbwait [KGDB] Stop kernel execution and enter the
1577 kernel debugger at the earliest opportunity.
1578
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001579 kmac= [MIPS] korina ethernet MAC address.
1580 Configure the RouterBoard 532 series on-chip
1581 Ethernet adapter MAC address.
1582
Catalin Marinas04f70332009-06-11 13:22:39 +01001583 kmemleak= [KNL] Boot-time kmemleak enable/disable
1584 Valid arguments: on, off
1585 Default: on
1586
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001587 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1588 Valid arguments: 0, 1, 2
1589 kmemcheck=0 (disabled)
1590 kmemcheck=1 (enabled)
1591 kmemcheck=2 (one-shot mode)
1592 Default: 2 (one-shot mode)
1593
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301594 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001595 in oops dumps.
1596
Andre Przywarafef07aa2009-07-10 14:20:35 +02001597 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1598 Default is 0 (don't ignore, but inject #GP)
1599
Xiao Guangronga182d872010-09-20 22:17:48 +08001600 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1601 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001602 Default is 0 (off)
1603
Andre Przywarafef07aa2009-07-10 14:20:35 +02001604 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001605 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001606
1607 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1608 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001609 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001610
Andre Przywarafef07aa2009-07-10 14:20:35 +02001611 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1612 (virtualized MMU) support on capable Intel chips.
1613 Default is 1 (enabled)
1614
1615 kvm-intel.emulate_invalid_guest_state=
1616 [KVM,Intel] Enable emulation of invalid guest states
1617 Default is 0 (disabled)
1618
1619 kvm-intel.flexpriority=
1620 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1621 Default is 1 (enabled)
1622
Sasha Levine1a72ae2011-08-09 14:28:35 +03001623 kvm-intel.nested=
1624 [KVM,Intel] Enable VMX nesting (nVMX).
1625 Default is 0 (disabled)
1626
Andre Przywarafef07aa2009-07-10 14:20:35 +02001627 kvm-intel.unrestricted_guest=
1628 [KVM,Intel] Disable unrestricted guest feature
1629 (virtualized real and unpaged mode) on capable
1630 Intel chips. Default is 1 (enabled)
1631
1632 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1633 feature (tagged TLBs) on capable Intel chips.
1634 Default is 1 (enabled)
1635
Linus Torvalds1da177e2005-04-16 15:20:36 -07001636 l2cr= [PPC]
1637
Robert Brosea78bfbf2008-03-29 07:20:23 +11001638 l3cr= [PPC]
1639
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001640 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001641 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001642
Suresh Siddha279f1462012-10-22 14:37:58 -07001643 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1644 value for LAPIC timer one-shot implementation. Default
1645 back to the programmable timer unit in the LAPIC.
1646
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301647 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001648 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001649
FD Camifcb71f62008-01-06 19:08:56 +01001650 libata.dma= [LIBATA] DMA control
1651 libata.dma=0 Disable all PATA and SATA DMA
1652 libata.dma=1 PATA and SATA Disk DMA only
1653 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001654 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001655 Combinations also work, so libata.dma=3 enables DMA
1656 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001657
Michael Prokop20308872009-08-06 00:14:10 +02001658 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1659 libata.ignore_hpa=0 keep BIOS limits (default)
1660 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001661
Dave Jones78e70c22007-09-27 11:50:13 -04001662 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1663 when set.
1664 Format: <int>
1665
Tejun Heo33267322008-02-13 09:15:09 +09001666 libata.force= [LIBATA] Force configurations. The format is comma
1667 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001668 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001669 matching port, link or device. Basically, it matches
1670 the ATA ID string printed on console by libata. If
1671 the whole ID part is omitted, the last PORT and DEVICE
1672 values are used. If ID hasn't been specified yet, the
1673 configuration applies to all ports, links and devices.
1674
1675 If only DEVICE is omitted, the parameter applies to
1676 the port and all links and devices behind it. DEVICE
1677 number of 0 either selects the first device or the
1678 first fan-out link behind PMP device. It does not
1679 select the host link. DEVICE number of 15 selects the
1680 host link and device attached to it.
1681
1682 The VAL specifies the configuration to force. As long
1683 as there's no ambiguity shortcut notation is allowed.
1684 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1685 The following configurations can be forced.
1686
1687 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1688 Any ID with matching PORT is used.
1689
1690 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1691
1692 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1693 udma[/][16,25,33,44,66,100,133] notation is also
1694 allowed.
1695
1696 * [no]ncq: Turn on or off NCQ.
1697
Tejun Heo05944bd2008-08-13 20:19:09 +09001698 * nohrst, nosrst, norst: suppress hard, soft
1699 and both resets.
1700
Dan Williamsca6d43b2012-06-21 23:41:41 -07001701 * rstonce: only attempt one reset during
1702 hot-unplug link recovery
1703
Tejun Heo43c9c592010-05-23 12:59:11 +02001704 * dump_id: dump IDENTIFY data.
1705
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001706 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1707
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001708 * disable: Disable this device.
1709
Tejun Heo33267322008-02-13 09:15:09 +09001710 If there are multiple matching configurations changing
1711 the same attribute, the last one is used.
1712
Yinghai Lu95f72d12010-07-12 14:36:09 +10001713 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001714
Linus Torvalds1da177e2005-04-16 15:20:36 -07001715 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001716 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001717
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001718 lockd.nlm_grace_period=P [NFS] Assign grace period.
1719 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001720
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001721 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1722 Format: <integer>
1723
1724 lockd.nlm_timeout=T [NFS] Assign timeout value.
1725 Format: <integer>
1726
1727 lockd.nlm_udpport=M [NFS] Assign UDP port.
1728 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001729
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001730 locktorture.nreaders_stress= [KNL]
1731 Set the number of locking read-acquisition kthreads.
1732 Defaults to being automatically set based on the
1733 number of online CPUs.
1734
1735 locktorture.nwriters_stress= [KNL]
1736 Set the number of locking write-acquisition kthreads.
1737
1738 locktorture.onoff_holdoff= [KNL]
1739 Set time (s) after boot for CPU-hotplug testing.
1740
1741 locktorture.onoff_interval= [KNL]
1742 Set time (s) between CPU-hotplug operations, or
1743 zero to disable CPU-hotplug testing.
1744
1745 locktorture.shuffle_interval= [KNL]
1746 Set task-shuffle interval (jiffies). Shuffling
1747 tasks allows some CPUs to go into dyntick-idle
1748 mode during the locktorture test.
1749
1750 locktorture.shutdown_secs= [KNL]
1751 Set time (s) after boot system shutdown. This
1752 is useful for hands-off automated testing.
1753
1754 locktorture.stat_interval= [KNL]
1755 Time (s) between statistics printk()s.
1756
1757 locktorture.stutter= [KNL]
1758 Time (s) to stutter testing, for example,
1759 specifying five seconds causes the test to run for
1760 five seconds, wait for five seconds, and so on.
1761 This tests the locking primitive's ability to
1762 transition abruptly to and from idle.
1763
1764 locktorture.torture_runnable= [BOOT]
1765 Start locktorture running at boot time.
1766
1767 locktorture.torture_type= [KNL]
1768 Specify the locking implementation to test.
1769
1770 locktorture.verbose= [KNL]
1771 Enable additional printk() statements.
1772
Linus Torvalds1da177e2005-04-16 15:20:36 -07001773 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1774 Format: <irq>
1775
1776 loglevel= All Kernel Messages with a loglevel smaller than the
1777 console loglevel will be printed to the console. It can
1778 also be changed with klogd or other programs. The
1779 loglevels are defined as follows:
1780
1781 0 (KERN_EMERG) system is unusable
1782 1 (KERN_ALERT) action must be taken immediately
1783 2 (KERN_CRIT) critical conditions
1784 3 (KERN_ERR) error conditions
1785 4 (KERN_WARNING) warning conditions
1786 5 (KERN_NOTICE) normal but significant condition
1787 6 (KERN_INFO) informational
1788 7 (KERN_DEBUG) debug-level messages
1789
Randy Dunlapc756d082011-02-20 20:08:35 -08001790 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001791 in bytes. n must be a power of two and greater
1792 than the minimal size. The minimal size is defined
1793 by LOG_BUF_SHIFT kernel config parameter. There is
1794 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1795 that allows to increase the default size depending on
1796 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001797
Randy Dunlapaccaa242007-10-16 01:29:37 -07001798 logo.nologo [FB] Disables display of the built-in Linux logo.
1799 This may be used to provide more screen space for
1800 kernel log messages and is useful when debugging
1801 kernel boot problems.
1802
Linus Torvalds1da177e2005-04-16 15:20:36 -07001803 lp=0 [LP] Specify parallel ports to use, e.g,
1804 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1805 lp=reset first parallel port). 'lp=0' disables the
1806 lp=auto printer driver. 'lp=reset' (which can be
1807 specified in addition to the ports) causes
1808 attached printers to be reset. Using
1809 lp=port1,port2,... specifies the parallel ports
1810 to associate lp devices with, starting with
1811 lp0. A port specification may be 'none' to skip
1812 that lp device, or a parport name such as
1813 'parport0'. Specifying 'lp=auto' instead of a
1814 port specification list means that device IDs
1815 from each port should be examined, to see if
1816 an IEEE 1284-compliant printer is attached; if
1817 so, the driver will manage that printer.
1818 See also header of drivers/char/lp.c.
1819
1820 lpj=n [KNL]
1821 Sets loops_per_jiffy to given constant, thus avoiding
1822 time-consuming boot-time autodetection (up to 250 ms per
1823 CPU). 0 enables autodetection (default). To determine
1824 the correct value for your kernel, boot with normal
1825 autodetection and see what value is printed. Note that
1826 on SMP systems the preset will be applied to all CPUs,
1827 which is likely to cause problems if your CPUs need
1828 significantly divergent settings. An incorrect value
1829 will cause delays in the kernel to be wrong, leading to
1830 unpredictable I/O errors and other breakage. Although
1831 unlikely, in the extreme case this might damage your
1832 hardware.
1833
1834 ltpc= [NET]
1835 Format: <io>,<irq>,<dma>
1836
Randy Dunlap16290242011-08-13 12:34:52 -07001837 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001838 (machvec) in a generic kernel.
1839 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001840
Wu Zhangjin3209e702009-07-02 23:27:12 +08001841 machtype= [Loongson] Share the same kernel image file between different
1842 yeeloong laptop.
1843 Example: machtype=lemote-yeeloong-2f-7inch
1844
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001845 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1846 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001847
1848 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001849 should make use of. maxcpus=n : n >= 0 limits the
1850 kernel to using 'n' processors. n=0 is a special case,
1851 it is equivalent to "nosmp", which also disables
1852 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001853
Kay Sieversd134b002011-07-31 22:08:04 +02001854 max_loop= [LOOP] The number of loop block devices that get
1855 (loop.max_loop) unconditionally pre-created at init time. The default
1856 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1857 of statically allocating a predefined number, loop
1858 devices can be requested on-demand with the
1859 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001860
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001861 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001862
Uwe Hermann71cced62008-10-20 09:32:21 -07001863 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001864
Linus Torvalds1da177e2005-04-16 15:20:36 -07001865 md= [HW] RAID subsystems devices and level
1866 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001867
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868 mdacon= [MDA]
1869 Format: <first>,<last>
1870 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001871
Linus Torvalds1da177e2005-04-16 15:20:36 -07001872 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1873 Amount of memory to be used when the kernel is not able
1874 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08001875 [X86] Work as limiting max address. Use together
1876 with memmap= to avoid physical address space collisions.
1877 Without memmap= PCI devices could be placed at addresses
1878 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001879
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001880 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001881 memory.
1882
Paul Mundt6902aa82008-09-21 17:14:42 +09001883 memchunk=nn[KMG]
1884 [KNL,SH] Allow user to override the default size for
1885 per-device physically contiguous DMA buffers.
1886
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301887 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001888 E820 memory map, as specified by the user.
1889 Such memmap=exactmap lines can be constructed based on
1890 BIOS output or other requirements. See the memmap=nn@ss
1891 option description.
1892
1893 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08001894 [KNL] Force usage of a specific region of memory.
1895 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001896
1897 memmap=nn[KMG]#ss[KMG]
1898 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08001899 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001900
1901 memmap=nn[KMG]$ss[KMG]
1902 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08001903 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001904 Example: Exclude memory from 0x18690000-0x1869ffff
1905 memmap=64K$0x18690000
1906 or
1907 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001908
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001909 memory_corruption_check=0/1 [X86]
1910 Some BIOSes seem to corrupt the first 64k of
1911 memory when doing things like suspend/resume.
1912 Setting this option will scan the memory
1913 looking for corruption. Enabling this will
1914 both detect corruption and prevent the kernel
1915 from using the memory being corrupted.
1916 However, its intended as a diagnostic tool; if
1917 repeatable BIOS-originated corruption always
1918 affects the same memory, you can use memmap=
1919 to prevent the kernel from using that memory.
1920
1921 memory_corruption_check_size=size [X86]
1922 By default it checks for corruption in the low
1923 64k, making this memory unavailable for normal
1924 use. Use this parameter to scan for
1925 corruption in more or less memory.
1926
1927 memory_corruption_check_period=seconds [X86]
1928 By default it checks for corruption every 60
1929 seconds. Use this parameter to check at some
1930 other rate. 0 disables periodic checking.
1931
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001932 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001933 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001934 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001935 Specifies the number of memtest passes to be
1936 performed. Each pass selects another test
1937 pattern from a given set of patterns. Memtest
1938 fills the memory with this pattern, validates
1939 memory contents and reserves bad memory
1940 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001941
Linus Torvalds1da177e2005-04-16 15:20:36 -07001942 meye.*= [HW] Set MotionEye Camera parameters
1943 See Documentation/video4linux/meye.txt.
1944
Andres Salomon8f368812007-10-12 23:04:06 +02001945 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1946 Multi-Function General Purpose Timers on AMD Geode
1947 platforms.
1948
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001949 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1950 the BIOS has incorrectly applied a workaround. TinyBIOS
1951 version 0.98 is known to be affected, 0.99 fixes the
1952 problem by letting the user disable the workaround.
1953
Linus Torvalds1da177e2005-04-16 15:20:36 -07001954 mga= [HW,DRM]
1955
Randy Dunlap1c207f92008-11-19 15:36:16 -08001956 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1957 physical address is ignored.
1958
Michel Pollet39f45d72009-05-20 11:10:31 +01001959 mini2440= [ARM,HW,KNL]
1960 Format:[0..2][b][c][t]
1961 Default: "0tb"
1962 MINI2440 configuration specification:
1963 0 - The attached screen is the 3.5" TFT
1964 1 - The attached screen is the 7" TFT
1965 2 - The VGA Shield is attached (1024x768)
1966 Leaving out the screen size parameter will not load
1967 the TFT driver, and the framebuffer will be left
1968 unconfigured.
1969 b - Enable backlight. The TFT backlight pin will be
1970 linked to the kernel VESA blanking code and a GPIO
1971 LED. This parameter is not necessary when using the
1972 VGA shield.
1973 c - Enable the s3c camera interface.
1974 t - Reserved for enabling touchscreen support. The
1975 touchscreen support is not enabled in the mainstream
1976 kernel as of 2.6.30, a preliminary port can be found
1977 in the "bleeding edge" mini2440 support kernel at
1978 http://repo.or.cz/w/linux-2.6/mini2440.git
1979
Mel Gorman6b74ab92008-07-23 21:26:49 -07001980 mminit_loglevel=
1981 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1982 parameter allows control of the logging verbosity for
1983 the additional memory initialisation checks. A value
1984 of 0 disables mminit logging and a level of 4 will
1985 log everything. Information is printed at KERN_DEBUG
1986 so loglevel=8 may also need to be specified.
1987
Rusty Russell106a4ee2012-09-26 10:09:40 +01001988 module.sig_enforce
1989 [KNL] When CONFIG_MODULE_SIG is set, this means that
1990 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01001991 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01001992 is always true, so this option does nothing.
1993
Linus Torvalds1da177e2005-04-16 15:20:36 -07001994 mousedev.tap_time=
1995 [MOUSE] Maximum time between finger touching and
1996 leaving touchpad surface for touch to be considered
1997 a tap and be reported as a left button click (for
1998 touchpads working in absolute mode only).
1999 Format: <msecs>
2000 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2001 reporting absolute coordinates, such as tablets
2002 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2003 reporting absolute coordinates, such as tablets
2004
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302005 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002006 is similar to kernelcore except it specifies the
2007 amount of memory used for migratable allocations.
2008 If both kernelcore and movablecore is specified,
2009 then kernelcore will be at *least* the specified
2010 value but may be more. If movablecore on its own
2011 is specified, the administrator must be careful
2012 that the amount of memory usable for all allocations
2013 is not too small.
2014
Tang Chenc5320922013-11-12 15:08:10 -08002015 movable_node [KNL,X86] Boot-time switch to enable the effects
2016 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2017
Linus Torvalds1da177e2005-04-16 15:20:36 -07002018 MTD_Partition= [MTD]
2019 Format: <name>,<region-number>,<size>,<offset>
2020
Randy Dunlapa9913042005-10-23 12:57:11 -07002021 MTD_Region= [MTD] Format:
2022 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002023
2024 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002025 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002026
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002027 multitce=off [PPC] This parameter disables the use of the pSeries
2028 firmware feature for updating multiple TCE entries
2029 at a time.
2030
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002031 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2032
2033 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2034
2035 boundary - index of last SLC block on Flex-OneNAND.
2036 The remaining blocks are configured as MLC blocks.
2037 lock - Configure if Flex-OneNAND boundary should be locked.
2038 Once locked, the boundary cannot be changed.
2039 1 indicates lock status, 0 indicates unlock status.
2040
Ben Dooks9db829f2008-07-03 11:24:29 +01002041 mtdset= [ARM]
2042 ARM/S3C2412 JIVE boot control
2043
2044 See arch/arm/mach-s3c2412/mach-jive.c
2045
Linus Torvalds1da177e2005-04-16 15:20:36 -07002046 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002047 [HW] Make the MicroTouch USB driver use raw coordinates
2048 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002049
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002050 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002051 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002052 that could hold holes aka. UC entries.
2053
2054 mtrr_gran_size=nn[KMG] [X86]
2055 Used for mtrr cleanup. It is granularity of mtrr block.
2056 Default is 1.
2057 Large value could prevent small alignment from
2058 using up MTRRs.
2059
2060 mtrr_spare_reg_nr=n [X86]
2061 Format: <integer>
2062 Range: 0,7 : spare reg number
2063 Default : 1
2064 Used for mtrr cleanup. It is spare mtrr entries number.
2065 Set to 2 or more if your graphical card needs more.
2066
Linus Torvalds1da177e2005-04-16 15:20:36 -07002067 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2068
Linus Torvalds1da177e2005-04-16 15:20:36 -07002069 netdev= [NET] Network devices parameters
2070 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2071 Note that mem_start is often overloaded to mean
2072 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002073 This usage is only documented in each driver source
2074 file if at all.
2075
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002076 nf_conntrack.acct=
2077 [NETFILTER] Enable connection tracking flow accounting
2078 0 to disable accounting
2079 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002080 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002081
Chuck Lever306a0752010-09-17 10:54:37 -04002082 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002083 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002084
2085 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002086 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087
Chuck Lever306a0752010-09-17 10:54:37 -04002088 nfsrootdebug [NFS] enable nfsroot debugging messages.
2089 See Documentation/filesystems/nfs/nfsroot.txt.
2090
Trond Myklebusta72b4422006-01-03 09:55:41 +01002091 nfs.callback_tcpport=
2092 [NFS] set the TCP port on which the NFSv4 callback
2093 channel should listen.
2094
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002095 nfs.cache_getent=
2096 [NFS] sets the pathname to the program which is used
2097 to update the NFS client cache entries.
2098
2099 nfs.cache_getent_timeout=
2100 [NFS] sets the timeout after which an attempt to
2101 update a cache entry is deemed to have failed.
2102
Trond Myklebust58df0952006-01-03 09:55:57 +01002103 nfs.idmap_cache_timeout=
2104 [NFS] set the maximum lifetime for idmapper cache
2105 entries.
2106
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002107 nfs.enable_ino64=
2108 [NFS] enable 64-bit inode numbers.
2109 If zero, the NFS client will fake up a 32-bit inode
2110 number for the readdir() and stat() syscalls instead
2111 of returning the full 64-bit number.
2112 The default is to return 64-bit inode numbers.
2113
Trond Myklebustef159e92012-02-06 19:50:40 -05002114 nfs.max_session_slots=
2115 [NFSv4.1] Sets the maximum number of session slots
2116 the client will attempt to negotiate with the server.
2117 This limits the number of simultaneous RPC requests
2118 that the client can send to the NFSv4.1 server.
2119 Note that there is little point in setting this
2120 value higher than the max_tcp_slot_table_limit.
2121
Trond Myklebustb064eca22011-02-22 15:44:32 -08002122 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002123 [NFSv4] When set to the default of '1', this option
2124 ensures that both the RPC level authentication
2125 scheme and the NFS level operations agree to use
2126 numeric uids/gids if the mount is using the
2127 'sec=sys' security flavour. In effect it is
2128 disabling idmapping, which can make migration from
2129 legacy NFSv2/v3 systems to NFSv4 easier.
2130 Servers that do not support this mode of operation
2131 will be autodetected by the client, and it will fall
2132 back to using the idmapper.
2133 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002134 nfs.nfs4_unique_id=
2135 [NFS4] Specify an additional fixed unique ident-
2136 ification string that NFSv4 clients can insert into
2137 their nfs_client_id4 string. This is typically a
2138 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002139
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002140 nfs.send_implementation_id =
2141 [NFSv4.1] Send client implementation identification
2142 information in exchange_id requests.
2143 If zero, no implementation identification information
2144 will be sent.
2145 The default is to send the implementation identification
2146 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002147
2148 nfs.recover_lost_locks =
2149 [NFSv4] Attempt to recover locks that were lost due
2150 to a lease timeout on the server. Please note that
2151 doing this risks data corruption, since there are
2152 no guarantees that the file will remain unchanged
2153 after the locks are lost.
2154 If you want to enable the kernel legacy behaviour of
2155 attempting to recover these locks, then set this
2156 parameter to '1'.
2157 The default parameter value of '0' causes the kernel
2158 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002159
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002160 nfsd.nfs4_disable_idmapping=
2161 [NFSv4] When set to the default of '1', the NFSv4
2162 server will return only numeric uids and gids to
2163 clients using auth_sys, and will accept numeric uids
2164 and gids from such clients. This is intended to ease
2165 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002166
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002167 objlayoutdriver.osd_login_prog=
2168 [NFS] [OBJLAYOUT] sets the pathname to the program which
2169 is used to automatically discover and login into new
2170 osd-targets. Please see:
2171 Documentation/filesystems/pnfs.txt for more explanations
2172
Paul Mundt1e1030d2009-09-01 17:38:32 +09002173 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002174 when a NMI is triggered.
2175 Format: [state][,regs][,debounce][,die]
2176
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302177 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002178 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05002179 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03002180 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002181 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002182 timeout occurs (or 'nopanic' to override the opposite
2183 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002184 This is useful when you use a panic=... timeout and
2185 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002186
Anton Vorontsovbff38772009-07-08 11:10:56 -07002187 netpoll.carrier_timeout=
2188 [NET] Specifies amount of time (in seconds) that
2189 netpoll should wait for a carrier. By default netpoll
2190 waits 4 seconds.
2191
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002192 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002193 emulation library even if a 387 maths coprocessor
2194 is present.
2195
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002196 no_console_suspend
2197 [HW] Never suspend the console
2198 Disable suspending of consoles during suspend and
2199 hibernate operations. Once disabled, debugging
2200 messages can reach various consoles while the rest
2201 of the system is being put to sleep (ie, while
2202 debugging driver suspend/resume hooks). This may
2203 not work reliably with all consoles, but is known
2204 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002205 To facilitate more flexible debugging, we also add
2206 console_suspend, a printk module parameter to control
2207 it. Users could use console_suspend (usually
2208 /sys/module/printk/parameters/console_suspend) to
2209 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002210
Christoph Lameterc1aee212007-05-31 00:40:47 -07002211 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2212 caches in the slab allocator. Saves per-node memory,
2213 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002214
Randy Dunlapa9913042005-10-23 12:57:11 -07002215 noalign [KNL,ARM]
2216
Linus Torvalds1da177e2005-04-16 15:20:36 -07002217 noapic [SMP,APIC] Tells the kernel to not make use of any
2218 IOAPICs that may be present in the system.
2219
Mike Galbraith5091faa2010-11-30 14:18:03 +01002220 noautogroup Disable scheduler automatic task group creation.
2221
Linus Torvalds1da177e2005-04-16 15:20:36 -07002222 nobats [PPC] Do not use BATs for mapping kernel lowmem
2223 on "Classic" PPC cores.
2224
2225 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002226
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002227 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2228
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002229 nodelayacct [KNL] Disable per-task delay accounting
2230
Linus Torvalds1da177e2005-04-16 15:20:36 -07002231 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2232
Paul Mundt6902aa82008-09-21 17:14:42 +09002233 nodsp [SH] Disable hardware DSP at boot time.
2234
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302235 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002236
Linus Torvalds1da177e2005-04-16 15:20:36 -07002237 noexec [IA-64]
2238
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302239 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002240 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002241 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002242 noexec=off: disable non-executable mappings
2243
H. Peter Anvin52b61792012-09-21 12:43:13 -07002244 nosmap [X86]
2245 Disable SMAP (Supervisor Mode Access Prevention)
2246 even if it is supported by processor.
2247
Fenghua Yude5397a2011-05-11 16:51:05 -07002248 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002249 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002250 even if it is supported by processor.
2251
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002252 noexec32 [X86-64]
2253 This affects only 32-bit executables.
2254 noexec32=on: enable non-executable mappings (default)
2255 read doesn't imply executable mappings
2256 noexec32=off: disable non-executable mappings
2257 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258
Paul Mundt6902aa82008-09-21 17:14:42 +09002259 nofpu [SH] Disable hardware FPU at boot time.
2260
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002261 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002262 register save and restore. The kernel will only save
2263 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002264
Suresh Siddha0c752a92009-05-22 12:17:45 -07002265 noxsave [BUGS=X86] Disables x86 extended register state save
2266 and restore using xsave. The kernel will fallback to
2267 enabling legacy floating-point and sse state.
2268
Fenghua Yub6f42a42014-05-29 11:12:31 -07002269 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2270 register states. The kernel will fall back to use
2271 xsave to save the states. By using this parameter,
2272 performance of saving the states is degraded because
2273 xsave doesn't support modified optimization while
2274 xsaveopt supports it on xsaveopt enabled systems.
2275
2276 noxsaves [X86] Disables xsaves and xrstors used in saving and
2277 restoring x86 extended register state in compacted
2278 form of xsave area. The kernel will fall back to use
2279 xsaveopt and xrstor to save and restore the states
2280 in standard form of xsave area. By using this
2281 parameter, xsave area per process might occupy more
2282 memory on xsaves enabled systems.
2283
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002284 eagerfpu= [X86]
Suresh Siddhae0022982012-09-10 10:32:32 -07002285 on enable eager fpu restore
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002286 off disable eager fpu restore
Suresh Siddhae0022982012-09-10 10:32:32 -07002287 auto selects the default scheme, which automatically
2288 enables eagerfpu restore for xsaveopt.
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002289
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002290 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2291 wfi(ARM) instruction doesn't work correctly and not to
2292 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002293
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002294 no_file_caps Tells the kernel not to honor file capabilities. The
2295 only way then for a file to be executed with privilege
2296 is to be setuid root or executed by root.
2297
Linus Torvalds1da177e2005-04-16 15:20:36 -07002298 nohalt [IA-64] Tells the kernel not to use the power saving
2299 function PAL_HALT_LIGHT when idle. This increases
2300 power-consumption. On the positive side, it reduces
2301 interrupt wake-up latency, which may improve performance
2302 in certain environments such as networked servers or
2303 real-time systems.
2304
Kees Cooka6e15a32014-06-13 13:30:35 -07002305 nohibernate [HIBERNATION] Disable hibernation and resume.
2306
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002307 nohz= [KNL] Boottime enable/disable dynamic ticks
2308 Valid arguments: on, off
2309 Default: on
2310
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002311 nohz_full= [KNL,BOOT]
2312 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002313 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002314 whenever possible. The boot CPU will be forced outside
2315 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002316 The CPUs in this range must also be included in the
2317 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002318
Paul Mundteeee7852009-04-02 12:31:16 +09002319 noiotrap [SH] Disables trapped I/O port accesses.
2320
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002321 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002322 disable unhandled interrupt sources.
2323
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302324 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002325 broken timer IRQ sources.
2326
Linus Torvalds1da177e2005-04-16 15:20:36 -07002327 noisapnp [ISAPNP] Disables ISA PnP code.
2328
2329 noinitrd [RAM] Tells the kernel not to load any configured
2330 initial RAM disk.
2331
Weidong Han03ea8152009-04-17 16:42:15 +08002332 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2333 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002334 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002335
Linus Torvalds1da177e2005-04-16 15:20:36 -07002336 nointroute [IA-64]
2337
Randy Dunlap16290242011-08-13 12:34:52 -07002338 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002339
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002340 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2341
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002342 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2343 fault handling.
2344
Glauber Costad910f5c2011-07-11 15:28:19 -04002345 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2346 steal time is computed, but won't influence scheduler
2347 behaviour
2348
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002349 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002350
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002351 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002352
Linus Torvalds1da177e2005-04-16 15:20:36 -07002353 noltlbs [PPC] Do not use large page/tlb entries for kernel
2354 lowmem mapping on PPC40x.
2355
Horms312f1f02006-02-22 09:57:55 +09002356 nomca [IA-64] Disable machine check abort handling
2357
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002358 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002359
Andres Salomon83d73842007-10-12 23:04:06 +02002360 nomfgpt [X86-32] Disable Multi-Function General Purpose
2361 Timer usage (for AMD Geode machines).
2362
Don Zickusbda62632011-10-13 15:14:27 -04002363 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2364 shutdown the other cpus. Instead use the REBOOT_VECTOR
2365 irq.
2366
Dave Young02608be2012-02-01 10:33:14 +08002367 nomodule Disable module load
2368
Jiri Kosina016ddd92010-01-18 17:05:40 +01002369 nopat [X86] Disable PAT (page attribute table extension of
2370 pagetables) support.
2371
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002372 norandmaps Don't use address space randomization. Equivalent to
2373 echo 0 > /proc/sys/kernel/randomize_va_space
2374
Jiri Kosinabbff2162010-08-11 18:34:09 +02002375 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002376
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002377 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002378 with UP alternatives
2379
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002380 nordrand [X86] Disable kernel use of the RDRAND and
2381 RDSEED instructions even if they are supported
2382 by the processor. RDRAND and RDSEED are still
2383 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002384
Randy Dunlapa9913042005-10-23 12:57:11 -07002385 noresume [SWSUSP] Disables resume and restores original swap
2386 space.
2387
Linus Torvalds1da177e2005-04-16 15:20:36 -07002388 no-scroll [VGA] Disables scrollback.
2389 This is required for the Braillex ib80-piezo Braille
2390 reader made by F.H. Papenmeier (Germany).
2391
2392 nosbagart [IA-64]
2393
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002394 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002395
Len Brown61ec7562007-08-16 03:34:22 -04002396 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2397 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002398
Dave Jones97842212007-07-15 23:41:05 -07002399 nosoftlockup [KNL] Disable the soft-lockup detector.
2400
Linus Torvalds1da177e2005-04-16 15:20:36 -07002401 nosync [HW,M68K] Disables sync negotiation for all devices.
2402
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002403 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002404
2405 nousb [USB] Disable the USB subsystem
2406
Ben Hutchings55142372011-01-02 23:02:42 +00002407 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04002408
Linus Torvalds1da177e2005-04-16 15:20:36 -07002409 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002410
Weidong Han2b2fd872009-04-17 16:42:12 +08002411 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2412
Fenghua Yuf78cff42012-11-13 11:32:38 -08002413 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2414 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2415 Some features depend on CPU0. Known dependencies are:
2416 1. Resume from suspend/hibernate depends on CPU0.
2417 Suspend/hibernate will fail if CPU0 is offline and you
2418 need to online CPU0 before suspend/hibernate.
2419 2. PIC interrupts also depend on CPU0. CPU0 can't be
2420 removed if a PIC interrupt is detected.
2421 It's said poweroff/reboot may depend on CPU0 on some
2422 machines although I haven't seen such issues so far
2423 after CPU0 is offline on a few tested machines.
2424 If the dependencies are under your control, you can
2425 turn on cpu0_hotplug.
2426
Randy Dunlap16290242011-08-13 12:34:52 -07002427 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002428 purges which is reported from either PAL_VM_SUMMARY or
2429 SAL PALO.
2430
Yinghai Lu2b633e32010-02-10 01:20:37 -08002431 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2432 could support. nr_cpus=n : n >= 1 limits the kernel to
2433 supporting 'n' processors. Later in runtime you can not
2434 use hotplug cpu feature to put more cpu back to online.
2435 just like you compile the kernel NR_CPUS=n
2436
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002437 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2438
Mel Gorman1a687c22012-11-22 11:16:36 +00002439 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2440 Allowed values are enable and disable
2441
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002442 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2443 one of ['zone', 'node', 'default'] can be specified
2444 This can be set from sysctl after boot.
2445 See Documentation/sysctl/vm.txt for details.
2446
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002447 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2448 See Documentation/debugging-via-ohci1394.txt for more
2449 info.
2450
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002451 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2452 Rather than timing out after 20 ms if an EC
2453 command is not properly ACKed, override the length
2454 of the timeout. We have interrupts disabled while
2455 waiting for the ACK, so if this is set too high
2456 interrupts *may* be lost!
2457
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002458 omap_mux= [OMAP] Override bootloader pin multiplexing.
2459 Format: <mux_mode0.mode_name=value>...
2460 For example, to override I2C bus2:
2461 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2462
Linus Torvalds1da177e2005-04-16 15:20:36 -07002463 oprofile.timer= [HW]
2464 Use timer interrupt instead of performance counters
2465
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002466 oprofile.cpu_type= Force an oprofile cpu type
2467 This might be useful if you have an older oprofile
2468 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002469 Format: { arch_perfmon }
2470 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002471 perfmon on Intel CPUs instead of the
2472 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002473 timer: [X86] Force use of architectural NMI
2474 timer mode (see also oprofile.timer
2475 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002476 [s390] Force legacy basic mode sampling
2477 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002478
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002479 oops=panic Always panic on oopses. Default is to just kill the
2480 process, but there is a small probability of
2481 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002482 This will also cause panics on machine check exceptions.
2483 Useful together with panic=30 to trigger a reboot.
2484
Randy Dunlapbcfde332010-06-07 17:10:38 -07002485 OSS [HW,OSS]
2486 See Documentation/sound/oss/oss-parameters.txt
2487
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002488 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002489 timeout > 0: seconds before rebooting
2490 timeout = 0: wait forever
2491 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002492 Format: <timeout>
2493
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002494 crash_kexec_post_notifiers
2495 Run kdump after running panic-notifiers and dumping
2496 kmsg. This only for the users who doubt kdump always
2497 succeeds in any situation.
2498 Note that this also increases risks of kdump failure,
2499 because some panic notifiers can make the crashed
2500 kernel more unstable.
2501
Linus Torvalds1da177e2005-04-16 15:20:36 -07002502 parkbd.port= [HW] Parallel port number the keyboard adapter is
2503 connected to, default is 0.
2504 Format: <parport#>
2505 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2506 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002507 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002508
Randy Dunlapa9913042005-10-23 12:57:11 -07002509 parport= [HW,PPT] Specify parallel ports. 0 disables.
2510 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2511 Use 'auto' to force the driver to use any
2512 IRQ/DMA settings detected (the default is to
2513 ignore detected IRQ/DMA settings because of
2514 possible conflicts). You can specify the base
2515 address, IRQ, and DMA settings; IRQ and DMA
2516 should be numbers, or 'auto' (for using detected
2517 settings on that particular port), or 'nofifo'
2518 (to avoid using a FIFO even if it is detected).
2519 Parallel ports are assigned in the order they
2520 are specified on the command line, starting
2521 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002522
Randy Dunlapa9913042005-10-23 12:57:11 -07002523 parport_init_mode= [HW,PPT]
2524 Configure VIA parallel port to operate in
2525 a specific mode. This is necessary on Pegasos
2526 computer where firmware has no options for setting
2527 up parallel port mode and sets it to spp.
2528 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002529 Format: [spp|ps2|epp|ecp|ecpepp]
2530
Andrew Mortondd287792006-03-23 03:00:57 -08002531 pause_on_oops=
2532 Halt all CPUs after the first oops has been printed for
2533 the specified number of seconds. This is to be used if
2534 your oopses keep scrolling off the screen.
2535
Linus Torvalds1da177e2005-04-16 15:20:36 -07002536 pcbit= [HW,ISDN]
2537
2538 pcd. [PARIDE]
2539 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002540 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002541
Randy Dunlapa9913042005-10-23 12:57:11 -07002542 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002543 earlydump [X86] dump PCI config space before the kernel
2544 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002545 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002546 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002547 the hardware directly. Use this if your machine
2548 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002549 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002550 hardware access methods are allowed. Use this
2551 if you experience crashes upon bootup and you
2552 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002553 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002554 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002555 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002556 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002557 noaer [PCIE] If the PCIEAER kernel config parameter is
2558 enabled, this kernel boot option can be used to
2559 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002560 nodomains [PCI] Disable support for multiple PCI
2561 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302562 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002563 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002564 check_enable_amd_mmconf [X86] check for and enable
2565 properly configured MMIO access to PCI
2566 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002567 nomsi [MSI] If the PCI_MSI kernel config parameter is
2568 enabled, this kernel boot option can be used to
2569 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002570 noioapicquirk [APIC] Disable all boot interrupt quirks.
2571 Safety option to keep boot IRQs enabled. This
2572 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002573 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2574 primary IO-APIC for bridges that cannot disable
2575 boot IRQs. This fixes a source of spurious IRQs
2576 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002577 noioapicreroute [APIC] Disable workaround that uses the
2578 boot IRQ equivalent of an IRQ that connects to
2579 a chipset where boot IRQs cannot be disabled.
2580 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002581 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002582 routing table. These calls are known to be buggy
2583 on several machines and they hang the machine
2584 when used, but on other computers it's the only
2585 way to get the interrupt routing table. Try
2586 this option if the kernel is unable to allocate
2587 IRQs or discover secondary PCI buses on your
2588 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002589 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002590 Use with caution as certain devices share
2591 address decoders between ROMs and other
2592 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002593 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002594 expansion ROMs that do not already have
2595 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002596 nobar [X86] Do not assign address space to the
2597 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002598 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002599 assigned automatically to PCI devices. You can
2600 make the kernel exclude IRQs of your ISA cards
2601 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002602 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002603 of the PIRQ table (normally generated
2604 by the BIOS) if it is outside the
2605 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002606 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002607 useful if the kernel is unable to find your
2608 secondary buses and you want to tell it
2609 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002610 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002611 numbers ourselves, overriding
2612 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002613 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002614 in the BIOS $PIR table. This is needed on
2615 some systems with broken BIOSes, notably
2616 some HP Pavilion N5400 and Omnibook XE3
2617 notebooks. This will have no effect if ACPI
2618 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002619 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002620 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002621 use_crs [X86] Use PCI host bridge window information
2622 from ACPI. On BIOSes from 2008 or later, this
2623 is enabled by default. If you need to use this,
2624 please report a bug.
2625 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2626 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002627 routeirq Do IRQ routing for all PCI devices.
2628 This is normally done in pci_enable_device(),
2629 so this option is a temporary workaround
2630 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002631 skip_isa_align [X86] do not align io start addr, so can
2632 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002633 firmware [ARM] Do not re-enumerate the bus but instead
2634 just use the configuration from the
2635 bootloader. This is currently used on
2636 IXP2000 systems where the bus has to be
2637 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002638 noearly [X86] Don't do any early type 1 scanning.
2639 This might help on some broken boards which
2640 machine check when some devices' config space
2641 is read. But various workarounds are disabled
2642 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002643 bfsort Sort PCI devices into breadth-first order.
2644 This sorting is done to get a device
2645 order compatible with older (<= 2.4) kernels.
2646 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002647 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2648 tuning and use the BIOS-configured MPS defaults.
2649 pcie_bus_safe Set every device's MPS to the largest value
2650 supported by all devices below the root complex.
2651 pcie_bus_perf Set device MPS to the largest allowable MPS
2652 based on its parent bus. Also set MRRS (Max
2653 Read Request Size) to the largest supported
2654 value (no larger than the MPS that the device
2655 or bus can support) for best performance.
2656 pcie_bus_peer2peer Set every device's MPS to 128B, which
2657 every device is guaranteed to support. This
2658 configuration allows peer-to-peer DMA between
2659 any pair of devices, possibly at the cost of
2660 reduced performance. This also guarantees
2661 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002662 cbiosize=nn[KMG] The fixed amount of bus space which is
2663 reserved for the CardBus bridge's IO window.
2664 The default value is 256 bytes.
2665 cbmemsize=nn[KMG] The fixed amount of bus space which is
2666 reserved for the CardBus bridge's memory
2667 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002668 resource_alignment=
2669 Format:
2670 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2671 Specifies alignment and device to reassign
2672 aligned memory resources.
2673 If <order of align> is not specified,
2674 PAGE_SIZE is used as alignment.
2675 PCI-PCI bridge can be specified, if resource
2676 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002677 ecrc= Enable/disable PCIe ECRC (transaction layer
2678 end-to-end CRC checking).
2679 bios: Use BIOS/firmware settings. This is the
2680 the default.
2681 off: Turn ECRC off
2682 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002683 hpiosize=nn[KMG] The fixed amount of bus space which is
2684 reserved for hotplug bridge's IO window.
2685 Default size is 256 bytes.
2686 hpmemsize=nn[KMG] The fixed amount of bus space which is
2687 reserved for hotplug bridge's memory window.
2688 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002689 realloc= Enable/disable reallocating PCI bridge resources
2690 if allocations done by BIOS are too small to
2691 accommodate resources required by all child
2692 devices.
2693 off: Turn realloc off
2694 on: Turn realloc on
2695 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002696 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002697 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2698 only look for one device below a PCIe downstream
2699 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002700
Chuck Ebberte5665a42008-09-24 20:40:34 -04002701 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2702 Management.
2703 off Disable ASPM.
2704 force Enable ASPM even on devices that claim not to support it.
2705 WARNING: Forcing ASPM on may cause system lockups.
2706
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002707 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2708 nomsi Do not use MSI for PCI Express Native Hotplug (this
2709 makes all PCIe ports use INTx for hotplug services).
2710
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002711 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002712 auto Ask the BIOS whether or not to use native PCIe services
2713 associated with PCIe ports (PME, hot-plug, AER). Use
2714 them only if that is allowed by the BIOS.
2715 native Use native PCIe services associated with PCIe ports
2716 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002717 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2718 ports driver.
2719
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002720 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002721 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002722 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002723
Linus Torvalds1da177e2005-04-16 15:20:36 -07002724 pcmv= [HW,PCMCIA] BadgePAD 4
2725
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302726 pd_ignore_unused
2727 [PM]
2728 Keep all power-domains already enabled by bootloader on,
2729 even if no driver has claimed them. This is useful
2730 for debug and development, but should not be
2731 needed on a platform with proper driver support.
2732
Linus Torvalds1da177e2005-04-16 15:20:36 -07002733 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002734 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002735
2736 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2737 boot time.
2738 Format: { 0 | 1 }
2739 See arch/parisc/kernel/pdc_chassis.c
2740
Tejun Heof58dc012009-08-14 15:00:50 +09002741 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002742 Currently supported values are "embed" and "page".
2743 Archs may support subset or none of the selections.
2744 See comments in mm/percpu.c for details on each
2745 allocator. This parameter is primarily for debugging
2746 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002747
Linus Torvalds1da177e2005-04-16 15:20:36 -07002748 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002749 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002750
2751 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002752 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002753
2754 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002755 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002756
2757 plip= [PPT,NET] Parallel port network link
2758 Format: { parport<nr> | timid | 0 }
2759 See also Documentation/parport.txt.
2760
Randy Dunlap16290242011-08-13 12:34:52 -07002761 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002762 Override pmtimer IOPort with a hex value.
2763 e.g. pmtmr=0x508
2764
Bjorn Helgaas96242112011-08-11 12:14:05 -06002765 pnp.debug=1 [PNP]
2766 Enable PNP debug messages (depends on the
2767 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2768 via /sys/module/pnp/parameters/debug. We always show
2769 current resource usage; turning this on also shows
2770 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002771
Linus Torvalds1da177e2005-04-16 15:20:36 -07002772 pnpacpi= [ACPI]
2773 { off }
2774
2775 pnpbios= [ISAPNP]
2776 { on | off | curr | res | no-curr | no-res }
2777
2778 pnp_reserve_irq=
2779 [ISAPNP] Exclude IRQs for the autoconfiguration
2780
2781 pnp_reserve_dma=
2782 [ISAPNP] Exclude DMAs for the autoconfiguration
2783
2784 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002785 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002786
2787 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002788 [ISAPNP] Exclude memory regions for the
2789 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002790 Ranges are in pairs (memory base and size).
2791
Randy Dunlap4af94f32009-04-17 18:30:28 -07002792 ports= [IP_VS_FTP] IPVS ftp helper module
2793 Default is 21.
2794 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2795 may be specified.
2796 Format: <port>,<port>....
2797
Ingo Molnar45807a12007-07-15 23:40:10 -07002798 print-fatal-signals=
2799 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002800
2801 If enabled, warn about various signal handling
2802 related application anomalies: too many signals,
2803 too many POSIX.1 timers, fatal signals causing a
2804 coredump - etc.
2805
2806 If you hit the warning due to signal overflow,
2807 you might want to try "ulimit -i unlimited".
2808
Ingo Molnar45807a12007-07-15 23:40:10 -07002809 default: off.
2810
Matthew Garrettc22ab332012-03-05 14:59:10 -08002811 printk.always_kmsg_dump=
2812 Trigger kmsg_dump for cases other than kernel oops or
2813 panics
2814 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2815 default: disabled
2816
Randy Dunlape84845c2007-07-15 23:40:25 -07002817 printk.time= Show timing data prefixed to each printk message line
2818 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2819
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002820 processor.max_cstate= [HW,ACPI]
2821 Limit processor to maximum C-state
2822 max_cstate=9 overrides any DMI blacklist limit.
2823
2824 processor.nocst [HW,ACPI]
2825 Ignore the _CST method to determine C-states,
2826 instead using the legacy FADT method
2827
Linus Torvalds1da177e2005-04-16 15:20:36 -07002828 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002829 Format: [schedule,]<number>
2830 Param: "schedule" - profile schedule points.
2831 Param: <number> - step/bucket size as a power of 2 for
2832 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002833 Param: "sleep" - profile D-state sleeping (millisecs).
2834 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002835 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002836
Linus Torvalds1da177e2005-04-16 15:20:36 -07002837 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2838 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002839 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002840
Randy Dunlapa9913042005-10-23 12:57:11 -07002841 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2842 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002843 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2844 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002845 psmouse.resetafter= [HW,MOUSE]
2846 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002847 (0 = never).
2848 psmouse.resolution=
2849 [HW,MOUSE] Set desired mouse resolution, in dpi.
2850 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002851 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002852 0 = disabled, 1 = enabled (default).
2853
Matthew Garrettdee28e72011-07-21 16:57:55 -04002854 pstore.backend= Specify the name of the pstore backend to use
2855
Linus Torvalds1da177e2005-04-16 15:20:36 -07002856 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002857 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002858
Kay Sieversdc8c8582007-08-15 12:25:38 +02002859 pty.legacy_count=
2860 [KNL] Number of legacy pty's. Overwrites compiled-in
2861 default number.
2862
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002863 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002864
Linus Torvalds1da177e2005-04-16 15:20:36 -07002865 r128= [HW,DRM]
2866
2867 raid= [HW,RAID]
2868 See Documentation/md.txt.
2869
Randy Dunlapa9913042005-10-23 12:57:11 -07002870 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002871 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002872
Linus Torvalds1da177e2005-04-16 15:20:36 -07002873 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002874 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002875
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002876 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002877 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2878 the specified list of CPUs to be no-callback CPUs.
2879 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08002880 be offloaded to "rcuox/N" kthreads created for
2881 that purpose, where "x" is "b" for RCU-bh, "p"
2882 for RCU-preempt, and "s" for RCU-sched, and "N"
2883 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002884 offloaded CPUs, which can be useful for HPC and
2885 real-time workloads. It can also improve energy
2886 efficiency for asymmetric multiprocessors.
2887
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002888 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002889 Rather than requiring that offloaded CPUs
2890 (specified by rcu_nocbs= above) explicitly
2891 awaken the corresponding "rcuoN" kthreads,
2892 make these kthreads poll for callbacks.
2893 This improves the real-time response for the
2894 offloaded CPUs by relieving them of the need to
2895 wake up the corresponding kthread, but degrades
2896 energy efficiency by requiring that the kthreads
2897 periodically wake up to do the polling.
2898
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002899 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002900 Set maximum number of finished RCU callbacks to
2901 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002902
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002903 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07002904 Increase the number of CPUs assigned to each
2905 leaf rcu_node structure. Useful for very large
2906 systems.
2907
Paul E. McKenney4a81e832014-06-20 16:49:01 -07002908 rcutree.jiffies_till_sched_qs= [KNL]
2909 Set required age in jiffies for a
2910 given grace period before RCU starts
2911 soliciting quiescent-state help from
2912 rcu_note_context_switch().
2913
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002914 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002915 Set delay from grace-period initialization to
2916 first attempt to force quiescent states.
2917 Units are jiffies, minimum value is zero,
2918 and maximum value is HZ.
2919
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002920 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002921 Set delay between subsequent attempts to force
2922 quiescent states. Units are jiffies, minimum
2923 value is one, and maximum value is HZ.
2924
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07002925 rcutree.rcu_nocb_leader_stride= [KNL]
2926 Set the number of NOCB kthread groups, which
2927 defaults to the square root of the number of
2928 CPUs. Larger numbers reduces the wakeup overhead
2929 on the per-CPU grace-period kthreads, but increases
2930 that same overhead on each group's leader.
2931
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002932 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002933 Set threshold of queued RCU callbacks beyond which
2934 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002935
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002936 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002937 Set threshold of queued RCU callbacks below which
2938 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002939
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002940 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002941 Set wakeup interval for idle CPUs that have
2942 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002943
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002944 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002945 Set wakeup interval for idle CPUs that have
2946 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2947 Lazy RCU callbacks are those which RCU can
2948 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002949
Paul E. McKenney38706bc2014-08-18 21:12:17 -07002950 rcutorture.cbflood_inter_holdoff= [KNL]
2951 Set holdoff time (jiffies) between successive
2952 callback-flood tests.
2953
2954 rcutorture.cbflood_intra_holdoff= [KNL]
2955 Set holdoff time (jiffies) between successive
2956 bursts of callbacks within a given callback-flood
2957 test.
2958
2959 rcutorture.cbflood_n_burst= [KNL]
2960 Set the number of bursts making up a given
2961 callback-flood test. Set this to zero to
2962 disable callback-flood testing.
2963
2964 rcutorture.cbflood_n_per_burst= [KNL]
2965 Set the number of callbacks to be registered
2966 in a given burst of a callback-flood test.
2967
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002968 rcutorture.fqs_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002969 Set duration of force_quiescent_state bursts.
2970
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002971 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002972 Set holdoff time within force_quiescent_state bursts.
2973
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002974 rcutorture.fqs_stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002975 Set wait time between force_quiescent_state bursts.
2976
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002977 rcutorture.gp_exp= [KNL]
2978 Use expedited update-side primitives.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002979
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002980 rcutorture.gp_normal= [KNL]
2981 Use normal (non-expedited) update-side primitives.
2982 If both gp_exp and gp_normal are set, do both.
2983 If neither gp_exp nor gp_normal are set, still
2984 do both.
2985
2986 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002987 Set callbacks/threads for rcu_barrier() testing.
2988
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002989 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002990 Set number of concurrent RCU writers. These just
2991 stress RCU, they don't participate in the actual
2992 test, hence the "fake".
2993
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002994 rcutorture.nreaders= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002995 Set number of RCU readers.
2996
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002997 rcutorture.object_debug= [KNL]
2998 Enable debug-object double-call_rcu() testing.
2999
3000 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003001 Set time (s) after boot for CPU-hotplug testing.
3002
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003003 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003004 Set time (s) between CPU-hotplug operations, or
3005 zero to disable CPU-hotplug testing.
3006
Paul E. McKenney59da22a2014-09-12 10:36:15 -07003007 rcutorture.torture_runnable= [BOOT]
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003008 Start rcutorture running at boot time.
3009
3010 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003011 Set task-shuffle interval (s). Shuffling tasks
3012 allows some CPUs to go into dyntick-idle mode
3013 during the rcutorture test.
3014
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003015 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003016 Set time (s) after boot system shutdown. This
3017 is useful for hands-off automated testing.
3018
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003019 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003020 Duration of CPU stall (s) to test RCU CPU stall
3021 warnings, zero to disable.
3022
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003023 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003024 Time to wait (s) after boot before inducing stall.
3025
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003026 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003027 Time (s) between statistics printk()s.
3028
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003029 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003030 Time (s) to stutter testing, for example, specifying
3031 five seconds causes the test to run for five seconds,
3032 wait for five seconds, and so on. This tests RCU's
3033 ability to transition abruptly to and from idle.
3034
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003035 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003036 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3037 "Maybe" means test if the RCU implementation
3038 under test support RCU priority boosting.
3039
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003040 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003041 Duration (s) of each individual boost test.
3042
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003043 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003044 Interval (s) between each boost test.
3045
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003046 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003047 Test RCU's dyntick-idle handling. See also the
3048 rcutorture.shuffle_interval parameter.
3049
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003050 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003051 Specify the RCU implementation to test.
3052
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003053 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003054 Enable additional printk() statements.
3055
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003056 rcupdate.rcu_expedited= [KNL]
3057 Use expedited grace-period primitives, for
3058 example, synchronize_rcu_expedited() instead
3059 of synchronize_rcu(). This reduces latency,
3060 but can increase CPU utilization, degrade
3061 real-time latency, and degrade energy efficiency.
3062
3063 rcupdate.rcu_cpu_stall_suppress= [KNL]
3064 Suppress RCU CPU stall warning messages.
3065
3066 rcupdate.rcu_cpu_stall_timeout= [KNL]
3067 Set timeout for RCU CPU stall warning messages.
3068
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003069 rcupdate.rcu_task_stall_timeout= [KNL]
3070 Set timeout in jiffies for RCU task stall warning
3071 messages. Disable with a value less than or equal
3072 to zero.
3073
Olof Johanssonffdfc402005-09-06 15:17:19 -07003074 rdinit= [KNL]
3075 Format: <full_path>
3076 Run specified binary instead of /init from the ramdisk,
3077 used for early userspace startup. See initrd.
3078
Robin Holt1b3a5d02013-07-08 16:01:42 -07003079 reboot= [KNL]
3080 Format (x86 or x86_64):
3081 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3082 [[,]s[mp]#### \
3083 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3084 [[,]f[orce]
3085 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3086 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3087 reboot_force is either force or not specified,
3088 reboot_cpu is s[mp]#### with #### being the processor
3089 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003090
Paul Jackson46b6d942008-07-04 10:00:09 -07003091 relax_domain_level=
3092 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01003093 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003094
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003095 relative_sleep_states=
3096 [SUSPEND] Use sleep state labeling where the deepest
3097 state available other than hibernation is always "mem".
3098 Format: { "0" | "1" }
3099 0 -- Traditional sleep state labels.
3100 1 -- Relative sleep state labels.
3101
Linus Torvalds1da177e2005-04-16 15:20:36 -07003102 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3103
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003104 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07003105 Format: nn[KMG]
3106 Reserves a hole at the top of the kernel virtual
3107 address space.
3108
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003109 reservelow= [X86]
3110 Format: nn[K]
3111 Set the amount of memory to reserve for BIOS at
3112 the bottom of the address space.
3113
Vivek Goyal7e962872006-09-27 01:50:44 -07003114 reset_devices [KNL] Force drivers to reset the underlying device
3115 during initialization.
3116
Randy Dunlapa9913042005-10-23 12:57:11 -07003117 resume= [SWSUSP]
3118 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003119 Format:
3120 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003121
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003122 resume_offset= [SWSUSP]
3123 Specify the offset from the beginning of the partition
3124 given by "resume=" at which the swap header is located,
3125 in <PAGE_SIZE> units (needed only for swap files).
3126 See Documentation/power/swsusp-and-swap-files.txt
3127
Barry Songf126f732011-10-10 23:38:41 +02003128 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3129 read the resume files
3130
Barry Song6f8d7022011-10-06 20:34:46 +02003131 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3132 Useful for devices that are detected asynchronously
3133 (e.g. USB and MMC devices).
3134
Bojan Smojverf996fc92010-09-09 23:06:23 +02003135 hibernate= [HIBERNATION]
3136 noresume Don't check if there's a hibernation image
3137 present during boot.
3138 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003139 no Disable hibernation and resume.
Bojan Smojverf996fc92010-09-09 23:06:23 +02003140
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003141 retain_initrd [RAM] Keep initrd memory after extraction
3142
Linus Torvalds1da177e2005-04-16 15:20:36 -07003143 rhash_entries= [KNL,NET]
3144 Set number of hash buckets for route cache
3145
Linus Torvalds1da177e2005-04-16 15:20:36 -07003146 ro [KNL] Mount root device read-only on boot
3147
3148 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07003149 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003150
3151 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3152 mount the root filesystem
3153
3154 rootflags= [KNL] Set root filesystem mount option string
3155
3156 rootfstype= [KNL] Set root filesystem type
3157
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003158 rootwait [KNL] Wait (indefinitely) for root device to show up.
3159 Useful for devices that are detected asynchronously
3160 (e.g. USB and MMC devices).
3161
Robert Tivy5c71d612013-03-28 18:41:46 -07003162 rproc_mem=nn[KMG][@address]
3163 [KNL,ARM,CMA] Remoteproc physical memory block.
3164 Memory area to be used by remote processor image,
3165 managed by CMA.
3166
Linus Torvalds1da177e2005-04-16 15:20:36 -07003167 rw [KNL] Mount root device read-write on boot
3168
3169 S [KNL] Run init in single mode
3170
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003171 s390_iommu= [HW,S390]
3172 Set s390 IOTLB flushing mode
3173 strict
3174 With strict flushing every unmap operation will result in
3175 an IOTLB flush. Default is lazy flushing before reuse,
3176 which is faster.
3177
Linus Torvalds1da177e2005-04-16 15:20:36 -07003178 sa1100ir [NET]
3179 See drivers/net/irda/sa1100_ir.c.
3180
Linus Torvalds1da177e2005-04-16 15:20:36 -07003181 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003182
Mike Travisf6630112009-11-17 18:22:15 -06003183 sched_debug [KNL] Enables verbose scheduler debug messages.
3184
Mike Galbraith5307c952012-05-08 12:20:58 +02003185 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3186 xtime_lock contention on larger systems, and/or RCU lock
3187 contention on all systems with CONFIG_MAXSMP set.
3188 Format: { "0" | "1" }
3189 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3190 1 -- enable.
3191 Note: increases power consumption, thus should only be
3192 enabled if running jitter sensitive (HPC/RT) workloads.
3193
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003194 security= [SECURITY] Choose a security module to enable at boot.
3195 If this boot parameter is not specified, only the first
3196 security module asking for security registration will be
3197 loaded. An invalid security module name will be treated
3198 as if no module has been chosen.
3199
3200 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003201 Format: { "0" | "1" }
3202 See security/selinux/Kconfig help text.
3203 0 -- disable.
3204 1 -- enable.
3205 Default value is set via kernel config option.
3206 If enabled at boot time, /selinux/disable can be used
3207 later to disable prior to initial policy load.
3208
John Johansenc1c124e2010-07-29 14:48:09 -07003209 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3210 Format: { "0" | "1" }
3211 See security/apparmor/Kconfig help text
3212 0 -- disable.
3213 1 -- enable.
3214 Default value is set via kernel config option.
3215
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003216 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003217
Linus Torvalds1da177e2005-04-16 15:20:36 -07003218 shapers= [NET]
3219 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003220
Yinghai Lub05f78f2008-08-22 01:32:50 -07003221 show_msr= [x86] show boot-time MSR settings
3222 Format: { <integer> }
3223 Show boot-time (BIOS-initialized) MSR settings.
3224 The parameter means the number of CPUs to show,
3225 for example 1 means boot CPU only.
3226
Linus Torvalds1da177e2005-04-16 15:20:36 -07003227 simeth= [IA-64]
3228 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003229
Linus Torvalds1da177e2005-04-16 15:20:36 -07003230 slram= [HW,MTD]
3231
Joonsoo Kim423c9292014-10-09 15:26:22 -07003232 slab_nomerge [MM]
3233 Disable merging of slabs with similar size. May be
3234 necessary if there is some reason to distinguish
3235 allocs to different slabs. Debug options disable
3236 merging on their own.
3237 For more information see Documentation/vm/slub.txt.
3238
David Rientjes3df1ccc2011-10-18 22:09:28 -07003239 slab_max_order= [MM, SLAB]
3240 Determines the maximum allowed order for slabs.
3241 A high setting may cause OOMs due to memory
3242 fragmentation. Defaults to 1 for systems with
3243 more than 32MB of RAM, 0 otherwise.
3244
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003245 slub_debug[=options[,slabs]] [MM, SLUB]
3246 Enabling slub_debug allows one to determine the
3247 culprit if slab objects become corrupted. Enabling
3248 slub_debug can create guard zones around objects and
3249 may poison objects when not in use. Also tracks the
3250 last alloc / free. For more information see
3251 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003252
3253 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003254 Determines the maximum allowed order for slabs.
3255 A high setting may cause OOMs due to memory
3256 fragmentation. For more information see
3257 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003258
3259 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003260 The minimum number of objects per slab. SLUB will
3261 increase the slab order up to slub_max_order to
3262 generate a sufficiently large slab able to contain
3263 the number of objects indicated. The higher the number
3264 of objects the smaller the overhead of tracking slabs
3265 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003266 For more information see Documentation/vm/slub.txt.
3267
3268 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003269 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003270 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003271 For more information see Documentation/vm/slub.txt.
3272
3273 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003274 Same with slab_nomerge. This is supported for legacy.
3275 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003276
Linus Torvalds1da177e2005-04-16 15:20:36 -07003277 smart2= [HW]
3278 Format: <io1>[,<io2>[,...,<io8>]]
3279
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003280 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3281 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3282 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3283 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3284 smsc-ircc2.ircc_irq= [HW] IRQ line
3285 smsc-ircc2.ircc_dma= [HW] DMA channel
3286 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3287 0: Toshiba Satellite 1800 (GP data pin select)
3288 1: Fast pin select (default)
3289 2: ATC IRMode
3290
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003291 softlockup_panic=
3292 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003293 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003294
Aaron Tomlined235872014-06-23 13:22:05 -07003295 softlockup_all_cpu_backtrace=
3296 [KNL] Should the soft-lockup detector generate
3297 backtraces on all cpus.
3298 Format: <integer>
3299
Linus Torvalds1da177e2005-04-16 15:20:36 -07003300 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003301 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003302
Linus Torvalds1da177e2005-04-16 15:20:36 -07003303 spia_io_base= [HW,MTD]
3304 spia_fio_base=
3305 spia_pedr=
3306 spia_peddr=
3307
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003308 stacktrace [FTRACE]
3309 Enabled the stack tracer on boot up.
3310
Steven Rostedt762e1202011-12-19 22:01:00 -05003311 stacktrace_filter=[function-list]
3312 [FTRACE] Limit the functions that the stack tracer
3313 will trace at boot up. function-list is a comma separated
3314 list of functions. This list can be changed at run
3315 time by the stack_trace_filter file in the debugfs
3316 tracing directory. Note, this enables stack tracing
3317 and the stacktrace above is not needed.
3318
Linus Torvalds1da177e2005-04-16 15:20:36 -07003319 sti= [PARISC,HW]
3320 Format: <num>
3321 Set the STI (builtin display/keyboard on the HP-PARISC
3322 machines) console (graphic card) which should be used
3323 as the initial boot-console.
3324 See also comment in drivers/video/console/sticore.c.
3325
3326 sti_font= [HW]
3327 See comment in drivers/video/console/sticore.c.
3328
3329 stifb= [HW]
3330 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3331
Trond Myklebustcbf11072009-08-09 15:06:19 -04003332 sunrpc.min_resvport=
3333 sunrpc.max_resvport=
3334 [NFS,SUNRPC]
3335 SunRPC servers often require that client requests
3336 originate from a privileged port (i.e. a port in the
3337 range 0 < portnr < 1024).
3338 An administrator who wishes to reserve some of these
3339 ports for other uses may adjust the range that the
3340 kernel's sunrpc client considers to be privileged
3341 using these two parameters to set the minimum and
3342 maximum port values.
3343
Greg Banks42a7fc42007-03-06 01:42:23 -08003344 sunrpc.pool_mode=
3345 [NFS]
3346 Control how the NFS server code allocates CPUs to
3347 service thread pools. Depending on how many NICs
3348 you have and where their interrupts are bound, this
3349 option will affect which CPUs will do NFS serving.
3350 Note: this parameter cannot be changed while the
3351 NFS server is running.
3352
3353 auto the server chooses an appropriate mode
3354 automatically using heuristics
3355 global a single global pool contains all CPUs
3356 percpu one pool for each CPU
3357 pernode one pool for each NUMA node (equivalent
3358 to global on non-NUMA machines)
3359
Trond Myklebustcbf11072009-08-09 15:06:19 -04003360 sunrpc.tcp_slot_table_entries=
3361 sunrpc.udp_slot_table_entries=
3362 [NFS,SUNRPC]
3363 Sets the upper limit on the number of simultaneous
3364 RPC calls that can be sent from the client to a
3365 server. Increasing these values may allow you to
3366 improve throughput, but will also increase the
3367 amount of memory reserved for use by the client.
3368
Michal Hocko07555ac2013-08-22 16:35:46 -07003369 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003370 [KNL] Enable accounting of swap in memory resource
3371 controller if no parameter or 1 is given or disable
3372 it if 0 is given (See Documentation/cgroups/memory.txt)
3373
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003374 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3375 Format: { <int> | force }
3376 <int> -- Number of I/O TLB slabs
3377 force -- force using of bounce buffers even if they
3378 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003379
Linus Torvalds1da177e2005-04-16 15:20:36 -07003380 switches= [HW,M68k]
3381
Andi Kleene52eec12010-09-08 16:54:17 +02003382 sysfs.deprecated=0|1 [KNL]
3383 Enable/disable old style sysfs layout for old udev
3384 on older distributions. When this option is enabled
3385 very new udev will not work anymore. When this option
3386 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3387 in older udev will not work anymore.
3388 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3389 the kernel configuration.
3390
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003391 sysrq_always_enabled
3392 [KNL]
3393 Ignore sysrq setting - this boot parameter will
3394 neutralize any effect of /proc/sys/kernel/sysrq.
3395 Useful for debugging.
3396
Linus Torvalds1da177e2005-04-16 15:20:36 -07003397 tdfx= [HW,DRM]
3398
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003399 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003400 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003401 standby suspend) or "freeze" (for suspend type freeze)
3402 as the system sleep state during system startup with
3403 the optional capability to repeat N number of times.
3404 The system is woken from this state using a
3405 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003406
Linus Torvalds1da177e2005-04-16 15:20:36 -07003407 thash_entries= [KNL,NET]
3408 Set number of hash buckets for TCP connection
3409
Len Brownf8707ec2007-08-12 00:12:54 -04003410 thermal.act= [HW,ACPI]
3411 -1: disable all active trip points in all thermal zones
3412 <degrees C>: override all lowest active trip points
3413
Len Brownc52a7412007-08-14 15:49:32 -04003414 thermal.crt= [HW,ACPI]
3415 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003416 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003417
Len Brownf5487142007-08-12 00:12:44 -04003418 thermal.nocrt= [HW,ACPI]
3419 Set to disable actions on ACPI thermal zone
3420 critical and hot trip points.
3421
Len Brown72b33ef2007-08-12 00:12:17 -04003422 thermal.off= [HW,ACPI]
3423 1: disable ACPI thermal control
3424
Len Browna70cdc52007-08-12 00:12:35 -04003425 thermal.psv= [HW,ACPI]
3426 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003427 <degrees C>: override all passive trip points to this
3428 value
Len Browna70cdc52007-08-12 00:12:35 -04003429
Len Brown730ff342007-08-12 00:12:26 -04003430 thermal.tzp= [HW,ACPI]
3431 Specify global default ACPI thermal zone polling rate
3432 <deci-seconds>: poll all this frequency
3433 0: no polling (default)
3434
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003435 threadirqs [KNL]
3436 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003437 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003438
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003439 tmem [KNL,XEN]
3440 Enable the Transcendent memory driver if built-in.
3441
3442 tmem.cleancache=0|1 [KNL, XEN]
3443 Default is on (1). Disable the usage of the cleancache
3444 API to send anonymous pages to the hypervisor.
3445
3446 tmem.frontswap=0|1 [KNL, XEN]
3447 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003448 API to send swap pages to the hypervisor. If disabled
3449 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003450
3451 tmem.selfballooning=0|1 [KNL, XEN]
3452 Default is on (1). Disable the driving of swap pages
3453 to the hypervisor.
3454
3455 tmem.selfshrinking=0|1 [KNL, XEN]
3456 Default is on (1). Partial swapoff that immediately
3457 transfers pages from Xen hypervisor back to the
3458 kernel based on different criteria.
3459
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003460 topology= [S390]
3461 Format: {off | on}
3462 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003463 topology information if the hardware supports this.
3464 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003465 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003466 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003467
Linus Torvalds1da177e2005-04-16 15:20:36 -07003468 tp720= [HW,PS2]
3469
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003470 tpm_suspend_pcr=[HW,TPM]
3471 Format: integer pcr id
3472 Specify that at suspend time, the tpm driver
3473 should extend the specified pcr with zeros,
3474 as a workaround for some chips which fail to
3475 flush the last written pcr on TPM_SaveState.
3476 This will guarantee that all the other pcrs
3477 are saved.
3478
Li Zefan9d612be2009-06-24 17:33:15 +08003479 trace_buf_size=nn[KMG]
3480 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003481
Li Zefan020e5f82009-07-01 10:47:05 +08003482 trace_event=[event-list]
3483 [FTRACE] Set and start specified trace events in order
3484 to facilitate early boot debugging.
3485 See also Documentation/trace/events.txt
3486
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003487 trace_options=[option-list]
3488 [FTRACE] Enable or disable tracer options at boot.
3489 The option-list is a comma delimited list of options
3490 that can be enabled or disabled just as if you were
3491 to echo the option name into
3492
3493 /sys/kernel/debug/tracing/trace_options
3494
3495 For example, to enable stacktrace option (to dump the
3496 stack trace of each event), add to the command line:
3497
3498 trace_options=stacktrace
3499
3500 See also Documentation/trace/ftrace.txt "trace options"
3501 section.
3502
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003503 traceoff_on_warning
3504 [FTRACE] enable this option to disable tracing when a
3505 warning is hit. This turns off "tracing_on". Tracing can
3506 be enabled again by echoing '1' into the "tracing_on"
3507 file located in /sys/kernel/debug/tracing/
3508
3509 This option is useful, as it disables the trace before
3510 the WARNING dump is called, which prevents the trace to
3511 be filled with content caused by the warning output.
3512
3513 This option can also be set at run time via the sysctl
3514 option: kernel/traceoff_on_warning
3515
Jiri Kosinafcf4d822012-03-21 16:34:02 -07003516 transparent_hugepage=
3517 [KNL]
3518 Format: [always|madvise|never]
3519 Can be used to control the default behavior of the system
3520 with respect to transparent hugepages.
3521 See Documentation/vm/transhuge.txt for more details.
3522
john stultzd3b8f882009-08-17 16:40:47 -07003523 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003524 Format: <string>
3525 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003526 disables clocksource verification at runtime, as well
3527 as the stability checks done at bootup. Used to enable
3528 high-resolution timer mode on older hardware, and in
3529 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003530 [x86] noirqtime: Do not use TSC to do irq accounting.
3531 Used to run time disable IRQ_TIME_ACCOUNTING on any
3532 platforms where RDTSC is slow and this accounting
3533 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003534
Randy Dunlapa9913042005-10-23 12:57:11 -07003535 turbografx.map[2|3]= [HW,JOY]
3536 TurboGraFX parallel port interface
3537 Format:
3538 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003539 See also Documentation/input/joystick-parport.txt
3540
Christian Kujaub6935f82011-05-31 15:22:05 +00003541 udbg-immortal [PPC] When debugging early kernel crashes that
3542 happen after console_init() and before a proper
3543 console driver takes over, this boot options might
3544 help "seeing" what's going on.
3545
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003546 uhash_entries= [KNL,NET]
3547 Set number of hash buckets for UDP/UDP-Lite connections
3548
Alan Stern5f8364b2006-12-05 16:29:55 -05003549 uhci-hcd.ignore_oc=
3550 [USB] Ignore overcurrent events (default N).
3551 Some badly-designed motherboards generate lots of
3552 bogus events, for ports that aren't wired to
3553 anything. Set this parameter to avoid log spamming.
3554 Note that genuine overcurrent events won't be
3555 reported either.
3556
Simon Arlotte3a61b02008-07-19 23:32:54 +01003557 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003558 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003559
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003560 usbcore.authorized_default=
3561 [USB] Default USB device authorization:
3562 (default -1 = authorized except for wireless USB,
3563 0 = not authorized, 1 = authorized)
3564
Alan Sternb5e795f2007-02-20 15:00:53 -05003565 usbcore.autosuspend=
3566 [USB] The autosuspend time delay (in seconds) used
3567 for newly-detected USB devices (default 2). This
3568 is the time required before an idle device will be
3569 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003570 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003571
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003572 usbcore.usbfs_snoop=
3573 [USB] Set to log all usbfs traffic (default 0 = off).
3574
3575 usbcore.blinkenlights=
3576 [USB] Set to cycle leds on hubs (default 0 = off).
3577
3578 usbcore.old_scheme_first=
3579 [USB] Start with the old device initialization
3580 scheme (default 0 = off).
3581
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003582 usbcore.usbfs_memory_mb=
3583 [USB] Memory limit (in MB) for buffers allocated by
3584 usbfs (default = 16, 0 = max = 2047).
3585
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003586 usbcore.use_both_schemes=
3587 [USB] Try the other device initialization scheme
3588 if the first one fails (default 1 = enabled).
3589
3590 usbcore.initial_descriptor_timeout=
3591 [USB] Specifies timeout for the initial 64-byte
3592 USB_REQ_GET_DESCRIPTOR request in milliseconds
3593 (default 5000 = 5.0 seconds).
3594
Linus Torvalds1da177e2005-04-16 15:20:36 -07003595 usbhid.mousepoll=
3596 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003597
Alan Sternd4f373e2008-11-10 14:07:45 -05003598 usb-storage.delay_use=
3599 [UMS] The delay in seconds before a new device is
3600 scanned for Logical Units (default 5).
3601
3602 usb-storage.quirks=
3603 [UMS] A list of quirks entries to supplement or
3604 override the built-in unusual_devs list. List
3605 entries are separated by commas. Each entry has
3606 the form VID:PID:Flags where VID and PID are Vendor
3607 and Product ID values (4-digit hex numbers) and
3608 Flags is a set of characters, each corresponding
3609 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003610 a = SANE_SENSE (collect more than 18 bytes
3611 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003612 b = BAD_SENSE (don't collect more than 18
3613 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003614 c = FIX_CAPACITY (decrease the reported
3615 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003616 d = NO_READ_DISC_INFO (don't use
3617 READ_DISC_INFO command);
3618 e = NO_READ_CAPACITY_16 (don't use
3619 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02003620 f = NO_REPORT_OPCODES (don't use report opcodes
3621 command, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05003622 h = CAPACITY_HEURISTICS (decrease the
3623 reported device capacity by one
3624 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003625 i = IGNORE_DEVICE (don't bind to this
3626 device);
3627 l = NOT_LOCKABLE (don't try to lock and
3628 unlock ejectable media);
3629 m = MAX_SECTORS_64 (don't transfer more
3630 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003631 n = INITIAL_READ10 (force a retry of the
3632 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003633 o = CAPACITY_OK (accept the capacity
3634 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003635 p = WRITE_CACHE (the device cache is ON
3636 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003637 r = IGNORE_RESIDUE (the device reports
3638 bogus residue values);
3639 s = SINGLE_LUN (the device has only one
3640 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02003641 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3642 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04003643 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05003644 w = NO_WP_DETECT (don't test whether the
3645 medium is write-protected).
3646 Example: quirks=0419:aaf5:rl,0421:0433:rc
3647
Stephen Boydac1667d2011-08-13 12:34:50 -07003648 user_debug= [KNL,ARM]
3649 Format: <int>
3650 See arch/arm/Kconfig.debug help text.
3651 1 - undefined instruction events
3652 2 - system calls
3653 4 - invalid data aborts
3654 8 - SIGSEGV faults
3655 16 - SIGBUS faults
3656 Example: user_debug=31
3657
Ian Campbell14315592010-02-17 10:38:10 +00003658 userpte=
3659 [X86] Flags controlling user PTE allocations.
3660
3661 nohigh = do not allocate PTE pages in
3662 HIGHMEM regardless of setting
3663 of CONFIG_HIGHPTE.
3664
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303665 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003666 On X86_32, this is an alias for vdso32=. Otherwise:
3667
3668 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07003669 vdso=0: disable VDSO mapping
3670
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003671 vdso32= [X86] Control the 32-bit vDSO
3672 vdso32=1: enable 32-bit VDSO
3673 vdso32=0 or vdso32=2: disable 32-bit VDSO
3674
3675 See the help text for CONFIG_COMPAT_VDSO for more
3676 details. If CONFIG_COMPAT_VDSO is set, the default is
3677 vdso32=0; otherwise, the default is vdso32=1.
3678
3679 For compatibility with older kernels, vdso32=2 is an
3680 alias for vdso32=0.
3681
3682 Try vdso32=0 if you encounter an error that says:
3683 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01003684
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003685 vector= [IA-64,SMP]
3686 vector=percpu: enable percpu vector domain
3687
Linus Torvalds1da177e2005-04-16 15:20:36 -07003688 video= [FB] Frame buffer configuration
3689 See Documentation/fb/modedb.txt.
3690
Aaron Lu3afe6da2013-06-20 15:08:55 +08003691 video.brightness_switch_enabled= [0,1]
3692 If set to 1, on receiving an ACPI notify event
3693 generated by hotkey, video driver will adjust brightness
3694 level and then send out the event to user space through
3695 the allocated input device; If set to 0, video driver
3696 will only send out the event without touching backlight
3697 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02003698 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08003699
Pawel Moll81a054c2012-05-09 18:30:16 +01003700 virtio_mmio.device=
3701 [VMMIO] Memory mapped virtio (platform) device.
3702
3703 <size>@<baseaddr>:<irq>[:<id>]
3704 where:
3705 <size> := size (can use standard suffixes
3706 like K, M and G)
3707 <baseaddr> := physical base address
3708 <irq> := interrupt number (as passed to
3709 request_irq())
3710 <id> := (optional) platform device id
3711 example:
3712 virtio_mmio.device=1K@0x100b0000:48:7
3713
3714 Can be used multiple times for multiple devices.
3715
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003716 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003717 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003718 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003719 Use vga=ask for menu.
3720 This is actually a boot loader parameter; the value is
3721 passed to the kernel using a special protocol.
3722
Randy Dunlapa9913042005-10-23 12:57:11 -07003723 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003724 size of <nn>. This can be used to increase the
3725 minimum size (128MB on x86). It can also be used to
3726 decrease the size and leave more room for directly
3727 mapped kernel RAM.
3728
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003729 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3730 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003731
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003732 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3733 Format: <command>
3734
3735 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3736 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003737
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003738 vsyscall= [X86-64]
3739 Controls the behavior of vsyscalls (i.e. calls to
3740 fixed addresses of 0xffffffffff600x00 from legacy
3741 code). Most statically-linked binaries and older
3742 versions of glibc use these calls. Because these
3743 functions are at fixed addresses, they make nice
3744 targets for exploits that can control RIP.
3745
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003746 emulate [default] Vsyscalls turn into traps and are
3747 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003748
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003749 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003750 This is a little bit faster than trapping
3751 and makes a few dynamic recompilers work
3752 better than they would in emulation mode.
3753 It also makes exploits much easier to write.
3754
3755 none Vsyscalls don't work at all. This makes
3756 them quite hard to use for exploits but
3757 might break your system.
3758
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003759 vt.color= [VT] Default text color.
3760 Format: 0xYX, X = foreground, Y = background.
3761 Default: 0x07 = light gray on black.
3762
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08003763 vt.cur_default= [VT] Default cursor shape.
3764 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3765 the parameters of the <Esc>[?A;B;Cc escape sequence;
3766 see VGA-softcursor.txt. Default: 2 = underline.
3767
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003768 vt.default_blu= [VT]
3769 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3770 Change the default blue palette of the console.
3771 This is a 16-member array composed of values
3772 ranging from 0-255.
3773
3774 vt.default_grn= [VT]
3775 Format: <green0>,<green1>,<green2>,...,<green15>
3776 Change the default green palette of the console.
3777 This is a 16-member array composed of values
3778 ranging from 0-255.
3779
3780 vt.default_red= [VT]
3781 Format: <red0>,<red1>,<red2>,...,<red15>
3782 Change the default red palette of the console.
3783 This is a 16-member array composed of values
3784 ranging from 0-255.
3785
3786 vt.default_utf8=
3787 [VT]
3788 Format=<0|1>
3789 Set system-wide default UTF-8 mode for all tty's.
3790 Default is 1, i.e. UTF-8 mode is enabled for all
3791 newly opened terminals.
3792
Matthew Garrettf6c06b62009-11-13 15:14:11 -05003793 vt.global_cursor_default=
3794 [VT]
3795 Format=<-1|0|1>
3796 Set system-wide default for whether a cursor
3797 is shown on new VTs. Default is -1,
3798 i.e. cursors will be created by default unless
3799 overridden by individual drivers. 0 will hide
3800 cursors, 1 will display them.
3801
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003802 vt.italic= [VT] Default color for italic text; 0-15.
3803 Default: 2 = green.
3804
3805 vt.underline= [VT] Default color for underlined text; 0-15.
3806 Default: 3 = cyan.
3807
Randy Dunlap4724ba572010-05-03 11:42:52 -07003808 watchdog timers [HW,WDT] For information on watchdog timers,
3809 see Documentation/watchdog/watchdog-parameters.txt
3810 or other driver-specific files in the
3811 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003812
Tejun Heod55262c2013-04-01 11:23:38 -07003813 workqueue.disable_numa
3814 By default, all work items queued to unbound
3815 workqueues are affine to the NUMA nodes they're
3816 issued on, which results in better behavior in
3817 general. If NUMA affinity needs to be disabled for
3818 whatever reason, this option can be used. Note
3819 that this also can be controlled per-workqueue for
3820 workqueues visible under /sys/bus/workqueue/.
3821
Viresh Kumarcee22a12013-04-08 16:45:40 +05303822 workqueue.power_efficient
3823 Per-cpu workqueues are generally preferred because
3824 they show better performance thanks to cache
3825 locality; unfortunately, per-cpu workqueues tend to
3826 be more power hungry than unbound workqueues.
3827
3828 Enabling this makes the per-cpu workqueues which
3829 were observed to contribute significantly to power
3830 consumption unbound, leading to measurably lower
3831 power usage at the cost of small performance
3832 overhead.
3833
3834 The default value of this parameter is determined by
3835 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3836
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003837 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3838 default x2apic cluster mode on platforms
3839 supporting x2apic.
3840
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003841 x86_intel_mid_timer= [X86-32,APBT]
3842 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07003843 Two valid options are apbt timer only and lapic timer
3844 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003845 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07003846
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003847 xen_emul_unplug= [HW,X86,XEN]
3848 Unplug Xen emulated devices
3849 Format: [unplug0,][unplug1]
3850 ide-disks -- unplug primary master IDE devices
3851 aux-ide-disks -- unplug non-primary-master IDE devices
3852 nics -- unplug network devices
3853 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01003854 unnecessary -- unplugging emulated devices is
3855 unnecessary even if the host did not respond to
3856 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01003857 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003858
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04003859 xen_nopvspin [X86,XEN]
3860 Disables the ticketlock slowpath using Xen PV
3861 optimizations.
3862
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04003863 xen_nopv [X86]
3864 Disables the PV optimizations forcing the HVM guest to
3865 run as generic HVM guest with no PV drivers.
3866
Linus Torvalds1da177e2005-04-16 15:20:36 -07003867 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07003868 Format:
3869 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003870
Randy Dunlapa9913042005-10-23 12:57:11 -07003871______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07003872
3873TODO:
3874
Linus Torvalds1da177e2005-04-16 15:20:36 -07003875 Add more DRM drivers.