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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]
608 Keep all clocks already enabled by bootloader on,
609 even if no driver has claimed them. This is useful
610 for debug and development, but should not be
611 needed on a platform with proper driver support.
612 For more information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100613
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700614 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700615 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200616 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700617 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200618 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700619 Format: { pit | tsc | cyclone | pmtmr }
620
John Stultz592913e2010-07-13 17:56:20 -0700621 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700622 Format: <string>
623 Override the default clocksource and use the clocksource
624 with the name specified.
625 Some clocksource names to choose from, depending on
626 the platform:
627 [all] jiffies (this is the base, fallback clocksource)
628 [ACPI] acpi_pm
629 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
630 pxa_timer,timer3,32k_counter,timer0_1
631 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700632 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700633 scx200_hrt on Geode; cyclone on IBM x440
634 [MIPS] MIPS
635 [PARISC] cr16
636 [S390] tod
637 [SH] SuperH
638 [SPARC64] tick
639 [X86-64] hpet,tsc
640
Andi Kleenac72e782008-01-30 13:33:21 +0100641 clearcpuid=BITNUM [X86]
642 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800643 arch/x86/include/asm/cpufeature.h for the valid bit
644 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100645 stable over kernel options, but the vendor specific
646 ones should be.
647 Also note that user programs calling CPUID directly
648 or using the feature without checking anything
649 will still see it. This just prevents it from
650 being used by the kernel or shown in /proc/cpuinfo.
651 Also note the kernel might malfunction if you disable
652 some critical bits.
653
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700654 cma=nn[MG]@[start[MG][-end[MG]]]
655 [ARM,X86,KNL]
656 Sets the size of kernel global memory area for
657 contiguous memory allocations and optionally the
658 placement constraint by the physical address range of
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100659 memory allocations. For more information, see
660 include/linux/dma-contiguous.h
661
Robert Jennings14f966e2009-04-15 05:55:32 +0000662 cmo_free_hint= [PPC] Format: { yes | no }
663 Specify whether pages are marked as being inactive
664 when they are freed. This is used in CMO environments
665 to determine OS memory pressure for page stealing by
666 a hypervisor.
667 Default: yes
668
Marek Szyprowskic7909502011-12-29 13:09:51 +0100669 coherent_pool=nn[KMG] [ARM,KNL]
670 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200671 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100672
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530673 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100674 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100675 Range: 0 - 8192
676 Default: 64
677
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700679 Format:
680 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700681
682 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
683 Format: <io>[,<irq>]
684
Randy Dunlapa9913042005-10-23 12:57:11 -0700685 com90xx= [HW,NET]
686 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 Format: <io>[,<irq>[,<memstart>]]
688
689 condev= [HW,S390] console device
690 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700691
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692 console= [KNL] Output console device and options.
693
694 tty<n> Use the virtual console device <n>.
695
696 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800697 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800699 the form "bbbbpnf", where "bbbb" is the baud rate,
700 "p" is parity ("n", "o", or "e"), "n" is number of
701 bits, and "f" is flow control ("r" for RTS or
702 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800704 See Documentation/serial-console.txt for more
705 information. See
706 Documentation/networking/netconsole.txt for an
707 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700709 uart[8250],io,<addr>[,options]
710 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700711 Start an early, polled-mode console on the 8250/16550
712 UART at the specified I/O port or MMIO address,
713 switching to the matching ttyS device later. The
714 options are the same as for ttyS, above.
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500715 hvc<n> Use the hypervisor console device <n>. This is for
716 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700717
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700718 If the device connected to the port is not a TTY but a braille
719 device, prepend "brl," before the device type, for instance
720 console=brl,ttyS0
721 For now, only VisioBraille is supported.
722
Daniel Mackf324edc2009-06-16 15:33:52 -0700723 consoleblank= [KNL] The console blank (screen saver) timeout in
724 seconds. Defaults to 10*60 = 10mins. A value of 0
725 disables the blank timer.
726
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800727 coredump_filter=
728 [KNL] Change the default value for
729 /proc/<pid>/coredump_filter.
730 See also Documentation/filesystems/proc.txt.
731
Len Brown62027ae2011-04-01 18:13:10 -0400732 cpuidle.off=1 [CPU_IDLE]
733 disable the cpuidle sub-system
734
Linus Torvalds1da177e2005-04-16 15:20:36 -0700735 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700736 Format:
737 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700738
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800739 crashkernel=size[KMG][@offset[KMG]]
740 [KNL] Using kexec, Linux can switch to a 'crash kernel'
741 upon panic. This parameter reserves the physical
742 memory region [offset, offset + size] for that kernel
743 image. If '@offset' is omitted, then a suitable offset
744 is selected automatically. Check
745 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700746
Bernhard Wallefb391592007-10-18 23:41:02 -0700747 crashkernel=range1:size1[,range2:size2,...][@offset]
748 [KNL] Same as above, but depends on the memory
749 in the running system. The syntax of range is
750 start-[end] where start and end are both
751 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800752 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700753
Yinghai Luadbc7422013-04-15 22:23:48 -0700754 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700755 [KNL, x86_64] range could be above 4G. Allow kernel
756 to allocate physical memory region from top, so could
757 be above 4G if system have more than 4G ram installed.
758 Otherwise memory region will be allocated below 4G, if
759 available.
760 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700761 crashkernel=size[KMG],low
762 [KNL, x86_64] range under 4G. When crashkernel=X,high
763 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700764 above 4G, that cause second kernel crash on system
765 that require some amount of low memory, e.g. swiotlb
766 requires at least 64M+32K low memory. Kernel would
767 try to allocate 72M below 4G automatically.
768 This one let user to specify own low range under 4G
769 for second kernel instead.
770 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700771 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700772 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700773
Linus Torvalds1da177e2005-04-16 15:20:36 -0700774 cs89x0_dma= [HW,NET]
775 Format: <dma>
776
777 cs89x0_media= [HW,NET]
778 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700779
Randy Dunlapa9913042005-10-23 12:57:11 -0700780 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700781 See header of drivers/s390/block/dasd_devmap.c.
782
783 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
784 (one device per port)
785 Format: <port#>,<type>
786 See also Documentation/input/joystick-parport.txt
787
Thomas Renningera648ec02010-08-06 16:11:02 +0200788 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
789 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600790 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200791
Linus Torvalds1da177e2005-04-16 15:20:36 -0700792 debug [KNL] Enable kernel debugging (events log level).
793
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700794 debug_locks_verbose=
795 [KNL] verbose self-tests
796 Format=<0|1>
797 Print debugging info while doing the locking API
798 self-tests.
799 We default to 0 (no extra messages), setting it to
800 1 will print _a lot_ more information - normally
801 only useful to kernel developers.
802
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700803 debug_objects [KNL] Enable object debugging
804
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500805 no_debug_objects
806 [KNL] Disable object debugging
807
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800808 debug_guardpage_minorder=
809 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
810 parameter allows control of the order of pages that will
811 be intentionally kept free (and hence protected) by the
812 buddy allocator. Bigger value increase the probability
813 of catching random memory corruption, but reduce the
814 amount of memory for normal system use. The maximum
815 possible value is MAX_ORDER/2. Setting this parameter
816 to 1 or 2 should be enough to identify most random
817 memory corruption problems caused by bugs in kernel or
818 driver code when a CPU writes to (or reads from) a
819 random memory location. Note that there exists a class
820 of memory corruptions problems caused by buggy H/W or
821 F/W or by drivers badly programing DMA (basically when
822 memory is written at bus level and the CPU MMU is
823 bypassed) which are not detectable by
824 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
825 tracking down these problems.
826
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200827 debugpat [X86] Enable PAT debugging
828
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200829 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 Format: <area>[,<node>]
831 See also Documentation/networking/decnet.txt.
832
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700833 default_hugepagesz=
834 [same as hugepagesz=] The size of the default
835 HugeTLB page size. This is the size represented by
836 the legacy /proc/ hugepages APIs, used for SHM, and
837 default size when mounting hugetlbfs filesystems.
838 Defaults to the default architecture's huge page size
839 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700840
Linus Torvalds1da177e2005-04-16 15:20:36 -0700841 dhash_entries= [KNL]
842 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700843
Brian Haleyb0f83b22010-02-04 13:36:50 -0800844 disable= [IPV6]
845 See Documentation/networking/ipv6.txt.
846
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900847 disable_cpu_apicid= [X86,APIC,SMP]
848 Format: <int>
849 The number of initial APIC ID for the
850 corresponding CPU to be disabled at boot,
851 mostly used for the kdump 2nd kernel to
852 disable BSP to wake up multiple CPUs without
853 causing system reset or hang due to sending
854 INIT from AP to BSP.
855
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000856 disable_ddw [PPC/PSERIES]
857 Disable Dynamic DMA Window support. Use this if
858 to workaround buggy firmware.
859
Brian Haleyb0f83b22010-02-04 13:36:50 -0800860 disable_ipv6= [IPV6]
861 See Documentation/networking/ipv6.txt.
862
Yinghai Lu95ffa242008-04-29 03:52:33 -0700863 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700864 The kernel tries to adjust MTRR layout from continuous
865 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700866 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700867
Yinghai Lu093af8d2008-01-30 13:33:32 +0100868 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100869 By default the kernel will trim any uncacheable
870 memory out of your available memory pool based on
871 MTRR settings. This parameter disables that behavior,
872 possibly causing your machine to run very slowly.
873
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530874 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700875 Disable PIN 1 of APIC timer
876 Can be useful to work around chipset bugs.
877
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700878 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
879 this option disables the debugging code at boot.
880
881 dma_debug_entries=<number>
882 This option allows to tune the number of preallocated
883 entries for DMA-API debugging code. One entry is
884 required per DMA-API allocation. Use this if the
885 DMA-API debugging code disables itself because the
886 architectural default is too low.
887
Joerg Roedel1745de52009-05-22 21:49:51 +0200888 dma_debug_driver=<driver_name>
889 With this option the DMA-API debugging driver
890 filter feature can be enabled at boot time. Just
891 pass the driver to filter for as the parameter.
892 The filter can be disabled or changed to another
893 driver later using sysfs.
894
Carsten Emdeda0df922012-03-18 22:37:33 +0100895 drm_kms_helper.edid_firmware=[<connector>:]<file>
896 Broken monitors, graphic adapters and KVMs may
897 send no or incorrect EDID data sets. This parameter
898 allows to specify an EDID data set in the
899 /lib/firmware directory that is used instead.
900 Generic built-in EDID data sets are used, if one of
901 edid/1024x768.bin, edid/1280x1024.bin,
902 edid/1680x1050.bin, or edid/1920x1080.bin is given
903 and no file with the same name exists. Details and
904 instructions how to build your own EDID data are
905 available in Documentation/EDID/HOWTO.txt. An EDID
906 data set will only be used for a particular connector,
907 if its name and a colon are prepended to the EDID
908 name.
909
Linus Torvalds1da177e2005-04-16 15:20:36 -0700910 dscc4.setup= [NET]
911
Jim Cromie29e36c92012-04-27 14:30:41 -0600912 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
913 module.dyndbg[="val"]
914 Enable debug messages at boot time. See
915 Documentation/dynamic-debug-howto.txt for details.
916
Mark Salter56aeeba2014-04-07 15:39:53 -0700917 early_ioremap_debug [KNL]
918 Enable debug messages in early_ioremap support. This
919 is useful for tracking down temporary early mappings
920 which are not unmapped.
921
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700922 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500923
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700924 uart[8250],io,<addr>[,options]
925 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700926 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700927 Start an early, polled-mode console on the 8250/16550
928 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700929 MMIO inter-register address stride is either 8-bit
930 (mmio) or 32-bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700931 The options are the same as for ttyS, above.
932
Rob Herring0d3c6732014-04-18 17:19:57 -0500933 pl011,<addr>
934 Start an early, polled-mode console on a pl011 serial
935 port at the specified address. The pl011 serial port
936 must already be setup and configured. Options are not
937 yet supported.
938
Rob Herringd50d7262014-04-18 17:19:58 -0500939 smh Use ARM semihosting calls for early console.
940
Finn Thain7913ad12014-04-12 23:48:56 +1000941 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700942 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +0100943 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500944 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700945 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -0700946 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500947 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500948 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700949
Dave Hansen147ea092013-04-10 14:03:38 -0700950 earlyprintk is useful when the kernel crashes before
951 the normal console is initialized. It is not enabled by
952 default because it has some cosmetic problems.
953
Randy Dunlapa9913042005-10-23 12:57:11 -0700954 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700955 takes over.
956
Matt Fleming72548e82013-10-04 09:36:56 +0100957 Only one of vga, efi, serial, or usb debug port can
958 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700959
Dave Hansen147ea092013-04-10 14:03:38 -0700960 Currently only ttyS0 and ttyS1 may be specified by
961 name. Other I/O ports may be explicitly specified
962 on some architectures (x86 and arm at least) by
963 replacing ttySn with an I/O port address, like this:
964 earlyprintk=serial,0x1008,115200
965 You can find the port for a given device in
966 /proc/tty/driver/serial:
967 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -0700968
969 Interaction with the standard serial driver is not
970 very good.
971
Matt Fleming72548e82013-10-04 09:36:56 +0100972 The VGA and EFI output is eventually overwritten by
973 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500975 The xen output can only be used by Xen PV guests.
976
Chen, Gongc700f012013-12-06 01:17:08 -0500977 edac_report= [HW,EDAC] Control how to report EDAC event
978 Format: {"on" | "off" | "force"}
979 on: enable EDAC to report H/W event. May be overridden
980 by other higher priority error reporting module.
981 off: disable H/W event reporting through EDAC.
982 force: enforce the use of EDAC to report H/W event.
983 default: on.
984
Jason Wessel97311912010-05-20 21:04:30 -0500985 ekgdboc= [X86,KGDB] Allow early kernel console debugging
986 ekgdboc=kbd
987
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300988 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -0500989 the boot argument: earlyprintk=vga
990
Linus Torvalds1da177e2005-04-16 15:20:36 -0700991 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700992 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700993
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +0100994 efi= [EFI]
995 Format: { "old_map" }
996 old_map [X86-64]: switch to the old ioremap-based EFI
997 runtime services mapping. 32-bit still uses this one by
998 default.
999
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001000 efi_no_storage_paranoia [EFI; X86]
1001 Using this parameter you can use more than 50% of
1002 your efi variable storage. Use this parameter only if
1003 you are really sure that your UEFI does sane gc and
1004 fulfills the spec otherwise your board may brick.
1005
Linus Torvalds1da177e2005-04-16 15:20:36 -07001006 eisa_irq_edge= [PARISC,HW]
1007 See header of drivers/parisc/eisa.c.
1008
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001009 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001010 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001011 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001012
1013 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001014 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001015 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001016 Documentation/block/deadline-iosched.txt for details.
1017
Michael Holzheud3bf37952011-10-30 15:16:37 +01001018 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001019 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001020 image elf header and optionally the size. Generally
1021 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001022 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001023
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001024 enable_mtrr_cleanup [X86]
1025 The kernel tries to adjust MTRR layout from continuous
1026 to discrete, to make X server driver able to add WB
1027 entry later. This parameter enables that.
1028
Randy Dunlapca1eda22009-05-06 16:02:58 -07001029 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001030 Enable PIN 1 of APIC timer
1031 Can be useful to work around chipset bugs
1032 (in particular on some ATI chipsets).
1033 The kernel tries to set a reasonable default.
1034
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035 enforcing [SELINUX] Set initial enforcing status.
1036 Format: {"0" | "1"}
1037 See security/selinux/Kconfig help text.
1038 0 -- permissive (log only, no denials).
1039 1 -- enforcing (deny and log).
1040 Default value is 0.
1041 Value can be changed at runtime via /selinux/enforce.
1042
Huang Yinga08f82d2010-05-18 14:35:21 +08001043 erst_disable [ACPI]
1044 Disable Error Record Serialization Table (ERST)
1045 support.
1046
Linus Torvalds1da177e2005-04-16 15:20:36 -07001047 ether= [HW,NET] Ethernet cards parameters
1048 This option is obsoleted by the "netdev=" option, which
1049 has equivalent usage. See its documentation for details.
1050
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001051 evm= [EVM]
1052 Format: { "fix" }
1053 Permit 'security.evm' to be updated regardless of
1054 current integrity status.
1055
Akinobu Mitade1ba092006-12-08 02:39:42 -08001056 failslab=
1057 fail_page_alloc=
1058 fail_make_request=[KNL]
1059 General fault injection mechanism.
1060 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001061 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001062
Linus Torvalds1da177e2005-04-16 15:20:36 -07001063 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001064 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065
Alex Chiangf13ae302008-05-08 14:03:23 -06001066 force_pal_cache_flush
1067 [IA-64] Avoid check_sal_cache_flush which may hang on
1068 buggy SAL_CACHE_FLUSH implementations. Using this
1069 parameter will force ia64_sal_cache_flush to call
1070 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1071
Chris Bainbridge69f23662014-03-07 18:40:42 +07001072 forcepae [X86-32]
1073 Forcefully enable Physical Address Extension (PAE).
1074 Many Pentium M systems disable PAE but may have a
1075 functionally usable PAE implementation.
1076 Warning: use of this parameter will taint the kernel
1077 and may cause unknown problems.
1078
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001079 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001080 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001081 as early as possible in order to facilitate early
1082 boot debugging.
1083
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001084 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001085 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001086 If no parameter is passed, ftrace will dump
1087 buffers of all CPUs, but if you pass orig_cpu, it will
1088 dump only the buffer of the CPU that triggered the
1089 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001090
1091 ftrace_filter=[function-list]
1092 [FTRACE] Limit the functions traced by the function
1093 tracer at boot up. function-list is a comma separated
1094 list of functions. This list can be changed at run
1095 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001096 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001097
1098 ftrace_notrace=[function-list]
1099 [FTRACE] Do not trace the functions specified in
1100 function-list. This list can be changed at run time
1101 by the set_ftrace_notrace file in the debugfs
1102 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001103
Stefan Assmann369bc182009-10-12 22:17:21 +02001104 ftrace_graph_filter=[function-list]
1105 [FTRACE] Limit the top level callers functions traced
1106 by the function graph tracer at boot up.
1107 function-list is a comma separated list of functions
1108 that can be changed at run time by the
1109 set_graph_function file in the debugfs tracing directory.
1110
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001111 ftrace_graph_notrace=[function-list]
1112 [FTRACE] Do not trace from the functions specified in
1113 function-list. This list is a comma separated list of
1114 functions that can be changed at run time by the
1115 set_graph_notrace file in the debugfs tracing directory.
1116
Linus Torvalds1da177e2005-04-16 15:20:36 -07001117 gamecon.map[2|3]=
1118 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1119 support via parallel port (up to 5 devices per port)
1120 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1121 See also Documentation/input/joystick-parport.txt
1122
1123 gamma= [HW,DRM]
1124
Yinghai Luaaf23042008-01-30 13:33:09 +01001125 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1126 Format: off | on
1127 default: on
1128
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001129 gcov_persist= [GCOV] When non-zero (default), profiling data for
1130 kernel modules is saved and remains accessible via
1131 debugfs, even when the module is unloaded/reloaded.
1132 When zero, profiling data is discarded and associated
1133 debugfs files are removed at module unload time.
1134
Linus Torvalds1da177e2005-04-16 15:20:36 -07001135 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001136 invalid Protective MBR to be treated as GPT. If the
1137 primary GPT is corrupted, it enables the backup/alternate
1138 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001139
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001140 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1141 the "Enable 0" bit of the configuration register.
1142 Format: 0 | 1
1143 Default: 0
1144 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1145 the "Enable 0" bit of the configuration register.
1146 Format: 0 | 1
1147 Default: 0
1148 grcan.select= [HW] Select which physical interface to use.
1149 Format: 0 | 1
1150 Default: 0
1151 grcan.txsize= [HW] Sets the size of the tx buffer.
1152 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1153 Default: 1024
1154 grcan.rxsize= [HW] Sets the size of the rx buffer.
1155 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1156 Default: 1024
1157
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 hashdist= [KNL,NUMA] Large hashes allocated during boot
1159 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001160 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001161 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001162
1163 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1164
1165 hd= [EIDE] (E)IDE hard drive subsystem geometry
1166 Format: <cyl>,<head>,<sect>
1167
Huang Yingea8c0712010-05-18 14:35:15 +08001168 hest_disable [ACPI]
1169 Disable Hardware Error Source Table (HEST) support;
1170 corresponding firmware-first mode error processing
1171 logic will be disabled.
1172
Linus Torvalds1da177e2005-04-16 15:20:36 -07001173 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1174 size of <nn>. This works even on boxes that have no
1175 highmem otherwise. This also works to reduce highmem
1176 size on bigger boxes.
1177
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001178 highres= [KNL] Enable/disable high resolution timer mode.
1179 Valid parameters: "on", "off"
1180 Default: "on"
1181
Linus Torvalds1da177e2005-04-16 15:20:36 -07001182 hisax= [HW,ISDN]
1183 See Documentation/isdn/README.HiSax.
1184
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001185 hlt [BUGS=ARM,SH]
1186
1187 hpet= [X86-32,HPET] option to control HPET usage
1188 Format: { enable (default) | disable | force |
1189 verbose }
1190 disable: disable HPET and use PIT instead
1191 force: allow force enabled of undocumented chips (ICH4,
1192 VIA, nVidia)
1193 verbose: show contents of HPET registers during setup
1194
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001195 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1196 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1197
Andi Kleenb4718e62008-07-23 21:27:51 -07001198 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1199 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001200 On x86-64 and powerpc, this option can be specified
1201 multiple times interleaved with hugepages= to reserve
1202 huge pages of different sizes. Valid pages sizes on
1203 x86-64 are 2M (when the CPU supports "pse") and 1G
1204 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -07001205 Note that 1GB pages can only be allocated at boot time
1206 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +09001207
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001208 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1209 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001210 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1211 If specified, z/VM IUCV HVC accepts connections
1212 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001213
James Hoganfdabf522012-10-09 11:00:27 +01001214 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1215 hardware thread id mappings.
1216 Format: <cpu>:<hwthread>
1217
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001218 keep_bootcon [KNL]
1219 Do not unregister boot console at start. This is only
1220 useful for debugging when something happens in the window
1221 between unregistering the boot console and initializing
1222 the real console.
1223
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001224 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001225 or register an additional I2C bus that is not
1226 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001227 Format:
1228 <bus_id>,<clkrate>
1229
Jiri Kosina36d95732008-10-06 02:51:09 -04001230 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001231 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001232 i8042.dumbkbd [HW] Pretend that controller can only read data from
1233 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001234 (Don't attempt to blink the leds)
1235 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001236 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001237 i8042.noloop [HW] Disable the AUX Loopback command while probing
1238 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001239 i8042.nomux [HW] Don't check presence of an active multiplexing
1240 controller
1241 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1242 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001243 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001244 i8042.reset [HW] Reset the controller during init and cleanup
1245 i8042.unlock [HW] Unlock (ignore) the keylock
1246
1247 i810= [HW,DRM]
1248
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001249 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1250 indicates that the driver is running on unsupported
1251 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001252 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1253 does not match list of supported models.
1254 i8k.power_status
1255 [HW] Report power status in /proc/i8k
1256 (disabled by default)
1257 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1258 capability is set.
1259
Carsten Emde4dca20e2012-03-15 15:56:26 +01001260 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001261 [DRM] Invert the sense of the variable that is used to
1262 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001263 brightness value of 0 indicates backlight switched off,
1264 and the maximum of the brightness value sets the backlight
1265 to maximum brightness. If this parameter is set to 0
1266 (default) and the machine requires it, or this parameter
1267 is set to 1, a brightness value of 0 sets the backlight
1268 to maximum brightness, and the maximum of the brightness
1269 value switches the backlight off.
1270 -1 -- never invert brightness
1271 0 -- machine default
1272 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001273
Linus Torvalds1da177e2005-04-16 15:20:36 -07001274 icn= [HW,ISDN]
1275 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1276
David Fries0af80c02009-02-25 20:28:21 +01001277 ide-core.nodma= [HW] (E)IDE subsystem
1278 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001279 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1280 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001281 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001282
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001283 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1284 Claim all unknown PCI IDE storage controllers.
1285
Andi Kleenf039b752007-05-02 19:27:12 +02001286 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001287 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001288 Poll forces a polling idle loop that can slightly
1289 improve the performance of waking up a idle CPU, but
1290 will use a lot of power and make the system run hot.
1291 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001292 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001293 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001294 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001295
Ingo Molnar792908222006-12-06 20:40:51 -08001296 ignore_loglevel [KNL]
1297 Ignore loglevel setting - this will print /all/
1298 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001299 We also add it as printk module parameter, so users
1300 could change it dynamically, usually by
1301 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001302
Linus Torvalds1da177e2005-04-16 15:20:36 -07001303 ihash_entries= [KNL]
1304 Set number of hash buckets for inode cache.
1305
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001306 ima_appraise= [IMA] appraise integrity measurements
1307 Format: { "off" | "enforce" | "fix" }
1308 default: "enforce"
1309
Mimi Zohar07f6a792011-03-09 22:25:48 -05001310 ima_appraise_tcb [IMA]
1311 The builtin appraise policy appraises all files
1312 owned by uid=0.
1313
Mimi Zohar3323eec2009-02-04 09:06:58 -05001314 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001315 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1316 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001317 default: "sha1"
1318
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001319 The list of supported hash algorithms is defined
1320 in crypto/hash_info.h.
1321
Eric Paris5789ba32009-05-21 15:47:06 -04001322 ima_tcb [IMA]
1323 Load a policy which meets the needs of the Trusted
1324 Computing Base. This means IMA will measure all
1325 programs exec'd, files mmap'd for exec, and all files
1326 opened for read by uid=0.
1327
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001328 ima_template= [IMA]
1329 Select one of defined IMA measurements template formats.
1330 Formats: { "ima" | "ima-ng" }
1331 Default: "ima-ng"
1332
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001333 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1334 Format: <min_file_size>
1335 Set the minimal file size for using asynchronous hash.
1336 If left unspecified, ahash usage is disabled.
1337
1338 ahash performance varies for different data sizes on
1339 different crypto accelerators. This option can be used
1340 to achieve the best performance for a particular HW.
1341
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001342 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1343 Format: <bufsize>
1344 Set hashing buffer size. Default: 4k.
1345
1346 ahash performance varies for different chunk sizes on
1347 different crypto accelerators. This option can be used
1348 to achieve best performance for particular HW.
1349
Linus Torvalds1da177e2005-04-16 15:20:36 -07001350 init= [KNL]
1351 Format: <full_path>
1352 Run specified binary instead of /sbin/init as init
1353 process.
1354
1355 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1356 for working out where the kernel is dying during
1357 startup.
1358
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001359 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1360 initcall functions. Useful for debugging built-in
1361 modules and initcalls.
1362
Linus Torvalds1da177e2005-04-16 15:20:36 -07001363 initrd= [BOOT] Specify the location of the initial ramdisk
1364
1365 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1366 Format: <irq>
1367
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001368 int_pln_enable [x86] Enable power limit notification interrupt
1369
Mimi Zohard726d8d2013-03-18 14:48:02 -04001370 integrity_audit=[IMA]
1371 Format: { "0" | "1" }
1372 0 -- basic integrity auditing messages. (Default)
1373 1 -- additional integrity auditing messages.
1374
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001375 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001376 on
1377 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001378 off
1379 Disable intel iommu driver.
1380 igfx_off [Default Off]
1381 By default, gfx is mapped as normal device. If a gfx
1382 device has a dedicated DMAR unit, the DMAR unit is
1383 bypassed by not enabling DMAR with this option. In
1384 this case, gfx device will use physical address for
1385 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001386 forcedac [x86_64]
1387 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001388 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001389 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001390 than 32-bit addressing. The default is to look
1391 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001392 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001393 strict [Default Off]
1394 With this option on every unmap_single operation will
1395 result in a hardware IOTLB flush operation as opposed
1396 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001397 sp_off [Default Off]
1398 By default, super page will be supported if Intel IOMMU
1399 has the capability. With this option, super page will
1400 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001401
1402 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1403 0 disables intel_idle and fall back on acpi_idle.
1404 1 to 6 specify maximum depth of C-state.
1405
Dirk Brandewie6be26492013-02-15 22:55:10 +01001406 intel_pstate= [X86]
1407 disable
1408 Do not enable intel_pstate as the default
1409 scaling driver for the supported processors
1410
Chris Wrightd1423d52010-07-20 11:06:49 -07001411 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001412 on enable Interrupt Remapping (default)
1413 off disable Interrupt Remapping
1414 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001415 no_x2apic_optout
1416 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001417
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001418 iomem= Disable strict checking of access to MMIO memory
1419 strict regions from userspace.
1420 relaxed
1421
1422 iommu= [x86]
1423 off
1424 force
1425 noforce
1426 biomerge
1427 panic
1428 nopanic
1429 merge
1430 nomerge
1431 forcesac
1432 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001433 pt [x86, IA-64]
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001434
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001435
1436 io7= [HW] IO7 for Marvel based alpha systems
1437 See comment before marvel_specify_io7 in
1438 arch/alpha/kernel/core_marvel.c.
1439
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301440 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001441 0x80
1442 Standard port 0x80 based delay
1443 0xed
1444 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001445 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001446 Simple two microseconds delay
1447 none
1448 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001449
Linus Torvalds1da177e2005-04-16 15:20:36 -07001450 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001451 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001452
Alan Cox200803d2005-06-28 20:45:18 -07001453 irqfixup [HW]
1454 When an interrupt is not handled search all handlers
1455 for it. Intended to get systems with badly broken
1456 firmware running.
1457
1458 irqpoll [HW]
1459 When an interrupt is not handled search all handlers
1460 for it. Also check all handlers each timer
1461 interrupt. Intended to get systems with badly broken
1462 firmware running.
1463
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001465 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001466
1467 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001468 Format:
1469 <cpu number>,...,<cpu number>
1470 or
Li Zefanb225d442008-11-06 12:53:39 -08001471 <cpu number>-<cpu number>
1472 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001473 or a mixture
1474 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001475
Linus Torvalds1da177e2005-04-16 15:20:36 -07001476 This option can be used to specify one or more CPUs
1477 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001478 algorithms. You can move a process onto or off an
1479 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001480 <cpu number> begins at 0 and the maximum value is
1481 "number of CPUs in system - 1".
1482
1483 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001484 alternative -- manually setting the CPU mask of all
1485 tasks in the system -- can cause problems and
1486 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001487
Randy Dunlapa9913042005-10-23 12:57:11 -07001488 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001490 ivrs_ioapic [HW,X86_64]
1491 Provide an override to the IOAPIC-ID<->DEVICE-ID
1492 mapping provided in the IVRS ACPI table. For
1493 example, to map IOAPIC-ID decimal 10 to
1494 PCI device 00:14.0 write the parameter as:
1495 ivrs_ioapic[10]=00:14.0
1496
1497 ivrs_hpet [HW,X86_64]
1498 Provide an override to the HPET-ID<->DEVICE-ID
1499 mapping provided in the IVRS ACPI table. For
1500 example, to map HPET-ID decimal 0 to
1501 PCI device 00:14.0 write the parameter as:
1502 ivrs_hpet[0]=00:14.0
1503
Linus Torvalds1da177e2005-04-16 15:20:36 -07001504 js= [HW,JOY] Analog joystick
1505 See Documentation/input/joystick.txt.
1506
Kees Cook24f2e022014-06-13 13:30:36 -07001507 kaslr/nokaslr [X86]
1508 Enable/disable kernel and module base offset ASLR
1509 (Address Space Layout Randomization) if built into
1510 the kernel. When CONFIG_HIBERNATION is selected,
1511 kASLR is disabled by default. When kASLR is enabled,
1512 hibernation will be disabled.
1513
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001514 keepinitrd [HW,ARM]
1515
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301516 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001517 specifies the amount of memory usable by the kernel
1518 for non-movable allocations. The requested amount is
1519 spread evenly throughout all nodes in the system. The
1520 remaining memory in each node is used for Movable
1521 pages. In the event, a node is too small to have both
1522 kernelcore and Movable pages, kernelcore pages will
1523 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001524 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001525 allocation of pages that may be reclaimed or moved
1526 by the page migration subsystem. This means that
1527 HugeTLB pages may not be allocated from this zone.
1528 Note that allocations like PTEs-from-HighMem still
1529 use the HighMem zone if it exists, and the Normal
1530 zone if it does not.
1531
Jason Wessel4fe1da42010-05-20 21:04:31 -05001532 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1533 Format: <Controller#>[,poll interval]
1534 The controller # is the number of the ehci usb debug
1535 port as it is probed via PCI. The poll interval is
1536 optional and is the number seconds in between
1537 each poll cycle to the debug port in case you need
1538 the functionality for interrupting the kernel with
1539 gdb or control-c on the dbgp connection. When
1540 not using this parameter you use sysrq-g to break into
1541 the kernel debugger.
1542
Jason Wessel84c08fd2010-05-20 21:04:24 -05001543 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001544 Requires a tty driver that supports console polling,
1545 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001546 Serial only format: <serial_device>[,baud]
1547 keyboard only format: kbd
1548 keyboard and serial format: kbd,<serial_device>[,baud]
1549 Optional Kernel mode setting:
1550 kms, kbd format: kms,kbd
1551 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001552
Jason Wessel84c08fd2010-05-20 21:04:24 -05001553 kgdbwait [KGDB] Stop kernel execution and enter the
1554 kernel debugger at the earliest opportunity.
1555
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001556 kmac= [MIPS] korina ethernet MAC address.
1557 Configure the RouterBoard 532 series on-chip
1558 Ethernet adapter MAC address.
1559
Catalin Marinas04f70332009-06-11 13:22:39 +01001560 kmemleak= [KNL] Boot-time kmemleak enable/disable
1561 Valid arguments: on, off
1562 Default: on
1563
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001564 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1565 Valid arguments: 0, 1, 2
1566 kmemcheck=0 (disabled)
1567 kmemcheck=1 (enabled)
1568 kmemcheck=2 (one-shot mode)
1569 Default: 2 (one-shot mode)
1570
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301571 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001572 in oops dumps.
1573
Andre Przywarafef07aa2009-07-10 14:20:35 +02001574 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1575 Default is 0 (don't ignore, but inject #GP)
1576
Xiao Guangronga182d872010-09-20 22:17:48 +08001577 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1578 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001579 Default is 0 (off)
1580
Andre Przywarafef07aa2009-07-10 14:20:35 +02001581 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001582 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001583
1584 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1585 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001586 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001587
Andre Przywarafef07aa2009-07-10 14:20:35 +02001588 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1589 (virtualized MMU) support on capable Intel chips.
1590 Default is 1 (enabled)
1591
1592 kvm-intel.emulate_invalid_guest_state=
1593 [KVM,Intel] Enable emulation of invalid guest states
1594 Default is 0 (disabled)
1595
1596 kvm-intel.flexpriority=
1597 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1598 Default is 1 (enabled)
1599
Sasha Levine1a72ae2011-08-09 14:28:35 +03001600 kvm-intel.nested=
1601 [KVM,Intel] Enable VMX nesting (nVMX).
1602 Default is 0 (disabled)
1603
Andre Przywarafef07aa2009-07-10 14:20:35 +02001604 kvm-intel.unrestricted_guest=
1605 [KVM,Intel] Disable unrestricted guest feature
1606 (virtualized real and unpaged mode) on capable
1607 Intel chips. Default is 1 (enabled)
1608
1609 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1610 feature (tagged TLBs) on capable Intel chips.
1611 Default is 1 (enabled)
1612
Linus Torvalds1da177e2005-04-16 15:20:36 -07001613 l2cr= [PPC]
1614
Robert Brosea78bfbf2008-03-29 07:20:23 +11001615 l3cr= [PPC]
1616
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001617 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001618 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001619
Suresh Siddha279f1462012-10-22 14:37:58 -07001620 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1621 value for LAPIC timer one-shot implementation. Default
1622 back to the programmable timer unit in the LAPIC.
1623
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301624 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001625 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001626
FD Camifcb71f62008-01-06 19:08:56 +01001627 libata.dma= [LIBATA] DMA control
1628 libata.dma=0 Disable all PATA and SATA DMA
1629 libata.dma=1 PATA and SATA Disk DMA only
1630 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001631 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001632 Combinations also work, so libata.dma=3 enables DMA
1633 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001634
Michael Prokop20308872009-08-06 00:14:10 +02001635 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1636 libata.ignore_hpa=0 keep BIOS limits (default)
1637 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001638
Dave Jones78e70c22007-09-27 11:50:13 -04001639 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1640 when set.
1641 Format: <int>
1642
Tejun Heo33267322008-02-13 09:15:09 +09001643 libata.force= [LIBATA] Force configurations. The format is comma
1644 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001645 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001646 matching port, link or device. Basically, it matches
1647 the ATA ID string printed on console by libata. If
1648 the whole ID part is omitted, the last PORT and DEVICE
1649 values are used. If ID hasn't been specified yet, the
1650 configuration applies to all ports, links and devices.
1651
1652 If only DEVICE is omitted, the parameter applies to
1653 the port and all links and devices behind it. DEVICE
1654 number of 0 either selects the first device or the
1655 first fan-out link behind PMP device. It does not
1656 select the host link. DEVICE number of 15 selects the
1657 host link and device attached to it.
1658
1659 The VAL specifies the configuration to force. As long
1660 as there's no ambiguity shortcut notation is allowed.
1661 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1662 The following configurations can be forced.
1663
1664 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1665 Any ID with matching PORT is used.
1666
1667 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1668
1669 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1670 udma[/][16,25,33,44,66,100,133] notation is also
1671 allowed.
1672
1673 * [no]ncq: Turn on or off NCQ.
1674
Tejun Heo05944bd2008-08-13 20:19:09 +09001675 * nohrst, nosrst, norst: suppress hard, soft
1676 and both resets.
1677
Dan Williamsca6d43b2012-06-21 23:41:41 -07001678 * rstonce: only attempt one reset during
1679 hot-unplug link recovery
1680
Tejun Heo43c9c592010-05-23 12:59:11 +02001681 * dump_id: dump IDENTIFY data.
1682
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001683 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1684
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001685 * disable: Disable this device.
1686
Tejun Heo33267322008-02-13 09:15:09 +09001687 If there are multiple matching configurations changing
1688 the same attribute, the last one is used.
1689
Yinghai Lu95f72d12010-07-12 14:36:09 +10001690 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001691
Linus Torvalds1da177e2005-04-16 15:20:36 -07001692 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001693 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001694
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001695 lockd.nlm_grace_period=P [NFS] Assign grace period.
1696 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001697
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001698 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1699 Format: <integer>
1700
1701 lockd.nlm_timeout=T [NFS] Assign timeout value.
1702 Format: <integer>
1703
1704 lockd.nlm_udpport=M [NFS] Assign UDP port.
1705 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001706
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001707 locktorture.nreaders_stress= [KNL]
1708 Set the number of locking read-acquisition kthreads.
1709 Defaults to being automatically set based on the
1710 number of online CPUs.
1711
1712 locktorture.nwriters_stress= [KNL]
1713 Set the number of locking write-acquisition kthreads.
1714
1715 locktorture.onoff_holdoff= [KNL]
1716 Set time (s) after boot for CPU-hotplug testing.
1717
1718 locktorture.onoff_interval= [KNL]
1719 Set time (s) between CPU-hotplug operations, or
1720 zero to disable CPU-hotplug testing.
1721
1722 locktorture.shuffle_interval= [KNL]
1723 Set task-shuffle interval (jiffies). Shuffling
1724 tasks allows some CPUs to go into dyntick-idle
1725 mode during the locktorture test.
1726
1727 locktorture.shutdown_secs= [KNL]
1728 Set time (s) after boot system shutdown. This
1729 is useful for hands-off automated testing.
1730
1731 locktorture.stat_interval= [KNL]
1732 Time (s) between statistics printk()s.
1733
1734 locktorture.stutter= [KNL]
1735 Time (s) to stutter testing, for example,
1736 specifying five seconds causes the test to run for
1737 five seconds, wait for five seconds, and so on.
1738 This tests the locking primitive's ability to
1739 transition abruptly to and from idle.
1740
1741 locktorture.torture_runnable= [BOOT]
1742 Start locktorture running at boot time.
1743
1744 locktorture.torture_type= [KNL]
1745 Specify the locking implementation to test.
1746
1747 locktorture.verbose= [KNL]
1748 Enable additional printk() statements.
1749
Linus Torvalds1da177e2005-04-16 15:20:36 -07001750 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1751 Format: <irq>
1752
1753 loglevel= All Kernel Messages with a loglevel smaller than the
1754 console loglevel will be printed to the console. It can
1755 also be changed with klogd or other programs. The
1756 loglevels are defined as follows:
1757
1758 0 (KERN_EMERG) system is unusable
1759 1 (KERN_ALERT) action must be taken immediately
1760 2 (KERN_CRIT) critical conditions
1761 3 (KERN_ERR) error conditions
1762 4 (KERN_WARNING) warning conditions
1763 5 (KERN_NOTICE) normal but significant condition
1764 6 (KERN_INFO) informational
1765 7 (KERN_DEBUG) debug-level messages
1766
Randy Dunlapc756d082011-02-20 20:08:35 -08001767 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001768 in bytes. n must be a power of two and greater
1769 than the minimal size. The minimal size is defined
1770 by LOG_BUF_SHIFT kernel config parameter. There is
1771 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1772 that allows to increase the default size depending on
1773 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001774
Randy Dunlapaccaa242007-10-16 01:29:37 -07001775 logo.nologo [FB] Disables display of the built-in Linux logo.
1776 This may be used to provide more screen space for
1777 kernel log messages and is useful when debugging
1778 kernel boot problems.
1779
Linus Torvalds1da177e2005-04-16 15:20:36 -07001780 lp=0 [LP] Specify parallel ports to use, e.g,
1781 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1782 lp=reset first parallel port). 'lp=0' disables the
1783 lp=auto printer driver. 'lp=reset' (which can be
1784 specified in addition to the ports) causes
1785 attached printers to be reset. Using
1786 lp=port1,port2,... specifies the parallel ports
1787 to associate lp devices with, starting with
1788 lp0. A port specification may be 'none' to skip
1789 that lp device, or a parport name such as
1790 'parport0'. Specifying 'lp=auto' instead of a
1791 port specification list means that device IDs
1792 from each port should be examined, to see if
1793 an IEEE 1284-compliant printer is attached; if
1794 so, the driver will manage that printer.
1795 See also header of drivers/char/lp.c.
1796
1797 lpj=n [KNL]
1798 Sets loops_per_jiffy to given constant, thus avoiding
1799 time-consuming boot-time autodetection (up to 250 ms per
1800 CPU). 0 enables autodetection (default). To determine
1801 the correct value for your kernel, boot with normal
1802 autodetection and see what value is printed. Note that
1803 on SMP systems the preset will be applied to all CPUs,
1804 which is likely to cause problems if your CPUs need
1805 significantly divergent settings. An incorrect value
1806 will cause delays in the kernel to be wrong, leading to
1807 unpredictable I/O errors and other breakage. Although
1808 unlikely, in the extreme case this might damage your
1809 hardware.
1810
1811 ltpc= [NET]
1812 Format: <io>,<irq>,<dma>
1813
Randy Dunlap16290242011-08-13 12:34:52 -07001814 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001815 (machvec) in a generic kernel.
1816 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001817
Wu Zhangjin3209e702009-07-02 23:27:12 +08001818 machtype= [Loongson] Share the same kernel image file between different
1819 yeeloong laptop.
1820 Example: machtype=lemote-yeeloong-2f-7inch
1821
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001822 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1823 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001824
1825 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001826 should make use of. maxcpus=n : n >= 0 limits the
1827 kernel to using 'n' processors. n=0 is a special case,
1828 it is equivalent to "nosmp", which also disables
1829 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001830
Kay Sieversd134b002011-07-31 22:08:04 +02001831 max_loop= [LOOP] The number of loop block devices that get
1832 (loop.max_loop) unconditionally pre-created at init time. The default
1833 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1834 of statically allocating a predefined number, loop
1835 devices can be requested on-demand with the
1836 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001837
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001838 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001839
Uwe Hermann71cced62008-10-20 09:32:21 -07001840 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001841
Linus Torvalds1da177e2005-04-16 15:20:36 -07001842 md= [HW] RAID subsystems devices and level
1843 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001844
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845 mdacon= [MDA]
1846 Format: <first>,<last>
1847 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001848
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1850 Amount of memory to be used when the kernel is not able
1851 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08001852 [X86] Work as limiting max address. Use together
1853 with memmap= to avoid physical address space collisions.
1854 Without memmap= PCI devices could be placed at addresses
1855 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001856
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001857 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001858 memory.
1859
Paul Mundt6902aa82008-09-21 17:14:42 +09001860 memchunk=nn[KMG]
1861 [KNL,SH] Allow user to override the default size for
1862 per-device physically contiguous DMA buffers.
1863
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301864 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001865 E820 memory map, as specified by the user.
1866 Such memmap=exactmap lines can be constructed based on
1867 BIOS output or other requirements. See the memmap=nn@ss
1868 option description.
1869
1870 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08001871 [KNL] Force usage of a specific region of memory.
1872 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001873
1874 memmap=nn[KMG]#ss[KMG]
1875 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08001876 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001877
1878 memmap=nn[KMG]$ss[KMG]
1879 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08001880 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001881 Example: Exclude memory from 0x18690000-0x1869ffff
1882 memmap=64K$0x18690000
1883 or
1884 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001885
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001886 memory_corruption_check=0/1 [X86]
1887 Some BIOSes seem to corrupt the first 64k of
1888 memory when doing things like suspend/resume.
1889 Setting this option will scan the memory
1890 looking for corruption. Enabling this will
1891 both detect corruption and prevent the kernel
1892 from using the memory being corrupted.
1893 However, its intended as a diagnostic tool; if
1894 repeatable BIOS-originated corruption always
1895 affects the same memory, you can use memmap=
1896 to prevent the kernel from using that memory.
1897
1898 memory_corruption_check_size=size [X86]
1899 By default it checks for corruption in the low
1900 64k, making this memory unavailable for normal
1901 use. Use this parameter to scan for
1902 corruption in more or less memory.
1903
1904 memory_corruption_check_period=seconds [X86]
1905 By default it checks for corruption every 60
1906 seconds. Use this parameter to check at some
1907 other rate. 0 disables periodic checking.
1908
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001909 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001910 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001911 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001912 Specifies the number of memtest passes to be
1913 performed. Each pass selects another test
1914 pattern from a given set of patterns. Memtest
1915 fills the memory with this pattern, validates
1916 memory contents and reserves bad memory
1917 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001918
Linus Torvalds1da177e2005-04-16 15:20:36 -07001919 meye.*= [HW] Set MotionEye Camera parameters
1920 See Documentation/video4linux/meye.txt.
1921
Andres Salomon8f368812007-10-12 23:04:06 +02001922 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1923 Multi-Function General Purpose Timers on AMD Geode
1924 platforms.
1925
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001926 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1927 the BIOS has incorrectly applied a workaround. TinyBIOS
1928 version 0.98 is known to be affected, 0.99 fixes the
1929 problem by letting the user disable the workaround.
1930
Linus Torvalds1da177e2005-04-16 15:20:36 -07001931 mga= [HW,DRM]
1932
Randy Dunlap1c207f92008-11-19 15:36:16 -08001933 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1934 physical address is ignored.
1935
Michel Pollet39f45d72009-05-20 11:10:31 +01001936 mini2440= [ARM,HW,KNL]
1937 Format:[0..2][b][c][t]
1938 Default: "0tb"
1939 MINI2440 configuration specification:
1940 0 - The attached screen is the 3.5" TFT
1941 1 - The attached screen is the 7" TFT
1942 2 - The VGA Shield is attached (1024x768)
1943 Leaving out the screen size parameter will not load
1944 the TFT driver, and the framebuffer will be left
1945 unconfigured.
1946 b - Enable backlight. The TFT backlight pin will be
1947 linked to the kernel VESA blanking code and a GPIO
1948 LED. This parameter is not necessary when using the
1949 VGA shield.
1950 c - Enable the s3c camera interface.
1951 t - Reserved for enabling touchscreen support. The
1952 touchscreen support is not enabled in the mainstream
1953 kernel as of 2.6.30, a preliminary port can be found
1954 in the "bleeding edge" mini2440 support kernel at
1955 http://repo.or.cz/w/linux-2.6/mini2440.git
1956
Mel Gorman6b74ab92008-07-23 21:26:49 -07001957 mminit_loglevel=
1958 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1959 parameter allows control of the logging verbosity for
1960 the additional memory initialisation checks. A value
1961 of 0 disables mminit logging and a level of 4 will
1962 log everything. Information is printed at KERN_DEBUG
1963 so loglevel=8 may also need to be specified.
1964
Rusty Russell106a4ee2012-09-26 10:09:40 +01001965 module.sig_enforce
1966 [KNL] When CONFIG_MODULE_SIG is set, this means that
1967 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01001968 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01001969 is always true, so this option does nothing.
1970
Linus Torvalds1da177e2005-04-16 15:20:36 -07001971 mousedev.tap_time=
1972 [MOUSE] Maximum time between finger touching and
1973 leaving touchpad surface for touch to be considered
1974 a tap and be reported as a left button click (for
1975 touchpads working in absolute mode only).
1976 Format: <msecs>
1977 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1978 reporting absolute coordinates, such as tablets
1979 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1980 reporting absolute coordinates, such as tablets
1981
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301982 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001983 is similar to kernelcore except it specifies the
1984 amount of memory used for migratable allocations.
1985 If both kernelcore and movablecore is specified,
1986 then kernelcore will be at *least* the specified
1987 value but may be more. If movablecore on its own
1988 is specified, the administrator must be careful
1989 that the amount of memory usable for all allocations
1990 is not too small.
1991
Tang Chenc5320922013-11-12 15:08:10 -08001992 movable_node [KNL,X86] Boot-time switch to enable the effects
1993 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1994
Linus Torvalds1da177e2005-04-16 15:20:36 -07001995 MTD_Partition= [MTD]
1996 Format: <name>,<region-number>,<size>,<offset>
1997
Randy Dunlapa9913042005-10-23 12:57:11 -07001998 MTD_Region= [MTD] Format:
1999 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000
2001 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002002 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002003
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002004 multitce=off [PPC] This parameter disables the use of the pSeries
2005 firmware feature for updating multiple TCE entries
2006 at a time.
2007
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002008 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2009
2010 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2011
2012 boundary - index of last SLC block on Flex-OneNAND.
2013 The remaining blocks are configured as MLC blocks.
2014 lock - Configure if Flex-OneNAND boundary should be locked.
2015 Once locked, the boundary cannot be changed.
2016 1 indicates lock status, 0 indicates unlock status.
2017
Ben Dooks9db829f2008-07-03 11:24:29 +01002018 mtdset= [ARM]
2019 ARM/S3C2412 JIVE boot control
2020
2021 See arch/arm/mach-s3c2412/mach-jive.c
2022
Linus Torvalds1da177e2005-04-16 15:20:36 -07002023 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002024 [HW] Make the MicroTouch USB driver use raw coordinates
2025 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002026
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002027 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002028 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002029 that could hold holes aka. UC entries.
2030
2031 mtrr_gran_size=nn[KMG] [X86]
2032 Used for mtrr cleanup. It is granularity of mtrr block.
2033 Default is 1.
2034 Large value could prevent small alignment from
2035 using up MTRRs.
2036
2037 mtrr_spare_reg_nr=n [X86]
2038 Format: <integer>
2039 Range: 0,7 : spare reg number
2040 Default : 1
2041 Used for mtrr cleanup. It is spare mtrr entries number.
2042 Set to 2 or more if your graphical card needs more.
2043
Linus Torvalds1da177e2005-04-16 15:20:36 -07002044 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2045
Linus Torvalds1da177e2005-04-16 15:20:36 -07002046 netdev= [NET] Network devices parameters
2047 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2048 Note that mem_start is often overloaded to mean
2049 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002050 This usage is only documented in each driver source
2051 file if at all.
2052
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002053 nf_conntrack.acct=
2054 [NETFILTER] Enable connection tracking flow accounting
2055 0 to disable accounting
2056 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002057 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002058
Chuck Lever306a0752010-09-17 10:54:37 -04002059 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002060 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002061
2062 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002063 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002064
Chuck Lever306a0752010-09-17 10:54:37 -04002065 nfsrootdebug [NFS] enable nfsroot debugging messages.
2066 See Documentation/filesystems/nfs/nfsroot.txt.
2067
Trond Myklebusta72b4422006-01-03 09:55:41 +01002068 nfs.callback_tcpport=
2069 [NFS] set the TCP port on which the NFSv4 callback
2070 channel should listen.
2071
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002072 nfs.cache_getent=
2073 [NFS] sets the pathname to the program which is used
2074 to update the NFS client cache entries.
2075
2076 nfs.cache_getent_timeout=
2077 [NFS] sets the timeout after which an attempt to
2078 update a cache entry is deemed to have failed.
2079
Trond Myklebust58df0952006-01-03 09:55:57 +01002080 nfs.idmap_cache_timeout=
2081 [NFS] set the maximum lifetime for idmapper cache
2082 entries.
2083
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002084 nfs.enable_ino64=
2085 [NFS] enable 64-bit inode numbers.
2086 If zero, the NFS client will fake up a 32-bit inode
2087 number for the readdir() and stat() syscalls instead
2088 of returning the full 64-bit number.
2089 The default is to return 64-bit inode numbers.
2090
Trond Myklebustef159e92012-02-06 19:50:40 -05002091 nfs.max_session_slots=
2092 [NFSv4.1] Sets the maximum number of session slots
2093 the client will attempt to negotiate with the server.
2094 This limits the number of simultaneous RPC requests
2095 that the client can send to the NFSv4.1 server.
2096 Note that there is little point in setting this
2097 value higher than the max_tcp_slot_table_limit.
2098
Trond Myklebustb064eca22011-02-22 15:44:32 -08002099 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002100 [NFSv4] When set to the default of '1', this option
2101 ensures that both the RPC level authentication
2102 scheme and the NFS level operations agree to use
2103 numeric uids/gids if the mount is using the
2104 'sec=sys' security flavour. In effect it is
2105 disabling idmapping, which can make migration from
2106 legacy NFSv2/v3 systems to NFSv4 easier.
2107 Servers that do not support this mode of operation
2108 will be autodetected by the client, and it will fall
2109 back to using the idmapper.
2110 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002111 nfs.nfs4_unique_id=
2112 [NFS4] Specify an additional fixed unique ident-
2113 ification string that NFSv4 clients can insert into
2114 their nfs_client_id4 string. This is typically a
2115 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002116
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002117 nfs.send_implementation_id =
2118 [NFSv4.1] Send client implementation identification
2119 information in exchange_id requests.
2120 If zero, no implementation identification information
2121 will be sent.
2122 The default is to send the implementation identification
2123 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002124
2125 nfs.recover_lost_locks =
2126 [NFSv4] Attempt to recover locks that were lost due
2127 to a lease timeout on the server. Please note that
2128 doing this risks data corruption, since there are
2129 no guarantees that the file will remain unchanged
2130 after the locks are lost.
2131 If you want to enable the kernel legacy behaviour of
2132 attempting to recover these locks, then set this
2133 parameter to '1'.
2134 The default parameter value of '0' causes the kernel
2135 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002136
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002137 nfsd.nfs4_disable_idmapping=
2138 [NFSv4] When set to the default of '1', the NFSv4
2139 server will return only numeric uids and gids to
2140 clients using auth_sys, and will accept numeric uids
2141 and gids from such clients. This is intended to ease
2142 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002143
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002144 objlayoutdriver.osd_login_prog=
2145 [NFS] [OBJLAYOUT] sets the pathname to the program which
2146 is used to automatically discover and login into new
2147 osd-targets. Please see:
2148 Documentation/filesystems/pnfs.txt for more explanations
2149
Paul Mundt1e1030d2009-09-01 17:38:32 +09002150 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002151 when a NMI is triggered.
2152 Format: [state][,regs][,debounce][,die]
2153
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302154 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002155 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05002156 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03002157 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002158 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002159 timeout occurs (or 'nopanic' to override the opposite
2160 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002161 This is useful when you use a panic=... timeout and
2162 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002163
Anton Vorontsovbff38772009-07-08 11:10:56 -07002164 netpoll.carrier_timeout=
2165 [NET] Specifies amount of time (in seconds) that
2166 netpoll should wait for a carrier. By default netpoll
2167 waits 4 seconds.
2168
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002169 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002170 emulation library even if a 387 maths coprocessor
2171 is present.
2172
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002173 no_console_suspend
2174 [HW] Never suspend the console
2175 Disable suspending of consoles during suspend and
2176 hibernate operations. Once disabled, debugging
2177 messages can reach various consoles while the rest
2178 of the system is being put to sleep (ie, while
2179 debugging driver suspend/resume hooks). This may
2180 not work reliably with all consoles, but is known
2181 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002182 To facilitate more flexible debugging, we also add
2183 console_suspend, a printk module parameter to control
2184 it. Users could use console_suspend (usually
2185 /sys/module/printk/parameters/console_suspend) to
2186 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002187
Christoph Lameterc1aee212007-05-31 00:40:47 -07002188 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2189 caches in the slab allocator. Saves per-node memory,
2190 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002191
Randy Dunlapa9913042005-10-23 12:57:11 -07002192 noalign [KNL,ARM]
2193
Linus Torvalds1da177e2005-04-16 15:20:36 -07002194 noapic [SMP,APIC] Tells the kernel to not make use of any
2195 IOAPICs that may be present in the system.
2196
Mike Galbraith5091faa2010-11-30 14:18:03 +01002197 noautogroup Disable scheduler automatic task group creation.
2198
Linus Torvalds1da177e2005-04-16 15:20:36 -07002199 nobats [PPC] Do not use BATs for mapping kernel lowmem
2200 on "Classic" PPC cores.
2201
2202 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002203
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002204 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2205
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002206 nodelayacct [KNL] Disable per-task delay accounting
2207
Linus Torvalds1da177e2005-04-16 15:20:36 -07002208 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2209
Paul Mundt6902aa82008-09-21 17:14:42 +09002210 nodsp [SH] Disable hardware DSP at boot time.
2211
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302212 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002213
Linus Torvalds1da177e2005-04-16 15:20:36 -07002214 noexec [IA-64]
2215
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302216 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002217 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002218 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002219 noexec=off: disable non-executable mappings
2220
H. Peter Anvin52b61792012-09-21 12:43:13 -07002221 nosmap [X86]
2222 Disable SMAP (Supervisor Mode Access Prevention)
2223 even if it is supported by processor.
2224
Fenghua Yude5397a2011-05-11 16:51:05 -07002225 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002226 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002227 even if it is supported by processor.
2228
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002229 noexec32 [X86-64]
2230 This affects only 32-bit executables.
2231 noexec32=on: enable non-executable mappings (default)
2232 read doesn't imply executable mappings
2233 noexec32=off: disable non-executable mappings
2234 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002235
Paul Mundt6902aa82008-09-21 17:14:42 +09002236 nofpu [SH] Disable hardware FPU at boot time.
2237
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002238 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002239 register save and restore. The kernel will only save
2240 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002241
Suresh Siddha0c752a92009-05-22 12:17:45 -07002242 noxsave [BUGS=X86] Disables x86 extended register state save
2243 and restore using xsave. The kernel will fallback to
2244 enabling legacy floating-point and sse state.
2245
Fenghua Yub6f42a42014-05-29 11:12:31 -07002246 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2247 register states. The kernel will fall back to use
2248 xsave to save the states. By using this parameter,
2249 performance of saving the states is degraded because
2250 xsave doesn't support modified optimization while
2251 xsaveopt supports it on xsaveopt enabled systems.
2252
2253 noxsaves [X86] Disables xsaves and xrstors used in saving and
2254 restoring x86 extended register state in compacted
2255 form of xsave area. The kernel will fall back to use
2256 xsaveopt and xrstor to save and restore the states
2257 in standard form of xsave area. By using this
2258 parameter, xsave area per process might occupy more
2259 memory on xsaves enabled systems.
2260
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002261 eagerfpu= [X86]
Suresh Siddhae0022982012-09-10 10:32:32 -07002262 on enable eager fpu restore
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002263 off disable eager fpu restore
Suresh Siddhae0022982012-09-10 10:32:32 -07002264 auto selects the default scheme, which automatically
2265 enables eagerfpu restore for xsaveopt.
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002266
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002267 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2268 wfi(ARM) instruction doesn't work correctly and not to
2269 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002270
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002271 no_file_caps Tells the kernel not to honor file capabilities. The
2272 only way then for a file to be executed with privilege
2273 is to be setuid root or executed by root.
2274
Linus Torvalds1da177e2005-04-16 15:20:36 -07002275 nohalt [IA-64] Tells the kernel not to use the power saving
2276 function PAL_HALT_LIGHT when idle. This increases
2277 power-consumption. On the positive side, it reduces
2278 interrupt wake-up latency, which may improve performance
2279 in certain environments such as networked servers or
2280 real-time systems.
2281
Kees Cooka6e15a32014-06-13 13:30:35 -07002282 nohibernate [HIBERNATION] Disable hibernation and resume.
2283
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002284 nohz= [KNL] Boottime enable/disable dynamic ticks
2285 Valid arguments: on, off
2286 Default: on
2287
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002288 nohz_full= [KNL,BOOT]
2289 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002290 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002291 whenever possible. The boot CPU will be forced outside
2292 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002293 The CPUs in this range must also be included in the
2294 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002295
Paul Mundteeee7852009-04-02 12:31:16 +09002296 noiotrap [SH] Disables trapped I/O port accesses.
2297
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002298 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002299 disable unhandled interrupt sources.
2300
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302301 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002302 broken timer IRQ sources.
2303
Linus Torvalds1da177e2005-04-16 15:20:36 -07002304 noisapnp [ISAPNP] Disables ISA PnP code.
2305
2306 noinitrd [RAM] Tells the kernel not to load any configured
2307 initial RAM disk.
2308
Weidong Han03ea8152009-04-17 16:42:15 +08002309 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2310 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002311 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002312
Linus Torvalds1da177e2005-04-16 15:20:36 -07002313 nointroute [IA-64]
2314
Randy Dunlap16290242011-08-13 12:34:52 -07002315 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002316
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002317 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2318
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002319 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2320 fault handling.
2321
Glauber Costad910f5c2011-07-11 15:28:19 -04002322 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2323 steal time is computed, but won't influence scheduler
2324 behaviour
2325
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002326 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002327
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002328 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002329
Linus Torvalds1da177e2005-04-16 15:20:36 -07002330 noltlbs [PPC] Do not use large page/tlb entries for kernel
2331 lowmem mapping on PPC40x.
2332
Horms312f1f02006-02-22 09:57:55 +09002333 nomca [IA-64] Disable machine check abort handling
2334
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002335 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002336
Andres Salomon83d73842007-10-12 23:04:06 +02002337 nomfgpt [X86-32] Disable Multi-Function General Purpose
2338 Timer usage (for AMD Geode machines).
2339
Don Zickusbda62632011-10-13 15:14:27 -04002340 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2341 shutdown the other cpus. Instead use the REBOOT_VECTOR
2342 irq.
2343
Dave Young02608be2012-02-01 10:33:14 +08002344 nomodule Disable module load
2345
Jiri Kosina016ddd92010-01-18 17:05:40 +01002346 nopat [X86] Disable PAT (page attribute table extension of
2347 pagetables) support.
2348
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002349 norandmaps Don't use address space randomization. Equivalent to
2350 echo 0 > /proc/sys/kernel/randomize_va_space
2351
Jiri Kosinabbff2162010-08-11 18:34:09 +02002352 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002353
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002354 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002355 with UP alternatives
2356
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002357 nordrand [X86] Disable kernel use of the RDRAND and
2358 RDSEED instructions even if they are supported
2359 by the processor. RDRAND and RDSEED are still
2360 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002361
Randy Dunlapa9913042005-10-23 12:57:11 -07002362 noresume [SWSUSP] Disables resume and restores original swap
2363 space.
2364
Linus Torvalds1da177e2005-04-16 15:20:36 -07002365 no-scroll [VGA] Disables scrollback.
2366 This is required for the Braillex ib80-piezo Braille
2367 reader made by F.H. Papenmeier (Germany).
2368
2369 nosbagart [IA-64]
2370
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002371 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002372
Len Brown61ec7562007-08-16 03:34:22 -04002373 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2374 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002375
Dave Jones97842212007-07-15 23:41:05 -07002376 nosoftlockup [KNL] Disable the soft-lockup detector.
2377
Linus Torvalds1da177e2005-04-16 15:20:36 -07002378 nosync [HW,M68K] Disables sync negotiation for all devices.
2379
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002380 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002381
2382 nousb [USB] Disable the USB subsystem
2383
Ben Hutchings55142372011-01-02 23:02:42 +00002384 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04002385
Linus Torvalds1da177e2005-04-16 15:20:36 -07002386 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002387
Weidong Han2b2fd872009-04-17 16:42:12 +08002388 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2389
Fenghua Yuf78cff42012-11-13 11:32:38 -08002390 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2391 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2392 Some features depend on CPU0. Known dependencies are:
2393 1. Resume from suspend/hibernate depends on CPU0.
2394 Suspend/hibernate will fail if CPU0 is offline and you
2395 need to online CPU0 before suspend/hibernate.
2396 2. PIC interrupts also depend on CPU0. CPU0 can't be
2397 removed if a PIC interrupt is detected.
2398 It's said poweroff/reboot may depend on CPU0 on some
2399 machines although I haven't seen such issues so far
2400 after CPU0 is offline on a few tested machines.
2401 If the dependencies are under your control, you can
2402 turn on cpu0_hotplug.
2403
Randy Dunlap16290242011-08-13 12:34:52 -07002404 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002405 purges which is reported from either PAL_VM_SUMMARY or
2406 SAL PALO.
2407
Yinghai Lu2b633e32010-02-10 01:20:37 -08002408 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2409 could support. nr_cpus=n : n >= 1 limits the kernel to
2410 supporting 'n' processors. Later in runtime you can not
2411 use hotplug cpu feature to put more cpu back to online.
2412 just like you compile the kernel NR_CPUS=n
2413
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002414 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2415
Mel Gorman1a687c22012-11-22 11:16:36 +00002416 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2417 Allowed values are enable and disable
2418
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002419 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2420 one of ['zone', 'node', 'default'] can be specified
2421 This can be set from sysctl after boot.
2422 See Documentation/sysctl/vm.txt for details.
2423
Randy Dunlap7c4be252009-01-06 14:42:44 -08002424 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2425 See Documentation/debugging-via-ohci1394.txt for more
2426 info.
2427
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002428 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2429 Rather than timing out after 20 ms if an EC
2430 command is not properly ACKed, override the length
2431 of the timeout. We have interrupts disabled while
2432 waiting for the ACK, so if this is set too high
2433 interrupts *may* be lost!
2434
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002435 omap_mux= [OMAP] Override bootloader pin multiplexing.
2436 Format: <mux_mode0.mode_name=value>...
2437 For example, to override I2C bus2:
2438 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2439
Linus Torvalds1da177e2005-04-16 15:20:36 -07002440 oprofile.timer= [HW]
2441 Use timer interrupt instead of performance counters
2442
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002443 oprofile.cpu_type= Force an oprofile cpu type
2444 This might be useful if you have an older oprofile
2445 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002446 Format: { arch_perfmon }
2447 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002448 perfmon on Intel CPUs instead of the
2449 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002450 timer: [X86] Force use of architectural NMI
2451 timer mode (see also oprofile.timer
2452 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002453 [s390] Force legacy basic mode sampling
2454 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002455
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002456 oops=panic Always panic on oopses. Default is to just kill the
2457 process, but there is a small probability of
2458 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002459 This will also cause panics on machine check exceptions.
2460 Useful together with panic=30 to trigger a reboot.
2461
Randy Dunlapbcfde332010-06-07 17:10:38 -07002462 OSS [HW,OSS]
2463 See Documentation/sound/oss/oss-parameters.txt
2464
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002465 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002466 timeout > 0: seconds before rebooting
2467 timeout = 0: wait forever
2468 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002469 Format: <timeout>
2470
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002471 crash_kexec_post_notifiers
2472 Run kdump after running panic-notifiers and dumping
2473 kmsg. This only for the users who doubt kdump always
2474 succeeds in any situation.
2475 Note that this also increases risks of kdump failure,
2476 because some panic notifiers can make the crashed
2477 kernel more unstable.
2478
Linus Torvalds1da177e2005-04-16 15:20:36 -07002479 parkbd.port= [HW] Parallel port number the keyboard adapter is
2480 connected to, default is 0.
2481 Format: <parport#>
2482 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2483 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002484 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002485
Randy Dunlapa9913042005-10-23 12:57:11 -07002486 parport= [HW,PPT] Specify parallel ports. 0 disables.
2487 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2488 Use 'auto' to force the driver to use any
2489 IRQ/DMA settings detected (the default is to
2490 ignore detected IRQ/DMA settings because of
2491 possible conflicts). You can specify the base
2492 address, IRQ, and DMA settings; IRQ and DMA
2493 should be numbers, or 'auto' (for using detected
2494 settings on that particular port), or 'nofifo'
2495 (to avoid using a FIFO even if it is detected).
2496 Parallel ports are assigned in the order they
2497 are specified on the command line, starting
2498 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002499
Randy Dunlapa9913042005-10-23 12:57:11 -07002500 parport_init_mode= [HW,PPT]
2501 Configure VIA parallel port to operate in
2502 a specific mode. This is necessary on Pegasos
2503 computer where firmware has no options for setting
2504 up parallel port mode and sets it to spp.
2505 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002506 Format: [spp|ps2|epp|ecp|ecpepp]
2507
Andrew Mortondd287792006-03-23 03:00:57 -08002508 pause_on_oops=
2509 Halt all CPUs after the first oops has been printed for
2510 the specified number of seconds. This is to be used if
2511 your oopses keep scrolling off the screen.
2512
Linus Torvalds1da177e2005-04-16 15:20:36 -07002513 pcbit= [HW,ISDN]
2514
2515 pcd. [PARIDE]
2516 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002517 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002518
Randy Dunlapa9913042005-10-23 12:57:11 -07002519 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002520 earlydump [X86] dump PCI config space before the kernel
2521 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002522 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002523 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002524 the hardware directly. Use this if your machine
2525 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002526 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002527 hardware access methods are allowed. Use this
2528 if you experience crashes upon bootup and you
2529 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002530 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002531 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002532 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002533 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002534 noaer [PCIE] If the PCIEAER kernel config parameter is
2535 enabled, this kernel boot option can be used to
2536 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002537 nodomains [PCI] Disable support for multiple PCI
2538 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302539 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002540 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002541 check_enable_amd_mmconf [X86] check for and enable
2542 properly configured MMIO access to PCI
2543 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002544 nomsi [MSI] If the PCI_MSI kernel config parameter is
2545 enabled, this kernel boot option can be used to
2546 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002547 noioapicquirk [APIC] Disable all boot interrupt quirks.
2548 Safety option to keep boot IRQs enabled. This
2549 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002550 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2551 primary IO-APIC for bridges that cannot disable
2552 boot IRQs. This fixes a source of spurious IRQs
2553 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002554 noioapicreroute [APIC] Disable workaround that uses the
2555 boot IRQ equivalent of an IRQ that connects to
2556 a chipset where boot IRQs cannot be disabled.
2557 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002558 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002559 routing table. These calls are known to be buggy
2560 on several machines and they hang the machine
2561 when used, but on other computers it's the only
2562 way to get the interrupt routing table. Try
2563 this option if the kernel is unable to allocate
2564 IRQs or discover secondary PCI buses on your
2565 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002566 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002567 Use with caution as certain devices share
2568 address decoders between ROMs and other
2569 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002570 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002571 expansion ROMs that do not already have
2572 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002573 nobar [X86] Do not assign address space to the
2574 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002575 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002576 assigned automatically to PCI devices. You can
2577 make the kernel exclude IRQs of your ISA cards
2578 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002579 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002580 of the PIRQ table (normally generated
2581 by the BIOS) if it is outside the
2582 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002583 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002584 useful if the kernel is unable to find your
2585 secondary buses and you want to tell it
2586 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002587 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002588 numbers ourselves, overriding
2589 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002590 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002591 in the BIOS $PIR table. This is needed on
2592 some systems with broken BIOSes, notably
2593 some HP Pavilion N5400 and Omnibook XE3
2594 notebooks. This will have no effect if ACPI
2595 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002596 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002597 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002598 use_crs [X86] Use PCI host bridge window information
2599 from ACPI. On BIOSes from 2008 or later, this
2600 is enabled by default. If you need to use this,
2601 please report a bug.
2602 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2603 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002604 routeirq Do IRQ routing for all PCI devices.
2605 This is normally done in pci_enable_device(),
2606 so this option is a temporary workaround
2607 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002608 skip_isa_align [X86] do not align io start addr, so can
2609 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002610 firmware [ARM] Do not re-enumerate the bus but instead
2611 just use the configuration from the
2612 bootloader. This is currently used on
2613 IXP2000 systems where the bus has to be
2614 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002615 noearly [X86] Don't do any early type 1 scanning.
2616 This might help on some broken boards which
2617 machine check when some devices' config space
2618 is read. But various workarounds are disabled
2619 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002620 bfsort Sort PCI devices into breadth-first order.
2621 This sorting is done to get a device
2622 order compatible with older (<= 2.4) kernels.
2623 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002624 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2625 tuning and use the BIOS-configured MPS defaults.
2626 pcie_bus_safe Set every device's MPS to the largest value
2627 supported by all devices below the root complex.
2628 pcie_bus_perf Set device MPS to the largest allowable MPS
2629 based on its parent bus. Also set MRRS (Max
2630 Read Request Size) to the largest supported
2631 value (no larger than the MPS that the device
2632 or bus can support) for best performance.
2633 pcie_bus_peer2peer Set every device's MPS to 128B, which
2634 every device is guaranteed to support. This
2635 configuration allows peer-to-peer DMA between
2636 any pair of devices, possibly at the cost of
2637 reduced performance. This also guarantees
2638 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002639 cbiosize=nn[KMG] The fixed amount of bus space which is
2640 reserved for the CardBus bridge's IO window.
2641 The default value is 256 bytes.
2642 cbmemsize=nn[KMG] The fixed amount of bus space which is
2643 reserved for the CardBus bridge's memory
2644 window. The default value is 64 megabytes.
Yuji Shimada32a9a682009-03-16 17:13:39 +09002645 resource_alignment=
2646 Format:
2647 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2648 Specifies alignment and device to reassign
2649 aligned memory resources.
2650 If <order of align> is not specified,
2651 PAGE_SIZE is used as alignment.
2652 PCI-PCI bridge can be specified, if resource
2653 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002654 ecrc= Enable/disable PCIe ECRC (transaction layer
2655 end-to-end CRC checking).
2656 bios: Use BIOS/firmware settings. This is the
2657 the default.
2658 off: Turn ECRC off
2659 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002660 hpiosize=nn[KMG] The fixed amount of bus space which is
2661 reserved for hotplug bridge's IO window.
2662 Default size is 256 bytes.
2663 hpmemsize=nn[KMG] The fixed amount of bus space which is
2664 reserved for hotplug bridge's memory window.
2665 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002666 realloc= Enable/disable reallocating PCI bridge resources
2667 if allocations done by BIOS are too small to
2668 accommodate resources required by all child
2669 devices.
2670 off: Turn realloc off
2671 on: Turn realloc on
2672 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002673 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002674 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2675 only look for one device below a PCIe downstream
2676 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002677
Chuck Ebberte5665a42008-09-24 20:40:34 -04002678 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2679 Management.
2680 off Disable ASPM.
2681 force Enable ASPM even on devices that claim not to support it.
2682 WARNING: Forcing ASPM on may cause system lockups.
2683
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002684 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2685 nomsi Do not use MSI for PCI Express Native Hotplug (this
2686 makes all PCIe ports use INTx for hotplug services).
2687
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002688 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002689 auto Ask the BIOS whether or not to use native PCIe services
2690 associated with PCIe ports (PME, hot-plug, AER). Use
2691 them only if that is allowed by the BIOS.
2692 native Use native PCIe services associated with PCIe ports
2693 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002694 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2695 ports driver.
2696
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002697 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002698 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002699 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002700
Linus Torvalds1da177e2005-04-16 15:20:36 -07002701 pcmv= [HW,PCMCIA] BadgePAD 4
2702
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302703 pd_ignore_unused
2704 [PM]
2705 Keep all power-domains already enabled by bootloader on,
2706 even if no driver has claimed them. This is useful
2707 for debug and development, but should not be
2708 needed on a platform with proper driver support.
2709
Linus Torvalds1da177e2005-04-16 15:20:36 -07002710 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002711 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002712
2713 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2714 boot time.
2715 Format: { 0 | 1 }
2716 See arch/parisc/kernel/pdc_chassis.c
2717
Tejun Heof58dc012009-08-14 15:00:50 +09002718 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002719 Currently supported values are "embed" and "page".
2720 Archs may support subset or none of the selections.
2721 See comments in mm/percpu.c for details on each
2722 allocator. This parameter is primarily for debugging
2723 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002724
Linus Torvalds1da177e2005-04-16 15:20:36 -07002725 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002726 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002727
2728 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002729 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002730
2731 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002732 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002733
2734 plip= [PPT,NET] Parallel port network link
2735 Format: { parport<nr> | timid | 0 }
2736 See also Documentation/parport.txt.
2737
Randy Dunlap16290242011-08-13 12:34:52 -07002738 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002739 Override pmtimer IOPort with a hex value.
2740 e.g. pmtmr=0x508
2741
Bjorn Helgaas96242112011-08-11 12:14:05 -06002742 pnp.debug=1 [PNP]
2743 Enable PNP debug messages (depends on the
2744 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2745 via /sys/module/pnp/parameters/debug. We always show
2746 current resource usage; turning this on also shows
2747 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002748
Linus Torvalds1da177e2005-04-16 15:20:36 -07002749 pnpacpi= [ACPI]
2750 { off }
2751
2752 pnpbios= [ISAPNP]
2753 { on | off | curr | res | no-curr | no-res }
2754
2755 pnp_reserve_irq=
2756 [ISAPNP] Exclude IRQs for the autoconfiguration
2757
2758 pnp_reserve_dma=
2759 [ISAPNP] Exclude DMAs for the autoconfiguration
2760
2761 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002762 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002763
2764 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002765 [ISAPNP] Exclude memory regions for the
2766 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002767 Ranges are in pairs (memory base and size).
2768
Randy Dunlap4af94f32009-04-17 18:30:28 -07002769 ports= [IP_VS_FTP] IPVS ftp helper module
2770 Default is 21.
2771 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2772 may be specified.
2773 Format: <port>,<port>....
2774
Ingo Molnar45807a12007-07-15 23:40:10 -07002775 print-fatal-signals=
2776 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002777
2778 If enabled, warn about various signal handling
2779 related application anomalies: too many signals,
2780 too many POSIX.1 timers, fatal signals causing a
2781 coredump - etc.
2782
2783 If you hit the warning due to signal overflow,
2784 you might want to try "ulimit -i unlimited".
2785
Ingo Molnar45807a12007-07-15 23:40:10 -07002786 default: off.
2787
Matthew Garrettc22ab332012-03-05 14:59:10 -08002788 printk.always_kmsg_dump=
2789 Trigger kmsg_dump for cases other than kernel oops or
2790 panics
2791 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2792 default: disabled
2793
Randy Dunlape84845c2007-07-15 23:40:25 -07002794 printk.time= Show timing data prefixed to each printk message line
2795 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2796
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002797 processor.max_cstate= [HW,ACPI]
2798 Limit processor to maximum C-state
2799 max_cstate=9 overrides any DMI blacklist limit.
2800
2801 processor.nocst [HW,ACPI]
2802 Ignore the _CST method to determine C-states,
2803 instead using the legacy FADT method
2804
Linus Torvalds1da177e2005-04-16 15:20:36 -07002805 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002806 Format: [schedule,]<number>
2807 Param: "schedule" - profile schedule points.
2808 Param: <number> - step/bucket size as a power of 2 for
2809 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002810 Param: "sleep" - profile D-state sleeping (millisecs).
2811 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002812 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002813
Linus Torvalds1da177e2005-04-16 15:20:36 -07002814 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2815 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002816 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002817
Randy Dunlapa9913042005-10-23 12:57:11 -07002818 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2819 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002820 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2821 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002822 psmouse.resetafter= [HW,MOUSE]
2823 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002824 (0 = never).
2825 psmouse.resolution=
2826 [HW,MOUSE] Set desired mouse resolution, in dpi.
2827 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002828 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002829 0 = disabled, 1 = enabled (default).
2830
Matthew Garrettdee28e72011-07-21 16:57:55 -04002831 pstore.backend= Specify the name of the pstore backend to use
2832
Linus Torvalds1da177e2005-04-16 15:20:36 -07002833 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002834 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002835
Kay Sieversdc8c8582007-08-15 12:25:38 +02002836 pty.legacy_count=
2837 [KNL] Number of legacy pty's. Overwrites compiled-in
2838 default number.
2839
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002840 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002841
Linus Torvalds1da177e2005-04-16 15:20:36 -07002842 r128= [HW,DRM]
2843
2844 raid= [HW,RAID]
2845 See Documentation/md.txt.
2846
Randy Dunlapa9913042005-10-23 12:57:11 -07002847 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002848 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002849
Linus Torvalds1da177e2005-04-16 15:20:36 -07002850 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002851 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002852
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002853 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002854 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2855 the specified list of CPUs to be no-callback CPUs.
2856 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08002857 be offloaded to "rcuox/N" kthreads created for
2858 that purpose, where "x" is "b" for RCU-bh, "p"
2859 for RCU-preempt, and "s" for RCU-sched, and "N"
2860 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002861 offloaded CPUs, which can be useful for HPC and
2862 real-time workloads. It can also improve energy
2863 efficiency for asymmetric multiprocessors.
2864
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002865 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002866 Rather than requiring that offloaded CPUs
2867 (specified by rcu_nocbs= above) explicitly
2868 awaken the corresponding "rcuoN" kthreads,
2869 make these kthreads poll for callbacks.
2870 This improves the real-time response for the
2871 offloaded CPUs by relieving them of the need to
2872 wake up the corresponding kthread, but degrades
2873 energy efficiency by requiring that the kthreads
2874 periodically wake up to do the polling.
2875
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002876 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002877 Set maximum number of finished RCU callbacks to
2878 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002879
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002880 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07002881 Increase the number of CPUs assigned to each
2882 leaf rcu_node structure. Useful for very large
2883 systems.
2884
Paul E. McKenney4a81e832014-06-20 16:49:01 -07002885 rcutree.jiffies_till_sched_qs= [KNL]
2886 Set required age in jiffies for a
2887 given grace period before RCU starts
2888 soliciting quiescent-state help from
2889 rcu_note_context_switch().
2890
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002891 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002892 Set delay from grace-period initialization to
2893 first attempt to force quiescent states.
2894 Units are jiffies, minimum value is zero,
2895 and maximum value is HZ.
2896
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002897 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002898 Set delay between subsequent attempts to force
2899 quiescent states. Units are jiffies, minimum
2900 value is one, and maximum value is HZ.
2901
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07002902 rcutree.rcu_nocb_leader_stride= [KNL]
2903 Set the number of NOCB kthread groups, which
2904 defaults to the square root of the number of
2905 CPUs. Larger numbers reduces the wakeup overhead
2906 on the per-CPU grace-period kthreads, but increases
2907 that same overhead on each group's leader.
2908
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002909 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002910 Set threshold of queued RCU callbacks beyond which
2911 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002912
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002913 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002914 Set threshold of queued RCU callbacks below which
2915 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002916
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002917 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002918 Set wakeup interval for idle CPUs that have
2919 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002920
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002921 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002922 Set wakeup interval for idle CPUs that have
2923 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2924 Lazy RCU callbacks are those which RCU can
2925 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002926
Paul E. McKenney38706bc2014-08-18 21:12:17 -07002927 rcutorture.cbflood_inter_holdoff= [KNL]
2928 Set holdoff time (jiffies) between successive
2929 callback-flood tests.
2930
2931 rcutorture.cbflood_intra_holdoff= [KNL]
2932 Set holdoff time (jiffies) between successive
2933 bursts of callbacks within a given callback-flood
2934 test.
2935
2936 rcutorture.cbflood_n_burst= [KNL]
2937 Set the number of bursts making up a given
2938 callback-flood test. Set this to zero to
2939 disable callback-flood testing.
2940
2941 rcutorture.cbflood_n_per_burst= [KNL]
2942 Set the number of callbacks to be registered
2943 in a given burst of a callback-flood test.
2944
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002945 rcutorture.fqs_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002946 Set duration of force_quiescent_state bursts.
2947
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002948 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002949 Set holdoff time within force_quiescent_state bursts.
2950
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002951 rcutorture.fqs_stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002952 Set wait time between force_quiescent_state bursts.
2953
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002954 rcutorture.gp_exp= [KNL]
2955 Use expedited update-side primitives.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002956
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002957 rcutorture.gp_normal= [KNL]
2958 Use normal (non-expedited) update-side primitives.
2959 If both gp_exp and gp_normal are set, do both.
2960 If neither gp_exp nor gp_normal are set, still
2961 do both.
2962
2963 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002964 Set callbacks/threads for rcu_barrier() testing.
2965
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002966 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002967 Set number of concurrent RCU writers. These just
2968 stress RCU, they don't participate in the actual
2969 test, hence the "fake".
2970
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002971 rcutorture.nreaders= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002972 Set number of RCU readers.
2973
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002974 rcutorture.object_debug= [KNL]
2975 Enable debug-object double-call_rcu() testing.
2976
2977 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002978 Set time (s) after boot for CPU-hotplug testing.
2979
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002980 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002981 Set time (s) between CPU-hotplug operations, or
2982 zero to disable CPU-hotplug testing.
2983
Paul E. McKenney59da22a2014-09-12 10:36:15 -07002984 rcutorture.torture_runnable= [BOOT]
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002985 Start rcutorture running at boot time.
2986
2987 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002988 Set task-shuffle interval (s). Shuffling tasks
2989 allows some CPUs to go into dyntick-idle mode
2990 during the rcutorture test.
2991
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002992 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002993 Set time (s) after boot system shutdown. This
2994 is useful for hands-off automated testing.
2995
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002996 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002997 Duration of CPU stall (s) to test RCU CPU stall
2998 warnings, zero to disable.
2999
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003000 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003001 Time to wait (s) after boot before inducing stall.
3002
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003003 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003004 Time (s) between statistics printk()s.
3005
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003006 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003007 Time (s) to stutter testing, for example, specifying
3008 five seconds causes the test to run for five seconds,
3009 wait for five seconds, and so on. This tests RCU's
3010 ability to transition abruptly to and from idle.
3011
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003012 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003013 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3014 "Maybe" means test if the RCU implementation
3015 under test support RCU priority boosting.
3016
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003017 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003018 Duration (s) of each individual boost test.
3019
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003020 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003021 Interval (s) between each boost test.
3022
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003023 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003024 Test RCU's dyntick-idle handling. See also the
3025 rcutorture.shuffle_interval parameter.
3026
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003027 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003028 Specify the RCU implementation to test.
3029
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003030 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003031 Enable additional printk() statements.
3032
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003033 rcupdate.rcu_expedited= [KNL]
3034 Use expedited grace-period primitives, for
3035 example, synchronize_rcu_expedited() instead
3036 of synchronize_rcu(). This reduces latency,
3037 but can increase CPU utilization, degrade
3038 real-time latency, and degrade energy efficiency.
3039
3040 rcupdate.rcu_cpu_stall_suppress= [KNL]
3041 Suppress RCU CPU stall warning messages.
3042
3043 rcupdate.rcu_cpu_stall_timeout= [KNL]
3044 Set timeout for RCU CPU stall warning messages.
3045
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003046 rcupdate.rcu_task_stall_timeout= [KNL]
3047 Set timeout in jiffies for RCU task stall warning
3048 messages. Disable with a value less than or equal
3049 to zero.
3050
Olof Johanssonffdfc402005-09-06 15:17:19 -07003051 rdinit= [KNL]
3052 Format: <full_path>
3053 Run specified binary instead of /init from the ramdisk,
3054 used for early userspace startup. See initrd.
3055
Robin Holt1b3a5d02013-07-08 16:01:42 -07003056 reboot= [KNL]
3057 Format (x86 or x86_64):
3058 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3059 [[,]s[mp]#### \
3060 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3061 [[,]f[orce]
3062 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3063 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3064 reboot_force is either force or not specified,
3065 reboot_cpu is s[mp]#### with #### being the processor
3066 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003067
Paul Jackson46b6d942008-07-04 10:00:09 -07003068 relax_domain_level=
3069 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01003070 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003071
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02003072 relative_sleep_states=
3073 [SUSPEND] Use sleep state labeling where the deepest
3074 state available other than hibernation is always "mem".
3075 Format: { "0" | "1" }
3076 0 -- Traditional sleep state labels.
3077 1 -- Relative sleep state labels.
3078
Linus Torvalds1da177e2005-04-16 15:20:36 -07003079 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3080
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003081 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07003082 Format: nn[KMG]
3083 Reserves a hole at the top of the kernel virtual
3084 address space.
3085
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003086 reservelow= [X86]
3087 Format: nn[K]
3088 Set the amount of memory to reserve for BIOS at
3089 the bottom of the address space.
3090
Vivek Goyal7e962872006-09-27 01:50:44 -07003091 reset_devices [KNL] Force drivers to reset the underlying device
3092 during initialization.
3093
Randy Dunlapa9913042005-10-23 12:57:11 -07003094 resume= [SWSUSP]
3095 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003096 Format:
3097 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003098
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003099 resume_offset= [SWSUSP]
3100 Specify the offset from the beginning of the partition
3101 given by "resume=" at which the swap header is located,
3102 in <PAGE_SIZE> units (needed only for swap files).
3103 See Documentation/power/swsusp-and-swap-files.txt
3104
Barry Songf126f732011-10-10 23:38:41 +02003105 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3106 read the resume files
3107
Barry Song6f8d7022011-10-06 20:34:46 +02003108 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3109 Useful for devices that are detected asynchronously
3110 (e.g. USB and MMC devices).
3111
Bojan Smojverf996fc92010-09-09 23:06:23 +02003112 hibernate= [HIBERNATION]
3113 noresume Don't check if there's a hibernation image
3114 present during boot.
3115 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003116 no Disable hibernation and resume.
Bojan Smojverf996fc92010-09-09 23:06:23 +02003117
Michael Neuling0a7b35c2007-02-10 01:44:33 -08003118 retain_initrd [RAM] Keep initrd memory after extraction
3119
Linus Torvalds1da177e2005-04-16 15:20:36 -07003120 rhash_entries= [KNL,NET]
3121 Set number of hash buckets for route cache
3122
Linus Torvalds1da177e2005-04-16 15:20:36 -07003123 ro [KNL] Mount root device read-only on boot
3124
3125 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07003126 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003127
3128 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3129 mount the root filesystem
3130
3131 rootflags= [KNL] Set root filesystem mount option string
3132
3133 rootfstype= [KNL] Set root filesystem type
3134
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003135 rootwait [KNL] Wait (indefinitely) for root device to show up.
3136 Useful for devices that are detected asynchronously
3137 (e.g. USB and MMC devices).
3138
Robert Tivy5c71d612013-03-28 18:41:46 -07003139 rproc_mem=nn[KMG][@address]
3140 [KNL,ARM,CMA] Remoteproc physical memory block.
3141 Memory area to be used by remote processor image,
3142 managed by CMA.
3143
Linus Torvalds1da177e2005-04-16 15:20:36 -07003144 rw [KNL] Mount root device read-write on boot
3145
3146 S [KNL] Run init in single mode
3147
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003148 s390_iommu= [HW,S390]
3149 Set s390 IOTLB flushing mode
3150 strict
3151 With strict flushing every unmap operation will result in
3152 an IOTLB flush. Default is lazy flushing before reuse,
3153 which is faster.
3154
Linus Torvalds1da177e2005-04-16 15:20:36 -07003155 sa1100ir [NET]
3156 See drivers/net/irda/sa1100_ir.c.
3157
Linus Torvalds1da177e2005-04-16 15:20:36 -07003158 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003159
Mike Travisf6630112009-11-17 18:22:15 -06003160 sched_debug [KNL] Enables verbose scheduler debug messages.
3161
Mike Galbraith5307c952012-05-08 12:20:58 +02003162 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3163 xtime_lock contention on larger systems, and/or RCU lock
3164 contention on all systems with CONFIG_MAXSMP set.
3165 Format: { "0" | "1" }
3166 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3167 1 -- enable.
3168 Note: increases power consumption, thus should only be
3169 enabled if running jitter sensitive (HPC/RT) workloads.
3170
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003171 security= [SECURITY] Choose a security module to enable at boot.
3172 If this boot parameter is not specified, only the first
3173 security module asking for security registration will be
3174 loaded. An invalid security module name will be treated
3175 as if no module has been chosen.
3176
3177 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003178 Format: { "0" | "1" }
3179 See security/selinux/Kconfig help text.
3180 0 -- disable.
3181 1 -- enable.
3182 Default value is set via kernel config option.
3183 If enabled at boot time, /selinux/disable can be used
3184 later to disable prior to initial policy load.
3185
John Johansenc1c124e2010-07-29 14:48:09 -07003186 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3187 Format: { "0" | "1" }
3188 See security/apparmor/Kconfig help text
3189 0 -- disable.
3190 1 -- enable.
3191 Default value is set via kernel config option.
3192
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003193 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003194
Linus Torvalds1da177e2005-04-16 15:20:36 -07003195 shapers= [NET]
3196 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003197
Yinghai Lub05f78f2008-08-22 01:32:50 -07003198 show_msr= [x86] show boot-time MSR settings
3199 Format: { <integer> }
3200 Show boot-time (BIOS-initialized) MSR settings.
3201 The parameter means the number of CPUs to show,
3202 for example 1 means boot CPU only.
3203
Linus Torvalds1da177e2005-04-16 15:20:36 -07003204 simeth= [IA-64]
3205 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003206
Linus Torvalds1da177e2005-04-16 15:20:36 -07003207 slram= [HW,MTD]
3208
David Rientjes3df1ccc2011-10-18 22:09:28 -07003209 slab_max_order= [MM, SLAB]
3210 Determines the maximum allowed order for slabs.
3211 A high setting may cause OOMs due to memory
3212 fragmentation. Defaults to 1 for systems with
3213 more than 32MB of RAM, 0 otherwise.
3214
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003215 slub_debug[=options[,slabs]] [MM, SLUB]
3216 Enabling slub_debug allows one to determine the
3217 culprit if slab objects become corrupted. Enabling
3218 slub_debug can create guard zones around objects and
3219 may poison objects when not in use. Also tracks the
3220 last alloc / free. For more information see
3221 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003222
3223 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003224 Determines the maximum allowed order for slabs.
3225 A high setting may cause OOMs due to memory
3226 fragmentation. For more information see
3227 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003228
3229 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003230 The minimum number of objects per slab. SLUB will
3231 increase the slab order up to slub_max_order to
3232 generate a sufficiently large slab able to contain
3233 the number of objects indicated. The higher the number
3234 of objects the smaller the overhead of tracking slabs
3235 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003236 For more information see Documentation/vm/slub.txt.
3237
3238 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003239 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003240 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003241 For more information see Documentation/vm/slub.txt.
3242
3243 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003244 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07003245 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003246 allocs to different slabs. Debug options disable
3247 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003248 For more information see Documentation/vm/slub.txt.
3249
Linus Torvalds1da177e2005-04-16 15:20:36 -07003250 smart2= [HW]
3251 Format: <io1>[,<io2>[,...,<io8>]]
3252
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003253 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3254 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3255 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3256 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3257 smsc-ircc2.ircc_irq= [HW] IRQ line
3258 smsc-ircc2.ircc_dma= [HW] DMA channel
3259 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3260 0: Toshiba Satellite 1800 (GP data pin select)
3261 1: Fast pin select (default)
3262 2: ATC IRMode
3263
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003264 softlockup_panic=
3265 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003266 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003267
Aaron Tomlined235872014-06-23 13:22:05 -07003268 softlockup_all_cpu_backtrace=
3269 [KNL] Should the soft-lockup detector generate
3270 backtraces on all cpus.
3271 Format: <integer>
3272
Linus Torvalds1da177e2005-04-16 15:20:36 -07003273 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003274 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003275
Linus Torvalds1da177e2005-04-16 15:20:36 -07003276 spia_io_base= [HW,MTD]
3277 spia_fio_base=
3278 spia_pedr=
3279 spia_peddr=
3280
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003281 stacktrace [FTRACE]
3282 Enabled the stack tracer on boot up.
3283
Steven Rostedt762e1202011-12-19 22:01:00 -05003284 stacktrace_filter=[function-list]
3285 [FTRACE] Limit the functions that the stack tracer
3286 will trace at boot up. function-list is a comma separated
3287 list of functions. This list can be changed at run
3288 time by the stack_trace_filter file in the debugfs
3289 tracing directory. Note, this enables stack tracing
3290 and the stacktrace above is not needed.
3291
Linus Torvalds1da177e2005-04-16 15:20:36 -07003292 sti= [PARISC,HW]
3293 Format: <num>
3294 Set the STI (builtin display/keyboard on the HP-PARISC
3295 machines) console (graphic card) which should be used
3296 as the initial boot-console.
3297 See also comment in drivers/video/console/sticore.c.
3298
3299 sti_font= [HW]
3300 See comment in drivers/video/console/sticore.c.
3301
3302 stifb= [HW]
3303 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3304
Trond Myklebustcbf11072009-08-09 15:06:19 -04003305 sunrpc.min_resvport=
3306 sunrpc.max_resvport=
3307 [NFS,SUNRPC]
3308 SunRPC servers often require that client requests
3309 originate from a privileged port (i.e. a port in the
3310 range 0 < portnr < 1024).
3311 An administrator who wishes to reserve some of these
3312 ports for other uses may adjust the range that the
3313 kernel's sunrpc client considers to be privileged
3314 using these two parameters to set the minimum and
3315 maximum port values.
3316
Greg Banks42a7fc42007-03-06 01:42:23 -08003317 sunrpc.pool_mode=
3318 [NFS]
3319 Control how the NFS server code allocates CPUs to
3320 service thread pools. Depending on how many NICs
3321 you have and where their interrupts are bound, this
3322 option will affect which CPUs will do NFS serving.
3323 Note: this parameter cannot be changed while the
3324 NFS server is running.
3325
3326 auto the server chooses an appropriate mode
3327 automatically using heuristics
3328 global a single global pool contains all CPUs
3329 percpu one pool for each CPU
3330 pernode one pool for each NUMA node (equivalent
3331 to global on non-NUMA machines)
3332
Trond Myklebustcbf11072009-08-09 15:06:19 -04003333 sunrpc.tcp_slot_table_entries=
3334 sunrpc.udp_slot_table_entries=
3335 [NFS,SUNRPC]
3336 Sets the upper limit on the number of simultaneous
3337 RPC calls that can be sent from the client to a
3338 server. Increasing these values may allow you to
3339 improve throughput, but will also increase the
3340 amount of memory reserved for use by the client.
3341
Michal Hocko07555ac2013-08-22 16:35:46 -07003342 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003343 [KNL] Enable accounting of swap in memory resource
3344 controller if no parameter or 1 is given or disable
3345 it if 0 is given (See Documentation/cgroups/memory.txt)
3346
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003347 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3348 Format: { <int> | force }
3349 <int> -- Number of I/O TLB slabs
3350 force -- force using of bounce buffers even if they
3351 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003352
Linus Torvalds1da177e2005-04-16 15:20:36 -07003353 switches= [HW,M68k]
3354
Andi Kleene52eec12010-09-08 16:54:17 +02003355 sysfs.deprecated=0|1 [KNL]
3356 Enable/disable old style sysfs layout for old udev
3357 on older distributions. When this option is enabled
3358 very new udev will not work anymore. When this option
3359 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3360 in older udev will not work anymore.
3361 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3362 the kernel configuration.
3363
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003364 sysrq_always_enabled
3365 [KNL]
3366 Ignore sysrq setting - this boot parameter will
3367 neutralize any effect of /proc/sys/kernel/sysrq.
3368 Useful for debugging.
3369
Linus Torvalds1da177e2005-04-16 15:20:36 -07003370 tdfx= [HW,DRM]
3371
David Brownell77437fd2008-07-23 21:28:33 -07003372 test_suspend= [SUSPEND]
3373 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3374 standby suspend) as the system sleep state to briefly
3375 enter during system startup. The system is woken from
3376 this state using a wakeup-capable RTC alarm.
3377
Linus Torvalds1da177e2005-04-16 15:20:36 -07003378 thash_entries= [KNL,NET]
3379 Set number of hash buckets for TCP connection
3380
Len Brownf8707ec2007-08-12 00:12:54 -04003381 thermal.act= [HW,ACPI]
3382 -1: disable all active trip points in all thermal zones
3383 <degrees C>: override all lowest active trip points
3384
Len Brownc52a7412007-08-14 15:49:32 -04003385 thermal.crt= [HW,ACPI]
3386 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003387 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003388
Len Brownf5487142007-08-12 00:12:44 -04003389 thermal.nocrt= [HW,ACPI]
3390 Set to disable actions on ACPI thermal zone
3391 critical and hot trip points.
3392
Len Brown72b33ef2007-08-12 00:12:17 -04003393 thermal.off= [HW,ACPI]
3394 1: disable ACPI thermal control
3395
Len Browna70cdc52007-08-12 00:12:35 -04003396 thermal.psv= [HW,ACPI]
3397 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003398 <degrees C>: override all passive trip points to this
3399 value
Len Browna70cdc52007-08-12 00:12:35 -04003400
Len Brown730ff342007-08-12 00:12:26 -04003401 thermal.tzp= [HW,ACPI]
3402 Specify global default ACPI thermal zone polling rate
3403 <deci-seconds>: poll all this frequency
3404 0: no polling (default)
3405
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003406 threadirqs [KNL]
3407 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003408 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003409
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003410 tmem [KNL,XEN]
3411 Enable the Transcendent memory driver if built-in.
3412
3413 tmem.cleancache=0|1 [KNL, XEN]
3414 Default is on (1). Disable the usage of the cleancache
3415 API to send anonymous pages to the hypervisor.
3416
3417 tmem.frontswap=0|1 [KNL, XEN]
3418 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003419 API to send swap pages to the hypervisor. If disabled
3420 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003421
3422 tmem.selfballooning=0|1 [KNL, XEN]
3423 Default is on (1). Disable the driving of swap pages
3424 to the hypervisor.
3425
3426 tmem.selfshrinking=0|1 [KNL, XEN]
3427 Default is on (1). Partial swapoff that immediately
3428 transfers pages from Xen hypervisor back to the
3429 kernel based on different criteria.
3430
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003431 topology= [S390]
3432 Format: {off | on}
3433 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003434 topology information if the hardware supports this.
3435 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003436 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003437 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003438
Linus Torvalds1da177e2005-04-16 15:20:36 -07003439 tp720= [HW,PS2]
3440
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003441 tpm_suspend_pcr=[HW,TPM]
3442 Format: integer pcr id
3443 Specify that at suspend time, the tpm driver
3444 should extend the specified pcr with zeros,
3445 as a workaround for some chips which fail to
3446 flush the last written pcr on TPM_SaveState.
3447 This will guarantee that all the other pcrs
3448 are saved.
3449
Li Zefan9d612be2009-06-24 17:33:15 +08003450 trace_buf_size=nn[KMG]
3451 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003452
Li Zefan020e5f82009-07-01 10:47:05 +08003453 trace_event=[event-list]
3454 [FTRACE] Set and start specified trace events in order
3455 to facilitate early boot debugging.
3456 See also Documentation/trace/events.txt
3457
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003458 trace_options=[option-list]
3459 [FTRACE] Enable or disable tracer options at boot.
3460 The option-list is a comma delimited list of options
3461 that can be enabled or disabled just as if you were
3462 to echo the option name into
3463
3464 /sys/kernel/debug/tracing/trace_options
3465
3466 For example, to enable stacktrace option (to dump the
3467 stack trace of each event), add to the command line:
3468
3469 trace_options=stacktrace
3470
3471 See also Documentation/trace/ftrace.txt "trace options"
3472 section.
3473
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003474 traceoff_on_warning
3475 [FTRACE] enable this option to disable tracing when a
3476 warning is hit. This turns off "tracing_on". Tracing can
3477 be enabled again by echoing '1' into the "tracing_on"
3478 file located in /sys/kernel/debug/tracing/
3479
3480 This option is useful, as it disables the trace before
3481 the WARNING dump is called, which prevents the trace to
3482 be filled with content caused by the warning output.
3483
3484 This option can also be set at run time via the sysctl
3485 option: kernel/traceoff_on_warning
3486
Jiri Kosinafcf4d822012-03-21 16:34:02 -07003487 transparent_hugepage=
3488 [KNL]
3489 Format: [always|madvise|never]
3490 Can be used to control the default behavior of the system
3491 with respect to transparent hugepages.
3492 See Documentation/vm/transhuge.txt for more details.
3493
john stultzd3b8f882009-08-17 16:40:47 -07003494 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003495 Format: <string>
3496 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003497 disables clocksource verification at runtime, as well
3498 as the stability checks done at bootup. Used to enable
3499 high-resolution timer mode on older hardware, and in
3500 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003501 [x86] noirqtime: Do not use TSC to do irq accounting.
3502 Used to run time disable IRQ_TIME_ACCOUNTING on any
3503 platforms where RDTSC is slow and this accounting
3504 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003505
Randy Dunlapa9913042005-10-23 12:57:11 -07003506 turbografx.map[2|3]= [HW,JOY]
3507 TurboGraFX parallel port interface
3508 Format:
3509 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003510 See also Documentation/input/joystick-parport.txt
3511
Christian Kujaub6935f82011-05-31 15:22:05 +00003512 udbg-immortal [PPC] When debugging early kernel crashes that
3513 happen after console_init() and before a proper
3514 console driver takes over, this boot options might
3515 help "seeing" what's going on.
3516
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003517 uhash_entries= [KNL,NET]
3518 Set number of hash buckets for UDP/UDP-Lite connections
3519
Alan Stern5f8364b2006-12-05 16:29:55 -05003520 uhci-hcd.ignore_oc=
3521 [USB] Ignore overcurrent events (default N).
3522 Some badly-designed motherboards generate lots of
3523 bogus events, for ports that aren't wired to
3524 anything. Set this parameter to avoid log spamming.
3525 Note that genuine overcurrent events won't be
3526 reported either.
3527
Simon Arlotte3a61b02008-07-19 23:32:54 +01003528 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003529 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003530
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003531 usbcore.authorized_default=
3532 [USB] Default USB device authorization:
3533 (default -1 = authorized except for wireless USB,
3534 0 = not authorized, 1 = authorized)
3535
Alan Sternb5e795f2007-02-20 15:00:53 -05003536 usbcore.autosuspend=
3537 [USB] The autosuspend time delay (in seconds) used
3538 for newly-detected USB devices (default 2). This
3539 is the time required before an idle device will be
3540 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003541 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003542
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003543 usbcore.usbfs_snoop=
3544 [USB] Set to log all usbfs traffic (default 0 = off).
3545
3546 usbcore.blinkenlights=
3547 [USB] Set to cycle leds on hubs (default 0 = off).
3548
3549 usbcore.old_scheme_first=
3550 [USB] Start with the old device initialization
3551 scheme (default 0 = off).
3552
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003553 usbcore.usbfs_memory_mb=
3554 [USB] Memory limit (in MB) for buffers allocated by
3555 usbfs (default = 16, 0 = max = 2047).
3556
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003557 usbcore.use_both_schemes=
3558 [USB] Try the other device initialization scheme
3559 if the first one fails (default 1 = enabled).
3560
3561 usbcore.initial_descriptor_timeout=
3562 [USB] Specifies timeout for the initial 64-byte
3563 USB_REQ_GET_DESCRIPTOR request in milliseconds
3564 (default 5000 = 5.0 seconds).
3565
Linus Torvalds1da177e2005-04-16 15:20:36 -07003566 usbhid.mousepoll=
3567 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003568
Alan Sternd4f373e2008-11-10 14:07:45 -05003569 usb-storage.delay_use=
3570 [UMS] The delay in seconds before a new device is
3571 scanned for Logical Units (default 5).
3572
3573 usb-storage.quirks=
3574 [UMS] A list of quirks entries to supplement or
3575 override the built-in unusual_devs list. List
3576 entries are separated by commas. Each entry has
3577 the form VID:PID:Flags where VID and PID are Vendor
3578 and Product ID values (4-digit hex numbers) and
3579 Flags is a set of characters, each corresponding
3580 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003581 a = SANE_SENSE (collect more than 18 bytes
3582 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003583 b = BAD_SENSE (don't collect more than 18
3584 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003585 c = FIX_CAPACITY (decrease the reported
3586 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003587 d = NO_READ_DISC_INFO (don't use
3588 READ_DISC_INFO command);
3589 e = NO_READ_CAPACITY_16 (don't use
3590 READ_CAPACITY_16 command);
Alan Sternc838ea42008-12-15 10:40:06 -05003591 h = CAPACITY_HEURISTICS (decrease the
3592 reported device capacity by one
3593 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003594 i = IGNORE_DEVICE (don't bind to this
3595 device);
3596 l = NOT_LOCKABLE (don't try to lock and
3597 unlock ejectable media);
3598 m = MAX_SECTORS_64 (don't transfer more
3599 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003600 n = INITIAL_READ10 (force a retry of the
3601 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003602 o = CAPACITY_OK (accept the capacity
3603 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003604 p = WRITE_CACHE (the device cache is ON
3605 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003606 r = IGNORE_RESIDUE (the device reports
3607 bogus residue values);
3608 s = SINGLE_LUN (the device has only one
3609 Logical Unit);
3610 w = NO_WP_DETECT (don't test whether the
3611 medium is write-protected).
3612 Example: quirks=0419:aaf5:rl,0421:0433:rc
3613
Stephen Boydac1667d2011-08-13 12:34:50 -07003614 user_debug= [KNL,ARM]
3615 Format: <int>
3616 See arch/arm/Kconfig.debug help text.
3617 1 - undefined instruction events
3618 2 - system calls
3619 4 - invalid data aborts
3620 8 - SIGSEGV faults
3621 16 - SIGBUS faults
3622 Example: user_debug=31
3623
Ian Campbell14315592010-02-17 10:38:10 +00003624 userpte=
3625 [X86] Flags controlling user PTE allocations.
3626
3627 nohigh = do not allocate PTE pages in
3628 HIGHMEM regardless of setting
3629 of CONFIG_HIGHPTE.
3630
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303631 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003632 On X86_32, this is an alias for vdso32=. Otherwise:
3633
3634 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07003635 vdso=0: disable VDSO mapping
3636
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003637 vdso32= [X86] Control the 32-bit vDSO
3638 vdso32=1: enable 32-bit VDSO
3639 vdso32=0 or vdso32=2: disable 32-bit VDSO
3640
3641 See the help text for CONFIG_COMPAT_VDSO for more
3642 details. If CONFIG_COMPAT_VDSO is set, the default is
3643 vdso32=0; otherwise, the default is vdso32=1.
3644
3645 For compatibility with older kernels, vdso32=2 is an
3646 alias for vdso32=0.
3647
3648 Try vdso32=0 if you encounter an error that says:
3649 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01003650
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003651 vector= [IA-64,SMP]
3652 vector=percpu: enable percpu vector domain
3653
Linus Torvalds1da177e2005-04-16 15:20:36 -07003654 video= [FB] Frame buffer configuration
3655 See Documentation/fb/modedb.txt.
3656
Aaron Lu3afe6da2013-06-20 15:08:55 +08003657 video.brightness_switch_enabled= [0,1]
3658 If set to 1, on receiving an ACPI notify event
3659 generated by hotkey, video driver will adjust brightness
3660 level and then send out the event to user space through
3661 the allocated input device; If set to 0, video driver
3662 will only send out the event without touching backlight
3663 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02003664 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08003665
Pawel Moll81a054c2012-05-09 18:30:16 +01003666 virtio_mmio.device=
3667 [VMMIO] Memory mapped virtio (platform) device.
3668
3669 <size>@<baseaddr>:<irq>[:<id>]
3670 where:
3671 <size> := size (can use standard suffixes
3672 like K, M and G)
3673 <baseaddr> := physical base address
3674 <irq> := interrupt number (as passed to
3675 request_irq())
3676 <id> := (optional) platform device id
3677 example:
3678 virtio_mmio.device=1K@0x100b0000:48:7
3679
3680 Can be used multiple times for multiple devices.
3681
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003682 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003683 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003684 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003685 Use vga=ask for menu.
3686 This is actually a boot loader parameter; the value is
3687 passed to the kernel using a special protocol.
3688
Randy Dunlapa9913042005-10-23 12:57:11 -07003689 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003690 size of <nn>. This can be used to increase the
3691 minimum size (128MB on x86). It can also be used to
3692 decrease the size and leave more room for directly
3693 mapped kernel RAM.
3694
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003695 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3696 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003697
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003698 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3699 Format: <command>
3700
3701 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3702 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003703
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003704 vsyscall= [X86-64]
3705 Controls the behavior of vsyscalls (i.e. calls to
3706 fixed addresses of 0xffffffffff600x00 from legacy
3707 code). Most statically-linked binaries and older
3708 versions of glibc use these calls. Because these
3709 functions are at fixed addresses, they make nice
3710 targets for exploits that can control RIP.
3711
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003712 emulate [default] Vsyscalls turn into traps and are
3713 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003714
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003715 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003716 This is a little bit faster than trapping
3717 and makes a few dynamic recompilers work
3718 better than they would in emulation mode.
3719 It also makes exploits much easier to write.
3720
3721 none Vsyscalls don't work at all. This makes
3722 them quite hard to use for exploits but
3723 might break your system.
3724
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003725 vt.color= [VT] Default text color.
3726 Format: 0xYX, X = foreground, Y = background.
3727 Default: 0x07 = light gray on black.
3728
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08003729 vt.cur_default= [VT] Default cursor shape.
3730 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3731 the parameters of the <Esc>[?A;B;Cc escape sequence;
3732 see VGA-softcursor.txt. Default: 2 = underline.
3733
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003734 vt.default_blu= [VT]
3735 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3736 Change the default blue palette of the console.
3737 This is a 16-member array composed of values
3738 ranging from 0-255.
3739
3740 vt.default_grn= [VT]
3741 Format: <green0>,<green1>,<green2>,...,<green15>
3742 Change the default green palette of the console.
3743 This is a 16-member array composed of values
3744 ranging from 0-255.
3745
3746 vt.default_red= [VT]
3747 Format: <red0>,<red1>,<red2>,...,<red15>
3748 Change the default red palette of the console.
3749 This is a 16-member array composed of values
3750 ranging from 0-255.
3751
3752 vt.default_utf8=
3753 [VT]
3754 Format=<0|1>
3755 Set system-wide default UTF-8 mode for all tty's.
3756 Default is 1, i.e. UTF-8 mode is enabled for all
3757 newly opened terminals.
3758
Matthew Garrettf6c06b62009-11-13 15:14:11 -05003759 vt.global_cursor_default=
3760 [VT]
3761 Format=<-1|0|1>
3762 Set system-wide default for whether a cursor
3763 is shown on new VTs. Default is -1,
3764 i.e. cursors will be created by default unless
3765 overridden by individual drivers. 0 will hide
3766 cursors, 1 will display them.
3767
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003768 vt.italic= [VT] Default color for italic text; 0-15.
3769 Default: 2 = green.
3770
3771 vt.underline= [VT] Default color for underlined text; 0-15.
3772 Default: 3 = cyan.
3773
Randy Dunlap4724ba52010-05-03 11:42:52 -07003774 watchdog timers [HW,WDT] For information on watchdog timers,
3775 see Documentation/watchdog/watchdog-parameters.txt
3776 or other driver-specific files in the
3777 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003778
Tejun Heod55262c2013-04-01 11:23:38 -07003779 workqueue.disable_numa
3780 By default, all work items queued to unbound
3781 workqueues are affine to the NUMA nodes they're
3782 issued on, which results in better behavior in
3783 general. If NUMA affinity needs to be disabled for
3784 whatever reason, this option can be used. Note
3785 that this also can be controlled per-workqueue for
3786 workqueues visible under /sys/bus/workqueue/.
3787
Viresh Kumarcee22a12013-04-08 16:45:40 +05303788 workqueue.power_efficient
3789 Per-cpu workqueues are generally preferred because
3790 they show better performance thanks to cache
3791 locality; unfortunately, per-cpu workqueues tend to
3792 be more power hungry than unbound workqueues.
3793
3794 Enabling this makes the per-cpu workqueues which
3795 were observed to contribute significantly to power
3796 consumption unbound, leading to measurably lower
3797 power usage at the cost of small performance
3798 overhead.
3799
3800 The default value of this parameter is determined by
3801 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3802
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003803 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3804 default x2apic cluster mode on platforms
3805 supporting x2apic.
3806
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003807 x86_intel_mid_timer= [X86-32,APBT]
3808 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07003809 Two valid options are apbt timer only and lapic timer
3810 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003811 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07003812
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003813 xen_emul_unplug= [HW,X86,XEN]
3814 Unplug Xen emulated devices
3815 Format: [unplug0,][unplug1]
3816 ide-disks -- unplug primary master IDE devices
3817 aux-ide-disks -- unplug non-primary-master IDE devices
3818 nics -- unplug network devices
3819 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01003820 unnecessary -- unplugging emulated devices is
3821 unnecessary even if the host did not respond to
3822 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01003823 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003824
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04003825 xen_nopvspin [X86,XEN]
3826 Disables the ticketlock slowpath using Xen PV
3827 optimizations.
3828
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04003829 xen_nopv [X86]
3830 Disables the PV optimizations forcing the HVM guest to
3831 run as generic HVM guest with no PV drivers.
3832
Linus Torvalds1da177e2005-04-16 15:20:36 -07003833 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07003834 Format:
3835 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003836
Randy Dunlapa9913042005-10-23 12:57:11 -07003837______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07003838
3839TODO:
3840
Linus Torvalds1da177e2005-04-16 15:20:36 -07003841 Add more DRM drivers.