blob: 6eaa9cdb7094b5785aecc54e55d4cb5bd08a8de9 [file] [log] [blame]
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
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100569 ccw_timeout_log [S390]
570 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571
Paul Menage8bab8dd2008-04-04 14:29:57 -0700572 cgroup_disable= [KNL] Disable a particular controller
573 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800574 The effects of cgroup_disable=foo are:
575 - foo isn't auto-mounted if you mount all cgroups in
576 a single hierarchy
577 - foo isn't visible as an individually mountable
578 subsystem
579 {Currently only "memory" controller deal with this and
580 cut the overhead, others just disable the usage. So
581 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700582
Linus Torvalds1da177e2005-04-16 15:20:36 -0700583 checkreqprot [SELINUX] Set initial checkreqprot flag value.
584 Format: { "0" | "1" }
585 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700586 0 -- check protection applied by kernel (includes
587 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700588 1 -- check protection requested by application.
589 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700590 Value can be changed at runtime via
591 /selinux/checkreqprot.
592
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100593 cio_ignore= [S390]
594 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700595 clk_ignore_unused
596 [CLK]
597 Keep all clocks already enabled by bootloader on,
598 even if no driver has claimed them. This is useful
599 for debug and development, but should not be
600 needed on a platform with proper driver support.
601 For more information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100602
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700603 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700604 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200605 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700606 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200607 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700608 Format: { pit | tsc | cyclone | pmtmr }
609
John Stultz592913e2010-07-13 17:56:20 -0700610 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700611 Format: <string>
612 Override the default clocksource and use the clocksource
613 with the name specified.
614 Some clocksource names to choose from, depending on
615 the platform:
616 [all] jiffies (this is the base, fallback clocksource)
617 [ACPI] acpi_pm
618 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
619 pxa_timer,timer3,32k_counter,timer0_1
620 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700621 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700622 scx200_hrt on Geode; cyclone on IBM x440
623 [MIPS] MIPS
624 [PARISC] cr16
625 [S390] tod
626 [SH] SuperH
627 [SPARC64] tick
628 [X86-64] hpet,tsc
629
Andi Kleenac72e782008-01-30 13:33:21 +0100630 clearcpuid=BITNUM [X86]
631 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800632 arch/x86/include/asm/cpufeature.h for the valid bit
633 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100634 stable over kernel options, but the vendor specific
635 ones should be.
636 Also note that user programs calling CPUID directly
637 or using the feature without checking anything
638 will still see it. This just prevents it from
639 being used by the kernel or shown in /proc/cpuinfo.
640 Also note the kernel might malfunction if you disable
641 some critical bits.
642
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700643 cma=nn[MG]@[start[MG][-end[MG]]]
644 [ARM,X86,KNL]
645 Sets the size of kernel global memory area for
646 contiguous memory allocations and optionally the
647 placement constraint by the physical address range of
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100648 memory allocations. For more information, see
649 include/linux/dma-contiguous.h
650
Robert Jennings14f966e2009-04-15 05:55:32 +0000651 cmo_free_hint= [PPC] Format: { yes | no }
652 Specify whether pages are marked as being inactive
653 when they are freed. This is used in CMO environments
654 to determine OS memory pressure for page stealing by
655 a hypervisor.
656 Default: yes
657
Marek Szyprowskic7909502011-12-29 13:09:51 +0100658 coherent_pool=nn[KMG] [ARM,KNL]
659 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200660 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100661
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530662 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100663 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100664 Range: 0 - 8192
665 Default: 64
666
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700668 Format:
669 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700670
671 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
672 Format: <io>[,<irq>]
673
Randy Dunlapa9913042005-10-23 12:57:11 -0700674 com90xx= [HW,NET]
675 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700676 Format: <io>[,<irq>[,<memstart>]]
677
678 condev= [HW,S390] console device
679 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700680
Linus Torvalds1da177e2005-04-16 15:20:36 -0700681 console= [KNL] Output console device and options.
682
683 tty<n> Use the virtual console device <n>.
684
685 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800686 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800688 the form "bbbbpnf", where "bbbb" is the baud rate,
689 "p" is parity ("n", "o", or "e"), "n" is number of
690 bits, and "f" is flow control ("r" for RTS or
691 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800693 See Documentation/serial-console.txt for more
694 information. See
695 Documentation/networking/netconsole.txt for an
696 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700697
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700698 uart[8250],io,<addr>[,options]
699 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700700 Start an early, polled-mode console on the 8250/16550
701 UART at the specified I/O port or MMIO address,
702 switching to the matching ttyS device later. The
703 options are the same as for ttyS, above.
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500704 hvc<n> Use the hypervisor console device <n>. This is for
705 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700706
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700707 If the device connected to the port is not a TTY but a braille
708 device, prepend "brl," before the device type, for instance
709 console=brl,ttyS0
710 For now, only VisioBraille is supported.
711
Daniel Mackf324edc2009-06-16 15:33:52 -0700712 consoleblank= [KNL] The console blank (screen saver) timeout in
713 seconds. Defaults to 10*60 = 10mins. A value of 0
714 disables the blank timer.
715
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800716 coredump_filter=
717 [KNL] Change the default value for
718 /proc/<pid>/coredump_filter.
719 See also Documentation/filesystems/proc.txt.
720
Len Brown62027ae2011-04-01 18:13:10 -0400721 cpuidle.off=1 [CPU_IDLE]
722 disable the cpuidle sub-system
723
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700725 Format:
726 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800728 crashkernel=size[KMG][@offset[KMG]]
729 [KNL] Using kexec, Linux can switch to a 'crash kernel'
730 upon panic. This parameter reserves the physical
731 memory region [offset, offset + size] for that kernel
732 image. If '@offset' is omitted, then a suitable offset
733 is selected automatically. Check
734 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700735
Bernhard Wallefb391592007-10-18 23:41:02 -0700736 crashkernel=range1:size1[,range2:size2,...][@offset]
737 [KNL] Same as above, but depends on the memory
738 in the running system. The syntax of range is
739 start-[end] where start and end are both
740 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800741 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700742
Yinghai Luadbc7422013-04-15 22:23:48 -0700743 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700744 [KNL, x86_64] range could be above 4G. Allow kernel
745 to allocate physical memory region from top, so could
746 be above 4G if system have more than 4G ram installed.
747 Otherwise memory region will be allocated below 4G, if
748 available.
749 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700750 crashkernel=size[KMG],low
751 [KNL, x86_64] range under 4G. When crashkernel=X,high
752 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700753 above 4G, that cause second kernel crash on system
754 that require some amount of low memory, e.g. swiotlb
755 requires at least 64M+32K low memory. Kernel would
756 try to allocate 72M below 4G automatically.
757 This one let user to specify own low range under 4G
758 for second kernel instead.
759 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700760 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700761 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700762
Linus Torvalds1da177e2005-04-16 15:20:36 -0700763 cs89x0_dma= [HW,NET]
764 Format: <dma>
765
766 cs89x0_media= [HW,NET]
767 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700768
Randy Dunlapa9913042005-10-23 12:57:11 -0700769 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700770 See header of drivers/s390/block/dasd_devmap.c.
771
772 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
773 (one device per port)
774 Format: <port#>,<type>
775 See also Documentation/input/joystick-parport.txt
776
Thomas Renningera648ec02010-08-06 16:11:02 +0200777 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
778 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600779 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200780
Linus Torvalds1da177e2005-04-16 15:20:36 -0700781 debug [KNL] Enable kernel debugging (events log level).
782
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700783 debug_locks_verbose=
784 [KNL] verbose self-tests
785 Format=<0|1>
786 Print debugging info while doing the locking API
787 self-tests.
788 We default to 0 (no extra messages), setting it to
789 1 will print _a lot_ more information - normally
790 only useful to kernel developers.
791
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700792 debug_objects [KNL] Enable object debugging
793
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500794 no_debug_objects
795 [KNL] Disable object debugging
796
Stanislaw Gruszkac0a32fc52012-01-10 15:07:28 -0800797 debug_guardpage_minorder=
798 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
799 parameter allows control of the order of pages that will
800 be intentionally kept free (and hence protected) by the
801 buddy allocator. Bigger value increase the probability
802 of catching random memory corruption, but reduce the
803 amount of memory for normal system use. The maximum
804 possible value is MAX_ORDER/2. Setting this parameter
805 to 1 or 2 should be enough to identify most random
806 memory corruption problems caused by bugs in kernel or
807 driver code when a CPU writes to (or reads from) a
808 random memory location. Note that there exists a class
809 of memory corruptions problems caused by buggy H/W or
810 F/W or by drivers badly programing DMA (basically when
811 memory is written at bus level and the CPU MMU is
812 bypassed) which are not detectable by
813 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
814 tracking down these problems.
815
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200816 debugpat [X86] Enable PAT debugging
817
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200818 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700819 Format: <area>[,<node>]
820 See also Documentation/networking/decnet.txt.
821
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700822 default_hugepagesz=
823 [same as hugepagesz=] The size of the default
824 HugeTLB page size. This is the size represented by
825 the legacy /proc/ hugepages APIs, used for SHM, and
826 default size when mounting hugetlbfs filesystems.
827 Defaults to the default architecture's huge page size
828 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700829
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 dhash_entries= [KNL]
831 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700832
Brian Haleyb0f83b22010-02-04 13:36:50 -0800833 disable= [IPV6]
834 See Documentation/networking/ipv6.txt.
835
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900836 disable_cpu_apicid= [X86,APIC,SMP]
837 Format: <int>
838 The number of initial APIC ID for the
839 corresponding CPU to be disabled at boot,
840 mostly used for the kdump 2nd kernel to
841 disable BSP to wake up multiple CPUs without
842 causing system reset or hang due to sending
843 INIT from AP to BSP.
844
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000845 disable_ddw [PPC/PSERIES]
846 Disable Dynamic DMA Window support. Use this if
847 to workaround buggy firmware.
848
Brian Haleyb0f83b22010-02-04 13:36:50 -0800849 disable_ipv6= [IPV6]
850 See Documentation/networking/ipv6.txt.
851
Yinghai Lu95ffa242008-04-29 03:52:33 -0700852 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700853 The kernel tries to adjust MTRR layout from continuous
854 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700855 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700856
Yinghai Lu093af8d2008-01-30 13:33:32 +0100857 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100858 By default the kernel will trim any uncacheable
859 memory out of your available memory pool based on
860 MTRR settings. This parameter disables that behavior,
861 possibly causing your machine to run very slowly.
862
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530863 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700864 Disable PIN 1 of APIC timer
865 Can be useful to work around chipset bugs.
866
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700867 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
868 this option disables the debugging code at boot.
869
870 dma_debug_entries=<number>
871 This option allows to tune the number of preallocated
872 entries for DMA-API debugging code. One entry is
873 required per DMA-API allocation. Use this if the
874 DMA-API debugging code disables itself because the
875 architectural default is too low.
876
Joerg Roedel1745de52009-05-22 21:49:51 +0200877 dma_debug_driver=<driver_name>
878 With this option the DMA-API debugging driver
879 filter feature can be enabled at boot time. Just
880 pass the driver to filter for as the parameter.
881 The filter can be disabled or changed to another
882 driver later using sysfs.
883
Carsten Emdeda0df922012-03-18 22:37:33 +0100884 drm_kms_helper.edid_firmware=[<connector>:]<file>
885 Broken monitors, graphic adapters and KVMs may
886 send no or incorrect EDID data sets. This parameter
887 allows to specify an EDID data set in the
888 /lib/firmware directory that is used instead.
889 Generic built-in EDID data sets are used, if one of
890 edid/1024x768.bin, edid/1280x1024.bin,
891 edid/1680x1050.bin, or edid/1920x1080.bin is given
892 and no file with the same name exists. Details and
893 instructions how to build your own EDID data are
894 available in Documentation/EDID/HOWTO.txt. An EDID
895 data set will only be used for a particular connector,
896 if its name and a colon are prepended to the EDID
897 name.
898
Linus Torvalds1da177e2005-04-16 15:20:36 -0700899 dscc4.setup= [NET]
900
Jim Cromie29e36c92012-04-27 14:30:41 -0600901 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
902 module.dyndbg[="val"]
903 Enable debug messages at boot time. See
904 Documentation/dynamic-debug-howto.txt for details.
905
Mark Salter56aeeba2014-04-07 15:39:53 -0700906 early_ioremap_debug [KNL]
907 Enable debug messages in early_ioremap support. This
908 is useful for tracking down temporary early mappings
909 which are not unmapped.
910
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700911 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500912
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700913 uart[8250],io,<addr>[,options]
914 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700915 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700916 Start an early, polled-mode console on the 8250/16550
917 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700918 MMIO inter-register address stride is either 8-bit
919 (mmio) or 32-bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700920 The options are the same as for ttyS, above.
921
Rob Herring0d3c6732014-04-18 17:19:57 -0500922 pl011,<addr>
923 Start an early, polled-mode console on a pl011 serial
924 port at the specified address. The pl011 serial port
925 must already be setup and configured. Options are not
926 yet supported.
927
Rob Herringd50d7262014-04-18 17:19:58 -0500928 smh Use ARM semihosting calls for early console.
929
Finn Thain7913ad12014-04-12 23:48:56 +1000930 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700931 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +0100932 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500933 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700934 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -0700935 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500936 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500937 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700938
Dave Hansen147ea092013-04-10 14:03:38 -0700939 earlyprintk is useful when the kernel crashes before
940 the normal console is initialized. It is not enabled by
941 default because it has some cosmetic problems.
942
Randy Dunlapa9913042005-10-23 12:57:11 -0700943 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700944 takes over.
945
Matt Fleming72548e82013-10-04 09:36:56 +0100946 Only one of vga, efi, serial, or usb debug port can
947 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700948
Dave Hansen147ea092013-04-10 14:03:38 -0700949 Currently only ttyS0 and ttyS1 may be specified by
950 name. Other I/O ports may be explicitly specified
951 on some architectures (x86 and arm at least) by
952 replacing ttySn with an I/O port address, like this:
953 earlyprintk=serial,0x1008,115200
954 You can find the port for a given device in
955 /proc/tty/driver/serial:
956 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -0700957
958 Interaction with the standard serial driver is not
959 very good.
960
Matt Fleming72548e82013-10-04 09:36:56 +0100961 The VGA and EFI output is eventually overwritten by
962 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700963
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500964 The xen output can only be used by Xen PV guests.
965
Chen, Gongc700f012013-12-06 01:17:08 -0500966 edac_report= [HW,EDAC] Control how to report EDAC event
967 Format: {"on" | "off" | "force"}
968 on: enable EDAC to report H/W event. May be overridden
969 by other higher priority error reporting module.
970 off: disable H/W event reporting through EDAC.
971 force: enforce the use of EDAC to report H/W event.
972 default: on.
973
Jason Wessel97311912010-05-20 21:04:30 -0500974 ekgdboc= [X86,KGDB] Allow early kernel console debugging
975 ekgdboc=kbd
976
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300977 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -0500978 the boot argument: earlyprintk=vga
979
Linus Torvalds1da177e2005-04-16 15:20:36 -0700980 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700981 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700982
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +0100983 efi= [EFI]
984 Format: { "old_map" }
985 old_map [X86-64]: switch to the old ioremap-based EFI
986 runtime services mapping. 32-bit still uses this one by
987 default.
988
Richard Weinberger8c58bf32013-04-17 01:00:53 +0200989 efi_no_storage_paranoia [EFI; X86]
990 Using this parameter you can use more than 50% of
991 your efi variable storage. Use this parameter only if
992 you are really sure that your UEFI does sane gc and
993 fulfills the spec otherwise your board may brick.
994
Linus Torvalds1da177e2005-04-16 15:20:36 -0700995 eisa_irq_edge= [PARISC,HW]
996 See header of drivers/parisc/eisa.c.
997
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700998 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700999 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001000 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001001
1002 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001003 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001004 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001005 Documentation/block/deadline-iosched.txt for details.
1006
Michael Holzheud3bf37952011-10-30 15:16:37 +01001007 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001008 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001009 image elf header and optionally the size. Generally
1010 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001011 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001012
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001013 enable_mtrr_cleanup [X86]
1014 The kernel tries to adjust MTRR layout from continuous
1015 to discrete, to make X server driver able to add WB
1016 entry later. This parameter enables that.
1017
Randy Dunlapca1eda22009-05-06 16:02:58 -07001018 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001019 Enable PIN 1 of APIC timer
1020 Can be useful to work around chipset bugs
1021 (in particular on some ATI chipsets).
1022 The kernel tries to set a reasonable default.
1023
Linus Torvalds1da177e2005-04-16 15:20:36 -07001024 enforcing [SELINUX] Set initial enforcing status.
1025 Format: {"0" | "1"}
1026 See security/selinux/Kconfig help text.
1027 0 -- permissive (log only, no denials).
1028 1 -- enforcing (deny and log).
1029 Default value is 0.
1030 Value can be changed at runtime via /selinux/enforce.
1031
Huang Yinga08f82d2010-05-18 14:35:21 +08001032 erst_disable [ACPI]
1033 Disable Error Record Serialization Table (ERST)
1034 support.
1035
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036 ether= [HW,NET] Ethernet cards parameters
1037 This option is obsoleted by the "netdev=" option, which
1038 has equivalent usage. See its documentation for details.
1039
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001040 evm= [EVM]
1041 Format: { "fix" }
1042 Permit 'security.evm' to be updated regardless of
1043 current integrity status.
1044
Akinobu Mitade1ba092006-12-08 02:39:42 -08001045 failslab=
1046 fail_page_alloc=
1047 fail_make_request=[KNL]
1048 General fault injection mechanism.
1049 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001050 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001051
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001053 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054
Alex Chiangf13ae302008-05-08 14:03:23 -06001055 force_pal_cache_flush
1056 [IA-64] Avoid check_sal_cache_flush which may hang on
1057 buggy SAL_CACHE_FLUSH implementations. Using this
1058 parameter will force ia64_sal_cache_flush to call
1059 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1060
Chris Bainbridge69f23662014-03-07 18:40:42 +07001061 forcepae [X86-32]
1062 Forcefully enable Physical Address Extension (PAE).
1063 Many Pentium M systems disable PAE but may have a
1064 functionally usable PAE implementation.
1065 Warning: use of this parameter will taint the kernel
1066 and may cause unknown problems.
1067
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001068 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001069 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001070 as early as possible in order to facilitate early
1071 boot debugging.
1072
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001073 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001074 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001075 If no parameter is passed, ftrace will dump
1076 buffers of all CPUs, but if you pass orig_cpu, it will
1077 dump only the buffer of the CPU that triggered the
1078 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001079
1080 ftrace_filter=[function-list]
1081 [FTRACE] Limit the functions traced by the function
1082 tracer at boot up. function-list is a comma separated
1083 list of functions. This list can be changed at run
1084 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001085 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001086
1087 ftrace_notrace=[function-list]
1088 [FTRACE] Do not trace the functions specified in
1089 function-list. This list can be changed at run time
1090 by the set_ftrace_notrace file in the debugfs
1091 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001092
Stefan Assmann369bc182009-10-12 22:17:21 +02001093 ftrace_graph_filter=[function-list]
1094 [FTRACE] Limit the top level callers functions traced
1095 by the function graph tracer at boot up.
1096 function-list is a comma separated list of functions
1097 that can be changed at run time by the
1098 set_graph_function file in the debugfs tracing directory.
1099
Linus Torvalds1da177e2005-04-16 15:20:36 -07001100 gamecon.map[2|3]=
1101 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1102 support via parallel port (up to 5 devices per port)
1103 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1104 See also Documentation/input/joystick-parport.txt
1105
1106 gamma= [HW,DRM]
1107
Yinghai Luaaf23042008-01-30 13:33:09 +01001108 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1109 Format: off | on
1110 default: on
1111
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001112 gcov_persist= [GCOV] When non-zero (default), profiling data for
1113 kernel modules is saved and remains accessible via
1114 debugfs, even when the module is unloaded/reloaded.
1115 When zero, profiling data is discarded and associated
1116 debugfs files are removed at module unload time.
1117
Linus Torvalds1da177e2005-04-16 15:20:36 -07001118 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001119 invalid Protective MBR to be treated as GPT. If the
1120 primary GPT is corrupted, it enables the backup/alternate
1121 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001122
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001123 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1124 the "Enable 0" bit of the configuration register.
1125 Format: 0 | 1
1126 Default: 0
1127 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1128 the "Enable 0" bit of the configuration register.
1129 Format: 0 | 1
1130 Default: 0
1131 grcan.select= [HW] Select which physical interface to use.
1132 Format: 0 | 1
1133 Default: 0
1134 grcan.txsize= [HW] Sets the size of the tx buffer.
1135 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1136 Default: 1024
1137 grcan.rxsize= [HW] Sets the size of the rx buffer.
1138 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1139 Default: 1024
1140
Linus Torvalds1da177e2005-04-16 15:20:36 -07001141 hashdist= [KNL,NUMA] Large hashes allocated during boot
1142 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001143 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001144 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145
1146 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1147
1148 hd= [EIDE] (E)IDE hard drive subsystem geometry
1149 Format: <cyl>,<head>,<sect>
1150
Huang Yingea8c0712010-05-18 14:35:15 +08001151 hest_disable [ACPI]
1152 Disable Hardware Error Source Table (HEST) support;
1153 corresponding firmware-first mode error processing
1154 logic will be disabled.
1155
Linus Torvalds1da177e2005-04-16 15:20:36 -07001156 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1157 size of <nn>. This works even on boxes that have no
1158 highmem otherwise. This also works to reduce highmem
1159 size on bigger boxes.
1160
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001161 highres= [KNL] Enable/disable high resolution timer mode.
1162 Valid parameters: "on", "off"
1163 Default: "on"
1164
Linus Torvalds1da177e2005-04-16 15:20:36 -07001165 hisax= [HW,ISDN]
1166 See Documentation/isdn/README.HiSax.
1167
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001168 hlt [BUGS=ARM,SH]
1169
1170 hpet= [X86-32,HPET] option to control HPET usage
1171 Format: { enable (default) | disable | force |
1172 verbose }
1173 disable: disable HPET and use PIT instead
1174 force: allow force enabled of undocumented chips (ICH4,
1175 VIA, nVidia)
1176 verbose: show contents of HPET registers during setup
1177
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001178 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1179 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1180
Andi Kleenb4718e62008-07-23 21:27:51 -07001181 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1182 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001183 On x86-64 and powerpc, this option can be specified
1184 multiple times interleaved with hugepages= to reserve
1185 huge pages of different sizes. Valid pages sizes on
1186 x86-64 are 2M (when the CPU supports "pse") and 1G
1187 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -07001188 Note that 1GB pages can only be allocated at boot time
1189 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +09001190
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001191 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1192 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001193 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1194 If specified, z/VM IUCV HVC accepts connections
1195 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001196
James Hoganfdabf522012-10-09 11:00:27 +01001197 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1198 hardware thread id mappings.
1199 Format: <cpu>:<hwthread>
1200
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001201 keep_bootcon [KNL]
1202 Do not unregister boot console at start. This is only
1203 useful for debugging when something happens in the window
1204 between unregistering the boot console and initializing
1205 the real console.
1206
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001207 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001208 or register an additional I2C bus that is not
1209 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001210 Format:
1211 <bus_id>,<clkrate>
1212
Jiri Kosina36d95732008-10-06 02:51:09 -04001213 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001214 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001215 i8042.dumbkbd [HW] Pretend that controller can only read data from
1216 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001217 (Don't attempt to blink the leds)
1218 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001219 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001220 i8042.noloop [HW] Disable the AUX Loopback command while probing
1221 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001222 i8042.nomux [HW] Don't check presence of an active multiplexing
1223 controller
1224 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1225 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001226 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001227 i8042.reset [HW] Reset the controller during init and cleanup
1228 i8042.unlock [HW] Unlock (ignore) the keylock
1229
1230 i810= [HW,DRM]
1231
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001232 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1233 indicates that the driver is running on unsupported
1234 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001235 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1236 does not match list of supported models.
1237 i8k.power_status
1238 [HW] Report power status in /proc/i8k
1239 (disabled by default)
1240 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1241 capability is set.
1242
Carsten Emde4dca20e2012-03-15 15:56:26 +01001243 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001244 [DRM] Invert the sense of the variable that is used to
1245 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001246 brightness value of 0 indicates backlight switched off,
1247 and the maximum of the brightness value sets the backlight
1248 to maximum brightness. If this parameter is set to 0
1249 (default) and the machine requires it, or this parameter
1250 is set to 1, a brightness value of 0 sets the backlight
1251 to maximum brightness, and the maximum of the brightness
1252 value switches the backlight off.
1253 -1 -- never invert brightness
1254 0 -- machine default
1255 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001256
Linus Torvalds1da177e2005-04-16 15:20:36 -07001257 icn= [HW,ISDN]
1258 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1259
David Fries0af80c02009-02-25 20:28:21 +01001260 ide-core.nodma= [HW] (E)IDE subsystem
1261 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001262 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1263 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001264 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001266 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1267 Claim all unknown PCI IDE storage controllers.
1268
Andi Kleenf039b752007-05-02 19:27:12 +02001269 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001270 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001271 Poll forces a polling idle loop that can slightly
1272 improve the performance of waking up a idle CPU, but
1273 will use a lot of power and make the system run hot.
1274 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001275 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001276 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001277 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001278
Ingo Molnar792908222006-12-06 20:40:51 -08001279 ignore_loglevel [KNL]
1280 Ignore loglevel setting - this will print /all/
1281 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001282 We also add it as printk module parameter, so users
1283 could change it dynamically, usually by
1284 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001285
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286 ihash_entries= [KNL]
1287 Set number of hash buckets for inode cache.
1288
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001289 ima_appraise= [IMA] appraise integrity measurements
1290 Format: { "off" | "enforce" | "fix" }
1291 default: "enforce"
1292
Mimi Zohar07f6a792011-03-09 22:25:48 -05001293 ima_appraise_tcb [IMA]
1294 The builtin appraise policy appraises all files
1295 owned by uid=0.
1296
Mimi Zohar3323eec92009-02-04 09:06:58 -05001297 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001298 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1299 | sha512 | ... }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001300 default: "sha1"
1301
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001302 The list of supported hash algorithms is defined
1303 in crypto/hash_info.h.
1304
Eric Paris5789ba32009-05-21 15:47:06 -04001305 ima_tcb [IMA]
1306 Load a policy which meets the needs of the Trusted
1307 Computing Base. This means IMA will measure all
1308 programs exec'd, files mmap'd for exec, and all files
1309 opened for read by uid=0.
1310
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001311 ima_template= [IMA]
1312 Select one of defined IMA measurements template formats.
1313 Formats: { "ima" | "ima-ng" }
1314 Default: "ima-ng"
1315
Linus Torvalds1da177e2005-04-16 15:20:36 -07001316 init= [KNL]
1317 Format: <full_path>
1318 Run specified binary instead of /sbin/init as init
1319 process.
1320
1321 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1322 for working out where the kernel is dying during
1323 startup.
1324
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001325 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1326 initcall functions. Useful for debugging built-in
1327 modules and initcalls.
1328
Linus Torvalds1da177e2005-04-16 15:20:36 -07001329 initrd= [BOOT] Specify the location of the initial ramdisk
1330
1331 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1332 Format: <irq>
1333
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001334 int_pln_enable [x86] Enable power limit notification interrupt
1335
Mimi Zohard726d8d2013-03-18 14:48:02 -04001336 integrity_audit=[IMA]
1337 Format: { "0" | "1" }
1338 0 -- basic integrity auditing messages. (Default)
1339 1 -- additional integrity auditing messages.
1340
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001341 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001342 on
1343 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001344 off
1345 Disable intel iommu driver.
1346 igfx_off [Default Off]
1347 By default, gfx is mapped as normal device. If a gfx
1348 device has a dedicated DMAR unit, the DMAR unit is
1349 bypassed by not enabling DMAR with this option. In
1350 this case, gfx device will use physical address for
1351 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001352 forcedac [x86_64]
1353 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001354 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001355 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001356 than 32-bit addressing. The default is to look
1357 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001358 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001359 strict [Default Off]
1360 With this option on every unmap_single operation will
1361 result in a hardware IOTLB flush operation as opposed
1362 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001363 sp_off [Default Off]
1364 By default, super page will be supported if Intel IOMMU
1365 has the capability. With this option, super page will
1366 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001367
1368 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1369 0 disables intel_idle and fall back on acpi_idle.
1370 1 to 6 specify maximum depth of C-state.
1371
Dirk Brandewie6be26492013-02-15 22:55:10 +01001372 intel_pstate= [X86]
1373 disable
1374 Do not enable intel_pstate as the default
1375 scaling driver for the supported processors
1376
Chris Wrightd1423d52010-07-20 11:06:49 -07001377 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001378 on enable Interrupt Remapping (default)
1379 off disable Interrupt Remapping
1380 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001381 no_x2apic_optout
1382 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001383
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001384 iomem= Disable strict checking of access to MMIO memory
1385 strict regions from userspace.
1386 relaxed
1387
1388 iommu= [x86]
1389 off
1390 force
1391 noforce
1392 biomerge
1393 panic
1394 nopanic
1395 merge
1396 nomerge
1397 forcesac
1398 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001399 pt [x86, IA-64]
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001400
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001401
1402 io7= [HW] IO7 for Marvel based alpha systems
1403 See comment before marvel_specify_io7 in
1404 arch/alpha/kernel/core_marvel.c.
1405
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301406 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001407 0x80
1408 Standard port 0x80 based delay
1409 0xed
1410 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001411 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001412 Simple two microseconds delay
1413 none
1414 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001415
Linus Torvalds1da177e2005-04-16 15:20:36 -07001416 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001417 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001418
1419 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001420 See comment before ip2_setup() in
1421 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001422
Alan Cox200803d2005-06-28 20:45:18 -07001423 irqfixup [HW]
1424 When an interrupt is not handled search all handlers
1425 for it. Intended to get systems with badly broken
1426 firmware running.
1427
1428 irqpoll [HW]
1429 When an interrupt is not handled search all handlers
1430 for it. Also check all handlers each timer
1431 interrupt. Intended to get systems with badly broken
1432 firmware running.
1433
Linus Torvalds1da177e2005-04-16 15:20:36 -07001434 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001435 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001436
1437 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001438 Format:
1439 <cpu number>,...,<cpu number>
1440 or
Li Zefanb225d442008-11-06 12:53:39 -08001441 <cpu number>-<cpu number>
1442 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001443 or a mixture
1444 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001445
Linus Torvalds1da177e2005-04-16 15:20:36 -07001446 This option can be used to specify one or more CPUs
1447 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001448 algorithms. You can move a process onto or off an
1449 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001450 <cpu number> begins at 0 and the maximum value is
1451 "number of CPUs in system - 1".
1452
1453 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001454 alternative -- manually setting the CPU mask of all
1455 tasks in the system -- can cause problems and
1456 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001457
Randy Dunlapa9913042005-10-23 12:57:11 -07001458 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001459
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001460 ivrs_ioapic [HW,X86_64]
1461 Provide an override to the IOAPIC-ID<->DEVICE-ID
1462 mapping provided in the IVRS ACPI table. For
1463 example, to map IOAPIC-ID decimal 10 to
1464 PCI device 00:14.0 write the parameter as:
1465 ivrs_ioapic[10]=00:14.0
1466
1467 ivrs_hpet [HW,X86_64]
1468 Provide an override to the HPET-ID<->DEVICE-ID
1469 mapping provided in the IVRS ACPI table. For
1470 example, to map HPET-ID decimal 0 to
1471 PCI device 00:14.0 write the parameter as:
1472 ivrs_hpet[0]=00:14.0
1473
Linus Torvalds1da177e2005-04-16 15:20:36 -07001474 js= [HW,JOY] Analog joystick
1475 See Documentation/input/joystick.txt.
1476
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001477 keepinitrd [HW,ARM]
1478
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301479 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001480 specifies the amount of memory usable by the kernel
1481 for non-movable allocations. The requested amount is
1482 spread evenly throughout all nodes in the system. The
1483 remaining memory in each node is used for Movable
1484 pages. In the event, a node is too small to have both
1485 kernelcore and Movable pages, kernelcore pages will
1486 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001487 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001488 allocation of pages that may be reclaimed or moved
1489 by the page migration subsystem. This means that
1490 HugeTLB pages may not be allocated from this zone.
1491 Note that allocations like PTEs-from-HighMem still
1492 use the HighMem zone if it exists, and the Normal
1493 zone if it does not.
1494
Jason Wessel4fe1da42010-05-20 21:04:31 -05001495 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1496 Format: <Controller#>[,poll interval]
1497 The controller # is the number of the ehci usb debug
1498 port as it is probed via PCI. The poll interval is
1499 optional and is the number seconds in between
1500 each poll cycle to the debug port in case you need
1501 the functionality for interrupting the kernel with
1502 gdb or control-c on the dbgp connection. When
1503 not using this parameter you use sysrq-g to break into
1504 the kernel debugger.
1505
Jason Wessel84c08fd2010-05-20 21:04:24 -05001506 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001507 Requires a tty driver that supports console polling,
1508 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001509 Serial only format: <serial_device>[,baud]
1510 keyboard only format: kbd
1511 keyboard and serial format: kbd,<serial_device>[,baud]
1512 Optional Kernel mode setting:
1513 kms, kbd format: kms,kbd
1514 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001515
Jason Wessel84c08fd2010-05-20 21:04:24 -05001516 kgdbwait [KGDB] Stop kernel execution and enter the
1517 kernel debugger at the earliest opportunity.
1518
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001519 kmac= [MIPS] korina ethernet MAC address.
1520 Configure the RouterBoard 532 series on-chip
1521 Ethernet adapter MAC address.
1522
Catalin Marinas04f70332009-06-11 13:22:39 +01001523 kmemleak= [KNL] Boot-time kmemleak enable/disable
1524 Valid arguments: on, off
1525 Default: on
1526
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001527 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1528 Valid arguments: 0, 1, 2
1529 kmemcheck=0 (disabled)
1530 kmemcheck=1 (enabled)
1531 kmemcheck=2 (one-shot mode)
1532 Default: 2 (one-shot mode)
1533
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301534 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001535 in oops dumps.
1536
Andre Przywarafef07aa2009-07-10 14:20:35 +02001537 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1538 Default is 0 (don't ignore, but inject #GP)
1539
Xiao Guangronga182d872010-09-20 22:17:48 +08001540 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1541 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001542 Default is 0 (off)
1543
Andre Przywarafef07aa2009-07-10 14:20:35 +02001544 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001545 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001546
1547 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1548 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001549 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001550
Andre Przywarafef07aa2009-07-10 14:20:35 +02001551 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1552 (virtualized MMU) support on capable Intel chips.
1553 Default is 1 (enabled)
1554
1555 kvm-intel.emulate_invalid_guest_state=
1556 [KVM,Intel] Enable emulation of invalid guest states
1557 Default is 0 (disabled)
1558
1559 kvm-intel.flexpriority=
1560 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1561 Default is 1 (enabled)
1562
Sasha Levine1a72ae2011-08-09 14:28:35 +03001563 kvm-intel.nested=
1564 [KVM,Intel] Enable VMX nesting (nVMX).
1565 Default is 0 (disabled)
1566
Andre Przywarafef07aa2009-07-10 14:20:35 +02001567 kvm-intel.unrestricted_guest=
1568 [KVM,Intel] Disable unrestricted guest feature
1569 (virtualized real and unpaged mode) on capable
1570 Intel chips. Default is 1 (enabled)
1571
1572 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1573 feature (tagged TLBs) on capable Intel chips.
1574 Default is 1 (enabled)
1575
Linus Torvalds1da177e2005-04-16 15:20:36 -07001576 l2cr= [PPC]
1577
Robert Brosea78bfbf2008-03-29 07:20:23 +11001578 l3cr= [PPC]
1579
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001580 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001581 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001582
Suresh Siddha279f1462012-10-22 14:37:58 -07001583 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1584 value for LAPIC timer one-shot implementation. Default
1585 back to the programmable timer unit in the LAPIC.
1586
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301587 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001588 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001589
FD Camifcb71f62008-01-06 19:08:56 +01001590 libata.dma= [LIBATA] DMA control
1591 libata.dma=0 Disable all PATA and SATA DMA
1592 libata.dma=1 PATA and SATA Disk DMA only
1593 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001594 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001595 Combinations also work, so libata.dma=3 enables DMA
1596 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001597
Michael Prokop20308872009-08-06 00:14:10 +02001598 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1599 libata.ignore_hpa=0 keep BIOS limits (default)
1600 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001601
Dave Jones78e70c22007-09-27 11:50:13 -04001602 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1603 when set.
1604 Format: <int>
1605
Tejun Heo33267322008-02-13 09:15:09 +09001606 libata.force= [LIBATA] Force configurations. The format is comma
1607 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001608 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001609 matching port, link or device. Basically, it matches
1610 the ATA ID string printed on console by libata. If
1611 the whole ID part is omitted, the last PORT and DEVICE
1612 values are used. If ID hasn't been specified yet, the
1613 configuration applies to all ports, links and devices.
1614
1615 If only DEVICE is omitted, the parameter applies to
1616 the port and all links and devices behind it. DEVICE
1617 number of 0 either selects the first device or the
1618 first fan-out link behind PMP device. It does not
1619 select the host link. DEVICE number of 15 selects the
1620 host link and device attached to it.
1621
1622 The VAL specifies the configuration to force. As long
1623 as there's no ambiguity shortcut notation is allowed.
1624 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1625 The following configurations can be forced.
1626
1627 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1628 Any ID with matching PORT is used.
1629
1630 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1631
1632 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1633 udma[/][16,25,33,44,66,100,133] notation is also
1634 allowed.
1635
1636 * [no]ncq: Turn on or off NCQ.
1637
Tejun Heo05944bd2008-08-13 20:19:09 +09001638 * nohrst, nosrst, norst: suppress hard, soft
1639 and both resets.
1640
Dan Williamsca6d43b2012-06-21 23:41:41 -07001641 * rstonce: only attempt one reset during
1642 hot-unplug link recovery
1643
Tejun Heo43c9c592010-05-23 12:59:11 +02001644 * dump_id: dump IDENTIFY data.
1645
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001646 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1647
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001648 * disable: Disable this device.
1649
Tejun Heo33267322008-02-13 09:15:09 +09001650 If there are multiple matching configurations changing
1651 the same attribute, the last one is used.
1652
Yinghai Lu95f72d12010-07-12 14:36:09 +10001653 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001654
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001656 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001657
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001658 lockd.nlm_grace_period=P [NFS] Assign grace period.
1659 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001660
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001661 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1662 Format: <integer>
1663
1664 lockd.nlm_timeout=T [NFS] Assign timeout value.
1665 Format: <integer>
1666
1667 lockd.nlm_udpport=M [NFS] Assign UDP port.
1668 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001669
1670 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1671 Format: <irq>
1672
1673 loglevel= All Kernel Messages with a loglevel smaller than the
1674 console loglevel will be printed to the console. It can
1675 also be changed with klogd or other programs. The
1676 loglevels are defined as follows:
1677
1678 0 (KERN_EMERG) system is unusable
1679 1 (KERN_ALERT) action must be taken immediately
1680 2 (KERN_CRIT) critical conditions
1681 3 (KERN_ERR) error conditions
1682 4 (KERN_WARNING) warning conditions
1683 5 (KERN_NOTICE) normal but significant condition
1684 6 (KERN_INFO) informational
1685 7 (KERN_DEBUG) debug-level messages
1686
Randy Dunlapc756d082011-02-20 20:08:35 -08001687 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1688 in bytes. n must be a power of two. The default
1689 size is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001690
Randy Dunlapaccaa242007-10-16 01:29:37 -07001691 logo.nologo [FB] Disables display of the built-in Linux logo.
1692 This may be used to provide more screen space for
1693 kernel log messages and is useful when debugging
1694 kernel boot problems.
1695
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696 lp=0 [LP] Specify parallel ports to use, e.g,
1697 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1698 lp=reset first parallel port). 'lp=0' disables the
1699 lp=auto printer driver. 'lp=reset' (which can be
1700 specified in addition to the ports) causes
1701 attached printers to be reset. Using
1702 lp=port1,port2,... specifies the parallel ports
1703 to associate lp devices with, starting with
1704 lp0. A port specification may be 'none' to skip
1705 that lp device, or a parport name such as
1706 'parport0'. Specifying 'lp=auto' instead of a
1707 port specification list means that device IDs
1708 from each port should be examined, to see if
1709 an IEEE 1284-compliant printer is attached; if
1710 so, the driver will manage that printer.
1711 See also header of drivers/char/lp.c.
1712
1713 lpj=n [KNL]
1714 Sets loops_per_jiffy to given constant, thus avoiding
1715 time-consuming boot-time autodetection (up to 250 ms per
1716 CPU). 0 enables autodetection (default). To determine
1717 the correct value for your kernel, boot with normal
1718 autodetection and see what value is printed. Note that
1719 on SMP systems the preset will be applied to all CPUs,
1720 which is likely to cause problems if your CPUs need
1721 significantly divergent settings. An incorrect value
1722 will cause delays in the kernel to be wrong, leading to
1723 unpredictable I/O errors and other breakage. Although
1724 unlikely, in the extreme case this might damage your
1725 hardware.
1726
1727 ltpc= [NET]
1728 Format: <io>,<irq>,<dma>
1729
Randy Dunlap16290242011-08-13 12:34:52 -07001730 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001731 (machvec) in a generic kernel.
1732 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001733
Wu Zhangjin3209e702009-07-02 23:27:12 +08001734 machtype= [Loongson] Share the same kernel image file between different
1735 yeeloong laptop.
1736 Example: machtype=lemote-yeeloong-2f-7inch
1737
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001738 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1739 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001740
1741 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001742 should make use of. maxcpus=n : n >= 0 limits the
1743 kernel to using 'n' processors. n=0 is a special case,
1744 it is equivalent to "nosmp", which also disables
1745 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001746
Kay Sieversd134b002011-07-31 22:08:04 +02001747 max_loop= [LOOP] The number of loop block devices that get
1748 (loop.max_loop) unconditionally pre-created at init time. The default
1749 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1750 of statically allocating a predefined number, loop
1751 devices can be requested on-demand with the
1752 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001753
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001754 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001755
Uwe Hermann71cced62008-10-20 09:32:21 -07001756 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001757
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758 md= [HW] RAID subsystems devices and level
1759 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001760
Linus Torvalds1da177e2005-04-16 15:20:36 -07001761 mdacon= [MDA]
1762 Format: <first>,<last>
1763 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001764
Linus Torvalds1da177e2005-04-16 15:20:36 -07001765 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1766 Amount of memory to be used when the kernel is not able
1767 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08001768 [X86] Work as limiting max address. Use together
1769 with memmap= to avoid physical address space collisions.
1770 Without memmap= PCI devices could be placed at addresses
1771 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001772
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001773 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001774 memory.
1775
Paul Mundt6902aa82008-09-21 17:14:42 +09001776 memchunk=nn[KMG]
1777 [KNL,SH] Allow user to override the default size for
1778 per-device physically contiguous DMA buffers.
1779
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301780 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001781 E820 memory map, as specified by the user.
1782 Such memmap=exactmap lines can be constructed based on
1783 BIOS output or other requirements. See the memmap=nn@ss
1784 option description.
1785
1786 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08001787 [KNL] Force usage of a specific region of memory.
1788 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001789
1790 memmap=nn[KMG]#ss[KMG]
1791 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08001792 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001793
1794 memmap=nn[KMG]$ss[KMG]
1795 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08001796 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001797 Example: Exclude memory from 0x18690000-0x1869ffff
1798 memmap=64K$0x18690000
1799 or
1800 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001801
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001802 memory_corruption_check=0/1 [X86]
1803 Some BIOSes seem to corrupt the first 64k of
1804 memory when doing things like suspend/resume.
1805 Setting this option will scan the memory
1806 looking for corruption. Enabling this will
1807 both detect corruption and prevent the kernel
1808 from using the memory being corrupted.
1809 However, its intended as a diagnostic tool; if
1810 repeatable BIOS-originated corruption always
1811 affects the same memory, you can use memmap=
1812 to prevent the kernel from using that memory.
1813
1814 memory_corruption_check_size=size [X86]
1815 By default it checks for corruption in the low
1816 64k, making this memory unavailable for normal
1817 use. Use this parameter to scan for
1818 corruption in more or less memory.
1819
1820 memory_corruption_check_period=seconds [X86]
1821 By default it checks for corruption every 60
1822 seconds. Use this parameter to check at some
1823 other rate. 0 disables periodic checking.
1824
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001825 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001826 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001827 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001828 Specifies the number of memtest passes to be
1829 performed. Each pass selects another test
1830 pattern from a given set of patterns. Memtest
1831 fills the memory with this pattern, validates
1832 memory contents and reserves bad memory
1833 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001834
Linus Torvalds1da177e2005-04-16 15:20:36 -07001835 meye.*= [HW] Set MotionEye Camera parameters
1836 See Documentation/video4linux/meye.txt.
1837
Andres Salomon8f368812007-10-12 23:04:06 +02001838 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1839 Multi-Function General Purpose Timers on AMD Geode
1840 platforms.
1841
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001842 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1843 the BIOS has incorrectly applied a workaround. TinyBIOS
1844 version 0.98 is known to be affected, 0.99 fixes the
1845 problem by letting the user disable the workaround.
1846
Linus Torvalds1da177e2005-04-16 15:20:36 -07001847 mga= [HW,DRM]
1848
Randy Dunlap1c207f92008-11-19 15:36:16 -08001849 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1850 physical address is ignored.
1851
Michel Pollet39f45d72009-05-20 11:10:31 +01001852 mini2440= [ARM,HW,KNL]
1853 Format:[0..2][b][c][t]
1854 Default: "0tb"
1855 MINI2440 configuration specification:
1856 0 - The attached screen is the 3.5" TFT
1857 1 - The attached screen is the 7" TFT
1858 2 - The VGA Shield is attached (1024x768)
1859 Leaving out the screen size parameter will not load
1860 the TFT driver, and the framebuffer will be left
1861 unconfigured.
1862 b - Enable backlight. The TFT backlight pin will be
1863 linked to the kernel VESA blanking code and a GPIO
1864 LED. This parameter is not necessary when using the
1865 VGA shield.
1866 c - Enable the s3c camera interface.
1867 t - Reserved for enabling touchscreen support. The
1868 touchscreen support is not enabled in the mainstream
1869 kernel as of 2.6.30, a preliminary port can be found
1870 in the "bleeding edge" mini2440 support kernel at
1871 http://repo.or.cz/w/linux-2.6/mini2440.git
1872
Mel Gorman6b74ab92008-07-23 21:26:49 -07001873 mminit_loglevel=
1874 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1875 parameter allows control of the logging verbosity for
1876 the additional memory initialisation checks. A value
1877 of 0 disables mminit logging and a level of 4 will
1878 log everything. Information is printed at KERN_DEBUG
1879 so loglevel=8 may also need to be specified.
1880
Rusty Russell106a4ee2012-09-26 10:09:40 +01001881 module.sig_enforce
1882 [KNL] When CONFIG_MODULE_SIG is set, this means that
1883 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01001884 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01001885 is always true, so this option does nothing.
1886
Linus Torvalds1da177e2005-04-16 15:20:36 -07001887 mousedev.tap_time=
1888 [MOUSE] Maximum time between finger touching and
1889 leaving touchpad surface for touch to be considered
1890 a tap and be reported as a left button click (for
1891 touchpads working in absolute mode only).
1892 Format: <msecs>
1893 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1894 reporting absolute coordinates, such as tablets
1895 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1896 reporting absolute coordinates, such as tablets
1897
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301898 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001899 is similar to kernelcore except it specifies the
1900 amount of memory used for migratable allocations.
1901 If both kernelcore and movablecore is specified,
1902 then kernelcore will be at *least* the specified
1903 value but may be more. If movablecore on its own
1904 is specified, the administrator must be careful
1905 that the amount of memory usable for all allocations
1906 is not too small.
1907
Tang Chenc5320922013-11-12 15:08:10 -08001908 movable_node [KNL,X86] Boot-time switch to enable the effects
1909 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1910
Linus Torvalds1da177e2005-04-16 15:20:36 -07001911 MTD_Partition= [MTD]
1912 Format: <name>,<region-number>,<size>,<offset>
1913
Randy Dunlapa9913042005-10-23 12:57:11 -07001914 MTD_Region= [MTD] Format:
1915 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001916
1917 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001918 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001919
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001920 multitce=off [PPC] This parameter disables the use of the pSeries
1921 firmware feature for updating multiple TCE entries
1922 at a time.
1923
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001924 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1925
1926 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1927
1928 boundary - index of last SLC block on Flex-OneNAND.
1929 The remaining blocks are configured as MLC blocks.
1930 lock - Configure if Flex-OneNAND boundary should be locked.
1931 Once locked, the boundary cannot be changed.
1932 1 indicates lock status, 0 indicates unlock status.
1933
Ben Dooks9db829f2008-07-03 11:24:29 +01001934 mtdset= [ARM]
1935 ARM/S3C2412 JIVE boot control
1936
1937 See arch/arm/mach-s3c2412/mach-jive.c
1938
Linus Torvalds1da177e2005-04-16 15:20:36 -07001939 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001940 [HW] Make the MicroTouch USB driver use raw coordinates
1941 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001942
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001943 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001944 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001945 that could hold holes aka. UC entries.
1946
1947 mtrr_gran_size=nn[KMG] [X86]
1948 Used for mtrr cleanup. It is granularity of mtrr block.
1949 Default is 1.
1950 Large value could prevent small alignment from
1951 using up MTRRs.
1952
1953 mtrr_spare_reg_nr=n [X86]
1954 Format: <integer>
1955 Range: 0,7 : spare reg number
1956 Default : 1
1957 Used for mtrr cleanup. It is spare mtrr entries number.
1958 Set to 2 or more if your graphical card needs more.
1959
Linus Torvalds1da177e2005-04-16 15:20:36 -07001960 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1961
Linus Torvalds1da177e2005-04-16 15:20:36 -07001962 netdev= [NET] Network devices parameters
1963 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1964 Note that mem_start is often overloaded to mean
1965 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001966 This usage is only documented in each driver source
1967 file if at all.
1968
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001969 nf_conntrack.acct=
1970 [NETFILTER] Enable connection tracking flow accounting
1971 0 to disable accounting
1972 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001973 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001974
Chuck Lever306a0752010-09-17 10:54:37 -04001975 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001976 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001977
1978 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001979 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001980
Chuck Lever306a0752010-09-17 10:54:37 -04001981 nfsrootdebug [NFS] enable nfsroot debugging messages.
1982 See Documentation/filesystems/nfs/nfsroot.txt.
1983
Trond Myklebusta72b4422006-01-03 09:55:41 +01001984 nfs.callback_tcpport=
1985 [NFS] set the TCP port on which the NFSv4 callback
1986 channel should listen.
1987
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001988 nfs.cache_getent=
1989 [NFS] sets the pathname to the program which is used
1990 to update the NFS client cache entries.
1991
1992 nfs.cache_getent_timeout=
1993 [NFS] sets the timeout after which an attempt to
1994 update a cache entry is deemed to have failed.
1995
Trond Myklebust58df0952006-01-03 09:55:57 +01001996 nfs.idmap_cache_timeout=
1997 [NFS] set the maximum lifetime for idmapper cache
1998 entries.
1999
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002000 nfs.enable_ino64=
2001 [NFS] enable 64-bit inode numbers.
2002 If zero, the NFS client will fake up a 32-bit inode
2003 number for the readdir() and stat() syscalls instead
2004 of returning the full 64-bit number.
2005 The default is to return 64-bit inode numbers.
2006
Trond Myklebustef159e92012-02-06 19:50:40 -05002007 nfs.max_session_slots=
2008 [NFSv4.1] Sets the maximum number of session slots
2009 the client will attempt to negotiate with the server.
2010 This limits the number of simultaneous RPC requests
2011 that the client can send to the NFSv4.1 server.
2012 Note that there is little point in setting this
2013 value higher than the max_tcp_slot_table_limit.
2014
Trond Myklebustb064eca22011-02-22 15:44:32 -08002015 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002016 [NFSv4] When set to the default of '1', this option
2017 ensures that both the RPC level authentication
2018 scheme and the NFS level operations agree to use
2019 numeric uids/gids if the mount is using the
2020 'sec=sys' security flavour. In effect it is
2021 disabling idmapping, which can make migration from
2022 legacy NFSv2/v3 systems to NFSv4 easier.
2023 Servers that do not support this mode of operation
2024 will be autodetected by the client, and it will fall
2025 back to using the idmapper.
2026 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002027 nfs.nfs4_unique_id=
2028 [NFS4] Specify an additional fixed unique ident-
2029 ification string that NFSv4 clients can insert into
2030 their nfs_client_id4 string. This is typically a
2031 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002032
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002033 nfs.send_implementation_id =
2034 [NFSv4.1] Send client implementation identification
2035 information in exchange_id requests.
2036 If zero, no implementation identification information
2037 will be sent.
2038 The default is to send the implementation identification
2039 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002040
2041 nfs.recover_lost_locks =
2042 [NFSv4] Attempt to recover locks that were lost due
2043 to a lease timeout on the server. Please note that
2044 doing this risks data corruption, since there are
2045 no guarantees that the file will remain unchanged
2046 after the locks are lost.
2047 If you want to enable the kernel legacy behaviour of
2048 attempting to recover these locks, then set this
2049 parameter to '1'.
2050 The default parameter value of '0' causes the kernel
2051 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002052
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002053 nfsd.nfs4_disable_idmapping=
2054 [NFSv4] When set to the default of '1', the NFSv4
2055 server will return only numeric uids and gids to
2056 clients using auth_sys, and will accept numeric uids
2057 and gids from such clients. This is intended to ease
2058 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002059
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002060 objlayoutdriver.osd_login_prog=
2061 [NFS] [OBJLAYOUT] sets the pathname to the program which
2062 is used to automatically discover and login into new
2063 osd-targets. Please see:
2064 Documentation/filesystems/pnfs.txt for more explanations
2065
Paul Mundt1e1030d2009-09-01 17:38:32 +09002066 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002067 when a NMI is triggered.
2068 Format: [state][,regs][,debounce][,die]
2069
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302070 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002071 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05002072 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03002073 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002074 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002075 timeout occurs (or 'nopanic' to override the opposite
2076 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002077 This is useful when you use a panic=... timeout and
2078 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002079
Anton Vorontsovbff38772009-07-08 11:10:56 -07002080 netpoll.carrier_timeout=
2081 [NET] Specifies amount of time (in seconds) that
2082 netpoll should wait for a carrier. By default netpoll
2083 waits 4 seconds.
2084
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002085 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002086 emulation library even if a 387 maths coprocessor
2087 is present.
2088
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002089 no_console_suspend
2090 [HW] Never suspend the console
2091 Disable suspending of consoles during suspend and
2092 hibernate operations. Once disabled, debugging
2093 messages can reach various consoles while the rest
2094 of the system is being put to sleep (ie, while
2095 debugging driver suspend/resume hooks). This may
2096 not work reliably with all consoles, but is known
2097 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002098 To facilitate more flexible debugging, we also add
2099 console_suspend, a printk module parameter to control
2100 it. Users could use console_suspend (usually
2101 /sys/module/printk/parameters/console_suspend) to
2102 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002103
Christoph Lameterc1aee212007-05-31 00:40:47 -07002104 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2105 caches in the slab allocator. Saves per-node memory,
2106 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002107
Randy Dunlapa9913042005-10-23 12:57:11 -07002108 noalign [KNL,ARM]
2109
Linus Torvalds1da177e2005-04-16 15:20:36 -07002110 noapic [SMP,APIC] Tells the kernel to not make use of any
2111 IOAPICs that may be present in the system.
2112
Kees Cook8ab38202013-10-10 17:18:14 -07002113 nokaslr [X86]
Kees Cooke2b32e62014-02-25 16:59:17 -08002114 Disable kernel and module base offset ASLR (Address
2115 Space Layout Randomization) if built into the kernel.
Kees Cook8ab38202013-10-10 17:18:14 -07002116
Mike Galbraith5091faa2010-11-30 14:18:03 +01002117 noautogroup Disable scheduler automatic task group creation.
2118
Linus Torvalds1da177e2005-04-16 15:20:36 -07002119 nobats [PPC] Do not use BATs for mapping kernel lowmem
2120 on "Classic" PPC cores.
2121
2122 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002123
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002124 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2125
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002126 nodelayacct [KNL] Disable per-task delay accounting
2127
Linus Torvalds1da177e2005-04-16 15:20:36 -07002128 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2129
Paul Mundt6902aa82008-09-21 17:14:42 +09002130 nodsp [SH] Disable hardware DSP at boot time.
2131
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302132 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002133
Linus Torvalds1da177e2005-04-16 15:20:36 -07002134 noexec [IA-64]
2135
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302136 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002137 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002138 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002139 noexec=off: disable non-executable mappings
2140
H. Peter Anvin52b61792012-09-21 12:43:13 -07002141 nosmap [X86]
2142 Disable SMAP (Supervisor Mode Access Prevention)
2143 even if it is supported by processor.
2144
Fenghua Yude5397a2011-05-11 16:51:05 -07002145 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002146 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002147 even if it is supported by processor.
2148
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002149 noexec32 [X86-64]
2150 This affects only 32-bit executables.
2151 noexec32=on: enable non-executable mappings (default)
2152 read doesn't imply executable mappings
2153 noexec32=off: disable non-executable mappings
2154 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002155
Paul Mundt6902aa82008-09-21 17:14:42 +09002156 nofpu [SH] Disable hardware FPU at boot time.
2157
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002158 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002159 register save and restore. The kernel will only save
2160 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002161
Suresh Siddha0c752a92009-05-22 12:17:45 -07002162 noxsave [BUGS=X86] Disables x86 extended register state save
2163 and restore using xsave. The kernel will fallback to
2164 enabling legacy floating-point and sse state.
2165
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002166 eagerfpu= [X86]
Suresh Siddhae0022982012-09-10 10:32:32 -07002167 on enable eager fpu restore
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002168 off disable eager fpu restore
Suresh Siddhae0022982012-09-10 10:32:32 -07002169 auto selects the default scheme, which automatically
2170 enables eagerfpu restore for xsaveopt.
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002171
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002172 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2173 wfi(ARM) instruction doesn't work correctly and not to
2174 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002175
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002176 no_file_caps Tells the kernel not to honor file capabilities. The
2177 only way then for a file to be executed with privilege
2178 is to be setuid root or executed by root.
2179
Linus Torvalds1da177e2005-04-16 15:20:36 -07002180 nohalt [IA-64] Tells the kernel not to use the power saving
2181 function PAL_HALT_LIGHT when idle. This increases
2182 power-consumption. On the positive side, it reduces
2183 interrupt wake-up latency, which may improve performance
2184 in certain environments such as networked servers or
2185 real-time systems.
2186
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002187 nohz= [KNL] Boottime enable/disable dynamic ticks
2188 Valid arguments: on, off
2189 Default: on
2190
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002191 nohz_full= [KNL,BOOT]
2192 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002193 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002194 whenever possible. The boot CPU will be forced outside
2195 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002196 The CPUs in this range must also be included in the
2197 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002198
Paul Mundteeee7852009-04-02 12:31:16 +09002199 noiotrap [SH] Disables trapped I/O port accesses.
2200
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002201 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002202 disable unhandled interrupt sources.
2203
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302204 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002205 broken timer IRQ sources.
2206
Linus Torvalds1da177e2005-04-16 15:20:36 -07002207 noisapnp [ISAPNP] Disables ISA PnP code.
2208
2209 noinitrd [RAM] Tells the kernel not to load any configured
2210 initial RAM disk.
2211
Weidong Han03ea8152009-04-17 16:42:15 +08002212 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2213 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002214 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002215
Linus Torvalds1da177e2005-04-16 15:20:36 -07002216 nointroute [IA-64]
2217
Randy Dunlap16290242011-08-13 12:34:52 -07002218 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002219
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002220 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2221
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002222 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2223 fault handling.
2224
Glauber Costad910f5c2011-07-11 15:28:19 -04002225 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2226 steal time is computed, but won't influence scheduler
2227 behaviour
2228
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002229 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002230
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002231 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002232
Linus Torvalds1da177e2005-04-16 15:20:36 -07002233 noltlbs [PPC] Do not use large page/tlb entries for kernel
2234 lowmem mapping on PPC40x.
2235
Horms312f1f02006-02-22 09:57:55 +09002236 nomca [IA-64] Disable machine check abort handling
2237
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002238 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002239
Andres Salomon83d73842007-10-12 23:04:06 +02002240 nomfgpt [X86-32] Disable Multi-Function General Purpose
2241 Timer usage (for AMD Geode machines).
2242
Don Zickusbda62632011-10-13 15:14:27 -04002243 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2244 shutdown the other cpus. Instead use the REBOOT_VECTOR
2245 irq.
2246
Dave Young02608be2012-02-01 10:33:14 +08002247 nomodule Disable module load
2248
Jiri Kosina016ddd92010-01-18 17:05:40 +01002249 nopat [X86] Disable PAT (page attribute table extension of
2250 pagetables) support.
2251
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002252 norandmaps Don't use address space randomization. Equivalent to
2253 echo 0 > /proc/sys/kernel/randomize_va_space
2254
Jiri Kosinabbff2162010-08-11 18:34:09 +02002255 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002256
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002257 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002258 with UP alternatives
2259
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002260 nordrand [X86] Disable kernel use of the RDRAND and
2261 RDSEED instructions even if they are supported
2262 by the processor. RDRAND and RDSEED are still
2263 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002264
Randy Dunlapa9913042005-10-23 12:57:11 -07002265 noresume [SWSUSP] Disables resume and restores original swap
2266 space.
2267
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268 no-scroll [VGA] Disables scrollback.
2269 This is required for the Braillex ib80-piezo Braille
2270 reader made by F.H. Papenmeier (Germany).
2271
2272 nosbagart [IA-64]
2273
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002274 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002275
Len Brown61ec7562007-08-16 03:34:22 -04002276 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2277 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002278
Dave Jones97842212007-07-15 23:41:05 -07002279 nosoftlockup [KNL] Disable the soft-lockup detector.
2280
Linus Torvalds1da177e2005-04-16 15:20:36 -07002281 nosync [HW,M68K] Disables sync negotiation for all devices.
2282
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002283 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002284
2285 nousb [USB] Disable the USB subsystem
2286
Ben Hutchings55142372011-01-02 23:02:42 +00002287 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04002288
Linus Torvalds1da177e2005-04-16 15:20:36 -07002289 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002290
Weidong Han2b2fd872009-04-17 16:42:12 +08002291 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2292
Fenghua Yuf78cff42012-11-13 11:32:38 -08002293 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2294 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2295 Some features depend on CPU0. Known dependencies are:
2296 1. Resume from suspend/hibernate depends on CPU0.
2297 Suspend/hibernate will fail if CPU0 is offline and you
2298 need to online CPU0 before suspend/hibernate.
2299 2. PIC interrupts also depend on CPU0. CPU0 can't be
2300 removed if a PIC interrupt is detected.
2301 It's said poweroff/reboot may depend on CPU0 on some
2302 machines although I haven't seen such issues so far
2303 after CPU0 is offline on a few tested machines.
2304 If the dependencies are under your control, you can
2305 turn on cpu0_hotplug.
2306
Randy Dunlap16290242011-08-13 12:34:52 -07002307 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002308 purges which is reported from either PAL_VM_SUMMARY or
2309 SAL PALO.
2310
Yinghai Lu2b633e32010-02-10 01:20:37 -08002311 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2312 could support. nr_cpus=n : n >= 1 limits the kernel to
2313 supporting 'n' processors. Later in runtime you can not
2314 use hotplug cpu feature to put more cpu back to online.
2315 just like you compile the kernel NR_CPUS=n
2316
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002317 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2318
Mel Gorman1a687c22012-11-22 11:16:36 +00002319 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2320 Allowed values are enable and disable
2321
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002322 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2323 one of ['zone', 'node', 'default'] can be specified
2324 This can be set from sysctl after boot.
2325 See Documentation/sysctl/vm.txt for details.
2326
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002327 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2328 See Documentation/debugging-via-ohci1394.txt for more
2329 info.
2330
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002331 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2332 Rather than timing out after 20 ms if an EC
2333 command is not properly ACKed, override the length
2334 of the timeout. We have interrupts disabled while
2335 waiting for the ACK, so if this is set too high
2336 interrupts *may* be lost!
2337
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002338 omap_mux= [OMAP] Override bootloader pin multiplexing.
2339 Format: <mux_mode0.mode_name=value>...
2340 For example, to override I2C bus2:
2341 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2342
Linus Torvalds1da177e2005-04-16 15:20:36 -07002343 oprofile.timer= [HW]
2344 Use timer interrupt instead of performance counters
2345
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002346 oprofile.cpu_type= Force an oprofile cpu type
2347 This might be useful if you have an older oprofile
2348 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002349 Format: { arch_perfmon }
2350 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002351 perfmon on Intel CPUs instead of the
2352 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002353 timer: [X86] Force use of architectural NMI
2354 timer mode (see also oprofile.timer
2355 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002356 [s390] Force legacy basic mode sampling
2357 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002358
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002359 oops=panic Always panic on oopses. Default is to just kill the
2360 process, but there is a small probability of
2361 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002362 This will also cause panics on machine check exceptions.
2363 Useful together with panic=30 to trigger a reboot.
2364
Randy Dunlapbcfde332010-06-07 17:10:38 -07002365 OSS [HW,OSS]
2366 See Documentation/sound/oss/oss-parameters.txt
2367
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002368 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002369 timeout > 0: seconds before rebooting
2370 timeout = 0: wait forever
2371 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002372 Format: <timeout>
2373
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002374 crash_kexec_post_notifiers
2375 Run kdump after running panic-notifiers and dumping
2376 kmsg. This only for the users who doubt kdump always
2377 succeeds in any situation.
2378 Note that this also increases risks of kdump failure,
2379 because some panic notifiers can make the crashed
2380 kernel more unstable.
2381
Linus Torvalds1da177e2005-04-16 15:20:36 -07002382 parkbd.port= [HW] Parallel port number the keyboard adapter is
2383 connected to, default is 0.
2384 Format: <parport#>
2385 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2386 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002387 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002388
Randy Dunlapa9913042005-10-23 12:57:11 -07002389 parport= [HW,PPT] Specify parallel ports. 0 disables.
2390 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2391 Use 'auto' to force the driver to use any
2392 IRQ/DMA settings detected (the default is to
2393 ignore detected IRQ/DMA settings because of
2394 possible conflicts). You can specify the base
2395 address, IRQ, and DMA settings; IRQ and DMA
2396 should be numbers, or 'auto' (for using detected
2397 settings on that particular port), or 'nofifo'
2398 (to avoid using a FIFO even if it is detected).
2399 Parallel ports are assigned in the order they
2400 are specified on the command line, starting
2401 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002402
Randy Dunlapa9913042005-10-23 12:57:11 -07002403 parport_init_mode= [HW,PPT]
2404 Configure VIA parallel port to operate in
2405 a specific mode. This is necessary on Pegasos
2406 computer where firmware has no options for setting
2407 up parallel port mode and sets it to spp.
2408 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002409 Format: [spp|ps2|epp|ecp|ecpepp]
2410
Andrew Mortondd287792006-03-23 03:00:57 -08002411 pause_on_oops=
2412 Halt all CPUs after the first oops has been printed for
2413 the specified number of seconds. This is to be used if
2414 your oopses keep scrolling off the screen.
2415
Linus Torvalds1da177e2005-04-16 15:20:36 -07002416 pcbit= [HW,ISDN]
2417
2418 pcd. [PARIDE]
2419 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002420 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002421
Randy Dunlapa9913042005-10-23 12:57:11 -07002422 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002423 earlydump [X86] dump PCI config space before the kernel
2424 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002425 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002426 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002427 the hardware directly. Use this if your machine
2428 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002429 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002430 hardware access methods are allowed. Use this
2431 if you experience crashes upon bootup and you
2432 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002433 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002434 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002435 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002436 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002437 noaer [PCIE] If the PCIEAER kernel config parameter is
2438 enabled, this kernel boot option can be used to
2439 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002440 nodomains [PCI] Disable support for multiple PCI
2441 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302442 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002443 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002444 check_enable_amd_mmconf [X86] check for and enable
2445 properly configured MMIO access to PCI
2446 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002447 nomsi [MSI] If the PCI_MSI kernel config parameter is
2448 enabled, this kernel boot option can be used to
2449 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002450 noioapicquirk [APIC] Disable all boot interrupt quirks.
2451 Safety option to keep boot IRQs enabled. This
2452 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002453 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2454 primary IO-APIC for bridges that cannot disable
2455 boot IRQs. This fixes a source of spurious IRQs
2456 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002457 noioapicreroute [APIC] Disable workaround that uses the
2458 boot IRQ equivalent of an IRQ that connects to
2459 a chipset where boot IRQs cannot be disabled.
2460 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002461 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002462 routing table. These calls are known to be buggy
2463 on several machines and they hang the machine
2464 when used, but on other computers it's the only
2465 way to get the interrupt routing table. Try
2466 this option if the kernel is unable to allocate
2467 IRQs or discover secondary PCI buses on your
2468 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002469 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002470 Use with caution as certain devices share
2471 address decoders between ROMs and other
2472 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002473 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002474 expansion ROMs that do not already have
2475 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002476 nobar [X86] Do not assign address space to the
2477 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002478 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002479 assigned automatically to PCI devices. You can
2480 make the kernel exclude IRQs of your ISA cards
2481 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002482 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002483 of the PIRQ table (normally generated
2484 by the BIOS) if it is outside the
2485 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002486 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002487 useful if the kernel is unable to find your
2488 secondary buses and you want to tell it
2489 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002490 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002491 numbers ourselves, overriding
2492 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002493 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002494 in the BIOS $PIR table. This is needed on
2495 some systems with broken BIOSes, notably
2496 some HP Pavilion N5400 and Omnibook XE3
2497 notebooks. This will have no effect if ACPI
2498 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002499 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002500 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002501 use_crs [X86] Use PCI host bridge window information
2502 from ACPI. On BIOSes from 2008 or later, this
2503 is enabled by default. If you need to use this,
2504 please report a bug.
2505 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2506 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002507 routeirq Do IRQ routing for all PCI devices.
2508 This is normally done in pci_enable_device(),
2509 so this option is a temporary workaround
2510 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002511 skip_isa_align [X86] do not align io start addr, so can
2512 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002513 firmware [ARM] Do not re-enumerate the bus but instead
2514 just use the configuration from the
2515 bootloader. This is currently used on
2516 IXP2000 systems where the bus has to be
2517 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002518 noearly [X86] Don't do any early type 1 scanning.
2519 This might help on some broken boards which
2520 machine check when some devices' config space
2521 is read. But various workarounds are disabled
2522 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002523 bfsort Sort PCI devices into breadth-first order.
2524 This sorting is done to get a device
2525 order compatible with older (<= 2.4) kernels.
2526 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002527 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2528 tuning and use the BIOS-configured MPS defaults.
2529 pcie_bus_safe Set every device's MPS to the largest value
2530 supported by all devices below the root complex.
2531 pcie_bus_perf Set device MPS to the largest allowable MPS
2532 based on its parent bus. Also set MRRS (Max
2533 Read Request Size) to the largest supported
2534 value (no larger than the MPS that the device
2535 or bus can support) for best performance.
2536 pcie_bus_peer2peer Set every device's MPS to 128B, which
2537 every device is guaranteed to support. This
2538 configuration allows peer-to-peer DMA between
2539 any pair of devices, possibly at the cost of
2540 reduced performance. This also guarantees
2541 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002542 cbiosize=nn[KMG] The fixed amount of bus space which is
2543 reserved for the CardBus bridge's IO window.
2544 The default value is 256 bytes.
2545 cbmemsize=nn[KMG] The fixed amount of bus space which is
2546 reserved for the CardBus bridge's memory
2547 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002548 resource_alignment=
2549 Format:
2550 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2551 Specifies alignment and device to reassign
2552 aligned memory resources.
2553 If <order of align> is not specified,
2554 PAGE_SIZE is used as alignment.
2555 PCI-PCI bridge can be specified, if resource
2556 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002557 ecrc= Enable/disable PCIe ECRC (transaction layer
2558 end-to-end CRC checking).
2559 bios: Use BIOS/firmware settings. This is the
2560 the default.
2561 off: Turn ECRC off
2562 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002563 hpiosize=nn[KMG] The fixed amount of bus space which is
2564 reserved for hotplug bridge's IO window.
2565 Default size is 256 bytes.
2566 hpmemsize=nn[KMG] The fixed amount of bus space which is
2567 reserved for hotplug bridge's memory window.
2568 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002569 realloc= Enable/disable reallocating PCI bridge resources
2570 if allocations done by BIOS are too small to
2571 accommodate resources required by all child
2572 devices.
2573 off: Turn realloc off
2574 on: Turn realloc on
2575 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002576 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002577 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2578 only look for one device below a PCIe downstream
2579 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002580
Chuck Ebberte5665a42008-09-24 20:40:34 -04002581 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2582 Management.
2583 off Disable ASPM.
2584 force Enable ASPM even on devices that claim not to support it.
2585 WARNING: Forcing ASPM on may cause system lockups.
2586
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002587 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2588 nomsi Do not use MSI for PCI Express Native Hotplug (this
2589 makes all PCIe ports use INTx for hotplug services).
2590
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002591 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002592 auto Ask the BIOS whether or not to use native PCIe services
2593 associated with PCIe ports (PME, hot-plug, AER). Use
2594 them only if that is allowed by the BIOS.
2595 native Use native PCIe services associated with PCIe ports
2596 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002597 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2598 ports driver.
2599
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002600 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002601 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002602 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002603
Linus Torvalds1da177e2005-04-16 15:20:36 -07002604 pcmv= [HW,PCMCIA] BadgePAD 4
2605
Tushar Behera39ac5ba2014-03-28 10:50:21 +05302606 pd_ignore_unused
2607 [PM]
2608 Keep all power-domains already enabled by bootloader on,
2609 even if no driver has claimed them. This is useful
2610 for debug and development, but should not be
2611 needed on a platform with proper driver support.
2612
Linus Torvalds1da177e2005-04-16 15:20:36 -07002613 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002614 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002615
2616 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2617 boot time.
2618 Format: { 0 | 1 }
2619 See arch/parisc/kernel/pdc_chassis.c
2620
Tejun Heof58dc012009-08-14 15:00:50 +09002621 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002622 Currently supported values are "embed" and "page".
2623 Archs may support subset or none of the selections.
2624 See comments in mm/percpu.c for details on each
2625 allocator. This parameter is primarily for debugging
2626 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002627
Linus Torvalds1da177e2005-04-16 15:20:36 -07002628 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002629 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002630
2631 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002632 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002633
2634 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002635 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002636
2637 plip= [PPT,NET] Parallel port network link
2638 Format: { parport<nr> | timid | 0 }
2639 See also Documentation/parport.txt.
2640
Randy Dunlap16290242011-08-13 12:34:52 -07002641 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002642 Override pmtimer IOPort with a hex value.
2643 e.g. pmtmr=0x508
2644
Bjorn Helgaas96242112011-08-11 12:14:05 -06002645 pnp.debug=1 [PNP]
2646 Enable PNP debug messages (depends on the
2647 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2648 via /sys/module/pnp/parameters/debug. We always show
2649 current resource usage; turning this on also shows
2650 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002651
Linus Torvalds1da177e2005-04-16 15:20:36 -07002652 pnpacpi= [ACPI]
2653 { off }
2654
2655 pnpbios= [ISAPNP]
2656 { on | off | curr | res | no-curr | no-res }
2657
2658 pnp_reserve_irq=
2659 [ISAPNP] Exclude IRQs for the autoconfiguration
2660
2661 pnp_reserve_dma=
2662 [ISAPNP] Exclude DMAs for the autoconfiguration
2663
2664 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002665 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002666
2667 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002668 [ISAPNP] Exclude memory regions for the
2669 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002670 Ranges are in pairs (memory base and size).
2671
Randy Dunlap4af94f32009-04-17 18:30:28 -07002672 ports= [IP_VS_FTP] IPVS ftp helper module
2673 Default is 21.
2674 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2675 may be specified.
2676 Format: <port>,<port>....
2677
Ingo Molnar45807a12007-07-15 23:40:10 -07002678 print-fatal-signals=
2679 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002680
2681 If enabled, warn about various signal handling
2682 related application anomalies: too many signals,
2683 too many POSIX.1 timers, fatal signals causing a
2684 coredump - etc.
2685
2686 If you hit the warning due to signal overflow,
2687 you might want to try "ulimit -i unlimited".
2688
Ingo Molnar45807a12007-07-15 23:40:10 -07002689 default: off.
2690
Matthew Garrettc22ab332012-03-05 14:59:10 -08002691 printk.always_kmsg_dump=
2692 Trigger kmsg_dump for cases other than kernel oops or
2693 panics
2694 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2695 default: disabled
2696
Randy Dunlape84845c2007-07-15 23:40:25 -07002697 printk.time= Show timing data prefixed to each printk message line
2698 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2699
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002700 processor.max_cstate= [HW,ACPI]
2701 Limit processor to maximum C-state
2702 max_cstate=9 overrides any DMI blacklist limit.
2703
2704 processor.nocst [HW,ACPI]
2705 Ignore the _CST method to determine C-states,
2706 instead using the legacy FADT method
2707
Linus Torvalds1da177e2005-04-16 15:20:36 -07002708 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002709 Format: [schedule,]<number>
2710 Param: "schedule" - profile schedule points.
2711 Param: <number> - step/bucket size as a power of 2 for
2712 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002713 Param: "sleep" - profile D-state sleeping (millisecs).
2714 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002715 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002716
Linus Torvalds1da177e2005-04-16 15:20:36 -07002717 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2718 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002719 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002720
Randy Dunlapa9913042005-10-23 12:57:11 -07002721 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2722 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002723 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2724 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002725 psmouse.resetafter= [HW,MOUSE]
2726 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002727 (0 = never).
2728 psmouse.resolution=
2729 [HW,MOUSE] Set desired mouse resolution, in dpi.
2730 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002731 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002732 0 = disabled, 1 = enabled (default).
2733
Matthew Garrettdee28e72011-07-21 16:57:55 -04002734 pstore.backend= Specify the name of the pstore backend to use
2735
Linus Torvalds1da177e2005-04-16 15:20:36 -07002736 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002737 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002738
Kay Sieversdc8c8582007-08-15 12:25:38 +02002739 pty.legacy_count=
2740 [KNL] Number of legacy pty's. Overwrites compiled-in
2741 default number.
2742
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002743 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002744
Linus Torvalds1da177e2005-04-16 15:20:36 -07002745 r128= [HW,DRM]
2746
2747 raid= [HW,RAID]
2748 See Documentation/md.txt.
2749
Randy Dunlapa9913042005-10-23 12:57:11 -07002750 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002751 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002752
Linus Torvalds1da177e2005-04-16 15:20:36 -07002753 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002754 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002755
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002756 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002757 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2758 the specified list of CPUs to be no-callback CPUs.
2759 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08002760 be offloaded to "rcuox/N" kthreads created for
2761 that purpose, where "x" is "b" for RCU-bh, "p"
2762 for RCU-preempt, and "s" for RCU-sched, and "N"
2763 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002764 offloaded CPUs, which can be useful for HPC and
2765 real-time workloads. It can also improve energy
2766 efficiency for asymmetric multiprocessors.
2767
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002768 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002769 Rather than requiring that offloaded CPUs
2770 (specified by rcu_nocbs= above) explicitly
2771 awaken the corresponding "rcuoN" kthreads,
2772 make these kthreads poll for callbacks.
2773 This improves the real-time response for the
2774 offloaded CPUs by relieving them of the need to
2775 wake up the corresponding kthread, but degrades
2776 energy efficiency by requiring that the kthreads
2777 periodically wake up to do the polling.
2778
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002779 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002780 Set maximum number of finished RCU callbacks to
2781 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002782
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002783 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07002784 Increase the number of CPUs assigned to each
2785 leaf rcu_node structure. Useful for very large
2786 systems.
2787
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002788 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002789 Set delay from grace-period initialization to
2790 first attempt to force quiescent states.
2791 Units are jiffies, minimum value is zero,
2792 and maximum value is HZ.
2793
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002794 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002795 Set delay between subsequent attempts to force
2796 quiescent states. Units are jiffies, minimum
2797 value is one, and maximum value is HZ.
2798
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002799 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002800 Set threshold of queued RCU callbacks beyond which
2801 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002802
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002803 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002804 Set threshold of queued RCU callbacks below which
2805 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002806
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002807 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002808 Set wakeup interval for idle CPUs that have
2809 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002810
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002811 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002812 Set wakeup interval for idle CPUs that have
2813 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2814 Lazy RCU callbacks are those which RCU can
2815 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002816
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002817 rcutorture.fqs_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002818 Set duration of force_quiescent_state bursts.
2819
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002820 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002821 Set holdoff time within force_quiescent_state bursts.
2822
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002823 rcutorture.fqs_stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002824 Set wait time between force_quiescent_state bursts.
2825
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002826 rcutorture.gp_exp= [KNL]
2827 Use expedited update-side primitives.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002828
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002829 rcutorture.gp_normal= [KNL]
2830 Use normal (non-expedited) update-side primitives.
2831 If both gp_exp and gp_normal are set, do both.
2832 If neither gp_exp nor gp_normal are set, still
2833 do both.
2834
2835 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002836 Set callbacks/threads for rcu_barrier() testing.
2837
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002838 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002839 Set number of concurrent RCU writers. These just
2840 stress RCU, they don't participate in the actual
2841 test, hence the "fake".
2842
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002843 rcutorture.nreaders= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002844 Set number of RCU readers.
2845
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002846 rcutorture.object_debug= [KNL]
2847 Enable debug-object double-call_rcu() testing.
2848
2849 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002850 Set time (s) after boot for CPU-hotplug testing.
2851
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002852 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002853 Set time (s) between CPU-hotplug operations, or
2854 zero to disable CPU-hotplug testing.
2855
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002856 rcutorture.rcutorture_runnable= [BOOT]
2857 Start rcutorture running at boot time.
2858
2859 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002860 Set task-shuffle interval (s). Shuffling tasks
2861 allows some CPUs to go into dyntick-idle mode
2862 during the rcutorture test.
2863
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002864 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002865 Set time (s) after boot system shutdown. This
2866 is useful for hands-off automated testing.
2867
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002868 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002869 Duration of CPU stall (s) to test RCU CPU stall
2870 warnings, zero to disable.
2871
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002872 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002873 Time to wait (s) after boot before inducing stall.
2874
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002875 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002876 Time (s) between statistics printk()s.
2877
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002878 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002879 Time (s) to stutter testing, for example, specifying
2880 five seconds causes the test to run for five seconds,
2881 wait for five seconds, and so on. This tests RCU's
2882 ability to transition abruptly to and from idle.
2883
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002884 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002885 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2886 "Maybe" means test if the RCU implementation
2887 under test support RCU priority boosting.
2888
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002889 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002890 Duration (s) of each individual boost test.
2891
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002892 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002893 Interval (s) between each boost test.
2894
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002895 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002896 Test RCU's dyntick-idle handling. See also the
2897 rcutorture.shuffle_interval parameter.
2898
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002899 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002900 Specify the RCU implementation to test.
2901
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002902 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002903 Enable additional printk() statements.
2904
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002905 rcupdate.rcu_expedited= [KNL]
2906 Use expedited grace-period primitives, for
2907 example, synchronize_rcu_expedited() instead
2908 of synchronize_rcu(). This reduces latency,
2909 but can increase CPU utilization, degrade
2910 real-time latency, and degrade energy efficiency.
2911
2912 rcupdate.rcu_cpu_stall_suppress= [KNL]
2913 Suppress RCU CPU stall warning messages.
2914
2915 rcupdate.rcu_cpu_stall_timeout= [KNL]
2916 Set timeout for RCU CPU stall warning messages.
2917
Olof Johanssonffdfc402005-09-06 15:17:19 -07002918 rdinit= [KNL]
2919 Format: <full_path>
2920 Run specified binary instead of /init from the ramdisk,
2921 used for early userspace startup. See initrd.
2922
Robin Holt1b3a5d02013-07-08 16:01:42 -07002923 reboot= [KNL]
2924 Format (x86 or x86_64):
2925 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2926 [[,]s[mp]#### \
2927 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2928 [[,]f[orce]
2929 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2930 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2931 reboot_force is either force or not specified,
2932 reboot_cpu is s[mp]#### with #### being the processor
2933 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002934
Paul Jackson46b6d942008-07-04 10:00:09 -07002935 relax_domain_level=
2936 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002937 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002938
Rafael J. Wysocki0399d4d2014-05-26 13:40:59 +02002939 relative_sleep_states=
2940 [SUSPEND] Use sleep state labeling where the deepest
2941 state available other than hibernation is always "mem".
2942 Format: { "0" | "1" }
2943 0 -- Traditional sleep state labels.
2944 1 -- Relative sleep state labels.
2945
Linus Torvalds1da177e2005-04-16 15:20:36 -07002946 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2947
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002948 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002949 Format: nn[KMG]
2950 Reserves a hole at the top of the kernel virtual
2951 address space.
2952
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002953 reservelow= [X86]
2954 Format: nn[K]
2955 Set the amount of memory to reserve for BIOS at
2956 the bottom of the address space.
2957
Vivek Goyal7e962872006-09-27 01:50:44 -07002958 reset_devices [KNL] Force drivers to reset the underlying device
2959 during initialization.
2960
Randy Dunlapa9913042005-10-23 12:57:11 -07002961 resume= [SWSUSP]
2962 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02002963 Format:
2964 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002965
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002966 resume_offset= [SWSUSP]
2967 Specify the offset from the beginning of the partition
2968 given by "resume=" at which the swap header is located,
2969 in <PAGE_SIZE> units (needed only for swap files).
2970 See Documentation/power/swsusp-and-swap-files.txt
2971
Barry Songf126f732011-10-10 23:38:41 +02002972 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2973 read the resume files
2974
Barry Song6f8d7022011-10-06 20:34:46 +02002975 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2976 Useful for devices that are detected asynchronously
2977 (e.g. USB and MMC devices).
2978
Bojan Smojverf996fc92010-09-09 23:06:23 +02002979 hibernate= [HIBERNATION]
2980 noresume Don't check if there's a hibernation image
2981 present during boot.
2982 nocompress Don't compress/decompress hibernation images.
2983
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002984 retain_initrd [RAM] Keep initrd memory after extraction
2985
Linus Torvalds1da177e2005-04-16 15:20:36 -07002986 rhash_entries= [KNL,NET]
2987 Set number of hash buckets for route cache
2988
Linus Torvalds1da177e2005-04-16 15:20:36 -07002989 ro [KNL] Mount root device read-only on boot
2990
2991 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07002992 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002993
2994 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2995 mount the root filesystem
2996
2997 rootflags= [KNL] Set root filesystem mount option string
2998
2999 rootfstype= [KNL] Set root filesystem type
3000
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003001 rootwait [KNL] Wait (indefinitely) for root device to show up.
3002 Useful for devices that are detected asynchronously
3003 (e.g. USB and MMC devices).
3004
Robert Tivy5c71d612013-03-28 18:41:46 -07003005 rproc_mem=nn[KMG][@address]
3006 [KNL,ARM,CMA] Remoteproc physical memory block.
3007 Memory area to be used by remote processor image,
3008 managed by CMA.
3009
Linus Torvalds1da177e2005-04-16 15:20:36 -07003010 rw [KNL] Mount root device read-write on boot
3011
3012 S [KNL] Run init in single mode
3013
3014 sa1100ir [NET]
3015 See drivers/net/irda/sa1100_ir.c.
3016
Linus Torvalds1da177e2005-04-16 15:20:36 -07003017 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003018
Mike Travisf6630112009-11-17 18:22:15 -06003019 sched_debug [KNL] Enables verbose scheduler debug messages.
3020
Mike Galbraith5307c952012-05-08 12:20:58 +02003021 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3022 xtime_lock contention on larger systems, and/or RCU lock
3023 contention on all systems with CONFIG_MAXSMP set.
3024 Format: { "0" | "1" }
3025 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3026 1 -- enable.
3027 Note: increases power consumption, thus should only be
3028 enabled if running jitter sensitive (HPC/RT) workloads.
3029
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003030 security= [SECURITY] Choose a security module to enable at boot.
3031 If this boot parameter is not specified, only the first
3032 security module asking for security registration will be
3033 loaded. An invalid security module name will be treated
3034 as if no module has been chosen.
3035
3036 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003037 Format: { "0" | "1" }
3038 See security/selinux/Kconfig help text.
3039 0 -- disable.
3040 1 -- enable.
3041 Default value is set via kernel config option.
3042 If enabled at boot time, /selinux/disable can be used
3043 later to disable prior to initial policy load.
3044
John Johansenc1c124e2010-07-29 14:48:09 -07003045 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3046 Format: { "0" | "1" }
3047 See security/apparmor/Kconfig help text
3048 0 -- disable.
3049 1 -- enable.
3050 Default value is set via kernel config option.
3051
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003052 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003053
Linus Torvalds1da177e2005-04-16 15:20:36 -07003054 shapers= [NET]
3055 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003056
Yinghai Lub05f78f2008-08-22 01:32:50 -07003057 show_msr= [x86] show boot-time MSR settings
3058 Format: { <integer> }
3059 Show boot-time (BIOS-initialized) MSR settings.
3060 The parameter means the number of CPUs to show,
3061 for example 1 means boot CPU only.
3062
Linus Torvalds1da177e2005-04-16 15:20:36 -07003063 simeth= [IA-64]
3064 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003065
Linus Torvalds1da177e2005-04-16 15:20:36 -07003066 slram= [HW,MTD]
3067
David Rientjes3df1ccc2011-10-18 22:09:28 -07003068 slab_max_order= [MM, SLAB]
3069 Determines the maximum allowed order for slabs.
3070 A high setting may cause OOMs due to memory
3071 fragmentation. Defaults to 1 for systems with
3072 more than 32MB of RAM, 0 otherwise.
3073
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003074 slub_debug[=options[,slabs]] [MM, SLUB]
3075 Enabling slub_debug allows one to determine the
3076 culprit if slab objects become corrupted. Enabling
3077 slub_debug can create guard zones around objects and
3078 may poison objects when not in use. Also tracks the
3079 last alloc / free. For more information see
3080 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003081
3082 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003083 Determines the maximum allowed order for slabs.
3084 A high setting may cause OOMs due to memory
3085 fragmentation. For more information see
3086 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003087
3088 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003089 The minimum number of objects per slab. SLUB will
3090 increase the slab order up to slub_max_order to
3091 generate a sufficiently large slab able to contain
3092 the number of objects indicated. The higher the number
3093 of objects the smaller the overhead of tracking slabs
3094 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003095 For more information see Documentation/vm/slub.txt.
3096
3097 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003098 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003099 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003100 For more information see Documentation/vm/slub.txt.
3101
3102 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003103 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07003104 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003105 allocs to different slabs. Debug options disable
3106 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003107 For more information see Documentation/vm/slub.txt.
3108
Linus Torvalds1da177e2005-04-16 15:20:36 -07003109 smart2= [HW]
3110 Format: <io1>[,<io2>[,...,<io8>]]
3111
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003112 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3113 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3114 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3115 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3116 smsc-ircc2.ircc_irq= [HW] IRQ line
3117 smsc-ircc2.ircc_dma= [HW] DMA channel
3118 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3119 0: Toshiba Satellite 1800 (GP data pin select)
3120 1: Fast pin select (default)
3121 2: ATC IRMode
3122
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003123 softlockup_panic=
3124 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003125 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003126
Linus Torvalds1da177e2005-04-16 15:20:36 -07003127 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003128 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003129
Linus Torvalds1da177e2005-04-16 15:20:36 -07003130 spia_io_base= [HW,MTD]
3131 spia_fio_base=
3132 spia_pedr=
3133 spia_peddr=
3134
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003135 stacktrace [FTRACE]
3136 Enabled the stack tracer on boot up.
3137
Steven Rostedt762e1202011-12-19 22:01:00 -05003138 stacktrace_filter=[function-list]
3139 [FTRACE] Limit the functions that the stack tracer
3140 will trace at boot up. function-list is a comma separated
3141 list of functions. This list can be changed at run
3142 time by the stack_trace_filter file in the debugfs
3143 tracing directory. Note, this enables stack tracing
3144 and the stacktrace above is not needed.
3145
Linus Torvalds1da177e2005-04-16 15:20:36 -07003146 sti= [PARISC,HW]
3147 Format: <num>
3148 Set the STI (builtin display/keyboard on the HP-PARISC
3149 machines) console (graphic card) which should be used
3150 as the initial boot-console.
3151 See also comment in drivers/video/console/sticore.c.
3152
3153 sti_font= [HW]
3154 See comment in drivers/video/console/sticore.c.
3155
3156 stifb= [HW]
3157 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3158
Trond Myklebustcbf11072009-08-09 15:06:19 -04003159 sunrpc.min_resvport=
3160 sunrpc.max_resvport=
3161 [NFS,SUNRPC]
3162 SunRPC servers often require that client requests
3163 originate from a privileged port (i.e. a port in the
3164 range 0 < portnr < 1024).
3165 An administrator who wishes to reserve some of these
3166 ports for other uses may adjust the range that the
3167 kernel's sunrpc client considers to be privileged
3168 using these two parameters to set the minimum and
3169 maximum port values.
3170
Greg Banks42a7fc42007-03-06 01:42:23 -08003171 sunrpc.pool_mode=
3172 [NFS]
3173 Control how the NFS server code allocates CPUs to
3174 service thread pools. Depending on how many NICs
3175 you have and where their interrupts are bound, this
3176 option will affect which CPUs will do NFS serving.
3177 Note: this parameter cannot be changed while the
3178 NFS server is running.
3179
3180 auto the server chooses an appropriate mode
3181 automatically using heuristics
3182 global a single global pool contains all CPUs
3183 percpu one pool for each CPU
3184 pernode one pool for each NUMA node (equivalent
3185 to global on non-NUMA machines)
3186
Trond Myklebustcbf11072009-08-09 15:06:19 -04003187 sunrpc.tcp_slot_table_entries=
3188 sunrpc.udp_slot_table_entries=
3189 [NFS,SUNRPC]
3190 Sets the upper limit on the number of simultaneous
3191 RPC calls that can be sent from the client to a
3192 server. Increasing these values may allow you to
3193 improve throughput, but will also increase the
3194 amount of memory reserved for use by the client.
3195
Michal Hocko07555ac2013-08-22 16:35:46 -07003196 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003197 [KNL] Enable accounting of swap in memory resource
3198 controller if no parameter or 1 is given or disable
3199 it if 0 is given (See Documentation/cgroups/memory.txt)
3200
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003201 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3202 Format: { <int> | force }
3203 <int> -- Number of I/O TLB slabs
3204 force -- force using of bounce buffers even if they
3205 wouldn't be automatically used by the kernel
Randy Dunlapa9913042005-10-23 12:57:11 -07003206
Linus Torvalds1da177e2005-04-16 15:20:36 -07003207 switches= [HW,M68k]
3208
Andi Kleene52eec12010-09-08 16:54:17 +02003209 sysfs.deprecated=0|1 [KNL]
3210 Enable/disable old style sysfs layout for old udev
3211 on older distributions. When this option is enabled
3212 very new udev will not work anymore. When this option
3213 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3214 in older udev will not work anymore.
3215 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3216 the kernel configuration.
3217
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003218 sysrq_always_enabled
3219 [KNL]
3220 Ignore sysrq setting - this boot parameter will
3221 neutralize any effect of /proc/sys/kernel/sysrq.
3222 Useful for debugging.
3223
Linus Torvalds1da177e2005-04-16 15:20:36 -07003224 tdfx= [HW,DRM]
3225
David Brownell77437fd2008-07-23 21:28:33 -07003226 test_suspend= [SUSPEND]
3227 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3228 standby suspend) as the system sleep state to briefly
3229 enter during system startup. The system is woken from
3230 this state using a wakeup-capable RTC alarm.
3231
Linus Torvalds1da177e2005-04-16 15:20:36 -07003232 thash_entries= [KNL,NET]
3233 Set number of hash buckets for TCP connection
3234
Len Brownf8707ec2007-08-12 00:12:54 -04003235 thermal.act= [HW,ACPI]
3236 -1: disable all active trip points in all thermal zones
3237 <degrees C>: override all lowest active trip points
3238
Len Brownc52a7412007-08-14 15:49:32 -04003239 thermal.crt= [HW,ACPI]
3240 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003241 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003242
Len Brownf5487142007-08-12 00:12:44 -04003243 thermal.nocrt= [HW,ACPI]
3244 Set to disable actions on ACPI thermal zone
3245 critical and hot trip points.
3246
Len Brown72b33ef2007-08-12 00:12:17 -04003247 thermal.off= [HW,ACPI]
3248 1: disable ACPI thermal control
3249
Len Browna70cdc52007-08-12 00:12:35 -04003250 thermal.psv= [HW,ACPI]
3251 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003252 <degrees C>: override all passive trip points to this
3253 value
Len Browna70cdc52007-08-12 00:12:35 -04003254
Len Brown730ff342007-08-12 00:12:26 -04003255 thermal.tzp= [HW,ACPI]
3256 Specify global default ACPI thermal zone polling rate
3257 <deci-seconds>: poll all this frequency
3258 0: no polling (default)
3259
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003260 threadirqs [KNL]
3261 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003262 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003263
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003264 tmem [KNL,XEN]
3265 Enable the Transcendent memory driver if built-in.
3266
3267 tmem.cleancache=0|1 [KNL, XEN]
3268 Default is on (1). Disable the usage of the cleancache
3269 API to send anonymous pages to the hypervisor.
3270
3271 tmem.frontswap=0|1 [KNL, XEN]
3272 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003273 API to send swap pages to the hypervisor. If disabled
3274 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003275
3276 tmem.selfballooning=0|1 [KNL, XEN]
3277 Default is on (1). Disable the driving of swap pages
3278 to the hypervisor.
3279
3280 tmem.selfshrinking=0|1 [KNL, XEN]
3281 Default is on (1). Partial swapoff that immediately
3282 transfers pages from Xen hypervisor back to the
3283 kernel based on different criteria.
3284
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003285 topology= [S390]
3286 Format: {off | on}
3287 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003288 topology information if the hardware supports this.
3289 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003290 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003291 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003292
Linus Torvalds1da177e2005-04-16 15:20:36 -07003293 tp720= [HW,PS2]
3294
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003295 tpm_suspend_pcr=[HW,TPM]
3296 Format: integer pcr id
3297 Specify that at suspend time, the tpm driver
3298 should extend the specified pcr with zeros,
3299 as a workaround for some chips which fail to
3300 flush the last written pcr on TPM_SaveState.
3301 This will guarantee that all the other pcrs
3302 are saved.
3303
Li Zefan9d612be2009-06-24 17:33:15 +08003304 trace_buf_size=nn[KMG]
3305 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003306
Li Zefan020e5f82009-07-01 10:47:05 +08003307 trace_event=[event-list]
3308 [FTRACE] Set and start specified trace events in order
3309 to facilitate early boot debugging.
3310 See also Documentation/trace/events.txt
3311
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003312 trace_options=[option-list]
3313 [FTRACE] Enable or disable tracer options at boot.
3314 The option-list is a comma delimited list of options
3315 that can be enabled or disabled just as if you were
3316 to echo the option name into
3317
3318 /sys/kernel/debug/tracing/trace_options
3319
3320 For example, to enable stacktrace option (to dump the
3321 stack trace of each event), add to the command line:
3322
3323 trace_options=stacktrace
3324
3325 See also Documentation/trace/ftrace.txt "trace options"
3326 section.
3327
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003328 traceoff_on_warning
3329 [FTRACE] enable this option to disable tracing when a
3330 warning is hit. This turns off "tracing_on". Tracing can
3331 be enabled again by echoing '1' into the "tracing_on"
3332 file located in /sys/kernel/debug/tracing/
3333
3334 This option is useful, as it disables the trace before
3335 the WARNING dump is called, which prevents the trace to
3336 be filled with content caused by the warning output.
3337
3338 This option can also be set at run time via the sysctl
3339 option: kernel/traceoff_on_warning
3340
Jiri Kosinafcf4d822012-03-21 16:34:02 -07003341 transparent_hugepage=
3342 [KNL]
3343 Format: [always|madvise|never]
3344 Can be used to control the default behavior of the system
3345 with respect to transparent hugepages.
3346 See Documentation/vm/transhuge.txt for more details.
3347
john stultzd3b8f882009-08-17 16:40:47 -07003348 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003349 Format: <string>
3350 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003351 disables clocksource verification at runtime, as well
3352 as the stability checks done at bootup. Used to enable
3353 high-resolution timer mode on older hardware, and in
3354 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003355 [x86] noirqtime: Do not use TSC to do irq accounting.
3356 Used to run time disable IRQ_TIME_ACCOUNTING on any
3357 platforms where RDTSC is slow and this accounting
3358 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003359
Randy Dunlapa9913042005-10-23 12:57:11 -07003360 turbografx.map[2|3]= [HW,JOY]
3361 TurboGraFX parallel port interface
3362 Format:
3363 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003364 See also Documentation/input/joystick-parport.txt
3365
Christian Kujaub6935f82011-05-31 15:22:05 +00003366 udbg-immortal [PPC] When debugging early kernel crashes that
3367 happen after console_init() and before a proper
3368 console driver takes over, this boot options might
3369 help "seeing" what's going on.
3370
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003371 uhash_entries= [KNL,NET]
3372 Set number of hash buckets for UDP/UDP-Lite connections
3373
Alan Stern5f8364b2006-12-05 16:29:55 -05003374 uhci-hcd.ignore_oc=
3375 [USB] Ignore overcurrent events (default N).
3376 Some badly-designed motherboards generate lots of
3377 bogus events, for ports that aren't wired to
3378 anything. Set this parameter to avoid log spamming.
3379 Note that genuine overcurrent events won't be
3380 reported either.
3381
Simon Arlotte3a61b02008-07-19 23:32:54 +01003382 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003383 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003384
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003385 usbcore.authorized_default=
3386 [USB] Default USB device authorization:
3387 (default -1 = authorized except for wireless USB,
3388 0 = not authorized, 1 = authorized)
3389
Alan Sternb5e795f2007-02-20 15:00:53 -05003390 usbcore.autosuspend=
3391 [USB] The autosuspend time delay (in seconds) used
3392 for newly-detected USB devices (default 2). This
3393 is the time required before an idle device will be
3394 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003395 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003396
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003397 usbcore.usbfs_snoop=
3398 [USB] Set to log all usbfs traffic (default 0 = off).
3399
3400 usbcore.blinkenlights=
3401 [USB] Set to cycle leds on hubs (default 0 = off).
3402
3403 usbcore.old_scheme_first=
3404 [USB] Start with the old device initialization
3405 scheme (default 0 = off).
3406
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003407 usbcore.usbfs_memory_mb=
3408 [USB] Memory limit (in MB) for buffers allocated by
3409 usbfs (default = 16, 0 = max = 2047).
3410
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003411 usbcore.use_both_schemes=
3412 [USB] Try the other device initialization scheme
3413 if the first one fails (default 1 = enabled).
3414
3415 usbcore.initial_descriptor_timeout=
3416 [USB] Specifies timeout for the initial 64-byte
3417 USB_REQ_GET_DESCRIPTOR request in milliseconds
3418 (default 5000 = 5.0 seconds).
3419
Linus Torvalds1da177e2005-04-16 15:20:36 -07003420 usbhid.mousepoll=
3421 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003422
Alan Sternd4f373e2008-11-10 14:07:45 -05003423 usb-storage.delay_use=
3424 [UMS] The delay in seconds before a new device is
3425 scanned for Logical Units (default 5).
3426
3427 usb-storage.quirks=
3428 [UMS] A list of quirks entries to supplement or
3429 override the built-in unusual_devs list. List
3430 entries are separated by commas. Each entry has
3431 the form VID:PID:Flags where VID and PID are Vendor
3432 and Product ID values (4-digit hex numbers) and
3433 Flags is a set of characters, each corresponding
3434 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003435 a = SANE_SENSE (collect more than 18 bytes
3436 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003437 b = BAD_SENSE (don't collect more than 18
3438 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003439 c = FIX_CAPACITY (decrease the reported
3440 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003441 d = NO_READ_DISC_INFO (don't use
3442 READ_DISC_INFO command);
3443 e = NO_READ_CAPACITY_16 (don't use
3444 READ_CAPACITY_16 command);
Alan Sternc838ea42008-12-15 10:40:06 -05003445 h = CAPACITY_HEURISTICS (decrease the
3446 reported device capacity by one
3447 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003448 i = IGNORE_DEVICE (don't bind to this
3449 device);
3450 l = NOT_LOCKABLE (don't try to lock and
3451 unlock ejectable media);
3452 m = MAX_SECTORS_64 (don't transfer more
3453 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003454 n = INITIAL_READ10 (force a retry of the
3455 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003456 o = CAPACITY_OK (accept the capacity
3457 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003458 p = WRITE_CACHE (the device cache is ON
3459 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003460 r = IGNORE_RESIDUE (the device reports
3461 bogus residue values);
3462 s = SINGLE_LUN (the device has only one
3463 Logical Unit);
3464 w = NO_WP_DETECT (don't test whether the
3465 medium is write-protected).
3466 Example: quirks=0419:aaf5:rl,0421:0433:rc
3467
Stephen Boydac1667d2011-08-13 12:34:50 -07003468 user_debug= [KNL,ARM]
3469 Format: <int>
3470 See arch/arm/Kconfig.debug help text.
3471 1 - undefined instruction events
3472 2 - system calls
3473 4 - invalid data aborts
3474 8 - SIGSEGV faults
3475 16 - SIGBUS faults
3476 Example: user_debug=31
3477
Ian Campbell14315592010-02-17 10:38:10 +00003478 userpte=
3479 [X86] Flags controlling user PTE allocations.
3480
3481 nohigh = do not allocate PTE pages in
3482 HIGHMEM regardless of setting
3483 of CONFIG_HIGHPTE.
3484
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303485 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003486 On X86_32, this is an alias for vdso32=. Otherwise:
3487
3488 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07003489 vdso=0: disable VDSO mapping
3490
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07003491 vdso32= [X86] Control the 32-bit vDSO
3492 vdso32=1: enable 32-bit VDSO
3493 vdso32=0 or vdso32=2: disable 32-bit VDSO
3494
3495 See the help text for CONFIG_COMPAT_VDSO for more
3496 details. If CONFIG_COMPAT_VDSO is set, the default is
3497 vdso32=0; otherwise, the default is vdso32=1.
3498
3499 For compatibility with older kernels, vdso32=2 is an
3500 alias for vdso32=0.
3501
3502 Try vdso32=0 if you encounter an error that says:
3503 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01003504
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003505 vector= [IA-64,SMP]
3506 vector=percpu: enable percpu vector domain
3507
Linus Torvalds1da177e2005-04-16 15:20:36 -07003508 video= [FB] Frame buffer configuration
3509 See Documentation/fb/modedb.txt.
3510
Aaron Lu3afe6da2013-06-20 15:08:55 +08003511 video.brightness_switch_enabled= [0,1]
3512 If set to 1, on receiving an ACPI notify event
3513 generated by hotkey, video driver will adjust brightness
3514 level and then send out the event to user space through
3515 the allocated input device; If set to 0, video driver
3516 will only send out the event without touching backlight
3517 brightness level.
Hans de Goede886129a2014-05-06 14:46:23 +02003518 default: 0
Aaron Lu3afe6da2013-06-20 15:08:55 +08003519
Pawel Moll81a054c2012-05-09 18:30:16 +01003520 virtio_mmio.device=
3521 [VMMIO] Memory mapped virtio (platform) device.
3522
3523 <size>@<baseaddr>:<irq>[:<id>]
3524 where:
3525 <size> := size (can use standard suffixes
3526 like K, M and G)
3527 <baseaddr> := physical base address
3528 <irq> := interrupt number (as passed to
3529 request_irq())
3530 <id> := (optional) platform device id
3531 example:
3532 virtio_mmio.device=1K@0x100b0000:48:7
3533
3534 Can be used multiple times for multiple devices.
3535
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003536 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003537 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003538 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003539 Use vga=ask for menu.
3540 This is actually a boot loader parameter; the value is
3541 passed to the kernel using a special protocol.
3542
Randy Dunlapa9913042005-10-23 12:57:11 -07003543 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003544 size of <nn>. This can be used to increase the
3545 minimum size (128MB on x86). It can also be used to
3546 decrease the size and leave more room for directly
3547 mapped kernel RAM.
3548
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003549 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3550 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003551
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003552 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3553 Format: <command>
3554
3555 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3556 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003557
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003558 vsyscall= [X86-64]
3559 Controls the behavior of vsyscalls (i.e. calls to
3560 fixed addresses of 0xffffffffff600x00 from legacy
3561 code). Most statically-linked binaries and older
3562 versions of glibc use these calls. Because these
3563 functions are at fixed addresses, they make nice
3564 targets for exploits that can control RIP.
3565
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003566 emulate [default] Vsyscalls turn into traps and are
3567 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003568
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003569 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003570 This is a little bit faster than trapping
3571 and makes a few dynamic recompilers work
3572 better than they would in emulation mode.
3573 It also makes exploits much easier to write.
3574
3575 none Vsyscalls don't work at all. This makes
3576 them quite hard to use for exploits but
3577 might break your system.
3578
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003579 vt.color= [VT] Default text color.
3580 Format: 0xYX, X = foreground, Y = background.
3581 Default: 0x07 = light gray on black.
3582
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08003583 vt.cur_default= [VT] Default cursor shape.
3584 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3585 the parameters of the <Esc>[?A;B;Cc escape sequence;
3586 see VGA-softcursor.txt. Default: 2 = underline.
3587
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003588 vt.default_blu= [VT]
3589 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3590 Change the default blue palette of the console.
3591 This is a 16-member array composed of values
3592 ranging from 0-255.
3593
3594 vt.default_grn= [VT]
3595 Format: <green0>,<green1>,<green2>,...,<green15>
3596 Change the default green palette of the console.
3597 This is a 16-member array composed of values
3598 ranging from 0-255.
3599
3600 vt.default_red= [VT]
3601 Format: <red0>,<red1>,<red2>,...,<red15>
3602 Change the default red palette of the console.
3603 This is a 16-member array composed of values
3604 ranging from 0-255.
3605
3606 vt.default_utf8=
3607 [VT]
3608 Format=<0|1>
3609 Set system-wide default UTF-8 mode for all tty's.
3610 Default is 1, i.e. UTF-8 mode is enabled for all
3611 newly opened terminals.
3612
Matthew Garrettf6c06b62009-11-13 15:14:11 -05003613 vt.global_cursor_default=
3614 [VT]
3615 Format=<-1|0|1>
3616 Set system-wide default for whether a cursor
3617 is shown on new VTs. Default is -1,
3618 i.e. cursors will be created by default unless
3619 overridden by individual drivers. 0 will hide
3620 cursors, 1 will display them.
3621
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003622 vt.italic= [VT] Default color for italic text; 0-15.
3623 Default: 2 = green.
3624
3625 vt.underline= [VT] Default color for underlined text; 0-15.
3626 Default: 3 = cyan.
3627
Randy Dunlap4724ba572010-05-03 11:42:52 -07003628 watchdog timers [HW,WDT] For information on watchdog timers,
3629 see Documentation/watchdog/watchdog-parameters.txt
3630 or other driver-specific files in the
3631 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003632
Tejun Heod55262c2013-04-01 11:23:38 -07003633 workqueue.disable_numa
3634 By default, all work items queued to unbound
3635 workqueues are affine to the NUMA nodes they're
3636 issued on, which results in better behavior in
3637 general. If NUMA affinity needs to be disabled for
3638 whatever reason, this option can be used. Note
3639 that this also can be controlled per-workqueue for
3640 workqueues visible under /sys/bus/workqueue/.
3641
Viresh Kumarcee22a12013-04-08 16:45:40 +05303642 workqueue.power_efficient
3643 Per-cpu workqueues are generally preferred because
3644 they show better performance thanks to cache
3645 locality; unfortunately, per-cpu workqueues tend to
3646 be more power hungry than unbound workqueues.
3647
3648 Enabling this makes the per-cpu workqueues which
3649 were observed to contribute significantly to power
3650 consumption unbound, leading to measurably lower
3651 power usage at the cost of small performance
3652 overhead.
3653
3654 The default value of this parameter is determined by
3655 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3656
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003657 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3658 default x2apic cluster mode on platforms
3659 supporting x2apic.
3660
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003661 x86_intel_mid_timer= [X86-32,APBT]
3662 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07003663 Two valid options are apbt timer only and lapic timer
3664 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003665 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07003666
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003667 xen_emul_unplug= [HW,X86,XEN]
3668 Unplug Xen emulated devices
3669 Format: [unplug0,][unplug1]
3670 ide-disks -- unplug primary master IDE devices
3671 aux-ide-disks -- unplug non-primary-master IDE devices
3672 nics -- unplug network devices
3673 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01003674 unnecessary -- unplugging emulated devices is
3675 unnecessary even if the host did not respond to
3676 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01003677 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003678
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04003679 xen_nopvspin [X86,XEN]
3680 Disables the ticketlock slowpath using Xen PV
3681 optimizations.
3682
Linus Torvalds1da177e2005-04-16 15:20:36 -07003683 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07003684 Format:
3685 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003686
Randy Dunlapa9913042005-10-23 12:57:11 -07003687______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07003688
3689TODO:
3690
Linus Torvalds1da177e2005-04-16 15:20:36 -07003691 Add more DRM drivers.