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Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
Linus Torvalds1da177e2005-04-16 15:20:36 -07003
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
Randy Dunlapca1eda22009-05-06 16:02:58 -070020Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22can also be entered as
23 log-buf-len=1M print_fatal_signals=1
24
25
Stefan Richtera901ebb2006-04-01 01:43:18 +020026This document may not be entirely up to date and comprehensive. The command
27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28module. Loadable modules, after being loaded into the running kernel, also
29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30parameters may be changed at runtime by the command
31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32
Stefan Richter6585fa82006-04-01 01:44:30 +020033The parameters listed below are only valid if certain kernel build options were
34enabled and if respective hardware is present. The text in square brackets at
35the beginning of each description states the restrictions within which a
36parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070037
38 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100039 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070040 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070043 ARM ARM architecture is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020044 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070045 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080046 BLACKFIN Blackfin architecture is enabled.
Olof Johansson1e435252013-04-27 14:10:18 -070047 CLK Common clock infrastructure is enabled.
Robert Tivy5c71d612013-03-28 18:41:46 -070048 CMA Contiguous Memory Area support is enabled.
Alan Cox9cfe2682011-01-25 14:18:38 +000049 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070051 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
Mimi Zohar7102ebc2011-05-12 18:33:20 -040054 EVM Extended Verification Module
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 FB The frame buffer device is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070056 FTRACE Function tracing enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070057 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050060 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070062 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080063 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070064 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd62010-05-20 21:04:24 -050067 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020068 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070069 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070070 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -070075 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070076 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070078 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070079 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070084 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070086 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070088 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070089 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -070097 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -070099 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -0700101 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900103 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300108 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500110 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
Pawel Moll81a054c2012-05-09 18:30:16 +0100114 VMMIO Driver for memory mapped virtio devices is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700119 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700122 Documentation/x86/x86_64/boot-options.txt .
Randy Dunlap16290242011-08-13 12:34:52 -0700123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100124 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125
126In addition, the following text indicates that the option:
127
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
131
132Parameters denoted with BOOT are actually interpreted by the boot
133loader, and have no meaning to the kernel directly.
134Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500135need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136
Karsten Weiss55588702007-02-13 13:26:21 +0100137There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700138See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100139
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141a trailing = on the name of any parameter states that that parameter will
142be entered as an environment variable, whereas its absence indicates that
143it will appear as a kernel argument readable via /proc/cmdline by programs
144running once the system is up.
145
jens m. noedler9c4751f2006-09-29 02:00:27 -0700146The number of kernel parameters is not limited, but the length of the
147complete command line (parameters including spaces etc.) is limited to
148a fixed number of characters. This limit depends on the architecture
149and is between 256 and 4096 characters. It is defined in the file
150./include/asm/setup.h as COMMAND_LINE_SIZE.
151
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800152Finally, the [KMG] suffix is commonly described after a number of kernel
153parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155bytes respectively. Such letter suffixes can also be entirely omitted.
156
jens m. noedler9c4751f2006-09-29 02:00:27 -0700157
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530158 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800159 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500160 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700164 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800166 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800167 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168
Paul Bolle395cf962011-08-15 02:02:26 +0200169 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170
Takao Indoh4996c022011-07-14 18:05:21 -0400171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
175
Len Browna1fdcc02007-03-11 03:26:14 -0400176 acpi_apic_instance= [ACPI, IOAPIC]
177 Format: <int>
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400180 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400181
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
184 acpi_backlight=video
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
188
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200212
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800216
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
219 default in APIC mode
220
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
223 default in PIC mode
224
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
227
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
229 use by PCI
230 Format: <irq>,<irq>...
231
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
233
234 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
236
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800238 acpi_osi="string1" # add string1
239 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800240 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800241 acpi_osi=! # disable all built-in OS vendor
242 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700243 acpi_osi= # disable all strings
244
Lv Zheng5dc17982013-07-22 16:08:25 +0800245 'acpi_osi=!' can be used in combination with single or
246 multiple 'acpi_osi="string1"' to support specific OS
247 vendor string(s). Note that such command can only
248 affect the default state of the OS vendor strings, thus
249 it cannot affect the default state of the feature group
250 strings and the current state of the OS vendor strings,
251 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800252 is meaningless. This command is useful when one do not
253 care about the state of the feature group strings which
254 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800255 Examples:
256 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258 can make '_OSI("Windows 2000")' TRUE.
259
260 'acpi_osi=' cannot be used in combination with other
261 'acpi_osi=' command lines, the _OSI method will not
262 exist in the ACPI namespace. NOTE that such command can
263 only affect the _OSI support state, thus specifying it
264 multiple times through kernel command line is also
265 meaningless.
266 Examples:
267 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
268 FALSE.
269
Lv Zheng741d8122013-07-22 16:08:36 +0800270 'acpi_osi=!*' can be used in combination with single or
271 multiple 'acpi_osi="string1"' to support specific
272 string(s). Note that such command can affect the
273 current state of both the OS vendor strings and the
274 feature group strings, thus specifying it multiple times
275 through kernel command line is meaningful. But it may
276 still not able to affect the final state of a string if
277 there are quirks related to this string. This command
278 is useful when one want to control the state of the
279 feature group strings to debug BIOS issues related to
280 the OSPM features.
281 Examples:
282 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283 '_OSI("Module Device")' FALSE.
284 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285 '_OSI("Module Device")' TRUE.
286 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
287 equivalent to
288 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
289 and
290 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291 they all will make '_OSI("Windows 2000")' TRUE.
292
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530293 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700294 Override the pmtimer bug detection: force the kernel
295 to assume that this machine's pmtimer latches its value
296 and always returns good values.
297
Randy Dunlap4af94f32009-04-17 18:30:28 -0700298 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
299 Format: { level | edge | high | low }
300
301 acpi_serialize [HW,ACPI] force serialization of AML methods
302
303 acpi_skip_timer_override [HW,ACPI]
304 Recognize and ignore IRQ0/pin2 Interrupt Override.
305 For broken nForce2 BIOS resulting in XT-PIC timer.
306
307 acpi_sleep= [HW,ACPI] Sleep options
308 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b0795c2011-05-10 21:09:38 +0200309 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700310 See Documentation/power/video.txt for information on
311 s3_bios and s3_mode.
312 s3_beep is for debugging; it makes the PC's speaker beep
313 as soon as the kernel's real-mode entry point is called.
314 s4_nohwsig prevents ACPI hardware signature from being
315 used during resume from hibernation.
316 old_ordering causes the ACPI 1.0 ordering of the _PTS
317 control method, with respect to putting devices into
318 low power states, to be enforced (the ACPI 2.0 ordering
319 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200320 nonvs prevents the kernel from saving/restoring the
321 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800322 sci_force_enable causes the kernel to set SCI_EN directly
323 on resume from S1/S3 (which is against the ACPI spec,
324 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700325
326 acpi_use_timer_override [HW,ACPI]
327 Use timer override. For some broken Nvidia NF5 boards
328 that require a timer override, but don't have HPET
329
Luca Tettamanti7e905602009-03-30 00:01:27 +0200330 acpi_enforce_resources= [ACPI]
331 { strict | lax | no }
332 Check for resource conflicts between native drivers
333 and ACPI OperationRegions (SystemIO and SystemMemory
334 only). IO ports and memory declared in ACPI might be
335 used by the ACPI subsystem in arbitrary AML code and
336 can interfere with legacy drivers.
337 strict (default): access to resources claimed by ACPI
338 is denied; legacy drivers trying to access reserved
339 resources will fail to bind to device using them.
340 lax: access to resources claimed by ACPI is allowed;
341 legacy drivers trying to access reserved resources
342 will bind successfully but a warning message is logged.
343 no: ACPI OperationRegions are not marked as reserved,
344 no further checks are performed.
345
Randy Dunlap4af94f32009-04-17 18:30:28 -0700346 add_efi_memmap [EFI; X86] Include EFI memory map in
347 kernel's map of available physical RAM.
348
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700349 agp= [AGP]
350 { off | try_unsupported }
351 off: disable AGP support
352 try_unsupported: try to drive unsupported chipsets
353 (may crash computer or cause data corruption)
354
Randy Dunlapbcfde332010-06-07 17:10:38 -0700355 ALSA [HW,ALSA]
356 See Documentation/sound/alsa/alsa-parameters.txt
357
Russell Kingd944d542010-02-20 16:13:29 +0000358 alignment= [KNL,ARM]
359 Allow the default userspace alignment fault handler
360 behaviour to be specified. Bit 0 enables warnings,
361 bit 1 enables fixups, and bit 2 sends a segfault.
362
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200363 align_va_addr= [X86-64]
364 Align virtual addresses by clearing slice [14:12] when
365 allocating a VMA at process creation time. This option
366 gives you up to 3% performance improvement on AMD F15h
367 machines (where it is enabled by default) for a
368 CPU-intensive style benchmark, and it can vary highly in
369 a microbenchmark depending on workload and compiler.
370
Borislav Petkov8360ee22011-11-21 12:10:19 +0100371 32: only for 32-bit processes
372 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200373 on: enable for both 32- and 64-bit processes
374 off: disable for both 32- and 64-bit processes
375
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500376 alloc_snapshot [FTRACE]
377 Allocate the ftrace snapshot buffer on boot up when the
378 main buffer is allocated. This is handy if debugging
379 and you need to use tracing_snapshot() on boot up, and
380 do not want to use tracing_snapshot_alloc() as it needs
381 to be done where GFP_KERNEL allocations are allowed.
382
Sedat Dilek89e0b9a32011-12-05 23:08:32 +0100383 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200384 Pass parameters to the AMD IOMMU driver in the system.
385 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900386 fullflush - enable flushing of IO/TLB entries when
387 they are unmapped. Otherwise they are
388 flushed before they will be reused, which
389 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200390 off - do not initialize any AMD IOMMU found in
391 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100392 force_isolation - Force device isolation for all
393 devices. The IOMMU driver is not
394 allowed anymore to lift isolation
395 requirements as needed. This option
396 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900397
Shuah Khanc099cf12012-05-24 15:58:25 -0600398 amd_iommu_dump= [HW,X86-64]
399 Enable AMD IOMMU driver option to dump the ACPI table
400 for AMD IOMMU. With this option enabled, AMD IOMMU
401 driver will print ACPI tables for AMD IOMMU during
402 IOMMU initialization.
403
Linus Torvalds1da177e2005-04-16 15:20:36 -0700404 amijoy.map= [HW,JOY] Amiga joystick support
405 Map of devices attached to JOY0DAT and JOY1DAT
406 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200407 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408
409 analog.map= [HW,JOY] Analog joystick and gamepad support
410 Specifies type or capabilities of an analog joystick
411 connected to one of 16 gameports
412 Format: <type1>,<type2>,..<type16>
413
Randy Dunlapa9913042005-10-23 12:57:11 -0700414 apc= [HW,SPARC]
415 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416 Format: noidle
417 Disable APC CPU standby support. SPARCstation-Fox does
418 not play well with APC CPU idle - disable it if you have
419 APC and your system crashes randomly.
420
Randy Dunlapca1eda22009-05-06 16:02:58 -0700421 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700422 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423 Format: { quiet (default) | verbose | debug }
424 Change the amount of debugging information output
425 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700426
Brian Haleyb0f83b22010-02-04 13:36:50 -0800427 autoconf= [IPV6]
428 See Documentation/networking/ipv6.txt.
429
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400430 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
431 Limit apic dumping. The parameter defines the maximal
432 number of local apics being dumped. Also it is possible
433 to set it to "all" by meaning -- no limit here.
434 Format: { 1 (default) | 2 | ... | all }.
435 The parameter valid if only apic=debug or
436 apic=verbose is specified.
437 Example: apic=debug show_lapic=all
438
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700440 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700441
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443 Format: <io>,<irq>,<nodeID>
444
445 ataflop= [HW,M68k]
446
447 atarimouse= [HW,MOUSE] Atari Mouse
448
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
450 EzKey and similar keyboards
451
452 atkbd.reset= [HW] Reset keyboard during initialization
453
Randy Dunlapa9913042005-10-23 12:57:11 -0700454 atkbd.set= [HW] Select keyboard code set
455 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456
457 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
458 keyboards
459
460 atkbd.softraw= [HW] Choose between synthetic and real raw mode
461 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700462
463 atkbd.softrepeat= [HW]
464 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700465
Linus Torvalds1da177e2005-04-16 15:20:36 -0700466 baycom_epp= [HW,AX25]
467 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700468
Linus Torvalds1da177e2005-04-16 15:20:36 -0700469 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
470 Format: <io>,<mode>
471 See header of drivers/net/hamradio/baycom_par.c.
472
Randy Dunlapa9913042005-10-23 12:57:11 -0700473 baycom_ser_fdx= [HW,AX25]
474 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475 Format: <io>,<irq>,<mode>[,<baud>]
476 See header of drivers/net/hamradio/baycom_ser_fdx.c.
477
Randy Dunlapa9913042005-10-23 12:57:11 -0700478 baycom_ser_hdx= [HW,AX25]
479 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 Format: <io>,<irq>,<mode>
481 See header of drivers/net/hamradio/baycom_ser_hdx.c.
482
Paul Gortmaker080506a2013-09-30 13:45:19 -0700483 blkdevparts= Manual partition parsing of block device(s) for
484 embedded devices based on command line input.
485 See Documentation/block/cmdline-partition.txt
486
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700487 boot_delay= Milliseconds to delay each printk during boot.
488 Values larger than 10 seconds (10000) are changed to
489 no delay (0).
490 Format: integer
491
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700492 bootmem_debug [KNL] Enable bootmem allocator debug messages.
493
Linus Torvalds1da177e2005-04-16 15:20:36 -0700494 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700495 bttv.radio= Most important insmod options are available as
496 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700497 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200498 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700499
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000500 bulk_remove=off [PPC] This parameter disables the use of the pSeries
501 firmware feature for flushing multiple hpte entries
502 at a time.
503
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504 c101= [NET] Moxa C101 synchronous serial card
505
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700506 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700507 Sometimes CPU hardware bugs make them report the cache
508 size incorrectly. The kernel will attempt work arounds
509 to fix known problems, but for some CPUs it is not
510 possible to determine what the correct size should be.
511 This option provides an override for these situations.
512
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100513 ccw_timeout_log [S390]
514 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700515
Paul Menage8bab8dd2008-04-04 14:29:57 -0700516 cgroup_disable= [KNL] Disable a particular controller
517 Format: {name of the controller(s) to disable}
518 {Currently supported controllers - "memory"}
519
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520 checkreqprot [SELINUX] Set initial checkreqprot flag value.
521 Format: { "0" | "1" }
522 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700523 0 -- check protection applied by kernel (includes
524 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 1 -- check protection requested by application.
526 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700527 Value can be changed at runtime via
528 /selinux/checkreqprot.
529
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100530 cio_ignore= [S390]
531 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700532 clk_ignore_unused
533 [CLK]
534 Keep all clocks already enabled by bootloader on,
535 even if no driver has claimed them. This is useful
536 for debug and development, but should not be
537 needed on a platform with proper driver support.
538 For more information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100539
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700540 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700541 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200542 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700543 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200544 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545 Format: { pit | tsc | cyclone | pmtmr }
546
John Stultz592913e2010-07-13 17:56:20 -0700547 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700548 Format: <string>
549 Override the default clocksource and use the clocksource
550 with the name specified.
551 Some clocksource names to choose from, depending on
552 the platform:
553 [all] jiffies (this is the base, fallback clocksource)
554 [ACPI] acpi_pm
555 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
556 pxa_timer,timer3,32k_counter,timer0_1
557 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700558 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700559 scx200_hrt on Geode; cyclone on IBM x440
560 [MIPS] MIPS
561 [PARISC] cr16
562 [S390] tod
563 [SH] SuperH
564 [SPARC64] tick
565 [X86-64] hpet,tsc
566
Andi Kleenac72e782008-01-30 13:33:21 +0100567 clearcpuid=BITNUM [X86]
568 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800569 arch/x86/include/asm/cpufeature.h for the valid bit
570 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100571 stable over kernel options, but the vendor specific
572 ones should be.
573 Also note that user programs calling CPUID directly
574 or using the feature without checking anything
575 will still see it. This just prevents it from
576 being used by the kernel or shown in /proc/cpuinfo.
577 Also note the kernel might malfunction if you disable
578 some critical bits.
579
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100580 cma=nn[MG] [ARM,KNL]
581 Sets the size of kernel global memory area for contiguous
582 memory allocations. For more information, see
583 include/linux/dma-contiguous.h
584
Robert Jennings14f966e2009-04-15 05:55:32 +0000585 cmo_free_hint= [PPC] Format: { yes | no }
586 Specify whether pages are marked as being inactive
587 when they are freed. This is used in CMO environments
588 to determine OS memory pressure for page stealing by
589 a hypervisor.
590 Default: yes
591
Marek Szyprowskic7909502011-12-29 13:09:51 +0100592 coherent_pool=nn[KMG] [ARM,KNL]
593 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200594 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100595
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530596 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100597 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100598 Range: 0 - 8192
599 Default: 64
600
Linus Torvalds1da177e2005-04-16 15:20:36 -0700601 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700602 Format:
603 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700604
605 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
606 Format: <io>[,<irq>]
607
Randy Dunlapa9913042005-10-23 12:57:11 -0700608 com90xx= [HW,NET]
609 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610 Format: <io>[,<irq>[,<memstart>]]
611
612 condev= [HW,S390] console device
613 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700614
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615 console= [KNL] Output console device and options.
616
617 tty<n> Use the virtual console device <n>.
618
619 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800620 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700621 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800622 the form "bbbbpnf", where "bbbb" is the baud rate,
623 "p" is parity ("n", "o", or "e"), "n" is number of
624 bits, and "f" is flow control ("r" for RTS or
625 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700626
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800627 See Documentation/serial-console.txt for more
628 information. See
629 Documentation/networking/netconsole.txt for an
630 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700632 uart[8250],io,<addr>[,options]
633 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700634 Start an early, polled-mode console on the 8250/16550
635 UART at the specified I/O port or MMIO address,
636 switching to the matching ttyS device later. The
637 options are the same as for ttyS, above.
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500638 hvc<n> Use the hypervisor console device <n>. This is for
639 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700640
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700641 If the device connected to the port is not a TTY but a braille
642 device, prepend "brl," before the device type, for instance
643 console=brl,ttyS0
644 For now, only VisioBraille is supported.
645
Daniel Mackf324edc2009-06-16 15:33:52 -0700646 consoleblank= [KNL] The console blank (screen saver) timeout in
647 seconds. Defaults to 10*60 = 10mins. A value of 0
648 disables the blank timer.
649
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800650 coredump_filter=
651 [KNL] Change the default value for
652 /proc/<pid>/coredump_filter.
653 See also Documentation/filesystems/proc.txt.
654
Len Brown62027ae2011-04-01 18:13:10 -0400655 cpuidle.off=1 [CPU_IDLE]
656 disable the cpuidle sub-system
657
Linus Torvalds1da177e2005-04-16 15:20:36 -0700658 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700659 Format:
660 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700661
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800662 crashkernel=size[KMG][@offset[KMG]]
663 [KNL] Using kexec, Linux can switch to a 'crash kernel'
664 upon panic. This parameter reserves the physical
665 memory region [offset, offset + size] for that kernel
666 image. If '@offset' is omitted, then a suitable offset
667 is selected automatically. Check
668 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700669
Bernhard Wallefb391592007-10-18 23:41:02 -0700670 crashkernel=range1:size1[,range2:size2,...][@offset]
671 [KNL] Same as above, but depends on the memory
672 in the running system. The syntax of range is
673 start-[end] where start and end are both
674 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800675 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700676
Yinghai Luadbc7422013-04-15 22:23:48 -0700677 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700678 [KNL, x86_64] range could be above 4G. Allow kernel
679 to allocate physical memory region from top, so could
680 be above 4G if system have more than 4G ram installed.
681 Otherwise memory region will be allocated below 4G, if
682 available.
683 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700684 crashkernel=size[KMG],low
685 [KNL, x86_64] range under 4G. When crashkernel=X,high
686 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700687 above 4G, that cause second kernel crash on system
688 that require some amount of low memory, e.g. swiotlb
689 requires at least 64M+32K low memory. Kernel would
690 try to allocate 72M below 4G automatically.
691 This one let user to specify own low range under 4G
692 for second kernel instead.
693 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700694 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700695 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700696
Linus Torvalds1da177e2005-04-16 15:20:36 -0700697 cs89x0_dma= [HW,NET]
698 Format: <dma>
699
700 cs89x0_media= [HW,NET]
701 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700702
Randy Dunlapa9913042005-10-23 12:57:11 -0700703 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704 See header of drivers/s390/block/dasd_devmap.c.
705
706 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
707 (one device per port)
708 Format: <port#>,<type>
709 See also Documentation/input/joystick-parport.txt
710
Thomas Renningera648ec02010-08-06 16:11:02 +0200711 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
712 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600713 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200714
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715 debug [KNL] Enable kernel debugging (events log level).
716
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700717 debug_locks_verbose=
718 [KNL] verbose self-tests
719 Format=<0|1>
720 Print debugging info while doing the locking API
721 self-tests.
722 We default to 0 (no extra messages), setting it to
723 1 will print _a lot_ more information - normally
724 only useful to kernel developers.
725
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700726 debug_objects [KNL] Enable object debugging
727
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500728 no_debug_objects
729 [KNL] Disable object debugging
730
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800731 debug_guardpage_minorder=
732 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
733 parameter allows control of the order of pages that will
734 be intentionally kept free (and hence protected) by the
735 buddy allocator. Bigger value increase the probability
736 of catching random memory corruption, but reduce the
737 amount of memory for normal system use. The maximum
738 possible value is MAX_ORDER/2. Setting this parameter
739 to 1 or 2 should be enough to identify most random
740 memory corruption problems caused by bugs in kernel or
741 driver code when a CPU writes to (or reads from) a
742 random memory location. Note that there exists a class
743 of memory corruptions problems caused by buggy H/W or
744 F/W or by drivers badly programing DMA (basically when
745 memory is written at bus level and the CPU MMU is
746 bypassed) which are not detectable by
747 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
748 tracking down these problems.
749
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200750 debugpat [X86] Enable PAT debugging
751
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200752 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700753 Format: <area>[,<node>]
754 See also Documentation/networking/decnet.txt.
755
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700756 default_hugepagesz=
757 [same as hugepagesz=] The size of the default
758 HugeTLB page size. This is the size represented by
759 the legacy /proc/ hugepages APIs, used for SHM, and
760 default size when mounting hugetlbfs filesystems.
761 Defaults to the default architecture's huge page size
762 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700763
Linus Torvalds1da177e2005-04-16 15:20:36 -0700764 dhash_entries= [KNL]
765 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700766
Linus Torvalds1da177e2005-04-16 15:20:36 -0700767 digi= [HW,SERIAL]
768 IO parameters + enable/disable command.
769
770 digiepca= [HW,SERIAL]
771 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000772 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773
Brian Haleyb0f83b22010-02-04 13:36:50 -0800774 disable= [IPV6]
775 See Documentation/networking/ipv6.txt.
776
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900777 disable_cpu_apicid= [X86,APIC,SMP]
778 Format: <int>
779 The number of initial APIC ID for the
780 corresponding CPU to be disabled at boot,
781 mostly used for the kdump 2nd kernel to
782 disable BSP to wake up multiple CPUs without
783 causing system reset or hang due to sending
784 INIT from AP to BSP.
785
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000786 disable_ddw [PPC/PSERIES]
787 Disable Dynamic DMA Window support. Use this if
788 to workaround buggy firmware.
789
Brian Haleyb0f83b22010-02-04 13:36:50 -0800790 disable_ipv6= [IPV6]
791 See Documentation/networking/ipv6.txt.
792
Yinghai Lu95ffa242008-04-29 03:52:33 -0700793 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700794 The kernel tries to adjust MTRR layout from continuous
795 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700796 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700797
Yinghai Lu093af8d2008-01-30 13:33:32 +0100798 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100799 By default the kernel will trim any uncacheable
800 memory out of your available memory pool based on
801 MTRR settings. This parameter disables that behavior,
802 possibly causing your machine to run very slowly.
803
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530804 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700805 Disable PIN 1 of APIC timer
806 Can be useful to work around chipset bugs.
807
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700808 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
809 this option disables the debugging code at boot.
810
811 dma_debug_entries=<number>
812 This option allows to tune the number of preallocated
813 entries for DMA-API debugging code. One entry is
814 required per DMA-API allocation. Use this if the
815 DMA-API debugging code disables itself because the
816 architectural default is too low.
817
Joerg Roedel1745de52009-05-22 21:49:51 +0200818 dma_debug_driver=<driver_name>
819 With this option the DMA-API debugging driver
820 filter feature can be enabled at boot time. Just
821 pass the driver to filter for as the parameter.
822 The filter can be disabled or changed to another
823 driver later using sysfs.
824
Carsten Emdeda0df922012-03-18 22:37:33 +0100825 drm_kms_helper.edid_firmware=[<connector>:]<file>
826 Broken monitors, graphic adapters and KVMs may
827 send no or incorrect EDID data sets. This parameter
828 allows to specify an EDID data set in the
829 /lib/firmware directory that is used instead.
830 Generic built-in EDID data sets are used, if one of
831 edid/1024x768.bin, edid/1280x1024.bin,
832 edid/1680x1050.bin, or edid/1920x1080.bin is given
833 and no file with the same name exists. Details and
834 instructions how to build your own EDID data are
835 available in Documentation/EDID/HOWTO.txt. An EDID
836 data set will only be used for a particular connector,
837 if its name and a colon are prepended to the EDID
838 name.
839
Linus Torvalds1da177e2005-04-16 15:20:36 -0700840 dscc4.setup= [NET]
841
Jim Cromie29e36c92012-04-27 14:30:41 -0600842 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
843 module.dyndbg[="val"]
844 Enable debug messages at boot time. See
845 Documentation/dynamic-debug-howto.txt for details.
846
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700847 earlycon= [KNL] Output early console device and options.
848 uart[8250],io,<addr>[,options]
849 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700850 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700851 Start an early, polled-mode console on the 8250/16550
852 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700853 MMIO inter-register address stride is either 8-bit
854 (mmio) or 32-bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700855 The options are the same as for ttyS, above.
856
Dave Hansen147ea092013-04-10 14:03:38 -0700857 earlyprintk= [X86,SH,BLACKFIN,ARM]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700858 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +0100859 earlyprintk=efi
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500860 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700861 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -0700862 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500863 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500864 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700865
Dave Hansen147ea092013-04-10 14:03:38 -0700866 earlyprintk is useful when the kernel crashes before
867 the normal console is initialized. It is not enabled by
868 default because it has some cosmetic problems.
869
Randy Dunlapa9913042005-10-23 12:57:11 -0700870 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700871 takes over.
872
Matt Fleming72548e82013-10-04 09:36:56 +0100873 Only one of vga, efi, serial, or usb debug port can
874 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875
Dave Hansen147ea092013-04-10 14:03:38 -0700876 Currently only ttyS0 and ttyS1 may be specified by
877 name. Other I/O ports may be explicitly specified
878 on some architectures (x86 and arm at least) by
879 replacing ttySn with an I/O port address, like this:
880 earlyprintk=serial,0x1008,115200
881 You can find the port for a given device in
882 /proc/tty/driver/serial:
883 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -0700884
885 Interaction with the standard serial driver is not
886 very good.
887
Matt Fleming72548e82013-10-04 09:36:56 +0100888 The VGA and EFI output is eventually overwritten by
889 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500891 The xen output can only be used by Xen PV guests.
892
Chen, Gongc700f012013-12-06 01:17:08 -0500893 edac_report= [HW,EDAC] Control how to report EDAC event
894 Format: {"on" | "off" | "force"}
895 on: enable EDAC to report H/W event. May be overridden
896 by other higher priority error reporting module.
897 off: disable H/W event reporting through EDAC.
898 force: enforce the use of EDAC to report H/W event.
899 default: on.
900
Jason Wessel97311912010-05-20 21:04:30 -0500901 ekgdboc= [X86,KGDB] Allow early kernel console debugging
902 ekgdboc=kbd
903
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300904 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -0500905 the boot argument: earlyprintk=vga
906
Linus Torvalds1da177e2005-04-16 15:20:36 -0700907 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700908 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700909
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +0100910 efi= [EFI]
911 Format: { "old_map" }
912 old_map [X86-64]: switch to the old ioremap-based EFI
913 runtime services mapping. 32-bit still uses this one by
914 default.
915
Richard Weinberger8c58bf32013-04-17 01:00:53 +0200916 efi_no_storage_paranoia [EFI; X86]
917 Using this parameter you can use more than 50% of
918 your efi variable storage. Use this parameter only if
919 you are really sure that your UEFI does sane gc and
920 fulfills the spec otherwise your board may brick.
921
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922 eisa_irq_edge= [PARISC,HW]
923 See header of drivers/parisc/eisa.c.
924
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700925 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700926 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700927 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700928
929 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +0100930 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +0200931 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -0700932 Documentation/block/deadline-iosched.txt for details.
933
Michael Holzheud3bf37952011-10-30 15:16:37 +0100934 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -0700935 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +0100936 image elf header and optionally the size. Generally
937 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -0800938 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700939
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700940 enable_mtrr_cleanup [X86]
941 The kernel tries to adjust MTRR layout from continuous
942 to discrete, to make X server driver able to add WB
943 entry later. This parameter enables that.
944
Randy Dunlapca1eda22009-05-06 16:02:58 -0700945 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700946 Enable PIN 1 of APIC timer
947 Can be useful to work around chipset bugs
948 (in particular on some ATI chipsets).
949 The kernel tries to set a reasonable default.
950
Linus Torvalds1da177e2005-04-16 15:20:36 -0700951 enforcing [SELINUX] Set initial enforcing status.
952 Format: {"0" | "1"}
953 See security/selinux/Kconfig help text.
954 0 -- permissive (log only, no denials).
955 1 -- enforcing (deny and log).
956 Default value is 0.
957 Value can be changed at runtime via /selinux/enforce.
958
Huang Yinga08f82d2010-05-18 14:35:21 +0800959 erst_disable [ACPI]
960 Disable Error Record Serialization Table (ERST)
961 support.
962
Linus Torvalds1da177e2005-04-16 15:20:36 -0700963 ether= [HW,NET] Ethernet cards parameters
964 This option is obsoleted by the "netdev=" option, which
965 has equivalent usage. See its documentation for details.
966
Mimi Zohar7102ebc2011-05-12 18:33:20 -0400967 evm= [EVM]
968 Format: { "fix" }
969 Permit 'security.evm' to be updated regardless of
970 current integrity status.
971
Akinobu Mitade1ba092006-12-08 02:39:42 -0800972 failslab=
973 fail_page_alloc=
974 fail_make_request=[KNL]
975 General fault injection mechanism.
976 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +0200977 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -0800978
Linus Torvalds1da177e2005-04-16 15:20:36 -0700979 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000980 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700981
Alex Chiangf13ae302008-05-08 14:03:23 -0600982 force_pal_cache_flush
983 [IA-64] Avoid check_sal_cache_flush which may hang on
984 buggy SAL_CACHE_FLUSH implementations. Using this
985 parameter will force ia64_sal_cache_flush to call
986 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
987
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100988 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400989 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100990 as early as possible in order to facilitate early
991 boot debugging.
992
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200993 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400994 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200995 If no parameter is passed, ftrace will dump
996 buffers of all CPUs, but if you pass orig_cpu, it will
997 dump only the buffer of the CPU that triggered the
998 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400999
1000 ftrace_filter=[function-list]
1001 [FTRACE] Limit the functions traced by the function
1002 tracer at boot up. function-list is a comma separated
1003 list of functions. This list can be changed at run
1004 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001005 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001006
1007 ftrace_notrace=[function-list]
1008 [FTRACE] Do not trace the functions specified in
1009 function-list. This list can be changed at run time
1010 by the set_ftrace_notrace file in the debugfs
1011 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001012
Stefan Assmann369bc182009-10-12 22:17:21 +02001013 ftrace_graph_filter=[function-list]
1014 [FTRACE] Limit the top level callers functions traced
1015 by the function graph tracer at boot up.
1016 function-list is a comma separated list of functions
1017 that can be changed at run time by the
1018 set_graph_function file in the debugfs tracing directory.
1019
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020 gamecon.map[2|3]=
1021 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1022 support via parallel port (up to 5 devices per port)
1023 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1024 See also Documentation/input/joystick-parport.txt
1025
1026 gamma= [HW,DRM]
1027
Yinghai Luaaf23042008-01-30 13:33:09 +01001028 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1029 Format: off | on
1030 default: on
1031
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001032 gcov_persist= [GCOV] When non-zero (default), profiling data for
1033 kernel modules is saved and remains accessible via
1034 debugfs, even when the module is unloaded/reloaded.
1035 When zero, profiling data is discarded and associated
1036 debugfs files are removed at module unload time.
1037
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038 gpt [EFI] Forces disk with valid GPT signature but
1039 invalid Protective MBR to be treated as GPT.
1040
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001041 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1042 the "Enable 0" bit of the configuration register.
1043 Format: 0 | 1
1044 Default: 0
1045 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1046 the "Enable 0" bit of the configuration register.
1047 Format: 0 | 1
1048 Default: 0
1049 grcan.select= [HW] Select which physical interface to use.
1050 Format: 0 | 1
1051 Default: 0
1052 grcan.txsize= [HW] Sets the size of the tx buffer.
1053 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1054 Default: 1024
1055 grcan.rxsize= [HW] Sets the size of the rx buffer.
1056 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1057 Default: 1024
1058
Linus Torvalds1da177e2005-04-16 15:20:36 -07001059 hashdist= [KNL,NUMA] Large hashes allocated during boot
1060 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001061 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001062 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001063
1064 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1065
1066 hd= [EIDE] (E)IDE hard drive subsystem geometry
1067 Format: <cyl>,<head>,<sect>
1068
Huang Yingea8c0712010-05-18 14:35:15 +08001069 hest_disable [ACPI]
1070 Disable Hardware Error Source Table (HEST) support;
1071 corresponding firmware-first mode error processing
1072 logic will be disabled.
1073
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1075 size of <nn>. This works even on boxes that have no
1076 highmem otherwise. This also works to reduce highmem
1077 size on bigger boxes.
1078
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001079 highres= [KNL] Enable/disable high resolution timer mode.
1080 Valid parameters: "on", "off"
1081 Default: "on"
1082
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083 hisax= [HW,ISDN]
1084 See Documentation/isdn/README.HiSax.
1085
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001086 hlt [BUGS=ARM,SH]
1087
1088 hpet= [X86-32,HPET] option to control HPET usage
1089 Format: { enable (default) | disable | force |
1090 verbose }
1091 disable: disable HPET and use PIT instead
1092 force: allow force enabled of undocumented chips (ICH4,
1093 VIA, nVidia)
1094 verbose: show contents of HPET registers during setup
1095
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001096 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1097 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1098
Andi Kleenb4718e62008-07-23 21:27:51 -07001099 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1100 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001101 On x86-64 and powerpc, this option can be specified
1102 multiple times interleaved with hugepages= to reserve
1103 huge pages of different sizes. Valid pages sizes on
1104 x86-64 are 2M (when the CPU supports "pse") and 1G
1105 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -07001106 Note that 1GB pages can only be allocated at boot time
1107 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +09001108
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001109 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1110 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001111 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1112 If specified, z/VM IUCV HVC accepts connections
1113 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001114
James Hoganfdabf522012-10-09 11:00:27 +01001115 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1116 hardware thread id mappings.
1117 Format: <cpu>:<hwthread>
1118
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001119 keep_bootcon [KNL]
1120 Do not unregister boot console at start. This is only
1121 useful for debugging when something happens in the window
1122 between unregistering the boot console and initializing
1123 the real console.
1124
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001125 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001126 or register an additional I2C bus that is not
1127 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001128 Format:
1129 <bus_id>,<clkrate>
1130
Jiri Kosina36d95732008-10-06 02:51:09 -04001131 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001133 i8042.dumbkbd [HW] Pretend that controller can only read data from
1134 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001135 (Don't attempt to blink the leds)
1136 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001137 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001138 i8042.noloop [HW] Disable the AUX Loopback command while probing
1139 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001140 i8042.nomux [HW] Don't check presence of an active multiplexing
1141 controller
1142 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1143 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001144 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145 i8042.reset [HW] Reset the controller during init and cleanup
1146 i8042.unlock [HW] Unlock (ignore) the keylock
1147
1148 i810= [HW,DRM]
1149
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001150 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1151 indicates that the driver is running on unsupported
1152 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001153 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1154 does not match list of supported models.
1155 i8k.power_status
1156 [HW] Report power status in /proc/i8k
1157 (disabled by default)
1158 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1159 capability is set.
1160
Carsten Emde4dca20e2012-03-15 15:56:26 +01001161 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001162 [DRM] Invert the sense of the variable that is used to
1163 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001164 brightness value of 0 indicates backlight switched off,
1165 and the maximum of the brightness value sets the backlight
1166 to maximum brightness. If this parameter is set to 0
1167 (default) and the machine requires it, or this parameter
1168 is set to 1, a brightness value of 0 sets the backlight
1169 to maximum brightness, and the maximum of the brightness
1170 value switches the backlight off.
1171 -1 -- never invert brightness
1172 0 -- machine default
1173 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001174
Linus Torvalds1da177e2005-04-16 15:20:36 -07001175 icn= [HW,ISDN]
1176 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1177
David Fries0af80c02009-02-25 20:28:21 +01001178 ide-core.nodma= [HW] (E)IDE subsystem
1179 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001180 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1181 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001182 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001183
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001184 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1185 Claim all unknown PCI IDE storage controllers.
1186
Andi Kleenf039b752007-05-02 19:27:12 +02001187 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001188 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001189 Poll forces a polling idle loop that can slightly
1190 improve the performance of waking up a idle CPU, but
1191 will use a lot of power and make the system run hot.
1192 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001193 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001194 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001195 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001196
Ingo Molnar792908222006-12-06 20:40:51 -08001197 ignore_loglevel [KNL]
1198 Ignore loglevel setting - this will print /all/
1199 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001200 We also add it as printk module parameter, so users
1201 could change it dynamically, usually by
1202 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001203
Linus Torvalds1da177e2005-04-16 15:20:36 -07001204 ihash_entries= [KNL]
1205 Set number of hash buckets for inode cache.
1206
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001207 ima_appraise= [IMA] appraise integrity measurements
1208 Format: { "off" | "enforce" | "fix" }
1209 default: "enforce"
1210
Mimi Zohar07f6a792011-03-09 22:25:48 -05001211 ima_appraise_tcb [IMA]
1212 The builtin appraise policy appraises all files
1213 owned by uid=0.
1214
Mimi Zohar3323eec2009-02-04 09:06:58 -05001215 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001216 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1217 | sha512 | ... }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001218 default: "sha1"
1219
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001220 The list of supported hash algorithms is defined
1221 in crypto/hash_info.h.
1222
Eric Paris5789ba32009-05-21 15:47:06 -04001223 ima_tcb [IMA]
1224 Load a policy which meets the needs of the Trusted
1225 Computing Base. This means IMA will measure all
1226 programs exec'd, files mmap'd for exec, and all files
1227 opened for read by uid=0.
1228
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001229 ima_template= [IMA]
1230 Select one of defined IMA measurements template formats.
1231 Formats: { "ima" | "ima-ng" }
1232 Default: "ima-ng"
1233
Linus Torvalds1da177e2005-04-16 15:20:36 -07001234 init= [KNL]
1235 Format: <full_path>
1236 Run specified binary instead of /sbin/init as init
1237 process.
1238
1239 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1240 for working out where the kernel is dying during
1241 startup.
1242
1243 initrd= [BOOT] Specify the location of the initial ramdisk
1244
1245 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1246 Format: <irq>
1247
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001248 int_pln_enable [x86] Enable power limit notification interrupt
1249
Mimi Zohard726d8d2013-03-18 14:48:02 -04001250 integrity_audit=[IMA]
1251 Format: { "0" | "1" }
1252 0 -- basic integrity auditing messages. (Default)
1253 1 -- additional integrity auditing messages.
1254
Keshavamurthy, Anil Sba3959272007-10-21 16:41:49 -07001255 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001256 on
1257 Enable intel iommu driver.
Keshavamurthy, Anil Sba3959272007-10-21 16:41:49 -07001258 off
1259 Disable intel iommu driver.
1260 igfx_off [Default Off]
1261 By default, gfx is mapped as normal device. If a gfx
1262 device has a dedicated DMAR unit, the DMAR unit is
1263 bypassed by not enabling DMAR with this option. In
1264 this case, gfx device will use physical address for
1265 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001266 forcedac [x86_64]
1267 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001268 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001269 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001270 than 32-bit addressing. The default is to look
1271 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001272 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001273 strict [Default Off]
1274 With this option on every unmap_single operation will
1275 result in a hardware IOTLB flush operation as opposed
1276 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001277 sp_off [Default Off]
1278 By default, super page will be supported if Intel IOMMU
1279 has the capability. With this option, super page will
1280 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001281
1282 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1283 0 disables intel_idle and fall back on acpi_idle.
1284 1 to 6 specify maximum depth of C-state.
1285
Dirk Brandewie6be26492013-02-15 22:55:10 +01001286 intel_pstate= [X86]
1287 disable
1288 Do not enable intel_pstate as the default
1289 scaling driver for the supported processors
1290
Chris Wrightd1423d52010-07-20 11:06:49 -07001291 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001292 on enable Interrupt Remapping (default)
1293 off disable Interrupt Remapping
1294 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001295 no_x2apic_optout
1296 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001297
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001298 iomem= Disable strict checking of access to MMIO memory
1299 strict regions from userspace.
1300 relaxed
1301
1302 iommu= [x86]
1303 off
1304 force
1305 noforce
1306 biomerge
1307 panic
1308 nopanic
1309 merge
1310 nomerge
1311 forcesac
1312 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001313 pt [x86, IA-64]
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001314
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001315
1316 io7= [HW] IO7 for Marvel based alpha systems
1317 See comment before marvel_specify_io7 in
1318 arch/alpha/kernel/core_marvel.c.
1319
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301320 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001321 0x80
1322 Standard port 0x80 based delay
1323 0xed
1324 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001325 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001326 Simple two microseconds delay
1327 none
1328 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001329
Linus Torvalds1da177e2005-04-16 15:20:36 -07001330 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001331 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332
1333 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001334 See comment before ip2_setup() in
1335 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001336
Alan Cox200803d2005-06-28 20:45:18 -07001337 irqfixup [HW]
1338 When an interrupt is not handled search all handlers
1339 for it. Intended to get systems with badly broken
1340 firmware running.
1341
1342 irqpoll [HW]
1343 When an interrupt is not handled search all handlers
1344 for it. Also check all handlers each timer
1345 interrupt. Intended to get systems with badly broken
1346 firmware running.
1347
Linus Torvalds1da177e2005-04-16 15:20:36 -07001348 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001349 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001350
1351 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001352 Format:
1353 <cpu number>,...,<cpu number>
1354 or
Li Zefanb225d442008-11-06 12:53:39 -08001355 <cpu number>-<cpu number>
1356 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001357 or a mixture
1358 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001359
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360 This option can be used to specify one or more CPUs
1361 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001362 algorithms. You can move a process onto or off an
1363 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001364 <cpu number> begins at 0 and the maximum value is
1365 "number of CPUs in system - 1".
1366
1367 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001368 alternative -- manually setting the CPU mask of all
1369 tasks in the system -- can cause problems and
1370 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371
Randy Dunlapa9913042005-10-23 12:57:11 -07001372 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001373
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001374 ivrs_ioapic [HW,X86_64]
1375 Provide an override to the IOAPIC-ID<->DEVICE-ID
1376 mapping provided in the IVRS ACPI table. For
1377 example, to map IOAPIC-ID decimal 10 to
1378 PCI device 00:14.0 write the parameter as:
1379 ivrs_ioapic[10]=00:14.0
1380
1381 ivrs_hpet [HW,X86_64]
1382 Provide an override to the HPET-ID<->DEVICE-ID
1383 mapping provided in the IVRS ACPI table. For
1384 example, to map HPET-ID decimal 0 to
1385 PCI device 00:14.0 write the parameter as:
1386 ivrs_hpet[0]=00:14.0
1387
Linus Torvalds1da177e2005-04-16 15:20:36 -07001388 js= [HW,JOY] Analog joystick
1389 See Documentation/input/joystick.txt.
1390
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001391 keepinitrd [HW,ARM]
1392
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301393 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001394 specifies the amount of memory usable by the kernel
1395 for non-movable allocations. The requested amount is
1396 spread evenly throughout all nodes in the system. The
1397 remaining memory in each node is used for Movable
1398 pages. In the event, a node is too small to have both
1399 kernelcore and Movable pages, kernelcore pages will
1400 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001401 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001402 allocation of pages that may be reclaimed or moved
1403 by the page migration subsystem. This means that
1404 HugeTLB pages may not be allocated from this zone.
1405 Note that allocations like PTEs-from-HighMem still
1406 use the HighMem zone if it exists, and the Normal
1407 zone if it does not.
1408
Jason Wessel4fe1da42010-05-20 21:04:31 -05001409 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1410 Format: <Controller#>[,poll interval]
1411 The controller # is the number of the ehci usb debug
1412 port as it is probed via PCI. The poll interval is
1413 optional and is the number seconds in between
1414 each poll cycle to the debug port in case you need
1415 the functionality for interrupting the kernel with
1416 gdb or control-c on the dbgp connection. When
1417 not using this parameter you use sysrq-g to break into
1418 the kernel debugger.
1419
Jason Wessel84c08fd62010-05-20 21:04:24 -05001420 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001421 Requires a tty driver that supports console polling,
1422 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001423 Serial only format: <serial_device>[,baud]
1424 keyboard only format: kbd
1425 keyboard and serial format: kbd,<serial_device>[,baud]
1426 Optional Kernel mode setting:
1427 kms, kbd format: kms,kbd
1428 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001429
Jason Wessel84c08fd62010-05-20 21:04:24 -05001430 kgdbwait [KGDB] Stop kernel execution and enter the
1431 kernel debugger at the earliest opportunity.
1432
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001433 kmac= [MIPS] korina ethernet MAC address.
1434 Configure the RouterBoard 532 series on-chip
1435 Ethernet adapter MAC address.
1436
Catalin Marinas04f70332009-06-11 13:22:39 +01001437 kmemleak= [KNL] Boot-time kmemleak enable/disable
1438 Valid arguments: on, off
1439 Default: on
1440
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301441 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001442 in oops dumps.
1443
Andre Przywarafef07aa2009-07-10 14:20:35 +02001444 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1445 Default is 0 (don't ignore, but inject #GP)
1446
Xiao Guangronga182d872010-09-20 22:17:48 +08001447 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1448 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001449 Default is 0 (off)
1450
Andre Przywarafef07aa2009-07-10 14:20:35 +02001451 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001452 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001453
1454 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1455 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001456 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001457
Andre Przywarafef07aa2009-07-10 14:20:35 +02001458 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1459 (virtualized MMU) support on capable Intel chips.
1460 Default is 1 (enabled)
1461
1462 kvm-intel.emulate_invalid_guest_state=
1463 [KVM,Intel] Enable emulation of invalid guest states
1464 Default is 0 (disabled)
1465
1466 kvm-intel.flexpriority=
1467 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1468 Default is 1 (enabled)
1469
Sasha Levine1a72ae2011-08-09 14:28:35 +03001470 kvm-intel.nested=
1471 [KVM,Intel] Enable VMX nesting (nVMX).
1472 Default is 0 (disabled)
1473
Andre Przywarafef07aa2009-07-10 14:20:35 +02001474 kvm-intel.unrestricted_guest=
1475 [KVM,Intel] Disable unrestricted guest feature
1476 (virtualized real and unpaged mode) on capable
1477 Intel chips. Default is 1 (enabled)
1478
1479 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1480 feature (tagged TLBs) on capable Intel chips.
1481 Default is 1 (enabled)
1482
Linus Torvalds1da177e2005-04-16 15:20:36 -07001483 l2cr= [PPC]
1484
Robert Brosea78bfbf2008-03-29 07:20:23 +11001485 l3cr= [PPC]
1486
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001487 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001488 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489
Suresh Siddha279f1462012-10-22 14:37:58 -07001490 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1491 value for LAPIC timer one-shot implementation. Default
1492 back to the programmable timer unit in the LAPIC.
1493
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301494 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001495 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001496
FD Camifcb71f62008-01-06 19:08:56 +01001497 libata.dma= [LIBATA] DMA control
1498 libata.dma=0 Disable all PATA and SATA DMA
1499 libata.dma=1 PATA and SATA Disk DMA only
1500 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001501 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001502 Combinations also work, so libata.dma=3 enables DMA
1503 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001504
Michael Prokop20308872009-08-06 00:14:10 +02001505 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1506 libata.ignore_hpa=0 keep BIOS limits (default)
1507 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001508
Dave Jones78e70c22007-09-27 11:50:13 -04001509 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1510 when set.
1511 Format: <int>
1512
Tejun Heo33267322008-02-13 09:15:09 +09001513 libata.force= [LIBATA] Force configurations. The format is comma
1514 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001515 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001516 matching port, link or device. Basically, it matches
1517 the ATA ID string printed on console by libata. If
1518 the whole ID part is omitted, the last PORT and DEVICE
1519 values are used. If ID hasn't been specified yet, the
1520 configuration applies to all ports, links and devices.
1521
1522 If only DEVICE is omitted, the parameter applies to
1523 the port and all links and devices behind it. DEVICE
1524 number of 0 either selects the first device or the
1525 first fan-out link behind PMP device. It does not
1526 select the host link. DEVICE number of 15 selects the
1527 host link and device attached to it.
1528
1529 The VAL specifies the configuration to force. As long
1530 as there's no ambiguity shortcut notation is allowed.
1531 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1532 The following configurations can be forced.
1533
1534 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1535 Any ID with matching PORT is used.
1536
1537 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1538
1539 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1540 udma[/][16,25,33,44,66,100,133] notation is also
1541 allowed.
1542
1543 * [no]ncq: Turn on or off NCQ.
1544
Tejun Heo05944bd2008-08-13 20:19:09 +09001545 * nohrst, nosrst, norst: suppress hard, soft
1546 and both resets.
1547
Dan Williamsca6d43b2012-06-21 23:41:41 -07001548 * rstonce: only attempt one reset during
1549 hot-unplug link recovery
1550
Tejun Heo43c9c592010-05-23 12:59:11 +02001551 * dump_id: dump IDENTIFY data.
1552
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001553 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1554
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001555 * disable: Disable this device.
1556
Tejun Heo33267322008-02-13 09:15:09 +09001557 If there are multiple matching configurations changing
1558 the same attribute, the last one is used.
1559
Yinghai Lu95f72d12010-07-12 14:36:09 +10001560 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001561
Linus Torvalds1da177e2005-04-16 15:20:36 -07001562 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001563 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001564
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001565 lockd.nlm_grace_period=P [NFS] Assign grace period.
1566 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001567
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001568 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1569 Format: <integer>
1570
1571 lockd.nlm_timeout=T [NFS] Assign timeout value.
1572 Format: <integer>
1573
1574 lockd.nlm_udpport=M [NFS] Assign UDP port.
1575 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001576
1577 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1578 Format: <irq>
1579
1580 loglevel= All Kernel Messages with a loglevel smaller than the
1581 console loglevel will be printed to the console. It can
1582 also be changed with klogd or other programs. The
1583 loglevels are defined as follows:
1584
1585 0 (KERN_EMERG) system is unusable
1586 1 (KERN_ALERT) action must be taken immediately
1587 2 (KERN_CRIT) critical conditions
1588 3 (KERN_ERR) error conditions
1589 4 (KERN_WARNING) warning conditions
1590 5 (KERN_NOTICE) normal but significant condition
1591 6 (KERN_INFO) informational
1592 7 (KERN_DEBUG) debug-level messages
1593
Randy Dunlapc756d082011-02-20 20:08:35 -08001594 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1595 in bytes. n must be a power of two. The default
1596 size is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001597
Randy Dunlapaccaa242007-10-16 01:29:37 -07001598 logo.nologo [FB] Disables display of the built-in Linux logo.
1599 This may be used to provide more screen space for
1600 kernel log messages and is useful when debugging
1601 kernel boot problems.
1602
Linus Torvalds1da177e2005-04-16 15:20:36 -07001603 lp=0 [LP] Specify parallel ports to use, e.g,
1604 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1605 lp=reset first parallel port). 'lp=0' disables the
1606 lp=auto printer driver. 'lp=reset' (which can be
1607 specified in addition to the ports) causes
1608 attached printers to be reset. Using
1609 lp=port1,port2,... specifies the parallel ports
1610 to associate lp devices with, starting with
1611 lp0. A port specification may be 'none' to skip
1612 that lp device, or a parport name such as
1613 'parport0'. Specifying 'lp=auto' instead of a
1614 port specification list means that device IDs
1615 from each port should be examined, to see if
1616 an IEEE 1284-compliant printer is attached; if
1617 so, the driver will manage that printer.
1618 See also header of drivers/char/lp.c.
1619
1620 lpj=n [KNL]
1621 Sets loops_per_jiffy to given constant, thus avoiding
1622 time-consuming boot-time autodetection (up to 250 ms per
1623 CPU). 0 enables autodetection (default). To determine
1624 the correct value for your kernel, boot with normal
1625 autodetection and see what value is printed. Note that
1626 on SMP systems the preset will be applied to all CPUs,
1627 which is likely to cause problems if your CPUs need
1628 significantly divergent settings. An incorrect value
1629 will cause delays in the kernel to be wrong, leading to
1630 unpredictable I/O errors and other breakage. Although
1631 unlikely, in the extreme case this might damage your
1632 hardware.
1633
1634 ltpc= [NET]
1635 Format: <io>,<irq>,<dma>
1636
Randy Dunlap16290242011-08-13 12:34:52 -07001637 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001638 (machvec) in a generic kernel.
1639 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001640
Wu Zhangjin3209e702009-07-02 23:27:12 +08001641 machtype= [Loongson] Share the same kernel image file between different
1642 yeeloong laptop.
1643 Example: machtype=lemote-yeeloong-2f-7inch
1644
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001645 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1646 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001647
1648 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001649 should make use of. maxcpus=n : n >= 0 limits the
1650 kernel to using 'n' processors. n=0 is a special case,
1651 it is equivalent to "nosmp", which also disables
1652 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001653
Kay Sieversd134b002011-07-31 22:08:04 +02001654 max_loop= [LOOP] The number of loop block devices that get
1655 (loop.max_loop) unconditionally pre-created at init time. The default
1656 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1657 of statically allocating a predefined number, loop
1658 devices can be requested on-demand with the
1659 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001660
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001661 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001662
Uwe Hermann71cced62008-10-20 09:32:21 -07001663 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001664
Linus Torvalds1da177e2005-04-16 15:20:36 -07001665 md= [HW] RAID subsystems devices and level
1666 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001667
Linus Torvalds1da177e2005-04-16 15:20:36 -07001668 mdacon= [MDA]
1669 Format: <first>,<last>
1670 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001671
Linus Torvalds1da177e2005-04-16 15:20:36 -07001672 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1673 Amount of memory to be used when the kernel is not able
1674 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08001675 [X86] Work as limiting max address. Use together
1676 with memmap= to avoid physical address space collisions.
1677 Without memmap= PCI devices could be placed at addresses
1678 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001679
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001680 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001681 memory.
1682
Paul Mundt6902aa82008-09-21 17:14:42 +09001683 memchunk=nn[KMG]
1684 [KNL,SH] Allow user to override the default size for
1685 per-device physically contiguous DMA buffers.
1686
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301687 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001688 E820 memory map, as specified by the user.
1689 Such memmap=exactmap lines can be constructed based on
1690 BIOS output or other requirements. See the memmap=nn@ss
1691 option description.
1692
1693 memmap=nn[KMG]@ss[KMG]
1694 [KNL] Force usage of a specific region of memory
1695 Region of memory to be used, from ss to ss+nn.
1696
1697 memmap=nn[KMG]#ss[KMG]
1698 [KNL,ACPI] Mark specific memory as ACPI data.
1699 Region of memory to be used, from ss to ss+nn.
1700
1701 memmap=nn[KMG]$ss[KMG]
1702 [KNL,ACPI] Mark specific memory as reserved.
1703 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001704 Example: Exclude memory from 0x18690000-0x1869ffff
1705 memmap=64K$0x18690000
1706 or
1707 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001708
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001709 memory_corruption_check=0/1 [X86]
1710 Some BIOSes seem to corrupt the first 64k of
1711 memory when doing things like suspend/resume.
1712 Setting this option will scan the memory
1713 looking for corruption. Enabling this will
1714 both detect corruption and prevent the kernel
1715 from using the memory being corrupted.
1716 However, its intended as a diagnostic tool; if
1717 repeatable BIOS-originated corruption always
1718 affects the same memory, you can use memmap=
1719 to prevent the kernel from using that memory.
1720
1721 memory_corruption_check_size=size [X86]
1722 By default it checks for corruption in the low
1723 64k, making this memory unavailable for normal
1724 use. Use this parameter to scan for
1725 corruption in more or less memory.
1726
1727 memory_corruption_check_period=seconds [X86]
1728 By default it checks for corruption every 60
1729 seconds. Use this parameter to check at some
1730 other rate. 0 disables periodic checking.
1731
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001732 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001733 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001734 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001735 Specifies the number of memtest passes to be
1736 performed. Each pass selects another test
1737 pattern from a given set of patterns. Memtest
1738 fills the memory with this pattern, validates
1739 memory contents and reserves bad memory
1740 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001741
Linus Torvalds1da177e2005-04-16 15:20:36 -07001742 meye.*= [HW] Set MotionEye Camera parameters
1743 See Documentation/video4linux/meye.txt.
1744
Andres Salomon8f368812007-10-12 23:04:06 +02001745 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1746 Multi-Function General Purpose Timers on AMD Geode
1747 platforms.
1748
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001749 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1750 the BIOS has incorrectly applied a workaround. TinyBIOS
1751 version 0.98 is known to be affected, 0.99 fixes the
1752 problem by letting the user disable the workaround.
1753
Linus Torvalds1da177e2005-04-16 15:20:36 -07001754 mga= [HW,DRM]
1755
Randy Dunlap1c207f952008-11-19 15:36:16 -08001756 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1757 physical address is ignored.
1758
Michel Pollet39f45d72009-05-20 11:10:31 +01001759 mini2440= [ARM,HW,KNL]
1760 Format:[0..2][b][c][t]
1761 Default: "0tb"
1762 MINI2440 configuration specification:
1763 0 - The attached screen is the 3.5" TFT
1764 1 - The attached screen is the 7" TFT
1765 2 - The VGA Shield is attached (1024x768)
1766 Leaving out the screen size parameter will not load
1767 the TFT driver, and the framebuffer will be left
1768 unconfigured.
1769 b - Enable backlight. The TFT backlight pin will be
1770 linked to the kernel VESA blanking code and a GPIO
1771 LED. This parameter is not necessary when using the
1772 VGA shield.
1773 c - Enable the s3c camera interface.
1774 t - Reserved for enabling touchscreen support. The
1775 touchscreen support is not enabled in the mainstream
1776 kernel as of 2.6.30, a preliminary port can be found
1777 in the "bleeding edge" mini2440 support kernel at
1778 http://repo.or.cz/w/linux-2.6/mini2440.git
1779
Mel Gorman6b74ab92008-07-23 21:26:49 -07001780 mminit_loglevel=
1781 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1782 parameter allows control of the logging verbosity for
1783 the additional memory initialisation checks. A value
1784 of 0 disables mminit logging and a level of 4 will
1785 log everything. Information is printed at KERN_DEBUG
1786 so loglevel=8 may also need to be specified.
1787
Rusty Russell106a4ee2012-09-26 10:09:40 +01001788 module.sig_enforce
1789 [KNL] When CONFIG_MODULE_SIG is set, this means that
1790 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01001791 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01001792 is always true, so this option does nothing.
1793
Linus Torvalds1da177e2005-04-16 15:20:36 -07001794 mousedev.tap_time=
1795 [MOUSE] Maximum time between finger touching and
1796 leaving touchpad surface for touch to be considered
1797 a tap and be reported as a left button click (for
1798 touchpads working in absolute mode only).
1799 Format: <msecs>
1800 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1801 reporting absolute coordinates, such as tablets
1802 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1803 reporting absolute coordinates, such as tablets
1804
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301805 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001806 is similar to kernelcore except it specifies the
1807 amount of memory used for migratable allocations.
1808 If both kernelcore and movablecore is specified,
1809 then kernelcore will be at *least* the specified
1810 value but may be more. If movablecore on its own
1811 is specified, the administrator must be careful
1812 that the amount of memory usable for all allocations
1813 is not too small.
1814
Tang Chenc5320922013-11-12 15:08:10 -08001815 movable_node [KNL,X86] Boot-time switch to enable the effects
1816 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1817
Linus Torvalds1da177e2005-04-16 15:20:36 -07001818 MTD_Partition= [MTD]
1819 Format: <name>,<region-number>,<size>,<offset>
1820
Randy Dunlapa9913042005-10-23 12:57:11 -07001821 MTD_Region= [MTD] Format:
1822 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001823
1824 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001825 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001826
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001827 multitce=off [PPC] This parameter disables the use of the pSeries
1828 firmware feature for updating multiple TCE entries
1829 at a time.
1830
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001831 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1832
1833 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1834
1835 boundary - index of last SLC block on Flex-OneNAND.
1836 The remaining blocks are configured as MLC blocks.
1837 lock - Configure if Flex-OneNAND boundary should be locked.
1838 Once locked, the boundary cannot be changed.
1839 1 indicates lock status, 0 indicates unlock status.
1840
Ben Dooks9db829f2008-07-03 11:24:29 +01001841 mtdset= [ARM]
1842 ARM/S3C2412 JIVE boot control
1843
1844 See arch/arm/mach-s3c2412/mach-jive.c
1845
Linus Torvalds1da177e2005-04-16 15:20:36 -07001846 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001847 [HW] Make the MicroTouch USB driver use raw coordinates
1848 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001850 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001851 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001852 that could hold holes aka. UC entries.
1853
1854 mtrr_gran_size=nn[KMG] [X86]
1855 Used for mtrr cleanup. It is granularity of mtrr block.
1856 Default is 1.
1857 Large value could prevent small alignment from
1858 using up MTRRs.
1859
1860 mtrr_spare_reg_nr=n [X86]
1861 Format: <integer>
1862 Range: 0,7 : spare reg number
1863 Default : 1
1864 Used for mtrr cleanup. It is spare mtrr entries number.
1865 Set to 2 or more if your graphical card needs more.
1866
Linus Torvalds1da177e2005-04-16 15:20:36 -07001867 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1868
Linus Torvalds1da177e2005-04-16 15:20:36 -07001869 netdev= [NET] Network devices parameters
1870 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1871 Note that mem_start is often overloaded to mean
1872 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001873 This usage is only documented in each driver source
1874 file if at all.
1875
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001876 nf_conntrack.acct=
1877 [NETFILTER] Enable connection tracking flow accounting
1878 0 to disable accounting
1879 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001880 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001881
Chuck Lever306a0752010-09-17 10:54:37 -04001882 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001883 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001884
1885 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001886 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001887
Chuck Lever306a0752010-09-17 10:54:37 -04001888 nfsrootdebug [NFS] enable nfsroot debugging messages.
1889 See Documentation/filesystems/nfs/nfsroot.txt.
1890
Trond Myklebusta72b4422006-01-03 09:55:41 +01001891 nfs.callback_tcpport=
1892 [NFS] set the TCP port on which the NFSv4 callback
1893 channel should listen.
1894
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001895 nfs.cache_getent=
1896 [NFS] sets the pathname to the program which is used
1897 to update the NFS client cache entries.
1898
1899 nfs.cache_getent_timeout=
1900 [NFS] sets the timeout after which an attempt to
1901 update a cache entry is deemed to have failed.
1902
Trond Myklebust58df0952006-01-03 09:55:57 +01001903 nfs.idmap_cache_timeout=
1904 [NFS] set the maximum lifetime for idmapper cache
1905 entries.
1906
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001907 nfs.enable_ino64=
1908 [NFS] enable 64-bit inode numbers.
1909 If zero, the NFS client will fake up a 32-bit inode
1910 number for the readdir() and stat() syscalls instead
1911 of returning the full 64-bit number.
1912 The default is to return 64-bit inode numbers.
1913
Trond Myklebustef159e92012-02-06 19:50:40 -05001914 nfs.max_session_slots=
1915 [NFSv4.1] Sets the maximum number of session slots
1916 the client will attempt to negotiate with the server.
1917 This limits the number of simultaneous RPC requests
1918 that the client can send to the NFSv4.1 server.
1919 Note that there is little point in setting this
1920 value higher than the max_tcp_slot_table_limit.
1921
Trond Myklebustb064eca22011-02-22 15:44:32 -08001922 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d122012-01-09 13:46:26 -05001923 [NFSv4] When set to the default of '1', this option
1924 ensures that both the RPC level authentication
1925 scheme and the NFS level operations agree to use
1926 numeric uids/gids if the mount is using the
1927 'sec=sys' security flavour. In effect it is
1928 disabling idmapping, which can make migration from
1929 legacy NFSv2/v3 systems to NFSv4 easier.
1930 Servers that do not support this mode of operation
1931 will be autodetected by the client, and it will fall
1932 back to using the idmapper.
1933 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04001934 nfs.nfs4_unique_id=
1935 [NFS4] Specify an additional fixed unique ident-
1936 ification string that NFSv4 clients can insert into
1937 their nfs_client_id4 string. This is typically a
1938 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08001939
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05001940 nfs.send_implementation_id =
1941 [NFSv4.1] Send client implementation identification
1942 information in exchange_id requests.
1943 If zero, no implementation identification information
1944 will be sent.
1945 The default is to send the implementation identification
1946 information.
Trond Myklebustf6de7a32013-09-04 10:08:54 -04001947
1948 nfs.recover_lost_locks =
1949 [NFSv4] Attempt to recover locks that were lost due
1950 to a lease timeout on the server. Please note that
1951 doing this risks data corruption, since there are
1952 no guarantees that the file will remain unchanged
1953 after the locks are lost.
1954 If you want to enable the kernel legacy behaviour of
1955 attempting to recover these locks, then set this
1956 parameter to '1'.
1957 The default parameter value of '0' causes the kernel
1958 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05001959
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04001960 nfsd.nfs4_disable_idmapping=
1961 [NFSv4] When set to the default of '1', the NFSv4
1962 server will return only numeric uids and gids to
1963 clients using auth_sys, and will accept numeric uids
1964 and gids from such clients. This is intended to ease
1965 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05001966
Sachin Bhamare18d98f62012-03-19 20:47:58 -07001967 objlayoutdriver.osd_login_prog=
1968 [NFS] [OBJLAYOUT] sets the pathname to the program which
1969 is used to automatically discover and login into new
1970 osd-targets. Please see:
1971 Documentation/filesystems/pnfs.txt for more explanations
1972
Paul Mundt1e1030d2009-09-01 17:38:32 +09001973 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001974 when a NMI is triggered.
1975 Format: [state][,regs][,debounce][,die]
1976
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301977 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07001978 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05001979 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001980 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001981 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07001982 timeout occurs (or 'nopanic' to override the opposite
1983 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001984 This is useful when you use a panic=... timeout and
1985 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001986
Anton Vorontsovbff38772009-07-08 11:10:56 -07001987 netpoll.carrier_timeout=
1988 [NET] Specifies amount of time (in seconds) that
1989 netpoll should wait for a carrier. By default netpoll
1990 waits 4 seconds.
1991
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001992 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001993 emulation library even if a 387 maths coprocessor
1994 is present.
1995
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001996 no_console_suspend
1997 [HW] Never suspend the console
1998 Disable suspending of consoles during suspend and
1999 hibernate operations. Once disabled, debugging
2000 messages can reach various consoles while the rest
2001 of the system is being put to sleep (ie, while
2002 debugging driver suspend/resume hooks). This may
2003 not work reliably with all consoles, but is known
2004 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002005 To facilitate more flexible debugging, we also add
2006 console_suspend, a printk module parameter to control
2007 it. Users could use console_suspend (usually
2008 /sys/module/printk/parameters/console_suspend) to
2009 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002010
Christoph Lameterc1aee212007-05-31 00:40:47 -07002011 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2012 caches in the slab allocator. Saves per-node memory,
2013 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002014
Randy Dunlapa9913042005-10-23 12:57:11 -07002015 noalign [KNL,ARM]
2016
Linus Torvalds1da177e2005-04-16 15:20:36 -07002017 noapic [SMP,APIC] Tells the kernel to not make use of any
2018 IOAPICs that may be present in the system.
2019
Kees Cook8ab38202013-10-10 17:18:14 -07002020 nokaslr [X86]
2021 Disable kernel base offset ASLR (Address Space
2022 Layout Randomization) if built into the kernel.
2023
Mike Galbraith5091faa2010-11-30 14:18:03 +01002024 noautogroup Disable scheduler automatic task group creation.
2025
Linus Torvalds1da177e2005-04-16 15:20:36 -07002026 nobats [PPC] Do not use BATs for mapping kernel lowmem
2027 on "Classic" PPC cores.
2028
2029 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002030
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002031 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2032
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002033 nodelayacct [KNL] Disable per-task delay accounting
2034
Linus Torvalds1da177e2005-04-16 15:20:36 -07002035 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2036
Paul Mundt6902aa82008-09-21 17:14:42 +09002037 nodsp [SH] Disable hardware DSP at boot time.
2038
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302039 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002040
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041 noexec [IA-64]
2042
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302043 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002044 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002045 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002046 noexec=off: disable non-executable mappings
2047
H. Peter Anvin52b61792012-09-21 12:43:13 -07002048 nosmap [X86]
2049 Disable SMAP (Supervisor Mode Access Prevention)
2050 even if it is supported by processor.
2051
Fenghua Yude5397a2011-05-11 16:51:05 -07002052 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002053 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002054 even if it is supported by processor.
2055
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002056 noexec32 [X86-64]
2057 This affects only 32-bit executables.
2058 noexec32=on: enable non-executable mappings (default)
2059 read doesn't imply executable mappings
2060 noexec32=off: disable non-executable mappings
2061 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002062
Paul Mundt6902aa82008-09-21 17:14:42 +09002063 nofpu [SH] Disable hardware FPU at boot time.
2064
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002065 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002066 register save and restore. The kernel will only save
2067 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002068
Suresh Siddha0c752a92009-05-22 12:17:45 -07002069 noxsave [BUGS=X86] Disables x86 extended register state save
2070 and restore using xsave. The kernel will fallback to
2071 enabling legacy floating-point and sse state.
2072
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002073 eagerfpu= [X86]
Suresh Siddhae0022982012-09-10 10:32:32 -07002074 on enable eager fpu restore
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002075 off disable eager fpu restore
Suresh Siddhae0022982012-09-10 10:32:32 -07002076 auto selects the default scheme, which automatically
2077 enables eagerfpu restore for xsaveopt.
Suresh Siddha5d2bd702012-09-06 14:58:52 -07002078
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002079 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2080 wfi(ARM) instruction doesn't work correctly and not to
2081 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002082
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002083 no_file_caps Tells the kernel not to honor file capabilities. The
2084 only way then for a file to be executed with privilege
2085 is to be setuid root or executed by root.
2086
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087 nohalt [IA-64] Tells the kernel not to use the power saving
2088 function PAL_HALT_LIGHT when idle. This increases
2089 power-consumption. On the positive side, it reduces
2090 interrupt wake-up latency, which may improve performance
2091 in certain environments such as networked servers or
2092 real-time systems.
2093
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002094 nohz= [KNL] Boottime enable/disable dynamic ticks
2095 Valid arguments: on, off
2096 Default: on
2097
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002098 nohz_full= [KNL,BOOT]
2099 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002100 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002101 whenever possible. The boot CPU will be forced outside
2102 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002103 The CPUs in this range must also be included in the
2104 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002105
Paul Mundteeee7852009-04-02 12:31:16 +09002106 noiotrap [SH] Disables trapped I/O port accesses.
2107
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002108 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002109 disable unhandled interrupt sources.
2110
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302111 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002112 broken timer IRQ sources.
2113
Linus Torvalds1da177e2005-04-16 15:20:36 -07002114 noisapnp [ISAPNP] Disables ISA PnP code.
2115
2116 noinitrd [RAM] Tells the kernel not to load any configured
2117 initial RAM disk.
2118
Weidong Han03ea8152009-04-17 16:42:15 +08002119 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2120 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002121 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002122
Linus Torvalds1da177e2005-04-16 15:20:36 -07002123 nointroute [IA-64]
2124
Randy Dunlap16290242011-08-13 12:34:52 -07002125 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002126
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002127 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2128
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002129 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2130 fault handling.
2131
Glauber Costad910f5c2011-07-11 15:28:19 -04002132 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2133 steal time is computed, but won't influence scheduler
2134 behaviour
2135
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002136 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002137
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002138 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002139
Linus Torvalds1da177e2005-04-16 15:20:36 -07002140 noltlbs [PPC] Do not use large page/tlb entries for kernel
2141 lowmem mapping on PPC40x.
2142
Horms312f1f02006-02-22 09:57:55 +09002143 nomca [IA-64] Disable machine check abort handling
2144
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002145 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002146
Andres Salomon83d73842007-10-12 23:04:06 +02002147 nomfgpt [X86-32] Disable Multi-Function General Purpose
2148 Timer usage (for AMD Geode machines).
2149
Don Zickusbda62632011-10-13 15:14:27 -04002150 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2151 shutdown the other cpus. Instead use the REBOOT_VECTOR
2152 irq.
2153
Dave Young02608be2012-02-01 10:33:14 +08002154 nomodule Disable module load
2155
Jiri Kosina016ddd92010-01-18 17:05:40 +01002156 nopat [X86] Disable PAT (page attribute table extension of
2157 pagetables) support.
2158
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002159 norandmaps Don't use address space randomization. Equivalent to
2160 echo 0 > /proc/sys/kernel/randomize_va_space
2161
Jiri Kosinabbff2162010-08-11 18:34:09 +02002162 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002163
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002164 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002165 with UP alternatives
2166
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002167 nordrand [X86] Disable the direct use of the RDRAND
2168 instruction even if it is supported by the
2169 processor. RDRAND is still available to user
2170 space applications.
2171
Randy Dunlapa9913042005-10-23 12:57:11 -07002172 noresume [SWSUSP] Disables resume and restores original swap
2173 space.
2174
Linus Torvalds1da177e2005-04-16 15:20:36 -07002175 no-scroll [VGA] Disables scrollback.
2176 This is required for the Braillex ib80-piezo Braille
2177 reader made by F.H. Papenmeier (Germany).
2178
2179 nosbagart [IA-64]
2180
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002181 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002182
Len Brown61ec7562007-08-16 03:34:22 -04002183 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2184 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002185
Dave Jones97842212007-07-15 23:41:05 -07002186 nosoftlockup [KNL] Disable the soft-lockup detector.
2187
Linus Torvalds1da177e2005-04-16 15:20:36 -07002188 nosync [HW,M68K] Disables sync negotiation for all devices.
2189
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002190 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002191
2192 nousb [USB] Disable the USB subsystem
2193
Ben Hutchings55142372011-01-02 23:02:42 +00002194 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04002195
Linus Torvalds1da177e2005-04-16 15:20:36 -07002196 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002197
Weidong Han2b2fd872009-04-17 16:42:12 +08002198 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2199
Fenghua Yuf78cff42012-11-13 11:32:38 -08002200 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2201 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2202 Some features depend on CPU0. Known dependencies are:
2203 1. Resume from suspend/hibernate depends on CPU0.
2204 Suspend/hibernate will fail if CPU0 is offline and you
2205 need to online CPU0 before suspend/hibernate.
2206 2. PIC interrupts also depend on CPU0. CPU0 can't be
2207 removed if a PIC interrupt is detected.
2208 It's said poweroff/reboot may depend on CPU0 on some
2209 machines although I haven't seen such issues so far
2210 after CPU0 is offline on a few tested machines.
2211 If the dependencies are under your control, you can
2212 turn on cpu0_hotplug.
2213
Randy Dunlap16290242011-08-13 12:34:52 -07002214 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002215 purges which is reported from either PAL_VM_SUMMARY or
2216 SAL PALO.
2217
Yinghai Lu2b633e32010-02-10 01:20:37 -08002218 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2219 could support. nr_cpus=n : n >= 1 limits the kernel to
2220 supporting 'n' processors. Later in runtime you can not
2221 use hotplug cpu feature to put more cpu back to online.
2222 just like you compile the kernel NR_CPUS=n
2223
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002224 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2225
Mel Gorman1a687c22012-11-22 11:16:36 +00002226 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2227 Allowed values are enable and disable
2228
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002229 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2230 one of ['zone', 'node', 'default'] can be specified
2231 This can be set from sysctl after boot.
2232 See Documentation/sysctl/vm.txt for details.
2233
Randy Dunlap7c4be252009-01-06 14:42:44 -08002234 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2235 See Documentation/debugging-via-ohci1394.txt for more
2236 info.
2237
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002238 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2239 Rather than timing out after 20 ms if an EC
2240 command is not properly ACKed, override the length
2241 of the timeout. We have interrupts disabled while
2242 waiting for the ACK, so if this is set too high
2243 interrupts *may* be lost!
2244
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002245 omap_mux= [OMAP] Override bootloader pin multiplexing.
2246 Format: <mux_mode0.mode_name=value>...
2247 For example, to override I2C bus2:
2248 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2249
Linus Torvalds1da177e2005-04-16 15:20:36 -07002250 oprofile.timer= [HW]
2251 Use timer interrupt instead of performance counters
2252
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002253 oprofile.cpu_type= Force an oprofile cpu type
2254 This might be useful if you have an older oprofile
2255 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002256 Format: { arch_perfmon }
2257 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002258 perfmon on Intel CPUs instead of the
2259 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002260 timer: [X86] Force use of architectural NMI
2261 timer mode (see also oprofile.timer
2262 for generic hr timer mode)
Andreas Krebbeldd3c46702011-11-25 20:03:05 +01002263 [s390] Force legacy basic mode sampling
2264 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002265
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002266 oops=panic Always panic on oopses. Default is to just kill the
2267 process, but there is a small probability of
2268 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002269 This will also cause panics on machine check exceptions.
2270 Useful together with panic=30 to trigger a reboot.
2271
Randy Dunlapbcfde332010-06-07 17:10:38 -07002272 OSS [HW,OSS]
2273 See Documentation/sound/oss/oss-parameters.txt
2274
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002275 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002276 timeout > 0: seconds before rebooting
2277 timeout = 0: wait forever
2278 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002279 Format: <timeout>
2280
2281 parkbd.port= [HW] Parallel port number the keyboard adapter is
2282 connected to, default is 0.
2283 Format: <parport#>
2284 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2285 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002286 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002287
Randy Dunlapa9913042005-10-23 12:57:11 -07002288 parport= [HW,PPT] Specify parallel ports. 0 disables.
2289 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2290 Use 'auto' to force the driver to use any
2291 IRQ/DMA settings detected (the default is to
2292 ignore detected IRQ/DMA settings because of
2293 possible conflicts). You can specify the base
2294 address, IRQ, and DMA settings; IRQ and DMA
2295 should be numbers, or 'auto' (for using detected
2296 settings on that particular port), or 'nofifo'
2297 (to avoid using a FIFO even if it is detected).
2298 Parallel ports are assigned in the order they
2299 are specified on the command line, starting
2300 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002301
Randy Dunlapa9913042005-10-23 12:57:11 -07002302 parport_init_mode= [HW,PPT]
2303 Configure VIA parallel port to operate in
2304 a specific mode. This is necessary on Pegasos
2305 computer where firmware has no options for setting
2306 up parallel port mode and sets it to spp.
2307 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002308 Format: [spp|ps2|epp|ecp|ecpepp]
2309
Andrew Mortondd287792006-03-23 03:00:57 -08002310 pause_on_oops=
2311 Halt all CPUs after the first oops has been printed for
2312 the specified number of seconds. This is to be used if
2313 your oopses keep scrolling off the screen.
2314
Linus Torvalds1da177e2005-04-16 15:20:36 -07002315 pcbit= [HW,ISDN]
2316
2317 pcd. [PARIDE]
2318 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002319 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002320
Randy Dunlapa9913042005-10-23 12:57:11 -07002321 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002322 earlydump [X86] dump PCI config space before the kernel
2323 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002324 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002325 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002326 the hardware directly. Use this if your machine
2327 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002328 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002329 hardware access methods are allowed. Use this
2330 if you experience crashes upon bootup and you
2331 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002332 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002333 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002334 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002335 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002336 noaer [PCIE] If the PCIEAER kernel config parameter is
2337 enabled, this kernel boot option can be used to
2338 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002339 nodomains [PCI] Disable support for multiple PCI
2340 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302341 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002342 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002343 check_enable_amd_mmconf [X86] check for and enable
2344 properly configured MMIO access to PCI
2345 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002346 nomsi [MSI] If the PCI_MSI kernel config parameter is
2347 enabled, this kernel boot option can be used to
2348 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002349 noioapicquirk [APIC] Disable all boot interrupt quirks.
2350 Safety option to keep boot IRQs enabled. This
2351 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002352 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2353 primary IO-APIC for bridges that cannot disable
2354 boot IRQs. This fixes a source of spurious IRQs
2355 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002356 noioapicreroute [APIC] Disable workaround that uses the
2357 boot IRQ equivalent of an IRQ that connects to
2358 a chipset where boot IRQs cannot be disabled.
2359 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002360 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002361 routing table. These calls are known to be buggy
2362 on several machines and they hang the machine
2363 when used, but on other computers it's the only
2364 way to get the interrupt routing table. Try
2365 this option if the kernel is unable to allocate
2366 IRQs or discover secondary PCI buses on your
2367 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002368 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002369 Use with caution as certain devices share
2370 address decoders between ROMs and other
2371 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002372 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002373 expansion ROMs that do not already have
2374 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002375 nobar [X86] Do not assign address space to the
2376 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002377 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002378 assigned automatically to PCI devices. You can
2379 make the kernel exclude IRQs of your ISA cards
2380 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002381 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002382 of the PIRQ table (normally generated
2383 by the BIOS) if it is outside the
2384 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002385 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002386 useful if the kernel is unable to find your
2387 secondary buses and you want to tell it
2388 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002389 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002390 numbers ourselves, overriding
2391 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002392 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002393 in the BIOS $PIR table. This is needed on
2394 some systems with broken BIOSes, notably
2395 some HP Pavilion N5400 and Omnibook XE3
2396 notebooks. This will have no effect if ACPI
2397 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002398 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002399 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002400 use_crs [X86] Use PCI host bridge window information
2401 from ACPI. On BIOSes from 2008 or later, this
2402 is enabled by default. If you need to use this,
2403 please report a bug.
2404 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2405 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002406 routeirq Do IRQ routing for all PCI devices.
2407 This is normally done in pci_enable_device(),
2408 so this option is a temporary workaround
2409 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002410 skip_isa_align [X86] do not align io start addr, so can
2411 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002412 firmware [ARM] Do not re-enumerate the bus but instead
2413 just use the configuration from the
2414 bootloader. This is currently used on
2415 IXP2000 systems where the bus has to be
2416 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002417 noearly [X86] Don't do any early type 1 scanning.
2418 This might help on some broken boards which
2419 machine check when some devices' config space
2420 is read. But various workarounds are disabled
2421 and some IOMMU drivers will not work.
Matt Domsch6b4b78fe2006-09-29 15:23:23 -05002422 bfsort Sort PCI devices into breadth-first order.
2423 This sorting is done to get a device
2424 order compatible with older (<= 2.4) kernels.
2425 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002426 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2427 tuning and use the BIOS-configured MPS defaults.
2428 pcie_bus_safe Set every device's MPS to the largest value
2429 supported by all devices below the root complex.
2430 pcie_bus_perf Set device MPS to the largest allowable MPS
2431 based on its parent bus. Also set MRRS (Max
2432 Read Request Size) to the largest supported
2433 value (no larger than the MPS that the device
2434 or bus can support) for best performance.
2435 pcie_bus_peer2peer Set every device's MPS to 128B, which
2436 every device is guaranteed to support. This
2437 configuration allows peer-to-peer DMA between
2438 any pair of devices, possibly at the cost of
2439 reduced performance. This also guarantees
2440 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002441 cbiosize=nn[KMG] The fixed amount of bus space which is
2442 reserved for the CardBus bridge's IO window.
2443 The default value is 256 bytes.
2444 cbmemsize=nn[KMG] The fixed amount of bus space which is
2445 reserved for the CardBus bridge's memory
2446 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002447 resource_alignment=
2448 Format:
2449 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2450 Specifies alignment and device to reassign
2451 aligned memory resources.
2452 If <order of align> is not specified,
2453 PAGE_SIZE is used as alignment.
2454 PCI-PCI bridge can be specified, if resource
2455 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002456 ecrc= Enable/disable PCIe ECRC (transaction layer
2457 end-to-end CRC checking).
2458 bios: Use BIOS/firmware settings. This is the
2459 the default.
2460 off: Turn ECRC off
2461 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002462 hpiosize=nn[KMG] The fixed amount of bus space which is
2463 reserved for hotplug bridge's IO window.
2464 Default size is 256 bytes.
2465 hpmemsize=nn[KMG] The fixed amount of bus space which is
2466 reserved for hotplug bridge's memory window.
2467 Default size is 2 megabytes.
Yinghai Lub55438f2012-02-23 19:23:30 -08002468 realloc= Enable/disable reallocating PCI bridge resources
2469 if allocations done by BIOS are too small to
2470 accommodate resources required by all child
2471 devices.
2472 off: Turn realloc off
2473 on: Turn realloc on
2474 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002475 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002476 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2477 only look for one device below a PCIe downstream
2478 port.
Matt Domsch6b4b78fe2006-09-29 15:23:23 -05002479
Chuck Ebberte5665a42008-09-24 20:40:34 -04002480 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2481 Management.
2482 off Disable ASPM.
2483 force Enable ASPM even on devices that claim not to support it.
2484 WARNING: Forcing ASPM on may cause system lockups.
2485
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002486 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2487 nomsi Do not use MSI for PCI Express Native Hotplug (this
2488 makes all PCIe ports use INTx for hotplug services).
2489
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002490 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002491 auto Ask the BIOS whether or not to use native PCIe services
2492 associated with PCIe ports (PME, hot-plug, AER). Use
2493 them only if that is allowed by the BIOS.
2494 native Use native PCIe services associated with PCIe ports
2495 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002496 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2497 ports driver.
2498
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002499 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002500 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002501 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002502
Linus Torvalds1da177e2005-04-16 15:20:36 -07002503 pcmv= [HW,PCMCIA] BadgePAD 4
2504
2505 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002506 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002507
2508 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2509 boot time.
2510 Format: { 0 | 1 }
2511 See arch/parisc/kernel/pdc_chassis.c
2512
Tejun Heof58dc012009-08-14 15:00:50 +09002513 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002514 Currently supported values are "embed" and "page".
2515 Archs may support subset or none of the selections.
2516 See comments in mm/percpu.c for details on each
2517 allocator. This parameter is primarily for debugging
2518 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002519
Linus Torvalds1da177e2005-04-16 15:20:36 -07002520 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002521 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002522
2523 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002524 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002525
2526 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002527 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002528
2529 plip= [PPT,NET] Parallel port network link
2530 Format: { parport<nr> | timid | 0 }
2531 See also Documentation/parport.txt.
2532
Randy Dunlap16290242011-08-13 12:34:52 -07002533 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002534 Override pmtimer IOPort with a hex value.
2535 e.g. pmtmr=0x508
2536
Bjorn Helgaas96242112011-08-11 12:14:05 -06002537 pnp.debug=1 [PNP]
2538 Enable PNP debug messages (depends on the
2539 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2540 via /sys/module/pnp/parameters/debug. We always show
2541 current resource usage; turning this on also shows
2542 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002543
Linus Torvalds1da177e2005-04-16 15:20:36 -07002544 pnpacpi= [ACPI]
2545 { off }
2546
2547 pnpbios= [ISAPNP]
2548 { on | off | curr | res | no-curr | no-res }
2549
2550 pnp_reserve_irq=
2551 [ISAPNP] Exclude IRQs for the autoconfiguration
2552
2553 pnp_reserve_dma=
2554 [ISAPNP] Exclude DMAs for the autoconfiguration
2555
2556 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002557 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002558
2559 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002560 [ISAPNP] Exclude memory regions for the
2561 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002562 Ranges are in pairs (memory base and size).
2563
Randy Dunlap4af94f32009-04-17 18:30:28 -07002564 ports= [IP_VS_FTP] IPVS ftp helper module
2565 Default is 21.
2566 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2567 may be specified.
2568 Format: <port>,<port>....
2569
Ingo Molnar45807a12007-07-15 23:40:10 -07002570 print-fatal-signals=
2571 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002572
2573 If enabled, warn about various signal handling
2574 related application anomalies: too many signals,
2575 too many POSIX.1 timers, fatal signals causing a
2576 coredump - etc.
2577
2578 If you hit the warning due to signal overflow,
2579 you might want to try "ulimit -i unlimited".
2580
Ingo Molnar45807a12007-07-15 23:40:10 -07002581 default: off.
2582
Matthew Garrettc22ab3322012-03-05 14:59:10 -08002583 printk.always_kmsg_dump=
2584 Trigger kmsg_dump for cases other than kernel oops or
2585 panics
2586 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2587 default: disabled
2588
Randy Dunlape84845c2007-07-15 23:40:25 -07002589 printk.time= Show timing data prefixed to each printk message line
2590 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2591
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002592 processor.max_cstate= [HW,ACPI]
2593 Limit processor to maximum C-state
2594 max_cstate=9 overrides any DMI blacklist limit.
2595
2596 processor.nocst [HW,ACPI]
2597 Ignore the _CST method to determine C-states,
2598 instead using the legacy FADT method
2599
Linus Torvalds1da177e2005-04-16 15:20:36 -07002600 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002601 Format: [schedule,]<number>
2602 Param: "schedule" - profile schedule points.
2603 Param: <number> - step/bucket size as a power of 2 for
2604 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002605 Param: "sleep" - profile D-state sleeping (millisecs).
2606 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002607 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002608
Linus Torvalds1da177e2005-04-16 15:20:36 -07002609 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2610 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002611 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002612
Randy Dunlapa9913042005-10-23 12:57:11 -07002613 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2614 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002615 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2616 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002617 psmouse.resetafter= [HW,MOUSE]
2618 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002619 (0 = never).
2620 psmouse.resolution=
2621 [HW,MOUSE] Set desired mouse resolution, in dpi.
2622 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002623 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002624 0 = disabled, 1 = enabled (default).
2625
Matthew Garrettdee28e72011-07-21 16:57:55 -04002626 pstore.backend= Specify the name of the pstore backend to use
2627
Linus Torvalds1da177e2005-04-16 15:20:36 -07002628 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002629 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002630
Kay Sieversdc8c8582007-08-15 12:25:38 +02002631 pty.legacy_count=
2632 [KNL] Number of legacy pty's. Overwrites compiled-in
2633 default number.
2634
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002635 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002636
Linus Torvalds1da177e2005-04-16 15:20:36 -07002637 r128= [HW,DRM]
2638
2639 raid= [HW,RAID]
2640 See Documentation/md.txt.
2641
Randy Dunlapa9913042005-10-23 12:57:11 -07002642 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002643 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002644
Linus Torvalds1da177e2005-04-16 15:20:36 -07002645 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002646 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002647
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002648 rcu_nocbs= [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002649 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2650 the specified list of CPUs to be no-callback CPUs.
2651 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08002652 be offloaded to "rcuox/N" kthreads created for
2653 that purpose, where "x" is "b" for RCU-bh, "p"
2654 for RCU-preempt, and "s" for RCU-sched, and "N"
2655 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002656 offloaded CPUs, which can be useful for HPC and
2657 real-time workloads. It can also improve energy
2658 efficiency for asymmetric multiprocessors.
2659
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002660 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002661 Rather than requiring that offloaded CPUs
2662 (specified by rcu_nocbs= above) explicitly
2663 awaken the corresponding "rcuoN" kthreads,
2664 make these kthreads poll for callbacks.
2665 This improves the real-time response for the
2666 offloaded CPUs by relieving them of the need to
2667 wake up the corresponding kthread, but degrades
2668 energy efficiency by requiring that the kthreads
2669 periodically wake up to do the polling.
2670
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002671 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002672 Set maximum number of finished RCU callbacks to
2673 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002674
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002675 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07002676 Increase the number of CPUs assigned to each
2677 leaf rcu_node structure. Useful for very large
2678 systems.
2679
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002680 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002681 Set delay from grace-period initialization to
2682 first attempt to force quiescent states.
2683 Units are jiffies, minimum value is zero,
2684 and maximum value is HZ.
2685
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002686 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002687 Set delay between subsequent attempts to force
2688 quiescent states. Units are jiffies, minimum
2689 value is one, and maximum value is HZ.
2690
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002691 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07002692 Set threshold of queued RCU callbacks beyond which
2693 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002694
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002695 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002696 Set threshold of queued RCU callbacks below which
2697 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002698
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002699 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002700 Set wakeup interval for idle CPUs that have
2701 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002702
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002703 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002704 Set wakeup interval for idle CPUs that have
2705 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2706 Lazy RCU callbacks are those which RCU can
2707 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002708
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002709 rcutorture.fqs_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002710 Set duration of force_quiescent_state bursts.
2711
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002712 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002713 Set holdoff time within force_quiescent_state bursts.
2714
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002715 rcutorture.fqs_stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002716 Set wait time between force_quiescent_state bursts.
2717
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002718 rcutorture.gp_exp= [KNL]
2719 Use expedited update-side primitives.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002720
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002721 rcutorture.gp_normal= [KNL]
2722 Use normal (non-expedited) update-side primitives.
2723 If both gp_exp and gp_normal are set, do both.
2724 If neither gp_exp nor gp_normal are set, still
2725 do both.
2726
2727 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002728 Set callbacks/threads for rcu_barrier() testing.
2729
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002730 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002731 Set number of concurrent RCU writers. These just
2732 stress RCU, they don't participate in the actual
2733 test, hence the "fake".
2734
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002735 rcutorture.nreaders= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002736 Set number of RCU readers.
2737
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002738 rcutorture.object_debug= [KNL]
2739 Enable debug-object double-call_rcu() testing.
2740
2741 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002742 Set time (s) after boot for CPU-hotplug testing.
2743
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002744 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002745 Set time (s) between CPU-hotplug operations, or
2746 zero to disable CPU-hotplug testing.
2747
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002748 rcutorture.rcutorture_runnable= [BOOT]
2749 Start rcutorture running at boot time.
2750
2751 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002752 Set task-shuffle interval (s). Shuffling tasks
2753 allows some CPUs to go into dyntick-idle mode
2754 during the rcutorture test.
2755
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002756 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002757 Set time (s) after boot system shutdown. This
2758 is useful for hands-off automated testing.
2759
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002760 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002761 Duration of CPU stall (s) to test RCU CPU stall
2762 warnings, zero to disable.
2763
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002764 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002765 Time to wait (s) after boot before inducing stall.
2766
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002767 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002768 Time (s) between statistics printk()s.
2769
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002770 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002771 Time (s) to stutter testing, for example, specifying
2772 five seconds causes the test to run for five seconds,
2773 wait for five seconds, and so on. This tests RCU's
2774 ability to transition abruptly to and from idle.
2775
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002776 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002777 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2778 "Maybe" means test if the RCU implementation
2779 under test support RCU priority boosting.
2780
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002781 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002782 Duration (s) of each individual boost test.
2783
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002784 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002785 Interval (s) between each boost test.
2786
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002787 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002788 Test RCU's dyntick-idle handling. See also the
2789 rcutorture.shuffle_interval parameter.
2790
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002791 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002792 Specify the RCU implementation to test.
2793
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002794 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002795 Enable additional printk() statements.
2796
Paul E. McKenney4102ada2013-10-08 20:23:47 -07002797 rcupdate.rcu_expedited= [KNL]
2798 Use expedited grace-period primitives, for
2799 example, synchronize_rcu_expedited() instead
2800 of synchronize_rcu(). This reduces latency,
2801 but can increase CPU utilization, degrade
2802 real-time latency, and degrade energy efficiency.
2803
2804 rcupdate.rcu_cpu_stall_suppress= [KNL]
2805 Suppress RCU CPU stall warning messages.
2806
2807 rcupdate.rcu_cpu_stall_timeout= [KNL]
2808 Set timeout for RCU CPU stall warning messages.
2809
Olof Johanssonffdfc402005-09-06 15:17:19 -07002810 rdinit= [KNL]
2811 Format: <full_path>
2812 Run specified binary instead of /init from the ramdisk,
2813 used for early userspace startup. See initrd.
2814
Robin Holt1b3a5d02013-07-08 16:01:42 -07002815 reboot= [KNL]
2816 Format (x86 or x86_64):
2817 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2818 [[,]s[mp]#### \
2819 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2820 [[,]f[orce]
2821 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2822 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2823 reboot_force is either force or not specified,
2824 reboot_cpu is s[mp]#### with #### being the processor
2825 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002826
Paul Jackson46b6d942008-07-04 10:00:09 -07002827 relax_domain_level=
2828 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002829 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002830
Linus Torvalds1da177e2005-04-16 15:20:36 -07002831 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2832
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002833 reservetop= [X86-32]
Zachary Amsden461a9aff2006-09-25 23:32:25 -07002834 Format: nn[KMG]
2835 Reserves a hole at the top of the kernel virtual
2836 address space.
2837
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002838 reservelow= [X86]
2839 Format: nn[K]
2840 Set the amount of memory to reserve for BIOS at
2841 the bottom of the address space.
2842
Vivek Goyal7e962872006-09-27 01:50:44 -07002843 reset_devices [KNL] Force drivers to reset the underlying device
2844 during initialization.
2845
Randy Dunlapa9913042005-10-23 12:57:11 -07002846 resume= [SWSUSP]
2847 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02002848 Format:
2849 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002850
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002851 resume_offset= [SWSUSP]
2852 Specify the offset from the beginning of the partition
2853 given by "resume=" at which the swap header is located,
2854 in <PAGE_SIZE> units (needed only for swap files).
2855 See Documentation/power/swsusp-and-swap-files.txt
2856
Barry Songf126f732011-10-10 23:38:41 +02002857 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2858 read the resume files
2859
Barry Song6f8d7022011-10-06 20:34:46 +02002860 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2861 Useful for devices that are detected asynchronously
2862 (e.g. USB and MMC devices).
2863
Bojan Smojverf996fc92010-09-09 23:06:23 +02002864 hibernate= [HIBERNATION]
2865 noresume Don't check if there's a hibernation image
2866 present during boot.
2867 nocompress Don't compress/decompress hibernation images.
2868
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08002869 retain_initrd [RAM] Keep initrd memory after extraction
2870
Linus Torvalds1da177e2005-04-16 15:20:36 -07002871 rhash_entries= [KNL,NET]
2872 Set number of hash buckets for route cache
2873
2874 riscom8= [HW,SERIAL]
2875 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2876
2877 ro [KNL] Mount root device read-only on boot
2878
2879 root= [KNL] Root filesystem
Will Drewryf2d34fd92011-08-03 16:21:08 -07002880 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002881
2882 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2883 mount the root filesystem
2884
2885 rootflags= [KNL] Set root filesystem mount option string
2886
2887 rootfstype= [KNL] Set root filesystem type
2888
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002889 rootwait [KNL] Wait (indefinitely) for root device to show up.
2890 Useful for devices that are detected asynchronously
2891 (e.g. USB and MMC devices).
2892
Robert Tivy5c71d612013-03-28 18:41:46 -07002893 rproc_mem=nn[KMG][@address]
2894 [KNL,ARM,CMA] Remoteproc physical memory block.
2895 Memory area to be used by remote processor image,
2896 managed by CMA.
2897
Linus Torvalds1da177e2005-04-16 15:20:36 -07002898 rw [KNL] Mount root device read-write on boot
2899
2900 S [KNL] Run init in single mode
2901
2902 sa1100ir [NET]
2903 See drivers/net/irda/sa1100_ir.c.
2904
Linus Torvalds1da177e2005-04-16 15:20:36 -07002905 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002906
Mike Travisf6630112009-11-17 18:22:15 -06002907 sched_debug [KNL] Enables verbose scheduler debug messages.
2908
Mike Galbraith5307c952012-05-08 12:20:58 +02002909 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2910 xtime_lock contention on larger systems, and/or RCU lock
2911 contention on all systems with CONFIG_MAXSMP set.
2912 Format: { "0" | "1" }
2913 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2914 1 -- enable.
2915 Note: increases power consumption, thus should only be
2916 enabled if running jitter sensitive (HPC/RT) workloads.
2917
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002918 security= [SECURITY] Choose a security module to enable at boot.
2919 If this boot parameter is not specified, only the first
2920 security module asking for security registration will be
2921 loaded. An invalid security module name will be treated
2922 as if no module has been chosen.
2923
2924 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002925 Format: { "0" | "1" }
2926 See security/selinux/Kconfig help text.
2927 0 -- disable.
2928 1 -- enable.
2929 Default value is set via kernel config option.
2930 If enabled at boot time, /selinux/disable can be used
2931 later to disable prior to initial policy load.
2932
John Johansenc1c124e2010-07-29 14:48:09 -07002933 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2934 Format: { "0" | "1" }
2935 See security/apparmor/Kconfig help text
2936 0 -- disable.
2937 1 -- enable.
2938 Default value is set via kernel config option.
2939
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002940 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002941
Linus Torvalds1da177e2005-04-16 15:20:36 -07002942 shapers= [NET]
2943 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002944
Yinghai Lub05f78f2008-08-22 01:32:50 -07002945 show_msr= [x86] show boot-time MSR settings
2946 Format: { <integer> }
2947 Show boot-time (BIOS-initialized) MSR settings.
2948 The parameter means the number of CPUs to show,
2949 for example 1 means boot CPU only.
2950
Linus Torvalds1da177e2005-04-16 15:20:36 -07002951 simeth= [IA-64]
2952 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002953
Linus Torvalds1da177e2005-04-16 15:20:36 -07002954 slram= [HW,MTD]
2955
David Rientjes3df1ccc2011-10-18 22:09:28 -07002956 slab_max_order= [MM, SLAB]
2957 Determines the maximum allowed order for slabs.
2958 A high setting may cause OOMs due to memory
2959 fragmentation. Defaults to 1 for systems with
2960 more than 32MB of RAM, 0 otherwise.
2961
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002962 slub_debug[=options[,slabs]] [MM, SLUB]
2963 Enabling slub_debug allows one to determine the
2964 culprit if slab objects become corrupted. Enabling
2965 slub_debug can create guard zones around objects and
2966 may poison objects when not in use. Also tracks the
2967 last alloc / free. For more information see
2968 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002969
2970 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002971 Determines the maximum allowed order for slabs.
2972 A high setting may cause OOMs due to memory
2973 fragmentation. For more information see
2974 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002975
2976 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002977 The minimum number of objects per slab. SLUB will
2978 increase the slab order up to slub_max_order to
2979 generate a sufficiently large slab able to contain
2980 the number of objects indicated. The higher the number
2981 of objects the smaller the overhead of tracking slabs
2982 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002983 For more information see Documentation/vm/slub.txt.
2984
2985 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09002986 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002987 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002988 For more information see Documentation/vm/slub.txt.
2989
2990 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002991 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002992 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002993 allocs to different slabs. Debug options disable
2994 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002995 For more information see Documentation/vm/slub.txt.
2996
Linus Torvalds1da177e2005-04-16 15:20:36 -07002997 smart2= [HW]
2998 Format: <io1>[,<io2>[,...,<io8>]]
2999
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003000 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3001 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3002 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3003 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3004 smsc-ircc2.ircc_irq= [HW] IRQ line
3005 smsc-ircc2.ircc_dma= [HW] DMA channel
3006 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3007 0: Toshiba Satellite 1800 (GP data pin select)
3008 1: Fast pin select (default)
3009 2: ATC IRMode
3010
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003011 softlockup_panic=
3012 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003013 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003014
Linus Torvalds1da177e2005-04-16 15:20:36 -07003015 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003016 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003017
3018 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003019 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003020
3021 spia_io_base= [HW,MTD]
3022 spia_fio_base=
3023 spia_pedr=
3024 spia_peddr=
3025
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003026 stacktrace [FTRACE]
3027 Enabled the stack tracer on boot up.
3028
Steven Rostedt762e1202011-12-19 22:01:00 -05003029 stacktrace_filter=[function-list]
3030 [FTRACE] Limit the functions that the stack tracer
3031 will trace at boot up. function-list is a comma separated
3032 list of functions. This list can be changed at run
3033 time by the stack_trace_filter file in the debugfs
3034 tracing directory. Note, this enables stack tracing
3035 and the stacktrace above is not needed.
3036
Linus Torvalds1da177e2005-04-16 15:20:36 -07003037 sti= [PARISC,HW]
3038 Format: <num>
3039 Set the STI (builtin display/keyboard on the HP-PARISC
3040 machines) console (graphic card) which should be used
3041 as the initial boot-console.
3042 See also comment in drivers/video/console/sticore.c.
3043
3044 sti_font= [HW]
3045 See comment in drivers/video/console/sticore.c.
3046
3047 stifb= [HW]
3048 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3049
Trond Myklebustcbf11072009-08-09 15:06:19 -04003050 sunrpc.min_resvport=
3051 sunrpc.max_resvport=
3052 [NFS,SUNRPC]
3053 SunRPC servers often require that client requests
3054 originate from a privileged port (i.e. a port in the
3055 range 0 < portnr < 1024).
3056 An administrator who wishes to reserve some of these
3057 ports for other uses may adjust the range that the
3058 kernel's sunrpc client considers to be privileged
3059 using these two parameters to set the minimum and
3060 maximum port values.
3061
Greg Banks42a7fc42007-03-06 01:42:23 -08003062 sunrpc.pool_mode=
3063 [NFS]
3064 Control how the NFS server code allocates CPUs to
3065 service thread pools. Depending on how many NICs
3066 you have and where their interrupts are bound, this
3067 option will affect which CPUs will do NFS serving.
3068 Note: this parameter cannot be changed while the
3069 NFS server is running.
3070
3071 auto the server chooses an appropriate mode
3072 automatically using heuristics
3073 global a single global pool contains all CPUs
3074 percpu one pool for each CPU
3075 pernode one pool for each NUMA node (equivalent
3076 to global on non-NUMA machines)
3077
Trond Myklebustcbf11072009-08-09 15:06:19 -04003078 sunrpc.tcp_slot_table_entries=
3079 sunrpc.udp_slot_table_entries=
3080 [NFS,SUNRPC]
3081 Sets the upper limit on the number of simultaneous
3082 RPC calls that can be sent from the client to a
3083 server. Increasing these values may allow you to
3084 improve throughput, but will also increase the
3085 amount of memory reserved for use by the client.
3086
Michal Hocko07555ac2013-08-22 16:35:46 -07003087 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003088 [KNL] Enable accounting of swap in memory resource
3089 controller if no parameter or 1 is given or disable
3090 it if 0 is given (See Documentation/cgroups/memory.txt)
3091
Linus Torvalds1da177e2005-04-16 15:20:36 -07003092 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07003093
Linus Torvalds1da177e2005-04-16 15:20:36 -07003094 switches= [HW,M68k]
3095
Andi Kleene52eec12010-09-08 16:54:17 +02003096 sysfs.deprecated=0|1 [KNL]
3097 Enable/disable old style sysfs layout for old udev
3098 on older distributions. When this option is enabled
3099 very new udev will not work anymore. When this option
3100 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3101 in older udev will not work anymore.
3102 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3103 the kernel configuration.
3104
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003105 sysrq_always_enabled
3106 [KNL]
3107 Ignore sysrq setting - this boot parameter will
3108 neutralize any effect of /proc/sys/kernel/sysrq.
3109 Useful for debugging.
3110
Linus Torvalds1da177e2005-04-16 15:20:36 -07003111 tdfx= [HW,DRM]
3112
David Brownell77437fd2008-07-23 21:28:33 -07003113 test_suspend= [SUSPEND]
3114 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3115 standby suspend) as the system sleep state to briefly
3116 enter during system startup. The system is woken from
3117 this state using a wakeup-capable RTC alarm.
3118
Linus Torvalds1da177e2005-04-16 15:20:36 -07003119 thash_entries= [KNL,NET]
3120 Set number of hash buckets for TCP connection
3121
Len Brownf8707ec2007-08-12 00:12:54 -04003122 thermal.act= [HW,ACPI]
3123 -1: disable all active trip points in all thermal zones
3124 <degrees C>: override all lowest active trip points
3125
Len Brownc52a7412007-08-14 15:49:32 -04003126 thermal.crt= [HW,ACPI]
3127 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003128 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003129
Len Brownf5487142007-08-12 00:12:44 -04003130 thermal.nocrt= [HW,ACPI]
3131 Set to disable actions on ACPI thermal zone
3132 critical and hot trip points.
3133
Len Brown72b33ef2007-08-12 00:12:17 -04003134 thermal.off= [HW,ACPI]
3135 1: disable ACPI thermal control
3136
Len Browna70cdc52007-08-12 00:12:35 -04003137 thermal.psv= [HW,ACPI]
3138 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003139 <degrees C>: override all passive trip points to this
3140 value
Len Browna70cdc52007-08-12 00:12:35 -04003141
Len Brown730ff342007-08-12 00:12:26 -04003142 thermal.tzp= [HW,ACPI]
3143 Specify global default ACPI thermal zone polling rate
3144 <deci-seconds>: poll all this frequency
3145 0: no polling (default)
3146
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003147 threadirqs [KNL]
3148 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003149 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003150
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003151 tmem [KNL,XEN]
3152 Enable the Transcendent memory driver if built-in.
3153
3154 tmem.cleancache=0|1 [KNL, XEN]
3155 Default is on (1). Disable the usage of the cleancache
3156 API to send anonymous pages to the hypervisor.
3157
3158 tmem.frontswap=0|1 [KNL, XEN]
3159 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003160 API to send swap pages to the hypervisor. If disabled
3161 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003162
3163 tmem.selfballooning=0|1 [KNL, XEN]
3164 Default is on (1). Disable the driving of swap pages
3165 to the hypervisor.
3166
3167 tmem.selfshrinking=0|1 [KNL, XEN]
3168 Default is on (1). Partial swapoff that immediately
3169 transfers pages from Xen hypervisor back to the
3170 kernel based on different criteria.
3171
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003172 topology= [S390]
3173 Format: {off | on}
3174 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003175 topology information if the hardware supports this.
3176 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003177 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003178 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003179
Linus Torvalds1da177e2005-04-16 15:20:36 -07003180 tp720= [HW,PS2]
3181
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003182 tpm_suspend_pcr=[HW,TPM]
3183 Format: integer pcr id
3184 Specify that at suspend time, the tpm driver
3185 should extend the specified pcr with zeros,
3186 as a workaround for some chips which fail to
3187 flush the last written pcr on TPM_SaveState.
3188 This will guarantee that all the other pcrs
3189 are saved.
3190
Li Zefan9d612be2009-06-24 17:33:15 +08003191 trace_buf_size=nn[KMG]
3192 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003193
Li Zefan020e5f82009-07-01 10:47:05 +08003194 trace_event=[event-list]
3195 [FTRACE] Set and start specified trace events in order
3196 to facilitate early boot debugging.
3197 See also Documentation/trace/events.txt
3198
Steven Rostedt7bcfaf54f52012-11-01 22:56:07 -04003199 trace_options=[option-list]
3200 [FTRACE] Enable or disable tracer options at boot.
3201 The option-list is a comma delimited list of options
3202 that can be enabled or disabled just as if you were
3203 to echo the option name into
3204
3205 /sys/kernel/debug/tracing/trace_options
3206
3207 For example, to enable stacktrace option (to dump the
3208 stack trace of each event), add to the command line:
3209
3210 trace_options=stacktrace
3211
3212 See also Documentation/trace/ftrace.txt "trace options"
3213 section.
3214
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04003215 traceoff_on_warning
3216 [FTRACE] enable this option to disable tracing when a
3217 warning is hit. This turns off "tracing_on". Tracing can
3218 be enabled again by echoing '1' into the "tracing_on"
3219 file located in /sys/kernel/debug/tracing/
3220
3221 This option is useful, as it disables the trace before
3222 the WARNING dump is called, which prevents the trace to
3223 be filled with content caused by the warning output.
3224
3225 This option can also be set at run time via the sysctl
3226 option: kernel/traceoff_on_warning
3227
Jiri Kosinafcf4d8212012-03-21 16:34:02 -07003228 transparent_hugepage=
3229 [KNL]
3230 Format: [always|madvise|never]
3231 Can be used to control the default behavior of the system
3232 with respect to transparent hugepages.
3233 See Documentation/vm/transhuge.txt for more details.
3234
john stultzd3b8f882009-08-17 16:40:47 -07003235 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07003236 Format: <string>
3237 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07003238 disables clocksource verification at runtime, as well
3239 as the stability checks done at bootup. Used to enable
3240 high-resolution timer mode on older hardware, and in
3241 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07003242 [x86] noirqtime: Do not use TSC to do irq accounting.
3243 Used to run time disable IRQ_TIME_ACCOUNTING on any
3244 platforms where RDTSC is slow and this accounting
3245 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07003246
Randy Dunlapa9913042005-10-23 12:57:11 -07003247 turbografx.map[2|3]= [HW,JOY]
3248 TurboGraFX parallel port interface
3249 Format:
3250 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003251 See also Documentation/input/joystick-parport.txt
3252
Christian Kujaub6935f82011-05-31 15:22:05 +00003253 udbg-immortal [PPC] When debugging early kernel crashes that
3254 happen after console_init() and before a proper
3255 console driver takes over, this boot options might
3256 help "seeing" what's going on.
3257
Eric Dumazetf86dcc52009-10-07 00:37:59 +00003258 uhash_entries= [KNL,NET]
3259 Set number of hash buckets for UDP/UDP-Lite connections
3260
Alan Stern5f8364b2006-12-05 16:29:55 -05003261 uhci-hcd.ignore_oc=
3262 [USB] Ignore overcurrent events (default N).
3263 Some badly-designed motherboards generate lots of
3264 bogus events, for ports that aren't wired to
3265 anything. Set this parameter to avoid log spamming.
3266 Note that genuine overcurrent events won't be
3267 reported either.
3268
Simon Arlotte3a61b02008-07-19 23:32:54 +01003269 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003270 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01003271
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02003272 usbcore.authorized_default=
3273 [USB] Default USB device authorization:
3274 (default -1 = authorized except for wireless USB,
3275 0 = not authorized, 1 = authorized)
3276
Alan Sternb5e795f2007-02-20 15:00:53 -05003277 usbcore.autosuspend=
3278 [USB] The autosuspend time delay (in seconds) used
3279 for newly-detected USB devices (default 2). This
3280 is the time required before an idle device will be
3281 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04003282 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05003283
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003284 usbcore.usbfs_snoop=
3285 [USB] Set to log all usbfs traffic (default 0 = off).
3286
3287 usbcore.blinkenlights=
3288 [USB] Set to cycle leds on hubs (default 0 = off).
3289
3290 usbcore.old_scheme_first=
3291 [USB] Start with the old device initialization
3292 scheme (default 0 = off).
3293
Alan Stern3f5eb8d2011-11-17 16:41:35 -05003294 usbcore.usbfs_memory_mb=
3295 [USB] Memory limit (in MB) for buffers allocated by
3296 usbfs (default = 16, 0 = max = 2047).
3297
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02003298 usbcore.use_both_schemes=
3299 [USB] Try the other device initialization scheme
3300 if the first one fails (default 1 = enabled).
3301
3302 usbcore.initial_descriptor_timeout=
3303 [USB] Specifies timeout for the initial 64-byte
3304 USB_REQ_GET_DESCRIPTOR request in milliseconds
3305 (default 5000 = 5.0 seconds).
3306
Linus Torvalds1da177e2005-04-16 15:20:36 -07003307 usbhid.mousepoll=
3308 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07003309
Alan Sternd4f373e2008-11-10 14:07:45 -05003310 usb-storage.delay_use=
3311 [UMS] The delay in seconds before a new device is
3312 scanned for Logical Units (default 5).
3313
3314 usb-storage.quirks=
3315 [UMS] A list of quirks entries to supplement or
3316 override the built-in unusual_devs list. List
3317 entries are separated by commas. Each entry has
3318 the form VID:PID:Flags where VID and PID are Vendor
3319 and Product ID values (4-digit hex numbers) and
3320 Flags is a set of characters, each corresponding
3321 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05003322 a = SANE_SENSE (collect more than 18 bytes
3323 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05003324 b = BAD_SENSE (don't collect more than 18
3325 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05003326 c = FIX_CAPACITY (decrease the reported
3327 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01003328 d = NO_READ_DISC_INFO (don't use
3329 READ_DISC_INFO command);
3330 e = NO_READ_CAPACITY_16 (don't use
3331 READ_CAPACITY_16 command);
Alan Sternc838ea42008-12-15 10:40:06 -05003332 h = CAPACITY_HEURISTICS (decrease the
3333 reported device capacity by one
3334 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05003335 i = IGNORE_DEVICE (don't bind to this
3336 device);
3337 l = NOT_LOCKABLE (don't try to lock and
3338 unlock ejectable media);
3339 m = MAX_SECTORS_64 (don't transfer more
3340 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04003341 n = INITIAL_READ10 (force a retry of the
3342 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05003343 o = CAPACITY_OK (accept the capacity
3344 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04003345 p = WRITE_CACHE (the device cache is ON
3346 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05003347 r = IGNORE_RESIDUE (the device reports
3348 bogus residue values);
3349 s = SINGLE_LUN (the device has only one
3350 Logical Unit);
3351 w = NO_WP_DETECT (don't test whether the
3352 medium is write-protected).
3353 Example: quirks=0419:aaf5:rl,0421:0433:rc
3354
Stephen Boydac1667d2011-08-13 12:34:50 -07003355 user_debug= [KNL,ARM]
3356 Format: <int>
3357 See arch/arm/Kconfig.debug help text.
3358 1 - undefined instruction events
3359 2 - system calls
3360 4 - invalid data aborts
3361 8 - SIGSEGV faults
3362 16 - SIGBUS faults
3363 Example: user_debug=31
3364
Ian Campbell14315592010-02-17 10:38:10 +00003365 userpte=
3366 [X86] Flags controlling user PTE allocations.
3367
3368 nohigh = do not allocate PTE pages in
3369 HIGHMEM regardless of setting
3370 of CONFIG_HIGHPTE.
3371
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303372 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02003373 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07003374 vdso=1: enable VDSO (default)
3375 vdso=0: disable VDSO mapping
3376
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303377 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01003378 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3379 vdso32=1: enable 32-bit VDSO (default)
3380 vdso32=0: disable 32-bit VDSO mapping
3381
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003382 vector= [IA-64,SMP]
3383 vector=percpu: enable percpu vector domain
3384
Linus Torvalds1da177e2005-04-16 15:20:36 -07003385 video= [FB] Frame buffer configuration
3386 See Documentation/fb/modedb.txt.
3387
Aaron Lu3afe6da2013-06-20 15:08:55 +08003388 video.brightness_switch_enabled= [0,1]
3389 If set to 1, on receiving an ACPI notify event
3390 generated by hotkey, video driver will adjust brightness
3391 level and then send out the event to user space through
3392 the allocated input device; If set to 0, video driver
3393 will only send out the event without touching backlight
3394 brightness level.
3395 default: 1
3396
Pawel Moll81a054c2012-05-09 18:30:16 +01003397 virtio_mmio.device=
3398 [VMMIO] Memory mapped virtio (platform) device.
3399
3400 <size>@<baseaddr>:<irq>[:<id>]
3401 where:
3402 <size> := size (can use standard suffixes
3403 like K, M and G)
3404 <baseaddr> := physical base address
3405 <irq> := interrupt number (as passed to
3406 request_irq())
3407 <id> := (optional) platform device id
3408 example:
3409 virtio_mmio.device=1K@0x100b0000:48:7
3410
3411 Can be used multiple times for multiple devices.
3412
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003413 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003414 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003415 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003416 Use vga=ask for menu.
3417 This is actually a boot loader parameter; the value is
3418 passed to the kernel using a special protocol.
3419
Randy Dunlapa9913042005-10-23 12:57:11 -07003420 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003421 size of <nn>. This can be used to increase the
3422 minimum size (128MB on x86). It can also be used to
3423 decrease the size and leave more room for directly
3424 mapped kernel RAM.
3425
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003426 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3427 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003428
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003429 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3430 Format: <command>
3431
3432 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3433 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003434
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003435 vsyscall= [X86-64]
3436 Controls the behavior of vsyscalls (i.e. calls to
3437 fixed addresses of 0xffffffffff600x00 from legacy
3438 code). Most statically-linked binaries and older
3439 versions of glibc use these calls. Because these
3440 functions are at fixed addresses, they make nice
3441 targets for exploits that can control RIP.
3442
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003443 emulate [default] Vsyscalls turn into traps and are
3444 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003445
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003446 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003447 This is a little bit faster than trapping
3448 and makes a few dynamic recompilers work
3449 better than they would in emulation mode.
3450 It also makes exploits much easier to write.
3451
3452 none Vsyscalls don't work at all. This makes
3453 them quite hard to use for exploits but
3454 might break your system.
3455
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003456 vt.color= [VT] Default text color.
3457 Format: 0xYX, X = foreground, Y = background.
3458 Default: 0x07 = light gray on black.
3459
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08003460 vt.cur_default= [VT] Default cursor shape.
3461 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3462 the parameters of the <Esc>[?A;B;Cc escape sequence;
3463 see VGA-softcursor.txt. Default: 2 = underline.
3464
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003465 vt.default_blu= [VT]
3466 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3467 Change the default blue palette of the console.
3468 This is a 16-member array composed of values
3469 ranging from 0-255.
3470
3471 vt.default_grn= [VT]
3472 Format: <green0>,<green1>,<green2>,...,<green15>
3473 Change the default green palette of the console.
3474 This is a 16-member array composed of values
3475 ranging from 0-255.
3476
3477 vt.default_red= [VT]
3478 Format: <red0>,<red1>,<red2>,...,<red15>
3479 Change the default red palette of the console.
3480 This is a 16-member array composed of values
3481 ranging from 0-255.
3482
3483 vt.default_utf8=
3484 [VT]
3485 Format=<0|1>
3486 Set system-wide default UTF-8 mode for all tty's.
3487 Default is 1, i.e. UTF-8 mode is enabled for all
3488 newly opened terminals.
3489
Matthew Garrettf6c06b62009-11-13 15:14:11 -05003490 vt.global_cursor_default=
3491 [VT]
3492 Format=<-1|0|1>
3493 Set system-wide default for whether a cursor
3494 is shown on new VTs. Default is -1,
3495 i.e. cursors will be created by default unless
3496 overridden by individual drivers. 0 will hide
3497 cursors, 1 will display them.
3498
Clemens Ladisch3855ae12013-08-04 13:09:50 +02003499 vt.italic= [VT] Default color for italic text; 0-15.
3500 Default: 2 = green.
3501
3502 vt.underline= [VT] Default color for underlined text; 0-15.
3503 Default: 3 = cyan.
3504
Randy Dunlap4724ba572010-05-03 11:42:52 -07003505 watchdog timers [HW,WDT] For information on watchdog timers,
3506 see Documentation/watchdog/watchdog-parameters.txt
3507 or other driver-specific files in the
3508 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003509
Tejun Heod55262c2013-04-01 11:23:38 -07003510 workqueue.disable_numa
3511 By default, all work items queued to unbound
3512 workqueues are affine to the NUMA nodes they're
3513 issued on, which results in better behavior in
3514 general. If NUMA affinity needs to be disabled for
3515 whatever reason, this option can be used. Note
3516 that this also can be controlled per-workqueue for
3517 workqueues visible under /sys/bus/workqueue/.
3518
Viresh Kumarcee22a12013-04-08 16:45:40 +05303519 workqueue.power_efficient
3520 Per-cpu workqueues are generally preferred because
3521 they show better performance thanks to cache
3522 locality; unfortunately, per-cpu workqueues tend to
3523 be more power hungry than unbound workqueues.
3524
3525 Enabling this makes the per-cpu workqueues which
3526 were observed to contribute significantly to power
3527 consumption unbound, leading to measurably lower
3528 power usage at the cost of small performance
3529 overhead.
3530
3531 The default value of this parameter is determined by
3532 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3533
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003534 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3535 default x2apic cluster mode on platforms
3536 supporting x2apic.
3537
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003538 x86_intel_mid_timer= [X86-32,APBT]
3539 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07003540 Two valid options are apbt timer only and lapic timer
3541 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07003542 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07003543
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003544 xen_emul_unplug= [HW,X86,XEN]
3545 Unplug Xen emulated devices
3546 Format: [unplug0,][unplug1]
3547 ide-disks -- unplug primary master IDE devices
3548 aux-ide-disks -- unplug non-primary-master IDE devices
3549 nics -- unplug network devices
3550 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01003551 unnecessary -- unplugging emulated devices is
3552 unnecessary even if the host did not respond to
3553 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01003554 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003555
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04003556 xen_nopvspin [X86,XEN]
3557 Disables the ticketlock slowpath using Xen PV
3558 optimizations.
3559
Linus Torvalds1da177e2005-04-16 15:20:36 -07003560 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07003561 Format:
3562 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003563
Randy Dunlapa9913042005-10-23 12:57:11 -07003564______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07003565
3566TODO:
3567
Linus Torvalds1da177e2005-04-16 15:20:36 -07003568 Add more DRM drivers.