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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.
Alan Cox9cfe2682011-01-25 14:18:38 +000047 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
Linus Torvalds1da177e2005-04-16 15:20:36 -070049 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
Mimi Zohar7102ebc2011-05-12 18:33:20 -040052 EVM Extended Verification Module
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 FB The frame buffer device is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070054 FTRACE Function tracing enabled.
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -070055 GCOV GCOV profiling is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070056 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070057 IA-64 IA-64 architecture is enabled.
Mimi Zohar6146f0d2009-02-04 09:06:57 -050058 IMA Integrity measurement architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070060 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Brian Haleyb0f83b22010-02-04 13:36:50 -080061 IPV6 IPv6 support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070062 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
Jason Wessel84c08fd2010-05-20 21:04:24 -050065 KGDB Kernel debugger support is enabled.
Andre Przywarafef07aa2009-07-10 14:20:35 +020066 KVM Kernel Virtual Machine support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070067 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 MDA MDA console support is enabled.
Randy Dunlap16290242011-08-13 12:34:52 -070074 MIPS MIPS architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070075 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070076 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070077 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070078 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070082 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070084 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070086 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
Randy Dunlap163475f2010-08-14 12:36:14 -070095 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
James Morris20510f22007-10-16 23:31:32 -070097 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070098 SELINUX SELinux support is enabled.
John Johansenc1c124e2010-07-29 14:48:09 -070099 APPARMOR AppArmor support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +0900101 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -0700104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
Rajiv Andrade225a9be2010-03-25 00:55:32 -0300106 TPM TPM drivers are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -0500108 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
Pawel Moll81a054c2012-05-09 18:30:16 +0100112 VMMIO Driver for memory mapped virtio devices is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700117 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700120 Documentation/x86/x86_64/boot-options.txt .
Randy Dunlap16290242011-08-13 12:34:52 -0700121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
Stefano Stabellinic1c54132010-05-14 12:44:30 +0100122 XEN Xen support is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123
124In addition, the following text indicates that the option:
125
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
129
130Parameters denoted with BOOT are actually interpreted by the boot
131loader, and have no meaning to the kernel directly.
132Do not modify the syntax of boot loader parameters without extreme
Kyle McMartin954a8b82009-02-19 16:48:14 -0500133need or coordination with <Documentation/x86/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134
Karsten Weiss55588702007-02-13 13:26:21 +0100135There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700136See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100137
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139a trailing = on the name of any parameter states that that parameter will
140be entered as an environment variable, whereas its absence indicates that
141it will appear as a kernel argument readable via /proc/cmdline by programs
142running once the system is up.
143
jens m. noedler9c4751f2006-09-29 02:00:27 -0700144The number of kernel parameters is not limited, but the length of the
145complete command line (parameters including spaces etc.) is limited to
146a fixed number of characters. This limit depends on the architecture
147and is between 256 and 4096 characters. It is defined in the file
148./include/asm/setup.h as COMMAND_LINE_SIZE.
149
Ahmed S. Darwish7a19a232011-02-20 20:08:35 -0800150Finally, the [KMG] suffix is commonly described after a number of kernel
151parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153bytes respectively. Such letter suffixes can also be entirely omitted.
154
jens m. noedler9c4751f2006-09-29 02:00:27 -0700155
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530156 acpi= [HW,ACPI,X86]
Bernhard Walle03d926f2007-03-06 02:29:44 -0800157 Advanced Configuration and Power Interface
Len Brown68ca4062010-02-19 00:09:22 -0500158 Format: { force | off | strict | noirq | rsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -0700162 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800164 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +0800165 copy_dsdt -- copy DSDT to memory
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166
Paul Bolle395cf962011-08-15 02:02:26 +0200167 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168
Takao Indoh4996c022011-07-14 18:05:21 -0400169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
173
Len Browna1fdcc02007-03-11 03:26:14 -0400174 acpi_apic_instance= [ACPI, IOAPIC]
175 Format: <int>
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400178 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400179
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
182 acpi_backlight=video
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
186
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200210
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800214
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
217 default in APIC mode
218
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
221 default in PIC mode
222
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
225
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
227 use by PCI
228 Format: <irq>,<irq>...
229
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
231
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
234
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
239
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530240 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
244
Randy Dunlap4af94f32009-04-17 18:30:28 -0700245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
247
248 acpi_serialize [HW,ACPI] force serialization of AML methods
249
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
253
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200256 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700257 See Documentation/power/video.txt for information on
258 s3_bios and s3_mode.
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700272
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
276
Luca Tettamanti7e905602009-03-30 00:01:27 +0200277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
292
Randy Dunlap4af94f32009-04-17 18:30:28 -0700293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
295
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700296 agp= [AGP]
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
301
Randy Dunlapbcfde332010-06-07 17:10:38 -0700302 ALSA [HW,ALSA]
303 See Documentation/sound/alsa/alsa-parameters.txt
304
Russell Kingd944d542010-02-20 16:13:29 +0000305 alignment= [KNL,ARM]
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
309
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
317
Borislav Petkov8360ee22011-11-21 12:10:19 +0100318 32: only for 32-bit processes
319 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
322
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100323 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200324 Pass parameters to the AMD IOMMU driver in the system.
325 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
329 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200330 off - do not initialize any AMD IOMMU found in
331 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900337
Shuah Khanc099cf12012-05-24 15:58:25 -0600338 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
343
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
346 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200347 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
353
Randy Dunlapa9913042005-10-23 12:57:11 -0700354 apc= [HW,SPARC]
355 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356 Format: noidle
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
360
Randy Dunlapca1eda22009-05-06 16:02:58 -0700361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700362 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700366
Brian Haleyb0f83b22010-02-04 13:36:50 -0800367 autoconf= [IPV6]
368 See Documentation/networking/ipv6.txt.
369
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
378
Linus Torvalds1da177e2005-04-16 15:20:36 -0700379 apm= [APM] Advanced Power Management
Pavel Machek71f770552008-07-04 09:59:43 -0700380 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
384
385 ataflop= [HW,M68k]
386
387 atarimouse= [HW,MOUSE] Atari Mouse
388
Linus Torvalds1da177e2005-04-16 15:20:36 -0700389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
391
392 atkbd.reset= [HW] Reset keyboard during initialization
393
Randy Dunlapa9913042005-10-23 12:57:11 -0700394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700396
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
398 keyboards
399
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700402
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405
Linus Torvalds1da177e2005-04-16 15:20:36 -0700406 baycom_epp= [HW,AX25]
407 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700408
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
410 Format: <io>,<mode>
411 See header of drivers/net/hamradio/baycom_par.c.
412
Randy Dunlapa9913042005-10-23 12:57:11 -0700413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
417
Randy Dunlapa9913042005-10-23 12:57:11 -0700418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
422
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
425 no delay (0).
426 Format: integer
427
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
429
Linus Torvalds1da177e2005-04-16 15:20:36 -0700430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700431 bttv.radio= Most important insmod options are available as
432 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200434 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
438 at a time.
439
Linus Torvalds1da177e2005-04-16 15:20:36 -0700440 c101= [NET] Moxa C101 synchronous serial card
441
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
448
James Morris20510f22007-10-16 23:31:32 -0700449 capability.disable=
450 [SECURITY] Disable capabilities. This would normally
451 be used only if an alternative security model is to be
452 configured. Potentially dangerous and should only be
453 used if you are entirely sure of the consequences.
454
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100455 ccw_timeout_log [S390]
456 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700457
Paul Menage8bab8dd2008-04-04 14:29:57 -0700458 cgroup_disable= [KNL] Disable a particular controller
459 Format: {name of the controller(s) to disable}
460 {Currently supported controllers - "memory"}
461
Linus Torvalds1da177e2005-04-16 15:20:36 -0700462 checkreqprot [SELINUX] Set initial checkreqprot flag value.
463 Format: { "0" | "1" }
464 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700465 0 -- check protection applied by kernel (includes
466 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700467 1 -- check protection requested by application.
468 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700469 Value can be changed at runtime via
470 /selinux/checkreqprot.
471
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100472 cio_ignore= [S390]
473 See Documentation/s390/CommonIO for details.
474
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700475 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700476 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200477 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700478 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200479 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 Format: { pit | tsc | cyclone | pmtmr }
481
John Stultz592913e2010-07-13 17:56:20 -0700482 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700483 Format: <string>
484 Override the default clocksource and use the clocksource
485 with the name specified.
486 Some clocksource names to choose from, depending on
487 the platform:
488 [all] jiffies (this is the base, fallback clocksource)
489 [ACPI] acpi_pm
490 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
491 pxa_timer,timer3,32k_counter,timer0_1
492 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700493 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700494 scx200_hrt on Geode; cyclone on IBM x440
495 [MIPS] MIPS
496 [PARISC] cr16
497 [S390] tod
498 [SH] SuperH
499 [SPARC64] tick
500 [X86-64] hpet,tsc
501
Andi Kleenac72e782008-01-30 13:33:21 +0100502 clearcpuid=BITNUM [X86]
503 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800504 arch/x86/include/asm/cpufeature.h for the valid bit
505 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100506 stable over kernel options, but the vendor specific
507 ones should be.
508 Also note that user programs calling CPUID directly
509 or using the feature without checking anything
510 will still see it. This just prevents it from
511 being used by the kernel or shown in /proc/cpuinfo.
512 Also note the kernel might malfunction if you disable
513 some critical bits.
514
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100515 cma=nn[MG] [ARM,KNL]
516 Sets the size of kernel global memory area for contiguous
517 memory allocations. For more information, see
518 include/linux/dma-contiguous.h
519
Robert Jennings14f966e2009-04-15 05:55:32 +0000520 cmo_free_hint= [PPC] Format: { yes | no }
521 Specify whether pages are marked as being inactive
522 when they are freed. This is used in CMO environments
523 to determine OS memory pressure for page stealing by
524 a hypervisor.
525 Default: yes
526
Marek Szyprowskic7909502011-12-29 13:09:51 +0100527 coherent_pool=nn[KMG] [ARM,KNL]
528 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200529 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100530
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530531 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100532 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100533 Range: 0 - 8192
534 Default: 64
535
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700537 Format:
538 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700539
540 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
541 Format: <io>[,<irq>]
542
Randy Dunlapa9913042005-10-23 12:57:11 -0700543 com90xx= [HW,NET]
544 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545 Format: <io>[,<irq>[,<memstart>]]
546
547 condev= [HW,S390] console device
548 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700549
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 console= [KNL] Output console device and options.
551
552 tty<n> Use the virtual console device <n>.
553
554 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800555 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700556 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800557 the form "bbbbpnf", where "bbbb" is the baud rate,
558 "p" is parity ("n", "o", or "e"), "n" is number of
559 bits, and "f" is flow control ("r" for RTS or
560 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700561
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800562 See Documentation/serial-console.txt for more
563 information. See
564 Documentation/networking/netconsole.txt for an
565 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700567 uart[8250],io,<addr>[,options]
568 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700569 Start an early, polled-mode console on the 8250/16550
570 UART at the specified I/O port or MMIO address,
571 switching to the matching ttyS device later. The
572 options are the same as for ttyS, above.
573
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700574 If the device connected to the port is not a TTY but a braille
575 device, prepend "brl," before the device type, for instance
576 console=brl,ttyS0
577 For now, only VisioBraille is supported.
578
Daniel Mackf324edc2009-06-16 15:33:52 -0700579 consoleblank= [KNL] The console blank (screen saver) timeout in
580 seconds. Defaults to 10*60 = 10mins. A value of 0
581 disables the blank timer.
582
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800583 coredump_filter=
584 [KNL] Change the default value for
585 /proc/<pid>/coredump_filter.
586 See also Documentation/filesystems/proc.txt.
587
Len Brown62027ae2011-04-01 18:13:10 -0400588 cpuidle.off=1 [CPU_IDLE]
589 disable the cpuidle sub-system
590
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700592 Format:
593 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700594
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800595 crashkernel=size[KMG][@offset[KMG]]
596 [KNL] Using kexec, Linux can switch to a 'crash kernel'
597 upon panic. This parameter reserves the physical
598 memory region [offset, offset + size] for that kernel
599 image. If '@offset' is omitted, then a suitable offset
600 is selected automatically. Check
601 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700602
Bernhard Wallefb391592007-10-18 23:41:02 -0700603 crashkernel=range1:size1[,range2:size2,...][@offset]
604 [KNL] Same as above, but depends on the memory
605 in the running system. The syntax of range is
606 start-[end] where start and end are both
607 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800608 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700609
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610 cs89x0_dma= [HW,NET]
611 Format: <dma>
612
613 cs89x0_media= [HW,NET]
614 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700615
Randy Dunlapa9913042005-10-23 12:57:11 -0700616 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700617 See header of drivers/s390/block/dasd_devmap.c.
618
619 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
620 (one device per port)
621 Format: <port#>,<type>
622 See also Documentation/input/joystick-parport.txt
623
Thomas Renningera648ec02010-08-06 16:11:02 +0200624 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
625 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600626 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200627
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628 debug [KNL] Enable kernel debugging (events log level).
629
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700630 debug_locks_verbose=
631 [KNL] verbose self-tests
632 Format=<0|1>
633 Print debugging info while doing the locking API
634 self-tests.
635 We default to 0 (no extra messages), setting it to
636 1 will print _a lot_ more information - normally
637 only useful to kernel developers.
638
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700639 debug_objects [KNL] Enable object debugging
640
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500641 no_debug_objects
642 [KNL] Disable object debugging
643
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800644 debug_guardpage_minorder=
645 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
646 parameter allows control of the order of pages that will
647 be intentionally kept free (and hence protected) by the
648 buddy allocator. Bigger value increase the probability
649 of catching random memory corruption, but reduce the
650 amount of memory for normal system use. The maximum
651 possible value is MAX_ORDER/2. Setting this parameter
652 to 1 or 2 should be enough to identify most random
653 memory corruption problems caused by bugs in kernel or
654 driver code when a CPU writes to (or reads from) a
655 random memory location. Note that there exists a class
656 of memory corruptions problems caused by buggy H/W or
657 F/W or by drivers badly programing DMA (basically when
658 memory is written at bus level and the CPU MMU is
659 bypassed) which are not detectable by
660 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
661 tracking down these problems.
662
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200663 debugpat [X86] Enable PAT debugging
664
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200665 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700666 Format: <area>[,<node>]
667 See also Documentation/networking/decnet.txt.
668
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700669 default_hugepagesz=
670 [same as hugepagesz=] The size of the default
671 HugeTLB page size. This is the size represented by
672 the legacy /proc/ hugepages APIs, used for SHM, and
673 default size when mounting hugetlbfs filesystems.
674 Defaults to the default architecture's huge page size
675 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700676
Linus Torvalds1da177e2005-04-16 15:20:36 -0700677 dhash_entries= [KNL]
678 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700679
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 digi= [HW,SERIAL]
681 IO parameters + enable/disable command.
682
683 digiepca= [HW,SERIAL]
684 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000685 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700686
Brian Haleyb0f83b22010-02-04 13:36:50 -0800687 disable= [IPV6]
688 See Documentation/networking/ipv6.txt.
689
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000690 disable_ddw [PPC/PSERIES]
691 Disable Dynamic DMA Window support. Use this if
692 to workaround buggy firmware.
693
Brian Haleyb0f83b22010-02-04 13:36:50 -0800694 disable_ipv6= [IPV6]
695 See Documentation/networking/ipv6.txt.
696
Yinghai Lu95ffa242008-04-29 03:52:33 -0700697 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700698 The kernel tries to adjust MTRR layout from continuous
699 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700700 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700701
Yinghai Lu093af8d2008-01-30 13:33:32 +0100702 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100703 By default the kernel will trim any uncacheable
704 memory out of your available memory pool based on
705 MTRR settings. This parameter disables that behavior,
706 possibly causing your machine to run very slowly.
707
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530708 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700709 Disable PIN 1 of APIC timer
710 Can be useful to work around chipset bugs.
711
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700712 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
713 this option disables the debugging code at boot.
714
715 dma_debug_entries=<number>
716 This option allows to tune the number of preallocated
717 entries for DMA-API debugging code. One entry is
718 required per DMA-API allocation. Use this if the
719 DMA-API debugging code disables itself because the
720 architectural default is too low.
721
Joerg Roedel1745de52009-05-22 21:49:51 +0200722 dma_debug_driver=<driver_name>
723 With this option the DMA-API debugging driver
724 filter feature can be enabled at boot time. Just
725 pass the driver to filter for as the parameter.
726 The filter can be disabled or changed to another
727 driver later using sysfs.
728
Carsten Emdeda0df922012-03-18 22:37:33 +0100729 drm_kms_helper.edid_firmware=[<connector>:]<file>
730 Broken monitors, graphic adapters and KVMs may
731 send no or incorrect EDID data sets. This parameter
732 allows to specify an EDID data set in the
733 /lib/firmware directory that is used instead.
734 Generic built-in EDID data sets are used, if one of
735 edid/1024x768.bin, edid/1280x1024.bin,
736 edid/1680x1050.bin, or edid/1920x1080.bin is given
737 and no file with the same name exists. Details and
738 instructions how to build your own EDID data are
739 available in Documentation/EDID/HOWTO.txt. An EDID
740 data set will only be used for a particular connector,
741 if its name and a colon are prepended to the EDID
742 name.
743
Linus Torvalds1da177e2005-04-16 15:20:36 -0700744 dscc4.setup= [NET]
745
Jim Cromie29e36c92012-04-27 14:30:41 -0600746 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
747 module.dyndbg[="val"]
748 Enable debug messages at boot time. See
749 Documentation/dynamic-debug-howto.txt for details.
750
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700751 earlycon= [KNL] Output early console device and options.
752 uart[8250],io,<addr>[,options]
753 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700754 uart[8250],mmio32,<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700755 Start an early, polled-mode console on the 8250/16550
756 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700757 MMIO inter-register address stride is either 8-bit
758 (mmio) or 32-bit (mmio32).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700759 The options are the same as for ttyS, above.
760
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530761 earlyprintk= [X86,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700762 earlyprintk=vga
763 earlyprintk=serial[,ttySn[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500764 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500765 earlyprintk=dbgp[debugController#]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700766
Randy Dunlapa9913042005-10-23 12:57:11 -0700767 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768 takes over.
769
Yinghai Lu5c059172008-07-24 17:29:40 -0700770 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700771
772 Currently only ttyS0 and ttyS1 are supported.
773
774 Interaction with the standard serial driver is not
775 very good.
776
777 The VGA output is eventually overwritten by the real
778 console.
779
Jason Wessel97311912010-05-20 21:04:30 -0500780 ekgdboc= [X86,KGDB] Allow early kernel console debugging
781 ekgdboc=kbd
782
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300783 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -0500784 the boot argument: earlyprintk=vga
785
Linus Torvalds1da177e2005-04-16 15:20:36 -0700786 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700787 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700788
Linus Torvalds1da177e2005-04-16 15:20:36 -0700789 eisa_irq_edge= [PARISC,HW]
790 See header of drivers/parisc/eisa.c.
791
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700792 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700793 See comment before function elanfreq_setup() in
Pavel Machek71f770552008-07-04 09:59:43 -0700794 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700795
796 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +0100797 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +0200798 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -0700799 Documentation/block/deadline-iosched.txt for details.
800
Michael Holzheud3bf3792011-10-30 15:16:37 +0100801 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -0700802 Specifies physical address of start of kernel core
Michael Holzheud3bf3792011-10-30 15:16:37 +0100803 image elf header and optionally the size. Generally
804 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -0800805 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700806
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700807 enable_mtrr_cleanup [X86]
808 The kernel tries to adjust MTRR layout from continuous
809 to discrete, to make X server driver able to add WB
810 entry later. This parameter enables that.
811
Randy Dunlapca1eda22009-05-06 16:02:58 -0700812 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700813 Enable PIN 1 of APIC timer
814 Can be useful to work around chipset bugs
815 (in particular on some ATI chipsets).
816 The kernel tries to set a reasonable default.
817
Linus Torvalds1da177e2005-04-16 15:20:36 -0700818 enforcing [SELINUX] Set initial enforcing status.
819 Format: {"0" | "1"}
820 See security/selinux/Kconfig help text.
821 0 -- permissive (log only, no denials).
822 1 -- enforcing (deny and log).
823 Default value is 0.
824 Value can be changed at runtime via /selinux/enforce.
825
Huang Yinga08f82d2010-05-18 14:35:21 +0800826 erst_disable [ACPI]
827 Disable Error Record Serialization Table (ERST)
828 support.
829
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 ether= [HW,NET] Ethernet cards parameters
831 This option is obsoleted by the "netdev=" option, which
832 has equivalent usage. See its documentation for details.
833
Mimi Zohar7102ebc2011-05-12 18:33:20 -0400834 evm= [EVM]
835 Format: { "fix" }
836 Permit 'security.evm' to be updated regardless of
837 current integrity status.
838
Akinobu Mitade1ba092006-12-08 02:39:42 -0800839 failslab=
840 fail_page_alloc=
841 fail_make_request=[KNL]
842 General fault injection mechanism.
843 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +0200844 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -0800845
Linus Torvalds1da177e2005-04-16 15:20:36 -0700846 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000847 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700848
Alex Chiangf13ae302008-05-08 14:03:23 -0600849 force_pal_cache_flush
850 [IA-64] Avoid check_sal_cache_flush which may hang on
851 buggy SAL_CACHE_FLUSH implementations. Using this
852 parameter will force ia64_sal_cache_flush to call
853 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
854
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100855 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400856 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100857 as early as possible in order to facilitate early
858 boot debugging.
859
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200860 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -0400861 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +0200862 If no parameter is passed, ftrace will dump
863 buffers of all CPUs, but if you pass orig_cpu, it will
864 dump only the buffer of the CPU that triggered the
865 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400866
867 ftrace_filter=[function-list]
868 [FTRACE] Limit the functions traced by the function
869 tracer at boot up. function-list is a comma separated
870 list of functions. This list can be changed at run
871 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -0700872 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -0400873
874 ftrace_notrace=[function-list]
875 [FTRACE] Do not trace the functions specified in
876 function-list. This list can be changed at run time
877 by the set_ftrace_notrace file in the debugfs
878 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100879
Stefan Assmann369bc182009-10-12 22:17:21 +0200880 ftrace_graph_filter=[function-list]
881 [FTRACE] Limit the top level callers functions traced
882 by the function graph tracer at boot up.
883 function-list is a comma separated list of functions
884 that can be changed at run time by the
885 set_graph_function file in the debugfs tracing directory.
886
Linus Torvalds1da177e2005-04-16 15:20:36 -0700887 gamecon.map[2|3]=
888 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
889 support via parallel port (up to 5 devices per port)
890 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
891 See also Documentation/input/joystick-parport.txt
892
893 gamma= [HW,DRM]
894
Yinghai Luaaf23042008-01-30 13:33:09 +0100895 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
896 Format: off | on
897 default: on
898
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -0700899 gcov_persist= [GCOV] When non-zero (default), profiling data for
900 kernel modules is saved and remains accessible via
901 debugfs, even when the module is unloaded/reloaded.
902 When zero, profiling data is discarded and associated
903 debugfs files are removed at module unload time.
904
Linus Torvalds1da177e2005-04-16 15:20:36 -0700905 gpt [EFI] Forces disk with valid GPT signature but
906 invalid Protective MBR to be treated as GPT.
907
Linus Torvalds1da177e2005-04-16 15:20:36 -0700908 hashdist= [KNL,NUMA] Large hashes allocated during boot
909 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -0700910 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700911 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700912
913 hcl= [IA-64] SGI's Hardware Graph compatibility layer
914
915 hd= [EIDE] (E)IDE hard drive subsystem geometry
916 Format: <cyl>,<head>,<sect>
917
Huang Yingea8c0712010-05-18 14:35:15 +0800918 hest_disable [ACPI]
919 Disable Hardware Error Source Table (HEST) support;
920 corresponding firmware-first mode error processing
921 logic will be disabled.
922
Linus Torvalds1da177e2005-04-16 15:20:36 -0700923 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
924 size of <nn>. This works even on boxes that have no
925 highmem otherwise. This also works to reduce highmem
926 size on bigger boxes.
927
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800928 highres= [KNL] Enable/disable high resolution timer mode.
929 Valid parameters: "on", "off"
930 Default: "on"
931
Linus Torvalds1da177e2005-04-16 15:20:36 -0700932 hisax= [HW,ISDN]
933 See Documentation/isdn/README.HiSax.
934
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700935 hlt [BUGS=ARM,SH]
936
937 hpet= [X86-32,HPET] option to control HPET usage
938 Format: { enable (default) | disable | force |
939 verbose }
940 disable: disable HPET and use PIT instead
941 force: allow force enabled of undocumented chips (ICH4,
942 VIA, nVidia)
943 verbose: show contents of HPET registers during setup
944
Andi Kleenb4718e62008-07-23 21:27:51 -0700945 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
946 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700947 On x86-64 and powerpc, this option can be specified
948 multiple times interleaved with hugepages= to reserve
949 huge pages of different sizes. Valid pages sizes on
950 x86-64 are 2M (when the CPU supports "pse") and 1G
951 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700952 Note that 1GB pages can only be allocated at boot time
953 using hugepages= and not freed afterwards.
Paul Mundt6902aa82008-09-21 17:14:42 +0900954
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100955 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
956 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +0100957 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
958 If specified, z/VM IUCV HVC accepts connections
959 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100960
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -0700961 keep_bootcon [KNL]
962 Do not unregister boot console at start. This is only
963 useful for debugging when something happens in the window
964 between unregistering the boot console and initializing
965 the real console.
966
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700967 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -0700968 or register an additional I2C bus that is not
969 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -0700970 Format:
971 <bus_id>,<clkrate>
972
Jiri Kosina36d95732008-10-06 02:51:09 -0400973 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200975 i8042.dumbkbd [HW] Pretend that controller can only read data from
976 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977 (Don't attempt to blink the leds)
978 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500979 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400980 i8042.noloop [HW] Disable the AUX Loopback command while probing
981 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700982 i8042.nomux [HW] Don't check presence of an active multiplexing
983 controller
984 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
985 controllers
Masanari Iida24775d62012-02-15 00:26:42 +0900986 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Linus Torvalds1da177e2005-04-16 15:20:36 -0700987 i8042.reset [HW] Reset the controller during init and cleanup
988 i8042.unlock [HW] Unlock (ignore) the keylock
989
990 i810= [HW,DRM]
991
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700992 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
993 indicates that the driver is running on unsupported
994 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700995 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
996 does not match list of supported models.
997 i8k.power_status
998 [HW] Report power status in /proc/i8k
999 (disabled by default)
1000 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1001 capability is set.
1002
Carsten Emde4dca20e2012-03-15 15:56:26 +01001003 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001004 [DRM] Invert the sense of the variable that is used to
1005 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001006 brightness value of 0 indicates backlight switched off,
1007 and the maximum of the brightness value sets the backlight
1008 to maximum brightness. If this parameter is set to 0
1009 (default) and the machine requires it, or this parameter
1010 is set to 1, a brightness value of 0 sets the backlight
1011 to maximum brightness, and the maximum of the brightness
1012 value switches the backlight off.
1013 -1 -- never invert brightness
1014 0 -- machine default
1015 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001016
Linus Torvalds1da177e2005-04-16 15:20:36 -07001017 icn= [HW,ISDN]
1018 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1019
David Fries0af80c02009-02-25 20:28:21 +01001020 ide-core.nodma= [HW] (E)IDE subsystem
1021 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001022 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1023 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001024 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001025
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001026 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1027 Claim all unknown PCI IDE storage controllers.
1028
Andi Kleenf039b752007-05-02 19:27:12 +02001029 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001030 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1031 Poll forces a polling idle loop that can slightly
1032 improve the performance of waking up a idle CPU, but
1033 will use a lot of power and make the system run hot.
1034 Not recommended.
1035 idle=mwait: On systems which support MONITOR/MWAIT but
1036 the kernel chose to not use it because it doesn't save
1037 as much power as a normal idle loop, use the
1038 MONITOR/MWAIT idle loop anyways. Performance should be
1039 the same as idle=poll.
1040 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001041 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001042 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001043
Ingo Molnar792908222006-12-06 20:40:51 -08001044 ignore_loglevel [KNL]
1045 Ignore loglevel setting - this will print /all/
1046 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001047 We also add it as printk module parameter, so users
1048 could change it dynamically, usually by
1049 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001050
Linus Torvalds1da177e2005-04-16 15:20:36 -07001051 ihash_entries= [KNL]
1052 Set number of hash buckets for inode cache.
1053
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001054 ima_appraise= [IMA] appraise integrity measurements
1055 Format: { "off" | "enforce" | "fix" }
1056 default: "enforce"
1057
Mimi Zohar07f6a792011-03-09 22:25:48 -05001058 ima_appraise_tcb [IMA]
1059 The builtin appraise policy appraises all files
1060 owned by uid=0.
1061
Mimi Zohar3323eec2009-02-04 09:06:58 -05001062 ima_audit= [IMA]
1063 Format: { "0" | "1" }
1064 0 -- integrity auditing messages. (Default)
1065 1 -- enable informational integrity auditing messages.
1066
1067 ima_hash= [IMA]
Stephen Hemmingera9ed83a2009-09-17 14:14:45 -07001068 Format: { "sha1" | "md5" }
Mimi Zohar3323eec2009-02-04 09:06:58 -05001069 default: "sha1"
1070
Eric Paris5789ba32009-05-21 15:47:06 -04001071 ima_tcb [IMA]
1072 Load a policy which meets the needs of the Trusted
1073 Computing Base. This means IMA will measure all
1074 programs exec'd, files mmap'd for exec, and all files
1075 opened for read by uid=0.
1076
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077 init= [KNL]
1078 Format: <full_path>
1079 Run specified binary instead of /sbin/init as init
1080 process.
1081
1082 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1083 for working out where the kernel is dying during
1084 startup.
1085
1086 initrd= [BOOT] Specify the location of the initial ramdisk
1087
1088 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1089 Format: <irq>
1090
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001091 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001092 on
1093 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001094 off
1095 Disable intel iommu driver.
1096 igfx_off [Default Off]
1097 By default, gfx is mapped as normal device. If a gfx
1098 device has a dedicated DMAR unit, the DMAR unit is
1099 bypassed by not enabling DMAR with this option. In
1100 this case, gfx device will use physical address for
1101 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001102 forcedac [x86_64]
1103 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001104 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001105 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001106 than 32-bit addressing. The default is to look
1107 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001108 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001109 strict [Default Off]
1110 With this option on every unmap_single operation will
1111 result in a hardware IOTLB flush operation as opposed
1112 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001113 sp_off [Default Off]
1114 By default, super page will be supported if Intel IOMMU
1115 has the capability. With this option, super page will
1116 not be supported.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001117
1118 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1119 0 disables intel_idle and fall back on acpi_idle.
1120 1 to 6 specify maximum depth of C-state.
1121
Chris Wrightd1423d52010-07-20 11:06:49 -07001122 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001123 on enable Interrupt Remapping (default)
1124 off disable Interrupt Remapping
1125 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001126 no_x2apic_optout
1127 BIOS x2APIC opt-out request will be ignored
Chris Wrightd1423d52010-07-20 11:06:49 -07001128
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001129 iomem= Disable strict checking of access to MMIO memory
1130 strict regions from userspace.
1131 relaxed
1132
1133 iommu= [x86]
1134 off
1135 force
1136 noforce
1137 biomerge
1138 panic
1139 nopanic
1140 merge
1141 nomerge
1142 forcesac
1143 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001144 pt [x86, IA-64]
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001145
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001146
1147 io7= [HW] IO7 for Marvel based alpha systems
1148 See comment before marvel_specify_io7 in
1149 arch/alpha/kernel/core_marvel.c.
1150
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301151 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001152 0x80
1153 Standard port 0x80 based delay
1154 0xed
1155 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001156 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001157 Simple two microseconds delay
1158 none
1159 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001160
Linus Torvalds1da177e2005-04-16 15:20:36 -07001161 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001162 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001163
1164 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001165 See comment before ip2_setup() in
1166 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001167
Alan Cox200803d2005-06-28 20:45:18 -07001168 irqfixup [HW]
1169 When an interrupt is not handled search all handlers
1170 for it. Intended to get systems with badly broken
1171 firmware running.
1172
1173 irqpoll [HW]
1174 When an interrupt is not handled search all handlers
1175 for it. Also check all handlers each timer
1176 interrupt. Intended to get systems with badly broken
1177 firmware running.
1178
Linus Torvalds1da177e2005-04-16 15:20:36 -07001179 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001180 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001181
1182 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001183 Format:
1184 <cpu number>,...,<cpu number>
1185 or
Li Zefanb225d442008-11-06 12:53:39 -08001186 <cpu number>-<cpu number>
1187 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001188 or a mixture
1189 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001190
Linus Torvalds1da177e2005-04-16 15:20:36 -07001191 This option can be used to specify one or more CPUs
1192 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001193 algorithms. You can move a process onto or off an
1194 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001195 <cpu number> begins at 0 and the maximum value is
1196 "number of CPUs in system - 1".
1197
1198 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001199 alternative -- manually setting the CPU mask of all
1200 tasks in the system -- can cause problems and
1201 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001202
Randy Dunlapa9913042005-10-23 12:57:11 -07001203 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001204
1205 js= [HW,JOY] Analog joystick
1206 See Documentation/input/joystick.txt.
1207
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001208 keepinitrd [HW,ARM]
1209
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301210 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001211 specifies the amount of memory usable by the kernel
1212 for non-movable allocations. The requested amount is
1213 spread evenly throughout all nodes in the system. The
1214 remaining memory in each node is used for Movable
1215 pages. In the event, a node is too small to have both
1216 kernelcore and Movable pages, kernelcore pages will
1217 take priority and other nodes will have a larger number
1218 of kernelcore pages. The Movable zone is used for the
1219 allocation of pages that may be reclaimed or moved
1220 by the page migration subsystem. This means that
1221 HugeTLB pages may not be allocated from this zone.
1222 Note that allocations like PTEs-from-HighMem still
1223 use the HighMem zone if it exists, and the Normal
1224 zone if it does not.
1225
Jason Wessel4fe1da42010-05-20 21:04:31 -05001226 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1227 Format: <Controller#>[,poll interval]
1228 The controller # is the number of the ehci usb debug
1229 port as it is probed via PCI. The poll interval is
1230 optional and is the number seconds in between
1231 each poll cycle to the debug port in case you need
1232 the functionality for interrupting the kernel with
1233 gdb or control-c on the dbgp connection. When
1234 not using this parameter you use sysrq-g to break into
1235 the kernel debugger.
1236
Jason Wessel84c08fd2010-05-20 21:04:24 -05001237 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001238 Requires a tty driver that supports console polling,
1239 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001240 Serial only format: <serial_device>[,baud]
1241 keyboard only format: kbd
1242 keyboard and serial format: kbd,<serial_device>[,baud]
1243 Optional Kernel mode setting:
1244 kms, kbd format: kms,kbd
1245 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001246
Jason Wessel84c08fd2010-05-20 21:04:24 -05001247 kgdbwait [KGDB] Stop kernel execution and enter the
1248 kernel debugger at the earliest opportunity.
1249
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001250 kmac= [MIPS] korina ethernet MAC address.
1251 Configure the RouterBoard 532 series on-chip
1252 Ethernet adapter MAC address.
1253
Catalin Marinas04f70332009-06-11 13:22:39 +01001254 kmemleak= [KNL] Boot-time kmemleak enable/disable
1255 Valid arguments: on, off
1256 Default: on
1257
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301258 kstack=N [X86] Print N words from the kernel stack
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001259 in oops dumps.
1260
Andre Przywarafef07aa2009-07-10 14:20:35 +02001261 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1262 Default is 0 (don't ignore, but inject #GP)
1263
Xiao Guangronga182d872010-09-20 22:17:48 +08001264 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1265 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001266 Default is 0 (off)
1267
Andre Przywarafef07aa2009-07-10 14:20:35 +02001268 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001269 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001270
1271 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1272 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001273 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001274
Andre Przywarafef07aa2009-07-10 14:20:35 +02001275 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1276 (virtualized MMU) support on capable Intel chips.
1277 Default is 1 (enabled)
1278
1279 kvm-intel.emulate_invalid_guest_state=
1280 [KVM,Intel] Enable emulation of invalid guest states
1281 Default is 0 (disabled)
1282
1283 kvm-intel.flexpriority=
1284 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1285 Default is 1 (enabled)
1286
Sasha Levine1a72ae2011-08-09 14:28:35 +03001287 kvm-intel.nested=
1288 [KVM,Intel] Enable VMX nesting (nVMX).
1289 Default is 0 (disabled)
1290
Andre Przywarafef07aa2009-07-10 14:20:35 +02001291 kvm-intel.unrestricted_guest=
1292 [KVM,Intel] Disable unrestricted guest feature
1293 (virtualized real and unpaged mode) on capable
1294 Intel chips. Default is 1 (enabled)
1295
1296 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1297 feature (tagged TLBs) on capable Intel chips.
1298 Default is 1 (enabled)
1299
Linus Torvalds1da177e2005-04-16 15:20:36 -07001300 l2cr= [PPC]
1301
Robert Brosea78bfbf2008-03-29 07:20:23 +11001302 l3cr= [PPC]
1303
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001304 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001305 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001306
Suresh Siddha279f1462012-10-22 14:37:58 -07001307 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1308 value for LAPIC timer one-shot implementation. Default
1309 back to the programmable timer unit in the LAPIC.
1310
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301311 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001312 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001313
FD Camifcb71f62008-01-06 19:08:56 +01001314 libata.dma= [LIBATA] DMA control
1315 libata.dma=0 Disable all PATA and SATA DMA
1316 libata.dma=1 PATA and SATA Disk DMA only
1317 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001318 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001319 Combinations also work, so libata.dma=3 enables DMA
1320 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001321
Michael Prokop20308872009-08-06 00:14:10 +02001322 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1323 libata.ignore_hpa=0 keep BIOS limits (default)
1324 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001325
Dave Jones78e70c22007-09-27 11:50:13 -04001326 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1327 when set.
1328 Format: <int>
1329
Tejun Heo33267322008-02-13 09:15:09 +09001330 libata.force= [LIBATA] Force configurations. The format is comma
1331 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001332 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001333 matching port, link or device. Basically, it matches
1334 the ATA ID string printed on console by libata. If
1335 the whole ID part is omitted, the last PORT and DEVICE
1336 values are used. If ID hasn't been specified yet, the
1337 configuration applies to all ports, links and devices.
1338
1339 If only DEVICE is omitted, the parameter applies to
1340 the port and all links and devices behind it. DEVICE
1341 number of 0 either selects the first device or the
1342 first fan-out link behind PMP device. It does not
1343 select the host link. DEVICE number of 15 selects the
1344 host link and device attached to it.
1345
1346 The VAL specifies the configuration to force. As long
1347 as there's no ambiguity shortcut notation is allowed.
1348 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1349 The following configurations can be forced.
1350
1351 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1352 Any ID with matching PORT is used.
1353
1354 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1355
1356 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1357 udma[/][16,25,33,44,66,100,133] notation is also
1358 allowed.
1359
1360 * [no]ncq: Turn on or off NCQ.
1361
Tejun Heo05944bd2008-08-13 20:19:09 +09001362 * nohrst, nosrst, norst: suppress hard, soft
1363 and both resets.
1364
Dan Williamsca6d43b2012-06-21 23:41:41 -07001365 * rstonce: only attempt one reset during
1366 hot-unplug link recovery
1367
Tejun Heo43c9c592010-05-23 12:59:11 +02001368 * dump_id: dump IDENTIFY data.
1369
Tejun Heo33267322008-02-13 09:15:09 +09001370 If there are multiple matching configurations changing
1371 the same attribute, the last one is used.
1372
Yinghai Lu95f72d12010-07-12 14:36:09 +10001373 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be252009-01-06 14:42:44 -08001374
Linus Torvalds1da177e2005-04-16 15:20:36 -07001375 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001376 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001377
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001378 lockd.nlm_grace_period=P [NFS] Assign grace period.
1379 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001380
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001381 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1382 Format: <integer>
1383
1384 lockd.nlm_timeout=T [NFS] Assign timeout value.
1385 Format: <integer>
1386
1387 lockd.nlm_udpport=M [NFS] Assign UDP port.
1388 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001389
1390 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1391 Format: <irq>
1392
1393 loglevel= All Kernel Messages with a loglevel smaller than the
1394 console loglevel will be printed to the console. It can
1395 also be changed with klogd or other programs. The
1396 loglevels are defined as follows:
1397
1398 0 (KERN_EMERG) system is unusable
1399 1 (KERN_ALERT) action must be taken immediately
1400 2 (KERN_CRIT) critical conditions
1401 3 (KERN_ERR) error conditions
1402 4 (KERN_WARNING) warning conditions
1403 5 (KERN_NOTICE) normal but significant condition
1404 6 (KERN_INFO) informational
1405 7 (KERN_DEBUG) debug-level messages
1406
Randy Dunlapc756d082011-02-20 20:08:35 -08001407 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1408 in bytes. n must be a power of two. The default
1409 size is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001410
Randy Dunlapaccaa242007-10-16 01:29:37 -07001411 logo.nologo [FB] Disables display of the built-in Linux logo.
1412 This may be used to provide more screen space for
1413 kernel log messages and is useful when debugging
1414 kernel boot problems.
1415
Linus Torvalds1da177e2005-04-16 15:20:36 -07001416 lp=0 [LP] Specify parallel ports to use, e.g,
1417 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1418 lp=reset first parallel port). 'lp=0' disables the
1419 lp=auto printer driver. 'lp=reset' (which can be
1420 specified in addition to the ports) causes
1421 attached printers to be reset. Using
1422 lp=port1,port2,... specifies the parallel ports
1423 to associate lp devices with, starting with
1424 lp0. A port specification may be 'none' to skip
1425 that lp device, or a parport name such as
1426 'parport0'. Specifying 'lp=auto' instead of a
1427 port specification list means that device IDs
1428 from each port should be examined, to see if
1429 an IEEE 1284-compliant printer is attached; if
1430 so, the driver will manage that printer.
1431 See also header of drivers/char/lp.c.
1432
1433 lpj=n [KNL]
1434 Sets loops_per_jiffy to given constant, thus avoiding
1435 time-consuming boot-time autodetection (up to 250 ms per
1436 CPU). 0 enables autodetection (default). To determine
1437 the correct value for your kernel, boot with normal
1438 autodetection and see what value is printed. Note that
1439 on SMP systems the preset will be applied to all CPUs,
1440 which is likely to cause problems if your CPUs need
1441 significantly divergent settings. An incorrect value
1442 will cause delays in the kernel to be wrong, leading to
1443 unpredictable I/O errors and other breakage. Although
1444 unlikely, in the extreme case this might damage your
1445 hardware.
1446
1447 ltpc= [NET]
1448 Format: <io>,<irq>,<dma>
1449
Randy Dunlap16290242011-08-13 12:34:52 -07001450 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07001451 (machvec) in a generic kernel.
1452 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001453
Wu Zhangjin3209e702009-07-02 23:27:12 +08001454 machtype= [Loongson] Share the same kernel image file between different
1455 yeeloong laptop.
1456 Example: machtype=lemote-yeeloong-2f-7inch
1457
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001458 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1459 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001460
1461 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001462 should make use of. maxcpus=n : n >= 0 limits the
1463 kernel to using 'n' processors. n=0 is a special case,
1464 it is equivalent to "nosmp", which also disables
1465 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001466
Kay Sieversd134b002011-07-31 22:08:04 +02001467 max_loop= [LOOP] The number of loop block devices that get
1468 (loop.max_loop) unconditionally pre-created at init time. The default
1469 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1470 of statically allocating a predefined number, loop
1471 devices can be requested on-demand with the
1472 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07001473
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001474 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001475
Uwe Hermann71cced62008-10-20 09:32:21 -07001476 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001477
Linus Torvalds1da177e2005-04-16 15:20:36 -07001478 md= [HW] RAID subsystems devices and level
1479 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001480
Linus Torvalds1da177e2005-04-16 15:20:36 -07001481 mdacon= [MDA]
1482 Format: <first>,<last>
1483 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001484
Linus Torvalds1da177e2005-04-16 15:20:36 -07001485 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1486 Amount of memory to be used when the kernel is not able
1487 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001488 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489 address space collisions. Without memmap= PCI devices
1490 could be placed at addresses belonging to unused RAM.
1491
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001492 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001493 memory.
1494
Paul Mundt6902aa82008-09-21 17:14:42 +09001495 memchunk=nn[KMG]
1496 [KNL,SH] Allow user to override the default size for
1497 per-device physically contiguous DMA buffers.
1498
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301499 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500 E820 memory map, as specified by the user.
1501 Such memmap=exactmap lines can be constructed based on
1502 BIOS output or other requirements. See the memmap=nn@ss
1503 option description.
1504
1505 memmap=nn[KMG]@ss[KMG]
1506 [KNL] Force usage of a specific region of memory
1507 Region of memory to be used, from ss to ss+nn.
1508
1509 memmap=nn[KMG]#ss[KMG]
1510 [KNL,ACPI] Mark specific memory as ACPI data.
1511 Region of memory to be used, from ss to ss+nn.
1512
1513 memmap=nn[KMG]$ss[KMG]
1514 [KNL,ACPI] Mark specific memory as reserved.
1515 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001516 Example: Exclude memory from 0x18690000-0x1869ffff
1517 memmap=64K$0x18690000
1518 or
1519 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001521 memory_corruption_check=0/1 [X86]
1522 Some BIOSes seem to corrupt the first 64k of
1523 memory when doing things like suspend/resume.
1524 Setting this option will scan the memory
1525 looking for corruption. Enabling this will
1526 both detect corruption and prevent the kernel
1527 from using the memory being corrupted.
1528 However, its intended as a diagnostic tool; if
1529 repeatable BIOS-originated corruption always
1530 affects the same memory, you can use memmap=
1531 to prevent the kernel from using that memory.
1532
1533 memory_corruption_check_size=size [X86]
1534 By default it checks for corruption in the low
1535 64k, making this memory unavailable for normal
1536 use. Use this parameter to scan for
1537 corruption in more or less memory.
1538
1539 memory_corruption_check_period=seconds [X86]
1540 By default it checks for corruption every 60
1541 seconds. Use this parameter to check at some
1542 other rate. 0 disables periodic checking.
1543
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001544 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001545 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07001546 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01001547 Specifies the number of memtest passes to be
1548 performed. Each pass selects another test
1549 pattern from a given set of patterns. Memtest
1550 fills the memory with this pattern, validates
1551 memory contents and reserves bad memory
1552 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07001553
Linus Torvalds1da177e2005-04-16 15:20:36 -07001554 meye.*= [HW] Set MotionEye Camera parameters
1555 See Documentation/video4linux/meye.txt.
1556
Andres Salomon8f368812007-10-12 23:04:06 +02001557 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1558 Multi-Function General Purpose Timers on AMD Geode
1559 platforms.
1560
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001561 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1562 the BIOS has incorrectly applied a workaround. TinyBIOS
1563 version 0.98 is known to be affected, 0.99 fixes the
1564 problem by letting the user disable the workaround.
1565
Linus Torvalds1da177e2005-04-16 15:20:36 -07001566 mga= [HW,DRM]
1567
Randy Dunlap1c207f92008-11-19 15:36:16 -08001568 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1569 physical address is ignored.
1570
Michel Pollet39f45d72009-05-20 11:10:31 +01001571 mini2440= [ARM,HW,KNL]
1572 Format:[0..2][b][c][t]
1573 Default: "0tb"
1574 MINI2440 configuration specification:
1575 0 - The attached screen is the 3.5" TFT
1576 1 - The attached screen is the 7" TFT
1577 2 - The VGA Shield is attached (1024x768)
1578 Leaving out the screen size parameter will not load
1579 the TFT driver, and the framebuffer will be left
1580 unconfigured.
1581 b - Enable backlight. The TFT backlight pin will be
1582 linked to the kernel VESA blanking code and a GPIO
1583 LED. This parameter is not necessary when using the
1584 VGA shield.
1585 c - Enable the s3c camera interface.
1586 t - Reserved for enabling touchscreen support. The
1587 touchscreen support is not enabled in the mainstream
1588 kernel as of 2.6.30, a preliminary port can be found
1589 in the "bleeding edge" mini2440 support kernel at
1590 http://repo.or.cz/w/linux-2.6/mini2440.git
1591
Mel Gorman6b74ab92008-07-23 21:26:49 -07001592 mminit_loglevel=
1593 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1594 parameter allows control of the logging verbosity for
1595 the additional memory initialisation checks. A value
1596 of 0 disables mminit logging and a level of 4 will
1597 log everything. Information is printed at KERN_DEBUG
1598 so loglevel=8 may also need to be specified.
1599
Rusty Russell106a4ee2012-09-26 10:09:40 +01001600 module.sig_enforce
1601 [KNL] When CONFIG_MODULE_SIG is set, this means that
1602 modules without (valid) signatures will fail to load.
1603 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1604 is always true, so this option does nothing.
1605
Linus Torvalds1da177e2005-04-16 15:20:36 -07001606 mousedev.tap_time=
1607 [MOUSE] Maximum time between finger touching and
1608 leaving touchpad surface for touch to be considered
1609 a tap and be reported as a left button click (for
1610 touchpads working in absolute mode only).
1611 Format: <msecs>
1612 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1613 reporting absolute coordinates, such as tablets
1614 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1615 reporting absolute coordinates, such as tablets
1616
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301617 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001618 is similar to kernelcore except it specifies the
1619 amount of memory used for migratable allocations.
1620 If both kernelcore and movablecore is specified,
1621 then kernelcore will be at *least* the specified
1622 value but may be more. If movablecore on its own
1623 is specified, the administrator must be careful
1624 that the amount of memory usable for all allocations
1625 is not too small.
1626
Linus Torvalds1da177e2005-04-16 15:20:36 -07001627 MTD_Partition= [MTD]
1628 Format: <name>,<region-number>,<size>,<offset>
1629
Randy Dunlapa9913042005-10-23 12:57:11 -07001630 MTD_Region= [MTD] Format:
1631 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001632
1633 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001634 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001635
Will Schmidt4e89a2d2010-09-28 15:33:12 +00001636 multitce=off [PPC] This parameter disables the use of the pSeries
1637 firmware feature for updating multiple TCE entries
1638 at a time.
1639
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07001640 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1641
1642 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1643
1644 boundary - index of last SLC block on Flex-OneNAND.
1645 The remaining blocks are configured as MLC blocks.
1646 lock - Configure if Flex-OneNAND boundary should be locked.
1647 Once locked, the boundary cannot be changed.
1648 1 indicates lock status, 0 indicates unlock status.
1649
Ben Dooks9db829f2008-07-03 11:24:29 +01001650 mtdset= [ARM]
1651 ARM/S3C2412 JIVE boot control
1652
1653 See arch/arm/mach-s3c2412/mach-jive.c
1654
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001656 [HW] Make the MicroTouch USB driver use raw coordinates
1657 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001658
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001659 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02001660 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001661 that could hold holes aka. UC entries.
1662
1663 mtrr_gran_size=nn[KMG] [X86]
1664 Used for mtrr cleanup. It is granularity of mtrr block.
1665 Default is 1.
1666 Large value could prevent small alignment from
1667 using up MTRRs.
1668
1669 mtrr_spare_reg_nr=n [X86]
1670 Format: <integer>
1671 Range: 0,7 : spare reg number
1672 Default : 1
1673 Used for mtrr cleanup. It is spare mtrr entries number.
1674 Set to 2 or more if your graphical card needs more.
1675
Linus Torvalds1da177e2005-04-16 15:20:36 -07001676 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1677
Linus Torvalds1da177e2005-04-16 15:20:36 -07001678 netdev= [NET] Network devices parameters
1679 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1680 Note that mem_start is often overloaded to mean
1681 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001682 This usage is only documented in each driver source
1683 file if at all.
1684
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001685 nf_conntrack.acct=
1686 [NETFILTER] Enable connection tracking flow accounting
1687 0 to disable accounting
1688 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02001689 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001690
Chuck Lever306a0752010-09-17 10:54:37 -04001691 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001692 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001693
1694 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001695 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696
Chuck Lever306a0752010-09-17 10:54:37 -04001697 nfsrootdebug [NFS] enable nfsroot debugging messages.
1698 See Documentation/filesystems/nfs/nfsroot.txt.
1699
Trond Myklebusta72b4422006-01-03 09:55:41 +01001700 nfs.callback_tcpport=
1701 [NFS] set the TCP port on which the NFSv4 callback
1702 channel should listen.
1703
Trond Myklebuste571cbf2009-08-19 18:12:27 -04001704 nfs.cache_getent=
1705 [NFS] sets the pathname to the program which is used
1706 to update the NFS client cache entries.
1707
1708 nfs.cache_getent_timeout=
1709 [NFS] sets the timeout after which an attempt to
1710 update a cache entry is deemed to have failed.
1711
Trond Myklebust58df0952006-01-03 09:55:57 +01001712 nfs.idmap_cache_timeout=
1713 [NFS] set the maximum lifetime for idmapper cache
1714 entries.
1715
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001716 nfs.enable_ino64=
1717 [NFS] enable 64-bit inode numbers.
1718 If zero, the NFS client will fake up a 32-bit inode
1719 number for the readdir() and stat() syscalls instead
1720 of returning the full 64-bit number.
1721 The default is to return 64-bit inode numbers.
1722
Trond Myklebustef159e92012-02-06 19:50:40 -05001723 nfs.max_session_slots=
1724 [NFSv4.1] Sets the maximum number of session slots
1725 the client will attempt to negotiate with the server.
1726 This limits the number of simultaneous RPC requests
1727 that the client can send to the NFSv4.1 server.
1728 Note that there is little point in setting this
1729 value higher than the max_tcp_slot_table_limit.
1730
Trond Myklebustb064eca22011-02-22 15:44:32 -08001731 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05001732 [NFSv4] When set to the default of '1', this option
1733 ensures that both the RPC level authentication
1734 scheme and the NFS level operations agree to use
1735 numeric uids/gids if the mount is using the
1736 'sec=sys' security flavour. In effect it is
1737 disabling idmapping, which can make migration from
1738 legacy NFSv2/v3 systems to NFSv4 easier.
1739 Servers that do not support this mode of operation
1740 will be autodetected by the client, and it will fall
1741 back to using the idmapper.
1742 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04001743 nfs.nfs4_unique_id=
1744 [NFS4] Specify an additional fixed unique ident-
1745 ification string that NFSv4 clients can insert into
1746 their nfs_client_id4 string. This is typically a
1747 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08001748
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05001749 nfs.send_implementation_id =
1750 [NFSv4.1] Send client implementation identification
1751 information in exchange_id requests.
1752 If zero, no implementation identification information
1753 will be sent.
1754 The default is to send the implementation identification
1755 information.
1756
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04001757 nfsd.nfs4_disable_idmapping=
1758 [NFSv4] When set to the default of '1', the NFSv4
1759 server will return only numeric uids and gids to
1760 clients using auth_sys, and will accept numeric uids
1761 and gids from such clients. This is intended to ease
1762 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05001763
Sachin Bhamare18d98f62012-03-19 20:47:58 -07001764 objlayoutdriver.osd_login_prog=
1765 [NFS] [OBJLAYOUT] sets the pathname to the program which
1766 is used to automatically discover and login into new
1767 osd-targets. Please see:
1768 Documentation/filesystems/pnfs.txt for more explanations
1769
Paul Mundt1e1030d2009-09-01 17:38:32 +09001770 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001771 when a NMI is triggered.
1772 Format: [state][,regs][,debounce][,die]
1773
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301774 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07001775 Format: [panic,][nopanic,][num]
Don Zickus5dc30552010-11-29 17:07:17 -05001776 Valid num: 0
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001777 0 - turn nmi_watchdog off
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001778 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07001779 timeout occurs (or 'nopanic' to override the opposite
1780 default).
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001781 This is useful when you use a panic=... timeout and
1782 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001783
Anton Vorontsovbff38772009-07-08 11:10:56 -07001784 netpoll.carrier_timeout=
1785 [NET] Specifies amount of time (in seconds) that
1786 netpoll should wait for a carrier. By default netpoll
1787 waits 4 seconds.
1788
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001789 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001790 emulation library even if a 387 maths coprocessor
1791 is present.
1792
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001793 no_console_suspend
1794 [HW] Never suspend the console
1795 Disable suspending of consoles during suspend and
1796 hibernate operations. Once disabled, debugging
1797 messages can reach various consoles while the rest
1798 of the system is being put to sleep (ie, while
1799 debugging driver suspend/resume hooks). This may
1800 not work reliably with all consoles, but is known
1801 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07001802 To facilitate more flexible debugging, we also add
1803 console_suspend, a printk module parameter to control
1804 it. Users could use console_suspend (usually
1805 /sys/module/printk/parameters/console_suspend) to
1806 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001807
Christoph Lameterc1aee212007-05-31 00:40:47 -07001808 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1809 caches in the slab allocator. Saves per-node memory,
1810 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001811
Randy Dunlapa9913042005-10-23 12:57:11 -07001812 noalign [KNL,ARM]
1813
Linus Torvalds1da177e2005-04-16 15:20:36 -07001814 noapic [SMP,APIC] Tells the kernel to not make use of any
1815 IOAPICs that may be present in the system.
1816
Mike Galbraith5091faa2010-11-30 14:18:03 +01001817 noautogroup Disable scheduler automatic task group creation.
1818
Linus Torvalds1da177e2005-04-16 15:20:36 -07001819 nobats [PPC] Do not use BATs for mapping kernel lowmem
1820 on "Classic" PPC cores.
1821
1822 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001823
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001824 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1825
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001826 nodelayacct [KNL] Disable per-task delay accounting
1827
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1829
Paul Mundt6902aa82008-09-21 17:14:42 +09001830 nodsp [SH] Disable hardware DSP at boot time.
1831
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301832 noefi [X86] Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001833
Linus Torvalds1da177e2005-04-16 15:20:36 -07001834 noexec [IA-64]
1835
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301836 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001837 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001838 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001839 noexec=off: disable non-executable mappings
1840
H. Peter Anvin52b61792012-09-21 12:43:13 -07001841 nosmap [X86]
1842 Disable SMAP (Supervisor Mode Access Prevention)
1843 even if it is supported by processor.
1844
Fenghua Yude5397a2011-05-11 16:51:05 -07001845 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07001846 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07001847 even if it is supported by processor.
1848
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001849 noexec32 [X86-64]
1850 This affects only 32-bit executables.
1851 noexec32=on: enable non-executable mappings (default)
1852 read doesn't imply executable mappings
1853 noexec32=off: disable non-executable mappings
1854 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001855
Paul Mundt6902aa82008-09-21 17:14:42 +09001856 nofpu [SH] Disable hardware FPU at boot time.
1857
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001858 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001859 register save and restore. The kernel will only save
1860 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001861
Suresh Siddha0c752a92009-05-22 12:17:45 -07001862 noxsave [BUGS=X86] Disables x86 extended register state save
1863 and restore using xsave. The kernel will fallback to
1864 enabling legacy floating-point and sse state.
1865
Suresh Siddha5d2bd702012-09-06 14:58:52 -07001866 eagerfpu= [X86]
Suresh Siddhae0022982012-09-10 10:32:32 -07001867 on enable eager fpu restore
Suresh Siddha5d2bd702012-09-06 14:58:52 -07001868 off disable eager fpu restore
Suresh Siddhae0022982012-09-10 10:32:32 -07001869 auto selects the default scheme, which automatically
1870 enables eagerfpu restore for xsaveopt.
Suresh Siddha5d2bd702012-09-06 14:58:52 -07001871
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01001872 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1873 wfi(ARM) instruction doesn't work correctly and not to
1874 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07001875
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001876 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001877 instruction doesn't work correctly and not to
1878 use it.
1879
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001880 no_file_caps Tells the kernel not to honor file capabilities. The
1881 only way then for a file to be executed with privilege
1882 is to be setuid root or executed by root.
1883
Linus Torvalds1da177e2005-04-16 15:20:36 -07001884 nohalt [IA-64] Tells the kernel not to use the power saving
1885 function PAL_HALT_LIGHT when idle. This increases
1886 power-consumption. On the positive side, it reduces
1887 interrupt wake-up latency, which may improve performance
1888 in certain environments such as networked servers or
1889 real-time systems.
1890
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001891 nohz= [KNL] Boottime enable/disable dynamic ticks
1892 Valid arguments: on, off
1893 Default: on
1894
Paul Mundteeee7852009-04-02 12:31:16 +09001895 noiotrap [SH] Disables trapped I/O port accesses.
1896
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001897 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001898 disable unhandled interrupt sources.
1899
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301900 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001901 broken timer IRQ sources.
1902
Linus Torvalds1da177e2005-04-16 15:20:36 -07001903 noisapnp [ISAPNP] Disables ISA PnP code.
1904
1905 noinitrd [RAM] Tells the kernel not to load any configured
1906 initial RAM disk.
1907
Weidong Han03ea8152009-04-17 16:42:15 +08001908 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1909 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07001910 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08001911
Linus Torvalds1da177e2005-04-16 15:20:36 -07001912 nointroute [IA-64]
1913
Randy Dunlap16290242011-08-13 12:34:52 -07001914 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07001915
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02001916 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1917
Gleb Natapovfd10cde2010-10-14 11:22:51 +02001918 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1919 fault handling.
1920
Glauber Costad910f5c2011-07-11 15:28:19 -04001921 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1922 steal time is computed, but won't influence scheduler
1923 behaviour
1924
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001925 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001926
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001927 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001928
Linus Torvalds1da177e2005-04-16 15:20:36 -07001929 noltlbs [PPC] Do not use large page/tlb entries for kernel
1930 lowmem mapping on PPC40x.
1931
Horms312f1f02006-02-22 09:57:55 +09001932 nomca [IA-64] Disable machine check abort handling
1933
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001934 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001935
Andres Salomon83d73842007-10-12 23:04:06 +02001936 nomfgpt [X86-32] Disable Multi-Function General Purpose
1937 Timer usage (for AMD Geode machines).
1938
Don Zickusbda62632011-10-13 15:14:27 -04001939 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1940 shutdown the other cpus. Instead use the REBOOT_VECTOR
1941 irq.
1942
Dave Young02608be2012-02-01 10:33:14 +08001943 nomodule Disable module load
1944
Jiri Kosina016ddd92010-01-18 17:05:40 +01001945 nopat [X86] Disable PAT (page attribute table extension of
1946 pagetables) support.
1947
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001948 norandmaps Don't use address space randomization. Equivalent to
1949 echo 0 > /proc/sys/kernel/randomize_va_space
1950
Jiri Kosinabbff2162010-08-11 18:34:09 +02001951 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001952
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001953 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001954 with UP alternatives
1955
Linus Torvalds1da177e2005-04-16 15:20:36 -07001956 noresidual [PPC] Don't use residual data on PReP machines.
1957
H. Peter Anvin49d859d2011-07-31 14:02:19 -07001958 nordrand [X86] Disable the direct use of the RDRAND
1959 instruction even if it is supported by the
1960 processor. RDRAND is still available to user
1961 space applications.
1962
Randy Dunlapa9913042005-10-23 12:57:11 -07001963 noresume [SWSUSP] Disables resume and restores original swap
1964 space.
1965
Linus Torvalds1da177e2005-04-16 15:20:36 -07001966 no-scroll [VGA] Disables scrollback.
1967 This is required for the Braillex ib80-piezo Braille
1968 reader made by F.H. Papenmeier (Germany).
1969
1970 nosbagart [IA-64]
1971
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001972 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001973
Len Brown61ec7562007-08-16 03:34:22 -04001974 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1975 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001976
Dave Jones97842212007-07-15 23:41:05 -07001977 nosoftlockup [KNL] Disable the soft-lockup detector.
1978
Linus Torvalds1da177e2005-04-16 15:20:36 -07001979 nosync [HW,M68K] Disables sync negotiation for all devices.
1980
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001981 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001982
1983 nousb [USB] Disable the USB subsystem
1984
Ben Hutchings55142372011-01-02 23:02:42 +00001985 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
Don Zickus58687ac2010-05-07 17:11:44 -04001986
Linus Torvalds1da177e2005-04-16 15:20:36 -07001987 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001988
Weidong Han2b2fd872009-04-17 16:42:12 +08001989 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1990
Randy Dunlap16290242011-08-13 12:34:52 -07001991 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07001992 purges which is reported from either PAL_VM_SUMMARY or
1993 SAL PALO.
1994
Yinghai Lu2b633e32010-02-10 01:20:37 -08001995 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1996 could support. nr_cpus=n : n >= 1 limits the kernel to
1997 supporting 'n' processors. Later in runtime you can not
1998 use hotplug cpu feature to put more cpu back to online.
1999 just like you compile the kernel NR_CPUS=n
2000
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002001 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2002
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002003 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2004 one of ['zone', 'node', 'default'] can be specified
2005 This can be set from sysctl after boot.
2006 See Documentation/sysctl/vm.txt for details.
2007
Randy Dunlap7c4be252009-01-06 14:42:44 -08002008 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2009 See Documentation/debugging-via-ohci1394.txt for more
2010 info.
2011
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002012 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2013 Rather than timing out after 20 ms if an EC
2014 command is not properly ACKed, override the length
2015 of the timeout. We have interrupts disabled while
2016 waiting for the ACK, so if this is set too high
2017 interrupts *may* be lost!
2018
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002019 omap_mux= [OMAP] Override bootloader pin multiplexing.
2020 Format: <mux_mode0.mode_name=value>...
2021 For example, to override I2C bus2:
2022 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2023
Linus Torvalds1da177e2005-04-16 15:20:36 -07002024 oprofile.timer= [HW]
2025 Use timer interrupt instead of performance counters
2026
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002027 oprofile.cpu_type= Force an oprofile cpu type
2028 This might be useful if you have an older oprofile
2029 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002030 Format: { arch_perfmon }
2031 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002032 perfmon on Intel CPUs instead of the
2033 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002034 timer: [X86] Force use of architectural NMI
2035 timer mode (see also oprofile.timer
2036 for generic hr timer mode)
Andreas Krebbeldd3c4672011-11-25 20:03:05 +01002037 [s390] Force legacy basic mode sampling
2038 (report cpu_type "timer")
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002039
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002040 oops=panic Always panic on oopses. Default is to just kill the
2041 process, but there is a small probability of
2042 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002043 This will also cause panics on machine check exceptions.
2044 Useful together with panic=30 to trigger a reboot.
2045
Randy Dunlapbcfde332010-06-07 17:10:38 -07002046 OSS [HW,OSS]
2047 See Documentation/sound/oss/oss-parameters.txt
2048
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002049 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002050 timeout > 0: seconds before rebooting
2051 timeout = 0: wait forever
2052 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002053 Format: <timeout>
2054
2055 parkbd.port= [HW] Parallel port number the keyboard adapter is
2056 connected to, default is 0.
2057 Format: <parport#>
2058 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2059 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002060 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002061
Randy Dunlapa9913042005-10-23 12:57:11 -07002062 parport= [HW,PPT] Specify parallel ports. 0 disables.
2063 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2064 Use 'auto' to force the driver to use any
2065 IRQ/DMA settings detected (the default is to
2066 ignore detected IRQ/DMA settings because of
2067 possible conflicts). You can specify the base
2068 address, IRQ, and DMA settings; IRQ and DMA
2069 should be numbers, or 'auto' (for using detected
2070 settings on that particular port), or 'nofifo'
2071 (to avoid using a FIFO even if it is detected).
2072 Parallel ports are assigned in the order they
2073 are specified on the command line, starting
2074 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002075
Randy Dunlapa9913042005-10-23 12:57:11 -07002076 parport_init_mode= [HW,PPT]
2077 Configure VIA parallel port to operate in
2078 a specific mode. This is necessary on Pegasos
2079 computer where firmware has no options for setting
2080 up parallel port mode and sets it to spp.
2081 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002082 Format: [spp|ps2|epp|ecp|ecpepp]
2083
Andrew Mortondd287792006-03-23 03:00:57 -08002084 pause_on_oops=
2085 Halt all CPUs after the first oops has been printed for
2086 the specified number of seconds. This is to be used if
2087 your oopses keep scrolling off the screen.
2088
Linus Torvalds1da177e2005-04-16 15:20:36 -07002089 pcbit= [HW,ISDN]
2090
2091 pcd. [PARIDE]
2092 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002093 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002094
Randy Dunlapa9913042005-10-23 12:57:11 -07002095 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002096 earlydump [X86] dump PCI config space before the kernel
2097 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002098 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002099 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002100 the hardware directly. Use this if your machine
2101 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002102 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002103 hardware access methods are allowed. Use this
2104 if you experience crashes upon bootup and you
2105 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002106 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002107 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02002108 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07002109 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07002110 noaer [PCIE] If the PCIEAER kernel config parameter is
2111 enabled, this kernel boot option can be used to
2112 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002113 nodomains [PCI] Disable support for multiple PCI
2114 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302115 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002116 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002117 check_enable_amd_mmconf [X86] check for and enable
2118 properly configured MMIO access to PCI
2119 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002120 nomsi [MSI] If the PCI_MSI kernel config parameter is
2121 enabled, this kernel boot option can be used to
2122 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002123 noioapicquirk [APIC] Disable all boot interrupt quirks.
2124 Safety option to keep boot IRQs enabled. This
2125 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002126 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2127 primary IO-APIC for bridges that cannot disable
2128 boot IRQs. This fixes a source of spurious IRQs
2129 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002130 noioapicreroute [APIC] Disable workaround that uses the
2131 boot IRQ equivalent of an IRQ that connects to
2132 a chipset where boot IRQs cannot be disabled.
2133 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002134 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002135 routing table. These calls are known to be buggy
2136 on several machines and they hang the machine
2137 when used, but on other computers it's the only
2138 way to get the interrupt routing table. Try
2139 this option if the kernel is unable to allocate
2140 IRQs or discover secondary PCI buses on your
2141 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002142 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002143 Use with caution as certain devices share
2144 address decoders between ROMs and other
2145 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002146 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002147 expansion ROMs that do not already have
2148 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002149 nobar [X86] Do not assign address space to the
2150 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002151 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002152 assigned automatically to PCI devices. You can
2153 make the kernel exclude IRQs of your ISA cards
2154 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002155 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002156 of the PIRQ table (normally generated
2157 by the BIOS) if it is outside the
2158 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002159 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002160 useful if the kernel is unable to find your
2161 secondary buses and you want to tell it
2162 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002163 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002164 numbers ourselves, overriding
2165 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002166 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002167 in the BIOS $PIR table. This is needed on
2168 some systems with broken BIOSes, notably
2169 some HP Pavilion N5400 and Omnibook XE3
2170 notebooks. This will have no effect if ACPI
2171 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002172 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002173 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002174 use_crs [X86] Use PCI host bridge window information
2175 from ACPI. On BIOSes from 2008 or later, this
2176 is enabled by default. If you need to use this,
2177 please report a bug.
2178 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2179 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002180 routeirq Do IRQ routing for all PCI devices.
2181 This is normally done in pci_enable_device(),
2182 so this option is a temporary workaround
2183 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002184 skip_isa_align [X86] do not align io start addr, so can
2185 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07002186 firmware [ARM] Do not re-enumerate the bus but instead
2187 just use the configuration from the
2188 bootloader. This is currently used on
2189 IXP2000 systems where the bus has to be
2190 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02002191 noearly [X86] Don't do any early type 1 scanning.
2192 This might help on some broken boards which
2193 machine check when some devices' config space
2194 is read. But various workarounds are disabled
2195 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002196 bfsort Sort PCI devices into breadth-first order.
2197 This sorting is done to get a device
2198 order compatible with older (<= 2.4) kernels.
2199 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002200 cbiosize=nn[KMG] The fixed amount of bus space which is
2201 reserved for the CardBus bridge's IO window.
2202 The default value is 256 bytes.
2203 cbmemsize=nn[KMG] The fixed amount of bus space which is
2204 reserved for the CardBus bridge's memory
2205 window. The default value is 64 megabytes.
Yuji Shimada32a9a682009-03-16 17:13:39 +09002206 resource_alignment=
2207 Format:
2208 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2209 Specifies alignment and device to reassign
2210 aligned memory resources.
2211 If <order of align> is not specified,
2212 PAGE_SIZE is used as alignment.
2213 PCI-PCI bridge can be specified, if resource
2214 windows need to be expanded.
Andrew Patterson43c16402009-04-22 16:52:09 -06002215 ecrc= Enable/disable PCIe ECRC (transaction layer
2216 end-to-end CRC checking).
2217 bios: Use BIOS/firmware settings. This is the
2218 the default.
2219 off: Turn ECRC off
2220 on: Turn ECRC on.
Yinghai Lub55438f2012-02-23 19:23:30 -08002221 realloc= Enable/disable reallocating PCI bridge resources
2222 if allocations done by BIOS are too small to
2223 accommodate resources required by all child
2224 devices.
2225 off: Turn realloc off
2226 on: Turn realloc on
2227 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002228 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002229 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2230 only look for one device below a PCIe downstream
2231 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002232
Chuck Ebberte5665a42008-09-24 20:40:34 -04002233 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2234 Management.
2235 off Disable ASPM.
2236 force Enable ASPM even on devices that claim not to support it.
2237 WARNING: Forcing ASPM on may cause system lockups.
2238
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002239 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2240 nomsi Do not use MSI for PCI Express Native Hotplug (this
2241 makes all PCIe ports use INTx for hotplug services).
2242
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002243 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002244 auto Ask the BIOS whether or not to use native PCIe services
2245 associated with PCIe ports (PME, hot-plug, AER). Use
2246 them only if that is allowed by the BIOS.
2247 native Use native PCIe services associated with PCIe ports
2248 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002249 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2250 ports driver.
2251
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002252 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002253 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002254 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002255
Linus Torvalds1da177e2005-04-16 15:20:36 -07002256 pcmv= [HW,PCMCIA] BadgePAD 4
2257
2258 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002259 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002260
2261 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2262 boot time.
2263 Format: { 0 | 1 }
2264 See arch/parisc/kernel/pdc_chassis.c
2265
Tejun Heof58dc012009-08-14 15:00:50 +09002266 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09002267 Currently supported values are "embed" and "page".
2268 Archs may support subset or none of the selections.
2269 See comments in mm/percpu.c for details on each
2270 allocator. This parameter is primarily for debugging
2271 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09002272
Linus Torvalds1da177e2005-04-16 15:20:36 -07002273 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002274 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002275
2276 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002277 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002278
2279 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07002280 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002281
2282 plip= [PPT,NET] Parallel port network link
2283 Format: { parport<nr> | timid | 0 }
2284 See also Documentation/parport.txt.
2285
Randy Dunlap16290242011-08-13 12:34:52 -07002286 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02002287 Override pmtimer IOPort with a hex value.
2288 e.g. pmtmr=0x508
2289
Bjorn Helgaas96242112011-08-11 12:14:05 -06002290 pnp.debug=1 [PNP]
2291 Enable PNP debug messages (depends on the
2292 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2293 via /sys/module/pnp/parameters/debug. We always show
2294 current resource usage; turning this on also shows
2295 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06002296
Linus Torvalds1da177e2005-04-16 15:20:36 -07002297 pnpacpi= [ACPI]
2298 { off }
2299
2300 pnpbios= [ISAPNP]
2301 { on | off | curr | res | no-curr | no-res }
2302
2303 pnp_reserve_irq=
2304 [ISAPNP] Exclude IRQs for the autoconfiguration
2305
2306 pnp_reserve_dma=
2307 [ISAPNP] Exclude DMAs for the autoconfiguration
2308
2309 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07002310 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002311
2312 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07002313 [ISAPNP] Exclude memory regions for the
2314 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002315 Ranges are in pairs (memory base and size).
2316
Randy Dunlap4af94f32009-04-17 18:30:28 -07002317 ports= [IP_VS_FTP] IPVS ftp helper module
2318 Default is 21.
2319 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2320 may be specified.
2321 Format: <port>,<port>....
2322
Ingo Molnar45807a12007-07-15 23:40:10 -07002323 print-fatal-signals=
2324 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09002325
2326 If enabled, warn about various signal handling
2327 related application anomalies: too many signals,
2328 too many POSIX.1 timers, fatal signals causing a
2329 coredump - etc.
2330
2331 If you hit the warning due to signal overflow,
2332 you might want to try "ulimit -i unlimited".
2333
Ingo Molnar45807a12007-07-15 23:40:10 -07002334 default: off.
2335
Matthew Garrettc22ab332012-03-05 14:59:10 -08002336 printk.always_kmsg_dump=
2337 Trigger kmsg_dump for cases other than kernel oops or
2338 panics
2339 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2340 default: disabled
2341
Randy Dunlape84845c2007-07-15 23:40:25 -07002342 printk.time= Show timing data prefixed to each printk message line
2343 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2344
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002345 processor.max_cstate= [HW,ACPI]
2346 Limit processor to maximum C-state
2347 max_cstate=9 overrides any DMI blacklist limit.
2348
2349 processor.nocst [HW,ACPI]
2350 Ignore the _CST method to determine C-states,
2351 instead using the legacy FADT method
2352
Linus Torvalds1da177e2005-04-16 15:20:36 -07002353 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07002354 Format: [schedule,]<number>
2355 Param: "schedule" - profile schedule points.
2356 Param: <number> - step/bucket size as a power of 2 for
2357 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02002358 Param: "sleep" - profile D-state sleeping (millisecs).
2359 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02002360 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002361
Linus Torvalds1da177e2005-04-16 15:20:36 -07002362 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2363 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002364 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002365
Randy Dunlapa9913042005-10-23 12:57:11 -07002366 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2367 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002368 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2369 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07002370 psmouse.resetafter= [HW,MOUSE]
2371 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07002372 (0 = never).
2373 psmouse.resolution=
2374 [HW,MOUSE] Set desired mouse resolution, in dpi.
2375 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07002376 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002377 0 = disabled, 1 = enabled (default).
2378
Matthew Garrettdee28e72011-07-21 16:57:55 -04002379 pstore.backend= Specify the name of the pstore backend to use
2380
Linus Torvalds1da177e2005-04-16 15:20:36 -07002381 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002382 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002383
Kay Sieversdc8c8582007-08-15 12:25:38 +02002384 pty.legacy_count=
2385 [KNL] Number of legacy pty's. Overwrites compiled-in
2386 default number.
2387
Randy Dunlap7d2c5022006-09-29 02:01:02 -07002388 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07002389
Linus Torvalds1da177e2005-04-16 15:20:36 -07002390 r128= [HW,DRM]
2391
2392 raid= [HW,RAID]
2393 See Documentation/md.txt.
2394
Randy Dunlapa9913042005-10-23 12:57:11 -07002395 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002396 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07002397
Linus Torvalds1da177e2005-04-16 15:20:36 -07002398 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002399 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002400
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002401 rcutree.blimit= [KNL,BOOT]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002402 Set maximum number of finished RCU callbacks to process
2403 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002404
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07002405 rcutree.fanout_leaf= [KNL,BOOT]
2406 Increase the number of CPUs assigned to each
2407 leaf rcu_node structure. Useful for very large
2408 systems.
2409
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002410 rcutree.qhimark= [KNL,BOOT]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002411 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002412 RCU callbacks over which batch limiting is disabled.
2413
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002414 rcutree.qlowmark= [KNL,BOOT]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02002415 Set threshold of queued RCU callbacks below which
2416 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08002417
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002418 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2419 Suppress RCU CPU stall warning messages.
2420
2421 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2422 Set timeout for RCU CPU stall warning messages.
2423
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07002424 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2425 Set delay from grace-period initialization to
2426 first attempt to force quiescent states.
2427 Units are jiffies, minimum value is zero,
2428 and maximum value is HZ.
2429
2430 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2431 Set delay between subsequent attempts to force
2432 quiescent states. Units are jiffies, minimum
2433 value is one, and maximum value is HZ.
2434
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07002435 rcutorture.fqs_duration= [KNL,BOOT]
2436 Set duration of force_quiescent_state bursts.
2437
2438 rcutorture.fqs_holdoff= [KNL,BOOT]
2439 Set holdoff time within force_quiescent_state bursts.
2440
2441 rcutorture.fqs_stutter= [KNL,BOOT]
2442 Set wait time between force_quiescent_state bursts.
2443
2444 rcutorture.irqreader= [KNL,BOOT]
2445 Test RCU readers from irq handlers.
2446
2447 rcutorture.n_barrier_cbs= [KNL,BOOT]
2448 Set callbacks/threads for rcu_barrier() testing.
2449
2450 rcutorture.nfakewriters= [KNL,BOOT]
2451 Set number of concurrent RCU writers. These just
2452 stress RCU, they don't participate in the actual
2453 test, hence the "fake".
2454
2455 rcutorture.nreaders= [KNL,BOOT]
2456 Set number of RCU readers.
2457
2458 rcutorture.onoff_holdoff= [KNL,BOOT]
2459 Set time (s) after boot for CPU-hotplug testing.
2460
2461 rcutorture.onoff_interval= [KNL,BOOT]
2462 Set time (s) between CPU-hotplug operations, or
2463 zero to disable CPU-hotplug testing.
2464
2465 rcutorture.shuffle_interval= [KNL,BOOT]
2466 Set task-shuffle interval (s). Shuffling tasks
2467 allows some CPUs to go into dyntick-idle mode
2468 during the rcutorture test.
2469
2470 rcutorture.shutdown_secs= [KNL,BOOT]
2471 Set time (s) after boot system shutdown. This
2472 is useful for hands-off automated testing.
2473
2474 rcutorture.stall_cpu= [KNL,BOOT]
2475 Duration of CPU stall (s) to test RCU CPU stall
2476 warnings, zero to disable.
2477
2478 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2479 Time to wait (s) after boot before inducing stall.
2480
2481 rcutorture.stat_interval= [KNL,BOOT]
2482 Time (s) between statistics printk()s.
2483
2484 rcutorture.stutter= [KNL,BOOT]
2485 Time (s) to stutter testing, for example, specifying
2486 five seconds causes the test to run for five seconds,
2487 wait for five seconds, and so on. This tests RCU's
2488 ability to transition abruptly to and from idle.
2489
2490 rcutorture.test_boost= [KNL,BOOT]
2491 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2492 "Maybe" means test if the RCU implementation
2493 under test support RCU priority boosting.
2494
2495 rcutorture.test_boost_duration= [KNL,BOOT]
2496 Duration (s) of each individual boost test.
2497
2498 rcutorture.test_boost_interval= [KNL,BOOT]
2499 Interval (s) between each boost test.
2500
2501 rcutorture.test_no_idle_hz= [KNL,BOOT]
2502 Test RCU's dyntick-idle handling. See also the
2503 rcutorture.shuffle_interval parameter.
2504
2505 rcutorture.torture_type= [KNL,BOOT]
2506 Specify the RCU implementation to test.
2507
2508 rcutorture.verbose= [KNL,BOOT]
2509 Enable additional printk() statements.
2510
Olof Johanssonffdfc402005-09-06 15:17:19 -07002511 rdinit= [KNL]
2512 Format: <full_path>
2513 Run specified binary instead of /init from the ramdisk,
2514 used for early userspace startup. See initrd.
2515
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002516 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07002517 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08002518 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07002519
Paul Jackson46b6d942008-07-04 10:00:09 -07002520 relax_domain_level=
2521 [KNL, SMP] Set scheduler's default relax_domain_level.
Thadeu Lima de Souza Cascardo21acb9c2009-02-04 10:12:08 +01002522 See Documentation/cgroups/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07002523
Linus Torvalds1da177e2005-04-16 15:20:36 -07002524 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2525
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002526 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07002527 Format: nn[KMG]
2528 Reserves a hole at the top of the kernel virtual
2529 address space.
2530
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07002531 reservelow= [X86]
2532 Format: nn[K]
2533 Set the amount of memory to reserve for BIOS at
2534 the bottom of the address space.
2535
Vivek Goyal7e962872006-09-27 01:50:44 -07002536 reset_devices [KNL] Force drivers to reset the underlying device
2537 during initialization.
2538
Randy Dunlapa9913042005-10-23 12:57:11 -07002539 resume= [SWSUSP]
2540 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02002541 Format:
2542 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002543
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08002544 resume_offset= [SWSUSP]
2545 Specify the offset from the beginning of the partition
2546 given by "resume=" at which the swap header is located,
2547 in <PAGE_SIZE> units (needed only for swap files).
2548 See Documentation/power/swsusp-and-swap-files.txt
2549
Barry Songf126f732011-10-10 23:38:41 +02002550 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2551 read the resume files
2552
Barry Song6f8d7022011-10-06 20:34:46 +02002553 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2554 Useful for devices that are detected asynchronously
2555 (e.g. USB and MMC devices).
2556
Bojan Smojverf996fc92010-09-09 23:06:23 +02002557 hibernate= [HIBERNATION]
2558 noresume Don't check if there's a hibernation image
2559 present during boot.
2560 nocompress Don't compress/decompress hibernation images.
2561
Michael Neuling0a7b35c2007-02-10 01:44:33 -08002562 retain_initrd [RAM] Keep initrd memory after extraction
2563
Linus Torvalds1da177e2005-04-16 15:20:36 -07002564 rhash_entries= [KNL,NET]
2565 Set number of hash buckets for route cache
2566
2567 riscom8= [HW,SERIAL]
2568 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2569
2570 ro [KNL] Mount root device read-only on boot
2571
2572 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07002573 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002574
2575 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2576 mount the root filesystem
2577
2578 rootflags= [KNL] Set root filesystem mount option string
2579
2580 rootfstype= [KNL] Set root filesystem type
2581
Pierre Ossmancc1ed752007-07-15 23:40:35 -07002582 rootwait [KNL] Wait (indefinitely) for root device to show up.
2583 Useful for devices that are detected asynchronously
2584 (e.g. USB and MMC devices).
2585
Linus Torvalds1da177e2005-04-16 15:20:36 -07002586 rw [KNL] Mount root device read-write on boot
2587
2588 S [KNL] Run init in single mode
2589
2590 sa1100ir [NET]
2591 See drivers/net/irda/sa1100_ir.c.
2592
Linus Torvalds1da177e2005-04-16 15:20:36 -07002593 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07002594
Mike Travisf6630112009-11-17 18:22:15 -06002595 sched_debug [KNL] Enables verbose scheduler debug messages.
2596
Mike Galbraith5307c952012-05-08 12:20:58 +02002597 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2598 xtime_lock contention on larger systems, and/or RCU lock
2599 contention on all systems with CONFIG_MAXSMP set.
2600 Format: { "0" | "1" }
2601 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2602 1 -- enable.
2603 Note: increases power consumption, thus should only be
2604 enabled if running jitter sensitive (HPC/RT) workloads.
2605
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002606 security= [SECURITY] Choose a security module to enable at boot.
2607 If this boot parameter is not specified, only the first
2608 security module asking for security registration will be
2609 loaded. An invalid security module name will be treated
2610 as if no module has been chosen.
2611
2612 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002613 Format: { "0" | "1" }
2614 See security/selinux/Kconfig help text.
2615 0 -- disable.
2616 1 -- enable.
2617 Default value is set via kernel config option.
2618 If enabled at boot time, /selinux/disable can be used
2619 later to disable prior to initial policy load.
2620
John Johansenc1c124e2010-07-29 14:48:09 -07002621 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2622 Format: { "0" | "1" }
2623 See security/apparmor/Kconfig help text
2624 0 -- disable.
2625 1 -- enable.
2626 Default value is set via kernel config option.
2627
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002628 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002629
Linus Torvalds1da177e2005-04-16 15:20:36 -07002630 shapers= [NET]
2631 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002632
Yinghai Lub05f78f2008-08-22 01:32:50 -07002633 show_msr= [x86] show boot-time MSR settings
2634 Format: { <integer> }
2635 Show boot-time (BIOS-initialized) MSR settings.
2636 The parameter means the number of CPUs to show,
2637 for example 1 means boot CPU only.
2638
Linus Torvalds1da177e2005-04-16 15:20:36 -07002639 simeth= [IA-64]
2640 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002641
Linus Torvalds1da177e2005-04-16 15:20:36 -07002642 slram= [HW,MTD]
2643
David Rientjes3df1ccc2011-10-18 22:09:28 -07002644 slab_max_order= [MM, SLAB]
2645 Determines the maximum allowed order for slabs.
2646 A high setting may cause OOMs due to memory
2647 fragmentation. Defaults to 1 for systems with
2648 more than 32MB of RAM, 0 otherwise.
2649
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002650 slub_debug[=options[,slabs]] [MM, SLUB]
2651 Enabling slub_debug allows one to determine the
2652 culprit if slab objects become corrupted. Enabling
2653 slub_debug can create guard zones around objects and
2654 may poison objects when not in use. Also tracks the
2655 last alloc / free. For more information see
2656 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002657
2658 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002659 Determines the maximum allowed order for slabs.
2660 A high setting may cause OOMs due to memory
2661 fragmentation. For more information see
2662 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002663
2664 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002665 The minimum number of objects per slab. SLUB will
2666 increase the slab order up to slub_max_order to
2667 generate a sufficiently large slab able to contain
2668 the number of objects indicated. The higher the number
2669 of objects the smaller the overhead of tracking slabs
2670 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002671 For more information see Documentation/vm/slub.txt.
2672
2673 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09002674 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002675 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002676 For more information see Documentation/vm/slub.txt.
2677
2678 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002679 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002680 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002681 allocs to different slabs. Debug options disable
2682 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002683 For more information see Documentation/vm/slub.txt.
2684
Linus Torvalds1da177e2005-04-16 15:20:36 -07002685 smart2= [HW]
2686 Format: <io1>[,<io2>[,...,<io8>]]
2687
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002688 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2689 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2690 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2691 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2692 smsc-ircc2.ircc_irq= [HW] IRQ line
2693 smsc-ircc2.ircc_dma= [HW] DMA channel
2694 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2695 0: Toshiba Satellite 1800 (GP data pin select)
2696 1: Fast pin select (default)
2697 2: ATC IRMode
2698
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002699 softlockup_panic=
2700 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002701 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002702
Linus Torvalds1da177e2005-04-16 15:20:36 -07002703 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02002704 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07002705
2706 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002707 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002708
2709 spia_io_base= [HW,MTD]
2710 spia_fio_base=
2711 spia_pedr=
2712 spia_peddr=
2713
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002714 stacktrace [FTRACE]
2715 Enabled the stack tracer on boot up.
2716
Steven Rostedt762e1202011-12-19 22:01:00 -05002717 stacktrace_filter=[function-list]
2718 [FTRACE] Limit the functions that the stack tracer
2719 will trace at boot up. function-list is a comma separated
2720 list of functions. This list can be changed at run
2721 time by the stack_trace_filter file in the debugfs
2722 tracing directory. Note, this enables stack tracing
2723 and the stacktrace above is not needed.
2724
Linus Torvalds1da177e2005-04-16 15:20:36 -07002725 sti= [PARISC,HW]
2726 Format: <num>
2727 Set the STI (builtin display/keyboard on the HP-PARISC
2728 machines) console (graphic card) which should be used
2729 as the initial boot-console.
2730 See also comment in drivers/video/console/sticore.c.
2731
2732 sti_font= [HW]
2733 See comment in drivers/video/console/sticore.c.
2734
2735 stifb= [HW]
2736 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2737
Trond Myklebustcbf11072009-08-09 15:06:19 -04002738 sunrpc.min_resvport=
2739 sunrpc.max_resvport=
2740 [NFS,SUNRPC]
2741 SunRPC servers often require that client requests
2742 originate from a privileged port (i.e. a port in the
2743 range 0 < portnr < 1024).
2744 An administrator who wishes to reserve some of these
2745 ports for other uses may adjust the range that the
2746 kernel's sunrpc client considers to be privileged
2747 using these two parameters to set the minimum and
2748 maximum port values.
2749
Greg Banks42a7fc42007-03-06 01:42:23 -08002750 sunrpc.pool_mode=
2751 [NFS]
2752 Control how the NFS server code allocates CPUs to
2753 service thread pools. Depending on how many NICs
2754 you have and where their interrupts are bound, this
2755 option will affect which CPUs will do NFS serving.
2756 Note: this parameter cannot be changed while the
2757 NFS server is running.
2758
2759 auto the server chooses an appropriate mode
2760 automatically using heuristics
2761 global a single global pool contains all CPUs
2762 percpu one pool for each CPU
2763 pernode one pool for each NUMA node (equivalent
2764 to global on non-NUMA machines)
2765
Trond Myklebustcbf11072009-08-09 15:06:19 -04002766 sunrpc.tcp_slot_table_entries=
2767 sunrpc.udp_slot_table_entries=
2768 [NFS,SUNRPC]
2769 Sets the upper limit on the number of simultaneous
2770 RPC calls that can be sent from the client to a
2771 server. Increasing these values may allow you to
2772 improve throughput, but will also increase the
2773 amount of memory reserved for use by the client.
2774
Michal Hockoa42c3902010-11-24 12:57:08 -08002775 swapaccount[=0|1]
2776 [KNL] Enable accounting of swap in memory resource
2777 controller if no parameter or 1 is given or disable
2778 it if 0 is given (See Documentation/cgroups/memory.txt)
2779
Linus Torvalds1da177e2005-04-16 15:20:36 -07002780 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002781
Linus Torvalds1da177e2005-04-16 15:20:36 -07002782 switches= [HW,M68k]
2783
Andi Kleene52eec12010-09-08 16:54:17 +02002784 sysfs.deprecated=0|1 [KNL]
2785 Enable/disable old style sysfs layout for old udev
2786 on older distributions. When this option is enabled
2787 very new udev will not work anymore. When this option
2788 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2789 in older udev will not work anymore.
2790 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2791 the kernel configuration.
2792
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002793 sysrq_always_enabled
2794 [KNL]
2795 Ignore sysrq setting - this boot parameter will
2796 neutralize any effect of /proc/sys/kernel/sysrq.
2797 Useful for debugging.
2798
Linus Torvalds1da177e2005-04-16 15:20:36 -07002799 tdfx= [HW,DRM]
2800
David Brownell77437fd2008-07-23 21:28:33 -07002801 test_suspend= [SUSPEND]
2802 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2803 standby suspend) as the system sleep state to briefly
2804 enter during system startup. The system is woken from
2805 this state using a wakeup-capable RTC alarm.
2806
Linus Torvalds1da177e2005-04-16 15:20:36 -07002807 thash_entries= [KNL,NET]
2808 Set number of hash buckets for TCP connection
2809
Len Brownf8707ec2007-08-12 00:12:54 -04002810 thermal.act= [HW,ACPI]
2811 -1: disable all active trip points in all thermal zones
2812 <degrees C>: override all lowest active trip points
2813
Len Brownc52a7412007-08-14 15:49:32 -04002814 thermal.crt= [HW,ACPI]
2815 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002816 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002817
Len Brownf5487142007-08-12 00:12:44 -04002818 thermal.nocrt= [HW,ACPI]
2819 Set to disable actions on ACPI thermal zone
2820 critical and hot trip points.
2821
Len Brown72b33ef2007-08-12 00:12:17 -04002822 thermal.off= [HW,ACPI]
2823 1: disable ACPI thermal control
2824
Len Browna70cdc52007-08-12 00:12:35 -04002825 thermal.psv= [HW,ACPI]
2826 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002827 <degrees C>: override all passive trip points to this
2828 value
Len Browna70cdc52007-08-12 00:12:35 -04002829
Len Brown730ff342007-08-12 00:12:26 -04002830 thermal.tzp= [HW,ACPI]
2831 Specify global default ACPI thermal zone polling rate
2832 <deci-seconds>: poll all this frequency
2833 0: no polling (default)
2834
Thomas Gleixner8d32a302011-02-23 23:52:23 +00002835 threadirqs [KNL]
2836 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09002837 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00002838
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002839 topology= [S390]
2840 Format: {off | on}
2841 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07002842 topology information if the hardware supports this.
2843 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002844 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02002845 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002846
Linus Torvalds1da177e2005-04-16 15:20:36 -07002847 tp720= [HW,PS2]
2848
Rajiv Andrade225a9be2010-03-25 00:55:32 -03002849 tpm_suspend_pcr=[HW,TPM]
2850 Format: integer pcr id
2851 Specify that at suspend time, the tpm driver
2852 should extend the specified pcr with zeros,
2853 as a workaround for some chips which fail to
2854 flush the last written pcr on TPM_SaveState.
2855 This will guarantee that all the other pcrs
2856 are saved.
2857
Li Zefan9d612be2009-06-24 17:33:15 +08002858 trace_buf_size=nn[KMG]
2859 [FTRACE] will set tracing buffer size.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09002860
Li Zefan020e5f82009-07-01 10:47:05 +08002861 trace_event=[event-list]
2862 [FTRACE] Set and start specified trace events in order
2863 to facilitate early boot debugging.
2864 See also Documentation/trace/events.txt
2865
Jiri Kosinafcf4d822012-03-21 16:34:02 -07002866 transparent_hugepage=
2867 [KNL]
2868 Format: [always|madvise|never]
2869 Can be used to control the default behavior of the system
2870 with respect to transparent hugepages.
2871 See Documentation/vm/transhuge.txt for more details.
2872
john stultzd3b8f882009-08-17 16:40:47 -07002873 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07002874 Format: <string>
2875 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07002876 disables clocksource verification at runtime, as well
2877 as the stability checks done at bootup. Used to enable
2878 high-resolution timer mode on older hardware, and in
2879 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07002880 [x86] noirqtime: Do not use TSC to do irq accounting.
2881 Used to run time disable IRQ_TIME_ACCOUNTING on any
2882 platforms where RDTSC is slow and this accounting
2883 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07002884
Randy Dunlapa9913042005-10-23 12:57:11 -07002885 turbografx.map[2|3]= [HW,JOY]
2886 TurboGraFX parallel port interface
2887 Format:
2888 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002889 See also Documentation/input/joystick-parport.txt
2890
Christian Kujaub6935f82011-05-31 15:22:05 +00002891 udbg-immortal [PPC] When debugging early kernel crashes that
2892 happen after console_init() and before a proper
2893 console driver takes over, this boot options might
2894 help "seeing" what's going on.
2895
Eric Dumazetf86dcc52009-10-07 00:37:59 +00002896 uhash_entries= [KNL,NET]
2897 Set number of hash buckets for UDP/UDP-Lite connections
2898
Alan Stern5f8364b2006-12-05 16:29:55 -05002899 uhci-hcd.ignore_oc=
2900 [USB] Ignore overcurrent events (default N).
2901 Some badly-designed motherboards generate lots of
2902 bogus events, for ports that aren't wired to
2903 anything. Set this parameter to avoid log spamming.
2904 Note that genuine overcurrent events won't be
2905 reported either.
2906
Simon Arlotte3a61b02008-07-19 23:32:54 +01002907 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002908 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01002909
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02002910 usbcore.authorized_default=
2911 [USB] Default USB device authorization:
2912 (default -1 = authorized except for wireless USB,
2913 0 = not authorized, 1 = authorized)
2914
Alan Sternb5e795f2007-02-20 15:00:53 -05002915 usbcore.autosuspend=
2916 [USB] The autosuspend time delay (in seconds) used
2917 for newly-detected USB devices (default 2). This
2918 is the time required before an idle device will be
2919 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002920 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002921
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002922 usbcore.usbfs_snoop=
2923 [USB] Set to log all usbfs traffic (default 0 = off).
2924
2925 usbcore.blinkenlights=
2926 [USB] Set to cycle leds on hubs (default 0 = off).
2927
2928 usbcore.old_scheme_first=
2929 [USB] Start with the old device initialization
2930 scheme (default 0 = off).
2931
Alan Stern3f5eb8d2011-11-17 16:41:35 -05002932 usbcore.usbfs_memory_mb=
2933 [USB] Memory limit (in MB) for buffers allocated by
2934 usbfs (default = 16, 0 = max = 2047).
2935
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002936 usbcore.use_both_schemes=
2937 [USB] Try the other device initialization scheme
2938 if the first one fails (default 1 = enabled).
2939
2940 usbcore.initial_descriptor_timeout=
2941 [USB] Specifies timeout for the initial 64-byte
2942 USB_REQ_GET_DESCRIPTOR request in milliseconds
2943 (default 5000 = 5.0 seconds).
2944
Linus Torvalds1da177e2005-04-16 15:20:36 -07002945 usbhid.mousepoll=
2946 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002947
Alan Sternd4f373e2008-11-10 14:07:45 -05002948 usb-storage.delay_use=
2949 [UMS] The delay in seconds before a new device is
2950 scanned for Logical Units (default 5).
2951
2952 usb-storage.quirks=
2953 [UMS] A list of quirks entries to supplement or
2954 override the built-in unusual_devs list. List
2955 entries are separated by commas. Each entry has
2956 the form VID:PID:Flags where VID and PID are Vendor
2957 and Product ID values (4-digit hex numbers) and
2958 Flags is a set of characters, each corresponding
2959 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002960 a = SANE_SENSE (collect more than 18 bytes
2961 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05002962 b = BAD_SENSE (don't collect more than 18
2963 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002964 c = FIX_CAPACITY (decrease the reported
2965 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01002966 d = NO_READ_DISC_INFO (don't use
2967 READ_DISC_INFO command);
2968 e = NO_READ_CAPACITY_16 (don't use
2969 READ_CAPACITY_16 command);
Alan Sternc838ea42008-12-15 10:40:06 -05002970 h = CAPACITY_HEURISTICS (decrease the
2971 reported device capacity by one
2972 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002973 i = IGNORE_DEVICE (don't bind to this
2974 device);
2975 l = NOT_LOCKABLE (don't try to lock and
2976 unlock ejectable media);
2977 m = MAX_SECTORS_64 (don't transfer more
2978 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04002979 n = INITIAL_READ10 (force a retry of the
2980 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05002981 o = CAPACITY_OK (accept the capacity
2982 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04002983 p = WRITE_CACHE (the device cache is ON
2984 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05002985 r = IGNORE_RESIDUE (the device reports
2986 bogus residue values);
2987 s = SINGLE_LUN (the device has only one
2988 Logical Unit);
2989 w = NO_WP_DETECT (don't test whether the
2990 medium is write-protected).
2991 Example: quirks=0419:aaf5:rl,0421:0433:rc
2992
Stephen Boydac1667d2011-08-13 12:34:50 -07002993 user_debug= [KNL,ARM]
2994 Format: <int>
2995 See arch/arm/Kconfig.debug help text.
2996 1 - undefined instruction events
2997 2 - system calls
2998 4 - invalid data aborts
2999 8 - SIGSEGV faults
3000 16 - SIGBUS faults
3001 Example: user_debug=31
3002
Ian Campbell14315592010-02-17 10:38:10 +00003003 userpte=
3004 [X86] Flags controlling user PTE allocations.
3005
3006 nohigh = do not allocate PTE pages in
3007 HIGHMEM regardless of setting
3008 of CONFIG_HIGHPTE.
3009
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303010 vdso= [X86,SH]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02003011 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07003012 vdso=1: enable VDSO (default)
3013 vdso=0: disable VDSO mapping
3014
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05303015 vdso32= [X86]
Roland McGrathaf65d642008-01-30 13:30:43 +01003016 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3017 vdso32=1: enable 32-bit VDSO (default)
3018 vdso32=0: disable 32-bit VDSO mapping
3019
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09003020 vector= [IA-64,SMP]
3021 vector=percpu: enable percpu vector domain
3022
Linus Torvalds1da177e2005-04-16 15:20:36 -07003023 video= [FB] Frame buffer configuration
3024 See Documentation/fb/modedb.txt.
3025
Pawel Moll81a054c2012-05-09 18:30:16 +01003026 virtio_mmio.device=
3027 [VMMIO] Memory mapped virtio (platform) device.
3028
3029 <size>@<baseaddr>:<irq>[:<id>]
3030 where:
3031 <size> := size (can use standard suffixes
3032 like K, M and G)
3033 <baseaddr> := physical base address
3034 <irq> := interrupt number (as passed to
3035 request_irq())
3036 <id> := (optional) platform device id
3037 example:
3038 virtio_mmio.device=1K@0x100b0000:48:7
3039
3040 Can be used multiple times for multiple devices.
3041
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003042 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05003043 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07003044 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003045 Use vga=ask for menu.
3046 This is actually a boot loader parameter; the value is
3047 passed to the kernel using a special protocol.
3048
Randy Dunlapa9913042005-10-23 12:57:11 -07003049 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07003050 size of <nn>. This can be used to increase the
3051 minimum size (128MB on x86). It can also be used to
3052 decrease the size and leave more room for directly
3053 mapped kernel RAM.
3054
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003055 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3056 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07003057
Peter Oberparleiter585c3042006-06-29 15:08:25 +02003058 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3059 Format: <command>
3060
3061 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3062 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07003063
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003064 vsyscall= [X86-64]
3065 Controls the behavior of vsyscalls (i.e. calls to
3066 fixed addresses of 0xffffffffff600x00 from legacy
3067 code). Most statically-linked binaries and older
3068 versions of glibc use these calls. Because these
3069 functions are at fixed addresses, they make nice
3070 targets for exploits that can control RIP.
3071
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003072 emulate [default] Vsyscalls turn into traps and are
3073 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003074
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08003075 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04003076 This is a little bit faster than trapping
3077 and makes a few dynamic recompilers work
3078 better than they would in emulation mode.
3079 It also makes exploits much easier to write.
3080
3081 none Vsyscalls don't work at all. This makes
3082 them quite hard to use for exploits but
3083 might break your system.
3084
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08003085 vt.cur_default= [VT] Default cursor shape.
3086 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3087 the parameters of the <Esc>[?A;B;Cc escape sequence;
3088 see VGA-softcursor.txt. Default: 2 = underline.
3089
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003090 vt.default_blu= [VT]
3091 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3092 Change the default blue palette of the console.
3093 This is a 16-member array composed of values
3094 ranging from 0-255.
3095
3096 vt.default_grn= [VT]
3097 Format: <green0>,<green1>,<green2>,...,<green15>
3098 Change the default green palette of the console.
3099 This is a 16-member array composed of values
3100 ranging from 0-255.
3101
3102 vt.default_red= [VT]
3103 Format: <red0>,<red1>,<red2>,...,<red15>
3104 Change the default red palette of the console.
3105 This is a 16-member array composed of values
3106 ranging from 0-255.
3107
3108 vt.default_utf8=
3109 [VT]
3110 Format=<0|1>
3111 Set system-wide default UTF-8 mode for all tty's.
3112 Default is 1, i.e. UTF-8 mode is enabled for all
3113 newly opened terminals.
3114
Matthew Garrettf6c06b62009-11-13 15:14:11 -05003115 vt.global_cursor_default=
3116 [VT]
3117 Format=<-1|0|1>
3118 Set system-wide default for whether a cursor
3119 is shown on new VTs. Default is -1,
3120 i.e. cursors will be created by default unless
3121 overridden by individual drivers. 0 will hide
3122 cursors, 1 will display them.
3123
Randy Dunlap4724ba52010-05-03 11:42:52 -07003124 watchdog timers [HW,WDT] For information on watchdog timers,
3125 see Documentation/watchdog/watchdog-parameters.txt
3126 or other driver-specific files in the
3127 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003128
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003129 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3130 default x2apic cluster mode on platforms
3131 supporting x2apic.
3132
Jacob Panbb24c472009-09-02 07:37:17 -07003133 x86_mrst_timer= [X86-32,APBT]
3134 Choose timer option for x86 Moorestown MID platform.
3135 Two valid options are apbt timer only and lapic timer
3136 plus one apbt timer for broadcast timer.
3137 x86_mrst_timer=apbt_only | lapic_and_apbt
3138
Linus Torvalds1da177e2005-04-16 15:20:36 -07003139 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3140 xd_geo= See header of drivers/block/xd.c.
3141
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003142 xen_emul_unplug= [HW,X86,XEN]
3143 Unplug Xen emulated devices
3144 Format: [unplug0,][unplug1]
3145 ide-disks -- unplug primary master IDE devices
3146 aux-ide-disks -- unplug non-primary-master IDE devices
3147 nics -- unplug network devices
3148 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01003149 unnecessary -- unplugging emulated devices is
3150 unnecessary even if the host did not respond to
3151 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01003152 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01003153
Linus Torvalds1da177e2005-04-16 15:20:36 -07003154 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07003155 Format:
3156 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003157
Randy Dunlapa9913042005-10-23 12:57:11 -07003158______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07003159
3160TODO:
3161
Linus Torvalds1da177e2005-04-16 15:20:36 -07003162 Add more DRM drivers.