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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
Stefan Richtera901ebb2006-04-01 01:43:18 +020020This document may not be entirely up to date and comprehensive. The command
21"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22module. Loadable modules, after being loaded into the running kernel, also
23reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24parameters may be changed at runtime by the command
25"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
26
Stefan Richter6585fa82006-04-01 01:44:30 +020027The parameters listed below are only valid if certain kernel build options were
28enabled and if respective hardware is present. The text in square brackets at
29the beginning of each description states the restrictions within which a
30parameter is applicable:
Linus Torvalds1da177e2005-04-16 15:20:36 -070031
32 ACPI ACPI support is enabled.
Chuck Ebbertc99c1082007-07-27 10:46:20 +100033 AGP AGP (Accelerated Graphics Port) is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070034 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +020037 AVR32 AVR32 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070038 AX25 Appropriate AX.25 support is enabled.
Robin Getz0ae53642007-10-09 17:24:49 +080039 BLACKFIN Blackfin architecture is enabled.
Randy Dunlapa9913042005-10-23 12:57:11 -070040 DRM Direct Rendering Management support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070041 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070046 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
Adrian Bunk41e2e8b2005-07-12 13:58:33 -070048 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070049 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
Kristen Carlson Accardi11ef6972006-09-28 11:29:01 -070052 LIBATA Libata driver is enabled
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
Matthew Wilcox309e57d2006-03-05 22:33:34 -070061 MSI Message Signaled Interrupts (PCI).
Randy Dunlapc8facbb2007-07-31 00:37:40 -070062 MTD MTD (Memory Technology Device) support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070063 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
john stultz734efb42006-06-26 00:25:05 -070065 GENERIC_TIME The generic timeofday code is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070066 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
Randy Dunlapc8facbb2007-07-31 00:37:40 -070068 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070070 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
Randy Dunlap7f785762007-10-05 13:17:58 -070072 PCIE PCI Express support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
James Morris20510f22007-10-16 23:31:32 -070079 ROOTPLUG The example Root Plug LSM is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
James Morris20510f22007-10-16 23:31:32 -070084 SECURITY Different security models are enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
Paul Mundte523d932007-02-28 18:30:01 +090087 SH SuperH architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070088 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
David Brownell77437fd2008-07-23 21:28:33 -070090 SWSUSP Software suspend (hibernation) is enabled.
91 SUSPEND System suspend states are enabled.
Steven Rostedtf38f1d22008-12-16 23:06:40 -050092 FTRACE Function tracing enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070093 TS Appropriate touchscreen support is enabled.
Alan Sternd4f373e2008-11-10 14:07:45 -050094 UMS USB Mass Storage support is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070095 USB USB support is enabled.
96 USBHID USB Human Interface Device support is enabled.
97 V4L Video For Linux support is enabled.
98 VGA The VGA console has been enabled.
99 VT Virtual terminal support is enabled.
100 WDT Watchdog support is enabled.
101 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700102 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 X86-64 X86-64 architecture is enabled.
104 More X86-64 boot options can be found in
Uwe Hermann71cced62008-10-20 09:32:21 -0700105 Documentation/x86/x86_64/boot-options.txt .
Andi Kleenc0115602008-08-22 09:53:39 +0200106 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107
108In addition, the following text indicates that the option:
109
110 BUGS= Relates to possible processor bugs on the said processor.
111 KNL Is a kernel start-up parameter.
112 BOOT Is a boot loader parameter.
113
114Parameters denoted with BOOT are actually interpreted by the boot
115loader, and have no meaning to the kernel directly.
116Do not modify the syntax of boot loader parameters without extreme
Uwe Hermann71cced62008-10-20 09:32:21 -0700117need or coordination with <Documentation/x86/i386/boot.txt>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118
Karsten Weiss55588702007-02-13 13:26:21 +0100119There are also arch-specific kernel-parameters not documented here.
Uwe Hermann71cced62008-10-20 09:32:21 -0700120See for example <Documentation/x86/x86_64/boot-options.txt>.
Karsten Weiss55588702007-02-13 13:26:21 +0100121
Linus Torvalds1da177e2005-04-16 15:20:36 -0700122Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
123a trailing = on the name of any parameter states that that parameter will
124be entered as an environment variable, whereas its absence indicates that
125it will appear as a kernel argument readable via /proc/cmdline by programs
126running once the system is up.
127
jens m. noedler9c4751f2006-09-29 02:00:27 -0700128The number of kernel parameters is not limited, but the length of the
129complete command line (parameters including spaces etc.) is limited to
130a fixed number of characters. This limit depends on the architecture
131and is between 256 and 4096 characters. It is defined in the file
132./include/asm/setup.h as COMMAND_LINE_SIZE.
133
134
Bernhard Walle03d926f2007-03-06 02:29:44 -0800135 acpi= [HW,ACPI,X86-64,i386]
136 Advanced Configuration and Power Interface
Randy Dunlapa9913042005-10-23 12:57:11 -0700137 Format: { force | off | ht | strict | noirq }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138 force -- enable ACPI if default was off
139 off -- disable ACPI if default was on
140 noirq -- do not use ACPI for IRQ routing
141 ht -- run only enough ACPI to enable Hyper Threading
Randy Dunlapa9913042005-10-23 12:57:11 -0700142 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +0800144 rsdt -- prefer RSDT over (default) XSDT
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145
Randy Dunlap53471122008-03-12 18:10:51 -0400146 See also Documentation/power/pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147
Len Browna1fdcc02007-03-11 03:26:14 -0400148 acpi_apic_instance= [ACPI, IOAPIC]
149 Format: <int>
150 2: use 2nd APIC table, if available
151 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400152 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400153
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154 acpi_sleep= [HW,ACPI] Sleep options
Rafael J. Wysockiba84ed92008-10-26 20:56:30 +0100155 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
156 old_ordering, s4_nonvs }
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800157 See Documentation/power/video.txt for information on
158 s3_bios and s3_mode.
Pavel Machek23b168d2008-02-05 19:27:12 +0100159 s3_beep is for debugging; it makes the PC's speaker beep
160 as soon as the kernel's real-mode entry point is called.
Shaohua Libdfe6b72008-07-23 21:28:41 -0700161 s4_nohwsig prevents ACPI hardware signature from being
162 used during resume from hibernation.
Rafael J. Wysockid8f3de02008-06-12 23:24:06 +0200163 old_ordering causes the ACPI 1.0 ordering of the _PTS
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800164 control method, with respect to putting devices into
165 low power states, to be enforced (the ACPI 2.0 ordering
166 of _PTS is used by default).
Rafael J. Wysockiba84ed92008-10-26 20:56:30 +0100167 s4_nonvs prevents the kernel from saving/restoring the
168 ACPI NVS memory during hibernation.
Randy Dunlapa9913042005-10-23 12:57:11 -0700169
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
Randy Dunlapa9913042005-10-23 12:57:11 -0700171 Format: { level | edge | high | low }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172
Randy Dunlapa9913042005-10-23 12:57:11 -0700173 acpi_irq_balance [HW,ACPI]
174 ACPI will balance active IRQs
175 default in APIC mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176
Randy Dunlapa9913042005-10-23 12:57:11 -0700177 acpi_irq_nobalance [HW,ACPI]
178 ACPI will not move active IRQs (default)
179 default in PIC mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180
Randy Dunlapa9913042005-10-23 12:57:11 -0700181 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
182 use by PCI
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183 Format: <irq>,<irq>...
184
Randy Dunlapa9913042005-10-23 12:57:11 -0700185 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186 Format: <irq>,<irq>...
187
Len Brown67effe82007-07-26 00:50:06 -0400188 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
189
Len Browna1f9e652006-01-25 23:47:36 -0500190 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
191 Format: To spoof as Windows 98: ="Microsoft Windows"
192
Len Brownae00d812007-05-29 18:43:33 -0400193 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
194 acpi_osi="string1" # add string1 -- only one string
195 acpi_osi="!string2" # remove built-in string2
196 acpi_osi= # disable all strings
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197
198 acpi_serialize [HW,ACPI] force serialization of AML methods
199
200 acpi_skip_timer_override [HW,ACPI]
201 Recognize and ignore IRQ0/pin2 Interrupt Override.
202 For broken nForce2 BIOS resulting in XT-PIC timer.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800203 acpi_use_timer_override [HW,ACPI]
Andi Kleenfa18f472006-11-14 16:57:46 +0100204 Use timer override. For some broken Nvidia NF5 boards
205 that require a timer override, but don't have
206 HPET
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207
Thomas Renningerc3d6de62008-08-01 17:37:55 +0200208 acpi_backlight= [HW,ACPI]
209 acpi_backlight=vendor
210 acpi_backlight=video
211 If set to vendor, prefer vendor specific driver
212 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
213 of the ACPI video.ko driver.
214
215 acpi_display_output= [HW,ACPI]
216 acpi_display_output=vendor
217 acpi_display_output=video
218 See above.
219
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700220 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
221 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700223 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
224 debug output. Bits in debug_layer correspond to a
225 _COMPONENT in an ACPI source file, e.g.,
226 #define _COMPONENT ACPI_PCI_COMPONENT
227 Bits in debug_level correspond to a level in
228 ACPI_DEBUG_PRINT statements, e.g.,
229 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600230 The debug_level mask defaults to "info". See
231 Documentation/acpi/debug.txt for more information about
232 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233
Bjorn Helgaase76f4272008-11-13 17:30:13 -0600234 Enable processor driver info messages:
235 acpi.debug_layer=0x20000000
236 Enable PCI/PCI interrupt routing info messages:
237 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700238 Enable AML "Debug" output, i.e., stores to the Debug
239 object while interpreting AML:
240 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700241 Enable all messages related to ACPI hardware:
242 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +0200243
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -0700244 Some values produce so much output that the system is
245 unusable. The "log_buf_len" parameter may be useful
246 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +0800247
Zhao Yakuif5adfaa2008-08-11 14:57:50 +0800248 acpi.power_nocheck= [HW,ACPI]
249 Format: 1/0 enable/disable the check of power state.
250 On some bogus BIOS the _PSC object/_STA object of
251 power resource can't return the correct device power
252 state. In such case it is unneccessary to check its
253 power state again in power transition.
254 1 : disable the power state check
255
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700256 acpi_pm_good [X86-32,X86-64]
john stultz5d0cf412006-06-26 00:25:12 -0700257 Override the pmtimer bug detection: force the kernel
258 to assume that this machine's pmtimer latches its value
259 and always returns good values.
260
Chuck Ebbertc99c1082007-07-27 10:46:20 +1000261 agp= [AGP]
262 { off | try_unsupported }
263 off: disable AGP support
264 try_unsupported: try to drive unsupported chipsets
265 (may crash computer or cause data corruption)
266
Chuck Ebbert66759a02005-09-12 18:49:25 +0200267 enable_timer_pin_1 [i386,x86-64]
268 Enable PIN 1 of APIC timer
Randy Dunlapa9913042005-10-23 12:57:11 -0700269 Can be useful to work around chipset bugs
270 (in particular on some ATI chipsets).
Chuck Ebbert66759a02005-09-12 18:49:25 +0200271 The kernel tries to set a reasonable default.
272
273 disable_timer_pin_1 [i386,x86-64]
274 Disable PIN 1 of APIC timer
275 Can be useful to work around chipset bugs.
276
Linus Torvalds1da177e2005-04-16 15:20:36 -0700277 ad1848= [HW,OSS]
278 Format: <io>,<irq>,<dma>,<dma2>,<type>
279
Linus Torvalds1da177e2005-04-16 15:20:36 -0700280 advansys= [HW,SCSI]
281 See header of drivers/scsi/advansys.c.
282
283 advwdt= [HW,WDT] Advantech WDT
284 Format: <iostart>,<iostop>
285
286 aedsp16= [HW,OSS] Audio Excel DSP 16
287 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
288 See also header of sound/oss/aedsp16.c.
Randy Dunlapa9913042005-10-23 12:57:11 -0700289
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290 aha152x= [HW,SCSI]
291 See Documentation/scsi/aha152x.txt.
292
293 aha1542= [HW,SCSI]
294 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
295
296 aic7xxx= [HW,SCSI]
297 See Documentation/scsi/aic7xxx.txt.
298
299 aic79xx= [HW,SCSI]
300 See Documentation/scsi/aic79xx.txt.
301
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
304 Possible values are:
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200305 isolate - enable device isolation (each device, as far
306 as possible, will get its own protection
Joerg Roedel3ce1f932008-11-17 15:09:20 +0100307 domain) [default]
Joerg Roedele5e1f602008-11-17 15:07:17 +0100308 share - put every device behind one IOMMU into the
309 same protection domain
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900310 fullflush - enable flushing of IO/TLB entries when
311 they are unmapped. Otherwise they are
312 flushed before they will be reused, which
313 is a lot of faster
314
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200315 amd_iommu_size= [HW,X86-64]
316 Define the size of the aperture for the AMD IOMMU
317 driver. Possible values are:
318 '32M', '64M' (default), '128M', '256M', '512M', '1G'
319
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 amijoy.map= [HW,JOY] Amiga joystick support
321 Map of devices attached to JOY0DAT and JOY1DAT
322 Format: <a>,<b>
323 See also Documentation/kernel/input/joystick.txt
324
325 analog.map= [HW,JOY] Analog joystick and gamepad support
326 Specifies type or capabilities of an analog joystick
327 connected to one of 16 gameports
328 Format: <type1>,<type2>,..<type16>
329
Randy Dunlapa9913042005-10-23 12:57:11 -0700330 apc= [HW,SPARC]
331 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700332 Format: noidle
333 Disable APC CPU standby support. SPARCstation-Fox does
334 not play well with APC CPU idle - disable it if you have
335 APC and your system crashes randomly.
336
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700337 apic= [APIC,i386] Advanced Programmable Interrupt Controller
338 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700339 Format: { quiet (default) | verbose | debug }
340 Change the amount of debugging information output
341 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700342
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700344 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345
Linus Torvalds1da177e2005-04-16 15:20:36 -0700346 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
347 Format: <io>,<irq>,<nodeID>
348
349 ataflop= [HW,M68k]
350
351 atarimouse= [HW,MOUSE] Atari Mouse
352
353 atascsi= [HW,SCSI] Atari SCSI
354
355 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
356 EzKey and similar keyboards
357
358 atkbd.reset= [HW] Reset keyboard during initialization
359
Randy Dunlapa9913042005-10-23 12:57:11 -0700360 atkbd.set= [HW] Select keyboard code set
361 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362
363 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
364 keyboards
365
366 atkbd.softraw= [HW] Choose between synthetic and real raw mode
367 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700368
369 atkbd.softrepeat= [HW]
370 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700371
372 autotest [IA64]
373
Linus Torvalds1da177e2005-04-16 15:20:36 -0700374 baycom_epp= [HW,AX25]
375 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700376
Linus Torvalds1da177e2005-04-16 15:20:36 -0700377 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
378 Format: <io>,<mode>
379 See header of drivers/net/hamradio/baycom_par.c.
380
Randy Dunlapa9913042005-10-23 12:57:11 -0700381 baycom_ser_fdx= [HW,AX25]
382 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383 Format: <io>,<irq>,<mode>[,<baud>]
384 See header of drivers/net/hamradio/baycom_ser_fdx.c.
385
Randy Dunlapa9913042005-10-23 12:57:11 -0700386 baycom_ser_hdx= [HW,AX25]
387 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700388 Format: <io>,<irq>,<mode>
389 See header of drivers/net/hamradio/baycom_ser_hdx.c.
390
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700391 boot_delay= Milliseconds to delay each printk during boot.
392 Values larger than 10 seconds (10000) are changed to
393 no delay (0).
394 Format: integer
395
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700396 bootmem_debug [KNL] Enable bootmem allocator debug messages.
397
Linus Torvalds1da177e2005-04-16 15:20:36 -0700398 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700399 bttv.radio= Most important insmod options are available as
400 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
402 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
403
404 BusLogic= [HW,SCSI]
405 See drivers/scsi/BusLogic.c, comment before function
406 BusLogic_ParseDriverOptions().
407
408 c101= [NET] Moxa C101 synchronous serial card
409
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700410 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411 Sometimes CPU hardware bugs make them report the cache
412 size incorrectly. The kernel will attempt work arounds
413 to fix known problems, but for some CPUs it is not
414 possible to determine what the correct size should be.
415 This option provides an override for these situations.
416
Ahmed S. Darwish076c54c2008-03-06 18:09:10 +0200417 security= [SECURITY] Choose a security module to enable at boot.
418 If this boot parameter is not specified, only the first
419 security module asking for security registration will be
420 loaded. An invalid security module name will be treated
421 as if no module has been chosen.
422
James Morris20510f22007-10-16 23:31:32 -0700423 capability.disable=
424 [SECURITY] Disable capabilities. This would normally
425 be used only if an alternative security model is to be
426 configured. Potentially dangerous and should only be
427 used if you are entirely sure of the consequences.
428
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100429 ccw_timeout_log [S390]
430 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431
Paul Menage8bab8dd2008-04-04 14:29:57 -0700432 cgroup_disable= [KNL] Disable a particular controller
433 Format: {name of the controller(s) to disable}
434 {Currently supported controllers - "memory"}
435
Linus Torvalds1da177e2005-04-16 15:20:36 -0700436 checkreqprot [SELINUX] Set initial checkreqprot flag value.
437 Format: { "0" | "1" }
438 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700439 0 -- check protection applied by kernel (includes
440 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700441 1 -- check protection requested by application.
442 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700443 Value can be changed at runtime via
444 /selinux/checkreqprot.
445
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100446 cio_ignore= [S390]
447 See Documentation/s390/CommonIO for details.
448
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700449 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700450 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200451 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700452 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200453 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454 Format: { pit | tsc | cyclone | pmtmr }
455
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700456 clocksource= [GENERIC_TIME] Override the default clocksource
457 Format: <string>
458 Override the default clocksource and use the clocksource
459 with the name specified.
460 Some clocksource names to choose from, depending on
461 the platform:
462 [all] jiffies (this is the base, fallback clocksource)
463 [ACPI] acpi_pm
464 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
465 pxa_timer,timer3,32k_counter,timer0_1
466 [AVR32] avr32
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700467 [X86-32] pit,hpet,tsc,vmi-timer;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700468 scx200_hrt on Geode; cyclone on IBM x440
469 [MIPS] MIPS
470 [PARISC] cr16
471 [S390] tod
472 [SH] SuperH
473 [SPARC64] tick
474 [X86-64] hpet,tsc
475
Andi Kleenac72e782008-01-30 13:33:21 +0100476 clearcpuid=BITNUM [X86]
477 Disable CPUID feature X for the kernel. See
Randy Dunlap07983f02009-01-06 14:42:41 -0800478 arch/x86/include/asm/cpufeature.h for the valid bit
479 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100480 stable over kernel options, but the vendor specific
481 ones should be.
482 Also note that user programs calling CPUID directly
483 or using the feature without checking anything
484 will still see it. This just prevents it from
485 being used by the kernel or shown in /proc/cpuinfo.
486 Also note the kernel might malfunction if you disable
487 some critical bits.
488
Arjan van de Vena25bd942008-01-30 13:33:08 +0100489 code_bytes [IA32/X86_64] How many bytes of object code to print
490 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100491 Range: 0 - 8192
492 Default: 64
493
Thomas Gleixnerb17530b2007-10-19 20:35:02 +0200494 hpet= [X86-32,HPET] option to control HPET usage
495 Format: { enable (default) | disable | force }
496 disable: disable HPET and use PIT instead
Carlos Corbachod79a5f82007-10-19 18:51:27 +0100497 force: allow force enabled of undocumented chips (ICH4,
498 VIA, nVidia)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700499
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700501 Format:
502 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700503
504 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
505 Format: <io>[,<irq>]
506
Randy Dunlapa9913042005-10-23 12:57:11 -0700507 com90xx= [HW,NET]
508 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509 Format: <io>[,<irq>[,<memstart>]]
510
511 condev= [HW,S390] console device
512 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700513
Linus Torvalds1da177e2005-04-16 15:20:36 -0700514 console= [KNL] Output console device and options.
515
516 tty<n> Use the virtual console device <n>.
517
518 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800519 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800521 the form "bbbbpnf", where "bbbb" is the baud rate,
522 "p" is parity ("n", "o", or "e"), "n" is number of
523 bits, and "f" is flow control ("r" for RTS or
524 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800526 See Documentation/serial-console.txt for more
527 information. See
528 Documentation/networking/netconsole.txt for an
529 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700531 uart[8250],io,<addr>[,options]
532 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533 Start an early, polled-mode console on the 8250/16550
534 UART at the specified I/O port or MMIO address,
535 switching to the matching ttyS device later. The
536 options are the same as for ttyS, above.
537
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700538 If the device connected to the port is not a TTY but a braille
539 device, prepend "brl," before the device type, for instance
540 console=brl,ttyS0
541 For now, only VisioBraille is supported.
542
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700543 earlycon= [KNL] Output early console device and options.
544 uart[8250],io,<addr>[,options]
545 uart[8250],mmio,<addr>[,options]
546 Start an early, polled-mode console on the 8250/16550
547 UART at the specified I/O port or MMIO address.
548 The options are the same as for ttyS, above.
549
Andres Salomon8f4ce8c2007-10-18 03:04:50 -0700550 no_console_suspend
551 [HW] Never suspend the console
552 Disable suspending of consoles during suspend and
553 hibernate operations. Once disabled, debugging
554 messages can reach various consoles while the rest
555 of the system is being put to sleep (ie, while
556 debugging driver suspend/resume hooks). This may
557 not work reliably with all consoles, but is known
558 to work with serial and VGA consoles.
559
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800560 coredump_filter=
561 [KNL] Change the default value for
562 /proc/<pid>/coredump_filter.
563 See also Documentation/filesystems/proc.txt.
564
Linus Torvalds1da177e2005-04-16 15:20:36 -0700565 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700566 Format:
567 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700568
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700569 crashkernel=nn[KMG]@ss[KMG]
570 [KNL] Reserve a chunk of physical memory to
571 hold a kernel to switch to with kexec on panic.
572
Bernhard Wallefb391592007-10-18 23:41:02 -0700573 crashkernel=range1:size1[,range2:size2,...][@offset]
574 [KNL] Same as above, but depends on the memory
575 in the running system. The syntax of range is
576 start-[end] where start and end are both
577 a memory unit (amount[KMG]). See also
578 Documentation/kdump/kdump.txt for a example.
579
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580 cs4232= [HW,OSS]
581 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
582
583 cs89x0_dma= [HW,NET]
584 Format: <dma>
585
586 cs89x0_media= [HW,NET]
587 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700588
Randy Dunlapa9913042005-10-23 12:57:11 -0700589 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590 See header of drivers/s390/block/dasd_devmap.c.
591
592 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
593 (one device per port)
594 Format: <port#>,<type>
595 See also Documentation/input/joystick-parport.txt
596
597 debug [KNL] Enable kernel debugging (events log level).
598
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700599 debug_locks_verbose=
600 [KNL] verbose self-tests
601 Format=<0|1>
602 Print debugging info while doing the locking API
603 self-tests.
604 We default to 0 (no extra messages), setting it to
605 1 will print _a lot_ more information - normally
606 only useful to kernel developers.
607
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700608 debug_objects [KNL] Enable object debugging
609
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200610 debugpat [X86] Enable PAT debugging
611
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200612 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613 Format: <area>[,<node>]
614 See also Documentation/networking/decnet.txt.
615
Samuel Thibaultecb77fa2008-01-03 16:17:54 +0000616 vt.default_blu= [VT]
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700617 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
618 Change the default blue palette of the console.
619 This is a 16-member array composed of values
620 ranging from 0-255.
621
Samuel Thibaultecb77fa2008-01-03 16:17:54 +0000622 vt.default_grn= [VT]
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700623 Format: <green0>,<green1>,<green2>,...,<green15>
624 Change the default green palette of the console.
625 This is a 16-member array composed of values
626 ranging from 0-255.
627
Samuel Thibaultecb77fa2008-01-03 16:17:54 +0000628 vt.default_red= [VT]
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700629 Format: <red0>,<red1>,<red2>,...,<red15>
630 Change the default red palette of the console.
631 This is a 16-member array composed of values
632 ranging from 0-255.
633
Samuel Thibaultecb77fa2008-01-03 16:17:54 +0000634 vt.default_utf8=
635 [VT]
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700636 Format=<0|1>
637 Set system-wide default UTF-8 mode for all tty's.
Samuel Thibaultecb77fa2008-01-03 16:17:54 +0000638 Default is 1, i.e. UTF-8 mode is enabled for all
639 newly opened terminals.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700640
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641 dhash_entries= [KNL]
642 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700643
Linus Torvalds1da177e2005-04-16 15:20:36 -0700644 digi= [HW,SERIAL]
645 IO parameters + enable/disable command.
646
647 digiepca= [HW,SERIAL]
648 See drivers/char/README.epca and
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000649 Documentation/serial/digiepca.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700650
Yinghai Lu95ffa242008-04-29 03:52:33 -0700651 disable_mtrr_cleanup [X86]
652 enable_mtrr_cleanup [X86]
653 The kernel tries to adjust MTRR layout from continuous
654 to discrete, to make X server driver able to add WB
655 entry later. This parameter enables/disables that.
656
657 mtrr_chunk_size=nn[KMG] [X86]
658 used for mtrr cleanup. It is largest continous chunk
659 that could hold holes aka. UC entries.
660
661 mtrr_gran_size=nn[KMG] [X86]
Yinghai Lu12031a62008-05-02 02:40:22 -0700662 Used for mtrr cleanup. It is granularity of mtrr block.
663 Default is 1.
664 Large value could prevent small alignment from
665 using up MTRRs.
666
667 mtrr_spare_reg_nr=n [X86]
668 Format: <integer>
669 Range: 0,7 : spare reg number
670 Default : 1
671 Used for mtrr cleanup. It is spare mtrr entries number.
672 Set to 2 or more if your graphical card needs more.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700673
Yinghai Lu093af8d2008-01-30 13:33:32 +0100674 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100675 By default the kernel will trim any uncacheable
676 memory out of your available memory pool based on
677 MTRR settings. This parameter disables that behavior,
678 possibly causing your machine to run very slowly.
679
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 dmasound= [HW,OSS] Sound subsystem buffers
681
682 dscc4.setup= [NET]
683
684 dtc3181e= [HW,SCSI]
685
Robin Getz0ae53642007-10-09 17:24:49 +0800686 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 earlyprintk=vga
688 earlyprintk=serial[,ttySn[,baudrate]]
Yinghai Lu5c059172008-07-24 17:29:40 -0700689 earlyprintk=dbgp
Linus Torvalds1da177e2005-04-16 15:20:36 -0700690
Randy Dunlapa9913042005-10-23 12:57:11 -0700691 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692 takes over.
693
Yinghai Lu5c059172008-07-24 17:29:40 -0700694 Only vga or serial or usb debug port at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700695
696 Currently only ttyS0 and ttyS1 are supported.
697
698 Interaction with the standard serial driver is not
699 very good.
700
701 The VGA output is eventually overwritten by the real
702 console.
703
704 eata= [HW,SCSI]
705
Linus Torvalds1da177e2005-04-16 15:20:36 -0700706 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -0700707 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708
Linus Torvalds1da177e2005-04-16 15:20:36 -0700709 eisa_irq_edge= [PARISC,HW]
710 See header of drivers/parisc/eisa.c.
711
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700712 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700713 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -0700714 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715
716 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800717 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700718 See Documentation/block/as-iosched.txt and
719 Documentation/block/deadline-iosched.txt for details.
720
Simon Hormane515a0d2008-10-18 20:28:27 -0700721 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
Randy Dunlapa9913042005-10-23 12:57:11 -0700722 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800723 image elf header. Generally kexec loader will
724 pass this option to capture kernel.
725 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700726
727 enforcing [SELINUX] Set initial enforcing status.
728 Format: {"0" | "1"}
729 See security/selinux/Kconfig help text.
730 0 -- permissive (log only, no denials).
731 1 -- enforcing (deny and log).
732 Default value is 0.
733 Value can be changed at runtime via /selinux/enforce.
734
Linus Torvalds1da177e2005-04-16 15:20:36 -0700735 es1371= [HW,OSS]
736 Format: <spdif>,[<nomix>,[<amplifier>]]
737 See also header of sound/oss/es1371.c.
Randy Dunlapa9913042005-10-23 12:57:11 -0700738
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739 ether= [HW,NET] Ethernet cards parameters
740 This option is obsoleted by the "netdev=" option, which
741 has equivalent usage. See its documentation for details.
742
743 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
744 Format: <io>[,<irq>]
745
Akinobu Mitade1ba092006-12-08 02:39:42 -0800746 failslab=
747 fail_page_alloc=
748 fail_make_request=[KNL]
749 General fault injection mechanism.
750 Format: <interval>,<probability>,<space>,<times>
751 See also /Documentation/fault-injection/.
752
Linus Torvalds1da177e2005-04-16 15:20:36 -0700753 fd_mcs= [HW,SCSI]
754 See header of drivers/scsi/fd_mcs.c.
755
756 fdomain= [HW,SCSI]
757 See header of drivers/scsi/fdomain.c.
758
759 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +0000760 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700761
Alex Chiangf13ae302008-05-08 14:03:23 -0600762 force_pal_cache_flush
763 [IA-64] Avoid check_sal_cache_flush which may hang on
764 buggy SAL_CACHE_FLUSH implementations. Using this
765 parameter will force ia64_sal_cache_flush to call
766 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
767
Peter Zijlstrad9e54072008-11-01 19:57:37 +0100768 ftrace=[tracer]
769 [ftrace] will set and start the specified tracer
770 as early as possible in order to facilitate early
771 boot debugging.
772
773 ftrace_dump_on_oops
774 [ftrace] will dump the trace buffers on oops.
775
Linus Torvalds1da177e2005-04-16 15:20:36 -0700776 gamecon.map[2|3]=
777 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
778 support via parallel port (up to 5 devices per port)
779 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
780 See also Documentation/input/joystick-parport.txt
781
782 gamma= [HW,DRM]
783
Yinghai Luaaf23042008-01-30 13:33:09 +0100784 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
785 Format: off | on
786 default: on
787
Linus Torvalds1da177e2005-04-16 15:20:36 -0700788 gdth= [HW,SCSI]
789 See header of drivers/scsi/gdth.c.
790
791 gpt [EFI] Forces disk with valid GPT signature but
792 invalid Protective MBR to be treated as GPT.
793
Linus Torvalds1da177e2005-04-16 15:20:36 -0700794 gvp11= [HW,SCSI]
795
796 hashdist= [KNL,NUMA] Large hashes allocated during boot
797 are distributed across NUMA nodes. Defaults on
798 for IA-64, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700799 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700800
801 hcl= [IA-64] SGI's Hardware Graph compatibility layer
802
803 hd= [EIDE] (E)IDE hard drive subsystem geometry
804 Format: <cyl>,<head>,<sect>
805
Linus Torvalds1da177e2005-04-16 15:20:36 -0700806 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
807 size of <nn>. This works even on boxes that have no
808 highmem otherwise. This also works to reduce highmem
809 size on bigger boxes.
810
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800811 highres= [KNL] Enable/disable high resolution timer mode.
812 Valid parameters: "on", "off"
813 Default: "on"
814
Linus Torvalds1da177e2005-04-16 15:20:36 -0700815 hisax= [HW,ISDN]
816 See Documentation/isdn/README.HiSax.
817
Andi Kleenb4718e62008-07-23 21:27:51 -0700818 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
819 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -0700820 On x86-64 and powerpc, this option can be specified
821 multiple times interleaved with hugepages= to reserve
822 huge pages of different sizes. Valid pages sizes on
823 x86-64 are 2M (when the CPU supports "pse") and 1G
824 (when the CPU supports the "pdpe1gb" cpuinfo flag)
Andi Kleenb4718e62008-07-23 21:27:51 -0700825 Note that 1GB pages can only be allocated at boot time
826 using hugepages= and not freed afterwards.
Nick Piggine11bfbf2008-07-23 21:27:52 -0700827 default_hugepagesz=
828 [same as hugepagesz=] The size of the default
829 HugeTLB page size. This is the size represented by
830 the legacy /proc/ hugepages APIs, used for SHM, and
831 default size when mounting hugetlbfs filesystems.
832 Defaults to the default architecture's huge page size
833 if not specified.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700834
Paul Mundt6902aa82008-09-21 17:14:42 +0900835 hlt [BUGS=ARM,SH]
836
Hendrik Brueckner555d61d2009-01-09 12:15:02 +0100837 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
838 terminal devices. Valid values: 0..8
Hendrik Bruecknercef71252008-12-25 13:39:55 +0100839
Jiri Kosina36d95732008-10-06 02:51:09 -0400840 i8042.debug [HW] Toggle i8042 debug mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700841 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200842 i8042.dumbkbd [HW] Pretend that controller can only read data from
843 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700844 (Don't attempt to blink the leds)
845 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500846 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400847 i8042.noloop [HW] Disable the AUX Loopback command while probing
848 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700849 i8042.nomux [HW] Don't check presence of an active multiplexing
850 controller
851 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
852 controllers
853 i8042.panicblink=
854 [HW] Frequency with which keyboard LEDs should blink
855 when kernel panics (default is 0.5 sec)
856 i8042.reset [HW] Reset the controller during init and cleanup
857 i8042.unlock [HW] Unlock (ignore) the keylock
858
859 i810= [HW,DRM]
860
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700861 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
862 indicates that the driver is running on unsupported
863 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
865 does not match list of supported models.
866 i8k.power_status
867 [HW] Report power status in /proc/i8k
868 (disabled by default)
869 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
870 capability is set.
871
872 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
873 See Documentation/mca.txt.
874
875 icn= [HW,ISDN]
876 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
877
878 ide= [HW] (E)IDE subsystem
Greg Kroah-Hartmana594eeb2008-04-18 00:46:20 +0200879 Format: ide=nodma or ide=doubler
Randy Dunlap1c10e932008-03-07 21:53:50 +0100880 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700881
Linus Torvalds1da177e2005-04-16 15:20:36 -0700882 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
Randy Dunlap1c10e932008-03-07 21:53:50 +0100883 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700884
Andi Kleenf039b752007-05-02 19:27:12 +0200885 idle= [X86]
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800886 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
887 Poll forces a polling idle loop that can slightly
888 improve the performance of waking up a idle CPU, but
889 will use a lot of power and make the system run hot.
890 Not recommended.
891 idle=mwait: On systems which support MONITOR/MWAIT but
892 the kernel chose to not use it because it doesn't save
893 as much power as a normal idle loop, use the
894 MONITOR/MWAIT idle loop anyways. Performance should be
895 the same as idle=poll.
896 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +0800897 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -0800898 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -0700899
Denis Cheng594765a2008-02-06 02:57:49 +0100900 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
901 Claim all unknown PCI IDE storage controllers.
902
Ingo Molnar792908222006-12-06 20:40:51 -0800903 ignore_loglevel [KNL]
904 Ignore loglevel setting - this will print /all/
905 kernel messages to the console. Useful for debugging.
906
Linus Torvalds1da177e2005-04-16 15:20:36 -0700907 ihash_entries= [KNL]
908 Set number of hash buckets for inode cache.
909
910 in2000= [HW,SCSI]
911 See header of drivers/scsi/in2000.c.
912
913 init= [KNL]
914 Format: <full_path>
915 Run specified binary instead of /sbin/init as init
916 process.
917
918 initcall_debug [KNL] Trace initcalls as they are executed. Useful
919 for working out where the kernel is dying during
920 startup.
921
922 initrd= [BOOT] Specify the location of the initial ramdisk
923
924 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
925 Format: <irq>
926
927 inttest= [IA64]
928
Arjan van de Vene8de1482008-10-22 19:55:31 -0700929 iomem= Disable strict checking of access to MMIO memory
930 strict regions from userspace.
931 relaxed
932
Pavel Machekb552da82008-03-19 15:58:11 +0100933 iommu= [x86]
934 off
935 force
936 noforce
937 biomerge
938 panic
939 nopanic
940 merge
941 nomerge
942 forcesac
943 soft
944
945
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700946 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
947 off
948 Disable intel iommu driver.
949 igfx_off [Default Off]
950 By default, gfx is mapped as normal device. If a gfx
951 device has a dedicated DMAR unit, the DMAR unit is
952 bypassed by not enabling DMAR with this option. In
953 this case, gfx device will use physical address for
954 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700955 forcedac [x86_64]
956 With this option iommu will not optimize to look
957 for io virtual address below 32 bit forcing dual
958 address cycle on pci bus for cards supporting greater
959 than 32 bit addressing. The default is to look
960 for translation below 32 bit and if not available
961 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -0800962 strict [Default Off]
963 With this option on every unmap_single operation will
964 result in a hardware IOTLB flush operation as opposed
965 to batching them for performance.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700966
Rene Hermanb02aae92008-01-30 13:30:05 +0100967 io_delay= [X86-32,X86-64] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100968 0x80
969 Standard port 0x80 based delay
970 0xed
971 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +0100972 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100973 Simple two microseconds delay
974 none
975 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +0100976
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977 io7= [HW] IO7 for Marvel based alpha systems
978 See comment before marvel_specify_io7 in
979 arch/alpha/kernel/core_marvel.c.
980
981 ip= [IP_PNP]
J. Bruce Fields6ded55d2008-04-07 15:59:03 -0400982 See Documentation/filesystems/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700983
984 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700985 See comment before ip2_setup() in
986 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700987
988 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
989 See header of drivers/scsi/ips.c.
990
Simon Horman72c4a132006-09-13 19:57:18 -0700991 ports= [IP_VS_FTP] IPVS ftp helper module
992 Default is 21.
993 Up to 8 (IP_VS_APP_MAX_PORTS) ports
994 may be specified.
995 Format: <port>,<port>....
996
Alan Cox200803d2005-06-28 20:45:18 -0700997 irqfixup [HW]
998 When an interrupt is not handled search all handlers
999 for it. Intended to get systems with badly broken
1000 firmware running.
1001
1002 irqpoll [HW]
1003 When an interrupt is not handled search all handlers
1004 for it. Also check all handlers each timer
1005 interrupt. Intended to get systems with badly broken
1006 firmware running.
1007
Linus Torvalds1da177e2005-04-16 15:20:36 -07001008 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001009 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001010
1011 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -08001012 Format:
1013 <cpu number>,...,<cpu number>
1014 or
Li Zefanb225d442008-11-06 12:53:39 -08001015 <cpu number>-<cpu number>
1016 (must be a positive range in ascending order)
Derek Fults22f2e282006-12-06 20:37:11 -08001017 or a mixture
1018 <cpu number>,...,<cpu number>-<cpu number>
Li Zefanb225d442008-11-06 12:53:39 -08001019
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020 This option can be used to specify one or more CPUs
1021 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001022 algorithms. You can move a process onto or off an
1023 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001024 <cpu number> begins at 0 and the maximum value is
1025 "number of CPUs in system - 1".
1026
1027 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001028 alternative -- manually setting the CPU mask of all
1029 tasks in the system -- can cause problems and
1030 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001031
Randy Dunlapa9913042005-10-23 12:57:11 -07001032 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033
1034 js= [HW,JOY] Analog joystick
1035 See Documentation/input/joystick.txt.
1036
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001037 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001038 specifies the amount of memory usable by the kernel
1039 for non-movable allocations. The requested amount is
1040 spread evenly throughout all nodes in the system. The
1041 remaining memory in each node is used for Movable
1042 pages. In the event, a node is too small to have both
1043 kernelcore and Movable pages, kernelcore pages will
1044 take priority and other nodes will have a larger number
1045 of kernelcore pages. The Movable zone is used for the
1046 allocation of pages that may be reclaimed or moved
1047 by the page migration subsystem. This means that
1048 HugeTLB pages may not be allocated from this zone.
1049 Note that allocations like PTEs-from-HighMem still
1050 use the HighMem zone if it exists, and the Normal
1051 zone if it does not.
1052
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001053 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
Mel Gorman7e63efe2007-07-17 04:03:15 -07001054 is similar to kernelcore except it specifies the
1055 amount of memory used for migratable allocations.
1056 If both kernelcore and movablecore is specified,
1057 then kernelcore will be at *least* the specified
1058 value but may be more. If movablecore on its own
1059 is specified, the administrator must be careful
1060 that the amount of memory usable for all allocations
1061 is not too small.
1062
Linus Torvalds1da177e2005-04-16 15:20:36 -07001063 keepinitrd [HW,ARM]
1064
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001065 kstack=N [X86-32,X86-64] Print N words from the kernel stack
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066 in oops dumps.
1067
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001068 kgdboc= [HW] kgdb over consoles.
1069 Requires a tty driver that supports console polling.
1070 (only serial suported for now)
1071 Format: <serial_device>[,baud]
1072
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001073 kmac= [MIPS] korina ethernet MAC address.
1074 Configure the RouterBoard 532 series on-chip
1075 Ethernet adapter MAC address.
1076
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077 l2cr= [PPC]
1078
Robert Brosea78bfbf2008-03-29 07:20:23 +11001079 l3cr= [PPC]
1080
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001081 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001082 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001084 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer
1085 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001086
FD Camifcb71f62008-01-06 19:08:56 +01001087 libata.dma= [LIBATA] DMA control
1088 libata.dma=0 Disable all PATA and SATA DMA
1089 libata.dma=1 PATA and SATA Disk DMA only
1090 libata.dma=2 ATAPI (CDROM) DMA only
1091 libata.dma=4 Compact Flash DMA only
1092 Combinations also work, so libata.dma=3 enables DMA
1093 for disks and CDROMs, but not CFs.
1094
Dave Jones78e70c22007-09-27 11:50:13 -04001095 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1096 when set.
1097 Format: <int>
1098
Tejun Heo33267322008-02-13 09:15:09 +09001099 libata.force= [LIBATA] Force configurations. The format is comma
1100 separated list of "[ID:]VAL" where ID is
1101 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1102 matching port, link or device. Basically, it matches
1103 the ATA ID string printed on console by libata. If
1104 the whole ID part is omitted, the last PORT and DEVICE
1105 values are used. If ID hasn't been specified yet, the
1106 configuration applies to all ports, links and devices.
1107
1108 If only DEVICE is omitted, the parameter applies to
1109 the port and all links and devices behind it. DEVICE
1110 number of 0 either selects the first device or the
1111 first fan-out link behind PMP device. It does not
1112 select the host link. DEVICE number of 15 selects the
1113 host link and device attached to it.
1114
1115 The VAL specifies the configuration to force. As long
1116 as there's no ambiguity shortcut notation is allowed.
1117 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1118 The following configurations can be forced.
1119
1120 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1121 Any ID with matching PORT is used.
1122
1123 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1124
1125 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1126 udma[/][16,25,33,44,66,100,133] notation is also
1127 allowed.
1128
1129 * [no]ncq: Turn on or off NCQ.
1130
Tejun Heo05944bd2008-08-13 20:19:09 +09001131 * nohrst, nosrst, norst: suppress hard, soft
1132 and both resets.
1133
Tejun Heo33267322008-02-13 09:15:09 +09001134 If there are multiple matching configurations changing
1135 the same attribute, the last one is used.
1136
Randy Dunlap7c4be252009-01-06 14:42:44 -08001137 lmb=debug [KNL] Enable lmb debug messages.
1138
Linus Torvalds1da177e2005-04-16 15:20:36 -07001139 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001140 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001141
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001142 lockd.nlm_grace_period=P [NFS] Assign grace period.
1143 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001144
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001145 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1146 Format: <integer>
1147
1148 lockd.nlm_timeout=T [NFS] Assign timeout value.
1149 Format: <integer>
1150
1151 lockd.nlm_udpport=M [NFS] Assign UDP port.
1152 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001153
1154 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1155 Format: <irq>
1156
1157 loglevel= All Kernel Messages with a loglevel smaller than the
1158 console loglevel will be printed to the console. It can
1159 also be changed with klogd or other programs. The
1160 loglevels are defined as follows:
1161
1162 0 (KERN_EMERG) system is unusable
1163 1 (KERN_ALERT) action must be taken immediately
1164 2 (KERN_CRIT) critical conditions
1165 3 (KERN_ERR) error conditions
1166 4 (KERN_WARNING) warning conditions
1167 5 (KERN_NOTICE) normal but significant condition
1168 6 (KERN_INFO) informational
1169 7 (KERN_DEBUG) debug-level messages
1170
1171 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001172 Format: { n | nk | nM }
1173 n must be a power of two. The default size
1174 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001175
Randy Dunlapaccaa242007-10-16 01:29:37 -07001176 logo.nologo [FB] Disables display of the built-in Linux logo.
1177 This may be used to provide more screen space for
1178 kernel log messages and is useful when debugging
1179 kernel boot problems.
1180
Linus Torvalds1da177e2005-04-16 15:20:36 -07001181 lp=0 [LP] Specify parallel ports to use, e.g,
1182 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1183 lp=reset first parallel port). 'lp=0' disables the
1184 lp=auto printer driver. 'lp=reset' (which can be
1185 specified in addition to the ports) causes
1186 attached printers to be reset. Using
1187 lp=port1,port2,... specifies the parallel ports
1188 to associate lp devices with, starting with
1189 lp0. A port specification may be 'none' to skip
1190 that lp device, or a parport name such as
1191 'parport0'. Specifying 'lp=auto' instead of a
1192 port specification list means that device IDs
1193 from each port should be examined, to see if
1194 an IEEE 1284-compliant printer is attached; if
1195 so, the driver will manage that printer.
1196 See also header of drivers/char/lp.c.
1197
1198 lpj=n [KNL]
1199 Sets loops_per_jiffy to given constant, thus avoiding
1200 time-consuming boot-time autodetection (up to 250 ms per
1201 CPU). 0 enables autodetection (default). To determine
1202 the correct value for your kernel, boot with normal
1203 autodetection and see what value is printed. Note that
1204 on SMP systems the preset will be applied to all CPUs,
1205 which is likely to cause problems if your CPUs need
1206 significantly divergent settings. An incorrect value
1207 will cause delays in the kernel to be wrong, leading to
1208 unpredictable I/O errors and other breakage. Although
1209 unlikely, in the extreme case this might damage your
1210 hardware.
1211
1212 ltpc= [NET]
1213 Format: <io>,<irq>,<dma>
1214
Randy Dunlapa9913042005-10-23 12:57:11 -07001215 mac5380= [HW,SCSI] Format:
1216 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001217
Randy Dunlapa9913042005-10-23 12:57:11 -07001218 machvec= [IA64] Force the use of a particular machine-vector
1219 (machvec) in a generic kernel.
1220 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001221
Randy Dunlapa9913042005-10-23 12:57:11 -07001222 max_loop= [LOOP] Maximum number of loopback devices that can
Linus Torvalds1da177e2005-04-16 15:20:36 -07001223 be mounted
1224 Format: <1-256>
1225
1226 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001227 should make use of. maxcpus=n : n >= 0 limits the
1228 kernel to using 'n' processors. n=0 is a special case,
1229 it is equivalent to "nosmp", which also disables
1230 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001231
Randy Dunlap1c207f92008-11-19 15:36:16 -08001232 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1233 or equal to this physical address is ignored.
Bob Picco2b2c3752005-06-29 18:00:00 -07001234
Randy Dunlapa9913042005-10-23 12:57:11 -07001235 max_luns= [SCSI] Maximum number of LUNs to probe.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001236 Should be between 1 and 2^32-1.
1237
1238 max_report_luns=
Randy Dunlapa9913042005-10-23 12:57:11 -07001239 [SCSI] Maximum number of LUNs received.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001240 Should be between 1 and 16384.
1241
Linus Torvalds1da177e2005-04-16 15:20:36 -07001242 mcatest= [IA-64]
1243
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001244 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001245
Uwe Hermann71cced62008-10-20 09:32:21 -07001246 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02001247
Linus Torvalds1da177e2005-04-16 15:20:36 -07001248 md= [HW] RAID subsystems devices and level
1249 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001250
Linus Torvalds1da177e2005-04-16 15:20:36 -07001251 mdacon= [MDA]
1252 Format: <first>,<last>
1253 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001254
Linus Torvalds1da177e2005-04-16 15:20:36 -07001255 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1256 Amount of memory to be used when the kernel is not able
1257 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001258 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001259 address space collisions. Without memmap= PCI devices
1260 could be placed at addresses belonging to unused RAM.
1261
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001262 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001263 memory.
1264
Paul Mundt6902aa82008-09-21 17:14:42 +09001265 memchunk=nn[KMG]
1266 [KNL,SH] Allow user to override the default size for
1267 per-device physically contiguous DMA buffers.
1268
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001269 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001270 E820 memory map, as specified by the user.
1271 Such memmap=exactmap lines can be constructed based on
1272 BIOS output or other requirements. See the memmap=nn@ss
1273 option description.
1274
1275 memmap=nn[KMG]@ss[KMG]
1276 [KNL] Force usage of a specific region of memory
1277 Region of memory to be used, from ss to ss+nn.
1278
1279 memmap=nn[KMG]#ss[KMG]
1280 [KNL,ACPI] Mark specific memory as ACPI data.
1281 Region of memory to be used, from ss to ss+nn.
1282
1283 memmap=nn[KMG]$ss[KMG]
1284 [KNL,ACPI] Mark specific memory as reserved.
1285 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001286 Example: Exclude memory from 0x18690000-0x1869ffff
1287 memmap=64K$0x18690000
1288 or
1289 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001290
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07001291 memory_corruption_check=0/1 [X86]
1292 Some BIOSes seem to corrupt the first 64k of
1293 memory when doing things like suspend/resume.
1294 Setting this option will scan the memory
1295 looking for corruption. Enabling this will
1296 both detect corruption and prevent the kernel
1297 from using the memory being corrupted.
1298 However, its intended as a diagnostic tool; if
1299 repeatable BIOS-originated corruption always
1300 affects the same memory, you can use memmap=
1301 to prevent the kernel from using that memory.
1302
1303 memory_corruption_check_size=size [X86]
1304 By default it checks for corruption in the low
1305 64k, making this memory unavailable for normal
1306 use. Use this parameter to scan for
1307 corruption in more or less memory.
1308
1309 memory_corruption_check_period=seconds [X86]
1310 By default it checks for corruption every 60
1311 seconds. Use this parameter to check at some
1312 other rate. 0 disables periodic checking.
1313
Yinghai Lucaadbdc2008-07-15 00:03:44 -07001314 memtest= [KNL,X86] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07001315 Format: <integer>
1316 range: 0,4 : pattern number
1317 default : 0 <disable>
1318
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319 meye.*= [HW] Set MotionEye Camera parameters
1320 See Documentation/video4linux/meye.txt.
1321
Andres Salomon8f368812007-10-12 23:04:06 +02001322 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1323 Multi-Function General Purpose Timers on AMD Geode
1324 platforms.
1325
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001326 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1327 the BIOS has incorrectly applied a workaround. TinyBIOS
1328 version 0.98 is known to be affected, 0.99 fixes the
1329 problem by letting the user disable the workaround.
1330
Linus Torvalds1da177e2005-04-16 15:20:36 -07001331 mga= [HW,DRM]
1332
Randy Dunlap1c207f92008-11-19 15:36:16 -08001333 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1334 physical address is ignored.
1335
Mel Gorman6b74ab92008-07-23 21:26:49 -07001336 mminit_loglevel=
1337 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1338 parameter allows control of the logging verbosity for
1339 the additional memory initialisation checks. A value
1340 of 0 disables mminit logging and a level of 4 will
1341 log everything. Information is printed at KERN_DEBUG
1342 so loglevel=8 may also need to be specified.
1343
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344 mousedev.tap_time=
1345 [MOUSE] Maximum time between finger touching and
1346 leaving touchpad surface for touch to be considered
1347 a tap and be reported as a left button click (for
1348 touchpads working in absolute mode only).
1349 Format: <msecs>
1350 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1351 reporting absolute coordinates, such as tablets
1352 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1353 reporting absolute coordinates, such as tablets
1354
1355 mpu401= [HW,OSS]
1356 Format: <io>,<irq>
1357
1358 MTD_Partition= [MTD]
1359 Format: <name>,<region-number>,<size>,<offset>
1360
Randy Dunlapa9913042005-10-23 12:57:11 -07001361 MTD_Region= [MTD] Format:
1362 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001363
1364 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001365 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001366
Ben Dooks9db829f2008-07-03 11:24:29 +01001367 mtdset= [ARM]
1368 ARM/S3C2412 JIVE boot control
1369
1370 See arch/arm/mach-s3c2412/mach-jive.c
1371
Linus Torvalds1da177e2005-04-16 15:20:36 -07001372 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001373 [HW] Make the MicroTouch USB driver use raw coordinates
1374 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001375
1376 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1377
1378 NCR_D700= [HW,SCSI]
1379 See header of drivers/scsi/NCR_D700.c.
1380
1381 ncr5380= [HW,SCSI]
1382
1383 ncr53c400= [HW,SCSI]
1384
1385 ncr53c400a= [HW,SCSI]
1386
1387 ncr53c406a= [HW,SCSI]
1388
1389 ncr53c8xx= [HW,SCSI]
1390
1391 netdev= [NET] Network devices parameters
1392 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1393 Note that mem_start is often overloaded to mean
1394 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001395 This usage is only documented in each driver source
1396 file if at all.
1397
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07001398 nf_conntrack.acct=
1399 [NETFILTER] Enable connection tracking flow accounting
1400 0 to disable accounting
1401 1 to enable accounting
1402 Default value depends on CONFIG_NF_CT_ACCT that is
1403 going to be removed in 2.6.29.
1404
Linus Torvalds1da177e2005-04-16 15:20:36 -07001405 nfsaddrs= [NFS]
J. Bruce Fields6ded55d2008-04-07 15:59:03 -04001406 See Documentation/filesystems/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407
1408 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fields6ded55d2008-04-07 15:59:03 -04001409 See Documentation/filesystems/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001410
Trond Myklebusta72b4422006-01-03 09:55:41 +01001411 nfs.callback_tcpport=
1412 [NFS] set the TCP port on which the NFSv4 callback
1413 channel should listen.
1414
Trond Myklebust58df0952006-01-03 09:55:57 +01001415 nfs.idmap_cache_timeout=
1416 [NFS] set the maximum lifetime for idmapper cache
1417 entries.
1418
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001419 nfs.enable_ino64=
1420 [NFS] enable 64-bit inode numbers.
1421 If zero, the NFS client will fake up a 32-bit inode
1422 number for the readdir() and stat() syscalls instead
1423 of returning the full 64-bit number.
1424 The default is to return 64-bit inode numbers.
1425
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001426 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1427 when a NMI is triggered.
1428 Format: [state][,regs][,debounce][,die]
1429
Cyrill Gorcunov5b9a0e12008-11-01 18:06:51 +03001430 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1431 Format: [panic,][num]
1432 Valid num: 0,1,2
1433 0 - turn nmi_watchdog off
1434 1 - use the IO-APIC timer for the NMI watchdog
1435 2 - use the local APIC for the NMI watchdog using
1436 a performance counter. Note: This will use one performance
1437 counter and the local APIC's performance vector.
1438 When panic is specified panic when an NMI watchdog timeout occurs.
1439 This is useful when you use a panic=... timeout and need the box
1440 quickly up again.
1441 Instead of 1 and 2 it is possible to use the following
1442 symbolic names: lapic and ioapic
1443 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
Linus Torvalds1da177e2005-04-16 15:20:36 -07001444
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001445 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001446 emulation library even if a 387 maths coprocessor
1447 is present.
1448
Christoph Lameterc1aee212007-05-31 00:40:47 -07001449 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1450 caches in the slab allocator. Saves per-node memory,
1451 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001452
Randy Dunlapa9913042005-10-23 12:57:11 -07001453 noalign [KNL,ARM]
1454
Linus Torvalds1da177e2005-04-16 15:20:36 -07001455 noapic [SMP,APIC] Tells the kernel to not make use of any
1456 IOAPICs that may be present in the system.
1457
Linus Torvalds1da177e2005-04-16 15:20:36 -07001458 nobats [PPC] Do not use BATs for mapping kernel lowmem
1459 on "Classic" PPC cores.
1460
1461 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001462
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001463 nodelayacct [KNL] Disable per-task delay accounting
1464
Linus Torvalds1da177e2005-04-16 15:20:36 -07001465 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1466
Paul Mundt6902aa82008-09-21 17:14:42 +09001467 nodsp [SH] Disable hardware DSP at boot time.
1468
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001469 noefi [X86-32,X86-64] Disable EFI runtime services support.
1470
Linus Torvalds1da177e2005-04-16 15:20:36 -07001471 noexec [IA-64]
1472
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001473 noexec [X86-32,X86-64]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001474 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001475 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02001476 noexec=off: disable non-executable mappings
1477
1478 noexec32 [X86-64]
1479 This affects only 32-bit executables.
1480 noexec32=on: enable non-executable mappings (default)
1481 read doesn't imply executable mappings
1482 noexec32=off: disable non-executable mappings
1483 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07001484
Paul Mundt6902aa82008-09-21 17:14:42 +09001485 nofpu [SH] Disable hardware FPU at boot time.
1486
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001487 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001488 register save and restore. The kernel will only save
1489 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001490
Andi Kleen191679f2008-01-30 13:33:21 +01001491 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1492
Paul Mundt6902aa82008-09-21 17:14:42 +09001493 nohlt [BUGS=ARM,SH]
Randy Dunlapa9913042005-10-23 12:57:11 -07001494
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001495 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001496 instruction doesn't work correctly and not to
1497 use it.
1498
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06001499 no_file_caps Tells the kernel not to honor file capabilities. The
1500 only way then for a file to be executed with privilege
1501 is to be setuid root or executed by root.
1502
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503 nohalt [IA-64] Tells the kernel not to use the power saving
1504 function PAL_HALT_LIGHT when idle. This increases
1505 power-consumption. On the positive side, it reduces
1506 interrupt wake-up latency, which may improve performance
1507 in certain environments such as networked servers or
1508 real-time systems.
1509
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001510 nohz= [KNL] Boottime enable/disable dynamic ticks
1511 Valid arguments: on, off
1512 Default: on
1513
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001514 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515 disable unhandled interrupt sources.
1516
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001517 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001518 broken timer IRQ sources.
1519
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520 noisapnp [ISAPNP] Disables ISA PnP code.
1521
1522 noinitrd [RAM] Tells the kernel not to load any configured
1523 initial RAM disk.
1524
1525 nointroute [IA-64]
1526
Tony Luck0aa366f2007-07-20 11:22:30 -07001527 nojitter [IA64] Disables jitter checking for ITC timers.
1528
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001529 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001530
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001531 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001532
Suresh Siddha6e1cb382008-07-10 11:16:58 -07001533 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1534
Suresh Siddhaaf9d1382008-07-11 13:11:57 -07001535 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1536 default x2apic cluster mode on platforms
1537 supporting x2apic.
1538
Linus Torvalds1da177e2005-04-16 15:20:36 -07001539 noltlbs [PPC] Do not use large page/tlb entries for kernel
1540 lowmem mapping on PPC40x.
1541
Horms312f1f02006-02-22 09:57:55 +09001542 nomca [IA-64] Disable machine check abort handling
1543
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001544 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001545
Andres Salomon83d73842007-10-12 23:04:06 +02001546 nomfgpt [X86-32] Disable Multi-Function General Purpose
1547 Timer usage (for AMD Geode machines).
1548
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001549 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001550
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001551 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001552 with UP alternatives
1553
Linus Torvalds1da177e2005-04-16 15:20:36 -07001554 noresidual [PPC] Don't use residual data on PReP machines.
1555
Randy Dunlapa9913042005-10-23 12:57:11 -07001556 noresume [SWSUSP] Disables resume and restores original swap
1557 space.
1558
Linus Torvalds1da177e2005-04-16 15:20:36 -07001559 no-scroll [VGA] Disables scrollback.
1560 This is required for the Braillex ib80-piezo Braille
1561 reader made by F.H. Papenmeier (Germany).
1562
1563 nosbagart [IA-64]
1564
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001565 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001566
Len Brown61ec7562007-08-16 03:34:22 -04001567 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1568 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001569
Dave Jones97842212007-07-15 23:41:05 -07001570 nosoftlockup [KNL] Disable the soft-lockup detector.
1571
KAMEZAWA Hiroyukic0777192009-01-07 18:07:57 -08001572 noswapaccount [KNL] Disable accounting of swap in memory resource
1573 controller. (See Documentation/controllers/memory.txt)
1574
Linus Torvalds1da177e2005-04-16 15:20:36 -07001575 nosync [HW,M68K] Disables sync negotiation for all devices.
1576
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001577 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001578
1579 nousb [USB] Disable the USB subsystem
1580
1581 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001582
Fenghua Yua6c75b862008-03-14 13:57:08 -07001583 nptcg= [IA64] Override max number of concurrent global TLB
1584 purges which is reported from either PAL_VM_SUMMARY or
1585 SAL PALO.
1586
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001587 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1588 one of ['zone', 'node', 'default'] can be specified
1589 This can be set from sysctl after boot.
1590 See Documentation/sysctl/vm.txt for details.
1591
Dave Jonesa61c2d72006-01-07 23:18:19 +00001592 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1593
Randy Dunlap7c4be252009-01-06 14:42:44 -08001594 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1595 See Documentation/debugging-via-ohci1394.txt for more
1596 info.
1597
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07001598 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1599 Rather than timing out after 20 ms if an EC
1600 command is not properly ACKed, override the length
1601 of the timeout. We have interrupts disabled while
1602 waiting for the ACK, so if this is set too high
1603 interrupts *may* be lost!
1604
Linus Torvalds1da177e2005-04-16 15:20:36 -07001605 opl3= [HW,OSS]
1606 Format: <io>
1607
Linus Torvalds1da177e2005-04-16 15:20:36 -07001608 oprofile.timer= [HW]
1609 Use timer interrupt instead of performance counters
1610
Linus Torvalds1da177e2005-04-16 15:20:36 -07001611 osst= [HW,SCSI] SCSI Tape Driver
1612 Format: <buffer_size>,<write_threshold>
1613 See also Documentation/scsi/st.txt.
1614
1615 panic= [KNL] Kernel behaviour on panic
1616 Format: <timeout>
1617
1618 parkbd.port= [HW] Parallel port number the keyboard adapter is
1619 connected to, default is 0.
1620 Format: <parport#>
1621 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1622 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001623 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001624
Randy Dunlapa9913042005-10-23 12:57:11 -07001625 parport= [HW,PPT] Specify parallel ports. 0 disables.
1626 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1627 Use 'auto' to force the driver to use any
1628 IRQ/DMA settings detected (the default is to
1629 ignore detected IRQ/DMA settings because of
1630 possible conflicts). You can specify the base
1631 address, IRQ, and DMA settings; IRQ and DMA
1632 should be numbers, or 'auto' (for using detected
1633 settings on that particular port), or 'nofifo'
1634 (to avoid using a FIFO even if it is detected).
1635 Parallel ports are assigned in the order they
1636 are specified on the command line, starting
1637 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001638
Randy Dunlapa9913042005-10-23 12:57:11 -07001639 parport_init_mode= [HW,PPT]
1640 Configure VIA parallel port to operate in
1641 a specific mode. This is necessary on Pegasos
1642 computer where firmware has no options for setting
1643 up parallel port mode and sets it to spp.
1644 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 Format: [spp|ps2|epp|ecp|ecpepp]
1646
Randy Dunlapa9913042005-10-23 12:57:11 -07001647 pas2= [HW,OSS] Format:
1648 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1649
Linus Torvalds1da177e2005-04-16 15:20:36 -07001650 pas16= [HW,SCSI]
1651 See header of drivers/scsi/pas16.c.
1652
Andrew Mortondd287792006-03-23 03:00:57 -08001653 pause_on_oops=
1654 Halt all CPUs after the first oops has been printed for
1655 the specified number of seconds. This is to be used if
1656 your oopses keep scrolling off the screen.
1657
Linus Torvalds1da177e2005-04-16 15:20:36 -07001658 pcbit= [HW,ISDN]
1659
1660 pcd. [PARIDE]
1661 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001662 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001663
Randy Dunlapa9913042005-10-23 12:57:11 -07001664 pci=option[,option...] [PCI] various PCI subsystem options:
Andi Kleenc0115602008-08-22 09:53:39 +02001665 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001666 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001667 the hardware directly. Use this if your machine
1668 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001669 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001670 hardware access methods are allowed. Use this
1671 if you experience crashes upon bootup and you
1672 suspect they are caused by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02001673 conf1 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001674 Mechanism 1.
Andi Kleenc0115602008-08-22 09:53:39 +02001675 conf2 [X86] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001676 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001677 noaer [PCIE] If the PCIEAER kernel config parameter is
1678 enabled, this kernel boot option can be used to
1679 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001680 nodomains [PCI] Disable support for multiple PCI
1681 root domains (aka PCI segments, in ACPI-speak).
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001682 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001683 Configuration
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001684 nomsi [MSI] If the PCI_MSI kernel config parameter is
1685 enabled, this kernel boot option can be used to
1686 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02001687 noioapicquirk [APIC] Disable all boot interrupt quirks.
1688 Safety option to keep boot IRQs enabled. This
1689 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02001690 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1691 primary IO-APIC for bridges that cannot disable
1692 boot IRQs. This fixes a source of spurious IRQs
1693 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02001694 noioapicreroute [APIC] Disable workaround that uses the
1695 boot IRQ equivalent of an IRQ that connects to
1696 a chipset where boot IRQs cannot be disabled.
1697 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001698 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001699 routing table. These calls are known to be buggy
1700 on several machines and they hang the machine
1701 when used, but on other computers it's the only
1702 way to get the interrupt routing table. Try
1703 this option if the kernel is unable to allocate
1704 IRQs or discover secondary PCI buses on your
1705 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02001706 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001707 Use with caution as certain devices share
1708 address decoders between ROMs and other
1709 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02001710 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07001711 expansion ROMs that do not already have
1712 BIOS assigned address ranges.
Andi Kleenc0115602008-08-22 09:53:39 +02001713 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001714 assigned automatically to PCI devices. You can
1715 make the kernel exclude IRQs of your ISA cards
1716 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02001717 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001718 of the PIRQ table (normally generated
1719 by the BIOS) if it is outside the
1720 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02001721 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001722 useful if the kernel is unable to find your
1723 secondary buses and you want to tell it
1724 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02001725 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001726 numbers ourselves, overriding
1727 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02001728 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001729 in the BIOS $PIR table. This is needed on
1730 some systems with broken BIOSes, notably
1731 some HP Pavilion N5400 and Omnibook XE3
1732 notebooks. This will have no effect if ACPI
1733 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02001734 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001735 or for PCI scanning.
Andi Kleenc0115602008-08-22 09:53:39 +02001736 use_crs [X86] Use _CRS for PCI resource
Gary Hade62f420f2007-10-03 15:56:51 -07001737 allocation.
Randy Dunlapa9913042005-10-23 12:57:11 -07001738 routeirq Do IRQ routing for all PCI devices.
1739 This is normally done in pci_enable_device(),
1740 so this option is a temporary workaround
1741 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07001742 skip_isa_align [X86] do not align io start addr, so can
1743 handle more pci cards
Randy Dunlapa9913042005-10-23 12:57:11 -07001744 firmware [ARM] Do not re-enumerate the bus but instead
1745 just use the configuration from the
1746 bootloader. This is currently used on
1747 IXP2000 systems where the bus has to be
1748 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001749 noearly [X86] Don't do any early type 1 scanning.
1750 This might help on some broken boards which
1751 machine check when some devices' config space
1752 is read. But various workarounds are disabled
1753 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001754 bfsort Sort PCI devices into breadth-first order.
1755 This sorting is done to get a device
1756 order compatible with older (<= 2.4) kernels.
1757 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001758 cbiosize=nn[KMG] The fixed amount of bus space which is
1759 reserved for the CardBus bridge's IO window.
1760 The default value is 256 bytes.
1761 cbmemsize=nn[KMG] The fixed amount of bus space which is
1762 reserved for the CardBus bridge's memory
1763 window. The default value is 64 megabytes.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001764
Chuck Ebberte5665a42008-09-24 20:40:34 -04001765 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1766 Management.
1767 off Disable ASPM.
1768 force Enable ASPM even on devices that claim not to support it.
1769 WARNING: Forcing ASPM on may cause system lockups.
1770
Linus Torvalds1da177e2005-04-16 15:20:36 -07001771 pcmv= [HW,PCMCIA] BadgePAD 4
1772
1773 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001774 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001775
1776 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1777 boot time.
1778 Format: { 0 | 1 }
1779 See arch/parisc/kernel/pdc_chassis.c
1780
1781 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001782 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001783
1784 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001785 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001786
1787 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07001788 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001789
1790 plip= [PPT,NET] Parallel port network link
1791 Format: { parport<nr> | timid | 0 }
1792 See also Documentation/parport.txt.
1793
Thomas Gleixnerde32a242008-07-12 05:33:30 +02001794 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1795 Override pmtimer IOPort with a hex value.
1796 e.g. pmtmr=0x508
1797
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06001798 pnp.debug [PNP]
1799 Enable PNP debug messages. This depends on the
1800 CONFIG_PNP_DEBUG_MESSAGES option.
1801
Linus Torvalds1da177e2005-04-16 15:20:36 -07001802 pnpacpi= [ACPI]
1803 { off }
1804
1805 pnpbios= [ISAPNP]
1806 { on | off | curr | res | no-curr | no-res }
1807
1808 pnp_reserve_irq=
1809 [ISAPNP] Exclude IRQs for the autoconfiguration
1810
1811 pnp_reserve_dma=
1812 [ISAPNP] Exclude DMAs for the autoconfiguration
1813
1814 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07001815 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001816
1817 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07001818 [ISAPNP] Exclude memory regions for the
1819 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001820 Ranges are in pairs (memory base and size).
1821
Randy Dunlapecb08d82009-01-06 14:42:44 -08001822 dynamic_printk Enables pr_debug()/dev_dbg() calls if
1823 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
1824 These can also be switched on/off via
1825 <debugfs>/dynamic_printk/modules
Jason Baron346e15b2008-08-12 16:46:19 -04001826
Ingo Molnar45807a12007-07-15 23:40:10 -07001827 print-fatal-signals=
1828 [KNL] debug: print fatal signals
1829 print-fatal-signals=1: print segfault info to
1830 the kernel console.
1831 default: off.
1832
Randy Dunlape84845c2007-07-15 23:40:25 -07001833 printk.time= Show timing data prefixed to each printk message line
1834 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1835
Linus Torvalds1da177e2005-04-16 15:20:36 -07001836 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07001837 Format: [schedule,]<number>
1838 Param: "schedule" - profile schedule points.
1839 Param: <number> - step/bucket size as a power of 2 for
1840 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02001841 Param: "sleep" - profile D-state sleeping (millisecs).
1842 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02001843 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001844
Randy Dunlapa9913042005-10-23 12:57:11 -07001845 processor.max_cstate= [HW,ACPI]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001846 Limit processor to maximum C-state
1847 max_cstate=9 overrides any DMI blacklist limit.
1848
Len Brown41c0d862005-12-28 12:43:51 -05001849 processor.nocst [HW,ACPI]
1850 Ignore the _CST method to determine C-states,
1851 instead using the legacy FADT method
1852
Linus Torvalds1da177e2005-04-16 15:20:36 -07001853 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1854 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001855 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001856
Randy Dunlapa9913042005-10-23 12:57:11 -07001857 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1858 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001859 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1860 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07001861 psmouse.resetafter= [HW,MOUSE]
1862 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07001863 (0 = never).
1864 psmouse.resolution=
1865 [HW,MOUSE] Set desired mouse resolution, in dpi.
1866 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07001867 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868 0 = disabled, 1 = enabled (default).
1869
1870 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
Randy Dunlapa9913042005-10-23 12:57:11 -07001871 Format:
1872 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001873
1874 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001875 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001876
Kay Sieversdc8c8582007-08-15 12:25:38 +02001877 pty.legacy_count=
1878 [KNL] Number of legacy pty's. Overwrites compiled-in
1879 default number.
1880
Randy Dunlap7d2c5022006-09-29 02:01:02 -07001881 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07001882
Linus Torvalds1da177e2005-04-16 15:20:36 -07001883 r128= [HW,DRM]
1884
1885 raid= [HW,RAID]
1886 See Documentation/md.txt.
1887
Randy Dunlapa9913042005-10-23 12:57:11 -07001888 ramdisk_blocksize= [RAM]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001889 See Documentation/blockdev/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001890
Linus Torvalds1da177e2005-04-16 15:20:36 -07001891 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001892 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001893
Robert P. J. Day24aaef82008-02-03 15:20:26 +02001894 rcupdate.blimit= [KNL,BOOT]
1895 Set maximum number of finished RCU callbacks to process
1896 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08001897
Robert P. J. Day24aaef82008-02-03 15:20:26 +02001898 rcupdate.qhimark= [KNL,BOOT]
1899 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08001900 RCU callbacks over which batch limiting is disabled.
1901
Robert P. J. Day24aaef82008-02-03 15:20:26 +02001902 rcupdate.qlowmark= [KNL,BOOT]
1903 Set threshold of queued RCU callbacks below which
1904 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08001905
Olof Johanssonffdfc402005-09-06 15:17:19 -07001906 rdinit= [KNL]
1907 Format: <full_path>
1908 Run specified binary instead of /init from the ramdisk,
1909 used for early userspace startup. See initrd.
1910
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001911 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001912 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Randy Dunlapecb08d82009-01-06 14:42:44 -08001913 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07001914
Paul Jackson46b6d942008-07-04 10:00:09 -07001915 relax_domain_level=
1916 [KNL, SMP] Set scheduler's default relax_domain_level.
1917 See Documentation/cpusets.txt.
1918
Linus Torvalds1da177e2005-04-16 15:20:36 -07001919 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1920
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001921 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07001922 Format: nn[KMG]
1923 Reserves a hole at the top of the kernel virtual
1924 address space.
1925
Vivek Goyal7e962872006-09-27 01:50:44 -07001926 reset_devices [KNL] Force drivers to reset the underlying device
1927 during initialization.
1928
Randy Dunlapa9913042005-10-23 12:57:11 -07001929 resume= [SWSUSP]
1930 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07001931
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08001932 resume_offset= [SWSUSP]
1933 Specify the offset from the beginning of the partition
1934 given by "resume=" at which the swap header is located,
1935 in <PAGE_SIZE> units (needed only for swap files).
1936 See Documentation/power/swsusp-and-swap-files.txt
1937
Michael Neuling0a7b35c2007-02-10 01:44:33 -08001938 retain_initrd [RAM] Keep initrd memory after extraction
1939
Linus Torvalds1da177e2005-04-16 15:20:36 -07001940 rhash_entries= [KNL,NET]
1941 Set number of hash buckets for route cache
1942
1943 riscom8= [HW,SERIAL]
1944 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1945
1946 ro [KNL] Mount root device read-only on boot
1947
1948 root= [KNL] Root filesystem
1949
1950 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1951 mount the root filesystem
1952
1953 rootflags= [KNL] Set root filesystem mount option string
1954
1955 rootfstype= [KNL] Set root filesystem type
1956
Pierre Ossmancc1ed752007-07-15 23:40:35 -07001957 rootwait [KNL] Wait (indefinitely) for root device to show up.
1958 Useful for devices that are detected asynchronously
1959 (e.g. USB and MMC devices).
1960
James Morris20510f22007-10-16 23:31:32 -07001961 root_plug.vendor_id=
1962 [ROOTPLUG] Override the default vendor ID
1963
1964 root_plug.product_id=
1965 [ROOTPLUG] Override the default product ID
1966
1967 root_plug.debug=
1968 [ROOTPLUG] Enable debugging output
1969
Linus Torvalds1da177e2005-04-16 15:20:36 -07001970 rw [KNL] Mount root device read-write on boot
1971
1972 S [KNL] Run init in single mode
1973
1974 sa1100ir [NET]
1975 See drivers/net/irda/sa1100_ir.c.
1976
Linus Torvalds1da177e2005-04-16 15:20:36 -07001977 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07001978
Linus Torvalds1da177e2005-04-16 15:20:36 -07001979 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1980 Format: <io>[,<timeout>[,<isapnp>]]
1981
1982 scsi_debug_*= [SCSI]
1983 See drivers/scsi/scsi_debug.c.
1984
1985 scsi_default_dev_flags=
1986 [SCSI] SCSI default device flags
1987 Format: <integer>
1988
1989 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1990 Format: <vendor>:<model>:<flags>
1991 (flags are integer value)
1992
Randy Dunlap6af66322007-11-14 16:52:25 -08001993 scsi_logging_level= [SCSI] a bit mask of logging levels
1994 See drivers/scsi/scsi_logging.h for bits. Also
1995 settable via sysctl at dev.scsi.logging_level
1996 (/proc/sys/dev/scsi/logging_level).
1997 There is also a nice 'scsi_logging_level' script in the
1998 S390-tools package, available for download at
1999 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000
Matthew Wilcox3e082a92006-09-28 15:19:20 -06002001 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2002 discovered. async scans them in kernel threads,
2003 allowing boot to proceed. none ignores them, expecting
2004 user space to do the scan.
2005
Linus Torvalds1da177e2005-04-16 15:20:36 -07002006 selinux [SELINUX] Disable or enable SELinux at boot time.
2007 Format: { "0" | "1" }
2008 See security/selinux/Kconfig help text.
2009 0 -- disable.
2010 1 -- enable.
2011 Default value is set via kernel config option.
2012 If enabled at boot time, /selinux/disable can be used
2013 later to disable prior to initial policy load.
2014
James Morris4e5ab4c2006-06-09 00:33:33 -07002015 selinux_compat_net =
2016 [SELINUX] Set initial selinux_compat_net flag value.
Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03002017 Format: { "0" | "1" }
2018 0 -- use new secmark-based packet controls
2019 1 -- use legacy packet controls
2020 Default value is 0 (preferred).
2021 Value can be changed at runtime via
2022 /selinux/compat_net.
James Morris4e5ab4c2006-06-09 00:33:33 -07002023
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002024 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002025
Linus Torvalds1da177e2005-04-16 15:20:36 -07002026 shapers= [NET]
2027 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07002028
Yinghai Lub05f78f2008-08-22 01:32:50 -07002029 show_msr= [x86] show boot-time MSR settings
2030 Format: { <integer> }
2031 Show boot-time (BIOS-initialized) MSR settings.
2032 The parameter means the number of CPUs to show,
2033 for example 1 means boot CPU only.
2034
Linus Torvalds1da177e2005-04-16 15:20:36 -07002035 sim710= [SCSI,HW]
2036 See header of drivers/scsi/sim710.c.
2037
2038 simeth= [IA-64]
2039 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07002040
Linus Torvalds1da177e2005-04-16 15:20:36 -07002041 slram= [HW,MTD]
2042
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002043 slub_debug[=options[,slabs]] [MM, SLUB]
2044 Enabling slub_debug allows one to determine the
2045 culprit if slab objects become corrupted. Enabling
2046 slub_debug can create guard zones around objects and
2047 may poison objects when not in use. Also tracks the
2048 last alloc / free. For more information see
2049 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002050
2051 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002052 Determines the maximum allowed order for slabs.
2053 A high setting may cause OOMs due to memory
2054 fragmentation. For more information see
2055 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002056
2057 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002058 The minimum number of objects per slab. SLUB will
2059 increase the slab order up to slub_max_order to
2060 generate a sufficiently large slab able to contain
2061 the number of objects indicated. The higher the number
2062 of objects the smaller the overhead of tracking slabs
2063 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002064 For more information see Documentation/vm/slub.txt.
2065
2066 slub_min_order= [MM, SLUB]
2067 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002068 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002069 For more information see Documentation/vm/slub.txt.
2070
2071 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002072 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07002073 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07002074 allocs to different slabs. Debug options disable
2075 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07002076 For more information see Documentation/vm/slub.txt.
2077
Linus Torvalds1da177e2005-04-16 15:20:36 -07002078 smart2= [HW]
2079 Format: <io1>[,<io2>[,...,<io8>]]
2080
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002081 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002082 attempt to substitute SMP alternatives once at boot.
2083
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07002084 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2085 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2086 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2087 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2088 smsc-ircc2.ircc_irq= [HW] IRQ line
2089 smsc-ircc2.ircc_dma= [HW] DMA channel
2090 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2091 0: Toshiba Satellite 1800 (GP data pin select)
2092 1: Fast pin select (default)
2093 2: ATC IRMode
2094
Linus Torvalds1da177e2005-04-16 15:20:36 -07002095 snd-ad1816a= [HW,ALSA]
2096
2097 snd-ad1848= [HW,ALSA]
2098
2099 snd-ali5451= [HW,ALSA]
2100
2101 snd-als100= [HW,ALSA]
2102
2103 snd-als4000= [HW,ALSA]
2104
2105 snd-azt2320= [HW,ALSA]
2106
2107 snd-cmi8330= [HW,ALSA]
2108
2109 snd-cmipci= [HW,ALSA]
2110
2111 snd-cs4231= [HW,ALSA]
2112
2113 snd-cs4232= [HW,ALSA]
2114
2115 snd-cs4236= [HW,ALSA]
2116
2117 snd-cs4281= [HW,ALSA]
2118
2119 snd-cs46xx= [HW,ALSA]
2120
2121 snd-dt019x= [HW,ALSA]
2122
2123 snd-dummy= [HW,ALSA]
2124
2125 snd-emu10k1= [HW,ALSA]
2126
2127 snd-ens1370= [HW,ALSA]
2128
2129 snd-ens1371= [HW,ALSA]
2130
2131 snd-es968= [HW,ALSA]
2132
2133 snd-es1688= [HW,ALSA]
2134
2135 snd-es18xx= [HW,ALSA]
2136
2137 snd-es1938= [HW,ALSA]
2138
2139 snd-es1968= [HW,ALSA]
2140
2141 snd-fm801= [HW,ALSA]
2142
2143 snd-gusclassic= [HW,ALSA]
2144
2145 snd-gusextreme= [HW,ALSA]
2146
2147 snd-gusmax= [HW,ALSA]
2148
2149 snd-hdsp= [HW,ALSA]
2150
2151 snd-ice1712= [HW,ALSA]
2152
2153 snd-intel8x0= [HW,ALSA]
2154
2155 snd-interwave= [HW,ALSA]
2156
2157 snd-interwave-stb=
2158 [HW,ALSA]
2159
2160 snd-korg1212= [HW,ALSA]
2161
2162 snd-maestro3= [HW,ALSA]
2163
2164 snd-mpu401= [HW,ALSA]
2165
2166 snd-mtpav= [HW,ALSA]
2167
2168 snd-nm256= [HW,ALSA]
2169
2170 snd-opl3sa2= [HW,ALSA]
2171
2172 snd-opti92x-ad1848=
2173 [HW,ALSA]
2174
2175 snd-opti92x-cs4231=
2176 [HW,ALSA]
2177
2178 snd-opti93x= [HW,ALSA]
2179
2180 snd-pmac= [HW,ALSA]
2181
2182 snd-rme32= [HW,ALSA]
2183
2184 snd-rme96= [HW,ALSA]
2185
2186 snd-rme9652= [HW,ALSA]
2187
2188 snd-sb8= [HW,ALSA]
2189
2190 snd-sb16= [HW,ALSA]
2191
2192 snd-sbawe= [HW,ALSA]
2193
2194 snd-serial= [HW,ALSA]
2195
2196 snd-sgalaxy= [HW,ALSA]
2197
2198 snd-sonicvibes= [HW,ALSA]
2199
2200 snd-sun-amd7930=
2201 [HW,ALSA]
2202
2203 snd-sun-cs4231= [HW,ALSA]
2204
2205 snd-trident= [HW,ALSA]
2206
2207 snd-usb-audio= [HW,ALSA,USB]
2208
2209 snd-via82xx= [HW,ALSA]
2210
2211 snd-virmidi= [HW,ALSA]
2212
2213 snd-wavefront= [HW,ALSA]
2214
2215 snd-ymfpci= [HW,ALSA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002216
Ingo Molnar9c44bc02008-05-12 21:21:04 +02002217 softlockup_panic=
2218 [KNL] Should the soft-lockup detector generate panics.
2219
Linus Torvalds1da177e2005-04-16 15:20:36 -07002220 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2221 See Documentation/sonypi.txt
2222
2223 specialix= [HW,SERIAL] Specialix multi-serial port adapter
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002224 See Documentation/serial/specialix.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002225
2226 spia_io_base= [HW,MTD]
2227 spia_fio_base=
2228 spia_pedr=
2229 spia_peddr=
2230
2231 sscape= [HW,OSS]
2232 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
Randy Dunlapa9913042005-10-23 12:57:11 -07002233
Linus Torvalds1da177e2005-04-16 15:20:36 -07002234 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2235 See Documentation/scsi/st.txt.
2236
Steven Rostedtf38f1d22008-12-16 23:06:40 -05002237 stacktrace [FTRACE]
2238 Enabled the stack tracer on boot up.
2239
Linus Torvalds1da177e2005-04-16 15:20:36 -07002240 sti= [PARISC,HW]
2241 Format: <num>
2242 Set the STI (builtin display/keyboard on the HP-PARISC
2243 machines) console (graphic card) which should be used
2244 as the initial boot-console.
2245 See also comment in drivers/video/console/sticore.c.
2246
2247 sti_font= [HW]
2248 See comment in drivers/video/console/sticore.c.
2249
2250 stifb= [HW]
2251 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2252
Greg Banks42a7fc42007-03-06 01:42:23 -08002253 sunrpc.pool_mode=
2254 [NFS]
2255 Control how the NFS server code allocates CPUs to
2256 service thread pools. Depending on how many NICs
2257 you have and where their interrupts are bound, this
2258 option will affect which CPUs will do NFS serving.
2259 Note: this parameter cannot be changed while the
2260 NFS server is running.
2261
2262 auto the server chooses an appropriate mode
2263 automatically using heuristics
2264 global a single global pool contains all CPUs
2265 percpu one pool for each CPU
2266 pernode one pool for each NUMA node (equivalent
2267 to global on non-NUMA machines)
2268
Linus Torvalds1da177e2005-04-16 15:20:36 -07002269 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07002270
Linus Torvalds1da177e2005-04-16 15:20:36 -07002271 switches= [HW,M68k]
2272
2273 sym53c416= [HW,SCSI]
2274 See header of drivers/scsi/sym53c416.c.
2275
Ingo Molnar5d6f6472006-12-13 00:34:36 -08002276 sysrq_always_enabled
2277 [KNL]
2278 Ignore sysrq setting - this boot parameter will
2279 neutralize any effect of /proc/sys/kernel/sysrq.
2280 Useful for debugging.
2281
Linus Torvalds1da177e2005-04-16 15:20:36 -07002282 t128= [HW,SCSI]
2283 See header of drivers/scsi/t128.c.
2284
2285 tdfx= [HW,DRM]
2286
David Brownell77437fd2008-07-23 21:28:33 -07002287 test_suspend= [SUSPEND]
2288 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2289 standby suspend) as the system sleep state to briefly
2290 enter during system startup. The system is woken from
2291 this state using a wakeup-capable RTC alarm.
2292
Linus Torvalds1da177e2005-04-16 15:20:36 -07002293 thash_entries= [KNL,NET]
2294 Set number of hash buckets for TCP connection
2295
Len Brownf8707ec2007-08-12 00:12:54 -04002296 thermal.act= [HW,ACPI]
2297 -1: disable all active trip points in all thermal zones
2298 <degrees C>: override all lowest active trip points
2299
Len Brownc52a7412007-08-14 15:49:32 -04002300 thermal.crt= [HW,ACPI]
2301 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04002302 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04002303
Len Brownf5487142007-08-12 00:12:44 -04002304 thermal.nocrt= [HW,ACPI]
2305 Set to disable actions on ACPI thermal zone
2306 critical and hot trip points.
2307
Len Brown72b33ef2007-08-12 00:12:17 -04002308 thermal.off= [HW,ACPI]
2309 1: disable ACPI thermal control
2310
Len Browna70cdc52007-08-12 00:12:35 -04002311 thermal.psv= [HW,ACPI]
2312 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08002313 <degrees C>: override all passive trip points to this
2314 value
Len Browna70cdc52007-08-12 00:12:35 -04002315
Len Brown730ff342007-08-12 00:12:26 -04002316 thermal.tzp= [HW,ACPI]
2317 Specify global default ACPI thermal zone polling rate
2318 <deci-seconds>: poll all this frequency
2319 0: no polling (default)
2320
Linus Torvalds1da177e2005-04-16 15:20:36 -07002321 tmscsim= [HW,SCSI]
2322 See comment before function dc390_setup() in
2323 drivers/scsi/tmscsim.c.
2324
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01002325 topology= [S390]
2326 Format: {off | on}
2327 Specify if the kernel should make use of the cpu
2328 topology informations if the hardware supports these.
2329 The scheduler will make use of these informations and
2330 e.g. base its process migration decisions on it.
2331 Default is off.
2332
Linus Torvalds1da177e2005-04-16 15:20:36 -07002333 tp720= [HW,PS2]
2334
2335 trix= [HW,OSS] MediaTrix AudioTrix Pro
Randy Dunlapa9913042005-10-23 12:57:11 -07002336 Format:
2337 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2338
Alok Kataria395628e2008-10-24 17:22:01 -07002339 tsc= Disable clocksource-must-verify flag for TSC.
2340 Format: <string>
2341 [x86] reliable: mark tsc clocksource as reliable, this
2342 disables clocksource verification at runtime.
2343 Used to enable high-resolution timer mode on older
2344 hardware, and in virtualized environment.
2345
Randy Dunlapa9913042005-10-23 12:57:11 -07002346 turbografx.map[2|3]= [HW,JOY]
2347 TurboGraFX parallel port interface
2348 Format:
2349 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002350 See also Documentation/input/joystick-parport.txt
2351
2352 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2353 See header of drivers/scsi/u14-34f.c.
2354
2355 uart401= [HW,OSS]
2356 Format: <io>,<irq>
2357
2358 uart6850= [HW,OSS]
2359 Format: <io>,<irq>
2360
Alan Stern5f8364b2006-12-05 16:29:55 -05002361 uhci-hcd.ignore_oc=
2362 [USB] Ignore overcurrent events (default N).
2363 Some badly-designed motherboards generate lots of
2364 bogus events, for ports that aren't wired to
2365 anything. Set this parameter to avoid log spamming.
2366 Note that genuine overcurrent events won't be
2367 reported either.
2368
Simon Arlotte3a61b02008-07-19 23:32:54 +01002369 unknown_nmi_panic
2370 [X86-32,X86-64]
2371 Set unknown_nmi_panic=1 early on boot.
2372
Alan Sternb5e795f2007-02-20 15:00:53 -05002373 usbcore.autosuspend=
2374 [USB] The autosuspend time delay (in seconds) used
2375 for newly-detected USB devices (default 2). This
2376 is the time required before an idle device will be
2377 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002378 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002379
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02002380 usbcore.usbfs_snoop=
2381 [USB] Set to log all usbfs traffic (default 0 = off).
2382
2383 usbcore.blinkenlights=
2384 [USB] Set to cycle leds on hubs (default 0 = off).
2385
2386 usbcore.old_scheme_first=
2387 [USB] Start with the old device initialization
2388 scheme (default 0 = off).
2389
2390 usbcore.use_both_schemes=
2391 [USB] Try the other device initialization scheme
2392 if the first one fails (default 1 = enabled).
2393
2394 usbcore.initial_descriptor_timeout=
2395 [USB] Specifies timeout for the initial 64-byte
2396 USB_REQ_GET_DESCRIPTOR request in milliseconds
2397 (default 5000 = 5.0 seconds).
2398
Linus Torvalds1da177e2005-04-16 15:20:36 -07002399 usbhid.mousepoll=
2400 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002401
Alan Sternd4f373e2008-11-10 14:07:45 -05002402 usb-storage.delay_use=
2403 [UMS] The delay in seconds before a new device is
2404 scanned for Logical Units (default 5).
2405
2406 usb-storage.quirks=
2407 [UMS] A list of quirks entries to supplement or
2408 override the built-in unusual_devs list. List
2409 entries are separated by commas. Each entry has
2410 the form VID:PID:Flags where VID and PID are Vendor
2411 and Product ID values (4-digit hex numbers) and
2412 Flags is a set of characters, each corresponding
2413 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05002414 a = SANE_SENSE (collect more than 18 bytes
2415 of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05002416 c = FIX_CAPACITY (decrease the reported
2417 device capacity by one sector);
Alan Sternc838ea42008-12-15 10:40:06 -05002418 h = CAPACITY_HEURISTICS (decrease the
2419 reported device capacity by one
2420 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05002421 i = IGNORE_DEVICE (don't bind to this
2422 device);
2423 l = NOT_LOCKABLE (don't try to lock and
2424 unlock ejectable media);
2425 m = MAX_SECTORS_64 (don't transfer more
2426 than 64 sectors = 32 KB at a time);
Alan Sternc838ea42008-12-15 10:40:06 -05002427 o = CAPACITY_OK (accept the capacity
2428 reported by the device);
Alan Sternd4f373e2008-11-10 14:07:45 -05002429 r = IGNORE_RESIDUE (the device reports
2430 bogus residue values);
2431 s = SINGLE_LUN (the device has only one
2432 Logical Unit);
2433 w = NO_WP_DETECT (don't test whether the
2434 medium is write-protected).
2435 Example: quirks=0419:aaf5:rl,0421:0433:rc
2436
Paul Jackson200001e2008-06-25 05:44:46 -07002437 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2438 kernel's map of available physical RAM.
2439
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002440 vdso= [X86-32,SH,x86-64]
Jeremy Fitzhardinge1dbf5272007-05-02 19:27:12 +02002441 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002442 vdso=1: enable VDSO (default)
2443 vdso=0: disable VDSO mapping
2444
Roland McGrathaf65d642008-01-30 13:30:43 +01002445 vdso32= [X86-32,X86-64]
2446 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2447 vdso32=1: enable 32-bit VDSO (default)
2448 vdso32=0: disable 32-bit VDSO mapping
2449
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002450 vector= [IA-64,SMP]
2451 vector=percpu: enable percpu vector domain
2452
Linus Torvalds1da177e2005-04-16 15:20:36 -07002453 video= [FB] Frame buffer configuration
2454 See Documentation/fb/modedb.txt.
2455
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002456 vga= [BOOT,X86-32] Select a particular video mode
Uwe Hermann71cced62008-10-20 09:32:21 -07002457 See Documentation/x86/i386/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07002458 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002459 Use vga=ask for menu.
2460 This is actually a boot loader parameter; the value is
2461 passed to the kernel using a special protocol.
2462
Randy Dunlapa9913042005-10-23 12:57:11 -07002463 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002464 size of <nn>. This can be used to increase the
2465 minimum size (128MB on x86). It can also be used to
2466 decrease the size and leave more room for directly
2467 mapped kernel RAM.
2468
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002469 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2470 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002471
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002472 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2473 Format: <command>
2474
2475 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2476 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002477
Linus Torvalds1da177e2005-04-16 15:20:36 -07002478 waveartist= [HW,OSS]
2479 Format: <io>,<irq>,<dma>,<dma2>
Randy Dunlapa9913042005-10-23 12:57:11 -07002480
Linus Torvalds1da177e2005-04-16 15:20:36 -07002481 wd33c93= [HW,SCSI]
2482 See header of drivers/scsi/wd33c93.c.
2483
2484 wd7000= [HW,SCSI]
2485 See header of drivers/scsi/wd7000.c.
2486
2487 wdt= [WDT] Watchdog
Gabriel C8dfe9c22007-08-10 13:01:00 -07002488 See Documentation/watchdog/wdt.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002489
2490 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2491 xd_geo= See header of drivers/block/xd.c.
2492
2493 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002494 Format:
2495 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002496
Randy Dunlapecb08d82009-01-06 14:42:44 -08002497 norandmaps Don't use address space randomization. Equivalent to
2498 echo 0 > /proc/sys/kernel/randomize_va_space
Andi Kleena62eaf12006-02-16 23:41:58 +01002499
Randy Dunlapa9913042005-10-23 12:57:11 -07002500______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002501
2502TODO:
2503
2504 Add documentation for ALSA options.
2505 Add more DRM drivers.