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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.
Randy Dunlapa9913042005-10-23 12:57:11 -070090 SWSUSP Software suspend is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070091 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -070099 X86-32 X86-32, aka i386 architecture is enabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
103
104In addition, the following text indicates that the option:
105
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
109
110Parameters denoted with BOOT are actually interpreted by the boot
111loader, and have no meaning to the kernel directly.
112Do not modify the syntax of boot loader parameters without extreme
113need or coordination with <Documentation/i386/boot.txt>.
114
Karsten Weiss55588702007-02-13 13:26:21 +0100115There are also arch-specific kernel-parameters not documented here.
116See for example <Documentation/x86_64/boot-options.txt>.
117
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119a trailing = on the name of any parameter states that that parameter will
120be entered as an environment variable, whereas its absence indicates that
121it will appear as a kernel argument readable via /proc/cmdline by programs
122running once the system is up.
123
jens m. noedler9c4751f2006-09-29 02:00:27 -0700124The number of kernel parameters is not limited, but the length of the
125complete command line (parameters including spaces etc.) is limited to
126a fixed number of characters. This limit depends on the architecture
127and is between 256 and 4096 characters. It is defined in the file
128./include/asm/setup.h as COMMAND_LINE_SIZE.
129
130
Bernhard Walle03d926f2007-03-06 02:29:44 -0800131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
Randy Dunlapa9913042005-10-23 12:57:11 -0700133 Format: { force | off | ht | strict | noirq }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
Randy Dunlapa9913042005-10-23 12:57:11 -0700138 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -0700139 strictly ACPI specification compliant.
140
Randy Dunlap53471122008-03-12 18:10:51 -0400141 See also Documentation/power/pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142
Len Browna1fdcc02007-03-11 03:26:14 -0400143 acpi_apic_instance= [ACPI, IOAPIC]
144 Format: <int>
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -0400147 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -0400148
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149 acpi_sleep= [HW,ACPI] Sleep options
Pavel Machek23b168d2008-02-05 19:27:12 +0100150 Format: { s3_bios, s3_mode, s3_beep }
151 See Documentation/power/video.txt for s3_bios and s3_mode.
152 s3_beep is for debugging; it makes the PC's speaker beep
153 as soon as the kernel's real-mode entry point is called.
Randy Dunlapa9913042005-10-23 12:57:11 -0700154
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
Randy Dunlapa9913042005-10-23 12:57:11 -0700156 Format: { level | edge | high | low }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157
Randy Dunlapa9913042005-10-23 12:57:11 -0700158 acpi_irq_balance [HW,ACPI]
159 ACPI will balance active IRQs
160 default in APIC mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161
Randy Dunlapa9913042005-10-23 12:57:11 -0700162 acpi_irq_nobalance [HW,ACPI]
163 ACPI will not move active IRQs (default)
164 default in PIC mode
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165
Randy Dunlapa9913042005-10-23 12:57:11 -0700166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
167 use by PCI
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168 Format: <irq>,<irq>...
169
Randy Dunlapa9913042005-10-23 12:57:11 -0700170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171 Format: <irq>,<irq>...
172
Len Brown67effe82007-07-26 00:50:06 -0400173 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
174
Len Browna1f9e652006-01-25 23:47:36 -0500175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
176 Format: To spoof as Windows 98: ="Microsoft Windows"
177
Len Brownae00d812007-05-29 18:43:33 -0400178 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
179 acpi_osi="string1" # add string1 -- only one string
180 acpi_osi="!string2" # remove built-in string2
181 acpi_osi= # disable all strings
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182
183 acpi_serialize [HW,ACPI] force serialization of AML methods
184
185 acpi_skip_timer_override [HW,ACPI]
186 Recognize and ignore IRQ0/pin2 Interrupt Override.
187 For broken nForce2 BIOS resulting in XT-PIC timer.
Andi Kleenfa18f472006-11-14 16:57:46 +0100188 acpi_use_timer_override [HW,ACPI}
189 Use timer override. For some broken Nvidia NF5 boards
190 that require a timer override, but don't have
191 HPET
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192
Zhang Ruif9891062007-04-24 13:53:22 +0800193 acpi.debug_layer= [HW,ACPI]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194 Format: <int>
Randy Dunlapa9913042005-10-23 12:57:11 -0700195 Each bit of the <int> indicates an ACPI debug layer,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196 1: enable, 0: disable. It is useful for boot time
197 debugging. After system has booted up, it can be set
Zhang Ruif9891062007-04-24 13:53:22 +0800198 via /sys/module/acpi/parameters/debug_layer.
199 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
200 Available bits (add the numbers together) to enable debug output
201 for specific parts of the ACPI subsystem:
202 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
203 0x10 namespace 0x20 parser 0x40 dispatcher
204 0x80 executer 0x100 resources 0x200 acpica debugger
205 0x400 os services 0x800 acpica disassembler.
206 The number can be in decimal or prefixed with 0x in hex.
207 Warning: Many of these options can produce a lot of
208 output and make your system unusable. Be very careful.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209
Zhang Ruif9891062007-04-24 13:53:22 +0800210 acpi.debug_level= [HW,ACPI]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211 Format: <int>
Randy Dunlapa9913042005-10-23 12:57:11 -0700212 Each bit of the <int> indicates an ACPI debug level,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213 1: enable, 0: disable. It is useful for boot time
214 debugging. After system has booted up, it can be set
Zhang Ruif9891062007-04-24 13:53:22 +0800215 via /sys/module/acpi/parameters/debug_level.
216 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
217 Available bits (add the numbers together) to enable different
218 debug output levels of the ACPI subsystem:
219 0x01 error 0x02 warn 0x04 init 0x08 debug object
220 0x10 info 0x20 init names 0x40 parse 0x80 load
221 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
222 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
223 0x10000 resources 0x20000 user requests 0x40000 package.
224 The number can be in decimal or prefixed with 0x in hex.
225 Warning: Many of these options can produce a lot of
226 output and make your system unusable. Be very careful.
227
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700228 acpi_pm_good [X86-32,X86-64]
john stultz5d0cf412006-06-26 00:25:12 -0700229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
232
Chuck Ebbertc99c1082007-07-27 10:46:20 +1000233 agp= [AGP]
234 { off | try_unsupported }
235 off: disable AGP support
236 try_unsupported: try to drive unsupported chipsets
237 (may crash computer or cause data corruption)
238
Chuck Ebbert66759a02005-09-12 18:49:25 +0200239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
Randy Dunlapa9913042005-10-23 12:57:11 -0700241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
Chuck Ebbert66759a02005-09-12 18:49:25 +0200243 The kernel tries to set a reasonable default.
244
245 disable_timer_pin_1 [i386,x86-64]
246 Disable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs.
248
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249 ad1848= [HW,OSS]
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
251
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252 advansys= [HW,SCSI]
253 See header of drivers/scsi/advansys.c.
254
255 advwdt= [HW,WDT] Advantech WDT
256 Format: <iostart>,<iostop>
257
258 aedsp16= [HW,OSS] Audio Excel DSP 16
259 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
260 See also header of sound/oss/aedsp16.c.
Randy Dunlapa9913042005-10-23 12:57:11 -0700261
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262 aha152x= [HW,SCSI]
263 See Documentation/scsi/aha152x.txt.
264
265 aha1542= [HW,SCSI]
266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
267
268 aic7xxx= [HW,SCSI]
269 See Documentation/scsi/aic7xxx.txt.
270
271 aic79xx= [HW,SCSI]
272 See Documentation/scsi/aic79xx.txt.
273
Linus Torvalds1da177e2005-04-16 15:20:36 -0700274 amijoy.map= [HW,JOY] Amiga joystick support
275 Map of devices attached to JOY0DAT and JOY1DAT
276 Format: <a>,<b>
277 See also Documentation/kernel/input/joystick.txt
278
279 analog.map= [HW,JOY] Analog joystick and gamepad support
280 Specifies type or capabilities of an analog joystick
281 connected to one of 16 gameports
282 Format: <type1>,<type2>,..<type16>
283
Randy Dunlapa9913042005-10-23 12:57:11 -0700284 apc= [HW,SPARC]
285 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286 Format: noidle
287 Disable APC CPU standby support. SPARCstation-Fox does
288 not play well with APC CPU idle - disable it if you have
289 APC and your system crashes randomly.
290
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700291 apic= [APIC,i386] Advanced Programmable Interrupt Controller
292 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700296
Linus Torvalds1da177e2005-04-16 15:20:36 -0700297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
299
Linus Torvalds1da177e2005-04-16 15:20:36 -0700300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
301 Format: <io>,<irq>,<nodeID>
302
303 ataflop= [HW,M68k]
304
305 atarimouse= [HW,MOUSE] Atari Mouse
306
307 atascsi= [HW,SCSI] Atari SCSI
308
309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
310 EzKey and similar keyboards
311
312 atkbd.reset= [HW] Reset keyboard during initialization
313
Randy Dunlapa9913042005-10-23 12:57:11 -0700314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316
317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
318 keyboards
319
320 atkbd.softraw= [HW] Choose between synthetic and real raw mode
321 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700322
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700325
326 autotest [IA64]
327
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328 baycom_epp= [HW,AX25]
329 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700330
Linus Torvalds1da177e2005-04-16 15:20:36 -0700331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
332 Format: <io>,<mode>
333 See header of drivers/net/hamradio/baycom_par.c.
334
Randy Dunlapa9913042005-10-23 12:57:11 -0700335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
339
Randy Dunlapa9913042005-10-23 12:57:11 -0700340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
344
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700345 boot_delay= Milliseconds to delay each printk during boot.
346 Values larger than 10 seconds (10000) are changed to
347 no delay (0).
348 Format: integer
349
Linus Torvalds1da177e2005-04-16 15:20:36 -0700350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700351 bttv.radio= Most important insmod options are available as
352 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
355
356 BusLogic= [HW,SCSI]
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
359
360 c101= [NET] Moxa C101 synchronous serial card
361
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
368
James Morris20510f22007-10-16 23:31:32 -0700369 capability.disable=
370 [SECURITY] Disable capabilities. This would normally
371 be used only if an alternative security model is to be
372 configured. Potentially dangerous and should only be
373 used if you are entirely sure of the consequences.
374
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100375 ccw_timeout_log [S390]
376 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700377
Paul Menage8bab8dd2008-04-04 14:29:57 -0700378 cgroup_disable= [KNL] Disable a particular controller
379 Format: {name of the controller(s) to disable}
380 {Currently supported controllers - "memory"}
381
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382 checkreqprot [SELINUX] Set initial checkreqprot flag value.
383 Format: { "0" | "1" }
384 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700385 0 -- check protection applied by kernel (includes
386 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387 1 -- check protection requested by application.
388 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700389 Value can be changed at runtime via
390 /selinux/checkreqprot.
391
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100392 cio_ignore= [S390]
393 See Documentation/s390/CommonIO for details.
394
395 cio_msg= [S390]
396 See Documentation/s390/CommonIO for details.
397
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700398 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700399 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200400 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700401 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200402 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403 Format: { pit | tsc | cyclone | pmtmr }
404
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700405 clocksource= [GENERIC_TIME] Override the default clocksource
406 Format: <string>
407 Override the default clocksource and use the clocksource
408 with the name specified.
409 Some clocksource names to choose from, depending on
410 the platform:
411 [all] jiffies (this is the base, fallback clocksource)
412 [ACPI] acpi_pm
413 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
414 pxa_timer,timer3,32k_counter,timer0_1
415 [AVR32] avr32
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700416 [X86-32] pit,hpet,tsc,vmi-timer;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700417 scx200_hrt on Geode; cyclone on IBM x440
418 [MIPS] MIPS
419 [PARISC] cr16
420 [S390] tod
421 [SH] SuperH
422 [SPARC64] tick
423 [X86-64] hpet,tsc
424
Andi Kleenac72e782008-01-30 13:33:21 +0100425 clearcpuid=BITNUM [X86]
426 Disable CPUID feature X for the kernel. See
427 include/asm-x86/cpufeature.h for the valid bit numbers.
428 Note the Linux specific bits are not necessarily
429 stable over kernel options, but the vendor specific
430 ones should be.
431 Also note that user programs calling CPUID directly
432 or using the feature without checking anything
433 will still see it. This just prevents it from
434 being used by the kernel or shown in /proc/cpuinfo.
435 Also note the kernel might malfunction if you disable
436 some critical bits.
437
Arjan van de Vena25bd942008-01-30 13:33:08 +0100438 code_bytes [IA32/X86_64] How many bytes of object code to print
439 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100440 Range: 0 - 8192
441 Default: 64
442
Andi Kleenf9262c12006-03-08 17:57:25 -0800443 disable_8254_timer
444 enable_8254_timer
445 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
446 over the 8254 in addition to over the IO-APIC. The
447 kernel tries to set a sensible default.
448
Thomas Gleixnerb17530b2007-10-19 20:35:02 +0200449 hpet= [X86-32,HPET] option to control HPET usage
450 Format: { enable (default) | disable | force }
451 disable: disable HPET and use PIT instead
Carlos Corbachod79a5f82007-10-19 18:51:27 +0100452 force: allow force enabled of undocumented chips (ICH4,
453 VIA, nVidia)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454
Linus Torvalds1da177e2005-04-16 15:20:36 -0700455 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700456 Format:
457 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458
459 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
460 Format: <io>[,<irq>]
461
Randy Dunlapa9913042005-10-23 12:57:11 -0700462 com90xx= [HW,NET]
463 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700464 Format: <io>[,<irq>[,<memstart>]]
465
466 condev= [HW,S390] console device
467 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700468
Linus Torvalds1da177e2005-04-16 15:20:36 -0700469 console= [KNL] Output console device and options.
470
471 tty<n> Use the virtual console device <n>.
472
473 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800474 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800476 the form "bbbbpnf", where "bbbb" is the baud rate,
477 "p" is parity ("n", "o", or "e"), "n" is number of
478 bits, and "f" is flow control ("r" for RTS or
479 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800481 See Documentation/serial-console.txt for more
482 information. See
483 Documentation/networking/netconsole.txt for an
484 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700485
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700486 uart[8250],io,<addr>[,options]
487 uart[8250],mmio,<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488 Start an early, polled-mode console on the 8250/16550
489 UART at the specified I/O port or MMIO address,
490 switching to the matching ttyS device later. The
491 options are the same as for ttyS, above.
492
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700493 earlycon= [KNL] Output early console device and options.
494 uart[8250],io,<addr>[,options]
495 uart[8250],mmio,<addr>[,options]
496 Start an early, polled-mode console on the 8250/16550
497 UART at the specified I/O port or MMIO address.
498 The options are the same as for ttyS, above.
499
Andres Salomon8f4ce8c2007-10-18 03:04:50 -0700500 no_console_suspend
501 [HW] Never suspend the console
502 Disable suspending of consoles during suspend and
503 hibernate operations. Once disabled, debugging
504 messages can reach various consoles while the rest
505 of the system is being put to sleep (ie, while
506 debugging driver suspend/resume hooks). This may
507 not work reliably with all consoles, but is known
508 to work with serial and VGA consoles.
509
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700511 Format:
512 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700514 crashkernel=nn[KMG]@ss[KMG]
515 [KNL] Reserve a chunk of physical memory to
516 hold a kernel to switch to with kexec on panic.
517
Bernhard Wallefb391592007-10-18 23:41:02 -0700518 crashkernel=range1:size1[,range2:size2,...][@offset]
519 [KNL] Same as above, but depends on the memory
520 in the running system. The syntax of range is
521 start-[end] where start and end are both
522 a memory unit (amount[KMG]). See also
523 Documentation/kdump/kdump.txt for a example.
524
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 cs4232= [HW,OSS]
526 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
527
528 cs89x0_dma= [HW,NET]
529 Format: <dma>
530
531 cs89x0_media= [HW,NET]
532 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700533
Randy Dunlapa9913042005-10-23 12:57:11 -0700534 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700535 See header of drivers/s390/block/dasd_devmap.c.
536
537 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
538 (one device per port)
539 Format: <port#>,<type>
540 See also Documentation/input/joystick-parport.txt
541
542 debug [KNL] Enable kernel debugging (events log level).
543
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700544 debug_locks_verbose=
545 [KNL] verbose self-tests
546 Format=<0|1>
547 Print debugging info while doing the locking API
548 self-tests.
549 We default to 0 (no extra messages), setting it to
550 1 will print _a lot_ more information - normally
551 only useful to kernel developers.
552
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200553 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700554 Format: <area>[,<node>]
555 See also Documentation/networking/decnet.txt.
556
Samuel Thibaultecb77fa2008-01-03 16:17:54 +0000557 vt.default_blu= [VT]
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700558 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
559 Change the default blue palette of the console.
560 This is a 16-member array composed of values
561 ranging from 0-255.
562
Samuel Thibaultecb77fa2008-01-03 16:17:54 +0000563 vt.default_grn= [VT]
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700564 Format: <green0>,<green1>,<green2>,...,<green15>
565 Change the default green palette of the console.
566 This is a 16-member array composed of values
567 ranging from 0-255.
568
Samuel Thibaultecb77fa2008-01-03 16:17:54 +0000569 vt.default_red= [VT]
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700570 Format: <red0>,<red1>,<red2>,...,<red15>
571 Change the default red palette of the console.
572 This is a 16-member array composed of values
573 ranging from 0-255.
574
Samuel Thibaultecb77fa2008-01-03 16:17:54 +0000575 vt.default_utf8=
576 [VT]
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700577 Format=<0|1>
578 Set system-wide default UTF-8 mode for all tty's.
Samuel Thibaultecb77fa2008-01-03 16:17:54 +0000579 Default is 1, i.e. UTF-8 mode is enabled for all
580 newly opened terminals.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700581
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582 dhash_entries= [KNL]
583 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700584
Linus Torvalds1da177e2005-04-16 15:20:36 -0700585 digi= [HW,SERIAL]
586 IO parameters + enable/disable command.
587
588 digiepca= [HW,SERIAL]
589 See drivers/char/README.epca and
590 Documentation/digiepca.txt.
591
Yinghai Lu093af8d2008-01-30 13:33:32 +0100592 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100593 By default the kernel will trim any uncacheable
594 memory out of your available memory pool based on
595 MTRR settings. This parameter disables that behavior,
596 possibly causing your machine to run very slowly.
597
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598 dmasound= [HW,OSS] Sound subsystem buffers
599
600 dscc4.setup= [NET]
601
602 dtc3181e= [HW,SCSI]
603
Robin Getz0ae53642007-10-09 17:24:49 +0800604 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700605 earlyprintk=vga
606 earlyprintk=serial[,ttySn[,baudrate]]
607
Randy Dunlapa9913042005-10-23 12:57:11 -0700608 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700609 takes over.
610
611 Only vga or serial at a time, not both.
612
613 Currently only ttyS0 and ttyS1 are supported.
614
615 Interaction with the standard serial driver is not
616 very good.
617
618 The VGA output is eventually overwritten by the real
619 console.
620
621 eata= [HW,SCSI]
622
Linus Torvalds1da177e2005-04-16 15:20:36 -0700623 edd= [EDD]
624 Format: {"of[f]" | "sk[ipmbr]"}
625 See comment in arch/i386/boot/edd.S
626
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627 eisa_irq_edge= [PARISC,HW]
628 See header of drivers/parisc/eisa.c.
629
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700630 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 See comment before function elanfreq_setup() in
632 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
633
634 elevator= [IOSCHED]
Randy Dunlap16ab3ad2006-01-14 13:21:20 -0800635 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
Randy Dunlapa9913042005-10-23 12:57:11 -0700636 See Documentation/block/as-iosched.txt and
637 Documentation/block/deadline-iosched.txt for details.
638
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700639 elfcorehdr= [X86-32, X86_64]
Randy Dunlapa9913042005-10-23 12:57:11 -0700640 Specifies physical address of start of kernel core
Vivek Goyalaac04b32006-01-09 20:51:47 -0800641 image elf header. Generally kexec loader will
642 pass this option to capture kernel.
643 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700644
645 enforcing [SELINUX] Set initial enforcing status.
646 Format: {"0" | "1"}
647 See security/selinux/Kconfig help text.
648 0 -- permissive (log only, no denials).
649 1 -- enforcing (deny and log).
650 Default value is 0.
651 Value can be changed at runtime via /selinux/enforce.
652
Linus Torvalds1da177e2005-04-16 15:20:36 -0700653 es1371= [HW,OSS]
654 Format: <spdif>,[<nomix>,[<amplifier>]]
655 See also header of sound/oss/es1371.c.
Randy Dunlapa9913042005-10-23 12:57:11 -0700656
Linus Torvalds1da177e2005-04-16 15:20:36 -0700657 ether= [HW,NET] Ethernet cards parameters
658 This option is obsoleted by the "netdev=" option, which
659 has equivalent usage. See its documentation for details.
660
661 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
662 Format: <io>[,<irq>]
663
Akinobu Mitade1ba092006-12-08 02:39:42 -0800664 failslab=
665 fail_page_alloc=
666 fail_make_request=[KNL]
667 General fault injection mechanism.
668 Format: <interval>,<probability>,<space>,<times>
669 See also /Documentation/fault-injection/.
670
Linus Torvalds1da177e2005-04-16 15:20:36 -0700671 fd_mcs= [HW,SCSI]
672 See header of drivers/scsi/fd_mcs.c.
673
674 fdomain= [HW,SCSI]
675 See header of drivers/scsi/fdomain.c.
676
677 floppy= [HW]
678 See Documentation/floppy.txt.
679
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 gamecon.map[2|3]=
681 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
682 support via parallel port (up to 5 devices per port)
683 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
684 See also Documentation/input/joystick-parport.txt
685
686 gamma= [HW,DRM]
687
Yinghai Luaaf23042008-01-30 13:33:09 +0100688 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
689 Format: off | on
690 default: on
691
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692 gdth= [HW,SCSI]
693 See header of drivers/scsi/gdth.c.
694
695 gpt [EFI] Forces disk with valid GPT signature but
696 invalid Protective MBR to be treated as GPT.
697
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698 gvp11= [HW,SCSI]
699
700 hashdist= [KNL,NUMA] Large hashes allocated during boot
701 are distributed across NUMA nodes. Defaults on
702 for IA-64, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -0700703 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704
705 hcl= [IA-64] SGI's Hardware Graph compatibility layer
706
707 hd= [EIDE] (E)IDE hard drive subsystem geometry
708 Format: <cyl>,<head>,<sect>
709
710 hd?= [HW] (E)IDE subsystem
Randy Dunlap1c10e932008-03-07 21:53:50 +0100711 hd?lun= See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712
713 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
714 size of <nn>. This works even on boxes that have no
715 highmem otherwise. This also works to reduce highmem
716 size on bigger boxes.
717
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -0800718 highres= [KNL] Enable/disable high resolution timer mode.
719 Valid parameters: "on", "off"
720 Default: "on"
721
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722 hisax= [HW,ISDN]
723 See Documentation/isdn/README.HiSax.
724
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700725 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
Jon Tollefson4ec161c2008-01-04 09:59:50 +1100726 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727
Linus Torvalds1da177e2005-04-16 15:20:36 -0700728 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +0200729 i8042.dumbkbd [HW] Pretend that controller can only read data from
730 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -0700731 (Don't attempt to blink the leds)
732 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -0500733 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -0400734 i8042.noloop [HW] Disable the AUX Loopback command while probing
735 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -0700736 i8042.nomux [HW] Don't check presence of an active multiplexing
737 controller
738 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
739 controllers
740 i8042.panicblink=
741 [HW] Frequency with which keyboard LEDs should blink
742 when kernel panics (default is 0.5 sec)
743 i8042.reset [HW] Reset the controller during init and cleanup
744 i8042.unlock [HW] Unlock (ignore) the keylock
745
746 i810= [HW,DRM]
747
Dmitry Torokhove70c9d52005-06-25 14:54:25 -0700748 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
749 indicates that the driver is running on unsupported
750 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700751 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
752 does not match list of supported models.
753 i8k.power_status
754 [HW] Report power status in /proc/i8k
755 (disabled by default)
756 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
757 capability is set.
758
759 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
760 See Documentation/mca.txt.
761
762 icn= [HW,ISDN]
763 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
764
765 ide= [HW] (E)IDE subsystem
766 Format: ide=nodma or ide=doubler or ide=reverse
Randy Dunlap1c10e932008-03-07 21:53:50 +0100767 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768
769 ide?= [HW] (E)IDE subsystem
770 Format: ide?=noprobe or chipset specific parameters.
Randy Dunlap1c10e932008-03-07 21:53:50 +0100771 See Documentation/ide/ide.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -0700772
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
Randy Dunlap1c10e932008-03-07 21:53:50 +0100774 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700775
Andi Kleenf039b752007-05-02 19:27:12 +0200776 idle= [X86]
777 Format: idle=poll or idle=mwait
778 Poll forces a polling idle loop that can slightly improves the performance
779 of waking up a idle CPU, but will use a lot of power and make the system
780 run hot. Not recommended.
781 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
782 to not use it because it doesn't save as much power as a normal idle
783 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
784 as idle=poll.
Randy Dunlapa9913042005-10-23 12:57:11 -0700785
Denis Cheng594765a2008-02-06 02:57:49 +0100786 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
787 Claim all unknown PCI IDE storage controllers.
788
Ingo Molnar792908222006-12-06 20:40:51 -0800789 ignore_loglevel [KNL]
790 Ignore loglevel setting - this will print /all/
791 kernel messages to the console. Useful for debugging.
792
Linus Torvalds1da177e2005-04-16 15:20:36 -0700793 ihash_entries= [KNL]
794 Set number of hash buckets for inode cache.
795
796 in2000= [HW,SCSI]
797 See header of drivers/scsi/in2000.c.
798
799 init= [KNL]
800 Format: <full_path>
801 Run specified binary instead of /sbin/init as init
802 process.
803
804 initcall_debug [KNL] Trace initcalls as they are executed. Useful
805 for working out where the kernel is dying during
806 startup.
807
808 initrd= [BOOT] Specify the location of the initial ramdisk
809
810 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
811 Format: <irq>
812
813 inttest= [IA64]
814
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700815 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
816 off
817 Disable intel iommu driver.
818 igfx_off [Default Off]
819 By default, gfx is mapped as normal device. If a gfx
820 device has a dedicated DMAR unit, the DMAR unit is
821 bypassed by not enabling DMAR with this option. In
822 this case, gfx device will use physical address for
823 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700824 forcedac [x86_64]
825 With this option iommu will not optimize to look
826 for io virtual address below 32 bit forcing dual
827 address cycle on pci bus for cards supporting greater
828 than 32 bit addressing. The default is to look
829 for translation below 32 bit and if not available
830 then look in the higher range.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700831
Rene Hermanb02aae92008-01-30 13:30:05 +0100832 io_delay= [X86-32,X86-64] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100833 0x80
834 Standard port 0x80 based delay
835 0xed
836 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +0100837 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100838 Simple two microseconds delay
839 none
840 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +0100841
Linus Torvalds1da177e2005-04-16 15:20:36 -0700842 io7= [HW] IO7 for Marvel based alpha systems
843 See comment before marvel_specify_io7 in
844 arch/alpha/kernel/core_marvel.c.
845
846 ip= [IP_PNP]
J. Bruce Fields6ded55d2008-04-07 15:59:03 -0400847 See Documentation/filesystems/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700848
849 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700850 See comment before ip2_setup() in
851 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700852
853 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
854 See header of drivers/scsi/ips.c.
855
Simon Horman72c4a132006-09-13 19:57:18 -0700856 ports= [IP_VS_FTP] IPVS ftp helper module
857 Default is 21.
858 Up to 8 (IP_VS_APP_MAX_PORTS) ports
859 may be specified.
860 Format: <port>,<port>....
861
Alan Cox200803d2005-06-28 20:45:18 -0700862 irqfixup [HW]
863 When an interrupt is not handled search all handlers
864 for it. Intended to get systems with badly broken
865 firmware running.
866
867 irqpoll [HW]
868 When an interrupt is not handled search all handlers
869 for it. Also check all handlers each timer
870 interrupt. Intended to get systems with badly broken
871 firmware running.
872
Linus Torvalds1da177e2005-04-16 15:20:36 -0700873 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -0700874 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875
876 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -0800877 Format:
878 <cpu number>,...,<cpu number>
879 or
880 <cpu number>-<cpu number> (must be a positive range in ascending order)
881 or a mixture
882 <cpu number>,...,<cpu number>-<cpu number>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700883 This option can be used to specify one or more CPUs
884 to isolate from the general SMP balancing and scheduling
885 algorithms. The only way to move a process onto or off
886 an "isolated" CPU is via the CPU affinity syscalls.
887 <cpu number> begins at 0 and the maximum value is
888 "number of CPUs in system - 1".
889
890 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -0700891 alternative -- manually setting the CPU mask of all
892 tasks in the system -- can cause problems and
893 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700894
Randy Dunlapa9913042005-10-23 12:57:11 -0700895 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700896
897 js= [HW,JOY] Analog joystick
898 See Documentation/input/joystick.txt.
899
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700900 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -0700901 specifies the amount of memory usable by the kernel
902 for non-movable allocations. The requested amount is
903 spread evenly throughout all nodes in the system. The
904 remaining memory in each node is used for Movable
905 pages. In the event, a node is too small to have both
906 kernelcore and Movable pages, kernelcore pages will
907 take priority and other nodes will have a larger number
908 of kernelcore pages. The Movable zone is used for the
909 allocation of pages that may be reclaimed or moved
910 by the page migration subsystem. This means that
911 HugeTLB pages may not be allocated from this zone.
912 Note that allocations like PTEs-from-HighMem still
913 use the HighMem zone if it exists, and the Normal
914 zone if it does not.
915
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700916 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
Mel Gorman7e63efe2007-07-17 04:03:15 -0700917 is similar to kernelcore except it specifies the
918 amount of memory used for migratable allocations.
919 If both kernelcore and movablecore is specified,
920 then kernelcore will be at *least* the specified
921 value but may be more. If movablecore on its own
922 is specified, the administrator must be careful
923 that the amount of memory usable for all allocations
924 is not too small.
925
Linus Torvalds1da177e2005-04-16 15:20:36 -0700926 keepinitrd [HW,ARM]
927
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700928 kstack=N [X86-32,X86-64] Print N words from the kernel stack
Linus Torvalds1da177e2005-04-16 15:20:36 -0700929 in oops dumps.
930
Jason Wessel6cdf6e02008-04-17 20:05:38 +0200931 kgdboc= [HW] kgdb over consoles.
932 Requires a tty driver that supports console polling.
933 (only serial suported for now)
934 Format: <serial_device>[,baud]
935
Linus Torvalds1da177e2005-04-16 15:20:36 -0700936 l2cr= [PPC]
937
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700938 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -0700939 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700940
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700941 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
Thomas Gleixnere585bef2007-03-23 16:08:01 +0100942 C2 power state.
943
FD Camifcb71f62008-01-06 19:08:56 +0100944 libata.dma= [LIBATA] DMA control
945 libata.dma=0 Disable all PATA and SATA DMA
946 libata.dma=1 PATA and SATA Disk DMA only
947 libata.dma=2 ATAPI (CDROM) DMA only
948 libata.dma=4 Compact Flash DMA only
949 Combinations also work, so libata.dma=3 enables DMA
950 for disks and CDROMs, but not CFs.
951
Dave Jones78e70c22007-09-27 11:50:13 -0400952 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
953 when set.
954 Format: <int>
955
Tejun Heo33267322008-02-13 09:15:09 +0900956 libata.force= [LIBATA] Force configurations. The format is comma
957 separated list of "[ID:]VAL" where ID is
958 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
959 matching port, link or device. Basically, it matches
960 the ATA ID string printed on console by libata. If
961 the whole ID part is omitted, the last PORT and DEVICE
962 values are used. If ID hasn't been specified yet, the
963 configuration applies to all ports, links and devices.
964
965 If only DEVICE is omitted, the parameter applies to
966 the port and all links and devices behind it. DEVICE
967 number of 0 either selects the first device or the
968 first fan-out link behind PMP device. It does not
969 select the host link. DEVICE number of 15 selects the
970 host link and device attached to it.
971
972 The VAL specifies the configuration to force. As long
973 as there's no ambiguity shortcut notation is allowed.
974 For example, both 1.5 and 1.5G would work for 1.5Gbps.
975 The following configurations can be forced.
976
977 * Cable type: 40c, 80c, short40c, unk, ign or sata.
978 Any ID with matching PORT is used.
979
980 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
981
982 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
983 udma[/][16,25,33,44,66,100,133] notation is also
984 allowed.
985
986 * [no]ncq: Turn on or off NCQ.
987
988 If there are multiple matching configurations changing
989 the same attribute, the last one is used.
990
Linus Torvalds1da177e2005-04-16 15:20:36 -0700991 load_ramdisk= [RAM] List of ramdisks to load from floppy
992 See Documentation/ramdisk.txt.
993
Randy Dunlapa6b25b62006-01-14 13:21:19 -0800994 lockd.nlm_grace_period=P [NFS] Assign grace period.
995 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700996
Randy Dunlapa6b25b62006-01-14 13:21:19 -0800997 lockd.nlm_tcpport=N [NFS] Assign TCP port.
998 Format: <integer>
999
1000 lockd.nlm_timeout=T [NFS] Assign timeout value.
1001 Format: <integer>
1002
1003 lockd.nlm_udpport=M [NFS] Assign UDP port.
1004 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001005
1006 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1007 Format: <irq>
1008
1009 loglevel= All Kernel Messages with a loglevel smaller than the
1010 console loglevel will be printed to the console. It can
1011 also be changed with klogd or other programs. The
1012 loglevels are defined as follows:
1013
1014 0 (KERN_EMERG) system is unusable
1015 1 (KERN_ALERT) action must be taken immediately
1016 2 (KERN_CRIT) critical conditions
1017 3 (KERN_ERR) error conditions
1018 4 (KERN_WARNING) warning conditions
1019 5 (KERN_NOTICE) normal but significant condition
1020 6 (KERN_INFO) informational
1021 7 (KERN_DEBUG) debug-level messages
1022
1023 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001024 Format: { n | nk | nM }
1025 n must be a power of two. The default size
1026 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001027
Randy Dunlapaccaa242007-10-16 01:29:37 -07001028 logo.nologo [FB] Disables display of the built-in Linux logo.
1029 This may be used to provide more screen space for
1030 kernel log messages and is useful when debugging
1031 kernel boot problems.
1032
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 lp=0 [LP] Specify parallel ports to use, e.g,
1034 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1035 lp=reset first parallel port). 'lp=0' disables the
1036 lp=auto printer driver. 'lp=reset' (which can be
1037 specified in addition to the ports) causes
1038 attached printers to be reset. Using
1039 lp=port1,port2,... specifies the parallel ports
1040 to associate lp devices with, starting with
1041 lp0. A port specification may be 'none' to skip
1042 that lp device, or a parport name such as
1043 'parport0'. Specifying 'lp=auto' instead of a
1044 port specification list means that device IDs
1045 from each port should be examined, to see if
1046 an IEEE 1284-compliant printer is attached; if
1047 so, the driver will manage that printer.
1048 See also header of drivers/char/lp.c.
1049
1050 lpj=n [KNL]
1051 Sets loops_per_jiffy to given constant, thus avoiding
1052 time-consuming boot-time autodetection (up to 250 ms per
1053 CPU). 0 enables autodetection (default). To determine
1054 the correct value for your kernel, boot with normal
1055 autodetection and see what value is printed. Note that
1056 on SMP systems the preset will be applied to all CPUs,
1057 which is likely to cause problems if your CPUs need
1058 significantly divergent settings. An incorrect value
1059 will cause delays in the kernel to be wrong, leading to
1060 unpredictable I/O errors and other breakage. Although
1061 unlikely, in the extreme case this might damage your
1062 hardware.
1063
1064 ltpc= [NET]
1065 Format: <io>,<irq>,<dma>
1066
Randy Dunlapa9913042005-10-23 12:57:11 -07001067 mac5380= [HW,SCSI] Format:
1068 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001069
Randy Dunlapa9913042005-10-23 12:57:11 -07001070 mac53c9x= [HW,SCSI] Format:
1071 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001072
Randy Dunlapa9913042005-10-23 12:57:11 -07001073 machvec= [IA64] Force the use of a particular machine-vector
1074 (machvec) in a generic kernel.
1075 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001076
Randy Dunlapa9913042005-10-23 12:57:11 -07001077 max_loop= [LOOP] Maximum number of loopback devices that can
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078 be mounted
1079 Format: <1-256>
1080
1081 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001082 should make use of. maxcpus=n : n >= 0 limits the
1083 kernel to using 'n' processors. n=0 is a special case,
1084 it is equivalent to "nosmp", which also disables
1085 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086
Bob Picco2b2c3752005-06-29 18:00:00 -07001087 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1088 equal to this physical address is ignored.
1089
Randy Dunlapa9913042005-10-23 12:57:11 -07001090 max_luns= [SCSI] Maximum number of LUNs to probe.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001091 Should be between 1 and 2^32-1.
1092
1093 max_report_luns=
Randy Dunlapa9913042005-10-23 12:57:11 -07001094 [SCSI] Maximum number of LUNs received.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095 Should be between 1 and 16384.
1096
Linus Torvalds1da177e2005-04-16 15:20:36 -07001097 mcatest= [IA-64]
1098
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001099 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001100
Andi Kleen909dd322007-10-17 18:04:38 +02001101 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1102
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103 md= [HW] RAID subsystems devices and level
1104 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001105
Linus Torvalds1da177e2005-04-16 15:20:36 -07001106 mdacon= [MDA]
1107 Format: <first>,<last>
1108 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001109
Linus Torvalds1da177e2005-04-16 15:20:36 -07001110 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1111 Amount of memory to be used when the kernel is not able
1112 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001113 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114 address space collisions. Without memmap= PCI devices
1115 could be placed at addresses belonging to unused RAM.
1116
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001117 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001118 memory.
1119
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001120 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121 E820 memory map, as specified by the user.
1122 Such memmap=exactmap lines can be constructed based on
1123 BIOS output or other requirements. See the memmap=nn@ss
1124 option description.
1125
1126 memmap=nn[KMG]@ss[KMG]
1127 [KNL] Force usage of a specific region of memory
1128 Region of memory to be used, from ss to ss+nn.
1129
1130 memmap=nn[KMG]#ss[KMG]
1131 [KNL,ACPI] Mark specific memory as ACPI data.
1132 Region of memory to be used, from ss to ss+nn.
1133
1134 memmap=nn[KMG]$ss[KMG]
1135 [KNL,ACPI] Mark specific memory as reserved.
1136 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001137 Example: Exclude memory from 0x18690000-0x1869ffff
1138 memmap=64K$0x18690000
1139 or
1140 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001141
1142 meye.*= [HW] Set MotionEye Camera parameters
1143 See Documentation/video4linux/meye.txt.
1144
Andres Salomon8f368812007-10-12 23:04:06 +02001145 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1146 Multi-Function General Purpose Timers on AMD Geode
1147 platforms.
1148
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001149 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1150 the BIOS has incorrectly applied a workaround. TinyBIOS
1151 version 0.98 is known to be affected, 0.99 fixes the
1152 problem by letting the user disable the workaround.
1153
Linus Torvalds1da177e2005-04-16 15:20:36 -07001154 mga= [HW,DRM]
1155
1156 mousedev.tap_time=
1157 [MOUSE] Maximum time between finger touching and
1158 leaving touchpad surface for touch to be considered
1159 a tap and be reported as a left button click (for
1160 touchpads working in absolute mode only).
1161 Format: <msecs>
1162 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1163 reporting absolute coordinates, such as tablets
1164 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1165 reporting absolute coordinates, such as tablets
1166
1167 mpu401= [HW,OSS]
1168 Format: <io>,<irq>
1169
1170 MTD_Partition= [MTD]
1171 Format: <name>,<region-number>,<size>,<offset>
1172
Randy Dunlapa9913042005-10-23 12:57:11 -07001173 MTD_Region= [MTD] Format:
1174 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001175
1176 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001177 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001178
1179 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001180 [HW] Make the MicroTouch USB driver use raw coordinates
1181 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001182
1183 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1184
1185 NCR_D700= [HW,SCSI]
1186 See header of drivers/scsi/NCR_D700.c.
1187
1188 ncr5380= [HW,SCSI]
1189
1190 ncr53c400= [HW,SCSI]
1191
1192 ncr53c400a= [HW,SCSI]
1193
1194 ncr53c406a= [HW,SCSI]
1195
1196 ncr53c8xx= [HW,SCSI]
1197
1198 netdev= [NET] Network devices parameters
1199 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1200 Note that mem_start is often overloaded to mean
1201 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001202 This usage is only documented in each driver source
1203 file if at all.
1204
Linus Torvalds1da177e2005-04-16 15:20:36 -07001205 nfsaddrs= [NFS]
J. Bruce Fields6ded55d2008-04-07 15:59:03 -04001206 See Documentation/filesystems/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001207
1208 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fields6ded55d2008-04-07 15:59:03 -04001209 See Documentation/filesystems/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001210
Trond Myklebusta72b4422006-01-03 09:55:41 +01001211 nfs.callback_tcpport=
1212 [NFS] set the TCP port on which the NFSv4 callback
1213 channel should listen.
1214
Trond Myklebust58df0952006-01-03 09:55:57 +01001215 nfs.idmap_cache_timeout=
1216 [NFS] set the maximum lifetime for idmapper cache
1217 entries.
1218
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001219 nfs.enable_ino64=
1220 [NFS] enable 64-bit inode numbers.
1221 If zero, the NFS client will fake up a 32-bit inode
1222 number for the readdir() and stat() syscalls instead
1223 of returning the full 64-bit number.
1224 The default is to return 64-bit inode numbers.
1225
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001226 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1227 when a NMI is triggered.
1228 Format: [state][,regs][,debounce][,die]
1229
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001230 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
Linus Torvalds1da177e2005-04-16 15:20:36 -07001231
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001232 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001233 emulation library even if a 387 maths coprocessor
1234 is present.
1235
Christoph Lameterc1aee212007-05-31 00:40:47 -07001236 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1237 caches in the slab allocator. Saves per-node memory,
1238 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001239
Randy Dunlapa9913042005-10-23 12:57:11 -07001240 noalign [KNL,ARM]
1241
Linus Torvalds1da177e2005-04-16 15:20:36 -07001242 noapic [SMP,APIC] Tells the kernel to not make use of any
1243 IOAPICs that may be present in the system.
1244
Linus Torvalds1da177e2005-04-16 15:20:36 -07001245 nobats [PPC] Do not use BATs for mapping kernel lowmem
1246 on "Classic" PPC cores.
1247
1248 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001249
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001250 nodelayacct [KNL] Disable per-task delay accounting
1251
Linus Torvalds1da177e2005-04-16 15:20:36 -07001252 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1253
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001254 noefi [X86-32,X86-64] Disable EFI runtime services support.
1255
Linus Torvalds1da177e2005-04-16 15:20:36 -07001256 noexec [IA-64]
1257
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001258 noexec [X86-32,X86-64]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001259 noexec=on: enable non-executable mappings (default)
1260 noexec=off: disable nn-executable mappings
1261
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001262 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001263 register save and restore. The kernel will only save
1264 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265
Andi Kleen191679f2008-01-30 13:33:21 +01001266 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1267
Linus Torvalds1da177e2005-04-16 15:20:36 -07001268 nohlt [BUGS=ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001269
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001270 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001271 instruction doesn't work correctly and not to
1272 use it.
1273
1274 nohalt [IA-64] Tells the kernel not to use the power saving
1275 function PAL_HALT_LIGHT when idle. This increases
1276 power-consumption. On the positive side, it reduces
1277 interrupt wake-up latency, which may improve performance
1278 in certain environments such as networked servers or
1279 real-time systems.
1280
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001281 nohz= [KNL] Boottime enable/disable dynamic ticks
1282 Valid arguments: on, off
1283 Default: on
1284
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001285 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
Zachary Amsden8542b202006-12-07 02:14:09 +01001286
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001287 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001288 disable unhandled interrupt sources.
1289
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001290 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001291 broken timer IRQ sources.
1292
Linus Torvalds1da177e2005-04-16 15:20:36 -07001293 noisapnp [ISAPNP] Disables ISA PnP code.
1294
1295 noinitrd [RAM] Tells the kernel not to load any configured
1296 initial RAM disk.
1297
1298 nointroute [IA-64]
1299
Tony Luck0aa366f2007-07-20 11:22:30 -07001300 nojitter [IA64] Disables jitter checking for ITC timers.
1301
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001302 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001303
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001304 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001305
Linus Torvalds1da177e2005-04-16 15:20:36 -07001306 noltlbs [PPC] Do not use large page/tlb entries for kernel
1307 lowmem mapping on PPC40x.
1308
Horms312f1f02006-02-22 09:57:55 +09001309 nomca [IA-64] Disable machine check abort handling
1310
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001311 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001312
Andres Salomon83d73842007-10-12 23:04:06 +02001313 nomfgpt [X86-32] Disable Multi-Function General Purpose
1314 Timer usage (for AMD Geode machines).
1315
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001316 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001317
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001318 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001319 with UP alternatives
1320
Linus Torvalds1da177e2005-04-16 15:20:36 -07001321 noresidual [PPC] Don't use residual data on PReP machines.
1322
Randy Dunlapa9913042005-10-23 12:57:11 -07001323 noresume [SWSUSP] Disables resume and restores original swap
1324 space.
1325
Linus Torvalds1da177e2005-04-16 15:20:36 -07001326 no-scroll [VGA] Disables scrollback.
1327 This is required for the Braillex ib80-piezo Braille
1328 reader made by F.H. Papenmeier (Germany).
1329
1330 nosbagart [IA-64]
1331
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001332 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001333
Len Brown61ec7562007-08-16 03:34:22 -04001334 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1335 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001336
Dave Jones97842212007-07-15 23:41:05 -07001337 nosoftlockup [KNL] Disable the soft-lockup detector.
1338
Linus Torvalds1da177e2005-04-16 15:20:36 -07001339 nosync [HW,M68K] Disables sync negotiation for all devices.
1340
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001341 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342
1343 nousb [USB] Disable the USB subsystem
1344
1345 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001346
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001347 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1348 one of ['zone', 'node', 'default'] can be specified
1349 This can be set from sysctl after boot.
1350 See Documentation/sysctl/vm.txt for details.
1351
Dave Jonesa61c2d72006-01-07 23:18:19 +00001352 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1353
Linus Torvalds1da177e2005-04-16 15:20:36 -07001354 opl3= [HW,OSS]
1355 Format: <io>
1356
Linus Torvalds1da177e2005-04-16 15:20:36 -07001357 oprofile.timer= [HW]
1358 Use timer interrupt instead of performance counters
1359
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360 osst= [HW,SCSI] SCSI Tape Driver
1361 Format: <buffer_size>,<write_threshold>
1362 See also Documentation/scsi/st.txt.
1363
1364 panic= [KNL] Kernel behaviour on panic
1365 Format: <timeout>
1366
1367 parkbd.port= [HW] Parallel port number the keyboard adapter is
1368 connected to, default is 0.
1369 Format: <parport#>
1370 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1371 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001372 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001373
Randy Dunlapa9913042005-10-23 12:57:11 -07001374 parport= [HW,PPT] Specify parallel ports. 0 disables.
1375 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1376 Use 'auto' to force the driver to use any
1377 IRQ/DMA settings detected (the default is to
1378 ignore detected IRQ/DMA settings because of
1379 possible conflicts). You can specify the base
1380 address, IRQ, and DMA settings; IRQ and DMA
1381 should be numbers, or 'auto' (for using detected
1382 settings on that particular port), or 'nofifo'
1383 (to avoid using a FIFO even if it is detected).
1384 Parallel ports are assigned in the order they
1385 are specified on the command line, starting
1386 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001387
Randy Dunlapa9913042005-10-23 12:57:11 -07001388 parport_init_mode= [HW,PPT]
1389 Configure VIA parallel port to operate in
1390 a specific mode. This is necessary on Pegasos
1391 computer where firmware has no options for setting
1392 up parallel port mode and sets it to spp.
1393 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001394 Format: [spp|ps2|epp|ecp|ecpepp]
1395
Randy Dunlapa9913042005-10-23 12:57:11 -07001396 pas2= [HW,OSS] Format:
1397 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1398
Linus Torvalds1da177e2005-04-16 15:20:36 -07001399 pas16= [HW,SCSI]
1400 See header of drivers/scsi/pas16.c.
1401
Andrew Mortondd287792006-03-23 03:00:57 -08001402 pause_on_oops=
1403 Halt all CPUs after the first oops has been printed for
1404 the specified number of seconds. This is to be used if
1405 your oopses keep scrolling off the screen.
1406
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407 pcbit= [HW,ISDN]
1408
1409 pcd. [PARIDE]
1410 See header of drivers/block/paride/pcd.c.
1411 See also Documentation/paride.txt.
1412
Randy Dunlapa9913042005-10-23 12:57:11 -07001413 pci=option[,option...] [PCI] various PCI subsystem options:
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001414 off [X86-32] don't probe for the PCI bus
1415 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001416 the hardware directly. Use this if your machine
1417 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001418 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001419 hardware access methods are allowed. Use this
1420 if you experience crashes upon bootup and you
1421 suspect they are caused by the BIOS.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001422 conf1 [X86-32] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001423 Mechanism 1.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001424 conf2 [X86-32] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001425 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001426 noaer [PCIE] If the PCIEAER kernel config parameter is
1427 enabled, this kernel boot option can be used to
1428 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001429 nodomains [PCI] Disable support for multiple PCI
1430 root domains (aka PCI segments, in ACPI-speak).
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001431 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001432 Configuration
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001433 nomsi [MSI] If the PCI_MSI kernel config parameter is
1434 enabled, this kernel boot option can be used to
1435 disable the use of MSI interrupts system-wide.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001436 nosort [X86-32] Don't sort PCI devices according to
Randy Dunlapa9913042005-10-23 12:57:11 -07001437 order given by the PCI BIOS. This sorting is
1438 done to get a device order compatible with
1439 older kernels.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001440 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001441 routing table. These calls are known to be buggy
1442 on several machines and they hang the machine
1443 when used, but on other computers it's the only
1444 way to get the interrupt routing table. Try
1445 this option if the kernel is unable to allocate
1446 IRQs or discover secondary PCI buses on your
1447 motherboard.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001448 rom [X86-32] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001449 Use with caution as certain devices share
1450 address decoders between ROMs and other
1451 resources.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001452 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001453 assigned automatically to PCI devices. You can
1454 make the kernel exclude IRQs of your ISA cards
1455 this way.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001456 pirqaddr=0xAAAAA [X86-32] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001457 of the PIRQ table (normally generated
1458 by the BIOS) if it is outside the
1459 F0000h-100000h range.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001460 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001461 useful if the kernel is unable to find your
1462 secondary buses and you want to tell it
1463 explicitly which ones they are.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001464 assign-busses [X86-32] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001465 numbers ourselves, overriding
1466 whatever the firmware may have done.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001467 usepirqmask [X86-32] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001468 in the BIOS $PIR table. This is needed on
1469 some systems with broken BIOSes, notably
1470 some HP Pavilion N5400 and Omnibook XE3
1471 notebooks. This will have no effect if ACPI
1472 IRQ routing is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001473 noacpi [X86-32] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001474 or for PCI scanning.
Gary Hade62f420f2007-10-03 15:56:51 -07001475 use_crs [X86-32] Use _CRS for PCI resource
1476 allocation.
Randy Dunlapa9913042005-10-23 12:57:11 -07001477 routeirq Do IRQ routing for all PCI devices.
1478 This is normally done in pci_enable_device(),
1479 so this option is a temporary workaround
1480 for broken drivers that don't call it.
1481 firmware [ARM] Do not re-enumerate the bus but instead
1482 just use the configuration from the
1483 bootloader. This is currently used on
1484 IXP2000 systems where the bus has to be
1485 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001486 noearly [X86] Don't do any early type 1 scanning.
1487 This might help on some broken boards which
1488 machine check when some devices' config space
1489 is read. But various workarounds are disabled
1490 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001491 bfsort Sort PCI devices into breadth-first order.
1492 This sorting is done to get a device
1493 order compatible with older (<= 2.4) kernels.
1494 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001495 cbiosize=nn[KMG] The fixed amount of bus space which is
1496 reserved for the CardBus bridge's IO window.
1497 The default value is 256 bytes.
1498 cbmemsize=nn[KMG] The fixed amount of bus space which is
1499 reserved for the CardBus bridge's memory
1500 window. The default value is 64 megabytes.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001501
Linus Torvalds1da177e2005-04-16 15:20:36 -07001502 pcmv= [HW,PCMCIA] BadgePAD 4
1503
1504 pd. [PARIDE]
1505 See Documentation/paride.txt.
1506
1507 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1508 boot time.
1509 Format: { 0 | 1 }
1510 See arch/parisc/kernel/pdc_chassis.c
1511
1512 pf. [PARIDE]
1513 See Documentation/paride.txt.
1514
1515 pg. [PARIDE]
1516 See Documentation/paride.txt.
1517
1518 pirq= [SMP,APIC] Manual mp-table setup
1519 See Documentation/i386/IO-APIC.txt.
1520
1521 plip= [PPT,NET] Parallel port network link
1522 Format: { parport<nr> | timid | 0 }
1523 See also Documentation/parport.txt.
1524
1525 pnpacpi= [ACPI]
1526 { off }
1527
1528 pnpbios= [ISAPNP]
1529 { on | off | curr | res | no-curr | no-res }
1530
1531 pnp_reserve_irq=
1532 [ISAPNP] Exclude IRQs for the autoconfiguration
1533
1534 pnp_reserve_dma=
1535 [ISAPNP] Exclude DMAs for the autoconfiguration
1536
1537 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07001538 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001539
1540 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07001541 [ISAPNP] Exclude memory regions for the
1542 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001543 Ranges are in pairs (memory base and size).
1544
Ingo Molnar45807a12007-07-15 23:40:10 -07001545 print-fatal-signals=
1546 [KNL] debug: print fatal signals
1547 print-fatal-signals=1: print segfault info to
1548 the kernel console.
1549 default: off.
1550
Randy Dunlape84845c2007-07-15 23:40:25 -07001551 printk.time= Show timing data prefixed to each printk message line
1552 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1553
Linus Torvalds1da177e2005-04-16 15:20:36 -07001554 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07001555 Format: [schedule,]<number>
1556 Param: "schedule" - profile schedule points.
1557 Param: <number> - step/bucket size as a power of 2 for
1558 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02001559 Param: "sleep" - profile D-state sleeping (millisecs).
1560 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02001561 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001562
Randy Dunlapa9913042005-10-23 12:57:11 -07001563 processor.max_cstate= [HW,ACPI]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001564 Limit processor to maximum C-state
1565 max_cstate=9 overrides any DMI blacklist limit.
1566
Len Brown41c0d862005-12-28 12:43:51 -05001567 processor.nocst [HW,ACPI]
1568 Ignore the _CST method to determine C-states,
1569 instead using the legacy FADT method
1570
Linus Torvalds1da177e2005-04-16 15:20:36 -07001571 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1572 before loading.
1573 See Documentation/ramdisk.txt.
1574
Randy Dunlapa9913042005-10-23 12:57:11 -07001575 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1576 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001577 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1578 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07001579 psmouse.resetafter= [HW,MOUSE]
1580 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07001581 (0 = never).
1582 psmouse.resolution=
1583 [HW,MOUSE] Set desired mouse resolution, in dpi.
1584 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07001585 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001586 0 = disabled, 1 = enabled (default).
1587
1588 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
Randy Dunlapa9913042005-10-23 12:57:11 -07001589 Format:
1590 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001591
1592 pt. [PARIDE]
1593 See Documentation/paride.txt.
1594
Kay Sieversdc8c8582007-08-15 12:25:38 +02001595 pty.legacy_count=
1596 [KNL] Number of legacy pty's. Overwrites compiled-in
1597 default number.
1598
Randy Dunlap7d2c5022006-09-29 02:01:02 -07001599 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07001600
Linus Torvalds1da177e2005-04-16 15:20:36 -07001601 r128= [HW,DRM]
1602
1603 raid= [HW,RAID]
1604 See Documentation/md.txt.
1605
Randy Dunlapa9913042005-10-23 12:57:11 -07001606 ramdisk_blocksize= [RAM]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001607 See Documentation/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001608
Linus Torvalds1da177e2005-04-16 15:20:36 -07001609 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Linus Torvalds1da177e2005-04-16 15:20:36 -07001610 See Documentation/ramdisk.txt.
1611
Robert P. J. Day24aaef82008-02-03 15:20:26 +02001612 rcupdate.blimit= [KNL,BOOT]
1613 Set maximum number of finished RCU callbacks to process
1614 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08001615
Robert P. J. Day24aaef82008-02-03 15:20:26 +02001616 rcupdate.qhimark= [KNL,BOOT]
1617 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08001618 RCU callbacks over which batch limiting is disabled.
1619
Robert P. J. Day24aaef82008-02-03 15:20:26 +02001620 rcupdate.qlowmark= [KNL,BOOT]
1621 Set threshold of queued RCU callbacks below which
1622 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08001623
Olof Johanssonffdfc402005-09-06 15:17:19 -07001624 rdinit= [KNL]
1625 Format: <full_path>
1626 Run specified binary instead of /init from the ramdisk,
1627 used for early userspace startup. See initrd.
1628
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001629 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001630 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001631 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07001632
1633 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1634
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001635 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07001636 Format: nn[KMG]
1637 Reserves a hole at the top of the kernel virtual
1638 address space.
1639
Vivek Goyal7e962872006-09-27 01:50:44 -07001640 reset_devices [KNL] Force drivers to reset the underlying device
1641 during initialization.
1642
Randy Dunlapa9913042005-10-23 12:57:11 -07001643 resume= [SWSUSP]
1644 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08001646 resume_offset= [SWSUSP]
1647 Specify the offset from the beginning of the partition
1648 given by "resume=" at which the swap header is located,
1649 in <PAGE_SIZE> units (needed only for swap files).
1650 See Documentation/power/swsusp-and-swap-files.txt
1651
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08001652 retain_initrd [RAM] Keep initrd memory after extraction
1653
Linus Torvalds1da177e2005-04-16 15:20:36 -07001654 rhash_entries= [KNL,NET]
1655 Set number of hash buckets for route cache
1656
1657 riscom8= [HW,SERIAL]
1658 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1659
1660 ro [KNL] Mount root device read-only on boot
1661
1662 root= [KNL] Root filesystem
1663
1664 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1665 mount the root filesystem
1666
1667 rootflags= [KNL] Set root filesystem mount option string
1668
1669 rootfstype= [KNL] Set root filesystem type
1670
Pierre Ossmancc1ed752007-07-15 23:40:35 -07001671 rootwait [KNL] Wait (indefinitely) for root device to show up.
1672 Useful for devices that are detected asynchronously
1673 (e.g. USB and MMC devices).
1674
James Morris20510f22007-10-16 23:31:32 -07001675 root_plug.vendor_id=
1676 [ROOTPLUG] Override the default vendor ID
1677
1678 root_plug.product_id=
1679 [ROOTPLUG] Override the default product ID
1680
1681 root_plug.debug=
1682 [ROOTPLUG] Enable debugging output
1683
Linus Torvalds1da177e2005-04-16 15:20:36 -07001684 rw [KNL] Mount root device read-write on boot
1685
1686 S [KNL] Run init in single mode
1687
1688 sa1100ir [NET]
1689 See drivers/net/irda/sa1100_ir.c.
1690
Linus Torvalds1da177e2005-04-16 15:20:36 -07001691 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07001692
Linus Torvalds1da177e2005-04-16 15:20:36 -07001693 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1694 Format: <io>[,<timeout>[,<isapnp>]]
1695
1696 scsi_debug_*= [SCSI]
1697 See drivers/scsi/scsi_debug.c.
1698
1699 scsi_default_dev_flags=
1700 [SCSI] SCSI default device flags
1701 Format: <integer>
1702
1703 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1704 Format: <vendor>:<model>:<flags>
1705 (flags are integer value)
1706
Randy Dunlap6af66322007-11-14 16:52:25 -08001707 scsi_logging_level= [SCSI] a bit mask of logging levels
1708 See drivers/scsi/scsi_logging.h for bits. Also
1709 settable via sysctl at dev.scsi.logging_level
1710 (/proc/sys/dev/scsi/logging_level).
1711 There is also a nice 'scsi_logging_level' script in the
1712 S390-tools package, available for download at
1713 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
Linus Torvalds1da177e2005-04-16 15:20:36 -07001714
Matthew Wilcox3e082a92006-09-28 15:19:20 -06001715 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1716 discovered. async scans them in kernel threads,
1717 allowing boot to proceed. none ignores them, expecting
1718 user space to do the scan.
1719
Linus Torvalds1da177e2005-04-16 15:20:36 -07001720 selinux [SELINUX] Disable or enable SELinux at boot time.
1721 Format: { "0" | "1" }
1722 See security/selinux/Kconfig help text.
1723 0 -- disable.
1724 1 -- enable.
1725 Default value is set via kernel config option.
1726 If enabled at boot time, /selinux/disable can be used
1727 later to disable prior to initial policy load.
1728
James Morris4e5ab4c2006-06-09 00:33:33 -07001729 selinux_compat_net =
1730 [SELINUX] Set initial selinux_compat_net flag value.
Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001731 Format: { "0" | "1" }
1732 0 -- use new secmark-based packet controls
1733 1 -- use legacy packet controls
1734 Default value is 0 (preferred).
1735 Value can be changed at runtime via
1736 /selinux/compat_net.
James Morris4e5ab4c2006-06-09 00:33:33 -07001737
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001738 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001739
Linus Torvalds1da177e2005-04-16 15:20:36 -07001740 shapers= [NET]
1741 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07001742
Linus Torvalds1da177e2005-04-16 15:20:36 -07001743 sim710= [SCSI,HW]
1744 See header of drivers/scsi/sim710.c.
1745
1746 simeth= [IA-64]
1747 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07001748
Linus Torvalds1da177e2005-04-16 15:20:36 -07001749 slram= [HW,MTD]
1750
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001751 slub_debug[=options[,slabs]] [MM, SLUB]
1752 Enabling slub_debug allows one to determine the
1753 culprit if slab objects become corrupted. Enabling
1754 slub_debug can create guard zones around objects and
1755 may poison objects when not in use. Also tracks the
1756 last alloc / free. For more information see
1757 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07001758
1759 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001760 Determines the maximum allowed order for slabs.
1761 A high setting may cause OOMs due to memory
1762 fragmentation. For more information see
1763 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07001764
1765 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001766 The minimum number of objects per slab. SLUB will
1767 increase the slab order up to slub_max_order to
1768 generate a sufficiently large slab able to contain
1769 the number of objects indicated. The higher the number
1770 of objects the smaller the overhead of tracking slabs
1771 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07001772 For more information see Documentation/vm/slub.txt.
1773
1774 slub_min_order= [MM, SLUB]
1775 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001776 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07001777 For more information see Documentation/vm/slub.txt.
1778
1779 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001780 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07001781 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001782 allocs to different slabs. Debug options disable
1783 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07001784 For more information see Documentation/vm/slub.txt.
1785
Linus Torvalds1da177e2005-04-16 15:20:36 -07001786 smart2= [HW]
1787 Format: <io1>[,<io2>[,...,<io8>]]
1788
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001789 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001790 attempt to substitute SMP alternatives once at boot.
1791
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07001792 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1793 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1794 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1795 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1796 smsc-ircc2.ircc_irq= [HW] IRQ line
1797 smsc-ircc2.ircc_dma= [HW] DMA channel
1798 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1799 0: Toshiba Satellite 1800 (GP data pin select)
1800 1: Fast pin select (default)
1801 2: ATC IRMode
1802
Linus Torvalds1da177e2005-04-16 15:20:36 -07001803 snd-ad1816a= [HW,ALSA]
1804
1805 snd-ad1848= [HW,ALSA]
1806
1807 snd-ali5451= [HW,ALSA]
1808
1809 snd-als100= [HW,ALSA]
1810
1811 snd-als4000= [HW,ALSA]
1812
1813 snd-azt2320= [HW,ALSA]
1814
1815 snd-cmi8330= [HW,ALSA]
1816
1817 snd-cmipci= [HW,ALSA]
1818
1819 snd-cs4231= [HW,ALSA]
1820
1821 snd-cs4232= [HW,ALSA]
1822
1823 snd-cs4236= [HW,ALSA]
1824
1825 snd-cs4281= [HW,ALSA]
1826
1827 snd-cs46xx= [HW,ALSA]
1828
1829 snd-dt019x= [HW,ALSA]
1830
1831 snd-dummy= [HW,ALSA]
1832
1833 snd-emu10k1= [HW,ALSA]
1834
1835 snd-ens1370= [HW,ALSA]
1836
1837 snd-ens1371= [HW,ALSA]
1838
1839 snd-es968= [HW,ALSA]
1840
1841 snd-es1688= [HW,ALSA]
1842
1843 snd-es18xx= [HW,ALSA]
1844
1845 snd-es1938= [HW,ALSA]
1846
1847 snd-es1968= [HW,ALSA]
1848
1849 snd-fm801= [HW,ALSA]
1850
1851 snd-gusclassic= [HW,ALSA]
1852
1853 snd-gusextreme= [HW,ALSA]
1854
1855 snd-gusmax= [HW,ALSA]
1856
1857 snd-hdsp= [HW,ALSA]
1858
1859 snd-ice1712= [HW,ALSA]
1860
1861 snd-intel8x0= [HW,ALSA]
1862
1863 snd-interwave= [HW,ALSA]
1864
1865 snd-interwave-stb=
1866 [HW,ALSA]
1867
1868 snd-korg1212= [HW,ALSA]
1869
1870 snd-maestro3= [HW,ALSA]
1871
1872 snd-mpu401= [HW,ALSA]
1873
1874 snd-mtpav= [HW,ALSA]
1875
1876 snd-nm256= [HW,ALSA]
1877
1878 snd-opl3sa2= [HW,ALSA]
1879
1880 snd-opti92x-ad1848=
1881 [HW,ALSA]
1882
1883 snd-opti92x-cs4231=
1884 [HW,ALSA]
1885
1886 snd-opti93x= [HW,ALSA]
1887
1888 snd-pmac= [HW,ALSA]
1889
1890 snd-rme32= [HW,ALSA]
1891
1892 snd-rme96= [HW,ALSA]
1893
1894 snd-rme9652= [HW,ALSA]
1895
1896 snd-sb8= [HW,ALSA]
1897
1898 snd-sb16= [HW,ALSA]
1899
1900 snd-sbawe= [HW,ALSA]
1901
1902 snd-serial= [HW,ALSA]
1903
1904 snd-sgalaxy= [HW,ALSA]
1905
1906 snd-sonicvibes= [HW,ALSA]
1907
1908 snd-sun-amd7930=
1909 [HW,ALSA]
1910
1911 snd-sun-cs4231= [HW,ALSA]
1912
1913 snd-trident= [HW,ALSA]
1914
1915 snd-usb-audio= [HW,ALSA,USB]
1916
1917 snd-via82xx= [HW,ALSA]
1918
1919 snd-virmidi= [HW,ALSA]
1920
1921 snd-wavefront= [HW,ALSA]
1922
1923 snd-ymfpci= [HW,ALSA]
Randy Dunlapa9913042005-10-23 12:57:11 -07001924
Linus Torvalds1da177e2005-04-16 15:20:36 -07001925 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1926 See Documentation/sonypi.txt
1927
1928 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1929 See Documentation/specialix.txt.
1930
1931 spia_io_base= [HW,MTD]
1932 spia_fio_base=
1933 spia_pedr=
1934 spia_peddr=
1935
1936 sscape= [HW,OSS]
1937 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
Randy Dunlapa9913042005-10-23 12:57:11 -07001938
Linus Torvalds1da177e2005-04-16 15:20:36 -07001939 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1940 See Documentation/scsi/st.txt.
1941
Linus Torvalds1da177e2005-04-16 15:20:36 -07001942 sti= [PARISC,HW]
1943 Format: <num>
1944 Set the STI (builtin display/keyboard on the HP-PARISC
1945 machines) console (graphic card) which should be used
1946 as the initial boot-console.
1947 See also comment in drivers/video/console/sticore.c.
1948
1949 sti_font= [HW]
1950 See comment in drivers/video/console/sticore.c.
1951
1952 stifb= [HW]
1953 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1954
Greg Banks42a7fc42007-03-06 01:42:23 -08001955 sunrpc.pool_mode=
1956 [NFS]
1957 Control how the NFS server code allocates CPUs to
1958 service thread pools. Depending on how many NICs
1959 you have and where their interrupts are bound, this
1960 option will affect which CPUs will do NFS serving.
1961 Note: this parameter cannot be changed while the
1962 NFS server is running.
1963
1964 auto the server chooses an appropriate mode
1965 automatically using heuristics
1966 global a single global pool contains all CPUs
1967 percpu one pool for each CPU
1968 pernode one pool for each NUMA node (equivalent
1969 to global on non-NUMA machines)
1970
Linus Torvalds1da177e2005-04-16 15:20:36 -07001971 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07001972
Linus Torvalds1da177e2005-04-16 15:20:36 -07001973 switches= [HW,M68k]
1974
1975 sym53c416= [HW,SCSI]
1976 See header of drivers/scsi/sym53c416.c.
1977
Ingo Molnar5d6f6472006-12-13 00:34:36 -08001978 sysrq_always_enabled
1979 [KNL]
1980 Ignore sysrq setting - this boot parameter will
1981 neutralize any effect of /proc/sys/kernel/sysrq.
1982 Useful for debugging.
1983
Linus Torvalds1da177e2005-04-16 15:20:36 -07001984 t128= [HW,SCSI]
1985 See header of drivers/scsi/t128.c.
1986
1987 tdfx= [HW,DRM]
1988
1989 thash_entries= [KNL,NET]
1990 Set number of hash buckets for TCP connection
1991
Len Brownf8707ec2007-08-12 00:12:54 -04001992 thermal.act= [HW,ACPI]
1993 -1: disable all active trip points in all thermal zones
1994 <degrees C>: override all lowest active trip points
1995
Len Brownc52a7412007-08-14 15:49:32 -04001996 thermal.crt= [HW,ACPI]
1997 -1: disable all critical trip points in all thermal zones
1998 <degrees C>: lower all critical trip points
1999
Len Brownf5487142007-08-12 00:12:44 -04002000 thermal.nocrt= [HW,ACPI]
2001 Set to disable actions on ACPI thermal zone
2002 critical and hot trip points.
2003
Len Brown72b33ef2007-08-12 00:12:17 -04002004 thermal.off= [HW,ACPI]
2005 1: disable ACPI thermal control
2006
Len Browna70cdc52007-08-12 00:12:35 -04002007 thermal.psv= [HW,ACPI]
2008 -1: disable all passive trip points
2009 <degrees C>: override all passive trip points to this value
2010
Len Brown730ff342007-08-12 00:12:26 -04002011 thermal.tzp= [HW,ACPI]
2012 Specify global default ACPI thermal zone polling rate
2013 <deci-seconds>: poll all this frequency
2014 0: no polling (default)
2015
Linus Torvalds1da177e2005-04-16 15:20:36 -07002016 tipar.timeout= [HW,PPT]
2017 Set communications timeout in tenths of a second
2018 (default 15).
2019
2020 tipar.delay= [HW,PPT]
2021 Set inter-bit delay in microseconds (default 10).
2022
Linus Torvalds1da177e2005-04-16 15:20:36 -07002023 tmscsim= [HW,SCSI]
2024 See comment before function dc390_setup() in
2025 drivers/scsi/tmscsim.c.
2026
2027 tp720= [HW,PS2]
2028
2029 trix= [HW,OSS] MediaTrix AudioTrix Pro
Randy Dunlapa9913042005-10-23 12:57:11 -07002030 Format:
2031 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2032
Randy Dunlapa9913042005-10-23 12:57:11 -07002033 turbografx.map[2|3]= [HW,JOY]
2034 TurboGraFX parallel port interface
2035 Format:
2036 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002037 See also Documentation/input/joystick-parport.txt
2038
2039 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2040 See header of drivers/scsi/u14-34f.c.
2041
2042 uart401= [HW,OSS]
2043 Format: <io>,<irq>
2044
2045 uart6850= [HW,OSS]
2046 Format: <io>,<irq>
2047
Alan Stern5f8364b2006-12-05 16:29:55 -05002048 uhci-hcd.ignore_oc=
2049 [USB] Ignore overcurrent events (default N).
2050 Some badly-designed motherboards generate lots of
2051 bogus events, for ports that aren't wired to
2052 anything. Set this parameter to avoid log spamming.
2053 Note that genuine overcurrent events won't be
2054 reported either.
2055
Alan Sternb5e795f2007-02-20 15:00:53 -05002056 usbcore.autosuspend=
2057 [USB] The autosuspend time delay (in seconds) used
2058 for newly-detected USB devices (default 2). This
2059 is the time required before an idle device will be
2060 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002061 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002062
Linus Torvalds1da177e2005-04-16 15:20:36 -07002063 usbhid.mousepoll=
2064 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002065
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002066 vdso= [X86-32,SH,x86-64]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002067 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002068 vdso=1: enable VDSO (default)
2069 vdso=0: disable VDSO mapping
2070
Roland McGrathaf65d642008-01-30 13:30:43 +01002071 vdso32= [X86-32,X86-64]
2072 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2073 vdso32=1: enable 32-bit VDSO (default)
2074 vdso32=0: disable 32-bit VDSO mapping
2075
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002076 vector= [IA-64,SMP]
2077 vector=percpu: enable percpu vector domain
2078
Linus Torvalds1da177e2005-04-16 15:20:36 -07002079 video= [FB] Frame buffer configuration
2080 See Documentation/fb/modedb.txt.
2081
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002082 vga= [BOOT,X86-32] Select a particular video mode
Randy Dunlapa9913042005-10-23 12:57:11 -07002083 See Documentation/i386/boot.txt and
2084 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002085 Use vga=ask for menu.
2086 This is actually a boot loader parameter; the value is
2087 passed to the kernel using a special protocol.
2088
Randy Dunlapa9913042005-10-23 12:57:11 -07002089 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002090 size of <nn>. This can be used to increase the
2091 minimum size (128MB on x86). It can also be used to
2092 decrease the size and leave more room for directly
2093 mapped kernel RAM.
2094
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002095 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2096 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002097
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002098 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2099 Format: <command>
2100
2101 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2102 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002103
Linus Torvalds1da177e2005-04-16 15:20:36 -07002104 waveartist= [HW,OSS]
2105 Format: <io>,<irq>,<dma>,<dma2>
Randy Dunlapa9913042005-10-23 12:57:11 -07002106
Linus Torvalds1da177e2005-04-16 15:20:36 -07002107 wd33c93= [HW,SCSI]
2108 See header of drivers/scsi/wd33c93.c.
2109
2110 wd7000= [HW,SCSI]
2111 See header of drivers/scsi/wd7000.c.
2112
2113 wdt= [WDT] Watchdog
Gabriel C8dfe9c22007-08-10 13:01:00 -07002114 See Documentation/watchdog/wdt.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002115
2116 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2117 xd_geo= See header of drivers/block/xd.c.
2118
2119 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002120 Format:
2121 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002122
Andi Kleena62eaf12006-02-16 23:41:58 +01002123 norandmaps Don't use address space randomization
2124 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2125
Randy Dunlapa9913042005-10-23 12:57:11 -07002126______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002127
2128TODO:
2129
2130 Add documentation for ALSA options.
2131 Add more DRM drivers.