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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
Pavel Machekb552da82008-03-19 15:58:11 +0100815 iommu= [x86]
816 off
817 force
818 noforce
819 biomerge
820 panic
821 nopanic
822 merge
823 nomerge
824 forcesac
825 soft
826
827
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700828 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
829 off
830 Disable intel iommu driver.
831 igfx_off [Default Off]
832 By default, gfx is mapped as normal device. If a gfx
833 device has a dedicated DMAR unit, the DMAR unit is
834 bypassed by not enabling DMAR with this option. In
835 this case, gfx device will use physical address for
836 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -0700837 forcedac [x86_64]
838 With this option iommu will not optimize to look
839 for io virtual address below 32 bit forcing dual
840 address cycle on pci bus for cards supporting greater
841 than 32 bit addressing. The default is to look
842 for translation below 32 bit and if not available
843 then look in the higher range.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -0700844
Rene Hermanb02aae92008-01-30 13:30:05 +0100845 io_delay= [X86-32,X86-64] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100846 0x80
847 Standard port 0x80 based delay
848 0xed
849 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +0100850 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +0100851 Simple two microseconds delay
852 none
853 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +0100854
Linus Torvalds1da177e2005-04-16 15:20:36 -0700855 io7= [HW] IO7 for Marvel based alpha systems
856 See comment before marvel_specify_io7 in
857 arch/alpha/kernel/core_marvel.c.
858
859 ip= [IP_PNP]
J. Bruce Fields6ded55d2008-04-07 15:59:03 -0400860 See Documentation/filesystems/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700861
862 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700863 See comment before ip2_setup() in
864 drivers/char/ip2/ip2base.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700865
866 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
867 See header of drivers/scsi/ips.c.
868
Simon Horman72c4a132006-09-13 19:57:18 -0700869 ports= [IP_VS_FTP] IPVS ftp helper module
870 Default is 21.
871 Up to 8 (IP_VS_APP_MAX_PORTS) ports
872 may be specified.
873 Format: <port>,<port>....
874
Alan Cox200803d2005-06-28 20:45:18 -0700875 irqfixup [HW]
876 When an interrupt is not handled search all handlers
877 for it. Intended to get systems with badly broken
878 firmware running.
879
880 irqpoll [HW]
881 When an interrupt is not handled search all handlers
882 for it. Also check all handlers each timer
883 interrupt. Intended to get systems with badly broken
884 firmware running.
885
Linus Torvalds1da177e2005-04-16 15:20:36 -0700886 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -0700887 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700888
889 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Derek Fults22f2e282006-12-06 20:37:11 -0800890 Format:
891 <cpu number>,...,<cpu number>
892 or
893 <cpu number>-<cpu number> (must be a positive range in ascending order)
894 or a mixture
895 <cpu number>,...,<cpu number>-<cpu number>
Linus Torvalds1da177e2005-04-16 15:20:36 -0700896 This option can be used to specify one or more CPUs
897 to isolate from the general SMP balancing and scheduling
898 algorithms. The only way to move a process onto or off
899 an "isolated" CPU is via the CPU affinity syscalls.
900 <cpu number> begins at 0 and the maximum value is
901 "number of CPUs in system - 1".
902
903 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -0700904 alternative -- manually setting the CPU mask of all
905 tasks in the system -- can cause problems and
906 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700907
Randy Dunlapa9913042005-10-23 12:57:11 -0700908 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700909
910 js= [HW,JOY] Analog joystick
911 See Documentation/input/joystick.txt.
912
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700913 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -0700914 specifies the amount of memory usable by the kernel
915 for non-movable allocations. The requested amount is
916 spread evenly throughout all nodes in the system. The
917 remaining memory in each node is used for Movable
918 pages. In the event, a node is too small to have both
919 kernelcore and Movable pages, kernelcore pages will
920 take priority and other nodes will have a larger number
921 of kernelcore pages. The Movable zone is used for the
922 allocation of pages that may be reclaimed or moved
923 by the page migration subsystem. This means that
924 HugeTLB pages may not be allocated from this zone.
925 Note that allocations like PTEs-from-HighMem still
926 use the HighMem zone if it exists, and the Normal
927 zone if it does not.
928
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700929 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
Mel Gorman7e63efe2007-07-17 04:03:15 -0700930 is similar to kernelcore except it specifies the
931 amount of memory used for migratable allocations.
932 If both kernelcore and movablecore is specified,
933 then kernelcore will be at *least* the specified
934 value but may be more. If movablecore on its own
935 is specified, the administrator must be careful
936 that the amount of memory usable for all allocations
937 is not too small.
938
Linus Torvalds1da177e2005-04-16 15:20:36 -0700939 keepinitrd [HW,ARM]
940
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700941 kstack=N [X86-32,X86-64] Print N words from the kernel stack
Linus Torvalds1da177e2005-04-16 15:20:36 -0700942 in oops dumps.
943
944 l2cr= [PPC]
945
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700946 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -0700947 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700948
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700949 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
Thomas Gleixnere585bef2007-03-23 16:08:01 +0100950 C2 power state.
951
FD Camifcb71f62008-01-06 19:08:56 +0100952 libata.dma= [LIBATA] DMA control
953 libata.dma=0 Disable all PATA and SATA DMA
954 libata.dma=1 PATA and SATA Disk DMA only
955 libata.dma=2 ATAPI (CDROM) DMA only
956 libata.dma=4 Compact Flash DMA only
957 Combinations also work, so libata.dma=3 enables DMA
958 for disks and CDROMs, but not CFs.
959
Dave Jones78e70c22007-09-27 11:50:13 -0400960 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
961 when set.
962 Format: <int>
963
Tejun Heo33267322008-02-13 09:15:09 +0900964 libata.force= [LIBATA] Force configurations. The format is comma
965 separated list of "[ID:]VAL" where ID is
966 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
967 matching port, link or device. Basically, it matches
968 the ATA ID string printed on console by libata. If
969 the whole ID part is omitted, the last PORT and DEVICE
970 values are used. If ID hasn't been specified yet, the
971 configuration applies to all ports, links and devices.
972
973 If only DEVICE is omitted, the parameter applies to
974 the port and all links and devices behind it. DEVICE
975 number of 0 either selects the first device or the
976 first fan-out link behind PMP device. It does not
977 select the host link. DEVICE number of 15 selects the
978 host link and device attached to it.
979
980 The VAL specifies the configuration to force. As long
981 as there's no ambiguity shortcut notation is allowed.
982 For example, both 1.5 and 1.5G would work for 1.5Gbps.
983 The following configurations can be forced.
984
985 * Cable type: 40c, 80c, short40c, unk, ign or sata.
986 Any ID with matching PORT is used.
987
988 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
989
990 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
991 udma[/][16,25,33,44,66,100,133] notation is also
992 allowed.
993
994 * [no]ncq: Turn on or off NCQ.
995
996 If there are multiple matching configurations changing
997 the same attribute, the last one is used.
998
Linus Torvalds1da177e2005-04-16 15:20:36 -0700999 load_ramdisk= [RAM] List of ramdisks to load from floppy
1000 See Documentation/ramdisk.txt.
1001
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001002 lockd.nlm_grace_period=P [NFS] Assign grace period.
1003 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001004
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001005 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1006 Format: <integer>
1007
1008 lockd.nlm_timeout=T [NFS] Assign timeout value.
1009 Format: <integer>
1010
1011 lockd.nlm_udpport=M [NFS] Assign UDP port.
1012 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001013
1014 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1015 Format: <irq>
1016
1017 loglevel= All Kernel Messages with a loglevel smaller than the
1018 console loglevel will be printed to the console. It can
1019 also be changed with klogd or other programs. The
1020 loglevels are defined as follows:
1021
1022 0 (KERN_EMERG) system is unusable
1023 1 (KERN_ALERT) action must be taken immediately
1024 2 (KERN_CRIT) critical conditions
1025 3 (KERN_ERR) error conditions
1026 4 (KERN_WARNING) warning conditions
1027 5 (KERN_NOTICE) normal but significant condition
1028 6 (KERN_INFO) informational
1029 7 (KERN_DEBUG) debug-level messages
1030
1031 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
Randy Dunlapa9913042005-10-23 12:57:11 -07001032 Format: { n | nk | nM }
1033 n must be a power of two. The default size
1034 is set in the kernel config file.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035
Randy Dunlapaccaa242007-10-16 01:29:37 -07001036 logo.nologo [FB] Disables display of the built-in Linux logo.
1037 This may be used to provide more screen space for
1038 kernel log messages and is useful when debugging
1039 kernel boot problems.
1040
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041 lp=0 [LP] Specify parallel ports to use, e.g,
1042 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1043 lp=reset first parallel port). 'lp=0' disables the
1044 lp=auto printer driver. 'lp=reset' (which can be
1045 specified in addition to the ports) causes
1046 attached printers to be reset. Using
1047 lp=port1,port2,... specifies the parallel ports
1048 to associate lp devices with, starting with
1049 lp0. A port specification may be 'none' to skip
1050 that lp device, or a parport name such as
1051 'parport0'. Specifying 'lp=auto' instead of a
1052 port specification list means that device IDs
1053 from each port should be examined, to see if
1054 an IEEE 1284-compliant printer is attached; if
1055 so, the driver will manage that printer.
1056 See also header of drivers/char/lp.c.
1057
1058 lpj=n [KNL]
1059 Sets loops_per_jiffy to given constant, thus avoiding
1060 time-consuming boot-time autodetection (up to 250 ms per
1061 CPU). 0 enables autodetection (default). To determine
1062 the correct value for your kernel, boot with normal
1063 autodetection and see what value is printed. Note that
1064 on SMP systems the preset will be applied to all CPUs,
1065 which is likely to cause problems if your CPUs need
1066 significantly divergent settings. An incorrect value
1067 will cause delays in the kernel to be wrong, leading to
1068 unpredictable I/O errors and other breakage. Although
1069 unlikely, in the extreme case this might damage your
1070 hardware.
1071
1072 ltpc= [NET]
1073 Format: <io>,<irq>,<dma>
1074
Randy Dunlapa9913042005-10-23 12:57:11 -07001075 mac5380= [HW,SCSI] Format:
1076 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077
Randy Dunlapa9913042005-10-23 12:57:11 -07001078 mac53c9x= [HW,SCSI] Format:
1079 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001080
Randy Dunlapa9913042005-10-23 12:57:11 -07001081 machvec= [IA64] Force the use of a particular machine-vector
1082 (machvec) in a generic kernel.
1083 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07001084
Randy Dunlapa9913042005-10-23 12:57:11 -07001085 max_loop= [LOOP] Maximum number of loopback devices that can
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086 be mounted
1087 Format: <1-256>
1088
1089 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Len Brown61ec7562007-08-16 03:34:22 -04001090 should make use of. maxcpus=n : n >= 0 limits the
1091 kernel to using 'n' processors. n=0 is a special case,
1092 it is equivalent to "nosmp", which also disables
1093 the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001094
Bob Picco2b2c3752005-06-29 18:00:00 -07001095 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1096 equal to this physical address is ignored.
1097
Randy Dunlapa9913042005-10-23 12:57:11 -07001098 max_luns= [SCSI] Maximum number of LUNs to probe.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001099 Should be between 1 and 2^32-1.
1100
1101 max_report_luns=
Randy Dunlapa9913042005-10-23 12:57:11 -07001102 [SCSI] Maximum number of LUNs received.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103 Should be between 1 and 16384.
1104
Linus Torvalds1da177e2005-04-16 15:20:36 -07001105 mcatest= [IA-64]
1106
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001107 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07001108
Andi Kleen909dd322007-10-17 18:04:38 +02001109 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1110
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111 md= [HW] RAID subsystems devices and level
1112 See Documentation/md.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001113
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114 mdacon= [MDA]
1115 Format: <first>,<last>
1116 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07001117
Linus Torvalds1da177e2005-04-16 15:20:36 -07001118 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1119 Amount of memory to be used when the kernel is not able
1120 to see the whole system memory or for test.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001121 [X86-32] Use together with memmap= to avoid physical
Linus Torvalds1da177e2005-04-16 15:20:36 -07001122 address space collisions. Without memmap= PCI devices
1123 could be placed at addresses belonging to unused RAM.
1124
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001125 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07001126 memory.
1127
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001128 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07001129 E820 memory map, as specified by the user.
1130 Such memmap=exactmap lines can be constructed based on
1131 BIOS output or other requirements. See the memmap=nn@ss
1132 option description.
1133
1134 memmap=nn[KMG]@ss[KMG]
1135 [KNL] Force usage of a specific region of memory
1136 Region of memory to be used, from ss to ss+nn.
1137
1138 memmap=nn[KMG]#ss[KMG]
1139 [KNL,ACPI] Mark specific memory as ACPI data.
1140 Region of memory to be used, from ss to ss+nn.
1141
1142 memmap=nn[KMG]$ss[KMG]
1143 [KNL,ACPI] Mark specific memory as reserved.
1144 Region of memory to be used, from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07001145 Example: Exclude memory from 0x18690000-0x1869ffff
1146 memmap=64K$0x18690000
1147 or
1148 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07001149
Yinghai Luc64df702008-03-21 18:56:19 -07001150 memtest= [KNL,X86_64] Enable memtest
1151 Format: <integer>
1152 range: 0,4 : pattern number
1153 default : 0 <disable>
1154
Linus Torvalds1da177e2005-04-16 15:20:36 -07001155 meye.*= [HW] Set MotionEye Camera parameters
1156 See Documentation/video4linux/meye.txt.
1157
Andres Salomon8f368812007-10-12 23:04:06 +02001158 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1159 Multi-Function General Purpose Timers on AMD Geode
1160 platforms.
1161
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01001162 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1163 the BIOS has incorrectly applied a workaround. TinyBIOS
1164 version 0.98 is known to be affected, 0.99 fixes the
1165 problem by letting the user disable the workaround.
1166
Linus Torvalds1da177e2005-04-16 15:20:36 -07001167 mga= [HW,DRM]
1168
1169 mousedev.tap_time=
1170 [MOUSE] Maximum time between finger touching and
1171 leaving touchpad surface for touch to be considered
1172 a tap and be reported as a left button click (for
1173 touchpads working in absolute mode only).
1174 Format: <msecs>
1175 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1176 reporting absolute coordinates, such as tablets
1177 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1178 reporting absolute coordinates, such as tablets
1179
1180 mpu401= [HW,OSS]
1181 Format: <io>,<irq>
1182
1183 MTD_Partition= [MTD]
1184 Format: <name>,<region-number>,<size>,<offset>
1185
Randy Dunlapa9913042005-10-23 12:57:11 -07001186 MTD_Region= [MTD] Format:
1187 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001188
1189 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07001190 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001191
1192 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07001193 [HW] Make the MicroTouch USB driver use raw coordinates
1194 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07001195
1196 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1197
1198 NCR_D700= [HW,SCSI]
1199 See header of drivers/scsi/NCR_D700.c.
1200
1201 ncr5380= [HW,SCSI]
1202
1203 ncr53c400= [HW,SCSI]
1204
1205 ncr53c400a= [HW,SCSI]
1206
1207 ncr53c406a= [HW,SCSI]
1208
1209 ncr53c8xx= [HW,SCSI]
1210
1211 netdev= [NET] Network devices parameters
1212 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1213 Note that mem_start is often overloaded to mean
1214 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07001215 This usage is only documented in each driver source
1216 file if at all.
1217
Linus Torvalds1da177e2005-04-16 15:20:36 -07001218 nfsaddrs= [NFS]
J. Bruce Fields6ded55d2008-04-07 15:59:03 -04001219 See Documentation/filesystems/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001220
1221 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fields6ded55d2008-04-07 15:59:03 -04001222 See Documentation/filesystems/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001223
Trond Myklebusta72b4422006-01-03 09:55:41 +01001224 nfs.callback_tcpport=
1225 [NFS] set the TCP port on which the NFSv4 callback
1226 channel should listen.
1227
Trond Myklebust58df0952006-01-03 09:55:57 +01001228 nfs.idmap_cache_timeout=
1229 [NFS] set the maximum lifetime for idmapper cache
1230 entries.
1231
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04001232 nfs.enable_ino64=
1233 [NFS] enable 64-bit inode numbers.
1234 If zero, the NFS client will fake up a 32-bit inode
1235 number for the readdir() and stat() syscalls instead
1236 of returning the full 64-bit number.
1237 The default is to return 64-bit inode numbers.
1238
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02001239 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1240 when a NMI is triggered.
1241 Format: [state][,regs][,debounce][,die]
1242
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001243 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
Linus Torvalds1da177e2005-04-16 15:20:36 -07001244
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001245 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07001246 emulation library even if a 387 maths coprocessor
1247 is present.
1248
Christoph Lameterc1aee212007-05-31 00:40:47 -07001249 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1250 caches in the slab allocator. Saves per-node memory,
1251 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08001252
Randy Dunlapa9913042005-10-23 12:57:11 -07001253 noalign [KNL,ARM]
1254
Linus Torvalds1da177e2005-04-16 15:20:36 -07001255 noapic [SMP,APIC] Tells the kernel to not make use of any
1256 IOAPICs that may be present in the system.
1257
Linus Torvalds1da177e2005-04-16 15:20:36 -07001258 nobats [PPC] Do not use BATs for mapping kernel lowmem
1259 on "Classic" PPC cores.
1260
1261 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001262
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07001263 nodelayacct [KNL] Disable per-task delay accounting
1264
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1266
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01001267 noefi [X86-32,X86-64] Disable EFI runtime services support.
1268
Linus Torvalds1da177e2005-04-16 15:20:36 -07001269 noexec [IA-64]
1270
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001271 noexec [X86-32,X86-64]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001272 noexec=on: enable non-executable mappings (default)
1273 noexec=off: disable nn-executable mappings
1274
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001275 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08001276 register save and restore. The kernel will only save
1277 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001278
Andi Kleen191679f2008-01-30 13:33:21 +01001279 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1280
Linus Torvalds1da177e2005-04-16 15:20:36 -07001281 nohlt [BUGS=ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001282
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001283 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
Linus Torvalds1da177e2005-04-16 15:20:36 -07001284 instruction doesn't work correctly and not to
1285 use it.
1286
1287 nohalt [IA-64] Tells the kernel not to use the power saving
1288 function PAL_HALT_LIGHT when idle. This increases
1289 power-consumption. On the positive side, it reduces
1290 interrupt wake-up latency, which may improve performance
1291 in certain environments such as networked servers or
1292 real-time systems.
1293
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08001294 nohz= [KNL] Boottime enable/disable dynamic ticks
1295 Valid arguments: on, off
1296 Default: on
1297
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001298 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
Zachary Amsden8542b202006-12-07 02:14:09 +01001299
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001300 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001301 disable unhandled interrupt sources.
1302
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001303 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01001304 broken timer IRQ sources.
1305
Linus Torvalds1da177e2005-04-16 15:20:36 -07001306 noisapnp [ISAPNP] Disables ISA PnP code.
1307
1308 noinitrd [RAM] Tells the kernel not to load any configured
1309 initial RAM disk.
1310
1311 nointroute [IA-64]
1312
Tony Luck0aa366f2007-07-20 11:22:30 -07001313 nojitter [IA64] Disables jitter checking for ITC timers.
1314
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001315 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001316
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001317 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08001318
Linus Torvalds1da177e2005-04-16 15:20:36 -07001319 noltlbs [PPC] Do not use large page/tlb entries for kernel
1320 lowmem mapping on PPC40x.
1321
Horms312f1f02006-02-22 09:57:55 +09001322 nomca [IA-64] Disable machine check abort handling
1323
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001324 nomce [X86-32] Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02001325
Andres Salomon83d73842007-10-12 23:04:06 +02001326 nomfgpt [X86-32] Disable Multi-Function General Purpose
1327 Timer usage (for AMD Geode machines).
1328
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001329 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02001330
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001331 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001332 with UP alternatives
1333
Linus Torvalds1da177e2005-04-16 15:20:36 -07001334 noresidual [PPC] Don't use residual data on PReP machines.
1335
Randy Dunlapa9913042005-10-23 12:57:11 -07001336 noresume [SWSUSP] Disables resume and restores original swap
1337 space.
1338
Linus Torvalds1da177e2005-04-16 15:20:36 -07001339 no-scroll [VGA] Disables scrollback.
1340 This is required for the Braillex ib80-piezo Braille
1341 reader made by F.H. Papenmeier (Germany).
1342
1343 nosbagart [IA-64]
1344
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001345 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08001346
Len Brown61ec7562007-08-16 03:34:22 -04001347 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1348 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349
Dave Jones97842212007-07-15 23:41:05 -07001350 nosoftlockup [KNL] Disable the soft-lockup detector.
1351
Linus Torvalds1da177e2005-04-16 15:20:36 -07001352 nosync [HW,M68K] Disables sync negotiation for all devices.
1353
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001354 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07001355
1356 nousb [USB] Disable the USB subsystem
1357
1358 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07001359
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07001360 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1361 one of ['zone', 'node', 'default'] can be specified
1362 This can be set from sysctl after boot.
1363 See Documentation/sysctl/vm.txt for details.
1364
Dave Jonesa61c2d72006-01-07 23:18:19 +00001365 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1366
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367 opl3= [HW,OSS]
1368 Format: <io>
1369
Linus Torvalds1da177e2005-04-16 15:20:36 -07001370 oprofile.timer= [HW]
1371 Use timer interrupt instead of performance counters
1372
Linus Torvalds1da177e2005-04-16 15:20:36 -07001373 osst= [HW,SCSI] SCSI Tape Driver
1374 Format: <buffer_size>,<write_threshold>
1375 See also Documentation/scsi/st.txt.
1376
1377 panic= [KNL] Kernel behaviour on panic
1378 Format: <timeout>
1379
1380 parkbd.port= [HW] Parallel port number the keyboard adapter is
1381 connected to, default is 0.
1382 Format: <parport#>
1383 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1384 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07001385 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001386
Randy Dunlapa9913042005-10-23 12:57:11 -07001387 parport= [HW,PPT] Specify parallel ports. 0 disables.
1388 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1389 Use 'auto' to force the driver to use any
1390 IRQ/DMA settings detected (the default is to
1391 ignore detected IRQ/DMA settings because of
1392 possible conflicts). You can specify the base
1393 address, IRQ, and DMA settings; IRQ and DMA
1394 should be numbers, or 'auto' (for using detected
1395 settings on that particular port), or 'nofifo'
1396 (to avoid using a FIFO even if it is detected).
1397 Parallel ports are assigned in the order they
1398 are specified on the command line, starting
1399 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001400
Randy Dunlapa9913042005-10-23 12:57:11 -07001401 parport_init_mode= [HW,PPT]
1402 Configure VIA parallel port to operate in
1403 a specific mode. This is necessary on Pegasos
1404 computer where firmware has no options for setting
1405 up parallel port mode and sets it to spp.
1406 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407 Format: [spp|ps2|epp|ecp|ecpepp]
1408
Randy Dunlapa9913042005-10-23 12:57:11 -07001409 pas2= [HW,OSS] Format:
1410 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1411
Linus Torvalds1da177e2005-04-16 15:20:36 -07001412 pas16= [HW,SCSI]
1413 See header of drivers/scsi/pas16.c.
1414
Andrew Mortondd287792006-03-23 03:00:57 -08001415 pause_on_oops=
1416 Halt all CPUs after the first oops has been printed for
1417 the specified number of seconds. This is to be used if
1418 your oopses keep scrolling off the screen.
1419
Linus Torvalds1da177e2005-04-16 15:20:36 -07001420 pcbit= [HW,ISDN]
1421
1422 pcd. [PARIDE]
1423 See header of drivers/block/paride/pcd.c.
1424 See also Documentation/paride.txt.
1425
Randy Dunlapa9913042005-10-23 12:57:11 -07001426 pci=option[,option...] [PCI] various PCI subsystem options:
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001427 off [X86-32] don't probe for the PCI bus
1428 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07001429 the hardware directly. Use this if your machine
1430 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001431 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07001432 hardware access methods are allowed. Use this
1433 if you experience crashes upon bootup and you
1434 suspect they are caused by the BIOS.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001435 conf1 [X86-32] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001436 Mechanism 1.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001437 conf2 [X86-32] Force use of PCI Configuration
Randy Dunlapa9913042005-10-23 12:57:11 -07001438 Mechanism 2.
Randy Dunlap7f785762007-10-05 13:17:58 -07001439 noaer [PCIE] If the PCIEAER kernel config parameter is
1440 enabled, this kernel boot option can be used to
1441 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04001442 nodomains [PCI] Disable support for multiple PCI
1443 root domains (aka PCI segments, in ACPI-speak).
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001444 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08001445 Configuration
Matthew Wilcox309e57d2006-03-05 22:33:34 -07001446 nomsi [MSI] If the PCI_MSI kernel config parameter is
1447 enabled, this kernel boot option can be used to
1448 disable the use of MSI interrupts system-wide.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001449 nosort [X86-32] Don't sort PCI devices according to
Randy Dunlapa9913042005-10-23 12:57:11 -07001450 order given by the PCI BIOS. This sorting is
1451 done to get a device order compatible with
1452 older kernels.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001453 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07001454 routing table. These calls are known to be buggy
1455 on several machines and they hang the machine
1456 when used, but on other computers it's the only
1457 way to get the interrupt routing table. Try
1458 this option if the kernel is unable to allocate
1459 IRQs or discover secondary PCI buses on your
1460 motherboard.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001461 rom [X86-32] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07001462 Use with caution as certain devices share
1463 address decoders between ROMs and other
1464 resources.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001465 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07001466 assigned automatically to PCI devices. You can
1467 make the kernel exclude IRQs of your ISA cards
1468 this way.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001469 pirqaddr=0xAAAAA [X86-32] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07001470 of the PIRQ table (normally generated
1471 by the BIOS) if it is outside the
1472 F0000h-100000h range.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001473 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07001474 useful if the kernel is unable to find your
1475 secondary buses and you want to tell it
1476 explicitly which ones they are.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001477 assign-busses [X86-32] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07001478 numbers ourselves, overriding
1479 whatever the firmware may have done.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001480 usepirqmask [X86-32] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07001481 in the BIOS $PIR table. This is needed on
1482 some systems with broken BIOSes, notably
1483 some HP Pavilion N5400 and Omnibook XE3
1484 notebooks. This will have no effect if ACPI
1485 IRQ routing is enabled.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001486 noacpi [X86-32] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07001487 or for PCI scanning.
Gary Hade62f420f2007-10-03 15:56:51 -07001488 use_crs [X86-32] Use _CRS for PCI resource
1489 allocation.
Randy Dunlapa9913042005-10-23 12:57:11 -07001490 routeirq Do IRQ routing for all PCI devices.
1491 This is normally done in pci_enable_device(),
1492 so this option is a temporary workaround
1493 for broken drivers that don't call it.
1494 firmware [ARM] Do not re-enumerate the bus but instead
1495 just use the configuration from the
1496 bootloader. This is currently used on
1497 IXP2000 systems where the bus has to be
1498 configured a certain way for adjunct CPUs.
Andi Kleen0637a702006-09-26 10:52:41 +02001499 noearly [X86] Don't do any early type 1 scanning.
1500 This might help on some broken boards which
1501 machine check when some devices' config space
1502 is read. But various workarounds are disabled
1503 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001504 bfsort Sort PCI devices into breadth-first order.
1505 This sorting is done to get a device
1506 order compatible with older (<= 2.4) kernels.
1507 nobfsort Don't sort PCI devices into breadth-first order.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08001508 cbiosize=nn[KMG] The fixed amount of bus space which is
1509 reserved for the CardBus bridge's IO window.
1510 The default value is 256 bytes.
1511 cbmemsize=nn[KMG] The fixed amount of bus space which is
1512 reserved for the CardBus bridge's memory
1513 window. The default value is 64 megabytes.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05001514
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515 pcmv= [HW,PCMCIA] BadgePAD 4
1516
1517 pd. [PARIDE]
1518 See Documentation/paride.txt.
1519
1520 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1521 boot time.
1522 Format: { 0 | 1 }
1523 See arch/parisc/kernel/pdc_chassis.c
1524
1525 pf. [PARIDE]
1526 See Documentation/paride.txt.
1527
1528 pg. [PARIDE]
1529 See Documentation/paride.txt.
1530
1531 pirq= [SMP,APIC] Manual mp-table setup
1532 See Documentation/i386/IO-APIC.txt.
1533
1534 plip= [PPT,NET] Parallel port network link
1535 Format: { parport<nr> | timid | 0 }
1536 See also Documentation/parport.txt.
1537
1538 pnpacpi= [ACPI]
1539 { off }
1540
1541 pnpbios= [ISAPNP]
1542 { on | off | curr | res | no-curr | no-res }
1543
1544 pnp_reserve_irq=
1545 [ISAPNP] Exclude IRQs for the autoconfiguration
1546
1547 pnp_reserve_dma=
1548 [ISAPNP] Exclude DMAs for the autoconfiguration
1549
1550 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07001551 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552
1553 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07001554 [ISAPNP] Exclude memory regions for the
1555 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001556 Ranges are in pairs (memory base and size).
1557
Ingo Molnar45807a12007-07-15 23:40:10 -07001558 print-fatal-signals=
1559 [KNL] debug: print fatal signals
1560 print-fatal-signals=1: print segfault info to
1561 the kernel console.
1562 default: off.
1563
Randy Dunlape84845c2007-07-15 23:40:25 -07001564 printk.time= Show timing data prefixed to each printk message line
1565 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1566
Linus Torvalds1da177e2005-04-16 15:20:36 -07001567 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07001568 Format: [schedule,]<number>
1569 Param: "schedule" - profile schedule points.
1570 Param: <number> - step/bucket size as a power of 2 for
1571 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02001572 Param: "sleep" - profile D-state sleeping (millisecs).
1573 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02001574 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001575
Randy Dunlapa9913042005-10-23 12:57:11 -07001576 processor.max_cstate= [HW,ACPI]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001577 Limit processor to maximum C-state
1578 max_cstate=9 overrides any DMI blacklist limit.
1579
Len Brown41c0d862005-12-28 12:43:51 -05001580 processor.nocst [HW,ACPI]
1581 Ignore the _CST method to determine C-states,
1582 instead using the legacy FADT method
1583
Linus Torvalds1da177e2005-04-16 15:20:36 -07001584 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1585 before loading.
1586 See Documentation/ramdisk.txt.
1587
Randy Dunlapa9913042005-10-23 12:57:11 -07001588 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1589 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001590 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1591 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07001592 psmouse.resetafter= [HW,MOUSE]
1593 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07001594 (0 = never).
1595 psmouse.resolution=
1596 [HW,MOUSE] Set desired mouse resolution, in dpi.
1597 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07001598 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001599 0 = disabled, 1 = enabled (default).
1600
1601 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
Randy Dunlapa9913042005-10-23 12:57:11 -07001602 Format:
1603 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001604
1605 pt. [PARIDE]
1606 See Documentation/paride.txt.
1607
Kay Sieversdc8c8582007-08-15 12:25:38 +02001608 pty.legacy_count=
1609 [KNL] Number of legacy pty's. Overwrites compiled-in
1610 default number.
1611
Randy Dunlap7d2c5022006-09-29 02:01:02 -07001612 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07001613
Linus Torvalds1da177e2005-04-16 15:20:36 -07001614 r128= [HW,DRM]
1615
1616 raid= [HW,RAID]
1617 See Documentation/md.txt.
1618
Randy Dunlapa9913042005-10-23 12:57:11 -07001619 ramdisk_blocksize= [RAM]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001620 See Documentation/ramdisk.txt.
Randy Dunlapa9913042005-10-23 12:57:11 -07001621
Linus Torvalds1da177e2005-04-16 15:20:36 -07001622 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Linus Torvalds1da177e2005-04-16 15:20:36 -07001623 See Documentation/ramdisk.txt.
1624
Robert P. J. Day24aaef82008-02-03 15:20:26 +02001625 rcupdate.blimit= [KNL,BOOT]
1626 Set maximum number of finished RCU callbacks to process
1627 in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08001628
Robert P. J. Day24aaef82008-02-03 15:20:26 +02001629 rcupdate.qhimark= [KNL,BOOT]
1630 Set threshold of queued
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08001631 RCU callbacks over which batch limiting is disabled.
1632
Robert P. J. Day24aaef82008-02-03 15:20:26 +02001633 rcupdate.qlowmark= [KNL,BOOT]
1634 Set threshold of queued RCU callbacks below which
1635 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08001636
Olof Johanssonffdfc402005-09-06 15:17:19 -07001637 rdinit= [KNL]
1638 Format: <full_path>
1639 Run specified binary instead of /init from the ramdisk,
1640 used for early userspace startup. See initrd.
1641
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001642 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Linus Torvalds1da177e2005-04-16 15:20:36 -07001643 Format: <reboot_mode>[,<reboot_mode2>[,...]]
Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001644 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645
1646 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1647
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001648 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07001649 Format: nn[KMG]
1650 Reserves a hole at the top of the kernel virtual
1651 address space.
1652
Vivek Goyal7e962872006-09-27 01:50:44 -07001653 reset_devices [KNL] Force drivers to reset the underlying device
1654 during initialization.
1655
Randy Dunlapa9913042005-10-23 12:57:11 -07001656 resume= [SWSUSP]
1657 Specify the partition device for software suspend
Linus Torvalds1da177e2005-04-16 15:20:36 -07001658
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08001659 resume_offset= [SWSUSP]
1660 Specify the offset from the beginning of the partition
1661 given by "resume=" at which the swap header is located,
1662 in <PAGE_SIZE> units (needed only for swap files).
1663 See Documentation/power/swsusp-and-swap-files.txt
1664
Michael Neuling0a7b35c2007-02-10 01:44:33 -08001665 retain_initrd [RAM] Keep initrd memory after extraction
1666
Linus Torvalds1da177e2005-04-16 15:20:36 -07001667 rhash_entries= [KNL,NET]
1668 Set number of hash buckets for route cache
1669
1670 riscom8= [HW,SERIAL]
1671 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1672
1673 ro [KNL] Mount root device read-only on boot
1674
1675 root= [KNL] Root filesystem
1676
1677 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1678 mount the root filesystem
1679
1680 rootflags= [KNL] Set root filesystem mount option string
1681
1682 rootfstype= [KNL] Set root filesystem type
1683
Pierre Ossmancc1ed752007-07-15 23:40:35 -07001684 rootwait [KNL] Wait (indefinitely) for root device to show up.
1685 Useful for devices that are detected asynchronously
1686 (e.g. USB and MMC devices).
1687
James Morris20510f22007-10-16 23:31:32 -07001688 root_plug.vendor_id=
1689 [ROOTPLUG] Override the default vendor ID
1690
1691 root_plug.product_id=
1692 [ROOTPLUG] Override the default product ID
1693
1694 root_plug.debug=
1695 [ROOTPLUG] Enable debugging output
1696
Linus Torvalds1da177e2005-04-16 15:20:36 -07001697 rw [KNL] Mount root device read-write on boot
1698
1699 S [KNL] Run init in single mode
1700
1701 sa1100ir [NET]
1702 See drivers/net/irda/sa1100_ir.c.
1703
Linus Torvalds1da177e2005-04-16 15:20:36 -07001704 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07001705
Linus Torvalds1da177e2005-04-16 15:20:36 -07001706 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1707 Format: <io>[,<timeout>[,<isapnp>]]
1708
1709 scsi_debug_*= [SCSI]
1710 See drivers/scsi/scsi_debug.c.
1711
1712 scsi_default_dev_flags=
1713 [SCSI] SCSI default device flags
1714 Format: <integer>
1715
1716 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1717 Format: <vendor>:<model>:<flags>
1718 (flags are integer value)
1719
Randy Dunlap6af66322007-11-14 16:52:25 -08001720 scsi_logging_level= [SCSI] a bit mask of logging levels
1721 See drivers/scsi/scsi_logging.h for bits. Also
1722 settable via sysctl at dev.scsi.logging_level
1723 (/proc/sys/dev/scsi/logging_level).
1724 There is also a nice 'scsi_logging_level' script in the
1725 S390-tools package, available for download at
1726 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
Linus Torvalds1da177e2005-04-16 15:20:36 -07001727
Matthew Wilcox3e082a92006-09-28 15:19:20 -06001728 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1729 discovered. async scans them in kernel threads,
1730 allowing boot to proceed. none ignores them, expecting
1731 user space to do the scan.
1732
Linus Torvalds1da177e2005-04-16 15:20:36 -07001733 selinux [SELINUX] Disable or enable SELinux at boot time.
1734 Format: { "0" | "1" }
1735 See security/selinux/Kconfig help text.
1736 0 -- disable.
1737 1 -- enable.
1738 Default value is set via kernel config option.
1739 If enabled at boot time, /selinux/disable can be used
1740 later to disable prior to initial policy load.
1741
James Morris4e5ab4c2006-06-09 00:33:33 -07001742 selinux_compat_net =
1743 [SELINUX] Set initial selinux_compat_net flag value.
Mauro Carvalho Chehabe53dd082007-09-15 07:38:47 -03001744 Format: { "0" | "1" }
1745 0 -- use new secmark-based packet controls
1746 1 -- use legacy packet controls
1747 Default value is 0 (preferred).
1748 Value can be changed at runtime via
1749 /selinux/compat_net.
James Morris4e5ab4c2006-06-09 00:33:33 -07001750
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001751 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001752
Linus Torvalds1da177e2005-04-16 15:20:36 -07001753 shapers= [NET]
1754 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07001755
Linus Torvalds1da177e2005-04-16 15:20:36 -07001756 sim710= [SCSI,HW]
1757 See header of drivers/scsi/sim710.c.
1758
1759 simeth= [IA-64]
1760 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07001761
Linus Torvalds1da177e2005-04-16 15:20:36 -07001762 slram= [HW,MTD]
1763
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001764 slub_debug[=options[,slabs]] [MM, SLUB]
1765 Enabling slub_debug allows one to determine the
1766 culprit if slab objects become corrupted. Enabling
1767 slub_debug can create guard zones around objects and
1768 may poison objects when not in use. Also tracks the
1769 last alloc / free. For more information see
1770 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07001771
1772 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001773 Determines the maximum allowed order for slabs.
1774 A high setting may cause OOMs due to memory
1775 fragmentation. For more information see
1776 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07001777
1778 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001779 The minimum number of objects per slab. SLUB will
1780 increase the slab order up to slub_max_order to
1781 generate a sufficiently large slab able to contain
1782 the number of objects indicated. The higher the number
1783 of objects the smaller the overhead of tracking slabs
1784 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07001785 For more information see Documentation/vm/slub.txt.
1786
1787 slub_min_order= [MM, SLUB]
1788 Determines the mininum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001789 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07001790 For more information see Documentation/vm/slub.txt.
1791
1792 slub_nomerge [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001793 Disable merging of slabs with similar size. May be
Christoph Lameterc1aee212007-05-31 00:40:47 -07001794 necessary if there is some reason to distinguish
Christoph Lameterf0630ff2007-07-15 23:38:14 -07001795 allocs to different slabs. Debug options disable
1796 merging on their own.
Christoph Lameterc1aee212007-05-31 00:40:47 -07001797 For more information see Documentation/vm/slub.txt.
1798
Linus Torvalds1da177e2005-04-16 15:20:36 -07001799 smart2= [HW]
1800 Format: <io1>[,<io2>[,...,<io8>]]
1801
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001802 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02001803 attempt to substitute SMP alternatives once at boot.
1804
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07001805 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1806 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1807 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1808 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1809 smsc-ircc2.ircc_irq= [HW] IRQ line
1810 smsc-ircc2.ircc_dma= [HW] DMA channel
1811 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1812 0: Toshiba Satellite 1800 (GP data pin select)
1813 1: Fast pin select (default)
1814 2: ATC IRMode
1815
Linus Torvalds1da177e2005-04-16 15:20:36 -07001816 snd-ad1816a= [HW,ALSA]
1817
1818 snd-ad1848= [HW,ALSA]
1819
1820 snd-ali5451= [HW,ALSA]
1821
1822 snd-als100= [HW,ALSA]
1823
1824 snd-als4000= [HW,ALSA]
1825
1826 snd-azt2320= [HW,ALSA]
1827
1828 snd-cmi8330= [HW,ALSA]
1829
1830 snd-cmipci= [HW,ALSA]
1831
1832 snd-cs4231= [HW,ALSA]
1833
1834 snd-cs4232= [HW,ALSA]
1835
1836 snd-cs4236= [HW,ALSA]
1837
1838 snd-cs4281= [HW,ALSA]
1839
1840 snd-cs46xx= [HW,ALSA]
1841
1842 snd-dt019x= [HW,ALSA]
1843
1844 snd-dummy= [HW,ALSA]
1845
1846 snd-emu10k1= [HW,ALSA]
1847
1848 snd-ens1370= [HW,ALSA]
1849
1850 snd-ens1371= [HW,ALSA]
1851
1852 snd-es968= [HW,ALSA]
1853
1854 snd-es1688= [HW,ALSA]
1855
1856 snd-es18xx= [HW,ALSA]
1857
1858 snd-es1938= [HW,ALSA]
1859
1860 snd-es1968= [HW,ALSA]
1861
1862 snd-fm801= [HW,ALSA]
1863
1864 snd-gusclassic= [HW,ALSA]
1865
1866 snd-gusextreme= [HW,ALSA]
1867
1868 snd-gusmax= [HW,ALSA]
1869
1870 snd-hdsp= [HW,ALSA]
1871
1872 snd-ice1712= [HW,ALSA]
1873
1874 snd-intel8x0= [HW,ALSA]
1875
1876 snd-interwave= [HW,ALSA]
1877
1878 snd-interwave-stb=
1879 [HW,ALSA]
1880
1881 snd-korg1212= [HW,ALSA]
1882
1883 snd-maestro3= [HW,ALSA]
1884
1885 snd-mpu401= [HW,ALSA]
1886
1887 snd-mtpav= [HW,ALSA]
1888
1889 snd-nm256= [HW,ALSA]
1890
1891 snd-opl3sa2= [HW,ALSA]
1892
1893 snd-opti92x-ad1848=
1894 [HW,ALSA]
1895
1896 snd-opti92x-cs4231=
1897 [HW,ALSA]
1898
1899 snd-opti93x= [HW,ALSA]
1900
1901 snd-pmac= [HW,ALSA]
1902
1903 snd-rme32= [HW,ALSA]
1904
1905 snd-rme96= [HW,ALSA]
1906
1907 snd-rme9652= [HW,ALSA]
1908
1909 snd-sb8= [HW,ALSA]
1910
1911 snd-sb16= [HW,ALSA]
1912
1913 snd-sbawe= [HW,ALSA]
1914
1915 snd-serial= [HW,ALSA]
1916
1917 snd-sgalaxy= [HW,ALSA]
1918
1919 snd-sonicvibes= [HW,ALSA]
1920
1921 snd-sun-amd7930=
1922 [HW,ALSA]
1923
1924 snd-sun-cs4231= [HW,ALSA]
1925
1926 snd-trident= [HW,ALSA]
1927
1928 snd-usb-audio= [HW,ALSA,USB]
1929
1930 snd-via82xx= [HW,ALSA]
1931
1932 snd-virmidi= [HW,ALSA]
1933
1934 snd-wavefront= [HW,ALSA]
1935
1936 snd-ymfpci= [HW,ALSA]
Randy Dunlapa9913042005-10-23 12:57:11 -07001937
Linus Torvalds1da177e2005-04-16 15:20:36 -07001938 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1939 See Documentation/sonypi.txt
1940
1941 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1942 See Documentation/specialix.txt.
1943
1944 spia_io_base= [HW,MTD]
1945 spia_fio_base=
1946 spia_pedr=
1947 spia_peddr=
1948
1949 sscape= [HW,OSS]
1950 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
Randy Dunlapa9913042005-10-23 12:57:11 -07001951
Linus Torvalds1da177e2005-04-16 15:20:36 -07001952 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1953 See Documentation/scsi/st.txt.
1954
Linus Torvalds1da177e2005-04-16 15:20:36 -07001955 sti= [PARISC,HW]
1956 Format: <num>
1957 Set the STI (builtin display/keyboard on the HP-PARISC
1958 machines) console (graphic card) which should be used
1959 as the initial boot-console.
1960 See also comment in drivers/video/console/sticore.c.
1961
1962 sti_font= [HW]
1963 See comment in drivers/video/console/sticore.c.
1964
1965 stifb= [HW]
1966 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1967
Greg Banks42a7fc42007-03-06 01:42:23 -08001968 sunrpc.pool_mode=
1969 [NFS]
1970 Control how the NFS server code allocates CPUs to
1971 service thread pools. Depending on how many NICs
1972 you have and where their interrupts are bound, this
1973 option will affect which CPUs will do NFS serving.
1974 Note: this parameter cannot be changed while the
1975 NFS server is running.
1976
1977 auto the server chooses an appropriate mode
1978 automatically using heuristics
1979 global a single global pool contains all CPUs
1980 percpu one pool for each CPU
1981 pernode one pool for each NUMA node (equivalent
1982 to global on non-NUMA machines)
1983
Linus Torvalds1da177e2005-04-16 15:20:36 -07001984 swiotlb= [IA-64] Number of I/O TLB slabs
Randy Dunlapa9913042005-10-23 12:57:11 -07001985
Linus Torvalds1da177e2005-04-16 15:20:36 -07001986 switches= [HW,M68k]
1987
1988 sym53c416= [HW,SCSI]
1989 See header of drivers/scsi/sym53c416.c.
1990
Ingo Molnar5d6f6472006-12-13 00:34:36 -08001991 sysrq_always_enabled
1992 [KNL]
1993 Ignore sysrq setting - this boot parameter will
1994 neutralize any effect of /proc/sys/kernel/sysrq.
1995 Useful for debugging.
1996
Linus Torvalds1da177e2005-04-16 15:20:36 -07001997 t128= [HW,SCSI]
1998 See header of drivers/scsi/t128.c.
1999
2000 tdfx= [HW,DRM]
2001
2002 thash_entries= [KNL,NET]
2003 Set number of hash buckets for TCP connection
2004
Len Brownf8707ec2007-08-12 00:12:54 -04002005 thermal.act= [HW,ACPI]
2006 -1: disable all active trip points in all thermal zones
2007 <degrees C>: override all lowest active trip points
2008
Len Brownc52a7412007-08-14 15:49:32 -04002009 thermal.crt= [HW,ACPI]
2010 -1: disable all critical trip points in all thermal zones
2011 <degrees C>: lower all critical trip points
2012
Len Brownf5487142007-08-12 00:12:44 -04002013 thermal.nocrt= [HW,ACPI]
2014 Set to disable actions on ACPI thermal zone
2015 critical and hot trip points.
2016
Len Brown72b33ef2007-08-12 00:12:17 -04002017 thermal.off= [HW,ACPI]
2018 1: disable ACPI thermal control
2019
Len Browna70cdc52007-08-12 00:12:35 -04002020 thermal.psv= [HW,ACPI]
2021 -1: disable all passive trip points
2022 <degrees C>: override all passive trip points to this value
2023
Len Brown730ff342007-08-12 00:12:26 -04002024 thermal.tzp= [HW,ACPI]
2025 Specify global default ACPI thermal zone polling rate
2026 <deci-seconds>: poll all this frequency
2027 0: no polling (default)
2028
Linus Torvalds1da177e2005-04-16 15:20:36 -07002029 tipar.timeout= [HW,PPT]
2030 Set communications timeout in tenths of a second
2031 (default 15).
2032
2033 tipar.delay= [HW,PPT]
2034 Set inter-bit delay in microseconds (default 10).
2035
Linus Torvalds1da177e2005-04-16 15:20:36 -07002036 tmscsim= [HW,SCSI]
2037 See comment before function dc390_setup() in
2038 drivers/scsi/tmscsim.c.
2039
2040 tp720= [HW,PS2]
2041
2042 trix= [HW,OSS] MediaTrix AudioTrix Pro
Randy Dunlapa9913042005-10-23 12:57:11 -07002043 Format:
2044 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2045
Randy Dunlapa9913042005-10-23 12:57:11 -07002046 turbografx.map[2|3]= [HW,JOY]
2047 TurboGraFX parallel port interface
2048 Format:
2049 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002050 See also Documentation/input/joystick-parport.txt
2051
2052 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2053 See header of drivers/scsi/u14-34f.c.
2054
2055 uart401= [HW,OSS]
2056 Format: <io>,<irq>
2057
2058 uart6850= [HW,OSS]
2059 Format: <io>,<irq>
2060
Alan Stern5f8364b2006-12-05 16:29:55 -05002061 uhci-hcd.ignore_oc=
2062 [USB] Ignore overcurrent events (default N).
2063 Some badly-designed motherboards generate lots of
2064 bogus events, for ports that aren't wired to
2065 anything. Set this parameter to avoid log spamming.
2066 Note that genuine overcurrent events won't be
2067 reported either.
2068
Alan Sternb5e795f2007-02-20 15:00:53 -05002069 usbcore.autosuspend=
2070 [USB] The autosuspend time delay (in seconds) used
2071 for newly-detected USB devices (default 2). This
2072 is the time required before an idle device will be
2073 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04002074 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05002075
Linus Torvalds1da177e2005-04-16 15:20:36 -07002076 usbhid.mousepoll=
2077 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07002078
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002079 vdso= [X86-32,SH,x86-64]
Jeremy Fitzhardinge1dbf527c2007-05-02 19:27:12 +02002080 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
Ingo Molnare6e54942006-06-27 02:53:50 -07002081 vdso=1: enable VDSO (default)
2082 vdso=0: disable VDSO mapping
2083
Roland McGrathaf65d642008-01-30 13:30:43 +01002084 vdso32= [X86-32,X86-64]
2085 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2086 vdso32=1: enable 32-bit VDSO (default)
2087 vdso32=0: disable 32-bit VDSO mapping
2088
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09002089 vector= [IA-64,SMP]
2090 vector=percpu: enable percpu vector domain
2091
Linus Torvalds1da177e2005-04-16 15:20:36 -07002092 video= [FB] Frame buffer configuration
2093 See Documentation/fb/modedb.txt.
2094
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002095 vga= [BOOT,X86-32] Select a particular video mode
Randy Dunlapa9913042005-10-23 12:57:11 -07002096 See Documentation/i386/boot.txt and
2097 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002098 Use vga=ask for menu.
2099 This is actually a boot loader parameter; the value is
2100 passed to the kernel using a special protocol.
2101
Randy Dunlapa9913042005-10-23 12:57:11 -07002102 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002103 size of <nn>. This can be used to increase the
2104 minimum size (128MB on x86). It can also be used to
2105 decrease the size and leave more room for directly
2106 mapped kernel RAM.
2107
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002108 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2109 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002110
Peter Oberparleiter585c3042006-06-29 15:08:25 +02002111 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2112 Format: <command>
2113
2114 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2115 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07002116
Linus Torvalds1da177e2005-04-16 15:20:36 -07002117 waveartist= [HW,OSS]
2118 Format: <io>,<irq>,<dma>,<dma2>
Randy Dunlapa9913042005-10-23 12:57:11 -07002119
Linus Torvalds1da177e2005-04-16 15:20:36 -07002120 wd33c93= [HW,SCSI]
2121 See header of drivers/scsi/wd33c93.c.
2122
2123 wd7000= [HW,SCSI]
2124 See header of drivers/scsi/wd7000.c.
2125
2126 wdt= [WDT] Watchdog
Gabriel C8dfe9c22007-08-10 13:01:00 -07002127 See Documentation/watchdog/wdt.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002128
2129 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2130 xd_geo= See header of drivers/block/xd.c.
2131
2132 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07002133 Format:
2134 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002135
Andi Kleena62eaf12006-02-16 23:41:58 +01002136 norandmaps Don't use address space randomization
2137 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2138
Randy Dunlapa9913042005-10-23 12:57:11 -07002139______________________________________________________________________
Linus Torvalds1da177e2005-04-16 15:20:36 -07002140
2141TODO:
2142
2143 Add documentation for ALSA options.
2144 Add more DRM drivers.