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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
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3
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
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20This 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
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27The 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:
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31
32 ACPI ACPI support is enabled.
c99c108a 33 AGP AGP (Accelerated Graphics Port) is enabled.
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34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
e7ba176b 37 AVR32 AVR32 architecture is enabled.
1da177e4 38 AX25 Appropriate AX.25 support is enabled.
0ae53640 39 BLACKFIN Blackfin architecture is enabled.
a9913044 40 DRM Direct Rendering Management support is enabled.
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41 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.
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46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
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49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
11ef697b 52 LIBATA Libata driver is enabled
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53 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.
309e57df 61 MSI Message Signaled Interrupts (PCI).
c8facbb6 62 MTD MTD (Memory Technology Device) support is enabled.
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63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
734efb46 65 GENERIC_TIME The generic timeofday code is enabled.
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66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
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68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
7f785763 72 PCIE PCI Express support is enabled.
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73 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.
20510f2f 79 ROOTPLUG The example Root Plug LSM is enabled.
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80 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/.
20510f2f 84 SECURITY Different security models are enabled.
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85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
e523d93c 87 SH SuperH architecture is enabled.
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88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
a9913044 90 SWSUSP Software suspend is enabled.
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91 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.
cd4f0ef7 99 X86-32 X86-32, aka i386 architecture is enabled.
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100 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
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115There are also arch-specific kernel-parameters not documented here.
116See for example <Documentation/x86_64/boot-options.txt>.
117
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118Note 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
9c4751fd 124The 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
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131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
a9913044 133 Format: { force | off | ht | strict | noirq }
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134 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
a9913044 138 strict -- Be less tolerant of platforms that are not
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139 strictly ACPI specification compliant.
140
53471121 141 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 142
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143 acpi_apic_instance= [ACPI, IOAPIC]
144 Format: <int>
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
4e381a4f 147 default: 0
a1fdcc0d 148
1da177e4 149 acpi_sleep= [HW,ACPI] Sleep options
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150 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.
a9913044 154
1da177e4 155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
a9913044 156 Format: { level | edge | high | low }
1da177e4 157
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158 acpi_irq_balance [HW,ACPI]
159 ACPI will balance active IRQs
160 default in APIC mode
1da177e4 161
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162 acpi_irq_nobalance [HW,ACPI]
163 ACPI will not move active IRQs (default)
164 default in PIC mode
1da177e4 165
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166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
167 use by PCI
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168 Format: <irq>,<irq>...
169
a9913044 170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
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171 Format: <irq>,<irq>...
172
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173 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
174
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175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
176 Format: To spoof as Windows 98: ="Microsoft Windows"
177
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178 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
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182
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.
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188 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
1da177e4 192
f989106c 193 acpi.debug_layer= [HW,ACPI]
1da177e4 194 Format: <int>
a9913044 195 Each bit of the <int> indicates an ACPI debug layer,
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196 1: enable, 0: disable. It is useful for boot time
197 debugging. After system has booted up, it can be set
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198 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.
209
210 acpi.debug_level= [HW,ACPI]
1da177e4 211 Format: <int>
a9913044 212 Each bit of the <int> indicates an ACPI debug level,
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213 1: enable, 0: disable. It is useful for boot time
214 debugging. After system has booted up, it can be set
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215 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
cd4f0ef7 228 acpi_pm_good [X86-32,X86-64]
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229 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
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233 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
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239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
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241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
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243 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
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249 ad1848= [HW,OSS]
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
251
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252 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.
a9913044 261
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262 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
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274 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
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284 apc= [HW,SPARC]
285 Power management functions (SPARCstation-4/5 + deriv.)
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286 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
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291 apic= [APIC,i386] Advanced Programmable Interrupt Controller
292 Change the output verbosity whilst booting
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293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
a9913044 296
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297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
299
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300 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
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314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
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316
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))
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322
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
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325
326 autotest [IA64]
327
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328 baycom_epp= [HW,AX25]
329 Format: <io>,<mode>
a9913044 330
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331 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
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335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
339
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340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
344
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345 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
1da177e4 350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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351 bttv.radio= Most important insmod options are available as
352 kernel args too.
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353 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
cd4f0ef7 362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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363 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
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369 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
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375 ccw_timeout_log [S390]
376 See Documentation/s390/CommonIO for details.
1da177e4 377
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378 cgroup_disable= [KNL] Disable a particular controller
379 Format: {name of the controller(s) to disable}
380 {Currently supported controllers - "memory"}
381
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382 checkreqprot [SELINUX] Set initial checkreqprot flag value.
383 Format: { "0" | "1" }
384 See security/selinux/Kconfig help text.
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385 0 -- check protection applied by kernel (includes
386 any implied execute protection).
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387 1 -- check protection requested by application.
388 Default value is set via a kernel config option.
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389 Value can be changed at runtime via
390 /selinux/checkreqprot.
391
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392 cio_ignore= [S390]
393 See Documentation/s390/CommonIO for details.
394
395 cio_msg= [S390]
396 See Documentation/s390/CommonIO for details.
397
cd4f0ef7 398 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 399 [Deprecated]
3f6dee9b 400 Forces specified clocksource (if available) to be used
734efb46 401 when calculating gettimeofday(). If specified
3f6dee9b 402 clocksource is not available, it defaults to PIT.
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403 Format: { pit | tsc | cyclone | pmtmr }
404
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405 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
cd4f0ef7 416 [X86-32] pit,hpet,tsc,vmi-timer;
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417 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
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425 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
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438 code_bytes [IA32/X86_64] How many bytes of object code to print
439 in an oops report.
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440 Range: 0 - 8192
441 Default: 64
442
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443 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
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449 hpet= [X86-32,HPET] option to control HPET usage
450 Format: { enable (default) | disable | force }
451 disable: disable HPET and use PIT instead
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452 force: allow force enabled of undocumented chips (ICH4,
453 VIA, nVidia)
1da177e4 454
1da177e4 455 com20020= [HW,NET] ARCnet - COM20020 chipset
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456 Format:
457 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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458
459 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
460 Format: <io>[,<irq>]
461
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462 com90xx= [HW,NET]
463 ARCnet - COM90xx chipset (memory-mapped buffers)
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464 Format: <io>[,<irq>[,<memstart>]]
465
466 condev= [HW,S390] console device
467 conmode=
a9913044 468
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469 console= [KNL] Output console device and options.
470
471 tty<n> Use the virtual console device <n>.
472
473 ttyS<n>[,options]
f1a1c2dc 474 ttyUSB0[,options]
1da177e4 475 Use the specified serial port. The options are of
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476 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".
480
481 See Documentation/serial-console.txt for more
482 information. See
483 Documentation/networking/netconsole.txt for an
484 alternative.
1da177e4 485
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486 uart[8250],io,<addr>[,options]
487 uart[8250],mmio,<addr>[,options]
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488 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
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493 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
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500 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
1da177e4 510 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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511 Format:
512 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 513
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514 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
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518 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
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525 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 }
a9913044 533
a9913044 534 dasd= [HW,NET]
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535 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
cae2ed9a
IM
544 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
2d27a966 553 decnet.addr= [HW,NET]
1da177e4
LT
554 Format: <area>[,<node>]
555 See also Documentation/networking/decnet.txt.
556
ecb77fa9 557 vt.default_blu= [VT]
55ff9780
AD
558 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
ecb77fa9 563 vt.default_grn= [VT]
55ff9780
AD
564 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
ecb77fa9 569 vt.default_red= [VT]
55ff9780
AD
570 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
ecb77fa9
ST
575 vt.default_utf8=
576 [VT]
55ff9780
AD
577 Format=<0|1>
578 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
579 Default is 1, i.e. UTF-8 mode is enabled for all
580 newly opened terminals.
55ff9780 581
1da177e4
LT
582 dhash_entries= [KNL]
583 Set number of hash buckets for dentry cache.
a9913044 584
1da177e4
LT
585 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
093af8d7 592 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
593 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
1da177e4
LT
598 dmasound= [HW,OSS] Sound subsystem buffers
599
600 dscc4.setup= [NET]
601
602 dtc3181e= [HW,SCSI]
603
0ae53640 604 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
605 earlyprintk=vga
606 earlyprintk=serial[,ttySn[,baudrate]]
607
a9913044 608 Append ",keep" to not disable it when the real console
1da177e4
LT
609 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
1da177e4
LT
623 edd= [EDD]
624 Format: {"of[f]" | "sk[ipmbr]"}
625 See comment in arch/i386/boot/edd.S
626
1da177e4
LT
627 eisa_irq_edge= [PARISC,HW]
628 See header of drivers/parisc/eisa.c.
629
cd4f0ef7 630 elanfreq= [X86-32]
1da177e4
LT
631 See comment before function elanfreq_setup() in
632 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
633
634 elevator= [IOSCHED]
16ab3adf 635 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
636 See Documentation/block/as-iosched.txt and
637 Documentation/block/deadline-iosched.txt for details.
638
cd4f0ef7 639 elfcorehdr= [X86-32, X86_64]
a9913044 640 Specifies physical address of start of kernel core
aac04b32
VG
641 image elf header. Generally kexec loader will
642 pass this option to capture kernel.
643 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
644
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
1da177e4
LT
653 es1371= [HW,OSS]
654 Format: <spdif>,[<nomix>,[<amplifier>]]
655 See also header of sound/oss/es1371.c.
a9913044 656
1da177e4
LT
657 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
de1ba09b
AM
664 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
1da177e4
LT
671 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
1da177e4
LT
680 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
aaf23042
YL
688 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
689 Format: off | on
690 default: on
691
1da177e4
LT
692 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
1da177e4
LT
698 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.
a9913044 703 Format: 0 | 1 (for off | on)
1da177e4
LT
704
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
1c10e938 711 hd?lun= See Documentation/ide/ide.txt.
1da177e4
LT
712
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
54cdfdb4
TG
718 highres= [KNL] Enable/disable high resolution timer mode.
719 Valid parameters: "on", "off"
720 Default: "on"
721
1da177e4
LT
722 hisax= [HW,ISDN]
723 See Documentation/isdn/README.HiSax.
724
cd4f0ef7 725 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 726 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 727
1da177e4 728 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
729 i8042.dumbkbd [HW] Pretend that controller can only read data from
730 keyboard and cannot control its state
1da177e4
LT
731 (Don't attempt to blink the leds)
732 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 733 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
734 i8042.noloop [HW] Disable the AUX Loopback command while probing
735 for the AUX port
1da177e4
LT
736 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
e70c9d5e
DT
748 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
749 indicates that the driver is running on unsupported
750 hardware.
1da177e4
LT
751 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
1c10e938 767 See Documentation/ide/ide.txt.
1da177e4
LT
768
769 ide?= [HW] (E)IDE subsystem
770 Format: ide?=noprobe or chipset specific parameters.
1c10e938 771 See Documentation/ide/ide.txt.
a9913044 772
1da177e4 773 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 774 See Documentation/ide/ide.txt.
1da177e4 775
f039b754
AK
776 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.
a9913044 785
594765a7
DC
786 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
787 Claim all unknown PCI IDE storage controllers.
788
79290822
IM
789 ignore_loglevel [KNL]
790 Ignore loglevel setting - this will print /all/
791 kernel messages to the console. Useful for debugging.
792
1da177e4
LT
793 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
b552da87
PM
815 iommu= [x86]
816 off
817 force
818 noforce
819 biomerge
820 panic
821 nopanic
822 merge
823 nomerge
824 forcesac
825 soft
826
827
ba395927
KA
828 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.
7d3b03ce
KA
837 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.
ba395927 844
b02aae9c 845 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
846 0x80
847 Standard port 0x80 based delay
848 0xed
849 Alternate port 0xed based delay (needed on some systems)
b02aae9c 850 udelay
6e7c4025
IM
851 Simple two microseconds delay
852 none
853 No delay
b02aae9c 854
1da177e4
LT
855 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]
6ded55da 860 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
861
862 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
863 See comment before ip2_setup() in
864 drivers/char/ip2/ip2base.c.
1da177e4
LT
865
866 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
867 See header of drivers/scsi/ips.c.
868
72c4a13a
SH
869 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
200803df
AC
875 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
1da177e4 886 isapnp= [ISAPNP]
a9913044 887 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
888
889 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
890 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>
1da177e4
LT
896 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
a9913044
RD
904 alternative -- manually setting the CPU mask of all
905 tasks in the system -- can cause problems and
906 suboptimal load balancer performance.
1da177e4 907
a9913044 908 iucv= [HW,NET]
1da177e4
LT
909
910 js= [HW,JOY] Analog joystick
911 See Documentation/input/joystick.txt.
912
cd4f0ef7 913 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
914 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
cd4f0ef7 929 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
930 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
1da177e4
LT
939 keepinitrd [HW,ARM]
940
cd4f0ef7 941 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
942 in oops dumps.
943
944 l2cr= [PPC]
945
cd4f0ef7 946 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 947 disabled it.
1da177e4 948
cd4f0ef7 949 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
950 C2 power state.
951
fcb71f6f
FC
952 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
78e70c23
DJ
960 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
961 when set.
962 Format: <int>
963
33267325
TH
964 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
1da177e4
LT
999 load_ramdisk= [RAM] List of ramdisks to load from floppy
1000 See Documentation/ramdisk.txt.
1001
a6b25b67
RD
1002 lockd.nlm_grace_period=P [NFS] Assign grace period.
1003 Format: <integer>
1da177e4 1004
a6b25b67
RD
1005 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>
1da177e4
LT
1013
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.
a9913044
RD
1032 Format: { n | nk | nM }
1033 n must be a power of two. The default size
1034 is set in the kernel config file.
1da177e4 1035
accaa24c
RD
1036 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
1da177e4
LT
1041 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
a9913044
RD
1075 mac5380= [HW,SCSI] Format:
1076 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1077
a9913044
RD
1078 mac53c9x= [HW,SCSI] Format:
1079 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1080
a9913044
RD
1081 machvec= [IA64] Force the use of a particular machine-vector
1082 (machvec) in a generic kernel.
1083 Example: machvec=hpzx1_swiotlb
1da177e4 1084
a9913044 1085 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1086 be mounted
1087 Format: <1-256>
1088
1089 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1090 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.
1da177e4 1094
2b2c3750
BP
1095 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1096 equal to this physical address is ignored.
1097
a9913044 1098 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1099 Should be between 1 and 2^32-1.
1100
1101 max_report_luns=
a9913044 1102 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1103 Should be between 1 and 16384.
1104
1da177e4
LT
1105 mcatest= [IA-64]
1106
cd4f0ef7 1107 mce [X86-32] Machine Check Exception
1da177e4 1108
909dd324
AK
1109 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1110
1da177e4
LT
1111 md= [HW] RAID subsystems devices and level
1112 See Documentation/md.txt.
a9913044 1113
1da177e4
LT
1114 mdacon= [MDA]
1115 Format: <first>,<last>
1116 Specifies range of consoles to be captured by the MDA.
a9913044 1117
1da177e4
LT
1118 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.
cd4f0ef7 1121 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1122 address space collisions. Without memmap= PCI devices
1123 could be placed at addresses belonging to unused RAM.
1124
cd4f0ef7 1125 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1126 memory.
1127
cd4f0ef7 1128 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1129 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.
1312848e
PM
1145 Example: Exclude memory from 0x18690000-0x1869ffff
1146 memmap=64K$0x18690000
1147 or
1148 memmap=0x10000$0x18690000
1da177e4
LT
1149
1150 meye.*= [HW] Set MotionEye Camera parameters
1151 See Documentation/video4linux/meye.txt.
1152
8f36881b
AS
1153 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1154 Multi-Function General Purpose Timers on AMD Geode
1155 platforms.
1156
e6c4dc6c
WT
1157 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1158 the BIOS has incorrectly applied a workaround. TinyBIOS
1159 version 0.98 is known to be affected, 0.99 fixes the
1160 problem by letting the user disable the workaround.
1161
1da177e4
LT
1162 mga= [HW,DRM]
1163
1164 mousedev.tap_time=
1165 [MOUSE] Maximum time between finger touching and
1166 leaving touchpad surface for touch to be considered
1167 a tap and be reported as a left button click (for
1168 touchpads working in absolute mode only).
1169 Format: <msecs>
1170 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1171 reporting absolute coordinates, such as tablets
1172 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1173 reporting absolute coordinates, such as tablets
1174
1175 mpu401= [HW,OSS]
1176 Format: <io>,<irq>
1177
1178 MTD_Partition= [MTD]
1179 Format: <name>,<region-number>,<size>,<offset>
1180
a9913044
RD
1181 MTD_Region= [MTD] Format:
1182 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1183
1184 mtdparts= [MTD]
c8facbb6 1185 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1186
1187 mtouchusb.raw_coordinates=
a9913044
RD
1188 [HW] Make the MicroTouch USB driver use raw coordinates
1189 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1190
1191 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1192
1193 NCR_D700= [HW,SCSI]
1194 See header of drivers/scsi/NCR_D700.c.
1195
1196 ncr5380= [HW,SCSI]
1197
1198 ncr53c400= [HW,SCSI]
1199
1200 ncr53c400a= [HW,SCSI]
1201
1202 ncr53c406a= [HW,SCSI]
1203
1204 ncr53c8xx= [HW,SCSI]
1205
1206 netdev= [NET] Network devices parameters
1207 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1208 Note that mem_start is often overloaded to mean
1209 something different and driver-specific.
a9913044
RD
1210 This usage is only documented in each driver source
1211 file if at all.
1212
1da177e4 1213 nfsaddrs= [NFS]
6ded55da 1214 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1215
1216 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1217 See Documentation/filesystems/nfsroot.txt.
1da177e4 1218
a72b4422
TM
1219 nfs.callback_tcpport=
1220 [NFS] set the TCP port on which the NFSv4 callback
1221 channel should listen.
1222
58df095b
TM
1223 nfs.idmap_cache_timeout=
1224 [NFS] set the maximum lifetime for idmapper cache
1225 entries.
1226
f43bf0be
TM
1227 nfs.enable_ino64=
1228 [NFS] enable 64-bit inode numbers.
1229 If zero, the NFS client will fake up a 32-bit inode
1230 number for the readdir() and stat() syscalls instead
1231 of returning the full 64-bit number.
1232 The default is to return 64-bit inode numbers.
1233
e7ba176b
HS
1234 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1235 when a NMI is triggered.
1236 Format: [state][,regs][,debounce][,die]
1237
cd4f0ef7 1238 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1239
cd4f0ef7 1240 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1241 emulation library even if a 387 maths coprocessor
1242 is present.
1243
c1aee215
CL
1244 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1245 caches in the slab allocator. Saves per-node memory,
1246 but will impact performance.
3395ee05 1247
a9913044
RD
1248 noalign [KNL,ARM]
1249
1da177e4
LT
1250 noapic [SMP,APIC] Tells the kernel to not make use of any
1251 IOAPICs that may be present in the system.
1252
1da177e4
LT
1253 nobats [PPC] Do not use BATs for mapping kernel lowmem
1254 on "Classic" PPC cores.
1255
1256 nocache [ARM]
a9913044 1257
163ecdff
SN
1258 nodelayacct [KNL] Disable per-task delay accounting
1259
1da177e4
LT
1260 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1261
8b2cb7a8
HY
1262 noefi [X86-32,X86-64] Disable EFI runtime services support.
1263
1da177e4
LT
1264 noexec [IA-64]
1265
cd4f0ef7 1266 noexec [X86-32,X86-64]
1da177e4
LT
1267 noexec=on: enable non-executable mappings (default)
1268 noexec=off: disable nn-executable mappings
1269
cd4f0ef7 1270 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1271 register save and restore. The kernel will only save
1272 legacy floating-point registers on task switch.
1da177e4 1273
191679fd
AK
1274 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1275
1da177e4 1276 nohlt [BUGS=ARM]
a9913044 1277
cd4f0ef7 1278 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1279 instruction doesn't work correctly and not to
1280 use it.
1281
1282 nohalt [IA-64] Tells the kernel not to use the power saving
1283 function PAL_HALT_LIGHT when idle. This increases
1284 power-consumption. On the positive side, it reduces
1285 interrupt wake-up latency, which may improve performance
1286 in certain environments such as networked servers or
1287 real-time systems.
1288
79bf2bb3
TG
1289 nohz= [KNL] Boottime enable/disable dynamic ticks
1290 Valid arguments: on, off
1291 Default: on
1292
cd4f0ef7 1293 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1294
cd4f0ef7 1295 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1296 disable unhandled interrupt sources.
1297
cd4f0ef7 1298 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1299 broken timer IRQ sources.
1300
1da177e4
LT
1301 noisapnp [ISAPNP] Disables ISA PnP code.
1302
1303 noinitrd [RAM] Tells the kernel not to load any configured
1304 initial RAM disk.
1305
1306 nointroute [IA-64]
1307
0aa366f3
TL
1308 nojitter [IA64] Disables jitter checking for ITC timers.
1309
cd4f0ef7 1310 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1311
cd4f0ef7 1312 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1313
1da177e4
LT
1314 noltlbs [PPC] Do not use large page/tlb entries for kernel
1315 lowmem mapping on PPC40x.
1316
312f1f01
H
1317 nomca [IA-64] Disable machine check abort handling
1318
cd4f0ef7 1319 nomce [X86-32] Machine Check Exception
abe37e5a 1320
83d7384f
AS
1321 nomfgpt [X86-32] Disable Multi-Function General Purpose
1322 Timer usage (for AMD Geode machines).
1323
cd4f0ef7 1324 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1325
cd4f0ef7 1326 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1327 with UP alternatives
1328
1da177e4
LT
1329 noresidual [PPC] Don't use residual data on PReP machines.
1330
a9913044
RD
1331 noresume [SWSUSP] Disables resume and restores original swap
1332 space.
1333
1da177e4
LT
1334 no-scroll [VGA] Disables scrollback.
1335 This is required for the Braillex ib80-piezo Braille
1336 reader made by F.H. Papenmeier (Germany).
1337
1338 nosbagart [IA-64]
1339
cd4f0ef7 1340 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1341
61ec7567
LB
1342 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1343 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1344
97842216
DJ
1345 nosoftlockup [KNL] Disable the soft-lockup detector.
1346
1da177e4
LT
1347 nosync [HW,M68K] Disables sync negotiation for all devices.
1348
cd4f0ef7 1349 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1350
1351 nousb [USB] Disable the USB subsystem
1352
1353 nowb [ARM]
a9913044 1354
f0c0b2b8
KH
1355 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1356 one of ['zone', 'node', 'default'] can be specified
1357 This can be set from sysctl after boot.
1358 See Documentation/sysctl/vm.txt for details.
1359
a61c2d78
DJ
1360 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1361
1da177e4
LT
1362 opl3= [HW,OSS]
1363 Format: <io>
1364
1da177e4
LT
1365 oprofile.timer= [HW]
1366 Use timer interrupt instead of performance counters
1367
1da177e4
LT
1368 osst= [HW,SCSI] SCSI Tape Driver
1369 Format: <buffer_size>,<write_threshold>
1370 See also Documentation/scsi/st.txt.
1371
1372 panic= [KNL] Kernel behaviour on panic
1373 Format: <timeout>
1374
1375 parkbd.port= [HW] Parallel port number the keyboard adapter is
1376 connected to, default is 0.
1377 Format: <parport#>
1378 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1379 0 for XT, 1 for AT (default is AT).
a9913044
RD
1380 Format: <mode>
1381
1382 parport= [HW,PPT] Specify parallel ports. 0 disables.
1383 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1384 Use 'auto' to force the driver to use any
1385 IRQ/DMA settings detected (the default is to
1386 ignore detected IRQ/DMA settings because of
1387 possible conflicts). You can specify the base
1388 address, IRQ, and DMA settings; IRQ and DMA
1389 should be numbers, or 'auto' (for using detected
1390 settings on that particular port), or 'nofifo'
1391 (to avoid using a FIFO even if it is detected).
1392 Parallel ports are assigned in the order they
1393 are specified on the command line, starting
1394 with parport0.
1395
1396 parport_init_mode= [HW,PPT]
1397 Configure VIA parallel port to operate in
1398 a specific mode. This is necessary on Pegasos
1399 computer where firmware has no options for setting
1400 up parallel port mode and sets it to spp.
1401 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1402 Format: [spp|ps2|epp|ecp|ecpepp]
1403
a9913044
RD
1404 pas2= [HW,OSS] Format:
1405 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1406
1da177e4
LT
1407 pas16= [HW,SCSI]
1408 See header of drivers/scsi/pas16.c.
1409
dd287796
AM
1410 pause_on_oops=
1411 Halt all CPUs after the first oops has been printed for
1412 the specified number of seconds. This is to be used if
1413 your oopses keep scrolling off the screen.
1414
1da177e4
LT
1415 pcbit= [HW,ISDN]
1416
1417 pcd. [PARIDE]
1418 See header of drivers/block/paride/pcd.c.
1419 See also Documentation/paride.txt.
1420
a9913044 1421 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1422 off [X86-32] don't probe for the PCI bus
1423 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1424 the hardware directly. Use this if your machine
1425 has a non-standard PCI host bridge.
cd4f0ef7 1426 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1427 hardware access methods are allowed. Use this
1428 if you experience crashes upon bootup and you
1429 suspect they are caused by the BIOS.
cd4f0ef7 1430 conf1 [X86-32] Force use of PCI Configuration
a9913044 1431 Mechanism 1.
cd4f0ef7 1432 conf2 [X86-32] Force use of PCI Configuration
a9913044 1433 Mechanism 2.
7f785763
RD
1434 noaer [PCIE] If the PCIEAER kernel config parameter is
1435 enabled, this kernel boot option can be used to
1436 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1437 nodomains [PCI] Disable support for multiple PCI
1438 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1439 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1440 Configuration
309e57df
MW
1441 nomsi [MSI] If the PCI_MSI kernel config parameter is
1442 enabled, this kernel boot option can be used to
1443 disable the use of MSI interrupts system-wide.
cd4f0ef7 1444 nosort [X86-32] Don't sort PCI devices according to
a9913044
RD
1445 order given by the PCI BIOS. This sorting is
1446 done to get a device order compatible with
1447 older kernels.
cd4f0ef7 1448 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1449 routing table. These calls are known to be buggy
1450 on several machines and they hang the machine
1451 when used, but on other computers it's the only
1452 way to get the interrupt routing table. Try
1453 this option if the kernel is unable to allocate
1454 IRQs or discover secondary PCI buses on your
1455 motherboard.
cd4f0ef7 1456 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1457 Use with caution as certain devices share
1458 address decoders between ROMs and other
1459 resources.
cd4f0ef7 1460 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1461 assigned automatically to PCI devices. You can
1462 make the kernel exclude IRQs of your ISA cards
1463 this way.
cd4f0ef7 1464 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1465 of the PIRQ table (normally generated
1466 by the BIOS) if it is outside the
1467 F0000h-100000h range.
cd4f0ef7 1468 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1469 useful if the kernel is unable to find your
1470 secondary buses and you want to tell it
1471 explicitly which ones they are.
cd4f0ef7 1472 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1473 numbers ourselves, overriding
1474 whatever the firmware may have done.
cd4f0ef7 1475 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1476 in the BIOS $PIR table. This is needed on
1477 some systems with broken BIOSes, notably
1478 some HP Pavilion N5400 and Omnibook XE3
1479 notebooks. This will have no effect if ACPI
1480 IRQ routing is enabled.
cd4f0ef7 1481 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1482 or for PCI scanning.
62f420f8
GH
1483 use_crs [X86-32] Use _CRS for PCI resource
1484 allocation.
a9913044
RD
1485 routeirq Do IRQ routing for all PCI devices.
1486 This is normally done in pci_enable_device(),
1487 so this option is a temporary workaround
1488 for broken drivers that don't call it.
1489 firmware [ARM] Do not re-enumerate the bus but instead
1490 just use the configuration from the
1491 bootloader. This is currently used on
1492 IXP2000 systems where the bus has to be
1493 configured a certain way for adjunct CPUs.
0637a70a
AK
1494 noearly [X86] Don't do any early type 1 scanning.
1495 This might help on some broken boards which
1496 machine check when some devices' config space
1497 is read. But various workarounds are disabled
1498 and some IOMMU drivers will not work.
6b4b78fe
MD
1499 bfsort Sort PCI devices into breadth-first order.
1500 This sorting is done to get a device
1501 order compatible with older (<= 2.4) kernels.
1502 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1503 cbiosize=nn[KMG] The fixed amount of bus space which is
1504 reserved for the CardBus bridge's IO window.
1505 The default value is 256 bytes.
1506 cbmemsize=nn[KMG] The fixed amount of bus space which is
1507 reserved for the CardBus bridge's memory
1508 window. The default value is 64 megabytes.
6b4b78fe 1509
1da177e4
LT
1510 pcmv= [HW,PCMCIA] BadgePAD 4
1511
1512 pd. [PARIDE]
1513 See Documentation/paride.txt.
1514
1515 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1516 boot time.
1517 Format: { 0 | 1 }
1518 See arch/parisc/kernel/pdc_chassis.c
1519
1520 pf. [PARIDE]
1521 See Documentation/paride.txt.
1522
1523 pg. [PARIDE]
1524 See Documentation/paride.txt.
1525
1526 pirq= [SMP,APIC] Manual mp-table setup
1527 See Documentation/i386/IO-APIC.txt.
1528
1529 plip= [PPT,NET] Parallel port network link
1530 Format: { parport<nr> | timid | 0 }
1531 See also Documentation/parport.txt.
1532
1533 pnpacpi= [ACPI]
1534 { off }
1535
1536 pnpbios= [ISAPNP]
1537 { on | off | curr | res | no-curr | no-res }
1538
1539 pnp_reserve_irq=
1540 [ISAPNP] Exclude IRQs for the autoconfiguration
1541
1542 pnp_reserve_dma=
1543 [ISAPNP] Exclude DMAs for the autoconfiguration
1544
1545 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1546 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1547
1548 pnp_reserve_mem=
a9913044
RD
1549 [ISAPNP] Exclude memory regions for the
1550 autoconfiguration.
1da177e4
LT
1551 Ranges are in pairs (memory base and size).
1552
45807a1d
IM
1553 print-fatal-signals=
1554 [KNL] debug: print fatal signals
1555 print-fatal-signals=1: print segfault info to
1556 the kernel console.
1557 default: off.
1558
e84845c4
RD
1559 printk.time= Show timing data prefixed to each printk message line
1560 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1561
1da177e4 1562 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1563 Format: [schedule,]<number>
1564 Param: "schedule" - profile schedule points.
1565 Param: <number> - step/bucket size as a power of 2 for
1566 statistical time based profiling.
b3da2a73
MG
1567 Param: "sleep" - profile D-state sleeping (millisecs).
1568 Requires CONFIG_SCHEDSTATS
c0fe2e69 1569 Param: "kvm" - profile VM exits.
1da177e4 1570
a9913044 1571 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1572 Limit processor to maximum C-state
1573 max_cstate=9 overrides any DMI blacklist limit.
1574
41c0d868
LB
1575 processor.nocst [HW,ACPI]
1576 Ignore the _CST method to determine C-states,
1577 instead using the legacy FADT method
1578
1da177e4
LT
1579 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1580 before loading.
1581 See Documentation/ramdisk.txt.
1582
a9913044
RD
1583 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1584 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1585 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1586 per second.
a9913044
RD
1587 psmouse.resetafter= [HW,MOUSE]
1588 Try to reset the device after so many bad packets
1da177e4
LT
1589 (0 = never).
1590 psmouse.resolution=
1591 [HW,MOUSE] Set desired mouse resolution, in dpi.
1592 psmouse.smartscroll=
a9913044 1593 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1594 0 = disabled, 1 = enabled (default).
1595
1596 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1597 Format:
1598 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1599
1600 pt. [PARIDE]
1601 See Documentation/paride.txt.
1602
dc8c8587
KS
1603 pty.legacy_count=
1604 [KNL] Number of legacy pty's. Overwrites compiled-in
1605 default number.
1606
7d2c502f 1607 quiet [KNL] Disable most log messages
a9913044 1608
1da177e4
LT
1609 r128= [HW,DRM]
1610
1611 raid= [HW,RAID]
1612 See Documentation/md.txt.
1613
a9913044 1614 ramdisk_blocksize= [RAM]
1da177e4 1615 See Documentation/ramdisk.txt.
a9913044 1616
1da177e4 1617 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1618 See Documentation/ramdisk.txt.
1619
24aaef8d
RD
1620 rcupdate.blimit= [KNL,BOOT]
1621 Set maximum number of finished RCU callbacks to process
1622 in one batch.
21a1ea9e 1623
24aaef8d
RD
1624 rcupdate.qhimark= [KNL,BOOT]
1625 Set threshold of queued
21a1ea9e
DS
1626 RCU callbacks over which batch limiting is disabled.
1627
24aaef8d
RD
1628 rcupdate.qlowmark= [KNL,BOOT]
1629 Set threshold of queued RCU callbacks below which
1630 batch limiting is re-enabled.
21a1ea9e 1631
ffdfc409
OJ
1632 rdinit= [KNL]
1633 Format: <full_path>
1634 Run specified binary instead of /init from the ramdisk,
1635 used for early userspace startup. See initrd.
1636
cd4f0ef7 1637 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1638 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1639 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1640
1641 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1642
cd4f0ef7 1643 reservetop= [X86-32]
461a9aff
ZA
1644 Format: nn[KMG]
1645 Reserves a hole at the top of the kernel virtual
1646 address space.
1647
7e96287d
VG
1648 reset_devices [KNL] Force drivers to reset the underlying device
1649 during initialization.
1650
a9913044
RD
1651 resume= [SWSUSP]
1652 Specify the partition device for software suspend
1da177e4 1653
ecbd0da1
RW
1654 resume_offset= [SWSUSP]
1655 Specify the offset from the beginning of the partition
1656 given by "resume=" at which the swap header is located,
1657 in <PAGE_SIZE> units (needed only for swap files).
1658 See Documentation/power/swsusp-and-swap-files.txt
1659
0a7b35cb
MN
1660 retain_initrd [RAM] Keep initrd memory after extraction
1661
1da177e4
LT
1662 rhash_entries= [KNL,NET]
1663 Set number of hash buckets for route cache
1664
1665 riscom8= [HW,SERIAL]
1666 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1667
1668 ro [KNL] Mount root device read-only on boot
1669
1670 root= [KNL] Root filesystem
1671
1672 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1673 mount the root filesystem
1674
1675 rootflags= [KNL] Set root filesystem mount option string
1676
1677 rootfstype= [KNL] Set root filesystem type
1678
cc1ed754
PO
1679 rootwait [KNL] Wait (indefinitely) for root device to show up.
1680 Useful for devices that are detected asynchronously
1681 (e.g. USB and MMC devices).
1682
20510f2f
JM
1683 root_plug.vendor_id=
1684 [ROOTPLUG] Override the default vendor ID
1685
1686 root_plug.product_id=
1687 [ROOTPLUG] Override the default product ID
1688
1689 root_plug.debug=
1690 [ROOTPLUG] Enable debugging output
1691
1da177e4
LT
1692 rw [KNL] Mount root device read-write on boot
1693
1694 S [KNL] Run init in single mode
1695
1696 sa1100ir [NET]
1697 See drivers/net/irda/sa1100_ir.c.
1698
1da177e4 1699 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1700
1da177e4
LT
1701 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1702 Format: <io>[,<timeout>[,<isapnp>]]
1703
1704 scsi_debug_*= [SCSI]
1705 See drivers/scsi/scsi_debug.c.
1706
1707 scsi_default_dev_flags=
1708 [SCSI] SCSI default device flags
1709 Format: <integer>
1710
1711 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1712 Format: <vendor>:<model>:<flags>
1713 (flags are integer value)
1714
6af6632a
RD
1715 scsi_logging_level= [SCSI] a bit mask of logging levels
1716 See drivers/scsi/scsi_logging.h for bits. Also
1717 settable via sysctl at dev.scsi.logging_level
1718 (/proc/sys/dev/scsi/logging_level).
1719 There is also a nice 'scsi_logging_level' script in the
1720 S390-tools package, available for download at
1721 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1722
3e082a91
MW
1723 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1724 discovered. async scans them in kernel threads,
1725 allowing boot to proceed. none ignores them, expecting
1726 user space to do the scan.
1727
1da177e4
LT
1728 selinux [SELINUX] Disable or enable SELinux at boot time.
1729 Format: { "0" | "1" }
1730 See security/selinux/Kconfig help text.
1731 0 -- disable.
1732 1 -- enable.
1733 Default value is set via kernel config option.
1734 If enabled at boot time, /selinux/disable can be used
1735 later to disable prior to initial policy load.
1736
4e5ab4cb
JM
1737 selinux_compat_net =
1738 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1739 Format: { "0" | "1" }
1740 0 -- use new secmark-based packet controls
1741 1 -- use legacy packet controls
1742 Default value is 0 (preferred).
1743 Value can be changed at runtime via
1744 /selinux/compat_net.
4e5ab4cb 1745
cd4f0ef7 1746 serialnumber [BUGS=X86-32]
1da177e4 1747
1da177e4
LT
1748 shapers= [NET]
1749 Maximal number of shapers.
a9913044 1750
1da177e4
LT
1751 sim710= [SCSI,HW]
1752 See header of drivers/scsi/sim710.c.
1753
1754 simeth= [IA-64]
1755 simscsi=
a9913044 1756
1da177e4
LT
1757 slram= [HW,MTD]
1758
f0630fff
CL
1759 slub_debug[=options[,slabs]] [MM, SLUB]
1760 Enabling slub_debug allows one to determine the
1761 culprit if slab objects become corrupted. Enabling
1762 slub_debug can create guard zones around objects and
1763 may poison objects when not in use. Also tracks the
1764 last alloc / free. For more information see
1765 Documentation/vm/slub.txt.
c1aee215
CL
1766
1767 slub_max_order= [MM, SLUB]
f0630fff
CL
1768 Determines the maximum allowed order for slabs.
1769 A high setting may cause OOMs due to memory
1770 fragmentation. For more information see
1771 Documentation/vm/slub.txt.
c1aee215
CL
1772
1773 slub_min_objects= [MM, SLUB]
f0630fff
CL
1774 The minimum number of objects per slab. SLUB will
1775 increase the slab order up to slub_max_order to
1776 generate a sufficiently large slab able to contain
1777 the number of objects indicated. The higher the number
1778 of objects the smaller the overhead of tracking slabs
1779 and the less frequently locks need to be acquired.
c1aee215
CL
1780 For more information see Documentation/vm/slub.txt.
1781
1782 slub_min_order= [MM, SLUB]
1783 Determines the mininum page order for slabs. Must be
f0630fff 1784 lower than slub_max_order.
c1aee215
CL
1785 For more information see Documentation/vm/slub.txt.
1786
1787 slub_nomerge [MM, SLUB]
f0630fff 1788 Disable merging of slabs with similar size. May be
c1aee215 1789 necessary if there is some reason to distinguish
f0630fff
CL
1790 allocs to different slabs. Debug options disable
1791 merging on their own.
c1aee215
CL
1792 For more information see Documentation/vm/slub.txt.
1793
1da177e4
LT
1794 smart2= [HW]
1795 Format: <io1>[,<io2>[,...,<io8>]]
1796
cd4f0ef7 1797 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1798 attempt to substitute SMP alternatives once at boot.
1799
d0d4f69b
BH
1800 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1801 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1802 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1803 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1804 smsc-ircc2.ircc_irq= [HW] IRQ line
1805 smsc-ircc2.ircc_dma= [HW] DMA channel
1806 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1807 0: Toshiba Satellite 1800 (GP data pin select)
1808 1: Fast pin select (default)
1809 2: ATC IRMode
1810
1da177e4
LT
1811 snd-ad1816a= [HW,ALSA]
1812
1813 snd-ad1848= [HW,ALSA]
1814
1815 snd-ali5451= [HW,ALSA]
1816
1817 snd-als100= [HW,ALSA]
1818
1819 snd-als4000= [HW,ALSA]
1820
1821 snd-azt2320= [HW,ALSA]
1822
1823 snd-cmi8330= [HW,ALSA]
1824
1825 snd-cmipci= [HW,ALSA]
1826
1827 snd-cs4231= [HW,ALSA]
1828
1829 snd-cs4232= [HW,ALSA]
1830
1831 snd-cs4236= [HW,ALSA]
1832
1833 snd-cs4281= [HW,ALSA]
1834
1835 snd-cs46xx= [HW,ALSA]
1836
1837 snd-dt019x= [HW,ALSA]
1838
1839 snd-dummy= [HW,ALSA]
1840
1841 snd-emu10k1= [HW,ALSA]
1842
1843 snd-ens1370= [HW,ALSA]
1844
1845 snd-ens1371= [HW,ALSA]
1846
1847 snd-es968= [HW,ALSA]
1848
1849 snd-es1688= [HW,ALSA]
1850
1851 snd-es18xx= [HW,ALSA]
1852
1853 snd-es1938= [HW,ALSA]
1854
1855 snd-es1968= [HW,ALSA]
1856
1857 snd-fm801= [HW,ALSA]
1858
1859 snd-gusclassic= [HW,ALSA]
1860
1861 snd-gusextreme= [HW,ALSA]
1862
1863 snd-gusmax= [HW,ALSA]
1864
1865 snd-hdsp= [HW,ALSA]
1866
1867 snd-ice1712= [HW,ALSA]
1868
1869 snd-intel8x0= [HW,ALSA]
1870
1871 snd-interwave= [HW,ALSA]
1872
1873 snd-interwave-stb=
1874 [HW,ALSA]
1875
1876 snd-korg1212= [HW,ALSA]
1877
1878 snd-maestro3= [HW,ALSA]
1879
1880 snd-mpu401= [HW,ALSA]
1881
1882 snd-mtpav= [HW,ALSA]
1883
1884 snd-nm256= [HW,ALSA]
1885
1886 snd-opl3sa2= [HW,ALSA]
1887
1888 snd-opti92x-ad1848=
1889 [HW,ALSA]
1890
1891 snd-opti92x-cs4231=
1892 [HW,ALSA]
1893
1894 snd-opti93x= [HW,ALSA]
1895
1896 snd-pmac= [HW,ALSA]
1897
1898 snd-rme32= [HW,ALSA]
1899
1900 snd-rme96= [HW,ALSA]
1901
1902 snd-rme9652= [HW,ALSA]
1903
1904 snd-sb8= [HW,ALSA]
1905
1906 snd-sb16= [HW,ALSA]
1907
1908 snd-sbawe= [HW,ALSA]
1909
1910 snd-serial= [HW,ALSA]
1911
1912 snd-sgalaxy= [HW,ALSA]
1913
1914 snd-sonicvibes= [HW,ALSA]
1915
1916 snd-sun-amd7930=
1917 [HW,ALSA]
1918
1919 snd-sun-cs4231= [HW,ALSA]
1920
1921 snd-trident= [HW,ALSA]
1922
1923 snd-usb-audio= [HW,ALSA,USB]
1924
1925 snd-via82xx= [HW,ALSA]
1926
1927 snd-virmidi= [HW,ALSA]
1928
1929 snd-wavefront= [HW,ALSA]
1930
1931 snd-ymfpci= [HW,ALSA]
a9913044 1932
1da177e4
LT
1933 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1934 See Documentation/sonypi.txt
1935
1936 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1937 See Documentation/specialix.txt.
1938
1939 spia_io_base= [HW,MTD]
1940 spia_fio_base=
1941 spia_pedr=
1942 spia_peddr=
1943
1944 sscape= [HW,OSS]
1945 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1946
1da177e4
LT
1947 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1948 See Documentation/scsi/st.txt.
1949
1da177e4
LT
1950 sti= [PARISC,HW]
1951 Format: <num>
1952 Set the STI (builtin display/keyboard on the HP-PARISC
1953 machines) console (graphic card) which should be used
1954 as the initial boot-console.
1955 See also comment in drivers/video/console/sticore.c.
1956
1957 sti_font= [HW]
1958 See comment in drivers/video/console/sticore.c.
1959
1960 stifb= [HW]
1961 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1962
42a7fc4a
GB
1963 sunrpc.pool_mode=
1964 [NFS]
1965 Control how the NFS server code allocates CPUs to
1966 service thread pools. Depending on how many NICs
1967 you have and where their interrupts are bound, this
1968 option will affect which CPUs will do NFS serving.
1969 Note: this parameter cannot be changed while the
1970 NFS server is running.
1971
1972 auto the server chooses an appropriate mode
1973 automatically using heuristics
1974 global a single global pool contains all CPUs
1975 percpu one pool for each CPU
1976 pernode one pool for each NUMA node (equivalent
1977 to global on non-NUMA machines)
1978
1da177e4 1979 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 1980
1da177e4
LT
1981 switches= [HW,M68k]
1982
1983 sym53c416= [HW,SCSI]
1984 See header of drivers/scsi/sym53c416.c.
1985
5d6f647f
IM
1986 sysrq_always_enabled
1987 [KNL]
1988 Ignore sysrq setting - this boot parameter will
1989 neutralize any effect of /proc/sys/kernel/sysrq.
1990 Useful for debugging.
1991
1da177e4
LT
1992 t128= [HW,SCSI]
1993 See header of drivers/scsi/t128.c.
1994
1995 tdfx= [HW,DRM]
1996
1997 thash_entries= [KNL,NET]
1998 Set number of hash buckets for TCP connection
1999
f8707ec9
LB
2000 thermal.act= [HW,ACPI]
2001 -1: disable all active trip points in all thermal zones
2002 <degrees C>: override all lowest active trip points
2003
c52a7419
LB
2004 thermal.crt= [HW,ACPI]
2005 -1: disable all critical trip points in all thermal zones
2006 <degrees C>: lower all critical trip points
2007
f5487145
LB
2008 thermal.nocrt= [HW,ACPI]
2009 Set to disable actions on ACPI thermal zone
2010 critical and hot trip points.
2011
72b33ef8
LB
2012 thermal.off= [HW,ACPI]
2013 1: disable ACPI thermal control
2014
a70cdc52
LB
2015 thermal.psv= [HW,ACPI]
2016 -1: disable all passive trip points
2017 <degrees C>: override all passive trip points to this value
2018
730ff34d
LB
2019 thermal.tzp= [HW,ACPI]
2020 Specify global default ACPI thermal zone polling rate
2021 <deci-seconds>: poll all this frequency
2022 0: no polling (default)
2023
1da177e4
LT
2024 tipar.timeout= [HW,PPT]
2025 Set communications timeout in tenths of a second
2026 (default 15).
2027
2028 tipar.delay= [HW,PPT]
2029 Set inter-bit delay in microseconds (default 10).
2030
1da177e4
LT
2031 tmscsim= [HW,SCSI]
2032 See comment before function dc390_setup() in
2033 drivers/scsi/tmscsim.c.
2034
2035 tp720= [HW,PS2]
2036
2037 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2038 Format:
2039 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2040
a9913044
RD
2041 turbografx.map[2|3]= [HW,JOY]
2042 TurboGraFX parallel port interface
2043 Format:
2044 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2045 See also Documentation/input/joystick-parport.txt
2046
2047 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2048 See header of drivers/scsi/u14-34f.c.
2049
2050 uart401= [HW,OSS]
2051 Format: <io>,<irq>
2052
2053 uart6850= [HW,OSS]
2054 Format: <io>,<irq>
2055
5f8364b7
AS
2056 uhci-hcd.ignore_oc=
2057 [USB] Ignore overcurrent events (default N).
2058 Some badly-designed motherboards generate lots of
2059 bogus events, for ports that aren't wired to
2060 anything. Set this parameter to avoid log spamming.
2061 Note that genuine overcurrent events won't be
2062 reported either.
2063
b5e795f8
AS
2064 usbcore.autosuspend=
2065 [USB] The autosuspend time delay (in seconds) used
2066 for newly-detected USB devices (default 2). This
2067 is the time required before an idle device will be
2068 autosuspended. Devices for which the delay is set
eaafbc3a 2069 to a negative value won't be autosuspended at all.
b5e795f8 2070
1da177e4
LT
2071 usbhid.mousepoll=
2072 [USBHID] The interval which mice are to be polled at.
a9913044 2073
cd4f0ef7 2074 vdso= [X86-32,SH,x86-64]
1dbf527c 2075 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2076 vdso=1: enable VDSO (default)
2077 vdso=0: disable VDSO mapping
2078
af65d648
RM
2079 vdso32= [X86-32,X86-64]
2080 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2081 vdso32=1: enable 32-bit VDSO (default)
2082 vdso32=0: disable 32-bit VDSO mapping
2083
d080d397
YI
2084 vector= [IA-64,SMP]
2085 vector=percpu: enable percpu vector domain
2086
1da177e4
LT
2087 video= [FB] Frame buffer configuration
2088 See Documentation/fb/modedb.txt.
2089
cd4f0ef7 2090 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2091 See Documentation/i386/boot.txt and
2092 Documentation/svga.txt.
1da177e4
LT
2093 Use vga=ask for menu.
2094 This is actually a boot loader parameter; the value is
2095 passed to the kernel using a special protocol.
2096
a9913044 2097 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2098 size of <nn>. This can be used to increase the
2099 minimum size (128MB on x86). It can also be used to
2100 decrease the size and leave more room for directly
2101 mapped kernel RAM.
2102
585c3047
PO
2103 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2104 Format: <command>
1da177e4 2105
585c3047
PO
2106 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2107 Format: <command>
2108
2109 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2110 Format: <command>
a9913044 2111
1da177e4
LT
2112 waveartist= [HW,OSS]
2113 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2114
1da177e4
LT
2115 wd33c93= [HW,SCSI]
2116 See header of drivers/scsi/wd33c93.c.
2117
2118 wd7000= [HW,SCSI]
2119 See header of drivers/scsi/wd7000.c.
2120
2121 wdt= [WDT] Watchdog
8dfe9c21 2122 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2123
2124 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2125 xd_geo= See header of drivers/block/xd.c.
2126
2127 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2128 Format:
2129 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2130
a62eaf15
AK
2131 norandmaps Don't use address space randomization
2132 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2133
a9913044 2134______________________________________________________________________
1da177e4
LT
2135
2136TODO:
2137
2138 Add documentation for ALSA options.
2139 Add more DRM drivers.