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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.
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377
378 checkreqprot [SELINUX] Set initial checkreqprot flag value.
379 Format: { "0" | "1" }
380 See security/selinux/Kconfig help text.
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381 0 -- check protection applied by kernel (includes
382 any implied execute protection).
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383 1 -- check protection requested by application.
384 Default value is set via a kernel config option.
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385 Value can be changed at runtime via
386 /selinux/checkreqprot.
387
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388 cio_ignore= [S390]
389 See Documentation/s390/CommonIO for details.
390
391 cio_msg= [S390]
392 See Documentation/s390/CommonIO for details.
393
cd4f0ef7 394 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 395 [Deprecated]
3f6dee9b 396 Forces specified clocksource (if available) to be used
734efb46 397 when calculating gettimeofday(). If specified
3f6dee9b 398 clocksource is not available, it defaults to PIT.
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399 Format: { pit | tsc | cyclone | pmtmr }
400
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401 clocksource= [GENERIC_TIME] Override the default clocksource
402 Format: <string>
403 Override the default clocksource and use the clocksource
404 with the name specified.
405 Some clocksource names to choose from, depending on
406 the platform:
407 [all] jiffies (this is the base, fallback clocksource)
408 [ACPI] acpi_pm
409 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
410 pxa_timer,timer3,32k_counter,timer0_1
411 [AVR32] avr32
cd4f0ef7 412 [X86-32] pit,hpet,tsc,vmi-timer;
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RD
413 scx200_hrt on Geode; cyclone on IBM x440
414 [MIPS] MIPS
415 [PARISC] cr16
416 [S390] tod
417 [SH] SuperH
418 [SPARC64] tick
419 [X86-64] hpet,tsc
420
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421 clearcpuid=BITNUM [X86]
422 Disable CPUID feature X for the kernel. See
423 include/asm-x86/cpufeature.h for the valid bit numbers.
424 Note the Linux specific bits are not necessarily
425 stable over kernel options, but the vendor specific
426 ones should be.
427 Also note that user programs calling CPUID directly
428 or using the feature without checking anything
429 will still see it. This just prevents it from
430 being used by the kernel or shown in /proc/cpuinfo.
431 Also note the kernel might malfunction if you disable
432 some critical bits.
433
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434 code_bytes [IA32/X86_64] How many bytes of object code to print
435 in an oops report.
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436 Range: 0 - 8192
437 Default: 64
438
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439 disable_8254_timer
440 enable_8254_timer
441 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
442 over the 8254 in addition to over the IO-APIC. The
443 kernel tries to set a sensible default.
444
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445 hpet= [X86-32,HPET] option to control HPET usage
446 Format: { enable (default) | disable | force }
447 disable: disable HPET and use PIT instead
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448 force: allow force enabled of undocumented chips (ICH4,
449 VIA, nVidia)
1da177e4 450
1da177e4 451 com20020= [HW,NET] ARCnet - COM20020 chipset
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RD
452 Format:
453 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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LT
454
455 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
456 Format: <io>[,<irq>]
457
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RD
458 com90xx= [HW,NET]
459 ARCnet - COM90xx chipset (memory-mapped buffers)
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LT
460 Format: <io>[,<irq>[,<memstart>]]
461
462 condev= [HW,S390] console device
463 conmode=
a9913044 464
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LT
465 console= [KNL] Output console device and options.
466
467 tty<n> Use the virtual console device <n>.
468
469 ttyS<n>[,options]
f1a1c2dc 470 ttyUSB0[,options]
1da177e4 471 Use the specified serial port. The options are of
f1a1c2dc
RD
472 the form "bbbbpnf", where "bbbb" is the baud rate,
473 "p" is parity ("n", "o", or "e"), "n" is number of
474 bits, and "f" is flow control ("r" for RTS or
475 omit it). Default is "9600n8".
476
477 See Documentation/serial-console.txt for more
478 information. See
479 Documentation/networking/netconsole.txt for an
480 alternative.
1da177e4 481
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YL
482 uart[8250],io,<addr>[,options]
483 uart[8250],mmio,<addr>[,options]
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LT
484 Start an early, polled-mode console on the 8250/16550
485 UART at the specified I/O port or MMIO address,
486 switching to the matching ttyS device later. The
487 options are the same as for ttyS, above.
488
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489 earlycon= [KNL] Output early console device and options.
490 uart[8250],io,<addr>[,options]
491 uart[8250],mmio,<addr>[,options]
492 Start an early, polled-mode console on the 8250/16550
493 UART at the specified I/O port or MMIO address.
494 The options are the same as for ttyS, above.
495
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496 no_console_suspend
497 [HW] Never suspend the console
498 Disable suspending of consoles during suspend and
499 hibernate operations. Once disabled, debugging
500 messages can reach various consoles while the rest
501 of the system is being put to sleep (ie, while
502 debugging driver suspend/resume hooks). This may
503 not work reliably with all consoles, but is known
504 to work with serial and VGA consoles.
505
1da177e4 506 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
507 Format:
508 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 509
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EB
510 crashkernel=nn[KMG]@ss[KMG]
511 [KNL] Reserve a chunk of physical memory to
512 hold a kernel to switch to with kexec on panic.
513
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514 crashkernel=range1:size1[,range2:size2,...][@offset]
515 [KNL] Same as above, but depends on the memory
516 in the running system. The syntax of range is
517 start-[end] where start and end are both
518 a memory unit (amount[KMG]). See also
519 Documentation/kdump/kdump.txt for a example.
520
1da177e4
LT
521 cs4232= [HW,OSS]
522 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
523
524 cs89x0_dma= [HW,NET]
525 Format: <dma>
526
527 cs89x0_media= [HW,NET]
528 Format: { rj45 | aui | bnc }
a9913044 529
a9913044 530 dasd= [HW,NET]
1da177e4
LT
531 See header of drivers/s390/block/dasd_devmap.c.
532
533 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
534 (one device per port)
535 Format: <port#>,<type>
536 See also Documentation/input/joystick-parport.txt
537
538 debug [KNL] Enable kernel debugging (events log level).
539
cae2ed9a
IM
540 debug_locks_verbose=
541 [KNL] verbose self-tests
542 Format=<0|1>
543 Print debugging info while doing the locking API
544 self-tests.
545 We default to 0 (no extra messages), setting it to
546 1 will print _a lot_ more information - normally
547 only useful to kernel developers.
548
2d27a966 549 decnet.addr= [HW,NET]
1da177e4
LT
550 Format: <area>[,<node>]
551 See also Documentation/networking/decnet.txt.
552
ecb77fa9 553 vt.default_blu= [VT]
55ff9780
AD
554 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
555 Change the default blue palette of the console.
556 This is a 16-member array composed of values
557 ranging from 0-255.
558
ecb77fa9 559 vt.default_grn= [VT]
55ff9780
AD
560 Format: <green0>,<green1>,<green2>,...,<green15>
561 Change the default green palette of the console.
562 This is a 16-member array composed of values
563 ranging from 0-255.
564
ecb77fa9 565 vt.default_red= [VT]
55ff9780
AD
566 Format: <red0>,<red1>,<red2>,...,<red15>
567 Change the default red palette of the console.
568 This is a 16-member array composed of values
569 ranging from 0-255.
570
ecb77fa9
ST
571 vt.default_utf8=
572 [VT]
55ff9780
AD
573 Format=<0|1>
574 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
575 Default is 1, i.e. UTF-8 mode is enabled for all
576 newly opened terminals.
55ff9780 577
1da177e4
LT
578 dhash_entries= [KNL]
579 Set number of hash buckets for dentry cache.
a9913044 580
1da177e4
LT
581 digi= [HW,SERIAL]
582 IO parameters + enable/disable command.
583
584 digiepca= [HW,SERIAL]
585 See drivers/char/README.epca and
586 Documentation/digiepca.txt.
587
093af8d7 588 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
589 By default the kernel will trim any uncacheable
590 memory out of your available memory pool based on
591 MTRR settings. This parameter disables that behavior,
592 possibly causing your machine to run very slowly.
593
1da177e4
LT
594 dmasound= [HW,OSS] Sound subsystem buffers
595
596 dscc4.setup= [NET]
597
598 dtc3181e= [HW,SCSI]
599
0ae53640 600 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
601 earlyprintk=vga
602 earlyprintk=serial[,ttySn[,baudrate]]
603
a9913044 604 Append ",keep" to not disable it when the real console
1da177e4
LT
605 takes over.
606
607 Only vga or serial at a time, not both.
608
609 Currently only ttyS0 and ttyS1 are supported.
610
611 Interaction with the standard serial driver is not
612 very good.
613
614 The VGA output is eventually overwritten by the real
615 console.
616
617 eata= [HW,SCSI]
618
1da177e4
LT
619 edd= [EDD]
620 Format: {"of[f]" | "sk[ipmbr]"}
621 See comment in arch/i386/boot/edd.S
622
1da177e4
LT
623 eisa_irq_edge= [PARISC,HW]
624 See header of drivers/parisc/eisa.c.
625
cd4f0ef7 626 elanfreq= [X86-32]
1da177e4
LT
627 See comment before function elanfreq_setup() in
628 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
629
630 elevator= [IOSCHED]
16ab3adf 631 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
632 See Documentation/block/as-iosched.txt and
633 Documentation/block/deadline-iosched.txt for details.
634
cd4f0ef7 635 elfcorehdr= [X86-32, X86_64]
a9913044 636 Specifies physical address of start of kernel core
aac04b32
VG
637 image elf header. Generally kexec loader will
638 pass this option to capture kernel.
639 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
640
641 enforcing [SELINUX] Set initial enforcing status.
642 Format: {"0" | "1"}
643 See security/selinux/Kconfig help text.
644 0 -- permissive (log only, no denials).
645 1 -- enforcing (deny and log).
646 Default value is 0.
647 Value can be changed at runtime via /selinux/enforce.
648
1da177e4
LT
649 es1371= [HW,OSS]
650 Format: <spdif>,[<nomix>,[<amplifier>]]
651 See also header of sound/oss/es1371.c.
a9913044 652
1da177e4
LT
653 ether= [HW,NET] Ethernet cards parameters
654 This option is obsoleted by the "netdev=" option, which
655 has equivalent usage. See its documentation for details.
656
657 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
658 Format: <io>[,<irq>]
659
de1ba09b
AM
660 failslab=
661 fail_page_alloc=
662 fail_make_request=[KNL]
663 General fault injection mechanism.
664 Format: <interval>,<probability>,<space>,<times>
665 See also /Documentation/fault-injection/.
666
1da177e4
LT
667 fd_mcs= [HW,SCSI]
668 See header of drivers/scsi/fd_mcs.c.
669
670 fdomain= [HW,SCSI]
671 See header of drivers/scsi/fdomain.c.
672
673 floppy= [HW]
674 See Documentation/floppy.txt.
675
1da177e4
LT
676 gamecon.map[2|3]=
677 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
678 support via parallel port (up to 5 devices per port)
679 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
680 See also Documentation/input/joystick-parport.txt
681
682 gamma= [HW,DRM]
683
aaf23042
YL
684 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
685 Format: off | on
686 default: on
687
1da177e4
LT
688 gdth= [HW,SCSI]
689 See header of drivers/scsi/gdth.c.
690
691 gpt [EFI] Forces disk with valid GPT signature but
692 invalid Protective MBR to be treated as GPT.
693
1da177e4
LT
694 gvp11= [HW,SCSI]
695
696 hashdist= [KNL,NUMA] Large hashes allocated during boot
697 are distributed across NUMA nodes. Defaults on
698 for IA-64, off otherwise.
a9913044 699 Format: 0 | 1 (for off | on)
1da177e4
LT
700
701 hcl= [IA-64] SGI's Hardware Graph compatibility layer
702
703 hd= [EIDE] (E)IDE hard drive subsystem geometry
704 Format: <cyl>,<head>,<sect>
705
706 hd?= [HW] (E)IDE subsystem
1c10e938 707 hd?lun= See Documentation/ide/ide.txt.
1da177e4
LT
708
709 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
710 size of <nn>. This works even on boxes that have no
711 highmem otherwise. This also works to reduce highmem
712 size on bigger boxes.
713
54cdfdb4
TG
714 highres= [KNL] Enable/disable high resolution timer mode.
715 Valid parameters: "on", "off"
716 Default: "on"
717
1da177e4
LT
718 hisax= [HW,ISDN]
719 See Documentation/isdn/README.HiSax.
720
cd4f0ef7 721 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 722 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 723
1da177e4 724 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
725 i8042.dumbkbd [HW] Pretend that controller can only read data from
726 keyboard and cannot control its state
1da177e4
LT
727 (Don't attempt to blink the leds)
728 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 729 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
730 i8042.noloop [HW] Disable the AUX Loopback command while probing
731 for the AUX port
1da177e4
LT
732 i8042.nomux [HW] Don't check presence of an active multiplexing
733 controller
734 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
735 controllers
736 i8042.panicblink=
737 [HW] Frequency with which keyboard LEDs should blink
738 when kernel panics (default is 0.5 sec)
739 i8042.reset [HW] Reset the controller during init and cleanup
740 i8042.unlock [HW] Unlock (ignore) the keylock
741
742 i810= [HW,DRM]
743
e70c9d5e
DT
744 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
745 indicates that the driver is running on unsupported
746 hardware.
1da177e4
LT
747 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
748 does not match list of supported models.
749 i8k.power_status
750 [HW] Report power status in /proc/i8k
751 (disabled by default)
752 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
753 capability is set.
754
755 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
756 See Documentation/mca.txt.
757
758 icn= [HW,ISDN]
759 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
760
761 ide= [HW] (E)IDE subsystem
762 Format: ide=nodma or ide=doubler or ide=reverse
1c10e938 763 See Documentation/ide/ide.txt.
1da177e4
LT
764
765 ide?= [HW] (E)IDE subsystem
766 Format: ide?=noprobe or chipset specific parameters.
1c10e938 767 See Documentation/ide/ide.txt.
a9913044 768
1da177e4 769 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 770 See Documentation/ide/ide.txt.
1da177e4 771
f039b754
AK
772 idle= [X86]
773 Format: idle=poll or idle=mwait
774 Poll forces a polling idle loop that can slightly improves the performance
775 of waking up a idle CPU, but will use a lot of power and make the system
776 run hot. Not recommended.
777 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
778 to not use it because it doesn't save as much power as a normal idle
779 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
780 as idle=poll.
a9913044 781
594765a7
DC
782 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
783 Claim all unknown PCI IDE storage controllers.
784
79290822
IM
785 ignore_loglevel [KNL]
786 Ignore loglevel setting - this will print /all/
787 kernel messages to the console. Useful for debugging.
788
1da177e4
LT
789 ihash_entries= [KNL]
790 Set number of hash buckets for inode cache.
791
792 in2000= [HW,SCSI]
793 See header of drivers/scsi/in2000.c.
794
795 init= [KNL]
796 Format: <full_path>
797 Run specified binary instead of /sbin/init as init
798 process.
799
800 initcall_debug [KNL] Trace initcalls as they are executed. Useful
801 for working out where the kernel is dying during
802 startup.
803
804 initrd= [BOOT] Specify the location of the initial ramdisk
805
806 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
807 Format: <irq>
808
809 inttest= [IA64]
810
ba395927
KA
811 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
812 off
813 Disable intel iommu driver.
814 igfx_off [Default Off]
815 By default, gfx is mapped as normal device. If a gfx
816 device has a dedicated DMAR unit, the DMAR unit is
817 bypassed by not enabling DMAR with this option. In
818 this case, gfx device will use physical address for
819 DMA.
7d3b03ce
KA
820 forcedac [x86_64]
821 With this option iommu will not optimize to look
822 for io virtual address below 32 bit forcing dual
823 address cycle on pci bus for cards supporting greater
824 than 32 bit addressing. The default is to look
825 for translation below 32 bit and if not available
826 then look in the higher range.
ba395927 827
b02aae9c 828 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
829 0x80
830 Standard port 0x80 based delay
831 0xed
832 Alternate port 0xed based delay (needed on some systems)
b02aae9c 833 udelay
6e7c4025
IM
834 Simple two microseconds delay
835 none
836 No delay
b02aae9c 837
1da177e4
LT
838 io7= [HW] IO7 for Marvel based alpha systems
839 See comment before marvel_specify_io7 in
840 arch/alpha/kernel/core_marvel.c.
841
842 ip= [IP_PNP]
843 See Documentation/nfsroot.txt.
844
845 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
846 See comment before ip2_setup() in
847 drivers/char/ip2/ip2base.c.
1da177e4
LT
848
849 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
850 See header of drivers/scsi/ips.c.
851
72c4a13a
SH
852 ports= [IP_VS_FTP] IPVS ftp helper module
853 Default is 21.
854 Up to 8 (IP_VS_APP_MAX_PORTS) ports
855 may be specified.
856 Format: <port>,<port>....
857
200803df
AC
858 irqfixup [HW]
859 When an interrupt is not handled search all handlers
860 for it. Intended to get systems with badly broken
861 firmware running.
862
863 irqpoll [HW]
864 When an interrupt is not handled search all handlers
865 for it. Also check all handlers each timer
866 interrupt. Intended to get systems with badly broken
867 firmware running.
868
1da177e4 869 isapnp= [ISAPNP]
a9913044 870 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
871
872 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
873 Format:
874 <cpu number>,...,<cpu number>
875 or
876 <cpu number>-<cpu number> (must be a positive range in ascending order)
877 or a mixture
878 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
879 This option can be used to specify one or more CPUs
880 to isolate from the general SMP balancing and scheduling
881 algorithms. The only way to move a process onto or off
882 an "isolated" CPU is via the CPU affinity syscalls.
883 <cpu number> begins at 0 and the maximum value is
884 "number of CPUs in system - 1".
885
886 This option is the preferred way to isolate CPUs. The
a9913044
RD
887 alternative -- manually setting the CPU mask of all
888 tasks in the system -- can cause problems and
889 suboptimal load balancer performance.
1da177e4 890
a9913044 891 iucv= [HW,NET]
1da177e4
LT
892
893 js= [HW,JOY] Analog joystick
894 See Documentation/input/joystick.txt.
895
cd4f0ef7 896 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
897 specifies the amount of memory usable by the kernel
898 for non-movable allocations. The requested amount is
899 spread evenly throughout all nodes in the system. The
900 remaining memory in each node is used for Movable
901 pages. In the event, a node is too small to have both
902 kernelcore and Movable pages, kernelcore pages will
903 take priority and other nodes will have a larger number
904 of kernelcore pages. The Movable zone is used for the
905 allocation of pages that may be reclaimed or moved
906 by the page migration subsystem. This means that
907 HugeTLB pages may not be allocated from this zone.
908 Note that allocations like PTEs-from-HighMem still
909 use the HighMem zone if it exists, and the Normal
910 zone if it does not.
911
cd4f0ef7 912 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
913 is similar to kernelcore except it specifies the
914 amount of memory used for migratable allocations.
915 If both kernelcore and movablecore is specified,
916 then kernelcore will be at *least* the specified
917 value but may be more. If movablecore on its own
918 is specified, the administrator must be careful
919 that the amount of memory usable for all allocations
920 is not too small.
921
1da177e4
LT
922 keepinitrd [HW,ARM]
923
cd4f0ef7 924 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
925 in oops dumps.
926
927 l2cr= [PPC]
928
cd4f0ef7 929 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 930 disabled it.
1da177e4 931
cd4f0ef7 932 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
933 C2 power state.
934
fcb71f6f
FC
935 libata.dma= [LIBATA] DMA control
936 libata.dma=0 Disable all PATA and SATA DMA
937 libata.dma=1 PATA and SATA Disk DMA only
938 libata.dma=2 ATAPI (CDROM) DMA only
939 libata.dma=4 Compact Flash DMA only
940 Combinations also work, so libata.dma=3 enables DMA
941 for disks and CDROMs, but not CFs.
942
78e70c23
DJ
943 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
944 when set.
945 Format: <int>
946
33267325
TH
947 libata.force= [LIBATA] Force configurations. The format is comma
948 separated list of "[ID:]VAL" where ID is
949 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
950 matching port, link or device. Basically, it matches
951 the ATA ID string printed on console by libata. If
952 the whole ID part is omitted, the last PORT and DEVICE
953 values are used. If ID hasn't been specified yet, the
954 configuration applies to all ports, links and devices.
955
956 If only DEVICE is omitted, the parameter applies to
957 the port and all links and devices behind it. DEVICE
958 number of 0 either selects the first device or the
959 first fan-out link behind PMP device. It does not
960 select the host link. DEVICE number of 15 selects the
961 host link and device attached to it.
962
963 The VAL specifies the configuration to force. As long
964 as there's no ambiguity shortcut notation is allowed.
965 For example, both 1.5 and 1.5G would work for 1.5Gbps.
966 The following configurations can be forced.
967
968 * Cable type: 40c, 80c, short40c, unk, ign or sata.
969 Any ID with matching PORT is used.
970
971 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
972
973 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
974 udma[/][16,25,33,44,66,100,133] notation is also
975 allowed.
976
977 * [no]ncq: Turn on or off NCQ.
978
979 If there are multiple matching configurations changing
980 the same attribute, the last one is used.
981
1da177e4
LT
982 load_ramdisk= [RAM] List of ramdisks to load from floppy
983 See Documentation/ramdisk.txt.
984
a6b25b67
RD
985 lockd.nlm_grace_period=P [NFS] Assign grace period.
986 Format: <integer>
1da177e4 987
a6b25b67
RD
988 lockd.nlm_tcpport=N [NFS] Assign TCP port.
989 Format: <integer>
990
991 lockd.nlm_timeout=T [NFS] Assign timeout value.
992 Format: <integer>
993
994 lockd.nlm_udpport=M [NFS] Assign UDP port.
995 Format: <integer>
1da177e4
LT
996
997 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
998 Format: <irq>
999
1000 loglevel= All Kernel Messages with a loglevel smaller than the
1001 console loglevel will be printed to the console. It can
1002 also be changed with klogd or other programs. The
1003 loglevels are defined as follows:
1004
1005 0 (KERN_EMERG) system is unusable
1006 1 (KERN_ALERT) action must be taken immediately
1007 2 (KERN_CRIT) critical conditions
1008 3 (KERN_ERR) error conditions
1009 4 (KERN_WARNING) warning conditions
1010 5 (KERN_NOTICE) normal but significant condition
1011 6 (KERN_INFO) informational
1012 7 (KERN_DEBUG) debug-level messages
1013
1014 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1015 Format: { n | nk | nM }
1016 n must be a power of two. The default size
1017 is set in the kernel config file.
1da177e4 1018
accaa24c
RD
1019 logo.nologo [FB] Disables display of the built-in Linux logo.
1020 This may be used to provide more screen space for
1021 kernel log messages and is useful when debugging
1022 kernel boot problems.
1023
1da177e4
LT
1024 lp=0 [LP] Specify parallel ports to use, e.g,
1025 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1026 lp=reset first parallel port). 'lp=0' disables the
1027 lp=auto printer driver. 'lp=reset' (which can be
1028 specified in addition to the ports) causes
1029 attached printers to be reset. Using
1030 lp=port1,port2,... specifies the parallel ports
1031 to associate lp devices with, starting with
1032 lp0. A port specification may be 'none' to skip
1033 that lp device, or a parport name such as
1034 'parport0'. Specifying 'lp=auto' instead of a
1035 port specification list means that device IDs
1036 from each port should be examined, to see if
1037 an IEEE 1284-compliant printer is attached; if
1038 so, the driver will manage that printer.
1039 See also header of drivers/char/lp.c.
1040
1041 lpj=n [KNL]
1042 Sets loops_per_jiffy to given constant, thus avoiding
1043 time-consuming boot-time autodetection (up to 250 ms per
1044 CPU). 0 enables autodetection (default). To determine
1045 the correct value for your kernel, boot with normal
1046 autodetection and see what value is printed. Note that
1047 on SMP systems the preset will be applied to all CPUs,
1048 which is likely to cause problems if your CPUs need
1049 significantly divergent settings. An incorrect value
1050 will cause delays in the kernel to be wrong, leading to
1051 unpredictable I/O errors and other breakage. Although
1052 unlikely, in the extreme case this might damage your
1053 hardware.
1054
1055 ltpc= [NET]
1056 Format: <io>,<irq>,<dma>
1057
a9913044
RD
1058 mac5380= [HW,SCSI] Format:
1059 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1060
a9913044
RD
1061 mac53c9x= [HW,SCSI] Format:
1062 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1063
a9913044
RD
1064 machvec= [IA64] Force the use of a particular machine-vector
1065 (machvec) in a generic kernel.
1066 Example: machvec=hpzx1_swiotlb
1da177e4 1067
a9913044 1068 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1069 be mounted
1070 Format: <1-256>
1071
1072 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1073 should make use of. maxcpus=n : n >= 0 limits the
1074 kernel to using 'n' processors. n=0 is a special case,
1075 it is equivalent to "nosmp", which also disables
1076 the IO APIC.
1da177e4 1077
2b2c3750
BP
1078 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1079 equal to this physical address is ignored.
1080
a9913044 1081 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1082 Should be between 1 and 2^32-1.
1083
1084 max_report_luns=
a9913044 1085 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1086 Should be between 1 and 16384.
1087
1da177e4
LT
1088 mcatest= [IA-64]
1089
cd4f0ef7 1090 mce [X86-32] Machine Check Exception
1da177e4 1091
909dd324
AK
1092 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1093
1da177e4
LT
1094 md= [HW] RAID subsystems devices and level
1095 See Documentation/md.txt.
a9913044 1096
1da177e4
LT
1097 mdacon= [MDA]
1098 Format: <first>,<last>
1099 Specifies range of consoles to be captured by the MDA.
a9913044 1100
1da177e4
LT
1101 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1102 Amount of memory to be used when the kernel is not able
1103 to see the whole system memory or for test.
cd4f0ef7 1104 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1105 address space collisions. Without memmap= PCI devices
1106 could be placed at addresses belonging to unused RAM.
1107
cd4f0ef7 1108 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1109 memory.
1110
cd4f0ef7 1111 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1112 E820 memory map, as specified by the user.
1113 Such memmap=exactmap lines can be constructed based on
1114 BIOS output or other requirements. See the memmap=nn@ss
1115 option description.
1116
1117 memmap=nn[KMG]@ss[KMG]
1118 [KNL] Force usage of a specific region of memory
1119 Region of memory to be used, from ss to ss+nn.
1120
1121 memmap=nn[KMG]#ss[KMG]
1122 [KNL,ACPI] Mark specific memory as ACPI data.
1123 Region of memory to be used, from ss to ss+nn.
1124
1125 memmap=nn[KMG]$ss[KMG]
1126 [KNL,ACPI] Mark specific memory as reserved.
1127 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1128 Example: Exclude memory from 0x18690000-0x1869ffff
1129 memmap=64K$0x18690000
1130 or
1131 memmap=0x10000$0x18690000
1da177e4
LT
1132
1133 meye.*= [HW] Set MotionEye Camera parameters
1134 See Documentation/video4linux/meye.txt.
1135
8f36881b
AS
1136 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1137 Multi-Function General Purpose Timers on AMD Geode
1138 platforms.
1139
e6c4dc6c
WT
1140 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1141 the BIOS has incorrectly applied a workaround. TinyBIOS
1142 version 0.98 is known to be affected, 0.99 fixes the
1143 problem by letting the user disable the workaround.
1144
1da177e4
LT
1145 mga= [HW,DRM]
1146
1147 mousedev.tap_time=
1148 [MOUSE] Maximum time between finger touching and
1149 leaving touchpad surface for touch to be considered
1150 a tap and be reported as a left button click (for
1151 touchpads working in absolute mode only).
1152 Format: <msecs>
1153 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1154 reporting absolute coordinates, such as tablets
1155 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1156 reporting absolute coordinates, such as tablets
1157
1158 mpu401= [HW,OSS]
1159 Format: <io>,<irq>
1160
1161 MTD_Partition= [MTD]
1162 Format: <name>,<region-number>,<size>,<offset>
1163
a9913044
RD
1164 MTD_Region= [MTD] Format:
1165 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1166
1167 mtdparts= [MTD]
c8facbb6 1168 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1169
1170 mtouchusb.raw_coordinates=
a9913044
RD
1171 [HW] Make the MicroTouch USB driver use raw coordinates
1172 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1173
1174 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1175
1176 NCR_D700= [HW,SCSI]
1177 See header of drivers/scsi/NCR_D700.c.
1178
1179 ncr5380= [HW,SCSI]
1180
1181 ncr53c400= [HW,SCSI]
1182
1183 ncr53c400a= [HW,SCSI]
1184
1185 ncr53c406a= [HW,SCSI]
1186
1187 ncr53c8xx= [HW,SCSI]
1188
1189 netdev= [NET] Network devices parameters
1190 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1191 Note that mem_start is often overloaded to mean
1192 something different and driver-specific.
a9913044
RD
1193 This usage is only documented in each driver source
1194 file if at all.
1195
1da177e4
LT
1196 nfsaddrs= [NFS]
1197 See Documentation/nfsroot.txt.
1198
1199 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1200 See Documentation/nfsroot.txt.
1201
a72b4422
TM
1202 nfs.callback_tcpport=
1203 [NFS] set the TCP port on which the NFSv4 callback
1204 channel should listen.
1205
58df095b
TM
1206 nfs.idmap_cache_timeout=
1207 [NFS] set the maximum lifetime for idmapper cache
1208 entries.
1209
f43bf0be
TM
1210 nfs.enable_ino64=
1211 [NFS] enable 64-bit inode numbers.
1212 If zero, the NFS client will fake up a 32-bit inode
1213 number for the readdir() and stat() syscalls instead
1214 of returning the full 64-bit number.
1215 The default is to return 64-bit inode numbers.
1216
e7ba176b
HS
1217 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1218 when a NMI is triggered.
1219 Format: [state][,regs][,debounce][,die]
1220
cd4f0ef7 1221 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1222
cd4f0ef7 1223 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1224 emulation library even if a 387 maths coprocessor
1225 is present.
1226
c1aee215
CL
1227 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1228 caches in the slab allocator. Saves per-node memory,
1229 but will impact performance.
3395ee05 1230
a9913044
RD
1231 noalign [KNL,ARM]
1232
1da177e4
LT
1233 noapic [SMP,APIC] Tells the kernel to not make use of any
1234 IOAPICs that may be present in the system.
1235
1da177e4
LT
1236 nobats [PPC] Do not use BATs for mapping kernel lowmem
1237 on "Classic" PPC cores.
1238
1239 nocache [ARM]
a9913044 1240
163ecdff
SN
1241 nodelayacct [KNL] Disable per-task delay accounting
1242
1da177e4
LT
1243 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1244
8b2cb7a8
HY
1245 noefi [X86-32,X86-64] Disable EFI runtime services support.
1246
1da177e4
LT
1247 noexec [IA-64]
1248
cd4f0ef7 1249 noexec [X86-32,X86-64]
1da177e4
LT
1250 noexec=on: enable non-executable mappings (default)
1251 noexec=off: disable nn-executable mappings
1252
cd4f0ef7 1253 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1254 register save and restore. The kernel will only save
1255 legacy floating-point registers on task switch.
1da177e4 1256
191679fd
AK
1257 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1258
1da177e4 1259 nohlt [BUGS=ARM]
a9913044 1260
cd4f0ef7 1261 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1262 instruction doesn't work correctly and not to
1263 use it.
1264
1265 nohalt [IA-64] Tells the kernel not to use the power saving
1266 function PAL_HALT_LIGHT when idle. This increases
1267 power-consumption. On the positive side, it reduces
1268 interrupt wake-up latency, which may improve performance
1269 in certain environments such as networked servers or
1270 real-time systems.
1271
79bf2bb3
TG
1272 nohz= [KNL] Boottime enable/disable dynamic ticks
1273 Valid arguments: on, off
1274 Default: on
1275
cd4f0ef7 1276 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1277
cd4f0ef7 1278 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1279 disable unhandled interrupt sources.
1280
cd4f0ef7 1281 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1282 broken timer IRQ sources.
1283
1da177e4
LT
1284 noisapnp [ISAPNP] Disables ISA PnP code.
1285
1286 noinitrd [RAM] Tells the kernel not to load any configured
1287 initial RAM disk.
1288
1289 nointroute [IA-64]
1290
0aa366f3
TL
1291 nojitter [IA64] Disables jitter checking for ITC timers.
1292
cd4f0ef7 1293 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1294
cd4f0ef7 1295 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1296
1da177e4
LT
1297 noltlbs [PPC] Do not use large page/tlb entries for kernel
1298 lowmem mapping on PPC40x.
1299
312f1f01
H
1300 nomca [IA-64] Disable machine check abort handling
1301
cd4f0ef7 1302 nomce [X86-32] Machine Check Exception
abe37e5a 1303
83d7384f
AS
1304 nomfgpt [X86-32] Disable Multi-Function General Purpose
1305 Timer usage (for AMD Geode machines).
1306
cd4f0ef7 1307 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1308
cd4f0ef7 1309 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1310 with UP alternatives
1311
1da177e4
LT
1312 noresidual [PPC] Don't use residual data on PReP machines.
1313
a9913044
RD
1314 noresume [SWSUSP] Disables resume and restores original swap
1315 space.
1316
1da177e4
LT
1317 no-scroll [VGA] Disables scrollback.
1318 This is required for the Braillex ib80-piezo Braille
1319 reader made by F.H. Papenmeier (Germany).
1320
1321 nosbagart [IA-64]
1322
cd4f0ef7 1323 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1324
61ec7567
LB
1325 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1326 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1327
97842216
DJ
1328 nosoftlockup [KNL] Disable the soft-lockup detector.
1329
1da177e4
LT
1330 nosync [HW,M68K] Disables sync negotiation for all devices.
1331
cd4f0ef7 1332 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1333
1334 nousb [USB] Disable the USB subsystem
1335
1336 nowb [ARM]
a9913044 1337
f0c0b2b8
KH
1338 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1339 one of ['zone', 'node', 'default'] can be specified
1340 This can be set from sysctl after boot.
1341 See Documentation/sysctl/vm.txt for details.
1342
a61c2d78
DJ
1343 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1344
1da177e4
LT
1345 opl3= [HW,OSS]
1346 Format: <io>
1347
1da177e4
LT
1348 oprofile.timer= [HW]
1349 Use timer interrupt instead of performance counters
1350
1da177e4
LT
1351 osst= [HW,SCSI] SCSI Tape Driver
1352 Format: <buffer_size>,<write_threshold>
1353 See also Documentation/scsi/st.txt.
1354
1355 panic= [KNL] Kernel behaviour on panic
1356 Format: <timeout>
1357
1358 parkbd.port= [HW] Parallel port number the keyboard adapter is
1359 connected to, default is 0.
1360 Format: <parport#>
1361 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1362 0 for XT, 1 for AT (default is AT).
a9913044
RD
1363 Format: <mode>
1364
1365 parport= [HW,PPT] Specify parallel ports. 0 disables.
1366 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1367 Use 'auto' to force the driver to use any
1368 IRQ/DMA settings detected (the default is to
1369 ignore detected IRQ/DMA settings because of
1370 possible conflicts). You can specify the base
1371 address, IRQ, and DMA settings; IRQ and DMA
1372 should be numbers, or 'auto' (for using detected
1373 settings on that particular port), or 'nofifo'
1374 (to avoid using a FIFO even if it is detected).
1375 Parallel ports are assigned in the order they
1376 are specified on the command line, starting
1377 with parport0.
1378
1379 parport_init_mode= [HW,PPT]
1380 Configure VIA parallel port to operate in
1381 a specific mode. This is necessary on Pegasos
1382 computer where firmware has no options for setting
1383 up parallel port mode and sets it to spp.
1384 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1385 Format: [spp|ps2|epp|ecp|ecpepp]
1386
a9913044
RD
1387 pas2= [HW,OSS] Format:
1388 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1389
1da177e4
LT
1390 pas16= [HW,SCSI]
1391 See header of drivers/scsi/pas16.c.
1392
dd287796
AM
1393 pause_on_oops=
1394 Halt all CPUs after the first oops has been printed for
1395 the specified number of seconds. This is to be used if
1396 your oopses keep scrolling off the screen.
1397
1da177e4
LT
1398 pcbit= [HW,ISDN]
1399
1400 pcd. [PARIDE]
1401 See header of drivers/block/paride/pcd.c.
1402 See also Documentation/paride.txt.
1403
a9913044 1404 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1405 off [X86-32] don't probe for the PCI bus
1406 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1407 the hardware directly. Use this if your machine
1408 has a non-standard PCI host bridge.
cd4f0ef7 1409 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1410 hardware access methods are allowed. Use this
1411 if you experience crashes upon bootup and you
1412 suspect they are caused by the BIOS.
cd4f0ef7 1413 conf1 [X86-32] Force use of PCI Configuration
a9913044 1414 Mechanism 1.
cd4f0ef7 1415 conf2 [X86-32] Force use of PCI Configuration
a9913044 1416 Mechanism 2.
7f785763
RD
1417 noaer [PCIE] If the PCIEAER kernel config parameter is
1418 enabled, this kernel boot option can be used to
1419 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1420 nodomains [PCI] Disable support for multiple PCI
1421 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1422 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1423 Configuration
309e57df
MW
1424 nomsi [MSI] If the PCI_MSI kernel config parameter is
1425 enabled, this kernel boot option can be used to
1426 disable the use of MSI interrupts system-wide.
cd4f0ef7 1427 nosort [X86-32] Don't sort PCI devices according to
a9913044
RD
1428 order given by the PCI BIOS. This sorting is
1429 done to get a device order compatible with
1430 older kernels.
cd4f0ef7 1431 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1432 routing table. These calls are known to be buggy
1433 on several machines and they hang the machine
1434 when used, but on other computers it's the only
1435 way to get the interrupt routing table. Try
1436 this option if the kernel is unable to allocate
1437 IRQs or discover secondary PCI buses on your
1438 motherboard.
cd4f0ef7 1439 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1440 Use with caution as certain devices share
1441 address decoders between ROMs and other
1442 resources.
cd4f0ef7 1443 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1444 assigned automatically to PCI devices. You can
1445 make the kernel exclude IRQs of your ISA cards
1446 this way.
cd4f0ef7 1447 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1448 of the PIRQ table (normally generated
1449 by the BIOS) if it is outside the
1450 F0000h-100000h range.
cd4f0ef7 1451 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1452 useful if the kernel is unable to find your
1453 secondary buses and you want to tell it
1454 explicitly which ones they are.
cd4f0ef7 1455 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1456 numbers ourselves, overriding
1457 whatever the firmware may have done.
cd4f0ef7 1458 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1459 in the BIOS $PIR table. This is needed on
1460 some systems with broken BIOSes, notably
1461 some HP Pavilion N5400 and Omnibook XE3
1462 notebooks. This will have no effect if ACPI
1463 IRQ routing is enabled.
cd4f0ef7 1464 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1465 or for PCI scanning.
62f420f8
GH
1466 use_crs [X86-32] Use _CRS for PCI resource
1467 allocation.
a9913044
RD
1468 routeirq Do IRQ routing for all PCI devices.
1469 This is normally done in pci_enable_device(),
1470 so this option is a temporary workaround
1471 for broken drivers that don't call it.
1472 firmware [ARM] Do not re-enumerate the bus but instead
1473 just use the configuration from the
1474 bootloader. This is currently used on
1475 IXP2000 systems where the bus has to be
1476 configured a certain way for adjunct CPUs.
0637a70a
AK
1477 noearly [X86] Don't do any early type 1 scanning.
1478 This might help on some broken boards which
1479 machine check when some devices' config space
1480 is read. But various workarounds are disabled
1481 and some IOMMU drivers will not work.
6b4b78fe
MD
1482 bfsort Sort PCI devices into breadth-first order.
1483 This sorting is done to get a device
1484 order compatible with older (<= 2.4) kernels.
1485 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1486 cbiosize=nn[KMG] The fixed amount of bus space which is
1487 reserved for the CardBus bridge's IO window.
1488 The default value is 256 bytes.
1489 cbmemsize=nn[KMG] The fixed amount of bus space which is
1490 reserved for the CardBus bridge's memory
1491 window. The default value is 64 megabytes.
6b4b78fe 1492
1da177e4
LT
1493 pcmv= [HW,PCMCIA] BadgePAD 4
1494
1495 pd. [PARIDE]
1496 See Documentation/paride.txt.
1497
1498 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1499 boot time.
1500 Format: { 0 | 1 }
1501 See arch/parisc/kernel/pdc_chassis.c
1502
1503 pf. [PARIDE]
1504 See Documentation/paride.txt.
1505
1506 pg. [PARIDE]
1507 See Documentation/paride.txt.
1508
1509 pirq= [SMP,APIC] Manual mp-table setup
1510 See Documentation/i386/IO-APIC.txt.
1511
1512 plip= [PPT,NET] Parallel port network link
1513 Format: { parport<nr> | timid | 0 }
1514 See also Documentation/parport.txt.
1515
1516 pnpacpi= [ACPI]
1517 { off }
1518
1519 pnpbios= [ISAPNP]
1520 { on | off | curr | res | no-curr | no-res }
1521
1522 pnp_reserve_irq=
1523 [ISAPNP] Exclude IRQs for the autoconfiguration
1524
1525 pnp_reserve_dma=
1526 [ISAPNP] Exclude DMAs for the autoconfiguration
1527
1528 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1529 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1530
1531 pnp_reserve_mem=
a9913044
RD
1532 [ISAPNP] Exclude memory regions for the
1533 autoconfiguration.
1da177e4
LT
1534 Ranges are in pairs (memory base and size).
1535
45807a1d
IM
1536 print-fatal-signals=
1537 [KNL] debug: print fatal signals
1538 print-fatal-signals=1: print segfault info to
1539 the kernel console.
1540 default: off.
1541
e84845c4
RD
1542 printk.time= Show timing data prefixed to each printk message line
1543 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1544
1da177e4 1545 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1546 Format: [schedule,]<number>
1547 Param: "schedule" - profile schedule points.
1548 Param: <number> - step/bucket size as a power of 2 for
1549 statistical time based profiling.
b3da2a73
MG
1550 Param: "sleep" - profile D-state sleeping (millisecs).
1551 Requires CONFIG_SCHEDSTATS
c0fe2e69 1552 Param: "kvm" - profile VM exits.
1da177e4 1553
a9913044 1554 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1555 Limit processor to maximum C-state
1556 max_cstate=9 overrides any DMI blacklist limit.
1557
41c0d868
LB
1558 processor.nocst [HW,ACPI]
1559 Ignore the _CST method to determine C-states,
1560 instead using the legacy FADT method
1561
1da177e4
LT
1562 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1563 before loading.
1564 See Documentation/ramdisk.txt.
1565
a9913044
RD
1566 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1567 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1568 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1569 per second.
a9913044
RD
1570 psmouse.resetafter= [HW,MOUSE]
1571 Try to reset the device after so many bad packets
1da177e4
LT
1572 (0 = never).
1573 psmouse.resolution=
1574 [HW,MOUSE] Set desired mouse resolution, in dpi.
1575 psmouse.smartscroll=
a9913044 1576 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1577 0 = disabled, 1 = enabled (default).
1578
1579 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1580 Format:
1581 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1582
1583 pt. [PARIDE]
1584 See Documentation/paride.txt.
1585
dc8c8587
KS
1586 pty.legacy_count=
1587 [KNL] Number of legacy pty's. Overwrites compiled-in
1588 default number.
1589
7d2c502f 1590 quiet [KNL] Disable most log messages
a9913044 1591
1da177e4
LT
1592 r128= [HW,DRM]
1593
1594 raid= [HW,RAID]
1595 See Documentation/md.txt.
1596
a9913044 1597 ramdisk_blocksize= [RAM]
1da177e4 1598 See Documentation/ramdisk.txt.
a9913044 1599
1da177e4 1600 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1601 See Documentation/ramdisk.txt.
1602
24aaef8d
RD
1603 rcupdate.blimit= [KNL,BOOT]
1604 Set maximum number of finished RCU callbacks to process
1605 in one batch.
21a1ea9e 1606
24aaef8d
RD
1607 rcupdate.qhimark= [KNL,BOOT]
1608 Set threshold of queued
21a1ea9e
DS
1609 RCU callbacks over which batch limiting is disabled.
1610
24aaef8d
RD
1611 rcupdate.qlowmark= [KNL,BOOT]
1612 Set threshold of queued RCU callbacks below which
1613 batch limiting is re-enabled.
21a1ea9e 1614
ffdfc409
OJ
1615 rdinit= [KNL]
1616 Format: <full_path>
1617 Run specified binary instead of /init from the ramdisk,
1618 used for early userspace startup. See initrd.
1619
cd4f0ef7 1620 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1621 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1622 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1623
1624 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1625
cd4f0ef7 1626 reservetop= [X86-32]
461a9aff
ZA
1627 Format: nn[KMG]
1628 Reserves a hole at the top of the kernel virtual
1629 address space.
1630
7e96287d
VG
1631 reset_devices [KNL] Force drivers to reset the underlying device
1632 during initialization.
1633
a9913044
RD
1634 resume= [SWSUSP]
1635 Specify the partition device for software suspend
1da177e4 1636
ecbd0da1
RW
1637 resume_offset= [SWSUSP]
1638 Specify the offset from the beginning of the partition
1639 given by "resume=" at which the swap header is located,
1640 in <PAGE_SIZE> units (needed only for swap files).
1641 See Documentation/power/swsusp-and-swap-files.txt
1642
0a7b35cb
MN
1643 retain_initrd [RAM] Keep initrd memory after extraction
1644
1da177e4
LT
1645 rhash_entries= [KNL,NET]
1646 Set number of hash buckets for route cache
1647
1648 riscom8= [HW,SERIAL]
1649 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1650
1651 ro [KNL] Mount root device read-only on boot
1652
1653 root= [KNL] Root filesystem
1654
1655 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1656 mount the root filesystem
1657
1658 rootflags= [KNL] Set root filesystem mount option string
1659
1660 rootfstype= [KNL] Set root filesystem type
1661
cc1ed754
PO
1662 rootwait [KNL] Wait (indefinitely) for root device to show up.
1663 Useful for devices that are detected asynchronously
1664 (e.g. USB and MMC devices).
1665
20510f2f
JM
1666 root_plug.vendor_id=
1667 [ROOTPLUG] Override the default vendor ID
1668
1669 root_plug.product_id=
1670 [ROOTPLUG] Override the default product ID
1671
1672 root_plug.debug=
1673 [ROOTPLUG] Enable debugging output
1674
1da177e4
LT
1675 rw [KNL] Mount root device read-write on boot
1676
1677 S [KNL] Run init in single mode
1678
1679 sa1100ir [NET]
1680 See drivers/net/irda/sa1100_ir.c.
1681
1da177e4 1682 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1683
1da177e4
LT
1684 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1685 Format: <io>[,<timeout>[,<isapnp>]]
1686
1687 scsi_debug_*= [SCSI]
1688 See drivers/scsi/scsi_debug.c.
1689
1690 scsi_default_dev_flags=
1691 [SCSI] SCSI default device flags
1692 Format: <integer>
1693
1694 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1695 Format: <vendor>:<model>:<flags>
1696 (flags are integer value)
1697
6af6632a
RD
1698 scsi_logging_level= [SCSI] a bit mask of logging levels
1699 See drivers/scsi/scsi_logging.h for bits. Also
1700 settable via sysctl at dev.scsi.logging_level
1701 (/proc/sys/dev/scsi/logging_level).
1702 There is also a nice 'scsi_logging_level' script in the
1703 S390-tools package, available for download at
1704 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1705
3e082a91
MW
1706 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1707 discovered. async scans them in kernel threads,
1708 allowing boot to proceed. none ignores them, expecting
1709 user space to do the scan.
1710
1da177e4
LT
1711 selinux [SELINUX] Disable or enable SELinux at boot time.
1712 Format: { "0" | "1" }
1713 See security/selinux/Kconfig help text.
1714 0 -- disable.
1715 1 -- enable.
1716 Default value is set via kernel config option.
1717 If enabled at boot time, /selinux/disable can be used
1718 later to disable prior to initial policy load.
1719
4e5ab4cb
JM
1720 selinux_compat_net =
1721 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1722 Format: { "0" | "1" }
1723 0 -- use new secmark-based packet controls
1724 1 -- use legacy packet controls
1725 Default value is 0 (preferred).
1726 Value can be changed at runtime via
1727 /selinux/compat_net.
4e5ab4cb 1728
cd4f0ef7 1729 serialnumber [BUGS=X86-32]
1da177e4 1730
1da177e4
LT
1731 shapers= [NET]
1732 Maximal number of shapers.
a9913044 1733
1da177e4
LT
1734 sim710= [SCSI,HW]
1735 See header of drivers/scsi/sim710.c.
1736
1737 simeth= [IA-64]
1738 simscsi=
a9913044 1739
1da177e4
LT
1740 slram= [HW,MTD]
1741
f0630fff
CL
1742 slub_debug[=options[,slabs]] [MM, SLUB]
1743 Enabling slub_debug allows one to determine the
1744 culprit if slab objects become corrupted. Enabling
1745 slub_debug can create guard zones around objects and
1746 may poison objects when not in use. Also tracks the
1747 last alloc / free. For more information see
1748 Documentation/vm/slub.txt.
c1aee215
CL
1749
1750 slub_max_order= [MM, SLUB]
f0630fff
CL
1751 Determines the maximum allowed order for slabs.
1752 A high setting may cause OOMs due to memory
1753 fragmentation. For more information see
1754 Documentation/vm/slub.txt.
c1aee215
CL
1755
1756 slub_min_objects= [MM, SLUB]
f0630fff
CL
1757 The minimum number of objects per slab. SLUB will
1758 increase the slab order up to slub_max_order to
1759 generate a sufficiently large slab able to contain
1760 the number of objects indicated. The higher the number
1761 of objects the smaller the overhead of tracking slabs
1762 and the less frequently locks need to be acquired.
c1aee215
CL
1763 For more information see Documentation/vm/slub.txt.
1764
1765 slub_min_order= [MM, SLUB]
1766 Determines the mininum page order for slabs. Must be
f0630fff 1767 lower than slub_max_order.
c1aee215
CL
1768 For more information see Documentation/vm/slub.txt.
1769
1770 slub_nomerge [MM, SLUB]
f0630fff 1771 Disable merging of slabs with similar size. May be
c1aee215 1772 necessary if there is some reason to distinguish
f0630fff
CL
1773 allocs to different slabs. Debug options disable
1774 merging on their own.
c1aee215
CL
1775 For more information see Documentation/vm/slub.txt.
1776
1da177e4
LT
1777 smart2= [HW]
1778 Format: <io1>[,<io2>[,...,<io8>]]
1779
cd4f0ef7 1780 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1781 attempt to substitute SMP alternatives once at boot.
1782
d0d4f69b
BH
1783 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1784 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1785 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1786 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1787 smsc-ircc2.ircc_irq= [HW] IRQ line
1788 smsc-ircc2.ircc_dma= [HW] DMA channel
1789 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1790 0: Toshiba Satellite 1800 (GP data pin select)
1791 1: Fast pin select (default)
1792 2: ATC IRMode
1793
1da177e4
LT
1794 snd-ad1816a= [HW,ALSA]
1795
1796 snd-ad1848= [HW,ALSA]
1797
1798 snd-ali5451= [HW,ALSA]
1799
1800 snd-als100= [HW,ALSA]
1801
1802 snd-als4000= [HW,ALSA]
1803
1804 snd-azt2320= [HW,ALSA]
1805
1806 snd-cmi8330= [HW,ALSA]
1807
1808 snd-cmipci= [HW,ALSA]
1809
1810 snd-cs4231= [HW,ALSA]
1811
1812 snd-cs4232= [HW,ALSA]
1813
1814 snd-cs4236= [HW,ALSA]
1815
1816 snd-cs4281= [HW,ALSA]
1817
1818 snd-cs46xx= [HW,ALSA]
1819
1820 snd-dt019x= [HW,ALSA]
1821
1822 snd-dummy= [HW,ALSA]
1823
1824 snd-emu10k1= [HW,ALSA]
1825
1826 snd-ens1370= [HW,ALSA]
1827
1828 snd-ens1371= [HW,ALSA]
1829
1830 snd-es968= [HW,ALSA]
1831
1832 snd-es1688= [HW,ALSA]
1833
1834 snd-es18xx= [HW,ALSA]
1835
1836 snd-es1938= [HW,ALSA]
1837
1838 snd-es1968= [HW,ALSA]
1839
1840 snd-fm801= [HW,ALSA]
1841
1842 snd-gusclassic= [HW,ALSA]
1843
1844 snd-gusextreme= [HW,ALSA]
1845
1846 snd-gusmax= [HW,ALSA]
1847
1848 snd-hdsp= [HW,ALSA]
1849
1850 snd-ice1712= [HW,ALSA]
1851
1852 snd-intel8x0= [HW,ALSA]
1853
1854 snd-interwave= [HW,ALSA]
1855
1856 snd-interwave-stb=
1857 [HW,ALSA]
1858
1859 snd-korg1212= [HW,ALSA]
1860
1861 snd-maestro3= [HW,ALSA]
1862
1863 snd-mpu401= [HW,ALSA]
1864
1865 snd-mtpav= [HW,ALSA]
1866
1867 snd-nm256= [HW,ALSA]
1868
1869 snd-opl3sa2= [HW,ALSA]
1870
1871 snd-opti92x-ad1848=
1872 [HW,ALSA]
1873
1874 snd-opti92x-cs4231=
1875 [HW,ALSA]
1876
1877 snd-opti93x= [HW,ALSA]
1878
1879 snd-pmac= [HW,ALSA]
1880
1881 snd-rme32= [HW,ALSA]
1882
1883 snd-rme96= [HW,ALSA]
1884
1885 snd-rme9652= [HW,ALSA]
1886
1887 snd-sb8= [HW,ALSA]
1888
1889 snd-sb16= [HW,ALSA]
1890
1891 snd-sbawe= [HW,ALSA]
1892
1893 snd-serial= [HW,ALSA]
1894
1895 snd-sgalaxy= [HW,ALSA]
1896
1897 snd-sonicvibes= [HW,ALSA]
1898
1899 snd-sun-amd7930=
1900 [HW,ALSA]
1901
1902 snd-sun-cs4231= [HW,ALSA]
1903
1904 snd-trident= [HW,ALSA]
1905
1906 snd-usb-audio= [HW,ALSA,USB]
1907
1908 snd-via82xx= [HW,ALSA]
1909
1910 snd-virmidi= [HW,ALSA]
1911
1912 snd-wavefront= [HW,ALSA]
1913
1914 snd-ymfpci= [HW,ALSA]
a9913044 1915
1da177e4
LT
1916 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1917 See Documentation/sonypi.txt
1918
1919 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1920 See Documentation/specialix.txt.
1921
1922 spia_io_base= [HW,MTD]
1923 spia_fio_base=
1924 spia_pedr=
1925 spia_peddr=
1926
1927 sscape= [HW,OSS]
1928 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1929
1da177e4
LT
1930 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1931 See Documentation/scsi/st.txt.
1932
1da177e4
LT
1933 sti= [PARISC,HW]
1934 Format: <num>
1935 Set the STI (builtin display/keyboard on the HP-PARISC
1936 machines) console (graphic card) which should be used
1937 as the initial boot-console.
1938 See also comment in drivers/video/console/sticore.c.
1939
1940 sti_font= [HW]
1941 See comment in drivers/video/console/sticore.c.
1942
1943 stifb= [HW]
1944 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1945
42a7fc4a
GB
1946 sunrpc.pool_mode=
1947 [NFS]
1948 Control how the NFS server code allocates CPUs to
1949 service thread pools. Depending on how many NICs
1950 you have and where their interrupts are bound, this
1951 option will affect which CPUs will do NFS serving.
1952 Note: this parameter cannot be changed while the
1953 NFS server is running.
1954
1955 auto the server chooses an appropriate mode
1956 automatically using heuristics
1957 global a single global pool contains all CPUs
1958 percpu one pool for each CPU
1959 pernode one pool for each NUMA node (equivalent
1960 to global on non-NUMA machines)
1961
1da177e4 1962 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 1963
1da177e4
LT
1964 switches= [HW,M68k]
1965
1966 sym53c416= [HW,SCSI]
1967 See header of drivers/scsi/sym53c416.c.
1968
5d6f647f
IM
1969 sysrq_always_enabled
1970 [KNL]
1971 Ignore sysrq setting - this boot parameter will
1972 neutralize any effect of /proc/sys/kernel/sysrq.
1973 Useful for debugging.
1974
1da177e4
LT
1975 t128= [HW,SCSI]
1976 See header of drivers/scsi/t128.c.
1977
1978 tdfx= [HW,DRM]
1979
1980 thash_entries= [KNL,NET]
1981 Set number of hash buckets for TCP connection
1982
f8707ec9
LB
1983 thermal.act= [HW,ACPI]
1984 -1: disable all active trip points in all thermal zones
1985 <degrees C>: override all lowest active trip points
1986
c52a7419
LB
1987 thermal.crt= [HW,ACPI]
1988 -1: disable all critical trip points in all thermal zones
1989 <degrees C>: lower all critical trip points
1990
f5487145
LB
1991 thermal.nocrt= [HW,ACPI]
1992 Set to disable actions on ACPI thermal zone
1993 critical and hot trip points.
1994
72b33ef8
LB
1995 thermal.off= [HW,ACPI]
1996 1: disable ACPI thermal control
1997
a70cdc52
LB
1998 thermal.psv= [HW,ACPI]
1999 -1: disable all passive trip points
2000 <degrees C>: override all passive trip points to this value
2001
730ff34d
LB
2002 thermal.tzp= [HW,ACPI]
2003 Specify global default ACPI thermal zone polling rate
2004 <deci-seconds>: poll all this frequency
2005 0: no polling (default)
2006
1da177e4
LT
2007 tipar.timeout= [HW,PPT]
2008 Set communications timeout in tenths of a second
2009 (default 15).
2010
2011 tipar.delay= [HW,PPT]
2012 Set inter-bit delay in microseconds (default 10).
2013
1da177e4
LT
2014 tmscsim= [HW,SCSI]
2015 See comment before function dc390_setup() in
2016 drivers/scsi/tmscsim.c.
2017
2018 tp720= [HW,PS2]
2019
2020 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2021 Format:
2022 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2023
a9913044
RD
2024 turbografx.map[2|3]= [HW,JOY]
2025 TurboGraFX parallel port interface
2026 Format:
2027 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2028 See also Documentation/input/joystick-parport.txt
2029
2030 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2031 See header of drivers/scsi/u14-34f.c.
2032
2033 uart401= [HW,OSS]
2034 Format: <io>,<irq>
2035
2036 uart6850= [HW,OSS]
2037 Format: <io>,<irq>
2038
5f8364b7
AS
2039 uhci-hcd.ignore_oc=
2040 [USB] Ignore overcurrent events (default N).
2041 Some badly-designed motherboards generate lots of
2042 bogus events, for ports that aren't wired to
2043 anything. Set this parameter to avoid log spamming.
2044 Note that genuine overcurrent events won't be
2045 reported either.
2046
b5e795f8
AS
2047 usbcore.autosuspend=
2048 [USB] The autosuspend time delay (in seconds) used
2049 for newly-detected USB devices (default 2). This
2050 is the time required before an idle device will be
2051 autosuspended. Devices for which the delay is set
eaafbc3a 2052 to a negative value won't be autosuspended at all.
b5e795f8 2053
1da177e4
LT
2054 usbhid.mousepoll=
2055 [USBHID] The interval which mice are to be polled at.
a9913044 2056
cd4f0ef7 2057 vdso= [X86-32,SH,x86-64]
1dbf527c 2058 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2059 vdso=1: enable VDSO (default)
2060 vdso=0: disable VDSO mapping
2061
af65d648
RM
2062 vdso32= [X86-32,X86-64]
2063 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2064 vdso32=1: enable 32-bit VDSO (default)
2065 vdso32=0: disable 32-bit VDSO mapping
2066
d080d397
YI
2067 vector= [IA-64,SMP]
2068 vector=percpu: enable percpu vector domain
2069
1da177e4
LT
2070 video= [FB] Frame buffer configuration
2071 See Documentation/fb/modedb.txt.
2072
cd4f0ef7 2073 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2074 See Documentation/i386/boot.txt and
2075 Documentation/svga.txt.
1da177e4
LT
2076 Use vga=ask for menu.
2077 This is actually a boot loader parameter; the value is
2078 passed to the kernel using a special protocol.
2079
a9913044 2080 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2081 size of <nn>. This can be used to increase the
2082 minimum size (128MB on x86). It can also be used to
2083 decrease the size and leave more room for directly
2084 mapped kernel RAM.
2085
585c3047
PO
2086 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2087 Format: <command>
1da177e4 2088
585c3047
PO
2089 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2090 Format: <command>
2091
2092 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2093 Format: <command>
a9913044 2094
1da177e4
LT
2095 waveartist= [HW,OSS]
2096 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2097
1da177e4
LT
2098 wd33c93= [HW,SCSI]
2099 See header of drivers/scsi/wd33c93.c.
2100
2101 wd7000= [HW,SCSI]
2102 See header of drivers/scsi/wd7000.c.
2103
2104 wdt= [WDT] Watchdog
8dfe9c21 2105 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2106
2107 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2108 xd_geo= See header of drivers/block/xd.c.
2109
2110 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2111 Format:
2112 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2113
a62eaf15
AK
2114 norandmaps Don't use address space randomization
2115 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2116
a9913044 2117______________________________________________________________________
1da177e4
LT
2118
2119TODO:
2120
2121 Add documentation for ALSA options.
2122 Add more DRM drivers.