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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 security= [SECURITY] Choose a security module to enable at boot.
370 If this boot parameter is not specified, only the first
371 security module asking for security registration will be
372 loaded. An invalid security module name will be treated
373 as if no module has been chosen.
374
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375 capability.disable=
376 [SECURITY] Disable capabilities. This would normally
377 be used only if an alternative security model is to be
378 configured. Potentially dangerous and should only be
379 used if you are entirely sure of the consequences.
380
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381 ccw_timeout_log [S390]
382 See Documentation/s390/CommonIO for details.
1da177e4 383
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384 cgroup_disable= [KNL] Disable a particular controller
385 Format: {name of the controller(s) to disable}
386 {Currently supported controllers - "memory"}
387
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388 checkreqprot [SELINUX] Set initial checkreqprot flag value.
389 Format: { "0" | "1" }
390 See security/selinux/Kconfig help text.
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391 0 -- check protection applied by kernel (includes
392 any implied execute protection).
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393 1 -- check protection requested by application.
394 Default value is set via a kernel config option.
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395 Value can be changed at runtime via
396 /selinux/checkreqprot.
397
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398 cio_ignore= [S390]
399 See Documentation/s390/CommonIO for details.
400
401 cio_msg= [S390]
402 See Documentation/s390/CommonIO for details.
403
cd4f0ef7 404 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 405 [Deprecated]
3f6dee9b 406 Forces specified clocksource (if available) to be used
734efb46 407 when calculating gettimeofday(). If specified
3f6dee9b 408 clocksource is not available, it defaults to PIT.
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409 Format: { pit | tsc | cyclone | pmtmr }
410
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411 clocksource= [GENERIC_TIME] Override the default clocksource
412 Format: <string>
413 Override the default clocksource and use the clocksource
414 with the name specified.
415 Some clocksource names to choose from, depending on
416 the platform:
417 [all] jiffies (this is the base, fallback clocksource)
418 [ACPI] acpi_pm
419 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
420 pxa_timer,timer3,32k_counter,timer0_1
421 [AVR32] avr32
cd4f0ef7 422 [X86-32] pit,hpet,tsc,vmi-timer;
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423 scx200_hrt on Geode; cyclone on IBM x440
424 [MIPS] MIPS
425 [PARISC] cr16
426 [S390] tod
427 [SH] SuperH
428 [SPARC64] tick
429 [X86-64] hpet,tsc
430
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431 clearcpuid=BITNUM [X86]
432 Disable CPUID feature X for the kernel. See
433 include/asm-x86/cpufeature.h for the valid bit numbers.
434 Note the Linux specific bits are not necessarily
435 stable over kernel options, but the vendor specific
436 ones should be.
437 Also note that user programs calling CPUID directly
438 or using the feature without checking anything
439 will still see it. This just prevents it from
440 being used by the kernel or shown in /proc/cpuinfo.
441 Also note the kernel might malfunction if you disable
442 some critical bits.
443
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444 code_bytes [IA32/X86_64] How many bytes of object code to print
445 in an oops report.
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446 Range: 0 - 8192
447 Default: 64
448
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449 disable_8254_timer
450 enable_8254_timer
451 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
452 over the 8254 in addition to over the IO-APIC. The
453 kernel tries to set a sensible default.
454
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455 hpet= [X86-32,HPET] option to control HPET usage
456 Format: { enable (default) | disable | force }
457 disable: disable HPET and use PIT instead
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458 force: allow force enabled of undocumented chips (ICH4,
459 VIA, nVidia)
1da177e4 460
1da177e4 461 com20020= [HW,NET] ARCnet - COM20020 chipset
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462 Format:
463 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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464
465 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
466 Format: <io>[,<irq>]
467
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468 com90xx= [HW,NET]
469 ARCnet - COM90xx chipset (memory-mapped buffers)
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470 Format: <io>[,<irq>[,<memstart>]]
471
472 condev= [HW,S390] console device
473 conmode=
a9913044 474
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475 console= [KNL] Output console device and options.
476
477 tty<n> Use the virtual console device <n>.
478
479 ttyS<n>[,options]
f1a1c2dc 480 ttyUSB0[,options]
1da177e4 481 Use the specified serial port. The options are of
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482 the form "bbbbpnf", where "bbbb" is the baud rate,
483 "p" is parity ("n", "o", or "e"), "n" is number of
484 bits, and "f" is flow control ("r" for RTS or
485 omit it). Default is "9600n8".
486
487 See Documentation/serial-console.txt for more
488 information. See
489 Documentation/networking/netconsole.txt for an
490 alternative.
1da177e4 491
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492 uart[8250],io,<addr>[,options]
493 uart[8250],mmio,<addr>[,options]
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494 Start an early, polled-mode console on the 8250/16550
495 UART at the specified I/O port or MMIO address,
496 switching to the matching ttyS device later. The
497 options are the same as for ttyS, above.
498
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499 If the device connected to the port is not a TTY but a braille
500 device, prepend "brl," before the device type, for instance
501 console=brl,ttyS0
502 For now, only VisioBraille is supported.
503
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504 earlycon= [KNL] Output early console device and options.
505 uart[8250],io,<addr>[,options]
506 uart[8250],mmio,<addr>[,options]
507 Start an early, polled-mode console on the 8250/16550
508 UART at the specified I/O port or MMIO address.
509 The options are the same as for ttyS, above.
510
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511 no_console_suspend
512 [HW] Never suspend the console
513 Disable suspending of consoles during suspend and
514 hibernate operations. Once disabled, debugging
515 messages can reach various consoles while the rest
516 of the system is being put to sleep (ie, while
517 debugging driver suspend/resume hooks). This may
518 not work reliably with all consoles, but is known
519 to work with serial and VGA consoles.
520
1da177e4 521 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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522 Format:
523 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 524
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525 crashkernel=nn[KMG]@ss[KMG]
526 [KNL] Reserve a chunk of physical memory to
527 hold a kernel to switch to with kexec on panic.
528
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529 crashkernel=range1:size1[,range2:size2,...][@offset]
530 [KNL] Same as above, but depends on the memory
531 in the running system. The syntax of range is
532 start-[end] where start and end are both
533 a memory unit (amount[KMG]). See also
534 Documentation/kdump/kdump.txt for a example.
535
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LT
536 cs4232= [HW,OSS]
537 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
538
539 cs89x0_dma= [HW,NET]
540 Format: <dma>
541
542 cs89x0_media= [HW,NET]
543 Format: { rj45 | aui | bnc }
a9913044 544
a9913044 545 dasd= [HW,NET]
1da177e4
LT
546 See header of drivers/s390/block/dasd_devmap.c.
547
548 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
549 (one device per port)
550 Format: <port#>,<type>
551 See also Documentation/input/joystick-parport.txt
552
553 debug [KNL] Enable kernel debugging (events log level).
554
cae2ed9a
IM
555 debug_locks_verbose=
556 [KNL] verbose self-tests
557 Format=<0|1>
558 Print debugging info while doing the locking API
559 self-tests.
560 We default to 0 (no extra messages), setting it to
561 1 will print _a lot_ more information - normally
562 only useful to kernel developers.
563
3ac7fe5a
TG
564 debug_objects [KNL] Enable object debugging
565
2d27a966 566 decnet.addr= [HW,NET]
1da177e4
LT
567 Format: <area>[,<node>]
568 See also Documentation/networking/decnet.txt.
569
ecb77fa9 570 vt.default_blu= [VT]
55ff9780
AD
571 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
572 Change the default blue palette of the console.
573 This is a 16-member array composed of values
574 ranging from 0-255.
575
ecb77fa9 576 vt.default_grn= [VT]
55ff9780
AD
577 Format: <green0>,<green1>,<green2>,...,<green15>
578 Change the default green palette of the console.
579 This is a 16-member array composed of values
580 ranging from 0-255.
581
ecb77fa9 582 vt.default_red= [VT]
55ff9780
AD
583 Format: <red0>,<red1>,<red2>,...,<red15>
584 Change the default red palette of the console.
585 This is a 16-member array composed of values
586 ranging from 0-255.
587
ecb77fa9
ST
588 vt.default_utf8=
589 [VT]
55ff9780
AD
590 Format=<0|1>
591 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
592 Default is 1, i.e. UTF-8 mode is enabled for all
593 newly opened terminals.
55ff9780 594
1da177e4
LT
595 dhash_entries= [KNL]
596 Set number of hash buckets for dentry cache.
a9913044 597
1da177e4
LT
598 digi= [HW,SERIAL]
599 IO parameters + enable/disable command.
600
601 digiepca= [HW,SERIAL]
602 See drivers/char/README.epca and
603 Documentation/digiepca.txt.
604
093af8d7 605 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
606 By default the kernel will trim any uncacheable
607 memory out of your available memory pool based on
608 MTRR settings. This parameter disables that behavior,
609 possibly causing your machine to run very slowly.
610
1da177e4
LT
611 dmasound= [HW,OSS] Sound subsystem buffers
612
613 dscc4.setup= [NET]
614
615 dtc3181e= [HW,SCSI]
616
0ae53640 617 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
618 earlyprintk=vga
619 earlyprintk=serial[,ttySn[,baudrate]]
620
a9913044 621 Append ",keep" to not disable it when the real console
1da177e4
LT
622 takes over.
623
624 Only vga or serial at a time, not both.
625
626 Currently only ttyS0 and ttyS1 are supported.
627
628 Interaction with the standard serial driver is not
629 very good.
630
631 The VGA output is eventually overwritten by the real
632 console.
633
634 eata= [HW,SCSI]
635
1da177e4 636 edd= [EDD]
8c4dd606 637 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 638
1da177e4
LT
639 eisa_irq_edge= [PARISC,HW]
640 See header of drivers/parisc/eisa.c.
641
cd4f0ef7 642 elanfreq= [X86-32]
1da177e4
LT
643 See comment before function elanfreq_setup() in
644 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
645
646 elevator= [IOSCHED]
16ab3adf 647 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
648 See Documentation/block/as-iosched.txt and
649 Documentation/block/deadline-iosched.txt for details.
650
cd4f0ef7 651 elfcorehdr= [X86-32, X86_64]
a9913044 652 Specifies physical address of start of kernel core
aac04b32
VG
653 image elf header. Generally kexec loader will
654 pass this option to capture kernel.
655 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
656
657 enforcing [SELINUX] Set initial enforcing status.
658 Format: {"0" | "1"}
659 See security/selinux/Kconfig help text.
660 0 -- permissive (log only, no denials).
661 1 -- enforcing (deny and log).
662 Default value is 0.
663 Value can be changed at runtime via /selinux/enforce.
664
1da177e4
LT
665 es1371= [HW,OSS]
666 Format: <spdif>,[<nomix>,[<amplifier>]]
667 See also header of sound/oss/es1371.c.
a9913044 668
1da177e4
LT
669 ether= [HW,NET] Ethernet cards parameters
670 This option is obsoleted by the "netdev=" option, which
671 has equivalent usage. See its documentation for details.
672
673 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
674 Format: <io>[,<irq>]
675
de1ba09b
AM
676 failslab=
677 fail_page_alloc=
678 fail_make_request=[KNL]
679 General fault injection mechanism.
680 Format: <interval>,<probability>,<space>,<times>
681 See also /Documentation/fault-injection/.
682
1da177e4
LT
683 fd_mcs= [HW,SCSI]
684 See header of drivers/scsi/fd_mcs.c.
685
686 fdomain= [HW,SCSI]
687 See header of drivers/scsi/fdomain.c.
688
689 floppy= [HW]
690 See Documentation/floppy.txt.
691
1da177e4
LT
692 gamecon.map[2|3]=
693 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
694 support via parallel port (up to 5 devices per port)
695 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
696 See also Documentation/input/joystick-parport.txt
697
698 gamma= [HW,DRM]
699
aaf23042
YL
700 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
701 Format: off | on
702 default: on
703
1da177e4
LT
704 gdth= [HW,SCSI]
705 See header of drivers/scsi/gdth.c.
706
707 gpt [EFI] Forces disk with valid GPT signature but
708 invalid Protective MBR to be treated as GPT.
709
1da177e4
LT
710 gvp11= [HW,SCSI]
711
712 hashdist= [KNL,NUMA] Large hashes allocated during boot
713 are distributed across NUMA nodes. Defaults on
714 for IA-64, off otherwise.
a9913044 715 Format: 0 | 1 (for off | on)
1da177e4
LT
716
717 hcl= [IA-64] SGI's Hardware Graph compatibility layer
718
719 hd= [EIDE] (E)IDE hard drive subsystem geometry
720 Format: <cyl>,<head>,<sect>
721
722 hd?= [HW] (E)IDE subsystem
1c10e938 723 hd?lun= See Documentation/ide/ide.txt.
1da177e4
LT
724
725 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
726 size of <nn>. This works even on boxes that have no
727 highmem otherwise. This also works to reduce highmem
728 size on bigger boxes.
729
54cdfdb4
TG
730 highres= [KNL] Enable/disable high resolution timer mode.
731 Valid parameters: "on", "off"
732 Default: "on"
733
1da177e4
LT
734 hisax= [HW,ISDN]
735 See Documentation/isdn/README.HiSax.
736
cd4f0ef7 737 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 738 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 739
1da177e4 740 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
741 i8042.dumbkbd [HW] Pretend that controller can only read data from
742 keyboard and cannot control its state
1da177e4
LT
743 (Don't attempt to blink the leds)
744 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 745 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
746 i8042.noloop [HW] Disable the AUX Loopback command while probing
747 for the AUX port
1da177e4
LT
748 i8042.nomux [HW] Don't check presence of an active multiplexing
749 controller
750 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
751 controllers
752 i8042.panicblink=
753 [HW] Frequency with which keyboard LEDs should blink
754 when kernel panics (default is 0.5 sec)
755 i8042.reset [HW] Reset the controller during init and cleanup
756 i8042.unlock [HW] Unlock (ignore) the keylock
757
758 i810= [HW,DRM]
759
e70c9d5e
DT
760 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
761 indicates that the driver is running on unsupported
762 hardware.
1da177e4
LT
763 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
764 does not match list of supported models.
765 i8k.power_status
766 [HW] Report power status in /proc/i8k
767 (disabled by default)
768 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
769 capability is set.
770
771 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
772 See Documentation/mca.txt.
773
774 icn= [HW,ISDN]
775 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
776
777 ide= [HW] (E)IDE subsystem
a594eeb1 778 Format: ide=nodma or ide=doubler
1c10e938 779 See Documentation/ide/ide.txt.
1da177e4 780
1da177e4 781 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 782 See Documentation/ide/ide.txt.
1da177e4 783
f039b754
AK
784 idle= [X86]
785 Format: idle=poll or idle=mwait
786 Poll forces a polling idle loop that can slightly improves the performance
787 of waking up a idle CPU, but will use a lot of power and make the system
788 run hot. Not recommended.
789 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
790 to not use it because it doesn't save as much power as a normal idle
791 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
792 as idle=poll.
a9913044 793
594765a7
DC
794 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
795 Claim all unknown PCI IDE storage controllers.
796
79290822
IM
797 ignore_loglevel [KNL]
798 Ignore loglevel setting - this will print /all/
799 kernel messages to the console. Useful for debugging.
800
1da177e4
LT
801 ihash_entries= [KNL]
802 Set number of hash buckets for inode cache.
803
804 in2000= [HW,SCSI]
805 See header of drivers/scsi/in2000.c.
806
807 init= [KNL]
808 Format: <full_path>
809 Run specified binary instead of /sbin/init as init
810 process.
811
812 initcall_debug [KNL] Trace initcalls as they are executed. Useful
813 for working out where the kernel is dying during
814 startup.
815
816 initrd= [BOOT] Specify the location of the initial ramdisk
817
818 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
819 Format: <irq>
820
821 inttest= [IA64]
822
b552da87
PM
823 iommu= [x86]
824 off
825 force
826 noforce
827 biomerge
828 panic
829 nopanic
830 merge
831 nomerge
832 forcesac
833 soft
834
835
ba395927
KA
836 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
837 off
838 Disable intel iommu driver.
839 igfx_off [Default Off]
840 By default, gfx is mapped as normal device. If a gfx
841 device has a dedicated DMAR unit, the DMAR unit is
842 bypassed by not enabling DMAR with this option. In
843 this case, gfx device will use physical address for
844 DMA.
7d3b03ce
KA
845 forcedac [x86_64]
846 With this option iommu will not optimize to look
847 for io virtual address below 32 bit forcing dual
848 address cycle on pci bus for cards supporting greater
849 than 32 bit addressing. The default is to look
850 for translation below 32 bit and if not available
851 then look in the higher range.
5e0d2a6f 852 strict [Default Off]
853 With this option on every unmap_single operation will
854 result in a hardware IOTLB flush operation as opposed
855 to batching them for performance.
ba395927 856
b02aae9c 857 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
858 0x80
859 Standard port 0x80 based delay
860 0xed
861 Alternate port 0xed based delay (needed on some systems)
b02aae9c 862 udelay
6e7c4025
IM
863 Simple two microseconds delay
864 none
865 No delay
b02aae9c 866
1da177e4
LT
867 io7= [HW] IO7 for Marvel based alpha systems
868 See comment before marvel_specify_io7 in
869 arch/alpha/kernel/core_marvel.c.
870
871 ip= [IP_PNP]
6ded55da 872 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
873
874 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
875 See comment before ip2_setup() in
876 drivers/char/ip2/ip2base.c.
1da177e4
LT
877
878 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
879 See header of drivers/scsi/ips.c.
880
72c4a13a
SH
881 ports= [IP_VS_FTP] IPVS ftp helper module
882 Default is 21.
883 Up to 8 (IP_VS_APP_MAX_PORTS) ports
884 may be specified.
885 Format: <port>,<port>....
886
200803df
AC
887 irqfixup [HW]
888 When an interrupt is not handled search all handlers
889 for it. Intended to get systems with badly broken
890 firmware running.
891
892 irqpoll [HW]
893 When an interrupt is not handled search all handlers
894 for it. Also check all handlers each timer
895 interrupt. Intended to get systems with badly broken
896 firmware running.
897
1da177e4 898 isapnp= [ISAPNP]
a9913044 899 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
900
901 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
902 Format:
903 <cpu number>,...,<cpu number>
904 or
905 <cpu number>-<cpu number> (must be a positive range in ascending order)
906 or a mixture
907 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
908 This option can be used to specify one or more CPUs
909 to isolate from the general SMP balancing and scheduling
910 algorithms. The only way to move a process onto or off
911 an "isolated" CPU is via the CPU affinity syscalls.
912 <cpu number> begins at 0 and the maximum value is
913 "number of CPUs in system - 1".
914
915 This option is the preferred way to isolate CPUs. The
a9913044
RD
916 alternative -- manually setting the CPU mask of all
917 tasks in the system -- can cause problems and
918 suboptimal load balancer performance.
1da177e4 919
a9913044 920 iucv= [HW,NET]
1da177e4
LT
921
922 js= [HW,JOY] Analog joystick
923 See Documentation/input/joystick.txt.
924
cd4f0ef7 925 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
926 specifies the amount of memory usable by the kernel
927 for non-movable allocations. The requested amount is
928 spread evenly throughout all nodes in the system. The
929 remaining memory in each node is used for Movable
930 pages. In the event, a node is too small to have both
931 kernelcore and Movable pages, kernelcore pages will
932 take priority and other nodes will have a larger number
933 of kernelcore pages. The Movable zone is used for the
934 allocation of pages that may be reclaimed or moved
935 by the page migration subsystem. This means that
936 HugeTLB pages may not be allocated from this zone.
937 Note that allocations like PTEs-from-HighMem still
938 use the HighMem zone if it exists, and the Normal
939 zone if it does not.
940
cd4f0ef7 941 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
942 is similar to kernelcore except it specifies the
943 amount of memory used for migratable allocations.
944 If both kernelcore and movablecore is specified,
945 then kernelcore will be at *least* the specified
946 value but may be more. If movablecore on its own
947 is specified, the administrator must be careful
948 that the amount of memory usable for all allocations
949 is not too small.
950
1da177e4
LT
951 keepinitrd [HW,ARM]
952
cd4f0ef7 953 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
954 in oops dumps.
955
6cdf6e06
JW
956 kgdboc= [HW] kgdb over consoles.
957 Requires a tty driver that supports console polling.
958 (only serial suported for now)
959 Format: <serial_device>[,baud]
960
1da177e4
LT
961 l2cr= [PPC]
962
a78bfbfc
RB
963 l3cr= [PPC]
964
cd4f0ef7 965 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 966 disabled it.
1da177e4 967
cd4f0ef7 968 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
969 C2 power state.
970
fcb71f6f
FC
971 libata.dma= [LIBATA] DMA control
972 libata.dma=0 Disable all PATA and SATA DMA
973 libata.dma=1 PATA and SATA Disk DMA only
974 libata.dma=2 ATAPI (CDROM) DMA only
975 libata.dma=4 Compact Flash DMA only
976 Combinations also work, so libata.dma=3 enables DMA
977 for disks and CDROMs, but not CFs.
978
78e70c23
DJ
979 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
980 when set.
981 Format: <int>
982
33267325
TH
983 libata.force= [LIBATA] Force configurations. The format is comma
984 separated list of "[ID:]VAL" where ID is
985 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
986 matching port, link or device. Basically, it matches
987 the ATA ID string printed on console by libata. If
988 the whole ID part is omitted, the last PORT and DEVICE
989 values are used. If ID hasn't been specified yet, the
990 configuration applies to all ports, links and devices.
991
992 If only DEVICE is omitted, the parameter applies to
993 the port and all links and devices behind it. DEVICE
994 number of 0 either selects the first device or the
995 first fan-out link behind PMP device. It does not
996 select the host link. DEVICE number of 15 selects the
997 host link and device attached to it.
998
999 The VAL specifies the configuration to force. As long
1000 as there's no ambiguity shortcut notation is allowed.
1001 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1002 The following configurations can be forced.
1003
1004 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1005 Any ID with matching PORT is used.
1006
1007 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1008
1009 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1010 udma[/][16,25,33,44,66,100,133] notation is also
1011 allowed.
1012
1013 * [no]ncq: Turn on or off NCQ.
1014
1015 If there are multiple matching configurations changing
1016 the same attribute, the last one is used.
1017
1da177e4
LT
1018 load_ramdisk= [RAM] List of ramdisks to load from floppy
1019 See Documentation/ramdisk.txt.
1020
a6b25b67
RD
1021 lockd.nlm_grace_period=P [NFS] Assign grace period.
1022 Format: <integer>
1da177e4 1023
a6b25b67
RD
1024 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1025 Format: <integer>
1026
1027 lockd.nlm_timeout=T [NFS] Assign timeout value.
1028 Format: <integer>
1029
1030 lockd.nlm_udpport=M [NFS] Assign UDP port.
1031 Format: <integer>
1da177e4
LT
1032
1033 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1034 Format: <irq>
1035
1036 loglevel= All Kernel Messages with a loglevel smaller than the
1037 console loglevel will be printed to the console. It can
1038 also be changed with klogd or other programs. The
1039 loglevels are defined as follows:
1040
1041 0 (KERN_EMERG) system is unusable
1042 1 (KERN_ALERT) action must be taken immediately
1043 2 (KERN_CRIT) critical conditions
1044 3 (KERN_ERR) error conditions
1045 4 (KERN_WARNING) warning conditions
1046 5 (KERN_NOTICE) normal but significant condition
1047 6 (KERN_INFO) informational
1048 7 (KERN_DEBUG) debug-level messages
1049
1050 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1051 Format: { n | nk | nM }
1052 n must be a power of two. The default size
1053 is set in the kernel config file.
1da177e4 1054
accaa24c
RD
1055 logo.nologo [FB] Disables display of the built-in Linux logo.
1056 This may be used to provide more screen space for
1057 kernel log messages and is useful when debugging
1058 kernel boot problems.
1059
1da177e4
LT
1060 lp=0 [LP] Specify parallel ports to use, e.g,
1061 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1062 lp=reset first parallel port). 'lp=0' disables the
1063 lp=auto printer driver. 'lp=reset' (which can be
1064 specified in addition to the ports) causes
1065 attached printers to be reset. Using
1066 lp=port1,port2,... specifies the parallel ports
1067 to associate lp devices with, starting with
1068 lp0. A port specification may be 'none' to skip
1069 that lp device, or a parport name such as
1070 'parport0'. Specifying 'lp=auto' instead of a
1071 port specification list means that device IDs
1072 from each port should be examined, to see if
1073 an IEEE 1284-compliant printer is attached; if
1074 so, the driver will manage that printer.
1075 See also header of drivers/char/lp.c.
1076
1077 lpj=n [KNL]
1078 Sets loops_per_jiffy to given constant, thus avoiding
1079 time-consuming boot-time autodetection (up to 250 ms per
1080 CPU). 0 enables autodetection (default). To determine
1081 the correct value for your kernel, boot with normal
1082 autodetection and see what value is printed. Note that
1083 on SMP systems the preset will be applied to all CPUs,
1084 which is likely to cause problems if your CPUs need
1085 significantly divergent settings. An incorrect value
1086 will cause delays in the kernel to be wrong, leading to
1087 unpredictable I/O errors and other breakage. Although
1088 unlikely, in the extreme case this might damage your
1089 hardware.
1090
1091 ltpc= [NET]
1092 Format: <io>,<irq>,<dma>
1093
a9913044
RD
1094 mac5380= [HW,SCSI] Format:
1095 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1096
a9913044
RD
1097 machvec= [IA64] Force the use of a particular machine-vector
1098 (machvec) in a generic kernel.
1099 Example: machvec=hpzx1_swiotlb
1da177e4 1100
a9913044 1101 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1102 be mounted
1103 Format: <1-256>
1104
1105 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1106 should make use of. maxcpus=n : n >= 0 limits the
1107 kernel to using 'n' processors. n=0 is a special case,
1108 it is equivalent to "nosmp", which also disables
1109 the IO APIC.
1da177e4 1110
2b2c3750
BP
1111 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1112 equal to this physical address is ignored.
1113
a9913044 1114 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1115 Should be between 1 and 2^32-1.
1116
1117 max_report_luns=
a9913044 1118 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1119 Should be between 1 and 16384.
1120
1da177e4
LT
1121 mcatest= [IA-64]
1122
cd4f0ef7 1123 mce [X86-32] Machine Check Exception
1da177e4 1124
909dd324
AK
1125 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1126
1da177e4
LT
1127 md= [HW] RAID subsystems devices and level
1128 See Documentation/md.txt.
a9913044 1129
1da177e4
LT
1130 mdacon= [MDA]
1131 Format: <first>,<last>
1132 Specifies range of consoles to be captured by the MDA.
a9913044 1133
1da177e4
LT
1134 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1135 Amount of memory to be used when the kernel is not able
1136 to see the whole system memory or for test.
cd4f0ef7 1137 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1138 address space collisions. Without memmap= PCI devices
1139 could be placed at addresses belonging to unused RAM.
1140
cd4f0ef7 1141 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1142 memory.
1143
cd4f0ef7 1144 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1145 E820 memory map, as specified by the user.
1146 Such memmap=exactmap lines can be constructed based on
1147 BIOS output or other requirements. See the memmap=nn@ss
1148 option description.
1149
1150 memmap=nn[KMG]@ss[KMG]
1151 [KNL] Force usage of a specific region of memory
1152 Region of memory to be used, from ss to ss+nn.
1153
1154 memmap=nn[KMG]#ss[KMG]
1155 [KNL,ACPI] Mark specific memory as ACPI data.
1156 Region of memory to be used, from ss to ss+nn.
1157
1158 memmap=nn[KMG]$ss[KMG]
1159 [KNL,ACPI] Mark specific memory as reserved.
1160 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1161 Example: Exclude memory from 0x18690000-0x1869ffff
1162 memmap=64K$0x18690000
1163 or
1164 memmap=0x10000$0x18690000
1da177e4 1165
c64df707
YL
1166 memtest= [KNL,X86_64] Enable memtest
1167 Format: <integer>
1168 range: 0,4 : pattern number
1169 default : 0 <disable>
1170
1da177e4
LT
1171 meye.*= [HW] Set MotionEye Camera parameters
1172 See Documentation/video4linux/meye.txt.
1173
8f36881b
AS
1174 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1175 Multi-Function General Purpose Timers on AMD Geode
1176 platforms.
1177
e6c4dc6c
WT
1178 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1179 the BIOS has incorrectly applied a workaround. TinyBIOS
1180 version 0.98 is known to be affected, 0.99 fixes the
1181 problem by letting the user disable the workaround.
1182
1da177e4
LT
1183 mga= [HW,DRM]
1184
1185 mousedev.tap_time=
1186 [MOUSE] Maximum time between finger touching and
1187 leaving touchpad surface for touch to be considered
1188 a tap and be reported as a left button click (for
1189 touchpads working in absolute mode only).
1190 Format: <msecs>
1191 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1192 reporting absolute coordinates, such as tablets
1193 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1194 reporting absolute coordinates, such as tablets
1195
1196 mpu401= [HW,OSS]
1197 Format: <io>,<irq>
1198
1199 MTD_Partition= [MTD]
1200 Format: <name>,<region-number>,<size>,<offset>
1201
a9913044
RD
1202 MTD_Region= [MTD] Format:
1203 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1204
1205 mtdparts= [MTD]
c8facbb6 1206 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1207
1208 mtouchusb.raw_coordinates=
a9913044
RD
1209 [HW] Make the MicroTouch USB driver use raw coordinates
1210 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1211
1212 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1213
1214 NCR_D700= [HW,SCSI]
1215 See header of drivers/scsi/NCR_D700.c.
1216
1217 ncr5380= [HW,SCSI]
1218
1219 ncr53c400= [HW,SCSI]
1220
1221 ncr53c400a= [HW,SCSI]
1222
1223 ncr53c406a= [HW,SCSI]
1224
1225 ncr53c8xx= [HW,SCSI]
1226
1227 netdev= [NET] Network devices parameters
1228 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1229 Note that mem_start is often overloaded to mean
1230 something different and driver-specific.
a9913044
RD
1231 This usage is only documented in each driver source
1232 file if at all.
1233
1da177e4 1234 nfsaddrs= [NFS]
6ded55da 1235 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1236
1237 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1238 See Documentation/filesystems/nfsroot.txt.
1da177e4 1239
a72b4422
TM
1240 nfs.callback_tcpport=
1241 [NFS] set the TCP port on which the NFSv4 callback
1242 channel should listen.
1243
58df095b
TM
1244 nfs.idmap_cache_timeout=
1245 [NFS] set the maximum lifetime for idmapper cache
1246 entries.
1247
f43bf0be
TM
1248 nfs.enable_ino64=
1249 [NFS] enable 64-bit inode numbers.
1250 If zero, the NFS client will fake up a 32-bit inode
1251 number for the readdir() and stat() syscalls instead
1252 of returning the full 64-bit number.
1253 The default is to return 64-bit inode numbers.
1254
e7ba176b
HS
1255 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1256 when a NMI is triggered.
1257 Format: [state][,regs][,debounce][,die]
1258
cd4f0ef7 1259 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1260
cd4f0ef7 1261 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1262 emulation library even if a 387 maths coprocessor
1263 is present.
1264
c1aee215
CL
1265 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1266 caches in the slab allocator. Saves per-node memory,
1267 but will impact performance.
3395ee05 1268
a9913044
RD
1269 noalign [KNL,ARM]
1270
1da177e4
LT
1271 noapic [SMP,APIC] Tells the kernel to not make use of any
1272 IOAPICs that may be present in the system.
1273
1da177e4
LT
1274 nobats [PPC] Do not use BATs for mapping kernel lowmem
1275 on "Classic" PPC cores.
1276
1277 nocache [ARM]
a9913044 1278
163ecdff
SN
1279 nodelayacct [KNL] Disable per-task delay accounting
1280
1da177e4
LT
1281 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1282
8b2cb7a8
HY
1283 noefi [X86-32,X86-64] Disable EFI runtime services support.
1284
1da177e4
LT
1285 noexec [IA-64]
1286
cd4f0ef7 1287 noexec [X86-32,X86-64]
f5a1b191 1288 On X86-32 available only on PAE configured kernels.
1da177e4 1289 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1290 noexec=off: disable non-executable mappings
1291
1292 noexec32 [X86-64]
1293 This affects only 32-bit executables.
1294 noexec32=on: enable non-executable mappings (default)
1295 read doesn't imply executable mappings
1296 noexec32=off: disable non-executable mappings
1297 read implies executable mappings
1da177e4 1298
cd4f0ef7 1299 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1300 register save and restore. The kernel will only save
1301 legacy floating-point registers on task switch.
1da177e4 1302
191679fd
AK
1303 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1304
1da177e4 1305 nohlt [BUGS=ARM]
a9913044 1306
cd4f0ef7 1307 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1308 instruction doesn't work correctly and not to
1309 use it.
1310
1311 nohalt [IA-64] Tells the kernel not to use the power saving
1312 function PAL_HALT_LIGHT when idle. This increases
1313 power-consumption. On the positive side, it reduces
1314 interrupt wake-up latency, which may improve performance
1315 in certain environments such as networked servers or
1316 real-time systems.
1317
79bf2bb3
TG
1318 nohz= [KNL] Boottime enable/disable dynamic ticks
1319 Valid arguments: on, off
1320 Default: on
1321
cd4f0ef7 1322 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1323
cd4f0ef7 1324 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1325 disable unhandled interrupt sources.
1326
cd4f0ef7 1327 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1328 broken timer IRQ sources.
1329
1da177e4
LT
1330 noisapnp [ISAPNP] Disables ISA PnP code.
1331
1332 noinitrd [RAM] Tells the kernel not to load any configured
1333 initial RAM disk.
1334
1335 nointroute [IA-64]
1336
0aa366f3
TL
1337 nojitter [IA64] Disables jitter checking for ITC timers.
1338
cd4f0ef7 1339 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1340
cd4f0ef7 1341 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1342
1da177e4
LT
1343 noltlbs [PPC] Do not use large page/tlb entries for kernel
1344 lowmem mapping on PPC40x.
1345
312f1f01
H
1346 nomca [IA-64] Disable machine check abort handling
1347
cd4f0ef7 1348 nomce [X86-32] Machine Check Exception
abe37e5a 1349
83d7384f
AS
1350 nomfgpt [X86-32] Disable Multi-Function General Purpose
1351 Timer usage (for AMD Geode machines).
1352
cd4f0ef7 1353 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1354
cd4f0ef7 1355 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1356 with UP alternatives
1357
1da177e4
LT
1358 noresidual [PPC] Don't use residual data on PReP machines.
1359
a9913044
RD
1360 noresume [SWSUSP] Disables resume and restores original swap
1361 space.
1362
1da177e4
LT
1363 no-scroll [VGA] Disables scrollback.
1364 This is required for the Braillex ib80-piezo Braille
1365 reader made by F.H. Papenmeier (Germany).
1366
1367 nosbagart [IA-64]
1368
cd4f0ef7 1369 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1370
61ec7567
LB
1371 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1372 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1373
97842216
DJ
1374 nosoftlockup [KNL] Disable the soft-lockup detector.
1375
1da177e4
LT
1376 nosync [HW,M68K] Disables sync negotiation for all devices.
1377
cd4f0ef7 1378 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1379
1380 nousb [USB] Disable the USB subsystem
1381
1382 nowb [ARM]
a9913044 1383
a6c75b86
FY
1384 nptcg= [IA64] Override max number of concurrent global TLB
1385 purges which is reported from either PAL_VM_SUMMARY or
1386 SAL PALO.
1387
f0c0b2b8
KH
1388 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1389 one of ['zone', 'node', 'default'] can be specified
1390 This can be set from sysctl after boot.
1391 See Documentation/sysctl/vm.txt for details.
1392
a61c2d78
DJ
1393 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1394
3ef0e1f8
AS
1395 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1396 Rather than timing out after 20 ms if an EC
1397 command is not properly ACKed, override the length
1398 of the timeout. We have interrupts disabled while
1399 waiting for the ACK, so if this is set too high
1400 interrupts *may* be lost!
1401
1da177e4
LT
1402 opl3= [HW,OSS]
1403 Format: <io>
1404
1da177e4
LT
1405 oprofile.timer= [HW]
1406 Use timer interrupt instead of performance counters
1407
1da177e4
LT
1408 osst= [HW,SCSI] SCSI Tape Driver
1409 Format: <buffer_size>,<write_threshold>
1410 See also Documentation/scsi/st.txt.
1411
1412 panic= [KNL] Kernel behaviour on panic
1413 Format: <timeout>
1414
1415 parkbd.port= [HW] Parallel port number the keyboard adapter is
1416 connected to, default is 0.
1417 Format: <parport#>
1418 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1419 0 for XT, 1 for AT (default is AT).
a9913044
RD
1420 Format: <mode>
1421
1422 parport= [HW,PPT] Specify parallel ports. 0 disables.
1423 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1424 Use 'auto' to force the driver to use any
1425 IRQ/DMA settings detected (the default is to
1426 ignore detected IRQ/DMA settings because of
1427 possible conflicts). You can specify the base
1428 address, IRQ, and DMA settings; IRQ and DMA
1429 should be numbers, or 'auto' (for using detected
1430 settings on that particular port), or 'nofifo'
1431 (to avoid using a FIFO even if it is detected).
1432 Parallel ports are assigned in the order they
1433 are specified on the command line, starting
1434 with parport0.
1435
1436 parport_init_mode= [HW,PPT]
1437 Configure VIA parallel port to operate in
1438 a specific mode. This is necessary on Pegasos
1439 computer where firmware has no options for setting
1440 up parallel port mode and sets it to spp.
1441 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1442 Format: [spp|ps2|epp|ecp|ecpepp]
1443
a9913044
RD
1444 pas2= [HW,OSS] Format:
1445 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1446
1da177e4
LT
1447 pas16= [HW,SCSI]
1448 See header of drivers/scsi/pas16.c.
1449
dd287796
AM
1450 pause_on_oops=
1451 Halt all CPUs after the first oops has been printed for
1452 the specified number of seconds. This is to be used if
1453 your oopses keep scrolling off the screen.
1454
1da177e4
LT
1455 pcbit= [HW,ISDN]
1456
1457 pcd. [PARIDE]
1458 See header of drivers/block/paride/pcd.c.
1459 See also Documentation/paride.txt.
1460
a9913044 1461 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1462 off [X86-32] don't probe for the PCI bus
1463 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1464 the hardware directly. Use this if your machine
1465 has a non-standard PCI host bridge.
cd4f0ef7 1466 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1467 hardware access methods are allowed. Use this
1468 if you experience crashes upon bootup and you
1469 suspect they are caused by the BIOS.
cd4f0ef7 1470 conf1 [X86-32] Force use of PCI Configuration
a9913044 1471 Mechanism 1.
cd4f0ef7 1472 conf2 [X86-32] Force use of PCI Configuration
a9913044 1473 Mechanism 2.
7f785763
RD
1474 noaer [PCIE] If the PCIEAER kernel config parameter is
1475 enabled, this kernel boot option can be used to
1476 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1477 nodomains [PCI] Disable support for multiple PCI
1478 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1479 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1480 Configuration
309e57df
MW
1481 nomsi [MSI] If the PCI_MSI kernel config parameter is
1482 enabled, this kernel boot option can be used to
1483 disable the use of MSI interrupts system-wide.
cd4f0ef7 1484 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1485 routing table. These calls are known to be buggy
1486 on several machines and they hang the machine
1487 when used, but on other computers it's the only
1488 way to get the interrupt routing table. Try
1489 this option if the kernel is unable to allocate
1490 IRQs or discover secondary PCI buses on your
1491 motherboard.
cd4f0ef7 1492 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1493 Use with caution as certain devices share
1494 address decoders between ROMs and other
1495 resources.
cd4f0ef7 1496 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1497 assigned automatically to PCI devices. You can
1498 make the kernel exclude IRQs of your ISA cards
1499 this way.
cd4f0ef7 1500 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1501 of the PIRQ table (normally generated
1502 by the BIOS) if it is outside the
1503 F0000h-100000h range.
cd4f0ef7 1504 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1505 useful if the kernel is unable to find your
1506 secondary buses and you want to tell it
1507 explicitly which ones they are.
cd4f0ef7 1508 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1509 numbers ourselves, overriding
1510 whatever the firmware may have done.
cd4f0ef7 1511 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1512 in the BIOS $PIR table. This is needed on
1513 some systems with broken BIOSes, notably
1514 some HP Pavilion N5400 and Omnibook XE3
1515 notebooks. This will have no effect if ACPI
1516 IRQ routing is enabled.
cd4f0ef7 1517 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1518 or for PCI scanning.
62f420f8
GH
1519 use_crs [X86-32] Use _CRS for PCI resource
1520 allocation.
a9913044
RD
1521 routeirq Do IRQ routing for all PCI devices.
1522 This is normally done in pci_enable_device(),
1523 so this option is a temporary workaround
1524 for broken drivers that don't call it.
13a6ddb0
YL
1525 skip_isa_align [X86] do not align io start addr, so can
1526 handle more pci cards
a9913044
RD
1527 firmware [ARM] Do not re-enumerate the bus but instead
1528 just use the configuration from the
1529 bootloader. This is currently used on
1530 IXP2000 systems where the bus has to be
1531 configured a certain way for adjunct CPUs.
0637a70a
AK
1532 noearly [X86] Don't do any early type 1 scanning.
1533 This might help on some broken boards which
1534 machine check when some devices' config space
1535 is read. But various workarounds are disabled
1536 and some IOMMU drivers will not work.
6b4b78fe
MD
1537 bfsort Sort PCI devices into breadth-first order.
1538 This sorting is done to get a device
1539 order compatible with older (<= 2.4) kernels.
1540 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1541 cbiosize=nn[KMG] The fixed amount of bus space which is
1542 reserved for the CardBus bridge's IO window.
1543 The default value is 256 bytes.
1544 cbmemsize=nn[KMG] The fixed amount of bus space which is
1545 reserved for the CardBus bridge's memory
1546 window. The default value is 64 megabytes.
6b4b78fe 1547
1da177e4
LT
1548 pcmv= [HW,PCMCIA] BadgePAD 4
1549
1550 pd. [PARIDE]
1551 See Documentation/paride.txt.
1552
1553 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1554 boot time.
1555 Format: { 0 | 1 }
1556 See arch/parisc/kernel/pdc_chassis.c
1557
1558 pf. [PARIDE]
1559 See Documentation/paride.txt.
1560
1561 pg. [PARIDE]
1562 See Documentation/paride.txt.
1563
1564 pirq= [SMP,APIC] Manual mp-table setup
1565 See Documentation/i386/IO-APIC.txt.
1566
1567 plip= [PPT,NET] Parallel port network link
1568 Format: { parport<nr> | timid | 0 }
1569 See also Documentation/parport.txt.
1570
1571 pnpacpi= [ACPI]
1572 { off }
1573
1574 pnpbios= [ISAPNP]
1575 { on | off | curr | res | no-curr | no-res }
1576
1577 pnp_reserve_irq=
1578 [ISAPNP] Exclude IRQs for the autoconfiguration
1579
1580 pnp_reserve_dma=
1581 [ISAPNP] Exclude DMAs for the autoconfiguration
1582
1583 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1584 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1585
1586 pnp_reserve_mem=
a9913044
RD
1587 [ISAPNP] Exclude memory regions for the
1588 autoconfiguration.
1da177e4
LT
1589 Ranges are in pairs (memory base and size).
1590
45807a1d
IM
1591 print-fatal-signals=
1592 [KNL] debug: print fatal signals
1593 print-fatal-signals=1: print segfault info to
1594 the kernel console.
1595 default: off.
1596
e84845c4
RD
1597 printk.time= Show timing data prefixed to each printk message line
1598 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1599
1da177e4 1600 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1601 Format: [schedule,]<number>
1602 Param: "schedule" - profile schedule points.
1603 Param: <number> - step/bucket size as a power of 2 for
1604 statistical time based profiling.
b3da2a73
MG
1605 Param: "sleep" - profile D-state sleeping (millisecs).
1606 Requires CONFIG_SCHEDSTATS
c0fe2e69 1607 Param: "kvm" - profile VM exits.
1da177e4 1608
a9913044 1609 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1610 Limit processor to maximum C-state
1611 max_cstate=9 overrides any DMI blacklist limit.
1612
41c0d868
LB
1613 processor.nocst [HW,ACPI]
1614 Ignore the _CST method to determine C-states,
1615 instead using the legacy FADT method
1616
1da177e4
LT
1617 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1618 before loading.
1619 See Documentation/ramdisk.txt.
1620
a9913044
RD
1621 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1622 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1623 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1624 per second.
a9913044
RD
1625 psmouse.resetafter= [HW,MOUSE]
1626 Try to reset the device after so many bad packets
1da177e4
LT
1627 (0 = never).
1628 psmouse.resolution=
1629 [HW,MOUSE] Set desired mouse resolution, in dpi.
1630 psmouse.smartscroll=
a9913044 1631 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1632 0 = disabled, 1 = enabled (default).
1633
1634 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1635 Format:
1636 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1637
1638 pt. [PARIDE]
1639 See Documentation/paride.txt.
1640
dc8c8587
KS
1641 pty.legacy_count=
1642 [KNL] Number of legacy pty's. Overwrites compiled-in
1643 default number.
1644
7d2c502f 1645 quiet [KNL] Disable most log messages
a9913044 1646
1da177e4
LT
1647 r128= [HW,DRM]
1648
1649 raid= [HW,RAID]
1650 See Documentation/md.txt.
1651
a9913044 1652 ramdisk_blocksize= [RAM]
1da177e4 1653 See Documentation/ramdisk.txt.
a9913044 1654
1da177e4 1655 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1656 See Documentation/ramdisk.txt.
1657
24aaef8d
RD
1658 rcupdate.blimit= [KNL,BOOT]
1659 Set maximum number of finished RCU callbacks to process
1660 in one batch.
21a1ea9e 1661
24aaef8d
RD
1662 rcupdate.qhimark= [KNL,BOOT]
1663 Set threshold of queued
21a1ea9e
DS
1664 RCU callbacks over which batch limiting is disabled.
1665
24aaef8d
RD
1666 rcupdate.qlowmark= [KNL,BOOT]
1667 Set threshold of queued RCU callbacks below which
1668 batch limiting is re-enabled.
21a1ea9e 1669
ffdfc409
OJ
1670 rdinit= [KNL]
1671 Format: <full_path>
1672 Run specified binary instead of /init from the ramdisk,
1673 used for early userspace startup. See initrd.
1674
cd4f0ef7 1675 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1676 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1677 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1678
1679 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1680
cd4f0ef7 1681 reservetop= [X86-32]
461a9aff
ZA
1682 Format: nn[KMG]
1683 Reserves a hole at the top of the kernel virtual
1684 address space.
1685
7e96287d
VG
1686 reset_devices [KNL] Force drivers to reset the underlying device
1687 during initialization.
1688
a9913044
RD
1689 resume= [SWSUSP]
1690 Specify the partition device for software suspend
1da177e4 1691
ecbd0da1
RW
1692 resume_offset= [SWSUSP]
1693 Specify the offset from the beginning of the partition
1694 given by "resume=" at which the swap header is located,
1695 in <PAGE_SIZE> units (needed only for swap files).
1696 See Documentation/power/swsusp-and-swap-files.txt
1697
0a7b35cb
MN
1698 retain_initrd [RAM] Keep initrd memory after extraction
1699
1da177e4
LT
1700 rhash_entries= [KNL,NET]
1701 Set number of hash buckets for route cache
1702
1703 riscom8= [HW,SERIAL]
1704 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1705
1706 ro [KNL] Mount root device read-only on boot
1707
1708 root= [KNL] Root filesystem
1709
1710 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1711 mount the root filesystem
1712
1713 rootflags= [KNL] Set root filesystem mount option string
1714
1715 rootfstype= [KNL] Set root filesystem type
1716
cc1ed754
PO
1717 rootwait [KNL] Wait (indefinitely) for root device to show up.
1718 Useful for devices that are detected asynchronously
1719 (e.g. USB and MMC devices).
1720
20510f2f
JM
1721 root_plug.vendor_id=
1722 [ROOTPLUG] Override the default vendor ID
1723
1724 root_plug.product_id=
1725 [ROOTPLUG] Override the default product ID
1726
1727 root_plug.debug=
1728 [ROOTPLUG] Enable debugging output
1729
1da177e4
LT
1730 rw [KNL] Mount root device read-write on boot
1731
1732 S [KNL] Run init in single mode
1733
1734 sa1100ir [NET]
1735 See drivers/net/irda/sa1100_ir.c.
1736
1da177e4 1737 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1738
1da177e4
LT
1739 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1740 Format: <io>[,<timeout>[,<isapnp>]]
1741
1742 scsi_debug_*= [SCSI]
1743 See drivers/scsi/scsi_debug.c.
1744
1745 scsi_default_dev_flags=
1746 [SCSI] SCSI default device flags
1747 Format: <integer>
1748
1749 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1750 Format: <vendor>:<model>:<flags>
1751 (flags are integer value)
1752
6af6632a
RD
1753 scsi_logging_level= [SCSI] a bit mask of logging levels
1754 See drivers/scsi/scsi_logging.h for bits. Also
1755 settable via sysctl at dev.scsi.logging_level
1756 (/proc/sys/dev/scsi/logging_level).
1757 There is also a nice 'scsi_logging_level' script in the
1758 S390-tools package, available for download at
1759 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1760
3e082a91
MW
1761 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1762 discovered. async scans them in kernel threads,
1763 allowing boot to proceed. none ignores them, expecting
1764 user space to do the scan.
1765
1da177e4
LT
1766 selinux [SELINUX] Disable or enable SELinux at boot time.
1767 Format: { "0" | "1" }
1768 See security/selinux/Kconfig help text.
1769 0 -- disable.
1770 1 -- enable.
1771 Default value is set via kernel config option.
1772 If enabled at boot time, /selinux/disable can be used
1773 later to disable prior to initial policy load.
1774
4e5ab4cb
JM
1775 selinux_compat_net =
1776 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1777 Format: { "0" | "1" }
1778 0 -- use new secmark-based packet controls
1779 1 -- use legacy packet controls
1780 Default value is 0 (preferred).
1781 Value can be changed at runtime via
1782 /selinux/compat_net.
4e5ab4cb 1783
cd4f0ef7 1784 serialnumber [BUGS=X86-32]
1da177e4 1785
1da177e4
LT
1786 shapers= [NET]
1787 Maximal number of shapers.
a9913044 1788
1da177e4
LT
1789 sim710= [SCSI,HW]
1790 See header of drivers/scsi/sim710.c.
1791
1792 simeth= [IA-64]
1793 simscsi=
a9913044 1794
1da177e4
LT
1795 slram= [HW,MTD]
1796
f0630fff
CL
1797 slub_debug[=options[,slabs]] [MM, SLUB]
1798 Enabling slub_debug allows one to determine the
1799 culprit if slab objects become corrupted. Enabling
1800 slub_debug can create guard zones around objects and
1801 may poison objects when not in use. Also tracks the
1802 last alloc / free. For more information see
1803 Documentation/vm/slub.txt.
c1aee215
CL
1804
1805 slub_max_order= [MM, SLUB]
f0630fff
CL
1806 Determines the maximum allowed order for slabs.
1807 A high setting may cause OOMs due to memory
1808 fragmentation. For more information see
1809 Documentation/vm/slub.txt.
c1aee215
CL
1810
1811 slub_min_objects= [MM, SLUB]
f0630fff
CL
1812 The minimum number of objects per slab. SLUB will
1813 increase the slab order up to slub_max_order to
1814 generate a sufficiently large slab able to contain
1815 the number of objects indicated. The higher the number
1816 of objects the smaller the overhead of tracking slabs
1817 and the less frequently locks need to be acquired.
c1aee215
CL
1818 For more information see Documentation/vm/slub.txt.
1819
1820 slub_min_order= [MM, SLUB]
1821 Determines the mininum page order for slabs. Must be
f0630fff 1822 lower than slub_max_order.
c1aee215
CL
1823 For more information see Documentation/vm/slub.txt.
1824
1825 slub_nomerge [MM, SLUB]
f0630fff 1826 Disable merging of slabs with similar size. May be
c1aee215 1827 necessary if there is some reason to distinguish
f0630fff
CL
1828 allocs to different slabs. Debug options disable
1829 merging on their own.
c1aee215
CL
1830 For more information see Documentation/vm/slub.txt.
1831
1da177e4
LT
1832 smart2= [HW]
1833 Format: <io1>[,<io2>[,...,<io8>]]
1834
cd4f0ef7 1835 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1836 attempt to substitute SMP alternatives once at boot.
1837
d0d4f69b
BH
1838 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1839 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1840 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1841 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1842 smsc-ircc2.ircc_irq= [HW] IRQ line
1843 smsc-ircc2.ircc_dma= [HW] DMA channel
1844 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1845 0: Toshiba Satellite 1800 (GP data pin select)
1846 1: Fast pin select (default)
1847 2: ATC IRMode
1848
1da177e4
LT
1849 snd-ad1816a= [HW,ALSA]
1850
1851 snd-ad1848= [HW,ALSA]
1852
1853 snd-ali5451= [HW,ALSA]
1854
1855 snd-als100= [HW,ALSA]
1856
1857 snd-als4000= [HW,ALSA]
1858
1859 snd-azt2320= [HW,ALSA]
1860
1861 snd-cmi8330= [HW,ALSA]
1862
1863 snd-cmipci= [HW,ALSA]
1864
1865 snd-cs4231= [HW,ALSA]
1866
1867 snd-cs4232= [HW,ALSA]
1868
1869 snd-cs4236= [HW,ALSA]
1870
1871 snd-cs4281= [HW,ALSA]
1872
1873 snd-cs46xx= [HW,ALSA]
1874
1875 snd-dt019x= [HW,ALSA]
1876
1877 snd-dummy= [HW,ALSA]
1878
1879 snd-emu10k1= [HW,ALSA]
1880
1881 snd-ens1370= [HW,ALSA]
1882
1883 snd-ens1371= [HW,ALSA]
1884
1885 snd-es968= [HW,ALSA]
1886
1887 snd-es1688= [HW,ALSA]
1888
1889 snd-es18xx= [HW,ALSA]
1890
1891 snd-es1938= [HW,ALSA]
1892
1893 snd-es1968= [HW,ALSA]
1894
1895 snd-fm801= [HW,ALSA]
1896
1897 snd-gusclassic= [HW,ALSA]
1898
1899 snd-gusextreme= [HW,ALSA]
1900
1901 snd-gusmax= [HW,ALSA]
1902
1903 snd-hdsp= [HW,ALSA]
1904
1905 snd-ice1712= [HW,ALSA]
1906
1907 snd-intel8x0= [HW,ALSA]
1908
1909 snd-interwave= [HW,ALSA]
1910
1911 snd-interwave-stb=
1912 [HW,ALSA]
1913
1914 snd-korg1212= [HW,ALSA]
1915
1916 snd-maestro3= [HW,ALSA]
1917
1918 snd-mpu401= [HW,ALSA]
1919
1920 snd-mtpav= [HW,ALSA]
1921
1922 snd-nm256= [HW,ALSA]
1923
1924 snd-opl3sa2= [HW,ALSA]
1925
1926 snd-opti92x-ad1848=
1927 [HW,ALSA]
1928
1929 snd-opti92x-cs4231=
1930 [HW,ALSA]
1931
1932 snd-opti93x= [HW,ALSA]
1933
1934 snd-pmac= [HW,ALSA]
1935
1936 snd-rme32= [HW,ALSA]
1937
1938 snd-rme96= [HW,ALSA]
1939
1940 snd-rme9652= [HW,ALSA]
1941
1942 snd-sb8= [HW,ALSA]
1943
1944 snd-sb16= [HW,ALSA]
1945
1946 snd-sbawe= [HW,ALSA]
1947
1948 snd-serial= [HW,ALSA]
1949
1950 snd-sgalaxy= [HW,ALSA]
1951
1952 snd-sonicvibes= [HW,ALSA]
1953
1954 snd-sun-amd7930=
1955 [HW,ALSA]
1956
1957 snd-sun-cs4231= [HW,ALSA]
1958
1959 snd-trident= [HW,ALSA]
1960
1961 snd-usb-audio= [HW,ALSA,USB]
1962
1963 snd-via82xx= [HW,ALSA]
1964
1965 snd-virmidi= [HW,ALSA]
1966
1967 snd-wavefront= [HW,ALSA]
1968
1969 snd-ymfpci= [HW,ALSA]
a9913044 1970
1da177e4
LT
1971 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1972 See Documentation/sonypi.txt
1973
1974 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1975 See Documentation/specialix.txt.
1976
1977 spia_io_base= [HW,MTD]
1978 spia_fio_base=
1979 spia_pedr=
1980 spia_peddr=
1981
1982 sscape= [HW,OSS]
1983 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1984
1da177e4
LT
1985 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1986 See Documentation/scsi/st.txt.
1987
1da177e4
LT
1988 sti= [PARISC,HW]
1989 Format: <num>
1990 Set the STI (builtin display/keyboard on the HP-PARISC
1991 machines) console (graphic card) which should be used
1992 as the initial boot-console.
1993 See also comment in drivers/video/console/sticore.c.
1994
1995 sti_font= [HW]
1996 See comment in drivers/video/console/sticore.c.
1997
1998 stifb= [HW]
1999 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2000
42a7fc4a
GB
2001 sunrpc.pool_mode=
2002 [NFS]
2003 Control how the NFS server code allocates CPUs to
2004 service thread pools. Depending on how many NICs
2005 you have and where their interrupts are bound, this
2006 option will affect which CPUs will do NFS serving.
2007 Note: this parameter cannot be changed while the
2008 NFS server is running.
2009
2010 auto the server chooses an appropriate mode
2011 automatically using heuristics
2012 global a single global pool contains all CPUs
2013 percpu one pool for each CPU
2014 pernode one pool for each NUMA node (equivalent
2015 to global on non-NUMA machines)
2016
1da177e4 2017 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2018
1da177e4
LT
2019 switches= [HW,M68k]
2020
2021 sym53c416= [HW,SCSI]
2022 See header of drivers/scsi/sym53c416.c.
2023
5d6f647f
IM
2024 sysrq_always_enabled
2025 [KNL]
2026 Ignore sysrq setting - this boot parameter will
2027 neutralize any effect of /proc/sys/kernel/sysrq.
2028 Useful for debugging.
2029
1da177e4
LT
2030 t128= [HW,SCSI]
2031 See header of drivers/scsi/t128.c.
2032
2033 tdfx= [HW,DRM]
2034
2035 thash_entries= [KNL,NET]
2036 Set number of hash buckets for TCP connection
2037
f8707ec9
LB
2038 thermal.act= [HW,ACPI]
2039 -1: disable all active trip points in all thermal zones
2040 <degrees C>: override all lowest active trip points
2041
c52a7419
LB
2042 thermal.crt= [HW,ACPI]
2043 -1: disable all critical trip points in all thermal zones
2044 <degrees C>: lower all critical trip points
2045
f5487145
LB
2046 thermal.nocrt= [HW,ACPI]
2047 Set to disable actions on ACPI thermal zone
2048 critical and hot trip points.
2049
72b33ef8
LB
2050 thermal.off= [HW,ACPI]
2051 1: disable ACPI thermal control
2052
a70cdc52
LB
2053 thermal.psv= [HW,ACPI]
2054 -1: disable all passive trip points
2055 <degrees C>: override all passive trip points to this value
2056
730ff34d
LB
2057 thermal.tzp= [HW,ACPI]
2058 Specify global default ACPI thermal zone polling rate
2059 <deci-seconds>: poll all this frequency
2060 0: no polling (default)
2061
1da177e4
LT
2062 tipar.timeout= [HW,PPT]
2063 Set communications timeout in tenths of a second
2064 (default 15).
2065
2066 tipar.delay= [HW,PPT]
2067 Set inter-bit delay in microseconds (default 10).
2068
1da177e4
LT
2069 tmscsim= [HW,SCSI]
2070 See comment before function dc390_setup() in
2071 drivers/scsi/tmscsim.c.
2072
2073 tp720= [HW,PS2]
2074
2075 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2076 Format:
2077 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2078
a9913044
RD
2079 turbografx.map[2|3]= [HW,JOY]
2080 TurboGraFX parallel port interface
2081 Format:
2082 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2083 See also Documentation/input/joystick-parport.txt
2084
2085 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2086 See header of drivers/scsi/u14-34f.c.
2087
2088 uart401= [HW,OSS]
2089 Format: <io>,<irq>
2090
2091 uart6850= [HW,OSS]
2092 Format: <io>,<irq>
2093
5f8364b7
AS
2094 uhci-hcd.ignore_oc=
2095 [USB] Ignore overcurrent events (default N).
2096 Some badly-designed motherboards generate lots of
2097 bogus events, for ports that aren't wired to
2098 anything. Set this parameter to avoid log spamming.
2099 Note that genuine overcurrent events won't be
2100 reported either.
2101
b5e795f8
AS
2102 usbcore.autosuspend=
2103 [USB] The autosuspend time delay (in seconds) used
2104 for newly-detected USB devices (default 2). This
2105 is the time required before an idle device will be
2106 autosuspended. Devices for which the delay is set
eaafbc3a 2107 to a negative value won't be autosuspended at all.
b5e795f8 2108
1da177e4
LT
2109 usbhid.mousepoll=
2110 [USBHID] The interval which mice are to be polled at.
a9913044 2111
cd4f0ef7 2112 vdso= [X86-32,SH,x86-64]
1dbf527c 2113 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2114 vdso=1: enable VDSO (default)
2115 vdso=0: disable VDSO mapping
2116
af65d648
RM
2117 vdso32= [X86-32,X86-64]
2118 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2119 vdso32=1: enable 32-bit VDSO (default)
2120 vdso32=0: disable 32-bit VDSO mapping
2121
d080d397
YI
2122 vector= [IA-64,SMP]
2123 vector=percpu: enable percpu vector domain
2124
1da177e4
LT
2125 video= [FB] Frame buffer configuration
2126 See Documentation/fb/modedb.txt.
2127
cd4f0ef7 2128 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2129 See Documentation/i386/boot.txt and
2130 Documentation/svga.txt.
1da177e4
LT
2131 Use vga=ask for menu.
2132 This is actually a boot loader parameter; the value is
2133 passed to the kernel using a special protocol.
2134
a9913044 2135 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2136 size of <nn>. This can be used to increase the
2137 minimum size (128MB on x86). It can also be used to
2138 decrease the size and leave more room for directly
2139 mapped kernel RAM.
2140
585c3047
PO
2141 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2142 Format: <command>
1da177e4 2143
585c3047
PO
2144 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2145 Format: <command>
2146
2147 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2148 Format: <command>
a9913044 2149
1da177e4
LT
2150 waveartist= [HW,OSS]
2151 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2152
1da177e4
LT
2153 wd33c93= [HW,SCSI]
2154 See header of drivers/scsi/wd33c93.c.
2155
2156 wd7000= [HW,SCSI]
2157 See header of drivers/scsi/wd7000.c.
2158
2159 wdt= [WDT] Watchdog
8dfe9c21 2160 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2161
2162 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2163 xd_geo= See header of drivers/block/xd.c.
2164
2165 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2166 Format:
2167 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2168
a62eaf15
AK
2169 norandmaps Don't use address space randomization
2170 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2171
a9913044 2172______________________________________________________________________
1da177e4
LT
2173
2174TODO:
2175
2176 Add documentation for ALSA options.
2177 Add more DRM drivers.