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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
cd4f0ef7 401 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 402 [Deprecated]
3f6dee9b 403 Forces specified clocksource (if available) to be used
734efb46 404 when calculating gettimeofday(). If specified
3f6dee9b 405 clocksource is not available, it defaults to PIT.
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406 Format: { pit | tsc | cyclone | pmtmr }
407
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408 clocksource= [GENERIC_TIME] Override the default clocksource
409 Format: <string>
410 Override the default clocksource and use the clocksource
411 with the name specified.
412 Some clocksource names to choose from, depending on
413 the platform:
414 [all] jiffies (this is the base, fallback clocksource)
415 [ACPI] acpi_pm
416 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
417 pxa_timer,timer3,32k_counter,timer0_1
418 [AVR32] avr32
cd4f0ef7 419 [X86-32] pit,hpet,tsc,vmi-timer;
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420 scx200_hrt on Geode; cyclone on IBM x440
421 [MIPS] MIPS
422 [PARISC] cr16
423 [S390] tod
424 [SH] SuperH
425 [SPARC64] tick
426 [X86-64] hpet,tsc
427
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428 clearcpuid=BITNUM [X86]
429 Disable CPUID feature X for the kernel. See
430 include/asm-x86/cpufeature.h for the valid bit numbers.
431 Note the Linux specific bits are not necessarily
432 stable over kernel options, but the vendor specific
433 ones should be.
434 Also note that user programs calling CPUID directly
435 or using the feature without checking anything
436 will still see it. This just prevents it from
437 being used by the kernel or shown in /proc/cpuinfo.
438 Also note the kernel might malfunction if you disable
439 some critical bits.
440
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441 code_bytes [IA32/X86_64] How many bytes of object code to print
442 in an oops report.
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443 Range: 0 - 8192
444 Default: 64
445
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446 disable_8254_timer
447 enable_8254_timer
448 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
449 over the 8254 in addition to over the IO-APIC. The
450 kernel tries to set a sensible default.
451
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452 hpet= [X86-32,HPET] option to control HPET usage
453 Format: { enable (default) | disable | force }
454 disable: disable HPET and use PIT instead
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455 force: allow force enabled of undocumented chips (ICH4,
456 VIA, nVidia)
1da177e4 457
1da177e4 458 com20020= [HW,NET] ARCnet - COM20020 chipset
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459 Format:
460 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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461
462 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
463 Format: <io>[,<irq>]
464
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465 com90xx= [HW,NET]
466 ARCnet - COM90xx chipset (memory-mapped buffers)
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467 Format: <io>[,<irq>[,<memstart>]]
468
469 condev= [HW,S390] console device
470 conmode=
a9913044 471
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472 console= [KNL] Output console device and options.
473
474 tty<n> Use the virtual console device <n>.
475
476 ttyS<n>[,options]
f1a1c2dc 477 ttyUSB0[,options]
1da177e4 478 Use the specified serial port. The options are of
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479 the form "bbbbpnf", where "bbbb" is the baud rate,
480 "p" is parity ("n", "o", or "e"), "n" is number of
481 bits, and "f" is flow control ("r" for RTS or
482 omit it). Default is "9600n8".
483
484 See Documentation/serial-console.txt for more
485 information. See
486 Documentation/networking/netconsole.txt for an
487 alternative.
1da177e4 488
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489 uart[8250],io,<addr>[,options]
490 uart[8250],mmio,<addr>[,options]
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491 Start an early, polled-mode console on the 8250/16550
492 UART at the specified I/O port or MMIO address,
493 switching to the matching ttyS device later. The
494 options are the same as for ttyS, above.
495
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496 If the device connected to the port is not a TTY but a braille
497 device, prepend "brl," before the device type, for instance
498 console=brl,ttyS0
499 For now, only VisioBraille is supported.
500
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501 earlycon= [KNL] Output early console device and options.
502 uart[8250],io,<addr>[,options]
503 uart[8250],mmio,<addr>[,options]
504 Start an early, polled-mode console on the 8250/16550
505 UART at the specified I/O port or MMIO address.
506 The options are the same as for ttyS, above.
507
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508 no_console_suspend
509 [HW] Never suspend the console
510 Disable suspending of consoles during suspend and
511 hibernate operations. Once disabled, debugging
512 messages can reach various consoles while the rest
513 of the system is being put to sleep (ie, while
514 debugging driver suspend/resume hooks). This may
515 not work reliably with all consoles, but is known
516 to work with serial and VGA consoles.
517
1da177e4 518 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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519 Format:
520 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 521
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522 crashkernel=nn[KMG]@ss[KMG]
523 [KNL] Reserve a chunk of physical memory to
524 hold a kernel to switch to with kexec on panic.
525
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526 crashkernel=range1:size1[,range2:size2,...][@offset]
527 [KNL] Same as above, but depends on the memory
528 in the running system. The syntax of range is
529 start-[end] where start and end are both
530 a memory unit (amount[KMG]). See also
531 Documentation/kdump/kdump.txt for a example.
532
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LT
533 cs4232= [HW,OSS]
534 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
535
536 cs89x0_dma= [HW,NET]
537 Format: <dma>
538
539 cs89x0_media= [HW,NET]
540 Format: { rj45 | aui | bnc }
a9913044 541
a9913044 542 dasd= [HW,NET]
1da177e4
LT
543 See header of drivers/s390/block/dasd_devmap.c.
544
545 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
546 (one device per port)
547 Format: <port#>,<type>
548 See also Documentation/input/joystick-parport.txt
549
550 debug [KNL] Enable kernel debugging (events log level).
551
cae2ed9a
IM
552 debug_locks_verbose=
553 [KNL] verbose self-tests
554 Format=<0|1>
555 Print debugging info while doing the locking API
556 self-tests.
557 We default to 0 (no extra messages), setting it to
558 1 will print _a lot_ more information - normally
559 only useful to kernel developers.
560
3ac7fe5a
TG
561 debug_objects [KNL] Enable object debugging
562
2d27a966 563 decnet.addr= [HW,NET]
1da177e4
LT
564 Format: <area>[,<node>]
565 See also Documentation/networking/decnet.txt.
566
ecb77fa9 567 vt.default_blu= [VT]
55ff9780
AD
568 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
569 Change the default blue palette of the console.
570 This is a 16-member array composed of values
571 ranging from 0-255.
572
ecb77fa9 573 vt.default_grn= [VT]
55ff9780
AD
574 Format: <green0>,<green1>,<green2>,...,<green15>
575 Change the default green palette of the console.
576 This is a 16-member array composed of values
577 ranging from 0-255.
578
ecb77fa9 579 vt.default_red= [VT]
55ff9780
AD
580 Format: <red0>,<red1>,<red2>,...,<red15>
581 Change the default red palette of the console.
582 This is a 16-member array composed of values
583 ranging from 0-255.
584
ecb77fa9
ST
585 vt.default_utf8=
586 [VT]
55ff9780
AD
587 Format=<0|1>
588 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
589 Default is 1, i.e. UTF-8 mode is enabled for all
590 newly opened terminals.
55ff9780 591
1da177e4
LT
592 dhash_entries= [KNL]
593 Set number of hash buckets for dentry cache.
a9913044 594
1da177e4
LT
595 digi= [HW,SERIAL]
596 IO parameters + enable/disable command.
597
598 digiepca= [HW,SERIAL]
599 See drivers/char/README.epca and
600 Documentation/digiepca.txt.
601
95ffa243
YL
602 disable_mtrr_cleanup [X86]
603 enable_mtrr_cleanup [X86]
604 The kernel tries to adjust MTRR layout from continuous
605 to discrete, to make X server driver able to add WB
606 entry later. This parameter enables/disables that.
607
608 mtrr_chunk_size=nn[KMG] [X86]
609 used for mtrr cleanup. It is largest continous chunk
610 that could hold holes aka. UC entries.
611
612 mtrr_gran_size=nn[KMG] [X86]
613 used for mtrr cleanup. It is granity of mtrr block.
614 Big value could prevent small alignment use up MTRRs.
615
093af8d7 616 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
617 By default the kernel will trim any uncacheable
618 memory out of your available memory pool based on
619 MTRR settings. This parameter disables that behavior,
620 possibly causing your machine to run very slowly.
621
1da177e4
LT
622 dmasound= [HW,OSS] Sound subsystem buffers
623
624 dscc4.setup= [NET]
625
626 dtc3181e= [HW,SCSI]
627
0ae53640 628 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
629 earlyprintk=vga
630 earlyprintk=serial[,ttySn[,baudrate]]
631
a9913044 632 Append ",keep" to not disable it when the real console
1da177e4
LT
633 takes over.
634
635 Only vga or serial at a time, not both.
636
637 Currently only ttyS0 and ttyS1 are supported.
638
639 Interaction with the standard serial driver is not
640 very good.
641
642 The VGA output is eventually overwritten by the real
643 console.
644
645 eata= [HW,SCSI]
646
1da177e4 647 edd= [EDD]
8c4dd606 648 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 649
1da177e4
LT
650 eisa_irq_edge= [PARISC,HW]
651 See header of drivers/parisc/eisa.c.
652
cd4f0ef7 653 elanfreq= [X86-32]
1da177e4
LT
654 See comment before function elanfreq_setup() in
655 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
656
657 elevator= [IOSCHED]
16ab3adf 658 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
659 See Documentation/block/as-iosched.txt and
660 Documentation/block/deadline-iosched.txt for details.
661
cd4f0ef7 662 elfcorehdr= [X86-32, X86_64]
a9913044 663 Specifies physical address of start of kernel core
aac04b32
VG
664 image elf header. Generally kexec loader will
665 pass this option to capture kernel.
666 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
667
668 enforcing [SELINUX] Set initial enforcing status.
669 Format: {"0" | "1"}
670 See security/selinux/Kconfig help text.
671 0 -- permissive (log only, no denials).
672 1 -- enforcing (deny and log).
673 Default value is 0.
674 Value can be changed at runtime via /selinux/enforce.
675
1da177e4
LT
676 es1371= [HW,OSS]
677 Format: <spdif>,[<nomix>,[<amplifier>]]
678 See also header of sound/oss/es1371.c.
a9913044 679
1da177e4
LT
680 ether= [HW,NET] Ethernet cards parameters
681 This option is obsoleted by the "netdev=" option, which
682 has equivalent usage. See its documentation for details.
683
684 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
685 Format: <io>[,<irq>]
686
de1ba09b
AM
687 failslab=
688 fail_page_alloc=
689 fail_make_request=[KNL]
690 General fault injection mechanism.
691 Format: <interval>,<probability>,<space>,<times>
692 See also /Documentation/fault-injection/.
693
1da177e4
LT
694 fd_mcs= [HW,SCSI]
695 See header of drivers/scsi/fd_mcs.c.
696
697 fdomain= [HW,SCSI]
698 See header of drivers/scsi/fdomain.c.
699
700 floppy= [HW]
701 See Documentation/floppy.txt.
702
f13ae30e
AC
703 force_pal_cache_flush
704 [IA-64] Avoid check_sal_cache_flush which may hang on
705 buggy SAL_CACHE_FLUSH implementations. Using this
706 parameter will force ia64_sal_cache_flush to call
707 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
708
1da177e4
LT
709 gamecon.map[2|3]=
710 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
711 support via parallel port (up to 5 devices per port)
712 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
713 See also Documentation/input/joystick-parport.txt
714
715 gamma= [HW,DRM]
716
aaf23042
YL
717 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
718 Format: off | on
719 default: on
720
1da177e4
LT
721 gdth= [HW,SCSI]
722 See header of drivers/scsi/gdth.c.
723
724 gpt [EFI] Forces disk with valid GPT signature but
725 invalid Protective MBR to be treated as GPT.
726
1da177e4
LT
727 gvp11= [HW,SCSI]
728
729 hashdist= [KNL,NUMA] Large hashes allocated during boot
730 are distributed across NUMA nodes. Defaults on
731 for IA-64, off otherwise.
a9913044 732 Format: 0 | 1 (for off | on)
1da177e4
LT
733
734 hcl= [IA-64] SGI's Hardware Graph compatibility layer
735
736 hd= [EIDE] (E)IDE hard drive subsystem geometry
737 Format: <cyl>,<head>,<sect>
738
739 hd?= [HW] (E)IDE subsystem
1c10e938 740 hd?lun= See Documentation/ide/ide.txt.
1da177e4
LT
741
742 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
743 size of <nn>. This works even on boxes that have no
744 highmem otherwise. This also works to reduce highmem
745 size on bigger boxes.
746
54cdfdb4
TG
747 highres= [KNL] Enable/disable high resolution timer mode.
748 Valid parameters: "on", "off"
749 Default: "on"
750
1da177e4
LT
751 hisax= [HW,ISDN]
752 See Documentation/isdn/README.HiSax.
753
cd4f0ef7 754 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 755 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 756
1da177e4 757 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
758 i8042.dumbkbd [HW] Pretend that controller can only read data from
759 keyboard and cannot control its state
1da177e4
LT
760 (Don't attempt to blink the leds)
761 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 762 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
763 i8042.noloop [HW] Disable the AUX Loopback command while probing
764 for the AUX port
1da177e4
LT
765 i8042.nomux [HW] Don't check presence of an active multiplexing
766 controller
767 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
768 controllers
769 i8042.panicblink=
770 [HW] Frequency with which keyboard LEDs should blink
771 when kernel panics (default is 0.5 sec)
772 i8042.reset [HW] Reset the controller during init and cleanup
773 i8042.unlock [HW] Unlock (ignore) the keylock
774
775 i810= [HW,DRM]
776
e70c9d5e
DT
777 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
778 indicates that the driver is running on unsupported
779 hardware.
1da177e4
LT
780 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
781 does not match list of supported models.
782 i8k.power_status
783 [HW] Report power status in /proc/i8k
784 (disabled by default)
785 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
786 capability is set.
787
788 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
789 See Documentation/mca.txt.
790
791 icn= [HW,ISDN]
792 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
793
794 ide= [HW] (E)IDE subsystem
a594eeb1 795 Format: ide=nodma or ide=doubler
1c10e938 796 See Documentation/ide/ide.txt.
1da177e4 797
1da177e4 798 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 799 See Documentation/ide/ide.txt.
1da177e4 800
f039b754
AK
801 idle= [X86]
802 Format: idle=poll or idle=mwait
803 Poll forces a polling idle loop that can slightly improves the performance
804 of waking up a idle CPU, but will use a lot of power and make the system
805 run hot. Not recommended.
806 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
807 to not use it because it doesn't save as much power as a normal idle
808 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
809 as idle=poll.
a9913044 810
594765a7
DC
811 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
812 Claim all unknown PCI IDE storage controllers.
813
79290822
IM
814 ignore_loglevel [KNL]
815 Ignore loglevel setting - this will print /all/
816 kernel messages to the console. Useful for debugging.
817
1da177e4
LT
818 ihash_entries= [KNL]
819 Set number of hash buckets for inode cache.
820
821 in2000= [HW,SCSI]
822 See header of drivers/scsi/in2000.c.
823
824 init= [KNL]
825 Format: <full_path>
826 Run specified binary instead of /sbin/init as init
827 process.
828
829 initcall_debug [KNL] Trace initcalls as they are executed. Useful
830 for working out where the kernel is dying during
831 startup.
832
833 initrd= [BOOT] Specify the location of the initial ramdisk
834
835 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
836 Format: <irq>
837
838 inttest= [IA64]
839
b552da87
PM
840 iommu= [x86]
841 off
842 force
843 noforce
844 biomerge
845 panic
846 nopanic
847 merge
848 nomerge
849 forcesac
850 soft
851
852
ba395927
KA
853 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
854 off
855 Disable intel iommu driver.
856 igfx_off [Default Off]
857 By default, gfx is mapped as normal device. If a gfx
858 device has a dedicated DMAR unit, the DMAR unit is
859 bypassed by not enabling DMAR with this option. In
860 this case, gfx device will use physical address for
861 DMA.
7d3b03ce
KA
862 forcedac [x86_64]
863 With this option iommu will not optimize to look
864 for io virtual address below 32 bit forcing dual
865 address cycle on pci bus for cards supporting greater
866 than 32 bit addressing. The default is to look
867 for translation below 32 bit and if not available
868 then look in the higher range.
5e0d2a6f 869 strict [Default Off]
870 With this option on every unmap_single operation will
871 result in a hardware IOTLB flush operation as opposed
872 to batching them for performance.
ba395927 873
b02aae9c 874 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
875 0x80
876 Standard port 0x80 based delay
877 0xed
878 Alternate port 0xed based delay (needed on some systems)
b02aae9c 879 udelay
6e7c4025
IM
880 Simple two microseconds delay
881 none
882 No delay
b02aae9c 883
1da177e4
LT
884 io7= [HW] IO7 for Marvel based alpha systems
885 See comment before marvel_specify_io7 in
886 arch/alpha/kernel/core_marvel.c.
887
888 ip= [IP_PNP]
6ded55da 889 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
890
891 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
892 See comment before ip2_setup() in
893 drivers/char/ip2/ip2base.c.
1da177e4
LT
894
895 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
896 See header of drivers/scsi/ips.c.
897
72c4a13a
SH
898 ports= [IP_VS_FTP] IPVS ftp helper module
899 Default is 21.
900 Up to 8 (IP_VS_APP_MAX_PORTS) ports
901 may be specified.
902 Format: <port>,<port>....
903
200803df
AC
904 irqfixup [HW]
905 When an interrupt is not handled search all handlers
906 for it. Intended to get systems with badly broken
907 firmware running.
908
909 irqpoll [HW]
910 When an interrupt is not handled search all handlers
911 for it. Also check all handlers each timer
912 interrupt. Intended to get systems with badly broken
913 firmware running.
914
1da177e4 915 isapnp= [ISAPNP]
a9913044 916 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
917
918 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
919 Format:
920 <cpu number>,...,<cpu number>
921 or
922 <cpu number>-<cpu number> (must be a positive range in ascending order)
923 or a mixture
924 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
925 This option can be used to specify one or more CPUs
926 to isolate from the general SMP balancing and scheduling
927 algorithms. The only way to move a process onto or off
928 an "isolated" CPU is via the CPU affinity syscalls.
929 <cpu number> begins at 0 and the maximum value is
930 "number of CPUs in system - 1".
931
932 This option is the preferred way to isolate CPUs. The
a9913044
RD
933 alternative -- manually setting the CPU mask of all
934 tasks in the system -- can cause problems and
935 suboptimal load balancer performance.
1da177e4 936
a9913044 937 iucv= [HW,NET]
1da177e4
LT
938
939 js= [HW,JOY] Analog joystick
940 See Documentation/input/joystick.txt.
941
cd4f0ef7 942 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
943 specifies the amount of memory usable by the kernel
944 for non-movable allocations. The requested amount is
945 spread evenly throughout all nodes in the system. The
946 remaining memory in each node is used for Movable
947 pages. In the event, a node is too small to have both
948 kernelcore and Movable pages, kernelcore pages will
949 take priority and other nodes will have a larger number
950 of kernelcore pages. The Movable zone is used for the
951 allocation of pages that may be reclaimed or moved
952 by the page migration subsystem. This means that
953 HugeTLB pages may not be allocated from this zone.
954 Note that allocations like PTEs-from-HighMem still
955 use the HighMem zone if it exists, and the Normal
956 zone if it does not.
957
cd4f0ef7 958 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
959 is similar to kernelcore except it specifies the
960 amount of memory used for migratable allocations.
961 If both kernelcore and movablecore is specified,
962 then kernelcore will be at *least* the specified
963 value but may be more. If movablecore on its own
964 is specified, the administrator must be careful
965 that the amount of memory usable for all allocations
966 is not too small.
967
1da177e4
LT
968 keepinitrd [HW,ARM]
969
cd4f0ef7 970 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
971 in oops dumps.
972
6cdf6e06
JW
973 kgdboc= [HW] kgdb over consoles.
974 Requires a tty driver that supports console polling.
975 (only serial suported for now)
976 Format: <serial_device>[,baud]
977
1da177e4
LT
978 l2cr= [PPC]
979
a78bfbfc
RB
980 l3cr= [PPC]
981
cd4f0ef7 982 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 983 disabled it.
1da177e4 984
cd4f0ef7 985 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
986 C2 power state.
987
fcb71f6f
FC
988 libata.dma= [LIBATA] DMA control
989 libata.dma=0 Disable all PATA and SATA DMA
990 libata.dma=1 PATA and SATA Disk DMA only
991 libata.dma=2 ATAPI (CDROM) DMA only
992 libata.dma=4 Compact Flash DMA only
993 Combinations also work, so libata.dma=3 enables DMA
994 for disks and CDROMs, but not CFs.
995
78e70c23
DJ
996 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
997 when set.
998 Format: <int>
999
33267325
TH
1000 libata.force= [LIBATA] Force configurations. The format is comma
1001 separated list of "[ID:]VAL" where ID is
1002 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1003 matching port, link or device. Basically, it matches
1004 the ATA ID string printed on console by libata. If
1005 the whole ID part is omitted, the last PORT and DEVICE
1006 values are used. If ID hasn't been specified yet, the
1007 configuration applies to all ports, links and devices.
1008
1009 If only DEVICE is omitted, the parameter applies to
1010 the port and all links and devices behind it. DEVICE
1011 number of 0 either selects the first device or the
1012 first fan-out link behind PMP device. It does not
1013 select the host link. DEVICE number of 15 selects the
1014 host link and device attached to it.
1015
1016 The VAL specifies the configuration to force. As long
1017 as there's no ambiguity shortcut notation is allowed.
1018 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1019 The following configurations can be forced.
1020
1021 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1022 Any ID with matching PORT is used.
1023
1024 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1025
1026 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1027 udma[/][16,25,33,44,66,100,133] notation is also
1028 allowed.
1029
1030 * [no]ncq: Turn on or off NCQ.
1031
1032 If there are multiple matching configurations changing
1033 the same attribute, the last one is used.
1034
1da177e4
LT
1035 load_ramdisk= [RAM] List of ramdisks to load from floppy
1036 See Documentation/ramdisk.txt.
1037
a6b25b67
RD
1038 lockd.nlm_grace_period=P [NFS] Assign grace period.
1039 Format: <integer>
1da177e4 1040
a6b25b67
RD
1041 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1042 Format: <integer>
1043
1044 lockd.nlm_timeout=T [NFS] Assign timeout value.
1045 Format: <integer>
1046
1047 lockd.nlm_udpport=M [NFS] Assign UDP port.
1048 Format: <integer>
1da177e4
LT
1049
1050 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1051 Format: <irq>
1052
1053 loglevel= All Kernel Messages with a loglevel smaller than the
1054 console loglevel will be printed to the console. It can
1055 also be changed with klogd or other programs. The
1056 loglevels are defined as follows:
1057
1058 0 (KERN_EMERG) system is unusable
1059 1 (KERN_ALERT) action must be taken immediately
1060 2 (KERN_CRIT) critical conditions
1061 3 (KERN_ERR) error conditions
1062 4 (KERN_WARNING) warning conditions
1063 5 (KERN_NOTICE) normal but significant condition
1064 6 (KERN_INFO) informational
1065 7 (KERN_DEBUG) debug-level messages
1066
1067 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1068 Format: { n | nk | nM }
1069 n must be a power of two. The default size
1070 is set in the kernel config file.
1da177e4 1071
accaa24c
RD
1072 logo.nologo [FB] Disables display of the built-in Linux logo.
1073 This may be used to provide more screen space for
1074 kernel log messages and is useful when debugging
1075 kernel boot problems.
1076
1da177e4
LT
1077 lp=0 [LP] Specify parallel ports to use, e.g,
1078 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1079 lp=reset first parallel port). 'lp=0' disables the
1080 lp=auto printer driver. 'lp=reset' (which can be
1081 specified in addition to the ports) causes
1082 attached printers to be reset. Using
1083 lp=port1,port2,... specifies the parallel ports
1084 to associate lp devices with, starting with
1085 lp0. A port specification may be 'none' to skip
1086 that lp device, or a parport name such as
1087 'parport0'. Specifying 'lp=auto' instead of a
1088 port specification list means that device IDs
1089 from each port should be examined, to see if
1090 an IEEE 1284-compliant printer is attached; if
1091 so, the driver will manage that printer.
1092 See also header of drivers/char/lp.c.
1093
1094 lpj=n [KNL]
1095 Sets loops_per_jiffy to given constant, thus avoiding
1096 time-consuming boot-time autodetection (up to 250 ms per
1097 CPU). 0 enables autodetection (default). To determine
1098 the correct value for your kernel, boot with normal
1099 autodetection and see what value is printed. Note that
1100 on SMP systems the preset will be applied to all CPUs,
1101 which is likely to cause problems if your CPUs need
1102 significantly divergent settings. An incorrect value
1103 will cause delays in the kernel to be wrong, leading to
1104 unpredictable I/O errors and other breakage. Although
1105 unlikely, in the extreme case this might damage your
1106 hardware.
1107
1108 ltpc= [NET]
1109 Format: <io>,<irq>,<dma>
1110
a9913044
RD
1111 mac5380= [HW,SCSI] Format:
1112 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1113
a9913044
RD
1114 machvec= [IA64] Force the use of a particular machine-vector
1115 (machvec) in a generic kernel.
1116 Example: machvec=hpzx1_swiotlb
1da177e4 1117
a9913044 1118 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1119 be mounted
1120 Format: <1-256>
1121
1122 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1123 should make use of. maxcpus=n : n >= 0 limits the
1124 kernel to using 'n' processors. n=0 is a special case,
1125 it is equivalent to "nosmp", which also disables
1126 the IO APIC.
1da177e4 1127
2b2c3750
BP
1128 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1129 equal to this physical address is ignored.
1130
a9913044 1131 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1132 Should be between 1 and 2^32-1.
1133
1134 max_report_luns=
a9913044 1135 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1136 Should be between 1 and 16384.
1137
1da177e4
LT
1138 mcatest= [IA-64]
1139
cd4f0ef7 1140 mce [X86-32] Machine Check Exception
1da177e4 1141
909dd324
AK
1142 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1143
1da177e4
LT
1144 md= [HW] RAID subsystems devices and level
1145 See Documentation/md.txt.
a9913044 1146
1da177e4
LT
1147 mdacon= [MDA]
1148 Format: <first>,<last>
1149 Specifies range of consoles to be captured by the MDA.
a9913044 1150
1da177e4
LT
1151 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1152 Amount of memory to be used when the kernel is not able
1153 to see the whole system memory or for test.
cd4f0ef7 1154 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1155 address space collisions. Without memmap= PCI devices
1156 could be placed at addresses belonging to unused RAM.
1157
cd4f0ef7 1158 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1159 memory.
1160
cd4f0ef7 1161 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1162 E820 memory map, as specified by the user.
1163 Such memmap=exactmap lines can be constructed based on
1164 BIOS output or other requirements. See the memmap=nn@ss
1165 option description.
1166
1167 memmap=nn[KMG]@ss[KMG]
1168 [KNL] Force usage of a specific region of memory
1169 Region of memory to be used, from ss to ss+nn.
1170
1171 memmap=nn[KMG]#ss[KMG]
1172 [KNL,ACPI] Mark specific memory as ACPI data.
1173 Region of memory to be used, from ss to ss+nn.
1174
1175 memmap=nn[KMG]$ss[KMG]
1176 [KNL,ACPI] Mark specific memory as reserved.
1177 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1178 Example: Exclude memory from 0x18690000-0x1869ffff
1179 memmap=64K$0x18690000
1180 or
1181 memmap=0x10000$0x18690000
1da177e4 1182
c64df707
YL
1183 memtest= [KNL,X86_64] Enable memtest
1184 Format: <integer>
1185 range: 0,4 : pattern number
1186 default : 0 <disable>
1187
1da177e4
LT
1188 meye.*= [HW] Set MotionEye Camera parameters
1189 See Documentation/video4linux/meye.txt.
1190
8f36881b
AS
1191 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1192 Multi-Function General Purpose Timers on AMD Geode
1193 platforms.
1194
e6c4dc6c
WT
1195 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1196 the BIOS has incorrectly applied a workaround. TinyBIOS
1197 version 0.98 is known to be affected, 0.99 fixes the
1198 problem by letting the user disable the workaround.
1199
1da177e4
LT
1200 mga= [HW,DRM]
1201
1202 mousedev.tap_time=
1203 [MOUSE] Maximum time between finger touching and
1204 leaving touchpad surface for touch to be considered
1205 a tap and be reported as a left button click (for
1206 touchpads working in absolute mode only).
1207 Format: <msecs>
1208 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1209 reporting absolute coordinates, such as tablets
1210 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1211 reporting absolute coordinates, such as tablets
1212
1213 mpu401= [HW,OSS]
1214 Format: <io>,<irq>
1215
1216 MTD_Partition= [MTD]
1217 Format: <name>,<region-number>,<size>,<offset>
1218
a9913044
RD
1219 MTD_Region= [MTD] Format:
1220 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1221
1222 mtdparts= [MTD]
c8facbb6 1223 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1224
1225 mtouchusb.raw_coordinates=
a9913044
RD
1226 [HW] Make the MicroTouch USB driver use raw coordinates
1227 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1228
1229 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1230
1231 NCR_D700= [HW,SCSI]
1232 See header of drivers/scsi/NCR_D700.c.
1233
1234 ncr5380= [HW,SCSI]
1235
1236 ncr53c400= [HW,SCSI]
1237
1238 ncr53c400a= [HW,SCSI]
1239
1240 ncr53c406a= [HW,SCSI]
1241
1242 ncr53c8xx= [HW,SCSI]
1243
1244 netdev= [NET] Network devices parameters
1245 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1246 Note that mem_start is often overloaded to mean
1247 something different and driver-specific.
a9913044
RD
1248 This usage is only documented in each driver source
1249 file if at all.
1250
1da177e4 1251 nfsaddrs= [NFS]
6ded55da 1252 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1253
1254 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1255 See Documentation/filesystems/nfsroot.txt.
1da177e4 1256
a72b4422
TM
1257 nfs.callback_tcpport=
1258 [NFS] set the TCP port on which the NFSv4 callback
1259 channel should listen.
1260
58df095b
TM
1261 nfs.idmap_cache_timeout=
1262 [NFS] set the maximum lifetime for idmapper cache
1263 entries.
1264
f43bf0be
TM
1265 nfs.enable_ino64=
1266 [NFS] enable 64-bit inode numbers.
1267 If zero, the NFS client will fake up a 32-bit inode
1268 number for the readdir() and stat() syscalls instead
1269 of returning the full 64-bit number.
1270 The default is to return 64-bit inode numbers.
1271
e7ba176b
HS
1272 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1273 when a NMI is triggered.
1274 Format: [state][,regs][,debounce][,die]
1275
cd4f0ef7 1276 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1277
cd4f0ef7 1278 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1279 emulation library even if a 387 maths coprocessor
1280 is present.
1281
c1aee215
CL
1282 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1283 caches in the slab allocator. Saves per-node memory,
1284 but will impact performance.
3395ee05 1285
a9913044
RD
1286 noalign [KNL,ARM]
1287
1da177e4
LT
1288 noapic [SMP,APIC] Tells the kernel to not make use of any
1289 IOAPICs that may be present in the system.
1290
1da177e4
LT
1291 nobats [PPC] Do not use BATs for mapping kernel lowmem
1292 on "Classic" PPC cores.
1293
1294 nocache [ARM]
a9913044 1295
163ecdff
SN
1296 nodelayacct [KNL] Disable per-task delay accounting
1297
1da177e4
LT
1298 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1299
8b2cb7a8
HY
1300 noefi [X86-32,X86-64] Disable EFI runtime services support.
1301
1da177e4
LT
1302 noexec [IA-64]
1303
cd4f0ef7 1304 noexec [X86-32,X86-64]
f5a1b191 1305 On X86-32 available only on PAE configured kernels.
1da177e4 1306 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1307 noexec=off: disable non-executable mappings
1308
1309 noexec32 [X86-64]
1310 This affects only 32-bit executables.
1311 noexec32=on: enable non-executable mappings (default)
1312 read doesn't imply executable mappings
1313 noexec32=off: disable non-executable mappings
1314 read implies executable mappings
1da177e4 1315
cd4f0ef7 1316 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1317 register save and restore. The kernel will only save
1318 legacy floating-point registers on task switch.
1da177e4 1319
191679fd
AK
1320 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1321
1da177e4 1322 nohlt [BUGS=ARM]
a9913044 1323
cd4f0ef7 1324 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1325 instruction doesn't work correctly and not to
1326 use it.
1327
1328 nohalt [IA-64] Tells the kernel not to use the power saving
1329 function PAL_HALT_LIGHT when idle. This increases
1330 power-consumption. On the positive side, it reduces
1331 interrupt wake-up latency, which may improve performance
1332 in certain environments such as networked servers or
1333 real-time systems.
1334
79bf2bb3
TG
1335 nohz= [KNL] Boottime enable/disable dynamic ticks
1336 Valid arguments: on, off
1337 Default: on
1338
cd4f0ef7 1339 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1340
cd4f0ef7 1341 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1342 disable unhandled interrupt sources.
1343
cd4f0ef7 1344 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1345 broken timer IRQ sources.
1346
1da177e4
LT
1347 noisapnp [ISAPNP] Disables ISA PnP code.
1348
1349 noinitrd [RAM] Tells the kernel not to load any configured
1350 initial RAM disk.
1351
1352 nointroute [IA-64]
1353
0aa366f3
TL
1354 nojitter [IA64] Disables jitter checking for ITC timers.
1355
cd4f0ef7 1356 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1357
cd4f0ef7 1358 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1359
1da177e4
LT
1360 noltlbs [PPC] Do not use large page/tlb entries for kernel
1361 lowmem mapping on PPC40x.
1362
312f1f01
H
1363 nomca [IA-64] Disable machine check abort handling
1364
cd4f0ef7 1365 nomce [X86-32] Machine Check Exception
abe37e5a 1366
83d7384f
AS
1367 nomfgpt [X86-32] Disable Multi-Function General Purpose
1368 Timer usage (for AMD Geode machines).
1369
cd4f0ef7 1370 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1371
cd4f0ef7 1372 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1373 with UP alternatives
1374
1da177e4
LT
1375 noresidual [PPC] Don't use residual data on PReP machines.
1376
a9913044
RD
1377 noresume [SWSUSP] Disables resume and restores original swap
1378 space.
1379
1da177e4
LT
1380 no-scroll [VGA] Disables scrollback.
1381 This is required for the Braillex ib80-piezo Braille
1382 reader made by F.H. Papenmeier (Germany).
1383
1384 nosbagart [IA-64]
1385
cd4f0ef7 1386 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1387
61ec7567
LB
1388 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1389 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1390
97842216
DJ
1391 nosoftlockup [KNL] Disable the soft-lockup detector.
1392
1da177e4
LT
1393 nosync [HW,M68K] Disables sync negotiation for all devices.
1394
cd4f0ef7 1395 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1396
1397 nousb [USB] Disable the USB subsystem
1398
1399 nowb [ARM]
a9913044 1400
a6c75b86
FY
1401 nptcg= [IA64] Override max number of concurrent global TLB
1402 purges which is reported from either PAL_VM_SUMMARY or
1403 SAL PALO.
1404
f0c0b2b8
KH
1405 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1406 one of ['zone', 'node', 'default'] can be specified
1407 This can be set from sysctl after boot.
1408 See Documentation/sysctl/vm.txt for details.
1409
a61c2d78
DJ
1410 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1411
3ef0e1f8
AS
1412 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1413 Rather than timing out after 20 ms if an EC
1414 command is not properly ACKed, override the length
1415 of the timeout. We have interrupts disabled while
1416 waiting for the ACK, so if this is set too high
1417 interrupts *may* be lost!
1418
1da177e4
LT
1419 opl3= [HW,OSS]
1420 Format: <io>
1421
1da177e4
LT
1422 oprofile.timer= [HW]
1423 Use timer interrupt instead of performance counters
1424
1da177e4
LT
1425 osst= [HW,SCSI] SCSI Tape Driver
1426 Format: <buffer_size>,<write_threshold>
1427 See also Documentation/scsi/st.txt.
1428
1429 panic= [KNL] Kernel behaviour on panic
1430 Format: <timeout>
1431
1432 parkbd.port= [HW] Parallel port number the keyboard adapter is
1433 connected to, default is 0.
1434 Format: <parport#>
1435 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1436 0 for XT, 1 for AT (default is AT).
a9913044
RD
1437 Format: <mode>
1438
1439 parport= [HW,PPT] Specify parallel ports. 0 disables.
1440 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1441 Use 'auto' to force the driver to use any
1442 IRQ/DMA settings detected (the default is to
1443 ignore detected IRQ/DMA settings because of
1444 possible conflicts). You can specify the base
1445 address, IRQ, and DMA settings; IRQ and DMA
1446 should be numbers, or 'auto' (for using detected
1447 settings on that particular port), or 'nofifo'
1448 (to avoid using a FIFO even if it is detected).
1449 Parallel ports are assigned in the order they
1450 are specified on the command line, starting
1451 with parport0.
1452
1453 parport_init_mode= [HW,PPT]
1454 Configure VIA parallel port to operate in
1455 a specific mode. This is necessary on Pegasos
1456 computer where firmware has no options for setting
1457 up parallel port mode and sets it to spp.
1458 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1459 Format: [spp|ps2|epp|ecp|ecpepp]
1460
a9913044
RD
1461 pas2= [HW,OSS] Format:
1462 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1463
1da177e4
LT
1464 pas16= [HW,SCSI]
1465 See header of drivers/scsi/pas16.c.
1466
dd287796
AM
1467 pause_on_oops=
1468 Halt all CPUs after the first oops has been printed for
1469 the specified number of seconds. This is to be used if
1470 your oopses keep scrolling off the screen.
1471
1da177e4
LT
1472 pcbit= [HW,ISDN]
1473
1474 pcd. [PARIDE]
1475 See header of drivers/block/paride/pcd.c.
1476 See also Documentation/paride.txt.
1477
a9913044 1478 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1479 off [X86-32] don't probe for the PCI bus
1480 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1481 the hardware directly. Use this if your machine
1482 has a non-standard PCI host bridge.
cd4f0ef7 1483 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1484 hardware access methods are allowed. Use this
1485 if you experience crashes upon bootup and you
1486 suspect they are caused by the BIOS.
cd4f0ef7 1487 conf1 [X86-32] Force use of PCI Configuration
a9913044 1488 Mechanism 1.
cd4f0ef7 1489 conf2 [X86-32] Force use of PCI Configuration
a9913044 1490 Mechanism 2.
7f785763
RD
1491 noaer [PCIE] If the PCIEAER kernel config parameter is
1492 enabled, this kernel boot option can be used to
1493 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1494 nodomains [PCI] Disable support for multiple PCI
1495 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1496 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1497 Configuration
309e57df
MW
1498 nomsi [MSI] If the PCI_MSI kernel config parameter is
1499 enabled, this kernel boot option can be used to
1500 disable the use of MSI interrupts system-wide.
cd4f0ef7 1501 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1502 routing table. These calls are known to be buggy
1503 on several machines and they hang the machine
1504 when used, but on other computers it's the only
1505 way to get the interrupt routing table. Try
1506 this option if the kernel is unable to allocate
1507 IRQs or discover secondary PCI buses on your
1508 motherboard.
cd4f0ef7 1509 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1510 Use with caution as certain devices share
1511 address decoders between ROMs and other
1512 resources.
cd4f0ef7 1513 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1514 assigned automatically to PCI devices. You can
1515 make the kernel exclude IRQs of your ISA cards
1516 this way.
cd4f0ef7 1517 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1518 of the PIRQ table (normally generated
1519 by the BIOS) if it is outside the
1520 F0000h-100000h range.
cd4f0ef7 1521 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1522 useful if the kernel is unable to find your
1523 secondary buses and you want to tell it
1524 explicitly which ones they are.
cd4f0ef7 1525 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1526 numbers ourselves, overriding
1527 whatever the firmware may have done.
cd4f0ef7 1528 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1529 in the BIOS $PIR table. This is needed on
1530 some systems with broken BIOSes, notably
1531 some HP Pavilion N5400 and Omnibook XE3
1532 notebooks. This will have no effect if ACPI
1533 IRQ routing is enabled.
cd4f0ef7 1534 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1535 or for PCI scanning.
62f420f8
GH
1536 use_crs [X86-32] Use _CRS for PCI resource
1537 allocation.
a9913044
RD
1538 routeirq Do IRQ routing for all PCI devices.
1539 This is normally done in pci_enable_device(),
1540 so this option is a temporary workaround
1541 for broken drivers that don't call it.
13a6ddb0
YL
1542 skip_isa_align [X86] do not align io start addr, so can
1543 handle more pci cards
a9913044
RD
1544 firmware [ARM] Do not re-enumerate the bus but instead
1545 just use the configuration from the
1546 bootloader. This is currently used on
1547 IXP2000 systems where the bus has to be
1548 configured a certain way for adjunct CPUs.
0637a70a
AK
1549 noearly [X86] Don't do any early type 1 scanning.
1550 This might help on some broken boards which
1551 machine check when some devices' config space
1552 is read. But various workarounds are disabled
1553 and some IOMMU drivers will not work.
6b4b78fe
MD
1554 bfsort Sort PCI devices into breadth-first order.
1555 This sorting is done to get a device
1556 order compatible with older (<= 2.4) kernels.
1557 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1558 cbiosize=nn[KMG] The fixed amount of bus space which is
1559 reserved for the CardBus bridge's IO window.
1560 The default value is 256 bytes.
1561 cbmemsize=nn[KMG] The fixed amount of bus space which is
1562 reserved for the CardBus bridge's memory
1563 window. The default value is 64 megabytes.
6b4b78fe 1564
1da177e4
LT
1565 pcmv= [HW,PCMCIA] BadgePAD 4
1566
1567 pd. [PARIDE]
1568 See Documentation/paride.txt.
1569
1570 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1571 boot time.
1572 Format: { 0 | 1 }
1573 See arch/parisc/kernel/pdc_chassis.c
1574
1575 pf. [PARIDE]
1576 See Documentation/paride.txt.
1577
1578 pg. [PARIDE]
1579 See Documentation/paride.txt.
1580
1581 pirq= [SMP,APIC] Manual mp-table setup
1582 See Documentation/i386/IO-APIC.txt.
1583
1584 plip= [PPT,NET] Parallel port network link
1585 Format: { parport<nr> | timid | 0 }
1586 See also Documentation/parport.txt.
1587
1588 pnpacpi= [ACPI]
1589 { off }
1590
1591 pnpbios= [ISAPNP]
1592 { on | off | curr | res | no-curr | no-res }
1593
1594 pnp_reserve_irq=
1595 [ISAPNP] Exclude IRQs for the autoconfiguration
1596
1597 pnp_reserve_dma=
1598 [ISAPNP] Exclude DMAs for the autoconfiguration
1599
1600 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1601 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1602
1603 pnp_reserve_mem=
a9913044
RD
1604 [ISAPNP] Exclude memory regions for the
1605 autoconfiguration.
1da177e4
LT
1606 Ranges are in pairs (memory base and size).
1607
45807a1d
IM
1608 print-fatal-signals=
1609 [KNL] debug: print fatal signals
1610 print-fatal-signals=1: print segfault info to
1611 the kernel console.
1612 default: off.
1613
e84845c4
RD
1614 printk.time= Show timing data prefixed to each printk message line
1615 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1616
1da177e4 1617 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1618 Format: [schedule,]<number>
1619 Param: "schedule" - profile schedule points.
1620 Param: <number> - step/bucket size as a power of 2 for
1621 statistical time based profiling.
b3da2a73
MG
1622 Param: "sleep" - profile D-state sleeping (millisecs).
1623 Requires CONFIG_SCHEDSTATS
c0fe2e69 1624 Param: "kvm" - profile VM exits.
1da177e4 1625
a9913044 1626 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1627 Limit processor to maximum C-state
1628 max_cstate=9 overrides any DMI blacklist limit.
1629
41c0d868
LB
1630 processor.nocst [HW,ACPI]
1631 Ignore the _CST method to determine C-states,
1632 instead using the legacy FADT method
1633
1da177e4
LT
1634 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1635 before loading.
1636 See Documentation/ramdisk.txt.
1637
a9913044
RD
1638 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1639 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1640 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1641 per second.
a9913044
RD
1642 psmouse.resetafter= [HW,MOUSE]
1643 Try to reset the device after so many bad packets
1da177e4
LT
1644 (0 = never).
1645 psmouse.resolution=
1646 [HW,MOUSE] Set desired mouse resolution, in dpi.
1647 psmouse.smartscroll=
a9913044 1648 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1649 0 = disabled, 1 = enabled (default).
1650
1651 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1652 Format:
1653 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1654
1655 pt. [PARIDE]
1656 See Documentation/paride.txt.
1657
dc8c8587
KS
1658 pty.legacy_count=
1659 [KNL] Number of legacy pty's. Overwrites compiled-in
1660 default number.
1661
7d2c502f 1662 quiet [KNL] Disable most log messages
a9913044 1663
1da177e4
LT
1664 r128= [HW,DRM]
1665
1666 raid= [HW,RAID]
1667 See Documentation/md.txt.
1668
a9913044 1669 ramdisk_blocksize= [RAM]
1da177e4 1670 See Documentation/ramdisk.txt.
a9913044 1671
1da177e4 1672 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1673 See Documentation/ramdisk.txt.
1674
24aaef8d
RD
1675 rcupdate.blimit= [KNL,BOOT]
1676 Set maximum number of finished RCU callbacks to process
1677 in one batch.
21a1ea9e 1678
24aaef8d
RD
1679 rcupdate.qhimark= [KNL,BOOT]
1680 Set threshold of queued
21a1ea9e
DS
1681 RCU callbacks over which batch limiting is disabled.
1682
24aaef8d
RD
1683 rcupdate.qlowmark= [KNL,BOOT]
1684 Set threshold of queued RCU callbacks below which
1685 batch limiting is re-enabled.
21a1ea9e 1686
ffdfc409
OJ
1687 rdinit= [KNL]
1688 Format: <full_path>
1689 Run specified binary instead of /init from the ramdisk,
1690 used for early userspace startup. See initrd.
1691
cd4f0ef7 1692 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1693 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1694 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1695
1696 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1697
cd4f0ef7 1698 reservetop= [X86-32]
461a9aff
ZA
1699 Format: nn[KMG]
1700 Reserves a hole at the top of the kernel virtual
1701 address space.
1702
7e96287d
VG
1703 reset_devices [KNL] Force drivers to reset the underlying device
1704 during initialization.
1705
a9913044
RD
1706 resume= [SWSUSP]
1707 Specify the partition device for software suspend
1da177e4 1708
ecbd0da1
RW
1709 resume_offset= [SWSUSP]
1710 Specify the offset from the beginning of the partition
1711 given by "resume=" at which the swap header is located,
1712 in <PAGE_SIZE> units (needed only for swap files).
1713 See Documentation/power/swsusp-and-swap-files.txt
1714
0a7b35cb
MN
1715 retain_initrd [RAM] Keep initrd memory after extraction
1716
1da177e4
LT
1717 rhash_entries= [KNL,NET]
1718 Set number of hash buckets for route cache
1719
1720 riscom8= [HW,SERIAL]
1721 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1722
1723 ro [KNL] Mount root device read-only on boot
1724
1725 root= [KNL] Root filesystem
1726
1727 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1728 mount the root filesystem
1729
1730 rootflags= [KNL] Set root filesystem mount option string
1731
1732 rootfstype= [KNL] Set root filesystem type
1733
cc1ed754
PO
1734 rootwait [KNL] Wait (indefinitely) for root device to show up.
1735 Useful for devices that are detected asynchronously
1736 (e.g. USB and MMC devices).
1737
20510f2f
JM
1738 root_plug.vendor_id=
1739 [ROOTPLUG] Override the default vendor ID
1740
1741 root_plug.product_id=
1742 [ROOTPLUG] Override the default product ID
1743
1744 root_plug.debug=
1745 [ROOTPLUG] Enable debugging output
1746
1da177e4
LT
1747 rw [KNL] Mount root device read-write on boot
1748
1749 S [KNL] Run init in single mode
1750
1751 sa1100ir [NET]
1752 See drivers/net/irda/sa1100_ir.c.
1753
1da177e4 1754 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1755
1da177e4
LT
1756 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1757 Format: <io>[,<timeout>[,<isapnp>]]
1758
1759 scsi_debug_*= [SCSI]
1760 See drivers/scsi/scsi_debug.c.
1761
1762 scsi_default_dev_flags=
1763 [SCSI] SCSI default device flags
1764 Format: <integer>
1765
1766 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1767 Format: <vendor>:<model>:<flags>
1768 (flags are integer value)
1769
6af6632a
RD
1770 scsi_logging_level= [SCSI] a bit mask of logging levels
1771 See drivers/scsi/scsi_logging.h for bits. Also
1772 settable via sysctl at dev.scsi.logging_level
1773 (/proc/sys/dev/scsi/logging_level).
1774 There is also a nice 'scsi_logging_level' script in the
1775 S390-tools package, available for download at
1776 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1777
3e082a91
MW
1778 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1779 discovered. async scans them in kernel threads,
1780 allowing boot to proceed. none ignores them, expecting
1781 user space to do the scan.
1782
1da177e4
LT
1783 selinux [SELINUX] Disable or enable SELinux at boot time.
1784 Format: { "0" | "1" }
1785 See security/selinux/Kconfig help text.
1786 0 -- disable.
1787 1 -- enable.
1788 Default value is set via kernel config option.
1789 If enabled at boot time, /selinux/disable can be used
1790 later to disable prior to initial policy load.
1791
4e5ab4cb
JM
1792 selinux_compat_net =
1793 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1794 Format: { "0" | "1" }
1795 0 -- use new secmark-based packet controls
1796 1 -- use legacy packet controls
1797 Default value is 0 (preferred).
1798 Value can be changed at runtime via
1799 /selinux/compat_net.
4e5ab4cb 1800
cd4f0ef7 1801 serialnumber [BUGS=X86-32]
1da177e4 1802
1da177e4
LT
1803 shapers= [NET]
1804 Maximal number of shapers.
a9913044 1805
1da177e4
LT
1806 sim710= [SCSI,HW]
1807 See header of drivers/scsi/sim710.c.
1808
1809 simeth= [IA-64]
1810 simscsi=
a9913044 1811
1da177e4
LT
1812 slram= [HW,MTD]
1813
f0630fff
CL
1814 slub_debug[=options[,slabs]] [MM, SLUB]
1815 Enabling slub_debug allows one to determine the
1816 culprit if slab objects become corrupted. Enabling
1817 slub_debug can create guard zones around objects and
1818 may poison objects when not in use. Also tracks the
1819 last alloc / free. For more information see
1820 Documentation/vm/slub.txt.
c1aee215
CL
1821
1822 slub_max_order= [MM, SLUB]
f0630fff
CL
1823 Determines the maximum allowed order for slabs.
1824 A high setting may cause OOMs due to memory
1825 fragmentation. For more information see
1826 Documentation/vm/slub.txt.
c1aee215
CL
1827
1828 slub_min_objects= [MM, SLUB]
f0630fff
CL
1829 The minimum number of objects per slab. SLUB will
1830 increase the slab order up to slub_max_order to
1831 generate a sufficiently large slab able to contain
1832 the number of objects indicated. The higher the number
1833 of objects the smaller the overhead of tracking slabs
1834 and the less frequently locks need to be acquired.
c1aee215
CL
1835 For more information see Documentation/vm/slub.txt.
1836
1837 slub_min_order= [MM, SLUB]
1838 Determines the mininum page order for slabs. Must be
f0630fff 1839 lower than slub_max_order.
c1aee215
CL
1840 For more information see Documentation/vm/slub.txt.
1841
1842 slub_nomerge [MM, SLUB]
f0630fff 1843 Disable merging of slabs with similar size. May be
c1aee215 1844 necessary if there is some reason to distinguish
f0630fff
CL
1845 allocs to different slabs. Debug options disable
1846 merging on their own.
c1aee215
CL
1847 For more information see Documentation/vm/slub.txt.
1848
1da177e4
LT
1849 smart2= [HW]
1850 Format: <io1>[,<io2>[,...,<io8>]]
1851
cd4f0ef7 1852 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1853 attempt to substitute SMP alternatives once at boot.
1854
d0d4f69b
BH
1855 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1856 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1857 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1858 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1859 smsc-ircc2.ircc_irq= [HW] IRQ line
1860 smsc-ircc2.ircc_dma= [HW] DMA channel
1861 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1862 0: Toshiba Satellite 1800 (GP data pin select)
1863 1: Fast pin select (default)
1864 2: ATC IRMode
1865
1da177e4
LT
1866 snd-ad1816a= [HW,ALSA]
1867
1868 snd-ad1848= [HW,ALSA]
1869
1870 snd-ali5451= [HW,ALSA]
1871
1872 snd-als100= [HW,ALSA]
1873
1874 snd-als4000= [HW,ALSA]
1875
1876 snd-azt2320= [HW,ALSA]
1877
1878 snd-cmi8330= [HW,ALSA]
1879
1880 snd-cmipci= [HW,ALSA]
1881
1882 snd-cs4231= [HW,ALSA]
1883
1884 snd-cs4232= [HW,ALSA]
1885
1886 snd-cs4236= [HW,ALSA]
1887
1888 snd-cs4281= [HW,ALSA]
1889
1890 snd-cs46xx= [HW,ALSA]
1891
1892 snd-dt019x= [HW,ALSA]
1893
1894 snd-dummy= [HW,ALSA]
1895
1896 snd-emu10k1= [HW,ALSA]
1897
1898 snd-ens1370= [HW,ALSA]
1899
1900 snd-ens1371= [HW,ALSA]
1901
1902 snd-es968= [HW,ALSA]
1903
1904 snd-es1688= [HW,ALSA]
1905
1906 snd-es18xx= [HW,ALSA]
1907
1908 snd-es1938= [HW,ALSA]
1909
1910 snd-es1968= [HW,ALSA]
1911
1912 snd-fm801= [HW,ALSA]
1913
1914 snd-gusclassic= [HW,ALSA]
1915
1916 snd-gusextreme= [HW,ALSA]
1917
1918 snd-gusmax= [HW,ALSA]
1919
1920 snd-hdsp= [HW,ALSA]
1921
1922 snd-ice1712= [HW,ALSA]
1923
1924 snd-intel8x0= [HW,ALSA]
1925
1926 snd-interwave= [HW,ALSA]
1927
1928 snd-interwave-stb=
1929 [HW,ALSA]
1930
1931 snd-korg1212= [HW,ALSA]
1932
1933 snd-maestro3= [HW,ALSA]
1934
1935 snd-mpu401= [HW,ALSA]
1936
1937 snd-mtpav= [HW,ALSA]
1938
1939 snd-nm256= [HW,ALSA]
1940
1941 snd-opl3sa2= [HW,ALSA]
1942
1943 snd-opti92x-ad1848=
1944 [HW,ALSA]
1945
1946 snd-opti92x-cs4231=
1947 [HW,ALSA]
1948
1949 snd-opti93x= [HW,ALSA]
1950
1951 snd-pmac= [HW,ALSA]
1952
1953 snd-rme32= [HW,ALSA]
1954
1955 snd-rme96= [HW,ALSA]
1956
1957 snd-rme9652= [HW,ALSA]
1958
1959 snd-sb8= [HW,ALSA]
1960
1961 snd-sb16= [HW,ALSA]
1962
1963 snd-sbawe= [HW,ALSA]
1964
1965 snd-serial= [HW,ALSA]
1966
1967 snd-sgalaxy= [HW,ALSA]
1968
1969 snd-sonicvibes= [HW,ALSA]
1970
1971 snd-sun-amd7930=
1972 [HW,ALSA]
1973
1974 snd-sun-cs4231= [HW,ALSA]
1975
1976 snd-trident= [HW,ALSA]
1977
1978 snd-usb-audio= [HW,ALSA,USB]
1979
1980 snd-via82xx= [HW,ALSA]
1981
1982 snd-virmidi= [HW,ALSA]
1983
1984 snd-wavefront= [HW,ALSA]
1985
1986 snd-ymfpci= [HW,ALSA]
a9913044 1987
1da177e4
LT
1988 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1989 See Documentation/sonypi.txt
1990
1991 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1992 See Documentation/specialix.txt.
1993
1994 spia_io_base= [HW,MTD]
1995 spia_fio_base=
1996 spia_pedr=
1997 spia_peddr=
1998
1999 sscape= [HW,OSS]
2000 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2001
1da177e4
LT
2002 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2003 See Documentation/scsi/st.txt.
2004
1da177e4
LT
2005 sti= [PARISC,HW]
2006 Format: <num>
2007 Set the STI (builtin display/keyboard on the HP-PARISC
2008 machines) console (graphic card) which should be used
2009 as the initial boot-console.
2010 See also comment in drivers/video/console/sticore.c.
2011
2012 sti_font= [HW]
2013 See comment in drivers/video/console/sticore.c.
2014
2015 stifb= [HW]
2016 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2017
42a7fc4a
GB
2018 sunrpc.pool_mode=
2019 [NFS]
2020 Control how the NFS server code allocates CPUs to
2021 service thread pools. Depending on how many NICs
2022 you have and where their interrupts are bound, this
2023 option will affect which CPUs will do NFS serving.
2024 Note: this parameter cannot be changed while the
2025 NFS server is running.
2026
2027 auto the server chooses an appropriate mode
2028 automatically using heuristics
2029 global a single global pool contains all CPUs
2030 percpu one pool for each CPU
2031 pernode one pool for each NUMA node (equivalent
2032 to global on non-NUMA machines)
2033
1da177e4 2034 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2035
1da177e4
LT
2036 switches= [HW,M68k]
2037
2038 sym53c416= [HW,SCSI]
2039 See header of drivers/scsi/sym53c416.c.
2040
5d6f647f
IM
2041 sysrq_always_enabled
2042 [KNL]
2043 Ignore sysrq setting - this boot parameter will
2044 neutralize any effect of /proc/sys/kernel/sysrq.
2045 Useful for debugging.
2046
1da177e4
LT
2047 t128= [HW,SCSI]
2048 See header of drivers/scsi/t128.c.
2049
2050 tdfx= [HW,DRM]
2051
2052 thash_entries= [KNL,NET]
2053 Set number of hash buckets for TCP connection
2054
f8707ec9
LB
2055 thermal.act= [HW,ACPI]
2056 -1: disable all active trip points in all thermal zones
2057 <degrees C>: override all lowest active trip points
2058
c52a7419
LB
2059 thermal.crt= [HW,ACPI]
2060 -1: disable all critical trip points in all thermal zones
2061 <degrees C>: lower all critical trip points
2062
f5487145
LB
2063 thermal.nocrt= [HW,ACPI]
2064 Set to disable actions on ACPI thermal zone
2065 critical and hot trip points.
2066
72b33ef8
LB
2067 thermal.off= [HW,ACPI]
2068 1: disable ACPI thermal control
2069
a70cdc52
LB
2070 thermal.psv= [HW,ACPI]
2071 -1: disable all passive trip points
2072 <degrees C>: override all passive trip points to this value
2073
730ff34d
LB
2074 thermal.tzp= [HW,ACPI]
2075 Specify global default ACPI thermal zone polling rate
2076 <deci-seconds>: poll all this frequency
2077 0: no polling (default)
2078
1da177e4
LT
2079 tipar.timeout= [HW,PPT]
2080 Set communications timeout in tenths of a second
2081 (default 15).
2082
2083 tipar.delay= [HW,PPT]
2084 Set inter-bit delay in microseconds (default 10).
2085
1da177e4
LT
2086 tmscsim= [HW,SCSI]
2087 See comment before function dc390_setup() in
2088 drivers/scsi/tmscsim.c.
2089
2090 tp720= [HW,PS2]
2091
2092 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2093 Format:
2094 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2095
a9913044
RD
2096 turbografx.map[2|3]= [HW,JOY]
2097 TurboGraFX parallel port interface
2098 Format:
2099 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2100 See also Documentation/input/joystick-parport.txt
2101
2102 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2103 See header of drivers/scsi/u14-34f.c.
2104
2105 uart401= [HW,OSS]
2106 Format: <io>,<irq>
2107
2108 uart6850= [HW,OSS]
2109 Format: <io>,<irq>
2110
5f8364b7
AS
2111 uhci-hcd.ignore_oc=
2112 [USB] Ignore overcurrent events (default N).
2113 Some badly-designed motherboards generate lots of
2114 bogus events, for ports that aren't wired to
2115 anything. Set this parameter to avoid log spamming.
2116 Note that genuine overcurrent events won't be
2117 reported either.
2118
b5e795f8
AS
2119 usbcore.autosuspend=
2120 [USB] The autosuspend time delay (in seconds) used
2121 for newly-detected USB devices (default 2). This
2122 is the time required before an idle device will be
2123 autosuspended. Devices for which the delay is set
eaafbc3a 2124 to a negative value won't be autosuspended at all.
b5e795f8 2125
1da177e4
LT
2126 usbhid.mousepoll=
2127 [USBHID] The interval which mice are to be polled at.
a9913044 2128
cd4f0ef7 2129 vdso= [X86-32,SH,x86-64]
1dbf527c 2130 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2131 vdso=1: enable VDSO (default)
2132 vdso=0: disable VDSO mapping
2133
af65d648
RM
2134 vdso32= [X86-32,X86-64]
2135 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2136 vdso32=1: enable 32-bit VDSO (default)
2137 vdso32=0: disable 32-bit VDSO mapping
2138
d080d397
YI
2139 vector= [IA-64,SMP]
2140 vector=percpu: enable percpu vector domain
2141
1da177e4
LT
2142 video= [FB] Frame buffer configuration
2143 See Documentation/fb/modedb.txt.
2144
cd4f0ef7 2145 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2146 See Documentation/i386/boot.txt and
2147 Documentation/svga.txt.
1da177e4
LT
2148 Use vga=ask for menu.
2149 This is actually a boot loader parameter; the value is
2150 passed to the kernel using a special protocol.
2151
a9913044 2152 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2153 size of <nn>. This can be used to increase the
2154 minimum size (128MB on x86). It can also be used to
2155 decrease the size and leave more room for directly
2156 mapped kernel RAM.
2157
585c3047
PO
2158 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2159 Format: <command>
1da177e4 2160
585c3047
PO
2161 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2162 Format: <command>
2163
2164 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2165 Format: <command>
a9913044 2166
1da177e4
LT
2167 waveartist= [HW,OSS]
2168 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2169
1da177e4
LT
2170 wd33c93= [HW,SCSI]
2171 See header of drivers/scsi/wd33c93.c.
2172
2173 wd7000= [HW,SCSI]
2174 See header of drivers/scsi/wd7000.c.
2175
2176 wdt= [WDT] Watchdog
8dfe9c21 2177 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2178
2179 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2180 xd_geo= See header of drivers/block/xd.c.
2181
2182 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2183 Format:
2184 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2185
a62eaf15
AK
2186 norandmaps Don't use address space randomization
2187 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2188
a9913044 2189______________________________________________________________________
1da177e4
LT
2190
2191TODO:
2192
2193 Add documentation for ALSA options.
2194 Add more DRM drivers.