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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 earlycon= [KNL] Output early console device and options.
500 uart[8250],io,<addr>[,options]
501 uart[8250],mmio,<addr>[,options]
502 Start an early, polled-mode console on the 8250/16550
503 UART at the specified I/O port or MMIO address.
504 The options are the same as for ttyS, above.
505
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506 no_console_suspend
507 [HW] Never suspend the console
508 Disable suspending of consoles during suspend and
509 hibernate operations. Once disabled, debugging
510 messages can reach various consoles while the rest
511 of the system is being put to sleep (ie, while
512 debugging driver suspend/resume hooks). This may
513 not work reliably with all consoles, but is known
514 to work with serial and VGA consoles.
515
1da177e4 516 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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517 Format:
518 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 519
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520 crashkernel=nn[KMG]@ss[KMG]
521 [KNL] Reserve a chunk of physical memory to
522 hold a kernel to switch to with kexec on panic.
523
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524 crashkernel=range1:size1[,range2:size2,...][@offset]
525 [KNL] Same as above, but depends on the memory
526 in the running system. The syntax of range is
527 start-[end] where start and end are both
528 a memory unit (amount[KMG]). See also
529 Documentation/kdump/kdump.txt for a example.
530
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531 cs4232= [HW,OSS]
532 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
533
534 cs89x0_dma= [HW,NET]
535 Format: <dma>
536
537 cs89x0_media= [HW,NET]
538 Format: { rj45 | aui | bnc }
a9913044 539
a9913044 540 dasd= [HW,NET]
1da177e4
LT
541 See header of drivers/s390/block/dasd_devmap.c.
542
543 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
544 (one device per port)
545 Format: <port#>,<type>
546 See also Documentation/input/joystick-parport.txt
547
548 debug [KNL] Enable kernel debugging (events log level).
549
cae2ed9a
IM
550 debug_locks_verbose=
551 [KNL] verbose self-tests
552 Format=<0|1>
553 Print debugging info while doing the locking API
554 self-tests.
555 We default to 0 (no extra messages), setting it to
556 1 will print _a lot_ more information - normally
557 only useful to kernel developers.
558
2d27a966 559 decnet.addr= [HW,NET]
1da177e4
LT
560 Format: <area>[,<node>]
561 See also Documentation/networking/decnet.txt.
562
ecb77fa9 563 vt.default_blu= [VT]
55ff9780
AD
564 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
565 Change the default blue palette of the console.
566 This is a 16-member array composed of values
567 ranging from 0-255.
568
ecb77fa9 569 vt.default_grn= [VT]
55ff9780
AD
570 Format: <green0>,<green1>,<green2>,...,<green15>
571 Change the default green palette of the console.
572 This is a 16-member array composed of values
573 ranging from 0-255.
574
ecb77fa9 575 vt.default_red= [VT]
55ff9780
AD
576 Format: <red0>,<red1>,<red2>,...,<red15>
577 Change the default red palette of the console.
578 This is a 16-member array composed of values
579 ranging from 0-255.
580
ecb77fa9
ST
581 vt.default_utf8=
582 [VT]
55ff9780
AD
583 Format=<0|1>
584 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
585 Default is 1, i.e. UTF-8 mode is enabled for all
586 newly opened terminals.
55ff9780 587
1da177e4
LT
588 dhash_entries= [KNL]
589 Set number of hash buckets for dentry cache.
a9913044 590
1da177e4
LT
591 digi= [HW,SERIAL]
592 IO parameters + enable/disable command.
593
594 digiepca= [HW,SERIAL]
595 See drivers/char/README.epca and
596 Documentation/digiepca.txt.
597
093af8d7 598 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
599 By default the kernel will trim any uncacheable
600 memory out of your available memory pool based on
601 MTRR settings. This parameter disables that behavior,
602 possibly causing your machine to run very slowly.
603
1da177e4
LT
604 dmasound= [HW,OSS] Sound subsystem buffers
605
606 dscc4.setup= [NET]
607
608 dtc3181e= [HW,SCSI]
609
0ae53640 610 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
611 earlyprintk=vga
612 earlyprintk=serial[,ttySn[,baudrate]]
613
a9913044 614 Append ",keep" to not disable it when the real console
1da177e4
LT
615 takes over.
616
617 Only vga or serial at a time, not both.
618
619 Currently only ttyS0 and ttyS1 are supported.
620
621 Interaction with the standard serial driver is not
622 very good.
623
624 The VGA output is eventually overwritten by the real
625 console.
626
627 eata= [HW,SCSI]
628
1da177e4
LT
629 edd= [EDD]
630 Format: {"of[f]" | "sk[ipmbr]"}
631 See comment in arch/i386/boot/edd.S
632
1da177e4
LT
633 eisa_irq_edge= [PARISC,HW]
634 See header of drivers/parisc/eisa.c.
635
cd4f0ef7 636 elanfreq= [X86-32]
1da177e4
LT
637 See comment before function elanfreq_setup() in
638 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
639
640 elevator= [IOSCHED]
16ab3adf 641 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
642 See Documentation/block/as-iosched.txt and
643 Documentation/block/deadline-iosched.txt for details.
644
cd4f0ef7 645 elfcorehdr= [X86-32, X86_64]
a9913044 646 Specifies physical address of start of kernel core
aac04b32
VG
647 image elf header. Generally kexec loader will
648 pass this option to capture kernel.
649 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
650
651 enforcing [SELINUX] Set initial enforcing status.
652 Format: {"0" | "1"}
653 See security/selinux/Kconfig help text.
654 0 -- permissive (log only, no denials).
655 1 -- enforcing (deny and log).
656 Default value is 0.
657 Value can be changed at runtime via /selinux/enforce.
658
1da177e4
LT
659 es1371= [HW,OSS]
660 Format: <spdif>,[<nomix>,[<amplifier>]]
661 See also header of sound/oss/es1371.c.
a9913044 662
1da177e4
LT
663 ether= [HW,NET] Ethernet cards parameters
664 This option is obsoleted by the "netdev=" option, which
665 has equivalent usage. See its documentation for details.
666
667 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
668 Format: <io>[,<irq>]
669
de1ba09b
AM
670 failslab=
671 fail_page_alloc=
672 fail_make_request=[KNL]
673 General fault injection mechanism.
674 Format: <interval>,<probability>,<space>,<times>
675 See also /Documentation/fault-injection/.
676
1da177e4
LT
677 fd_mcs= [HW,SCSI]
678 See header of drivers/scsi/fd_mcs.c.
679
680 fdomain= [HW,SCSI]
681 See header of drivers/scsi/fdomain.c.
682
683 floppy= [HW]
684 See Documentation/floppy.txt.
685
1da177e4
LT
686 gamecon.map[2|3]=
687 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
688 support via parallel port (up to 5 devices per port)
689 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
690 See also Documentation/input/joystick-parport.txt
691
692 gamma= [HW,DRM]
693
aaf23042
YL
694 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
695 Format: off | on
696 default: on
697
1da177e4
LT
698 gdth= [HW,SCSI]
699 See header of drivers/scsi/gdth.c.
700
701 gpt [EFI] Forces disk with valid GPT signature but
702 invalid Protective MBR to be treated as GPT.
703
1da177e4
LT
704 gvp11= [HW,SCSI]
705
706 hashdist= [KNL,NUMA] Large hashes allocated during boot
707 are distributed across NUMA nodes. Defaults on
708 for IA-64, off otherwise.
a9913044 709 Format: 0 | 1 (for off | on)
1da177e4
LT
710
711 hcl= [IA-64] SGI's Hardware Graph compatibility layer
712
713 hd= [EIDE] (E)IDE hard drive subsystem geometry
714 Format: <cyl>,<head>,<sect>
715
716 hd?= [HW] (E)IDE subsystem
1c10e938 717 hd?lun= See Documentation/ide/ide.txt.
1da177e4
LT
718
719 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
720 size of <nn>. This works even on boxes that have no
721 highmem otherwise. This also works to reduce highmem
722 size on bigger boxes.
723
54cdfdb4
TG
724 highres= [KNL] Enable/disable high resolution timer mode.
725 Valid parameters: "on", "off"
726 Default: "on"
727
1da177e4
LT
728 hisax= [HW,ISDN]
729 See Documentation/isdn/README.HiSax.
730
cd4f0ef7 731 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 732 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 733
1da177e4 734 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
735 i8042.dumbkbd [HW] Pretend that controller can only read data from
736 keyboard and cannot control its state
1da177e4
LT
737 (Don't attempt to blink the leds)
738 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 739 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
740 i8042.noloop [HW] Disable the AUX Loopback command while probing
741 for the AUX port
1da177e4
LT
742 i8042.nomux [HW] Don't check presence of an active multiplexing
743 controller
744 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
745 controllers
746 i8042.panicblink=
747 [HW] Frequency with which keyboard LEDs should blink
748 when kernel panics (default is 0.5 sec)
749 i8042.reset [HW] Reset the controller during init and cleanup
750 i8042.unlock [HW] Unlock (ignore) the keylock
751
752 i810= [HW,DRM]
753
e70c9d5e
DT
754 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
755 indicates that the driver is running on unsupported
756 hardware.
1da177e4
LT
757 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
758 does not match list of supported models.
759 i8k.power_status
760 [HW] Report power status in /proc/i8k
761 (disabled by default)
762 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
763 capability is set.
764
765 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
766 See Documentation/mca.txt.
767
768 icn= [HW,ISDN]
769 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
770
771 ide= [HW] (E)IDE subsystem
a594eeb1 772 Format: ide=nodma or ide=doubler
1c10e938 773 See Documentation/ide/ide.txt.
1da177e4 774
1da177e4 775 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 776 See Documentation/ide/ide.txt.
1da177e4 777
f039b754
AK
778 idle= [X86]
779 Format: idle=poll or idle=mwait
780 Poll forces a polling idle loop that can slightly improves the performance
781 of waking up a idle CPU, but will use a lot of power and make the system
782 run hot. Not recommended.
783 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
784 to not use it because it doesn't save as much power as a normal idle
785 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
786 as idle=poll.
a9913044 787
594765a7
DC
788 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
789 Claim all unknown PCI IDE storage controllers.
790
79290822
IM
791 ignore_loglevel [KNL]
792 Ignore loglevel setting - this will print /all/
793 kernel messages to the console. Useful for debugging.
794
1da177e4
LT
795 ihash_entries= [KNL]
796 Set number of hash buckets for inode cache.
797
798 in2000= [HW,SCSI]
799 See header of drivers/scsi/in2000.c.
800
801 init= [KNL]
802 Format: <full_path>
803 Run specified binary instead of /sbin/init as init
804 process.
805
806 initcall_debug [KNL] Trace initcalls as they are executed. Useful
807 for working out where the kernel is dying during
808 startup.
809
810 initrd= [BOOT] Specify the location of the initial ramdisk
811
812 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
813 Format: <irq>
814
815 inttest= [IA64]
816
b552da87
PM
817 iommu= [x86]
818 off
819 force
820 noforce
821 biomerge
822 panic
823 nopanic
824 merge
825 nomerge
826 forcesac
827 soft
828
829
ba395927
KA
830 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
831 off
832 Disable intel iommu driver.
833 igfx_off [Default Off]
834 By default, gfx is mapped as normal device. If a gfx
835 device has a dedicated DMAR unit, the DMAR unit is
836 bypassed by not enabling DMAR with this option. In
837 this case, gfx device will use physical address for
838 DMA.
7d3b03ce
KA
839 forcedac [x86_64]
840 With this option iommu will not optimize to look
841 for io virtual address below 32 bit forcing dual
842 address cycle on pci bus for cards supporting greater
843 than 32 bit addressing. The default is to look
844 for translation below 32 bit and if not available
845 then look in the higher range.
5e0d2a6f 846 strict [Default Off]
847 With this option on every unmap_single operation will
848 result in a hardware IOTLB flush operation as opposed
849 to batching them for performance.
ba395927 850
b02aae9c 851 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
852 0x80
853 Standard port 0x80 based delay
854 0xed
855 Alternate port 0xed based delay (needed on some systems)
b02aae9c 856 udelay
6e7c4025
IM
857 Simple two microseconds delay
858 none
859 No delay
b02aae9c 860
1da177e4
LT
861 io7= [HW] IO7 for Marvel based alpha systems
862 See comment before marvel_specify_io7 in
863 arch/alpha/kernel/core_marvel.c.
864
865 ip= [IP_PNP]
6ded55da 866 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
867
868 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
869 See comment before ip2_setup() in
870 drivers/char/ip2/ip2base.c.
1da177e4
LT
871
872 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
873 See header of drivers/scsi/ips.c.
874
72c4a13a
SH
875 ports= [IP_VS_FTP] IPVS ftp helper module
876 Default is 21.
877 Up to 8 (IP_VS_APP_MAX_PORTS) ports
878 may be specified.
879 Format: <port>,<port>....
880
200803df
AC
881 irqfixup [HW]
882 When an interrupt is not handled search all handlers
883 for it. Intended to get systems with badly broken
884 firmware running.
885
886 irqpoll [HW]
887 When an interrupt is not handled search all handlers
888 for it. Also check all handlers each timer
889 interrupt. Intended to get systems with badly broken
890 firmware running.
891
1da177e4 892 isapnp= [ISAPNP]
a9913044 893 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
894
895 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
896 Format:
897 <cpu number>,...,<cpu number>
898 or
899 <cpu number>-<cpu number> (must be a positive range in ascending order)
900 or a mixture
901 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
902 This option can be used to specify one or more CPUs
903 to isolate from the general SMP balancing and scheduling
904 algorithms. The only way to move a process onto or off
905 an "isolated" CPU is via the CPU affinity syscalls.
906 <cpu number> begins at 0 and the maximum value is
907 "number of CPUs in system - 1".
908
909 This option is the preferred way to isolate CPUs. The
a9913044
RD
910 alternative -- manually setting the CPU mask of all
911 tasks in the system -- can cause problems and
912 suboptimal load balancer performance.
1da177e4 913
a9913044 914 iucv= [HW,NET]
1da177e4
LT
915
916 js= [HW,JOY] Analog joystick
917 See Documentation/input/joystick.txt.
918
cd4f0ef7 919 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
920 specifies the amount of memory usable by the kernel
921 for non-movable allocations. The requested amount is
922 spread evenly throughout all nodes in the system. The
923 remaining memory in each node is used for Movable
924 pages. In the event, a node is too small to have both
925 kernelcore and Movable pages, kernelcore pages will
926 take priority and other nodes will have a larger number
927 of kernelcore pages. The Movable zone is used for the
928 allocation of pages that may be reclaimed or moved
929 by the page migration subsystem. This means that
930 HugeTLB pages may not be allocated from this zone.
931 Note that allocations like PTEs-from-HighMem still
932 use the HighMem zone if it exists, and the Normal
933 zone if it does not.
934
cd4f0ef7 935 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
936 is similar to kernelcore except it specifies the
937 amount of memory used for migratable allocations.
938 If both kernelcore and movablecore is specified,
939 then kernelcore will be at *least* the specified
940 value but may be more. If movablecore on its own
941 is specified, the administrator must be careful
942 that the amount of memory usable for all allocations
943 is not too small.
944
1da177e4
LT
945 keepinitrd [HW,ARM]
946
cd4f0ef7 947 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
948 in oops dumps.
949
6cdf6e06
JW
950 kgdboc= [HW] kgdb over consoles.
951 Requires a tty driver that supports console polling.
952 (only serial suported for now)
953 Format: <serial_device>[,baud]
954
1da177e4
LT
955 l2cr= [PPC]
956
a78bfbfc
RB
957 l3cr= [PPC]
958
cd4f0ef7 959 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 960 disabled it.
1da177e4 961
cd4f0ef7 962 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
963 C2 power state.
964
fcb71f6f
FC
965 libata.dma= [LIBATA] DMA control
966 libata.dma=0 Disable all PATA and SATA DMA
967 libata.dma=1 PATA and SATA Disk DMA only
968 libata.dma=2 ATAPI (CDROM) DMA only
969 libata.dma=4 Compact Flash DMA only
970 Combinations also work, so libata.dma=3 enables DMA
971 for disks and CDROMs, but not CFs.
972
78e70c23
DJ
973 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
974 when set.
975 Format: <int>
976
33267325
TH
977 libata.force= [LIBATA] Force configurations. The format is comma
978 separated list of "[ID:]VAL" where ID is
979 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
980 matching port, link or device. Basically, it matches
981 the ATA ID string printed on console by libata. If
982 the whole ID part is omitted, the last PORT and DEVICE
983 values are used. If ID hasn't been specified yet, the
984 configuration applies to all ports, links and devices.
985
986 If only DEVICE is omitted, the parameter applies to
987 the port and all links and devices behind it. DEVICE
988 number of 0 either selects the first device or the
989 first fan-out link behind PMP device. It does not
990 select the host link. DEVICE number of 15 selects the
991 host link and device attached to it.
992
993 The VAL specifies the configuration to force. As long
994 as there's no ambiguity shortcut notation is allowed.
995 For example, both 1.5 and 1.5G would work for 1.5Gbps.
996 The following configurations can be forced.
997
998 * Cable type: 40c, 80c, short40c, unk, ign or sata.
999 Any ID with matching PORT is used.
1000
1001 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1002
1003 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1004 udma[/][16,25,33,44,66,100,133] notation is also
1005 allowed.
1006
1007 * [no]ncq: Turn on or off NCQ.
1008
1009 If there are multiple matching configurations changing
1010 the same attribute, the last one is used.
1011
1da177e4
LT
1012 load_ramdisk= [RAM] List of ramdisks to load from floppy
1013 See Documentation/ramdisk.txt.
1014
a6b25b67
RD
1015 lockd.nlm_grace_period=P [NFS] Assign grace period.
1016 Format: <integer>
1da177e4 1017
a6b25b67
RD
1018 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1019 Format: <integer>
1020
1021 lockd.nlm_timeout=T [NFS] Assign timeout value.
1022 Format: <integer>
1023
1024 lockd.nlm_udpport=M [NFS] Assign UDP port.
1025 Format: <integer>
1da177e4
LT
1026
1027 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1028 Format: <irq>
1029
1030 loglevel= All Kernel Messages with a loglevel smaller than the
1031 console loglevel will be printed to the console. It can
1032 also be changed with klogd or other programs. The
1033 loglevels are defined as follows:
1034
1035 0 (KERN_EMERG) system is unusable
1036 1 (KERN_ALERT) action must be taken immediately
1037 2 (KERN_CRIT) critical conditions
1038 3 (KERN_ERR) error conditions
1039 4 (KERN_WARNING) warning conditions
1040 5 (KERN_NOTICE) normal but significant condition
1041 6 (KERN_INFO) informational
1042 7 (KERN_DEBUG) debug-level messages
1043
1044 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1045 Format: { n | nk | nM }
1046 n must be a power of two. The default size
1047 is set in the kernel config file.
1da177e4 1048
accaa24c
RD
1049 logo.nologo [FB] Disables display of the built-in Linux logo.
1050 This may be used to provide more screen space for
1051 kernel log messages and is useful when debugging
1052 kernel boot problems.
1053
1da177e4
LT
1054 lp=0 [LP] Specify parallel ports to use, e.g,
1055 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1056 lp=reset first parallel port). 'lp=0' disables the
1057 lp=auto printer driver. 'lp=reset' (which can be
1058 specified in addition to the ports) causes
1059 attached printers to be reset. Using
1060 lp=port1,port2,... specifies the parallel ports
1061 to associate lp devices with, starting with
1062 lp0. A port specification may be 'none' to skip
1063 that lp device, or a parport name such as
1064 'parport0'. Specifying 'lp=auto' instead of a
1065 port specification list means that device IDs
1066 from each port should be examined, to see if
1067 an IEEE 1284-compliant printer is attached; if
1068 so, the driver will manage that printer.
1069 See also header of drivers/char/lp.c.
1070
1071 lpj=n [KNL]
1072 Sets loops_per_jiffy to given constant, thus avoiding
1073 time-consuming boot-time autodetection (up to 250 ms per
1074 CPU). 0 enables autodetection (default). To determine
1075 the correct value for your kernel, boot with normal
1076 autodetection and see what value is printed. Note that
1077 on SMP systems the preset will be applied to all CPUs,
1078 which is likely to cause problems if your CPUs need
1079 significantly divergent settings. An incorrect value
1080 will cause delays in the kernel to be wrong, leading to
1081 unpredictable I/O errors and other breakage. Although
1082 unlikely, in the extreme case this might damage your
1083 hardware.
1084
1085 ltpc= [NET]
1086 Format: <io>,<irq>,<dma>
1087
a9913044
RD
1088 mac5380= [HW,SCSI] Format:
1089 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1090
a9913044
RD
1091 mac53c9x= [HW,SCSI] Format:
1092 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1093
a9913044
RD
1094 machvec= [IA64] Force the use of a particular machine-vector
1095 (machvec) in a generic kernel.
1096 Example: machvec=hpzx1_swiotlb
1da177e4 1097
a9913044 1098 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1099 be mounted
1100 Format: <1-256>
1101
1102 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1103 should make use of. maxcpus=n : n >= 0 limits the
1104 kernel to using 'n' processors. n=0 is a special case,
1105 it is equivalent to "nosmp", which also disables
1106 the IO APIC.
1da177e4 1107
2b2c3750
BP
1108 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1109 equal to this physical address is ignored.
1110
a9913044 1111 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1112 Should be between 1 and 2^32-1.
1113
1114 max_report_luns=
a9913044 1115 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1116 Should be between 1 and 16384.
1117
1da177e4
LT
1118 mcatest= [IA-64]
1119
cd4f0ef7 1120 mce [X86-32] Machine Check Exception
1da177e4 1121
909dd324
AK
1122 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1123
1da177e4
LT
1124 md= [HW] RAID subsystems devices and level
1125 See Documentation/md.txt.
a9913044 1126
1da177e4
LT
1127 mdacon= [MDA]
1128 Format: <first>,<last>
1129 Specifies range of consoles to be captured by the MDA.
a9913044 1130
1da177e4
LT
1131 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1132 Amount of memory to be used when the kernel is not able
1133 to see the whole system memory or for test.
cd4f0ef7 1134 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1135 address space collisions. Without memmap= PCI devices
1136 could be placed at addresses belonging to unused RAM.
1137
cd4f0ef7 1138 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1139 memory.
1140
cd4f0ef7 1141 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1142 E820 memory map, as specified by the user.
1143 Such memmap=exactmap lines can be constructed based on
1144 BIOS output or other requirements. See the memmap=nn@ss
1145 option description.
1146
1147 memmap=nn[KMG]@ss[KMG]
1148 [KNL] Force usage of a specific region of memory
1149 Region of memory to be used, from ss to ss+nn.
1150
1151 memmap=nn[KMG]#ss[KMG]
1152 [KNL,ACPI] Mark specific memory as ACPI data.
1153 Region of memory to be used, from ss to ss+nn.
1154
1155 memmap=nn[KMG]$ss[KMG]
1156 [KNL,ACPI] Mark specific memory as reserved.
1157 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1158 Example: Exclude memory from 0x18690000-0x1869ffff
1159 memmap=64K$0x18690000
1160 or
1161 memmap=0x10000$0x18690000
1da177e4 1162
c64df707
YL
1163 memtest= [KNL,X86_64] Enable memtest
1164 Format: <integer>
1165 range: 0,4 : pattern number
1166 default : 0 <disable>
1167
1da177e4
LT
1168 meye.*= [HW] Set MotionEye Camera parameters
1169 See Documentation/video4linux/meye.txt.
1170
8f36881b
AS
1171 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1172 Multi-Function General Purpose Timers on AMD Geode
1173 platforms.
1174
e6c4dc6c
WT
1175 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1176 the BIOS has incorrectly applied a workaround. TinyBIOS
1177 version 0.98 is known to be affected, 0.99 fixes the
1178 problem by letting the user disable the workaround.
1179
1da177e4
LT
1180 mga= [HW,DRM]
1181
1182 mousedev.tap_time=
1183 [MOUSE] Maximum time between finger touching and
1184 leaving touchpad surface for touch to be considered
1185 a tap and be reported as a left button click (for
1186 touchpads working in absolute mode only).
1187 Format: <msecs>
1188 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1189 reporting absolute coordinates, such as tablets
1190 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1191 reporting absolute coordinates, such as tablets
1192
1193 mpu401= [HW,OSS]
1194 Format: <io>,<irq>
1195
1196 MTD_Partition= [MTD]
1197 Format: <name>,<region-number>,<size>,<offset>
1198
a9913044
RD
1199 MTD_Region= [MTD] Format:
1200 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1201
1202 mtdparts= [MTD]
c8facbb6 1203 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1204
1205 mtouchusb.raw_coordinates=
a9913044
RD
1206 [HW] Make the MicroTouch USB driver use raw coordinates
1207 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1208
1209 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1210
1211 NCR_D700= [HW,SCSI]
1212 See header of drivers/scsi/NCR_D700.c.
1213
1214 ncr5380= [HW,SCSI]
1215
1216 ncr53c400= [HW,SCSI]
1217
1218 ncr53c400a= [HW,SCSI]
1219
1220 ncr53c406a= [HW,SCSI]
1221
1222 ncr53c8xx= [HW,SCSI]
1223
1224 netdev= [NET] Network devices parameters
1225 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1226 Note that mem_start is often overloaded to mean
1227 something different and driver-specific.
a9913044
RD
1228 This usage is only documented in each driver source
1229 file if at all.
1230
1da177e4 1231 nfsaddrs= [NFS]
6ded55da 1232 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1233
1234 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1235 See Documentation/filesystems/nfsroot.txt.
1da177e4 1236
a72b4422
TM
1237 nfs.callback_tcpport=
1238 [NFS] set the TCP port on which the NFSv4 callback
1239 channel should listen.
1240
58df095b
TM
1241 nfs.idmap_cache_timeout=
1242 [NFS] set the maximum lifetime for idmapper cache
1243 entries.
1244
f43bf0be
TM
1245 nfs.enable_ino64=
1246 [NFS] enable 64-bit inode numbers.
1247 If zero, the NFS client will fake up a 32-bit inode
1248 number for the readdir() and stat() syscalls instead
1249 of returning the full 64-bit number.
1250 The default is to return 64-bit inode numbers.
1251
e7ba176b
HS
1252 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1253 when a NMI is triggered.
1254 Format: [state][,regs][,debounce][,die]
1255
cd4f0ef7 1256 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1257
cd4f0ef7 1258 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1259 emulation library even if a 387 maths coprocessor
1260 is present.
1261
c1aee215
CL
1262 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1263 caches in the slab allocator. Saves per-node memory,
1264 but will impact performance.
3395ee05 1265
a9913044
RD
1266 noalign [KNL,ARM]
1267
1da177e4
LT
1268 noapic [SMP,APIC] Tells the kernel to not make use of any
1269 IOAPICs that may be present in the system.
1270
1da177e4
LT
1271 nobats [PPC] Do not use BATs for mapping kernel lowmem
1272 on "Classic" PPC cores.
1273
1274 nocache [ARM]
a9913044 1275
163ecdff
SN
1276 nodelayacct [KNL] Disable per-task delay accounting
1277
1da177e4
LT
1278 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1279
8b2cb7a8
HY
1280 noefi [X86-32,X86-64] Disable EFI runtime services support.
1281
1da177e4
LT
1282 noexec [IA-64]
1283
cd4f0ef7 1284 noexec [X86-32,X86-64]
f5a1b191 1285 On X86-32 available only on PAE configured kernels.
1da177e4 1286 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1287 noexec=off: disable non-executable mappings
1288
1289 noexec32 [X86-64]
1290 This affects only 32-bit executables.
1291 noexec32=on: enable non-executable mappings (default)
1292 read doesn't imply executable mappings
1293 noexec32=off: disable non-executable mappings
1294 read implies executable mappings
1da177e4 1295
cd4f0ef7 1296 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1297 register save and restore. The kernel will only save
1298 legacy floating-point registers on task switch.
1da177e4 1299
191679fd
AK
1300 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1301
1da177e4 1302 nohlt [BUGS=ARM]
a9913044 1303
cd4f0ef7 1304 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1305 instruction doesn't work correctly and not to
1306 use it.
1307
1308 nohalt [IA-64] Tells the kernel not to use the power saving
1309 function PAL_HALT_LIGHT when idle. This increases
1310 power-consumption. On the positive side, it reduces
1311 interrupt wake-up latency, which may improve performance
1312 in certain environments such as networked servers or
1313 real-time systems.
1314
79bf2bb3
TG
1315 nohz= [KNL] Boottime enable/disable dynamic ticks
1316 Valid arguments: on, off
1317 Default: on
1318
cd4f0ef7 1319 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1320
cd4f0ef7 1321 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1322 disable unhandled interrupt sources.
1323
cd4f0ef7 1324 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1325 broken timer IRQ sources.
1326
1da177e4
LT
1327 noisapnp [ISAPNP] Disables ISA PnP code.
1328
1329 noinitrd [RAM] Tells the kernel not to load any configured
1330 initial RAM disk.
1331
1332 nointroute [IA-64]
1333
0aa366f3
TL
1334 nojitter [IA64] Disables jitter checking for ITC timers.
1335
cd4f0ef7 1336 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1337
cd4f0ef7 1338 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1339
1da177e4
LT
1340 noltlbs [PPC] Do not use large page/tlb entries for kernel
1341 lowmem mapping on PPC40x.
1342
312f1f01
H
1343 nomca [IA-64] Disable machine check abort handling
1344
cd4f0ef7 1345 nomce [X86-32] Machine Check Exception
abe37e5a 1346
83d7384f
AS
1347 nomfgpt [X86-32] Disable Multi-Function General Purpose
1348 Timer usage (for AMD Geode machines).
1349
cd4f0ef7 1350 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1351
cd4f0ef7 1352 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1353 with UP alternatives
1354
1da177e4
LT
1355 noresidual [PPC] Don't use residual data on PReP machines.
1356
a9913044
RD
1357 noresume [SWSUSP] Disables resume and restores original swap
1358 space.
1359
1da177e4
LT
1360 no-scroll [VGA] Disables scrollback.
1361 This is required for the Braillex ib80-piezo Braille
1362 reader made by F.H. Papenmeier (Germany).
1363
1364 nosbagart [IA-64]
1365
cd4f0ef7 1366 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1367
61ec7567
LB
1368 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1369 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1370
97842216
DJ
1371 nosoftlockup [KNL] Disable the soft-lockup detector.
1372
1da177e4
LT
1373 nosync [HW,M68K] Disables sync negotiation for all devices.
1374
cd4f0ef7 1375 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1376
1377 nousb [USB] Disable the USB subsystem
1378
1379 nowb [ARM]
a9913044 1380
a6c75b86
FY
1381 nptcg= [IA64] Override max number of concurrent global TLB
1382 purges which is reported from either PAL_VM_SUMMARY or
1383 SAL PALO.
1384
f0c0b2b8
KH
1385 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1386 one of ['zone', 'node', 'default'] can be specified
1387 This can be set from sysctl after boot.
1388 See Documentation/sysctl/vm.txt for details.
1389
a61c2d78
DJ
1390 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1391
3ef0e1f8
AS
1392 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1393 Rather than timing out after 20 ms if an EC
1394 command is not properly ACKed, override the length
1395 of the timeout. We have interrupts disabled while
1396 waiting for the ACK, so if this is set too high
1397 interrupts *may* be lost!
1398
1da177e4
LT
1399 opl3= [HW,OSS]
1400 Format: <io>
1401
1da177e4
LT
1402 oprofile.timer= [HW]
1403 Use timer interrupt instead of performance counters
1404
1da177e4
LT
1405 osst= [HW,SCSI] SCSI Tape Driver
1406 Format: <buffer_size>,<write_threshold>
1407 See also Documentation/scsi/st.txt.
1408
1409 panic= [KNL] Kernel behaviour on panic
1410 Format: <timeout>
1411
1412 parkbd.port= [HW] Parallel port number the keyboard adapter is
1413 connected to, default is 0.
1414 Format: <parport#>
1415 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1416 0 for XT, 1 for AT (default is AT).
a9913044
RD
1417 Format: <mode>
1418
1419 parport= [HW,PPT] Specify parallel ports. 0 disables.
1420 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1421 Use 'auto' to force the driver to use any
1422 IRQ/DMA settings detected (the default is to
1423 ignore detected IRQ/DMA settings because of
1424 possible conflicts). You can specify the base
1425 address, IRQ, and DMA settings; IRQ and DMA
1426 should be numbers, or 'auto' (for using detected
1427 settings on that particular port), or 'nofifo'
1428 (to avoid using a FIFO even if it is detected).
1429 Parallel ports are assigned in the order they
1430 are specified on the command line, starting
1431 with parport0.
1432
1433 parport_init_mode= [HW,PPT]
1434 Configure VIA parallel port to operate in
1435 a specific mode. This is necessary on Pegasos
1436 computer where firmware has no options for setting
1437 up parallel port mode and sets it to spp.
1438 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1439 Format: [spp|ps2|epp|ecp|ecpepp]
1440
a9913044
RD
1441 pas2= [HW,OSS] Format:
1442 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1443
1da177e4
LT
1444 pas16= [HW,SCSI]
1445 See header of drivers/scsi/pas16.c.
1446
dd287796
AM
1447 pause_on_oops=
1448 Halt all CPUs after the first oops has been printed for
1449 the specified number of seconds. This is to be used if
1450 your oopses keep scrolling off the screen.
1451
1da177e4
LT
1452 pcbit= [HW,ISDN]
1453
1454 pcd. [PARIDE]
1455 See header of drivers/block/paride/pcd.c.
1456 See also Documentation/paride.txt.
1457
a9913044 1458 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1459 off [X86-32] don't probe for the PCI bus
1460 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1461 the hardware directly. Use this if your machine
1462 has a non-standard PCI host bridge.
cd4f0ef7 1463 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1464 hardware access methods are allowed. Use this
1465 if you experience crashes upon bootup and you
1466 suspect they are caused by the BIOS.
cd4f0ef7 1467 conf1 [X86-32] Force use of PCI Configuration
a9913044 1468 Mechanism 1.
cd4f0ef7 1469 conf2 [X86-32] Force use of PCI Configuration
a9913044 1470 Mechanism 2.
7f785763
RD
1471 noaer [PCIE] If the PCIEAER kernel config parameter is
1472 enabled, this kernel boot option can be used to
1473 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1474 nodomains [PCI] Disable support for multiple PCI
1475 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1476 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1477 Configuration
309e57df
MW
1478 nomsi [MSI] If the PCI_MSI kernel config parameter is
1479 enabled, this kernel boot option can be used to
1480 disable the use of MSI interrupts system-wide.
cd4f0ef7 1481 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1482 routing table. These calls are known to be buggy
1483 on several machines and they hang the machine
1484 when used, but on other computers it's the only
1485 way to get the interrupt routing table. Try
1486 this option if the kernel is unable to allocate
1487 IRQs or discover secondary PCI buses on your
1488 motherboard.
cd4f0ef7 1489 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1490 Use with caution as certain devices share
1491 address decoders between ROMs and other
1492 resources.
cd4f0ef7 1493 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1494 assigned automatically to PCI devices. You can
1495 make the kernel exclude IRQs of your ISA cards
1496 this way.
cd4f0ef7 1497 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1498 of the PIRQ table (normally generated
1499 by the BIOS) if it is outside the
1500 F0000h-100000h range.
cd4f0ef7 1501 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1502 useful if the kernel is unable to find your
1503 secondary buses and you want to tell it
1504 explicitly which ones they are.
cd4f0ef7 1505 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1506 numbers ourselves, overriding
1507 whatever the firmware may have done.
cd4f0ef7 1508 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1509 in the BIOS $PIR table. This is needed on
1510 some systems with broken BIOSes, notably
1511 some HP Pavilion N5400 and Omnibook XE3
1512 notebooks. This will have no effect if ACPI
1513 IRQ routing is enabled.
cd4f0ef7 1514 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1515 or for PCI scanning.
62f420f8
GH
1516 use_crs [X86-32] Use _CRS for PCI resource
1517 allocation.
a9913044
RD
1518 routeirq Do IRQ routing for all PCI devices.
1519 This is normally done in pci_enable_device(),
1520 so this option is a temporary workaround
1521 for broken drivers that don't call it.
1522 firmware [ARM] Do not re-enumerate the bus but instead
1523 just use the configuration from the
1524 bootloader. This is currently used on
1525 IXP2000 systems where the bus has to be
1526 configured a certain way for adjunct CPUs.
0637a70a
AK
1527 noearly [X86] Don't do any early type 1 scanning.
1528 This might help on some broken boards which
1529 machine check when some devices' config space
1530 is read. But various workarounds are disabled
1531 and some IOMMU drivers will not work.
6b4b78fe
MD
1532 bfsort Sort PCI devices into breadth-first order.
1533 This sorting is done to get a device
1534 order compatible with older (<= 2.4) kernels.
1535 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1536 cbiosize=nn[KMG] The fixed amount of bus space which is
1537 reserved for the CardBus bridge's IO window.
1538 The default value is 256 bytes.
1539 cbmemsize=nn[KMG] The fixed amount of bus space which is
1540 reserved for the CardBus bridge's memory
1541 window. The default value is 64 megabytes.
6b4b78fe 1542
1da177e4
LT
1543 pcmv= [HW,PCMCIA] BadgePAD 4
1544
1545 pd. [PARIDE]
1546 See Documentation/paride.txt.
1547
1548 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1549 boot time.
1550 Format: { 0 | 1 }
1551 See arch/parisc/kernel/pdc_chassis.c
1552
1553 pf. [PARIDE]
1554 See Documentation/paride.txt.
1555
1556 pg. [PARIDE]
1557 See Documentation/paride.txt.
1558
1559 pirq= [SMP,APIC] Manual mp-table setup
1560 See Documentation/i386/IO-APIC.txt.
1561
1562 plip= [PPT,NET] Parallel port network link
1563 Format: { parport<nr> | timid | 0 }
1564 See also Documentation/parport.txt.
1565
1566 pnpacpi= [ACPI]
1567 { off }
1568
1569 pnpbios= [ISAPNP]
1570 { on | off | curr | res | no-curr | no-res }
1571
1572 pnp_reserve_irq=
1573 [ISAPNP] Exclude IRQs for the autoconfiguration
1574
1575 pnp_reserve_dma=
1576 [ISAPNP] Exclude DMAs for the autoconfiguration
1577
1578 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1579 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1580
1581 pnp_reserve_mem=
a9913044
RD
1582 [ISAPNP] Exclude memory regions for the
1583 autoconfiguration.
1da177e4
LT
1584 Ranges are in pairs (memory base and size).
1585
45807a1d
IM
1586 print-fatal-signals=
1587 [KNL] debug: print fatal signals
1588 print-fatal-signals=1: print segfault info to
1589 the kernel console.
1590 default: off.
1591
e84845c4
RD
1592 printk.time= Show timing data prefixed to each printk message line
1593 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1594
1da177e4 1595 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1596 Format: [schedule,]<number>
1597 Param: "schedule" - profile schedule points.
1598 Param: <number> - step/bucket size as a power of 2 for
1599 statistical time based profiling.
b3da2a73
MG
1600 Param: "sleep" - profile D-state sleeping (millisecs).
1601 Requires CONFIG_SCHEDSTATS
c0fe2e69 1602 Param: "kvm" - profile VM exits.
1da177e4 1603
a9913044 1604 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1605 Limit processor to maximum C-state
1606 max_cstate=9 overrides any DMI blacklist limit.
1607
41c0d868
LB
1608 processor.nocst [HW,ACPI]
1609 Ignore the _CST method to determine C-states,
1610 instead using the legacy FADT method
1611
1da177e4
LT
1612 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1613 before loading.
1614 See Documentation/ramdisk.txt.
1615
a9913044
RD
1616 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1617 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1618 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1619 per second.
a9913044
RD
1620 psmouse.resetafter= [HW,MOUSE]
1621 Try to reset the device after so many bad packets
1da177e4
LT
1622 (0 = never).
1623 psmouse.resolution=
1624 [HW,MOUSE] Set desired mouse resolution, in dpi.
1625 psmouse.smartscroll=
a9913044 1626 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1627 0 = disabled, 1 = enabled (default).
1628
1629 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1630 Format:
1631 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1632
1633 pt. [PARIDE]
1634 See Documentation/paride.txt.
1635
dc8c8587
KS
1636 pty.legacy_count=
1637 [KNL] Number of legacy pty's. Overwrites compiled-in
1638 default number.
1639
7d2c502f 1640 quiet [KNL] Disable most log messages
a9913044 1641
1da177e4
LT
1642 r128= [HW,DRM]
1643
1644 raid= [HW,RAID]
1645 See Documentation/md.txt.
1646
a9913044 1647 ramdisk_blocksize= [RAM]
1da177e4 1648 See Documentation/ramdisk.txt.
a9913044 1649
1da177e4 1650 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1651 See Documentation/ramdisk.txt.
1652
24aaef8d
RD
1653 rcupdate.blimit= [KNL,BOOT]
1654 Set maximum number of finished RCU callbacks to process
1655 in one batch.
21a1ea9e 1656
24aaef8d
RD
1657 rcupdate.qhimark= [KNL,BOOT]
1658 Set threshold of queued
21a1ea9e
DS
1659 RCU callbacks over which batch limiting is disabled.
1660
24aaef8d
RD
1661 rcupdate.qlowmark= [KNL,BOOT]
1662 Set threshold of queued RCU callbacks below which
1663 batch limiting is re-enabled.
21a1ea9e 1664
ffdfc409
OJ
1665 rdinit= [KNL]
1666 Format: <full_path>
1667 Run specified binary instead of /init from the ramdisk,
1668 used for early userspace startup. See initrd.
1669
cd4f0ef7 1670 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1671 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1672 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1673
1674 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1675
cd4f0ef7 1676 reservetop= [X86-32]
461a9aff
ZA
1677 Format: nn[KMG]
1678 Reserves a hole at the top of the kernel virtual
1679 address space.
1680
7e96287d
VG
1681 reset_devices [KNL] Force drivers to reset the underlying device
1682 during initialization.
1683
a9913044
RD
1684 resume= [SWSUSP]
1685 Specify the partition device for software suspend
1da177e4 1686
ecbd0da1
RW
1687 resume_offset= [SWSUSP]
1688 Specify the offset from the beginning of the partition
1689 given by "resume=" at which the swap header is located,
1690 in <PAGE_SIZE> units (needed only for swap files).
1691 See Documentation/power/swsusp-and-swap-files.txt
1692
0a7b35cb
MN
1693 retain_initrd [RAM] Keep initrd memory after extraction
1694
1da177e4
LT
1695 rhash_entries= [KNL,NET]
1696 Set number of hash buckets for route cache
1697
1698 riscom8= [HW,SERIAL]
1699 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1700
1701 ro [KNL] Mount root device read-only on boot
1702
1703 root= [KNL] Root filesystem
1704
1705 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1706 mount the root filesystem
1707
1708 rootflags= [KNL] Set root filesystem mount option string
1709
1710 rootfstype= [KNL] Set root filesystem type
1711
cc1ed754
PO
1712 rootwait [KNL] Wait (indefinitely) for root device to show up.
1713 Useful for devices that are detected asynchronously
1714 (e.g. USB and MMC devices).
1715
20510f2f
JM
1716 root_plug.vendor_id=
1717 [ROOTPLUG] Override the default vendor ID
1718
1719 root_plug.product_id=
1720 [ROOTPLUG] Override the default product ID
1721
1722 root_plug.debug=
1723 [ROOTPLUG] Enable debugging output
1724
1da177e4
LT
1725 rw [KNL] Mount root device read-write on boot
1726
1727 S [KNL] Run init in single mode
1728
1729 sa1100ir [NET]
1730 See drivers/net/irda/sa1100_ir.c.
1731
1da177e4 1732 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1733
1da177e4
LT
1734 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1735 Format: <io>[,<timeout>[,<isapnp>]]
1736
1737 scsi_debug_*= [SCSI]
1738 See drivers/scsi/scsi_debug.c.
1739
1740 scsi_default_dev_flags=
1741 [SCSI] SCSI default device flags
1742 Format: <integer>
1743
1744 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1745 Format: <vendor>:<model>:<flags>
1746 (flags are integer value)
1747
6af6632a
RD
1748 scsi_logging_level= [SCSI] a bit mask of logging levels
1749 See drivers/scsi/scsi_logging.h for bits. Also
1750 settable via sysctl at dev.scsi.logging_level
1751 (/proc/sys/dev/scsi/logging_level).
1752 There is also a nice 'scsi_logging_level' script in the
1753 S390-tools package, available for download at
1754 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1755
3e082a91
MW
1756 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1757 discovered. async scans them in kernel threads,
1758 allowing boot to proceed. none ignores them, expecting
1759 user space to do the scan.
1760
1da177e4
LT
1761 selinux [SELINUX] Disable or enable SELinux at boot time.
1762 Format: { "0" | "1" }
1763 See security/selinux/Kconfig help text.
1764 0 -- disable.
1765 1 -- enable.
1766 Default value is set via kernel config option.
1767 If enabled at boot time, /selinux/disable can be used
1768 later to disable prior to initial policy load.
1769
4e5ab4cb
JM
1770 selinux_compat_net =
1771 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1772 Format: { "0" | "1" }
1773 0 -- use new secmark-based packet controls
1774 1 -- use legacy packet controls
1775 Default value is 0 (preferred).
1776 Value can be changed at runtime via
1777 /selinux/compat_net.
4e5ab4cb 1778
cd4f0ef7 1779 serialnumber [BUGS=X86-32]
1da177e4 1780
1da177e4
LT
1781 shapers= [NET]
1782 Maximal number of shapers.
a9913044 1783
1da177e4
LT
1784 sim710= [SCSI,HW]
1785 See header of drivers/scsi/sim710.c.
1786
1787 simeth= [IA-64]
1788 simscsi=
a9913044 1789
1da177e4
LT
1790 slram= [HW,MTD]
1791
f0630fff
CL
1792 slub_debug[=options[,slabs]] [MM, SLUB]
1793 Enabling slub_debug allows one to determine the
1794 culprit if slab objects become corrupted. Enabling
1795 slub_debug can create guard zones around objects and
1796 may poison objects when not in use. Also tracks the
1797 last alloc / free. For more information see
1798 Documentation/vm/slub.txt.
c1aee215
CL
1799
1800 slub_max_order= [MM, SLUB]
f0630fff
CL
1801 Determines the maximum allowed order for slabs.
1802 A high setting may cause OOMs due to memory
1803 fragmentation. For more information see
1804 Documentation/vm/slub.txt.
c1aee215
CL
1805
1806 slub_min_objects= [MM, SLUB]
f0630fff
CL
1807 The minimum number of objects per slab. SLUB will
1808 increase the slab order up to slub_max_order to
1809 generate a sufficiently large slab able to contain
1810 the number of objects indicated. The higher the number
1811 of objects the smaller the overhead of tracking slabs
1812 and the less frequently locks need to be acquired.
c1aee215
CL
1813 For more information see Documentation/vm/slub.txt.
1814
1815 slub_min_order= [MM, SLUB]
1816 Determines the mininum page order for slabs. Must be
f0630fff 1817 lower than slub_max_order.
c1aee215
CL
1818 For more information see Documentation/vm/slub.txt.
1819
1820 slub_nomerge [MM, SLUB]
f0630fff 1821 Disable merging of slabs with similar size. May be
c1aee215 1822 necessary if there is some reason to distinguish
f0630fff
CL
1823 allocs to different slabs. Debug options disable
1824 merging on their own.
c1aee215
CL
1825 For more information see Documentation/vm/slub.txt.
1826
1da177e4
LT
1827 smart2= [HW]
1828 Format: <io1>[,<io2>[,...,<io8>]]
1829
cd4f0ef7 1830 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1831 attempt to substitute SMP alternatives once at boot.
1832
d0d4f69b
BH
1833 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1834 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1835 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1836 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1837 smsc-ircc2.ircc_irq= [HW] IRQ line
1838 smsc-ircc2.ircc_dma= [HW] DMA channel
1839 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1840 0: Toshiba Satellite 1800 (GP data pin select)
1841 1: Fast pin select (default)
1842 2: ATC IRMode
1843
1da177e4
LT
1844 snd-ad1816a= [HW,ALSA]
1845
1846 snd-ad1848= [HW,ALSA]
1847
1848 snd-ali5451= [HW,ALSA]
1849
1850 snd-als100= [HW,ALSA]
1851
1852 snd-als4000= [HW,ALSA]
1853
1854 snd-azt2320= [HW,ALSA]
1855
1856 snd-cmi8330= [HW,ALSA]
1857
1858 snd-cmipci= [HW,ALSA]
1859
1860 snd-cs4231= [HW,ALSA]
1861
1862 snd-cs4232= [HW,ALSA]
1863
1864 snd-cs4236= [HW,ALSA]
1865
1866 snd-cs4281= [HW,ALSA]
1867
1868 snd-cs46xx= [HW,ALSA]
1869
1870 snd-dt019x= [HW,ALSA]
1871
1872 snd-dummy= [HW,ALSA]
1873
1874 snd-emu10k1= [HW,ALSA]
1875
1876 snd-ens1370= [HW,ALSA]
1877
1878 snd-ens1371= [HW,ALSA]
1879
1880 snd-es968= [HW,ALSA]
1881
1882 snd-es1688= [HW,ALSA]
1883
1884 snd-es18xx= [HW,ALSA]
1885
1886 snd-es1938= [HW,ALSA]
1887
1888 snd-es1968= [HW,ALSA]
1889
1890 snd-fm801= [HW,ALSA]
1891
1892 snd-gusclassic= [HW,ALSA]
1893
1894 snd-gusextreme= [HW,ALSA]
1895
1896 snd-gusmax= [HW,ALSA]
1897
1898 snd-hdsp= [HW,ALSA]
1899
1900 snd-ice1712= [HW,ALSA]
1901
1902 snd-intel8x0= [HW,ALSA]
1903
1904 snd-interwave= [HW,ALSA]
1905
1906 snd-interwave-stb=
1907 [HW,ALSA]
1908
1909 snd-korg1212= [HW,ALSA]
1910
1911 snd-maestro3= [HW,ALSA]
1912
1913 snd-mpu401= [HW,ALSA]
1914
1915 snd-mtpav= [HW,ALSA]
1916
1917 snd-nm256= [HW,ALSA]
1918
1919 snd-opl3sa2= [HW,ALSA]
1920
1921 snd-opti92x-ad1848=
1922 [HW,ALSA]
1923
1924 snd-opti92x-cs4231=
1925 [HW,ALSA]
1926
1927 snd-opti93x= [HW,ALSA]
1928
1929 snd-pmac= [HW,ALSA]
1930
1931 snd-rme32= [HW,ALSA]
1932
1933 snd-rme96= [HW,ALSA]
1934
1935 snd-rme9652= [HW,ALSA]
1936
1937 snd-sb8= [HW,ALSA]
1938
1939 snd-sb16= [HW,ALSA]
1940
1941 snd-sbawe= [HW,ALSA]
1942
1943 snd-serial= [HW,ALSA]
1944
1945 snd-sgalaxy= [HW,ALSA]
1946
1947 snd-sonicvibes= [HW,ALSA]
1948
1949 snd-sun-amd7930=
1950 [HW,ALSA]
1951
1952 snd-sun-cs4231= [HW,ALSA]
1953
1954 snd-trident= [HW,ALSA]
1955
1956 snd-usb-audio= [HW,ALSA,USB]
1957
1958 snd-via82xx= [HW,ALSA]
1959
1960 snd-virmidi= [HW,ALSA]
1961
1962 snd-wavefront= [HW,ALSA]
1963
1964 snd-ymfpci= [HW,ALSA]
a9913044 1965
1da177e4
LT
1966 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1967 See Documentation/sonypi.txt
1968
1969 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1970 See Documentation/specialix.txt.
1971
1972 spia_io_base= [HW,MTD]
1973 spia_fio_base=
1974 spia_pedr=
1975 spia_peddr=
1976
1977 sscape= [HW,OSS]
1978 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1979
1da177e4
LT
1980 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1981 See Documentation/scsi/st.txt.
1982
1da177e4
LT
1983 sti= [PARISC,HW]
1984 Format: <num>
1985 Set the STI (builtin display/keyboard on the HP-PARISC
1986 machines) console (graphic card) which should be used
1987 as the initial boot-console.
1988 See also comment in drivers/video/console/sticore.c.
1989
1990 sti_font= [HW]
1991 See comment in drivers/video/console/sticore.c.
1992
1993 stifb= [HW]
1994 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1995
42a7fc4a
GB
1996 sunrpc.pool_mode=
1997 [NFS]
1998 Control how the NFS server code allocates CPUs to
1999 service thread pools. Depending on how many NICs
2000 you have and where their interrupts are bound, this
2001 option will affect which CPUs will do NFS serving.
2002 Note: this parameter cannot be changed while the
2003 NFS server is running.
2004
2005 auto the server chooses an appropriate mode
2006 automatically using heuristics
2007 global a single global pool contains all CPUs
2008 percpu one pool for each CPU
2009 pernode one pool for each NUMA node (equivalent
2010 to global on non-NUMA machines)
2011
1da177e4 2012 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2013
1da177e4
LT
2014 switches= [HW,M68k]
2015
2016 sym53c416= [HW,SCSI]
2017 See header of drivers/scsi/sym53c416.c.
2018
5d6f647f
IM
2019 sysrq_always_enabled
2020 [KNL]
2021 Ignore sysrq setting - this boot parameter will
2022 neutralize any effect of /proc/sys/kernel/sysrq.
2023 Useful for debugging.
2024
1da177e4
LT
2025 t128= [HW,SCSI]
2026 See header of drivers/scsi/t128.c.
2027
2028 tdfx= [HW,DRM]
2029
2030 thash_entries= [KNL,NET]
2031 Set number of hash buckets for TCP connection
2032
f8707ec9
LB
2033 thermal.act= [HW,ACPI]
2034 -1: disable all active trip points in all thermal zones
2035 <degrees C>: override all lowest active trip points
2036
c52a7419
LB
2037 thermal.crt= [HW,ACPI]
2038 -1: disable all critical trip points in all thermal zones
2039 <degrees C>: lower all critical trip points
2040
f5487145
LB
2041 thermal.nocrt= [HW,ACPI]
2042 Set to disable actions on ACPI thermal zone
2043 critical and hot trip points.
2044
72b33ef8
LB
2045 thermal.off= [HW,ACPI]
2046 1: disable ACPI thermal control
2047
a70cdc52
LB
2048 thermal.psv= [HW,ACPI]
2049 -1: disable all passive trip points
2050 <degrees C>: override all passive trip points to this value
2051
730ff34d
LB
2052 thermal.tzp= [HW,ACPI]
2053 Specify global default ACPI thermal zone polling rate
2054 <deci-seconds>: poll all this frequency
2055 0: no polling (default)
2056
1da177e4
LT
2057 tipar.timeout= [HW,PPT]
2058 Set communications timeout in tenths of a second
2059 (default 15).
2060
2061 tipar.delay= [HW,PPT]
2062 Set inter-bit delay in microseconds (default 10).
2063
1da177e4
LT
2064 tmscsim= [HW,SCSI]
2065 See comment before function dc390_setup() in
2066 drivers/scsi/tmscsim.c.
2067
2068 tp720= [HW,PS2]
2069
2070 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2071 Format:
2072 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2073
a9913044
RD
2074 turbografx.map[2|3]= [HW,JOY]
2075 TurboGraFX parallel port interface
2076 Format:
2077 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2078 See also Documentation/input/joystick-parport.txt
2079
2080 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2081 See header of drivers/scsi/u14-34f.c.
2082
2083 uart401= [HW,OSS]
2084 Format: <io>,<irq>
2085
2086 uart6850= [HW,OSS]
2087 Format: <io>,<irq>
2088
5f8364b7
AS
2089 uhci-hcd.ignore_oc=
2090 [USB] Ignore overcurrent events (default N).
2091 Some badly-designed motherboards generate lots of
2092 bogus events, for ports that aren't wired to
2093 anything. Set this parameter to avoid log spamming.
2094 Note that genuine overcurrent events won't be
2095 reported either.
2096
b5e795f8
AS
2097 usbcore.autosuspend=
2098 [USB] The autosuspend time delay (in seconds) used
2099 for newly-detected USB devices (default 2). This
2100 is the time required before an idle device will be
2101 autosuspended. Devices for which the delay is set
eaafbc3a 2102 to a negative value won't be autosuspended at all.
b5e795f8 2103
1da177e4
LT
2104 usbhid.mousepoll=
2105 [USBHID] The interval which mice are to be polled at.
a9913044 2106
cd4f0ef7 2107 vdso= [X86-32,SH,x86-64]
1dbf527c 2108 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2109 vdso=1: enable VDSO (default)
2110 vdso=0: disable VDSO mapping
2111
af65d648
RM
2112 vdso32= [X86-32,X86-64]
2113 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2114 vdso32=1: enable 32-bit VDSO (default)
2115 vdso32=0: disable 32-bit VDSO mapping
2116
d080d397
YI
2117 vector= [IA-64,SMP]
2118 vector=percpu: enable percpu vector domain
2119
1da177e4
LT
2120 video= [FB] Frame buffer configuration
2121 See Documentation/fb/modedb.txt.
2122
cd4f0ef7 2123 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2124 See Documentation/i386/boot.txt and
2125 Documentation/svga.txt.
1da177e4
LT
2126 Use vga=ask for menu.
2127 This is actually a boot loader parameter; the value is
2128 passed to the kernel using a special protocol.
2129
a9913044 2130 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2131 size of <nn>. This can be used to increase the
2132 minimum size (128MB on x86). It can also be used to
2133 decrease the size and leave more room for directly
2134 mapped kernel RAM.
2135
585c3047
PO
2136 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2137 Format: <command>
1da177e4 2138
585c3047
PO
2139 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2140 Format: <command>
2141
2142 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2143 Format: <command>
a9913044 2144
1da177e4
LT
2145 waveartist= [HW,OSS]
2146 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2147
1da177e4
LT
2148 wd33c93= [HW,SCSI]
2149 See header of drivers/scsi/wd33c93.c.
2150
2151 wd7000= [HW,SCSI]
2152 See header of drivers/scsi/wd7000.c.
2153
2154 wdt= [WDT] Watchdog
8dfe9c21 2155 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2156
2157 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2158 xd_geo= See header of drivers/block/xd.c.
2159
2160 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2161 Format:
2162 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2163
a62eaf15
AK
2164 norandmaps Don't use address space randomization
2165 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2166
a9913044 2167______________________________________________________________________
1da177e4
LT
2168
2169TODO:
2170
2171 Add documentation for ALSA options.
2172 Add more DRM drivers.