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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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LT
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
LT
774
775 ide?= [HW] (E)IDE subsystem
f01674e4 776 Format: ide?=ata66 or chipset specific parameters.
1c10e938 777 See Documentation/ide/ide.txt.
a9913044 778
1da177e4 779 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 780 See Documentation/ide/ide.txt.
1da177e4 781
f039b754
AK
782 idle= [X86]
783 Format: idle=poll or idle=mwait
784 Poll forces a polling idle loop that can slightly improves the performance
785 of waking up a idle CPU, but will use a lot of power and make the system
786 run hot. Not recommended.
787 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
788 to not use it because it doesn't save as much power as a normal idle
789 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
790 as idle=poll.
a9913044 791
594765a7
DC
792 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
793 Claim all unknown PCI IDE storage controllers.
794
79290822
IM
795 ignore_loglevel [KNL]
796 Ignore loglevel setting - this will print /all/
797 kernel messages to the console. Useful for debugging.
798
1da177e4
LT
799 ihash_entries= [KNL]
800 Set number of hash buckets for inode cache.
801
802 in2000= [HW,SCSI]
803 See header of drivers/scsi/in2000.c.
804
805 init= [KNL]
806 Format: <full_path>
807 Run specified binary instead of /sbin/init as init
808 process.
809
810 initcall_debug [KNL] Trace initcalls as they are executed. Useful
811 for working out where the kernel is dying during
812 startup.
813
814 initrd= [BOOT] Specify the location of the initial ramdisk
815
816 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
817 Format: <irq>
818
819 inttest= [IA64]
820
b552da87
PM
821 iommu= [x86]
822 off
823 force
824 noforce
825 biomerge
826 panic
827 nopanic
828 merge
829 nomerge
830 forcesac
831 soft
832
833
ba395927
KA
834 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
835 off
836 Disable intel iommu driver.
837 igfx_off [Default Off]
838 By default, gfx is mapped as normal device. If a gfx
839 device has a dedicated DMAR unit, the DMAR unit is
840 bypassed by not enabling DMAR with this option. In
841 this case, gfx device will use physical address for
842 DMA.
7d3b03ce
KA
843 forcedac [x86_64]
844 With this option iommu will not optimize to look
845 for io virtual address below 32 bit forcing dual
846 address cycle on pci bus for cards supporting greater
847 than 32 bit addressing. The default is to look
848 for translation below 32 bit and if not available
849 then look in the higher range.
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
cd4f0ef7 957 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 958 disabled it.
1da177e4 959
cd4f0ef7 960 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
961 C2 power state.
962
fcb71f6f
FC
963 libata.dma= [LIBATA] DMA control
964 libata.dma=0 Disable all PATA and SATA DMA
965 libata.dma=1 PATA and SATA Disk DMA only
966 libata.dma=2 ATAPI (CDROM) DMA only
967 libata.dma=4 Compact Flash DMA only
968 Combinations also work, so libata.dma=3 enables DMA
969 for disks and CDROMs, but not CFs.
970
78e70c23
DJ
971 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
972 when set.
973 Format: <int>
974
33267325
TH
975 libata.force= [LIBATA] Force configurations. The format is comma
976 separated list of "[ID:]VAL" where ID is
977 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
978 matching port, link or device. Basically, it matches
979 the ATA ID string printed on console by libata. If
980 the whole ID part is omitted, the last PORT and DEVICE
981 values are used. If ID hasn't been specified yet, the
982 configuration applies to all ports, links and devices.
983
984 If only DEVICE is omitted, the parameter applies to
985 the port and all links and devices behind it. DEVICE
986 number of 0 either selects the first device or the
987 first fan-out link behind PMP device. It does not
988 select the host link. DEVICE number of 15 selects the
989 host link and device attached to it.
990
991 The VAL specifies the configuration to force. As long
992 as there's no ambiguity shortcut notation is allowed.
993 For example, both 1.5 and 1.5G would work for 1.5Gbps.
994 The following configurations can be forced.
995
996 * Cable type: 40c, 80c, short40c, unk, ign or sata.
997 Any ID with matching PORT is used.
998
999 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1000
1001 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1002 udma[/][16,25,33,44,66,100,133] notation is also
1003 allowed.
1004
1005 * [no]ncq: Turn on or off NCQ.
1006
1007 If there are multiple matching configurations changing
1008 the same attribute, the last one is used.
1009
1da177e4
LT
1010 load_ramdisk= [RAM] List of ramdisks to load from floppy
1011 See Documentation/ramdisk.txt.
1012
a6b25b67
RD
1013 lockd.nlm_grace_period=P [NFS] Assign grace period.
1014 Format: <integer>
1da177e4 1015
a6b25b67
RD
1016 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1017 Format: <integer>
1018
1019 lockd.nlm_timeout=T [NFS] Assign timeout value.
1020 Format: <integer>
1021
1022 lockd.nlm_udpport=M [NFS] Assign UDP port.
1023 Format: <integer>
1da177e4
LT
1024
1025 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1026 Format: <irq>
1027
1028 loglevel= All Kernel Messages with a loglevel smaller than the
1029 console loglevel will be printed to the console. It can
1030 also be changed with klogd or other programs. The
1031 loglevels are defined as follows:
1032
1033 0 (KERN_EMERG) system is unusable
1034 1 (KERN_ALERT) action must be taken immediately
1035 2 (KERN_CRIT) critical conditions
1036 3 (KERN_ERR) error conditions
1037 4 (KERN_WARNING) warning conditions
1038 5 (KERN_NOTICE) normal but significant condition
1039 6 (KERN_INFO) informational
1040 7 (KERN_DEBUG) debug-level messages
1041
1042 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1043 Format: { n | nk | nM }
1044 n must be a power of two. The default size
1045 is set in the kernel config file.
1da177e4 1046
accaa24c
RD
1047 logo.nologo [FB] Disables display of the built-in Linux logo.
1048 This may be used to provide more screen space for
1049 kernel log messages and is useful when debugging
1050 kernel boot problems.
1051
1da177e4
LT
1052 lp=0 [LP] Specify parallel ports to use, e.g,
1053 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1054 lp=reset first parallel port). 'lp=0' disables the
1055 lp=auto printer driver. 'lp=reset' (which can be
1056 specified in addition to the ports) causes
1057 attached printers to be reset. Using
1058 lp=port1,port2,... specifies the parallel ports
1059 to associate lp devices with, starting with
1060 lp0. A port specification may be 'none' to skip
1061 that lp device, or a parport name such as
1062 'parport0'. Specifying 'lp=auto' instead of a
1063 port specification list means that device IDs
1064 from each port should be examined, to see if
1065 an IEEE 1284-compliant printer is attached; if
1066 so, the driver will manage that printer.
1067 See also header of drivers/char/lp.c.
1068
1069 lpj=n [KNL]
1070 Sets loops_per_jiffy to given constant, thus avoiding
1071 time-consuming boot-time autodetection (up to 250 ms per
1072 CPU). 0 enables autodetection (default). To determine
1073 the correct value for your kernel, boot with normal
1074 autodetection and see what value is printed. Note that
1075 on SMP systems the preset will be applied to all CPUs,
1076 which is likely to cause problems if your CPUs need
1077 significantly divergent settings. An incorrect value
1078 will cause delays in the kernel to be wrong, leading to
1079 unpredictable I/O errors and other breakage. Although
1080 unlikely, in the extreme case this might damage your
1081 hardware.
1082
1083 ltpc= [NET]
1084 Format: <io>,<irq>,<dma>
1085
a9913044
RD
1086 mac5380= [HW,SCSI] Format:
1087 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1088
a9913044
RD
1089 mac53c9x= [HW,SCSI] Format:
1090 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1091
a9913044
RD
1092 machvec= [IA64] Force the use of a particular machine-vector
1093 (machvec) in a generic kernel.
1094 Example: machvec=hpzx1_swiotlb
1da177e4 1095
a9913044 1096 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1097 be mounted
1098 Format: <1-256>
1099
1100 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1101 should make use of. maxcpus=n : n >= 0 limits the
1102 kernel to using 'n' processors. n=0 is a special case,
1103 it is equivalent to "nosmp", which also disables
1104 the IO APIC.
1da177e4 1105
2b2c3750
BP
1106 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1107 equal to this physical address is ignored.
1108
a9913044 1109 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1110 Should be between 1 and 2^32-1.
1111
1112 max_report_luns=
a9913044 1113 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1114 Should be between 1 and 16384.
1115
1da177e4
LT
1116 mcatest= [IA-64]
1117
cd4f0ef7 1118 mce [X86-32] Machine Check Exception
1da177e4 1119
909dd324
AK
1120 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1121
1da177e4
LT
1122 md= [HW] RAID subsystems devices and level
1123 See Documentation/md.txt.
a9913044 1124
1da177e4
LT
1125 mdacon= [MDA]
1126 Format: <first>,<last>
1127 Specifies range of consoles to be captured by the MDA.
a9913044 1128
1da177e4
LT
1129 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1130 Amount of memory to be used when the kernel is not able
1131 to see the whole system memory or for test.
cd4f0ef7 1132 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1133 address space collisions. Without memmap= PCI devices
1134 could be placed at addresses belonging to unused RAM.
1135
cd4f0ef7 1136 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1137 memory.
1138
cd4f0ef7 1139 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1140 E820 memory map, as specified by the user.
1141 Such memmap=exactmap lines can be constructed based on
1142 BIOS output or other requirements. See the memmap=nn@ss
1143 option description.
1144
1145 memmap=nn[KMG]@ss[KMG]
1146 [KNL] Force usage of a specific region of memory
1147 Region of memory to be used, from ss to ss+nn.
1148
1149 memmap=nn[KMG]#ss[KMG]
1150 [KNL,ACPI] Mark specific memory as ACPI data.
1151 Region of memory to be used, from ss to ss+nn.
1152
1153 memmap=nn[KMG]$ss[KMG]
1154 [KNL,ACPI] Mark specific memory as reserved.
1155 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1156 Example: Exclude memory from 0x18690000-0x1869ffff
1157 memmap=64K$0x18690000
1158 or
1159 memmap=0x10000$0x18690000
1da177e4 1160
c64df707
YL
1161 memtest= [KNL,X86_64] Enable memtest
1162 Format: <integer>
1163 range: 0,4 : pattern number
1164 default : 0 <disable>
1165
1da177e4
LT
1166 meye.*= [HW] Set MotionEye Camera parameters
1167 See Documentation/video4linux/meye.txt.
1168
8f36881b
AS
1169 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1170 Multi-Function General Purpose Timers on AMD Geode
1171 platforms.
1172
e6c4dc6c
WT
1173 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1174 the BIOS has incorrectly applied a workaround. TinyBIOS
1175 version 0.98 is known to be affected, 0.99 fixes the
1176 problem by letting the user disable the workaround.
1177
1da177e4
LT
1178 mga= [HW,DRM]
1179
1180 mousedev.tap_time=
1181 [MOUSE] Maximum time between finger touching and
1182 leaving touchpad surface for touch to be considered
1183 a tap and be reported as a left button click (for
1184 touchpads working in absolute mode only).
1185 Format: <msecs>
1186 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1187 reporting absolute coordinates, such as tablets
1188 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1189 reporting absolute coordinates, such as tablets
1190
1191 mpu401= [HW,OSS]
1192 Format: <io>,<irq>
1193
1194 MTD_Partition= [MTD]
1195 Format: <name>,<region-number>,<size>,<offset>
1196
a9913044
RD
1197 MTD_Region= [MTD] Format:
1198 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1199
1200 mtdparts= [MTD]
c8facbb6 1201 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1202
1203 mtouchusb.raw_coordinates=
a9913044
RD
1204 [HW] Make the MicroTouch USB driver use raw coordinates
1205 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1206
1207 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1208
1209 NCR_D700= [HW,SCSI]
1210 See header of drivers/scsi/NCR_D700.c.
1211
1212 ncr5380= [HW,SCSI]
1213
1214 ncr53c400= [HW,SCSI]
1215
1216 ncr53c400a= [HW,SCSI]
1217
1218 ncr53c406a= [HW,SCSI]
1219
1220 ncr53c8xx= [HW,SCSI]
1221
1222 netdev= [NET] Network devices parameters
1223 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1224 Note that mem_start is often overloaded to mean
1225 something different and driver-specific.
a9913044
RD
1226 This usage is only documented in each driver source
1227 file if at all.
1228
1da177e4 1229 nfsaddrs= [NFS]
6ded55da 1230 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1231
1232 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1233 See Documentation/filesystems/nfsroot.txt.
1da177e4 1234
a72b4422
TM
1235 nfs.callback_tcpport=
1236 [NFS] set the TCP port on which the NFSv4 callback
1237 channel should listen.
1238
58df095b
TM
1239 nfs.idmap_cache_timeout=
1240 [NFS] set the maximum lifetime for idmapper cache
1241 entries.
1242
f43bf0be
TM
1243 nfs.enable_ino64=
1244 [NFS] enable 64-bit inode numbers.
1245 If zero, the NFS client will fake up a 32-bit inode
1246 number for the readdir() and stat() syscalls instead
1247 of returning the full 64-bit number.
1248 The default is to return 64-bit inode numbers.
1249
e7ba176b
HS
1250 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1251 when a NMI is triggered.
1252 Format: [state][,regs][,debounce][,die]
1253
cd4f0ef7 1254 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1255
cd4f0ef7 1256 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1257 emulation library even if a 387 maths coprocessor
1258 is present.
1259
c1aee215
CL
1260 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1261 caches in the slab allocator. Saves per-node memory,
1262 but will impact performance.
3395ee05 1263
a9913044
RD
1264 noalign [KNL,ARM]
1265
1da177e4
LT
1266 noapic [SMP,APIC] Tells the kernel to not make use of any
1267 IOAPICs that may be present in the system.
1268
1da177e4
LT
1269 nobats [PPC] Do not use BATs for mapping kernel lowmem
1270 on "Classic" PPC cores.
1271
1272 nocache [ARM]
a9913044 1273
163ecdff
SN
1274 nodelayacct [KNL] Disable per-task delay accounting
1275
1da177e4
LT
1276 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1277
8b2cb7a8
HY
1278 noefi [X86-32,X86-64] Disable EFI runtime services support.
1279
1da177e4
LT
1280 noexec [IA-64]
1281
cd4f0ef7 1282 noexec [X86-32,X86-64]
1da177e4
LT
1283 noexec=on: enable non-executable mappings (default)
1284 noexec=off: disable nn-executable mappings
1285
cd4f0ef7 1286 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1287 register save and restore. The kernel will only save
1288 legacy floating-point registers on task switch.
1da177e4 1289
191679fd
AK
1290 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1291
1da177e4 1292 nohlt [BUGS=ARM]
a9913044 1293
cd4f0ef7 1294 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1295 instruction doesn't work correctly and not to
1296 use it.
1297
1298 nohalt [IA-64] Tells the kernel not to use the power saving
1299 function PAL_HALT_LIGHT when idle. This increases
1300 power-consumption. On the positive side, it reduces
1301 interrupt wake-up latency, which may improve performance
1302 in certain environments such as networked servers or
1303 real-time systems.
1304
79bf2bb3
TG
1305 nohz= [KNL] Boottime enable/disable dynamic ticks
1306 Valid arguments: on, off
1307 Default: on
1308
cd4f0ef7 1309 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1310
cd4f0ef7 1311 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1312 disable unhandled interrupt sources.
1313
cd4f0ef7 1314 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1315 broken timer IRQ sources.
1316
1da177e4
LT
1317 noisapnp [ISAPNP] Disables ISA PnP code.
1318
1319 noinitrd [RAM] Tells the kernel not to load any configured
1320 initial RAM disk.
1321
1322 nointroute [IA-64]
1323
0aa366f3
TL
1324 nojitter [IA64] Disables jitter checking for ITC timers.
1325
cd4f0ef7 1326 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1327
cd4f0ef7 1328 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1329
1da177e4
LT
1330 noltlbs [PPC] Do not use large page/tlb entries for kernel
1331 lowmem mapping on PPC40x.
1332
312f1f01
H
1333 nomca [IA-64] Disable machine check abort handling
1334
cd4f0ef7 1335 nomce [X86-32] Machine Check Exception
abe37e5a 1336
83d7384f
AS
1337 nomfgpt [X86-32] Disable Multi-Function General Purpose
1338 Timer usage (for AMD Geode machines).
1339
cd4f0ef7 1340 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1341
cd4f0ef7 1342 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1343 with UP alternatives
1344
1da177e4
LT
1345 noresidual [PPC] Don't use residual data on PReP machines.
1346
a9913044
RD
1347 noresume [SWSUSP] Disables resume and restores original swap
1348 space.
1349
1da177e4
LT
1350 no-scroll [VGA] Disables scrollback.
1351 This is required for the Braillex ib80-piezo Braille
1352 reader made by F.H. Papenmeier (Germany).
1353
1354 nosbagart [IA-64]
1355
cd4f0ef7 1356 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1357
61ec7567
LB
1358 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1359 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1360
97842216
DJ
1361 nosoftlockup [KNL] Disable the soft-lockup detector.
1362
1da177e4
LT
1363 nosync [HW,M68K] Disables sync negotiation for all devices.
1364
cd4f0ef7 1365 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1366
1367 nousb [USB] Disable the USB subsystem
1368
1369 nowb [ARM]
a9913044 1370
a6c75b86
FY
1371 nptcg= [IA64] Override max number of concurrent global TLB
1372 purges which is reported from either PAL_VM_SUMMARY or
1373 SAL PALO.
1374
f0c0b2b8
KH
1375 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1376 one of ['zone', 'node', 'default'] can be specified
1377 This can be set from sysctl after boot.
1378 See Documentation/sysctl/vm.txt for details.
1379
a61c2d78
DJ
1380 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1381
1da177e4
LT
1382 opl3= [HW,OSS]
1383 Format: <io>
1384
1da177e4
LT
1385 oprofile.timer= [HW]
1386 Use timer interrupt instead of performance counters
1387
1da177e4
LT
1388 osst= [HW,SCSI] SCSI Tape Driver
1389 Format: <buffer_size>,<write_threshold>
1390 See also Documentation/scsi/st.txt.
1391
1392 panic= [KNL] Kernel behaviour on panic
1393 Format: <timeout>
1394
1395 parkbd.port= [HW] Parallel port number the keyboard adapter is
1396 connected to, default is 0.
1397 Format: <parport#>
1398 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1399 0 for XT, 1 for AT (default is AT).
a9913044
RD
1400 Format: <mode>
1401
1402 parport= [HW,PPT] Specify parallel ports. 0 disables.
1403 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1404 Use 'auto' to force the driver to use any
1405 IRQ/DMA settings detected (the default is to
1406 ignore detected IRQ/DMA settings because of
1407 possible conflicts). You can specify the base
1408 address, IRQ, and DMA settings; IRQ and DMA
1409 should be numbers, or 'auto' (for using detected
1410 settings on that particular port), or 'nofifo'
1411 (to avoid using a FIFO even if it is detected).
1412 Parallel ports are assigned in the order they
1413 are specified on the command line, starting
1414 with parport0.
1415
1416 parport_init_mode= [HW,PPT]
1417 Configure VIA parallel port to operate in
1418 a specific mode. This is necessary on Pegasos
1419 computer where firmware has no options for setting
1420 up parallel port mode and sets it to spp.
1421 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1422 Format: [spp|ps2|epp|ecp|ecpepp]
1423
a9913044
RD
1424 pas2= [HW,OSS] Format:
1425 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1426
1da177e4
LT
1427 pas16= [HW,SCSI]
1428 See header of drivers/scsi/pas16.c.
1429
dd287796
AM
1430 pause_on_oops=
1431 Halt all CPUs after the first oops has been printed for
1432 the specified number of seconds. This is to be used if
1433 your oopses keep scrolling off the screen.
1434
1da177e4
LT
1435 pcbit= [HW,ISDN]
1436
1437 pcd. [PARIDE]
1438 See header of drivers/block/paride/pcd.c.
1439 See also Documentation/paride.txt.
1440
a9913044 1441 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1442 off [X86-32] don't probe for the PCI bus
1443 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1444 the hardware directly. Use this if your machine
1445 has a non-standard PCI host bridge.
cd4f0ef7 1446 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1447 hardware access methods are allowed. Use this
1448 if you experience crashes upon bootup and you
1449 suspect they are caused by the BIOS.
cd4f0ef7 1450 conf1 [X86-32] Force use of PCI Configuration
a9913044 1451 Mechanism 1.
cd4f0ef7 1452 conf2 [X86-32] Force use of PCI Configuration
a9913044 1453 Mechanism 2.
7f785763
RD
1454 noaer [PCIE] If the PCIEAER kernel config parameter is
1455 enabled, this kernel boot option can be used to
1456 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1457 nodomains [PCI] Disable support for multiple PCI
1458 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1459 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1460 Configuration
309e57df
MW
1461 nomsi [MSI] If the PCI_MSI kernel config parameter is
1462 enabled, this kernel boot option can be used to
1463 disable the use of MSI interrupts system-wide.
cd4f0ef7 1464 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1465 routing table. These calls are known to be buggy
1466 on several machines and they hang the machine
1467 when used, but on other computers it's the only
1468 way to get the interrupt routing table. Try
1469 this option if the kernel is unable to allocate
1470 IRQs or discover secondary PCI buses on your
1471 motherboard.
cd4f0ef7 1472 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1473 Use with caution as certain devices share
1474 address decoders between ROMs and other
1475 resources.
cd4f0ef7 1476 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1477 assigned automatically to PCI devices. You can
1478 make the kernel exclude IRQs of your ISA cards
1479 this way.
cd4f0ef7 1480 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1481 of the PIRQ table (normally generated
1482 by the BIOS) if it is outside the
1483 F0000h-100000h range.
cd4f0ef7 1484 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1485 useful if the kernel is unable to find your
1486 secondary buses and you want to tell it
1487 explicitly which ones they are.
cd4f0ef7 1488 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1489 numbers ourselves, overriding
1490 whatever the firmware may have done.
cd4f0ef7 1491 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1492 in the BIOS $PIR table. This is needed on
1493 some systems with broken BIOSes, notably
1494 some HP Pavilion N5400 and Omnibook XE3
1495 notebooks. This will have no effect if ACPI
1496 IRQ routing is enabled.
cd4f0ef7 1497 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1498 or for PCI scanning.
62f420f8
GH
1499 use_crs [X86-32] Use _CRS for PCI resource
1500 allocation.
a9913044
RD
1501 routeirq Do IRQ routing for all PCI devices.
1502 This is normally done in pci_enable_device(),
1503 so this option is a temporary workaround
1504 for broken drivers that don't call it.
1505 firmware [ARM] Do not re-enumerate the bus but instead
1506 just use the configuration from the
1507 bootloader. This is currently used on
1508 IXP2000 systems where the bus has to be
1509 configured a certain way for adjunct CPUs.
0637a70a
AK
1510 noearly [X86] Don't do any early type 1 scanning.
1511 This might help on some broken boards which
1512 machine check when some devices' config space
1513 is read. But various workarounds are disabled
1514 and some IOMMU drivers will not work.
6b4b78fe
MD
1515 bfsort Sort PCI devices into breadth-first order.
1516 This sorting is done to get a device
1517 order compatible with older (<= 2.4) kernels.
1518 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1519 cbiosize=nn[KMG] The fixed amount of bus space which is
1520 reserved for the CardBus bridge's IO window.
1521 The default value is 256 bytes.
1522 cbmemsize=nn[KMG] The fixed amount of bus space which is
1523 reserved for the CardBus bridge's memory
1524 window. The default value is 64 megabytes.
6b4b78fe 1525
1da177e4
LT
1526 pcmv= [HW,PCMCIA] BadgePAD 4
1527
1528 pd. [PARIDE]
1529 See Documentation/paride.txt.
1530
1531 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1532 boot time.
1533 Format: { 0 | 1 }
1534 See arch/parisc/kernel/pdc_chassis.c
1535
1536 pf. [PARIDE]
1537 See Documentation/paride.txt.
1538
1539 pg. [PARIDE]
1540 See Documentation/paride.txt.
1541
1542 pirq= [SMP,APIC] Manual mp-table setup
1543 See Documentation/i386/IO-APIC.txt.
1544
1545 plip= [PPT,NET] Parallel port network link
1546 Format: { parport<nr> | timid | 0 }
1547 See also Documentation/parport.txt.
1548
1549 pnpacpi= [ACPI]
1550 { off }
1551
1552 pnpbios= [ISAPNP]
1553 { on | off | curr | res | no-curr | no-res }
1554
1555 pnp_reserve_irq=
1556 [ISAPNP] Exclude IRQs for the autoconfiguration
1557
1558 pnp_reserve_dma=
1559 [ISAPNP] Exclude DMAs for the autoconfiguration
1560
1561 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1562 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1563
1564 pnp_reserve_mem=
a9913044
RD
1565 [ISAPNP] Exclude memory regions for the
1566 autoconfiguration.
1da177e4
LT
1567 Ranges are in pairs (memory base and size).
1568
45807a1d
IM
1569 print-fatal-signals=
1570 [KNL] debug: print fatal signals
1571 print-fatal-signals=1: print segfault info to
1572 the kernel console.
1573 default: off.
1574
e84845c4
RD
1575 printk.time= Show timing data prefixed to each printk message line
1576 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1577
1da177e4 1578 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1579 Format: [schedule,]<number>
1580 Param: "schedule" - profile schedule points.
1581 Param: <number> - step/bucket size as a power of 2 for
1582 statistical time based profiling.
b3da2a73
MG
1583 Param: "sleep" - profile D-state sleeping (millisecs).
1584 Requires CONFIG_SCHEDSTATS
c0fe2e69 1585 Param: "kvm" - profile VM exits.
1da177e4 1586
a9913044 1587 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1588 Limit processor to maximum C-state
1589 max_cstate=9 overrides any DMI blacklist limit.
1590
41c0d868
LB
1591 processor.nocst [HW,ACPI]
1592 Ignore the _CST method to determine C-states,
1593 instead using the legacy FADT method
1594
1da177e4
LT
1595 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1596 before loading.
1597 See Documentation/ramdisk.txt.
1598
a9913044
RD
1599 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1600 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1601 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1602 per second.
a9913044
RD
1603 psmouse.resetafter= [HW,MOUSE]
1604 Try to reset the device after so many bad packets
1da177e4
LT
1605 (0 = never).
1606 psmouse.resolution=
1607 [HW,MOUSE] Set desired mouse resolution, in dpi.
1608 psmouse.smartscroll=
a9913044 1609 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1610 0 = disabled, 1 = enabled (default).
1611
1612 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1613 Format:
1614 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1615
1616 pt. [PARIDE]
1617 See Documentation/paride.txt.
1618
dc8c8587
KS
1619 pty.legacy_count=
1620 [KNL] Number of legacy pty's. Overwrites compiled-in
1621 default number.
1622
7d2c502f 1623 quiet [KNL] Disable most log messages
a9913044 1624
1da177e4
LT
1625 r128= [HW,DRM]
1626
1627 raid= [HW,RAID]
1628 See Documentation/md.txt.
1629
a9913044 1630 ramdisk_blocksize= [RAM]
1da177e4 1631 See Documentation/ramdisk.txt.
a9913044 1632
1da177e4 1633 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1634 See Documentation/ramdisk.txt.
1635
24aaef8d
RD
1636 rcupdate.blimit= [KNL,BOOT]
1637 Set maximum number of finished RCU callbacks to process
1638 in one batch.
21a1ea9e 1639
24aaef8d
RD
1640 rcupdate.qhimark= [KNL,BOOT]
1641 Set threshold of queued
21a1ea9e
DS
1642 RCU callbacks over which batch limiting is disabled.
1643
24aaef8d
RD
1644 rcupdate.qlowmark= [KNL,BOOT]
1645 Set threshold of queued RCU callbacks below which
1646 batch limiting is re-enabled.
21a1ea9e 1647
ffdfc409
OJ
1648 rdinit= [KNL]
1649 Format: <full_path>
1650 Run specified binary instead of /init from the ramdisk,
1651 used for early userspace startup. See initrd.
1652
cd4f0ef7 1653 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1654 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1655 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1656
1657 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1658
cd4f0ef7 1659 reservetop= [X86-32]
461a9aff
ZA
1660 Format: nn[KMG]
1661 Reserves a hole at the top of the kernel virtual
1662 address space.
1663
7e96287d
VG
1664 reset_devices [KNL] Force drivers to reset the underlying device
1665 during initialization.
1666
a9913044
RD
1667 resume= [SWSUSP]
1668 Specify the partition device for software suspend
1da177e4 1669
ecbd0da1
RW
1670 resume_offset= [SWSUSP]
1671 Specify the offset from the beginning of the partition
1672 given by "resume=" at which the swap header is located,
1673 in <PAGE_SIZE> units (needed only for swap files).
1674 See Documentation/power/swsusp-and-swap-files.txt
1675
0a7b35cb
MN
1676 retain_initrd [RAM] Keep initrd memory after extraction
1677
1da177e4
LT
1678 rhash_entries= [KNL,NET]
1679 Set number of hash buckets for route cache
1680
1681 riscom8= [HW,SERIAL]
1682 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1683
1684 ro [KNL] Mount root device read-only on boot
1685
1686 root= [KNL] Root filesystem
1687
1688 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1689 mount the root filesystem
1690
1691 rootflags= [KNL] Set root filesystem mount option string
1692
1693 rootfstype= [KNL] Set root filesystem type
1694
cc1ed754
PO
1695 rootwait [KNL] Wait (indefinitely) for root device to show up.
1696 Useful for devices that are detected asynchronously
1697 (e.g. USB and MMC devices).
1698
20510f2f
JM
1699 root_plug.vendor_id=
1700 [ROOTPLUG] Override the default vendor ID
1701
1702 root_plug.product_id=
1703 [ROOTPLUG] Override the default product ID
1704
1705 root_plug.debug=
1706 [ROOTPLUG] Enable debugging output
1707
1da177e4
LT
1708 rw [KNL] Mount root device read-write on boot
1709
1710 S [KNL] Run init in single mode
1711
1712 sa1100ir [NET]
1713 See drivers/net/irda/sa1100_ir.c.
1714
1da177e4 1715 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1716
1da177e4
LT
1717 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1718 Format: <io>[,<timeout>[,<isapnp>]]
1719
1720 scsi_debug_*= [SCSI]
1721 See drivers/scsi/scsi_debug.c.
1722
1723 scsi_default_dev_flags=
1724 [SCSI] SCSI default device flags
1725 Format: <integer>
1726
1727 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1728 Format: <vendor>:<model>:<flags>
1729 (flags are integer value)
1730
6af6632a
RD
1731 scsi_logging_level= [SCSI] a bit mask of logging levels
1732 See drivers/scsi/scsi_logging.h for bits. Also
1733 settable via sysctl at dev.scsi.logging_level
1734 (/proc/sys/dev/scsi/logging_level).
1735 There is also a nice 'scsi_logging_level' script in the
1736 S390-tools package, available for download at
1737 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1738
3e082a91
MW
1739 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1740 discovered. async scans them in kernel threads,
1741 allowing boot to proceed. none ignores them, expecting
1742 user space to do the scan.
1743
1da177e4
LT
1744 selinux [SELINUX] Disable or enable SELinux at boot time.
1745 Format: { "0" | "1" }
1746 See security/selinux/Kconfig help text.
1747 0 -- disable.
1748 1 -- enable.
1749 Default value is set via kernel config option.
1750 If enabled at boot time, /selinux/disable can be used
1751 later to disable prior to initial policy load.
1752
4e5ab4cb
JM
1753 selinux_compat_net =
1754 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1755 Format: { "0" | "1" }
1756 0 -- use new secmark-based packet controls
1757 1 -- use legacy packet controls
1758 Default value is 0 (preferred).
1759 Value can be changed at runtime via
1760 /selinux/compat_net.
4e5ab4cb 1761
cd4f0ef7 1762 serialnumber [BUGS=X86-32]
1da177e4 1763
1da177e4
LT
1764 shapers= [NET]
1765 Maximal number of shapers.
a9913044 1766
1da177e4
LT
1767 sim710= [SCSI,HW]
1768 See header of drivers/scsi/sim710.c.
1769
1770 simeth= [IA-64]
1771 simscsi=
a9913044 1772
1da177e4
LT
1773 slram= [HW,MTD]
1774
f0630fff
CL
1775 slub_debug[=options[,slabs]] [MM, SLUB]
1776 Enabling slub_debug allows one to determine the
1777 culprit if slab objects become corrupted. Enabling
1778 slub_debug can create guard zones around objects and
1779 may poison objects when not in use. Also tracks the
1780 last alloc / free. For more information see
1781 Documentation/vm/slub.txt.
c1aee215
CL
1782
1783 slub_max_order= [MM, SLUB]
f0630fff
CL
1784 Determines the maximum allowed order for slabs.
1785 A high setting may cause OOMs due to memory
1786 fragmentation. For more information see
1787 Documentation/vm/slub.txt.
c1aee215
CL
1788
1789 slub_min_objects= [MM, SLUB]
f0630fff
CL
1790 The minimum number of objects per slab. SLUB will
1791 increase the slab order up to slub_max_order to
1792 generate a sufficiently large slab able to contain
1793 the number of objects indicated. The higher the number
1794 of objects the smaller the overhead of tracking slabs
1795 and the less frequently locks need to be acquired.
c1aee215
CL
1796 For more information see Documentation/vm/slub.txt.
1797
1798 slub_min_order= [MM, SLUB]
1799 Determines the mininum page order for slabs. Must be
f0630fff 1800 lower than slub_max_order.
c1aee215
CL
1801 For more information see Documentation/vm/slub.txt.
1802
1803 slub_nomerge [MM, SLUB]
f0630fff 1804 Disable merging of slabs with similar size. May be
c1aee215 1805 necessary if there is some reason to distinguish
f0630fff
CL
1806 allocs to different slabs. Debug options disable
1807 merging on their own.
c1aee215
CL
1808 For more information see Documentation/vm/slub.txt.
1809
1da177e4
LT
1810 smart2= [HW]
1811 Format: <io1>[,<io2>[,...,<io8>]]
1812
cd4f0ef7 1813 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1814 attempt to substitute SMP alternatives once at boot.
1815
d0d4f69b
BH
1816 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1817 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1818 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1819 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1820 smsc-ircc2.ircc_irq= [HW] IRQ line
1821 smsc-ircc2.ircc_dma= [HW] DMA channel
1822 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1823 0: Toshiba Satellite 1800 (GP data pin select)
1824 1: Fast pin select (default)
1825 2: ATC IRMode
1826
1da177e4
LT
1827 snd-ad1816a= [HW,ALSA]
1828
1829 snd-ad1848= [HW,ALSA]
1830
1831 snd-ali5451= [HW,ALSA]
1832
1833 snd-als100= [HW,ALSA]
1834
1835 snd-als4000= [HW,ALSA]
1836
1837 snd-azt2320= [HW,ALSA]
1838
1839 snd-cmi8330= [HW,ALSA]
1840
1841 snd-cmipci= [HW,ALSA]
1842
1843 snd-cs4231= [HW,ALSA]
1844
1845 snd-cs4232= [HW,ALSA]
1846
1847 snd-cs4236= [HW,ALSA]
1848
1849 snd-cs4281= [HW,ALSA]
1850
1851 snd-cs46xx= [HW,ALSA]
1852
1853 snd-dt019x= [HW,ALSA]
1854
1855 snd-dummy= [HW,ALSA]
1856
1857 snd-emu10k1= [HW,ALSA]
1858
1859 snd-ens1370= [HW,ALSA]
1860
1861 snd-ens1371= [HW,ALSA]
1862
1863 snd-es968= [HW,ALSA]
1864
1865 snd-es1688= [HW,ALSA]
1866
1867 snd-es18xx= [HW,ALSA]
1868
1869 snd-es1938= [HW,ALSA]
1870
1871 snd-es1968= [HW,ALSA]
1872
1873 snd-fm801= [HW,ALSA]
1874
1875 snd-gusclassic= [HW,ALSA]
1876
1877 snd-gusextreme= [HW,ALSA]
1878
1879 snd-gusmax= [HW,ALSA]
1880
1881 snd-hdsp= [HW,ALSA]
1882
1883 snd-ice1712= [HW,ALSA]
1884
1885 snd-intel8x0= [HW,ALSA]
1886
1887 snd-interwave= [HW,ALSA]
1888
1889 snd-interwave-stb=
1890 [HW,ALSA]
1891
1892 snd-korg1212= [HW,ALSA]
1893
1894 snd-maestro3= [HW,ALSA]
1895
1896 snd-mpu401= [HW,ALSA]
1897
1898 snd-mtpav= [HW,ALSA]
1899
1900 snd-nm256= [HW,ALSA]
1901
1902 snd-opl3sa2= [HW,ALSA]
1903
1904 snd-opti92x-ad1848=
1905 [HW,ALSA]
1906
1907 snd-opti92x-cs4231=
1908 [HW,ALSA]
1909
1910 snd-opti93x= [HW,ALSA]
1911
1912 snd-pmac= [HW,ALSA]
1913
1914 snd-rme32= [HW,ALSA]
1915
1916 snd-rme96= [HW,ALSA]
1917
1918 snd-rme9652= [HW,ALSA]
1919
1920 snd-sb8= [HW,ALSA]
1921
1922 snd-sb16= [HW,ALSA]
1923
1924 snd-sbawe= [HW,ALSA]
1925
1926 snd-serial= [HW,ALSA]
1927
1928 snd-sgalaxy= [HW,ALSA]
1929
1930 snd-sonicvibes= [HW,ALSA]
1931
1932 snd-sun-amd7930=
1933 [HW,ALSA]
1934
1935 snd-sun-cs4231= [HW,ALSA]
1936
1937 snd-trident= [HW,ALSA]
1938
1939 snd-usb-audio= [HW,ALSA,USB]
1940
1941 snd-via82xx= [HW,ALSA]
1942
1943 snd-virmidi= [HW,ALSA]
1944
1945 snd-wavefront= [HW,ALSA]
1946
1947 snd-ymfpci= [HW,ALSA]
a9913044 1948
1da177e4
LT
1949 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1950 See Documentation/sonypi.txt
1951
1952 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1953 See Documentation/specialix.txt.
1954
1955 spia_io_base= [HW,MTD]
1956 spia_fio_base=
1957 spia_pedr=
1958 spia_peddr=
1959
1960 sscape= [HW,OSS]
1961 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1962
1da177e4
LT
1963 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1964 See Documentation/scsi/st.txt.
1965
1da177e4
LT
1966 sti= [PARISC,HW]
1967 Format: <num>
1968 Set the STI (builtin display/keyboard on the HP-PARISC
1969 machines) console (graphic card) which should be used
1970 as the initial boot-console.
1971 See also comment in drivers/video/console/sticore.c.
1972
1973 sti_font= [HW]
1974 See comment in drivers/video/console/sticore.c.
1975
1976 stifb= [HW]
1977 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1978
42a7fc4a
GB
1979 sunrpc.pool_mode=
1980 [NFS]
1981 Control how the NFS server code allocates CPUs to
1982 service thread pools. Depending on how many NICs
1983 you have and where their interrupts are bound, this
1984 option will affect which CPUs will do NFS serving.
1985 Note: this parameter cannot be changed while the
1986 NFS server is running.
1987
1988 auto the server chooses an appropriate mode
1989 automatically using heuristics
1990 global a single global pool contains all CPUs
1991 percpu one pool for each CPU
1992 pernode one pool for each NUMA node (equivalent
1993 to global on non-NUMA machines)
1994
1da177e4 1995 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 1996
1da177e4
LT
1997 switches= [HW,M68k]
1998
1999 sym53c416= [HW,SCSI]
2000 See header of drivers/scsi/sym53c416.c.
2001
5d6f647f
IM
2002 sysrq_always_enabled
2003 [KNL]
2004 Ignore sysrq setting - this boot parameter will
2005 neutralize any effect of /proc/sys/kernel/sysrq.
2006 Useful for debugging.
2007
1da177e4
LT
2008 t128= [HW,SCSI]
2009 See header of drivers/scsi/t128.c.
2010
2011 tdfx= [HW,DRM]
2012
2013 thash_entries= [KNL,NET]
2014 Set number of hash buckets for TCP connection
2015
f8707ec9
LB
2016 thermal.act= [HW,ACPI]
2017 -1: disable all active trip points in all thermal zones
2018 <degrees C>: override all lowest active trip points
2019
c52a7419
LB
2020 thermal.crt= [HW,ACPI]
2021 -1: disable all critical trip points in all thermal zones
2022 <degrees C>: lower all critical trip points
2023
f5487145
LB
2024 thermal.nocrt= [HW,ACPI]
2025 Set to disable actions on ACPI thermal zone
2026 critical and hot trip points.
2027
72b33ef8
LB
2028 thermal.off= [HW,ACPI]
2029 1: disable ACPI thermal control
2030
a70cdc52
LB
2031 thermal.psv= [HW,ACPI]
2032 -1: disable all passive trip points
2033 <degrees C>: override all passive trip points to this value
2034
730ff34d
LB
2035 thermal.tzp= [HW,ACPI]
2036 Specify global default ACPI thermal zone polling rate
2037 <deci-seconds>: poll all this frequency
2038 0: no polling (default)
2039
1da177e4
LT
2040 tipar.timeout= [HW,PPT]
2041 Set communications timeout in tenths of a second
2042 (default 15).
2043
2044 tipar.delay= [HW,PPT]
2045 Set inter-bit delay in microseconds (default 10).
2046
1da177e4
LT
2047 tmscsim= [HW,SCSI]
2048 See comment before function dc390_setup() in
2049 drivers/scsi/tmscsim.c.
2050
2051 tp720= [HW,PS2]
2052
2053 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2054 Format:
2055 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2056
a9913044
RD
2057 turbografx.map[2|3]= [HW,JOY]
2058 TurboGraFX parallel port interface
2059 Format:
2060 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2061 See also Documentation/input/joystick-parport.txt
2062
2063 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2064 See header of drivers/scsi/u14-34f.c.
2065
2066 uart401= [HW,OSS]
2067 Format: <io>,<irq>
2068
2069 uart6850= [HW,OSS]
2070 Format: <io>,<irq>
2071
5f8364b7
AS
2072 uhci-hcd.ignore_oc=
2073 [USB] Ignore overcurrent events (default N).
2074 Some badly-designed motherboards generate lots of
2075 bogus events, for ports that aren't wired to
2076 anything. Set this parameter to avoid log spamming.
2077 Note that genuine overcurrent events won't be
2078 reported either.
2079
b5e795f8
AS
2080 usbcore.autosuspend=
2081 [USB] The autosuspend time delay (in seconds) used
2082 for newly-detected USB devices (default 2). This
2083 is the time required before an idle device will be
2084 autosuspended. Devices for which the delay is set
eaafbc3a 2085 to a negative value won't be autosuspended at all.
b5e795f8 2086
1da177e4
LT
2087 usbhid.mousepoll=
2088 [USBHID] The interval which mice are to be polled at.
a9913044 2089
cd4f0ef7 2090 vdso= [X86-32,SH,x86-64]
1dbf527c 2091 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2092 vdso=1: enable VDSO (default)
2093 vdso=0: disable VDSO mapping
2094
af65d648
RM
2095 vdso32= [X86-32,X86-64]
2096 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2097 vdso32=1: enable 32-bit VDSO (default)
2098 vdso32=0: disable 32-bit VDSO mapping
2099
d080d397
YI
2100 vector= [IA-64,SMP]
2101 vector=percpu: enable percpu vector domain
2102
1da177e4
LT
2103 video= [FB] Frame buffer configuration
2104 See Documentation/fb/modedb.txt.
2105
cd4f0ef7 2106 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2107 See Documentation/i386/boot.txt and
2108 Documentation/svga.txt.
1da177e4
LT
2109 Use vga=ask for menu.
2110 This is actually a boot loader parameter; the value is
2111 passed to the kernel using a special protocol.
2112
a9913044 2113 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2114 size of <nn>. This can be used to increase the
2115 minimum size (128MB on x86). It can also be used to
2116 decrease the size and leave more room for directly
2117 mapped kernel RAM.
2118
585c3047
PO
2119 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2120 Format: <command>
1da177e4 2121
585c3047
PO
2122 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2123 Format: <command>
2124
2125 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2126 Format: <command>
a9913044 2127
1da177e4
LT
2128 waveartist= [HW,OSS]
2129 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2130
1da177e4
LT
2131 wd33c93= [HW,SCSI]
2132 See header of drivers/scsi/wd33c93.c.
2133
2134 wd7000= [HW,SCSI]
2135 See header of drivers/scsi/wd7000.c.
2136
2137 wdt= [WDT] Watchdog
8dfe9c21 2138 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2139
2140 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2141 xd_geo= See header of drivers/block/xd.c.
2142
2143 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2144 Format:
2145 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2146
a62eaf15
AK
2147 norandmaps Don't use address space randomization
2148 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2149
a9913044 2150______________________________________________________________________
1da177e4
LT
2151
2152TODO:
2153
2154 Add documentation for ALSA options.
2155 Add more DRM drivers.