[S390] Remove last traces of cio_msg=.
[deliverable/linux.git] / Documentation / kernel-parameters.txt
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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]
5d0cf410 229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
232
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233 agp= [AGP]
234 { off | try_unsupported }
235 off: disable AGP support
236 try_unsupported: try to drive unsupported chipsets
237 (may crash computer or cause data corruption)
238
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239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
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241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
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243 The kernel tries to set a reasonable default.
244
245 disable_timer_pin_1 [i386,x86-64]
246 Disable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs.
248
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249 ad1848= [HW,OSS]
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
251
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252 advansys= [HW,SCSI]
253 See header of drivers/scsi/advansys.c.
254
255 advwdt= [HW,WDT] Advantech WDT
256 Format: <iostart>,<iostop>
257
258 aedsp16= [HW,OSS] Audio Excel DSP 16
259 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
260 See also header of sound/oss/aedsp16.c.
a9913044 261
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262 aha152x= [HW,SCSI]
263 See Documentation/scsi/aha152x.txt.
264
265 aha1542= [HW,SCSI]
266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
267
268 aic7xxx= [HW,SCSI]
269 See Documentation/scsi/aic7xxx.txt.
270
271 aic79xx= [HW,SCSI]
272 See Documentation/scsi/aic79xx.txt.
273
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274 amijoy.map= [HW,JOY] Amiga joystick support
275 Map of devices attached to JOY0DAT and JOY1DAT
276 Format: <a>,<b>
277 See also Documentation/kernel/input/joystick.txt
278
279 analog.map= [HW,JOY] Analog joystick and gamepad support
280 Specifies type or capabilities of an analog joystick
281 connected to one of 16 gameports
282 Format: <type1>,<type2>,..<type16>
283
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284 apc= [HW,SPARC]
285 Power management functions (SPARCstation-4/5 + deriv.)
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286 Format: noidle
287 Disable APC CPU standby support. SPARCstation-Fox does
288 not play well with APC CPU idle - disable it if you have
289 APC and your system crashes randomly.
290
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291 apic= [APIC,i386] Advanced Programmable Interrupt Controller
292 Change the output verbosity whilst booting
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293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
a9913044 296
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297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
299
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300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
301 Format: <io>,<irq>,<nodeID>
302
303 ataflop= [HW,M68k]
304
305 atarimouse= [HW,MOUSE] Atari Mouse
306
307 atascsi= [HW,SCSI] Atari SCSI
308
309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
310 EzKey and similar keyboards
311
312 atkbd.reset= [HW] Reset keyboard during initialization
313
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314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
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316
317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
318 keyboards
319
320 atkbd.softraw= [HW] Choose between synthetic and real raw mode
321 Format: <bool> (0 = real, 1 = synthetic (default))
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322
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
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325
326 autotest [IA64]
327
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328 baycom_epp= [HW,AX25]
329 Format: <io>,<mode>
a9913044 330
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331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
332 Format: <io>,<mode>
333 See header of drivers/net/hamradio/baycom_par.c.
334
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335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
339
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340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
344
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345 boot_delay= Milliseconds to delay each printk during boot.
346 Values larger than 10 seconds (10000) are changed to
347 no delay (0).
348 Format: integer
349
1da177e4 350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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351 bttv.radio= Most important insmod options are available as
352 kernel args too.
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353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
355
356 BusLogic= [HW,SCSI]
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
359
360 c101= [NET] Moxa C101 synchronous serial card
361
cd4f0ef7 362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
368
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369 security= [SECURITY] Choose a security module to enable at boot.
370 If this boot parameter is not specified, only the first
371 security module asking for security registration will be
372 loaded. An invalid security module name will be treated
373 as if no module has been chosen.
374
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375 capability.disable=
376 [SECURITY] Disable capabilities. This would normally
377 be used only if an alternative security model is to be
378 configured. Potentially dangerous and should only be
379 used if you are entirely sure of the consequences.
380
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381 ccw_timeout_log [S390]
382 See Documentation/s390/CommonIO for details.
1da177e4 383
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384 cgroup_disable= [KNL] Disable a particular controller
385 Format: {name of the controller(s) to disable}
386 {Currently supported controllers - "memory"}
387
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388 checkreqprot [SELINUX] Set initial checkreqprot flag value.
389 Format: { "0" | "1" }
390 See security/selinux/Kconfig help text.
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391 0 -- check protection applied by kernel (includes
392 any implied execute protection).
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393 1 -- check protection requested by application.
394 Default value is set via a kernel config option.
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395 Value can be changed at runtime via
396 /selinux/checkreqprot.
397
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398 cio_ignore= [S390]
399 See Documentation/s390/CommonIO for details.
400
cd4f0ef7 401 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 402 [Deprecated]
3f6dee9b 403 Forces specified clocksource (if available) to be used
734efb46 404 when calculating gettimeofday(). If specified
3f6dee9b 405 clocksource is not available, it defaults to PIT.
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406 Format: { pit | tsc | cyclone | pmtmr }
407
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408 clocksource= [GENERIC_TIME] Override the default clocksource
409 Format: <string>
410 Override the default clocksource and use the clocksource
411 with the name specified.
412 Some clocksource names to choose from, depending on
413 the platform:
414 [all] jiffies (this is the base, fallback clocksource)
415 [ACPI] acpi_pm
416 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
417 pxa_timer,timer3,32k_counter,timer0_1
418 [AVR32] avr32
cd4f0ef7 419 [X86-32] pit,hpet,tsc,vmi-timer;
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420 scx200_hrt on Geode; cyclone on IBM x440
421 [MIPS] MIPS
422 [PARISC] cr16
423 [S390] tod
424 [SH] SuperH
425 [SPARC64] tick
426 [X86-64] hpet,tsc
427
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428 clearcpuid=BITNUM [X86]
429 Disable CPUID feature X for the kernel. See
430 include/asm-x86/cpufeature.h for the valid bit numbers.
431 Note the Linux specific bits are not necessarily
432 stable over kernel options, but the vendor specific
433 ones should be.
434 Also note that user programs calling CPUID directly
435 or using the feature without checking anything
436 will still see it. This just prevents it from
437 being used by the kernel or shown in /proc/cpuinfo.
438 Also note the kernel might malfunction if you disable
439 some critical bits.
440
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441 code_bytes [IA32/X86_64] How many bytes of object code to print
442 in an oops report.
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443 Range: 0 - 8192
444 Default: 64
445
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446 disable_8254_timer
447 enable_8254_timer
448 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
449 over the 8254 in addition to over the IO-APIC. The
450 kernel tries to set a sensible default.
451
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452 hpet= [X86-32,HPET] option to control HPET usage
453 Format: { enable (default) | disable | force }
454 disable: disable HPET and use PIT instead
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455 force: allow force enabled of undocumented chips (ICH4,
456 VIA, nVidia)
1da177e4 457
1da177e4 458 com20020= [HW,NET] ARCnet - COM20020 chipset
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459 Format:
460 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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461
462 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
463 Format: <io>[,<irq>]
464
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465 com90xx= [HW,NET]
466 ARCnet - COM90xx chipset (memory-mapped buffers)
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467 Format: <io>[,<irq>[,<memstart>]]
468
469 condev= [HW,S390] console device
470 conmode=
a9913044 471
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472 console= [KNL] Output console device and options.
473
474 tty<n> Use the virtual console device <n>.
475
476 ttyS<n>[,options]
f1a1c2dc 477 ttyUSB0[,options]
1da177e4 478 Use the specified serial port. The options are of
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479 the form "bbbbpnf", where "bbbb" is the baud rate,
480 "p" is parity ("n", "o", or "e"), "n" is number of
481 bits, and "f" is flow control ("r" for RTS or
482 omit it). Default is "9600n8".
483
484 See Documentation/serial-console.txt for more
485 information. See
486 Documentation/networking/netconsole.txt for an
487 alternative.
1da177e4 488
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489 uart[8250],io,<addr>[,options]
490 uart[8250],mmio,<addr>[,options]
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491 Start an early, polled-mode console on the 8250/16550
492 UART at the specified I/O port or MMIO address,
493 switching to the matching ttyS device later. The
494 options are the same as for ttyS, above.
495
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496 If the device connected to the port is not a TTY but a braille
497 device, prepend "brl," before the device type, for instance
498 console=brl,ttyS0
499 For now, only VisioBraille is supported.
500
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501 earlycon= [KNL] Output early console device and options.
502 uart[8250],io,<addr>[,options]
503 uart[8250],mmio,<addr>[,options]
504 Start an early, polled-mode console on the 8250/16550
505 UART at the specified I/O port or MMIO address.
506 The options are the same as for ttyS, above.
507
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508 no_console_suspend
509 [HW] Never suspend the console
510 Disable suspending of consoles during suspend and
511 hibernate operations. Once disabled, debugging
512 messages can reach various consoles while the rest
513 of the system is being put to sleep (ie, while
514 debugging driver suspend/resume hooks). This may
515 not work reliably with all consoles, but is known
516 to work with serial and VGA consoles.
517
1da177e4 518 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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519 Format:
520 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 521
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522 crashkernel=nn[KMG]@ss[KMG]
523 [KNL] Reserve a chunk of physical memory to
524 hold a kernel to switch to with kexec on panic.
525
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526 crashkernel=range1:size1[,range2:size2,...][@offset]
527 [KNL] Same as above, but depends on the memory
528 in the running system. The syntax of range is
529 start-[end] where start and end are both
530 a memory unit (amount[KMG]). See also
531 Documentation/kdump/kdump.txt for a example.
532
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533 cs4232= [HW,OSS]
534 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
535
536 cs89x0_dma= [HW,NET]
537 Format: <dma>
538
539 cs89x0_media= [HW,NET]
540 Format: { rj45 | aui | bnc }
a9913044 541
a9913044 542 dasd= [HW,NET]
1da177e4
LT
543 See header of drivers/s390/block/dasd_devmap.c.
544
545 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
546 (one device per port)
547 Format: <port#>,<type>
548 See also Documentation/input/joystick-parport.txt
549
550 debug [KNL] Enable kernel debugging (events log level).
551
cae2ed9a
IM
552 debug_locks_verbose=
553 [KNL] verbose self-tests
554 Format=<0|1>
555 Print debugging info while doing the locking API
556 self-tests.
557 We default to 0 (no extra messages), setting it to
558 1 will print _a lot_ more information - normally
559 only useful to kernel developers.
560
3ac7fe5a
TG
561 debug_objects [KNL] Enable object debugging
562
2d27a966 563 decnet.addr= [HW,NET]
1da177e4
LT
564 Format: <area>[,<node>]
565 See also Documentation/networking/decnet.txt.
566
ecb77fa9 567 vt.default_blu= [VT]
55ff9780
AD
568 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
569 Change the default blue palette of the console.
570 This is a 16-member array composed of values
571 ranging from 0-255.
572
ecb77fa9 573 vt.default_grn= [VT]
55ff9780
AD
574 Format: <green0>,<green1>,<green2>,...,<green15>
575 Change the default green palette of the console.
576 This is a 16-member array composed of values
577 ranging from 0-255.
578
ecb77fa9 579 vt.default_red= [VT]
55ff9780
AD
580 Format: <red0>,<red1>,<red2>,...,<red15>
581 Change the default red palette of the console.
582 This is a 16-member array composed of values
583 ranging from 0-255.
584
ecb77fa9
ST
585 vt.default_utf8=
586 [VT]
55ff9780
AD
587 Format=<0|1>
588 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
589 Default is 1, i.e. UTF-8 mode is enabled for all
590 newly opened terminals.
55ff9780 591
1da177e4
LT
592 dhash_entries= [KNL]
593 Set number of hash buckets for dentry cache.
a9913044 594
1da177e4
LT
595 digi= [HW,SERIAL]
596 IO parameters + enable/disable command.
597
598 digiepca= [HW,SERIAL]
599 See drivers/char/README.epca and
600 Documentation/digiepca.txt.
601
093af8d7 602 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
603 By default the kernel will trim any uncacheable
604 memory out of your available memory pool based on
605 MTRR settings. This parameter disables that behavior,
606 possibly causing your machine to run very slowly.
607
1da177e4
LT
608 dmasound= [HW,OSS] Sound subsystem buffers
609
610 dscc4.setup= [NET]
611
612 dtc3181e= [HW,SCSI]
613
0ae53640 614 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
615 earlyprintk=vga
616 earlyprintk=serial[,ttySn[,baudrate]]
617
a9913044 618 Append ",keep" to not disable it when the real console
1da177e4
LT
619 takes over.
620
621 Only vga or serial at a time, not both.
622
623 Currently only ttyS0 and ttyS1 are supported.
624
625 Interaction with the standard serial driver is not
626 very good.
627
628 The VGA output is eventually overwritten by the real
629 console.
630
631 eata= [HW,SCSI]
632
1da177e4 633 edd= [EDD]
8c4dd606 634 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 635
1da177e4
LT
636 eisa_irq_edge= [PARISC,HW]
637 See header of drivers/parisc/eisa.c.
638
cd4f0ef7 639 elanfreq= [X86-32]
1da177e4
LT
640 See comment before function elanfreq_setup() in
641 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
642
643 elevator= [IOSCHED]
16ab3adf 644 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
645 See Documentation/block/as-iosched.txt and
646 Documentation/block/deadline-iosched.txt for details.
647
cd4f0ef7 648 elfcorehdr= [X86-32, X86_64]
a9913044 649 Specifies physical address of start of kernel core
aac04b32
VG
650 image elf header. Generally kexec loader will
651 pass this option to capture kernel.
652 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
653
654 enforcing [SELINUX] Set initial enforcing status.
655 Format: {"0" | "1"}
656 See security/selinux/Kconfig help text.
657 0 -- permissive (log only, no denials).
658 1 -- enforcing (deny and log).
659 Default value is 0.
660 Value can be changed at runtime via /selinux/enforce.
661
1da177e4
LT
662 es1371= [HW,OSS]
663 Format: <spdif>,[<nomix>,[<amplifier>]]
664 See also header of sound/oss/es1371.c.
a9913044 665
1da177e4
LT
666 ether= [HW,NET] Ethernet cards parameters
667 This option is obsoleted by the "netdev=" option, which
668 has equivalent usage. See its documentation for details.
669
670 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
671 Format: <io>[,<irq>]
672
de1ba09b
AM
673 failslab=
674 fail_page_alloc=
675 fail_make_request=[KNL]
676 General fault injection mechanism.
677 Format: <interval>,<probability>,<space>,<times>
678 See also /Documentation/fault-injection/.
679
1da177e4
LT
680 fd_mcs= [HW,SCSI]
681 See header of drivers/scsi/fd_mcs.c.
682
683 fdomain= [HW,SCSI]
684 See header of drivers/scsi/fdomain.c.
685
686 floppy= [HW]
687 See Documentation/floppy.txt.
688
1da177e4
LT
689 gamecon.map[2|3]=
690 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
691 support via parallel port (up to 5 devices per port)
692 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
693 See also Documentation/input/joystick-parport.txt
694
695 gamma= [HW,DRM]
696
aaf23042
YL
697 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
698 Format: off | on
699 default: on
700
1da177e4
LT
701 gdth= [HW,SCSI]
702 See header of drivers/scsi/gdth.c.
703
704 gpt [EFI] Forces disk with valid GPT signature but
705 invalid Protective MBR to be treated as GPT.
706
1da177e4
LT
707 gvp11= [HW,SCSI]
708
709 hashdist= [KNL,NUMA] Large hashes allocated during boot
710 are distributed across NUMA nodes. Defaults on
711 for IA-64, off otherwise.
a9913044 712 Format: 0 | 1 (for off | on)
1da177e4
LT
713
714 hcl= [IA-64] SGI's Hardware Graph compatibility layer
715
716 hd= [EIDE] (E)IDE hard drive subsystem geometry
717 Format: <cyl>,<head>,<sect>
718
719 hd?= [HW] (E)IDE subsystem
1c10e938 720 hd?lun= See Documentation/ide/ide.txt.
1da177e4
LT
721
722 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
723 size of <nn>. This works even on boxes that have no
724 highmem otherwise. This also works to reduce highmem
725 size on bigger boxes.
726
54cdfdb4
TG
727 highres= [KNL] Enable/disable high resolution timer mode.
728 Valid parameters: "on", "off"
729 Default: "on"
730
1da177e4
LT
731 hisax= [HW,ISDN]
732 See Documentation/isdn/README.HiSax.
733
cd4f0ef7 734 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 735 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 736
1da177e4 737 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
738 i8042.dumbkbd [HW] Pretend that controller can only read data from
739 keyboard and cannot control its state
1da177e4
LT
740 (Don't attempt to blink the leds)
741 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 742 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
743 i8042.noloop [HW] Disable the AUX Loopback command while probing
744 for the AUX port
1da177e4
LT
745 i8042.nomux [HW] Don't check presence of an active multiplexing
746 controller
747 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
748 controllers
749 i8042.panicblink=
750 [HW] Frequency with which keyboard LEDs should blink
751 when kernel panics (default is 0.5 sec)
752 i8042.reset [HW] Reset the controller during init and cleanup
753 i8042.unlock [HW] Unlock (ignore) the keylock
754
755 i810= [HW,DRM]
756
e70c9d5e
DT
757 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
758 indicates that the driver is running on unsupported
759 hardware.
1da177e4
LT
760 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
761 does not match list of supported models.
762 i8k.power_status
763 [HW] Report power status in /proc/i8k
764 (disabled by default)
765 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
766 capability is set.
767
768 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
769 See Documentation/mca.txt.
770
771 icn= [HW,ISDN]
772 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
773
774 ide= [HW] (E)IDE subsystem
a594eeb1 775 Format: ide=nodma or ide=doubler
1c10e938 776 See Documentation/ide/ide.txt.
1da177e4 777
1da177e4 778 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 779 See Documentation/ide/ide.txt.
1da177e4 780
f039b754
AK
781 idle= [X86]
782 Format: idle=poll or idle=mwait
783 Poll forces a polling idle loop that can slightly improves the performance
784 of waking up a idle CPU, but will use a lot of power and make the system
785 run hot. Not recommended.
786 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
787 to not use it because it doesn't save as much power as a normal idle
788 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
789 as idle=poll.
a9913044 790
594765a7
DC
791 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
792 Claim all unknown PCI IDE storage controllers.
793
79290822
IM
794 ignore_loglevel [KNL]
795 Ignore loglevel setting - this will print /all/
796 kernel messages to the console. Useful for debugging.
797
1da177e4
LT
798 ihash_entries= [KNL]
799 Set number of hash buckets for inode cache.
800
801 in2000= [HW,SCSI]
802 See header of drivers/scsi/in2000.c.
803
804 init= [KNL]
805 Format: <full_path>
806 Run specified binary instead of /sbin/init as init
807 process.
808
809 initcall_debug [KNL] Trace initcalls as they are executed. Useful
810 for working out where the kernel is dying during
811 startup.
812
813 initrd= [BOOT] Specify the location of the initial ramdisk
814
815 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
816 Format: <irq>
817
818 inttest= [IA64]
819
b552da87
PM
820 iommu= [x86]
821 off
822 force
823 noforce
824 biomerge
825 panic
826 nopanic
827 merge
828 nomerge
829 forcesac
830 soft
831
832
ba395927
KA
833 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
834 off
835 Disable intel iommu driver.
836 igfx_off [Default Off]
837 By default, gfx is mapped as normal device. If a gfx
838 device has a dedicated DMAR unit, the DMAR unit is
839 bypassed by not enabling DMAR with this option. In
840 this case, gfx device will use physical address for
841 DMA.
7d3b03ce
KA
842 forcedac [x86_64]
843 With this option iommu will not optimize to look
844 for io virtual address below 32 bit forcing dual
845 address cycle on pci bus for cards supporting greater
846 than 32 bit addressing. The default is to look
847 for translation below 32 bit and if not available
848 then look in the higher range.
5e0d2a6f 849 strict [Default Off]
850 With this option on every unmap_single operation will
851 result in a hardware IOTLB flush operation as opposed
852 to batching them for performance.
ba395927 853
b02aae9c 854 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
855 0x80
856 Standard port 0x80 based delay
857 0xed
858 Alternate port 0xed based delay (needed on some systems)
b02aae9c 859 udelay
6e7c4025
IM
860 Simple two microseconds delay
861 none
862 No delay
b02aae9c 863
1da177e4
LT
864 io7= [HW] IO7 for Marvel based alpha systems
865 See comment before marvel_specify_io7 in
866 arch/alpha/kernel/core_marvel.c.
867
868 ip= [IP_PNP]
6ded55da 869 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
870
871 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
872 See comment before ip2_setup() in
873 drivers/char/ip2/ip2base.c.
1da177e4
LT
874
875 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
876 See header of drivers/scsi/ips.c.
877
72c4a13a
SH
878 ports= [IP_VS_FTP] IPVS ftp helper module
879 Default is 21.
880 Up to 8 (IP_VS_APP_MAX_PORTS) ports
881 may be specified.
882 Format: <port>,<port>....
883
200803df
AC
884 irqfixup [HW]
885 When an interrupt is not handled search all handlers
886 for it. Intended to get systems with badly broken
887 firmware running.
888
889 irqpoll [HW]
890 When an interrupt is not handled search all handlers
891 for it. Also check all handlers each timer
892 interrupt. Intended to get systems with badly broken
893 firmware running.
894
1da177e4 895 isapnp= [ISAPNP]
a9913044 896 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
897
898 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
899 Format:
900 <cpu number>,...,<cpu number>
901 or
902 <cpu number>-<cpu number> (must be a positive range in ascending order)
903 or a mixture
904 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
905 This option can be used to specify one or more CPUs
906 to isolate from the general SMP balancing and scheduling
907 algorithms. The only way to move a process onto or off
908 an "isolated" CPU is via the CPU affinity syscalls.
909 <cpu number> begins at 0 and the maximum value is
910 "number of CPUs in system - 1".
911
912 This option is the preferred way to isolate CPUs. The
a9913044
RD
913 alternative -- manually setting the CPU mask of all
914 tasks in the system -- can cause problems and
915 suboptimal load balancer performance.
1da177e4 916
a9913044 917 iucv= [HW,NET]
1da177e4
LT
918
919 js= [HW,JOY] Analog joystick
920 See Documentation/input/joystick.txt.
921
cd4f0ef7 922 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
923 specifies the amount of memory usable by the kernel
924 for non-movable allocations. The requested amount is
925 spread evenly throughout all nodes in the system. The
926 remaining memory in each node is used for Movable
927 pages. In the event, a node is too small to have both
928 kernelcore and Movable pages, kernelcore pages will
929 take priority and other nodes will have a larger number
930 of kernelcore pages. The Movable zone is used for the
931 allocation of pages that may be reclaimed or moved
932 by the page migration subsystem. This means that
933 HugeTLB pages may not be allocated from this zone.
934 Note that allocations like PTEs-from-HighMem still
935 use the HighMem zone if it exists, and the Normal
936 zone if it does not.
937
cd4f0ef7 938 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
939 is similar to kernelcore except it specifies the
940 amount of memory used for migratable allocations.
941 If both kernelcore and movablecore is specified,
942 then kernelcore will be at *least* the specified
943 value but may be more. If movablecore on its own
944 is specified, the administrator must be careful
945 that the amount of memory usable for all allocations
946 is not too small.
947
1da177e4
LT
948 keepinitrd [HW,ARM]
949
cd4f0ef7 950 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
951 in oops dumps.
952
6cdf6e06
JW
953 kgdboc= [HW] kgdb over consoles.
954 Requires a tty driver that supports console polling.
955 (only serial suported for now)
956 Format: <serial_device>[,baud]
957
1da177e4
LT
958 l2cr= [PPC]
959
a78bfbfc
RB
960 l3cr= [PPC]
961
cd4f0ef7 962 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 963 disabled it.
1da177e4 964
cd4f0ef7 965 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
966 C2 power state.
967
fcb71f6f
FC
968 libata.dma= [LIBATA] DMA control
969 libata.dma=0 Disable all PATA and SATA DMA
970 libata.dma=1 PATA and SATA Disk DMA only
971 libata.dma=2 ATAPI (CDROM) DMA only
972 libata.dma=4 Compact Flash DMA only
973 Combinations also work, so libata.dma=3 enables DMA
974 for disks and CDROMs, but not CFs.
975
78e70c23
DJ
976 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
977 when set.
978 Format: <int>
979
33267325
TH
980 libata.force= [LIBATA] Force configurations. The format is comma
981 separated list of "[ID:]VAL" where ID is
982 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
983 matching port, link or device. Basically, it matches
984 the ATA ID string printed on console by libata. If
985 the whole ID part is omitted, the last PORT and DEVICE
986 values are used. If ID hasn't been specified yet, the
987 configuration applies to all ports, links and devices.
988
989 If only DEVICE is omitted, the parameter applies to
990 the port and all links and devices behind it. DEVICE
991 number of 0 either selects the first device or the
992 first fan-out link behind PMP device. It does not
993 select the host link. DEVICE number of 15 selects the
994 host link and device attached to it.
995
996 The VAL specifies the configuration to force. As long
997 as there's no ambiguity shortcut notation is allowed.
998 For example, both 1.5 and 1.5G would work for 1.5Gbps.
999 The following configurations can be forced.
1000
1001 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1002 Any ID with matching PORT is used.
1003
1004 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1005
1006 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1007 udma[/][16,25,33,44,66,100,133] notation is also
1008 allowed.
1009
1010 * [no]ncq: Turn on or off NCQ.
1011
1012 If there are multiple matching configurations changing
1013 the same attribute, the last one is used.
1014
1da177e4
LT
1015 load_ramdisk= [RAM] List of ramdisks to load from floppy
1016 See Documentation/ramdisk.txt.
1017
a6b25b67
RD
1018 lockd.nlm_grace_period=P [NFS] Assign grace period.
1019 Format: <integer>
1da177e4 1020
a6b25b67
RD
1021 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1022 Format: <integer>
1023
1024 lockd.nlm_timeout=T [NFS] Assign timeout value.
1025 Format: <integer>
1026
1027 lockd.nlm_udpport=M [NFS] Assign UDP port.
1028 Format: <integer>
1da177e4
LT
1029
1030 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1031 Format: <irq>
1032
1033 loglevel= All Kernel Messages with a loglevel smaller than the
1034 console loglevel will be printed to the console. It can
1035 also be changed with klogd or other programs. The
1036 loglevels are defined as follows:
1037
1038 0 (KERN_EMERG) system is unusable
1039 1 (KERN_ALERT) action must be taken immediately
1040 2 (KERN_CRIT) critical conditions
1041 3 (KERN_ERR) error conditions
1042 4 (KERN_WARNING) warning conditions
1043 5 (KERN_NOTICE) normal but significant condition
1044 6 (KERN_INFO) informational
1045 7 (KERN_DEBUG) debug-level messages
1046
1047 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1048 Format: { n | nk | nM }
1049 n must be a power of two. The default size
1050 is set in the kernel config file.
1da177e4 1051
accaa24c
RD
1052 logo.nologo [FB] Disables display of the built-in Linux logo.
1053 This may be used to provide more screen space for
1054 kernel log messages and is useful when debugging
1055 kernel boot problems.
1056
1da177e4
LT
1057 lp=0 [LP] Specify parallel ports to use, e.g,
1058 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1059 lp=reset first parallel port). 'lp=0' disables the
1060 lp=auto printer driver. 'lp=reset' (which can be
1061 specified in addition to the ports) causes
1062 attached printers to be reset. Using
1063 lp=port1,port2,... specifies the parallel ports
1064 to associate lp devices with, starting with
1065 lp0. A port specification may be 'none' to skip
1066 that lp device, or a parport name such as
1067 'parport0'. Specifying 'lp=auto' instead of a
1068 port specification list means that device IDs
1069 from each port should be examined, to see if
1070 an IEEE 1284-compliant printer is attached; if
1071 so, the driver will manage that printer.
1072 See also header of drivers/char/lp.c.
1073
1074 lpj=n [KNL]
1075 Sets loops_per_jiffy to given constant, thus avoiding
1076 time-consuming boot-time autodetection (up to 250 ms per
1077 CPU). 0 enables autodetection (default). To determine
1078 the correct value for your kernel, boot with normal
1079 autodetection and see what value is printed. Note that
1080 on SMP systems the preset will be applied to all CPUs,
1081 which is likely to cause problems if your CPUs need
1082 significantly divergent settings. An incorrect value
1083 will cause delays in the kernel to be wrong, leading to
1084 unpredictable I/O errors and other breakage. Although
1085 unlikely, in the extreme case this might damage your
1086 hardware.
1087
1088 ltpc= [NET]
1089 Format: <io>,<irq>,<dma>
1090
a9913044
RD
1091 mac5380= [HW,SCSI] Format:
1092 <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.
13a6ddb0
YL
1522 skip_isa_align [X86] do not align io start addr, so can
1523 handle more pci cards
a9913044
RD
1524 firmware [ARM] Do not re-enumerate the bus but instead
1525 just use the configuration from the
1526 bootloader. This is currently used on
1527 IXP2000 systems where the bus has to be
1528 configured a certain way for adjunct CPUs.
0637a70a
AK
1529 noearly [X86] Don't do any early type 1 scanning.
1530 This might help on some broken boards which
1531 machine check when some devices' config space
1532 is read. But various workarounds are disabled
1533 and some IOMMU drivers will not work.
6b4b78fe
MD
1534 bfsort Sort PCI devices into breadth-first order.
1535 This sorting is done to get a device
1536 order compatible with older (<= 2.4) kernels.
1537 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1538 cbiosize=nn[KMG] The fixed amount of bus space which is
1539 reserved for the CardBus bridge's IO window.
1540 The default value is 256 bytes.
1541 cbmemsize=nn[KMG] The fixed amount of bus space which is
1542 reserved for the CardBus bridge's memory
1543 window. The default value is 64 megabytes.
6b4b78fe 1544
1da177e4
LT
1545 pcmv= [HW,PCMCIA] BadgePAD 4
1546
1547 pd. [PARIDE]
1548 See Documentation/paride.txt.
1549
1550 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1551 boot time.
1552 Format: { 0 | 1 }
1553 See arch/parisc/kernel/pdc_chassis.c
1554
1555 pf. [PARIDE]
1556 See Documentation/paride.txt.
1557
1558 pg. [PARIDE]
1559 See Documentation/paride.txt.
1560
1561 pirq= [SMP,APIC] Manual mp-table setup
1562 See Documentation/i386/IO-APIC.txt.
1563
1564 plip= [PPT,NET] Parallel port network link
1565 Format: { parport<nr> | timid | 0 }
1566 See also Documentation/parport.txt.
1567
1568 pnpacpi= [ACPI]
1569 { off }
1570
1571 pnpbios= [ISAPNP]
1572 { on | off | curr | res | no-curr | no-res }
1573
1574 pnp_reserve_irq=
1575 [ISAPNP] Exclude IRQs for the autoconfiguration
1576
1577 pnp_reserve_dma=
1578 [ISAPNP] Exclude DMAs for the autoconfiguration
1579
1580 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1581 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1582
1583 pnp_reserve_mem=
a9913044
RD
1584 [ISAPNP] Exclude memory regions for the
1585 autoconfiguration.
1da177e4
LT
1586 Ranges are in pairs (memory base and size).
1587
45807a1d
IM
1588 print-fatal-signals=
1589 [KNL] debug: print fatal signals
1590 print-fatal-signals=1: print segfault info to
1591 the kernel console.
1592 default: off.
1593
e84845c4
RD
1594 printk.time= Show timing data prefixed to each printk message line
1595 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1596
1da177e4 1597 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1598 Format: [schedule,]<number>
1599 Param: "schedule" - profile schedule points.
1600 Param: <number> - step/bucket size as a power of 2 for
1601 statistical time based profiling.
b3da2a73
MG
1602 Param: "sleep" - profile D-state sleeping (millisecs).
1603 Requires CONFIG_SCHEDSTATS
c0fe2e69 1604 Param: "kvm" - profile VM exits.
1da177e4 1605
a9913044 1606 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1607 Limit processor to maximum C-state
1608 max_cstate=9 overrides any DMI blacklist limit.
1609
41c0d868
LB
1610 processor.nocst [HW,ACPI]
1611 Ignore the _CST method to determine C-states,
1612 instead using the legacy FADT method
1613
1da177e4
LT
1614 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1615 before loading.
1616 See Documentation/ramdisk.txt.
1617
a9913044
RD
1618 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1619 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1620 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1621 per second.
a9913044
RD
1622 psmouse.resetafter= [HW,MOUSE]
1623 Try to reset the device after so many bad packets
1da177e4
LT
1624 (0 = never).
1625 psmouse.resolution=
1626 [HW,MOUSE] Set desired mouse resolution, in dpi.
1627 psmouse.smartscroll=
a9913044 1628 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1629 0 = disabled, 1 = enabled (default).
1630
1631 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1632 Format:
1633 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1634
1635 pt. [PARIDE]
1636 See Documentation/paride.txt.
1637
dc8c8587
KS
1638 pty.legacy_count=
1639 [KNL] Number of legacy pty's. Overwrites compiled-in
1640 default number.
1641
7d2c502f 1642 quiet [KNL] Disable most log messages
a9913044 1643
1da177e4
LT
1644 r128= [HW,DRM]
1645
1646 raid= [HW,RAID]
1647 See Documentation/md.txt.
1648
a9913044 1649 ramdisk_blocksize= [RAM]
1da177e4 1650 See Documentation/ramdisk.txt.
a9913044 1651
1da177e4 1652 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1653 See Documentation/ramdisk.txt.
1654
24aaef8d
RD
1655 rcupdate.blimit= [KNL,BOOT]
1656 Set maximum number of finished RCU callbacks to process
1657 in one batch.
21a1ea9e 1658
24aaef8d
RD
1659 rcupdate.qhimark= [KNL,BOOT]
1660 Set threshold of queued
21a1ea9e
DS
1661 RCU callbacks over which batch limiting is disabled.
1662
24aaef8d
RD
1663 rcupdate.qlowmark= [KNL,BOOT]
1664 Set threshold of queued RCU callbacks below which
1665 batch limiting is re-enabled.
21a1ea9e 1666
ffdfc409
OJ
1667 rdinit= [KNL]
1668 Format: <full_path>
1669 Run specified binary instead of /init from the ramdisk,
1670 used for early userspace startup. See initrd.
1671
cd4f0ef7 1672 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1673 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1674 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1675
1676 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1677
cd4f0ef7 1678 reservetop= [X86-32]
461a9aff
ZA
1679 Format: nn[KMG]
1680 Reserves a hole at the top of the kernel virtual
1681 address space.
1682
7e96287d
VG
1683 reset_devices [KNL] Force drivers to reset the underlying device
1684 during initialization.
1685
a9913044
RD
1686 resume= [SWSUSP]
1687 Specify the partition device for software suspend
1da177e4 1688
ecbd0da1
RW
1689 resume_offset= [SWSUSP]
1690 Specify the offset from the beginning of the partition
1691 given by "resume=" at which the swap header is located,
1692 in <PAGE_SIZE> units (needed only for swap files).
1693 See Documentation/power/swsusp-and-swap-files.txt
1694
0a7b35cb
MN
1695 retain_initrd [RAM] Keep initrd memory after extraction
1696
1da177e4
LT
1697 rhash_entries= [KNL,NET]
1698 Set number of hash buckets for route cache
1699
1700 riscom8= [HW,SERIAL]
1701 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1702
1703 ro [KNL] Mount root device read-only on boot
1704
1705 root= [KNL] Root filesystem
1706
1707 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1708 mount the root filesystem
1709
1710 rootflags= [KNL] Set root filesystem mount option string
1711
1712 rootfstype= [KNL] Set root filesystem type
1713
cc1ed754
PO
1714 rootwait [KNL] Wait (indefinitely) for root device to show up.
1715 Useful for devices that are detected asynchronously
1716 (e.g. USB and MMC devices).
1717
20510f2f
JM
1718 root_plug.vendor_id=
1719 [ROOTPLUG] Override the default vendor ID
1720
1721 root_plug.product_id=
1722 [ROOTPLUG] Override the default product ID
1723
1724 root_plug.debug=
1725 [ROOTPLUG] Enable debugging output
1726
1da177e4
LT
1727 rw [KNL] Mount root device read-write on boot
1728
1729 S [KNL] Run init in single mode
1730
1731 sa1100ir [NET]
1732 See drivers/net/irda/sa1100_ir.c.
1733
1da177e4 1734 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1735
1da177e4
LT
1736 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1737 Format: <io>[,<timeout>[,<isapnp>]]
1738
1739 scsi_debug_*= [SCSI]
1740 See drivers/scsi/scsi_debug.c.
1741
1742 scsi_default_dev_flags=
1743 [SCSI] SCSI default device flags
1744 Format: <integer>
1745
1746 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1747 Format: <vendor>:<model>:<flags>
1748 (flags are integer value)
1749
6af6632a
RD
1750 scsi_logging_level= [SCSI] a bit mask of logging levels
1751 See drivers/scsi/scsi_logging.h for bits. Also
1752 settable via sysctl at dev.scsi.logging_level
1753 (/proc/sys/dev/scsi/logging_level).
1754 There is also a nice 'scsi_logging_level' script in the
1755 S390-tools package, available for download at
1756 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1757
3e082a91
MW
1758 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1759 discovered. async scans them in kernel threads,
1760 allowing boot to proceed. none ignores them, expecting
1761 user space to do the scan.
1762
1da177e4
LT
1763 selinux [SELINUX] Disable or enable SELinux at boot time.
1764 Format: { "0" | "1" }
1765 See security/selinux/Kconfig help text.
1766 0 -- disable.
1767 1 -- enable.
1768 Default value is set via kernel config option.
1769 If enabled at boot time, /selinux/disable can be used
1770 later to disable prior to initial policy load.
1771
4e5ab4cb
JM
1772 selinux_compat_net =
1773 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1774 Format: { "0" | "1" }
1775 0 -- use new secmark-based packet controls
1776 1 -- use legacy packet controls
1777 Default value is 0 (preferred).
1778 Value can be changed at runtime via
1779 /selinux/compat_net.
4e5ab4cb 1780
cd4f0ef7 1781 serialnumber [BUGS=X86-32]
1da177e4 1782
1da177e4
LT
1783 shapers= [NET]
1784 Maximal number of shapers.
a9913044 1785
1da177e4
LT
1786 sim710= [SCSI,HW]
1787 See header of drivers/scsi/sim710.c.
1788
1789 simeth= [IA-64]
1790 simscsi=
a9913044 1791
1da177e4
LT
1792 slram= [HW,MTD]
1793
f0630fff
CL
1794 slub_debug[=options[,slabs]] [MM, SLUB]
1795 Enabling slub_debug allows one to determine the
1796 culprit if slab objects become corrupted. Enabling
1797 slub_debug can create guard zones around objects and
1798 may poison objects when not in use. Also tracks the
1799 last alloc / free. For more information see
1800 Documentation/vm/slub.txt.
c1aee215
CL
1801
1802 slub_max_order= [MM, SLUB]
f0630fff
CL
1803 Determines the maximum allowed order for slabs.
1804 A high setting may cause OOMs due to memory
1805 fragmentation. For more information see
1806 Documentation/vm/slub.txt.
c1aee215
CL
1807
1808 slub_min_objects= [MM, SLUB]
f0630fff
CL
1809 The minimum number of objects per slab. SLUB will
1810 increase the slab order up to slub_max_order to
1811 generate a sufficiently large slab able to contain
1812 the number of objects indicated. The higher the number
1813 of objects the smaller the overhead of tracking slabs
1814 and the less frequently locks need to be acquired.
c1aee215
CL
1815 For more information see Documentation/vm/slub.txt.
1816
1817 slub_min_order= [MM, SLUB]
1818 Determines the mininum page order for slabs. Must be
f0630fff 1819 lower than slub_max_order.
c1aee215
CL
1820 For more information see Documentation/vm/slub.txt.
1821
1822 slub_nomerge [MM, SLUB]
f0630fff 1823 Disable merging of slabs with similar size. May be
c1aee215 1824 necessary if there is some reason to distinguish
f0630fff
CL
1825 allocs to different slabs. Debug options disable
1826 merging on their own.
c1aee215
CL
1827 For more information see Documentation/vm/slub.txt.
1828
1da177e4
LT
1829 smart2= [HW]
1830 Format: <io1>[,<io2>[,...,<io8>]]
1831
cd4f0ef7 1832 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1833 attempt to substitute SMP alternatives once at boot.
1834
d0d4f69b
BH
1835 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1836 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1837 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1838 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1839 smsc-ircc2.ircc_irq= [HW] IRQ line
1840 smsc-ircc2.ircc_dma= [HW] DMA channel
1841 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1842 0: Toshiba Satellite 1800 (GP data pin select)
1843 1: Fast pin select (default)
1844 2: ATC IRMode
1845
1da177e4
LT
1846 snd-ad1816a= [HW,ALSA]
1847
1848 snd-ad1848= [HW,ALSA]
1849
1850 snd-ali5451= [HW,ALSA]
1851
1852 snd-als100= [HW,ALSA]
1853
1854 snd-als4000= [HW,ALSA]
1855
1856 snd-azt2320= [HW,ALSA]
1857
1858 snd-cmi8330= [HW,ALSA]
1859
1860 snd-cmipci= [HW,ALSA]
1861
1862 snd-cs4231= [HW,ALSA]
1863
1864 snd-cs4232= [HW,ALSA]
1865
1866 snd-cs4236= [HW,ALSA]
1867
1868 snd-cs4281= [HW,ALSA]
1869
1870 snd-cs46xx= [HW,ALSA]
1871
1872 snd-dt019x= [HW,ALSA]
1873
1874 snd-dummy= [HW,ALSA]
1875
1876 snd-emu10k1= [HW,ALSA]
1877
1878 snd-ens1370= [HW,ALSA]
1879
1880 snd-ens1371= [HW,ALSA]
1881
1882 snd-es968= [HW,ALSA]
1883
1884 snd-es1688= [HW,ALSA]
1885
1886 snd-es18xx= [HW,ALSA]
1887
1888 snd-es1938= [HW,ALSA]
1889
1890 snd-es1968= [HW,ALSA]
1891
1892 snd-fm801= [HW,ALSA]
1893
1894 snd-gusclassic= [HW,ALSA]
1895
1896 snd-gusextreme= [HW,ALSA]
1897
1898 snd-gusmax= [HW,ALSA]
1899
1900 snd-hdsp= [HW,ALSA]
1901
1902 snd-ice1712= [HW,ALSA]
1903
1904 snd-intel8x0= [HW,ALSA]
1905
1906 snd-interwave= [HW,ALSA]
1907
1908 snd-interwave-stb=
1909 [HW,ALSA]
1910
1911 snd-korg1212= [HW,ALSA]
1912
1913 snd-maestro3= [HW,ALSA]
1914
1915 snd-mpu401= [HW,ALSA]
1916
1917 snd-mtpav= [HW,ALSA]
1918
1919 snd-nm256= [HW,ALSA]
1920
1921 snd-opl3sa2= [HW,ALSA]
1922
1923 snd-opti92x-ad1848=
1924 [HW,ALSA]
1925
1926 snd-opti92x-cs4231=
1927 [HW,ALSA]
1928
1929 snd-opti93x= [HW,ALSA]
1930
1931 snd-pmac= [HW,ALSA]
1932
1933 snd-rme32= [HW,ALSA]
1934
1935 snd-rme96= [HW,ALSA]
1936
1937 snd-rme9652= [HW,ALSA]
1938
1939 snd-sb8= [HW,ALSA]
1940
1941 snd-sb16= [HW,ALSA]
1942
1943 snd-sbawe= [HW,ALSA]
1944
1945 snd-serial= [HW,ALSA]
1946
1947 snd-sgalaxy= [HW,ALSA]
1948
1949 snd-sonicvibes= [HW,ALSA]
1950
1951 snd-sun-amd7930=
1952 [HW,ALSA]
1953
1954 snd-sun-cs4231= [HW,ALSA]
1955
1956 snd-trident= [HW,ALSA]
1957
1958 snd-usb-audio= [HW,ALSA,USB]
1959
1960 snd-via82xx= [HW,ALSA]
1961
1962 snd-virmidi= [HW,ALSA]
1963
1964 snd-wavefront= [HW,ALSA]
1965
1966 snd-ymfpci= [HW,ALSA]
a9913044 1967
1da177e4
LT
1968 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1969 See Documentation/sonypi.txt
1970
1971 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1972 See Documentation/specialix.txt.
1973
1974 spia_io_base= [HW,MTD]
1975 spia_fio_base=
1976 spia_pedr=
1977 spia_peddr=
1978
1979 sscape= [HW,OSS]
1980 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1981
1da177e4
LT
1982 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1983 See Documentation/scsi/st.txt.
1984
1da177e4
LT
1985 sti= [PARISC,HW]
1986 Format: <num>
1987 Set the STI (builtin display/keyboard on the HP-PARISC
1988 machines) console (graphic card) which should be used
1989 as the initial boot-console.
1990 See also comment in drivers/video/console/sticore.c.
1991
1992 sti_font= [HW]
1993 See comment in drivers/video/console/sticore.c.
1994
1995 stifb= [HW]
1996 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1997
42a7fc4a
GB
1998 sunrpc.pool_mode=
1999 [NFS]
2000 Control how the NFS server code allocates CPUs to
2001 service thread pools. Depending on how many NICs
2002 you have and where their interrupts are bound, this
2003 option will affect which CPUs will do NFS serving.
2004 Note: this parameter cannot be changed while the
2005 NFS server is running.
2006
2007 auto the server chooses an appropriate mode
2008 automatically using heuristics
2009 global a single global pool contains all CPUs
2010 percpu one pool for each CPU
2011 pernode one pool for each NUMA node (equivalent
2012 to global on non-NUMA machines)
2013
1da177e4 2014 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2015
1da177e4
LT
2016 switches= [HW,M68k]
2017
2018 sym53c416= [HW,SCSI]
2019 See header of drivers/scsi/sym53c416.c.
2020
5d6f647f
IM
2021 sysrq_always_enabled
2022 [KNL]
2023 Ignore sysrq setting - this boot parameter will
2024 neutralize any effect of /proc/sys/kernel/sysrq.
2025 Useful for debugging.
2026
1da177e4
LT
2027 t128= [HW,SCSI]
2028 See header of drivers/scsi/t128.c.
2029
2030 tdfx= [HW,DRM]
2031
2032 thash_entries= [KNL,NET]
2033 Set number of hash buckets for TCP connection
2034
f8707ec9
LB
2035 thermal.act= [HW,ACPI]
2036 -1: disable all active trip points in all thermal zones
2037 <degrees C>: override all lowest active trip points
2038
c52a7419
LB
2039 thermal.crt= [HW,ACPI]
2040 -1: disable all critical trip points in all thermal zones
2041 <degrees C>: lower all critical trip points
2042
f5487145
LB
2043 thermal.nocrt= [HW,ACPI]
2044 Set to disable actions on ACPI thermal zone
2045 critical and hot trip points.
2046
72b33ef8
LB
2047 thermal.off= [HW,ACPI]
2048 1: disable ACPI thermal control
2049
a70cdc52
LB
2050 thermal.psv= [HW,ACPI]
2051 -1: disable all passive trip points
2052 <degrees C>: override all passive trip points to this value
2053
730ff34d
LB
2054 thermal.tzp= [HW,ACPI]
2055 Specify global default ACPI thermal zone polling rate
2056 <deci-seconds>: poll all this frequency
2057 0: no polling (default)
2058
1da177e4
LT
2059 tipar.timeout= [HW,PPT]
2060 Set communications timeout in tenths of a second
2061 (default 15).
2062
2063 tipar.delay= [HW,PPT]
2064 Set inter-bit delay in microseconds (default 10).
2065
1da177e4
LT
2066 tmscsim= [HW,SCSI]
2067 See comment before function dc390_setup() in
2068 drivers/scsi/tmscsim.c.
2069
2070 tp720= [HW,PS2]
2071
2072 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2073 Format:
2074 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2075
a9913044
RD
2076 turbografx.map[2|3]= [HW,JOY]
2077 TurboGraFX parallel port interface
2078 Format:
2079 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2080 See also Documentation/input/joystick-parport.txt
2081
2082 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2083 See header of drivers/scsi/u14-34f.c.
2084
2085 uart401= [HW,OSS]
2086 Format: <io>,<irq>
2087
2088 uart6850= [HW,OSS]
2089 Format: <io>,<irq>
2090
5f8364b7
AS
2091 uhci-hcd.ignore_oc=
2092 [USB] Ignore overcurrent events (default N).
2093 Some badly-designed motherboards generate lots of
2094 bogus events, for ports that aren't wired to
2095 anything. Set this parameter to avoid log spamming.
2096 Note that genuine overcurrent events won't be
2097 reported either.
2098
b5e795f8
AS
2099 usbcore.autosuspend=
2100 [USB] The autosuspend time delay (in seconds) used
2101 for newly-detected USB devices (default 2). This
2102 is the time required before an idle device will be
2103 autosuspended. Devices for which the delay is set
eaafbc3a 2104 to a negative value won't be autosuspended at all.
b5e795f8 2105
1da177e4
LT
2106 usbhid.mousepoll=
2107 [USBHID] The interval which mice are to be polled at.
a9913044 2108
cd4f0ef7 2109 vdso= [X86-32,SH,x86-64]
1dbf527c 2110 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2111 vdso=1: enable VDSO (default)
2112 vdso=0: disable VDSO mapping
2113
af65d648
RM
2114 vdso32= [X86-32,X86-64]
2115 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2116 vdso32=1: enable 32-bit VDSO (default)
2117 vdso32=0: disable 32-bit VDSO mapping
2118
d080d397
YI
2119 vector= [IA-64,SMP]
2120 vector=percpu: enable percpu vector domain
2121
1da177e4
LT
2122 video= [FB] Frame buffer configuration
2123 See Documentation/fb/modedb.txt.
2124
cd4f0ef7 2125 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2126 See Documentation/i386/boot.txt and
2127 Documentation/svga.txt.
1da177e4
LT
2128 Use vga=ask for menu.
2129 This is actually a boot loader parameter; the value is
2130 passed to the kernel using a special protocol.
2131
a9913044 2132 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2133 size of <nn>. This can be used to increase the
2134 minimum size (128MB on x86). It can also be used to
2135 decrease the size and leave more room for directly
2136 mapped kernel RAM.
2137
585c3047
PO
2138 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2139 Format: <command>
1da177e4 2140
585c3047
PO
2141 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2142 Format: <command>
2143
2144 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2145 Format: <command>
a9913044 2146
1da177e4
LT
2147 waveartist= [HW,OSS]
2148 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2149
1da177e4
LT
2150 wd33c93= [HW,SCSI]
2151 See header of drivers/scsi/wd33c93.c.
2152
2153 wd7000= [HW,SCSI]
2154 See header of drivers/scsi/wd7000.c.
2155
2156 wdt= [WDT] Watchdog
8dfe9c21 2157 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2158
2159 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2160 xd_geo= See header of drivers/block/xd.c.
2161
2162 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2163 Format:
2164 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2165
a62eaf15
AK
2166 norandmaps Don't use address space randomization
2167 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2168
a9913044 2169______________________________________________________________________
1da177e4
LT
2170
2171TODO:
2172
2173 Add documentation for ALSA options.
2174 Add more DRM drivers.
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