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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
1da177e4 297 apm= [APM] Advanced Power Management
71f77055 298 See header of arch/x86/kernel/apm_32.c.
1da177e4 299
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300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
301 Format: <io>,<irq>,<nodeID>
302
303 ataflop= [HW,M68k]
304
305 atarimouse= [HW,MOUSE] Atari Mouse
306
307 atascsi= [HW,SCSI] Atari SCSI
308
309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
310 EzKey and similar keyboards
311
312 atkbd.reset= [HW] Reset keyboard during initialization
313
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314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
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316
317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
318 keyboards
319
320 atkbd.softraw= [HW] Choose between synthetic and real raw mode
321 Format: <bool> (0 = real, 1 = synthetic (default))
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322
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
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325
326 autotest [IA64]
327
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328 baycom_epp= [HW,AX25]
329 Format: <io>,<mode>
a9913044 330
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331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
332 Format: <io>,<mode>
333 See header of drivers/net/hamradio/baycom_par.c.
334
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335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
339
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340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
344
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345 boot_delay= Milliseconds to delay each printk during boot.
346 Values larger than 10 seconds (10000) are changed to
347 no delay (0).
348 Format: integer
349
1da177e4 350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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351 bttv.radio= Most important insmod options are available as
352 kernel args too.
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353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
355
356 BusLogic= [HW,SCSI]
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
359
360 c101= [NET] Moxa C101 synchronous serial card
361
cd4f0ef7 362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
368
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369 security= [SECURITY] Choose a security module to enable at boot.
370 If this boot parameter is not specified, only the first
371 security module asking for security registration will be
372 loaded. An invalid security module name will be treated
373 as if no module has been chosen.
374
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375 capability.disable=
376 [SECURITY] Disable capabilities. This would normally
377 be used only if an alternative security model is to be
378 configured. Potentially dangerous and should only be
379 used if you are entirely sure of the consequences.
380
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381 ccw_timeout_log [S390]
382 See Documentation/s390/CommonIO for details.
1da177e4 383
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384 cgroup_disable= [KNL] Disable a particular controller
385 Format: {name of the controller(s) to disable}
386 {Currently supported controllers - "memory"}
387
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388 checkreqprot [SELINUX] Set initial checkreqprot flag value.
389 Format: { "0" | "1" }
390 See security/selinux/Kconfig help text.
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391 0 -- check protection applied by kernel (includes
392 any implied execute protection).
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393 1 -- check protection requested by application.
394 Default value is set via a kernel config option.
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395 Value can be changed at runtime via
396 /selinux/checkreqprot.
397
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398 cio_ignore= [S390]
399 See Documentation/s390/CommonIO for details.
400
cd4f0ef7 401 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 402 [Deprecated]
3f6dee9b 403 Forces specified clocksource (if available) to be used
734efb46 404 when calculating gettimeofday(). If specified
3f6dee9b 405 clocksource is not available, it defaults to PIT.
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406 Format: { pit | tsc | cyclone | pmtmr }
407
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408 clocksource= [GENERIC_TIME] Override the default clocksource
409 Format: <string>
410 Override the default clocksource and use the clocksource
411 with the name specified.
412 Some clocksource names to choose from, depending on
413 the platform:
414 [all] jiffies (this is the base, fallback clocksource)
415 [ACPI] acpi_pm
416 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
417 pxa_timer,timer3,32k_counter,timer0_1
418 [AVR32] avr32
cd4f0ef7 419 [X86-32] pit,hpet,tsc,vmi-timer;
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420 scx200_hrt on Geode; cyclone on IBM x440
421 [MIPS] MIPS
422 [PARISC] cr16
423 [S390] tod
424 [SH] SuperH
425 [SPARC64] tick
426 [X86-64] hpet,tsc
427
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428 clearcpuid=BITNUM [X86]
429 Disable CPUID feature X for the kernel. See
430 include/asm-x86/cpufeature.h for the valid bit numbers.
431 Note the Linux specific bits are not necessarily
432 stable over kernel options, but the vendor specific
433 ones should be.
434 Also note that user programs calling CPUID directly
435 or using the feature without checking anything
436 will still see it. This just prevents it from
437 being used by the kernel or shown in /proc/cpuinfo.
438 Also note the kernel might malfunction if you disable
439 some critical bits.
440
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441 code_bytes [IA32/X86_64] How many bytes of object code to print
442 in an oops report.
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443 Range: 0 - 8192
444 Default: 64
445
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446 disable_8254_timer
447 enable_8254_timer
448 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
449 over the 8254 in addition to over the IO-APIC. The
450 kernel tries to set a sensible default.
451
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452 hpet= [X86-32,HPET] option to control HPET usage
453 Format: { enable (default) | disable | force }
454 disable: disable HPET and use PIT instead
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455 force: allow force enabled of undocumented chips (ICH4,
456 VIA, nVidia)
1da177e4 457
1da177e4 458 com20020= [HW,NET] ARCnet - COM20020 chipset
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459 Format:
460 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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461
462 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
463 Format: <io>[,<irq>]
464
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465 com90xx= [HW,NET]
466 ARCnet - COM90xx chipset (memory-mapped buffers)
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467 Format: <io>[,<irq>[,<memstart>]]
468
469 condev= [HW,S390] console device
470 conmode=
a9913044 471
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472 console= [KNL] Output console device and options.
473
474 tty<n> Use the virtual console device <n>.
475
476 ttyS<n>[,options]
f1a1c2dc 477 ttyUSB0[,options]
1da177e4 478 Use the specified serial port. The options are of
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479 the form "bbbbpnf", where "bbbb" is the baud rate,
480 "p" is parity ("n", "o", or "e"), "n" is number of
481 bits, and "f" is flow control ("r" for RTS or
482 omit it). Default is "9600n8".
483
484 See Documentation/serial-console.txt for more
485 information. See
486 Documentation/networking/netconsole.txt for an
487 alternative.
1da177e4 488
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489 uart[8250],io,<addr>[,options]
490 uart[8250],mmio,<addr>[,options]
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491 Start an early, polled-mode console on the 8250/16550
492 UART at the specified I/O port or MMIO address,
493 switching to the matching ttyS device later. The
494 options are the same as for ttyS, above.
495
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496 If the device connected to the port is not a TTY but a braille
497 device, prepend "brl," before the device type, for instance
498 console=brl,ttyS0
499 For now, only VisioBraille is supported.
500
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501 earlycon= [KNL] Output early console device and options.
502 uart[8250],io,<addr>[,options]
503 uart[8250],mmio,<addr>[,options]
504 Start an early, polled-mode console on the 8250/16550
505 UART at the specified I/O port or MMIO address.
506 The options are the same as for ttyS, above.
507
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508 no_console_suspend
509 [HW] Never suspend the console
510 Disable suspending of consoles during suspend and
511 hibernate operations. Once disabled, debugging
512 messages can reach various consoles while the rest
513 of the system is being put to sleep (ie, while
514 debugging driver suspend/resume hooks). This may
515 not work reliably with all consoles, but is known
516 to work with serial and VGA consoles.
517
1da177e4 518 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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519 Format:
520 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 521
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522 crashkernel=nn[KMG]@ss[KMG]
523 [KNL] Reserve a chunk of physical memory to
524 hold a kernel to switch to with kexec on panic.
525
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526 crashkernel=range1:size1[,range2:size2,...][@offset]
527 [KNL] Same as above, but depends on the memory
528 in the running system. The syntax of range is
529 start-[end] where start and end are both
530 a memory unit (amount[KMG]). See also
531 Documentation/kdump/kdump.txt for a example.
532
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LT
533 cs4232= [HW,OSS]
534 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
535
536 cs89x0_dma= [HW,NET]
537 Format: <dma>
538
539 cs89x0_media= [HW,NET]
540 Format: { rj45 | aui | bnc }
a9913044 541
a9913044 542 dasd= [HW,NET]
1da177e4
LT
543 See header of drivers/s390/block/dasd_devmap.c.
544
545 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
546 (one device per port)
547 Format: <port#>,<type>
548 See also Documentation/input/joystick-parport.txt
549
550 debug [KNL] Enable kernel debugging (events log level).
551
cae2ed9a
IM
552 debug_locks_verbose=
553 [KNL] verbose self-tests
554 Format=<0|1>
555 Print debugging info while doing the locking API
556 self-tests.
557 We default to 0 (no extra messages), setting it to
558 1 will print _a lot_ more information - normally
559 only useful to kernel developers.
560
3ac7fe5a
TG
561 debug_objects [KNL] Enable object debugging
562
2d27a966 563 decnet.addr= [HW,NET]
1da177e4
LT
564 Format: <area>[,<node>]
565 See also Documentation/networking/decnet.txt.
566
ecb77fa9 567 vt.default_blu= [VT]
55ff9780
AD
568 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
569 Change the default blue palette of the console.
570 This is a 16-member array composed of values
571 ranging from 0-255.
572
ecb77fa9 573 vt.default_grn= [VT]
55ff9780
AD
574 Format: <green0>,<green1>,<green2>,...,<green15>
575 Change the default green palette of the console.
576 This is a 16-member array composed of values
577 ranging from 0-255.
578
ecb77fa9 579 vt.default_red= [VT]
55ff9780
AD
580 Format: <red0>,<red1>,<red2>,...,<red15>
581 Change the default red palette of the console.
582 This is a 16-member array composed of values
583 ranging from 0-255.
584
ecb77fa9
ST
585 vt.default_utf8=
586 [VT]
55ff9780
AD
587 Format=<0|1>
588 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
589 Default is 1, i.e. UTF-8 mode is enabled for all
590 newly opened terminals.
55ff9780 591
1da177e4
LT
592 dhash_entries= [KNL]
593 Set number of hash buckets for dentry cache.
a9913044 594
1da177e4
LT
595 digi= [HW,SERIAL]
596 IO parameters + enable/disable command.
597
598 digiepca= [HW,SERIAL]
599 See drivers/char/README.epca and
600 Documentation/digiepca.txt.
601
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 640 See comment before function elanfreq_setup() in
71f77055 641 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
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
f13ae30e
AC
689 force_pal_cache_flush
690 [IA-64] Avoid check_sal_cache_flush which may hang on
691 buggy SAL_CACHE_FLUSH implementations. Using this
692 parameter will force ia64_sal_cache_flush to call
693 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
694
1da177e4
LT
695 gamecon.map[2|3]=
696 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
697 support via parallel port (up to 5 devices per port)
698 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
699 See also Documentation/input/joystick-parport.txt
700
701 gamma= [HW,DRM]
702
aaf23042
YL
703 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
704 Format: off | on
705 default: on
706
1da177e4
LT
707 gdth= [HW,SCSI]
708 See header of drivers/scsi/gdth.c.
709
710 gpt [EFI] Forces disk with valid GPT signature but
711 invalid Protective MBR to be treated as GPT.
712
1da177e4
LT
713 gvp11= [HW,SCSI]
714
715 hashdist= [KNL,NUMA] Large hashes allocated during boot
716 are distributed across NUMA nodes. Defaults on
717 for IA-64, off otherwise.
a9913044 718 Format: 0 | 1 (for off | on)
1da177e4
LT
719
720 hcl= [IA-64] SGI's Hardware Graph compatibility layer
721
722 hd= [EIDE] (E)IDE hard drive subsystem geometry
723 Format: <cyl>,<head>,<sect>
724
725 hd?= [HW] (E)IDE subsystem
1c10e938 726 hd?lun= See Documentation/ide/ide.txt.
1da177e4
LT
727
728 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
729 size of <nn>. This works even on boxes that have no
730 highmem otherwise. This also works to reduce highmem
731 size on bigger boxes.
732
54cdfdb4
TG
733 highres= [KNL] Enable/disable high resolution timer mode.
734 Valid parameters: "on", "off"
735 Default: "on"
736
1da177e4
LT
737 hisax= [HW,ISDN]
738 See Documentation/isdn/README.HiSax.
739
cd4f0ef7 740 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 741 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 742
1da177e4 743 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
744 i8042.dumbkbd [HW] Pretend that controller can only read data from
745 keyboard and cannot control its state
1da177e4
LT
746 (Don't attempt to blink the leds)
747 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 748 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
749 i8042.noloop [HW] Disable the AUX Loopback command while probing
750 for the AUX port
1da177e4
LT
751 i8042.nomux [HW] Don't check presence of an active multiplexing
752 controller
753 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
754 controllers
755 i8042.panicblink=
756 [HW] Frequency with which keyboard LEDs should blink
757 when kernel panics (default is 0.5 sec)
758 i8042.reset [HW] Reset the controller during init and cleanup
759 i8042.unlock [HW] Unlock (ignore) the keylock
760
761 i810= [HW,DRM]
762
e70c9d5e
DT
763 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
764 indicates that the driver is running on unsupported
765 hardware.
1da177e4
LT
766 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
767 does not match list of supported models.
768 i8k.power_status
769 [HW] Report power status in /proc/i8k
770 (disabled by default)
771 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
772 capability is set.
773
774 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
775 See Documentation/mca.txt.
776
777 icn= [HW,ISDN]
778 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
779
780 ide= [HW] (E)IDE subsystem
a594eeb1 781 Format: ide=nodma or ide=doubler
1c10e938 782 See Documentation/ide/ide.txt.
1da177e4 783
1da177e4 784 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 785 See Documentation/ide/ide.txt.
1da177e4 786
f039b754
AK
787 idle= [X86]
788 Format: idle=poll or idle=mwait
789 Poll forces a polling idle loop that can slightly improves the performance
790 of waking up a idle CPU, but will use a lot of power and make the system
791 run hot. Not recommended.
792 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
793 to not use it because it doesn't save as much power as a normal idle
794 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
795 as idle=poll.
a9913044 796
594765a7
DC
797 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
798 Claim all unknown PCI IDE storage controllers.
799
79290822
IM
800 ignore_loglevel [KNL]
801 Ignore loglevel setting - this will print /all/
802 kernel messages to the console. Useful for debugging.
803
1da177e4
LT
804 ihash_entries= [KNL]
805 Set number of hash buckets for inode cache.
806
807 in2000= [HW,SCSI]
808 See header of drivers/scsi/in2000.c.
809
810 init= [KNL]
811 Format: <full_path>
812 Run specified binary instead of /sbin/init as init
813 process.
814
815 initcall_debug [KNL] Trace initcalls as they are executed. Useful
816 for working out where the kernel is dying during
817 startup.
818
819 initrd= [BOOT] Specify the location of the initial ramdisk
820
821 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
822 Format: <irq>
823
824 inttest= [IA64]
825
b552da87
PM
826 iommu= [x86]
827 off
828 force
829 noforce
830 biomerge
831 panic
832 nopanic
833 merge
834 nomerge
835 forcesac
836 soft
837
838
ba395927
KA
839 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
840 off
841 Disable intel iommu driver.
842 igfx_off [Default Off]
843 By default, gfx is mapped as normal device. If a gfx
844 device has a dedicated DMAR unit, the DMAR unit is
845 bypassed by not enabling DMAR with this option. In
846 this case, gfx device will use physical address for
847 DMA.
7d3b03ce
KA
848 forcedac [x86_64]
849 With this option iommu will not optimize to look
850 for io virtual address below 32 bit forcing dual
851 address cycle on pci bus for cards supporting greater
852 than 32 bit addressing. The default is to look
853 for translation below 32 bit and if not available
854 then look in the higher range.
5e0d2a6f 855 strict [Default Off]
856 With this option on every unmap_single operation will
857 result in a hardware IOTLB flush operation as opposed
858 to batching them for performance.
ba395927 859
b02aae9c 860 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
861 0x80
862 Standard port 0x80 based delay
863 0xed
864 Alternate port 0xed based delay (needed on some systems)
b02aae9c 865 udelay
6e7c4025
IM
866 Simple two microseconds delay
867 none
868 No delay
b02aae9c 869
1da177e4
LT
870 io7= [HW] IO7 for Marvel based alpha systems
871 See comment before marvel_specify_io7 in
872 arch/alpha/kernel/core_marvel.c.
873
874 ip= [IP_PNP]
6ded55da 875 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
876
877 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
878 See comment before ip2_setup() in
879 drivers/char/ip2/ip2base.c.
1da177e4
LT
880
881 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
882 See header of drivers/scsi/ips.c.
883
72c4a13a
SH
884 ports= [IP_VS_FTP] IPVS ftp helper module
885 Default is 21.
886 Up to 8 (IP_VS_APP_MAX_PORTS) ports
887 may be specified.
888 Format: <port>,<port>....
889
200803df
AC
890 irqfixup [HW]
891 When an interrupt is not handled search all handlers
892 for it. Intended to get systems with badly broken
893 firmware running.
894
895 irqpoll [HW]
896 When an interrupt is not handled search all handlers
897 for it. Also check all handlers each timer
898 interrupt. Intended to get systems with badly broken
899 firmware running.
900
1da177e4 901 isapnp= [ISAPNP]
a9913044 902 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
903
904 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
905 Format:
906 <cpu number>,...,<cpu number>
907 or
908 <cpu number>-<cpu number> (must be a positive range in ascending order)
909 or a mixture
910 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
911 This option can be used to specify one or more CPUs
912 to isolate from the general SMP balancing and scheduling
913 algorithms. The only way to move a process onto or off
914 an "isolated" CPU is via the CPU affinity syscalls.
915 <cpu number> begins at 0 and the maximum value is
916 "number of CPUs in system - 1".
917
918 This option is the preferred way to isolate CPUs. The
a9913044
RD
919 alternative -- manually setting the CPU mask of all
920 tasks in the system -- can cause problems and
921 suboptimal load balancer performance.
1da177e4 922
a9913044 923 iucv= [HW,NET]
1da177e4
LT
924
925 js= [HW,JOY] Analog joystick
926 See Documentation/input/joystick.txt.
927
cd4f0ef7 928 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
929 specifies the amount of memory usable by the kernel
930 for non-movable allocations. The requested amount is
931 spread evenly throughout all nodes in the system. The
932 remaining memory in each node is used for Movable
933 pages. In the event, a node is too small to have both
934 kernelcore and Movable pages, kernelcore pages will
935 take priority and other nodes will have a larger number
936 of kernelcore pages. The Movable zone is used for the
937 allocation of pages that may be reclaimed or moved
938 by the page migration subsystem. This means that
939 HugeTLB pages may not be allocated from this zone.
940 Note that allocations like PTEs-from-HighMem still
941 use the HighMem zone if it exists, and the Normal
942 zone if it does not.
943
cd4f0ef7 944 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
945 is similar to kernelcore except it specifies the
946 amount of memory used for migratable allocations.
947 If both kernelcore and movablecore is specified,
948 then kernelcore will be at *least* the specified
949 value but may be more. If movablecore on its own
950 is specified, the administrator must be careful
951 that the amount of memory usable for all allocations
952 is not too small.
953
1da177e4
LT
954 keepinitrd [HW,ARM]
955
cd4f0ef7 956 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
957 in oops dumps.
958
6cdf6e06
JW
959 kgdboc= [HW] kgdb over consoles.
960 Requires a tty driver that supports console polling.
961 (only serial suported for now)
962 Format: <serial_device>[,baud]
963
1da177e4
LT
964 l2cr= [PPC]
965
a78bfbfc
RB
966 l3cr= [PPC]
967
cd4f0ef7 968 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 969 disabled it.
1da177e4 970
cd4f0ef7 971 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
972 C2 power state.
973
fcb71f6f
FC
974 libata.dma= [LIBATA] DMA control
975 libata.dma=0 Disable all PATA and SATA DMA
976 libata.dma=1 PATA and SATA Disk DMA only
977 libata.dma=2 ATAPI (CDROM) DMA only
978 libata.dma=4 Compact Flash DMA only
979 Combinations also work, so libata.dma=3 enables DMA
980 for disks and CDROMs, but not CFs.
981
78e70c23
DJ
982 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
983 when set.
984 Format: <int>
985
33267325
TH
986 libata.force= [LIBATA] Force configurations. The format is comma
987 separated list of "[ID:]VAL" where ID is
988 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
989 matching port, link or device. Basically, it matches
990 the ATA ID string printed on console by libata. If
991 the whole ID part is omitted, the last PORT and DEVICE
992 values are used. If ID hasn't been specified yet, the
993 configuration applies to all ports, links and devices.
994
995 If only DEVICE is omitted, the parameter applies to
996 the port and all links and devices behind it. DEVICE
997 number of 0 either selects the first device or the
998 first fan-out link behind PMP device. It does not
999 select the host link. DEVICE number of 15 selects the
1000 host link and device attached to it.
1001
1002 The VAL specifies the configuration to force. As long
1003 as there's no ambiguity shortcut notation is allowed.
1004 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1005 The following configurations can be forced.
1006
1007 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1008 Any ID with matching PORT is used.
1009
1010 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1011
1012 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1013 udma[/][16,25,33,44,66,100,133] notation is also
1014 allowed.
1015
1016 * [no]ncq: Turn on or off NCQ.
1017
1018 If there are multiple matching configurations changing
1019 the same attribute, the last one is used.
1020
1da177e4
LT
1021 load_ramdisk= [RAM] List of ramdisks to load from floppy
1022 See Documentation/ramdisk.txt.
1023
a6b25b67
RD
1024 lockd.nlm_grace_period=P [NFS] Assign grace period.
1025 Format: <integer>
1da177e4 1026
a6b25b67
RD
1027 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1028 Format: <integer>
1029
1030 lockd.nlm_timeout=T [NFS] Assign timeout value.
1031 Format: <integer>
1032
1033 lockd.nlm_udpport=M [NFS] Assign UDP port.
1034 Format: <integer>
1da177e4
LT
1035
1036 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1037 Format: <irq>
1038
1039 loglevel= All Kernel Messages with a loglevel smaller than the
1040 console loglevel will be printed to the console. It can
1041 also be changed with klogd or other programs. The
1042 loglevels are defined as follows:
1043
1044 0 (KERN_EMERG) system is unusable
1045 1 (KERN_ALERT) action must be taken immediately
1046 2 (KERN_CRIT) critical conditions
1047 3 (KERN_ERR) error conditions
1048 4 (KERN_WARNING) warning conditions
1049 5 (KERN_NOTICE) normal but significant condition
1050 6 (KERN_INFO) informational
1051 7 (KERN_DEBUG) debug-level messages
1052
1053 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1054 Format: { n | nk | nM }
1055 n must be a power of two. The default size
1056 is set in the kernel config file.
1da177e4 1057
accaa24c
RD
1058 logo.nologo [FB] Disables display of the built-in Linux logo.
1059 This may be used to provide more screen space for
1060 kernel log messages and is useful when debugging
1061 kernel boot problems.
1062
1da177e4
LT
1063 lp=0 [LP] Specify parallel ports to use, e.g,
1064 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1065 lp=reset first parallel port). 'lp=0' disables the
1066 lp=auto printer driver. 'lp=reset' (which can be
1067 specified in addition to the ports) causes
1068 attached printers to be reset. Using
1069 lp=port1,port2,... specifies the parallel ports
1070 to associate lp devices with, starting with
1071 lp0. A port specification may be 'none' to skip
1072 that lp device, or a parport name such as
1073 'parport0'. Specifying 'lp=auto' instead of a
1074 port specification list means that device IDs
1075 from each port should be examined, to see if
1076 an IEEE 1284-compliant printer is attached; if
1077 so, the driver will manage that printer.
1078 See also header of drivers/char/lp.c.
1079
1080 lpj=n [KNL]
1081 Sets loops_per_jiffy to given constant, thus avoiding
1082 time-consuming boot-time autodetection (up to 250 ms per
1083 CPU). 0 enables autodetection (default). To determine
1084 the correct value for your kernel, boot with normal
1085 autodetection and see what value is printed. Note that
1086 on SMP systems the preset will be applied to all CPUs,
1087 which is likely to cause problems if your CPUs need
1088 significantly divergent settings. An incorrect value
1089 will cause delays in the kernel to be wrong, leading to
1090 unpredictable I/O errors and other breakage. Although
1091 unlikely, in the extreme case this might damage your
1092 hardware.
1093
1094 ltpc= [NET]
1095 Format: <io>,<irq>,<dma>
1096
a9913044
RD
1097 mac5380= [HW,SCSI] Format:
1098 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1099
a9913044
RD
1100 machvec= [IA64] Force the use of a particular machine-vector
1101 (machvec) in a generic kernel.
1102 Example: machvec=hpzx1_swiotlb
1da177e4 1103
a9913044 1104 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1105 be mounted
1106 Format: <1-256>
1107
1108 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1109 should make use of. maxcpus=n : n >= 0 limits the
1110 kernel to using 'n' processors. n=0 is a special case,
1111 it is equivalent to "nosmp", which also disables
1112 the IO APIC.
1da177e4 1113
2b2c3750
BP
1114 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1115 equal to this physical address is ignored.
1116
a9913044 1117 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1118 Should be between 1 and 2^32-1.
1119
1120 max_report_luns=
a9913044 1121 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1122 Should be between 1 and 16384.
1123
1da177e4
LT
1124 mcatest= [IA-64]
1125
cd4f0ef7 1126 mce [X86-32] Machine Check Exception
1da177e4 1127
909dd324
AK
1128 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1129
1da177e4
LT
1130 md= [HW] RAID subsystems devices and level
1131 See Documentation/md.txt.
a9913044 1132
1da177e4
LT
1133 mdacon= [MDA]
1134 Format: <first>,<last>
1135 Specifies range of consoles to be captured by the MDA.
a9913044 1136
1da177e4
LT
1137 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1138 Amount of memory to be used when the kernel is not able
1139 to see the whole system memory or for test.
cd4f0ef7 1140 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1141 address space collisions. Without memmap= PCI devices
1142 could be placed at addresses belonging to unused RAM.
1143
cd4f0ef7 1144 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1145 memory.
1146
cd4f0ef7 1147 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1148 E820 memory map, as specified by the user.
1149 Such memmap=exactmap lines can be constructed based on
1150 BIOS output or other requirements. See the memmap=nn@ss
1151 option description.
1152
1153 memmap=nn[KMG]@ss[KMG]
1154 [KNL] Force usage of a specific region of memory
1155 Region of memory to be used, from ss to ss+nn.
1156
1157 memmap=nn[KMG]#ss[KMG]
1158 [KNL,ACPI] Mark specific memory as ACPI data.
1159 Region of memory to be used, from ss to ss+nn.
1160
1161 memmap=nn[KMG]$ss[KMG]
1162 [KNL,ACPI] Mark specific memory as reserved.
1163 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1164 Example: Exclude memory from 0x18690000-0x1869ffff
1165 memmap=64K$0x18690000
1166 or
1167 memmap=0x10000$0x18690000
1da177e4 1168
c64df707
YL
1169 memtest= [KNL,X86_64] Enable memtest
1170 Format: <integer>
1171 range: 0,4 : pattern number
1172 default : 0 <disable>
1173
1da177e4
LT
1174 meye.*= [HW] Set MotionEye Camera parameters
1175 See Documentation/video4linux/meye.txt.
1176
8f36881b
AS
1177 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1178 Multi-Function General Purpose Timers on AMD Geode
1179 platforms.
1180
e6c4dc6c
WT
1181 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1182 the BIOS has incorrectly applied a workaround. TinyBIOS
1183 version 0.98 is known to be affected, 0.99 fixes the
1184 problem by letting the user disable the workaround.
1185
1da177e4
LT
1186 mga= [HW,DRM]
1187
1188 mousedev.tap_time=
1189 [MOUSE] Maximum time between finger touching and
1190 leaving touchpad surface for touch to be considered
1191 a tap and be reported as a left button click (for
1192 touchpads working in absolute mode only).
1193 Format: <msecs>
1194 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1195 reporting absolute coordinates, such as tablets
1196 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1197 reporting absolute coordinates, such as tablets
1198
1199 mpu401= [HW,OSS]
1200 Format: <io>,<irq>
1201
1202 MTD_Partition= [MTD]
1203 Format: <name>,<region-number>,<size>,<offset>
1204
a9913044
RD
1205 MTD_Region= [MTD] Format:
1206 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1207
1208 mtdparts= [MTD]
c8facbb6 1209 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1210
1211 mtouchusb.raw_coordinates=
a9913044
RD
1212 [HW] Make the MicroTouch USB driver use raw coordinates
1213 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1214
1215 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1216
1217 NCR_D700= [HW,SCSI]
1218 See header of drivers/scsi/NCR_D700.c.
1219
1220 ncr5380= [HW,SCSI]
1221
1222 ncr53c400= [HW,SCSI]
1223
1224 ncr53c400a= [HW,SCSI]
1225
1226 ncr53c406a= [HW,SCSI]
1227
1228 ncr53c8xx= [HW,SCSI]
1229
1230 netdev= [NET] Network devices parameters
1231 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1232 Note that mem_start is often overloaded to mean
1233 something different and driver-specific.
a9913044
RD
1234 This usage is only documented in each driver source
1235 file if at all.
1236
1da177e4 1237 nfsaddrs= [NFS]
6ded55da 1238 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1239
1240 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1241 See Documentation/filesystems/nfsroot.txt.
1da177e4 1242
a72b4422
TM
1243 nfs.callback_tcpport=
1244 [NFS] set the TCP port on which the NFSv4 callback
1245 channel should listen.
1246
58df095b
TM
1247 nfs.idmap_cache_timeout=
1248 [NFS] set the maximum lifetime for idmapper cache
1249 entries.
1250
f43bf0be
TM
1251 nfs.enable_ino64=
1252 [NFS] enable 64-bit inode numbers.
1253 If zero, the NFS client will fake up a 32-bit inode
1254 number for the readdir() and stat() syscalls instead
1255 of returning the full 64-bit number.
1256 The default is to return 64-bit inode numbers.
1257
e7ba176b
HS
1258 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1259 when a NMI is triggered.
1260 Format: [state][,regs][,debounce][,die]
1261
cd4f0ef7 1262 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1263
cd4f0ef7 1264 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1265 emulation library even if a 387 maths coprocessor
1266 is present.
1267
c1aee215
CL
1268 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1269 caches in the slab allocator. Saves per-node memory,
1270 but will impact performance.
3395ee05 1271
a9913044
RD
1272 noalign [KNL,ARM]
1273
1da177e4
LT
1274 noapic [SMP,APIC] Tells the kernel to not make use of any
1275 IOAPICs that may be present in the system.
1276
1da177e4
LT
1277 nobats [PPC] Do not use BATs for mapping kernel lowmem
1278 on "Classic" PPC cores.
1279
1280 nocache [ARM]
a9913044 1281
163ecdff
SN
1282 nodelayacct [KNL] Disable per-task delay accounting
1283
1da177e4
LT
1284 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1285
8b2cb7a8
HY
1286 noefi [X86-32,X86-64] Disable EFI runtime services support.
1287
1da177e4
LT
1288 noexec [IA-64]
1289
cd4f0ef7 1290 noexec [X86-32,X86-64]
f5a1b191 1291 On X86-32 available only on PAE configured kernels.
1da177e4 1292 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1293 noexec=off: disable non-executable mappings
1294
1295 noexec32 [X86-64]
1296 This affects only 32-bit executables.
1297 noexec32=on: enable non-executable mappings (default)
1298 read doesn't imply executable mappings
1299 noexec32=off: disable non-executable mappings
1300 read implies executable mappings
1da177e4 1301
cd4f0ef7 1302 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1303 register save and restore. The kernel will only save
1304 legacy floating-point registers on task switch.
1da177e4 1305
191679fd
AK
1306 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1307
1da177e4 1308 nohlt [BUGS=ARM]
a9913044 1309
cd4f0ef7 1310 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1311 instruction doesn't work correctly and not to
1312 use it.
1313
1314 nohalt [IA-64] Tells the kernel not to use the power saving
1315 function PAL_HALT_LIGHT when idle. This increases
1316 power-consumption. On the positive side, it reduces
1317 interrupt wake-up latency, which may improve performance
1318 in certain environments such as networked servers or
1319 real-time systems.
1320
79bf2bb3
TG
1321 nohz= [KNL] Boottime enable/disable dynamic ticks
1322 Valid arguments: on, off
1323 Default: on
1324
cd4f0ef7 1325 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1326
cd4f0ef7 1327 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1328 disable unhandled interrupt sources.
1329
cd4f0ef7 1330 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1331 broken timer IRQ sources.
1332
1da177e4
LT
1333 noisapnp [ISAPNP] Disables ISA PnP code.
1334
1335 noinitrd [RAM] Tells the kernel not to load any configured
1336 initial RAM disk.
1337
1338 nointroute [IA-64]
1339
0aa366f3
TL
1340 nojitter [IA64] Disables jitter checking for ITC timers.
1341
cd4f0ef7 1342 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1343
cd4f0ef7 1344 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1345
1da177e4
LT
1346 noltlbs [PPC] Do not use large page/tlb entries for kernel
1347 lowmem mapping on PPC40x.
1348
312f1f01
H
1349 nomca [IA-64] Disable machine check abort handling
1350
cd4f0ef7 1351 nomce [X86-32] Machine Check Exception
abe37e5a 1352
83d7384f
AS
1353 nomfgpt [X86-32] Disable Multi-Function General Purpose
1354 Timer usage (for AMD Geode machines).
1355
cd4f0ef7 1356 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1357
cd4f0ef7 1358 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1359 with UP alternatives
1360
1da177e4
LT
1361 noresidual [PPC] Don't use residual data on PReP machines.
1362
a9913044
RD
1363 noresume [SWSUSP] Disables resume and restores original swap
1364 space.
1365
1da177e4
LT
1366 no-scroll [VGA] Disables scrollback.
1367 This is required for the Braillex ib80-piezo Braille
1368 reader made by F.H. Papenmeier (Germany).
1369
1370 nosbagart [IA-64]
1371
cd4f0ef7 1372 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1373
61ec7567
LB
1374 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1375 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1376
97842216
DJ
1377 nosoftlockup [KNL] Disable the soft-lockup detector.
1378
1da177e4
LT
1379 nosync [HW,M68K] Disables sync negotiation for all devices.
1380
cd4f0ef7 1381 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1382
1383 nousb [USB] Disable the USB subsystem
1384
1385 nowb [ARM]
a9913044 1386
a6c75b86
FY
1387 nptcg= [IA64] Override max number of concurrent global TLB
1388 purges which is reported from either PAL_VM_SUMMARY or
1389 SAL PALO.
1390
f0c0b2b8
KH
1391 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1392 one of ['zone', 'node', 'default'] can be specified
1393 This can be set from sysctl after boot.
1394 See Documentation/sysctl/vm.txt for details.
1395
a61c2d78
DJ
1396 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1397
3ef0e1f8
AS
1398 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1399 Rather than timing out after 20 ms if an EC
1400 command is not properly ACKed, override the length
1401 of the timeout. We have interrupts disabled while
1402 waiting for the ACK, so if this is set too high
1403 interrupts *may* be lost!
1404
1da177e4
LT
1405 opl3= [HW,OSS]
1406 Format: <io>
1407
1da177e4
LT
1408 oprofile.timer= [HW]
1409 Use timer interrupt instead of performance counters
1410
1da177e4
LT
1411 osst= [HW,SCSI] SCSI Tape Driver
1412 Format: <buffer_size>,<write_threshold>
1413 See also Documentation/scsi/st.txt.
1414
1415 panic= [KNL] Kernel behaviour on panic
1416 Format: <timeout>
1417
1418 parkbd.port= [HW] Parallel port number the keyboard adapter is
1419 connected to, default is 0.
1420 Format: <parport#>
1421 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1422 0 for XT, 1 for AT (default is AT).
a9913044
RD
1423 Format: <mode>
1424
1425 parport= [HW,PPT] Specify parallel ports. 0 disables.
1426 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1427 Use 'auto' to force the driver to use any
1428 IRQ/DMA settings detected (the default is to
1429 ignore detected IRQ/DMA settings because of
1430 possible conflicts). You can specify the base
1431 address, IRQ, and DMA settings; IRQ and DMA
1432 should be numbers, or 'auto' (for using detected
1433 settings on that particular port), or 'nofifo'
1434 (to avoid using a FIFO even if it is detected).
1435 Parallel ports are assigned in the order they
1436 are specified on the command line, starting
1437 with parport0.
1438
1439 parport_init_mode= [HW,PPT]
1440 Configure VIA parallel port to operate in
1441 a specific mode. This is necessary on Pegasos
1442 computer where firmware has no options for setting
1443 up parallel port mode and sets it to spp.
1444 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1445 Format: [spp|ps2|epp|ecp|ecpepp]
1446
a9913044
RD
1447 pas2= [HW,OSS] Format:
1448 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1449
1da177e4
LT
1450 pas16= [HW,SCSI]
1451 See header of drivers/scsi/pas16.c.
1452
dd287796
AM
1453 pause_on_oops=
1454 Halt all CPUs after the first oops has been printed for
1455 the specified number of seconds. This is to be used if
1456 your oopses keep scrolling off the screen.
1457
1da177e4
LT
1458 pcbit= [HW,ISDN]
1459
1460 pcd. [PARIDE]
1461 See header of drivers/block/paride/pcd.c.
1462 See also Documentation/paride.txt.
1463
a9913044 1464 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1465 off [X86-32] don't probe for the PCI bus
1466 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1467 the hardware directly. Use this if your machine
1468 has a non-standard PCI host bridge.
cd4f0ef7 1469 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1470 hardware access methods are allowed. Use this
1471 if you experience crashes upon bootup and you
1472 suspect they are caused by the BIOS.
cd4f0ef7 1473 conf1 [X86-32] Force use of PCI Configuration
a9913044 1474 Mechanism 1.
cd4f0ef7 1475 conf2 [X86-32] Force use of PCI Configuration
a9913044 1476 Mechanism 2.
7f785763
RD
1477 noaer [PCIE] If the PCIEAER kernel config parameter is
1478 enabled, this kernel boot option can be used to
1479 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1480 nodomains [PCI] Disable support for multiple PCI
1481 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1482 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1483 Configuration
309e57df
MW
1484 nomsi [MSI] If the PCI_MSI kernel config parameter is
1485 enabled, this kernel boot option can be used to
1486 disable the use of MSI interrupts system-wide.
cd4f0ef7 1487 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1488 routing table. These calls are known to be buggy
1489 on several machines and they hang the machine
1490 when used, but on other computers it's the only
1491 way to get the interrupt routing table. Try
1492 this option if the kernel is unable to allocate
1493 IRQs or discover secondary PCI buses on your
1494 motherboard.
cd4f0ef7 1495 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1496 Use with caution as certain devices share
1497 address decoders between ROMs and other
1498 resources.
cd4f0ef7 1499 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1500 assigned automatically to PCI devices. You can
1501 make the kernel exclude IRQs of your ISA cards
1502 this way.
cd4f0ef7 1503 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1504 of the PIRQ table (normally generated
1505 by the BIOS) if it is outside the
1506 F0000h-100000h range.
cd4f0ef7 1507 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1508 useful if the kernel is unable to find your
1509 secondary buses and you want to tell it
1510 explicitly which ones they are.
cd4f0ef7 1511 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1512 numbers ourselves, overriding
1513 whatever the firmware may have done.
cd4f0ef7 1514 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1515 in the BIOS $PIR table. This is needed on
1516 some systems with broken BIOSes, notably
1517 some HP Pavilion N5400 and Omnibook XE3
1518 notebooks. This will have no effect if ACPI
1519 IRQ routing is enabled.
cd4f0ef7 1520 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1521 or for PCI scanning.
62f420f8
GH
1522 use_crs [X86-32] Use _CRS for PCI resource
1523 allocation.
a9913044
RD
1524 routeirq Do IRQ routing for all PCI devices.
1525 This is normally done in pci_enable_device(),
1526 so this option is a temporary workaround
1527 for broken drivers that don't call it.
13a6ddb0
YL
1528 skip_isa_align [X86] do not align io start addr, so can
1529 handle more pci cards
a9913044
RD
1530 firmware [ARM] Do not re-enumerate the bus but instead
1531 just use the configuration from the
1532 bootloader. This is currently used on
1533 IXP2000 systems where the bus has to be
1534 configured a certain way for adjunct CPUs.
0637a70a
AK
1535 noearly [X86] Don't do any early type 1 scanning.
1536 This might help on some broken boards which
1537 machine check when some devices' config space
1538 is read. But various workarounds are disabled
1539 and some IOMMU drivers will not work.
6b4b78fe
MD
1540 bfsort Sort PCI devices into breadth-first order.
1541 This sorting is done to get a device
1542 order compatible with older (<= 2.4) kernels.
1543 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1544 cbiosize=nn[KMG] The fixed amount of bus space which is
1545 reserved for the CardBus bridge's IO window.
1546 The default value is 256 bytes.
1547 cbmemsize=nn[KMG] The fixed amount of bus space which is
1548 reserved for the CardBus bridge's memory
1549 window. The default value is 64 megabytes.
6b4b78fe 1550
1da177e4
LT
1551 pcmv= [HW,PCMCIA] BadgePAD 4
1552
1553 pd. [PARIDE]
1554 See Documentation/paride.txt.
1555
1556 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1557 boot time.
1558 Format: { 0 | 1 }
1559 See arch/parisc/kernel/pdc_chassis.c
1560
1561 pf. [PARIDE]
1562 See Documentation/paride.txt.
1563
1564 pg. [PARIDE]
1565 See Documentation/paride.txt.
1566
1567 pirq= [SMP,APIC] Manual mp-table setup
1568 See Documentation/i386/IO-APIC.txt.
1569
1570 plip= [PPT,NET] Parallel port network link
1571 Format: { parport<nr> | timid | 0 }
1572 See also Documentation/parport.txt.
1573
1574 pnpacpi= [ACPI]
1575 { off }
1576
1577 pnpbios= [ISAPNP]
1578 { on | off | curr | res | no-curr | no-res }
1579
1580 pnp_reserve_irq=
1581 [ISAPNP] Exclude IRQs for the autoconfiguration
1582
1583 pnp_reserve_dma=
1584 [ISAPNP] Exclude DMAs for the autoconfiguration
1585
1586 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1587 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1588
1589 pnp_reserve_mem=
a9913044
RD
1590 [ISAPNP] Exclude memory regions for the
1591 autoconfiguration.
1da177e4
LT
1592 Ranges are in pairs (memory base and size).
1593
45807a1d
IM
1594 print-fatal-signals=
1595 [KNL] debug: print fatal signals
1596 print-fatal-signals=1: print segfault info to
1597 the kernel console.
1598 default: off.
1599
e84845c4
RD
1600 printk.time= Show timing data prefixed to each printk message line
1601 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1602
1da177e4 1603 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1604 Format: [schedule,]<number>
1605 Param: "schedule" - profile schedule points.
1606 Param: <number> - step/bucket size as a power of 2 for
1607 statistical time based profiling.
b3da2a73
MG
1608 Param: "sleep" - profile D-state sleeping (millisecs).
1609 Requires CONFIG_SCHEDSTATS
c0fe2e69 1610 Param: "kvm" - profile VM exits.
1da177e4 1611
a9913044 1612 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1613 Limit processor to maximum C-state
1614 max_cstate=9 overrides any DMI blacklist limit.
1615
41c0d868
LB
1616 processor.nocst [HW,ACPI]
1617 Ignore the _CST method to determine C-states,
1618 instead using the legacy FADT method
1619
1da177e4
LT
1620 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1621 before loading.
1622 See Documentation/ramdisk.txt.
1623
a9913044
RD
1624 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1625 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1626 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1627 per second.
a9913044
RD
1628 psmouse.resetafter= [HW,MOUSE]
1629 Try to reset the device after so many bad packets
1da177e4
LT
1630 (0 = never).
1631 psmouse.resolution=
1632 [HW,MOUSE] Set desired mouse resolution, in dpi.
1633 psmouse.smartscroll=
a9913044 1634 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1635 0 = disabled, 1 = enabled (default).
1636
1637 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1638 Format:
1639 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1640
1641 pt. [PARIDE]
1642 See Documentation/paride.txt.
1643
dc8c8587
KS
1644 pty.legacy_count=
1645 [KNL] Number of legacy pty's. Overwrites compiled-in
1646 default number.
1647
7d2c502f 1648 quiet [KNL] Disable most log messages
a9913044 1649
1da177e4
LT
1650 r128= [HW,DRM]
1651
1652 raid= [HW,RAID]
1653 See Documentation/md.txt.
1654
a9913044 1655 ramdisk_blocksize= [RAM]
1da177e4 1656 See Documentation/ramdisk.txt.
a9913044 1657
1da177e4 1658 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1659 See Documentation/ramdisk.txt.
1660
24aaef8d
RD
1661 rcupdate.blimit= [KNL,BOOT]
1662 Set maximum number of finished RCU callbacks to process
1663 in one batch.
21a1ea9e 1664
24aaef8d
RD
1665 rcupdate.qhimark= [KNL,BOOT]
1666 Set threshold of queued
21a1ea9e
DS
1667 RCU callbacks over which batch limiting is disabled.
1668
24aaef8d
RD
1669 rcupdate.qlowmark= [KNL,BOOT]
1670 Set threshold of queued RCU callbacks below which
1671 batch limiting is re-enabled.
21a1ea9e 1672
ffdfc409
OJ
1673 rdinit= [KNL]
1674 Format: <full_path>
1675 Run specified binary instead of /init from the ramdisk,
1676 used for early userspace startup. See initrd.
1677
cd4f0ef7 1678 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1679 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1680 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1681
1682 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1683
cd4f0ef7 1684 reservetop= [X86-32]
461a9aff
ZA
1685 Format: nn[KMG]
1686 Reserves a hole at the top of the kernel virtual
1687 address space.
1688
7e96287d
VG
1689 reset_devices [KNL] Force drivers to reset the underlying device
1690 during initialization.
1691
a9913044
RD
1692 resume= [SWSUSP]
1693 Specify the partition device for software suspend
1da177e4 1694
ecbd0da1
RW
1695 resume_offset= [SWSUSP]
1696 Specify the offset from the beginning of the partition
1697 given by "resume=" at which the swap header is located,
1698 in <PAGE_SIZE> units (needed only for swap files).
1699 See Documentation/power/swsusp-and-swap-files.txt
1700
0a7b35cb
MN
1701 retain_initrd [RAM] Keep initrd memory after extraction
1702
1da177e4
LT
1703 rhash_entries= [KNL,NET]
1704 Set number of hash buckets for route cache
1705
1706 riscom8= [HW,SERIAL]
1707 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1708
1709 ro [KNL] Mount root device read-only on boot
1710
1711 root= [KNL] Root filesystem
1712
1713 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1714 mount the root filesystem
1715
1716 rootflags= [KNL] Set root filesystem mount option string
1717
1718 rootfstype= [KNL] Set root filesystem type
1719
cc1ed754
PO
1720 rootwait [KNL] Wait (indefinitely) for root device to show up.
1721 Useful for devices that are detected asynchronously
1722 (e.g. USB and MMC devices).
1723
20510f2f
JM
1724 root_plug.vendor_id=
1725 [ROOTPLUG] Override the default vendor ID
1726
1727 root_plug.product_id=
1728 [ROOTPLUG] Override the default product ID
1729
1730 root_plug.debug=
1731 [ROOTPLUG] Enable debugging output
1732
1da177e4
LT
1733 rw [KNL] Mount root device read-write on boot
1734
1735 S [KNL] Run init in single mode
1736
1737 sa1100ir [NET]
1738 See drivers/net/irda/sa1100_ir.c.
1739
1da177e4 1740 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1741
1da177e4
LT
1742 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1743 Format: <io>[,<timeout>[,<isapnp>]]
1744
1745 scsi_debug_*= [SCSI]
1746 See drivers/scsi/scsi_debug.c.
1747
1748 scsi_default_dev_flags=
1749 [SCSI] SCSI default device flags
1750 Format: <integer>
1751
1752 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1753 Format: <vendor>:<model>:<flags>
1754 (flags are integer value)
1755
6af6632a
RD
1756 scsi_logging_level= [SCSI] a bit mask of logging levels
1757 See drivers/scsi/scsi_logging.h for bits. Also
1758 settable via sysctl at dev.scsi.logging_level
1759 (/proc/sys/dev/scsi/logging_level).
1760 There is also a nice 'scsi_logging_level' script in the
1761 S390-tools package, available for download at
1762 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1763
3e082a91
MW
1764 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1765 discovered. async scans them in kernel threads,
1766 allowing boot to proceed. none ignores them, expecting
1767 user space to do the scan.
1768
1da177e4
LT
1769 selinux [SELINUX] Disable or enable SELinux at boot time.
1770 Format: { "0" | "1" }
1771 See security/selinux/Kconfig help text.
1772 0 -- disable.
1773 1 -- enable.
1774 Default value is set via kernel config option.
1775 If enabled at boot time, /selinux/disable can be used
1776 later to disable prior to initial policy load.
1777
4e5ab4cb
JM
1778 selinux_compat_net =
1779 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1780 Format: { "0" | "1" }
1781 0 -- use new secmark-based packet controls
1782 1 -- use legacy packet controls
1783 Default value is 0 (preferred).
1784 Value can be changed at runtime via
1785 /selinux/compat_net.
4e5ab4cb 1786
cd4f0ef7 1787 serialnumber [BUGS=X86-32]
1da177e4 1788
1da177e4
LT
1789 shapers= [NET]
1790 Maximal number of shapers.
a9913044 1791
1da177e4
LT
1792 sim710= [SCSI,HW]
1793 See header of drivers/scsi/sim710.c.
1794
1795 simeth= [IA-64]
1796 simscsi=
a9913044 1797
1da177e4
LT
1798 slram= [HW,MTD]
1799
f0630fff
CL
1800 slub_debug[=options[,slabs]] [MM, SLUB]
1801 Enabling slub_debug allows one to determine the
1802 culprit if slab objects become corrupted. Enabling
1803 slub_debug can create guard zones around objects and
1804 may poison objects when not in use. Also tracks the
1805 last alloc / free. For more information see
1806 Documentation/vm/slub.txt.
c1aee215
CL
1807
1808 slub_max_order= [MM, SLUB]
f0630fff
CL
1809 Determines the maximum allowed order for slabs.
1810 A high setting may cause OOMs due to memory
1811 fragmentation. For more information see
1812 Documentation/vm/slub.txt.
c1aee215
CL
1813
1814 slub_min_objects= [MM, SLUB]
f0630fff
CL
1815 The minimum number of objects per slab. SLUB will
1816 increase the slab order up to slub_max_order to
1817 generate a sufficiently large slab able to contain
1818 the number of objects indicated. The higher the number
1819 of objects the smaller the overhead of tracking slabs
1820 and the less frequently locks need to be acquired.
c1aee215
CL
1821 For more information see Documentation/vm/slub.txt.
1822
1823 slub_min_order= [MM, SLUB]
1824 Determines the mininum page order for slabs. Must be
f0630fff 1825 lower than slub_max_order.
c1aee215
CL
1826 For more information see Documentation/vm/slub.txt.
1827
1828 slub_nomerge [MM, SLUB]
f0630fff 1829 Disable merging of slabs with similar size. May be
c1aee215 1830 necessary if there is some reason to distinguish
f0630fff
CL
1831 allocs to different slabs. Debug options disable
1832 merging on their own.
c1aee215
CL
1833 For more information see Documentation/vm/slub.txt.
1834
1da177e4
LT
1835 smart2= [HW]
1836 Format: <io1>[,<io2>[,...,<io8>]]
1837
cd4f0ef7 1838 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1839 attempt to substitute SMP alternatives once at boot.
1840
d0d4f69b
BH
1841 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1842 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1843 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1844 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1845 smsc-ircc2.ircc_irq= [HW] IRQ line
1846 smsc-ircc2.ircc_dma= [HW] DMA channel
1847 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1848 0: Toshiba Satellite 1800 (GP data pin select)
1849 1: Fast pin select (default)
1850 2: ATC IRMode
1851
1da177e4
LT
1852 snd-ad1816a= [HW,ALSA]
1853
1854 snd-ad1848= [HW,ALSA]
1855
1856 snd-ali5451= [HW,ALSA]
1857
1858 snd-als100= [HW,ALSA]
1859
1860 snd-als4000= [HW,ALSA]
1861
1862 snd-azt2320= [HW,ALSA]
1863
1864 snd-cmi8330= [HW,ALSA]
1865
1866 snd-cmipci= [HW,ALSA]
1867
1868 snd-cs4231= [HW,ALSA]
1869
1870 snd-cs4232= [HW,ALSA]
1871
1872 snd-cs4236= [HW,ALSA]
1873
1874 snd-cs4281= [HW,ALSA]
1875
1876 snd-cs46xx= [HW,ALSA]
1877
1878 snd-dt019x= [HW,ALSA]
1879
1880 snd-dummy= [HW,ALSA]
1881
1882 snd-emu10k1= [HW,ALSA]
1883
1884 snd-ens1370= [HW,ALSA]
1885
1886 snd-ens1371= [HW,ALSA]
1887
1888 snd-es968= [HW,ALSA]
1889
1890 snd-es1688= [HW,ALSA]
1891
1892 snd-es18xx= [HW,ALSA]
1893
1894 snd-es1938= [HW,ALSA]
1895
1896 snd-es1968= [HW,ALSA]
1897
1898 snd-fm801= [HW,ALSA]
1899
1900 snd-gusclassic= [HW,ALSA]
1901
1902 snd-gusextreme= [HW,ALSA]
1903
1904 snd-gusmax= [HW,ALSA]
1905
1906 snd-hdsp= [HW,ALSA]
1907
1908 snd-ice1712= [HW,ALSA]
1909
1910 snd-intel8x0= [HW,ALSA]
1911
1912 snd-interwave= [HW,ALSA]
1913
1914 snd-interwave-stb=
1915 [HW,ALSA]
1916
1917 snd-korg1212= [HW,ALSA]
1918
1919 snd-maestro3= [HW,ALSA]
1920
1921 snd-mpu401= [HW,ALSA]
1922
1923 snd-mtpav= [HW,ALSA]
1924
1925 snd-nm256= [HW,ALSA]
1926
1927 snd-opl3sa2= [HW,ALSA]
1928
1929 snd-opti92x-ad1848=
1930 [HW,ALSA]
1931
1932 snd-opti92x-cs4231=
1933 [HW,ALSA]
1934
1935 snd-opti93x= [HW,ALSA]
1936
1937 snd-pmac= [HW,ALSA]
1938
1939 snd-rme32= [HW,ALSA]
1940
1941 snd-rme96= [HW,ALSA]
1942
1943 snd-rme9652= [HW,ALSA]
1944
1945 snd-sb8= [HW,ALSA]
1946
1947 snd-sb16= [HW,ALSA]
1948
1949 snd-sbawe= [HW,ALSA]
1950
1951 snd-serial= [HW,ALSA]
1952
1953 snd-sgalaxy= [HW,ALSA]
1954
1955 snd-sonicvibes= [HW,ALSA]
1956
1957 snd-sun-amd7930=
1958 [HW,ALSA]
1959
1960 snd-sun-cs4231= [HW,ALSA]
1961
1962 snd-trident= [HW,ALSA]
1963
1964 snd-usb-audio= [HW,ALSA,USB]
1965
1966 snd-via82xx= [HW,ALSA]
1967
1968 snd-virmidi= [HW,ALSA]
1969
1970 snd-wavefront= [HW,ALSA]
1971
1972 snd-ymfpci= [HW,ALSA]
a9913044 1973
1da177e4
LT
1974 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1975 See Documentation/sonypi.txt
1976
1977 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1978 See Documentation/specialix.txt.
1979
1980 spia_io_base= [HW,MTD]
1981 spia_fio_base=
1982 spia_pedr=
1983 spia_peddr=
1984
1985 sscape= [HW,OSS]
1986 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1987
1da177e4
LT
1988 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1989 See Documentation/scsi/st.txt.
1990
1da177e4
LT
1991 sti= [PARISC,HW]
1992 Format: <num>
1993 Set the STI (builtin display/keyboard on the HP-PARISC
1994 machines) console (graphic card) which should be used
1995 as the initial boot-console.
1996 See also comment in drivers/video/console/sticore.c.
1997
1998 sti_font= [HW]
1999 See comment in drivers/video/console/sticore.c.
2000
2001 stifb= [HW]
2002 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2003
42a7fc4a
GB
2004 sunrpc.pool_mode=
2005 [NFS]
2006 Control how the NFS server code allocates CPUs to
2007 service thread pools. Depending on how many NICs
2008 you have and where their interrupts are bound, this
2009 option will affect which CPUs will do NFS serving.
2010 Note: this parameter cannot be changed while the
2011 NFS server is running.
2012
2013 auto the server chooses an appropriate mode
2014 automatically using heuristics
2015 global a single global pool contains all CPUs
2016 percpu one pool for each CPU
2017 pernode one pool for each NUMA node (equivalent
2018 to global on non-NUMA machines)
2019
1da177e4 2020 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2021
1da177e4
LT
2022 switches= [HW,M68k]
2023
2024 sym53c416= [HW,SCSI]
2025 See header of drivers/scsi/sym53c416.c.
2026
5d6f647f
IM
2027 sysrq_always_enabled
2028 [KNL]
2029 Ignore sysrq setting - this boot parameter will
2030 neutralize any effect of /proc/sys/kernel/sysrq.
2031 Useful for debugging.
2032
1da177e4
LT
2033 t128= [HW,SCSI]
2034 See header of drivers/scsi/t128.c.
2035
2036 tdfx= [HW,DRM]
2037
2038 thash_entries= [KNL,NET]
2039 Set number of hash buckets for TCP connection
2040
f8707ec9
LB
2041 thermal.act= [HW,ACPI]
2042 -1: disable all active trip points in all thermal zones
2043 <degrees C>: override all lowest active trip points
2044
c52a7419
LB
2045 thermal.crt= [HW,ACPI]
2046 -1: disable all critical trip points in all thermal zones
2047 <degrees C>: lower all critical trip points
2048
f5487145
LB
2049 thermal.nocrt= [HW,ACPI]
2050 Set to disable actions on ACPI thermal zone
2051 critical and hot trip points.
2052
72b33ef8
LB
2053 thermal.off= [HW,ACPI]
2054 1: disable ACPI thermal control
2055
a70cdc52
LB
2056 thermal.psv= [HW,ACPI]
2057 -1: disable all passive trip points
2058 <degrees C>: override all passive trip points to this value
2059
730ff34d
LB
2060 thermal.tzp= [HW,ACPI]
2061 Specify global default ACPI thermal zone polling rate
2062 <deci-seconds>: poll all this frequency
2063 0: no polling (default)
2064
1da177e4
LT
2065 tipar.timeout= [HW,PPT]
2066 Set communications timeout in tenths of a second
2067 (default 15).
2068
2069 tipar.delay= [HW,PPT]
2070 Set inter-bit delay in microseconds (default 10).
2071
1da177e4
LT
2072 tmscsim= [HW,SCSI]
2073 See comment before function dc390_setup() in
2074 drivers/scsi/tmscsim.c.
2075
2076 tp720= [HW,PS2]
2077
2078 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2079 Format:
2080 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2081
a9913044
RD
2082 turbografx.map[2|3]= [HW,JOY]
2083 TurboGraFX parallel port interface
2084 Format:
2085 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2086 See also Documentation/input/joystick-parport.txt
2087
2088 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2089 See header of drivers/scsi/u14-34f.c.
2090
2091 uart401= [HW,OSS]
2092 Format: <io>,<irq>
2093
2094 uart6850= [HW,OSS]
2095 Format: <io>,<irq>
2096
5f8364b7
AS
2097 uhci-hcd.ignore_oc=
2098 [USB] Ignore overcurrent events (default N).
2099 Some badly-designed motherboards generate lots of
2100 bogus events, for ports that aren't wired to
2101 anything. Set this parameter to avoid log spamming.
2102 Note that genuine overcurrent events won't be
2103 reported either.
2104
b5e795f8
AS
2105 usbcore.autosuspend=
2106 [USB] The autosuspend time delay (in seconds) used
2107 for newly-detected USB devices (default 2). This
2108 is the time required before an idle device will be
2109 autosuspended. Devices for which the delay is set
eaafbc3a 2110 to a negative value won't be autosuspended at all.
b5e795f8 2111
1da177e4
LT
2112 usbhid.mousepoll=
2113 [USBHID] The interval which mice are to be polled at.
a9913044 2114
cd4f0ef7 2115 vdso= [X86-32,SH,x86-64]
1dbf527c 2116 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2117 vdso=1: enable VDSO (default)
2118 vdso=0: disable VDSO mapping
2119
af65d648
RM
2120 vdso32= [X86-32,X86-64]
2121 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2122 vdso32=1: enable 32-bit VDSO (default)
2123 vdso32=0: disable 32-bit VDSO mapping
2124
d080d397
YI
2125 vector= [IA-64,SMP]
2126 vector=percpu: enable percpu vector domain
2127
1da177e4
LT
2128 video= [FB] Frame buffer configuration
2129 See Documentation/fb/modedb.txt.
2130
cd4f0ef7 2131 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2132 See Documentation/i386/boot.txt and
2133 Documentation/svga.txt.
1da177e4
LT
2134 Use vga=ask for menu.
2135 This is actually a boot loader parameter; the value is
2136 passed to the kernel using a special protocol.
2137
a9913044 2138 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2139 size of <nn>. This can be used to increase the
2140 minimum size (128MB on x86). It can also be used to
2141 decrease the size and leave more room for directly
2142 mapped kernel RAM.
2143
585c3047
PO
2144 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2145 Format: <command>
1da177e4 2146
585c3047
PO
2147 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2148 Format: <command>
2149
2150 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2151 Format: <command>
a9913044 2152
1da177e4
LT
2153 waveartist= [HW,OSS]
2154 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2155
1da177e4
LT
2156 wd33c93= [HW,SCSI]
2157 See header of drivers/scsi/wd33c93.c.
2158
2159 wd7000= [HW,SCSI]
2160 See header of drivers/scsi/wd7000.c.
2161
2162 wdt= [WDT] Watchdog
8dfe9c21 2163 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2164
2165 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2166 xd_geo= See header of drivers/block/xd.c.
2167
2168 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2169 Format:
2170 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2171
a62eaf15
AK
2172 norandmaps Don't use address space randomization
2173 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2174
a9913044 2175______________________________________________________________________
1da177e4
LT
2176
2177TODO:
2178
2179 Add documentation for ALSA options.
2180 Add more DRM drivers.