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0ee9d71f 1 Kernel Parameters
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2 ~~~~~~~~~~~~~~~~~
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.
33 ALSA ALSA sound support is enabled.
34 APIC APIC support is enabled.
35 APM Advanced Power Management support is enabled.
36 AX25 Appropriate AX.25 support is enabled.
37 CD Appropriate CD support is enabled.
a9913044 38 DRM Direct Rendering Management support is enabled.
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39 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
40 EFI EFI Partitioning (GPT) is enabled
41 EIDE EIDE/ATAPI support is enabled.
42 FB The frame buffer device is enabled.
43 HW Appropriate hardware is enabled.
44 IA-32 IA-32 aka i386 architecture is enabled.
45 IA-64 IA-64 architecture is enabled.
46 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 47 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
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48 ISAPNP ISA PnP code is enabled.
49 ISDN Appropriate ISDN support is enabled.
50 JOY Appropriate joystick support is enabled.
51 LP Printer support is enabled.
52 LOOP Loopback device support is enabled.
53 M68k M68k architecture is enabled.
54 These options have more detailed description inside of
55 Documentation/m68k/kernel-options.txt.
56 MCA MCA bus support is enabled.
57 MDA MDA console support is enabled.
58 MOUSE Appropriate mouse support is enabled.
309e57df 59 MSI Message Signaled Interrupts (PCI).
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60 MTD MTD support is enabled.
61 NET Appropriate network support is enabled.
62 NUMA NUMA support is enabled.
734efb46 63 GENERIC_TIME The generic timeofday code is enabled.
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64 NFS Appropriate NFS support is enabled.
65 OSS OSS sound support is enabled.
66 PARIDE The ParIDE subsystem is enabled.
67 PARISC The PA-RISC architecture is enabled.
68 PCI PCI bus support is enabled.
69 PCMCIA The PCMCIA subsystem is enabled.
70 PNP Plug & Play support is enabled.
71 PPC PowerPC architecture is enabled.
72 PPT Parallel port support is enabled.
73 PS2 Appropriate PS/2 support is enabled.
74 RAM RAM disk support is enabled.
75 S390 S390 architecture is enabled.
76 SCSI Appropriate SCSI support is enabled.
77 A lot of drivers has their options described inside of
78 Documentation/scsi/.
79 SELINUX SELinux support is enabled.
80 SERIAL Serial support is enabled.
81 SMP The kernel is an SMP kernel.
82 SPARC Sparc architecture is enabled.
a9913044 83 SWSUSP Software suspend is enabled.
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84 TS Appropriate touchscreen support is enabled.
85 USB USB support is enabled.
86 USBHID USB Human Interface Device support is enabled.
87 V4L Video For Linux support is enabled.
88 VGA The VGA console has been enabled.
89 VT Virtual terminal support is enabled.
90 WDT Watchdog support is enabled.
91 XT IBM PC/XT MFM hard disk support is enabled.
92 X86-64 X86-64 architecture is enabled.
93 More X86-64 boot options can be found in
94 Documentation/x86_64/boot-options.txt .
95
96In addition, the following text indicates that the option:
97
98 BUGS= Relates to possible processor bugs on the said processor.
99 KNL Is a kernel start-up parameter.
100 BOOT Is a boot loader parameter.
101
102Parameters denoted with BOOT are actually interpreted by the boot
103loader, and have no meaning to the kernel directly.
104Do not modify the syntax of boot loader parameters without extreme
105need or coordination with <Documentation/i386/boot.txt>.
106
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107There are also arch-specific kernel-parameters not documented here.
108See for example <Documentation/x86_64/boot-options.txt>.
109
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110Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
111a trailing = on the name of any parameter states that that parameter will
112be entered as an environment variable, whereas its absence indicates that
113it will appear as a kernel argument readable via /proc/cmdline by programs
114running once the system is up.
115
9c4751fd 116The number of kernel parameters is not limited, but the length of the
117complete command line (parameters including spaces etc.) is limited to
118a fixed number of characters. This limit depends on the architecture
119and is between 256 and 4096 characters. It is defined in the file
120./include/asm/setup.h as COMMAND_LINE_SIZE.
121
122
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123 53c7xx= [HW,SCSI] Amiga SCSI controllers
124 See header of drivers/scsi/53c7xx.c.
125 See also Documentation/scsi/ncr53c7xx.txt.
126
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127 acpi= [HW,ACPI] Advanced Configuration and Power Interface
128 Format: { force | off | ht | strict | noirq }
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129 force -- enable ACPI if default was off
130 off -- disable ACPI if default was on
131 noirq -- do not use ACPI for IRQ routing
132 ht -- run only enough ACPI to enable Hyper Threading
a9913044 133 strict -- Be less tolerant of platforms that are not
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134 strictly ACPI specification compliant.
135
136 See also Documentation/pm.txt, pci=noacpi
137
138 acpi_sleep= [HW,ACPI] Sleep options
139 Format: { s3_bios, s3_mode }
140 See Documentation/power/video.txt
a9913044 141
1da177e4 142 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
a9913044 143 Format: { level | edge | high | low }
1da177e4 144
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145 acpi_irq_balance [HW,ACPI]
146 ACPI will balance active IRQs
147 default in APIC mode
1da177e4 148
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149 acpi_irq_nobalance [HW,ACPI]
150 ACPI will not move active IRQs (default)
151 default in PIC mode
1da177e4 152
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153 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
154 use by PCI
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155 Format: <irq>,<irq>...
156
a9913044 157 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
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158 Format: <irq>,<irq>...
159
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160 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
161 Format: To spoof as Windows 98: ="Microsoft Windows"
162
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163 acpi_osi= [HW,ACPI] empty param disables _OSI
164
165 acpi_serialize [HW,ACPI] force serialization of AML methods
166
167 acpi_skip_timer_override [HW,ACPI]
168 Recognize and ignore IRQ0/pin2 Interrupt Override.
169 For broken nForce2 BIOS resulting in XT-PIC timer.
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170 acpi_use_timer_override [HW,ACPI}
171 Use timer override. For some broken Nvidia NF5 boards
172 that require a timer override, but don't have
173 HPET
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174
175 acpi_dbg_layer= [HW,ACPI]
176 Format: <int>
a9913044 177 Each bit of the <int> indicates an ACPI debug layer,
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178 1: enable, 0: disable. It is useful for boot time
179 debugging. After system has booted up, it can be set
180 via /proc/acpi/debug_layer.
181
182 acpi_dbg_level= [HW,ACPI]
183 Format: <int>
a9913044 184 Each bit of the <int> indicates an ACPI debug level,
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185 1: enable, 0: disable. It is useful for boot time
186 debugging. After system has booted up, it can be set
187 via /proc/acpi/debug_level.
188
189 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
190
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191 acpi_generic_hotkey [HW,ACPI]
192 Allow consolidated generic hotkey driver to
a9913044 193 override platform specific driver.
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194 See also Documentation/acpi-hotkey.txt.
195
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196 acpi_pm_good [IA-32,X86-64]
197 Override the pmtimer bug detection: force the kernel
198 to assume that this machine's pmtimer latches its value
199 and always returns good values.
200
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201 enable_timer_pin_1 [i386,x86-64]
202 Enable PIN 1 of APIC timer
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203 Can be useful to work around chipset bugs
204 (in particular on some ATI chipsets).
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205 The kernel tries to set a reasonable default.
206
207 disable_timer_pin_1 [i386,x86-64]
208 Disable PIN 1 of APIC timer
209 Can be useful to work around chipset bugs.
210
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211 ad1816= [HW,OSS]
212 Format: <io>,<irq>,<dma>,<dma2>
213 See also Documentation/sound/oss/AD1816.
214
215 ad1848= [HW,OSS]
216 Format: <io>,<irq>,<dma>,<dma2>,<type>
217
218 adlib= [HW,OSS]
219 Format: <io>
a9913044 220
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221 advansys= [HW,SCSI]
222 See header of drivers/scsi/advansys.c.
223
224 advwdt= [HW,WDT] Advantech WDT
225 Format: <iostart>,<iostop>
226
227 aedsp16= [HW,OSS] Audio Excel DSP 16
228 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
229 See also header of sound/oss/aedsp16.c.
a9913044 230
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231 aha152x= [HW,SCSI]
232 See Documentation/scsi/aha152x.txt.
233
234 aha1542= [HW,SCSI]
235 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
236
237 aic7xxx= [HW,SCSI]
238 See Documentation/scsi/aic7xxx.txt.
239
240 aic79xx= [HW,SCSI]
241 See Documentation/scsi/aic79xx.txt.
242
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243 amijoy.map= [HW,JOY] Amiga joystick support
244 Map of devices attached to JOY0DAT and JOY1DAT
245 Format: <a>,<b>
246 See also Documentation/kernel/input/joystick.txt
247
248 analog.map= [HW,JOY] Analog joystick and gamepad support
249 Specifies type or capabilities of an analog joystick
250 connected to one of 16 gameports
251 Format: <type1>,<type2>,..<type16>
252
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253 apc= [HW,SPARC]
254 Power management functions (SPARCstation-4/5 + deriv.)
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255 Format: noidle
256 Disable APC CPU standby support. SPARCstation-Fox does
257 not play well with APC CPU idle - disable it if you have
258 APC and your system crashes randomly.
259
a9913044 260 apic= [APIC,i386] Change the output verbosity whilst booting
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261 Format: { quiet (default) | verbose | debug }
262 Change the amount of debugging information output
263 when initialising the APIC and IO-APIC components.
a9913044 264
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265 apm= [APM] Advanced Power Management
266 See header of arch/i386/kernel/apm.c.
267
268 applicom= [HW]
269 Format: <mem>,<irq>
a9913044 270
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271 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
272 Format: <io>,<irq>,<nodeID>
273
274 ataflop= [HW,M68k]
275
276 atarimouse= [HW,MOUSE] Atari Mouse
277
278 atascsi= [HW,SCSI] Atari SCSI
279
280 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
281 EzKey and similar keyboards
282
283 atkbd.reset= [HW] Reset keyboard during initialization
284
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285 atkbd.set= [HW] Select keyboard code set
286 Format: <int> (2 = AT (default), 3 = PS/2)
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287
288 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
289 keyboards
290
291 atkbd.softraw= [HW] Choose between synthetic and real raw mode
292 Format: <bool> (0 = real, 1 = synthetic (default))
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293
294 atkbd.softrepeat= [HW]
295 Use software keyboard repeat
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296
297 autotest [IA64]
298
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299 aztcd= [HW,CD] Aztech CD268 CDROM driver
300 Format: <io>,0x79 (?)
301
302 baycom_epp= [HW,AX25]
303 Format: <io>,<mode>
a9913044 304
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305 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
306 Format: <io>,<mode>
307 See header of drivers/net/hamradio/baycom_par.c.
308
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309 baycom_ser_fdx= [HW,AX25]
310 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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311 Format: <io>,<irq>,<mode>[,<baud>]
312 See header of drivers/net/hamradio/baycom_ser_fdx.c.
313
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314 baycom_ser_hdx= [HW,AX25]
315 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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316 Format: <io>,<irq>,<mode>
317 See header of drivers/net/hamradio/baycom_ser_hdx.c.
318
319 blkmtd_device= [HW,MTD]
320 blkmtd_erasesz=
321 blkmtd_ro=
322 blkmtd_bs=
323 blkmtd_count=
324
325 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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326 bttv.radio= Most important insmod options are available as
327 kernel args too.
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328 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
329 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
330
331 BusLogic= [HW,SCSI]
332 See drivers/scsi/BusLogic.c, comment before function
333 BusLogic_ParseDriverOptions().
334
335 c101= [NET] Moxa C101 synchronous serial card
336
337 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
338 Sometimes CPU hardware bugs make them report the cache
339 size incorrectly. The kernel will attempt work arounds
340 to fix known problems, but for some CPUs it is not
341 possible to determine what the correct size should be.
342 This option provides an override for these situations.
343
344 cdu31a= [HW,CD]
345 Format: <io>,<irq>[,PAS]
346 See header of drivers/cdrom/cdu31a.c.
347
348 chandev= [HW,NET] Generic channel device initialisation
349
350 checkreqprot [SELINUX] Set initial checkreqprot flag value.
351 Format: { "0" | "1" }
352 See security/selinux/Kconfig help text.
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353 0 -- check protection applied by kernel (includes
354 any implied execute protection).
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355 1 -- check protection requested by application.
356 Default value is set via a kernel config option.
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357 Value can be changed at runtime via
358 /selinux/checkreqprot.
359
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360 clock= [BUGS=IA-32, HW] gettimeofday clocksource override.
361 [Deprecated]
3f6dee9b 362 Forces specified clocksource (if available) to be used
734efb46 363 when calculating gettimeofday(). If specified
3f6dee9b 364 clocksource is not available, it defaults to PIT.
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365 Format: { pit | tsc | cyclone | pmtmr }
366
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367 disable_8254_timer
368 enable_8254_timer
369 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
370 over the 8254 in addition to over the IO-APIC. The
371 kernel tries to set a sensible default.
372
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373 hpet= [IA-32,HPET] option to disable HPET and use PIT.
374 Format: disable
375
376 cm206= [HW,CD]
377 Format: { auto | [<io>,][<irq>] }
378
379 com20020= [HW,NET] ARCnet - COM20020 chipset
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380 Format:
381 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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382
383 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
384 Format: <io>[,<irq>]
385
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386 com90xx= [HW,NET]
387 ARCnet - COM90xx chipset (memory-mapped buffers)
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388 Format: <io>[,<irq>[,<memstart>]]
389
390 condev= [HW,S390] console device
391 conmode=
a9913044 392
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393 console= [KNL] Output console device and options.
394
395 tty<n> Use the virtual console device <n>.
396
397 ttyS<n>[,options]
f1a1c2dc 398 ttyUSB0[,options]
1da177e4 399 Use the specified serial port. The options are of
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400 the form "bbbbpnf", where "bbbb" is the baud rate,
401 "p" is parity ("n", "o", or "e"), "n" is number of
402 bits, and "f" is flow control ("r" for RTS or
403 omit it). Default is "9600n8".
404
405 See Documentation/serial-console.txt for more
406 information. See
407 Documentation/networking/netconsole.txt for an
408 alternative.
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409
410 uart,io,<addr>[,options]
411 uart,mmio,<addr>[,options]
412 Start an early, polled-mode console on the 8250/16550
413 UART at the specified I/O port or MMIO address,
414 switching to the matching ttyS device later. The
415 options are the same as for ttyS, above.
416
417 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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418 Format:
419 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
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420
421 cpia_pp= [HW,PPT]
422 Format: { parport<nr> | auto | none }
423
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424 crashkernel=nn[KMG]@ss[KMG]
425 [KNL] Reserve a chunk of physical memory to
426 hold a kernel to switch to with kexec on panic.
427
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428 cs4232= [HW,OSS]
429 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
430
431 cs89x0_dma= [HW,NET]
432 Format: <dma>
433
434 cs89x0_media= [HW,NET]
435 Format: { rj45 | aui | bnc }
a9913044 436
1da177e4 437 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
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438
439 dasd= [HW,NET]
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440 See header of drivers/s390/block/dasd_devmap.c.
441
442 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
443 (one device per port)
444 Format: <port#>,<type>
445 See also Documentation/input/joystick-parport.txt
446
447 debug [KNL] Enable kernel debugging (events log level).
448
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449 debug_locks_verbose=
450 [KNL] verbose self-tests
451 Format=<0|1>
452 Print debugging info while doing the locking API
453 self-tests.
454 We default to 0 (no extra messages), setting it to
455 1 will print _a lot_ more information - normally
456 only useful to kernel developers.
457
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458 decnet= [HW,NET]
459 Format: <area>[,<node>]
460 See also Documentation/networking/decnet.txt.
461
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462 dhash_entries= [KNL]
463 Set number of hash buckets for dentry cache.
a9913044 464
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465 digi= [HW,SERIAL]
466 IO parameters + enable/disable command.
467
468 digiepca= [HW,SERIAL]
469 See drivers/char/README.epca and
470 Documentation/digiepca.txt.
471
472 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
473 support available.
474 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
475
476 dmasound= [HW,OSS] Sound subsystem buffers
477
478 dscc4.setup= [NET]
479
480 dtc3181e= [HW,SCSI]
481
a9913044 482 earlyprintk= [IA-32,X86-64]
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483 earlyprintk=vga
484 earlyprintk=serial[,ttySn[,baudrate]]
485
a9913044 486 Append ",keep" to not disable it when the real console
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487 takes over.
488
489 Only vga or serial at a time, not both.
490
491 Currently only ttyS0 and ttyS1 are supported.
492
493 Interaction with the standard serial driver is not
494 very good.
495
496 The VGA output is eventually overwritten by the real
497 console.
498
499 eata= [HW,SCSI]
500
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501 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
502 Format: <int>
503 0: polling mode
504 non-0: interrupt mode (default)
505
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506 eda= [HW,PS2]
507
508 edb= [HW,PS2]
509
510 edd= [EDD]
511 Format: {"of[f]" | "sk[ipmbr]"}
512 See comment in arch/i386/boot/edd.S
513
a9913044 514 eicon= [HW,ISDN]
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515 Format: <id>,<membase>,<irq>
516
517 eisa_irq_edge= [PARISC,HW]
518 See header of drivers/parisc/eisa.c.
519
520 elanfreq= [IA-32]
521 See comment before function elanfreq_setup() in
522 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
523
524 elevator= [IOSCHED]
16ab3adf 525 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
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526 See Documentation/block/as-iosched.txt and
527 Documentation/block/deadline-iosched.txt for details.
528
aac04b32 529 elfcorehdr= [IA-32, X86_64]
a9913044 530 Specifies physical address of start of kernel core
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531 image elf header. Generally kexec loader will
532 pass this option to capture kernel.
533 See Documentation/kdump/kdump.txt for details.
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534
535 enforcing [SELINUX] Set initial enforcing status.
536 Format: {"0" | "1"}
537 See security/selinux/Kconfig help text.
538 0 -- permissive (log only, no denials).
539 1 -- enforcing (deny and log).
540 Default value is 0.
541 Value can be changed at runtime via /selinux/enforce.
542
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543 es1371= [HW,OSS]
544 Format: <spdif>,[<nomix>,[<amplifier>]]
545 See also header of sound/oss/es1371.c.
a9913044 546
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547 ether= [HW,NET] Ethernet cards parameters
548 This option is obsoleted by the "netdev=" option, which
549 has equivalent usage. See its documentation for details.
550
551 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
552 Format: <io>[,<irq>]
553
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554 failslab=
555 fail_page_alloc=
556 fail_make_request=[KNL]
557 General fault injection mechanism.
558 Format: <interval>,<probability>,<space>,<times>
559 See also /Documentation/fault-injection/.
560
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561 fd_mcs= [HW,SCSI]
562 See header of drivers/scsi/fd_mcs.c.
563
564 fdomain= [HW,SCSI]
565 See header of drivers/scsi/fdomain.c.
566
567 floppy= [HW]
568 See Documentation/floppy.txt.
569
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570 gamecon.map[2|3]=
571 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
572 support via parallel port (up to 5 devices per port)
573 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
574 See also Documentation/input/joystick-parport.txt
575
576 gamma= [HW,DRM]
577
578 gdth= [HW,SCSI]
579 See header of drivers/scsi/gdth.c.
580
581 gpt [EFI] Forces disk with valid GPT signature but
582 invalid Protective MBR to be treated as GPT.
583
584 gscd= [HW,CD]
585 Format: <io>
586
1da177e4
LT
587 gvp11= [HW,SCSI]
588
589 hashdist= [KNL,NUMA] Large hashes allocated during boot
590 are distributed across NUMA nodes. Defaults on
591 for IA-64, off otherwise.
a9913044 592 Format: 0 | 1 (for off | on)
1da177e4
LT
593
594 hcl= [IA-64] SGI's Hardware Graph compatibility layer
595
596 hd= [EIDE] (E)IDE hard drive subsystem geometry
597 Format: <cyl>,<head>,<sect>
598
599 hd?= [HW] (E)IDE subsystem
600 hd?lun= See Documentation/ide.txt.
601
602 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
603 size of <nn>. This works even on boxes that have no
604 highmem otherwise. This also works to reduce highmem
605 size on bigger boxes.
606
607 hisax= [HW,ISDN]
608 See Documentation/isdn/README.HiSax.
609
610 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
611
1da177e4 612 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
613 i8042.dumbkbd [HW] Pretend that controller can only read data from
614 keyboard and cannot control its state
1da177e4
LT
615 (Don't attempt to blink the leds)
616 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 617 i8042.nokbd [HW] Don't check/create keyboard port
1da177e4
LT
618 i8042.nomux [HW] Don't check presence of an active multiplexing
619 controller
620 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
621 controllers
622 i8042.panicblink=
623 [HW] Frequency with which keyboard LEDs should blink
624 when kernel panics (default is 0.5 sec)
625 i8042.reset [HW] Reset the controller during init and cleanup
626 i8042.unlock [HW] Unlock (ignore) the keylock
627
628 i810= [HW,DRM]
629
e70c9d5e
DT
630 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
631 indicates that the driver is running on unsupported
632 hardware.
1da177e4
LT
633 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
634 does not match list of supported models.
635 i8k.power_status
636 [HW] Report power status in /proc/i8k
637 (disabled by default)
638 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
639 capability is set.
640
641 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
642 See Documentation/mca.txt.
643
644 icn= [HW,ISDN]
645 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
646
647 ide= [HW] (E)IDE subsystem
648 Format: ide=nodma or ide=doubler or ide=reverse
649 See Documentation/ide.txt.
650
651 ide?= [HW] (E)IDE subsystem
652 Format: ide?=noprobe or chipset specific parameters.
653 See Documentation/ide.txt.
a9913044 654
1da177e4
LT
655 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
656 See Documentation/ide.txt.
657
658 idle= [HW]
659 Format: idle=poll or idle=halt
a9913044 660
79290822
IM
661 ignore_loglevel [KNL]
662 Ignore loglevel setting - this will print /all/
663 kernel messages to the console. Useful for debugging.
664
1da177e4
LT
665 ihash_entries= [KNL]
666 Set number of hash buckets for inode cache.
667
668 in2000= [HW,SCSI]
669 See header of drivers/scsi/in2000.c.
670
671 init= [KNL]
672 Format: <full_path>
673 Run specified binary instead of /sbin/init as init
674 process.
675
676 initcall_debug [KNL] Trace initcalls as they are executed. Useful
677 for working out where the kernel is dying during
678 startup.
679
680 initrd= [BOOT] Specify the location of the initial ramdisk
681
682 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
683 Format: <irq>
684
2bd0fa3b
JB
685 combined_mode= [HW] control which driver uses IDE ports in combined
686 mode: legacy IDE driver, libata, or both
687 (in the libata case, libata.atapi_enabled=1 may be
688 useful as well). Note that using the ide or libata
689 options may affect your device naming (e.g. by
690 changing hdc to sdb).
691 Format: combined (default), ide, or libata
692
1da177e4
LT
693 inttest= [IA64]
694
695 io7= [HW] IO7 for Marvel based alpha systems
696 See comment before marvel_specify_io7 in
697 arch/alpha/kernel/core_marvel.c.
698
699 ip= [IP_PNP]
700 See Documentation/nfsroot.txt.
701
702 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
703 See comment before ip2_setup() in drivers/char/ip2.c.
704
705 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
706 See header of drivers/scsi/ips.c.
707
72c4a13a
SH
708 ports= [IP_VS_FTP] IPVS ftp helper module
709 Default is 21.
710 Up to 8 (IP_VS_APP_MAX_PORTS) ports
711 may be specified.
712 Format: <port>,<port>....
713
200803df
AC
714 irqfixup [HW]
715 When an interrupt is not handled search all handlers
716 for it. Intended to get systems with badly broken
717 firmware running.
718
719 irqpoll [HW]
720 When an interrupt is not handled search all handlers
721 for it. Also check all handlers each timer
722 interrupt. Intended to get systems with badly broken
723 firmware running.
724
1da177e4 725 isapnp= [ISAPNP]
a9913044 726 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
727
728 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
729 Format:
730 <cpu number>,...,<cpu number>
731 or
732 <cpu number>-<cpu number> (must be a positive range in ascending order)
733 or a mixture
734 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
735 This option can be used to specify one or more CPUs
736 to isolate from the general SMP balancing and scheduling
737 algorithms. The only way to move a process onto or off
738 an "isolated" CPU is via the CPU affinity syscalls.
739 <cpu number> begins at 0 and the maximum value is
740 "number of CPUs in system - 1".
741
742 This option is the preferred way to isolate CPUs. The
a9913044
RD
743 alternative -- manually setting the CPU mask of all
744 tasks in the system -- can cause problems and
745 suboptimal load balancer performance.
1da177e4
LT
746
747 isp16= [HW,CD]
748 Format: <io>,<irq>,<dma>,<setup>
749
a9913044 750 iucv= [HW,NET]
1da177e4
LT
751
752 js= [HW,JOY] Analog joystick
753 See Documentation/input/joystick.txt.
754
755 keepinitrd [HW,ARM]
756
a9913044 757 kstack=N [IA-32,X86-64] Print N words from the kernel stack
1da177e4
LT
758 in oops dumps.
759
760 l2cr= [PPC]
761
a9913044
RD
762 lapic [IA-32,APIC] Enable the local APIC even if BIOS
763 disabled it.
1da177e4
LT
764
765 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
766 Format: addr:<io>,irq:<irq>
767
a9913044
RD
768 llsc*= [IA64] See function print_params() in
769 arch/ia64/sn/kernel/llsc4.c.
1da177e4
LT
770
771 load_ramdisk= [RAM] List of ramdisks to load from floppy
772 See Documentation/ramdisk.txt.
773
a6b25b67
RD
774 lockd.nlm_grace_period=P [NFS] Assign grace period.
775 Format: <integer>
1da177e4 776
a6b25b67
RD
777 lockd.nlm_tcpport=N [NFS] Assign TCP port.
778 Format: <integer>
779
780 lockd.nlm_timeout=T [NFS] Assign timeout value.
781 Format: <integer>
782
783 lockd.nlm_udpport=M [NFS] Assign UDP port.
784 Format: <integer>
1da177e4
LT
785
786 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
787 Format: <irq>
788
789 loglevel= All Kernel Messages with a loglevel smaller than the
790 console loglevel will be printed to the console. It can
791 also be changed with klogd or other programs. The
792 loglevels are defined as follows:
793
794 0 (KERN_EMERG) system is unusable
795 1 (KERN_ALERT) action must be taken immediately
796 2 (KERN_CRIT) critical conditions
797 3 (KERN_ERR) error conditions
798 4 (KERN_WARNING) warning conditions
799 5 (KERN_NOTICE) normal but significant condition
800 6 (KERN_INFO) informational
801 7 (KERN_DEBUG) debug-level messages
802
803 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
804 Format: { n | nk | nM }
805 n must be a power of two. The default size
806 is set in the kernel config file.
1da177e4
LT
807
808 lp=0 [LP] Specify parallel ports to use, e.g,
809 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
810 lp=reset first parallel port). 'lp=0' disables the
811 lp=auto printer driver. 'lp=reset' (which can be
812 specified in addition to the ports) causes
813 attached printers to be reset. Using
814 lp=port1,port2,... specifies the parallel ports
815 to associate lp devices with, starting with
816 lp0. A port specification may be 'none' to skip
817 that lp device, or a parport name such as
818 'parport0'. Specifying 'lp=auto' instead of a
819 port specification list means that device IDs
820 from each port should be examined, to see if
821 an IEEE 1284-compliant printer is attached; if
822 so, the driver will manage that printer.
823 See also header of drivers/char/lp.c.
824
825 lpj=n [KNL]
826 Sets loops_per_jiffy to given constant, thus avoiding
827 time-consuming boot-time autodetection (up to 250 ms per
828 CPU). 0 enables autodetection (default). To determine
829 the correct value for your kernel, boot with normal
830 autodetection and see what value is printed. Note that
831 on SMP systems the preset will be applied to all CPUs,
832 which is likely to cause problems if your CPUs need
833 significantly divergent settings. An incorrect value
834 will cause delays in the kernel to be wrong, leading to
835 unpredictable I/O errors and other breakage. Although
836 unlikely, in the extreme case this might damage your
837 hardware.
838
839 ltpc= [NET]
840 Format: <io>,<irq>,<dma>
841
a9913044
RD
842 mac5380= [HW,SCSI] Format:
843 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 844
a9913044
RD
845 mac53c9x= [HW,SCSI] Format:
846 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 847
a9913044
RD
848 machvec= [IA64] Force the use of a particular machine-vector
849 (machvec) in a generic kernel.
850 Example: machvec=hpzx1_swiotlb
1da177e4 851
a9913044 852 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
853 be mounted
854 Format: <1-256>
855
856 maxcpus= [SMP] Maximum number of processors that an SMP kernel
857 should make use of
858
2b2c3750
BP
859 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
860 equal to this physical address is ignored.
861
a9913044 862 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
863 Should be between 1 and 2^32-1.
864
865 max_report_luns=
a9913044 866 [SCSI] Maximum number of LUNs received.
1da177e4
LT
867 Should be between 1 and 16384.
868
869 mca-pentium [BUGS=IA-32]
870
871 mcatest= [IA-64]
872
873 mcd= [HW,CD]
874 Format: <port>,<irq>,<mitsumi_bug_93_wait>
875
876 mcdx= [HW,CD]
877
878 mce [IA-32] Machine Check Exception
879
880 md= [HW] RAID subsystems devices and level
881 See Documentation/md.txt.
a9913044 882
1da177e4
LT
883 mdacon= [MDA]
884 Format: <first>,<last>
885 Specifies range of consoles to be captured by the MDA.
a9913044 886
1da177e4
LT
887 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
888 Amount of memory to be used when the kernel is not able
889 to see the whole system memory or for test.
890 [IA-32] Use together with memmap= to avoid physical
891 address space collisions. Without memmap= PCI devices
892 could be placed at addresses belonging to unused RAM.
893
894 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
895 memory.
896
69cda7b1 897 memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
1da177e4
LT
898 E820 memory map, as specified by the user.
899 Such memmap=exactmap lines can be constructed based on
900 BIOS output or other requirements. See the memmap=nn@ss
901 option description.
902
903 memmap=nn[KMG]@ss[KMG]
904 [KNL] Force usage of a specific region of memory
905 Region of memory to be used, from ss to ss+nn.
906
907 memmap=nn[KMG]#ss[KMG]
908 [KNL,ACPI] Mark specific memory as ACPI data.
909 Region of memory to be used, from ss to ss+nn.
910
911 memmap=nn[KMG]$ss[KMG]
912 [KNL,ACPI] Mark specific memory as reserved.
913 Region of memory to be used, from ss to ss+nn.
914
915 meye.*= [HW] Set MotionEye Camera parameters
916 See Documentation/video4linux/meye.txt.
917
918 mga= [HW,DRM]
919
198e2f18 920 migration_cost=
921 [KNL,SMP] debug: override scheduler migration costs
922 Format: <level-1-usecs>,<level-2-usecs>,...
923 This debugging option can be used to override the
924 default scheduler migration cost matrix. The numbers
925 are indexed by 'CPU domain distance'.
926 E.g. migration_cost=1000,2000,3000 on an SMT NUMA
927 box will set up an intra-core migration cost of
928 1 msec, an inter-core migration cost of 2 msecs,
929 and an inter-node migration cost of 3 msecs.
930
931 WARNING: using the wrong values here can break
932 scheduler performance, so it's only for scheduler
933 development purposes, not production environments.
934
935 migration_debug=
936 [KNL,SMP] migration cost auto-detect verbosity
937 Format=<0|1|2>
938 If a system's migration matrix reported at bootup
939 seems erroneous then this option can be used to
940 increase verbosity of the detection process.
941 We default to 0 (no extra messages), 1 will print
942 some more information, and 2 will be really
943 verbose (probably only useful if you also have a
944 serial console attached to the system).
945
946 migration_factor=
947 [KNL,SMP] multiply/divide migration costs by a factor
948 Format=<percent>
949 This debug option can be used to proportionally
950 increase or decrease the auto-detected migration
951 costs for all entries of the migration matrix.
952 E.g. migration_factor=150 will increase migration
953 costs by 50%. (and thus the scheduler will be less
954 eager migrating cache-hot tasks)
955 migration_factor=80 will decrease migration costs
956 by 20%. (thus the scheduler will be more eager to
957 migrate tasks)
958
959 WARNING: using the wrong values here can break
960 scheduler performance, so it's only for scheduler
961 development purposes, not production environments.
962
1da177e4
LT
963 mousedev.tap_time=
964 [MOUSE] Maximum time between finger touching and
965 leaving touchpad surface for touch to be considered
966 a tap and be reported as a left button click (for
967 touchpads working in absolute mode only).
968 Format: <msecs>
969 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
970 reporting absolute coordinates, such as tablets
971 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
972 reporting absolute coordinates, such as tablets
973
974 mpu401= [HW,OSS]
975 Format: <io>,<irq>
976
977 MTD_Partition= [MTD]
978 Format: <name>,<region-number>,<size>,<offset>
979
a9913044
RD
980 MTD_Region= [MTD] Format:
981 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
982
983 mtdparts= [MTD]
984 See drivers/mtd/cmdline.c.
985
986 mtouchusb.raw_coordinates=
a9913044
RD
987 [HW] Make the MicroTouch USB driver use raw coordinates
988 ('y', default) or cooked coordinates ('n')
1da177e4
LT
989
990 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
991
992 NCR_D700= [HW,SCSI]
993 See header of drivers/scsi/NCR_D700.c.
994
995 ncr5380= [HW,SCSI]
996
997 ncr53c400= [HW,SCSI]
998
999 ncr53c400a= [HW,SCSI]
1000
1001 ncr53c406a= [HW,SCSI]
1002
1003 ncr53c8xx= [HW,SCSI]
1004
1005 netdev= [NET] Network devices parameters
1006 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1007 Note that mem_start is often overloaded to mean
1008 something different and driver-specific.
a9913044
RD
1009 This usage is only documented in each driver source
1010 file if at all.
1011
1da177e4
LT
1012 nfsaddrs= [NFS]
1013 See Documentation/nfsroot.txt.
1014
1015 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1016 See Documentation/nfsroot.txt.
1017
a72b4422
TM
1018 nfs.callback_tcpport=
1019 [NFS] set the TCP port on which the NFSv4 callback
1020 channel should listen.
1021
58df095b
TM
1022 nfs.idmap_cache_timeout=
1023 [NFS] set the maximum lifetime for idmapper cache
1024 entries.
1025
1da177e4
LT
1026 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
1027
1028 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
1029 emulation library even if a 387 maths coprocessor
1030 is present.
1031
3395ee05
PM
1032 noaliencache [MM, NUMA] Disables the allcoation of alien caches in
1033 the slab allocator. Saves per-node memory, but will
1034 impact performance on real NUMA hardware.
1035
a9913044
RD
1036 noalign [KNL,ARM]
1037
1da177e4
LT
1038 noapic [SMP,APIC] Tells the kernel to not make use of any
1039 IOAPICs that may be present in the system.
1040
1041 noasync [HW,M68K] Disables async and sync negotiation for
1042 all devices.
1043
1044 nobats [PPC] Do not use BATs for mapping kernel lowmem
1045 on "Classic" PPC cores.
1046
1047 nocache [ARM]
a9913044 1048
163ecdff
SN
1049 nodelayacct [KNL] Disable per-task delay accounting
1050
1da177e4
LT
1051 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1052
1053 noexec [IA-64]
1054
a9913044 1055 noexec [IA-32,X86-64]
1da177e4
LT
1056 noexec=on: enable non-executable mappings (default)
1057 noexec=off: disable nn-executable mappings
1058
4f886511
CE
1059 nofxsr [BUGS=IA-32] Disables x86 floating point extended
1060 register save and restore. The kernel will only save
1061 legacy floating-point registers on task switch.
1da177e4
LT
1062
1063 nohlt [BUGS=ARM]
a9913044 1064
1da177e4
LT
1065 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
1066 instruction doesn't work correctly and not to
1067 use it.
1068
1069 nohalt [IA-64] Tells the kernel not to use the power saving
1070 function PAL_HALT_LIGHT when idle. This increases
1071 power-consumption. On the positive side, it reduces
1072 interrupt wake-up latency, which may improve performance
1073 in certain environments such as networked servers or
1074 real-time systems.
1075
8542b200
ZA
1076 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
1077
1da177e4
LT
1078 noirqdebug [IA-32] Disables the code which attempts to detect and
1079 disable unhandled interrupt sources.
1080
8542b200
ZA
1081 no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for
1082 broken timer IRQ sources.
1083
1da177e4
LT
1084 noisapnp [ISAPNP] Disables ISA PnP code.
1085
1086 noinitrd [RAM] Tells the kernel not to load any configured
1087 initial RAM disk.
1088
1089 nointroute [IA-64]
1090
1091 nolapic [IA-32,APIC] Do not enable or use the local APIC.
1092
1093 noltlbs [PPC] Do not use large page/tlb entries for kernel
1094 lowmem mapping on PPC40x.
1095
312f1f01
H
1096 nomca [IA-64] Disable machine check abort handling
1097
abe37e5a
H
1098 nomce [IA-32] Machine Check Exception
1099
1da177e4
LT
1100 noresidual [PPC] Don't use residual data on PReP machines.
1101
a9913044
RD
1102 noresume [SWSUSP] Disables resume and restores original swap
1103 space.
1104
1da177e4
LT
1105 no-scroll [VGA] Disables scrollback.
1106 This is required for the Braillex ib80-piezo Braille
1107 reader made by F.H. Papenmeier (Germany).
1108
1109 nosbagart [IA-64]
1110
4f886511
CE
1111 nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1112
1da177e4
LT
1113 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1114
1115 nosync [HW,M68K] Disables sync negotiation for all devices.
1116
1117 notsc [BUGS=IA-32] Disable Time Stamp Counter
1118
1119 nousb [USB] Disable the USB subsystem
1120
1121 nowb [ARM]
a9913044 1122
a61c2d78
DJ
1123 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1124
1da177e4
LT
1125 opl3= [HW,OSS]
1126 Format: <io>
1127
a9913044
RD
1128 opl3sa2= [HW,OSS] Format:
1129 <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
1130
1da177e4
LT
1131 oprofile.timer= [HW]
1132 Use timer interrupt instead of performance counters
1133
1134 optcd= [HW,CD]
1135 Format: <io>
1136
1137 osst= [HW,SCSI] SCSI Tape Driver
1138 Format: <buffer_size>,<write_threshold>
1139 See also Documentation/scsi/st.txt.
1140
1141 panic= [KNL] Kernel behaviour on panic
1142 Format: <timeout>
1143
1144 parkbd.port= [HW] Parallel port number the keyboard adapter is
1145 connected to, default is 0.
1146 Format: <parport#>
1147 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1148 0 for XT, 1 for AT (default is AT).
a9913044
RD
1149 Format: <mode>
1150
1151 parport= [HW,PPT] Specify parallel ports. 0 disables.
1152 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1153 Use 'auto' to force the driver to use any
1154 IRQ/DMA settings detected (the default is to
1155 ignore detected IRQ/DMA settings because of
1156 possible conflicts). You can specify the base
1157 address, IRQ, and DMA settings; IRQ and DMA
1158 should be numbers, or 'auto' (for using detected
1159 settings on that particular port), or 'nofifo'
1160 (to avoid using a FIFO even if it is detected).
1161 Parallel ports are assigned in the order they
1162 are specified on the command line, starting
1163 with parport0.
1164
1165 parport_init_mode= [HW,PPT]
1166 Configure VIA parallel port to operate in
1167 a specific mode. This is necessary on Pegasos
1168 computer where firmware has no options for setting
1169 up parallel port mode and sets it to spp.
1170 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1171 Format: [spp|ps2|epp|ecp|ecpepp]
1172
a9913044
RD
1173 pas2= [HW,OSS] Format:
1174 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1175
1da177e4
LT
1176 pas16= [HW,SCSI]
1177 See header of drivers/scsi/pas16.c.
1178
dd287796
AM
1179 pause_on_oops=
1180 Halt all CPUs after the first oops has been printed for
1181 the specified number of seconds. This is to be used if
1182 your oopses keep scrolling off the screen.
1183
1da177e4
LT
1184 pcbit= [HW,ISDN]
1185
1186 pcd. [PARIDE]
1187 See header of drivers/block/paride/pcd.c.
1188 See also Documentation/paride.txt.
1189
a9913044
RD
1190 pci=option[,option...] [PCI] various PCI subsystem options:
1191 off [IA-32] don't probe for the PCI bus
1192 bios [IA-32] force use of PCI BIOS, don't access
1193 the hardware directly. Use this if your machine
1194 has a non-standard PCI host bridge.
1195 nobios [IA-32] disallow use of PCI BIOS, only direct
1196 hardware access methods are allowed. Use this
1197 if you experience crashes upon bootup and you
1198 suspect they are caused by the BIOS.
1199 conf1 [IA-32] Force use of PCI Configuration
1200 Mechanism 1.
1201 conf2 [IA-32] Force use of PCI Configuration
1202 Mechanism 2.
61be6d66
BH
1203 nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
1204 Configuration
309e57df
MW
1205 nomsi [MSI] If the PCI_MSI kernel config parameter is
1206 enabled, this kernel boot option can be used to
1207 disable the use of MSI interrupts system-wide.
a9913044
RD
1208 nosort [IA-32] Don't sort PCI devices according to
1209 order given by the PCI BIOS. This sorting is
1210 done to get a device order compatible with
1211 older kernels.
1212 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1213 routing table. These calls are known to be buggy
1214 on several machines and they hang the machine
1215 when used, but on other computers it's the only
1216 way to get the interrupt routing table. Try
1217 this option if the kernel is unable to allocate
1218 IRQs or discover secondary PCI buses on your
1219 motherboard.
1220 rom [IA-32] Assign address space to expansion ROMs.
1221 Use with caution as certain devices share
1222 address decoders between ROMs and other
1223 resources.
1224 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1225 assigned automatically to PCI devices. You can
1226 make the kernel exclude IRQs of your ISA cards
1227 this way.
120bb424 1228 pirqaddr=0xAAAAA [IA-32] Specify the physical address
a9913044
RD
1229 of the PIRQ table (normally generated
1230 by the BIOS) if it is outside the
1231 F0000h-100000h range.
1232 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1233 useful if the kernel is unable to find your
1234 secondary buses and you want to tell it
1235 explicitly which ones they are.
1236 assign-busses [IA-32] Always assign all PCI bus
1237 numbers ourselves, overriding
1238 whatever the firmware may have done.
1239 usepirqmask [IA-32] Honor the possible IRQ mask stored
1240 in the BIOS $PIR table. This is needed on
1241 some systems with broken BIOSes, notably
1242 some HP Pavilion N5400 and Omnibook XE3
1243 notebooks. This will have no effect if ACPI
1244 IRQ routing is enabled.
1245 noacpi [IA-32] Do not use ACPI for IRQ routing
1246 or for PCI scanning.
1247 routeirq Do IRQ routing for all PCI devices.
1248 This is normally done in pci_enable_device(),
1249 so this option is a temporary workaround
1250 for broken drivers that don't call it.
1251 firmware [ARM] Do not re-enumerate the bus but instead
1252 just use the configuration from the
1253 bootloader. This is currently used on
1254 IXP2000 systems where the bus has to be
1255 configured a certain way for adjunct CPUs.
0637a70a
AK
1256 noearly [X86] Don't do any early type 1 scanning.
1257 This might help on some broken boards which
1258 machine check when some devices' config space
1259 is read. But various workarounds are disabled
1260 and some IOMMU drivers will not work.
6b4b78fe
MD
1261 bfsort Sort PCI devices into breadth-first order.
1262 This sorting is done to get a device
1263 order compatible with older (<= 2.4) kernels.
1264 nobfsort Don't sort PCI devices into breadth-first order.
1265
1da177e4
LT
1266 pcmv= [HW,PCMCIA] BadgePAD 4
1267
1268 pd. [PARIDE]
1269 See Documentation/paride.txt.
1270
1271 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1272 boot time.
1273 Format: { 0 | 1 }
1274 See arch/parisc/kernel/pdc_chassis.c
1275
1276 pf. [PARIDE]
1277 See Documentation/paride.txt.
1278
1279 pg. [PARIDE]
1280 See Documentation/paride.txt.
1281
1282 pirq= [SMP,APIC] Manual mp-table setup
1283 See Documentation/i386/IO-APIC.txt.
1284
1285 plip= [PPT,NET] Parallel port network link
1286 Format: { parport<nr> | timid | 0 }
1287 See also Documentation/parport.txt.
1288
1289 pnpacpi= [ACPI]
1290 { off }
1291
1292 pnpbios= [ISAPNP]
1293 { on | off | curr | res | no-curr | no-res }
1294
1295 pnp_reserve_irq=
1296 [ISAPNP] Exclude IRQs for the autoconfiguration
1297
1298 pnp_reserve_dma=
1299 [ISAPNP] Exclude DMAs for the autoconfiguration
1300
1301 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1302 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1303
1304 pnp_reserve_mem=
a9913044
RD
1305 [ISAPNP] Exclude memory regions for the
1306 autoconfiguration.
1da177e4
LT
1307 Ranges are in pairs (memory base and size).
1308
1309 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1310 Format: [schedule,]<number>
1311 Param: "schedule" - profile schedule points.
1312 Param: <number> - step/bucket size as a power of 2 for
1313 statistical time based profiling.
ece8a684 1314 Param: "sleep" - profile D-state sleeping (millisecs)
1da177e4 1315
a9913044 1316 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1317 Limit processor to maximum C-state
1318 max_cstate=9 overrides any DMI blacklist limit.
1319
41c0d868
LB
1320 processor.nocst [HW,ACPI]
1321 Ignore the _CST method to determine C-states,
1322 instead using the legacy FADT method
1323
1da177e4
LT
1324 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1325 before loading.
1326 See Documentation/ramdisk.txt.
1327
a9913044
RD
1328 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1329 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1330 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1331 per second.
a9913044
RD
1332 psmouse.resetafter= [HW,MOUSE]
1333 Try to reset the device after so many bad packets
1da177e4
LT
1334 (0 = never).
1335 psmouse.resolution=
1336 [HW,MOUSE] Set desired mouse resolution, in dpi.
1337 psmouse.smartscroll=
a9913044 1338 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1339 0 = disabled, 1 = enabled (default).
1340
1341 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1342 Format:
1343 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1344
1345 pt. [PARIDE]
1346 See Documentation/paride.txt.
1347
7d2c502f 1348 quiet [KNL] Disable most log messages
a9913044 1349
1da177e4
LT
1350 r128= [HW,DRM]
1351
1352 raid= [HW,RAID]
1353 See Documentation/md.txt.
1354
1355 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1356 See Documentation/ramdisk.txt.
1357
a9913044 1358 ramdisk_blocksize= [RAM]
1da177e4 1359 See Documentation/ramdisk.txt.
a9913044 1360
1da177e4
LT
1361 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1362 New name for the ramdisk parameter.
1363 See Documentation/ramdisk.txt.
1364
21a1ea9e
DS
1365 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1366 RCU callbacks to process in one batch.
1367
1368 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1369 RCU callbacks over which batch limiting is disabled.
1370
1371 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1372 RCU callbacks below which batch limiting is re-enabled.
1373
ffdfc409
OJ
1374 rdinit= [KNL]
1375 Format: <full_path>
1376 Run specified binary instead of /init from the ramdisk,
1377 used for early userspace startup. See initrd.
1378
1da177e4
LT
1379 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1380 Format: <reboot_mode>[,<reboot_mode2>[,...]]
f3e299fe 1381 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1382
1383 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1384
461a9aff
ZA
1385 reservetop= [IA-32]
1386 Format: nn[KMG]
1387 Reserves a hole at the top of the kernel virtual
1388 address space.
1389
7e96287d
VG
1390 reset_devices [KNL] Force drivers to reset the underlying device
1391 during initialization.
1392
a9913044
RD
1393 resume= [SWSUSP]
1394 Specify the partition device for software suspend
1da177e4 1395
ecbd0da1
RW
1396 resume_offset= [SWSUSP]
1397 Specify the offset from the beginning of the partition
1398 given by "resume=" at which the swap header is located,
1399 in <PAGE_SIZE> units (needed only for swap files).
1400 See Documentation/power/swsusp-and-swap-files.txt
1401
0a7b35cb
MN
1402 retain_initrd [RAM] Keep initrd memory after extraction
1403
1da177e4
LT
1404 rhash_entries= [KNL,NET]
1405 Set number of hash buckets for route cache
1406
1407 riscom8= [HW,SERIAL]
1408 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1409
1410 ro [KNL] Mount root device read-only on boot
1411
1412 root= [KNL] Root filesystem
1413
1414 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1415 mount the root filesystem
1416
1417 rootflags= [KNL] Set root filesystem mount option string
1418
1419 rootfstype= [KNL] Set root filesystem type
1420
1421 rw [KNL] Mount root device read-write on boot
1422
1423 S [KNL] Run init in single mode
1424
1425 sa1100ir [NET]
1426 See drivers/net/irda/sa1100_ir.c.
1427
1428 sb= [HW,OSS]
1429 Format: <io>,<irq>,<dma>,<dma2>
1430
1431 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1432
1da177e4
LT
1433 sbpcd= [HW,CD] Soundblaster CD adapter
1434 Format: <io>,<type>
1435 See a comment before function sbpcd_setup() in
1436 drivers/cdrom/sbpcd.c.
1437
1438 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1439 Format: <io>[,<timeout>[,<isapnp>]]
1440
1441 scsi_debug_*= [SCSI]
1442 See drivers/scsi/scsi_debug.c.
1443
1444 scsi_default_dev_flags=
1445 [SCSI] SCSI default device flags
1446 Format: <integer>
1447
1448 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1449 Format: <vendor>:<model>:<flags>
1450 (flags are integer value)
1451
1452 scsi_logging= [SCSI]
1453
3e082a91
MW
1454 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1455 discovered. async scans them in kernel threads,
1456 allowing boot to proceed. none ignores them, expecting
1457 user space to do the scan.
1458
1da177e4
LT
1459 selinux [SELINUX] Disable or enable SELinux at boot time.
1460 Format: { "0" | "1" }
1461 See security/selinux/Kconfig help text.
1462 0 -- disable.
1463 1 -- enable.
1464 Default value is set via kernel config option.
1465 If enabled at boot time, /selinux/disable can be used
1466 later to disable prior to initial policy load.
1467
4e5ab4cb
JM
1468 selinux_compat_net =
1469 [SELINUX] Set initial selinux_compat_net flag value.
1470 Format: { "0" | "1" }
1471 0 -- use new secmark-based packet controls
1472 1 -- use legacy packet controls
1473 Default value is 0 (preferred).
1474 Value can be changed at runtime via
1475 /selinux/compat_net.
1476
1da177e4
LT
1477 serialnumber [BUGS=IA-32]
1478
a9913044
RD
1479 sg_def_reserved_size= [SCSI]
1480
1da177e4
LT
1481 shapers= [NET]
1482 Maximal number of shapers.
a9913044 1483
1da177e4
LT
1484 sim710= [SCSI,HW]
1485 See header of drivers/scsi/sim710.c.
1486
1487 simeth= [IA-64]
1488 simscsi=
a9913044 1489
1da177e4
LT
1490 sjcd= [HW,CD]
1491 Format: <io>,<irq>,<dma>
1492 See header of drivers/cdrom/sjcd.c.
1493
1494 slram= [HW,MTD]
1495
1496 smart2= [HW]
1497 Format: <io1>[,<io2>[,...,<io8>]]
1498
1499 snd-ad1816a= [HW,ALSA]
1500
1501 snd-ad1848= [HW,ALSA]
1502
1503 snd-ali5451= [HW,ALSA]
1504
1505 snd-als100= [HW,ALSA]
1506
1507 snd-als4000= [HW,ALSA]
1508
1509 snd-azt2320= [HW,ALSA]
1510
1511 snd-cmi8330= [HW,ALSA]
1512
1513 snd-cmipci= [HW,ALSA]
1514
1515 snd-cs4231= [HW,ALSA]
1516
1517 snd-cs4232= [HW,ALSA]
1518
1519 snd-cs4236= [HW,ALSA]
1520
1521 snd-cs4281= [HW,ALSA]
1522
1523 snd-cs46xx= [HW,ALSA]
1524
1525 snd-dt019x= [HW,ALSA]
1526
1527 snd-dummy= [HW,ALSA]
1528
1529 snd-emu10k1= [HW,ALSA]
1530
1531 snd-ens1370= [HW,ALSA]
1532
1533 snd-ens1371= [HW,ALSA]
1534
1535 snd-es968= [HW,ALSA]
1536
1537 snd-es1688= [HW,ALSA]
1538
1539 snd-es18xx= [HW,ALSA]
1540
1541 snd-es1938= [HW,ALSA]
1542
1543 snd-es1968= [HW,ALSA]
1544
1545 snd-fm801= [HW,ALSA]
1546
1547 snd-gusclassic= [HW,ALSA]
1548
1549 snd-gusextreme= [HW,ALSA]
1550
1551 snd-gusmax= [HW,ALSA]
1552
1553 snd-hdsp= [HW,ALSA]
1554
1555 snd-ice1712= [HW,ALSA]
1556
1557 snd-intel8x0= [HW,ALSA]
1558
1559 snd-interwave= [HW,ALSA]
1560
1561 snd-interwave-stb=
1562 [HW,ALSA]
1563
1564 snd-korg1212= [HW,ALSA]
1565
1566 snd-maestro3= [HW,ALSA]
1567
1568 snd-mpu401= [HW,ALSA]
1569
1570 snd-mtpav= [HW,ALSA]
1571
1572 snd-nm256= [HW,ALSA]
1573
1574 snd-opl3sa2= [HW,ALSA]
1575
1576 snd-opti92x-ad1848=
1577 [HW,ALSA]
1578
1579 snd-opti92x-cs4231=
1580 [HW,ALSA]
1581
1582 snd-opti93x= [HW,ALSA]
1583
1584 snd-pmac= [HW,ALSA]
1585
1586 snd-rme32= [HW,ALSA]
1587
1588 snd-rme96= [HW,ALSA]
1589
1590 snd-rme9652= [HW,ALSA]
1591
1592 snd-sb8= [HW,ALSA]
1593
1594 snd-sb16= [HW,ALSA]
1595
1596 snd-sbawe= [HW,ALSA]
1597
1598 snd-serial= [HW,ALSA]
1599
1600 snd-sgalaxy= [HW,ALSA]
1601
1602 snd-sonicvibes= [HW,ALSA]
1603
1604 snd-sun-amd7930=
1605 [HW,ALSA]
1606
1607 snd-sun-cs4231= [HW,ALSA]
1608
1609 snd-trident= [HW,ALSA]
1610
1611 snd-usb-audio= [HW,ALSA,USB]
1612
1613 snd-via82xx= [HW,ALSA]
1614
1615 snd-virmidi= [HW,ALSA]
1616
1617 snd-wavefront= [HW,ALSA]
1618
1619 snd-ymfpci= [HW,ALSA]
a9913044 1620
1da177e4
LT
1621 sonycd535= [HW,CD]
1622 Format: <io>[,<irq>]
1623
1624 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1625 See Documentation/sonypi.txt
1626
1627 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1628 See Documentation/specialix.txt.
1629
1630 spia_io_base= [HW,MTD]
1631 spia_fio_base=
1632 spia_pedr=
1633 spia_peddr=
1634
1635 sscape= [HW,OSS]
1636 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1637
1da177e4
LT
1638 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1639 See Documentation/scsi/st.txt.
1640
1641 st0x= [HW,SCSI]
1642 See header of drivers/scsi/seagate.c.
1643
1644 sti= [PARISC,HW]
1645 Format: <num>
1646 Set the STI (builtin display/keyboard on the HP-PARISC
1647 machines) console (graphic card) which should be used
1648 as the initial boot-console.
1649 See also comment in drivers/video/console/sticore.c.
1650
1651 sti_font= [HW]
1652 See comment in drivers/video/console/sticore.c.
1653
1654 stifb= [HW]
1655 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1656
1da177e4 1657 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 1658
1da177e4
LT
1659 switches= [HW,M68k]
1660
1661 sym53c416= [HW,SCSI]
1662 See header of drivers/scsi/sym53c416.c.
1663
5d6f647f
IM
1664 sysrq_always_enabled
1665 [KNL]
1666 Ignore sysrq setting - this boot parameter will
1667 neutralize any effect of /proc/sys/kernel/sysrq.
1668 Useful for debugging.
1669
1da177e4
LT
1670 t128= [HW,SCSI]
1671 See header of drivers/scsi/t128.c.
1672
1673 tdfx= [HW,DRM]
1674
1675 thash_entries= [KNL,NET]
1676 Set number of hash buckets for TCP connection
1677
1678 time Show timing data prefixed to each printk message line
1679
734efb46
JS
1680 clocksource= [GENERIC_TIME] Override the default clocksource
1681 Override the default clocksource and use the clocksource
1682 with the name specified.
1683
1da177e4
LT
1684 tipar.timeout= [HW,PPT]
1685 Set communications timeout in tenths of a second
1686 (default 15).
1687
1688 tipar.delay= [HW,PPT]
1689 Set inter-bit delay in microseconds (default 10).
1690
1691 tmc8xx= [HW,SCSI]
1692 See header of drivers/scsi/seagate.c.
1693
1694 tmscsim= [HW,SCSI]
1695 See comment before function dc390_setup() in
1696 drivers/scsi/tmscsim.c.
1697
1698 tp720= [HW,PS2]
1699
1700 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
1701 Format:
1702 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1703
1da177e4
LT
1704 tsdev.xres= [TS] Horizontal screen resolution.
1705 tsdev.yres= [TS] Vertical screen resolution.
1706
a9913044
RD
1707 turbografx.map[2|3]= [HW,JOY]
1708 TurboGraFX parallel port interface
1709 Format:
1710 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
1711 See also Documentation/input/joystick-parport.txt
1712
1713 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1714 See header of drivers/scsi/u14-34f.c.
1715
1716 uart401= [HW,OSS]
1717 Format: <io>,<irq>
1718
1719 uart6850= [HW,OSS]
1720 Format: <io>,<irq>
1721
5f8364b7
AS
1722 uhci-hcd.ignore_oc=
1723 [USB] Ignore overcurrent events (default N).
1724 Some badly-designed motherboards generate lots of
1725 bogus events, for ports that aren't wired to
1726 anything. Set this parameter to avoid log spamming.
1727 Note that genuine overcurrent events won't be
1728 reported either.
1729
1da177e4
LT
1730 usbhid.mousepoll=
1731 [USBHID] The interval which mice are to be polled at.
a9913044 1732
e6e5494c
IM
1733 vdso= [IA-32]
1734 vdso=1: enable VDSO (default)
1735 vdso=0: disable VDSO mapping
1736
1da177e4
LT
1737 video= [FB] Frame buffer configuration
1738 See Documentation/fb/modedb.txt.
1739
1740 vga= [BOOT,IA-32] Select a particular video mode
a9913044
RD
1741 See Documentation/i386/boot.txt and
1742 Documentation/svga.txt.
1da177e4
LT
1743 Use vga=ask for menu.
1744 This is actually a boot loader parameter; the value is
1745 passed to the kernel using a special protocol.
1746
a9913044 1747 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
1748 size of <nn>. This can be used to increase the
1749 minimum size (128MB on x86). It can also be used to
1750 decrease the size and leave more room for directly
1751 mapped kernel RAM.
1752
585c3047
PO
1753 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1754 Format: <command>
1da177e4 1755
585c3047
PO
1756 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1757 Format: <command>
1758
1759 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1760 Format: <command>
a9913044 1761
1da177e4
LT
1762 waveartist= [HW,OSS]
1763 Format: <io>,<irq>,<dma>,<dma2>
a9913044 1764
1da177e4
LT
1765 wd33c93= [HW,SCSI]
1766 See header of drivers/scsi/wd33c93.c.
1767
1768 wd7000= [HW,SCSI]
1769 See header of drivers/scsi/wd7000.c.
1770
1771 wdt= [WDT] Watchdog
1772 See Documentation/watchdog/watchdog.txt.
1773
1774 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1775 xd_geo= See header of drivers/block/xd.c.
1776
1777 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
1778 Format:
1779 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 1780
a62eaf15
AK
1781 norandmaps Don't use address space randomization
1782 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1783
6d0185ea
JB
1784 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1785 This is useful to get more information why
1786 you got a "dwarf2 unwinder stuck"
1da177e4 1787
a9913044 1788______________________________________________________________________
1da177e4
LT
1789
1790TODO:
1791
1792 Add documentation for ALSA options.
1793 Add more DRM drivers.