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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.
11ef697b 51 LIBATA Libata driver is enabled
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52 LP Printer support is enabled.
53 LOOP Loopback device support is enabled.
54 M68k M68k architecture is enabled.
55 These options have more detailed description inside of
56 Documentation/m68k/kernel-options.txt.
57 MCA MCA bus support is enabled.
58 MDA MDA console support is enabled.
59 MOUSE Appropriate mouse support is enabled.
309e57df 60 MSI Message Signaled Interrupts (PCI).
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61 MTD MTD support is enabled.
62 NET Appropriate network support is enabled.
63 NUMA NUMA support is enabled.
734efb46 64 GENERIC_TIME The generic timeofday code is enabled.
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65 NFS Appropriate NFS support is enabled.
66 OSS OSS sound support is enabled.
67 PARIDE The ParIDE subsystem is enabled.
68 PARISC The PA-RISC architecture is enabled.
69 PCI PCI bus support is enabled.
70 PCMCIA The PCMCIA subsystem is enabled.
71 PNP Plug & Play support is enabled.
72 PPC PowerPC architecture is enabled.
73 PPT Parallel port support is enabled.
74 PS2 Appropriate PS/2 support is enabled.
75 RAM RAM disk support is enabled.
76 S390 S390 architecture is enabled.
77 SCSI Appropriate SCSI support is enabled.
78 A lot of drivers has their options described inside of
79 Documentation/scsi/.
80 SELINUX SELinux support is enabled.
81 SERIAL Serial support is enabled.
82 SMP The kernel is an SMP kernel.
83 SPARC Sparc architecture is enabled.
a9913044 84 SWSUSP Software suspend is enabled.
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85 TS Appropriate touchscreen support is enabled.
86 USB USB support is enabled.
87 USBHID USB Human Interface Device support is enabled.
88 V4L Video For Linux support is enabled.
89 VGA The VGA console has been enabled.
90 VT Virtual terminal support is enabled.
91 WDT Watchdog support is enabled.
92 XT IBM PC/XT MFM hard disk support is enabled.
93 X86-64 X86-64 architecture is enabled.
94 More X86-64 boot options can be found in
95 Documentation/x86_64/boot-options.txt .
96
97In addition, the following text indicates that the option:
98
99 BUGS= Relates to possible processor bugs on the said processor.
100 KNL Is a kernel start-up parameter.
101 BOOT Is a boot loader parameter.
102
103Parameters denoted with BOOT are actually interpreted by the boot
104loader, and have no meaning to the kernel directly.
105Do not modify the syntax of boot loader parameters without extreme
106need or coordination with <Documentation/i386/boot.txt>.
107
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108There are also arch-specific kernel-parameters not documented here.
109See for example <Documentation/x86_64/boot-options.txt>.
110
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111Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
112a trailing = on the name of any parameter states that that parameter will
113be entered as an environment variable, whereas its absence indicates that
114it will appear as a kernel argument readable via /proc/cmdline by programs
115running once the system is up.
116
9c4751fd 117The number of kernel parameters is not limited, but the length of the
118complete command line (parameters including spaces etc.) is limited to
119a fixed number of characters. This limit depends on the architecture
120and is between 256 and 4096 characters. It is defined in the file
121./include/asm/setup.h as COMMAND_LINE_SIZE.
122
123
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124 53c7xx= [HW,SCSI] Amiga SCSI controllers
125 See header of drivers/scsi/53c7xx.c.
126 See also Documentation/scsi/ncr53c7xx.txt.
127
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128 acpi= [HW,ACPI] Advanced Configuration and Power Interface
129 Format: { force | off | ht | strict | noirq }
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130 force -- enable ACPI if default was off
131 off -- disable ACPI if default was on
132 noirq -- do not use ACPI for IRQ routing
133 ht -- run only enough ACPI to enable Hyper Threading
a9913044 134 strict -- Be less tolerant of platforms that are not
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135 strictly ACPI specification compliant.
136
137 See also Documentation/pm.txt, pci=noacpi
138
139 acpi_sleep= [HW,ACPI] Sleep options
140 Format: { s3_bios, s3_mode }
141 See Documentation/power/video.txt
a9913044 142
1da177e4 143 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
a9913044 144 Format: { level | edge | high | low }
1da177e4 145
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146 acpi_irq_balance [HW,ACPI]
147 ACPI will balance active IRQs
148 default in APIC mode
1da177e4 149
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150 acpi_irq_nobalance [HW,ACPI]
151 ACPI will not move active IRQs (default)
152 default in PIC mode
1da177e4 153
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154 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
155 use by PCI
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156 Format: <irq>,<irq>...
157
a9913044 158 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
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159 Format: <irq>,<irq>...
160
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161 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
162 Format: To spoof as Windows 98: ="Microsoft Windows"
163
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164 acpi_osi= [HW,ACPI] empty param disables _OSI
165
166 acpi_serialize [HW,ACPI] force serialization of AML methods
167
168 acpi_skip_timer_override [HW,ACPI]
169 Recognize and ignore IRQ0/pin2 Interrupt Override.
170 For broken nForce2 BIOS resulting in XT-PIC timer.
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171 acpi_use_timer_override [HW,ACPI}
172 Use timer override. For some broken Nvidia NF5 boards
173 that require a timer override, but don't have
174 HPET
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175
176 acpi_dbg_layer= [HW,ACPI]
177 Format: <int>
a9913044 178 Each bit of the <int> indicates an ACPI debug layer,
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179 1: enable, 0: disable. It is useful for boot time
180 debugging. After system has booted up, it can be set
181 via /proc/acpi/debug_layer.
182
183 acpi_dbg_level= [HW,ACPI]
184 Format: <int>
a9913044 185 Each bit of the <int> indicates an ACPI debug level,
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186 1: enable, 0: disable. It is useful for boot time
187 debugging. After system has booted up, it can be set
188 via /proc/acpi/debug_level.
189
190 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
191
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192 acpi_generic_hotkey [HW,ACPI]
193 Allow consolidated generic hotkey driver to
a9913044 194 override platform specific driver.
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195 See also Documentation/acpi-hotkey.txt.
196
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197 acpi_pm_good [IA-32,X86-64]
198 Override the pmtimer bug detection: force the kernel
199 to assume that this machine's pmtimer latches its value
200 and always returns good values.
201
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202 enable_timer_pin_1 [i386,x86-64]
203 Enable PIN 1 of APIC timer
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204 Can be useful to work around chipset bugs
205 (in particular on some ATI chipsets).
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206 The kernel tries to set a reasonable default.
207
208 disable_timer_pin_1 [i386,x86-64]
209 Disable PIN 1 of APIC timer
210 Can be useful to work around chipset bugs.
211
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212 ad1816= [HW,OSS]
213 Format: <io>,<irq>,<dma>,<dma2>
214 See also Documentation/sound/oss/AD1816.
215
216 ad1848= [HW,OSS]
217 Format: <io>,<irq>,<dma>,<dma2>,<type>
218
219 adlib= [HW,OSS]
220 Format: <io>
a9913044 221
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222 advansys= [HW,SCSI]
223 See header of drivers/scsi/advansys.c.
224
225 advwdt= [HW,WDT] Advantech WDT
226 Format: <iostart>,<iostop>
227
228 aedsp16= [HW,OSS] Audio Excel DSP 16
229 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
230 See also header of sound/oss/aedsp16.c.
a9913044 231
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232 aha152x= [HW,SCSI]
233 See Documentation/scsi/aha152x.txt.
234
235 aha1542= [HW,SCSI]
236 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
237
238 aic7xxx= [HW,SCSI]
239 See Documentation/scsi/aic7xxx.txt.
240
241 aic79xx= [HW,SCSI]
242 See Documentation/scsi/aic79xx.txt.
243
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244 amijoy.map= [HW,JOY] Amiga joystick support
245 Map of devices attached to JOY0DAT and JOY1DAT
246 Format: <a>,<b>
247 See also Documentation/kernel/input/joystick.txt
248
249 analog.map= [HW,JOY] Analog joystick and gamepad support
250 Specifies type or capabilities of an analog joystick
251 connected to one of 16 gameports
252 Format: <type1>,<type2>,..<type16>
253
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254 apc= [HW,SPARC]
255 Power management functions (SPARCstation-4/5 + deriv.)
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256 Format: noidle
257 Disable APC CPU standby support. SPARCstation-Fox does
258 not play well with APC CPU idle - disable it if you have
259 APC and your system crashes randomly.
260
a9913044 261 apic= [APIC,i386] Change the output verbosity whilst booting
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262 Format: { quiet (default) | verbose | debug }
263 Change the amount of debugging information output
264 when initialising the APIC and IO-APIC components.
a9913044 265
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266 apm= [APM] Advanced Power Management
267 See header of arch/i386/kernel/apm.c.
268
269 applicom= [HW]
270 Format: <mem>,<irq>
a9913044 271
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272 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
273 Format: <io>,<irq>,<nodeID>
274
275 ataflop= [HW,M68k]
276
277 atarimouse= [HW,MOUSE] Atari Mouse
278
279 atascsi= [HW,SCSI] Atari SCSI
280
281 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
282 EzKey and similar keyboards
283
284 atkbd.reset= [HW] Reset keyboard during initialization
285
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286 atkbd.set= [HW] Select keyboard code set
287 Format: <int> (2 = AT (default), 3 = PS/2)
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288
289 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
290 keyboards
291
292 atkbd.softraw= [HW] Choose between synthetic and real raw mode
293 Format: <bool> (0 = real, 1 = synthetic (default))
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294
295 atkbd.softrepeat= [HW]
296 Use software keyboard repeat
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297
298 autotest [IA64]
299
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300 aztcd= [HW,CD] Aztech CD268 CDROM driver
301 Format: <io>,0x79 (?)
302
303 baycom_epp= [HW,AX25]
304 Format: <io>,<mode>
a9913044 305
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306 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
307 Format: <io>,<mode>
308 See header of drivers/net/hamradio/baycom_par.c.
309
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310 baycom_ser_fdx= [HW,AX25]
311 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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312 Format: <io>,<irq>,<mode>[,<baud>]
313 See header of drivers/net/hamradio/baycom_ser_fdx.c.
314
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315 baycom_ser_hdx= [HW,AX25]
316 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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317 Format: <io>,<irq>,<mode>
318 See header of drivers/net/hamradio/baycom_ser_hdx.c.
319
320 blkmtd_device= [HW,MTD]
321 blkmtd_erasesz=
322 blkmtd_ro=
323 blkmtd_bs=
324 blkmtd_count=
325
326 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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327 bttv.radio= Most important insmod options are available as
328 kernel args too.
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329 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
330 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
331
332 BusLogic= [HW,SCSI]
333 See drivers/scsi/BusLogic.c, comment before function
334 BusLogic_ParseDriverOptions().
335
336 c101= [NET] Moxa C101 synchronous serial card
337
338 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
339 Sometimes CPU hardware bugs make them report the cache
340 size incorrectly. The kernel will attempt work arounds
341 to fix known problems, but for some CPUs it is not
342 possible to determine what the correct size should be.
343 This option provides an override for these situations.
344
345 cdu31a= [HW,CD]
346 Format: <io>,<irq>[,PAS]
347 See header of drivers/cdrom/cdu31a.c.
348
349 chandev= [HW,NET] Generic channel device initialisation
350
351 checkreqprot [SELINUX] Set initial checkreqprot flag value.
352 Format: { "0" | "1" }
353 See security/selinux/Kconfig help text.
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354 0 -- check protection applied by kernel (includes
355 any implied execute protection).
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356 1 -- check protection requested by application.
357 Default value is set via a kernel config option.
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358 Value can be changed at runtime via
359 /selinux/checkreqprot.
360
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361 clock= [BUGS=IA-32, HW] gettimeofday clocksource override.
362 [Deprecated]
3f6dee9b 363 Forces specified clocksource (if available) to be used
734efb46 364 when calculating gettimeofday(). If specified
3f6dee9b 365 clocksource is not available, it defaults to PIT.
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366 Format: { pit | tsc | cyclone | pmtmr }
367
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368 code_bytes [IA32] How many bytes of object code to print in an
369 oops report.
370 Range: 0 - 8192
371 Default: 64
372
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373 disable_8254_timer
374 enable_8254_timer
375 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
376 over the 8254 in addition to over the IO-APIC. The
377 kernel tries to set a sensible default.
378
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379 hpet= [IA-32,HPET] option to disable HPET and use PIT.
380 Format: disable
381
382 cm206= [HW,CD]
383 Format: { auto | [<io>,][<irq>] }
384
385 com20020= [HW,NET] ARCnet - COM20020 chipset
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386 Format:
387 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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388
389 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
390 Format: <io>[,<irq>]
391
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392 com90xx= [HW,NET]
393 ARCnet - COM90xx chipset (memory-mapped buffers)
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394 Format: <io>[,<irq>[,<memstart>]]
395
396 condev= [HW,S390] console device
397 conmode=
a9913044 398
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399 console= [KNL] Output console device and options.
400
401 tty<n> Use the virtual console device <n>.
402
403 ttyS<n>[,options]
f1a1c2dc 404 ttyUSB0[,options]
1da177e4 405 Use the specified serial port. The options are of
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406 the form "bbbbpnf", where "bbbb" is the baud rate,
407 "p" is parity ("n", "o", or "e"), "n" is number of
408 bits, and "f" is flow control ("r" for RTS or
409 omit it). Default is "9600n8".
410
411 See Documentation/serial-console.txt for more
412 information. See
413 Documentation/networking/netconsole.txt for an
414 alternative.
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415
416 uart,io,<addr>[,options]
417 uart,mmio,<addr>[,options]
418 Start an early, polled-mode console on the 8250/16550
419 UART at the specified I/O port or MMIO address,
420 switching to the matching ttyS device later. The
421 options are the same as for ttyS, above.
422
423 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
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424 Format:
425 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
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426
427 cpia_pp= [HW,PPT]
428 Format: { parport<nr> | auto | none }
429
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430 crashkernel=nn[KMG]@ss[KMG]
431 [KNL] Reserve a chunk of physical memory to
432 hold a kernel to switch to with kexec on panic.
433
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434 cs4232= [HW,OSS]
435 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
436
437 cs89x0_dma= [HW,NET]
438 Format: <dma>
439
440 cs89x0_media= [HW,NET]
441 Format: { rj45 | aui | bnc }
a9913044 442
1da177e4 443 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
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444
445 dasd= [HW,NET]
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446 See header of drivers/s390/block/dasd_devmap.c.
447
448 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
449 (one device per port)
450 Format: <port#>,<type>
451 See also Documentation/input/joystick-parport.txt
452
453 debug [KNL] Enable kernel debugging (events log level).
454
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455 debug_locks_verbose=
456 [KNL] verbose self-tests
457 Format=<0|1>
458 Print debugging info while doing the locking API
459 self-tests.
460 We default to 0 (no extra messages), setting it to
461 1 will print _a lot_ more information - normally
462 only useful to kernel developers.
463
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464 decnet= [HW,NET]
465 Format: <area>[,<node>]
466 See also Documentation/networking/decnet.txt.
467
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468 dhash_entries= [KNL]
469 Set number of hash buckets for dentry cache.
a9913044 470
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471 digi= [HW,SERIAL]
472 IO parameters + enable/disable command.
473
474 digiepca= [HW,SERIAL]
475 See drivers/char/README.epca and
476 Documentation/digiepca.txt.
477
478 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
479 support available.
480 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
481
482 dmasound= [HW,OSS] Sound subsystem buffers
483
484 dscc4.setup= [NET]
485
486 dtc3181e= [HW,SCSI]
487
a9913044 488 earlyprintk= [IA-32,X86-64]
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489 earlyprintk=vga
490 earlyprintk=serial[,ttySn[,baudrate]]
491
a9913044 492 Append ",keep" to not disable it when the real console
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493 takes over.
494
495 Only vga or serial at a time, not both.
496
497 Currently only ttyS0 and ttyS1 are supported.
498
499 Interaction with the standard serial driver is not
500 very good.
501
502 The VGA output is eventually overwritten by the real
503 console.
504
505 eata= [HW,SCSI]
506
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507 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
508 Format: <int>
509 0: polling mode
510 non-0: interrupt mode (default)
511
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512 eda= [HW,PS2]
513
514 edb= [HW,PS2]
515
516 edd= [EDD]
517 Format: {"of[f]" | "sk[ipmbr]"}
518 See comment in arch/i386/boot/edd.S
519
a9913044 520 eicon= [HW,ISDN]
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521 Format: <id>,<membase>,<irq>
522
523 eisa_irq_edge= [PARISC,HW]
524 See header of drivers/parisc/eisa.c.
525
526 elanfreq= [IA-32]
527 See comment before function elanfreq_setup() in
528 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
529
530 elevator= [IOSCHED]
16ab3adf 531 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
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532 See Documentation/block/as-iosched.txt and
533 Documentation/block/deadline-iosched.txt for details.
534
aac04b32 535 elfcorehdr= [IA-32, X86_64]
a9913044 536 Specifies physical address of start of kernel core
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537 image elf header. Generally kexec loader will
538 pass this option to capture kernel.
539 See Documentation/kdump/kdump.txt for details.
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540
541 enforcing [SELINUX] Set initial enforcing status.
542 Format: {"0" | "1"}
543 See security/selinux/Kconfig help text.
544 0 -- permissive (log only, no denials).
545 1 -- enforcing (deny and log).
546 Default value is 0.
547 Value can be changed at runtime via /selinux/enforce.
548
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549 es1371= [HW,OSS]
550 Format: <spdif>,[<nomix>,[<amplifier>]]
551 See also header of sound/oss/es1371.c.
a9913044 552
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553 ether= [HW,NET] Ethernet cards parameters
554 This option is obsoleted by the "netdev=" option, which
555 has equivalent usage. See its documentation for details.
556
557 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
558 Format: <io>[,<irq>]
559
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560 failslab=
561 fail_page_alloc=
562 fail_make_request=[KNL]
563 General fault injection mechanism.
564 Format: <interval>,<probability>,<space>,<times>
565 See also /Documentation/fault-injection/.
566
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567 fd_mcs= [HW,SCSI]
568 See header of drivers/scsi/fd_mcs.c.
569
570 fdomain= [HW,SCSI]
571 See header of drivers/scsi/fdomain.c.
572
573 floppy= [HW]
574 See Documentation/floppy.txt.
575
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576 gamecon.map[2|3]=
577 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
578 support via parallel port (up to 5 devices per port)
579 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
580 See also Documentation/input/joystick-parport.txt
581
582 gamma= [HW,DRM]
583
584 gdth= [HW,SCSI]
585 See header of drivers/scsi/gdth.c.
586
587 gpt [EFI] Forces disk with valid GPT signature but
588 invalid Protective MBR to be treated as GPT.
589
590 gscd= [HW,CD]
591 Format: <io>
592
1da177e4
LT
593 gvp11= [HW,SCSI]
594
595 hashdist= [KNL,NUMA] Large hashes allocated during boot
596 are distributed across NUMA nodes. Defaults on
597 for IA-64, off otherwise.
a9913044 598 Format: 0 | 1 (for off | on)
1da177e4
LT
599
600 hcl= [IA-64] SGI's Hardware Graph compatibility layer
601
602 hd= [EIDE] (E)IDE hard drive subsystem geometry
603 Format: <cyl>,<head>,<sect>
604
605 hd?= [HW] (E)IDE subsystem
606 hd?lun= See Documentation/ide.txt.
607
608 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
609 size of <nn>. This works even on boxes that have no
610 highmem otherwise. This also works to reduce highmem
611 size on bigger boxes.
612
54cdfdb4
TG
613 highres= [KNL] Enable/disable high resolution timer mode.
614 Valid parameters: "on", "off"
615 Default: "on"
616
1da177e4
LT
617 hisax= [HW,ISDN]
618 See Documentation/isdn/README.HiSax.
619
620 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
621
1da177e4 622 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
623 i8042.dumbkbd [HW] Pretend that controller can only read data from
624 keyboard and cannot control its state
1da177e4
LT
625 (Don't attempt to blink the leds)
626 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 627 i8042.nokbd [HW] Don't check/create keyboard port
1da177e4
LT
628 i8042.nomux [HW] Don't check presence of an active multiplexing
629 controller
630 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
631 controllers
632 i8042.panicblink=
633 [HW] Frequency with which keyboard LEDs should blink
634 when kernel panics (default is 0.5 sec)
635 i8042.reset [HW] Reset the controller during init and cleanup
636 i8042.unlock [HW] Unlock (ignore) the keylock
637
638 i810= [HW,DRM]
639
e70c9d5e
DT
640 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
641 indicates that the driver is running on unsupported
642 hardware.
1da177e4
LT
643 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
644 does not match list of supported models.
645 i8k.power_status
646 [HW] Report power status in /proc/i8k
647 (disabled by default)
648 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
649 capability is set.
650
651 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
652 See Documentation/mca.txt.
653
654 icn= [HW,ISDN]
655 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
656
657 ide= [HW] (E)IDE subsystem
658 Format: ide=nodma or ide=doubler or ide=reverse
659 See Documentation/ide.txt.
660
661 ide?= [HW] (E)IDE subsystem
662 Format: ide?=noprobe or chipset specific parameters.
663 See Documentation/ide.txt.
a9913044 664
1da177e4
LT
665 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
666 See Documentation/ide.txt.
667
668 idle= [HW]
669 Format: idle=poll or idle=halt
a9913044 670
79290822
IM
671 ignore_loglevel [KNL]
672 Ignore loglevel setting - this will print /all/
673 kernel messages to the console. Useful for debugging.
674
1da177e4
LT
675 ihash_entries= [KNL]
676 Set number of hash buckets for inode cache.
677
678 in2000= [HW,SCSI]
679 See header of drivers/scsi/in2000.c.
680
681 init= [KNL]
682 Format: <full_path>
683 Run specified binary instead of /sbin/init as init
684 process.
685
686 initcall_debug [KNL] Trace initcalls as they are executed. Useful
687 for working out where the kernel is dying during
688 startup.
689
690 initrd= [BOOT] Specify the location of the initial ramdisk
691
692 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
693 Format: <irq>
694
2bd0fa3b
JB
695 combined_mode= [HW] control which driver uses IDE ports in combined
696 mode: legacy IDE driver, libata, or both
697 (in the libata case, libata.atapi_enabled=1 may be
698 useful as well). Note that using the ide or libata
699 options may affect your device naming (e.g. by
700 changing hdc to sdb).
701 Format: combined (default), ide, or libata
702
1da177e4
LT
703 inttest= [IA64]
704
705 io7= [HW] IO7 for Marvel based alpha systems
706 See comment before marvel_specify_io7 in
707 arch/alpha/kernel/core_marvel.c.
708
709 ip= [IP_PNP]
710 See Documentation/nfsroot.txt.
711
712 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
713 See comment before ip2_setup() in drivers/char/ip2.c.
714
715 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
716 See header of drivers/scsi/ips.c.
717
72c4a13a
SH
718 ports= [IP_VS_FTP] IPVS ftp helper module
719 Default is 21.
720 Up to 8 (IP_VS_APP_MAX_PORTS) ports
721 may be specified.
722 Format: <port>,<port>....
723
200803df
AC
724 irqfixup [HW]
725 When an interrupt is not handled search all handlers
726 for it. Intended to get systems with badly broken
727 firmware running.
728
729 irqpoll [HW]
730 When an interrupt is not handled search all handlers
731 for it. Also check all handlers each timer
732 interrupt. Intended to get systems with badly broken
733 firmware running.
734
1da177e4 735 isapnp= [ISAPNP]
a9913044 736 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
737
738 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
739 Format:
740 <cpu number>,...,<cpu number>
741 or
742 <cpu number>-<cpu number> (must be a positive range in ascending order)
743 or a mixture
744 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
745 This option can be used to specify one or more CPUs
746 to isolate from the general SMP balancing and scheduling
747 algorithms. The only way to move a process onto or off
748 an "isolated" CPU is via the CPU affinity syscalls.
749 <cpu number> begins at 0 and the maximum value is
750 "number of CPUs in system - 1".
751
752 This option is the preferred way to isolate CPUs. The
a9913044
RD
753 alternative -- manually setting the CPU mask of all
754 tasks in the system -- can cause problems and
755 suboptimal load balancer performance.
1da177e4
LT
756
757 isp16= [HW,CD]
758 Format: <io>,<irq>,<dma>,<setup>
759
a9913044 760 iucv= [HW,NET]
1da177e4
LT
761
762 js= [HW,JOY] Analog joystick
763 See Documentation/input/joystick.txt.
764
765 keepinitrd [HW,ARM]
766
a9913044 767 kstack=N [IA-32,X86-64] Print N words from the kernel stack
1da177e4
LT
768 in oops dumps.
769
770 l2cr= [PPC]
771
a9913044
RD
772 lapic [IA-32,APIC] Enable the local APIC even if BIOS
773 disabled it.
1da177e4
LT
774
775 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
776 Format: addr:<io>,irq:<irq>
777
a9913044
RD
778 llsc*= [IA64] See function print_params() in
779 arch/ia64/sn/kernel/llsc4.c.
1da177e4
LT
780
781 load_ramdisk= [RAM] List of ramdisks to load from floppy
782 See Documentation/ramdisk.txt.
783
a6b25b67
RD
784 lockd.nlm_grace_period=P [NFS] Assign grace period.
785 Format: <integer>
1da177e4 786
a6b25b67
RD
787 lockd.nlm_tcpport=N [NFS] Assign TCP port.
788 Format: <integer>
789
790 lockd.nlm_timeout=T [NFS] Assign timeout value.
791 Format: <integer>
792
793 lockd.nlm_udpport=M [NFS] Assign UDP port.
794 Format: <integer>
1da177e4
LT
795
796 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
797 Format: <irq>
798
799 loglevel= All Kernel Messages with a loglevel smaller than the
800 console loglevel will be printed to the console. It can
801 also be changed with klogd or other programs. The
802 loglevels are defined as follows:
803
804 0 (KERN_EMERG) system is unusable
805 1 (KERN_ALERT) action must be taken immediately
806 2 (KERN_CRIT) critical conditions
807 3 (KERN_ERR) error conditions
808 4 (KERN_WARNING) warning conditions
809 5 (KERN_NOTICE) normal but significant condition
810 6 (KERN_INFO) informational
811 7 (KERN_DEBUG) debug-level messages
812
813 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
814 Format: { n | nk | nM }
815 n must be a power of two. The default size
816 is set in the kernel config file.
1da177e4
LT
817
818 lp=0 [LP] Specify parallel ports to use, e.g,
819 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
820 lp=reset first parallel port). 'lp=0' disables the
821 lp=auto printer driver. 'lp=reset' (which can be
822 specified in addition to the ports) causes
823 attached printers to be reset. Using
824 lp=port1,port2,... specifies the parallel ports
825 to associate lp devices with, starting with
826 lp0. A port specification may be 'none' to skip
827 that lp device, or a parport name such as
828 'parport0'. Specifying 'lp=auto' instead of a
829 port specification list means that device IDs
830 from each port should be examined, to see if
831 an IEEE 1284-compliant printer is attached; if
832 so, the driver will manage that printer.
833 See also header of drivers/char/lp.c.
834
835 lpj=n [KNL]
836 Sets loops_per_jiffy to given constant, thus avoiding
837 time-consuming boot-time autodetection (up to 250 ms per
838 CPU). 0 enables autodetection (default). To determine
839 the correct value for your kernel, boot with normal
840 autodetection and see what value is printed. Note that
841 on SMP systems the preset will be applied to all CPUs,
842 which is likely to cause problems if your CPUs need
843 significantly divergent settings. An incorrect value
844 will cause delays in the kernel to be wrong, leading to
845 unpredictable I/O errors and other breakage. Although
846 unlikely, in the extreme case this might damage your
847 hardware.
848
849 ltpc= [NET]
850 Format: <io>,<irq>,<dma>
851
a9913044
RD
852 mac5380= [HW,SCSI] Format:
853 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 854
a9913044
RD
855 mac53c9x= [HW,SCSI] Format:
856 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 857
a9913044
RD
858 machvec= [IA64] Force the use of a particular machine-vector
859 (machvec) in a generic kernel.
860 Example: machvec=hpzx1_swiotlb
1da177e4 861
a9913044 862 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
863 be mounted
864 Format: <1-256>
865
866 maxcpus= [SMP] Maximum number of processors that an SMP kernel
78f92a82
RD
867 should make use of.
868 Using "nosmp" or "maxcpus=0" will disable SMP
869 entirely (the MPS table probe still happens, though).
870 A command-line option of "maxcpus=<NUM>", where <NUM>
871 is an integer greater than 0, limits the maximum number
872 of CPUs activated in SMP mode to <NUM>.
873 Using "maxcpus=1" on an SMP kernel is the trivial
874 case of an SMP kernel with only one CPU.
1da177e4 875
2b2c3750
BP
876 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
877 equal to this physical address is ignored.
878
a9913044 879 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
880 Should be between 1 and 2^32-1.
881
882 max_report_luns=
a9913044 883 [SCSI] Maximum number of LUNs received.
1da177e4
LT
884 Should be between 1 and 16384.
885
886 mca-pentium [BUGS=IA-32]
887
888 mcatest= [IA-64]
889
890 mcd= [HW,CD]
891 Format: <port>,<irq>,<mitsumi_bug_93_wait>
892
893 mcdx= [HW,CD]
894
895 mce [IA-32] Machine Check Exception
896
897 md= [HW] RAID subsystems devices and level
898 See Documentation/md.txt.
a9913044 899
1da177e4
LT
900 mdacon= [MDA]
901 Format: <first>,<last>
902 Specifies range of consoles to be captured by the MDA.
a9913044 903
1da177e4
LT
904 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
905 Amount of memory to be used when the kernel is not able
906 to see the whole system memory or for test.
907 [IA-32] Use together with memmap= to avoid physical
908 address space collisions. Without memmap= PCI devices
909 could be placed at addresses belonging to unused RAM.
910
911 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
912 memory.
913
69cda7b1 914 memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
1da177e4
LT
915 E820 memory map, as specified by the user.
916 Such memmap=exactmap lines can be constructed based on
917 BIOS output or other requirements. See the memmap=nn@ss
918 option description.
919
920 memmap=nn[KMG]@ss[KMG]
921 [KNL] Force usage of a specific region of memory
922 Region of memory to be used, from ss to ss+nn.
923
924 memmap=nn[KMG]#ss[KMG]
925 [KNL,ACPI] Mark specific memory as ACPI data.
926 Region of memory to be used, from ss to ss+nn.
927
928 memmap=nn[KMG]$ss[KMG]
929 [KNL,ACPI] Mark specific memory as reserved.
930 Region of memory to be used, from ss to ss+nn.
931
932 meye.*= [HW] Set MotionEye Camera parameters
933 See Documentation/video4linux/meye.txt.
934
935 mga= [HW,DRM]
936
198e2f18 937 migration_cost=
938 [KNL,SMP] debug: override scheduler migration costs
939 Format: <level-1-usecs>,<level-2-usecs>,...
940 This debugging option can be used to override the
941 default scheduler migration cost matrix. The numbers
942 are indexed by 'CPU domain distance'.
943 E.g. migration_cost=1000,2000,3000 on an SMT NUMA
944 box will set up an intra-core migration cost of
945 1 msec, an inter-core migration cost of 2 msecs,
946 and an inter-node migration cost of 3 msecs.
947
948 WARNING: using the wrong values here can break
949 scheduler performance, so it's only for scheduler
950 development purposes, not production environments.
951
952 migration_debug=
953 [KNL,SMP] migration cost auto-detect verbosity
954 Format=<0|1|2>
955 If a system's migration matrix reported at bootup
956 seems erroneous then this option can be used to
957 increase verbosity of the detection process.
958 We default to 0 (no extra messages), 1 will print
959 some more information, and 2 will be really
960 verbose (probably only useful if you also have a
961 serial console attached to the system).
962
963 migration_factor=
964 [KNL,SMP] multiply/divide migration costs by a factor
965 Format=<percent>
966 This debug option can be used to proportionally
967 increase or decrease the auto-detected migration
968 costs for all entries of the migration matrix.
969 E.g. migration_factor=150 will increase migration
970 costs by 50%. (and thus the scheduler will be less
971 eager migrating cache-hot tasks)
972 migration_factor=80 will decrease migration costs
973 by 20%. (thus the scheduler will be more eager to
974 migrate tasks)
975
976 WARNING: using the wrong values here can break
977 scheduler performance, so it's only for scheduler
978 development purposes, not production environments.
979
1da177e4
LT
980 mousedev.tap_time=
981 [MOUSE] Maximum time between finger touching and
982 leaving touchpad surface for touch to be considered
983 a tap and be reported as a left button click (for
984 touchpads working in absolute mode only).
985 Format: <msecs>
986 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
987 reporting absolute coordinates, such as tablets
988 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
989 reporting absolute coordinates, such as tablets
990
991 mpu401= [HW,OSS]
992 Format: <io>,<irq>
993
994 MTD_Partition= [MTD]
995 Format: <name>,<region-number>,<size>,<offset>
996
a9913044
RD
997 MTD_Region= [MTD] Format:
998 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
999
1000 mtdparts= [MTD]
1001 See drivers/mtd/cmdline.c.
1002
1003 mtouchusb.raw_coordinates=
a9913044
RD
1004 [HW] Make the MicroTouch USB driver use raw coordinates
1005 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1006
1007 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1008
1009 NCR_D700= [HW,SCSI]
1010 See header of drivers/scsi/NCR_D700.c.
1011
1012 ncr5380= [HW,SCSI]
1013
1014 ncr53c400= [HW,SCSI]
1015
1016 ncr53c400a= [HW,SCSI]
1017
1018 ncr53c406a= [HW,SCSI]
1019
1020 ncr53c8xx= [HW,SCSI]
1021
1022 netdev= [NET] Network devices parameters
1023 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1024 Note that mem_start is often overloaded to mean
1025 something different and driver-specific.
a9913044
RD
1026 This usage is only documented in each driver source
1027 file if at all.
1028
1da177e4
LT
1029 nfsaddrs= [NFS]
1030 See Documentation/nfsroot.txt.
1031
1032 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1033 See Documentation/nfsroot.txt.
1034
a72b4422
TM
1035 nfs.callback_tcpport=
1036 [NFS] set the TCP port on which the NFSv4 callback
1037 channel should listen.
1038
58df095b
TM
1039 nfs.idmap_cache_timeout=
1040 [NFS] set the maximum lifetime for idmapper cache
1041 entries.
1042
1da177e4
LT
1043 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
1044
1045 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
1046 emulation library even if a 387 maths coprocessor
1047 is present.
1048
11ef697b
KCA
1049 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1050 when set.
1051 Format: <int>
1052
3395ee05
PM
1053 noaliencache [MM, NUMA] Disables the allcoation of alien caches in
1054 the slab allocator. Saves per-node memory, but will
1055 impact performance on real NUMA hardware.
1056
a9913044
RD
1057 noalign [KNL,ARM]
1058
1da177e4
LT
1059 noapic [SMP,APIC] Tells the kernel to not make use of any
1060 IOAPICs that may be present in the system.
1061
1062 noasync [HW,M68K] Disables async and sync negotiation for
1063 all devices.
1064
1065 nobats [PPC] Do not use BATs for mapping kernel lowmem
1066 on "Classic" PPC cores.
1067
1068 nocache [ARM]
a9913044 1069
163ecdff
SN
1070 nodelayacct [KNL] Disable per-task delay accounting
1071
1da177e4
LT
1072 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1073
1074 noexec [IA-64]
1075
a9913044 1076 noexec [IA-32,X86-64]
1da177e4
LT
1077 noexec=on: enable non-executable mappings (default)
1078 noexec=off: disable nn-executable mappings
1079
4f886511
CE
1080 nofxsr [BUGS=IA-32] Disables x86 floating point extended
1081 register save and restore. The kernel will only save
1082 legacy floating-point registers on task switch.
1da177e4
LT
1083
1084 nohlt [BUGS=ARM]
a9913044 1085
1da177e4
LT
1086 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
1087 instruction doesn't work correctly and not to
1088 use it.
1089
1090 nohalt [IA-64] Tells the kernel not to use the power saving
1091 function PAL_HALT_LIGHT when idle. This increases
1092 power-consumption. On the positive side, it reduces
1093 interrupt wake-up latency, which may improve performance
1094 in certain environments such as networked servers or
1095 real-time systems.
1096
79bf2bb3
TG
1097 nohz= [KNL] Boottime enable/disable dynamic ticks
1098 Valid arguments: on, off
1099 Default: on
1100
8542b200
ZA
1101 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
1102
1da177e4
LT
1103 noirqdebug [IA-32] Disables the code which attempts to detect and
1104 disable unhandled interrupt sources.
1105
8542b200
ZA
1106 no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for
1107 broken timer IRQ sources.
1108
1da177e4
LT
1109 noisapnp [ISAPNP] Disables ISA PnP code.
1110
1111 noinitrd [RAM] Tells the kernel not to load any configured
1112 initial RAM disk.
1113
1114 nointroute [IA-64]
1115
1116 nolapic [IA-32,APIC] Do not enable or use the local APIC.
1117
1118 noltlbs [PPC] Do not use large page/tlb entries for kernel
1119 lowmem mapping on PPC40x.
1120
312f1f01
H
1121 nomca [IA-64] Disable machine check abort handling
1122
abe37e5a
H
1123 nomce [IA-32] Machine Check Exception
1124
1da177e4
LT
1125 noresidual [PPC] Don't use residual data on PReP machines.
1126
a9913044
RD
1127 noresume [SWSUSP] Disables resume and restores original swap
1128 space.
1129
1da177e4
LT
1130 no-scroll [VGA] Disables scrollback.
1131 This is required for the Braillex ib80-piezo Braille
1132 reader made by F.H. Papenmeier (Germany).
1133
1134 nosbagart [IA-64]
1135
4f886511
CE
1136 nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1137
1da177e4
LT
1138 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1139
1140 nosync [HW,M68K] Disables sync negotiation for all devices.
1141
1142 notsc [BUGS=IA-32] Disable Time Stamp Counter
1143
1144 nousb [USB] Disable the USB subsystem
1145
1146 nowb [ARM]
a9913044 1147
a61c2d78
DJ
1148 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1149
1da177e4
LT
1150 opl3= [HW,OSS]
1151 Format: <io>
1152
a9913044
RD
1153 opl3sa2= [HW,OSS] Format:
1154 <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
1155
1da177e4
LT
1156 oprofile.timer= [HW]
1157 Use timer interrupt instead of performance counters
1158
1159 optcd= [HW,CD]
1160 Format: <io>
1161
1162 osst= [HW,SCSI] SCSI Tape Driver
1163 Format: <buffer_size>,<write_threshold>
1164 See also Documentation/scsi/st.txt.
1165
1166 panic= [KNL] Kernel behaviour on panic
1167 Format: <timeout>
1168
1169 parkbd.port= [HW] Parallel port number the keyboard adapter is
1170 connected to, default is 0.
1171 Format: <parport#>
1172 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1173 0 for XT, 1 for AT (default is AT).
a9913044
RD
1174 Format: <mode>
1175
1176 parport= [HW,PPT] Specify parallel ports. 0 disables.
1177 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1178 Use 'auto' to force the driver to use any
1179 IRQ/DMA settings detected (the default is to
1180 ignore detected IRQ/DMA settings because of
1181 possible conflicts). You can specify the base
1182 address, IRQ, and DMA settings; IRQ and DMA
1183 should be numbers, or 'auto' (for using detected
1184 settings on that particular port), or 'nofifo'
1185 (to avoid using a FIFO even if it is detected).
1186 Parallel ports are assigned in the order they
1187 are specified on the command line, starting
1188 with parport0.
1189
1190 parport_init_mode= [HW,PPT]
1191 Configure VIA parallel port to operate in
1192 a specific mode. This is necessary on Pegasos
1193 computer where firmware has no options for setting
1194 up parallel port mode and sets it to spp.
1195 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1196 Format: [spp|ps2|epp|ecp|ecpepp]
1197
a9913044
RD
1198 pas2= [HW,OSS] Format:
1199 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1200
1da177e4
LT
1201 pas16= [HW,SCSI]
1202 See header of drivers/scsi/pas16.c.
1203
dd287796
AM
1204 pause_on_oops=
1205 Halt all CPUs after the first oops has been printed for
1206 the specified number of seconds. This is to be used if
1207 your oopses keep scrolling off the screen.
1208
1da177e4
LT
1209 pcbit= [HW,ISDN]
1210
1211 pcd. [PARIDE]
1212 See header of drivers/block/paride/pcd.c.
1213 See also Documentation/paride.txt.
1214
a9913044
RD
1215 pci=option[,option...] [PCI] various PCI subsystem options:
1216 off [IA-32] don't probe for the PCI bus
1217 bios [IA-32] force use of PCI BIOS, don't access
1218 the hardware directly. Use this if your machine
1219 has a non-standard PCI host bridge.
1220 nobios [IA-32] disallow use of PCI BIOS, only direct
1221 hardware access methods are allowed. Use this
1222 if you experience crashes upon bootup and you
1223 suspect they are caused by the BIOS.
1224 conf1 [IA-32] Force use of PCI Configuration
1225 Mechanism 1.
1226 conf2 [IA-32] Force use of PCI Configuration
1227 Mechanism 2.
61be6d66
BH
1228 nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
1229 Configuration
309e57df
MW
1230 nomsi [MSI] If the PCI_MSI kernel config parameter is
1231 enabled, this kernel boot option can be used to
1232 disable the use of MSI interrupts system-wide.
a9913044
RD
1233 nosort [IA-32] Don't sort PCI devices according to
1234 order given by the PCI BIOS. This sorting is
1235 done to get a device order compatible with
1236 older kernels.
1237 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1238 routing table. These calls are known to be buggy
1239 on several machines and they hang the machine
1240 when used, but on other computers it's the only
1241 way to get the interrupt routing table. Try
1242 this option if the kernel is unable to allocate
1243 IRQs or discover secondary PCI buses on your
1244 motherboard.
1245 rom [IA-32] Assign address space to expansion ROMs.
1246 Use with caution as certain devices share
1247 address decoders between ROMs and other
1248 resources.
1249 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1250 assigned automatically to PCI devices. You can
1251 make the kernel exclude IRQs of your ISA cards
1252 this way.
120bb424 1253 pirqaddr=0xAAAAA [IA-32] Specify the physical address
a9913044
RD
1254 of the PIRQ table (normally generated
1255 by the BIOS) if it is outside the
1256 F0000h-100000h range.
1257 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1258 useful if the kernel is unable to find your
1259 secondary buses and you want to tell it
1260 explicitly which ones they are.
1261 assign-busses [IA-32] Always assign all PCI bus
1262 numbers ourselves, overriding
1263 whatever the firmware may have done.
1264 usepirqmask [IA-32] Honor the possible IRQ mask stored
1265 in the BIOS $PIR table. This is needed on
1266 some systems with broken BIOSes, notably
1267 some HP Pavilion N5400 and Omnibook XE3
1268 notebooks. This will have no effect if ACPI
1269 IRQ routing is enabled.
1270 noacpi [IA-32] Do not use ACPI for IRQ routing
1271 or for PCI scanning.
1272 routeirq Do IRQ routing for all PCI devices.
1273 This is normally done in pci_enable_device(),
1274 so this option is a temporary workaround
1275 for broken drivers that don't call it.
1276 firmware [ARM] Do not re-enumerate the bus but instead
1277 just use the configuration from the
1278 bootloader. This is currently used on
1279 IXP2000 systems where the bus has to be
1280 configured a certain way for adjunct CPUs.
0637a70a
AK
1281 noearly [X86] Don't do any early type 1 scanning.
1282 This might help on some broken boards which
1283 machine check when some devices' config space
1284 is read. But various workarounds are disabled
1285 and some IOMMU drivers will not work.
6b4b78fe
MD
1286 bfsort Sort PCI devices into breadth-first order.
1287 This sorting is done to get a device
1288 order compatible with older (<= 2.4) kernels.
1289 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1290 cbiosize=nn[KMG] The fixed amount of bus space which is
1291 reserved for the CardBus bridge's IO window.
1292 The default value is 256 bytes.
1293 cbmemsize=nn[KMG] The fixed amount of bus space which is
1294 reserved for the CardBus bridge's memory
1295 window. The default value is 64 megabytes.
6b4b78fe 1296
1da177e4
LT
1297 pcmv= [HW,PCMCIA] BadgePAD 4
1298
1299 pd. [PARIDE]
1300 See Documentation/paride.txt.
1301
1302 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1303 boot time.
1304 Format: { 0 | 1 }
1305 See arch/parisc/kernel/pdc_chassis.c
1306
1307 pf. [PARIDE]
1308 See Documentation/paride.txt.
1309
1310 pg. [PARIDE]
1311 See Documentation/paride.txt.
1312
1313 pirq= [SMP,APIC] Manual mp-table setup
1314 See Documentation/i386/IO-APIC.txt.
1315
1316 plip= [PPT,NET] Parallel port network link
1317 Format: { parport<nr> | timid | 0 }
1318 See also Documentation/parport.txt.
1319
1320 pnpacpi= [ACPI]
1321 { off }
1322
1323 pnpbios= [ISAPNP]
1324 { on | off | curr | res | no-curr | no-res }
1325
1326 pnp_reserve_irq=
1327 [ISAPNP] Exclude IRQs for the autoconfiguration
1328
1329 pnp_reserve_dma=
1330 [ISAPNP] Exclude DMAs for the autoconfiguration
1331
1332 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1333 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1334
1335 pnp_reserve_mem=
a9913044
RD
1336 [ISAPNP] Exclude memory regions for the
1337 autoconfiguration.
1da177e4
LT
1338 Ranges are in pairs (memory base and size).
1339
1340 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1341 Format: [schedule,]<number>
1342 Param: "schedule" - profile schedule points.
1343 Param: <number> - step/bucket size as a power of 2 for
1344 statistical time based profiling.
ece8a684 1345 Param: "sleep" - profile D-state sleeping (millisecs)
1da177e4 1346
a9913044 1347 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1348 Limit processor to maximum C-state
1349 max_cstate=9 overrides any DMI blacklist limit.
1350
41c0d868
LB
1351 processor.nocst [HW,ACPI]
1352 Ignore the _CST method to determine C-states,
1353 instead using the legacy FADT method
1354
1da177e4
LT
1355 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1356 before loading.
1357 See Documentation/ramdisk.txt.
1358
a9913044
RD
1359 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1360 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1361 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1362 per second.
a9913044
RD
1363 psmouse.resetafter= [HW,MOUSE]
1364 Try to reset the device after so many bad packets
1da177e4
LT
1365 (0 = never).
1366 psmouse.resolution=
1367 [HW,MOUSE] Set desired mouse resolution, in dpi.
1368 psmouse.smartscroll=
a9913044 1369 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1370 0 = disabled, 1 = enabled (default).
1371
1372 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1373 Format:
1374 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1375
1376 pt. [PARIDE]
1377 See Documentation/paride.txt.
1378
7d2c502f 1379 quiet [KNL] Disable most log messages
a9913044 1380
1da177e4
LT
1381 r128= [HW,DRM]
1382
1383 raid= [HW,RAID]
1384 See Documentation/md.txt.
1385
1386 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1387 See Documentation/ramdisk.txt.
1388
a9913044 1389 ramdisk_blocksize= [RAM]
1da177e4 1390 See Documentation/ramdisk.txt.
a9913044 1391
1da177e4
LT
1392 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1393 New name for the ramdisk parameter.
1394 See Documentation/ramdisk.txt.
1395
21a1ea9e
DS
1396 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1397 RCU callbacks to process in one batch.
1398
1399 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1400 RCU callbacks over which batch limiting is disabled.
1401
1402 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1403 RCU callbacks below which batch limiting is re-enabled.
1404
ffdfc409
OJ
1405 rdinit= [KNL]
1406 Format: <full_path>
1407 Run specified binary instead of /init from the ramdisk,
1408 used for early userspace startup. See initrd.
1409
1da177e4
LT
1410 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1411 Format: <reboot_mode>[,<reboot_mode2>[,...]]
f3e299fe 1412 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1413
1414 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1415
461a9aff
ZA
1416 reservetop= [IA-32]
1417 Format: nn[KMG]
1418 Reserves a hole at the top of the kernel virtual
1419 address space.
1420
7e96287d
VG
1421 reset_devices [KNL] Force drivers to reset the underlying device
1422 during initialization.
1423
a9913044
RD
1424 resume= [SWSUSP]
1425 Specify the partition device for software suspend
1da177e4 1426
ecbd0da1
RW
1427 resume_offset= [SWSUSP]
1428 Specify the offset from the beginning of the partition
1429 given by "resume=" at which the swap header is located,
1430 in <PAGE_SIZE> units (needed only for swap files).
1431 See Documentation/power/swsusp-and-swap-files.txt
1432
0a7b35cb
MN
1433 retain_initrd [RAM] Keep initrd memory after extraction
1434
1da177e4
LT
1435 rhash_entries= [KNL,NET]
1436 Set number of hash buckets for route cache
1437
1438 riscom8= [HW,SERIAL]
1439 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1440
1441 ro [KNL] Mount root device read-only on boot
1442
1443 root= [KNL] Root filesystem
1444
1445 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1446 mount the root filesystem
1447
1448 rootflags= [KNL] Set root filesystem mount option string
1449
1450 rootfstype= [KNL] Set root filesystem type
1451
1452 rw [KNL] Mount root device read-write on boot
1453
1454 S [KNL] Run init in single mode
1455
1456 sa1100ir [NET]
1457 See drivers/net/irda/sa1100_ir.c.
1458
1459 sb= [HW,OSS]
1460 Format: <io>,<irq>,<dma>,<dma2>
1461
1462 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1463
1da177e4
LT
1464 sbpcd= [HW,CD] Soundblaster CD adapter
1465 Format: <io>,<type>
1466 See a comment before function sbpcd_setup() in
1467 drivers/cdrom/sbpcd.c.
1468
1469 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1470 Format: <io>[,<timeout>[,<isapnp>]]
1471
1472 scsi_debug_*= [SCSI]
1473 See drivers/scsi/scsi_debug.c.
1474
1475 scsi_default_dev_flags=
1476 [SCSI] SCSI default device flags
1477 Format: <integer>
1478
1479 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1480 Format: <vendor>:<model>:<flags>
1481 (flags are integer value)
1482
1483 scsi_logging= [SCSI]
1484
3e082a91
MW
1485 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1486 discovered. async scans them in kernel threads,
1487 allowing boot to proceed. none ignores them, expecting
1488 user space to do the scan.
1489
1da177e4
LT
1490 selinux [SELINUX] Disable or enable SELinux at boot time.
1491 Format: { "0" | "1" }
1492 See security/selinux/Kconfig help text.
1493 0 -- disable.
1494 1 -- enable.
1495 Default value is set via kernel config option.
1496 If enabled at boot time, /selinux/disable can be used
1497 later to disable prior to initial policy load.
1498
4e5ab4cb
JM
1499 selinux_compat_net =
1500 [SELINUX] Set initial selinux_compat_net flag value.
1501 Format: { "0" | "1" }
1502 0 -- use new secmark-based packet controls
1503 1 -- use legacy packet controls
1504 Default value is 0 (preferred).
1505 Value can be changed at runtime via
1506 /selinux/compat_net.
1507
1da177e4
LT
1508 serialnumber [BUGS=IA-32]
1509
a9913044
RD
1510 sg_def_reserved_size= [SCSI]
1511
1da177e4
LT
1512 shapers= [NET]
1513 Maximal number of shapers.
a9913044 1514
1da177e4
LT
1515 sim710= [SCSI,HW]
1516 See header of drivers/scsi/sim710.c.
1517
1518 simeth= [IA-64]
1519 simscsi=
a9913044 1520
1da177e4
LT
1521 sjcd= [HW,CD]
1522 Format: <io>,<irq>,<dma>
1523 See header of drivers/cdrom/sjcd.c.
1524
1525 slram= [HW,MTD]
1526
1527 smart2= [HW]
1528 Format: <io1>[,<io2>[,...,<io8>]]
1529
1530 snd-ad1816a= [HW,ALSA]
1531
1532 snd-ad1848= [HW,ALSA]
1533
1534 snd-ali5451= [HW,ALSA]
1535
1536 snd-als100= [HW,ALSA]
1537
1538 snd-als4000= [HW,ALSA]
1539
1540 snd-azt2320= [HW,ALSA]
1541
1542 snd-cmi8330= [HW,ALSA]
1543
1544 snd-cmipci= [HW,ALSA]
1545
1546 snd-cs4231= [HW,ALSA]
1547
1548 snd-cs4232= [HW,ALSA]
1549
1550 snd-cs4236= [HW,ALSA]
1551
1552 snd-cs4281= [HW,ALSA]
1553
1554 snd-cs46xx= [HW,ALSA]
1555
1556 snd-dt019x= [HW,ALSA]
1557
1558 snd-dummy= [HW,ALSA]
1559
1560 snd-emu10k1= [HW,ALSA]
1561
1562 snd-ens1370= [HW,ALSA]
1563
1564 snd-ens1371= [HW,ALSA]
1565
1566 snd-es968= [HW,ALSA]
1567
1568 snd-es1688= [HW,ALSA]
1569
1570 snd-es18xx= [HW,ALSA]
1571
1572 snd-es1938= [HW,ALSA]
1573
1574 snd-es1968= [HW,ALSA]
1575
1576 snd-fm801= [HW,ALSA]
1577
1578 snd-gusclassic= [HW,ALSA]
1579
1580 snd-gusextreme= [HW,ALSA]
1581
1582 snd-gusmax= [HW,ALSA]
1583
1584 snd-hdsp= [HW,ALSA]
1585
1586 snd-ice1712= [HW,ALSA]
1587
1588 snd-intel8x0= [HW,ALSA]
1589
1590 snd-interwave= [HW,ALSA]
1591
1592 snd-interwave-stb=
1593 [HW,ALSA]
1594
1595 snd-korg1212= [HW,ALSA]
1596
1597 snd-maestro3= [HW,ALSA]
1598
1599 snd-mpu401= [HW,ALSA]
1600
1601 snd-mtpav= [HW,ALSA]
1602
1603 snd-nm256= [HW,ALSA]
1604
1605 snd-opl3sa2= [HW,ALSA]
1606
1607 snd-opti92x-ad1848=
1608 [HW,ALSA]
1609
1610 snd-opti92x-cs4231=
1611 [HW,ALSA]
1612
1613 snd-opti93x= [HW,ALSA]
1614
1615 snd-pmac= [HW,ALSA]
1616
1617 snd-rme32= [HW,ALSA]
1618
1619 snd-rme96= [HW,ALSA]
1620
1621 snd-rme9652= [HW,ALSA]
1622
1623 snd-sb8= [HW,ALSA]
1624
1625 snd-sb16= [HW,ALSA]
1626
1627 snd-sbawe= [HW,ALSA]
1628
1629 snd-serial= [HW,ALSA]
1630
1631 snd-sgalaxy= [HW,ALSA]
1632
1633 snd-sonicvibes= [HW,ALSA]
1634
1635 snd-sun-amd7930=
1636 [HW,ALSA]
1637
1638 snd-sun-cs4231= [HW,ALSA]
1639
1640 snd-trident= [HW,ALSA]
1641
1642 snd-usb-audio= [HW,ALSA,USB]
1643
1644 snd-via82xx= [HW,ALSA]
1645
1646 snd-virmidi= [HW,ALSA]
1647
1648 snd-wavefront= [HW,ALSA]
1649
1650 snd-ymfpci= [HW,ALSA]
a9913044 1651
1da177e4
LT
1652 sonycd535= [HW,CD]
1653 Format: <io>[,<irq>]
1654
1655 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1656 See Documentation/sonypi.txt
1657
1658 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1659 See Documentation/specialix.txt.
1660
1661 spia_io_base= [HW,MTD]
1662 spia_fio_base=
1663 spia_pedr=
1664 spia_peddr=
1665
1666 sscape= [HW,OSS]
1667 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1668
1da177e4
LT
1669 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1670 See Documentation/scsi/st.txt.
1671
1672 st0x= [HW,SCSI]
1673 See header of drivers/scsi/seagate.c.
1674
1675 sti= [PARISC,HW]
1676 Format: <num>
1677 Set the STI (builtin display/keyboard on the HP-PARISC
1678 machines) console (graphic card) which should be used
1679 as the initial boot-console.
1680 See also comment in drivers/video/console/sticore.c.
1681
1682 sti_font= [HW]
1683 See comment in drivers/video/console/sticore.c.
1684
1685 stifb= [HW]
1686 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1687
1da177e4 1688 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 1689
1da177e4
LT
1690 switches= [HW,M68k]
1691
1692 sym53c416= [HW,SCSI]
1693 See header of drivers/scsi/sym53c416.c.
1694
5d6f647f
IM
1695 sysrq_always_enabled
1696 [KNL]
1697 Ignore sysrq setting - this boot parameter will
1698 neutralize any effect of /proc/sys/kernel/sysrq.
1699 Useful for debugging.
1700
1da177e4
LT
1701 t128= [HW,SCSI]
1702 See header of drivers/scsi/t128.c.
1703
1704 tdfx= [HW,DRM]
1705
1706 thash_entries= [KNL,NET]
1707 Set number of hash buckets for TCP connection
1708
1709 time Show timing data prefixed to each printk message line
1710
734efb46
JS
1711 clocksource= [GENERIC_TIME] Override the default clocksource
1712 Override the default clocksource and use the clocksource
1713 with the name specified.
1714
1da177e4
LT
1715 tipar.timeout= [HW,PPT]
1716 Set communications timeout in tenths of a second
1717 (default 15).
1718
1719 tipar.delay= [HW,PPT]
1720 Set inter-bit delay in microseconds (default 10).
1721
1722 tmc8xx= [HW,SCSI]
1723 See header of drivers/scsi/seagate.c.
1724
1725 tmscsim= [HW,SCSI]
1726 See comment before function dc390_setup() in
1727 drivers/scsi/tmscsim.c.
1728
1729 tp720= [HW,PS2]
1730
1731 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
1732 Format:
1733 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1734
1da177e4
LT
1735 tsdev.xres= [TS] Horizontal screen resolution.
1736 tsdev.yres= [TS] Vertical screen resolution.
1737
a9913044
RD
1738 turbografx.map[2|3]= [HW,JOY]
1739 TurboGraFX parallel port interface
1740 Format:
1741 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
1742 See also Documentation/input/joystick-parport.txt
1743
1744 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1745 See header of drivers/scsi/u14-34f.c.
1746
1747 uart401= [HW,OSS]
1748 Format: <io>,<irq>
1749
1750 uart6850= [HW,OSS]
1751 Format: <io>,<irq>
1752
5f8364b7
AS
1753 uhci-hcd.ignore_oc=
1754 [USB] Ignore overcurrent events (default N).
1755 Some badly-designed motherboards generate lots of
1756 bogus events, for ports that aren't wired to
1757 anything. Set this parameter to avoid log spamming.
1758 Note that genuine overcurrent events won't be
1759 reported either.
1760
1da177e4
LT
1761 usbhid.mousepoll=
1762 [USBHID] The interval which mice are to be polled at.
a9913044 1763
e6e5494c
IM
1764 vdso= [IA-32]
1765 vdso=1: enable VDSO (default)
1766 vdso=0: disable VDSO mapping
1767
1da177e4
LT
1768 video= [FB] Frame buffer configuration
1769 See Documentation/fb/modedb.txt.
1770
1771 vga= [BOOT,IA-32] Select a particular video mode
a9913044
RD
1772 See Documentation/i386/boot.txt and
1773 Documentation/svga.txt.
1da177e4
LT
1774 Use vga=ask for menu.
1775 This is actually a boot loader parameter; the value is
1776 passed to the kernel using a special protocol.
1777
a9913044 1778 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
1779 size of <nn>. This can be used to increase the
1780 minimum size (128MB on x86). It can also be used to
1781 decrease the size and leave more room for directly
1782 mapped kernel RAM.
1783
585c3047
PO
1784 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1785 Format: <command>
1da177e4 1786
585c3047
PO
1787 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1788 Format: <command>
1789
1790 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1791 Format: <command>
a9913044 1792
1da177e4
LT
1793 waveartist= [HW,OSS]
1794 Format: <io>,<irq>,<dma>,<dma2>
a9913044 1795
1da177e4
LT
1796 wd33c93= [HW,SCSI]
1797 See header of drivers/scsi/wd33c93.c.
1798
1799 wd7000= [HW,SCSI]
1800 See header of drivers/scsi/wd7000.c.
1801
1802 wdt= [WDT] Watchdog
1803 See Documentation/watchdog/watchdog.txt.
1804
1805 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1806 xd_geo= See header of drivers/block/xd.c.
1807
1808 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
1809 Format:
1810 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 1811
a62eaf15
AK
1812 norandmaps Don't use address space randomization
1813 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1814
6d0185ea
JB
1815 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1816 This is useful to get more information why
1817 you got a "dwarf2 unwinder stuck"
1da177e4 1818
a9913044 1819______________________________________________________________________
1da177e4
LT
1820
1821TODO:
1822
1823 Add documentation for ALSA options.
1824 Add more DRM drivers.