]> bbs.cooldavid.org Git - net-next-2.6.git/blame - Documentation/kernel-parameters.txt
slab: add a flag to prevent debug_free checks on a kmem_cache
[net-next-2.6.git] / Documentation / kernel-parameters.txt
CommitLineData
e53dd083
MCC
1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
1da177e4
LT
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
a901ebb9
SR
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
6585fa8a
SR
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:
1da177e4
LT
31
32 ACPI ACPI support is enabled.
c99c108a 33 AGP AGP (Accelerated Graphics Port) is enabled.
1da177e4
LT
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
e7ba176b 37 AVR32 AVR32 architecture is enabled.
1da177e4 38 AX25 Appropriate AX.25 support is enabled.
0ae53640 39 BLACKFIN Blackfin architecture is enabled.
a9913044 40 DRM Direct Rendering Management support is enabled.
1da177e4
LT
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
1da177e4
LT
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
1da177e4
LT
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
11ef697b 52 LIBATA Libata driver is enabled
1da177e4
LT
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
309e57df 61 MSI Message Signaled Interrupts (PCI).
c8facbb6 62 MTD MTD (Memory Technology Device) support is enabled.
1da177e4
LT
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
734efb46 65 GENERIC_TIME The generic timeofday code is enabled.
1da177e4
LT
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
c8facbb6
RD
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
1da177e4
LT
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
7f785763 72 PCIE PCI Express support is enabled.
1da177e4
LT
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
20510f2f 79 ROOTPLUG The example Root Plug LSM is enabled.
1da177e4
LT
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
20510f2f 84 SECURITY Different security models are enabled.
1da177e4
LT
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
e523d93c 87 SH SuperH architecture is enabled.
1da177e4
LT
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
a9913044 90 SWSUSP Software suspend is enabled.
1da177e4
LT
91 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 99 X86-32 X86-32, aka i386 architecture is enabled.
1da177e4
LT
100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
103
104In addition, the following text indicates that the option:
105
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
109
110Parameters denoted with BOOT are actually interpreted by the boot
111loader, and have no meaning to the kernel directly.
112Do not modify the syntax of boot loader parameters without extreme
113need or coordination with <Documentation/i386/boot.txt>.
114
5558870b
KW
115There are also arch-specific kernel-parameters not documented here.
116See for example <Documentation/x86_64/boot-options.txt>.
117
1da177e4
LT
118Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119a trailing = on the name of any parameter states that that parameter will
120be entered as an environment variable, whereas its absence indicates that
121it will appear as a kernel argument readable via /proc/cmdline by programs
122running once the system is up.
123
9c4751fd 124The number of kernel parameters is not limited, but the length of the
125complete command line (parameters including spaces etc.) is limited to
126a fixed number of characters. This limit depends on the architecture
127and is between 256 and 4096 characters. It is defined in the file
128./include/asm/setup.h as COMMAND_LINE_SIZE.
129
130
03d926f8
BW
131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
a9913044 133 Format: { force | off | ht | strict | noirq }
1da177e4
LT
134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
a9913044 138 strict -- Be less tolerant of platforms that are not
1da177e4
LT
139 strictly ACPI specification compliant.
140
53471121 141 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 142
a1fdcc0d
LB
143 acpi_apic_instance= [ACPI, IOAPIC]
144 Format: <int>
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
4e381a4f 147 default: 0
a1fdcc0d 148
1da177e4 149 acpi_sleep= [HW,ACPI] Sleep options
23b168d4
PM
150 Format: { s3_bios, s3_mode, s3_beep }
151 See Documentation/power/video.txt for s3_bios and s3_mode.
152 s3_beep is for debugging; it makes the PC's speaker beep
153 as soon as the kernel's real-mode entry point is called.
a9913044 154
1da177e4 155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
a9913044 156 Format: { level | edge | high | low }
1da177e4 157
a9913044
RD
158 acpi_irq_balance [HW,ACPI]
159 ACPI will balance active IRQs
160 default in APIC mode
1da177e4 161
a9913044
RD
162 acpi_irq_nobalance [HW,ACPI]
163 ACPI will not move active IRQs (default)
164 default in PIC mode
1da177e4 165
a9913044
RD
166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
167 use by PCI
1da177e4
LT
168 Format: <irq>,<irq>...
169
a9913044 170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
1da177e4
LT
171 Format: <irq>,<irq>...
172
67effe8f
LB
173 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
174
a1f9e65e
LB
175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
176 Format: To spoof as Windows 98: ="Microsoft Windows"
177
ae00d812
LB
178 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
179 acpi_osi="string1" # add string1 -- only one string
180 acpi_osi="!string2" # remove built-in string2
181 acpi_osi= # disable all strings
1da177e4
LT
182
183 acpi_serialize [HW,ACPI] force serialization of AML methods
184
185 acpi_skip_timer_override [HW,ACPI]
186 Recognize and ignore IRQ0/pin2 Interrupt Override.
187 For broken nForce2 BIOS resulting in XT-PIC timer.
fa18f477
AK
188 acpi_use_timer_override [HW,ACPI}
189 Use timer override. For some broken Nvidia NF5 boards
190 that require a timer override, but don't have
191 HPET
1da177e4 192
f989106c 193 acpi.debug_layer= [HW,ACPI]
1da177e4 194 Format: <int>
a9913044 195 Each bit of the <int> indicates an ACPI debug layer,
1da177e4
LT
196 1: enable, 0: disable. It is useful for boot time
197 debugging. After system has booted up, it can be set
f989106c
ZR
198 via /sys/module/acpi/parameters/debug_layer.
199 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
200 Available bits (add the numbers together) to enable debug output
201 for specific parts of the ACPI subsystem:
202 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
203 0x10 namespace 0x20 parser 0x40 dispatcher
204 0x80 executer 0x100 resources 0x200 acpica debugger
205 0x400 os services 0x800 acpica disassembler.
206 The number can be in decimal or prefixed with 0x in hex.
207 Warning: Many of these options can produce a lot of
208 output and make your system unusable. Be very careful.
209
210 acpi.debug_level= [HW,ACPI]
1da177e4 211 Format: <int>
a9913044 212 Each bit of the <int> indicates an ACPI debug level,
1da177e4
LT
213 1: enable, 0: disable. It is useful for boot time
214 debugging. After system has booted up, it can be set
f989106c
ZR
215 via /sys/module/acpi/parameters/debug_level.
216 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
217 Available bits (add the numbers together) to enable different
218 debug output levels of the ACPI subsystem:
219 0x01 error 0x02 warn 0x04 init 0x08 debug object
220 0x10 info 0x20 init names 0x40 parse 0x80 load
221 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
222 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
223 0x10000 resources 0x20000 user requests 0x40000 package.
224 The number can be in decimal or prefixed with 0x in hex.
225 Warning: Many of these options can produce a lot of
226 output and make your system unusable. Be very careful.
227
cd4f0ef7 228 acpi_pm_good [X86-32,X86-64]
5d0cf410
JS
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
232
c99c108a
CE
233 agp= [AGP]
234 { off | try_unsupported }
235 off: disable AGP support
236 try_unsupported: try to drive unsupported chipsets
237 (may crash computer or cause data corruption)
238
66759a01
CE
239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
a9913044
RD
241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
66759a01
CE
243 The kernel tries to set a reasonable default.
244
245 disable_timer_pin_1 [i386,x86-64]
246 Disable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs.
248
1da177e4
LT
249 ad1848= [HW,OSS]
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
251
1da177e4
LT
252 advansys= [HW,SCSI]
253 See header of drivers/scsi/advansys.c.
254
255 advwdt= [HW,WDT] Advantech WDT
256 Format: <iostart>,<iostop>
257
258 aedsp16= [HW,OSS] Audio Excel DSP 16
259 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
260 See also header of sound/oss/aedsp16.c.
a9913044 261
1da177e4
LT
262 aha152x= [HW,SCSI]
263 See Documentation/scsi/aha152x.txt.
264
265 aha1542= [HW,SCSI]
266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
267
268 aic7xxx= [HW,SCSI]
269 See Documentation/scsi/aic7xxx.txt.
270
271 aic79xx= [HW,SCSI]
272 See Documentation/scsi/aic79xx.txt.
273
1da177e4
LT
274 amijoy.map= [HW,JOY] Amiga joystick support
275 Map of devices attached to JOY0DAT and JOY1DAT
276 Format: <a>,<b>
277 See also Documentation/kernel/input/joystick.txt
278
279 analog.map= [HW,JOY] Analog joystick and gamepad support
280 Specifies type or capabilities of an analog joystick
281 connected to one of 16 gameports
282 Format: <type1>,<type2>,..<type16>
283
a9913044
RD
284 apc= [HW,SPARC]
285 Power management functions (SPARCstation-4/5 + deriv.)
1da177e4
LT
286 Format: noidle
287 Disable APC CPU standby support. SPARCstation-Fox does
288 not play well with APC CPU idle - disable it if you have
289 APC and your system crashes randomly.
290
c8facbb6
RD
291 apic= [APIC,i386] Advanced Programmable Interrupt Controller
292 Change the output verbosity whilst booting
1da177e4
LT
293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
a9913044 296
1da177e4
LT
297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
299
1da177e4
LT
300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
301 Format: <io>,<irq>,<nodeID>
302
303 ataflop= [HW,M68k]
304
305 atarimouse= [HW,MOUSE] Atari Mouse
306
307 atascsi= [HW,SCSI] Atari SCSI
308
309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
310 EzKey and similar keyboards
311
312 atkbd.reset= [HW] Reset keyboard during initialization
313
a9913044
RD
314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
1da177e4
LT
316
317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
318 keyboards
319
320 atkbd.softraw= [HW] Choose between synthetic and real raw mode
321 Format: <bool> (0 = real, 1 = synthetic (default))
a9913044
RD
322
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
1da177e4
LT
325
326 autotest [IA64]
327
1da177e4
LT
328 baycom_epp= [HW,AX25]
329 Format: <io>,<mode>
a9913044 330
1da177e4
LT
331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
332 Format: <io>,<mode>
333 See header of drivers/net/hamradio/baycom_par.c.
334
a9913044
RD
335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
1da177e4
LT
337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
339
a9913044
RD
340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
1da177e4
LT
342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
344
bfe8df3d
RD
345 boot_delay= Milliseconds to delay each printk during boot.
346 Values larger than 10 seconds (10000) are changed to
347 no delay (0).
348 Format: integer
349
1da177e4 350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
a9913044
RD
351 bttv.radio= Most important insmod options are available as
352 kernel args too.
1da177e4
LT
353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
355
356 BusLogic= [HW,SCSI]
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
359
360 c101= [NET] Moxa C101 synchronous serial card
361
cd4f0ef7 362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
1da177e4
LT
363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
368
076c54c5
AD
369 security= [SECURITY] Choose a security module to enable at boot.
370 If this boot parameter is not specified, only the first
371 security module asking for security registration will be
372 loaded. An invalid security module name will be treated
373 as if no module has been chosen.
374
20510f2f
JM
375 capability.disable=
376 [SECURITY] Disable capabilities. This would normally
377 be used only if an alternative security model is to be
378 configured. Potentially dangerous and should only be
379 used if you are entirely sure of the consequences.
380
14ff56bb
SO
381 ccw_timeout_log [S390]
382 See Documentation/s390/CommonIO for details.
1da177e4 383
8bab8dde
PM
384 cgroup_disable= [KNL] Disable a particular controller
385 Format: {name of the controller(s) to disable}
386 {Currently supported controllers - "memory"}
387
1da177e4
LT
388 checkreqprot [SELINUX] Set initial checkreqprot flag value.
389 Format: { "0" | "1" }
390 See security/selinux/Kconfig help text.
a9913044
RD
391 0 -- check protection applied by kernel (includes
392 any implied execute protection).
1da177e4
LT
393 1 -- check protection requested by application.
394 Default value is set via a kernel config option.
a9913044
RD
395 Value can be changed at runtime via
396 /selinux/checkreqprot.
397
661ca0da
SO
398 cio_ignore= [S390]
399 See Documentation/s390/CommonIO for details.
400
401 cio_msg= [S390]
402 See Documentation/s390/CommonIO for details.
403
cd4f0ef7 404 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 405 [Deprecated]
3f6dee9b 406 Forces specified clocksource (if available) to be used
734efb46 407 when calculating gettimeofday(). If specified
3f6dee9b 408 clocksource is not available, it defaults to PIT.
1da177e4
LT
409 Format: { pit | tsc | cyclone | pmtmr }
410
3d6ac984
RD
411 clocksource= [GENERIC_TIME] Override the default clocksource
412 Format: <string>
413 Override the default clocksource and use the clocksource
414 with the name specified.
415 Some clocksource names to choose from, depending on
416 the platform:
417 [all] jiffies (this is the base, fallback clocksource)
418 [ACPI] acpi_pm
419 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
420 pxa_timer,timer3,32k_counter,timer0_1
421 [AVR32] avr32
cd4f0ef7 422 [X86-32] pit,hpet,tsc,vmi-timer;
3d6ac984
RD
423 scx200_hrt on Geode; cyclone on IBM x440
424 [MIPS] MIPS
425 [PARISC] cr16
426 [S390] tod
427 [SH] SuperH
428 [SPARC64] tick
429 [X86-64] hpet,tsc
430
ac72e788
AK
431 clearcpuid=BITNUM [X86]
432 Disable CPUID feature X for the kernel. See
433 include/asm-x86/cpufeature.h for the valid bit numbers.
434 Note the Linux specific bits are not necessarily
435 stable over kernel options, but the vendor specific
436 ones should be.
437 Also note that user programs calling CPUID directly
438 or using the feature without checking anything
439 will still see it. This just prevents it from
440 being used by the kernel or shown in /proc/cpuinfo.
441 Also note the kernel might malfunction if you disable
442 some critical bits.
443
a25bd949
AV
444 code_bytes [IA32/X86_64] How many bytes of object code to print
445 in an oops report.
86c41837
CE
446 Range: 0 - 8192
447 Default: 64
448
f9262c12
AK
449 disable_8254_timer
450 enable_8254_timer
451 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
452 over the 8254 in addition to over the IO-APIC. The
453 kernel tries to set a sensible default.
454
b17530bd
TG
455 hpet= [X86-32,HPET] option to control HPET usage
456 Format: { enable (default) | disable | force }
457 disable: disable HPET and use PIT instead
d79a5f80
CC
458 force: allow force enabled of undocumented chips (ICH4,
459 VIA, nVidia)
1da177e4 460
1da177e4 461 com20020= [HW,NET] ARCnet - COM20020 chipset
a9913044
RD
462 Format:
463 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
1da177e4
LT
464
465 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
466 Format: <io>[,<irq>]
467
a9913044
RD
468 com90xx= [HW,NET]
469 ARCnet - COM90xx chipset (memory-mapped buffers)
1da177e4
LT
470 Format: <io>[,<irq>[,<memstart>]]
471
472 condev= [HW,S390] console device
473 conmode=
a9913044 474
1da177e4
LT
475 console= [KNL] Output console device and options.
476
477 tty<n> Use the virtual console device <n>.
478
479 ttyS<n>[,options]
f1a1c2dc 480 ttyUSB0[,options]
1da177e4 481 Use the specified serial port. The options are of
f1a1c2dc
RD
482 the form "bbbbpnf", where "bbbb" is the baud rate,
483 "p" is parity ("n", "o", or "e"), "n" is number of
484 bits, and "f" is flow control ("r" for RTS or
485 omit it). Default is "9600n8".
486
487 See Documentation/serial-console.txt for more
488 information. See
489 Documentation/networking/netconsole.txt for an
490 alternative.
1da177e4 491
18a8bd94
YL
492 uart[8250],io,<addr>[,options]
493 uart[8250],mmio,<addr>[,options]
1da177e4
LT
494 Start an early, polled-mode console on the 8250/16550
495 UART at the specified I/O port or MMIO address,
496 switching to the matching ttyS device later. The
497 options are the same as for ttyS, above.
498
f7511d5f
ST
499 If the device connected to the port is not a TTY but a braille
500 device, prepend "brl," before the device type, for instance
501 console=brl,ttyS0
502 For now, only VisioBraille is supported.
503
18a8bd94
YL
504 earlycon= [KNL] Output early console device and options.
505 uart[8250],io,<addr>[,options]
506 uart[8250],mmio,<addr>[,options]
507 Start an early, polled-mode console on the 8250/16550
508 UART at the specified I/O port or MMIO address.
509 The options are the same as for ttyS, above.
510
8f4ce8c3
AS
511 no_console_suspend
512 [HW] Never suspend the console
513 Disable suspending of consoles during suspend and
514 hibernate operations. Once disabled, debugging
515 messages can reach various consoles while the rest
516 of the system is being put to sleep (ie, while
517 debugging driver suspend/resume hooks). This may
518 not work reliably with all consoles, but is known
519 to work with serial and VGA consoles.
520
1da177e4 521 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
522 Format:
523 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 524
dc009d92
EB
525 crashkernel=nn[KMG]@ss[KMG]
526 [KNL] Reserve a chunk of physical memory to
527 hold a kernel to switch to with kexec on panic.
528
fb391599
BW
529 crashkernel=range1:size1[,range2:size2,...][@offset]
530 [KNL] Same as above, but depends on the memory
531 in the running system. The syntax of range is
532 start-[end] where start and end are both
533 a memory unit (amount[KMG]). See also
534 Documentation/kdump/kdump.txt for a example.
535
1da177e4
LT
536 cs4232= [HW,OSS]
537 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
538
539 cs89x0_dma= [HW,NET]
540 Format: <dma>
541
542 cs89x0_media= [HW,NET]
543 Format: { rj45 | aui | bnc }
a9913044 544
a9913044 545 dasd= [HW,NET]
1da177e4
LT
546 See header of drivers/s390/block/dasd_devmap.c.
547
548 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
549 (one device per port)
550 Format: <port#>,<type>
551 See also Documentation/input/joystick-parport.txt
552
553 debug [KNL] Enable kernel debugging (events log level).
554
cae2ed9a
IM
555 debug_locks_verbose=
556 [KNL] verbose self-tests
557 Format=<0|1>
558 Print debugging info while doing the locking API
559 self-tests.
560 We default to 0 (no extra messages), setting it to
561 1 will print _a lot_ more information - normally
562 only useful to kernel developers.
563
2d27a966 564 decnet.addr= [HW,NET]
1da177e4
LT
565 Format: <area>[,<node>]
566 See also Documentation/networking/decnet.txt.
567
ecb77fa9 568 vt.default_blu= [VT]
55ff9780
AD
569 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
570 Change the default blue palette of the console.
571 This is a 16-member array composed of values
572 ranging from 0-255.
573
ecb77fa9 574 vt.default_grn= [VT]
55ff9780
AD
575 Format: <green0>,<green1>,<green2>,...,<green15>
576 Change the default green palette of the console.
577 This is a 16-member array composed of values
578 ranging from 0-255.
579
ecb77fa9 580 vt.default_red= [VT]
55ff9780
AD
581 Format: <red0>,<red1>,<red2>,...,<red15>
582 Change the default red palette of the console.
583 This is a 16-member array composed of values
584 ranging from 0-255.
585
ecb77fa9
ST
586 vt.default_utf8=
587 [VT]
55ff9780
AD
588 Format=<0|1>
589 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
590 Default is 1, i.e. UTF-8 mode is enabled for all
591 newly opened terminals.
55ff9780 592
1da177e4
LT
593 dhash_entries= [KNL]
594 Set number of hash buckets for dentry cache.
a9913044 595
1da177e4
LT
596 digi= [HW,SERIAL]
597 IO parameters + enable/disable command.
598
599 digiepca= [HW,SERIAL]
600 See drivers/char/README.epca and
601 Documentation/digiepca.txt.
602
093af8d7 603 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
604 By default the kernel will trim any uncacheable
605 memory out of your available memory pool based on
606 MTRR settings. This parameter disables that behavior,
607 possibly causing your machine to run very slowly.
608
1da177e4
LT
609 dmasound= [HW,OSS] Sound subsystem buffers
610
611 dscc4.setup= [NET]
612
613 dtc3181e= [HW,SCSI]
614
0ae53640 615 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
616 earlyprintk=vga
617 earlyprintk=serial[,ttySn[,baudrate]]
618
a9913044 619 Append ",keep" to not disable it when the real console
1da177e4
LT
620 takes over.
621
622 Only vga or serial at a time, not both.
623
624 Currently only ttyS0 and ttyS1 are supported.
625
626 Interaction with the standard serial driver is not
627 very good.
628
629 The VGA output is eventually overwritten by the real
630 console.
631
632 eata= [HW,SCSI]
633
1da177e4 634 edd= [EDD]
8c4dd606 635 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 636
1da177e4
LT
637 eisa_irq_edge= [PARISC,HW]
638 See header of drivers/parisc/eisa.c.
639
cd4f0ef7 640 elanfreq= [X86-32]
1da177e4
LT
641 See comment before function elanfreq_setup() in
642 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
643
644 elevator= [IOSCHED]
16ab3adf 645 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
646 See Documentation/block/as-iosched.txt and
647 Documentation/block/deadline-iosched.txt for details.
648
cd4f0ef7 649 elfcorehdr= [X86-32, X86_64]
a9913044 650 Specifies physical address of start of kernel core
aac04b32
VG
651 image elf header. Generally kexec loader will
652 pass this option to capture kernel.
653 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
654
655 enforcing [SELINUX] Set initial enforcing status.
656 Format: {"0" | "1"}
657 See security/selinux/Kconfig help text.
658 0 -- permissive (log only, no denials).
659 1 -- enforcing (deny and log).
660 Default value is 0.
661 Value can be changed at runtime via /selinux/enforce.
662
1da177e4
LT
663 es1371= [HW,OSS]
664 Format: <spdif>,[<nomix>,[<amplifier>]]
665 See also header of sound/oss/es1371.c.
a9913044 666
1da177e4
LT
667 ether= [HW,NET] Ethernet cards parameters
668 This option is obsoleted by the "netdev=" option, which
669 has equivalent usage. See its documentation for details.
670
671 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
672 Format: <io>[,<irq>]
673
de1ba09b
AM
674 failslab=
675 fail_page_alloc=
676 fail_make_request=[KNL]
677 General fault injection mechanism.
678 Format: <interval>,<probability>,<space>,<times>
679 See also /Documentation/fault-injection/.
680
1da177e4
LT
681 fd_mcs= [HW,SCSI]
682 See header of drivers/scsi/fd_mcs.c.
683
684 fdomain= [HW,SCSI]
685 See header of drivers/scsi/fdomain.c.
686
687 floppy= [HW]
688 See Documentation/floppy.txt.
689
1da177e4
LT
690 gamecon.map[2|3]=
691 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
692 support via parallel port (up to 5 devices per port)
693 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
694 See also Documentation/input/joystick-parport.txt
695
696 gamma= [HW,DRM]
697
aaf23042
YL
698 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
699 Format: off | on
700 default: on
701
1da177e4
LT
702 gdth= [HW,SCSI]
703 See header of drivers/scsi/gdth.c.
704
705 gpt [EFI] Forces disk with valid GPT signature but
706 invalid Protective MBR to be treated as GPT.
707
1da177e4
LT
708 gvp11= [HW,SCSI]
709
710 hashdist= [KNL,NUMA] Large hashes allocated during boot
711 are distributed across NUMA nodes. Defaults on
712 for IA-64, off otherwise.
a9913044 713 Format: 0 | 1 (for off | on)
1da177e4
LT
714
715 hcl= [IA-64] SGI's Hardware Graph compatibility layer
716
717 hd= [EIDE] (E)IDE hard drive subsystem geometry
718 Format: <cyl>,<head>,<sect>
719
720 hd?= [HW] (E)IDE subsystem
1c10e938 721 hd?lun= See Documentation/ide/ide.txt.
1da177e4
LT
722
723 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
724 size of <nn>. This works even on boxes that have no
725 highmem otherwise. This also works to reduce highmem
726 size on bigger boxes.
727
54cdfdb4
TG
728 highres= [KNL] Enable/disable high resolution timer mode.
729 Valid parameters: "on", "off"
730 Default: "on"
731
1da177e4
LT
732 hisax= [HW,ISDN]
733 See Documentation/isdn/README.HiSax.
734
cd4f0ef7 735 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 736 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 737
1da177e4 738 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
739 i8042.dumbkbd [HW] Pretend that controller can only read data from
740 keyboard and cannot control its state
1da177e4
LT
741 (Don't attempt to blink the leds)
742 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 743 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
744 i8042.noloop [HW] Disable the AUX Loopback command while probing
745 for the AUX port
1da177e4
LT
746 i8042.nomux [HW] Don't check presence of an active multiplexing
747 controller
748 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
749 controllers
750 i8042.panicblink=
751 [HW] Frequency with which keyboard LEDs should blink
752 when kernel panics (default is 0.5 sec)
753 i8042.reset [HW] Reset the controller during init and cleanup
754 i8042.unlock [HW] Unlock (ignore) the keylock
755
756 i810= [HW,DRM]
757
e70c9d5e
DT
758 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
759 indicates that the driver is running on unsupported
760 hardware.
1da177e4
LT
761 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
762 does not match list of supported models.
763 i8k.power_status
764 [HW] Report power status in /proc/i8k
765 (disabled by default)
766 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
767 capability is set.
768
769 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
770 See Documentation/mca.txt.
771
772 icn= [HW,ISDN]
773 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
774
775 ide= [HW] (E)IDE subsystem
a594eeb1 776 Format: ide=nodma or ide=doubler
1c10e938 777 See Documentation/ide/ide.txt.
1da177e4 778
1da177e4 779 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 780 See Documentation/ide/ide.txt.
1da177e4 781
f039b754
AK
782 idle= [X86]
783 Format: idle=poll or idle=mwait
784 Poll forces a polling idle loop that can slightly improves the performance
785 of waking up a idle CPU, but will use a lot of power and make the system
786 run hot. Not recommended.
787 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
788 to not use it because it doesn't save as much power as a normal idle
789 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
790 as idle=poll.
a9913044 791
594765a7
DC
792 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
793 Claim all unknown PCI IDE storage controllers.
794
79290822
IM
795 ignore_loglevel [KNL]
796 Ignore loglevel setting - this will print /all/
797 kernel messages to the console. Useful for debugging.
798
1da177e4
LT
799 ihash_entries= [KNL]
800 Set number of hash buckets for inode cache.
801
802 in2000= [HW,SCSI]
803 See header of drivers/scsi/in2000.c.
804
805 init= [KNL]
806 Format: <full_path>
807 Run specified binary instead of /sbin/init as init
808 process.
809
810 initcall_debug [KNL] Trace initcalls as they are executed. Useful
811 for working out where the kernel is dying during
812 startup.
813
814 initrd= [BOOT] Specify the location of the initial ramdisk
815
816 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
817 Format: <irq>
818
819 inttest= [IA64]
820
b552da87
PM
821 iommu= [x86]
822 off
823 force
824 noforce
825 biomerge
826 panic
827 nopanic
828 merge
829 nomerge
830 forcesac
831 soft
832
833
ba395927
KA
834 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
835 off
836 Disable intel iommu driver.
837 igfx_off [Default Off]
838 By default, gfx is mapped as normal device. If a gfx
839 device has a dedicated DMAR unit, the DMAR unit is
840 bypassed by not enabling DMAR with this option. In
841 this case, gfx device will use physical address for
842 DMA.
7d3b03ce
KA
843 forcedac [x86_64]
844 With this option iommu will not optimize to look
845 for io virtual address below 32 bit forcing dual
846 address cycle on pci bus for cards supporting greater
847 than 32 bit addressing. The default is to look
848 for translation below 32 bit and if not available
849 then look in the higher range.
5e0d2a6f 850 strict [Default Off]
851 With this option on every unmap_single operation will
852 result in a hardware IOTLB flush operation as opposed
853 to batching them for performance.
ba395927 854
b02aae9c 855 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
856 0x80
857 Standard port 0x80 based delay
858 0xed
859 Alternate port 0xed based delay (needed on some systems)
b02aae9c 860 udelay
6e7c4025
IM
861 Simple two microseconds delay
862 none
863 No delay
b02aae9c 864
1da177e4
LT
865 io7= [HW] IO7 for Marvel based alpha systems
866 See comment before marvel_specify_io7 in
867 arch/alpha/kernel/core_marvel.c.
868
869 ip= [IP_PNP]
6ded55da 870 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
871
872 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
873 See comment before ip2_setup() in
874 drivers/char/ip2/ip2base.c.
1da177e4
LT
875
876 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
877 See header of drivers/scsi/ips.c.
878
72c4a13a
SH
879 ports= [IP_VS_FTP] IPVS ftp helper module
880 Default is 21.
881 Up to 8 (IP_VS_APP_MAX_PORTS) ports
882 may be specified.
883 Format: <port>,<port>....
884
200803df
AC
885 irqfixup [HW]
886 When an interrupt is not handled search all handlers
887 for it. Intended to get systems with badly broken
888 firmware running.
889
890 irqpoll [HW]
891 When an interrupt is not handled search all handlers
892 for it. Also check all handlers each timer
893 interrupt. Intended to get systems with badly broken
894 firmware running.
895
1da177e4 896 isapnp= [ISAPNP]
a9913044 897 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
898
899 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
900 Format:
901 <cpu number>,...,<cpu number>
902 or
903 <cpu number>-<cpu number> (must be a positive range in ascending order)
904 or a mixture
905 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
906 This option can be used to specify one or more CPUs
907 to isolate from the general SMP balancing and scheduling
908 algorithms. The only way to move a process onto or off
909 an "isolated" CPU is via the CPU affinity syscalls.
910 <cpu number> begins at 0 and the maximum value is
911 "number of CPUs in system - 1".
912
913 This option is the preferred way to isolate CPUs. The
a9913044
RD
914 alternative -- manually setting the CPU mask of all
915 tasks in the system -- can cause problems and
916 suboptimal load balancer performance.
1da177e4 917
a9913044 918 iucv= [HW,NET]
1da177e4
LT
919
920 js= [HW,JOY] Analog joystick
921 See Documentation/input/joystick.txt.
922
cd4f0ef7 923 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
924 specifies the amount of memory usable by the kernel
925 for non-movable allocations. The requested amount is
926 spread evenly throughout all nodes in the system. The
927 remaining memory in each node is used for Movable
928 pages. In the event, a node is too small to have both
929 kernelcore and Movable pages, kernelcore pages will
930 take priority and other nodes will have a larger number
931 of kernelcore pages. The Movable zone is used for the
932 allocation of pages that may be reclaimed or moved
933 by the page migration subsystem. This means that
934 HugeTLB pages may not be allocated from this zone.
935 Note that allocations like PTEs-from-HighMem still
936 use the HighMem zone if it exists, and the Normal
937 zone if it does not.
938
cd4f0ef7 939 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
940 is similar to kernelcore except it specifies the
941 amount of memory used for migratable allocations.
942 If both kernelcore and movablecore is specified,
943 then kernelcore will be at *least* the specified
944 value but may be more. If movablecore on its own
945 is specified, the administrator must be careful
946 that the amount of memory usable for all allocations
947 is not too small.
948
1da177e4
LT
949 keepinitrd [HW,ARM]
950
cd4f0ef7 951 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
952 in oops dumps.
953
6cdf6e06
JW
954 kgdboc= [HW] kgdb over consoles.
955 Requires a tty driver that supports console polling.
956 (only serial suported for now)
957 Format: <serial_device>[,baud]
958
1da177e4
LT
959 l2cr= [PPC]
960
a78bfbfc
RB
961 l3cr= [PPC]
962
cd4f0ef7 963 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 964 disabled it.
1da177e4 965
cd4f0ef7 966 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
967 C2 power state.
968
fcb71f6f
FC
969 libata.dma= [LIBATA] DMA control
970 libata.dma=0 Disable all PATA and SATA DMA
971 libata.dma=1 PATA and SATA Disk DMA only
972 libata.dma=2 ATAPI (CDROM) DMA only
973 libata.dma=4 Compact Flash DMA only
974 Combinations also work, so libata.dma=3 enables DMA
975 for disks and CDROMs, but not CFs.
976
78e70c23
DJ
977 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
978 when set.
979 Format: <int>
980
33267325
TH
981 libata.force= [LIBATA] Force configurations. The format is comma
982 separated list of "[ID:]VAL" where ID is
983 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
984 matching port, link or device. Basically, it matches
985 the ATA ID string printed on console by libata. If
986 the whole ID part is omitted, the last PORT and DEVICE
987 values are used. If ID hasn't been specified yet, the
988 configuration applies to all ports, links and devices.
989
990 If only DEVICE is omitted, the parameter applies to
991 the port and all links and devices behind it. DEVICE
992 number of 0 either selects the first device or the
993 first fan-out link behind PMP device. It does not
994 select the host link. DEVICE number of 15 selects the
995 host link and device attached to it.
996
997 The VAL specifies the configuration to force. As long
998 as there's no ambiguity shortcut notation is allowed.
999 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1000 The following configurations can be forced.
1001
1002 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1003 Any ID with matching PORT is used.
1004
1005 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1006
1007 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1008 udma[/][16,25,33,44,66,100,133] notation is also
1009 allowed.
1010
1011 * [no]ncq: Turn on or off NCQ.
1012
1013 If there are multiple matching configurations changing
1014 the same attribute, the last one is used.
1015
1da177e4
LT
1016 load_ramdisk= [RAM] List of ramdisks to load from floppy
1017 See Documentation/ramdisk.txt.
1018
a6b25b67
RD
1019 lockd.nlm_grace_period=P [NFS] Assign grace period.
1020 Format: <integer>
1da177e4 1021
a6b25b67
RD
1022 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1023 Format: <integer>
1024
1025 lockd.nlm_timeout=T [NFS] Assign timeout value.
1026 Format: <integer>
1027
1028 lockd.nlm_udpport=M [NFS] Assign UDP port.
1029 Format: <integer>
1da177e4
LT
1030
1031 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1032 Format: <irq>
1033
1034 loglevel= All Kernel Messages with a loglevel smaller than the
1035 console loglevel will be printed to the console. It can
1036 also be changed with klogd or other programs. The
1037 loglevels are defined as follows:
1038
1039 0 (KERN_EMERG) system is unusable
1040 1 (KERN_ALERT) action must be taken immediately
1041 2 (KERN_CRIT) critical conditions
1042 3 (KERN_ERR) error conditions
1043 4 (KERN_WARNING) warning conditions
1044 5 (KERN_NOTICE) normal but significant condition
1045 6 (KERN_INFO) informational
1046 7 (KERN_DEBUG) debug-level messages
1047
1048 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1049 Format: { n | nk | nM }
1050 n must be a power of two. The default size
1051 is set in the kernel config file.
1da177e4 1052
accaa24c
RD
1053 logo.nologo [FB] Disables display of the built-in Linux logo.
1054 This may be used to provide more screen space for
1055 kernel log messages and is useful when debugging
1056 kernel boot problems.
1057
1da177e4
LT
1058 lp=0 [LP] Specify parallel ports to use, e.g,
1059 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1060 lp=reset first parallel port). 'lp=0' disables the
1061 lp=auto printer driver. 'lp=reset' (which can be
1062 specified in addition to the ports) causes
1063 attached printers to be reset. Using
1064 lp=port1,port2,... specifies the parallel ports
1065 to associate lp devices with, starting with
1066 lp0. A port specification may be 'none' to skip
1067 that lp device, or a parport name such as
1068 'parport0'. Specifying 'lp=auto' instead of a
1069 port specification list means that device IDs
1070 from each port should be examined, to see if
1071 an IEEE 1284-compliant printer is attached; if
1072 so, the driver will manage that printer.
1073 See also header of drivers/char/lp.c.
1074
1075 lpj=n [KNL]
1076 Sets loops_per_jiffy to given constant, thus avoiding
1077 time-consuming boot-time autodetection (up to 250 ms per
1078 CPU). 0 enables autodetection (default). To determine
1079 the correct value for your kernel, boot with normal
1080 autodetection and see what value is printed. Note that
1081 on SMP systems the preset will be applied to all CPUs,
1082 which is likely to cause problems if your CPUs need
1083 significantly divergent settings. An incorrect value
1084 will cause delays in the kernel to be wrong, leading to
1085 unpredictable I/O errors and other breakage. Although
1086 unlikely, in the extreme case this might damage your
1087 hardware.
1088
1089 ltpc= [NET]
1090 Format: <io>,<irq>,<dma>
1091
a9913044
RD
1092 mac5380= [HW,SCSI] Format:
1093 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1094
a9913044
RD
1095 mac53c9x= [HW,SCSI] Format:
1096 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1097
a9913044
RD
1098 machvec= [IA64] Force the use of a particular machine-vector
1099 (machvec) in a generic kernel.
1100 Example: machvec=hpzx1_swiotlb
1da177e4 1101
a9913044 1102 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1103 be mounted
1104 Format: <1-256>
1105
1106 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1107 should make use of. maxcpus=n : n >= 0 limits the
1108 kernel to using 'n' processors. n=0 is a special case,
1109 it is equivalent to "nosmp", which also disables
1110 the IO APIC.
1da177e4 1111
2b2c3750
BP
1112 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1113 equal to this physical address is ignored.
1114
a9913044 1115 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1116 Should be between 1 and 2^32-1.
1117
1118 max_report_luns=
a9913044 1119 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1120 Should be between 1 and 16384.
1121
1da177e4
LT
1122 mcatest= [IA-64]
1123
cd4f0ef7 1124 mce [X86-32] Machine Check Exception
1da177e4 1125
909dd324
AK
1126 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1127
1da177e4
LT
1128 md= [HW] RAID subsystems devices and level
1129 See Documentation/md.txt.
a9913044 1130
1da177e4
LT
1131 mdacon= [MDA]
1132 Format: <first>,<last>
1133 Specifies range of consoles to be captured by the MDA.
a9913044 1134
1da177e4
LT
1135 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1136 Amount of memory to be used when the kernel is not able
1137 to see the whole system memory or for test.
cd4f0ef7 1138 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1139 address space collisions. Without memmap= PCI devices
1140 could be placed at addresses belonging to unused RAM.
1141
cd4f0ef7 1142 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1143 memory.
1144
cd4f0ef7 1145 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1146 E820 memory map, as specified by the user.
1147 Such memmap=exactmap lines can be constructed based on
1148 BIOS output or other requirements. See the memmap=nn@ss
1149 option description.
1150
1151 memmap=nn[KMG]@ss[KMG]
1152 [KNL] Force usage of a specific region of memory
1153 Region of memory to be used, from ss to ss+nn.
1154
1155 memmap=nn[KMG]#ss[KMG]
1156 [KNL,ACPI] Mark specific memory as ACPI data.
1157 Region of memory to be used, from ss to ss+nn.
1158
1159 memmap=nn[KMG]$ss[KMG]
1160 [KNL,ACPI] Mark specific memory as reserved.
1161 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1162 Example: Exclude memory from 0x18690000-0x1869ffff
1163 memmap=64K$0x18690000
1164 or
1165 memmap=0x10000$0x18690000
1da177e4 1166
c64df707
YL
1167 memtest= [KNL,X86_64] Enable memtest
1168 Format: <integer>
1169 range: 0,4 : pattern number
1170 default : 0 <disable>
1171
1da177e4
LT
1172 meye.*= [HW] Set MotionEye Camera parameters
1173 See Documentation/video4linux/meye.txt.
1174
8f36881b
AS
1175 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1176 Multi-Function General Purpose Timers on AMD Geode
1177 platforms.
1178
e6c4dc6c
WT
1179 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1180 the BIOS has incorrectly applied a workaround. TinyBIOS
1181 version 0.98 is known to be affected, 0.99 fixes the
1182 problem by letting the user disable the workaround.
1183
1da177e4
LT
1184 mga= [HW,DRM]
1185
1186 mousedev.tap_time=
1187 [MOUSE] Maximum time between finger touching and
1188 leaving touchpad surface for touch to be considered
1189 a tap and be reported as a left button click (for
1190 touchpads working in absolute mode only).
1191 Format: <msecs>
1192 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1193 reporting absolute coordinates, such as tablets
1194 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1195 reporting absolute coordinates, such as tablets
1196
1197 mpu401= [HW,OSS]
1198 Format: <io>,<irq>
1199
1200 MTD_Partition= [MTD]
1201 Format: <name>,<region-number>,<size>,<offset>
1202
a9913044
RD
1203 MTD_Region= [MTD] Format:
1204 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1205
1206 mtdparts= [MTD]
c8facbb6 1207 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1208
1209 mtouchusb.raw_coordinates=
a9913044
RD
1210 [HW] Make the MicroTouch USB driver use raw coordinates
1211 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1212
1213 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1214
1215 NCR_D700= [HW,SCSI]
1216 See header of drivers/scsi/NCR_D700.c.
1217
1218 ncr5380= [HW,SCSI]
1219
1220 ncr53c400= [HW,SCSI]
1221
1222 ncr53c400a= [HW,SCSI]
1223
1224 ncr53c406a= [HW,SCSI]
1225
1226 ncr53c8xx= [HW,SCSI]
1227
1228 netdev= [NET] Network devices parameters
1229 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1230 Note that mem_start is often overloaded to mean
1231 something different and driver-specific.
a9913044
RD
1232 This usage is only documented in each driver source
1233 file if at all.
1234
1da177e4 1235 nfsaddrs= [NFS]
6ded55da 1236 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1237
1238 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1239 See Documentation/filesystems/nfsroot.txt.
1da177e4 1240
a72b4422
TM
1241 nfs.callback_tcpport=
1242 [NFS] set the TCP port on which the NFSv4 callback
1243 channel should listen.
1244
58df095b
TM
1245 nfs.idmap_cache_timeout=
1246 [NFS] set the maximum lifetime for idmapper cache
1247 entries.
1248
f43bf0be
TM
1249 nfs.enable_ino64=
1250 [NFS] enable 64-bit inode numbers.
1251 If zero, the NFS client will fake up a 32-bit inode
1252 number for the readdir() and stat() syscalls instead
1253 of returning the full 64-bit number.
1254 The default is to return 64-bit inode numbers.
1255
e7ba176b
HS
1256 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1257 when a NMI is triggered.
1258 Format: [state][,regs][,debounce][,die]
1259
cd4f0ef7 1260 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1261
cd4f0ef7 1262 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1263 emulation library even if a 387 maths coprocessor
1264 is present.
1265
c1aee215
CL
1266 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1267 caches in the slab allocator. Saves per-node memory,
1268 but will impact performance.
3395ee05 1269
a9913044
RD
1270 noalign [KNL,ARM]
1271
1da177e4
LT
1272 noapic [SMP,APIC] Tells the kernel to not make use of any
1273 IOAPICs that may be present in the system.
1274
1da177e4
LT
1275 nobats [PPC] Do not use BATs for mapping kernel lowmem
1276 on "Classic" PPC cores.
1277
1278 nocache [ARM]
a9913044 1279
163ecdff
SN
1280 nodelayacct [KNL] Disable per-task delay accounting
1281
1da177e4
LT
1282 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1283
8b2cb7a8
HY
1284 noefi [X86-32,X86-64] Disable EFI runtime services support.
1285
1da177e4
LT
1286 noexec [IA-64]
1287
cd4f0ef7 1288 noexec [X86-32,X86-64]
f5a1b191 1289 On X86-32 available only on PAE configured kernels.
1da177e4 1290 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1291 noexec=off: disable non-executable mappings
1292
1293 noexec32 [X86-64]
1294 This affects only 32-bit executables.
1295 noexec32=on: enable non-executable mappings (default)
1296 read doesn't imply executable mappings
1297 noexec32=off: disable non-executable mappings
1298 read implies executable mappings
1da177e4 1299
cd4f0ef7 1300 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1301 register save and restore. The kernel will only save
1302 legacy floating-point registers on task switch.
1da177e4 1303
191679fd
AK
1304 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1305
1da177e4 1306 nohlt [BUGS=ARM]
a9913044 1307
cd4f0ef7 1308 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1309 instruction doesn't work correctly and not to
1310 use it.
1311
1312 nohalt [IA-64] Tells the kernel not to use the power saving
1313 function PAL_HALT_LIGHT when idle. This increases
1314 power-consumption. On the positive side, it reduces
1315 interrupt wake-up latency, which may improve performance
1316 in certain environments such as networked servers or
1317 real-time systems.
1318
79bf2bb3
TG
1319 nohz= [KNL] Boottime enable/disable dynamic ticks
1320 Valid arguments: on, off
1321 Default: on
1322
cd4f0ef7 1323 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1324
cd4f0ef7 1325 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1326 disable unhandled interrupt sources.
1327
cd4f0ef7 1328 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1329 broken timer IRQ sources.
1330
1da177e4
LT
1331 noisapnp [ISAPNP] Disables ISA PnP code.
1332
1333 noinitrd [RAM] Tells the kernel not to load any configured
1334 initial RAM disk.
1335
1336 nointroute [IA-64]
1337
0aa366f3
TL
1338 nojitter [IA64] Disables jitter checking for ITC timers.
1339
cd4f0ef7 1340 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1341
cd4f0ef7 1342 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1343
1da177e4
LT
1344 noltlbs [PPC] Do not use large page/tlb entries for kernel
1345 lowmem mapping on PPC40x.
1346
312f1f01
H
1347 nomca [IA-64] Disable machine check abort handling
1348
cd4f0ef7 1349 nomce [X86-32] Machine Check Exception
abe37e5a 1350
83d7384f
AS
1351 nomfgpt [X86-32] Disable Multi-Function General Purpose
1352 Timer usage (for AMD Geode machines).
1353
cd4f0ef7 1354 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1355
cd4f0ef7 1356 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1357 with UP alternatives
1358
1da177e4
LT
1359 noresidual [PPC] Don't use residual data on PReP machines.
1360
a9913044
RD
1361 noresume [SWSUSP] Disables resume and restores original swap
1362 space.
1363
1da177e4
LT
1364 no-scroll [VGA] Disables scrollback.
1365 This is required for the Braillex ib80-piezo Braille
1366 reader made by F.H. Papenmeier (Germany).
1367
1368 nosbagart [IA-64]
1369
cd4f0ef7 1370 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1371
61ec7567
LB
1372 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1373 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1374
97842216
DJ
1375 nosoftlockup [KNL] Disable the soft-lockup detector.
1376
1da177e4
LT
1377 nosync [HW,M68K] Disables sync negotiation for all devices.
1378
cd4f0ef7 1379 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1380
1381 nousb [USB] Disable the USB subsystem
1382
1383 nowb [ARM]
a9913044 1384
a6c75b86
FY
1385 nptcg= [IA64] Override max number of concurrent global TLB
1386 purges which is reported from either PAL_VM_SUMMARY or
1387 SAL PALO.
1388
f0c0b2b8
KH
1389 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1390 one of ['zone', 'node', 'default'] can be specified
1391 This can be set from sysctl after boot.
1392 See Documentation/sysctl/vm.txt for details.
1393
a61c2d78
DJ
1394 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1395
3ef0e1f8
AS
1396 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1397 Rather than timing out after 20 ms if an EC
1398 command is not properly ACKed, override the length
1399 of the timeout. We have interrupts disabled while
1400 waiting for the ACK, so if this is set too high
1401 interrupts *may* be lost!
1402
1da177e4
LT
1403 opl3= [HW,OSS]
1404 Format: <io>
1405
1da177e4
LT
1406 oprofile.timer= [HW]
1407 Use timer interrupt instead of performance counters
1408
1da177e4
LT
1409 osst= [HW,SCSI] SCSI Tape Driver
1410 Format: <buffer_size>,<write_threshold>
1411 See also Documentation/scsi/st.txt.
1412
1413 panic= [KNL] Kernel behaviour on panic
1414 Format: <timeout>
1415
1416 parkbd.port= [HW] Parallel port number the keyboard adapter is
1417 connected to, default is 0.
1418 Format: <parport#>
1419 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1420 0 for XT, 1 for AT (default is AT).
a9913044
RD
1421 Format: <mode>
1422
1423 parport= [HW,PPT] Specify parallel ports. 0 disables.
1424 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1425 Use 'auto' to force the driver to use any
1426 IRQ/DMA settings detected (the default is to
1427 ignore detected IRQ/DMA settings because of
1428 possible conflicts). You can specify the base
1429 address, IRQ, and DMA settings; IRQ and DMA
1430 should be numbers, or 'auto' (for using detected
1431 settings on that particular port), or 'nofifo'
1432 (to avoid using a FIFO even if it is detected).
1433 Parallel ports are assigned in the order they
1434 are specified on the command line, starting
1435 with parport0.
1436
1437 parport_init_mode= [HW,PPT]
1438 Configure VIA parallel port to operate in
1439 a specific mode. This is necessary on Pegasos
1440 computer where firmware has no options for setting
1441 up parallel port mode and sets it to spp.
1442 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1443 Format: [spp|ps2|epp|ecp|ecpepp]
1444
a9913044
RD
1445 pas2= [HW,OSS] Format:
1446 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1447
1da177e4
LT
1448 pas16= [HW,SCSI]
1449 See header of drivers/scsi/pas16.c.
1450
dd287796
AM
1451 pause_on_oops=
1452 Halt all CPUs after the first oops has been printed for
1453 the specified number of seconds. This is to be used if
1454 your oopses keep scrolling off the screen.
1455
1da177e4
LT
1456 pcbit= [HW,ISDN]
1457
1458 pcd. [PARIDE]
1459 See header of drivers/block/paride/pcd.c.
1460 See also Documentation/paride.txt.
1461
a9913044 1462 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1463 off [X86-32] don't probe for the PCI bus
1464 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1465 the hardware directly. Use this if your machine
1466 has a non-standard PCI host bridge.
cd4f0ef7 1467 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1468 hardware access methods are allowed. Use this
1469 if you experience crashes upon bootup and you
1470 suspect they are caused by the BIOS.
cd4f0ef7 1471 conf1 [X86-32] Force use of PCI Configuration
a9913044 1472 Mechanism 1.
cd4f0ef7 1473 conf2 [X86-32] Force use of PCI Configuration
a9913044 1474 Mechanism 2.
7f785763
RD
1475 noaer [PCIE] If the PCIEAER kernel config parameter is
1476 enabled, this kernel boot option can be used to
1477 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1478 nodomains [PCI] Disable support for multiple PCI
1479 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1480 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1481 Configuration
309e57df
MW
1482 nomsi [MSI] If the PCI_MSI kernel config parameter is
1483 enabled, this kernel boot option can be used to
1484 disable the use of MSI interrupts system-wide.
cd4f0ef7 1485 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1486 routing table. These calls are known to be buggy
1487 on several machines and they hang the machine
1488 when used, but on other computers it's the only
1489 way to get the interrupt routing table. Try
1490 this option if the kernel is unable to allocate
1491 IRQs or discover secondary PCI buses on your
1492 motherboard.
cd4f0ef7 1493 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1494 Use with caution as certain devices share
1495 address decoders between ROMs and other
1496 resources.
cd4f0ef7 1497 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1498 assigned automatically to PCI devices. You can
1499 make the kernel exclude IRQs of your ISA cards
1500 this way.
cd4f0ef7 1501 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1502 of the PIRQ table (normally generated
1503 by the BIOS) if it is outside the
1504 F0000h-100000h range.
cd4f0ef7 1505 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1506 useful if the kernel is unable to find your
1507 secondary buses and you want to tell it
1508 explicitly which ones they are.
cd4f0ef7 1509 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1510 numbers ourselves, overriding
1511 whatever the firmware may have done.
cd4f0ef7 1512 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1513 in the BIOS $PIR table. This is needed on
1514 some systems with broken BIOSes, notably
1515 some HP Pavilion N5400 and Omnibook XE3
1516 notebooks. This will have no effect if ACPI
1517 IRQ routing is enabled.
cd4f0ef7 1518 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1519 or for PCI scanning.
62f420f8
GH
1520 use_crs [X86-32] Use _CRS for PCI resource
1521 allocation.
a9913044
RD
1522 routeirq Do IRQ routing for all PCI devices.
1523 This is normally done in pci_enable_device(),
1524 so this option is a temporary workaround
1525 for broken drivers that don't call it.
1526 firmware [ARM] Do not re-enumerate the bus but instead
1527 just use the configuration from the
1528 bootloader. This is currently used on
1529 IXP2000 systems where the bus has to be
1530 configured a certain way for adjunct CPUs.
0637a70a
AK
1531 noearly [X86] Don't do any early type 1 scanning.
1532 This might help on some broken boards which
1533 machine check when some devices' config space
1534 is read. But various workarounds are disabled
1535 and some IOMMU drivers will not work.
6b4b78fe
MD
1536 bfsort Sort PCI devices into breadth-first order.
1537 This sorting is done to get a device
1538 order compatible with older (<= 2.4) kernels.
1539 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1540 cbiosize=nn[KMG] The fixed amount of bus space which is
1541 reserved for the CardBus bridge's IO window.
1542 The default value is 256 bytes.
1543 cbmemsize=nn[KMG] The fixed amount of bus space which is
1544 reserved for the CardBus bridge's memory
1545 window. The default value is 64 megabytes.
6b4b78fe 1546
1da177e4
LT
1547 pcmv= [HW,PCMCIA] BadgePAD 4
1548
1549 pd. [PARIDE]
1550 See Documentation/paride.txt.
1551
1552 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1553 boot time.
1554 Format: { 0 | 1 }
1555 See arch/parisc/kernel/pdc_chassis.c
1556
1557 pf. [PARIDE]
1558 See Documentation/paride.txt.
1559
1560 pg. [PARIDE]
1561 See Documentation/paride.txt.
1562
1563 pirq= [SMP,APIC] Manual mp-table setup
1564 See Documentation/i386/IO-APIC.txt.
1565
1566 plip= [PPT,NET] Parallel port network link
1567 Format: { parport<nr> | timid | 0 }
1568 See also Documentation/parport.txt.
1569
1570 pnpacpi= [ACPI]
1571 { off }
1572
1573 pnpbios= [ISAPNP]
1574 { on | off | curr | res | no-curr | no-res }
1575
1576 pnp_reserve_irq=
1577 [ISAPNP] Exclude IRQs for the autoconfiguration
1578
1579 pnp_reserve_dma=
1580 [ISAPNP] Exclude DMAs for the autoconfiguration
1581
1582 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1583 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1584
1585 pnp_reserve_mem=
a9913044
RD
1586 [ISAPNP] Exclude memory regions for the
1587 autoconfiguration.
1da177e4
LT
1588 Ranges are in pairs (memory base and size).
1589
45807a1d
IM
1590 print-fatal-signals=
1591 [KNL] debug: print fatal signals
1592 print-fatal-signals=1: print segfault info to
1593 the kernel console.
1594 default: off.
1595
e84845c4
RD
1596 printk.time= Show timing data prefixed to each printk message line
1597 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1598
1da177e4 1599 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1600 Format: [schedule,]<number>
1601 Param: "schedule" - profile schedule points.
1602 Param: <number> - step/bucket size as a power of 2 for
1603 statistical time based profiling.
b3da2a73
MG
1604 Param: "sleep" - profile D-state sleeping (millisecs).
1605 Requires CONFIG_SCHEDSTATS
c0fe2e69 1606 Param: "kvm" - profile VM exits.
1da177e4 1607
a9913044 1608 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1609 Limit processor to maximum C-state
1610 max_cstate=9 overrides any DMI blacklist limit.
1611
41c0d868
LB
1612 processor.nocst [HW,ACPI]
1613 Ignore the _CST method to determine C-states,
1614 instead using the legacy FADT method
1615
1da177e4
LT
1616 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1617 before loading.
1618 See Documentation/ramdisk.txt.
1619
a9913044
RD
1620 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1621 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1622 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1623 per second.
a9913044
RD
1624 psmouse.resetafter= [HW,MOUSE]
1625 Try to reset the device after so many bad packets
1da177e4
LT
1626 (0 = never).
1627 psmouse.resolution=
1628 [HW,MOUSE] Set desired mouse resolution, in dpi.
1629 psmouse.smartscroll=
a9913044 1630 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1631 0 = disabled, 1 = enabled (default).
1632
1633 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1634 Format:
1635 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1636
1637 pt. [PARIDE]
1638 See Documentation/paride.txt.
1639
dc8c8587
KS
1640 pty.legacy_count=
1641 [KNL] Number of legacy pty's. Overwrites compiled-in
1642 default number.
1643
7d2c502f 1644 quiet [KNL] Disable most log messages
a9913044 1645
1da177e4
LT
1646 r128= [HW,DRM]
1647
1648 raid= [HW,RAID]
1649 See Documentation/md.txt.
1650
a9913044 1651 ramdisk_blocksize= [RAM]
1da177e4 1652 See Documentation/ramdisk.txt.
a9913044 1653
1da177e4 1654 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1655 See Documentation/ramdisk.txt.
1656
24aaef8d
RD
1657 rcupdate.blimit= [KNL,BOOT]
1658 Set maximum number of finished RCU callbacks to process
1659 in one batch.
21a1ea9e 1660
24aaef8d
RD
1661 rcupdate.qhimark= [KNL,BOOT]
1662 Set threshold of queued
21a1ea9e
DS
1663 RCU callbacks over which batch limiting is disabled.
1664
24aaef8d
RD
1665 rcupdate.qlowmark= [KNL,BOOT]
1666 Set threshold of queued RCU callbacks below which
1667 batch limiting is re-enabled.
21a1ea9e 1668
ffdfc409
OJ
1669 rdinit= [KNL]
1670 Format: <full_path>
1671 Run specified binary instead of /init from the ramdisk,
1672 used for early userspace startup. See initrd.
1673
cd4f0ef7 1674 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1675 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1676 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1677
1678 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1679
cd4f0ef7 1680 reservetop= [X86-32]
461a9aff
ZA
1681 Format: nn[KMG]
1682 Reserves a hole at the top of the kernel virtual
1683 address space.
1684
7e96287d
VG
1685 reset_devices [KNL] Force drivers to reset the underlying device
1686 during initialization.
1687
a9913044
RD
1688 resume= [SWSUSP]
1689 Specify the partition device for software suspend
1da177e4 1690
ecbd0da1
RW
1691 resume_offset= [SWSUSP]
1692 Specify the offset from the beginning of the partition
1693 given by "resume=" at which the swap header is located,
1694 in <PAGE_SIZE> units (needed only for swap files).
1695 See Documentation/power/swsusp-and-swap-files.txt
1696
0a7b35cb
MN
1697 retain_initrd [RAM] Keep initrd memory after extraction
1698
1da177e4
LT
1699 rhash_entries= [KNL,NET]
1700 Set number of hash buckets for route cache
1701
1702 riscom8= [HW,SERIAL]
1703 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1704
1705 ro [KNL] Mount root device read-only on boot
1706
1707 root= [KNL] Root filesystem
1708
1709 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1710 mount the root filesystem
1711
1712 rootflags= [KNL] Set root filesystem mount option string
1713
1714 rootfstype= [KNL] Set root filesystem type
1715
cc1ed754
PO
1716 rootwait [KNL] Wait (indefinitely) for root device to show up.
1717 Useful for devices that are detected asynchronously
1718 (e.g. USB and MMC devices).
1719
20510f2f
JM
1720 root_plug.vendor_id=
1721 [ROOTPLUG] Override the default vendor ID
1722
1723 root_plug.product_id=
1724 [ROOTPLUG] Override the default product ID
1725
1726 root_plug.debug=
1727 [ROOTPLUG] Enable debugging output
1728
1da177e4
LT
1729 rw [KNL] Mount root device read-write on boot
1730
1731 S [KNL] Run init in single mode
1732
1733 sa1100ir [NET]
1734 See drivers/net/irda/sa1100_ir.c.
1735
1da177e4 1736 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1737
1da177e4
LT
1738 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1739 Format: <io>[,<timeout>[,<isapnp>]]
1740
1741 scsi_debug_*= [SCSI]
1742 See drivers/scsi/scsi_debug.c.
1743
1744 scsi_default_dev_flags=
1745 [SCSI] SCSI default device flags
1746 Format: <integer>
1747
1748 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1749 Format: <vendor>:<model>:<flags>
1750 (flags are integer value)
1751
6af6632a
RD
1752 scsi_logging_level= [SCSI] a bit mask of logging levels
1753 See drivers/scsi/scsi_logging.h for bits. Also
1754 settable via sysctl at dev.scsi.logging_level
1755 (/proc/sys/dev/scsi/logging_level).
1756 There is also a nice 'scsi_logging_level' script in the
1757 S390-tools package, available for download at
1758 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1759
3e082a91
MW
1760 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1761 discovered. async scans them in kernel threads,
1762 allowing boot to proceed. none ignores them, expecting
1763 user space to do the scan.
1764
1da177e4
LT
1765 selinux [SELINUX] Disable or enable SELinux at boot time.
1766 Format: { "0" | "1" }
1767 See security/selinux/Kconfig help text.
1768 0 -- disable.
1769 1 -- enable.
1770 Default value is set via kernel config option.
1771 If enabled at boot time, /selinux/disable can be used
1772 later to disable prior to initial policy load.
1773
4e5ab4cb
JM
1774 selinux_compat_net =
1775 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1776 Format: { "0" | "1" }
1777 0 -- use new secmark-based packet controls
1778 1 -- use legacy packet controls
1779 Default value is 0 (preferred).
1780 Value can be changed at runtime via
1781 /selinux/compat_net.
4e5ab4cb 1782
cd4f0ef7 1783 serialnumber [BUGS=X86-32]
1da177e4 1784
1da177e4
LT
1785 shapers= [NET]
1786 Maximal number of shapers.
a9913044 1787
1da177e4
LT
1788 sim710= [SCSI,HW]
1789 See header of drivers/scsi/sim710.c.
1790
1791 simeth= [IA-64]
1792 simscsi=
a9913044 1793
1da177e4
LT
1794 slram= [HW,MTD]
1795
f0630fff
CL
1796 slub_debug[=options[,slabs]] [MM, SLUB]
1797 Enabling slub_debug allows one to determine the
1798 culprit if slab objects become corrupted. Enabling
1799 slub_debug can create guard zones around objects and
1800 may poison objects when not in use. Also tracks the
1801 last alloc / free. For more information see
1802 Documentation/vm/slub.txt.
c1aee215
CL
1803
1804 slub_max_order= [MM, SLUB]
f0630fff
CL
1805 Determines the maximum allowed order for slabs.
1806 A high setting may cause OOMs due to memory
1807 fragmentation. For more information see
1808 Documentation/vm/slub.txt.
c1aee215
CL
1809
1810 slub_min_objects= [MM, SLUB]
f0630fff
CL
1811 The minimum number of objects per slab. SLUB will
1812 increase the slab order up to slub_max_order to
1813 generate a sufficiently large slab able to contain
1814 the number of objects indicated. The higher the number
1815 of objects the smaller the overhead of tracking slabs
1816 and the less frequently locks need to be acquired.
c1aee215
CL
1817 For more information see Documentation/vm/slub.txt.
1818
1819 slub_min_order= [MM, SLUB]
1820 Determines the mininum page order for slabs. Must be
f0630fff 1821 lower than slub_max_order.
c1aee215
CL
1822 For more information see Documentation/vm/slub.txt.
1823
1824 slub_nomerge [MM, SLUB]
f0630fff 1825 Disable merging of slabs with similar size. May be
c1aee215 1826 necessary if there is some reason to distinguish
f0630fff
CL
1827 allocs to different slabs. Debug options disable
1828 merging on their own.
c1aee215
CL
1829 For more information see Documentation/vm/slub.txt.
1830
1da177e4
LT
1831 smart2= [HW]
1832 Format: <io1>[,<io2>[,...,<io8>]]
1833
cd4f0ef7 1834 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1835 attempt to substitute SMP alternatives once at boot.
1836
d0d4f69b
BH
1837 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1838 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1839 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1840 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1841 smsc-ircc2.ircc_irq= [HW] IRQ line
1842 smsc-ircc2.ircc_dma= [HW] DMA channel
1843 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1844 0: Toshiba Satellite 1800 (GP data pin select)
1845 1: Fast pin select (default)
1846 2: ATC IRMode
1847
1da177e4
LT
1848 snd-ad1816a= [HW,ALSA]
1849
1850 snd-ad1848= [HW,ALSA]
1851
1852 snd-ali5451= [HW,ALSA]
1853
1854 snd-als100= [HW,ALSA]
1855
1856 snd-als4000= [HW,ALSA]
1857
1858 snd-azt2320= [HW,ALSA]
1859
1860 snd-cmi8330= [HW,ALSA]
1861
1862 snd-cmipci= [HW,ALSA]
1863
1864 snd-cs4231= [HW,ALSA]
1865
1866 snd-cs4232= [HW,ALSA]
1867
1868 snd-cs4236= [HW,ALSA]
1869
1870 snd-cs4281= [HW,ALSA]
1871
1872 snd-cs46xx= [HW,ALSA]
1873
1874 snd-dt019x= [HW,ALSA]
1875
1876 snd-dummy= [HW,ALSA]
1877
1878 snd-emu10k1= [HW,ALSA]
1879
1880 snd-ens1370= [HW,ALSA]
1881
1882 snd-ens1371= [HW,ALSA]
1883
1884 snd-es968= [HW,ALSA]
1885
1886 snd-es1688= [HW,ALSA]
1887
1888 snd-es18xx= [HW,ALSA]
1889
1890 snd-es1938= [HW,ALSA]
1891
1892 snd-es1968= [HW,ALSA]
1893
1894 snd-fm801= [HW,ALSA]
1895
1896 snd-gusclassic= [HW,ALSA]
1897
1898 snd-gusextreme= [HW,ALSA]
1899
1900 snd-gusmax= [HW,ALSA]
1901
1902 snd-hdsp= [HW,ALSA]
1903
1904 snd-ice1712= [HW,ALSA]
1905
1906 snd-intel8x0= [HW,ALSA]
1907
1908 snd-interwave= [HW,ALSA]
1909
1910 snd-interwave-stb=
1911 [HW,ALSA]
1912
1913 snd-korg1212= [HW,ALSA]
1914
1915 snd-maestro3= [HW,ALSA]
1916
1917 snd-mpu401= [HW,ALSA]
1918
1919 snd-mtpav= [HW,ALSA]
1920
1921 snd-nm256= [HW,ALSA]
1922
1923 snd-opl3sa2= [HW,ALSA]
1924
1925 snd-opti92x-ad1848=
1926 [HW,ALSA]
1927
1928 snd-opti92x-cs4231=
1929 [HW,ALSA]
1930
1931 snd-opti93x= [HW,ALSA]
1932
1933 snd-pmac= [HW,ALSA]
1934
1935 snd-rme32= [HW,ALSA]
1936
1937 snd-rme96= [HW,ALSA]
1938
1939 snd-rme9652= [HW,ALSA]
1940
1941 snd-sb8= [HW,ALSA]
1942
1943 snd-sb16= [HW,ALSA]
1944
1945 snd-sbawe= [HW,ALSA]
1946
1947 snd-serial= [HW,ALSA]
1948
1949 snd-sgalaxy= [HW,ALSA]
1950
1951 snd-sonicvibes= [HW,ALSA]
1952
1953 snd-sun-amd7930=
1954 [HW,ALSA]
1955
1956 snd-sun-cs4231= [HW,ALSA]
1957
1958 snd-trident= [HW,ALSA]
1959
1960 snd-usb-audio= [HW,ALSA,USB]
1961
1962 snd-via82xx= [HW,ALSA]
1963
1964 snd-virmidi= [HW,ALSA]
1965
1966 snd-wavefront= [HW,ALSA]
1967
1968 snd-ymfpci= [HW,ALSA]
a9913044 1969
1da177e4
LT
1970 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1971 See Documentation/sonypi.txt
1972
1973 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1974 See Documentation/specialix.txt.
1975
1976 spia_io_base= [HW,MTD]
1977 spia_fio_base=
1978 spia_pedr=
1979 spia_peddr=
1980
1981 sscape= [HW,OSS]
1982 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1983
1da177e4
LT
1984 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1985 See Documentation/scsi/st.txt.
1986
1da177e4
LT
1987 sti= [PARISC,HW]
1988 Format: <num>
1989 Set the STI (builtin display/keyboard on the HP-PARISC
1990 machines) console (graphic card) which should be used
1991 as the initial boot-console.
1992 See also comment in drivers/video/console/sticore.c.
1993
1994 sti_font= [HW]
1995 See comment in drivers/video/console/sticore.c.
1996
1997 stifb= [HW]
1998 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1999
42a7fc4a
GB
2000 sunrpc.pool_mode=
2001 [NFS]
2002 Control how the NFS server code allocates CPUs to
2003 service thread pools. Depending on how many NICs
2004 you have and where their interrupts are bound, this
2005 option will affect which CPUs will do NFS serving.
2006 Note: this parameter cannot be changed while the
2007 NFS server is running.
2008
2009 auto the server chooses an appropriate mode
2010 automatically using heuristics
2011 global a single global pool contains all CPUs
2012 percpu one pool for each CPU
2013 pernode one pool for each NUMA node (equivalent
2014 to global on non-NUMA machines)
2015
1da177e4 2016 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2017
1da177e4
LT
2018 switches= [HW,M68k]
2019
2020 sym53c416= [HW,SCSI]
2021 See header of drivers/scsi/sym53c416.c.
2022
5d6f647f
IM
2023 sysrq_always_enabled
2024 [KNL]
2025 Ignore sysrq setting - this boot parameter will
2026 neutralize any effect of /proc/sys/kernel/sysrq.
2027 Useful for debugging.
2028
1da177e4
LT
2029 t128= [HW,SCSI]
2030 See header of drivers/scsi/t128.c.
2031
2032 tdfx= [HW,DRM]
2033
2034 thash_entries= [KNL,NET]
2035 Set number of hash buckets for TCP connection
2036
f8707ec9
LB
2037 thermal.act= [HW,ACPI]
2038 -1: disable all active trip points in all thermal zones
2039 <degrees C>: override all lowest active trip points
2040
c52a7419
LB
2041 thermal.crt= [HW,ACPI]
2042 -1: disable all critical trip points in all thermal zones
2043 <degrees C>: lower all critical trip points
2044
f5487145
LB
2045 thermal.nocrt= [HW,ACPI]
2046 Set to disable actions on ACPI thermal zone
2047 critical and hot trip points.
2048
72b33ef8
LB
2049 thermal.off= [HW,ACPI]
2050 1: disable ACPI thermal control
2051
a70cdc52
LB
2052 thermal.psv= [HW,ACPI]
2053 -1: disable all passive trip points
2054 <degrees C>: override all passive trip points to this value
2055
730ff34d
LB
2056 thermal.tzp= [HW,ACPI]
2057 Specify global default ACPI thermal zone polling rate
2058 <deci-seconds>: poll all this frequency
2059 0: no polling (default)
2060
1da177e4
LT
2061 tipar.timeout= [HW,PPT]
2062 Set communications timeout in tenths of a second
2063 (default 15).
2064
2065 tipar.delay= [HW,PPT]
2066 Set inter-bit delay in microseconds (default 10).
2067
1da177e4
LT
2068 tmscsim= [HW,SCSI]
2069 See comment before function dc390_setup() in
2070 drivers/scsi/tmscsim.c.
2071
2072 tp720= [HW,PS2]
2073
2074 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2075 Format:
2076 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2077
a9913044
RD
2078 turbografx.map[2|3]= [HW,JOY]
2079 TurboGraFX parallel port interface
2080 Format:
2081 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2082 See also Documentation/input/joystick-parport.txt
2083
2084 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2085 See header of drivers/scsi/u14-34f.c.
2086
2087 uart401= [HW,OSS]
2088 Format: <io>,<irq>
2089
2090 uart6850= [HW,OSS]
2091 Format: <io>,<irq>
2092
5f8364b7
AS
2093 uhci-hcd.ignore_oc=
2094 [USB] Ignore overcurrent events (default N).
2095 Some badly-designed motherboards generate lots of
2096 bogus events, for ports that aren't wired to
2097 anything. Set this parameter to avoid log spamming.
2098 Note that genuine overcurrent events won't be
2099 reported either.
2100
b5e795f8
AS
2101 usbcore.autosuspend=
2102 [USB] The autosuspend time delay (in seconds) used
2103 for newly-detected USB devices (default 2). This
2104 is the time required before an idle device will be
2105 autosuspended. Devices for which the delay is set
eaafbc3a 2106 to a negative value won't be autosuspended at all.
b5e795f8 2107
1da177e4
LT
2108 usbhid.mousepoll=
2109 [USBHID] The interval which mice are to be polled at.
a9913044 2110
cd4f0ef7 2111 vdso= [X86-32,SH,x86-64]
1dbf527c 2112 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2113 vdso=1: enable VDSO (default)
2114 vdso=0: disable VDSO mapping
2115
af65d648
RM
2116 vdso32= [X86-32,X86-64]
2117 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2118 vdso32=1: enable 32-bit VDSO (default)
2119 vdso32=0: disable 32-bit VDSO mapping
2120
d080d397
YI
2121 vector= [IA-64,SMP]
2122 vector=percpu: enable percpu vector domain
2123
1da177e4
LT
2124 video= [FB] Frame buffer configuration
2125 See Documentation/fb/modedb.txt.
2126
cd4f0ef7 2127 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2128 See Documentation/i386/boot.txt and
2129 Documentation/svga.txt.
1da177e4
LT
2130 Use vga=ask for menu.
2131 This is actually a boot loader parameter; the value is
2132 passed to the kernel using a special protocol.
2133
a9913044 2134 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2135 size of <nn>. This can be used to increase the
2136 minimum size (128MB on x86). It can also be used to
2137 decrease the size and leave more room for directly
2138 mapped kernel RAM.
2139
585c3047
PO
2140 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2141 Format: <command>
1da177e4 2142
585c3047
PO
2143 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2144 Format: <command>
2145
2146 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2147 Format: <command>
a9913044 2148
1da177e4
LT
2149 waveartist= [HW,OSS]
2150 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2151
1da177e4
LT
2152 wd33c93= [HW,SCSI]
2153 See header of drivers/scsi/wd33c93.c.
2154
2155 wd7000= [HW,SCSI]
2156 See header of drivers/scsi/wd7000.c.
2157
2158 wdt= [WDT] Watchdog
8dfe9c21 2159 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2160
2161 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2162 xd_geo= See header of drivers/block/xd.c.
2163
2164 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2165 Format:
2166 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2167
a62eaf15
AK
2168 norandmaps Don't use address space randomization
2169 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2170
a9913044 2171______________________________________________________________________
1da177e4
LT
2172
2173TODO:
2174
2175 Add documentation for ALSA options.
2176 Add more DRM drivers.