x86: move mp_bus_id_to_node to numa.c
[GitHub/mt8127/android_kernel_alcatel_ttab.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
20510f2f
JM
369 capability.disable=
370 [SECURITY] Disable capabilities. This would normally
371 be used only if an alternative security model is to be
372 configured. Potentially dangerous and should only be
373 used if you are entirely sure of the consequences.
374
14ff56bb
SO
375 ccw_timeout_log [S390]
376 See Documentation/s390/CommonIO for details.
1da177e4 377
8bab8dde
PM
378 cgroup_disable= [KNL] Disable a particular controller
379 Format: {name of the controller(s) to disable}
380 {Currently supported controllers - "memory"}
381
1da177e4
LT
382 checkreqprot [SELINUX] Set initial checkreqprot flag value.
383 Format: { "0" | "1" }
384 See security/selinux/Kconfig help text.
a9913044
RD
385 0 -- check protection applied by kernel (includes
386 any implied execute protection).
1da177e4
LT
387 1 -- check protection requested by application.
388 Default value is set via a kernel config option.
a9913044
RD
389 Value can be changed at runtime via
390 /selinux/checkreqprot.
391
661ca0da
SO
392 cio_ignore= [S390]
393 See Documentation/s390/CommonIO for details.
394
395 cio_msg= [S390]
396 See Documentation/s390/CommonIO for details.
397
cd4f0ef7 398 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 399 [Deprecated]
3f6dee9b 400 Forces specified clocksource (if available) to be used
734efb46 401 when calculating gettimeofday(). If specified
3f6dee9b 402 clocksource is not available, it defaults to PIT.
1da177e4
LT
403 Format: { pit | tsc | cyclone | pmtmr }
404
3d6ac984
RD
405 clocksource= [GENERIC_TIME] Override the default clocksource
406 Format: <string>
407 Override the default clocksource and use the clocksource
408 with the name specified.
409 Some clocksource names to choose from, depending on
410 the platform:
411 [all] jiffies (this is the base, fallback clocksource)
412 [ACPI] acpi_pm
413 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
414 pxa_timer,timer3,32k_counter,timer0_1
415 [AVR32] avr32
cd4f0ef7 416 [X86-32] pit,hpet,tsc,vmi-timer;
3d6ac984
RD
417 scx200_hrt on Geode; cyclone on IBM x440
418 [MIPS] MIPS
419 [PARISC] cr16
420 [S390] tod
421 [SH] SuperH
422 [SPARC64] tick
423 [X86-64] hpet,tsc
424
ac72e788
AK
425 clearcpuid=BITNUM [X86]
426 Disable CPUID feature X for the kernel. See
427 include/asm-x86/cpufeature.h for the valid bit numbers.
428 Note the Linux specific bits are not necessarily
429 stable over kernel options, but the vendor specific
430 ones should be.
431 Also note that user programs calling CPUID directly
432 or using the feature without checking anything
433 will still see it. This just prevents it from
434 being used by the kernel or shown in /proc/cpuinfo.
435 Also note the kernel might malfunction if you disable
436 some critical bits.
437
a25bd949
AV
438 code_bytes [IA32/X86_64] How many bytes of object code to print
439 in an oops report.
86c41837
CE
440 Range: 0 - 8192
441 Default: 64
442
f9262c12
AK
443 disable_8254_timer
444 enable_8254_timer
445 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
446 over the 8254 in addition to over the IO-APIC. The
447 kernel tries to set a sensible default.
448
b17530bd
TG
449 hpet= [X86-32,HPET] option to control HPET usage
450 Format: { enable (default) | disable | force }
451 disable: disable HPET and use PIT instead
d79a5f80
CC
452 force: allow force enabled of undocumented chips (ICH4,
453 VIA, nVidia)
1da177e4 454
1da177e4 455 com20020= [HW,NET] ARCnet - COM20020 chipset
a9913044
RD
456 Format:
457 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
1da177e4
LT
458
459 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
460 Format: <io>[,<irq>]
461
a9913044
RD
462 com90xx= [HW,NET]
463 ARCnet - COM90xx chipset (memory-mapped buffers)
1da177e4
LT
464 Format: <io>[,<irq>[,<memstart>]]
465
466 condev= [HW,S390] console device
467 conmode=
a9913044 468
1da177e4
LT
469 console= [KNL] Output console device and options.
470
471 tty<n> Use the virtual console device <n>.
472
473 ttyS<n>[,options]
f1a1c2dc 474 ttyUSB0[,options]
1da177e4 475 Use the specified serial port. The options are of
f1a1c2dc
RD
476 the form "bbbbpnf", where "bbbb" is the baud rate,
477 "p" is parity ("n", "o", or "e"), "n" is number of
478 bits, and "f" is flow control ("r" for RTS or
479 omit it). Default is "9600n8".
480
481 See Documentation/serial-console.txt for more
482 information. See
483 Documentation/networking/netconsole.txt for an
484 alternative.
1da177e4 485
18a8bd94
YL
486 uart[8250],io,<addr>[,options]
487 uart[8250],mmio,<addr>[,options]
1da177e4
LT
488 Start an early, polled-mode console on the 8250/16550
489 UART at the specified I/O port or MMIO address,
490 switching to the matching ttyS device later. The
491 options are the same as for ttyS, above.
492
18a8bd94
YL
493 earlycon= [KNL] Output early console device and options.
494 uart[8250],io,<addr>[,options]
495 uart[8250],mmio,<addr>[,options]
496 Start an early, polled-mode console on the 8250/16550
497 UART at the specified I/O port or MMIO address.
498 The options are the same as for ttyS, above.
499
8f4ce8c3
AS
500 no_console_suspend
501 [HW] Never suspend the console
502 Disable suspending of consoles during suspend and
503 hibernate operations. Once disabled, debugging
504 messages can reach various consoles while the rest
505 of the system is being put to sleep (ie, while
506 debugging driver suspend/resume hooks). This may
507 not work reliably with all consoles, but is known
508 to work with serial and VGA consoles.
509
1da177e4 510 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
511 Format:
512 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 513
dc009d92
EB
514 crashkernel=nn[KMG]@ss[KMG]
515 [KNL] Reserve a chunk of physical memory to
516 hold a kernel to switch to with kexec on panic.
517
fb391599
BW
518 crashkernel=range1:size1[,range2:size2,...][@offset]
519 [KNL] Same as above, but depends on the memory
520 in the running system. The syntax of range is
521 start-[end] where start and end are both
522 a memory unit (amount[KMG]). See also
523 Documentation/kdump/kdump.txt for a example.
524
1da177e4
LT
525 cs4232= [HW,OSS]
526 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
527
528 cs89x0_dma= [HW,NET]
529 Format: <dma>
530
531 cs89x0_media= [HW,NET]
532 Format: { rj45 | aui | bnc }
a9913044 533
a9913044 534 dasd= [HW,NET]
1da177e4
LT
535 See header of drivers/s390/block/dasd_devmap.c.
536
537 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
538 (one device per port)
539 Format: <port#>,<type>
540 See also Documentation/input/joystick-parport.txt
541
542 debug [KNL] Enable kernel debugging (events log level).
543
cae2ed9a
IM
544 debug_locks_verbose=
545 [KNL] verbose self-tests
546 Format=<0|1>
547 Print debugging info while doing the locking API
548 self-tests.
549 We default to 0 (no extra messages), setting it to
550 1 will print _a lot_ more information - normally
551 only useful to kernel developers.
552
2d27a966 553 decnet.addr= [HW,NET]
1da177e4
LT
554 Format: <area>[,<node>]
555 See also Documentation/networking/decnet.txt.
556
ecb77fa9 557 vt.default_blu= [VT]
55ff9780
AD
558 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
559 Change the default blue palette of the console.
560 This is a 16-member array composed of values
561 ranging from 0-255.
562
ecb77fa9 563 vt.default_grn= [VT]
55ff9780
AD
564 Format: <green0>,<green1>,<green2>,...,<green15>
565 Change the default green palette of the console.
566 This is a 16-member array composed of values
567 ranging from 0-255.
568
ecb77fa9 569 vt.default_red= [VT]
55ff9780
AD
570 Format: <red0>,<red1>,<red2>,...,<red15>
571 Change the default red palette of the console.
572 This is a 16-member array composed of values
573 ranging from 0-255.
574
ecb77fa9
ST
575 vt.default_utf8=
576 [VT]
55ff9780
AD
577 Format=<0|1>
578 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
579 Default is 1, i.e. UTF-8 mode is enabled for all
580 newly opened terminals.
55ff9780 581
1da177e4
LT
582 dhash_entries= [KNL]
583 Set number of hash buckets for dentry cache.
a9913044 584
1da177e4
LT
585 digi= [HW,SERIAL]
586 IO parameters + enable/disable command.
587
588 digiepca= [HW,SERIAL]
589 See drivers/char/README.epca and
590 Documentation/digiepca.txt.
591
093af8d7 592 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
593 By default the kernel will trim any uncacheable
594 memory out of your available memory pool based on
595 MTRR settings. This parameter disables that behavior,
596 possibly causing your machine to run very slowly.
597
1da177e4
LT
598 dmasound= [HW,OSS] Sound subsystem buffers
599
600 dscc4.setup= [NET]
601
602 dtc3181e= [HW,SCSI]
603
0ae53640 604 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
605 earlyprintk=vga
606 earlyprintk=serial[,ttySn[,baudrate]]
607
a9913044 608 Append ",keep" to not disable it when the real console
1da177e4
LT
609 takes over.
610
611 Only vga or serial at a time, not both.
612
613 Currently only ttyS0 and ttyS1 are supported.
614
615 Interaction with the standard serial driver is not
616 very good.
617
618 The VGA output is eventually overwritten by the real
619 console.
620
621 eata= [HW,SCSI]
622
1da177e4
LT
623 edd= [EDD]
624 Format: {"of[f]" | "sk[ipmbr]"}
625 See comment in arch/i386/boot/edd.S
626
1da177e4
LT
627 eisa_irq_edge= [PARISC,HW]
628 See header of drivers/parisc/eisa.c.
629
cd4f0ef7 630 elanfreq= [X86-32]
1da177e4
LT
631 See comment before function elanfreq_setup() in
632 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
633
634 elevator= [IOSCHED]
16ab3adf 635 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
636 See Documentation/block/as-iosched.txt and
637 Documentation/block/deadline-iosched.txt for details.
638
cd4f0ef7 639 elfcorehdr= [X86-32, X86_64]
a9913044 640 Specifies physical address of start of kernel core
aac04b32
VG
641 image elf header. Generally kexec loader will
642 pass this option to capture kernel.
643 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
644
645 enforcing [SELINUX] Set initial enforcing status.
646 Format: {"0" | "1"}
647 See security/selinux/Kconfig help text.
648 0 -- permissive (log only, no denials).
649 1 -- enforcing (deny and log).
650 Default value is 0.
651 Value can be changed at runtime via /selinux/enforce.
652
1da177e4
LT
653 es1371= [HW,OSS]
654 Format: <spdif>,[<nomix>,[<amplifier>]]
655 See also header of sound/oss/es1371.c.
a9913044 656
1da177e4
LT
657 ether= [HW,NET] Ethernet cards parameters
658 This option is obsoleted by the "netdev=" option, which
659 has equivalent usage. See its documentation for details.
660
661 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
662 Format: <io>[,<irq>]
663
de1ba09b
AM
664 failslab=
665 fail_page_alloc=
666 fail_make_request=[KNL]
667 General fault injection mechanism.
668 Format: <interval>,<probability>,<space>,<times>
669 See also /Documentation/fault-injection/.
670
1da177e4
LT
671 fd_mcs= [HW,SCSI]
672 See header of drivers/scsi/fd_mcs.c.
673
674 fdomain= [HW,SCSI]
675 See header of drivers/scsi/fdomain.c.
676
677 floppy= [HW]
678 See Documentation/floppy.txt.
679
1da177e4
LT
680 gamecon.map[2|3]=
681 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
682 support via parallel port (up to 5 devices per port)
683 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
684 See also Documentation/input/joystick-parport.txt
685
686 gamma= [HW,DRM]
687
aaf23042
YL
688 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
689 Format: off | on
690 default: on
691
1da177e4
LT
692 gdth= [HW,SCSI]
693 See header of drivers/scsi/gdth.c.
694
695 gpt [EFI] Forces disk with valid GPT signature but
696 invalid Protective MBR to be treated as GPT.
697
1da177e4
LT
698 gvp11= [HW,SCSI]
699
700 hashdist= [KNL,NUMA] Large hashes allocated during boot
701 are distributed across NUMA nodes. Defaults on
702 for IA-64, off otherwise.
a9913044 703 Format: 0 | 1 (for off | on)
1da177e4
LT
704
705 hcl= [IA-64] SGI's Hardware Graph compatibility layer
706
707 hd= [EIDE] (E)IDE hard drive subsystem geometry
708 Format: <cyl>,<head>,<sect>
709
710 hd?= [HW] (E)IDE subsystem
1c10e938 711 hd?lun= See Documentation/ide/ide.txt.
1da177e4
LT
712
713 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
714 size of <nn>. This works even on boxes that have no
715 highmem otherwise. This also works to reduce highmem
716 size on bigger boxes.
717
54cdfdb4
TG
718 highres= [KNL] Enable/disable high resolution timer mode.
719 Valid parameters: "on", "off"
720 Default: "on"
721
1da177e4
LT
722 hisax= [HW,ISDN]
723 See Documentation/isdn/README.HiSax.
724
cd4f0ef7 725 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
4ec161cf 726 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
1da177e4 727
1da177e4 728 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
729 i8042.dumbkbd [HW] Pretend that controller can only read data from
730 keyboard and cannot control its state
1da177e4
LT
731 (Don't attempt to blink the leds)
732 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 733 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
734 i8042.noloop [HW] Disable the AUX Loopback command while probing
735 for the AUX port
1da177e4
LT
736 i8042.nomux [HW] Don't check presence of an active multiplexing
737 controller
738 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
739 controllers
740 i8042.panicblink=
741 [HW] Frequency with which keyboard LEDs should blink
742 when kernel panics (default is 0.5 sec)
743 i8042.reset [HW] Reset the controller during init and cleanup
744 i8042.unlock [HW] Unlock (ignore) the keylock
745
746 i810= [HW,DRM]
747
e70c9d5e
DT
748 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
749 indicates that the driver is running on unsupported
750 hardware.
1da177e4
LT
751 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
752 does not match list of supported models.
753 i8k.power_status
754 [HW] Report power status in /proc/i8k
755 (disabled by default)
756 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
757 capability is set.
758
759 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
760 See Documentation/mca.txt.
761
762 icn= [HW,ISDN]
763 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
764
765 ide= [HW] (E)IDE subsystem
766 Format: ide=nodma or ide=doubler or ide=reverse
1c10e938 767 See Documentation/ide/ide.txt.
1da177e4
LT
768
769 ide?= [HW] (E)IDE subsystem
770 Format: ide?=noprobe or chipset specific parameters.
1c10e938 771 See Documentation/ide/ide.txt.
a9913044 772
1da177e4 773 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 774 See Documentation/ide/ide.txt.
1da177e4 775
f039b754
AK
776 idle= [X86]
777 Format: idle=poll or idle=mwait
778 Poll forces a polling idle loop that can slightly improves the performance
779 of waking up a idle CPU, but will use a lot of power and make the system
780 run hot. Not recommended.
781 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
782 to not use it because it doesn't save as much power as a normal idle
783 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
784 as idle=poll.
a9913044 785
594765a7
DC
786 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
787 Claim all unknown PCI IDE storage controllers.
788
79290822
IM
789 ignore_loglevel [KNL]
790 Ignore loglevel setting - this will print /all/
791 kernel messages to the console. Useful for debugging.
792
1da177e4
LT
793 ihash_entries= [KNL]
794 Set number of hash buckets for inode cache.
795
796 in2000= [HW,SCSI]
797 See header of drivers/scsi/in2000.c.
798
799 init= [KNL]
800 Format: <full_path>
801 Run specified binary instead of /sbin/init as init
802 process.
803
804 initcall_debug [KNL] Trace initcalls as they are executed. Useful
805 for working out where the kernel is dying during
806 startup.
807
808 initrd= [BOOT] Specify the location of the initial ramdisk
809
810 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
811 Format: <irq>
812
813 inttest= [IA64]
814
ba395927
KA
815 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
816 off
817 Disable intel iommu driver.
818 igfx_off [Default Off]
819 By default, gfx is mapped as normal device. If a gfx
820 device has a dedicated DMAR unit, the DMAR unit is
821 bypassed by not enabling DMAR with this option. In
822 this case, gfx device will use physical address for
823 DMA.
7d3b03ce
KA
824 forcedac [x86_64]
825 With this option iommu will not optimize to look
826 for io virtual address below 32 bit forcing dual
827 address cycle on pci bus for cards supporting greater
828 than 32 bit addressing. The default is to look
829 for translation below 32 bit and if not available
830 then look in the higher range.
ba395927 831
b02aae9c 832 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
833 0x80
834 Standard port 0x80 based delay
835 0xed
836 Alternate port 0xed based delay (needed on some systems)
b02aae9c 837 udelay
6e7c4025
IM
838 Simple two microseconds delay
839 none
840 No delay
b02aae9c 841
1da177e4
LT
842 io7= [HW] IO7 for Marvel based alpha systems
843 See comment before marvel_specify_io7 in
844 arch/alpha/kernel/core_marvel.c.
845
846 ip= [IP_PNP]
6ded55da 847 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
848
849 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
850 See comment before ip2_setup() in
851 drivers/char/ip2/ip2base.c.
1da177e4
LT
852
853 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
854 See header of drivers/scsi/ips.c.
855
72c4a13a
SH
856 ports= [IP_VS_FTP] IPVS ftp helper module
857 Default is 21.
858 Up to 8 (IP_VS_APP_MAX_PORTS) ports
859 may be specified.
860 Format: <port>,<port>....
861
200803df
AC
862 irqfixup [HW]
863 When an interrupt is not handled search all handlers
864 for it. Intended to get systems with badly broken
865 firmware running.
866
867 irqpoll [HW]
868 When an interrupt is not handled search all handlers
869 for it. Also check all handlers each timer
870 interrupt. Intended to get systems with badly broken
871 firmware running.
872
1da177e4 873 isapnp= [ISAPNP]
a9913044 874 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
875
876 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
877 Format:
878 <cpu number>,...,<cpu number>
879 or
880 <cpu number>-<cpu number> (must be a positive range in ascending order)
881 or a mixture
882 <cpu number>,...,<cpu number>-<cpu number>
1da177e4
LT
883 This option can be used to specify one or more CPUs
884 to isolate from the general SMP balancing and scheduling
885 algorithms. The only way to move a process onto or off
886 an "isolated" CPU is via the CPU affinity syscalls.
887 <cpu number> begins at 0 and the maximum value is
888 "number of CPUs in system - 1".
889
890 This option is the preferred way to isolate CPUs. The
a9913044
RD
891 alternative -- manually setting the CPU mask of all
892 tasks in the system -- can cause problems and
893 suboptimal load balancer performance.
1da177e4 894
a9913044 895 iucv= [HW,NET]
1da177e4
LT
896
897 js= [HW,JOY] Analog joystick
898 See Documentation/input/joystick.txt.
899
cd4f0ef7 900 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
901 specifies the amount of memory usable by the kernel
902 for non-movable allocations. The requested amount is
903 spread evenly throughout all nodes in the system. The
904 remaining memory in each node is used for Movable
905 pages. In the event, a node is too small to have both
906 kernelcore and Movable pages, kernelcore pages will
907 take priority and other nodes will have a larger number
908 of kernelcore pages. The Movable zone is used for the
909 allocation of pages that may be reclaimed or moved
910 by the page migration subsystem. This means that
911 HugeTLB pages may not be allocated from this zone.
912 Note that allocations like PTEs-from-HighMem still
913 use the HighMem zone if it exists, and the Normal
914 zone if it does not.
915
cd4f0ef7 916 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
917 is similar to kernelcore except it specifies the
918 amount of memory used for migratable allocations.
919 If both kernelcore and movablecore is specified,
920 then kernelcore will be at *least* the specified
921 value but may be more. If movablecore on its own
922 is specified, the administrator must be careful
923 that the amount of memory usable for all allocations
924 is not too small.
925
1da177e4
LT
926 keepinitrd [HW,ARM]
927
cd4f0ef7 928 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
929 in oops dumps.
930
931 l2cr= [PPC]
932
cd4f0ef7 933 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 934 disabled it.
1da177e4 935
cd4f0ef7 936 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
937 C2 power state.
938
fcb71f6f
FC
939 libata.dma= [LIBATA] DMA control
940 libata.dma=0 Disable all PATA and SATA DMA
941 libata.dma=1 PATA and SATA Disk DMA only
942 libata.dma=2 ATAPI (CDROM) DMA only
943 libata.dma=4 Compact Flash DMA only
944 Combinations also work, so libata.dma=3 enables DMA
945 for disks and CDROMs, but not CFs.
946
78e70c23
DJ
947 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
948 when set.
949 Format: <int>
950
33267325
TH
951 libata.force= [LIBATA] Force configurations. The format is comma
952 separated list of "[ID:]VAL" where ID is
953 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
954 matching port, link or device. Basically, it matches
955 the ATA ID string printed on console by libata. If
956 the whole ID part is omitted, the last PORT and DEVICE
957 values are used. If ID hasn't been specified yet, the
958 configuration applies to all ports, links and devices.
959
960 If only DEVICE is omitted, the parameter applies to
961 the port and all links and devices behind it. DEVICE
962 number of 0 either selects the first device or the
963 first fan-out link behind PMP device. It does not
964 select the host link. DEVICE number of 15 selects the
965 host link and device attached to it.
966
967 The VAL specifies the configuration to force. As long
968 as there's no ambiguity shortcut notation is allowed.
969 For example, both 1.5 and 1.5G would work for 1.5Gbps.
970 The following configurations can be forced.
971
972 * Cable type: 40c, 80c, short40c, unk, ign or sata.
973 Any ID with matching PORT is used.
974
975 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
976
977 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
978 udma[/][16,25,33,44,66,100,133] notation is also
979 allowed.
980
981 * [no]ncq: Turn on or off NCQ.
982
983 If there are multiple matching configurations changing
984 the same attribute, the last one is used.
985
1da177e4
LT
986 load_ramdisk= [RAM] List of ramdisks to load from floppy
987 See Documentation/ramdisk.txt.
988
a6b25b67
RD
989 lockd.nlm_grace_period=P [NFS] Assign grace period.
990 Format: <integer>
1da177e4 991
a6b25b67
RD
992 lockd.nlm_tcpport=N [NFS] Assign TCP port.
993 Format: <integer>
994
995 lockd.nlm_timeout=T [NFS] Assign timeout value.
996 Format: <integer>
997
998 lockd.nlm_udpport=M [NFS] Assign UDP port.
999 Format: <integer>
1da177e4
LT
1000
1001 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1002 Format: <irq>
1003
1004 loglevel= All Kernel Messages with a loglevel smaller than the
1005 console loglevel will be printed to the console. It can
1006 also be changed with klogd or other programs. The
1007 loglevels are defined as follows:
1008
1009 0 (KERN_EMERG) system is unusable
1010 1 (KERN_ALERT) action must be taken immediately
1011 2 (KERN_CRIT) critical conditions
1012 3 (KERN_ERR) error conditions
1013 4 (KERN_WARNING) warning conditions
1014 5 (KERN_NOTICE) normal but significant condition
1015 6 (KERN_INFO) informational
1016 7 (KERN_DEBUG) debug-level messages
1017
1018 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1019 Format: { n | nk | nM }
1020 n must be a power of two. The default size
1021 is set in the kernel config file.
1da177e4 1022
accaa24c
RD
1023 logo.nologo [FB] Disables display of the built-in Linux logo.
1024 This may be used to provide more screen space for
1025 kernel log messages and is useful when debugging
1026 kernel boot problems.
1027
1da177e4
LT
1028 lp=0 [LP] Specify parallel ports to use, e.g,
1029 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1030 lp=reset first parallel port). 'lp=0' disables the
1031 lp=auto printer driver. 'lp=reset' (which can be
1032 specified in addition to the ports) causes
1033 attached printers to be reset. Using
1034 lp=port1,port2,... specifies the parallel ports
1035 to associate lp devices with, starting with
1036 lp0. A port specification may be 'none' to skip
1037 that lp device, or a parport name such as
1038 'parport0'. Specifying 'lp=auto' instead of a
1039 port specification list means that device IDs
1040 from each port should be examined, to see if
1041 an IEEE 1284-compliant printer is attached; if
1042 so, the driver will manage that printer.
1043 See also header of drivers/char/lp.c.
1044
1045 lpj=n [KNL]
1046 Sets loops_per_jiffy to given constant, thus avoiding
1047 time-consuming boot-time autodetection (up to 250 ms per
1048 CPU). 0 enables autodetection (default). To determine
1049 the correct value for your kernel, boot with normal
1050 autodetection and see what value is printed. Note that
1051 on SMP systems the preset will be applied to all CPUs,
1052 which is likely to cause problems if your CPUs need
1053 significantly divergent settings. An incorrect value
1054 will cause delays in the kernel to be wrong, leading to
1055 unpredictable I/O errors and other breakage. Although
1056 unlikely, in the extreme case this might damage your
1057 hardware.
1058
1059 ltpc= [NET]
1060 Format: <io>,<irq>,<dma>
1061
a9913044
RD
1062 mac5380= [HW,SCSI] Format:
1063 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1064
a9913044
RD
1065 mac53c9x= [HW,SCSI] Format:
1066 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1067
a9913044
RD
1068 machvec= [IA64] Force the use of a particular machine-vector
1069 (machvec) in a generic kernel.
1070 Example: machvec=hpzx1_swiotlb
1da177e4 1071
a9913044 1072 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1073 be mounted
1074 Format: <1-256>
1075
1076 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1077 should make use of. maxcpus=n : n >= 0 limits the
1078 kernel to using 'n' processors. n=0 is a special case,
1079 it is equivalent to "nosmp", which also disables
1080 the IO APIC.
1da177e4 1081
2b2c3750
BP
1082 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1083 equal to this physical address is ignored.
1084
a9913044 1085 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1086 Should be between 1 and 2^32-1.
1087
1088 max_report_luns=
a9913044 1089 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1090 Should be between 1 and 16384.
1091
1da177e4
LT
1092 mcatest= [IA-64]
1093
cd4f0ef7 1094 mce [X86-32] Machine Check Exception
1da177e4 1095
909dd324
AK
1096 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1097
1da177e4
LT
1098 md= [HW] RAID subsystems devices and level
1099 See Documentation/md.txt.
a9913044 1100
1da177e4
LT
1101 mdacon= [MDA]
1102 Format: <first>,<last>
1103 Specifies range of consoles to be captured by the MDA.
a9913044 1104
1da177e4
LT
1105 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1106 Amount of memory to be used when the kernel is not able
1107 to see the whole system memory or for test.
cd4f0ef7 1108 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1109 address space collisions. Without memmap= PCI devices
1110 could be placed at addresses belonging to unused RAM.
1111
cd4f0ef7 1112 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1113 memory.
1114
cd4f0ef7 1115 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1116 E820 memory map, as specified by the user.
1117 Such memmap=exactmap lines can be constructed based on
1118 BIOS output or other requirements. See the memmap=nn@ss
1119 option description.
1120
1121 memmap=nn[KMG]@ss[KMG]
1122 [KNL] Force usage of a specific region of memory
1123 Region of memory to be used, from ss to ss+nn.
1124
1125 memmap=nn[KMG]#ss[KMG]
1126 [KNL,ACPI] Mark specific memory as ACPI data.
1127 Region of memory to be used, from ss to ss+nn.
1128
1129 memmap=nn[KMG]$ss[KMG]
1130 [KNL,ACPI] Mark specific memory as reserved.
1131 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1132 Example: Exclude memory from 0x18690000-0x1869ffff
1133 memmap=64K$0x18690000
1134 or
1135 memmap=0x10000$0x18690000
1da177e4
LT
1136
1137 meye.*= [HW] Set MotionEye Camera parameters
1138 See Documentation/video4linux/meye.txt.
1139
8f36881b
AS
1140 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1141 Multi-Function General Purpose Timers on AMD Geode
1142 platforms.
1143
e6c4dc6c
WT
1144 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1145 the BIOS has incorrectly applied a workaround. TinyBIOS
1146 version 0.98 is known to be affected, 0.99 fixes the
1147 problem by letting the user disable the workaround.
1148
1da177e4
LT
1149 mga= [HW,DRM]
1150
1151 mousedev.tap_time=
1152 [MOUSE] Maximum time between finger touching and
1153 leaving touchpad surface for touch to be considered
1154 a tap and be reported as a left button click (for
1155 touchpads working in absolute mode only).
1156 Format: <msecs>
1157 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1158 reporting absolute coordinates, such as tablets
1159 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1160 reporting absolute coordinates, such as tablets
1161
1162 mpu401= [HW,OSS]
1163 Format: <io>,<irq>
1164
1165 MTD_Partition= [MTD]
1166 Format: <name>,<region-number>,<size>,<offset>
1167
a9913044
RD
1168 MTD_Region= [MTD] Format:
1169 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1170
1171 mtdparts= [MTD]
c8facbb6 1172 See drivers/mtd/cmdlinepart.c.
1da177e4
LT
1173
1174 mtouchusb.raw_coordinates=
a9913044
RD
1175 [HW] Make the MicroTouch USB driver use raw coordinates
1176 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1177
1178 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1179
1180 NCR_D700= [HW,SCSI]
1181 See header of drivers/scsi/NCR_D700.c.
1182
1183 ncr5380= [HW,SCSI]
1184
1185 ncr53c400= [HW,SCSI]
1186
1187 ncr53c400a= [HW,SCSI]
1188
1189 ncr53c406a= [HW,SCSI]
1190
1191 ncr53c8xx= [HW,SCSI]
1192
1193 netdev= [NET] Network devices parameters
1194 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1195 Note that mem_start is often overloaded to mean
1196 something different and driver-specific.
a9913044
RD
1197 This usage is only documented in each driver source
1198 file if at all.
1199
1da177e4 1200 nfsaddrs= [NFS]
6ded55da 1201 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1202
1203 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1204 See Documentation/filesystems/nfsroot.txt.
1da177e4 1205
a72b4422
TM
1206 nfs.callback_tcpport=
1207 [NFS] set the TCP port on which the NFSv4 callback
1208 channel should listen.
1209
58df095b
TM
1210 nfs.idmap_cache_timeout=
1211 [NFS] set the maximum lifetime for idmapper cache
1212 entries.
1213
f43bf0be
TM
1214 nfs.enable_ino64=
1215 [NFS] enable 64-bit inode numbers.
1216 If zero, the NFS client will fake up a 32-bit inode
1217 number for the readdir() and stat() syscalls instead
1218 of returning the full 64-bit number.
1219 The default is to return 64-bit inode numbers.
1220
e7ba176b
HS
1221 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1222 when a NMI is triggered.
1223 Format: [state][,regs][,debounce][,die]
1224
cd4f0ef7 1225 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1226
cd4f0ef7 1227 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1228 emulation library even if a 387 maths coprocessor
1229 is present.
1230
c1aee215
CL
1231 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1232 caches in the slab allocator. Saves per-node memory,
1233 but will impact performance.
3395ee05 1234
a9913044
RD
1235 noalign [KNL,ARM]
1236
1da177e4
LT
1237 noapic [SMP,APIC] Tells the kernel to not make use of any
1238 IOAPICs that may be present in the system.
1239
1da177e4
LT
1240 nobats [PPC] Do not use BATs for mapping kernel lowmem
1241 on "Classic" PPC cores.
1242
1243 nocache [ARM]
a9913044 1244
163ecdff
SN
1245 nodelayacct [KNL] Disable per-task delay accounting
1246
1da177e4
LT
1247 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1248
8b2cb7a8
HY
1249 noefi [X86-32,X86-64] Disable EFI runtime services support.
1250
1da177e4
LT
1251 noexec [IA-64]
1252
cd4f0ef7 1253 noexec [X86-32,X86-64]
1da177e4
LT
1254 noexec=on: enable non-executable mappings (default)
1255 noexec=off: disable nn-executable mappings
1256
cd4f0ef7 1257 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1258 register save and restore. The kernel will only save
1259 legacy floating-point registers on task switch.
1da177e4 1260
191679fd
AK
1261 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1262
1da177e4 1263 nohlt [BUGS=ARM]
a9913044 1264
cd4f0ef7 1265 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1266 instruction doesn't work correctly and not to
1267 use it.
1268
1269 nohalt [IA-64] Tells the kernel not to use the power saving
1270 function PAL_HALT_LIGHT when idle. This increases
1271 power-consumption. On the positive side, it reduces
1272 interrupt wake-up latency, which may improve performance
1273 in certain environments such as networked servers or
1274 real-time systems.
1275
79bf2bb3
TG
1276 nohz= [KNL] Boottime enable/disable dynamic ticks
1277 Valid arguments: on, off
1278 Default: on
1279
cd4f0ef7 1280 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
8542b200 1281
cd4f0ef7 1282 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1283 disable unhandled interrupt sources.
1284
cd4f0ef7 1285 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1286 broken timer IRQ sources.
1287
1da177e4
LT
1288 noisapnp [ISAPNP] Disables ISA PnP code.
1289
1290 noinitrd [RAM] Tells the kernel not to load any configured
1291 initial RAM disk.
1292
1293 nointroute [IA-64]
1294
0aa366f3
TL
1295 nojitter [IA64] Disables jitter checking for ITC timers.
1296
cd4f0ef7 1297 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1298
cd4f0ef7 1299 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1300
1da177e4
LT
1301 noltlbs [PPC] Do not use large page/tlb entries for kernel
1302 lowmem mapping on PPC40x.
1303
312f1f01
H
1304 nomca [IA-64] Disable machine check abort handling
1305
cd4f0ef7 1306 nomce [X86-32] Machine Check Exception
abe37e5a 1307
83d7384f
AS
1308 nomfgpt [X86-32] Disable Multi-Function General Purpose
1309 Timer usage (for AMD Geode machines).
1310
cd4f0ef7 1311 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1312
cd4f0ef7 1313 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1314 with UP alternatives
1315
1da177e4
LT
1316 noresidual [PPC] Don't use residual data on PReP machines.
1317
a9913044
RD
1318 noresume [SWSUSP] Disables resume and restores original swap
1319 space.
1320
1da177e4
LT
1321 no-scroll [VGA] Disables scrollback.
1322 This is required for the Braillex ib80-piezo Braille
1323 reader made by F.H. Papenmeier (Germany).
1324
1325 nosbagart [IA-64]
1326
cd4f0ef7 1327 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1328
61ec7567
LB
1329 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1330 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1331
97842216
DJ
1332 nosoftlockup [KNL] Disable the soft-lockup detector.
1333
1da177e4
LT
1334 nosync [HW,M68K] Disables sync negotiation for all devices.
1335
cd4f0ef7 1336 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1337
1338 nousb [USB] Disable the USB subsystem
1339
1340 nowb [ARM]
a9913044 1341
f0c0b2b8
KH
1342 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1343 one of ['zone', 'node', 'default'] can be specified
1344 This can be set from sysctl after boot.
1345 See Documentation/sysctl/vm.txt for details.
1346
a61c2d78
DJ
1347 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1348
1da177e4
LT
1349 opl3= [HW,OSS]
1350 Format: <io>
1351
1da177e4
LT
1352 oprofile.timer= [HW]
1353 Use timer interrupt instead of performance counters
1354
1da177e4
LT
1355 osst= [HW,SCSI] SCSI Tape Driver
1356 Format: <buffer_size>,<write_threshold>
1357 See also Documentation/scsi/st.txt.
1358
1359 panic= [KNL] Kernel behaviour on panic
1360 Format: <timeout>
1361
1362 parkbd.port= [HW] Parallel port number the keyboard adapter is
1363 connected to, default is 0.
1364 Format: <parport#>
1365 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1366 0 for XT, 1 for AT (default is AT).
a9913044
RD
1367 Format: <mode>
1368
1369 parport= [HW,PPT] Specify parallel ports. 0 disables.
1370 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1371 Use 'auto' to force the driver to use any
1372 IRQ/DMA settings detected (the default is to
1373 ignore detected IRQ/DMA settings because of
1374 possible conflicts). You can specify the base
1375 address, IRQ, and DMA settings; IRQ and DMA
1376 should be numbers, or 'auto' (for using detected
1377 settings on that particular port), or 'nofifo'
1378 (to avoid using a FIFO even if it is detected).
1379 Parallel ports are assigned in the order they
1380 are specified on the command line, starting
1381 with parport0.
1382
1383 parport_init_mode= [HW,PPT]
1384 Configure VIA parallel port to operate in
1385 a specific mode. This is necessary on Pegasos
1386 computer where firmware has no options for setting
1387 up parallel port mode and sets it to spp.
1388 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1389 Format: [spp|ps2|epp|ecp|ecpepp]
1390
a9913044
RD
1391 pas2= [HW,OSS] Format:
1392 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1393
1da177e4
LT
1394 pas16= [HW,SCSI]
1395 See header of drivers/scsi/pas16.c.
1396
dd287796
AM
1397 pause_on_oops=
1398 Halt all CPUs after the first oops has been printed for
1399 the specified number of seconds. This is to be used if
1400 your oopses keep scrolling off the screen.
1401
1da177e4
LT
1402 pcbit= [HW,ISDN]
1403
1404 pcd. [PARIDE]
1405 See header of drivers/block/paride/pcd.c.
1406 See also Documentation/paride.txt.
1407
a9913044 1408 pci=option[,option...] [PCI] various PCI subsystem options:
cd4f0ef7
AC
1409 off [X86-32] don't probe for the PCI bus
1410 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1411 the hardware directly. Use this if your machine
1412 has a non-standard PCI host bridge.
cd4f0ef7 1413 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1414 hardware access methods are allowed. Use this
1415 if you experience crashes upon bootup and you
1416 suspect they are caused by the BIOS.
cd4f0ef7 1417 conf1 [X86-32] Force use of PCI Configuration
a9913044 1418 Mechanism 1.
cd4f0ef7 1419 conf2 [X86-32] Force use of PCI Configuration
a9913044 1420 Mechanism 2.
7f785763
RD
1421 noaer [PCIE] If the PCIEAER kernel config parameter is
1422 enabled, this kernel boot option can be used to
1423 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1424 nodomains [PCI] Disable support for multiple PCI
1425 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1426 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1427 Configuration
309e57df
MW
1428 nomsi [MSI] If the PCI_MSI kernel config parameter is
1429 enabled, this kernel boot option can be used to
1430 disable the use of MSI interrupts system-wide.
cd4f0ef7 1431 nosort [X86-32] Don't sort PCI devices according to
a9913044
RD
1432 order given by the PCI BIOS. This sorting is
1433 done to get a device order compatible with
1434 older kernels.
cd4f0ef7 1435 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1436 routing table. These calls are known to be buggy
1437 on several machines and they hang the machine
1438 when used, but on other computers it's the only
1439 way to get the interrupt routing table. Try
1440 this option if the kernel is unable to allocate
1441 IRQs or discover secondary PCI buses on your
1442 motherboard.
cd4f0ef7 1443 rom [X86-32] Assign address space to expansion ROMs.
a9913044
RD
1444 Use with caution as certain devices share
1445 address decoders between ROMs and other
1446 resources.
cd4f0ef7 1447 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
a9913044
RD
1448 assigned automatically to PCI devices. You can
1449 make the kernel exclude IRQs of your ISA cards
1450 this way.
cd4f0ef7 1451 pirqaddr=0xAAAAA [X86-32] Specify the physical address
a9913044
RD
1452 of the PIRQ table (normally generated
1453 by the BIOS) if it is outside the
1454 F0000h-100000h range.
cd4f0ef7 1455 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
a9913044
RD
1456 useful if the kernel is unable to find your
1457 secondary buses and you want to tell it
1458 explicitly which ones they are.
cd4f0ef7 1459 assign-busses [X86-32] Always assign all PCI bus
a9913044
RD
1460 numbers ourselves, overriding
1461 whatever the firmware may have done.
cd4f0ef7 1462 usepirqmask [X86-32] Honor the possible IRQ mask stored
a9913044
RD
1463 in the BIOS $PIR table. This is needed on
1464 some systems with broken BIOSes, notably
1465 some HP Pavilion N5400 and Omnibook XE3
1466 notebooks. This will have no effect if ACPI
1467 IRQ routing is enabled.
cd4f0ef7 1468 noacpi [X86-32] Do not use ACPI for IRQ routing
a9913044 1469 or for PCI scanning.
62f420f8
GH
1470 use_crs [X86-32] Use _CRS for PCI resource
1471 allocation.
a9913044
RD
1472 routeirq Do IRQ routing for all PCI devices.
1473 This is normally done in pci_enable_device(),
1474 so this option is a temporary workaround
1475 for broken drivers that don't call it.
1476 firmware [ARM] Do not re-enumerate the bus but instead
1477 just use the configuration from the
1478 bootloader. This is currently used on
1479 IXP2000 systems where the bus has to be
1480 configured a certain way for adjunct CPUs.
0637a70a
AK
1481 noearly [X86] Don't do any early type 1 scanning.
1482 This might help on some broken boards which
1483 machine check when some devices' config space
1484 is read. But various workarounds are disabled
1485 and some IOMMU drivers will not work.
6b4b78fe
MD
1486 bfsort Sort PCI devices into breadth-first order.
1487 This sorting is done to get a device
1488 order compatible with older (<= 2.4) kernels.
1489 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1490 cbiosize=nn[KMG] The fixed amount of bus space which is
1491 reserved for the CardBus bridge's IO window.
1492 The default value is 256 bytes.
1493 cbmemsize=nn[KMG] The fixed amount of bus space which is
1494 reserved for the CardBus bridge's memory
1495 window. The default value is 64 megabytes.
6b4b78fe 1496
1da177e4
LT
1497 pcmv= [HW,PCMCIA] BadgePAD 4
1498
1499 pd. [PARIDE]
1500 See Documentation/paride.txt.
1501
1502 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1503 boot time.
1504 Format: { 0 | 1 }
1505 See arch/parisc/kernel/pdc_chassis.c
1506
1507 pf. [PARIDE]
1508 See Documentation/paride.txt.
1509
1510 pg. [PARIDE]
1511 See Documentation/paride.txt.
1512
1513 pirq= [SMP,APIC] Manual mp-table setup
1514 See Documentation/i386/IO-APIC.txt.
1515
1516 plip= [PPT,NET] Parallel port network link
1517 Format: { parport<nr> | timid | 0 }
1518 See also Documentation/parport.txt.
1519
1520 pnpacpi= [ACPI]
1521 { off }
1522
1523 pnpbios= [ISAPNP]
1524 { on | off | curr | res | no-curr | no-res }
1525
1526 pnp_reserve_irq=
1527 [ISAPNP] Exclude IRQs for the autoconfiguration
1528
1529 pnp_reserve_dma=
1530 [ISAPNP] Exclude DMAs for the autoconfiguration
1531
1532 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1533 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1534
1535 pnp_reserve_mem=
a9913044
RD
1536 [ISAPNP] Exclude memory regions for the
1537 autoconfiguration.
1da177e4
LT
1538 Ranges are in pairs (memory base and size).
1539
45807a1d
IM
1540 print-fatal-signals=
1541 [KNL] debug: print fatal signals
1542 print-fatal-signals=1: print segfault info to
1543 the kernel console.
1544 default: off.
1545
e84845c4
RD
1546 printk.time= Show timing data prefixed to each printk message line
1547 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1548
1da177e4 1549 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1550 Format: [schedule,]<number>
1551 Param: "schedule" - profile schedule points.
1552 Param: <number> - step/bucket size as a power of 2 for
1553 statistical time based profiling.
b3da2a73
MG
1554 Param: "sleep" - profile D-state sleeping (millisecs).
1555 Requires CONFIG_SCHEDSTATS
c0fe2e69 1556 Param: "kvm" - profile VM exits.
1da177e4 1557
a9913044 1558 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1559 Limit processor to maximum C-state
1560 max_cstate=9 overrides any DMI blacklist limit.
1561
41c0d868
LB
1562 processor.nocst [HW,ACPI]
1563 Ignore the _CST method to determine C-states,
1564 instead using the legacy FADT method
1565
1da177e4
LT
1566 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1567 before loading.
1568 See Documentation/ramdisk.txt.
1569
a9913044
RD
1570 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1571 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1572 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1573 per second.
a9913044
RD
1574 psmouse.resetafter= [HW,MOUSE]
1575 Try to reset the device after so many bad packets
1da177e4
LT
1576 (0 = never).
1577 psmouse.resolution=
1578 [HW,MOUSE] Set desired mouse resolution, in dpi.
1579 psmouse.smartscroll=
a9913044 1580 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1581 0 = disabled, 1 = enabled (default).
1582
1583 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1584 Format:
1585 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1586
1587 pt. [PARIDE]
1588 See Documentation/paride.txt.
1589
dc8c8587
KS
1590 pty.legacy_count=
1591 [KNL] Number of legacy pty's. Overwrites compiled-in
1592 default number.
1593
7d2c502f 1594 quiet [KNL] Disable most log messages
a9913044 1595
1da177e4
LT
1596 r128= [HW,DRM]
1597
1598 raid= [HW,RAID]
1599 See Documentation/md.txt.
1600
a9913044 1601 ramdisk_blocksize= [RAM]
1da177e4 1602 See Documentation/ramdisk.txt.
a9913044 1603
1da177e4 1604 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1da177e4
LT
1605 See Documentation/ramdisk.txt.
1606
24aaef8d
RD
1607 rcupdate.blimit= [KNL,BOOT]
1608 Set maximum number of finished RCU callbacks to process
1609 in one batch.
21a1ea9e 1610
24aaef8d
RD
1611 rcupdate.qhimark= [KNL,BOOT]
1612 Set threshold of queued
21a1ea9e
DS
1613 RCU callbacks over which batch limiting is disabled.
1614
24aaef8d
RD
1615 rcupdate.qlowmark= [KNL,BOOT]
1616 Set threshold of queued RCU callbacks below which
1617 batch limiting is re-enabled.
21a1ea9e 1618
ffdfc409
OJ
1619 rdinit= [KNL]
1620 Format: <full_path>
1621 Run specified binary instead of /init from the ramdisk,
1622 used for early userspace startup. See initrd.
1623
cd4f0ef7 1624 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1625 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1626 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4
LT
1627
1628 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1629
cd4f0ef7 1630 reservetop= [X86-32]
461a9aff
ZA
1631 Format: nn[KMG]
1632 Reserves a hole at the top of the kernel virtual
1633 address space.
1634
7e96287d
VG
1635 reset_devices [KNL] Force drivers to reset the underlying device
1636 during initialization.
1637
a9913044
RD
1638 resume= [SWSUSP]
1639 Specify the partition device for software suspend
1da177e4 1640
ecbd0da1
RW
1641 resume_offset= [SWSUSP]
1642 Specify the offset from the beginning of the partition
1643 given by "resume=" at which the swap header is located,
1644 in <PAGE_SIZE> units (needed only for swap files).
1645 See Documentation/power/swsusp-and-swap-files.txt
1646
0a7b35cb
MN
1647 retain_initrd [RAM] Keep initrd memory after extraction
1648
1da177e4
LT
1649 rhash_entries= [KNL,NET]
1650 Set number of hash buckets for route cache
1651
1652 riscom8= [HW,SERIAL]
1653 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1654
1655 ro [KNL] Mount root device read-only on boot
1656
1657 root= [KNL] Root filesystem
1658
1659 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1660 mount the root filesystem
1661
1662 rootflags= [KNL] Set root filesystem mount option string
1663
1664 rootfstype= [KNL] Set root filesystem type
1665
cc1ed754
PO
1666 rootwait [KNL] Wait (indefinitely) for root device to show up.
1667 Useful for devices that are detected asynchronously
1668 (e.g. USB and MMC devices).
1669
20510f2f
JM
1670 root_plug.vendor_id=
1671 [ROOTPLUG] Override the default vendor ID
1672
1673 root_plug.product_id=
1674 [ROOTPLUG] Override the default product ID
1675
1676 root_plug.debug=
1677 [ROOTPLUG] Enable debugging output
1678
1da177e4
LT
1679 rw [KNL] Mount root device read-write on boot
1680
1681 S [KNL] Run init in single mode
1682
1683 sa1100ir [NET]
1684 See drivers/net/irda/sa1100_ir.c.
1685
1da177e4 1686 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1687
1da177e4
LT
1688 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1689 Format: <io>[,<timeout>[,<isapnp>]]
1690
1691 scsi_debug_*= [SCSI]
1692 See drivers/scsi/scsi_debug.c.
1693
1694 scsi_default_dev_flags=
1695 [SCSI] SCSI default device flags
1696 Format: <integer>
1697
1698 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1699 Format: <vendor>:<model>:<flags>
1700 (flags are integer value)
1701
6af6632a
RD
1702 scsi_logging_level= [SCSI] a bit mask of logging levels
1703 See drivers/scsi/scsi_logging.h for bits. Also
1704 settable via sysctl at dev.scsi.logging_level
1705 (/proc/sys/dev/scsi/logging_level).
1706 There is also a nice 'scsi_logging_level' script in the
1707 S390-tools package, available for download at
1708 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1709
3e082a91
MW
1710 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1711 discovered. async scans them in kernel threads,
1712 allowing boot to proceed. none ignores them, expecting
1713 user space to do the scan.
1714
1da177e4
LT
1715 selinux [SELINUX] Disable or enable SELinux at boot time.
1716 Format: { "0" | "1" }
1717 See security/selinux/Kconfig help text.
1718 0 -- disable.
1719 1 -- enable.
1720 Default value is set via kernel config option.
1721 If enabled at boot time, /selinux/disable can be used
1722 later to disable prior to initial policy load.
1723
4e5ab4cb
JM
1724 selinux_compat_net =
1725 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1726 Format: { "0" | "1" }
1727 0 -- use new secmark-based packet controls
1728 1 -- use legacy packet controls
1729 Default value is 0 (preferred).
1730 Value can be changed at runtime via
1731 /selinux/compat_net.
4e5ab4cb 1732
cd4f0ef7 1733 serialnumber [BUGS=X86-32]
1da177e4 1734
1da177e4
LT
1735 shapers= [NET]
1736 Maximal number of shapers.
a9913044 1737
1da177e4
LT
1738 sim710= [SCSI,HW]
1739 See header of drivers/scsi/sim710.c.
1740
1741 simeth= [IA-64]
1742 simscsi=
a9913044 1743
1da177e4
LT
1744 slram= [HW,MTD]
1745
f0630fff
CL
1746 slub_debug[=options[,slabs]] [MM, SLUB]
1747 Enabling slub_debug allows one to determine the
1748 culprit if slab objects become corrupted. Enabling
1749 slub_debug can create guard zones around objects and
1750 may poison objects when not in use. Also tracks the
1751 last alloc / free. For more information see
1752 Documentation/vm/slub.txt.
c1aee215
CL
1753
1754 slub_max_order= [MM, SLUB]
f0630fff
CL
1755 Determines the maximum allowed order for slabs.
1756 A high setting may cause OOMs due to memory
1757 fragmentation. For more information see
1758 Documentation/vm/slub.txt.
c1aee215
CL
1759
1760 slub_min_objects= [MM, SLUB]
f0630fff
CL
1761 The minimum number of objects per slab. SLUB will
1762 increase the slab order up to slub_max_order to
1763 generate a sufficiently large slab able to contain
1764 the number of objects indicated. The higher the number
1765 of objects the smaller the overhead of tracking slabs
1766 and the less frequently locks need to be acquired.
c1aee215
CL
1767 For more information see Documentation/vm/slub.txt.
1768
1769 slub_min_order= [MM, SLUB]
1770 Determines the mininum page order for slabs. Must be
f0630fff 1771 lower than slub_max_order.
c1aee215
CL
1772 For more information see Documentation/vm/slub.txt.
1773
1774 slub_nomerge [MM, SLUB]
f0630fff 1775 Disable merging of slabs with similar size. May be
c1aee215 1776 necessary if there is some reason to distinguish
f0630fff
CL
1777 allocs to different slabs. Debug options disable
1778 merging on their own.
c1aee215
CL
1779 For more information see Documentation/vm/slub.txt.
1780
1da177e4
LT
1781 smart2= [HW]
1782 Format: <io1>[,<io2>[,...,<io8>]]
1783
cd4f0ef7 1784 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
1785 attempt to substitute SMP alternatives once at boot.
1786
d0d4f69b
BH
1787 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1788 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1789 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1790 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1791 smsc-ircc2.ircc_irq= [HW] IRQ line
1792 smsc-ircc2.ircc_dma= [HW] DMA channel
1793 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1794 0: Toshiba Satellite 1800 (GP data pin select)
1795 1: Fast pin select (default)
1796 2: ATC IRMode
1797
1da177e4
LT
1798 snd-ad1816a= [HW,ALSA]
1799
1800 snd-ad1848= [HW,ALSA]
1801
1802 snd-ali5451= [HW,ALSA]
1803
1804 snd-als100= [HW,ALSA]
1805
1806 snd-als4000= [HW,ALSA]
1807
1808 snd-azt2320= [HW,ALSA]
1809
1810 snd-cmi8330= [HW,ALSA]
1811
1812 snd-cmipci= [HW,ALSA]
1813
1814 snd-cs4231= [HW,ALSA]
1815
1816 snd-cs4232= [HW,ALSA]
1817
1818 snd-cs4236= [HW,ALSA]
1819
1820 snd-cs4281= [HW,ALSA]
1821
1822 snd-cs46xx= [HW,ALSA]
1823
1824 snd-dt019x= [HW,ALSA]
1825
1826 snd-dummy= [HW,ALSA]
1827
1828 snd-emu10k1= [HW,ALSA]
1829
1830 snd-ens1370= [HW,ALSA]
1831
1832 snd-ens1371= [HW,ALSA]
1833
1834 snd-es968= [HW,ALSA]
1835
1836 snd-es1688= [HW,ALSA]
1837
1838 snd-es18xx= [HW,ALSA]
1839
1840 snd-es1938= [HW,ALSA]
1841
1842 snd-es1968= [HW,ALSA]
1843
1844 snd-fm801= [HW,ALSA]
1845
1846 snd-gusclassic= [HW,ALSA]
1847
1848 snd-gusextreme= [HW,ALSA]
1849
1850 snd-gusmax= [HW,ALSA]
1851
1852 snd-hdsp= [HW,ALSA]
1853
1854 snd-ice1712= [HW,ALSA]
1855
1856 snd-intel8x0= [HW,ALSA]
1857
1858 snd-interwave= [HW,ALSA]
1859
1860 snd-interwave-stb=
1861 [HW,ALSA]
1862
1863 snd-korg1212= [HW,ALSA]
1864
1865 snd-maestro3= [HW,ALSA]
1866
1867 snd-mpu401= [HW,ALSA]
1868
1869 snd-mtpav= [HW,ALSA]
1870
1871 snd-nm256= [HW,ALSA]
1872
1873 snd-opl3sa2= [HW,ALSA]
1874
1875 snd-opti92x-ad1848=
1876 [HW,ALSA]
1877
1878 snd-opti92x-cs4231=
1879 [HW,ALSA]
1880
1881 snd-opti93x= [HW,ALSA]
1882
1883 snd-pmac= [HW,ALSA]
1884
1885 snd-rme32= [HW,ALSA]
1886
1887 snd-rme96= [HW,ALSA]
1888
1889 snd-rme9652= [HW,ALSA]
1890
1891 snd-sb8= [HW,ALSA]
1892
1893 snd-sb16= [HW,ALSA]
1894
1895 snd-sbawe= [HW,ALSA]
1896
1897 snd-serial= [HW,ALSA]
1898
1899 snd-sgalaxy= [HW,ALSA]
1900
1901 snd-sonicvibes= [HW,ALSA]
1902
1903 snd-sun-amd7930=
1904 [HW,ALSA]
1905
1906 snd-sun-cs4231= [HW,ALSA]
1907
1908 snd-trident= [HW,ALSA]
1909
1910 snd-usb-audio= [HW,ALSA,USB]
1911
1912 snd-via82xx= [HW,ALSA]
1913
1914 snd-virmidi= [HW,ALSA]
1915
1916 snd-wavefront= [HW,ALSA]
1917
1918 snd-ymfpci= [HW,ALSA]
a9913044 1919
1da177e4
LT
1920 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1921 See Documentation/sonypi.txt
1922
1923 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1924 See Documentation/specialix.txt.
1925
1926 spia_io_base= [HW,MTD]
1927 spia_fio_base=
1928 spia_pedr=
1929 spia_peddr=
1930
1931 sscape= [HW,OSS]
1932 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 1933
1da177e4
LT
1934 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1935 See Documentation/scsi/st.txt.
1936
1da177e4
LT
1937 sti= [PARISC,HW]
1938 Format: <num>
1939 Set the STI (builtin display/keyboard on the HP-PARISC
1940 machines) console (graphic card) which should be used
1941 as the initial boot-console.
1942 See also comment in drivers/video/console/sticore.c.
1943
1944 sti_font= [HW]
1945 See comment in drivers/video/console/sticore.c.
1946
1947 stifb= [HW]
1948 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1949
42a7fc4a
GB
1950 sunrpc.pool_mode=
1951 [NFS]
1952 Control how the NFS server code allocates CPUs to
1953 service thread pools. Depending on how many NICs
1954 you have and where their interrupts are bound, this
1955 option will affect which CPUs will do NFS serving.
1956 Note: this parameter cannot be changed while the
1957 NFS server is running.
1958
1959 auto the server chooses an appropriate mode
1960 automatically using heuristics
1961 global a single global pool contains all CPUs
1962 percpu one pool for each CPU
1963 pernode one pool for each NUMA node (equivalent
1964 to global on non-NUMA machines)
1965
1da177e4 1966 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 1967
1da177e4
LT
1968 switches= [HW,M68k]
1969
1970 sym53c416= [HW,SCSI]
1971 See header of drivers/scsi/sym53c416.c.
1972
5d6f647f
IM
1973 sysrq_always_enabled
1974 [KNL]
1975 Ignore sysrq setting - this boot parameter will
1976 neutralize any effect of /proc/sys/kernel/sysrq.
1977 Useful for debugging.
1978
1da177e4
LT
1979 t128= [HW,SCSI]
1980 See header of drivers/scsi/t128.c.
1981
1982 tdfx= [HW,DRM]
1983
1984 thash_entries= [KNL,NET]
1985 Set number of hash buckets for TCP connection
1986
f8707ec9
LB
1987 thermal.act= [HW,ACPI]
1988 -1: disable all active trip points in all thermal zones
1989 <degrees C>: override all lowest active trip points
1990
c52a7419
LB
1991 thermal.crt= [HW,ACPI]
1992 -1: disable all critical trip points in all thermal zones
1993 <degrees C>: lower all critical trip points
1994
f5487145
LB
1995 thermal.nocrt= [HW,ACPI]
1996 Set to disable actions on ACPI thermal zone
1997 critical and hot trip points.
1998
72b33ef8
LB
1999 thermal.off= [HW,ACPI]
2000 1: disable ACPI thermal control
2001
a70cdc52
LB
2002 thermal.psv= [HW,ACPI]
2003 -1: disable all passive trip points
2004 <degrees C>: override all passive trip points to this value
2005
730ff34d
LB
2006 thermal.tzp= [HW,ACPI]
2007 Specify global default ACPI thermal zone polling rate
2008 <deci-seconds>: poll all this frequency
2009 0: no polling (default)
2010
1da177e4
LT
2011 tipar.timeout= [HW,PPT]
2012 Set communications timeout in tenths of a second
2013 (default 15).
2014
2015 tipar.delay= [HW,PPT]
2016 Set inter-bit delay in microseconds (default 10).
2017
1da177e4
LT
2018 tmscsim= [HW,SCSI]
2019 See comment before function dc390_setup() in
2020 drivers/scsi/tmscsim.c.
2021
2022 tp720= [HW,PS2]
2023
2024 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2025 Format:
2026 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2027
a9913044
RD
2028 turbografx.map[2|3]= [HW,JOY]
2029 TurboGraFX parallel port interface
2030 Format:
2031 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2032 See also Documentation/input/joystick-parport.txt
2033
2034 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2035 See header of drivers/scsi/u14-34f.c.
2036
2037 uart401= [HW,OSS]
2038 Format: <io>,<irq>
2039
2040 uart6850= [HW,OSS]
2041 Format: <io>,<irq>
2042
5f8364b7
AS
2043 uhci-hcd.ignore_oc=
2044 [USB] Ignore overcurrent events (default N).
2045 Some badly-designed motherboards generate lots of
2046 bogus events, for ports that aren't wired to
2047 anything. Set this parameter to avoid log spamming.
2048 Note that genuine overcurrent events won't be
2049 reported either.
2050
b5e795f8
AS
2051 usbcore.autosuspend=
2052 [USB] The autosuspend time delay (in seconds) used
2053 for newly-detected USB devices (default 2). This
2054 is the time required before an idle device will be
2055 autosuspended. Devices for which the delay is set
eaafbc3a 2056 to a negative value won't be autosuspended at all.
b5e795f8 2057
1da177e4
LT
2058 usbhid.mousepoll=
2059 [USBHID] The interval which mice are to be polled at.
a9913044 2060
cd4f0ef7 2061 vdso= [X86-32,SH,x86-64]
1dbf527c 2062 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2063 vdso=1: enable VDSO (default)
2064 vdso=0: disable VDSO mapping
2065
af65d648
RM
2066 vdso32= [X86-32,X86-64]
2067 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2068 vdso32=1: enable 32-bit VDSO (default)
2069 vdso32=0: disable 32-bit VDSO mapping
2070
d080d397
YI
2071 vector= [IA-64,SMP]
2072 vector=percpu: enable percpu vector domain
2073
1da177e4
LT
2074 video= [FB] Frame buffer configuration
2075 See Documentation/fb/modedb.txt.
2076
cd4f0ef7 2077 vga= [BOOT,X86-32] Select a particular video mode
a9913044
RD
2078 See Documentation/i386/boot.txt and
2079 Documentation/svga.txt.
1da177e4
LT
2080 Use vga=ask for menu.
2081 This is actually a boot loader parameter; the value is
2082 passed to the kernel using a special protocol.
2083
a9913044 2084 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2085 size of <nn>. This can be used to increase the
2086 minimum size (128MB on x86). It can also be used to
2087 decrease the size and leave more room for directly
2088 mapped kernel RAM.
2089
585c3047
PO
2090 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2091 Format: <command>
1da177e4 2092
585c3047
PO
2093 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2094 Format: <command>
2095
2096 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2097 Format: <command>
a9913044 2098
1da177e4
LT
2099 waveartist= [HW,OSS]
2100 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2101
1da177e4
LT
2102 wd33c93= [HW,SCSI]
2103 See header of drivers/scsi/wd33c93.c.
2104
2105 wd7000= [HW,SCSI]
2106 See header of drivers/scsi/wd7000.c.
2107
2108 wdt= [WDT] Watchdog
8dfe9c21 2109 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2110
2111 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2112 xd_geo= See header of drivers/block/xd.c.
2113
2114 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2115 Format:
2116 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2117
a62eaf15
AK
2118 norandmaps Don't use address space randomization
2119 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2120
a9913044 2121______________________________________________________________________
1da177e4
LT
2122
2123TODO:
2124
2125 Add documentation for ALSA options.
2126 Add more DRM drivers.