]> git.proxmox.com Git - mirror_ubuntu-artful-kernel.git/blame_incremental - Documentation/kernel-parameters.txt
MIPS: RB532: Convert to GPIO lib
[mirror_ubuntu-artful-kernel.git] / Documentation / kernel-parameters.txt
... / ...
CommitLineData
1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
3
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
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
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:
31
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
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.
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 LIBATA Libata driver is enabled
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.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
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.
79 ROOTPLUG The example Root Plug LSM is enabled.
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/.
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend (hibernation) is enabled.
91 SUSPEND System suspend states are enabled.
92 TS Appropriate touchscreen support is enabled.
93 USB USB support is enabled.
94 USBHID USB Human Interface Device support is enabled.
95 V4L Video For Linux support is enabled.
96 VGA The VGA console has been enabled.
97 VT Virtual terminal support is enabled.
98 WDT Watchdog support is enabled.
99 XT IBM PC/XT MFM hard disk support is enabled.
100 X86-32 X86-32, aka i386 architecture is enabled.
101 X86-64 X86-64 architecture is enabled.
102 More X86-64 boot options can be found in
103 Documentation/x86_64/boot-options.txt .
104
105In addition, the following text indicates that the option:
106
107 BUGS= Relates to possible processor bugs on the said processor.
108 KNL Is a kernel start-up parameter.
109 BOOT Is a boot loader parameter.
110
111Parameters denoted with BOOT are actually interpreted by the boot
112loader, and have no meaning to the kernel directly.
113Do not modify the syntax of boot loader parameters without extreme
114need or coordination with <Documentation/i386/boot.txt>.
115
116There are also arch-specific kernel-parameters not documented here.
117See for example <Documentation/x86_64/boot-options.txt>.
118
119Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
120a trailing = on the name of any parameter states that that parameter will
121be entered as an environment variable, whereas its absence indicates that
122it will appear as a kernel argument readable via /proc/cmdline by programs
123running once the system is up.
124
125The number of kernel parameters is not limited, but the length of the
126complete command line (parameters including spaces etc.) is limited to
127a fixed number of characters. This limit depends on the architecture
128and is between 256 and 4096 characters. It is defined in the file
129./include/asm/setup.h as COMMAND_LINE_SIZE.
130
131
132 acpi= [HW,ACPI,X86-64,i386]
133 Advanced Configuration and Power Interface
134 Format: { force | off | ht | strict | noirq }
135 force -- enable ACPI if default was off
136 off -- disable ACPI if default was on
137 noirq -- do not use ACPI for IRQ routing
138 ht -- run only enough ACPI to enable Hyper Threading
139 strict -- Be less tolerant of platforms that are not
140 strictly ACPI specification compliant.
141
142 See also Documentation/power/pm.txt, pci=noacpi
143
144 acpi_apic_instance= [ACPI, IOAPIC]
145 Format: <int>
146 2: use 2nd APIC table, if available
147 1,0: use 1st APIC table
148 default: 0
149
150 acpi_sleep= [HW,ACPI] Sleep options
151 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
152 See Documentation/power/video.txt for s3_bios and s3_mode.
153 s3_beep is for debugging; it makes the PC's speaker beep
154 as soon as the kernel's real-mode entry point is called.
155 s4_nohwsig prevents ACPI hardware signature from being
156 used during resume from hibernation.
157 old_ordering causes the ACPI 1.0 ordering of the _PTS
158 control method, wrt putting devices into low power
159 states, to be enforced (the ACPI 2.0 ordering of _PTS is
160 used by default).
161
162 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
163 Format: { level | edge | high | low }
164
165 acpi_irq_balance [HW,ACPI]
166 ACPI will balance active IRQs
167 default in APIC mode
168
169 acpi_irq_nobalance [HW,ACPI]
170 ACPI will not move active IRQs (default)
171 default in PIC mode
172
173 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
174 use by PCI
175 Format: <irq>,<irq>...
176
177 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
178 Format: <irq>,<irq>...
179
180 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
181
182 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
183 Format: To spoof as Windows 98: ="Microsoft Windows"
184
185 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
186 acpi_osi="string1" # add string1 -- only one string
187 acpi_osi="!string2" # remove built-in string2
188 acpi_osi= # disable all strings
189
190 acpi_serialize [HW,ACPI] force serialization of AML methods
191
192 acpi_skip_timer_override [HW,ACPI]
193 Recognize and ignore IRQ0/pin2 Interrupt Override.
194 For broken nForce2 BIOS resulting in XT-PIC timer.
195 acpi_use_timer_override [HW,ACPI}
196 Use timer override. For some broken Nvidia NF5 boards
197 that require a timer override, but don't have
198 HPET
199
200 acpi.debug_layer= [HW,ACPI]
201 Format: <int>
202 Each bit of the <int> indicates an ACPI debug layer,
203 1: enable, 0: disable. It is useful for boot time
204 debugging. After system has booted up, it can be set
205 via /sys/module/acpi/parameters/debug_layer.
206 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
207 Available bits (add the numbers together) to enable debug output
208 for specific parts of the ACPI subsystem:
209 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
210 0x10 namespace 0x20 parser 0x40 dispatcher
211 0x80 executer 0x100 resources 0x200 acpica debugger
212 0x400 os services 0x800 acpica disassembler.
213 The number can be in decimal or prefixed with 0x in hex.
214 Warning: Many of these options can produce a lot of
215 output and make your system unusable. Be very careful.
216
217 acpi.debug_level= [HW,ACPI]
218 Format: <int>
219 Each bit of the <int> indicates an ACPI debug level,
220 1: enable, 0: disable. It is useful for boot time
221 debugging. After system has booted up, it can be set
222 via /sys/module/acpi/parameters/debug_level.
223 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
224 Available bits (add the numbers together) to enable different
225 debug output levels of the ACPI subsystem:
226 0x01 error 0x02 warn 0x04 init 0x08 debug object
227 0x10 info 0x20 init names 0x40 parse 0x80 load
228 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
229 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
230 0x10000 resources 0x20000 user requests 0x40000 package.
231 The number can be in decimal or prefixed with 0x in hex.
232 Warning: Many of these options can produce a lot of
233 output and make your system unusable. Be very careful.
234
235 acpi_pm_good [X86-32,X86-64]
236 Override the pmtimer bug detection: force the kernel
237 to assume that this machine's pmtimer latches its value
238 and always returns good values.
239
240 agp= [AGP]
241 { off | try_unsupported }
242 off: disable AGP support
243 try_unsupported: try to drive unsupported chipsets
244 (may crash computer or cause data corruption)
245
246 enable_timer_pin_1 [i386,x86-64]
247 Enable PIN 1 of APIC timer
248 Can be useful to work around chipset bugs
249 (in particular on some ATI chipsets).
250 The kernel tries to set a reasonable default.
251
252 disable_timer_pin_1 [i386,x86-64]
253 Disable PIN 1 of APIC timer
254 Can be useful to work around chipset bugs.
255
256 ad1848= [HW,OSS]
257 Format: <io>,<irq>,<dma>,<dma2>,<type>
258
259 advansys= [HW,SCSI]
260 See header of drivers/scsi/advansys.c.
261
262 advwdt= [HW,WDT] Advantech WDT
263 Format: <iostart>,<iostop>
264
265 aedsp16= [HW,OSS] Audio Excel DSP 16
266 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
267 See also header of sound/oss/aedsp16.c.
268
269 aha152x= [HW,SCSI]
270 See Documentation/scsi/aha152x.txt.
271
272 aha1542= [HW,SCSI]
273 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
274
275 aic7xxx= [HW,SCSI]
276 See Documentation/scsi/aic7xxx.txt.
277
278 aic79xx= [HW,SCSI]
279 See Documentation/scsi/aic79xx.txt.
280
281 amd_iommu= [HW,X86-84]
282 Pass parameters to the AMD IOMMU driver in the system.
283 Possible values are:
284 isolate - enable device isolation (each device, as far
285 as possible, will get its own protection
286 domain)
287 amd_iommu_size= [HW,X86-64]
288 Define the size of the aperture for the AMD IOMMU
289 driver. Possible values are:
290 '32M', '64M' (default), '128M', '256M', '512M', '1G'
291
292 amijoy.map= [HW,JOY] Amiga joystick support
293 Map of devices attached to JOY0DAT and JOY1DAT
294 Format: <a>,<b>
295 See also Documentation/kernel/input/joystick.txt
296
297 analog.map= [HW,JOY] Analog joystick and gamepad support
298 Specifies type or capabilities of an analog joystick
299 connected to one of 16 gameports
300 Format: <type1>,<type2>,..<type16>
301
302 apc= [HW,SPARC]
303 Power management functions (SPARCstation-4/5 + deriv.)
304 Format: noidle
305 Disable APC CPU standby support. SPARCstation-Fox does
306 not play well with APC CPU idle - disable it if you have
307 APC and your system crashes randomly.
308
309 apic= [APIC,i386] Advanced Programmable Interrupt Controller
310 Change the output verbosity whilst booting
311 Format: { quiet (default) | verbose | debug }
312 Change the amount of debugging information output
313 when initialising the APIC and IO-APIC components.
314
315 apm= [APM] Advanced Power Management
316 See header of arch/x86/kernel/apm_32.c.
317
318 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
319 Format: <io>,<irq>,<nodeID>
320
321 ataflop= [HW,M68k]
322
323 atarimouse= [HW,MOUSE] Atari Mouse
324
325 atascsi= [HW,SCSI] Atari SCSI
326
327 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
328 EzKey and similar keyboards
329
330 atkbd.reset= [HW] Reset keyboard during initialization
331
332 atkbd.set= [HW] Select keyboard code set
333 Format: <int> (2 = AT (default), 3 = PS/2)
334
335 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
336 keyboards
337
338 atkbd.softraw= [HW] Choose between synthetic and real raw mode
339 Format: <bool> (0 = real, 1 = synthetic (default))
340
341 atkbd.softrepeat= [HW]
342 Use software keyboard repeat
343
344 autotest [IA64]
345
346 baycom_epp= [HW,AX25]
347 Format: <io>,<mode>
348
349 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
350 Format: <io>,<mode>
351 See header of drivers/net/hamradio/baycom_par.c.
352
353 baycom_ser_fdx= [HW,AX25]
354 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
355 Format: <io>,<irq>,<mode>[,<baud>]
356 See header of drivers/net/hamradio/baycom_ser_fdx.c.
357
358 baycom_ser_hdx= [HW,AX25]
359 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
360 Format: <io>,<irq>,<mode>
361 See header of drivers/net/hamradio/baycom_ser_hdx.c.
362
363 boot_delay= Milliseconds to delay each printk during boot.
364 Values larger than 10 seconds (10000) are changed to
365 no delay (0).
366 Format: integer
367
368 bootmem_debug [KNL] Enable bootmem allocator debug messages.
369
370 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
371 bttv.radio= Most important insmod options are available as
372 kernel args too.
373 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
374 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
375
376 BusLogic= [HW,SCSI]
377 See drivers/scsi/BusLogic.c, comment before function
378 BusLogic_ParseDriverOptions().
379
380 c101= [NET] Moxa C101 synchronous serial card
381
382 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
383 Sometimes CPU hardware bugs make them report the cache
384 size incorrectly. The kernel will attempt work arounds
385 to fix known problems, but for some CPUs it is not
386 possible to determine what the correct size should be.
387 This option provides an override for these situations.
388
389 security= [SECURITY] Choose a security module to enable at boot.
390 If this boot parameter is not specified, only the first
391 security module asking for security registration will be
392 loaded. An invalid security module name will be treated
393 as if no module has been chosen.
394
395 capability.disable=
396 [SECURITY] Disable capabilities. This would normally
397 be used only if an alternative security model is to be
398 configured. Potentially dangerous and should only be
399 used if you are entirely sure of the consequences.
400
401 ccw_timeout_log [S390]
402 See Documentation/s390/CommonIO for details.
403
404 cgroup_disable= [KNL] Disable a particular controller
405 Format: {name of the controller(s) to disable}
406 {Currently supported controllers - "memory"}
407
408 checkreqprot [SELINUX] Set initial checkreqprot flag value.
409 Format: { "0" | "1" }
410 See security/selinux/Kconfig help text.
411 0 -- check protection applied by kernel (includes
412 any implied execute protection).
413 1 -- check protection requested by application.
414 Default value is set via a kernel config option.
415 Value can be changed at runtime via
416 /selinux/checkreqprot.
417
418 cio_ignore= [S390]
419 See Documentation/s390/CommonIO for details.
420
421 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
422 [Deprecated]
423 Forces specified clocksource (if available) to be used
424 when calculating gettimeofday(). If specified
425 clocksource is not available, it defaults to PIT.
426 Format: { pit | tsc | cyclone | pmtmr }
427
428 clocksource= [GENERIC_TIME] Override the default clocksource
429 Format: <string>
430 Override the default clocksource and use the clocksource
431 with the name specified.
432 Some clocksource names to choose from, depending on
433 the platform:
434 [all] jiffies (this is the base, fallback clocksource)
435 [ACPI] acpi_pm
436 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
437 pxa_timer,timer3,32k_counter,timer0_1
438 [AVR32] avr32
439 [X86-32] pit,hpet,tsc,vmi-timer;
440 scx200_hrt on Geode; cyclone on IBM x440
441 [MIPS] MIPS
442 [PARISC] cr16
443 [S390] tod
444 [SH] SuperH
445 [SPARC64] tick
446 [X86-64] hpet,tsc
447
448 clearcpuid=BITNUM [X86]
449 Disable CPUID feature X for the kernel. See
450 include/asm-x86/cpufeature.h for the valid bit numbers.
451 Note the Linux specific bits are not necessarily
452 stable over kernel options, but the vendor specific
453 ones should be.
454 Also note that user programs calling CPUID directly
455 or using the feature without checking anything
456 will still see it. This just prevents it from
457 being used by the kernel or shown in /proc/cpuinfo.
458 Also note the kernel might malfunction if you disable
459 some critical bits.
460
461 code_bytes [IA32/X86_64] How many bytes of object code to print
462 in an oops report.
463 Range: 0 - 8192
464 Default: 64
465
466 hpet= [X86-32,HPET] option to control HPET usage
467 Format: { enable (default) | disable | force }
468 disable: disable HPET and use PIT instead
469 force: allow force enabled of undocumented chips (ICH4,
470 VIA, nVidia)
471
472 com20020= [HW,NET] ARCnet - COM20020 chipset
473 Format:
474 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
475
476 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
477 Format: <io>[,<irq>]
478
479 com90xx= [HW,NET]
480 ARCnet - COM90xx chipset (memory-mapped buffers)
481 Format: <io>[,<irq>[,<memstart>]]
482
483 condev= [HW,S390] console device
484 conmode=
485
486 console= [KNL] Output console device and options.
487
488 tty<n> Use the virtual console device <n>.
489
490 ttyS<n>[,options]
491 ttyUSB0[,options]
492 Use the specified serial port. The options are of
493 the form "bbbbpnf", where "bbbb" is the baud rate,
494 "p" is parity ("n", "o", or "e"), "n" is number of
495 bits, and "f" is flow control ("r" for RTS or
496 omit it). Default is "9600n8".
497
498 See Documentation/serial-console.txt for more
499 information. See
500 Documentation/networking/netconsole.txt for an
501 alternative.
502
503 uart[8250],io,<addr>[,options]
504 uart[8250],mmio,<addr>[,options]
505 Start an early, polled-mode console on the 8250/16550
506 UART at the specified I/O port or MMIO address,
507 switching to the matching ttyS device later. The
508 options are the same as for ttyS, above.
509
510 If the device connected to the port is not a TTY but a braille
511 device, prepend "brl," before the device type, for instance
512 console=brl,ttyS0
513 For now, only VisioBraille is supported.
514
515 earlycon= [KNL] Output early console device and options.
516 uart[8250],io,<addr>[,options]
517 uart[8250],mmio,<addr>[,options]
518 Start an early, polled-mode console on the 8250/16550
519 UART at the specified I/O port or MMIO address.
520 The options are the same as for ttyS, above.
521
522 no_console_suspend
523 [HW] Never suspend the console
524 Disable suspending of consoles during suspend and
525 hibernate operations. Once disabled, debugging
526 messages can reach various consoles while the rest
527 of the system is being put to sleep (ie, while
528 debugging driver suspend/resume hooks). This may
529 not work reliably with all consoles, but is known
530 to work with serial and VGA consoles.
531
532 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
533 Format:
534 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
535
536 crashkernel=nn[KMG]@ss[KMG]
537 [KNL] Reserve a chunk of physical memory to
538 hold a kernel to switch to with kexec on panic.
539
540 crashkernel=range1:size1[,range2:size2,...][@offset]
541 [KNL] Same as above, but depends on the memory
542 in the running system. The syntax of range is
543 start-[end] where start and end are both
544 a memory unit (amount[KMG]). See also
545 Documentation/kdump/kdump.txt for a example.
546
547 cs4232= [HW,OSS]
548 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
549
550 cs89x0_dma= [HW,NET]
551 Format: <dma>
552
553 cs89x0_media= [HW,NET]
554 Format: { rj45 | aui | bnc }
555
556 dasd= [HW,NET]
557 See header of drivers/s390/block/dasd_devmap.c.
558
559 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
560 (one device per port)
561 Format: <port#>,<type>
562 See also Documentation/input/joystick-parport.txt
563
564 debug [KNL] Enable kernel debugging (events log level).
565
566 debug_locks_verbose=
567 [KNL] verbose self-tests
568 Format=<0|1>
569 Print debugging info while doing the locking API
570 self-tests.
571 We default to 0 (no extra messages), setting it to
572 1 will print _a lot_ more information - normally
573 only useful to kernel developers.
574
575 debug_objects [KNL] Enable object debugging
576
577 debugpat [X86] Enable PAT debugging
578
579 decnet.addr= [HW,NET]
580 Format: <area>[,<node>]
581 See also Documentation/networking/decnet.txt.
582
583 vt.default_blu= [VT]
584 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
585 Change the default blue palette of the console.
586 This is a 16-member array composed of values
587 ranging from 0-255.
588
589 vt.default_grn= [VT]
590 Format: <green0>,<green1>,<green2>,...,<green15>
591 Change the default green palette of the console.
592 This is a 16-member array composed of values
593 ranging from 0-255.
594
595 vt.default_red= [VT]
596 Format: <red0>,<red1>,<red2>,...,<red15>
597 Change the default red palette of the console.
598 This is a 16-member array composed of values
599 ranging from 0-255.
600
601 vt.default_utf8=
602 [VT]
603 Format=<0|1>
604 Set system-wide default UTF-8 mode for all tty's.
605 Default is 1, i.e. UTF-8 mode is enabled for all
606 newly opened terminals.
607
608 dhash_entries= [KNL]
609 Set number of hash buckets for dentry cache.
610
611 digi= [HW,SERIAL]
612 IO parameters + enable/disable command.
613
614 digiepca= [HW,SERIAL]
615 See drivers/char/README.epca and
616 Documentation/digiepca.txt.
617
618 disable_mtrr_cleanup [X86]
619 enable_mtrr_cleanup [X86]
620 The kernel tries to adjust MTRR layout from continuous
621 to discrete, to make X server driver able to add WB
622 entry later. This parameter enables/disables that.
623
624 mtrr_chunk_size=nn[KMG] [X86]
625 used for mtrr cleanup. It is largest continous chunk
626 that could hold holes aka. UC entries.
627
628 mtrr_gran_size=nn[KMG] [X86]
629 Used for mtrr cleanup. It is granularity of mtrr block.
630 Default is 1.
631 Large value could prevent small alignment from
632 using up MTRRs.
633
634 mtrr_spare_reg_nr=n [X86]
635 Format: <integer>
636 Range: 0,7 : spare reg number
637 Default : 1
638 Used for mtrr cleanup. It is spare mtrr entries number.
639 Set to 2 or more if your graphical card needs more.
640
641 disable_mtrr_trim [X86, Intel and AMD only]
642 By default the kernel will trim any uncacheable
643 memory out of your available memory pool based on
644 MTRR settings. This parameter disables that behavior,
645 possibly causing your machine to run very slowly.
646
647 dmasound= [HW,OSS] Sound subsystem buffers
648
649 dscc4.setup= [NET]
650
651 dtc3181e= [HW,SCSI]
652
653 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
654 earlyprintk=vga
655 earlyprintk=serial[,ttySn[,baudrate]]
656
657 Append ",keep" to not disable it when the real console
658 takes over.
659
660 Only vga or serial at a time, not both.
661
662 Currently only ttyS0 and ttyS1 are supported.
663
664 Interaction with the standard serial driver is not
665 very good.
666
667 The VGA output is eventually overwritten by the real
668 console.
669
670 eata= [HW,SCSI]
671
672 edd= [EDD]
673 Format: {"off" | "on" | "skip[mbr]"}
674
675 eisa_irq_edge= [PARISC,HW]
676 See header of drivers/parisc/eisa.c.
677
678 elanfreq= [X86-32]
679 See comment before function elanfreq_setup() in
680 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
681
682 elevator= [IOSCHED]
683 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
684 See Documentation/block/as-iosched.txt and
685 Documentation/block/deadline-iosched.txt for details.
686
687 elfcorehdr= [X86-32, X86_64]
688 Specifies physical address of start of kernel core
689 image elf header. Generally kexec loader will
690 pass this option to capture kernel.
691 See Documentation/kdump/kdump.txt for details.
692
693 enforcing [SELINUX] Set initial enforcing status.
694 Format: {"0" | "1"}
695 See security/selinux/Kconfig help text.
696 0 -- permissive (log only, no denials).
697 1 -- enforcing (deny and log).
698 Default value is 0.
699 Value can be changed at runtime via /selinux/enforce.
700
701 es1371= [HW,OSS]
702 Format: <spdif>,[<nomix>,[<amplifier>]]
703 See also header of sound/oss/es1371.c.
704
705 ether= [HW,NET] Ethernet cards parameters
706 This option is obsoleted by the "netdev=" option, which
707 has equivalent usage. See its documentation for details.
708
709 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
710 Format: <io>[,<irq>]
711
712 failslab=
713 fail_page_alloc=
714 fail_make_request=[KNL]
715 General fault injection mechanism.
716 Format: <interval>,<probability>,<space>,<times>
717 See also /Documentation/fault-injection/.
718
719 fd_mcs= [HW,SCSI]
720 See header of drivers/scsi/fd_mcs.c.
721
722 fdomain= [HW,SCSI]
723 See header of drivers/scsi/fdomain.c.
724
725 floppy= [HW]
726 See Documentation/floppy.txt.
727
728 force_pal_cache_flush
729 [IA-64] Avoid check_sal_cache_flush which may hang on
730 buggy SAL_CACHE_FLUSH implementations. Using this
731 parameter will force ia64_sal_cache_flush to call
732 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
733
734 gamecon.map[2|3]=
735 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
736 support via parallel port (up to 5 devices per port)
737 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
738 See also Documentation/input/joystick-parport.txt
739
740 gamma= [HW,DRM]
741
742 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
743 Format: off | on
744 default: on
745
746 gdth= [HW,SCSI]
747 See header of drivers/scsi/gdth.c.
748
749 gpt [EFI] Forces disk with valid GPT signature but
750 invalid Protective MBR to be treated as GPT.
751
752 gvp11= [HW,SCSI]
753
754 hashdist= [KNL,NUMA] Large hashes allocated during boot
755 are distributed across NUMA nodes. Defaults on
756 for IA-64, off otherwise.
757 Format: 0 | 1 (for off | on)
758
759 hcl= [IA-64] SGI's Hardware Graph compatibility layer
760
761 hd= [EIDE] (E)IDE hard drive subsystem geometry
762 Format: <cyl>,<head>,<sect>
763
764 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
765 size of <nn>. This works even on boxes that have no
766 highmem otherwise. This also works to reduce highmem
767 size on bigger boxes.
768
769 highres= [KNL] Enable/disable high resolution timer mode.
770 Valid parameters: "on", "off"
771 Default: "on"
772
773 hisax= [HW,ISDN]
774 See Documentation/isdn/README.HiSax.
775
776 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
777 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
778 On x86-64 and powerpc, this option can be specified
779 multiple times interleaved with hugepages= to reserve
780 huge pages of different sizes. Valid pages sizes on
781 x86-64 are 2M (when the CPU supports "pse") and 1G
782 (when the CPU supports the "pdpe1gb" cpuinfo flag)
783 Note that 1GB pages can only be allocated at boot time
784 using hugepages= and not freed afterwards.
785 default_hugepagesz=
786 [same as hugepagesz=] The size of the default
787 HugeTLB page size. This is the size represented by
788 the legacy /proc/ hugepages APIs, used for SHM, and
789 default size when mounting hugetlbfs filesystems.
790 Defaults to the default architecture's huge page size
791 if not specified.
792
793 i8042.direct [HW] Put keyboard port into non-translated mode
794 i8042.dumbkbd [HW] Pretend that controller can only read data from
795 keyboard and cannot control its state
796 (Don't attempt to blink the leds)
797 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
798 i8042.nokbd [HW] Don't check/create keyboard port
799 i8042.noloop [HW] Disable the AUX Loopback command while probing
800 for the AUX port
801 i8042.nomux [HW] Don't check presence of an active multiplexing
802 controller
803 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
804 controllers
805 i8042.panicblink=
806 [HW] Frequency with which keyboard LEDs should blink
807 when kernel panics (default is 0.5 sec)
808 i8042.reset [HW] Reset the controller during init and cleanup
809 i8042.unlock [HW] Unlock (ignore) the keylock
810
811 i810= [HW,DRM]
812
813 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
814 indicates that the driver is running on unsupported
815 hardware.
816 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
817 does not match list of supported models.
818 i8k.power_status
819 [HW] Report power status in /proc/i8k
820 (disabled by default)
821 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
822 capability is set.
823
824 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
825 See Documentation/mca.txt.
826
827 icn= [HW,ISDN]
828 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
829
830 ide= [HW] (E)IDE subsystem
831 Format: ide=nodma or ide=doubler
832 See Documentation/ide/ide.txt.
833
834 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
835 See Documentation/ide/ide.txt.
836
837 idle= [X86]
838 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
839 Poll forces a polling idle loop that can slightly improves the performance
840 of waking up a idle CPU, but will use a lot of power and make the system
841 run hot. Not recommended.
842 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
843 to not use it because it doesn't save as much power as a normal idle
844 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
845 as idle=poll.
846 idle=halt. Halt is forced to be used for CPU idle.
847 In such case C2/C3 won't be used again.
848 idle=nomwait. Disable mwait for CPU C-states
849
850 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
851 Claim all unknown PCI IDE storage controllers.
852
853 ignore_loglevel [KNL]
854 Ignore loglevel setting - this will print /all/
855 kernel messages to the console. Useful for debugging.
856
857 ihash_entries= [KNL]
858 Set number of hash buckets for inode cache.
859
860 in2000= [HW,SCSI]
861 See header of drivers/scsi/in2000.c.
862
863 init= [KNL]
864 Format: <full_path>
865 Run specified binary instead of /sbin/init as init
866 process.
867
868 initcall_debug [KNL] Trace initcalls as they are executed. Useful
869 for working out where the kernel is dying during
870 startup.
871
872 initrd= [BOOT] Specify the location of the initial ramdisk
873
874 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
875 Format: <irq>
876
877 inttest= [IA64]
878
879 iommu= [x86]
880 off
881 force
882 noforce
883 biomerge
884 panic
885 nopanic
886 merge
887 nomerge
888 forcesac
889 soft
890
891
892 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
893 off
894 Disable intel iommu driver.
895 igfx_off [Default Off]
896 By default, gfx is mapped as normal device. If a gfx
897 device has a dedicated DMAR unit, the DMAR unit is
898 bypassed by not enabling DMAR with this option. In
899 this case, gfx device will use physical address for
900 DMA.
901 forcedac [x86_64]
902 With this option iommu will not optimize to look
903 for io virtual address below 32 bit forcing dual
904 address cycle on pci bus for cards supporting greater
905 than 32 bit addressing. The default is to look
906 for translation below 32 bit and if not available
907 then look in the higher range.
908 strict [Default Off]
909 With this option on every unmap_single operation will
910 result in a hardware IOTLB flush operation as opposed
911 to batching them for performance.
912
913 io_delay= [X86-32,X86-64] I/O delay method
914 0x80
915 Standard port 0x80 based delay
916 0xed
917 Alternate port 0xed based delay (needed on some systems)
918 udelay
919 Simple two microseconds delay
920 none
921 No delay
922
923 io7= [HW] IO7 for Marvel based alpha systems
924 See comment before marvel_specify_io7 in
925 arch/alpha/kernel/core_marvel.c.
926
927 ip= [IP_PNP]
928 See Documentation/filesystems/nfsroot.txt.
929
930 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
931 See comment before ip2_setup() in
932 drivers/char/ip2/ip2base.c.
933
934 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
935 See header of drivers/scsi/ips.c.
936
937 ports= [IP_VS_FTP] IPVS ftp helper module
938 Default is 21.
939 Up to 8 (IP_VS_APP_MAX_PORTS) ports
940 may be specified.
941 Format: <port>,<port>....
942
943 irqfixup [HW]
944 When an interrupt is not handled search all handlers
945 for it. Intended to get systems with badly broken
946 firmware running.
947
948 irqpoll [HW]
949 When an interrupt is not handled search all handlers
950 for it. Also check all handlers each timer
951 interrupt. Intended to get systems with badly broken
952 firmware running.
953
954 isapnp= [ISAPNP]
955 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
956
957 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
958 Format:
959 <cpu number>,...,<cpu number>
960 or
961 <cpu number>-<cpu number> (must be a positive range in ascending order)
962 or a mixture
963 <cpu number>,...,<cpu number>-<cpu number>
964 This option can be used to specify one or more CPUs
965 to isolate from the general SMP balancing and scheduling
966 algorithms. The only way to move a process onto or off
967 an "isolated" CPU is via the CPU affinity syscalls.
968 <cpu number> begins at 0 and the maximum value is
969 "number of CPUs in system - 1".
970
971 This option is the preferred way to isolate CPUs. The
972 alternative -- manually setting the CPU mask of all
973 tasks in the system -- can cause problems and
974 suboptimal load balancer performance.
975
976 iucv= [HW,NET]
977
978 js= [HW,JOY] Analog joystick
979 See Documentation/input/joystick.txt.
980
981 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
982 specifies the amount of memory usable by the kernel
983 for non-movable allocations. The requested amount is
984 spread evenly throughout all nodes in the system. The
985 remaining memory in each node is used for Movable
986 pages. In the event, a node is too small to have both
987 kernelcore and Movable pages, kernelcore pages will
988 take priority and other nodes will have a larger number
989 of kernelcore pages. The Movable zone is used for the
990 allocation of pages that may be reclaimed or moved
991 by the page migration subsystem. This means that
992 HugeTLB pages may not be allocated from this zone.
993 Note that allocations like PTEs-from-HighMem still
994 use the HighMem zone if it exists, and the Normal
995 zone if it does not.
996
997 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
998 is similar to kernelcore except it specifies the
999 amount of memory used for migratable allocations.
1000 If both kernelcore and movablecore is specified,
1001 then kernelcore will be at *least* the specified
1002 value but may be more. If movablecore on its own
1003 is specified, the administrator must be careful
1004 that the amount of memory usable for all allocations
1005 is not too small.
1006
1007 keepinitrd [HW,ARM]
1008
1009 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1010 in oops dumps.
1011
1012 kgdboc= [HW] kgdb over consoles.
1013 Requires a tty driver that supports console polling.
1014 (only serial suported for now)
1015 Format: <serial_device>[,baud]
1016
1017 l2cr= [PPC]
1018
1019 l3cr= [PPC]
1020
1021 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1022 disabled it.
1023
1024 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
1025 C2 power state.
1026
1027 libata.dma= [LIBATA] DMA control
1028 libata.dma=0 Disable all PATA and SATA DMA
1029 libata.dma=1 PATA and SATA Disk DMA only
1030 libata.dma=2 ATAPI (CDROM) DMA only
1031 libata.dma=4 Compact Flash DMA only
1032 Combinations also work, so libata.dma=3 enables DMA
1033 for disks and CDROMs, but not CFs.
1034
1035 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1036 when set.
1037 Format: <int>
1038
1039 libata.force= [LIBATA] Force configurations. The format is comma
1040 separated list of "[ID:]VAL" where ID is
1041 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1042 matching port, link or device. Basically, it matches
1043 the ATA ID string printed on console by libata. If
1044 the whole ID part is omitted, the last PORT and DEVICE
1045 values are used. If ID hasn't been specified yet, the
1046 configuration applies to all ports, links and devices.
1047
1048 If only DEVICE is omitted, the parameter applies to
1049 the port and all links and devices behind it. DEVICE
1050 number of 0 either selects the first device or the
1051 first fan-out link behind PMP device. It does not
1052 select the host link. DEVICE number of 15 selects the
1053 host link and device attached to it.
1054
1055 The VAL specifies the configuration to force. As long
1056 as there's no ambiguity shortcut notation is allowed.
1057 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1058 The following configurations can be forced.
1059
1060 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1061 Any ID with matching PORT is used.
1062
1063 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1064
1065 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1066 udma[/][16,25,33,44,66,100,133] notation is also
1067 allowed.
1068
1069 * [no]ncq: Turn on or off NCQ.
1070
1071 * nohrst, nosrst, norst: suppress hard, soft
1072 and both resets.
1073
1074 If there are multiple matching configurations changing
1075 the same attribute, the last one is used.
1076
1077 load_ramdisk= [RAM] List of ramdisks to load from floppy
1078 See Documentation/ramdisk.txt.
1079
1080 lockd.nlm_grace_period=P [NFS] Assign grace period.
1081 Format: <integer>
1082
1083 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1084 Format: <integer>
1085
1086 lockd.nlm_timeout=T [NFS] Assign timeout value.
1087 Format: <integer>
1088
1089 lockd.nlm_udpport=M [NFS] Assign UDP port.
1090 Format: <integer>
1091
1092 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1093 Format: <irq>
1094
1095 loglevel= All Kernel Messages with a loglevel smaller than the
1096 console loglevel will be printed to the console. It can
1097 also be changed with klogd or other programs. The
1098 loglevels are defined as follows:
1099
1100 0 (KERN_EMERG) system is unusable
1101 1 (KERN_ALERT) action must be taken immediately
1102 2 (KERN_CRIT) critical conditions
1103 3 (KERN_ERR) error conditions
1104 4 (KERN_WARNING) warning conditions
1105 5 (KERN_NOTICE) normal but significant condition
1106 6 (KERN_INFO) informational
1107 7 (KERN_DEBUG) debug-level messages
1108
1109 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1110 Format: { n | nk | nM }
1111 n must be a power of two. The default size
1112 is set in the kernel config file.
1113
1114 logo.nologo [FB] Disables display of the built-in Linux logo.
1115 This may be used to provide more screen space for
1116 kernel log messages and is useful when debugging
1117 kernel boot problems.
1118
1119 lp=0 [LP] Specify parallel ports to use, e.g,
1120 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1121 lp=reset first parallel port). 'lp=0' disables the
1122 lp=auto printer driver. 'lp=reset' (which can be
1123 specified in addition to the ports) causes
1124 attached printers to be reset. Using
1125 lp=port1,port2,... specifies the parallel ports
1126 to associate lp devices with, starting with
1127 lp0. A port specification may be 'none' to skip
1128 that lp device, or a parport name such as
1129 'parport0'. Specifying 'lp=auto' instead of a
1130 port specification list means that device IDs
1131 from each port should be examined, to see if
1132 an IEEE 1284-compliant printer is attached; if
1133 so, the driver will manage that printer.
1134 See also header of drivers/char/lp.c.
1135
1136 lpj=n [KNL]
1137 Sets loops_per_jiffy to given constant, thus avoiding
1138 time-consuming boot-time autodetection (up to 250 ms per
1139 CPU). 0 enables autodetection (default). To determine
1140 the correct value for your kernel, boot with normal
1141 autodetection and see what value is printed. Note that
1142 on SMP systems the preset will be applied to all CPUs,
1143 which is likely to cause problems if your CPUs need
1144 significantly divergent settings. An incorrect value
1145 will cause delays in the kernel to be wrong, leading to
1146 unpredictable I/O errors and other breakage. Although
1147 unlikely, in the extreme case this might damage your
1148 hardware.
1149
1150 ltpc= [NET]
1151 Format: <io>,<irq>,<dma>
1152
1153 mac5380= [HW,SCSI] Format:
1154 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1155
1156 machvec= [IA64] Force the use of a particular machine-vector
1157 (machvec) in a generic kernel.
1158 Example: machvec=hpzx1_swiotlb
1159
1160 max_loop= [LOOP] Maximum number of loopback devices that can
1161 be mounted
1162 Format: <1-256>
1163
1164 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1165 should make use of. maxcpus=n : n >= 0 limits the
1166 kernel to using 'n' processors. n=0 is a special case,
1167 it is equivalent to "nosmp", which also disables
1168 the IO APIC.
1169
1170 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1171 equal to this physical address is ignored.
1172
1173 max_luns= [SCSI] Maximum number of LUNs to probe.
1174 Should be between 1 and 2^32-1.
1175
1176 max_report_luns=
1177 [SCSI] Maximum number of LUNs received.
1178 Should be between 1 and 16384.
1179
1180 mcatest= [IA-64]
1181
1182 mce [X86-32] Machine Check Exception
1183
1184 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1185
1186 md= [HW] RAID subsystems devices and level
1187 See Documentation/md.txt.
1188
1189 mdacon= [MDA]
1190 Format: <first>,<last>
1191 Specifies range of consoles to be captured by the MDA.
1192
1193 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1194 Amount of memory to be used when the kernel is not able
1195 to see the whole system memory or for test.
1196 [X86-32] Use together with memmap= to avoid physical
1197 address space collisions. Without memmap= PCI devices
1198 could be placed at addresses belonging to unused RAM.
1199
1200 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1201 memory.
1202
1203 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1204 E820 memory map, as specified by the user.
1205 Such memmap=exactmap lines can be constructed based on
1206 BIOS output or other requirements. See the memmap=nn@ss
1207 option description.
1208
1209 memmap=nn[KMG]@ss[KMG]
1210 [KNL] Force usage of a specific region of memory
1211 Region of memory to be used, from ss to ss+nn.
1212
1213 memmap=nn[KMG]#ss[KMG]
1214 [KNL,ACPI] Mark specific memory as ACPI data.
1215 Region of memory to be used, from ss to ss+nn.
1216
1217 memmap=nn[KMG]$ss[KMG]
1218 [KNL,ACPI] Mark specific memory as reserved.
1219 Region of memory to be used, from ss to ss+nn.
1220 Example: Exclude memory from 0x18690000-0x1869ffff
1221 memmap=64K$0x18690000
1222 or
1223 memmap=0x10000$0x18690000
1224
1225 memtest= [KNL,X86] Enable memtest
1226 Format: <integer>
1227 range: 0,4 : pattern number
1228 default : 0 <disable>
1229
1230 meye.*= [HW] Set MotionEye Camera parameters
1231 See Documentation/video4linux/meye.txt.
1232
1233 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1234 Multi-Function General Purpose Timers on AMD Geode
1235 platforms.
1236
1237 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1238 the BIOS has incorrectly applied a workaround. TinyBIOS
1239 version 0.98 is known to be affected, 0.99 fixes the
1240 problem by letting the user disable the workaround.
1241
1242 mga= [HW,DRM]
1243
1244 mminit_loglevel=
1245 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1246 parameter allows control of the logging verbosity for
1247 the additional memory initialisation checks. A value
1248 of 0 disables mminit logging and a level of 4 will
1249 log everything. Information is printed at KERN_DEBUG
1250 so loglevel=8 may also need to be specified.
1251
1252 mousedev.tap_time=
1253 [MOUSE] Maximum time between finger touching and
1254 leaving touchpad surface for touch to be considered
1255 a tap and be reported as a left button click (for
1256 touchpads working in absolute mode only).
1257 Format: <msecs>
1258 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1259 reporting absolute coordinates, such as tablets
1260 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1261 reporting absolute coordinates, such as tablets
1262
1263 mpu401= [HW,OSS]
1264 Format: <io>,<irq>
1265
1266 MTD_Partition= [MTD]
1267 Format: <name>,<region-number>,<size>,<offset>
1268
1269 MTD_Region= [MTD] Format:
1270 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1271
1272 mtdparts= [MTD]
1273 See drivers/mtd/cmdlinepart.c.
1274
1275 mtdset= [ARM]
1276 ARM/S3C2412 JIVE boot control
1277
1278 See arch/arm/mach-s3c2412/mach-jive.c
1279
1280 mtouchusb.raw_coordinates=
1281 [HW] Make the MicroTouch USB driver use raw coordinates
1282 ('y', default) or cooked coordinates ('n')
1283
1284 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1285
1286 NCR_D700= [HW,SCSI]
1287 See header of drivers/scsi/NCR_D700.c.
1288
1289 ncr5380= [HW,SCSI]
1290
1291 ncr53c400= [HW,SCSI]
1292
1293 ncr53c400a= [HW,SCSI]
1294
1295 ncr53c406a= [HW,SCSI]
1296
1297 ncr53c8xx= [HW,SCSI]
1298
1299 netdev= [NET] Network devices parameters
1300 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1301 Note that mem_start is often overloaded to mean
1302 something different and driver-specific.
1303 This usage is only documented in each driver source
1304 file if at all.
1305
1306 nf_conntrack.acct=
1307 [NETFILTER] Enable connection tracking flow accounting
1308 0 to disable accounting
1309 1 to enable accounting
1310 Default value depends on CONFIG_NF_CT_ACCT that is
1311 going to be removed in 2.6.29.
1312
1313 nfsaddrs= [NFS]
1314 See Documentation/filesystems/nfsroot.txt.
1315
1316 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1317 See Documentation/filesystems/nfsroot.txt.
1318
1319 nfs.callback_tcpport=
1320 [NFS] set the TCP port on which the NFSv4 callback
1321 channel should listen.
1322
1323 nfs.idmap_cache_timeout=
1324 [NFS] set the maximum lifetime for idmapper cache
1325 entries.
1326
1327 nfs.enable_ino64=
1328 [NFS] enable 64-bit inode numbers.
1329 If zero, the NFS client will fake up a 32-bit inode
1330 number for the readdir() and stat() syscalls instead
1331 of returning the full 64-bit number.
1332 The default is to return 64-bit inode numbers.
1333
1334 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1335 when a NMI is triggered.
1336 Format: [state][,regs][,debounce][,die]
1337
1338 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1339
1340 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1341 emulation library even if a 387 maths coprocessor
1342 is present.
1343
1344 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1345 caches in the slab allocator. Saves per-node memory,
1346 but will impact performance.
1347
1348 noalign [KNL,ARM]
1349
1350 noapic [SMP,APIC] Tells the kernel to not make use of any
1351 IOAPICs that may be present in the system.
1352
1353 nobats [PPC] Do not use BATs for mapping kernel lowmem
1354 on "Classic" PPC cores.
1355
1356 nocache [ARM]
1357
1358 nodelayacct [KNL] Disable per-task delay accounting
1359
1360 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1361
1362 noefi [X86-32,X86-64] Disable EFI runtime services support.
1363
1364 noexec [IA-64]
1365
1366 noexec [X86-32,X86-64]
1367 On X86-32 available only on PAE configured kernels.
1368 noexec=on: enable non-executable mappings (default)
1369 noexec=off: disable non-executable mappings
1370
1371 noexec32 [X86-64]
1372 This affects only 32-bit executables.
1373 noexec32=on: enable non-executable mappings (default)
1374 read doesn't imply executable mappings
1375 noexec32=off: disable non-executable mappings
1376 read implies executable mappings
1377
1378 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1379 register save and restore. The kernel will only save
1380 legacy floating-point registers on task switch.
1381
1382 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1383
1384 nohlt [BUGS=ARM]
1385
1386 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1387 instruction doesn't work correctly and not to
1388 use it.
1389
1390 nohalt [IA-64] Tells the kernel not to use the power saving
1391 function PAL_HALT_LIGHT when idle. This increases
1392 power-consumption. On the positive side, it reduces
1393 interrupt wake-up latency, which may improve performance
1394 in certain environments such as networked servers or
1395 real-time systems.
1396
1397 nohz= [KNL] Boottime enable/disable dynamic ticks
1398 Valid arguments: on, off
1399 Default: on
1400
1401 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1402
1403 noirqdebug [X86-32] Disables the code which attempts to detect and
1404 disable unhandled interrupt sources.
1405
1406 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1407 broken timer IRQ sources.
1408
1409 noisapnp [ISAPNP] Disables ISA PnP code.
1410
1411 noinitrd [RAM] Tells the kernel not to load any configured
1412 initial RAM disk.
1413
1414 nointroute [IA-64]
1415
1416 nojitter [IA64] Disables jitter checking for ITC timers.
1417
1418 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1419
1420 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1421
1422 noltlbs [PPC] Do not use large page/tlb entries for kernel
1423 lowmem mapping on PPC40x.
1424
1425 nomca [IA-64] Disable machine check abort handling
1426
1427 nomce [X86-32] Machine Check Exception
1428
1429 nomfgpt [X86-32] Disable Multi-Function General Purpose
1430 Timer usage (for AMD Geode machines).
1431
1432 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1433
1434 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1435 with UP alternatives
1436
1437 noresidual [PPC] Don't use residual data on PReP machines.
1438
1439 noresume [SWSUSP] Disables resume and restores original swap
1440 space.
1441
1442 no-scroll [VGA] Disables scrollback.
1443 This is required for the Braillex ib80-piezo Braille
1444 reader made by F.H. Papenmeier (Germany).
1445
1446 nosbagart [IA-64]
1447
1448 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1449
1450 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1451 and disable the IO APIC. legacy for "maxcpus=0".
1452
1453 nosoftlockup [KNL] Disable the soft-lockup detector.
1454
1455 nosync [HW,M68K] Disables sync negotiation for all devices.
1456
1457 notsc [BUGS=X86-32] Disable Time Stamp Counter
1458
1459 nousb [USB] Disable the USB subsystem
1460
1461 nowb [ARM]
1462
1463 nptcg= [IA64] Override max number of concurrent global TLB
1464 purges which is reported from either PAL_VM_SUMMARY or
1465 SAL PALO.
1466
1467 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1468 one of ['zone', 'node', 'default'] can be specified
1469 This can be set from sysctl after boot.
1470 See Documentation/sysctl/vm.txt for details.
1471
1472 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1473
1474 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1475 Rather than timing out after 20 ms if an EC
1476 command is not properly ACKed, override the length
1477 of the timeout. We have interrupts disabled while
1478 waiting for the ACK, so if this is set too high
1479 interrupts *may* be lost!
1480
1481 opl3= [HW,OSS]
1482 Format: <io>
1483
1484 oprofile.timer= [HW]
1485 Use timer interrupt instead of performance counters
1486
1487 osst= [HW,SCSI] SCSI Tape Driver
1488 Format: <buffer_size>,<write_threshold>
1489 See also Documentation/scsi/st.txt.
1490
1491 panic= [KNL] Kernel behaviour on panic
1492 Format: <timeout>
1493
1494 parkbd.port= [HW] Parallel port number the keyboard adapter is
1495 connected to, default is 0.
1496 Format: <parport#>
1497 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1498 0 for XT, 1 for AT (default is AT).
1499 Format: <mode>
1500
1501 parport= [HW,PPT] Specify parallel ports. 0 disables.
1502 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1503 Use 'auto' to force the driver to use any
1504 IRQ/DMA settings detected (the default is to
1505 ignore detected IRQ/DMA settings because of
1506 possible conflicts). You can specify the base
1507 address, IRQ, and DMA settings; IRQ and DMA
1508 should be numbers, or 'auto' (for using detected
1509 settings on that particular port), or 'nofifo'
1510 (to avoid using a FIFO even if it is detected).
1511 Parallel ports are assigned in the order they
1512 are specified on the command line, starting
1513 with parport0.
1514
1515 parport_init_mode= [HW,PPT]
1516 Configure VIA parallel port to operate in
1517 a specific mode. This is necessary on Pegasos
1518 computer where firmware has no options for setting
1519 up parallel port mode and sets it to spp.
1520 Currently this function knows 686a and 8231 chips.
1521 Format: [spp|ps2|epp|ecp|ecpepp]
1522
1523 pas2= [HW,OSS] Format:
1524 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1525
1526 pas16= [HW,SCSI]
1527 See header of drivers/scsi/pas16.c.
1528
1529 pause_on_oops=
1530 Halt all CPUs after the first oops has been printed for
1531 the specified number of seconds. This is to be used if
1532 your oopses keep scrolling off the screen.
1533
1534 pcbit= [HW,ISDN]
1535
1536 pcd. [PARIDE]
1537 See header of drivers/block/paride/pcd.c.
1538 See also Documentation/paride.txt.
1539
1540 pci=option[,option...] [PCI] various PCI subsystem options:
1541 off [X86-32] don't probe for the PCI bus
1542 bios [X86-32] force use of PCI BIOS, don't access
1543 the hardware directly. Use this if your machine
1544 has a non-standard PCI host bridge.
1545 nobios [X86-32] disallow use of PCI BIOS, only direct
1546 hardware access methods are allowed. Use this
1547 if you experience crashes upon bootup and you
1548 suspect they are caused by the BIOS.
1549 conf1 [X86-32] Force use of PCI Configuration
1550 Mechanism 1.
1551 conf2 [X86-32] Force use of PCI Configuration
1552 Mechanism 2.
1553 noaer [PCIE] If the PCIEAER kernel config parameter is
1554 enabled, this kernel boot option can be used to
1555 disable the use of PCIE advanced error reporting.
1556 nodomains [PCI] Disable support for multiple PCI
1557 root domains (aka PCI segments, in ACPI-speak).
1558 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1559 Configuration
1560 nomsi [MSI] If the PCI_MSI kernel config parameter is
1561 enabled, this kernel boot option can be used to
1562 disable the use of MSI interrupts system-wide.
1563 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1564 routing table. These calls are known to be buggy
1565 on several machines and they hang the machine
1566 when used, but on other computers it's the only
1567 way to get the interrupt routing table. Try
1568 this option if the kernel is unable to allocate
1569 IRQs or discover secondary PCI buses on your
1570 motherboard.
1571 rom [X86-32] Assign address space to expansion ROMs.
1572 Use with caution as certain devices share
1573 address decoders between ROMs and other
1574 resources.
1575 norom [X86-32,X86_64] Do not assign address space to
1576 expansion ROMs that do not already have
1577 BIOS assigned address ranges.
1578 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1579 assigned automatically to PCI devices. You can
1580 make the kernel exclude IRQs of your ISA cards
1581 this way.
1582 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1583 of the PIRQ table (normally generated
1584 by the BIOS) if it is outside the
1585 F0000h-100000h range.
1586 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1587 useful if the kernel is unable to find your
1588 secondary buses and you want to tell it
1589 explicitly which ones they are.
1590 assign-busses [X86-32] Always assign all PCI bus
1591 numbers ourselves, overriding
1592 whatever the firmware may have done.
1593 usepirqmask [X86-32] Honor the possible IRQ mask stored
1594 in the BIOS $PIR table. This is needed on
1595 some systems with broken BIOSes, notably
1596 some HP Pavilion N5400 and Omnibook XE3
1597 notebooks. This will have no effect if ACPI
1598 IRQ routing is enabled.
1599 noacpi [X86-32] Do not use ACPI for IRQ routing
1600 or for PCI scanning.
1601 use_crs [X86-32] Use _CRS for PCI resource
1602 allocation.
1603 routeirq Do IRQ routing for all PCI devices.
1604 This is normally done in pci_enable_device(),
1605 so this option is a temporary workaround
1606 for broken drivers that don't call it.
1607 skip_isa_align [X86] do not align io start addr, so can
1608 handle more pci cards
1609 firmware [ARM] Do not re-enumerate the bus but instead
1610 just use the configuration from the
1611 bootloader. This is currently used on
1612 IXP2000 systems where the bus has to be
1613 configured a certain way for adjunct CPUs.
1614 noearly [X86] Don't do any early type 1 scanning.
1615 This might help on some broken boards which
1616 machine check when some devices' config space
1617 is read. But various workarounds are disabled
1618 and some IOMMU drivers will not work.
1619 bfsort Sort PCI devices into breadth-first order.
1620 This sorting is done to get a device
1621 order compatible with older (<= 2.4) kernels.
1622 nobfsort Don't sort PCI devices into breadth-first order.
1623 cbiosize=nn[KMG] The fixed amount of bus space which is
1624 reserved for the CardBus bridge's IO window.
1625 The default value is 256 bytes.
1626 cbmemsize=nn[KMG] The fixed amount of bus space which is
1627 reserved for the CardBus bridge's memory
1628 window. The default value is 64 megabytes.
1629
1630 pcmv= [HW,PCMCIA] BadgePAD 4
1631
1632 pd. [PARIDE]
1633 See Documentation/paride.txt.
1634
1635 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1636 boot time.
1637 Format: { 0 | 1 }
1638 See arch/parisc/kernel/pdc_chassis.c
1639
1640 pf. [PARIDE]
1641 See Documentation/paride.txt.
1642
1643 pg. [PARIDE]
1644 See Documentation/paride.txt.
1645
1646 pirq= [SMP,APIC] Manual mp-table setup
1647 See Documentation/i386/IO-APIC.txt.
1648
1649 plip= [PPT,NET] Parallel port network link
1650 Format: { parport<nr> | timid | 0 }
1651 See also Documentation/parport.txt.
1652
1653 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1654 Override pmtimer IOPort with a hex value.
1655 e.g. pmtmr=0x508
1656
1657 pnpacpi= [ACPI]
1658 { off }
1659
1660 pnpbios= [ISAPNP]
1661 { on | off | curr | res | no-curr | no-res }
1662
1663 pnp_reserve_irq=
1664 [ISAPNP] Exclude IRQs for the autoconfiguration
1665
1666 pnp_reserve_dma=
1667 [ISAPNP] Exclude DMAs for the autoconfiguration
1668
1669 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1670 Ranges are in pairs (I/O port base and size).
1671
1672 pnp_reserve_mem=
1673 [ISAPNP] Exclude memory regions for the
1674 autoconfiguration.
1675 Ranges are in pairs (memory base and size).
1676
1677 print-fatal-signals=
1678 [KNL] debug: print fatal signals
1679 print-fatal-signals=1: print segfault info to
1680 the kernel console.
1681 default: off.
1682
1683 printk.time= Show timing data prefixed to each printk message line
1684 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1685
1686 profile= [KNL] Enable kernel profiling via /proc/profile
1687 Format: [schedule,]<number>
1688 Param: "schedule" - profile schedule points.
1689 Param: <number> - step/bucket size as a power of 2 for
1690 statistical time based profiling.
1691 Param: "sleep" - profile D-state sleeping (millisecs).
1692 Requires CONFIG_SCHEDSTATS
1693 Param: "kvm" - profile VM exits.
1694
1695 processor.max_cstate= [HW,ACPI]
1696 Limit processor to maximum C-state
1697 max_cstate=9 overrides any DMI blacklist limit.
1698
1699 processor.nocst [HW,ACPI]
1700 Ignore the _CST method to determine C-states,
1701 instead using the legacy FADT method
1702
1703 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1704 before loading.
1705 See Documentation/ramdisk.txt.
1706
1707 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1708 probe for; one of (bare|imps|exps|lifebook|any).
1709 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1710 per second.
1711 psmouse.resetafter= [HW,MOUSE]
1712 Try to reset the device after so many bad packets
1713 (0 = never).
1714 psmouse.resolution=
1715 [HW,MOUSE] Set desired mouse resolution, in dpi.
1716 psmouse.smartscroll=
1717 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1718 0 = disabled, 1 = enabled (default).
1719
1720 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1721 Format:
1722 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1723
1724 pt. [PARIDE]
1725 See Documentation/paride.txt.
1726
1727 pty.legacy_count=
1728 [KNL] Number of legacy pty's. Overwrites compiled-in
1729 default number.
1730
1731 quiet [KNL] Disable most log messages
1732
1733 r128= [HW,DRM]
1734
1735 raid= [HW,RAID]
1736 See Documentation/md.txt.
1737
1738 ramdisk_blocksize= [RAM]
1739 See Documentation/ramdisk.txt.
1740
1741 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1742 See Documentation/ramdisk.txt.
1743
1744 rcupdate.blimit= [KNL,BOOT]
1745 Set maximum number of finished RCU callbacks to process
1746 in one batch.
1747
1748 rcupdate.qhimark= [KNL,BOOT]
1749 Set threshold of queued
1750 RCU callbacks over which batch limiting is disabled.
1751
1752 rcupdate.qlowmark= [KNL,BOOT]
1753 Set threshold of queued RCU callbacks below which
1754 batch limiting is re-enabled.
1755
1756 rdinit= [KNL]
1757 Format: <full_path>
1758 Run specified binary instead of /init from the ramdisk,
1759 used for early userspace startup. See initrd.
1760
1761 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1762 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1763 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1764
1765 relax_domain_level=
1766 [KNL, SMP] Set scheduler's default relax_domain_level.
1767 See Documentation/cpusets.txt.
1768
1769 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1770
1771 reservetop= [X86-32]
1772 Format: nn[KMG]
1773 Reserves a hole at the top of the kernel virtual
1774 address space.
1775
1776 reset_devices [KNL] Force drivers to reset the underlying device
1777 during initialization.
1778
1779 resume= [SWSUSP]
1780 Specify the partition device for software suspend
1781
1782 resume_offset= [SWSUSP]
1783 Specify the offset from the beginning of the partition
1784 given by "resume=" at which the swap header is located,
1785 in <PAGE_SIZE> units (needed only for swap files).
1786 See Documentation/power/swsusp-and-swap-files.txt
1787
1788 retain_initrd [RAM] Keep initrd memory after extraction
1789
1790 rhash_entries= [KNL,NET]
1791 Set number of hash buckets for route cache
1792
1793 riscom8= [HW,SERIAL]
1794 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1795
1796 ro [KNL] Mount root device read-only on boot
1797
1798 root= [KNL] Root filesystem
1799
1800 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1801 mount the root filesystem
1802
1803 rootflags= [KNL] Set root filesystem mount option string
1804
1805 rootfstype= [KNL] Set root filesystem type
1806
1807 rootwait [KNL] Wait (indefinitely) for root device to show up.
1808 Useful for devices that are detected asynchronously
1809 (e.g. USB and MMC devices).
1810
1811 root_plug.vendor_id=
1812 [ROOTPLUG] Override the default vendor ID
1813
1814 root_plug.product_id=
1815 [ROOTPLUG] Override the default product ID
1816
1817 root_plug.debug=
1818 [ROOTPLUG] Enable debugging output
1819
1820 rw [KNL] Mount root device read-write on boot
1821
1822 S [KNL] Run init in single mode
1823
1824 sa1100ir [NET]
1825 See drivers/net/irda/sa1100_ir.c.
1826
1827 sbni= [NET] Granch SBNI12 leased line adapter
1828
1829 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1830 Format: <io>[,<timeout>[,<isapnp>]]
1831
1832 scsi_debug_*= [SCSI]
1833 See drivers/scsi/scsi_debug.c.
1834
1835 scsi_default_dev_flags=
1836 [SCSI] SCSI default device flags
1837 Format: <integer>
1838
1839 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1840 Format: <vendor>:<model>:<flags>
1841 (flags are integer value)
1842
1843 scsi_logging_level= [SCSI] a bit mask of logging levels
1844 See drivers/scsi/scsi_logging.h for bits. Also
1845 settable via sysctl at dev.scsi.logging_level
1846 (/proc/sys/dev/scsi/logging_level).
1847 There is also a nice 'scsi_logging_level' script in the
1848 S390-tools package, available for download at
1849 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1850
1851 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1852 discovered. async scans them in kernel threads,
1853 allowing boot to proceed. none ignores them, expecting
1854 user space to do the scan.
1855
1856 selinux [SELINUX] Disable or enable SELinux at boot time.
1857 Format: { "0" | "1" }
1858 See security/selinux/Kconfig help text.
1859 0 -- disable.
1860 1 -- enable.
1861 Default value is set via kernel config option.
1862 If enabled at boot time, /selinux/disable can be used
1863 later to disable prior to initial policy load.
1864
1865 selinux_compat_net =
1866 [SELINUX] Set initial selinux_compat_net flag value.
1867 Format: { "0" | "1" }
1868 0 -- use new secmark-based packet controls
1869 1 -- use legacy packet controls
1870 Default value is 0 (preferred).
1871 Value can be changed at runtime via
1872 /selinux/compat_net.
1873
1874 serialnumber [BUGS=X86-32]
1875
1876 shapers= [NET]
1877 Maximal number of shapers.
1878
1879 show_msr= [x86] show boot-time MSR settings
1880 Format: { <integer> }
1881 Show boot-time (BIOS-initialized) MSR settings.
1882 The parameter means the number of CPUs to show,
1883 for example 1 means boot CPU only.
1884
1885 sim710= [SCSI,HW]
1886 See header of drivers/scsi/sim710.c.
1887
1888 simeth= [IA-64]
1889 simscsi=
1890
1891 slram= [HW,MTD]
1892
1893 slub_debug[=options[,slabs]] [MM, SLUB]
1894 Enabling slub_debug allows one to determine the
1895 culprit if slab objects become corrupted. Enabling
1896 slub_debug can create guard zones around objects and
1897 may poison objects when not in use. Also tracks the
1898 last alloc / free. For more information see
1899 Documentation/vm/slub.txt.
1900
1901 slub_max_order= [MM, SLUB]
1902 Determines the maximum allowed order for slabs.
1903 A high setting may cause OOMs due to memory
1904 fragmentation. For more information see
1905 Documentation/vm/slub.txt.
1906
1907 slub_min_objects= [MM, SLUB]
1908 The minimum number of objects per slab. SLUB will
1909 increase the slab order up to slub_max_order to
1910 generate a sufficiently large slab able to contain
1911 the number of objects indicated. The higher the number
1912 of objects the smaller the overhead of tracking slabs
1913 and the less frequently locks need to be acquired.
1914 For more information see Documentation/vm/slub.txt.
1915
1916 slub_min_order= [MM, SLUB]
1917 Determines the mininum page order for slabs. Must be
1918 lower than slub_max_order.
1919 For more information see Documentation/vm/slub.txt.
1920
1921 slub_nomerge [MM, SLUB]
1922 Disable merging of slabs with similar size. May be
1923 necessary if there is some reason to distinguish
1924 allocs to different slabs. Debug options disable
1925 merging on their own.
1926 For more information see Documentation/vm/slub.txt.
1927
1928 smart2= [HW]
1929 Format: <io1>[,<io2>[,...,<io8>]]
1930
1931 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1932 attempt to substitute SMP alternatives once at boot.
1933
1934 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1935 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1936 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1937 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1938 smsc-ircc2.ircc_irq= [HW] IRQ line
1939 smsc-ircc2.ircc_dma= [HW] DMA channel
1940 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1941 0: Toshiba Satellite 1800 (GP data pin select)
1942 1: Fast pin select (default)
1943 2: ATC IRMode
1944
1945 snd-ad1816a= [HW,ALSA]
1946
1947 snd-ad1848= [HW,ALSA]
1948
1949 snd-ali5451= [HW,ALSA]
1950
1951 snd-als100= [HW,ALSA]
1952
1953 snd-als4000= [HW,ALSA]
1954
1955 snd-azt2320= [HW,ALSA]
1956
1957 snd-cmi8330= [HW,ALSA]
1958
1959 snd-cmipci= [HW,ALSA]
1960
1961 snd-cs4231= [HW,ALSA]
1962
1963 snd-cs4232= [HW,ALSA]
1964
1965 snd-cs4236= [HW,ALSA]
1966
1967 snd-cs4281= [HW,ALSA]
1968
1969 snd-cs46xx= [HW,ALSA]
1970
1971 snd-dt019x= [HW,ALSA]
1972
1973 snd-dummy= [HW,ALSA]
1974
1975 snd-emu10k1= [HW,ALSA]
1976
1977 snd-ens1370= [HW,ALSA]
1978
1979 snd-ens1371= [HW,ALSA]
1980
1981 snd-es968= [HW,ALSA]
1982
1983 snd-es1688= [HW,ALSA]
1984
1985 snd-es18xx= [HW,ALSA]
1986
1987 snd-es1938= [HW,ALSA]
1988
1989 snd-es1968= [HW,ALSA]
1990
1991 snd-fm801= [HW,ALSA]
1992
1993 snd-gusclassic= [HW,ALSA]
1994
1995 snd-gusextreme= [HW,ALSA]
1996
1997 snd-gusmax= [HW,ALSA]
1998
1999 snd-hdsp= [HW,ALSA]
2000
2001 snd-ice1712= [HW,ALSA]
2002
2003 snd-intel8x0= [HW,ALSA]
2004
2005 snd-interwave= [HW,ALSA]
2006
2007 snd-interwave-stb=
2008 [HW,ALSA]
2009
2010 snd-korg1212= [HW,ALSA]
2011
2012 snd-maestro3= [HW,ALSA]
2013
2014 snd-mpu401= [HW,ALSA]
2015
2016 snd-mtpav= [HW,ALSA]
2017
2018 snd-nm256= [HW,ALSA]
2019
2020 snd-opl3sa2= [HW,ALSA]
2021
2022 snd-opti92x-ad1848=
2023 [HW,ALSA]
2024
2025 snd-opti92x-cs4231=
2026 [HW,ALSA]
2027
2028 snd-opti93x= [HW,ALSA]
2029
2030 snd-pmac= [HW,ALSA]
2031
2032 snd-rme32= [HW,ALSA]
2033
2034 snd-rme96= [HW,ALSA]
2035
2036 snd-rme9652= [HW,ALSA]
2037
2038 snd-sb8= [HW,ALSA]
2039
2040 snd-sb16= [HW,ALSA]
2041
2042 snd-sbawe= [HW,ALSA]
2043
2044 snd-serial= [HW,ALSA]
2045
2046 snd-sgalaxy= [HW,ALSA]
2047
2048 snd-sonicvibes= [HW,ALSA]
2049
2050 snd-sun-amd7930=
2051 [HW,ALSA]
2052
2053 snd-sun-cs4231= [HW,ALSA]
2054
2055 snd-trident= [HW,ALSA]
2056
2057 snd-usb-audio= [HW,ALSA,USB]
2058
2059 snd-via82xx= [HW,ALSA]
2060
2061 snd-virmidi= [HW,ALSA]
2062
2063 snd-wavefront= [HW,ALSA]
2064
2065 snd-ymfpci= [HW,ALSA]
2066
2067 softlockup_panic=
2068 [KNL] Should the soft-lockup detector generate panics.
2069
2070 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2071 See Documentation/sonypi.txt
2072
2073 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2074 See Documentation/specialix.txt.
2075
2076 spia_io_base= [HW,MTD]
2077 spia_fio_base=
2078 spia_pedr=
2079 spia_peddr=
2080
2081 sscape= [HW,OSS]
2082 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2083
2084 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2085 See Documentation/scsi/st.txt.
2086
2087 sti= [PARISC,HW]
2088 Format: <num>
2089 Set the STI (builtin display/keyboard on the HP-PARISC
2090 machines) console (graphic card) which should be used
2091 as the initial boot-console.
2092 See also comment in drivers/video/console/sticore.c.
2093
2094 sti_font= [HW]
2095 See comment in drivers/video/console/sticore.c.
2096
2097 stifb= [HW]
2098 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2099
2100 sunrpc.pool_mode=
2101 [NFS]
2102 Control how the NFS server code allocates CPUs to
2103 service thread pools. Depending on how many NICs
2104 you have and where their interrupts are bound, this
2105 option will affect which CPUs will do NFS serving.
2106 Note: this parameter cannot be changed while the
2107 NFS server is running.
2108
2109 auto the server chooses an appropriate mode
2110 automatically using heuristics
2111 global a single global pool contains all CPUs
2112 percpu one pool for each CPU
2113 pernode one pool for each NUMA node (equivalent
2114 to global on non-NUMA machines)
2115
2116 swiotlb= [IA-64] Number of I/O TLB slabs
2117
2118 switches= [HW,M68k]
2119
2120 sym53c416= [HW,SCSI]
2121 See header of drivers/scsi/sym53c416.c.
2122
2123 sysrq_always_enabled
2124 [KNL]
2125 Ignore sysrq setting - this boot parameter will
2126 neutralize any effect of /proc/sys/kernel/sysrq.
2127 Useful for debugging.
2128
2129 t128= [HW,SCSI]
2130 See header of drivers/scsi/t128.c.
2131
2132 tdfx= [HW,DRM]
2133
2134 test_suspend= [SUSPEND]
2135 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2136 standby suspend) as the system sleep state to briefly
2137 enter during system startup. The system is woken from
2138 this state using a wakeup-capable RTC alarm.
2139
2140 thash_entries= [KNL,NET]
2141 Set number of hash buckets for TCP connection
2142
2143 thermal.act= [HW,ACPI]
2144 -1: disable all active trip points in all thermal zones
2145 <degrees C>: override all lowest active trip points
2146
2147 thermal.crt= [HW,ACPI]
2148 -1: disable all critical trip points in all thermal zones
2149 <degrees C>: lower all critical trip points
2150
2151 thermal.nocrt= [HW,ACPI]
2152 Set to disable actions on ACPI thermal zone
2153 critical and hot trip points.
2154
2155 thermal.off= [HW,ACPI]
2156 1: disable ACPI thermal control
2157
2158 thermal.psv= [HW,ACPI]
2159 -1: disable all passive trip points
2160 <degrees C>: override all passive trip points to this value
2161
2162 thermal.tzp= [HW,ACPI]
2163 Specify global default ACPI thermal zone polling rate
2164 <deci-seconds>: poll all this frequency
2165 0: no polling (default)
2166
2167 tmscsim= [HW,SCSI]
2168 See comment before function dc390_setup() in
2169 drivers/scsi/tmscsim.c.
2170
2171 tp720= [HW,PS2]
2172
2173 trix= [HW,OSS] MediaTrix AudioTrix Pro
2174 Format:
2175 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2176
2177 turbografx.map[2|3]= [HW,JOY]
2178 TurboGraFX parallel port interface
2179 Format:
2180 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2181 See also Documentation/input/joystick-parport.txt
2182
2183 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2184 See header of drivers/scsi/u14-34f.c.
2185
2186 uart401= [HW,OSS]
2187 Format: <io>,<irq>
2188
2189 uart6850= [HW,OSS]
2190 Format: <io>,<irq>
2191
2192 uhci-hcd.ignore_oc=
2193 [USB] Ignore overcurrent events (default N).
2194 Some badly-designed motherboards generate lots of
2195 bogus events, for ports that aren't wired to
2196 anything. Set this parameter to avoid log spamming.
2197 Note that genuine overcurrent events won't be
2198 reported either.
2199
2200 unknown_nmi_panic
2201 [X86-32,X86-64]
2202 Set unknown_nmi_panic=1 early on boot.
2203
2204 usbcore.autosuspend=
2205 [USB] The autosuspend time delay (in seconds) used
2206 for newly-detected USB devices (default 2). This
2207 is the time required before an idle device will be
2208 autosuspended. Devices for which the delay is set
2209 to a negative value won't be autosuspended at all.
2210
2211 usbhid.mousepoll=
2212 [USBHID] The interval which mice are to be polled at.
2213
2214 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2215 kernel's map of available physical RAM.
2216
2217 vdso= [X86-32,SH,x86-64]
2218 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2219 vdso=1: enable VDSO (default)
2220 vdso=0: disable VDSO mapping
2221
2222 vdso32= [X86-32,X86-64]
2223 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2224 vdso32=1: enable 32-bit VDSO (default)
2225 vdso32=0: disable 32-bit VDSO mapping
2226
2227 vector= [IA-64,SMP]
2228 vector=percpu: enable percpu vector domain
2229
2230 video= [FB] Frame buffer configuration
2231 See Documentation/fb/modedb.txt.
2232
2233 vga= [BOOT,X86-32] Select a particular video mode
2234 See Documentation/i386/boot.txt and
2235 Documentation/svga.txt.
2236 Use vga=ask for menu.
2237 This is actually a boot loader parameter; the value is
2238 passed to the kernel using a special protocol.
2239
2240 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2241 size of <nn>. This can be used to increase the
2242 minimum size (128MB on x86). It can also be used to
2243 decrease the size and leave more room for directly
2244 mapped kernel RAM.
2245
2246 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2247 Format: <command>
2248
2249 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2250 Format: <command>
2251
2252 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2253 Format: <command>
2254
2255 waveartist= [HW,OSS]
2256 Format: <io>,<irq>,<dma>,<dma2>
2257
2258 wd33c93= [HW,SCSI]
2259 See header of drivers/scsi/wd33c93.c.
2260
2261 wd7000= [HW,SCSI]
2262 See header of drivers/scsi/wd7000.c.
2263
2264 wdt= [WDT] Watchdog
2265 See Documentation/watchdog/wdt.txt.
2266
2267 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2268 xd_geo= See header of drivers/block/xd.c.
2269
2270 xirc2ps_cs= [NET,PCMCIA]
2271 Format:
2272 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2273
2274 norandmaps Don't use address space randomization
2275 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2276
2277______________________________________________________________________
2278
2279TODO:
2280
2281 Add documentation for ALSA options.
2282 Add more DRM drivers.