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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The 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
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
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 is enabled.
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.
99 X86-32 X86-32, aka i386 architecture is enabled.
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 .
104 In addition, the following text indicates that the option:
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.
110 Parameters denoted with BOOT are actually interpreted by the boot
111 loader, and have no meaning to the kernel directly.
112 Do not modify the syntax of boot loader parameters without extreme
113 need or coordination with <Documentation/i386/boot.txt>.
115 There are also arch-specific kernel-parameters not documented here.
116 See for example <Documentation/x86_64/boot-options.txt>.
118 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119 a trailing = on the name of any parameter states that that parameter will
120 be entered as an environment variable, whereas its absence indicates that
121 it will appear as a kernel argument readable via /proc/cmdline by programs
122 running once the system is up.
124 The number of kernel parameters is not limited, but the length of the
125 complete command line (parameters including spaces etc.) is limited to
126 a fixed number of characters. This limit depends on the architecture
127 and is between 256 and 4096 characters. It is defined in the file
128 ./include/asm/setup.h as COMMAND_LINE_SIZE.
131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
133 Format: { force | off | ht | strict | noirq }
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
138 strict -- Be less tolerant of platforms that are not
139 strictly ACPI specification compliant.
141 See also Documentation/power/pm.txt, pci=noacpi
143 acpi_apic_instance= [ACPI, IOAPIC]
144 Format: <int>
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
147 default: 0
149 acpi_sleep= [HW,ACPI] Sleep options
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.
155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
156 Format: { level | edge | high | low }
158 acpi_irq_balance [HW,ACPI]
159 ACPI will balance active IRQs
160 default in APIC mode
162 acpi_irq_nobalance [HW,ACPI]
163 ACPI will not move active IRQs (default)
164 default in PIC mode
166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
167 use by PCI
168 Format: <irq>,<irq>...
170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
171 Format: <irq>,<irq>...
173 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
176 Format: To spoof as Windows 98: ="Microsoft Windows"
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
183 acpi_serialize [HW,ACPI] force serialization of AML methods
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.
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
193 acpi.debug_layer= [HW,ACPI]
194 Format: <int>
195 Each bit of the <int> indicates an ACPI debug layer,
196 1: enable, 0: disable. It is useful for boot time
197 debugging. After system has booted up, it can be set
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.
210 acpi.debug_level= [HW,ACPI]
211 Format: <int>
212 Each bit of the <int> indicates an ACPI debug level,
213 1: enable, 0: disable. It is useful for boot time
214 debugging. After system has booted up, it can be set
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.
228 acpi_pm_good [X86-32,X86-64]
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.
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)
239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
243 The kernel tries to set a reasonable default.
245 disable_timer_pin_1 [i386,x86-64]
246 Disable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs.
249 ad1848= [HW,OSS]
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
252 advansys= [HW,SCSI]
253 See header of drivers/scsi/advansys.c.
255 advwdt= [HW,WDT] Advantech WDT
256 Format: <iostart>,<iostop>
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.
262 aha152x= [HW,SCSI]
263 See Documentation/scsi/aha152x.txt.
265 aha1542= [HW,SCSI]
266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
268 aic7xxx= [HW,SCSI]
269 See Documentation/scsi/aic7xxx.txt.
271 aic79xx= [HW,SCSI]
272 See Documentation/scsi/aic79xx.txt.
274 amd_iommu= [HW,X86-84]
275 Pass parameters to the AMD IOMMU driver in the system.
276 Possible values are:
277 isolate - enable device isolation (each device, as far
278 as possible, will get its own protection
279 domain)
280 amd_iommu_size= [HW,X86-64]
281 Define the size of the aperture for the AMD IOMMU
282 driver. Possible values are:
283 '32M', '64M' (default), '128M', '256M', '512M', '1G'
285 amijoy.map= [HW,JOY] Amiga joystick support
286 Map of devices attached to JOY0DAT and JOY1DAT
287 Format: <a>,<b>
288 See also Documentation/kernel/input/joystick.txt
290 analog.map= [HW,JOY] Analog joystick and gamepad support
291 Specifies type or capabilities of an analog joystick
292 connected to one of 16 gameports
293 Format: <type1>,<type2>,..<type16>
295 apc= [HW,SPARC]
296 Power management functions (SPARCstation-4/5 + deriv.)
297 Format: noidle
298 Disable APC CPU standby support. SPARCstation-Fox does
299 not play well with APC CPU idle - disable it if you have
300 APC and your system crashes randomly.
302 apic= [APIC,i386] Advanced Programmable Interrupt Controller
303 Change the output verbosity whilst booting
304 Format: { quiet (default) | verbose | debug }
305 Change the amount of debugging information output
306 when initialising the APIC and IO-APIC components.
308 apm= [APM] Advanced Power Management
309 See header of arch/x86/kernel/apm_32.c.
311 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
312 Format: <io>,<irq>,<nodeID>
314 ataflop= [HW,M68k]
316 atarimouse= [HW,MOUSE] Atari Mouse
318 atascsi= [HW,SCSI] Atari SCSI
320 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
321 EzKey and similar keyboards
323 atkbd.reset= [HW] Reset keyboard during initialization
325 atkbd.set= [HW] Select keyboard code set
326 Format: <int> (2 = AT (default), 3 = PS/2)
328 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
329 keyboards
331 atkbd.softraw= [HW] Choose between synthetic and real raw mode
332 Format: <bool> (0 = real, 1 = synthetic (default))
334 atkbd.softrepeat= [HW]
335 Use software keyboard repeat
337 autotest [IA64]
339 baycom_epp= [HW,AX25]
340 Format: <io>,<mode>
342 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
343 Format: <io>,<mode>
344 See header of drivers/net/hamradio/baycom_par.c.
346 baycom_ser_fdx= [HW,AX25]
347 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
348 Format: <io>,<irq>,<mode>[,<baud>]
349 See header of drivers/net/hamradio/baycom_ser_fdx.c.
351 baycom_ser_hdx= [HW,AX25]
352 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
353 Format: <io>,<irq>,<mode>
354 See header of drivers/net/hamradio/baycom_ser_hdx.c.
356 boot_delay= Milliseconds to delay each printk during boot.
357 Values larger than 10 seconds (10000) are changed to
358 no delay (0).
359 Format: integer
361 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
362 bttv.radio= Most important insmod options are available as
363 kernel args too.
364 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
365 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
367 BusLogic= [HW,SCSI]
368 See drivers/scsi/BusLogic.c, comment before function
369 BusLogic_ParseDriverOptions().
371 c101= [NET] Moxa C101 synchronous serial card
373 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
374 Sometimes CPU hardware bugs make them report the cache
375 size incorrectly. The kernel will attempt work arounds
376 to fix known problems, but for some CPUs it is not
377 possible to determine what the correct size should be.
378 This option provides an override for these situations.
380 security= [SECURITY] Choose a security module to enable at boot.
381 If this boot parameter is not specified, only the first
382 security module asking for security registration will be
383 loaded. An invalid security module name will be treated
384 as if no module has been chosen.
386 capability.disable=
387 [SECURITY] Disable capabilities. This would normally
388 be used only if an alternative security model is to be
389 configured. Potentially dangerous and should only be
390 used if you are entirely sure of the consequences.
392 ccw_timeout_log [S390]
393 See Documentation/s390/CommonIO for details.
395 cgroup_disable= [KNL] Disable a particular controller
396 Format: {name of the controller(s) to disable}
397 {Currently supported controllers - "memory"}
399 checkreqprot [SELINUX] Set initial checkreqprot flag value.
400 Format: { "0" | "1" }
401 See security/selinux/Kconfig help text.
402 0 -- check protection applied by kernel (includes
403 any implied execute protection).
404 1 -- check protection requested by application.
405 Default value is set via a kernel config option.
406 Value can be changed at runtime via
407 /selinux/checkreqprot.
409 cio_ignore= [S390]
410 See Documentation/s390/CommonIO for details.
412 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
413 [Deprecated]
414 Forces specified clocksource (if available) to be used
415 when calculating gettimeofday(). If specified
416 clocksource is not available, it defaults to PIT.
417 Format: { pit | tsc | cyclone | pmtmr }
419 clocksource= [GENERIC_TIME] Override the default clocksource
420 Format: <string>
421 Override the default clocksource and use the clocksource
422 with the name specified.
423 Some clocksource names to choose from, depending on
424 the platform:
425 [all] jiffies (this is the base, fallback clocksource)
426 [ACPI] acpi_pm
427 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
428 pxa_timer,timer3,32k_counter,timer0_1
429 [AVR32] avr32
430 [X86-32] pit,hpet,tsc,vmi-timer;
431 scx200_hrt on Geode; cyclone on IBM x440
432 [MIPS] MIPS
433 [PARISC] cr16
434 [S390] tod
435 [SH] SuperH
436 [SPARC64] tick
437 [X86-64] hpet,tsc
439 clearcpuid=BITNUM [X86]
440 Disable CPUID feature X for the kernel. See
441 include/asm-x86/cpufeature.h for the valid bit numbers.
442 Note the Linux specific bits are not necessarily
443 stable over kernel options, but the vendor specific
444 ones should be.
445 Also note that user programs calling CPUID directly
446 or using the feature without checking anything
447 will still see it. This just prevents it from
448 being used by the kernel or shown in /proc/cpuinfo.
449 Also note the kernel might malfunction if you disable
450 some critical bits.
452 code_bytes [IA32/X86_64] How many bytes of object code to print
453 in an oops report.
454 Range: 0 - 8192
455 Default: 64
457 disable_8254_timer
458 enable_8254_timer
459 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
460 over the 8254 in addition to over the IO-APIC. The
461 kernel tries to set a sensible default.
463 hpet= [X86-32,HPET] option to control HPET usage
464 Format: { enable (default) | disable | force }
465 disable: disable HPET and use PIT instead
466 force: allow force enabled of undocumented chips (ICH4,
467 VIA, nVidia)
469 com20020= [HW,NET] ARCnet - COM20020 chipset
470 Format:
471 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
473 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
474 Format: <io>[,<irq>]
476 com90xx= [HW,NET]
477 ARCnet - COM90xx chipset (memory-mapped buffers)
478 Format: <io>[,<irq>[,<memstart>]]
480 condev= [HW,S390] console device
481 conmode=
483 console= [KNL] Output console device and options.
485 tty<n> Use the virtual console device <n>.
487 ttyS<n>[,options]
488 ttyUSB0[,options]
489 Use the specified serial port. The options are of
490 the form "bbbbpnf", where "bbbb" is the baud rate,
491 "p" is parity ("n", "o", or "e"), "n" is number of
492 bits, and "f" is flow control ("r" for RTS or
493 omit it). Default is "9600n8".
495 See Documentation/serial-console.txt for more
496 information. See
497 Documentation/networking/netconsole.txt for an
498 alternative.
500 uart[8250],io,<addr>[,options]
501 uart[8250],mmio,<addr>[,options]
502 Start an early, polled-mode console on the 8250/16550
503 UART at the specified I/O port or MMIO address,
504 switching to the matching ttyS device later. The
505 options are the same as for ttyS, above.
507 If the device connected to the port is not a TTY but a braille
508 device, prepend "brl," before the device type, for instance
509 console=brl,ttyS0
510 For now, only VisioBraille is supported.
512 earlycon= [KNL] Output early console device and options.
513 uart[8250],io,<addr>[,options]
514 uart[8250],mmio,<addr>[,options]
515 Start an early, polled-mode console on the 8250/16550
516 UART at the specified I/O port or MMIO address.
517 The options are the same as for ttyS, above.
519 no_console_suspend
520 [HW] Never suspend the console
521 Disable suspending of consoles during suspend and
522 hibernate operations. Once disabled, debugging
523 messages can reach various consoles while the rest
524 of the system is being put to sleep (ie, while
525 debugging driver suspend/resume hooks). This may
526 not work reliably with all consoles, but is known
527 to work with serial and VGA consoles.
529 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
530 Format:
531 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
533 crashkernel=nn[KMG]@ss[KMG]
534 [KNL] Reserve a chunk of physical memory to
535 hold a kernel to switch to with kexec on panic.
537 crashkernel=range1:size1[,range2:size2,...][@offset]
538 [KNL] Same as above, but depends on the memory
539 in the running system. The syntax of range is
540 start-[end] where start and end are both
541 a memory unit (amount[KMG]). See also
542 Documentation/kdump/kdump.txt for a example.
544 cs4232= [HW,OSS]
545 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
547 cs89x0_dma= [HW,NET]
548 Format: <dma>
550 cs89x0_media= [HW,NET]
551 Format: { rj45 | aui | bnc }
553 dasd= [HW,NET]
554 See header of drivers/s390/block/dasd_devmap.c.
556 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
557 (one device per port)
558 Format: <port#>,<type>
559 See also Documentation/input/joystick-parport.txt
561 debug [KNL] Enable kernel debugging (events log level).
563 debug_locks_verbose=
564 [KNL] verbose self-tests
565 Format=<0|1>
566 Print debugging info while doing the locking API
567 self-tests.
568 We default to 0 (no extra messages), setting it to
569 1 will print _a lot_ more information - normally
570 only useful to kernel developers.
572 debug_objects [KNL] Enable object debugging
574 decnet.addr= [HW,NET]
575 Format: <area>[,<node>]
576 See also Documentation/networking/decnet.txt.
578 vt.default_blu= [VT]
579 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
580 Change the default blue palette of the console.
581 This is a 16-member array composed of values
582 ranging from 0-255.
584 vt.default_grn= [VT]
585 Format: <green0>,<green1>,<green2>,...,<green15>
586 Change the default green palette of the console.
587 This is a 16-member array composed of values
588 ranging from 0-255.
590 vt.default_red= [VT]
591 Format: <red0>,<red1>,<red2>,...,<red15>
592 Change the default red palette of the console.
593 This is a 16-member array composed of values
594 ranging from 0-255.
596 vt.default_utf8=
597 [VT]
598 Format=<0|1>
599 Set system-wide default UTF-8 mode for all tty's.
600 Default is 1, i.e. UTF-8 mode is enabled for all
601 newly opened terminals.
603 dhash_entries= [KNL]
604 Set number of hash buckets for dentry cache.
606 digi= [HW,SERIAL]
607 IO parameters + enable/disable command.
609 digiepca= [HW,SERIAL]
610 See drivers/char/README.epca and
611 Documentation/digiepca.txt.
613 disable_mtrr_cleanup [X86]
614 enable_mtrr_cleanup [X86]
615 The kernel tries to adjust MTRR layout from continuous
616 to discrete, to make X server driver able to add WB
617 entry later. This parameter enables/disables that.
619 mtrr_chunk_size=nn[KMG] [X86]
620 used for mtrr cleanup. It is largest continous chunk
621 that could hold holes aka. UC entries.
623 mtrr_gran_size=nn[KMG] [X86]
624 Used for mtrr cleanup. It is granularity of mtrr block.
625 Default is 1.
626 Large value could prevent small alignment from
627 using up MTRRs.
629 mtrr_spare_reg_nr=n [X86]
630 Format: <integer>
631 Range: 0,7 : spare reg number
632 Default : 1
633 Used for mtrr cleanup. It is spare mtrr entries number.
634 Set to 2 or more if your graphical card needs more.
636 disable_mtrr_trim [X86, Intel and AMD only]
637 By default the kernel will trim any uncacheable
638 memory out of your available memory pool based on
639 MTRR settings. This parameter disables that behavior,
640 possibly causing your machine to run very slowly.
642 dmasound= [HW,OSS] Sound subsystem buffers
644 dscc4.setup= [NET]
646 dtc3181e= [HW,SCSI]
648 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
649 earlyprintk=vga
650 earlyprintk=serial[,ttySn[,baudrate]]
652 Append ",keep" to not disable it when the real console
653 takes over.
655 Only vga or serial at a time, not both.
657 Currently only ttyS0 and ttyS1 are supported.
659 Interaction with the standard serial driver is not
660 very good.
662 The VGA output is eventually overwritten by the real
663 console.
665 eata= [HW,SCSI]
667 edd= [EDD]
668 Format: {"off" | "on" | "skip[mbr]"}
670 eisa_irq_edge= [PARISC,HW]
671 See header of drivers/parisc/eisa.c.
673 elanfreq= [X86-32]
674 See comment before function elanfreq_setup() in
675 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
677 elevator= [IOSCHED]
678 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
679 See Documentation/block/as-iosched.txt and
680 Documentation/block/deadline-iosched.txt for details.
682 elfcorehdr= [X86-32, X86_64]
683 Specifies physical address of start of kernel core
684 image elf header. Generally kexec loader will
685 pass this option to capture kernel.
686 See Documentation/kdump/kdump.txt for details.
688 enforcing [SELINUX] Set initial enforcing status.
689 Format: {"0" | "1"}
690 See security/selinux/Kconfig help text.
691 0 -- permissive (log only, no denials).
692 1 -- enforcing (deny and log).
693 Default value is 0.
694 Value can be changed at runtime via /selinux/enforce.
696 es1371= [HW,OSS]
697 Format: <spdif>,[<nomix>,[<amplifier>]]
698 See also header of sound/oss/es1371.c.
700 ether= [HW,NET] Ethernet cards parameters
701 This option is obsoleted by the "netdev=" option, which
702 has equivalent usage. See its documentation for details.
704 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
705 Format: <io>[,<irq>]
707 failslab=
708 fail_page_alloc=
709 fail_make_request=[KNL]
710 General fault injection mechanism.
711 Format: <interval>,<probability>,<space>,<times>
712 See also /Documentation/fault-injection/.
714 fd_mcs= [HW,SCSI]
715 See header of drivers/scsi/fd_mcs.c.
717 fdomain= [HW,SCSI]
718 See header of drivers/scsi/fdomain.c.
720 floppy= [HW]
721 See Documentation/floppy.txt.
723 force_pal_cache_flush
724 [IA-64] Avoid check_sal_cache_flush which may hang on
725 buggy SAL_CACHE_FLUSH implementations. Using this
726 parameter will force ia64_sal_cache_flush to call
727 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
729 gamecon.map[2|3]=
730 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
731 support via parallel port (up to 5 devices per port)
732 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
733 See also Documentation/input/joystick-parport.txt
735 gamma= [HW,DRM]
737 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
738 Format: off | on
739 default: on
741 gdth= [HW,SCSI]
742 See header of drivers/scsi/gdth.c.
744 gpt [EFI] Forces disk with valid GPT signature but
745 invalid Protective MBR to be treated as GPT.
747 gvp11= [HW,SCSI]
749 hashdist= [KNL,NUMA] Large hashes allocated during boot
750 are distributed across NUMA nodes. Defaults on
751 for IA-64, off otherwise.
752 Format: 0 | 1 (for off | on)
754 hcl= [IA-64] SGI's Hardware Graph compatibility layer
756 hd= [EIDE] (E)IDE hard drive subsystem geometry
757 Format: <cyl>,<head>,<sect>
759 hd?= [HW] (E)IDE subsystem
760 hd?lun= See Documentation/ide/ide.txt.
762 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
763 size of <nn>. This works even on boxes that have no
764 highmem otherwise. This also works to reduce highmem
765 size on bigger boxes.
767 highres= [KNL] Enable/disable high resolution timer mode.
768 Valid parameters: "on", "off"
769 Default: "on"
771 hisax= [HW,ISDN]
772 See Documentation/isdn/README.HiSax.
774 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
775 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
777 i8042.direct [HW] Put keyboard port into non-translated mode
778 i8042.dumbkbd [HW] Pretend that controller can only read data from
779 keyboard and cannot control its state
780 (Don't attempt to blink the leds)
781 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
782 i8042.nokbd [HW] Don't check/create keyboard port
783 i8042.noloop [HW] Disable the AUX Loopback command while probing
784 for the AUX port
785 i8042.nomux [HW] Don't check presence of an active multiplexing
786 controller
787 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
788 controllers
789 i8042.panicblink=
790 [HW] Frequency with which keyboard LEDs should blink
791 when kernel panics (default is 0.5 sec)
792 i8042.reset [HW] Reset the controller during init and cleanup
793 i8042.unlock [HW] Unlock (ignore) the keylock
795 i810= [HW,DRM]
797 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
798 indicates that the driver is running on unsupported
799 hardware.
800 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
801 does not match list of supported models.
802 i8k.power_status
803 [HW] Report power status in /proc/i8k
804 (disabled by default)
805 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
806 capability is set.
808 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
809 See Documentation/mca.txt.
811 icn= [HW,ISDN]
812 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
814 ide= [HW] (E)IDE subsystem
815 Format: ide=nodma or ide=doubler
816 See Documentation/ide/ide.txt.
818 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
819 See Documentation/ide/ide.txt.
821 idle= [X86]
822 Format: idle=poll or idle=mwait
823 Poll forces a polling idle loop that can slightly improves the performance
824 of waking up a idle CPU, but will use a lot of power and make the system
825 run hot. Not recommended.
826 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
827 to not use it because it doesn't save as much power as a normal idle
828 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
829 as idle=poll.
831 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
832 Claim all unknown PCI IDE storage controllers.
834 ignore_loglevel [KNL]
835 Ignore loglevel setting - this will print /all/
836 kernel messages to the console. Useful for debugging.
838 ihash_entries= [KNL]
839 Set number of hash buckets for inode cache.
841 in2000= [HW,SCSI]
842 See header of drivers/scsi/in2000.c.
844 init= [KNL]
845 Format: <full_path>
846 Run specified binary instead of /sbin/init as init
847 process.
849 initcall_debug [KNL] Trace initcalls as they are executed. Useful
850 for working out where the kernel is dying during
851 startup.
853 initrd= [BOOT] Specify the location of the initial ramdisk
855 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
856 Format: <irq>
858 inttest= [IA64]
860 iommu= [x86]
861 off
862 force
863 noforce
864 biomerge
865 panic
866 nopanic
867 merge
868 nomerge
869 forcesac
870 soft
873 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
874 off
875 Disable intel iommu driver.
876 igfx_off [Default Off]
877 By default, gfx is mapped as normal device. If a gfx
878 device has a dedicated DMAR unit, the DMAR unit is
879 bypassed by not enabling DMAR with this option. In
880 this case, gfx device will use physical address for
881 DMA.
882 forcedac [x86_64]
883 With this option iommu will not optimize to look
884 for io virtual address below 32 bit forcing dual
885 address cycle on pci bus for cards supporting greater
886 than 32 bit addressing. The default is to look
887 for translation below 32 bit and if not available
888 then look in the higher range.
889 strict [Default Off]
890 With this option on every unmap_single operation will
891 result in a hardware IOTLB flush operation as opposed
892 to batching them for performance.
894 io_delay= [X86-32,X86-64] I/O delay method
895 0x80
896 Standard port 0x80 based delay
897 0xed
898 Alternate port 0xed based delay (needed on some systems)
899 udelay
900 Simple two microseconds delay
901 none
902 No delay
904 io7= [HW] IO7 for Marvel based alpha systems
905 See comment before marvel_specify_io7 in
906 arch/alpha/kernel/core_marvel.c.
908 ip= [IP_PNP]
909 See Documentation/filesystems/nfsroot.txt.
911 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
912 See comment before ip2_setup() in
913 drivers/char/ip2/ip2base.c.
915 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
916 See header of drivers/scsi/ips.c.
918 ports= [IP_VS_FTP] IPVS ftp helper module
919 Default is 21.
920 Up to 8 (IP_VS_APP_MAX_PORTS) ports
921 may be specified.
922 Format: <port>,<port>....
924 irqfixup [HW]
925 When an interrupt is not handled search all handlers
926 for it. Intended to get systems with badly broken
927 firmware running.
929 irqpoll [HW]
930 When an interrupt is not handled search all handlers
931 for it. Also check all handlers each timer
932 interrupt. Intended to get systems with badly broken
933 firmware running.
935 isapnp= [ISAPNP]
936 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
938 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
939 Format:
940 <cpu number>,...,<cpu number>
941 or
942 <cpu number>-<cpu number> (must be a positive range in ascending order)
943 or a mixture
944 <cpu number>,...,<cpu number>-<cpu number>
945 This option can be used to specify one or more CPUs
946 to isolate from the general SMP balancing and scheduling
947 algorithms. The only way to move a process onto or off
948 an "isolated" CPU is via the CPU affinity syscalls.
949 <cpu number> begins at 0 and the maximum value is
950 "number of CPUs in system - 1".
952 This option is the preferred way to isolate CPUs. The
953 alternative -- manually setting the CPU mask of all
954 tasks in the system -- can cause problems and
955 suboptimal load balancer performance.
957 iucv= [HW,NET]
959 js= [HW,JOY] Analog joystick
960 See Documentation/input/joystick.txt.
962 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
963 specifies the amount of memory usable by the kernel
964 for non-movable allocations. The requested amount is
965 spread evenly throughout all nodes in the system. The
966 remaining memory in each node is used for Movable
967 pages. In the event, a node is too small to have both
968 kernelcore and Movable pages, kernelcore pages will
969 take priority and other nodes will have a larger number
970 of kernelcore pages. The Movable zone is used for the
971 allocation of pages that may be reclaimed or moved
972 by the page migration subsystem. This means that
973 HugeTLB pages may not be allocated from this zone.
974 Note that allocations like PTEs-from-HighMem still
975 use the HighMem zone if it exists, and the Normal
976 zone if it does not.
978 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
979 is similar to kernelcore except it specifies the
980 amount of memory used for migratable allocations.
981 If both kernelcore and movablecore is specified,
982 then kernelcore will be at *least* the specified
983 value but may be more. If movablecore on its own
984 is specified, the administrator must be careful
985 that the amount of memory usable for all allocations
986 is not too small.
988 keepinitrd [HW,ARM]
990 kstack=N [X86-32,X86-64] Print N words from the kernel stack
991 in oops dumps.
993 kgdboc= [HW] kgdb over consoles.
994 Requires a tty driver that supports console polling.
995 (only serial suported for now)
996 Format: <serial_device>[,baud]
998 l2cr= [PPC]
1000 l3cr= [PPC]
1002 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1003 disabled it.
1005 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
1006 C2 power state.
1008 libata.dma= [LIBATA] DMA control
1009 libata.dma=0 Disable all PATA and SATA DMA
1010 libata.dma=1 PATA and SATA Disk DMA only
1011 libata.dma=2 ATAPI (CDROM) DMA only
1012 libata.dma=4 Compact Flash DMA only
1013 Combinations also work, so libata.dma=3 enables DMA
1014 for disks and CDROMs, but not CFs.
1016 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1017 when set.
1018 Format: <int>
1020 libata.force= [LIBATA] Force configurations. The format is comma
1021 separated list of "[ID:]VAL" where ID is
1022 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1023 matching port, link or device. Basically, it matches
1024 the ATA ID string printed on console by libata. If
1025 the whole ID part is omitted, the last PORT and DEVICE
1026 values are used. If ID hasn't been specified yet, the
1027 configuration applies to all ports, links and devices.
1029 If only DEVICE is omitted, the parameter applies to
1030 the port and all links and devices behind it. DEVICE
1031 number of 0 either selects the first device or the
1032 first fan-out link behind PMP device. It does not
1033 select the host link. DEVICE number of 15 selects the
1034 host link and device attached to it.
1036 The VAL specifies the configuration to force. As long
1037 as there's no ambiguity shortcut notation is allowed.
1038 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1039 The following configurations can be forced.
1041 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1042 Any ID with matching PORT is used.
1044 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1046 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1047 udma[/][16,25,33,44,66,100,133] notation is also
1048 allowed.
1050 * [no]ncq: Turn on or off NCQ.
1052 If there are multiple matching configurations changing
1053 the same attribute, the last one is used.
1055 load_ramdisk= [RAM] List of ramdisks to load from floppy
1056 See Documentation/ramdisk.txt.
1058 lockd.nlm_grace_period=P [NFS] Assign grace period.
1059 Format: <integer>
1061 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1062 Format: <integer>
1064 lockd.nlm_timeout=T [NFS] Assign timeout value.
1065 Format: <integer>
1067 lockd.nlm_udpport=M [NFS] Assign UDP port.
1068 Format: <integer>
1070 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1071 Format: <irq>
1073 loglevel= All Kernel Messages with a loglevel smaller than the
1074 console loglevel will be printed to the console. It can
1075 also be changed with klogd or other programs. The
1076 loglevels are defined as follows:
1078 0 (KERN_EMERG) system is unusable
1079 1 (KERN_ALERT) action must be taken immediately
1080 2 (KERN_CRIT) critical conditions
1081 3 (KERN_ERR) error conditions
1082 4 (KERN_WARNING) warning conditions
1083 5 (KERN_NOTICE) normal but significant condition
1084 6 (KERN_INFO) informational
1085 7 (KERN_DEBUG) debug-level messages
1087 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1088 Format: { n | nk | nM }
1089 n must be a power of two. The default size
1090 is set in the kernel config file.
1092 logo.nologo [FB] Disables display of the built-in Linux logo.
1093 This may be used to provide more screen space for
1094 kernel log messages and is useful when debugging
1095 kernel boot problems.
1097 lp=0 [LP] Specify parallel ports to use, e.g,
1098 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1099 lp=reset first parallel port). 'lp=0' disables the
1100 lp=auto printer driver. 'lp=reset' (which can be
1101 specified in addition to the ports) causes
1102 attached printers to be reset. Using
1103 lp=port1,port2,... specifies the parallel ports
1104 to associate lp devices with, starting with
1105 lp0. A port specification may be 'none' to skip
1106 that lp device, or a parport name such as
1107 'parport0'. Specifying 'lp=auto' instead of a
1108 port specification list means that device IDs
1109 from each port should be examined, to see if
1110 an IEEE 1284-compliant printer is attached; if
1111 so, the driver will manage that printer.
1112 See also header of drivers/char/lp.c.
1114 lpj=n [KNL]
1115 Sets loops_per_jiffy to given constant, thus avoiding
1116 time-consuming boot-time autodetection (up to 250 ms per
1117 CPU). 0 enables autodetection (default). To determine
1118 the correct value for your kernel, boot with normal
1119 autodetection and see what value is printed. Note that
1120 on SMP systems the preset will be applied to all CPUs,
1121 which is likely to cause problems if your CPUs need
1122 significantly divergent settings. An incorrect value
1123 will cause delays in the kernel to be wrong, leading to
1124 unpredictable I/O errors and other breakage. Although
1125 unlikely, in the extreme case this might damage your
1126 hardware.
1128 ltpc= [NET]
1129 Format: <io>,<irq>,<dma>
1131 mac5380= [HW,SCSI] Format:
1132 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1134 machvec= [IA64] Force the use of a particular machine-vector
1135 (machvec) in a generic kernel.
1136 Example: machvec=hpzx1_swiotlb
1138 max_loop= [LOOP] Maximum number of loopback devices that can
1139 be mounted
1140 Format: <1-256>
1142 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1143 should make use of. maxcpus=n : n >= 0 limits the
1144 kernel to using 'n' processors. n=0 is a special case,
1145 it is equivalent to "nosmp", which also disables
1146 the IO APIC.
1148 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1149 equal to this physical address is ignored.
1151 max_luns= [SCSI] Maximum number of LUNs to probe.
1152 Should be between 1 and 2^32-1.
1154 max_report_luns=
1155 [SCSI] Maximum number of LUNs received.
1156 Should be between 1 and 16384.
1158 mcatest= [IA-64]
1160 mce [X86-32] Machine Check Exception
1162 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1164 md= [HW] RAID subsystems devices and level
1165 See Documentation/md.txt.
1167 mdacon= [MDA]
1168 Format: <first>,<last>
1169 Specifies range of consoles to be captured by the MDA.
1171 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1172 Amount of memory to be used when the kernel is not able
1173 to see the whole system memory or for test.
1174 [X86-32] Use together with memmap= to avoid physical
1175 address space collisions. Without memmap= PCI devices
1176 could be placed at addresses belonging to unused RAM.
1178 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1179 memory.
1181 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1182 E820 memory map, as specified by the user.
1183 Such memmap=exactmap lines can be constructed based on
1184 BIOS output or other requirements. See the memmap=nn@ss
1185 option description.
1187 memmap=nn[KMG]@ss[KMG]
1188 [KNL] Force usage of a specific region of memory
1189 Region of memory to be used, from ss to ss+nn.
1191 memmap=nn[KMG]#ss[KMG]
1192 [KNL,ACPI] Mark specific memory as ACPI data.
1193 Region of memory to be used, from ss to ss+nn.
1195 memmap=nn[KMG]$ss[KMG]
1196 [KNL,ACPI] Mark specific memory as reserved.
1197 Region of memory to be used, from ss to ss+nn.
1198 Example: Exclude memory from 0x18690000-0x1869ffff
1199 memmap=64K$0x18690000
1200 or
1201 memmap=0x10000$0x18690000
1203 memtest= [KNL,X86_64] Enable memtest
1204 Format: <integer>
1205 range: 0,4 : pattern number
1206 default : 0 <disable>
1208 meye.*= [HW] Set MotionEye Camera parameters
1209 See Documentation/video4linux/meye.txt.
1211 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1212 Multi-Function General Purpose Timers on AMD Geode
1213 platforms.
1215 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1216 the BIOS has incorrectly applied a workaround. TinyBIOS
1217 version 0.98 is known to be affected, 0.99 fixes the
1218 problem by letting the user disable the workaround.
1220 mga= [HW,DRM]
1222 mousedev.tap_time=
1223 [MOUSE] Maximum time between finger touching and
1224 leaving touchpad surface for touch to be considered
1225 a tap and be reported as a left button click (for
1226 touchpads working in absolute mode only).
1227 Format: <msecs>
1228 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1229 reporting absolute coordinates, such as tablets
1230 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1231 reporting absolute coordinates, such as tablets
1233 mpu401= [HW,OSS]
1234 Format: <io>,<irq>
1236 MTD_Partition= [MTD]
1237 Format: <name>,<region-number>,<size>,<offset>
1239 MTD_Region= [MTD] Format:
1240 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1242 mtdparts= [MTD]
1243 See drivers/mtd/cmdlinepart.c.
1245 mtdset= [ARM]
1246 ARM/S3C2412 JIVE boot control
1248 See arch/arm/mach-s3c2412/mach-jive.c
1250 mtouchusb.raw_coordinates=
1251 [HW] Make the MicroTouch USB driver use raw coordinates
1252 ('y', default) or cooked coordinates ('n')
1254 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1256 NCR_D700= [HW,SCSI]
1257 See header of drivers/scsi/NCR_D700.c.
1259 ncr5380= [HW,SCSI]
1261 ncr53c400= [HW,SCSI]
1263 ncr53c400a= [HW,SCSI]
1265 ncr53c406a= [HW,SCSI]
1267 ncr53c8xx= [HW,SCSI]
1269 netdev= [NET] Network devices parameters
1270 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1271 Note that mem_start is often overloaded to mean
1272 something different and driver-specific.
1273 This usage is only documented in each driver source
1274 file if at all.
1276 nfsaddrs= [NFS]
1277 See Documentation/filesystems/nfsroot.txt.
1279 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1280 See Documentation/filesystems/nfsroot.txt.
1282 nfs.callback_tcpport=
1283 [NFS] set the TCP port on which the NFSv4 callback
1284 channel should listen.
1286 nfs.idmap_cache_timeout=
1287 [NFS] set the maximum lifetime for idmapper cache
1288 entries.
1290 nfs.enable_ino64=
1291 [NFS] enable 64-bit inode numbers.
1292 If zero, the NFS client will fake up a 32-bit inode
1293 number for the readdir() and stat() syscalls instead
1294 of returning the full 64-bit number.
1295 The default is to return 64-bit inode numbers.
1297 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1298 when a NMI is triggered.
1299 Format: [state][,regs][,debounce][,die]
1301 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1303 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1304 emulation library even if a 387 maths coprocessor
1305 is present.
1307 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1308 caches in the slab allocator. Saves per-node memory,
1309 but will impact performance.
1311 noalign [KNL,ARM]
1313 noapic [SMP,APIC] Tells the kernel to not make use of any
1314 IOAPICs that may be present in the system.
1316 nobats [PPC] Do not use BATs for mapping kernel lowmem
1317 on "Classic" PPC cores.
1319 nocache [ARM]
1321 nodelayacct [KNL] Disable per-task delay accounting
1323 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1325 noefi [X86-32,X86-64] Disable EFI runtime services support.
1327 noexec [IA-64]
1329 noexec [X86-32,X86-64]
1330 On X86-32 available only on PAE configured kernels.
1331 noexec=on: enable non-executable mappings (default)
1332 noexec=off: disable non-executable mappings
1334 noexec32 [X86-64]
1335 This affects only 32-bit executables.
1336 noexec32=on: enable non-executable mappings (default)
1337 read doesn't imply executable mappings
1338 noexec32=off: disable non-executable mappings
1339 read implies executable mappings
1341 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1342 register save and restore. The kernel will only save
1343 legacy floating-point registers on task switch.
1345 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1347 nohlt [BUGS=ARM]
1349 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1350 instruction doesn't work correctly and not to
1351 use it.
1353 nohalt [IA-64] Tells the kernel not to use the power saving
1354 function PAL_HALT_LIGHT when idle. This increases
1355 power-consumption. On the positive side, it reduces
1356 interrupt wake-up latency, which may improve performance
1357 in certain environments such as networked servers or
1358 real-time systems.
1360 nohz= [KNL] Boottime enable/disable dynamic ticks
1361 Valid arguments: on, off
1362 Default: on
1364 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1366 noirqdebug [X86-32] Disables the code which attempts to detect and
1367 disable unhandled interrupt sources.
1369 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1370 broken timer IRQ sources.
1372 noisapnp [ISAPNP] Disables ISA PnP code.
1374 noinitrd [RAM] Tells the kernel not to load any configured
1375 initial RAM disk.
1377 nointroute [IA-64]
1379 nojitter [IA64] Disables jitter checking for ITC timers.
1381 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1383 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1385 noltlbs [PPC] Do not use large page/tlb entries for kernel
1386 lowmem mapping on PPC40x.
1388 nomca [IA-64] Disable machine check abort handling
1390 nomce [X86-32] Machine Check Exception
1392 nomfgpt [X86-32] Disable Multi-Function General Purpose
1393 Timer usage (for AMD Geode machines).
1395 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1397 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1398 with UP alternatives
1400 noresidual [PPC] Don't use residual data on PReP machines.
1402 noresume [SWSUSP] Disables resume and restores original swap
1403 space.
1405 no-scroll [VGA] Disables scrollback.
1406 This is required for the Braillex ib80-piezo Braille
1407 reader made by F.H. Papenmeier (Germany).
1409 nosbagart [IA-64]
1411 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1413 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1414 and disable the IO APIC. legacy for "maxcpus=0".
1416 nosoftlockup [KNL] Disable the soft-lockup detector.
1418 nosync [HW,M68K] Disables sync negotiation for all devices.
1420 notsc [BUGS=X86-32] Disable Time Stamp Counter
1422 nousb [USB] Disable the USB subsystem
1424 nowb [ARM]
1426 nptcg= [IA64] Override max number of concurrent global TLB
1427 purges which is reported from either PAL_VM_SUMMARY or
1428 SAL PALO.
1430 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1431 one of ['zone', 'node', 'default'] can be specified
1432 This can be set from sysctl after boot.
1433 See Documentation/sysctl/vm.txt for details.
1435 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1437 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1438 Rather than timing out after 20 ms if an EC
1439 command is not properly ACKed, override the length
1440 of the timeout. We have interrupts disabled while
1441 waiting for the ACK, so if this is set too high
1442 interrupts *may* be lost!
1444 opl3= [HW,OSS]
1445 Format: <io>
1447 oprofile.timer= [HW]
1448 Use timer interrupt instead of performance counters
1450 osst= [HW,SCSI] SCSI Tape Driver
1451 Format: <buffer_size>,<write_threshold>
1452 See also Documentation/scsi/st.txt.
1454 panic= [KNL] Kernel behaviour on panic
1455 Format: <timeout>
1457 parkbd.port= [HW] Parallel port number the keyboard adapter is
1458 connected to, default is 0.
1459 Format: <parport#>
1460 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1461 0 for XT, 1 for AT (default is AT).
1462 Format: <mode>
1464 parport= [HW,PPT] Specify parallel ports. 0 disables.
1465 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1466 Use 'auto' to force the driver to use any
1467 IRQ/DMA settings detected (the default is to
1468 ignore detected IRQ/DMA settings because of
1469 possible conflicts). You can specify the base
1470 address, IRQ, and DMA settings; IRQ and DMA
1471 should be numbers, or 'auto' (for using detected
1472 settings on that particular port), or 'nofifo'
1473 (to avoid using a FIFO even if it is detected).
1474 Parallel ports are assigned in the order they
1475 are specified on the command line, starting
1476 with parport0.
1478 parport_init_mode= [HW,PPT]
1479 Configure VIA parallel port to operate in
1480 a specific mode. This is necessary on Pegasos
1481 computer where firmware has no options for setting
1482 up parallel port mode and sets it to spp.
1483 Currently this function knows 686a and 8231 chips.
1484 Format: [spp|ps2|epp|ecp|ecpepp]
1486 pas2= [HW,OSS] Format:
1487 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1489 pas16= [HW,SCSI]
1490 See header of drivers/scsi/pas16.c.
1492 pause_on_oops=
1493 Halt all CPUs after the first oops has been printed for
1494 the specified number of seconds. This is to be used if
1495 your oopses keep scrolling off the screen.
1497 pcbit= [HW,ISDN]
1499 pcd. [PARIDE]
1500 See header of drivers/block/paride/pcd.c.
1501 See also Documentation/paride.txt.
1503 pci=option[,option...] [PCI] various PCI subsystem options:
1504 off [X86-32] don't probe for the PCI bus
1505 bios [X86-32] force use of PCI BIOS, don't access
1506 the hardware directly. Use this if your machine
1507 has a non-standard PCI host bridge.
1508 nobios [X86-32] disallow use of PCI BIOS, only direct
1509 hardware access methods are allowed. Use this
1510 if you experience crashes upon bootup and you
1511 suspect they are caused by the BIOS.
1512 conf1 [X86-32] Force use of PCI Configuration
1513 Mechanism 1.
1514 conf2 [X86-32] Force use of PCI Configuration
1515 Mechanism 2.
1516 noaer [PCIE] If the PCIEAER kernel config parameter is
1517 enabled, this kernel boot option can be used to
1518 disable the use of PCIE advanced error reporting.
1519 nodomains [PCI] Disable support for multiple PCI
1520 root domains (aka PCI segments, in ACPI-speak).
1521 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1522 Configuration
1523 nomsi [MSI] If the PCI_MSI kernel config parameter is
1524 enabled, this kernel boot option can be used to
1525 disable the use of MSI interrupts system-wide.
1526 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1527 routing table. These calls are known to be buggy
1528 on several machines and they hang the machine
1529 when used, but on other computers it's the only
1530 way to get the interrupt routing table. Try
1531 this option if the kernel is unable to allocate
1532 IRQs or discover secondary PCI buses on your
1533 motherboard.
1534 rom [X86-32] Assign address space to expansion ROMs.
1535 Use with caution as certain devices share
1536 address decoders between ROMs and other
1537 resources.
1538 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1539 assigned automatically to PCI devices. You can
1540 make the kernel exclude IRQs of your ISA cards
1541 this way.
1542 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1543 of the PIRQ table (normally generated
1544 by the BIOS) if it is outside the
1545 F0000h-100000h range.
1546 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1547 useful if the kernel is unable to find your
1548 secondary buses and you want to tell it
1549 explicitly which ones they are.
1550 assign-busses [X86-32] Always assign all PCI bus
1551 numbers ourselves, overriding
1552 whatever the firmware may have done.
1553 usepirqmask [X86-32] Honor the possible IRQ mask stored
1554 in the BIOS $PIR table. This is needed on
1555 some systems with broken BIOSes, notably
1556 some HP Pavilion N5400 and Omnibook XE3
1557 notebooks. This will have no effect if ACPI
1558 IRQ routing is enabled.
1559 noacpi [X86-32] Do not use ACPI for IRQ routing
1560 or for PCI scanning.
1561 use_crs [X86-32] Use _CRS for PCI resource
1562 allocation.
1563 routeirq Do IRQ routing for all PCI devices.
1564 This is normally done in pci_enable_device(),
1565 so this option is a temporary workaround
1566 for broken drivers that don't call it.
1567 skip_isa_align [X86] do not align io start addr, so can
1568 handle more pci cards
1569 firmware [ARM] Do not re-enumerate the bus but instead
1570 just use the configuration from the
1571 bootloader. This is currently used on
1572 IXP2000 systems where the bus has to be
1573 configured a certain way for adjunct CPUs.
1574 noearly [X86] Don't do any early type 1 scanning.
1575 This might help on some broken boards which
1576 machine check when some devices' config space
1577 is read. But various workarounds are disabled
1578 and some IOMMU drivers will not work.
1579 bfsort Sort PCI devices into breadth-first order.
1580 This sorting is done to get a device
1581 order compatible with older (<= 2.4) kernels.
1582 nobfsort Don't sort PCI devices into breadth-first order.
1583 cbiosize=nn[KMG] The fixed amount of bus space which is
1584 reserved for the CardBus bridge's IO window.
1585 The default value is 256 bytes.
1586 cbmemsize=nn[KMG] The fixed amount of bus space which is
1587 reserved for the CardBus bridge's memory
1588 window. The default value is 64 megabytes.
1590 pcmv= [HW,PCMCIA] BadgePAD 4
1592 pd. [PARIDE]
1593 See Documentation/paride.txt.
1595 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1596 boot time.
1597 Format: { 0 | 1 }
1598 See arch/parisc/kernel/pdc_chassis.c
1600 pf. [PARIDE]
1601 See Documentation/paride.txt.
1603 pg. [PARIDE]
1604 See Documentation/paride.txt.
1606 pirq= [SMP,APIC] Manual mp-table setup
1607 See Documentation/i386/IO-APIC.txt.
1609 plip= [PPT,NET] Parallel port network link
1610 Format: { parport<nr> | timid | 0 }
1611 See also Documentation/parport.txt.
1613 pnpacpi= [ACPI]
1614 { off }
1616 pnpbios= [ISAPNP]
1617 { on | off | curr | res | no-curr | no-res }
1619 pnp_reserve_irq=
1620 [ISAPNP] Exclude IRQs for the autoconfiguration
1622 pnp_reserve_dma=
1623 [ISAPNP] Exclude DMAs for the autoconfiguration
1625 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1626 Ranges are in pairs (I/O port base and size).
1628 pnp_reserve_mem=
1629 [ISAPNP] Exclude memory regions for the
1630 autoconfiguration.
1631 Ranges are in pairs (memory base and size).
1633 print-fatal-signals=
1634 [KNL] debug: print fatal signals
1635 print-fatal-signals=1: print segfault info to
1636 the kernel console.
1637 default: off.
1639 printk.time= Show timing data prefixed to each printk message line
1640 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1642 profile= [KNL] Enable kernel profiling via /proc/profile
1643 Format: [schedule,]<number>
1644 Param: "schedule" - profile schedule points.
1645 Param: <number> - step/bucket size as a power of 2 for
1646 statistical time based profiling.
1647 Param: "sleep" - profile D-state sleeping (millisecs).
1648 Requires CONFIG_SCHEDSTATS
1649 Param: "kvm" - profile VM exits.
1651 processor.max_cstate= [HW,ACPI]
1652 Limit processor to maximum C-state
1653 max_cstate=9 overrides any DMI blacklist limit.
1655 processor.nocst [HW,ACPI]
1656 Ignore the _CST method to determine C-states,
1657 instead using the legacy FADT method
1659 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1660 before loading.
1661 See Documentation/ramdisk.txt.
1663 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1664 probe for; one of (bare|imps|exps|lifebook|any).
1665 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1666 per second.
1667 psmouse.resetafter= [HW,MOUSE]
1668 Try to reset the device after so many bad packets
1669 (0 = never).
1670 psmouse.resolution=
1671 [HW,MOUSE] Set desired mouse resolution, in dpi.
1672 psmouse.smartscroll=
1673 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1674 0 = disabled, 1 = enabled (default).
1676 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1677 Format:
1678 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1680 pt. [PARIDE]
1681 See Documentation/paride.txt.
1683 pty.legacy_count=
1684 [KNL] Number of legacy pty's. Overwrites compiled-in
1685 default number.
1687 quiet [KNL] Disable most log messages
1689 r128= [HW,DRM]
1691 raid= [HW,RAID]
1692 See Documentation/md.txt.
1694 ramdisk_blocksize= [RAM]
1695 See Documentation/ramdisk.txt.
1697 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1698 See Documentation/ramdisk.txt.
1700 rcupdate.blimit= [KNL,BOOT]
1701 Set maximum number of finished RCU callbacks to process
1702 in one batch.
1704 rcupdate.qhimark= [KNL,BOOT]
1705 Set threshold of queued
1706 RCU callbacks over which batch limiting is disabled.
1708 rcupdate.qlowmark= [KNL,BOOT]
1709 Set threshold of queued RCU callbacks below which
1710 batch limiting is re-enabled.
1712 rdinit= [KNL]
1713 Format: <full_path>
1714 Run specified binary instead of /init from the ramdisk,
1715 used for early userspace startup. See initrd.
1717 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1718 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1719 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1721 relax_domain_level=
1722 [KNL, SMP] Set scheduler's default relax_domain_level.
1723 See Documentation/cpusets.txt.
1725 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1727 reservetop= [X86-32]
1728 Format: nn[KMG]
1729 Reserves a hole at the top of the kernel virtual
1730 address space.
1732 reset_devices [KNL] Force drivers to reset the underlying device
1733 during initialization.
1735 resume= [SWSUSP]
1736 Specify the partition device for software suspend
1738 resume_offset= [SWSUSP]
1739 Specify the offset from the beginning of the partition
1740 given by "resume=" at which the swap header is located,
1741 in <PAGE_SIZE> units (needed only for swap files).
1742 See Documentation/power/swsusp-and-swap-files.txt
1744 retain_initrd [RAM] Keep initrd memory after extraction
1746 rhash_entries= [KNL,NET]
1747 Set number of hash buckets for route cache
1749 riscom8= [HW,SERIAL]
1750 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1752 ro [KNL] Mount root device read-only on boot
1754 root= [KNL] Root filesystem
1756 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1757 mount the root filesystem
1759 rootflags= [KNL] Set root filesystem mount option string
1761 rootfstype= [KNL] Set root filesystem type
1763 rootwait [KNL] Wait (indefinitely) for root device to show up.
1764 Useful for devices that are detected asynchronously
1765 (e.g. USB and MMC devices).
1767 root_plug.vendor_id=
1768 [ROOTPLUG] Override the default vendor ID
1770 root_plug.product_id=
1771 [ROOTPLUG] Override the default product ID
1773 root_plug.debug=
1774 [ROOTPLUG] Enable debugging output
1776 rw [KNL] Mount root device read-write on boot
1778 S [KNL] Run init in single mode
1780 sa1100ir [NET]
1781 See drivers/net/irda/sa1100_ir.c.
1783 sbni= [NET] Granch SBNI12 leased line adapter
1785 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1786 Format: <io>[,<timeout>[,<isapnp>]]
1788 scsi_debug_*= [SCSI]
1789 See drivers/scsi/scsi_debug.c.
1791 scsi_default_dev_flags=
1792 [SCSI] SCSI default device flags
1793 Format: <integer>
1795 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1796 Format: <vendor>:<model>:<flags>
1797 (flags are integer value)
1799 scsi_logging_level= [SCSI] a bit mask of logging levels
1800 See drivers/scsi/scsi_logging.h for bits. Also
1801 settable via sysctl at dev.scsi.logging_level
1802 (/proc/sys/dev/scsi/logging_level).
1803 There is also a nice 'scsi_logging_level' script in the
1804 S390-tools package, available for download at
1805 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1807 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1808 discovered. async scans them in kernel threads,
1809 allowing boot to proceed. none ignores them, expecting
1810 user space to do the scan.
1812 selinux [SELINUX] Disable or enable SELinux at boot time.
1813 Format: { "0" | "1" }
1814 See security/selinux/Kconfig help text.
1815 0 -- disable.
1816 1 -- enable.
1817 Default value is set via kernel config option.
1818 If enabled at boot time, /selinux/disable can be used
1819 later to disable prior to initial policy load.
1821 selinux_compat_net =
1822 [SELINUX] Set initial selinux_compat_net flag value.
1823 Format: { "0" | "1" }
1824 0 -- use new secmark-based packet controls
1825 1 -- use legacy packet controls
1826 Default value is 0 (preferred).
1827 Value can be changed at runtime via
1828 /selinux/compat_net.
1830 serialnumber [BUGS=X86-32]
1832 shapers= [NET]
1833 Maximal number of shapers.
1835 sim710= [SCSI,HW]
1836 See header of drivers/scsi/sim710.c.
1838 simeth= [IA-64]
1839 simscsi=
1841 slram= [HW,MTD]
1843 slub_debug[=options[,slabs]] [MM, SLUB]
1844 Enabling slub_debug allows one to determine the
1845 culprit if slab objects become corrupted. Enabling
1846 slub_debug can create guard zones around objects and
1847 may poison objects when not in use. Also tracks the
1848 last alloc / free. For more information see
1849 Documentation/vm/slub.txt.
1851 slub_max_order= [MM, SLUB]
1852 Determines the maximum allowed order for slabs.
1853 A high setting may cause OOMs due to memory
1854 fragmentation. For more information see
1855 Documentation/vm/slub.txt.
1857 slub_min_objects= [MM, SLUB]
1858 The minimum number of objects per slab. SLUB will
1859 increase the slab order up to slub_max_order to
1860 generate a sufficiently large slab able to contain
1861 the number of objects indicated. The higher the number
1862 of objects the smaller the overhead of tracking slabs
1863 and the less frequently locks need to be acquired.
1864 For more information see Documentation/vm/slub.txt.
1866 slub_min_order= [MM, SLUB]
1867 Determines the mininum page order for slabs. Must be
1868 lower than slub_max_order.
1869 For more information see Documentation/vm/slub.txt.
1871 slub_nomerge [MM, SLUB]
1872 Disable merging of slabs with similar size. May be
1873 necessary if there is some reason to distinguish
1874 allocs to different slabs. Debug options disable
1875 merging on their own.
1876 For more information see Documentation/vm/slub.txt.
1878 smart2= [HW]
1879 Format: <io1>[,<io2>[,...,<io8>]]
1881 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1882 attempt to substitute SMP alternatives once at boot.
1884 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1885 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1886 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1887 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1888 smsc-ircc2.ircc_irq= [HW] IRQ line
1889 smsc-ircc2.ircc_dma= [HW] DMA channel
1890 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1891 0: Toshiba Satellite 1800 (GP data pin select)
1892 1: Fast pin select (default)
1893 2: ATC IRMode
1895 snd-ad1816a= [HW,ALSA]
1897 snd-ad1848= [HW,ALSA]
1899 snd-ali5451= [HW,ALSA]
1901 snd-als100= [HW,ALSA]
1903 snd-als4000= [HW,ALSA]
1905 snd-azt2320= [HW,ALSA]
1907 snd-cmi8330= [HW,ALSA]
1909 snd-cmipci= [HW,ALSA]
1911 snd-cs4231= [HW,ALSA]
1913 snd-cs4232= [HW,ALSA]
1915 snd-cs4236= [HW,ALSA]
1917 snd-cs4281= [HW,ALSA]
1919 snd-cs46xx= [HW,ALSA]
1921 snd-dt019x= [HW,ALSA]
1923 snd-dummy= [HW,ALSA]
1925 snd-emu10k1= [HW,ALSA]
1927 snd-ens1370= [HW,ALSA]
1929 snd-ens1371= [HW,ALSA]
1931 snd-es968= [HW,ALSA]
1933 snd-es1688= [HW,ALSA]
1935 snd-es18xx= [HW,ALSA]
1937 snd-es1938= [HW,ALSA]
1939 snd-es1968= [HW,ALSA]
1941 snd-fm801= [HW,ALSA]
1943 snd-gusclassic= [HW,ALSA]
1945 snd-gusextreme= [HW,ALSA]
1947 snd-gusmax= [HW,ALSA]
1949 snd-hdsp= [HW,ALSA]
1951 snd-ice1712= [HW,ALSA]
1953 snd-intel8x0= [HW,ALSA]
1955 snd-interwave= [HW,ALSA]
1957 snd-interwave-stb=
1958 [HW,ALSA]
1960 snd-korg1212= [HW,ALSA]
1962 snd-maestro3= [HW,ALSA]
1964 snd-mpu401= [HW,ALSA]
1966 snd-mtpav= [HW,ALSA]
1968 snd-nm256= [HW,ALSA]
1970 snd-opl3sa2= [HW,ALSA]
1972 snd-opti92x-ad1848=
1973 [HW,ALSA]
1975 snd-opti92x-cs4231=
1976 [HW,ALSA]
1978 snd-opti93x= [HW,ALSA]
1980 snd-pmac= [HW,ALSA]
1982 snd-rme32= [HW,ALSA]
1984 snd-rme96= [HW,ALSA]
1986 snd-rme9652= [HW,ALSA]
1988 snd-sb8= [HW,ALSA]
1990 snd-sb16= [HW,ALSA]
1992 snd-sbawe= [HW,ALSA]
1994 snd-serial= [HW,ALSA]
1996 snd-sgalaxy= [HW,ALSA]
1998 snd-sonicvibes= [HW,ALSA]
2000 snd-sun-amd7930=
2001 [HW,ALSA]
2003 snd-sun-cs4231= [HW,ALSA]
2005 snd-trident= [HW,ALSA]
2007 snd-usb-audio= [HW,ALSA,USB]
2009 snd-via82xx= [HW,ALSA]
2011 snd-virmidi= [HW,ALSA]
2013 snd-wavefront= [HW,ALSA]
2015 snd-ymfpci= [HW,ALSA]
2017 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2018 See Documentation/sonypi.txt
2020 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2021 See Documentation/specialix.txt.
2023 spia_io_base= [HW,MTD]
2024 spia_fio_base=
2025 spia_pedr=
2026 spia_peddr=
2028 sscape= [HW,OSS]
2029 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2031 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2032 See Documentation/scsi/st.txt.
2034 sti= [PARISC,HW]
2035 Format: <num>
2036 Set the STI (builtin display/keyboard on the HP-PARISC
2037 machines) console (graphic card) which should be used
2038 as the initial boot-console.
2039 See also comment in drivers/video/console/sticore.c.
2041 sti_font= [HW]
2042 See comment in drivers/video/console/sticore.c.
2044 stifb= [HW]
2045 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2047 sunrpc.pool_mode=
2048 [NFS]
2049 Control how the NFS server code allocates CPUs to
2050 service thread pools. Depending on how many NICs
2051 you have and where their interrupts are bound, this
2052 option will affect which CPUs will do NFS serving.
2053 Note: this parameter cannot be changed while the
2054 NFS server is running.
2056 auto the server chooses an appropriate mode
2057 automatically using heuristics
2058 global a single global pool contains all CPUs
2059 percpu one pool for each CPU
2060 pernode one pool for each NUMA node (equivalent
2061 to global on non-NUMA machines)
2063 swiotlb= [IA-64] Number of I/O TLB slabs
2065 switches= [HW,M68k]
2067 sym53c416= [HW,SCSI]
2068 See header of drivers/scsi/sym53c416.c.
2070 sysrq_always_enabled
2071 [KNL]
2072 Ignore sysrq setting - this boot parameter will
2073 neutralize any effect of /proc/sys/kernel/sysrq.
2074 Useful for debugging.
2076 t128= [HW,SCSI]
2077 See header of drivers/scsi/t128.c.
2079 tdfx= [HW,DRM]
2081 thash_entries= [KNL,NET]
2082 Set number of hash buckets for TCP connection
2084 thermal.act= [HW,ACPI]
2085 -1: disable all active trip points in all thermal zones
2086 <degrees C>: override all lowest active trip points
2088 thermal.crt= [HW,ACPI]
2089 -1: disable all critical trip points in all thermal zones
2090 <degrees C>: lower all critical trip points
2092 thermal.nocrt= [HW,ACPI]
2093 Set to disable actions on ACPI thermal zone
2094 critical and hot trip points.
2096 thermal.off= [HW,ACPI]
2097 1: disable ACPI thermal control
2099 thermal.psv= [HW,ACPI]
2100 -1: disable all passive trip points
2101 <degrees C>: override all passive trip points to this value
2103 thermal.tzp= [HW,ACPI]
2104 Specify global default ACPI thermal zone polling rate
2105 <deci-seconds>: poll all this frequency
2106 0: no polling (default)
2108 tipar.timeout= [HW,PPT]
2109 Set communications timeout in tenths of a second
2110 (default 15).
2112 tipar.delay= [HW,PPT]
2113 Set inter-bit delay in microseconds (default 10).
2115 tmscsim= [HW,SCSI]
2116 See comment before function dc390_setup() in
2117 drivers/scsi/tmscsim.c.
2119 tp720= [HW,PS2]
2121 trix= [HW,OSS] MediaTrix AudioTrix Pro
2122 Format:
2123 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2125 turbografx.map[2|3]= [HW,JOY]
2126 TurboGraFX parallel port interface
2127 Format:
2128 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2129 See also Documentation/input/joystick-parport.txt
2131 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2132 See header of drivers/scsi/u14-34f.c.
2134 uart401= [HW,OSS]
2135 Format: <io>,<irq>
2137 uart6850= [HW,OSS]
2138 Format: <io>,<irq>
2140 uhci-hcd.ignore_oc=
2141 [USB] Ignore overcurrent events (default N).
2142 Some badly-designed motherboards generate lots of
2143 bogus events, for ports that aren't wired to
2144 anything. Set this parameter to avoid log spamming.
2145 Note that genuine overcurrent events won't be
2146 reported either.
2148 usbcore.autosuspend=
2149 [USB] The autosuspend time delay (in seconds) used
2150 for newly-detected USB devices (default 2). This
2151 is the time required before an idle device will be
2152 autosuspended. Devices for which the delay is set
2153 to a negative value won't be autosuspended at all.
2155 usbhid.mousepoll=
2156 [USBHID] The interval which mice are to be polled at.
2158 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2159 kernel's map of available physical RAM.
2161 vdso= [X86-32,SH,x86-64]
2162 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2163 vdso=1: enable VDSO (default)
2164 vdso=0: disable VDSO mapping
2166 vdso32= [X86-32,X86-64]
2167 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2168 vdso32=1: enable 32-bit VDSO (default)
2169 vdso32=0: disable 32-bit VDSO mapping
2171 vector= [IA-64,SMP]
2172 vector=percpu: enable percpu vector domain
2174 video= [FB] Frame buffer configuration
2175 See Documentation/fb/modedb.txt.
2177 vga= [BOOT,X86-32] Select a particular video mode
2178 See Documentation/i386/boot.txt and
2179 Documentation/svga.txt.
2180 Use vga=ask for menu.
2181 This is actually a boot loader parameter; the value is
2182 passed to the kernel using a special protocol.
2184 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2185 size of <nn>. This can be used to increase the
2186 minimum size (128MB on x86). It can also be used to
2187 decrease the size and leave more room for directly
2188 mapped kernel RAM.
2190 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2191 Format: <command>
2193 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2194 Format: <command>
2196 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2197 Format: <command>
2199 waveartist= [HW,OSS]
2200 Format: <io>,<irq>,<dma>,<dma2>
2202 wd33c93= [HW,SCSI]
2203 See header of drivers/scsi/wd33c93.c.
2205 wd7000= [HW,SCSI]
2206 See header of drivers/scsi/wd7000.c.
2208 wdt= [WDT] Watchdog
2209 See Documentation/watchdog/wdt.txt.
2211 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2212 xd_geo= See header of drivers/block/xd.c.
2214 xirc2ps_cs= [NET,PCMCIA]
2215 Format:
2216 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2218 norandmaps Don't use address space randomization
2219 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2221 ______________________________________________________________________
2223 TODO:
2225 Add documentation for ALSA options.
2226 Add more DRM drivers.